**Meet the editor**

Prof. Dr. Uner Tan (born May 1, 1937) is a Turkish neuroscientist, best known for his discovery and study of human quadrupedalism with cognitive decline (Uner Tan syndrome). He taught at various universities in Germany and Turkey. Tan is the honorary member of the Turkish Academy of Sciences and won numerous awards including the Science Award from the Turkish

Scientific and Technical Council, Einstein and Nobel Medals for Science and Peace (Albert Einstein Foundation, USA), and Gold Record for Brain Research (American Biographical Institute). Tan's scientific studies include the cerebrospinal motor systems of humans and animals, walking gaits, cerebral lateralization, intelligence, handedness, finger-length patterns, and Uner Tan syndrome (quadrupedalism and cognitive decline).

## Contents

## **Preface XI**

	- Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe, Pooja Kulkarni, Suhasini Pai, Ritu Varghese and Amruta Paranjape

## Preface

Chapter 7 **After Stroke Movement Impairments: A Review of Current**

Saavedra, Enrique Germany and Britam Gómez

Chapter 8 **Stem Cell Therapy in Pediatric Neurological Disabilities 117**

Pablo Aqueveque, Paulina Ortega, Esteban Pino, Francisco

Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe, Pooja Kulkarni, Suhasini Pai, Ritu Varghese and Amruta

**Technologies for Rehabilitation 95**

Chapter 9 **Skeletal Muscle Dysfunction in Critical Illness 143**

Yuki Iida and Kunihiro Sakuma

Paranjape

**VI** Contents

This book presents studies covering a wide range of physical disabilities, i. e., pathological conditions limiting the healthy physical activities. In other words, a physical disability may be defined as a physical impairment (partial or total) that causes difficulty or error in motor actions. Various aspects of this condition will be dealt with in the present book.

Chapter 1, by Zohreh Salimi and Martin W. Ferguson-Pell, "Validity in Rehabilitation Re‐ search: Description and Classification," considering all of the available classification data, provides an all-inclusive classification of different types of research validity. In addition, a review of the literature was also conducted.

Chapter 2, by Gurusidheshwar Wali and Gautam Wali, titled "Rare and Disabled Movement Disorders: An Indian Experience," presents Uner Tan syndrome cases with habitual quadru‐ pedal locomotion and impaired cognition recently discovered in India. It also considers the transport defects in subcellular organelles in these cases, including the potential rectification with known drugs raising hopes for their cure.

In Chapter 3, "Five-Wheeled Wheelchair with an Add-On Mechanism and Its Semiautomat‐ ic Step-Climbing and Step-Descending Function," the authors, Masayoshi Wada and Yu Mu‐ nakata, propose a novel add-on electric drive system for propelling a manual wheelchair on the floor together with an advanced function to climb and descend a step with no human support.

Chapter 4, "Participation and Environmental Factors of Children with Physical Disabilities in Taiwan," by Lin-Ju Kang, Ai-Wen Hwang, and Chia-Ling Chen, reports that "participa‐ tion is a critical health and education outcome of children and can be optimized by environ‐ mental supports; children with physical disabilities often experience participation restriction and environmental barriers."

Chapter 5, by Marta Rodríguez-Hernández, Carmen Fernández-Panadero, Olga López-Mar‐ tín, and Begoña Polonio-López, under the title "Hand Rehabilitation after Chronic Brain Damage-Effectiveness, Usability, and Acceptance of Technological Devices: A Pilot Study," deals with an overview of existing tools for hand rehabilitation after brain injury and a pilot study to test HandTutor in patients with chronic brain damage, concluding that this chapter is a step further to evaluating the acceptance of technological devices in patients with chron‐ ic brain damage.

Chapter 6, written by Nina Sladekova, Elena Ziakova, Jaroslav Kresanek, Stanislava Klo‐ bucka, Jana Havlova, and Miroslav Malay, is, as the title suggested, focused on the impact of non–robot-assisted therapy for paretic upper extremity caused by cerebral palsy, using Ar‐ meo Therapy. The authors compare it to classical kinesiotherapy.

Chapter 7, "After-Stroke Movement Impairments: A Review of Current Technologies for Re‐ habilitation," by Pablo Aqueveque, Paulina Ortega, Esteban Pino, Francisco Saavedra, Enri‐ que Germany, and Britam Gomez, provides a review of the rehabilitation technologies for people who have suffered a stroke.

Chapter 8, written by Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe, Pooja Kulkarni, Suhasini Pai, Ritu Varghese, and Amruta Paranjape, deals with stem cell therapy in pediatric neurological disabilities. In the chapter, the use of novel monitoring tools such as MRI MSK and PET-CT scan to track the changes occurring at the cellular level after stem cell therapy is described.

Finally, Chapter 9, by Yuki Iida and Kunihiro Sakuma, presents a review of the literature regarding critical illness-induced muscle wasting and describes potential treatment of exces‐ sive muscle catabolism.

### **Acknowledgment**

I am grateful to the Turkish Academy of Sciences (Ankara, Turkey) as well as InTech's pub‐ lishing team for the support during the review process.

**Prof. Dr. Uner Tan**

Honorary Member of the Turkish Academy of Sciences, Ankara, Turkey Cukurova University, Medical School, Department of Physiology, Adana, Turkey

## **Validity in Rehabilitation Research: Description and Classification**

Zohreh Salimi and Martin W. Ferguson‐Pell

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67389

#### **Abstract**

Chapter 7, "After-Stroke Movement Impairments: A Review of Current Technologies for Re‐ habilitation," by Pablo Aqueveque, Paulina Ortega, Esteban Pino, Francisco Saavedra, Enri‐ que Germany, and Britam Gomez, provides a review of the rehabilitation technologies for

Chapter 8, written by Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe, Pooja Kulkarni, Suhasini Pai, Ritu Varghese, and Amruta Paranjape, deals with stem cell therapy in pediatric neurological disabilities. In the chapter, the use of novel monitoring tools such as MRI MSK and PET-CT scan to track the changes occurring at the cellular level

Finally, Chapter 9, by Yuki Iida and Kunihiro Sakuma, presents a review of the literature regarding critical illness-induced muscle wasting and describes potential treatment of exces‐

I am grateful to the Turkish Academy of Sciences (Ankara, Turkey) as well as InTech's pub‐

Honorary Member of the Turkish Academy of Sciences, Ankara, Turkey

Cukurova University, Medical School, Department of Physiology, Adana, Turkey

**Prof. Dr. Uner Tan**

people who have suffered a stroke.

after stem cell therapy is described.

lishing team for the support during the review process.

sive muscle catabolism.

**Acknowledgment**

VIII Preface

There is a considerable body of literature on research validity across different disciplines. With regard to rehabilitation research, however, this body is narrow and warrants further consideration. Classification of research validity has been considered and developed over the past six decades; however, a literature search returned no comprehensive discussion that has gathered all available classifications under an overarching umbrella. The aim of this chapter is to provide an all‐inclusive classification of different types of research validity, focusing on rehabilitation research. A basic review of the body of literature available was conducted. Different classifications of validity in the literature were recognized, considered, unified, and are presented in this chapter. Moreover, the main threats to each type of validity and some strategies to minimize them are discussed. A classification of all types of validity in rehabilitation research is presented in this chapter. Furthermore, the matter of priority between these research validities is discussed. It is concluded that while all types of research validities are important to be considered, maximizing all of them in one research project is sometimes controversial. Thus, researchers should make a situation‐based trade‐off between different aspects of validity in order to optimize the overall validity of their research.

**Keywords:** research validity, construct validity, classification, threats to validity, rehabilitation research

## **1. Introduction**

Getting concerned with the validity of a research is ensuring its empirical integrity [1]. The level of validity of a study is an indicator of cost‐effectiveness and accountability of it [1]. A research study is considered valid when (1) it is able to correctly find the relationship between the variables, (2) it measures what it claims to be measuring, (3) the findings are generalizable,

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

and also (4) it has adequate statistical power to reject a false null hypothesis. On the other hand, the power of a study is its ability to find the truth: correctly rejecting a false‐null hypothesis or supporting a true‐null hypothesis. Therefore, a valid study is also a powerful study, because its findings are the true results of that study.

All researchers need to ensure the validity of the tests and instruments they use before conducting research studies, but this is of particular importance for rehabilitation researchers: in a review study, 100 data-based studies were reviewed and by a *post hoc* power calculation, it was shown that there is a high possibility for the occurrence of type II error in rehabilitation research studies [1]. Type II error refers to supporting a false‐null hypothesis, which leads to a false‐negative conclusion. In the rehabilitation studies reviewed in this study, the medians of power for detecting small‐, medium‐, and large‐effect sizes have been only equal to 0.08, 0.26, and 0.56, respectively. These low‐power values clearly show the importance of accounting for power and validity of the study in rehabilitation research, before starting to conduct one. This is because the purpose of all studies is truly discovering the relationship among variables [2], and if a study does not have validity, the results obtained from it will not be trustworthy.

Validity of the research should be considered for all research studies. Research studies concerned with validity have been done for a large variety of different fields of knowledge, including Education [3–12], Psychology [13–16], Marketing [17], Management [18], Employment [19], Nursing [20], Criminal issues [21], Animal studies [22], Sports [23], Nutrition and Food Science [24], Health [25–27], and Rehabilitation Science [1, 2]. Regarding the number of research studies about validity that are available in the literature for different disciplines, Education, Psychology, and Marketing are the fields that are most prominent. However, the body of literature in this context for health studies is narrow, and even narrower for rehabilitation science. This highlights the necessity of addressing this issue for health sciences in general, and rehabilitation sciences in particular. In this chapter, the validity of different types of rehabilitation studies will be discussed. In doing so, the main focus will be on one type of validity that is a more complicated aspect of validation: construct validity. We will discourse some threats to each type of validity along with providing some strategies to prevent them, and hence how to power up the study, as we pass through each validation type.

## **2. What is validity?**

Validity principles are applicable to all studies, whether they are based on questionnaires, observational studies, or other types of assessments [7]. Research validity helps us to know how true the claims and propositions made in a study are. This judgment can be based on the characteristics of a study, such as the research design, adequacy of sample size, the recruitment procedure, instruments and tests used, and the appropriateness of statistical methods used [28].

## **3. Types of research validity**

and also (4) it has adequate statistical power to reject a false null hypothesis. On the other hand, the power of a study is its ability to find the truth: correctly rejecting a false‐null hypothesis or supporting a true‐null hypothesis. Therefore, a valid study is also a powerful study,

All researchers need to ensure the validity of the tests and instruments they use before conducting research studies, but this is of particular importance for rehabilitation researchers: in a review study, 100 data-based studies were reviewed and by a *post hoc* power calculation, it was shown that there is a high possibility for the occurrence of type II error in rehabilitation research studies [1]. Type II error refers to supporting a false‐null hypothesis, which leads to a false‐negative conclusion. In the rehabilitation studies reviewed in this study, the medians of power for detecting small‐, medium‐, and large‐effect sizes have been only equal to 0.08, 0.26, and 0.56, respectively. These low‐power values clearly show the importance of accounting for power and validity of the study in rehabilitation research, before starting to conduct one. This is because the purpose of all studies is truly discovering the relationship among variables [2], and if a study does not have validity, the results obtained from it will

Validity of the research should be considered for all research studies. Research studies concerned with validity have been done for a large variety of different fields of knowledge, including Education [3–12], Psychology [13–16], Marketing [17], Management [18], Employment [19], Nursing [20], Criminal issues [21], Animal studies [22], Sports [23], Nutrition and Food Science [24], Health [25–27], and Rehabilitation Science [1, 2]. Regarding the number of research studies about validity that are available in the literature for different disciplines, Education, Psychology, and Marketing are the fields that are most prominent. However, the body of literature in this context for health studies is narrow, and even narrower for rehabilitation science. This highlights the necessity of addressing this issue for health sciences in general, and rehabilitation sciences in particular. In this chapter, the validity of different types of rehabilitation studies will be discussed. In doing so, the main focus will be on one type of validity that is a more complicated aspect of validation: construct validity. We will discourse some threats to each type of validity along with providing some strategies to prevent them, and hence how to power up the study, as we pass

Validity principles are applicable to all studies, whether they are based on questionnaires, observational studies, or other types of assessments [7]. Research validity helps us to know how true the claims and propositions made in a study are. This judgment can be based on the characteristics of a study, such as the research design, adequacy of sample size, the recruitment procedure, instruments and tests used, and the appropriateness of statistical methods

because its findings are the true results of that study.

2 Physical Disabilities - Therapeutic Implications

not be trustworthy.

through each validation type.

**2. What is validity?**

used [28].

Research validity can be categorized into two types: internal validity and external validity [29]. Internal validity refers to the amount of credit that can be attributed to the relationship between variables that is true, and external validity refers to how generalizable are the findings. In another approach [28], research validity has been divided into four types: internal validity, statistical conclusion validity, construct validity, and external validity. These four types of validity address four basic questions that practicing researchers face and so it is more practical. Those basic questions are as follows:

The second classification is actually drawn by dividing each of the first classification components in two [28]: the statistical conclusion validity is differentiated from internal validity to distinguish between the relationship that is affected by covariates and the true relationship between the two variables that are of interest. In other words, internal validity takes care of the validity of the relationship obtained between the two main variables of interest, while the statistical validity makes sure that this relationship is not contaminated (and if so, is correctly taken care of) by other variables that may influence the relationship, but are not of the interest in the study.

Also, construct validity is differentiated from external validity to make a distinction between generalization of the constructs of cause and effect to higher‐order constructs and generalization of the findings to the other settings and the population. In other words, the second classification explicitly states what was implicitly covered in the first classification.

The second classification of validity is now widely accepted and is being used by researchers in different fields [1, 2]. We will briefly introduce each of these types of validity in the following sections of this chapter. Furthermore, some threats to each type of validity as well as some strategies to power up that validity will be discussed.

#### **3.1. Statistical conclusion validity**

Statistical conclusion validity can be defined as the approximate precision of interpretations concluded about the covariations based on the statistical methods used and the fitness of the research design [2]. In other words, any statistical issue that could influence the results of the study would be a threat to statistical conclusion validity, including small sample size, lack of statistical power for the study [1], and any random error that could happen by chance, despite appropriate use of statistics, for example, type I and type II errors [30]. These threats to validity happen when the research conditions and statistical process of the study are not rigorous enough [22]. This type of validity is the *most important* type of validity, but in rehabilitation research, it has received little attention [1].

Some of the main threats to statistical conclusion validity are [2, 28] as follows:

#### **3.2. Internal validity**

Internal validity deals with whether the treatment used in the research study has an actual effect on the outcome variable [30]. Thus, internal validity is the extent to which we can be confident that there is a certain type of relationship (e.g., causal) between the dependent and the independent variables of the study [2]. If a study has lack of internal validity, then there are some factors in that study, other than the independent variables, that affect the outcome to some extent, but they have not been accounted for [2, 30]. These unaccounted factors are threats to internal validity. There are many threats to internal validity which can be applicable to different types of research. Some of the most common threats are [2, 28, 30] as follows:

If participants know about other participants in a different group, they may get dissatisfied with the group that they are in and with the treatment type they are receiving and thus they may become disappointed and less motivated to appropriately continue with the treatment (e.g., performing some exercises), which may affect their compliance. Any protection against chances of getting cues about other participants will help to prevent sharing of data. Any strategies that can be taken against hypothesis guessing by participants and also performing a good concealment for the randomization will also contribute to this aim.

#### **3.3. External validity**

study would be a threat to statistical conclusion validity, including small sample size, lack of statistical power for the study [1], and any random error that could happen by chance, despite appropriate use of statistics, for example, type I and type II errors [30]. These threats to validity happen when the research conditions and statistical process of the study are not rigorous enough [22]. This type of validity is the *most important* type of validity, but in rehabilitation

• **Low statistical power:** This will reduce the power of the study to reject the null hypothesis. To prevent this threat, researchers should define their experiment characteristics, for example, sample size and eligibility criteria, in order to provide an acceptable statistical

• **Violated statistical assumptions**: Each statistical procedure is based on some assumptions, for example, normal distribution of population, homogeneity of variance, and linearity. If these assumptions are violated, those statistical procedures will not be credible anymore. To prevent this threat, the researcher should ensure that the underlying assumptions are

• **Performing multiple statistical tests on a single data set**: This increases the likelihood of type I error and is another threat to statistical validity. This is because the Alpha level of the study as a whole is the sum of the Alpha level of all comparisons made. To prevent this threat, researchers can reduce the number of comparisons by a careful preplanning. Another technique is to determine the Alpha level of each *t*‐test in a way that the cumulative Alpha

• **Lack of inter‐ and intra‐rater reliability of the study**: Lack of consistency in conditions of

• **Lack of reliability of measures:** This would result in both type I and type II errors (e.g., they might show no correlation between two variables, when there is a good correlation, and vice versa). To prevent this threat, researchers must only use reliable measures or tools.

Internal validity deals with whether the treatment used in the research study has an actual effect on the outcome variable [30]. Thus, internal validity is the extent to which we can be confident that there is a certain type of relationship (e.g., causal) between the dependent and the independent variables of the study [2]. If a study has lack of internal validity, then there are some factors in that study, other than the independent variables, that affect the outcome to some extent, but they have not been accounted for [2, 30]. These unaccounted factors are threats to internal validity. There are many threats to internal validity which can be applicable to different types of research. Some of the most common threats are [2, 28, 30]

Some of the main threats to statistical conclusion validity are [2, 28] as follows:

research, it has received little attention [1].

4 Physical Disabilities - Therapeutic Implications

met, for example, normality of sample data.

implementing experiments is a threat to validity.

In fact, reliability is a necessary condition for validity [14].

power for the research.

would be desired.

**3.2. Internal validity**

as follows:

External validity refers to the population that the study findings can validly be generalized to. In other words, the greater the population the findings can be applied to, both in number and in diversity, the higher the external validity of that study. This, however, depends significantly on the sample used in the study and the population that this sample is actually representing. A simple example of for this is that if you are aiming for generalizing your findings to all wheelchair users but you only recruit male wheelchair users, you have a problem in external validity of your research. Also, the instruments used in the study and other conditions of the experiments have roles in determining the population the study findings can be generalized to and so in defining the external validity of the study.

This type of validity addresses the generalizability of the findings, which is of particular importance for rehabilitation practitioners, because they need to make inferences from the sample under the study to the treatment provided to a greater population [2]. For making those inferences, we either should perform the same experiment on in different occasions in time, settings, participants, and so on, or one should perform a systematic review with meta‐analysis on the body of literature on a particular issue [30]. However, randomly selecting participants in a study (i.e., random sampling) will provide the best protection against threats to external validity of that study and therefore makes the findings generalizable to the population [2]. Some of the main threats to external validity are [2] as follows:

#### **3.4. Construct validity**

For performing powerful studies and also proper clinical accomplishments, we need to make use of robust measures, considering the fact that "science rests on the adequacy of its measurement" [14]. Using proper and robust measures pertains to construct validity. Construct validity deals with whether an instrument or measurement tool or a test is measuring what it claims to be measuring [11]. In other words, construct validity concerns whether the measurement obtained is really representing the underlying construct [14].

The matter of validity is analogous to a study that has a clear hypothesis; researchers should gather as much evidence as they can to prove the hypothesis about validity of the inference [11, 13, 14]. Researchers should continue gathering convincing evidence until they feel that they have a large enough set of evidence to prove the construct validity. There is no best way to validate a study, although there are several methods in use [11]. Up to four subclasses of construct validity have been defined: face validity, content validity, criterion‐related validity, and construct validity. Some researchers [11, 14, 30, 31] believe that all these subclasses should be grouped and gathered under one overarching umbrella which is the construct validity. This is called the unified view of construct validity. Each of the subclasses of construct validity will be discussed below.

#### *3.4.1. Face validity*

experiments have roles in determining the population the study findings can be generalized

This type of validity addresses the generalizability of the findings, which is of particular importance for rehabilitation practitioners, because they need to make inferences from the sample under the study to the treatment provided to a greater population [2]. For making those inferences, we either should perform the same experiment on in different occasions in time, settings, participants, and so on, or one should perform a systematic review with meta‐analysis on the body of literature on a particular issue [30]. However, randomly selecting participants in a study (i.e., random sampling) will provide the best protection against threats to external validity of that study and therefore makes the findings generalizable to the

• **Sample characteristics** (e.g., age, gender, race, education, urban versus rural) restrict the population that the findings can be generalized to. Samples should be a good representative of the desired population. Random sampling helps considerably to this aim, but it does

• **Intervention characteristics** also restrict the findings to the settings with similar features, for example, instruments. Some strategies to prevent this threat include making the use of different examiners (when intra‐rater reliability is realized) and using multiple measures

• **Context characteristics:** There are some conditions that may influence the way subjects react or respond in the experiment, which inhibit generalization of the findings to the situations with different conditions. For instance, some participants try to provide "correct" responses, which are responses that they believe examiners like to see, but are not representative of their real state. Moreover, sometimes subjects receive multiple treatments at the same time, which may restrict the findings to those people that are on similar treatment regimes.

• **Sensitization:** In research designs where participants receive the same assessment (e.g., questionnaire) pre‐ and post‐test, their knowledge on the way they will be evaluated might affect the outcomes. Since this situation might not be the same as when there is no sensitiza-

For performing powerful studies and also proper clinical accomplishments, we need to make use of robust measures, considering the fact that "science rests on the adequacy of its measurement" [14]. Using proper and robust measures pertains to construct validity. Construct validity deals with whether an instrument or measurement tool or a test is measuring what it claims to be measuring [11]. In other words, construct validity concerns whether the measure-

The matter of validity is analogous to a study that has a clear hypothesis; researchers should gather as much evidence as they can to prove the hypothesis about validity of the inference

tion on the construct under study, this is a threat to external validity.

ment obtained is really representing the underlying construct [14].

population [2]. Some of the main threats to external validity are [2] as follows:

to and so in defining the external validity of the study.

6 Physical Disabilities - Therapeutic Implications

not guarantee that this threat would be eliminated.

that are taken from multiple setting.

**3.4. Construct validity**

This is the first judgment about the validity of an instrument by just looking at the appearance of it. It is only guesswork and provides little evidence for validity of the instrument. Besides, some snags can happen when talking about face validity [14]: the fallibility of verdicts that are based on appearance, different interpretations of appearance between developers and users, and some occasions that the judgment based on the appearance of an instrument is contrary to its contents. Therefore, using only face validity is never sufficient.

#### *3.4.2. Content validity*

This type of validity concerns the items or elements of a measurement and the extent to which these elements reflect the area they are supposed to be measuring [31, 32]. The adequacy and fitness of each element of the measurement tool in measuring the targeted construct is discussed under content validity. In other words, the targeted construct guides selecting the content of an assessment tool, and on the other hand the content and elements of the assessment tool selected define the construct that is actually being investigated [32]. Content validity is particularly important in assessing the validity of questionnaires.

Using an instrument that is invalid due to content, results in erroneous conclusions because some aspects of the construct are not represented properly, whether underrepresented or overrepresented. Not accounting for content validity in the study could also result in inaccuracy in finding a significant treatment effect [31].

Content validity is dynamic in nature, because the domain and definition of constructs change by time, and accordingly the elements of an instrument should be changed to be representative of that construct [31]. Content validity of an assessment instrument is dependent on the function of the instrument, population under study, and the situation in which the instrument is used. Therefore, close attention should be taken in order to maintain an acceptable validity for the assessment instrument. Often, a panel of experts is contacted to judge content validity of an assessment or instrument [11, 31].

One example of threats to content validity are is occasions where the definition of one term in researchers' language is different from the commonly accepted definition of it. In this situation, the readers' interpretations of the contents, results, and reports of the study might be different from the author's and researcher's intent. In these cases, a proper clarification of the constructs is advised [2].

## *3.4.3. Criterion‐related validity*

In criterion validity, correlation of the instrument or assessment with a "criterion" is examined [11]. Criterion has to be a "superior" measure that is more accurate than the measure being evaluated; otherwise, the failure in validation might be due to a flaw of the criterion, itself [32]. There are two types of criterion validity [11, 32]: concurrent and predictive, which are introduced briefly, here as follows:

## *3.4.4. Construct validity*

In construct validity, we experimentally investigate whether a construct is actually measuring what it claims to be measuring [11]. The concept of construct validity emerged when researchers realized there are many occasions that there is not any "superior" criterion to correlate the instrument under validation study with it [32]. Two types of validity can be distinguished within construct validity [32]:

Lack of construct validity causes two deficits: [30]

Some threats to construct validity are listed hereafter [2, 11, 13]:

different from the author's and researcher's intent. In these cases, a proper clarification of the

In criterion validity, correlation of the instrument or assessment with a "criterion" is examined [11]. Criterion has to be a "superior" measure that is more accurate than the measure being evaluated; otherwise, the failure in validation might be due to a flaw of the criterion, itself [32]. There are two types of criterion validity [11, 32]: concurrent and predictive, which

In construct validity, we experimentally investigate whether a construct is actually measuring what it claims to be measuring [11]. The concept of construct validity emerged when researchers realized there are many occasions that there is not any "superior" criterion to correlate the instrument under validation study with it [32]. Two types of validity can be distinguished

• Contamination: When the scores obtained by the assessment tool represent features that

• Deficiency: When there are aspects of the construct being studied that are not included in

sessed, while they are used to measure the same construct [33].

Lack of construct validity causes two deficits: [30]

are not part of the construct being studied.

constructs is advised [2].

*3.4.3. Criterion‐related validity*

8 Physical Disabilities - Therapeutic Implications

are introduced briefly, here as follows:

pressure measurement tools [32].

validation should be used [32].

*3.4.4. Construct validity*

sults [33].

the assessment tool.

within construct validity [32]:

divided to one placebo group and one treatment group. A more solid design will establish multigroup and sets different dosage of the drug for each group.

• **Poor construct definition:** This is when the construct is misdefined (e.g., assessing anxiety instead of depression), or has not been defined properly (e.g., assessing job satisfaction to represent overall happiness). Researchers should get advice from experts in the field before starting the study, to prevent this threat.

**Figure 1** depicts a summary of this paper: the overall classification of validities and main issues that threaten different types of validity.

**Figure 1.** Overall classification of validities and main issues that threaten different types of validity (sparks).

## **4. Discussion**

divided to one placebo group and one treatment group. A more solid design will establish

• **Poor construct definition:** This is when the construct is misdefined (e.g., assessing anxiety instead of depression), or has not been defined properly (e.g., assessing job satisfaction to represent overall happiness). Researchers should get advice from experts in the field before

**Figure 1** depicts a summary of this paper: the overall classification of validities and main

**Figure 1.** Overall classification of validities and main issues that threaten different types of validity (sparks).

multigroup and sets different dosage of the drug for each group.

starting the study, to prevent this threat.

10 Physical Disabilities - Therapeutic Implications

issues that threaten different types of validity.

In this paper, four types of research validity with their subclasses were described. Now, one may ask, among these different types of validity, which one of them is more important and has priority in consideration in validity study? The answer is rather complicated due to different opinions existing in the literature, which will be described here.

Among different types of validity, construct validity is the one that more frequently has been subject to consideration, research, and publication (e.g., see [11, 13, 18]). This is because it appears that for some researchers, construct validity (and its subclasses) are the only concepts of research validity. Although this frequency of consideration relative to the other types of validity could be an indication of relatively greater importance for this type of validity, the authors could not find any explicit declaration of that.

However, as it was pointed out in the "statistical conclusion validity" section, Ottenbacher and Barrett Kathryn [1] believe that this type of validity (statistical conclusion validity) is the most important type of validity, though it has received little attention in rehabilitation research. The importance of this type of validity is that one should make sure that the findings are obtained as a result of a real covariation between variables, rather than chance.

Cook's and Compbell [28] and Mitchell [30], however, do not believe so, since they declare that the internal validity is the most important validity, and hence one should be more concerned about it. This is because this group of researchers believes that as long as a study does not have internal validity, the data achieved from it are not appropriate and trustworthy, and as a result they are not eligible to be generalized to other situations. Mitchell says that most authors are not concerned with external validity and they just put it under "further research" heading [30]. Bellini and Rumrill gather between these two former opinions for studies that investigate an unknown relationship between variables [2].

Some researchers, however, argue that at the end of the day, we need to generalize our data to other situations, and hence if they are valid but unable to be generalized, they are useless. They, therefore, believe that external validity deserves higher priority than what it has received in health research so far [34].

Another point that is worth noting here is the point drawn by Shadish et al. that construct validity is not a necessary condition for external validity, because "we can generalize across entities known to be confounded albeit less usefully than across accurately labeled entities" [35].

Bellini and Rumrill [2] state that in fact, all four research validities are important in turn, and one should try to have all of them in the higher level possible, but there is a logical order for them: first statistical conclusion validity should be established, to show that two variables covary. The second validity to be established is the internal validity, which focuses on the obtained relationship between variables. Then the researcher should be concerned with the construct validity which speaks about the construct that is involved in the relationship. Eventually, the importance of external validity would arise that is concerned with the generalization of the results to other settings.

To sum up, it should be noted that all validities are of great importance of value for all research. However, one may not be able to maximize all of them at the same time, since maximizing one of them could be dependent on decreasing the other one. For instance, for increasing statistical conclusion validity with a given sample size, one may need to restrict the population under study, in order to decrease the variation between samples and increase the statistical power of the study. This, in turn, obviously leads to a reduction of generalizability of his/her results (lower external validity). Researchers, therefore, need to make trade‐offs between different aspects of research validity—considering the conditions they are in, so that they could end up with the optimum validity for their research study.

## **Acknowledgements**

The authors like to thank Dr. Susan Armijo‐Olive for her invaluable guidance to writing this chapter. Also, we greatly appreciate the comments and feedback offered by Dr. Pamela Bentley.

## **Author details**

Zohreh Salimi and Martin W. Ferguson‐Pell\*

\*Address all correspondence to<EMAIL_ADDRESS>
Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada

## **References**

[6] Messick S. The standard problem meaning and values in measurement and evaluation. Am Psychol. 1975:955–966.

Eventually, the importance of external validity would arise that is concerned with the gener-

To sum up, it should be noted that all validities are of great importance of value for all research. However, one may not be able to maximize all of them at the same time, since maximizing one of them could be dependent on decreasing the other one. For instance, for increasing statistical conclusion validity with a given sample size, one may need to restrict the population under study, in order to decrease the variation between samples and increase the statistical power of the study. This, in turn, obviously leads to a reduction of generalizability of his/her results (lower external validity). Researchers, therefore, need to make trade‐offs between different aspects of research validity—considering the conditions they are in, so that they could

The authors like to thank Dr. Susan Armijo‐Olive for her invaluable guidance to writing this chapter. Also, we greatly appreciate the comments and feedback offered by Dr. Pamela Bentley.

Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada

[1] Ottenbacher KJ, Barrett Kathryn A. Statistical conclusion validity of rehabilitation

[2] Bellini JL, Rumrill PD. Perspectives on scientific inquiry: Validity in rehabilitation

[3] Messick S. The interplay of evidence and consequences in the validation of performance

[4] Messick S. Validity and washback in language testing. Lang Test. 1996;**13**(3):241–256.

[5] Messick S. Meaning and values in test validation: The science and of assessment. Educ

assessments. Educ Res. 1994;**23**(2):13–23. DOI: 10.3102/0013189X023002013

alization of the results to other settings.

12 Physical Disabilities - Therapeutic Implications

**Acknowledgements**

**Author details**

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end up with the optimum validity for their research study.

Zohreh Salimi and Martin W. Ferguson‐Pell\*

\*Address all correspondence to<EMAIL_ADDRESS>
research. Am J Phys Med Rehabil. 1991;**70**(1):138–143.

Res. 1989;**18**(2):5–11. DOI: 10.3102/0013189X018002005

research. J Vocat Rehabil. 1999;**13**:131–138.

DOI: 10.1177/026553229601300302

## **Rare and Disabling Movement Disorders: An Indian Experience**

Gurusidheshwar Wali and Gautam Wali

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67598

#### **Abstract**

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[30] Mitchell TR. An evaluation of the validity of correlational research conducted in organi-

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[32] Kaplan RM, Bush JW, Berry CC. Health status: types of validity and the index of well‐

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14 Physical Disabilities - Therapeutic Implications

Recent decades have seen exciting developments in the field of movement disorders. These include identification of rare clinical syndromes and use of technological advances to understand their pathogenesis. Three such disorders are discussed here. The description of the Uner Tan syndrome from Turkey and surrounding regions provoked research into the controversial field of genetically induced devolution. Such cases with few addi‐ tional findings have now been described from India. Sepiapterin reductase deficiency is a rare treatable autosomal recessive form of dopa responsive dystonia. Indian litera‐ ture has recently added five confirmed cases to the international database. Such cases are eminently treatable. Successful application of modern technology in understanding the pathogenesis of progressive neurodegenerative disorder has been highlighted in the section on hereditary spastic paraplegias. Hitherto undescribed subcellular organelle transport defects and their potential rectification with known drugs have been demon‐ strated raising hopes for their cure.

**Keywords:** movement disorders, Uner Tan syndrome, neurogenetics, sepiapterin reductase deficiency, hereditary spastic paraplegia, stem cell modelling of HSP

## **1. Introduction**

Movement disorders is a relatively young but fast growing sub‐speciality of neurology. Recent developments in the clinical, genetics and treatment aspects of this group of disorders are exciting. The nature of movement disorders seen in India differ from the western cases. The vast population of the country where consanguineous marriages are still prevalent is a source of large number of rare movement disorders. Modern technology including whole genome sequencing has promoted in‐depth understanding of such cases. In addition, such rare disor‐ ders can lead to physical disability especially in children when they remain undiagnosed and

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

untreated. This paper highlights selected Indian contributions to such developments with an intention to increase awareness about such rare disorders. Some of them are potentially treatable. The topics discussed here include Uner Tan syndrome, sepiapterin reductase defi‐ ciency and hereditary spastic paraplegia.

## **2. Uner Tan syndrome**

In the year 2005, Uner Tan from Turkey discovered and described an autosomal recessive genetic syndrome, at present, recognized as Uner Tan syndrome (UTS), which composed of habitual quadrupedalism, impaired intelligence, primitive language and no conscious expe‐ rience [1]. The cases described by him had quadrupedal locomotion (Q/L) using two palms and two feet with extended legs. Some of them later developed bipedal locomotion (B/L) although Q/L remained the preferred mode of locomotion. Recently he has described similar cases presenting with infantile hypotonia which disappeared by adolescence to be replaced by quadrupedal locomotion [2]. The cases without infantile hypotonia are now identified as UTS Type I and those associated with infantile hypotonia are identified as UTS Type II cases. Considering the unusual psychomotor behaviour of these cases, resembling that of sub‐human primates, Uner Tan proposed the theory of 'genetically induced devolution' to explain the genesis of this syndrome. This theory has been questioned by other researchers [3]. This chapter documents two new families of UTS from India. Additional features of dys‐ tonia, which appear with their bipedal locomotion, are highlighted.

#### **2.1. Indian cases of UTS**

The present chapter describes clinical and radiological findings in three cases of UTS belong‐ ing to two Indian families [4] (**Figure 1**). Both of these families resided in Mantur, a small vil‐ lage belonging to Belagavi district in the state of Karnataka. The village is close to semi urban cities with exposure to modern lifestyle practices. Family A had one female case, whereas Family B had two male cases affected by the syndrome. Autosomal recessive type of trans‐ mission was identified in each of the families. There was no history of birth asphyxia, trauma or encephalitis in any of the cases. Haematological and biochemical tests, including serum parathormone, vitamin D3, B‐12, copper and ceruloplasmin levels, were measured and found to be within normal limits. The VLDL receptor gene was negative in all the cases. For sake of brevity, the girl belonging to Family A is designated as Case A‐1 and the brothers belonging to Family B are designated as Case B‐1 (elder) and Case B‐2 (younger), respectively.

#### *2.1.1. Case A‐1*

This girl who was born of post‐term pregnancy as a large baby had remained floppy until the age of 5 years. She developed Q/L at the age of 6 years and B/L at the age of 11 years. She had features of severe mental retardation with a MMSE score of 0/30. Speech was absent but she repeatedly mumbled a meaningless word. She responded to few commonly used non‐verbal commands. Self‐care was poor. Most often she moved using Q/L, but at times attempted walking with a wide‐based ataxic bipedal gait. She suffered sleep onset epileptic seizures

Rare and Disabling Movement Disorders: An Indian Experience http://dx.doi.org/10.5772/67598 17

**Figure 1.** The top section of the figure shows the genogram of Families A and B. The lower section of the figure shows MRI/CT brain images of patients A‐1 and B‐2, respectively. The images reveal the presence of cerebellar atrophy.

from the age of 18 months, which were partly controlled with phenobarbitone. MRI of the brain revealed moderately severe hypoplasia of the cerebellum including the vermis along with mild cerebral cortical thinning.

#### *2.1.2. Case B‐1*

untreated. This paper highlights selected Indian contributions to such developments with an intention to increase awareness about such rare disorders. Some of them are potentially treatable. The topics discussed here include Uner Tan syndrome, sepiapterin reductase defi‐

In the year 2005, Uner Tan from Turkey discovered and described an autosomal recessive genetic syndrome, at present, recognized as Uner Tan syndrome (UTS), which composed of habitual quadrupedalism, impaired intelligence, primitive language and no conscious expe‐ rience [1]. The cases described by him had quadrupedal locomotion (Q/L) using two palms and two feet with extended legs. Some of them later developed bipedal locomotion (B/L) although Q/L remained the preferred mode of locomotion. Recently he has described similar cases presenting with infantile hypotonia which disappeared by adolescence to be replaced by quadrupedal locomotion [2]. The cases without infantile hypotonia are now identified as UTS Type I and those associated with infantile hypotonia are identified as UTS Type II cases. Considering the unusual psychomotor behaviour of these cases, resembling that of sub‐human primates, Uner Tan proposed the theory of 'genetically induced devolution' to explain the genesis of this syndrome. This theory has been questioned by other researchers [3]. This chapter documents two new families of UTS from India. Additional features of dys‐

The present chapter describes clinical and radiological findings in three cases of UTS belong‐ ing to two Indian families [4] (**Figure 1**). Both of these families resided in Mantur, a small vil‐ lage belonging to Belagavi district in the state of Karnataka. The village is close to semi urban cities with exposure to modern lifestyle practices. Family A had one female case, whereas Family B had two male cases affected by the syndrome. Autosomal recessive type of trans‐ mission was identified in each of the families. There was no history of birth asphyxia, trauma or encephalitis in any of the cases. Haematological and biochemical tests, including serum parathormone, vitamin D3, B‐12, copper and ceruloplasmin levels, were measured and found to be within normal limits. The VLDL receptor gene was negative in all the cases. For sake of brevity, the girl belonging to Family A is designated as Case A‐1 and the brothers belonging

to Family B are designated as Case B‐1 (elder) and Case B‐2 (younger), respectively.

This girl who was born of post‐term pregnancy as a large baby had remained floppy until the age of 5 years. She developed Q/L at the age of 6 years and B/L at the age of 11 years. She had features of severe mental retardation with a MMSE score of 0/30. Speech was absent but she repeatedly mumbled a meaningless word. She responded to few commonly used non‐verbal commands. Self‐care was poor. Most often she moved using Q/L, but at times attempted walking with a wide‐based ataxic bipedal gait. She suffered sleep onset epileptic seizures

tonia, which appear with their bipedal locomotion, are highlighted.

ciency and hereditary spastic paraplegia.

**2. Uner Tan syndrome**

16 Physical Disabilities - Therapeutic Implications

**2.1. Indian cases of UTS**

*2.1.1. Case A‐1*

This 35‐year‐old male who was born of full‐term normal home delivery had no infantile hypo‐ tonia. Features of severe mental retardation were present with no speech but he was able to follow few non‐verbal commands. MMSE score was 0/30 and self‐care was poor. He exhibited severe autistic behaviour avoiding eye to eye contact with others. He used only Q/L which had appeared at the age of 7 years (**Figure 2**). He never attempted B/L. He could be made to stand with support for few seconds using a wide base support. He suffered rare episodes of general‐ ized tonic‐clonic seizures which remained untreated. Neuroimaging was not possible in him.

**Figure 2.** The figure is a still photography of Case B‐1 showing the quadrupedal locomotion. Note the diagonal sequencing of the limbs and the extension of the lower extremities at the knee.

#### *2.1.3. Case B‐2*

This 30‐year‐old younger brother of Case B‐1 and born of normal home delivery had evidence of severe mental retardation with no speech and MMSE score of 0/30. He exhibited autistic behaviour shunning crowds and often strayed away silently. He had developed Q/L at the age of 7 years and B/L at the age of 25 years. His bipedal gait was wide‐based and short‐stride but not ataxic. He had camptocormia and almost continuous dystonia abductor posturing of his right arm during bipedal locomotion. Presently, he prefers to move bipedally for most of the time. A CT scan of the head revealed evidence of cerebellar hypoplasia.

#### *2.1.4. Discussion*

The diagnosis of UTS was made in these cases based on the presence of the cardinal features of the syndrome as mentioned above.

Most cases reported by Uner Tan resided in remote villages of Turkey having poor communication with the outer world. He proposed that their alienation from outside world, low socio‐economic status, poor nutrition and poor parental care may be contributing to the causation of the syndrome [1]. In contrast although our cases resided in a village, they were exposed to modern lifestyle practices in view of close proximity to urban settings. These sibs lived protected as members of 'nuclear families', a concept still prevalent in rural India.

In addition to the cardinal features of the syndrome, these patients had (i) microcephaly with facial dysmorphism, (ii) restrictive repetitive behaviours and stereotypies and (iii) poor social interaction. Head circumference in relation to body height measurements mentioned in the table indicates the presence of mild microcephaly in all the cases. While Case A‐1 had the feature of repetitive mumbling of a meaningless word, a form of verbal stereotypy, Case B‐1 and Case B‐2 had extremely shy behaviour avoiding eye to eye contact, social interaction and communication. Dystonic limb posturing was present in cases 2 and 3 during attempted bipedal locomotion.

The pathophysiology of habitual quadrupedalism is unclear. The role of central pattern gen‐ erators (CPG) present in the cervical and the lumbosacral spinal segments has been discussed in this regard. Reorganization and adaptation of CPG networks is possibly involved in the appearance of human quadrupedal locomotion [5]. Considering the complex balance mecha‐ nisms needed for a well‐balanced bipedal locomotion, walking on all the four is much easier since the overall base of support of the body is better in the latter type of locomotion [6]. In this regard, the possibility of quadrupedalism appearing as an epiphenomenon secondary to very early onset balance problem cannot be ruled out. The Indian cases were noted to have mild forms of limb dystonia, which became obvious when they attempted bipedal locomotion. In one of his reviews, Uner Tan pointed out that basal ganglia signs were absent [7]. Future stud‐ ies in UTS may need to incorporate these clinical features to revise our present understanding of this interesting syndrome.

In summary, the clinical observations made in the Indian cases of UTS suggest that components of limb dystonia may be part of the clinical presentation of the syndrome.

## **3. Sepiapterin reductase deficiency, a rare but treatable paediatric movement disorder**

*2.1.3. Case B‐2*

18 Physical Disabilities - Therapeutic Implications

*2.1.4. Discussion*

of the syndrome as mentioned above.

This 30‐year‐old younger brother of Case B‐1 and born of normal home delivery had evidence of severe mental retardation with no speech and MMSE score of 0/30. He exhibited autistic behaviour shunning crowds and often strayed away silently. He had developed Q/L at the age of 7 years and B/L at the age of 25 years. His bipedal gait was wide‐based and short‐stride but not ataxic. He had camptocormia and almost continuous dystonia abductor posturing of his right arm during bipedal locomotion. Presently, he prefers to move bipedally for most of

**Figure 2.** The figure is a still photography of Case B‐1 showing the quadrupedal locomotion. Note the diagonal

The diagnosis of UTS was made in these cases based on the presence of the cardinal features

Most cases reported by Uner Tan resided in remote villages of Turkey having poor communication with the outer world. He proposed that their alienation from outside world,

the time. A CT scan of the head revealed evidence of cerebellar hypoplasia.

sequencing of the limbs and the extension of the lower extremities at the knee.

Dopa responsive dystonias (DRDs) are a genetically heterogeneous subgroup of paediatric neurotransmitter diseases (PNDs), which occur due to defective tetrahydrobiopterin (BH4) metabolism. Since hyperphenylalaninemia, which is a useful marker in the screening of such diseases, is not always present, the disorders are classified based on the presence or absence of hyperphenylalaninemia. BH4 defects without hyperphenylalaninemia include dopa respon‐ sive dystonia (Segawa disease), sepiapterin reductase deficiency (SRD) and dihydrobiopterin reductase deficiency. BH4 defects without hyperphenylalaninemia include autosomal reces‐ sive GTP‐1 cytohydroxylase deficiency, 6‐pyruvoyl‐teytrahydropterin synthase deficiency (6‐PTS) and dihydropteridine reductase deficiency without hyperphenylalaninemia. In addi‐ tion primary defects of monoamine synthesis include Tyrosine hydroxylase deficiency (TH) and Aromatic l‐amino acid decarboxylase deficiency (AADC).

Examples of autosomal dominant and recessive types of dopa responsive dystonias are described. Segawa disease with autosomal dominant inheritance is a landmark in this group of diseases. Sepiapterin reductase deficiency (SRD) is a rare example of autosomal recessive variety [8]. It is caused by mutation in the SPR gene, located on the chromosome 2p14‐p12 [9]. The clinical presentation includes cognitive delay along with dopa responsive mixed motor disorder often masquerading as cerebral palsy [10]. Neonatal screening tests are not helpful in the diagnosis of this disease since it is not associated with hyperphenylalaninemia. However the presence of certain additional clinical features like oculogyric crisis, diurnal fluctuation of the symptoms and hypersomnia provide a clue to the clinical suspicion. Clinical response to dopamine therapy is often rewarding and at times dramatic. The laboratory diag‐ nosis of SRD is based on CSF analysis of neurotransmitter metabolites and pterins. The clas‐ sical CSF findings in SRD include increased levels of sepiapterin along with reduced levels of 5‐hydroxyindolacetic acid and homovanillic acid. The diagnosis can be confirmed by study‐ ing the SR activity in the fibroblasts and mutational analysis of the SPR gene.

The following paragraphs provide an overview of the clinical profile of SRD based on the information obtained from various case reports and recent reviews [11, 12] of Indian cases have been summarized.

#### **3.1. Demography**

Till date, a total number of 43 cases have been recognized from all over the world and are reviewed by Friedman et al. [11]. These include cases which are published and those docu‐ mented in the international database maintained by the PND society. Both genders are equally represented. The cases belong to a wide ethnic background from various countries including India. A founder effect was suspected in the seven patients reported from Malta.

#### **3.2. Clinical profile**

#### *3.2.1. Mixed motor signs and symptom*

SRD causes symptoms related to dopamine and serotonin metabolism disturbances. The salient clinical features include motor and language delay associated with axial hypotonia, limb weakness, dystonia with diurnal fluctuation and oculogyric crisis. The latter group of symptoms often show sleep benefit. Other symptoms include parkinsonism, limb hypotonia, hypertonia and dysarthria. As against Segawa disease, the occurrence of dystonia is not uni‐ versal in SRD. It is present in only about half of the cases. Less common neurological features include chorea, myoclonus and seizures.

The symptoms of SRD usually appear in age‐related pattern [12]. The symptoms of axial hypotonia, tremors, hypersomnia, oculogyric crisis and sleep benefit usually appear in the first year of life while limb spasticity, diurnal fluctuation, dysarthria and dystonia become obvious between the ages of 2 and 6 years. The triad of oculogyric crisis, paroxysmal stiffen‐ ing and axial hypotonia may be considered as a strong clue to suspect the diagnosis of SRD in the infantile group. However, these symptoms may persist or appear during late child‐ hood as well. It is not unusual for the paroxysmal episodes to be misdiagnosed as seizure phenomenon resulting in delayed diagnosis and unwanted use of anticonvulsants. 'Cerebral palsy' is the commonest diagnosis in majority of the cases before reaching a final diagnosis.

#### *3.2.2. Non‐motor neurological features*

These include sleep disturbances, behavioural changes and cognitive disabilities. Hypersomnia is the commonest sleep disturbance and present in nearly 50% cases especially in the infantile age group. Behavioural changes are also seen in slightly more than half of the cases. Cognitive disabilities of varying degree are seen in almost 90% cases. Nearly half of them have mental retardation, whereas others have mild‐to‐moderate disability.

## *3.2.3. Other features*

Examples of autosomal dominant and recessive types of dopa responsive dystonias are described. Segawa disease with autosomal dominant inheritance is a landmark in this group of diseases. Sepiapterin reductase deficiency (SRD) is a rare example of autosomal recessive variety [8]. It is caused by mutation in the SPR gene, located on the chromosome 2p14‐p12 [9]. The clinical presentation includes cognitive delay along with dopa responsive mixed motor disorder often masquerading as cerebral palsy [10]. Neonatal screening tests are not helpful in the diagnosis of this disease since it is not associated with hyperphenylalaninemia. However the presence of certain additional clinical features like oculogyric crisis, diurnal fluctuation of the symptoms and hypersomnia provide a clue to the clinical suspicion. Clinical response to dopamine therapy is often rewarding and at times dramatic. The laboratory diag‐ nosis of SRD is based on CSF analysis of neurotransmitter metabolites and pterins. The clas‐ sical CSF findings in SRD include increased levels of sepiapterin along with reduced levels of 5‐hydroxyindolacetic acid and homovanillic acid. The diagnosis can be confirmed by study‐

The following paragraphs provide an overview of the clinical profile of SRD based on the information obtained from various case reports and recent reviews [11, 12] of Indian cases

Till date, a total number of 43 cases have been recognized from all over the world and are reviewed by Friedman et al. [11]. These include cases which are published and those docu‐ mented in the international database maintained by the PND society. Both genders are equally represented. The cases belong to a wide ethnic background from various countries including

SRD causes symptoms related to dopamine and serotonin metabolism disturbances. The salient clinical features include motor and language delay associated with axial hypotonia, limb weakness, dystonia with diurnal fluctuation and oculogyric crisis. The latter group of symptoms often show sleep benefit. Other symptoms include parkinsonism, limb hypotonia, hypertonia and dysarthria. As against Segawa disease, the occurrence of dystonia is not uni‐ versal in SRD. It is present in only about half of the cases. Less common neurological features

The symptoms of SRD usually appear in age‐related pattern [12]. The symptoms of axial hypotonia, tremors, hypersomnia, oculogyric crisis and sleep benefit usually appear in the first year of life while limb spasticity, diurnal fluctuation, dysarthria and dystonia become obvious between the ages of 2 and 6 years. The triad of oculogyric crisis, paroxysmal stiffen‐ ing and axial hypotonia may be considered as a strong clue to suspect the diagnosis of SRD in the infantile group. However, these symptoms may persist or appear during late child‐ hood as well. It is not unusual for the paroxysmal episodes to be misdiagnosed as seizure

ing the SR activity in the fibroblasts and mutational analysis of the SPR gene.

India. A founder effect was suspected in the seven patients reported from Malta.

have been summarized.

20 Physical Disabilities - Therapeutic Implications

**3.1. Demography**

**3.2. Clinical profile**

*3.2.1. Mixed motor signs and symptom*

include chorea, myoclonus and seizures.

Non‐specific non‐neurological features have been reported in SRD. These include pulmonary symptoms, vegetative symptoms such as gastrointestinal disturbances, hyperhidrosis, pre‐ mature greying of hairs and menstrual abnormalities.

#### *3.2.4. Salient investigations*

CSF analysis is the mainstay of the diagnosis of SRD. The classical findings include

The study of SR activity in the fibroblast cultures has been performed in few cases and found to be confirmative. SR activity is either less or absent in such cases.

Genotyping of the documented 42 cases has revealed 16 mutations in the SPR gene. The intronic homozygous variant c596‐2A>G is the most common genotype.

#### *3.2.5. Treatment responses and outcomes*

Substitution therapy is the mainstay of treatment in SRD. Most cases were treated either with l‐dopa/carbidopa or benserazide (doses ranging from 1.45 mg to 20 mgm/kg/day) or 5‐hydroxytryptophan (doses ranging from 0.65 to 5.9 mgm/kg/day). Combination therapy is also useful and in some cases better than the use of single drug. Other drugs used to treat include BH4, bromocriptine, anticholinergics, selegiline, sertraline and melatonin.

The response to treatment is always rewarding and at times dramatic. Patients may show improvement in motor activity and sleep disturbances within few hours of administering medication. Children who have been chair‐bound or bed‐bound may start moving and enjoy the unexpected relief with tremendous excitement. The rapid recovery is usually associated with appearance of choreiform dyskinesias requiring dose titration. Few cases show par‐ tial improvement. Favourable response to treatment is noted even in those cases who have received the treatment late in the course of their illness due to delayed diagnosis. Long‐term follow‐up has shown that few cases may require mild escalation in the dose of the drugs to maintain the favourable benefit. It also shows that response to therapy is not as complete as seen in Segawa disease. Residual motor and cognitive dysfunction may persist. Early treat‐ ment is associated with better recovery.

#### *3.2.6. Indian cases of SRD*

Five Indian cases (three males and two females) of chemically and genetically proven SRD have been documented in the international database maintained by the PND society (BIODEF database IDs # 526,527,637,638 and 639) [13]. All of these cases have been reported from the Belgaum region of North Karnataka [11, 14]. These cases with consanguineous parenthood belonged to two independent families. The referring diagnosis in all these cases was 'cerebral palsy'. All cases showed very favourable and sustained response to l‐dopa therapy (**Figure 3**). They have been followed up clinically for the past 5 years. The average maintenance dose of l‐dopa was 1.5–2 mg/kg body weight in all these cases. All cases had the *core symptom complex* inclusive of psychomotor delay, axial hypotonia, limb hypotonia/hypertonia, acral dystonia/ athetosis, diurnal variation and sleep benefit. **Table 1** summarises the clinical data which was present in addition to this core symptom complex.

**Figure 3.** This figure reveals the clinical state of the patient (BIODEF #523) of SRD before and after administration of levodopa. The left half of the figure shows evidence of truncal hypotonia and spastic‐dystonia limb posturing. The right half of the figure shows the clinical state of the patient after administration of a single low dose of levodopa/carbidopa. The response was dramatic and seen within 12 hours.

**Table 1.** Clinical summary of Indian cases of SRD.

seen in Segawa disease. Residual motor and cognitive dysfunction may persist. Early treat‐

Five Indian cases (three males and two females) of chemically and genetically proven SRD have been documented in the international database maintained by the PND society (BIODEF database IDs # 526,527,637,638 and 639) [13]. All of these cases have been reported from the Belgaum region of North Karnataka [11, 14]. These cases with consanguineous parenthood belonged to two independent families. The referring diagnosis in all these cases was 'cerebral palsy'. All cases showed very favourable and sustained response to l‐dopa therapy (**Figure 3**). They have been followed up clinically for the past 5 years. The average maintenance dose of l‐dopa was 1.5–2 mg/kg body weight in all these cases. All cases had the *core symptom complex* inclusive of psychomotor delay, axial hypotonia, limb hypotonia/hypertonia, acral dystonia/ athetosis, diurnal variation and sleep benefit. **Table 1** summarises the clinical data which was

**Figure 3.** This figure reveals the clinical state of the patient (BIODEF #523) of SRD before and after administration of levodopa. The left half of the figure shows evidence of truncal hypotonia and spastic‐dystonia limb posturing. The right half of the figure shows the clinical state of the patient after administration of a single low dose of levodopa/carbidopa.

ment is associated with better recovery.

22 Physical Disabilities - Therapeutic Implications

present in addition to this core symptom complex.

The response was dramatic and seen within 12 hours.

*3.2.6. Indian cases of SRD*

It is likely that SRD is more common all over the world but possibly remains under‐diagnosed due to lack of awareness and inadequate laboratory services. Such cases are likely to masquer‐ ade as 'cerebral palsy' and remain untreated for life.

## **4. Hereditary spastic paraplegia**

Hereditary spastic paraplegia (HSP) is an untreatable rare genetic disorder, which causes long‐term physical disability in the affected individuals. There is a high degree of genetic het‐ erogeneity with over 60 causative genes identified so far. A collaborative study using whole genome sequencing (WSG) was performed in 10 HSP families from Belgaum in Karnataka, India. Pathogenic variants were identified in four consanguineous families. This included a novel frameshift homozygous deletion in *CYP2U1* (c.782\_785delTCTG) gene in one family and a novel homozygous donor splice site variant in *DDHD2* (c.1125+1G>T) gene in another family. A probable genetic cause was identified in 40% of the families limited to consanguine‐ ous families in whom a family study was possible. Mutations were found in genes causing metabolic disorders such as Zellweger spectrum disorder and GM1 gangliosidosis. This study supports a role of WGS as a diagnostic tool in HSP [15].

#### **4.1. Stem cell modelling of HSP**

HSP is characterised by degeneration of long axons along the corticospinal tract, leading to lower limb spasticity. The mechanisms underlying HSP mutations that lead to degeneration of the long axons are unclear. Researchers have recently used patient‐derived cells from the olfactory mucosa, a population of neural progenitor cells, derived from biopsies of the olfac‐ tory mucosa from HSP patients with SPAST mutations and from healthy controls, in order to identify cell functions altered in HSP [16]. Mutations in the SPAST gene account for the largest group of adult‐onset HSP patients. These researchers show that SPAST patient‐derived cells have reduced expression of protein Spastin (encoded by SPAST), reduced expression of stabi‐ lized microtubules, alterations in transport of cellular cargo and increased oxidative stress [17] (**Figure 4**). Based on their findings, Gautam Wali and colleagues propose that the downstream effects of SPAST mutations may cause a chronic state of oxidative stress in cortical motor neu‐ rons and other neurons, which ultimately leads to their degeneration, eventually manifesting the disease. They also show that the defects observed in the patient cells can be rescued using a microtubule‐binding drug, Epothilone D. Epothilone D can cross the blood‐brain barrier, making it a potential drug for HSP therapy [18].

**Figure 4.** This figure summarises the mechanism of cell organelle dysfunction in HSP as confirmed by Gautam Wali and colleagues using patient‐derived olfactory stem cells. They suggest a mechanism whereby *SPAST* mutations lead to reduced levels of stable microtubules which compromises cargo trafficking and leads to increased oxidative stress. These downstream effects of SPAST mutations may cause a chronic state of oxidative stress in cortical motor neurons and other neurons, which ultimately leads to their degeneration, eventually manifesting the disease. They also showed that Epothilone D, a microtubule‐binding drug, can rescue the cell function defects in patient cells, making it a potential candidate for a future therapy for HSP.

## **Author details**

**4.1. Stem cell modelling of HSP**

24 Physical Disabilities - Therapeutic Implications

making it a potential drug for HSP therapy [18].

candidate for a future therapy for HSP.

HSP is characterised by degeneration of long axons along the corticospinal tract, leading to lower limb spasticity. The mechanisms underlying HSP mutations that lead to degeneration of the long axons are unclear. Researchers have recently used patient‐derived cells from the olfactory mucosa, a population of neural progenitor cells, derived from biopsies of the olfac‐ tory mucosa from HSP patients with SPAST mutations and from healthy controls, in order to identify cell functions altered in HSP [16]. Mutations in the SPAST gene account for the largest group of adult‐onset HSP patients. These researchers show that SPAST patient‐derived cells have reduced expression of protein Spastin (encoded by SPAST), reduced expression of stabi‐ lized microtubules, alterations in transport of cellular cargo and increased oxidative stress [17] (**Figure 4**). Based on their findings, Gautam Wali and colleagues propose that the downstream effects of SPAST mutations may cause a chronic state of oxidative stress in cortical motor neu‐ rons and other neurons, which ultimately leads to their degeneration, eventually manifesting the disease. They also show that the defects observed in the patient cells can be rescued using a microtubule‐binding drug, Epothilone D. Epothilone D can cross the blood‐brain barrier,

**Figure 4.** This figure summarises the mechanism of cell organelle dysfunction in HSP as confirmed by Gautam Wali and colleagues using patient‐derived olfactory stem cells. They suggest a mechanism whereby *SPAST* mutations lead to reduced levels of stable microtubules which compromises cargo trafficking and leads to increased oxidative stress. These downstream effects of SPAST mutations may cause a chronic state of oxidative stress in cortical motor neurons and other neurons, which ultimately leads to their degeneration, eventually manifesting the disease. They also showed that Epothilone D, a microtubule‐binding drug, can rescue the cell function defects in patient cells, making it a potential Gurusidheshwar Wali1,2\* and Gautam Wali<sup>3</sup>

## **References**

## **Five-Wheeled Wheelchair with an Add-On Mechanism and Its Semiautomatic Step-Climbing and -Descending Function**

Masayoshi Wada and Yu Munakata

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67558

#### **Abstract**

[12] Dill P, Wagner M, Somerville A, Thony B, Blau N Weber P. Paroxysmal stiffening, upward gaze and hypotonia. Hallmarks of sepiapterin reductase deficiency. Neurology

[14] Wali GM, Thony B, Blau N. Sepiapterin reductase deficiency : two Indian siblings with

[15] Kishore R Kumar, Gurusidheshwar Wali, Mahesh Kamate, et al. Defining genetic causes of hereditary spastic paraplegia with whole genome sequencing. 13th International Congress of Human Genetics, Kyoto, Japan 2016; Abstract 91220, 2014;42(3):174183. [16] Abrahamsen G, Fan Y, Matigian N, et al. A patient‐derived stem cell model of hereditary spastic paraplegia with SPAST mutations. Dis Models Mech 2013;6(2):489–502.

[17] Wali G, Sutharsan R, Fan Y, et al. Mechanism of impaired microtubule‐dependent per‐ oxisome trafficking and oxidative stress in SPAST‐mutated cells from patients with

[18] Fan Y, Wali G, Sutharsan R, et al. Low dose tubulin‐binding drugs rescue peroxisome trafficking deficit in patient‐derived stem cells in Hereditary Spastic Paraplegia. Biol

unusual clinical features. Mov Disord 2010;25:954–955.

Hereditary Spastic Paraplegia. Sci Rep 2016;6:27004.

2012;78: e 29–32.

26 Physical Disabilities - Therapeutic Implications

Open 2014;3:494–502.

[13] www.biopku.org

In this chapter, we propose a novel add-on electric drive system for propelling a manual wheelchair on the floor together with an advanced function to climb and descend a step with no human support. The proposed add-on mechanism consists of an active-caster drive wheel and a reconfigurable link mechanism with a linear actuator to change the location of the drive wheel relative to a wheelchair. By attaching the mechanism to a manual wheelchair, we build a five-wheeled wheelchair. Since the drive wheel is attached on the back of the wheelchair, a risk of falling to the back is significantly reduced. To surmount a step with no help, we develop a step-climbing and -descending strategy by using the proposed wheelchair with a reconfigurable link mechanism. The five-wheel configuration guarantees a static stability of the wheelchair when some wheels are hovered from the ground. The function is used in step-climbing and -descending strategies to realize the transfer of a wheelchair user. In order to reduce the effort of a wheelchair user to control the complicated step surmount strategies, semiautomatic system is installed on the prototype wheelchair whose availability is verified through experiments.

**Keywords:** active-caster, wheelchair add-on electric drive, step-climbing and -descending, semiautomatic control

## **1. Introduction**

For the aging society worldwide, need for machines that can support human moving capabilities gets more and more importance in recent years. Electric wheelchairs [1] are one of the most popular solutions for overcoming the aging problem in the past few decades. Electricpowered wheelchairs are used as one of the moving support devices not only for injured

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

people but also for the elderly. Among the electric-driven wheelchairs, a "motorized wheelchair" has become popular in recent years. Different from a standard electric wheelchair, which is designed as electric-driven, a motorized wheelchair is composed of a manual wheelchair frame and an add-on electric drive module. Because it is foldable and light weight, users may carry it by cars to travel long distances easily.

A pair of electric drive modules for propelling left and right large wheels of a manual wheelchair are popular and commercially available (**Figure 1(a)**) [2]. Since the main parts are from a manual wheelchair, the diameter of a front caster is quite small, which prevents a motorized wheelchair from passing over a few centimeters step. Addition to this, if drive motors on the left and right provides large torque when the front casters stack into the gap or step, a wheelchair might fall in back since the reaction torques of the drive motors are applied to the wheelchair frame. In contrast, a five-wheeled wheelchair composed of a manual wheelchair and a single-wheel drive system was proposed (**Figure 1(b)**) [3]. The installed drive wheel is a standard orientable wheel, which can change its orientation at a steady point on the ground. This type of wheel has a nonholonomic constraint in its sideways direction and cannot control two degrees of freedom (2DOF) motion independently.

Toward the problem of step-climbing and -descending of wheelchairs, a lot of systems and mechanisms have been conducted. Wheelchairs with additional legs [4], some spoke wheels [5, 6], step-climbing method by the dynamic control as the inverted pendulum [7, 8], triangle frame with three wheels at the triangle vertices [9–11], and tracks on each side [12] have been proposed. The iBot wheelchair [13], which has the dynamic balancing functionality as an inverted pendulum, and Scaleve [14], which has additional tracks to climb over steps, have also been introduced. However, they are too heavy to carry them by personal cars.

A step-climbing method of the front casters with steering shafts fixed by the special mechanism [15], and a step-climbing and -descending strategies with a partner robot [16] are proposed to enhance the step-climbing capability of a manual wheelchair. The former is the step-climbing method only for the front casters and step-descending method has not been reported. The real-world applications of the latter system are quite limited.

In this paper, we propose an add-on mechanism to satisfy the step-climbing and -descending strategies, and in the both the strategies, the wheelchair approaches a step from the front. In our previous works, we proposed a five-wheeled wheelchair equipped with an add-on mechanism on the back of a manual wheelchair [17]. The add-on mechanism is composed of an active-caster, a linear actuator, and some link frames, which is connected to a manual

**Figure 1.** Conventional motorized wheelchair. (a) Dual-wheel drive system [2]. (b) Single-wheel drive system [3].

wheelchair frame. The active-caster [18] is used as a propelling mechanism for the manual wheelchair. The linear actuator is used as the wheelchair's posture change mechanism. In the climbing process of the front casters, they can be hovered from the ground by changing the location of the active-caster to backward of the wheelchair using the linear actuator. The large wheels and the drive wheel can be hovered from the ground, and pass over a step using the same method as that in the front casters. In the descending motion, the large wheels of the wheelchair can be landed on the ground by applying the hovering motion of the front casters to avoid the wheelchair frame from leaning forward. We derive the mechanical design condition for satisfying the static stability during the proposed step-climbing and -descending strategy. We determine the link configuration parameters of the add-on mechanism based on the derived mechanical condition and that of the step-climbing strategy. The descending abilities are realized together with the step-climbing function by constructing the add-on mechanism prototype. Also, we propose the semiautomatic control system for the proposed step-climbing and -descending strategies. By using the step detecting system, the front casters are hovered from the ground. Moreover, we propose the control method of the add-on mechanism in each process of the step-climbing and -descending motion. We have subsequently confirmed that the user could pass over a step automatically, using the proposed step-climbing and -descending strategies after the prototype assembly.

## **2. An add-on drive system**

#### **2.1. Active-caster**

people but also for the elderly. Among the electric-driven wheelchairs, a "motorized wheelchair" has become popular in recent years. Different from a standard electric wheelchair, which is designed as electric-driven, a motorized wheelchair is composed of a manual wheelchair frame and an add-on electric drive module. Because it is foldable and light weight,

A pair of electric drive modules for propelling left and right large wheels of a manual wheelchair are popular and commercially available (**Figure 1(a)**) [2]. Since the main parts are from a manual wheelchair, the diameter of a front caster is quite small, which prevents a motorized wheelchair from passing over a few centimeters step. Addition to this, if drive motors on the left and right provides large torque when the front casters stack into the gap or step, a wheelchair might fall in back since the reaction torques of the drive motors are applied to the wheelchair frame. In contrast, a five-wheeled wheelchair composed of a manual wheelchair and a single-wheel drive system was proposed (**Figure 1(b)**) [3]. The installed drive wheel is a standard orientable wheel, which can change its orientation at a steady point on the ground. This type of wheel has a nonholonomic constraint in its sideways direction and cannot control

Toward the problem of step-climbing and -descending of wheelchairs, a lot of systems and mechanisms have been conducted. Wheelchairs with additional legs [4], some spoke wheels [5, 6], step-climbing method by the dynamic control as the inverted pendulum [7, 8], triangle frame with three wheels at the triangle vertices [9–11], and tracks on each side [12] have been proposed. The iBot wheelchair [13], which has the dynamic balancing functionality as an inverted pendulum, and Scaleve [14], which has additional tracks to climb over steps, have

A step-climbing method of the front casters with steering shafts fixed by the special mechanism [15], and a step-climbing and -descending strategies with a partner robot [16] are proposed to enhance the step-climbing capability of a manual wheelchair. The former is the step-climbing method only for the front casters and step-descending method has not been

In this paper, we propose an add-on mechanism to satisfy the step-climbing and -descending strategies, and in the both the strategies, the wheelchair approaches a step from the front. In our previous works, we proposed a five-wheeled wheelchair equipped with an add-on mechanism on the back of a manual wheelchair [17]. The add-on mechanism is composed of an active-caster, a linear actuator, and some link frames, which is connected to a manual

**Figure 1.** Conventional motorized wheelchair. (a) Dual-wheel drive system [2]. (b) Single-wheel drive system [3].

also been introduced. However, they are too heavy to carry them by personal cars.

reported. The real-world applications of the latter system are quite limited.

users may carry it by cars to travel long distances easily.

28 Physical Disabilities - Therapeutic Implications

two degrees of freedom (2DOF) motion independently.

**Figure 2** shows a schematic top view of an active-caster and an overview of the drive unit whose wheel axis is located in an offset position of the steering axis as a passive caster. The distance between the axes is called "caster-offset" as indicated by a parameter "s" in the figure.

The active-caster is used as a drive wheel by actuating a wheel shaft and a steering shaft by respective motors. To provide a traction power in an arbitrary direction with an arbitrary magnitude, a wheel rotation and a steering rotation are coordinated by a control law represented in Eq. (1). The equation includes cosine and sine functions of wheel orientation *θ* to derive the wheel and steering rotations, *ωw* and *ω<sup>s</sup>* . The wheel angle *θ* is measured by an absolute angle sensor and drive wheel, and steering axes are driven by the independent motors in appropriate ratios of angle *θ*, as represented in Eq. (1).

**Figure 2.** Active-caster. (a) Active-caster (top view). (b) Active-caster drive mechanism.

$$
\begin{bmatrix}
\omega\_u\\\omega\_s
\end{bmatrix} = \begin{bmatrix}
\frac{\cos\theta}{r} & 0\\0 & \frac{\sin\theta}{s}
\end{bmatrix} v \tag{1}
$$

where, *θ*: angle between the velocity vector and wheel,

The active-caster was developed for holonomic and omnidirectional mobile robots by installing two or more numbers of active-caster units on a robotic platform [19]. However, one active-caster unit is used for the electric drive system for propelling the five-wheeled wheelchair whose top view is shown in **Figure 3**. The active-caster generates 2DOF velocity vector whose components are represented by *vs* and *vw* as shown in **Figure 2(a)**. These components are generated independently by a coordinated control, 2DOF of the wheelchair frame, which can be controlled independently as well. The relationships of the wheelchair motion and the active-caster velocity components are represented in Eq. (2), where *xp* is a location of the active-caster steering shaft relative to the midpoint of large wheels of the manual wheelchair as shown in **Figure 3**. From Eqs. (1) and (2), we can derive a control law of the proposed five-wheeled wheelchair as in Eq. (3) to control it in the same manner as a standard electric wheelchair using a joystick.

**Figure 3.** Five-wheeled wheelchair with an add-on active-caster drive wheel.

$$
\begin{bmatrix} V\_x \\ V\_y \end{bmatrix} = \begin{bmatrix} 1 & 0 \\ 0 & x\_p \end{bmatrix} \begin{bmatrix} V \\ \Omega \end{bmatrix} \tag{2}
$$

Five-Wheeled Wheelchair with an Add-On Mechanism and Its Semiautomatic... http://dx.doi.org/10.5772/67558 31

$$
\begin{bmatrix}
\omega\_w\\ \omega\_s
\end{bmatrix} = \begin{bmatrix}
\frac{\cos\phi}{r} & \frac{x\_r \sin\phi}{r} \\
\frac{-\sin\phi}{s} & \frac{x\_r \cos\phi}{s}
\end{bmatrix} \begin{bmatrix} V\\ \mathcal{Q} \end{bmatrix} \tag{3}
$$

where *V* is a translation velocity and *Ω* is an angular velocity of a wheelchair frame while *ϕ* is an orientation of the active-caster relative to the wheelchair frame.

#### **2.2. A reconfigurable link mechanism**

[

30 Physical Disabilities - Therapeutic Implications

*ωw*: rotation of wheel axis,

whose components are represented by *vs*

wheelchair using a joystick.

[

: rotation of steering axis, and

*v*: required velocity vector on the steering shaft.

*r*: wheel radius, *s*: caster offset,

*ωs*

where, *θ*: angle between the velocity vector and wheel,

*ωw <sup>ω</sup>s*] <sup>=</sup> [

\_\_\_\_\_ cos*θ <sup>r</sup>* 0 0 \_\_\_\_ sin*<sup>θ</sup> <sup>s</sup>* ]

The active-caster was developed for holonomic and omnidirectional mobile robots by installing two or more numbers of active-caster units on a robotic platform [19]. However, one active-caster unit is used for the electric drive system for propelling the five-wheeled wheelchair whose top view is shown in **Figure 3**. The active-caster generates 2DOF velocity vector

are generated independently by a coordinated control, 2DOF of the wheelchair frame, which can be controlled independently as well. The relationships of the wheelchair motion and

active-caster steering shaft relative to the midpoint of large wheels of the manual wheelchair as shown in **Figure 3**. From Eqs. (1) and (2), we can derive a control law of the proposed five-wheeled wheelchair as in Eq. (3) to control it in the same manner as a standard electric

the active-caster velocity components are represented in Eq. (2), where *xp*

*Vx Vy*] <sup>=</sup> [

**Figure 3.** Five-wheeled wheelchair with an add-on active-caster drive wheel.

1 0 0 *xp*][

*V*

*<sup>Ω</sup>*] (2)

*v* (1)

and *vw* as shown in **Figure 2(a)**. These components

is a location of the

A five-wheeled wheelchair is composed of a manual wheelchair and the active-caster drive unit. To connect these, we develop a reconfigurable link mechanism to change the location of the active-caster depending on its environments. The major purpose of installing the link mechanism is to surmount a step with no support of caregivers. To vary the location and the height of the active-caster relative to a wheelchair frame, we design a link mechanism whose configuration can be varied by a linear actuator. **Figure 4(a)** shows a schematic side view of the link mechanism with a wheelchair frame and the active-caster. The link mechanism includes three links AB, AC, and BD. The active-caster is installed at point C and touches to the ground. Those links are connected by pin joints at point A, B, and D. The links AC and BD are made of aluminum bars with constant lengths while link AB is composed by cylinder of a linear actuator whose length can be varied by motor actuation. As the length of AB changes, the overall link configuration changes, which results in the change of the location of the active-caster. As the linear actuator extends as shown in **Figure 4(b)**, the active-caster moves backward and the active-caster gets closer to the wheelchair and simultaneously pushes the ground when the linear actuator shrinks as in **Figure 4(c)**.

**Figure 4.** A reconfigurable link mechanism and its motions. (a) Link configuration. (b) When linear actuator extends. (c) When linear actuator shrinks.

## **3. Step-climbing and -descending strategies for five-wheeled wheelchair**

#### **3.1. Step-climbing strategy**

The series of motions performed by the wheelchair is shown in **Figure 5**. First, the wheelchair stops in front of the step (**Figure 5(a)**). Next, the wheelchair performs a static wheelie motion and the front casters are hovered from the ground (**Figure 5(b)**). Then, the wheelchair moves forward by maintaining the static wheelie and the front casters reaches on the top of the

**Figure 5.** A step-climbing strategy for a five-wheeled wheelchair.

step (**Figure 5(c)**). Note that the center of gravity locates in the area defined by the two large wheels and the drive wheel; therefore, a wheelchair user can move forward with maintaining the posture of the static wheelie without a balancing control. After the front casters climbing, the large wheels are lifted by pushing down the active-caster to the ground (**Figure 5(d)**). By the forward motion, the large wheels pass over the step (**Figure 5(e)**). After the large wheels climbing, the wheelchair performs a static wheelie motion on the step (**Figure 5(f)**). After the completion of the static wheelie, large wheels are locked by the braking mechanism of the wheelchair. By coordinated motions of the drive wheel and the linear actuator (**Figure 5(g)**), the drive wheel climbs up the wall of a step and reaches to the top. Thus, a series of stepclimbing sequence is completed (**Figure 5(h)**).

#### **3.2. Step-descending strategy**

We then explain the step-descending strategy in which a user approaches a step from the front side of the wheelchair. To avoid a risk of falling from the top of a step to the ground, we apply the static wheelie motion in the step-descending process as well. **Figure 6** shows the series of motions for the step-descending process. First, the wheelchair stops in front of the step (**Figure 6(a)**). Next, the wheelchair performs a static wheelie to hover the front casters and

**Figure 6.** A step-descending strategy for a five-wheeled wheelchair.

moves to the edge of the step (**Figure 6(b)**). After applying gentle brake to the large wheels of a wheelchair for reducing an impact of landing on the ground, the wheelchair starts to descend a step by maintaining the static wheelie situation (**Figure 6(c)**). The breaks are unlocked after the large wheel lands on the ground, the front casters can then be landed on the ground using the linear actuator motion (**Figure 6(d)**). The drive wheel lands on the ground after the forward movement of the wheelchair (**Figure 6(e)**). Thus, the step-descending motion of the wheelchair is completed.

## **4. Design of a reconfigurable link mechanism**

step (**Figure 5(c)**). Note that the center of gravity locates in the area defined by the two large wheels and the drive wheel; therefore, a wheelchair user can move forward with maintaining the posture of the static wheelie without a balancing control. After the front casters climbing, the large wheels are lifted by pushing down the active-caster to the ground (**Figure 5(d)**). By the forward motion, the large wheels pass over the step (**Figure 5(e)**). After the large wheels climbing, the wheelchair performs a static wheelie motion on the step (**Figure 5(f)**). After the completion of the static wheelie, large wheels are locked by the braking mechanism of the wheelchair. By coordinated motions of the drive wheel and the linear actuator (**Figure 5(g)**), the drive wheel climbs up the wall of a step and reaches to the top. Thus, a series of step-

We then explain the step-descending strategy in which a user approaches a step from the front side of the wheelchair. To avoid a risk of falling from the top of a step to the ground, we apply the static wheelie motion in the step-descending process as well. **Figure 6** shows the series of motions for the step-descending process. First, the wheelchair stops in front of the step (**Figure 6(a)**). Next, the wheelchair performs a static wheelie to hover the front casters and

climbing sequence is completed (**Figure 5(h)**).

**Figure 6.** A step-descending strategy for a five-wheeled wheelchair.

**Figure 5.** A step-climbing strategy for a five-wheeled wheelchair.

**3.2. Step-descending strategy**

32 Physical Disabilities - Therapeutic Implications

#### **4.1. Geometry model of the reconfigurable link mechanism**

In this section, we derive a geometry model of the proposed link mechanism. **Figure 7** shows a schematic side view of the reconfigurable link mechanism with a manual wheelchair. We define a coordinate system of the wheelchair *Σ-XwZw*, where the origin of the coordinate is at the point of contact between the large wheel and the ground as shown in **Figure 7**. The linear actuator on the link mechanism is attached at the back of the wheelchair frame at an angle *α.* Other links are connected to the linear actuator body, point *B*, and a top of the cylinder, point *A*. Coordinates of points A, C, and D are derived as the relative position from point B.

$$
\begin{bmatrix} \mathbf{x}\_a \\ \mathbf{z}\_a \end{bmatrix} = \begin{bmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{bmatrix} \begin{bmatrix} 0 \\ u\_t \end{bmatrix} + \begin{bmatrix} \mathbf{x}\_b \\ \mathbf{z}\_b \end{bmatrix} \tag{4}
$$

$$
\begin{bmatrix} \mathbf{x}\_c \\ \mathbf{z}\_c \end{bmatrix} = \begin{bmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{bmatrix} \begin{bmatrix} -l\_0 \sin \beta \\ u\_L - l\_0 \cos \beta \end{bmatrix} + \begin{bmatrix} \mathbf{x}\_b \\ \mathbf{z}\_b \end{bmatrix} \tag{5}
$$

$$
\begin{bmatrix} \mathbf{x}\_d \\ \mathbf{z}\_d \end{bmatrix} = \begin{bmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{bmatrix} \begin{bmatrix} -l\_\circ \sin \beta \\ u\_\perp - l\_\circ \cos \beta \end{bmatrix} + \begin{bmatrix} \mathbf{x}\_b \\ \mathbf{z}\_b \end{bmatrix} \tag{6}
$$

Here, *uL* is the length of the link AB, which can be varied by the motion of the linear actuator, *l* {0, 1, 2} are the lengths of the links AC, AD, and BD, *x*{*a*, *b*, *c*, *d*} and *z*{*a*, *b*, *c*, *d*} are the coordinates of

**Figure 7.** Geometry of a reconfigurable link mechanism.

the points A, B, C, and D along *Σ-XwZw* axis, respectively. The constant angle *α* is the inclination of the linear actuator relative to the vertical axis *Zw* and *β* is a variable angle between the link AD and the link AB (∠BAD). We will derive geometric conditions of the link lengths of the mechanism to realize the proposed step-climbing and -descending strategies for the fivewheeled wheelchair.

#### **4.2. Design conditions for climbing up a 100 mm step**

Now, we set our target of the surmountable maximum step height to 100 mm, under the assumption that a 100 mm step-climbing capability might allow disable persons to extend their activity in public spots including transfer to trains, passing over steps and gaps in outdoor environments.

At first, we confirm design conditions about the step-climbing of the front casters. In the proposed step-climbing method, the front casters must be hovered 100 mm off the ground for the static wheelie motion. In this motion, the wheelchair frame inclines to the backside. To realize the motion, the link mechanism changes the shape as shown in **Figure 8(a)** in which the active-caster moves backward. The inclination of the wheelchair *γ* for climbing over a 100 mm high step is represented by the following equation:

$$\gamma = \tan^{-1} \left( \frac{h}{l\_{\uparrow}} \right) = 16 \text{(deg)} \tag{7}$$

where, *h* is the height of the step, and *l f* is the length between the large wheels and front casters.

Secondly, we confirm the designing condition about the step-climbing of the large wheels. In the proposed method, the large wheels must be hovered 100 mm from the ground. For hovering the motion of the large wheels, the linear actuator changes the height of the drive wheel to locate at 100 mm lower than the ground level as shown in **Figure 8(b)**.

#### **4.3. Design conditions for descending a 100 mm step**

**Figure 9** shows a schematic view of the wheelchair at a transient moment in which the large wheels descend a step. To prevent wheelchair to fall in the forward direction, a required

**Figure 8.** Configurations of a link mechanism. (a) Configuration for static wheelie. (b) Configuration for large wheel hovering.

Five-Wheeled Wheelchair with an Add-On Mechanism and Its Semiautomatic... http://dx.doi.org/10.5772/67558 35

**Figure 9.** Step-descending model of a five-wheeled wheelchair.

condition for the wheelchair is to maintain the center of gravity not to go beyond the step edge. The condition is represented by a coordinate of the wheelchair along X-axis, *xg* as,

$$x\_{\underline{\boldsymbol{x}}} = R\cos\theta - L\_{\underline{\boldsymbol{\gamma}}}\cos\theta\_{\underline{\boldsymbol{\gamma}}} \le 0 \tag{8}$$

where, *R* is a radius of the large wheel, *Ll* is the length between the drive wheel and the center of gravity, and *θ<sup>l</sup>* is the angle between the line *Ll* and the *Xw* axis as shown in **Figure 9**.

#### **4.4. Design of the link mechanism**

the points A, B, C, and D along *Σ-XwZw* axis, respectively. The constant angle *α* is the inclination of the linear actuator relative to the vertical axis *Zw* and *β* is a variable angle between the link AD and the link AB (∠BAD). We will derive geometric conditions of the link lengths of the mechanism to realize the proposed step-climbing and -descending strategies for the five-

Now, we set our target of the surmountable maximum step height to 100 mm, under the assumption that a 100 mm step-climbing capability might allow disable persons to extend their activity in public spots including transfer to trains, passing over steps and gaps in out-

At first, we confirm design conditions about the step-climbing of the front casters. In the proposed step-climbing method, the front casters must be hovered 100 mm off the ground for the static wheelie motion. In this motion, the wheelchair frame inclines to the backside. To realize the motion, the link mechanism changes the shape as shown in **Figure 8(a)** in which the active-caster moves backward. The inclination of the wheelchair *γ* for climbing over a 100

> ( \_\_*h l*

Secondly, we confirm the designing condition about the step-climbing of the large wheels. In the proposed method, the large wheels must be hovered 100 mm from the ground. For hovering the motion of the large wheels, the linear actuator changes the height of the drive wheel to

**Figure 9** shows a schematic view of the wheelchair at a transient moment in which the large wheels descend a step. To prevent wheelchair to fall in the forward direction, a required

**Figure 8.** Configurations of a link mechanism. (a) Configuration for static wheelie. (b) Configuration for large wheel

*f*

locate at 100 mm lower than the ground level as shown in **Figure 8(b)**.

*<sup>f</sup>*) <sup>=</sup> <sup>16</sup>(deg) (7)

is the length between the large wheels and front

wheeled wheelchair.

34 Physical Disabilities - Therapeutic Implications

door environments.

casters.

hovering.

**4.2. Design conditions for climbing up a 100 mm step**

mm high step is represented by the following equation:

**4.3. Design conditions for descending a 100 mm step**

*γ* = tan<sup>−</sup><sup>1</sup>

where, *h* is the height of the step, and *l*

To satisfy the conditions derived above, we determined the parameters of link mechanism for a prototype wheelchair as shown in **Table 1**.

**Table 1.** Parameters of the prototype wheelchair and the link mechanism.

**Figure 10.** Calculated trajectory of the link mechanism.

By using these parameters, we calculated the motion of the link mechanism. According to the change in the length of link AB, we plotted the trajectories of the points A, C, and D of the proposed mechanism by using Eqs. (4)–(6).

The result is shown in **Figure 10**. As the linear actuator stretches, the drive wheel moves to the back of the wheelchair, by which the inclination *γ* satisfies the requirement for the static wheelie. Hence as the linear actuator shrinks, the drive wheel gets closer to the wheelchair and pushes the ground for hovering the large wheels to reach a 0.1m high.

## **5. Semiautomatic control system for step-surmounting motion**

In this study, we use laser range finder (LRF) to measure the height of the step and the distance between the wheelchair and the step as shown in **Figure 11(a)**. The measurement result of the step by LRF is shown in **Figure 11(b)**. In **Figure 11(b)**, the positions (i)–(iv) are shown

**Figure 11.** Measurement of the step height and the distance by LRF.

as corresponding to **Figure 11(a)**. The each measurement point by LRF has the coordinates, *x* and *y*, on the coordinates system at the center of LRF.

From the LRF data, three lines are identified: the first one represents the top surface of a step, the second one represents the ground, and the last one represents the wall of a step. Those lines are represented as:

(iii)
am a me nast one represents me wan or a step. I more

 $x = ay + b$ : step surface

 $x = a'y + b'$ : ground

 $x = a'y + b'$ : step wall

By using constants in these equations, the height of the step, *h*, and the distance between LRF and the step, *LS* , are derived by the following equations:

$$L\_s = \frac{|b^\ast|}{\sqrt{a^\ast + 1}} \tag{10}$$

$$h = (L' - L)\sin\theta\_s = \left(\frac{|b'|}{\sqrt{a^2 + 1}} - \frac{|b|}{\sqrt{a^2 + 1}}\right)\sin\theta\_s \tag{11}$$

where *L* and *L′* are the distances from LRF sensor to a step surface and the ground, respectively. An angle *θ<sup>s</sup>* represents an inclination of a laser scan surface and the ground which can be known as a constant.

By using the measured height of the step *h*, and the distance to the step *Ls* , the static wheelie motion and translation motion of the wheelchair can be performed simultaneously to minimize the time for approaching to a step. Moreover, coordinated controls of the linear actuator and the active-caster can be realized for maintaining certain contacts between the large wheels and a step edge for climbing the large wheels.

## **6. Prototyping**

By using these parameters, we calculated the motion of the link mechanism. According to the change in the length of link AB, we plotted the trajectories of the points A, C, and D of the

The result is shown in **Figure 10**. As the linear actuator stretches, the drive wheel moves to the back of the wheelchair, by which the inclination *γ* satisfies the requirement for the static wheelie. Hence as the linear actuator shrinks, the drive wheel gets closer to the wheelchair and

In this study, we use laser range finder (LRF) to measure the height of the step and the distance between the wheelchair and the step as shown in **Figure 11(a)**. The measurement result of the step by LRF is shown in **Figure 11(b)**. In **Figure 11(b)**, the positions (i)–(iv) are shown

pushes the ground for hovering the large wheels to reach a 0.1m high.

**5. Semiautomatic control system for step-surmounting motion**

proposed mechanism by using Eqs. (4)–(6).

**Figure 11.** Measurement of the step height and the distance by LRF.

**Figure 10.** Calculated trajectory of the link mechanism.

36 Physical Disabilities - Therapeutic Implications

The prototype wheelchair was designed and built whose 3-dimensional Computer Aided Design (3D CAD) models are shown in **Figure 12**. The add-on mechanism, which includes the active-caster and the reconfigurable link mechanism with a linear actuator, is attached on the back of a frame of a manual wheelchair. The stroke of the linear actuator is 200 mm and the maximum power is 144 W. To drive the active-caster, two motors are installed, whose capacities are 200 W each. The diameter of the drive wheel is 130 mm with 45 mm caster offset. Two sensors (LRF) are attached on the side of the wheelchair frame to measure the step whose locations are illustrated in **Figure 13**.

For maneuvering the wheelchair around normal environments, a user can operate the wheelchair by using a joystick on an arm rest as same as in the standard electric wheelchair.

To surmount a step, a user gives a command to a PC (which is not shown in the Figures) to launch the semiautomatic program, which controls the step surmount strategies based on the measured step height and the distance detected by LRFs.

**Figure 12.** Prototype of a five-wheeled wheelchair with an add-on mechanism. (a) Add-on mechanism. (b) Diagonal view of a wheelchair prototype.

**Figure 13.** Laser sensors for semiautomatic system. (a) Side view. (b) Front view.

## **7. Experiment**

We propose an add-on electric drive system with a reconfigurable link mechanism for a manual wheelchair. We also propose a semiautomatic system for reducing the user effort to operate a wheelchair to surmount a step. To verify the availability of the prototype wheelchair with the semiautomatic system, we tested the step-climbing and -descending processes of the wheelchair using the prototype. In the experiment, we tested the step-climbing and -descending of a 100 mm step.

#### **7.1. Step climbing**

The experimental results are shown in **Figure 14**. In **Figure 14(a)**–**(h)**, each snapshot of the wheelchair corresponds to **Figure 5(a)**–**(h)**. The experiments were performed by using the semiautomatic operating system. First, the wheelchair is stopped in front of the step by the user operation using joystick (**Figure 14(a)**). After the user commanded to start the semiautomatic operation, LRFs measured the step height and the distance to the step. Then, the wheelchair approached to the step by performing a static wheelie motion with hovering the front casters not to collide with a step (**Figure 14(b)**). After the large wheels contact the step edge, the wheelchair climbed the step by pushing the active-caster down the ground to lift up the large wheels with maintaining the contacts between the large wheels and the step edge (**Figure 14(c)**–**(e)**). After the climbing of the large wheels, the static wheelie motion was performed on the top of the step (**Figure 14(f)**). The brake mechanism was then activated after the completion of the static wheelie, for preventing the large wheel to rotate for the drive wheel climbing process. Then the linear actuator changed the link mechanism to locate the drive wheel closer to the wheelchair frame to provide an enough load to the step wall. Together with the linear actuator movements, the drive wheel rotated for climbing the step

**Figure 14.** Semiautomatic assist system (step-climbing strategy).

**7. Experiment**

view of a wheelchair prototype.

38 Physical Disabilities - Therapeutic Implications

ing of a 100 mm step.

**7.1. Step climbing**

We propose an add-on electric drive system with a reconfigurable link mechanism for a manual wheelchair. We also propose a semiautomatic system for reducing the user effort to operate a wheelchair to surmount a step. To verify the availability of the prototype wheelchair with the semiautomatic system, we tested the step-climbing and -descending processes of the wheelchair using the prototype. In the experiment, we tested the step-climbing and -descend-

**Figure 12.** Prototype of a five-wheeled wheelchair with an add-on mechanism. (a) Add-on mechanism. (b) Diagonal

**Figure 13.** Laser sensors for semiautomatic system. (a) Side view. (b) Front view.

The experimental results are shown in **Figure 14**. In **Figure 14(a)**–**(h)**, each snapshot of the wheelchair corresponds to **Figure 5(a)**–**(h)**. The experiments were performed by using the semiautomatic operating system. First, the wheelchair is stopped in front of the step by the user operation using joystick (**Figure 14(a)**). After the user commanded to start the semiautomatic operation, LRFs measured the step height and the distance to the step. Then, the wheelchair approached to the step by performing a static wheelie motion with hovering the front casters not to collide with a step (**Figure 14(b)**). After the large wheels contact the step edge, the wheelchair climbed the step by pushing the active-caster down the ground to lift up the large wheels with maintaining the contacts between the large wheels and the step wall (**Figure 14(g)**). Even though the step height was much higher than the diameter of the drive wheel, the drive wheel was successfully able to climb up the step wall since enough load was applied to the step wall by the linear actuator. By unlocking the brake for the large wheels, the step-climbing process was completed (**Figure 14(h)**). From the above all, we confirmed that the wheelchair could climb over a step by the semiautomatic system.

## **7.2. Step descending**

**Figure 15** shows the experimental results of the step-descending motion with the semiautomatic operation system. First, the wheelchair stopped in front of the step by the user operation using joystick (**Figure 15(a)**). After the user commanded to start the semiautomatic motion, LRFs measured the step height and the distance between the step edge and the wheelchair. Then, the wheelchair approached to the step by performing a static wheelie motion and stopped to locate the point of contact of the large wheels on the edge of the step (**Figure 15(b)**). After the gentle brakes of the large wheels were activated, the wheelchair descended the step by propelling the drive wheel, which made the large wheels to get down the ground (**Figure 15(c)**). Since the wheelchair performed a static wheelie during the stepdescending motion, the user could avoid leaning in the forward direction. After large wheels descending motion, the drive wheel approached to the step edge by contacting the front casters to the ground (**Figure 15(d)**). Finally, the drive wheel reached the ground by decreasing the speed of the drive wheel (**Figure 15(e)**).

In this experiment, the wheelchair was able to descend the step by approaching from the front side of a wheelchair. Thus, by the proposed strategy, we realized the step-descending motion with a reduction of a mental burden.

**Figure 15.** Semiautomatic assist system (step-descending strategy).

## **8. Conclusion**

wall (**Figure 14(g)**). Even though the step height was much higher than the diameter of the drive wheel, the drive wheel was successfully able to climb up the step wall since enough load was applied to the step wall by the linear actuator. By unlocking the brake for the large wheels, the step-climbing process was completed (**Figure 14(h)**). From the above all, we con-

**Figure 15** shows the experimental results of the step-descending motion with the semiautomatic operation system. First, the wheelchair stopped in front of the step by the user operation using joystick (**Figure 15(a)**). After the user commanded to start the semiautomatic motion, LRFs measured the step height and the distance between the step edge and the wheelchair. Then, the wheelchair approached to the step by performing a static wheelie motion and stopped to locate the point of contact of the large wheels on the edge of the step (**Figure 15(b)**). After the gentle brakes of the large wheels were activated, the wheelchair descended the step by propelling the drive wheel, which made the large wheels to get down the ground (**Figure 15(c)**). Since the wheelchair performed a static wheelie during the stepdescending motion, the user could avoid leaning in the forward direction. After large wheels descending motion, the drive wheel approached to the step edge by contacting the front casters to the ground (**Figure 15(d)**). Finally, the drive wheel reached the ground by decreasing

In this experiment, the wheelchair was able to descend the step by approaching from the front side of a wheelchair. Thus, by the proposed strategy, we realized the step-descending motion

firmed that the wheelchair could climb over a step by the semiautomatic system.

**7.2. Step descending**

40 Physical Disabilities - Therapeutic Implications

the speed of the drive wheel (**Figure 15(e)**).

**Figure 15.** Semiautomatic assist system (step-descending strategy).

with a reduction of a mental burden.

In this study, we developed a novel add-on mechanism with a reconfigurable link mechanism for a manual wheelchair and realized the step-climbing and -descending strategies. In the climbing motion of the front casters, we proposed the static wheelie motion, in which the large wheels and the drive wheel maintain the static stability with the three-point contact with the ground while the front casters hover from the ground. In the other situation, the large wheels were hovered from the ground by pushing the drive wheel down to the ground using the link mechanism with the linear actuator. We also proposed the climbing motion of the drive wheel by controlling the drive wheel and the linear actuator.

We also proposed the step-descending strategy for approaching a step from the front side of a wheelchair. We derived the design condition of the add-on mechanism for satisfying the static stability of the wheelchair during the proposed descending strategy.

We determined the link length and the position of the add-on mechanism from the design conditions derived from geometric studies. We then confirmed to satisfy the design condition for realizing both of the step-climbing and -descending strategies by link trajectory calculations.

We built the prototype based on the analysis and tested the step-climbing and -descending motions. In the experiments, we confirmed that the proposed wheelchair could climb and descend the step using the proposed strategy and mechanism.

## **Author details**

Masayoshi Wada\* and Yu Munakata

\*Address all correspondence to<EMAIL_ADDRESS>
Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo, Japan

## **References**

## **Participation and Environmental Factors of Children with Physical Disabilities in Taiwan**

Lin-Ju Kang, Ai-Wen Hwang and Chia-Ling Chen

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67425

#### **Abstract**

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