*Article* **Research on Modeling and Fault-Tolerant Control of Distributed Electric Propulsion Aircraft**

**Jiacheng Li 1,\* , Jie Yang 2 and Haibo Zhang 1**

**Abstract:** Distributed electric propulsion (DEP) aircrafts have high propulsion efficiency and low fuel consumption, which is very promising for propulsion. The redundant thrusters of DEP aircrafts increase the risk of fault in the propulsion system, so it is necessary to study fault-tolerant control to ensure flight safety. There has been little research on coordinated thrust control, and research on fault-tolerant control of the propulsion system for DEP aircrafts is also in the preliminary stage. In this study, a mathematical model of DEP aircrafts was built. Aiming at the lateral and longitudinal control of DEP aircrafts, a coordinated thrust control method based on total energy control and total heading control was designed. Furthermore, a fault-tolerant control strategy and control method was developed for faults in the propulsion system. Simulation results showed that the controller could control the thrust to the prefault level. The correctness and effectiveness of the designed coordinated thrust control method and the fault-tolerant control method for DEP aircrafts were theoretically verified. This study provides a theoretical basis for future engineering application and development of the control system for DEP aircrafts.

**Keywords:** distributed electric propulsion; coordinated thrust control; fault-tolerant control; flight simulation


2.1.2. Untoward effects of ginger

A literature review reported that ginger is not a safe herb. It is a potential abortifacient with high doses (>1000 mg daily consumption). Higher doses of ginger can cause thinning of blood, stomach discomfort and heartburn [24–27].

#### 2.2. Garlic (Allium sativa)

Garlic is a perennial herb cultivated in different countries. It is commonly used as a food ingredient and as a spice in different countries [28].


**6. Uses of essential oils in perfumery**

The essential oils that are used in the perfume industries are classified according to their diffusion rate in air and volatility:

*Base note*: these are the least volatile essential oils and last for a longtime period. These remain for longtime duration including several hours. Some essential oils that are used as the base notes are the Myrrh, vanilla, sandalwood, and frankincense.

*Middle note*: these sorts of essential oils are tending to be spicy or floral and give body to blends; their time duration is less and remain up-to 1 hour. These include Ylang-ylang, jasmine, geranium, clove, and lavender.

*Top note*: these are the most volatile and the first perceptible odors from the perfume. Their time duration is too much less and remains maximum for 30 minutes. These include berry, bergamot, cinnamon, juniper, and gardenia.

Perfumes are formulated mostly using alcohol, though these may contain the cloudy solutions. Eau de types of perfumes are mostly formulated using the essential oils generally amber color because of their natural oils color but normally they are clear.

## **6.1 Percentage of essential oils in different perfumes products**

#### **6.2 Increasing the sales of essential oils to the home appliances**

All over the world, people are shifting toward the herbal products for the treatment of skin diseases compared to medicines and synthetic drugs. The essential oil is pure and does not have any side effects. The demand for essential oil is increasing because of their usage in daily life and it is mostly used for the relaxation purpose and people prefer it because of its no side effects. Aura Cacia that is manufacturer of Iowa-based care products said that the essential oil sale was increased 90% between the 2009 and 2012, and the sale of household items that contains the essential oil was increased from 6 to 12%.

**43**

**Figure 4.**

*Applications of essential oils in daily life.*

*Biological Importance of Essential Oils*

*DOI: http://dx.doi.org/10.5772/intechopen.87198*

Falcon Young living (**Figure 4**) [25].

*6.3.1 Bergamot*

**6.3 Some major essential oils and their applications**

Essential oils play a key role in treating the dermatological issues including the rashes, acne, hives, eczema, and psoriasis which made the essential oil suitable for the skin treatment care products that enhance the growth of skin industry. The market of essential oils is growing because it has no side effects, and other synthetic chemicals have side effects, so they are less preferred. Essential oils market of home care products and cleaning products will be increased to 550 million USD by 2024. The growth in essential oil market along with the companies that are introducing the products with supplementary benefits such as better cleaning, easy fragrance, and germ fighting. The essential oils market of France will be increased up to 8.5% by 2024. Major cosmetics industries used essential oils in cosmetics and imported these oil products worldwide. Companies used the marketing strategies to spread the awareness to the people regarding the usage and benefits of essential oils, and the aromatherapy markets gets more enhanced customers to buy these products. The essential oil market of India will be exceeding up to 790 million USD by 2024. Since being a large country, India used the large-scale agricultural techniques to grow crops of essential oil plants including lemon, mint, and spices, and its aromatherapy market are growing day by day.

Lavender oil market will be reached up to 20 kilotons by 2024. It is used in fighting the serious health conditions, including the chronic anxiety, relieves pain, cancer, stress with reverse sign of the ageing, headache, cosmetics applications, pharmaceuticals applications, aromatherapy etc. as shown in (**Figure 4**). The major companies that share large market size of essential oil-based products are Firmenich, Frutarom, Flaex, Rock Mountain Moksha Lifestyle, and Florihana

The essential oil of bergamot obtained from the peel of the fruits of the *Citrus bergamia* is known as the bitter orange tree. The extract of the bergamot is used in flavoring

### *Biological Importance of Essential Oils DOI: http://dx.doi.org/10.5772/intechopen.87198*

*Essential Oils - Oils of Nature*

promote the wound healing [23].

frankincense.

**6. Uses of essential oils in perfumery**

to their diffusion rate in air and volatility:

Ylang-ylang, jasmine, geranium, clove, and lavender.

their fragrance, and 80–90% alcohol.

grance, and 80–90% alcohol [24].

70% alcohol.

was increased from 6 to 12%.

These include berry, bergamot, cinnamon, juniper, and gardenia.

**6.1 Percentage of essential oils in different perfumes products**

**6.2 Increasing the sales of essential oils to the home appliances**

medications among the other products and personal care products. Essential oils have various advantages in wound healing, rejuvenation, and relaxation. Alongside their applications in the betterment of the health issues, the most common health issues such as migraines and nausea are cured from the essential oils. It is also used in the food industries because of their preservative potential in contrast to the foodborne pathogens, antibacterial, antimicrobial, and antifungal characteristics. The use of aromatherapy as the harmonizing care is speedup due to their unique characteristics which include the coping with some of side effects of cancer and to

The essential oils that are used in the perfume industries are classified according

*Middle note*: these sorts of essential oils are tending to be spicy or floral and give body to blends; their time duration is less and remain up-to 1 hour. These include

*Top note*: these are the most volatile and the first perceptible odors from the perfume. Their time duration is too much less and remains maximum for 30 minutes.

Perfumes are formulated mostly using alcohol, though these may contain the cloudy

• Eau de perfume usually contains 8–15% amount of essential oils or sometimes

• Splash cologens usually contain 1–3% fragrance or essential oil, and 80% alcohol.

• Eau de cologne usually contains 3–5% of fragrance or essential oil, and up to

• Eau de toilette usually contains the essential oil between 4 and 8% or its fra-

All over the world, people are shifting toward the herbal products for the treatment of skin diseases compared to medicines and synthetic drugs. The essential oil is pure and does not have any side effects. The demand for essential oil is increasing because of their usage in daily life and it is mostly used for the relaxation purpose and people prefer it because of its no side effects. Aura Cacia that is manufacturer of Iowa-based care products said that the essential oil sale was increased 90% between the 2009 and 2012, and the sale of household items that contains the essential oil

solutions. Eau de types of perfumes are mostly formulated using the essential oils generally amber color because of their natural oils color but normally they are clear.

*Base note*: these are the least volatile essential oils and last for a longtime period. These remain for longtime duration including several hours. Some essential oils that are used as the base notes are the Myrrh, vanilla, sandalwood, and

**42**

Essential oils play a key role in treating the dermatological issues including the rashes, acne, hives, eczema, and psoriasis which made the essential oil suitable for the skin treatment care products that enhance the growth of skin industry. The market of essential oils is growing because it has no side effects, and other synthetic chemicals have side effects, so they are less preferred. Essential oils market of home care products and cleaning products will be increased to 550 million USD by 2024. The growth in essential oil market along with the companies that are introducing the products with supplementary benefits such as better cleaning, easy fragrance, and germ fighting.

The essential oils market of France will be increased up to 8.5% by 2024. Major cosmetics industries used essential oils in cosmetics and imported these oil products worldwide. Companies used the marketing strategies to spread the awareness to the people regarding the usage and benefits of essential oils, and the aromatherapy markets gets more enhanced customers to buy these products. The essential oil market of India will be exceeding up to 790 million USD by 2024. Since being a large country, India used the large-scale agricultural techniques to grow crops of essential oil plants including lemon, mint, and spices, and its aromatherapy market are growing day by day.

Lavender oil market will be reached up to 20 kilotons by 2024. It is used in fighting the serious health conditions, including the chronic anxiety, relieves pain, cancer, stress with reverse sign of the ageing, headache, cosmetics applications, pharmaceuticals applications, aromatherapy etc. as shown in (**Figure 4**). The major companies that share large market size of essential oil-based products are Firmenich, Frutarom, Flaex, Rock Mountain Moksha Lifestyle, and Florihana Falcon Young living (**Figure 4**) [25].


*3.4. Polyphenol Carriers*

Materials used for encapsulation, which makes a protective shell, should be biodegradable and food-grade. They also must be able to establish a barrier between an internal phase and its surroundings [13]. Selection of coating material influences encapsulation efficiency and encapsulates stability [24]. Commonly used materials are carbohydrates such as maltodextrin, cyclodextrins, gum Arabic and modified starch. These materials lead to an increase in the glass transition temperature of the dried product. By trapping a bioactive compound, they enable its preservation against stickiness, temperature, enzymatic and chemical changes [13].

Maltodextrin is one of the most often used carriers, having a low bulk density and viscosity and high solubility at high solids contents [16,24]. It is obtained by partial hydrolysis of starch using an enzyme or acid. Maltodextrin has the ability to retain volatile compounds. Its disadvantages, such as low emulsibility, are often overcome by combining maltodextrin with other materials [16].

Cyclodextrins are safe for food applications and broadly studied as hosts for encapsulation [3]. The commonly used cyclodextrins are α-, β- and γ-cyclodextrin. They possess a hydrophobic central cavity and a hydrophilic external part [32]. Due to this structure, guest molecules (different organic and inorganic molecules) are able to be accommodated into the cavity. The hydrophilic external surface provides aqueous solubility [3,24]. The application of cyclodextrins in spray-drying is limited due to their low water solubility (1.8%). This limitation can be overcome by cyclodextrin modification. An example of such modification is hydroxypropyl-β-cyclodextrin which has a higher water solubility (60%) and thus can be subjected to drying techniques [24].

Gum Arabic consists of galactose, rhamnose, arabinose, 4-O-methyglucuronic acid and glucuronic acid and its natural source is the acacia plant (stems and branches). Furthermore, its low viscosity and high solubility, stable emulsions and high retention rates of volatile compounds have enabled a broad range of applications of this polymer [16]. On the other hand, some disadvantages such as low production yield and a consequently higher price make it less accessible [33].

#### **4. Application of Spray-Drying and Freeze-Drying for Encapsulation of Polyphenols**

During freeze-drying of foods rich in polyphenols, cells are disrupted, and therefore exposed to an increased enzyme activity (polyphenol oxidase and peroxidase enzyme) upon thawing, and the degradation of the polyphenols can occur [34,35]. However, some studies have shown that the amount of polyphenols may increase after this process. The flavonol content in freeze-dried onions increased, which can be attributed to the release of polyphenols from the matrix [36]. Wilkowska et al. [24] observed that freeze-dried powders had 1.5 times higher retention of anthocyanins than spray-dried ones. From studying the values of total polyphenols content, it has been noticed that when applying spray-drying, 73% of compounds were lost. Encapsulates of polyphenols in coffee grounds extract achieved by freeze-drying and spray-drying with maltodextrin, gum Arabic and maltodextrin:gum Arabic (1:1) as carrier materials were evaluated for total polyphenols content and flavonoid content. The results showed that freeze-drying was a more effective technique for retention of polyphenols and flavonoids and maltodextrin a more efficient carrier. On the other hand, spray-dried particles possessed a higher antioxidant activity than freeze-dried ones [2]. One interesting investigation was conducted on developing novel protein ingredients fortified with blackcurrant concentrate. As a source of protein, they used whey protein isolate and freeze-drying and spray-drying techniques. Encapsulates obtained by spray-drying possessed a higher total polyphenols content, anthocyanins content and encapsulation efficiency compared to the freeze-dried ones [28]. Robert et al. [37] encapsulated polyphenols from pomegranate juice and ethanolic extract by spray-drying, and observed a higher encapsulation efficiency when soy protein isolates were used compared to the maltodextrin. On the other hand, capsules with maltodextrin, stored at 60 ◦C in an oven for 56 days, resulted in a lower degradation of polyphenols and anthocyanins. Wu et al. [38] investigated the physicochemical properties and nutritional characteristics of functional cookies with incorporated encapsulated blackcurrant polyphenols. For the preparation of encapsulates, whey protein isolate and blackcurrant concentrate were used and the applied encapsulating techniques used were freeze-drying and spray-drying. The results of total polyphenols content were higher for enriched cookies with freeze-dried encapsulates than for those with spray-dried encapsulates.

Ersus and Yurdagel [39] observed that during spray-drying, maltodextrins with higher DE (equivalents of dextrose) are more sensitive to higher outlet air temperatures. Heating could lead to structural deformations due to shorter chains and oxidation of free glucose functional groups at the open ends. Their results confirmed the encapsulation of black carrot anthocyanins using maltodextrin DE 20-21 for 20% feed solid content and

160–180 ◦C drying temperatures. Gomes et al. [40] obtained a higher retention of papaya pulp polyphenol and flavonoid compounds in spray-dried products than in freeze-dried products. Vanillic acid had an enormous decrease of 76% after freeze-drying. Enzymatic reactions with the action of peroxidase and polyphenol oxidase are likely to occur in the freeze-drying process. Moreover, the disrupted material structure caused by the formation of ice crystals and lower exposure to oxygen can cause the liberation of these enzymes. Furthermore, artepillin C concentration increased three times after drying, which can lead to the false-positive results of the spray-drying technique. It is known that processes at high temperatures may release more bound polyphenols which cannot be detected in fresh samples [40]. Saikia et al. [41] encapsulated polyphenols from *Averrhoa carambola* pomace using maltodextrin and freeze-drying and spray-drying methods. The authors obtained a higher encapsulation efficiency in freeze-dried encapsulates. It might be that some polyphenols are destroyed during spray-drying, due to their sensitivity to heat. During the spray-drying process, fine misty droplets with increased surface are obtained and due to that higher surface, they are more exposed to heat. Moreover, during atomization, some amount of carrier can be eliminated from the core material and the partially covered capsules thus obtained can be destroyed by heat. During the freeze-drying process, no atomization or heat exposure are present. These authors also observed a decrease in surface polyphenols with higher maltodextrin content [41]. On the other hand, high inlet temperatures applied in spray-drying are short-lived, so this technique is less destructive for bioactive compounds compared to the other conventional thermal processes [42]. It has to be taken into consideration that in the freeze-drying process, obtained powders are ground and this process increases the possibility of contact with air, resulting in oxidation reactions [42,43]. In the freeze-drying process, the formation of a sawdust-like form is usual, leading to a lower surface area/volume ratio. Additionally, by the spray-drying process, smaller sized microspheres with a larger surface area were obtained using the spray-drying process (for the same amount of material as for freeze-drying), which led to the deterioration of the surface polyphenols [2]. Considering the short time of exposure to high temperatures during spray-drying, this technique seems good for the encapsulation of polyphenols. Dealing with thermosensitive and highly valuable materials, freeze-drying is a suitable method [33]. Tables 1–3 present the studies on the encapsulation of polyphenols using freeze-drying and spray-drying techniques.

**Table 1.** Studies of spray-drying application for encapsulation of polyphenols from different sources.

**Table 2.** Studies of freeze-drying application for encapsulation of polyphenols from different sources.

**Table 3.** Studies of spray-drying (SD) and freeze-drying (FD) applications for encapsulation of polyphenols from different sources.