OPTIMIZATION OF A NONLINEAR ELECTRICAL–THERMAL MODEL OF THE SKIN
This paper presents modified equations for a nonlinear electrical–thermal model of the skin, and optimizes the parameters of the model by a genetic algorithm. In publications, an electrical–thermal model for the skin has been presented. Although, the model is sophisticated and includes the most of physical phenomena occurring in the skin; however, mathematical equations used in this model for the capacitance and dissipated power are incompletely stated so that they sometimes cause instability in solving the equations. In this paper, the equations given previously for the capacitance current and the dissipated power are first modified. We have considered different inward and outward current in the model, since there are different ions which make this two currents in the skin. Then, a special kind of genetic algorithm is applied to estimate the parameters of the model. The used algorithm is a powerful optimization tool against high-dimensional problems and can overcome the curse of dimensionality. In each iteration, it divides variable sets into two groups: a small set still variable and a large set frozen on their best values. Finally, modeling results are compared with experimental results. The comparison shows there is a good agreement between the modeling and experimental results especially in the steady state regime.