Taguchi-genetic-algorithm in helicopter H_∞ control design with robust flying quality

The purpose of this paper is to design an optimal linear H_∞ helicopter control system via Taguchi-genetic-algorithm (TGA) to improve its stability and performance. Firstly, the nonlinear mathematical model of Lynx, an England Westland helicopter, is established from the nonlinear six degree-of-freedom dynamic equations. Secondly, the linear H_∞ feedback control law is applied to design a linear H_∞ controller, which is then integrated into the nonlinear helicopter model to simulate dynamic responses. Thirdly, Taguchi experimental method is served as a rough searching tool for the best genetic parameters in genetic algorithm (GA), which includes population size, crossover rate, mutation rate and the remaining size of parent. Meanwhile, GA is served as a fine searching tool for the weighting functions of H_∞ controller. Two helicopter flying quality indices, quickness index and phase delay margin, are adopted to test the robustness of H_∞ controller. The results show that TGA-type linear H_∞ controller can maintain the flight specifications in the level-1 standard, while the forward velocity of helicopter is changing.