Optimal design of robust FOPID for the aircraft pitch control system using multi-objective GA

Nature inspired algorithms are nowadays aiding in solving several complex multi-objective engineering problems. In this paper, robust pitch control of a flight control system has been designed using fractional order controllers. In order to obtain the optimal values of the controller gains & orders such that the system offers robust response, the mixed sensitivity formulation has been expressed as multi-objective optimization problem based on generate first choose later (GFCL) approach. Multi-objective genetic algorithm has been used for designing the fractional order controllers. From the simulations it is clear that, all the controllers designed using MOGA offers robust response and the value of the infinity norm of sensitivity and complementary sensitivity function is also less than one. On the contrary, the classical method of Ziegler Nichols gives a non robust and oscillatory response.