In this paper, robust PID controller parameters like proportional gain KP, integral time constant Ti, derivative time constant Td and filter time constant Td/N are optimized for single input single output (SISO) process by utilizing multi objective evolutionary algorithms. The SISO processes considered are phase locked loop (PLL) structure with motor control and magnetic levitation system. Moreover to get better output, a filter structure is introduced with robust PID controller design. The robust stability and closed performance like set-point tracking, load disturbance rejection and control energy are considered as multi objectives and hence, the multi objective algorithms are utilized. The performance of the controller is optimized by non dominated sorting genetic algorithm –II and modified non dominated sorting genetic algorithm –II and the results are compared. The comparison results show that MNSGA-II algorithm is better than NSGA –II in both the SISO processes.

Keywords: Robust proportional integral derivative (PID) controller, Evolutionary algorithms, Non dominated sorting genetic algorithm (NSGA)-II, Modified non dominated sorting genetic algorithm (MNSGA)-II