Robust stability of nonlinear dynamic systems using sliding mode controller

In this paper existing sliding mode control for nonlinear dynamic systems is demonstrated and its performance is evaluated against conventional PID controller . The changes in system dynamics occurs due to parametric uncertainties and external disturbances. Here it is shown that the sliding mode control based on the variable structure control is a robust control technique against parametric uncertainties and external disturbances. The effect of chattering in SMC is reduced using a boundary layer approach. The PID controller being a fixed structure control system is sensitive to parametric uncertainties and external disturbances. The sliding mode control and PID controller are illustrated in computer simulation for modeled spring-mass dashpot system and coupled tank system. Finally the performances of SMC are compared with conventional PID controller for the above systems to show the dominance of SMC over conventional PID controller.