The Effects of Nonlinearities on the Robustness of Various Controllers: Application on a DC Motor

Real life systems are mostly nonlinear. Controlling nonlinear systems is accomplished in several ways, mostly linearizing the system which may cause problems regarding the robustness of the controller. The controllers, on the other hand may be linear or nonlinear. This paper investigates the effects of nonlinearities on the robustness of various controllers (linear controllers, such as PID with first order derivative filter, state-feedback with integral control and, CRONE, and nonlinear controllers, such as smoothed first-order integral SMC) with an application on a DC motor. The motor's model includes four types on nonlinearities (voltage saturation, current saturation, dead zone, and backlash deadband). The performance of the different controllers is presented and compared using the nonlinear model, the linearized model, uncertainty in the model, and harmonic load disturbance.