Position Control of Permanent Magnet Stepper Motor Considering Model Uncertainty Using Type-2 Fuzzy Robust Control Method

Permanent Magnet (PM) stepper motors are widely used in precise systems which are affected by external disturbances, parameters uncertainty and saturated control. Also, an appropriate nonlinear controller is required when the problem is to track reference signal. This paper presents a robust adaptive controller to control rotor angular position in stepper motors. The main idea to make a robust controller is to use an adaptive control system based on type-2 fuzzy sets. Type-2 fuzzy set estimates nonlinear and uncertain functions existing in the stepper motor equations and then, parameters of type-2 fuzzy set are tuned online by adaptive rules obtained from Lyapunov theory. Finally, simulations are performed to control stepper motor position in two cases: certain and uncertain equations. To apply uncertainty into the system model in simulations, values of rotor and load inertia (J) and viscous friction coefficient (P) are considered as a range of numbers. Actually, a limited parametric uncertainty is applied to the system. Simulation results show that the proposed controller has a better performance in tracking and robustness compare to type-1 fuzzy controller