A unified approach to adaptive nonlinear control of stepper motors

In this paper, a robust adaptive nonlinear controller for various types of stepper motors is presented. The control design is applicable to both variable reluctance and permanent magnet stepper motors. It is also shown that the methodology is applicable to other peculiar configurations of stepper motors (e.g. Sawyer motors). Furthermore, the motors may be either rotary or linear. To this end, a general electromechanical model of stepper motors is utilized. The model is comprised of the mechanical dynamics and electrical dynamics of the motor including the effects of cogging, viscous friction, winding resistance or other uncertainties. The robust adaptive design is based on our earlier work (1997) and does utilizes backstepping in the case that voltage level control is used rather than current controls. Simulation studies are presented to show the efficacy of the control design approach.