Permanent magnet stepper motor control via position-only feedback

In this paper, a robust nonlinear dynamic controller is designed to achieve global practical stabilization for position tracking error of a voltage-fed permanent-magnet stepper motor. The control design is an output-feedback design that utilizes only rotor position measurement. Rotor velocity and stator phase currents are not available for feedback. Furthermore, only upper and lower bounds are required for the electromechanical parameters of the motor. The proposed controller is robust to load torques, friction, cogging forces, and other disturbances satisfying certain bounds. These results can also be extended to other classes of motors.