Voltage-fed permanent magnet stepper motor control with position only feedback

A robust adaptive nonlinear dynamic controller is designed to achieve 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 positions measurements. Rotor velocity and stator phase currents are not available for feedback. Furthermore, the only motor parameter that is required to be known is the time constant of the electrical subsystem. Adaptations are utilized so that no other knowledge of motor parameters is required. 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.