Nonlinear position control for permanent magnet stepper motor using only position feedback

In this paper, we present a nonlinear controller for position tracking of permanent magnet stepper motors (PMSMs) using only position feedback. A virtual velocity is designed to improve the position tracking performance and virtual currents are proposed in order to guarantee the virtual velocity. An integrator of position tracking error is added into the virtual currents for reducing the steady-state error in position tracking caused by the load torque. The proposed controller guarantees that the position, velocity and currents tracking errors globally exponentially converge to zero. Furthermore, the proposed controller is robust against the load torque. By using passive properties of PMSMs, the requirements of the velocity and current measurements were removed. Simulation results validate the effectiveness of the proposed controller.