Observer-based controller for position regulation of stepping motor

The design of a controller-observer scheme for the exponential stabilisation of a permanent magnet stepper motor is proposed. The technique is based on sliding-mode techniques and nonlinear observers. Representing the stepper motor model as a singularly perturbed nonlinear system, a position regulation controller is obtained. Since this controller depends on the mechanical variables, load torque and equilibrium point, under the assumption that the rotor position is available for measurement, an observer design is presented to estimate the angular speed and load torque. Furthermore, a stability analysis of the closed-loop system is also made to provide sufficient conditions for the exponential stability of the full-order closed-loop system when the angular speed and load torque are estimated by means of the observer. The proposed scheme is applied to the model of a permanent-magnet stepper motor.