Performance comparison of the feedback linearization control and sliding mode controls for a permanent magnet stepper motor

The permanent magnet stepper motor (PMSM) has a slotted stator with two phases and a permanent magnet rotor. This PMSM operates by the interactions between the rotor magnet biasing flux and the magnetomotive forces generated by applied current in the stator windings. The PMSM is considered for use in high-accuracy positioning systems affected by parametric uncertainties, external disturbances, and control saturations. The three different sliding mode controls, (1) the traditional sliding mode control, (2) the method of system center, and (3) the dynamic sliding manifold approach, are applied to the high accuracy position control design for the PMSM. The sliding mode control functions rely on a high speed switching process to achieve the desired output tracking. High speed switching called chattering is usually undesirable, because chattering causes high frequency plant process dynamics which could produce instabilities in the system. The "boundary layer" approach is employed to eliminate the control chattering. The feedback linearization control for the PMSM is also designed to study its performance in tracking the desired output profile. The performance of the PMSM system with both designed sliding mode controls and the designed feedback linearization control are compared on the basis of a computer simulation. Three sliding mode controls demonstrate the higher robustness to parametric variations and external disturbances than the feedback linearization control.