Design of brushless DC position servo systems using integral variable structure approach

The authors consider brushless DC position control systems with unknown external load disturbance and plant parameter variations. Since the dynamic characteristics of such systems are very complex and highly nonlinear, a conventional linear controller design may not assure satisfactory requirements. To improve the dynamic response of such systems, an integral-compensated variable structure control (IVSC) has been proposed. The approach comprises an integral controller for achieving a zero steady-state error response under step input, and a variable structure controller for enhancing the robustness. Simulation results show that the proposed approach gives a rather accurate servo-tracking result and is fairly robust to plant parameter variations and external load disturbance