A variable-structure control law for brushless DC motors supplied by six-transistor inverter drives

A variable-structure strategy (VSS) for the control of brushless DC motors (BLDCMs) for servo applications is described. A VSS control method is proposed and examined whose variable structure nature is commensurable with the inherent characteristics of the inverter. Also presented is a control law whose formulation is based on the conventional design procedure associated with VSSs. Using computer simulations, a comparison between the two methods is presented. Compared with the conventional VSS design, the proposed approach eliminated the trail-error procedure of proper gain selection. The simulation results also show that this controller provides good robustness against parameter error and external torque disturbance. The simulation results suggest that, in the step input case, the proposed VSS is better than the conventional VSS when driving a nonlinear load