Instantaneous torque control

Abstract

Permanent-magnet brushless dc drives can have excellent performance in direct-drive servo applications provided suitable control techniques are implemented. A digital torque control scheme is proposed which uses the variable structure approach to generate the on-off switching patterns (vectors) directly with a microprocessor. At every switching instant, the optimum vector is selected to force the developed torque to follow the torque reference while keeping the direct axis current as close to zero as possible for the highest efficiency. The instantaneous torque feedback signal can be estimated from the terminal quantities of the motor. Simulation results are presented.