Commutation strategies for brushless DC motors: influence on instant torque

A solution to obtaining torque smoothness of a brushless DC drive within a wide speed range is presented. The voltage between the neural point of the inverter and the neutral point of the machine is not always zero. This voltage disturbs the phase currents during commutation. Since, in the case of real EMFs, the limited loop bandwidths of the current controller does not allow the currents to follow the adapted reference, a compensative and a predictive term have been added to the controller output. The robustness of the concept in the case of parameter variations is studied.>