Closed-loop control of torsional harmonics in a permanent magnet synchronous machine without use of a position encoder

A hall-effect sensor-based position observer is developed and coupled to a torque ripple sensor to provide encoderless feedback-based torque ripple mitigation. The observer includes a routine to compensate for offset in placement of sensors, which is shown to be necessary for effective control of torque harmonics. Using the position observer, the overall cost of ripple mitigation is significantly reduced, with relatively minor penalties in system performance. The strategy has been validated in simulation and hardware