Patent ID: 8981692
Filing Date: 2015-03-17
Classification: H02P

Abstract:
1. An electric motor system comprising: a motor configured to produce a torque signal in response to a torque command, the torque signal having a fundamental frequency component, a first ripple harmonic and a second ripple harmonic; wherein the first ripple harmonic is an integer multiple of the fundamental frequency component and the second ripple harmonic is an integer multiple of the first ripple harmonic; a controller operatively connected to the motor and configured to generate a first and a second cancellation command to cancel the first and the second ripple harmonic, respectively; wherein the controller is configured to project the second cancellation command onto the first cancellation command through a transformation matrix to thereby generate a combined cancellation command to simultaneously cancel the first and the second ripple harmonic in the torque signal; wherein the transformation matrix is dependent on a first harmonic angle (θ wherein the transformation matrix is an inverse matrix of a first matrix (T and wherein the controller is configured to generate a ripple reduction signal in response to the torque command, the ripple reduction signal being dependent upon the combined cancellation command and predetermined characteristics of the motor.