Evaluation of ripple compensation algorithm for PM motors

A torque ripple compensation algorithm has been evaluated during tests on a permanent magnet synchronous motor (PMSM). A control system with the ripple compensation algorithm implemented was compared with a conventional control system. The control systems were implemented in Simulink and tested using dSPACE. The results are presented as a relative comparison of the sixth harmonic torque ripple between the control systems. The tests show that the ripple compensation algorithm did have a positive effect on the sixth harmonic torque ripple which was reduced. At 20 rpm with nominal load the reduction of the sixth harmonic torque was approximately 70 %, but went down as the speed increased, due to the mechanical resonance of the test-rig. The sixth torque harmonic is the most important component to reduce, since it is the main contributor of the torque ripple in servo motors of the kind used in servo applications.