Optimal Commutation Laws in the Frequency Domain For PM Synchronous Direct-Drive Motors

This paper presents a new model for torque generation of permanent-magnet synchronous motors and their control based on Fourier coefficients. A new commutation strategy delivers ripple-free torque and simultaneously minimizes copper losses for the case when the motor’s servo amplifier dynamics are negligible. However, multipole motors give rise to high frequency control signals, and often the dynamics of the current amplifier are no longer negligible. For this case, we present a new commutation strategy which minimizes the torque ripple and the velocity induced change in the torque transfer function. The performance of both commutation laws is validated via simulations based on experimental data from a synchronous motor. Minimal computational requirements make these algorithms ideal for real time implementation.