Adaptive feedforward control to compensate cogging torque and current measurement errors for PMSMs

Torque ripple minimisation is achieved by an adaptive feedforward control method to reduce cogging torque and current measurement errors. Experiments have been conducted to show that torque ripples are highly sensitive to changes in current offset and cogging torque. An easy way to adapt to cogging torque changes (due to temperature) is proposed and implemented after an initial estimation of the cogging torque is done. This initial estimation is necessary for manufacturing inaccuracies and ongoing adaptation is to cope with operating conditions changes. Higher harmonics of the cogging torque can also be compensated through this way. Current offset which contributes to a large proportion of the torque ripple is also compensated through an adaptive method. The advantages of the proposed scheme combine the benefits of preprogrammed waveform methods which are easy to implement and a simple adaptive system to effectively reduce RMS torque ripple factor from 11.30% to 1.7%.