| Abstract |
PM synchronous motor drives are widely used for high-performance direct-drive servo applications
where torque smoothness is an essential requirement. However, parasitic torque pulsations do exist in
PMSM drive. These oscillations are due to the non-sinusoidal flux density distribution around the airgap,
variable magnetic reluctance of the air-gap due to stator slots, residual DC offsets and scaling
errors in phase current measurement. A consequence of these torque ripples is speed oscillations that
deteriorate the drive performance particularly at low speeds. In this paper, we propose a simple
modular iterative learning control (ILC) scheme which generates a compensation reference current
based on the error between the desired and actual motor torques. When this compensation current is
augmented with the main reference current, the resultant current reduces the periodic torque ripples.
Being a modular unit the proposed ILC controller can be applied in conjunction with the conventional
(open-loop) torque controller and therefore can be easily integrated to any of the existing PMSM drive
system. Experimental test results obtained from a 1.2 kW PMSM drive system validates the
effectiveness of the proposed ILC control scheme in reducing periodic torque ripples. |
