Load torque observer for minimising torque ripple in PMSM

Permanent magnet synchronous motors generate parasitic torque pulsations owing to distortion of the stator flux linkage distribution and variable magnetic reluctance at the stator slots. The consequences are speed oscillations which deteriorate the performance drive in various applications. In this paper, the pulsating torque are analysed and modelled under Matlab/Simulink using an approach lead by fields calculations (flux2D). With this model, a dynamic and robust torque control system for PMSM drives based on a RST controller and on load torque observer is studied. The regulator´s design is based on a pole placement strategy. The instantaneous speed and disturbance torque are accurately estimated what enables to define active control schemes which modify the excitation to correct any of the nonideal characteristics of the motor. The drive´s performance with regard to load torque variation and ripple torque are then analysed.