Study on torque ripple suppression of permanent magnetic in-wheel motor under rotor eccentricity by separated harmonic current injection

Abstract

In electric motorcycles and light electric cars, permanent magnetic synchronous motor (PMSM) of outer-rotor type are preferred, due to its concise structure and flexible control. Since the body mass and road impact causes vertical eccentricity on shaft bearings, vibration and noise take place during vehicle cruising along with a torque and speed ripple. The torque ripples contain significant features closely related to eccentricity, and those special components can be compensated by an injection current with proper frequency, phase and amplitude. In this paper, a novel control method is used to regulate the injection current to restrain torque ripples. By coarse turning with quadratic spline curve fitting and fine turning with successive approximation, the method can response sudden disturbance and drive the specific torque ripple to minimum in a very short time, so that the performance on ride comfort and handling stability of the vehicle could be improved. Experimental tests show that the method performs favorably with rapid convergence and validity.