Suppression of Torque Ripple Caused by Misalignment of the Gearbox by Using Harmonic Current Injection Method

This article proposes a method to suppress the torque ripple caused by misalignment of the gearbox. Misalignment is a common fault caused by the manufacturing tolerances, and generates torque ripple. Therefore, even if a constant electromagnetic torque is transmitted from the motor to the gearbox, a large torque ripple may be transmitted to the load because of misalignment. In the proposed method, a harmonic current injection method, in which harmonic current is injected into the armature current, is used to suppress the torque ripple produced by misalignment. The amplitude and phase of the harmonic current are calculated using the misalignment torque ripple, and a method for estimating the misalignment torque ripple, which does not require a torque sensor, has been presented. Using the estimation method and harmonic current injection method, the misalignment torque ripple can be suppressed effectively. The phenomenon of torque ripple production by misalignment is analyzed, and a current control algorithm based on harmonic current injection method is proposed. The effectiveness of the proposed method is verified through experiments at various load torque. Using this method, a high degree of torque control can be achieved with even a low-quality gearbox.