Proposal of position sensorless control and torque ripple compensation based on torque sensor feedback

This paper presents the following two methods based on torque sensor feedback: new position sensorless control method for surface-mounted permanent magnet synchronous machines (SPMSMs) and torque ripple compensation. The position sensorless techniques can be classified into two categories: the techniques based on the back electromotive force (back-EMF) and the techniques based on the high frequency injection (HFI). However, in general, the former category is weak in low speed, and the later one can not drive without the saliency. Furthermore, both of the categories have a problem that torque ripples are caused by transient position estimation errors. Meanwhile, in the field of robot research in recent years, the developments of torque sensors are active. This situation has suggested that small and reasonable torque sensors will be available in the foreseeable future. Therefore, we developed the torque sensor which can be attached to SPMSMs and the new position sensorless control method based on the torque sensor feedback. Using the proposed method, the position sensorlesss drive corresponding to the entire speed range including zero is achieved. Moreover, this method is applicable to SPMSMs which do not have saliency. In addition, the torque ripples are well suppressed. Effectiveness of the proposed method is verified by experimental results.