Transparent Torque Sensor-less Impedance Rendering for Low-cost Direct Drive Motor

Low-cost outer runner Direct Drive (DD) motor has been spotlighted in recent robotic applications. However, torque ripple caused by the low production quality of the motor lowers not only the torque control performance but also impedance rendering performance. This paper proposes transparent sensor-less impedance control to improve impedance rendering performance for the low-cost DD motor. The novel criteria impedance rendering transparency is derived to define the problem of sensor-less impedance control by using low-cost DD motor. Torque ripple, the main problem, is measured and analyzed to develop the high-performance impedance controller. The phase synchronization method is also added to release the implementation issue. Experimental verification has conducted the performance of the proposed method.