Enhanced sensor-less speed control approach based on mechanical offset for dual-stator brushless DC motor drives

In this study, the radial displacement of the stators is proposed to improve sensor-less speed control for dual-stator brush-less DC motor drives. The mechanical offset between stators leads to the double number of edges in the zero-crossing signal (ZCS) and thus, a more accurate speed estimation. Moreover, updating the speed in the control process will become faster that can decrease speed control error. As stators' axes are displaced 90 degrees electrical, the distance between ZCS edges becomes symmetrical. Therefore, it would provide a uniform estimated speed updating, and can effectively decrease speed ripple. Also, asymmetrical stators displacement can decrease speed ripple compared to the aligned structure when the distance between adjacent zero-crossing points is appropriate. In addition, stators displacement is well known as an efficient technique to decrease torque ripple. This idea is verified via computer simulations and experimental results.