Position sensorless control method at zero speed region for permanent magnet synchronous motors based on block commutation drive

A new position sensor-less method has been developed for permanent magnet synchronous motor (PMSM) drives in zero speed regions. This method utilizes the induced voltage caused by magnetic saturation (IVMS) of PMSM. The rotor position can be detected by IVMS. Furthermore, we introduce a bi-polar pulse modulation to the zero-speed region. By this modulation, both the normal and reversal direction IVMS can be detected and the bi-direction drive achieved. The principle of the proposed method and the experimental results are discussed in this paper.