Design of position detection strategy of sensorless permanent magnet motors at standstill using transient finite-element analysis

Sensorless control of permanent magnet (PM) motors at standstill and low speed is very challenging to implement. In this paper, a methodology to design and optimize the position detection strategy of PM motors using transient finite-element analysis (FEA) of magnetic field is presented. It addresses effects arising from both the iron core saturation and the transient characteristics of signals. A combined inductance which is sensitive to the rotor position throughout the complete cycle is proposed for the realization of position detection. The advantage of the proposed novel algorithm is that the rotor's position at low speeds down to standstill can be easily and robustly detected. A two-phase PM motor with salient structure is used to serve as an example to demonstrate the method.