Control strategies enabling high frequency injections for PMSM position estimation

The aim of this paper is to present two different control approaches with injection of high frequency signals for estimation of rotor position and speed of a permanent magnet synchronous motor (PMSM) due its anisotropy. There are selected and modified two methods, a sliding mode control and a direct torque control which are not usually used for injecting high frequency signals because they do not use a PWM modulator. Therefore the injection of the high frequency signal and its backward demodulation is a quite challenging task. Another drawback of used control algorithms is the necessity of short sampling period; the main control algorithm including the injection and the demodulation (position estimation) can not be computationally demanding. It is proved by simulations and experiments that both algorithms enable injecting of the high frequency signal. All experiments were carried out on a laboratory prototype of the drive with rated power of 250 W.