Low speed performance improvement in a self-commissioned sensorless PMSM drive based on rotor flux observer

A self-commissioning sensorless algorithm for surface mounted permanent magnet synchronous motors is shown in this paper. The sensorless method is based on rotor flux observer and, differently from methods based on motor anisotropy, it does not require high frequency voltage injection; therefore, it does not cause additional losses and acoustic noise. The aim of this paper is to evaluate sensorless behavior in the low speed region, where performance of methods without high frequency voltage injection generally worsen. In particular, motor starting with rated torque at standstill and with intermittent torque is analyzed. Regarding self-commissioning algorithm, the estimation of motor parameters becomes crucial if this algorithm is used together with sensorless control, since the estimated values not only are used to realize the motion control (e.g., field oriented control) but also to estimate rotor position. Sensorless algorithm sensitiveness to motor parameter uncertainties is investigated. Experimental results are shown, using four different motors of various sizing.