Development and evaluation of sensorless control systems for SPMSM drives in the extreme low-speed region

Sensorless algorithms for Permanent Magnet Synchronous Motors (PMSMs) are widely studied in the technical literature. Active methods are based on high-frequency voltage injection, have the advantage of working in the low-speed region and at standstill, but they have some drawbacks such as acoustic noise, additional losses, and torque ripple. Passive methods, on the other hand, do not require the injection of additional signals, however, their performance deteriorates significantly in the low-speed region. Many observers are studied in the technical literature. However, it is difficult to perform a fair comparison among the proposed algorithms since the conditions in which the experimental tests are carried out are always different. Indeed, different studies perform different tests (i.e., with different speed and torque profiles) and with different test benches. The aim of this paper is to make a fair comparison between four different passive algorithms, selected among the most promising proposed in the technical literature. For all the algorithms same tests are performed using the same Surface PMSM test bench.