Algorithm for rotor position and speed estimation in permanent magnet ac motors

This paper presents an algorithm for estimating speed and rotor position in permanent magnet synchronous motors (PMSMs). Stator voltage and current measurements are used to build a nonlinear reduced-order observer. Back electromotive forces (EMFs) are estimated first, and then rotor position and speed are reconstructed from the estimated EMFs. The observer is implemented and tested with a commercial permanent magnet ac drive (PMACD). The experimental results show that the observer gives a good estimation of speed and rotor position over a wide speed range.