A singular perturbation approach to sensorless control of a permanent magnet synchronous motor drive

For most surface mounted permanent magnet synchronous motors, the electrical time constant is relatively small due to its large air gap. This has been exploited with small parameter perturbation techniques to develop observers for the position and speed using measurements of currents. In this paper, a singular perturbation algorithm is experimentally evaluated for both current commutation and closed loop speed control of a permanent magnet synchronous motor drive. An improved algorithm is then proposed and related implementation issues are presented.