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

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