Evaluating closed loop performance of a PM synchronous motor using a position observer

A set of linear reduced order observers which use current measurements to estimate the rotor position and velocity is proposed and analysed. Assuming that the velocity is approximately constant over the transient period of the position observer, a reduced order observer for a linearised state model is used to estimate the position. The observed position error has been shown to be bounded by the velocity error while the derivative of the observed position, under mild assumptions, gives the actual velocity. Thus an accurate velocity estimate can be generated which is iteratively used to improve the position estimate. This set of observers is now used to close the loop for position and velocity control of a permanent magnet synchronous motor. Both simulation and experimental results on the performance of these observers in a closed loop control context are presented