Speed and position estimation for PM synchronous motor with back-EMF observer

This paper presents a sensorless scheme for PM synchronous motors, based on back-EMF observer. It provides full analytical description of the back-EMF observer, and the calculation of the position estimation error, taking into account the variation of the electrical parameters of the motor, i.e. stator resistance and synchronous inductance, and the variation of the feeding voltage. The knowledge of such characteristics could be used to improve the performance and the robustness of the sensorless drive by a specific real-time compensation mechanism. Verifications and comparisons are carried out in three steps: a) a time-continuous simulation model (using Matlab-Simulink,) is developed to confirm the analytical results; b) a real time simulator of the sensorless drive is used, to evaluate the influence of the time-discrete implementation; c) an experimental DSP based implementation is used to compare actual results.