Sensorless vector control of PMSM drive using heterodyne technique

Sensorless speed and position control of permanent magnet synchronous machine still is a challenge especially for surface mounted permanent magnet synchronous machines. This paper describes the high frequency signal injection based technique for control of surface mounted permanent magnet synchronous motor. Due to the fact that it does not use the fundamental machine model, which fails at standstill it is possible to control the speed and position of the machine even at low speeds. The observer tracks the saliency that exists in the machine and based on that calculates the speed and position. High frequency signals are injected in machine´s stationary axis and demodulation of responding H.F currents gives speed and position, which is independent of machine parameters. So this technique is independent on machine parameters and easily adaptable to different machines. As only the high frequency currents are processed for the speed and position estimation no extra hardware circuitry is required besides that for vector control scheme of AC drives. Vector control of speed and position was carried out on a single fixed point DSP processor TMS320F2811.