High performance sensorless controls based on HF excitation: A viable solution for future AC motor drives?

Sensorless AC motor control strategies exploiting the injection of high frequency signals to detect magnetic, or geometrical, saliencies have been investigated since '90s, in order to overcome key deficiencies of model based methodologies. However, even if several techniques are nowadays practically used on some market available industrial AC drives, the development of a methodology of general applicability is still an open problem. In this paper the authors outline the state of the art in the development of control strategies based on the injection of high frequency signals. Implementation issues are then described, highlighting the challenges that must be won, in order to made sensorless motor drives exploiting high frequency signal injection, fully pursuing their sensored counterparts, in terms of operating range extension, performance, robustness and reliability.