Sensorless position control of permanent magnet motors with pulsating current injection considering end-effect

The sensorless position control of permanent magnet motors is successfully implemented superimposing an high-frequency voltage signal on the voltage reference or adding a high-frequency current signal to the current reference. The former approach is usually preferred because of its simplicity although the latter one may allow better performance. This paper presents a new algorithm for sensorless control of low-saliency permanent magnet synchronous motors based on high-frequency sinusoidal current signal injection into the d-axis. Differently from the related literature, the position information is derived by analyzing the measured high-frequency currents. The amplitude of the d-axis voltage reference is also exploited to improve performance. A proportional integral controller plus resonant term is adopted to ensure accurate tracking of both the dc and high-frequency components of the d-axis current reference. The main advantages of the proposed approach are the increased accuracy and sensitivity with respect to the approach based on voltage injection, the insensitiveness to inverter non-linearities that are compensated by the current regulation loop, the actual control on the injected current value, and practical absence of acoustic noise. Experiments on a linear tubular permanent magnet synchronous motor prototype have been carried out to verify the above mentioned advantages. The paper also presents a discussion of the parameters of proportional integral controller plus resonant term.