Estimation of the Back-EMFs of a PMSM using an Analog Sliding Mode Observer

Sensorless techniques for driving and controlling PMSMs (Permanent Magnet Synchronous Motors) are based on the extrapolation of mechanical quantities, like angular position and speed of the rotor, from the sensed electrical quantities by means of suitable observers. In this work, a classical SMO (Sliding Mode Observer) for the estimation of the BEMFs (back-electro-motive force) of a low-power PMSM is implemented digitally on a microcontroller and the obtained estimated BEMFs are compared to an analog implementation of the same observer. This analog implementation is based on a dedicated stand-alone analog circuitry that is created on purpose. The BEMFs are then processed in order to estimate the mechanical quantities of a PMSM. Experimental results will be shown and discussed.