Sensorless Control of Multi-Motors PMSM using Back-EMF Sliding Mode Observer

This article presents a sensorless control system based on back-EMF (back electromotive force)sliding mode observer for control of rigid coupling of PMSM multi-motors. The back-EMF e
_α
and e
_β
are provided by a sliding mode observer in order to estimate the rotor speed and position. The main advantage of the sensorless control consists in eliminating the speed transducers thus contributing to the increased reliability of the entire system. The control structure presented is cascaded, following the FOC (Field Oriented Control)principles, where the inner current loop has the reference I
_d
set to be equal to zero, and the I
_q
reference is set by the PI-type speed controller in the outer loop. Considering that the load torque distributed to the two motors can be balanced or unbalanced, the main task of the multi-motor PMSM sensorless control system is to maintain the same speed of the slave system and the master system and that both systems match the required speed profile. Real time implementation of the multi-motor PMSM sensorless control system is recommended by the good results obtained from numerical simulations.