Robust observer based VSS tracking control of an IM servodrive

A control approach for robust accurate trajectory tracking of an induction motor (IM) servodrive based on variable structure system (VSS) theory is described. The modified sliding observer of the rotor magnetizing current is used to improve flux control. The synthesis of the VSS controller for motion control is based on the PI estimator of torque disturbance and estimated value of acceleration. The developed control algorithm eliminates the initial conditions mismatch, parameter variations and external influences, and also assures accurate trajectory tracking by the prescribed dynamics. The validity of the proposed algorithm was verified by simulation and experiment. The experimental system consists of a T 805 transputer and a MC 68000 microcontroller and enables parallel processing.