VSS robust control techniques for AC motor drives

Robust control of AC asynchronous motor drives in the presence of strong parameter uncertainties is considered. Due to the different bandwidths associated with the controlled variables, a cascade structure is used. A multivariable sliding mode closed-loop controller with a hysteresis region is used to transform the voltage source inverter into a current source (CS) one. On the assumption of a CS inverter, the field-orientation principle is adopted for the design of a simplified torque and flux controller. A modified binary controller, ensuring robustness to mechanical parameter variations, is used in the outer velocity loop of the cascade control structure. Modifications to the basic binary controller are introduced to improve tracking capabilities. Performances of the proposed structure are verified by simulating a robotic application. Tracking of a velocity trajectory for a single-link robotic arm is considered. Simulation results show the feasibility and good performance of the robust control structure.