A unifying approach to the robust control of electrical motor drives

A three-level cascade structure for robust velocity-tracking control of electrical motor drives is presented. Motivations for the cascade structure and the adopted number of control levels are given, DC motors, both permanent magnet and separately excited, as well as AC synchronous, induction, and variable reluctance motors are considered. With a cascade control structure, adaptation of the controller to different motors can easily be accomplished, and the robustness problems can be solved with the most suitable technique at each control level. It is shown how the explicit torque-to-current conversion block used in the control scheme can be designed to get optimal performance with respect to some cost indexes (power losses, control voltage, etc.). In addition. quite general robust algorithms based on variable structure control techniques are proposed at the different control levels, and it is shown how they can be adapted to different motors