Optimal Regulation of Electric Drives With Constant Load Torque

Optimal time trajectories, based on the Pontryagin's maximum principle, are deduced for a squirrel-cage induction motor with constant load torque. These trajectories are valid for acceleration and deceleration with or without the load torque and for a loaded or unloaded motor, and ensure the minimal time transients with the stator current limited to the previously fixed value. Moreover, the optimal trajectories place the motor at the end of the transient at the minimum current point, which is close to the one of maximum efficiency, thus combining the brevity of the transients with the saving of energy. An optimal-time control system that implements these trajectories is designed. The results of the simulation of the proposed control system and the results of the experiments on a real drive are presented.