A new control scheme for improving disturbance rejection in speed control of permanent magnet synchronous motors

The major hurdle encountered in achieving high performance in servo speed control is the occurrence of large relative errors at low speeds due to torque variations. In this paper, it is shown that this problem can be tackled in the case of synchronous motors, by keeping the stator current and the rotor flux nonorthogonal and including an inner position control loop to improve the transient behavior of the system. Such a scheme substantially improves disturbance rejection at the cost of accentuating the nonlinearities of the system and increasing the copper losses. In view of the pronounced nonlinearities encountered here, adaptive control using neural networks is resorted to.