Enhanced Speed Control of a Drive With Rejection of Periodical Disturbances

The present work deals with the enhancement of the speed control of an electrical drive under a repetitive mechanical load. In such a system, the load torque changes periodically according to the angular position of the rotor causing speed oscillations. In this article, two methods for mitigating speed oscillations are proposed. One is based on a load torque feedforward control scheme, where the load torque is presented in the form of Fourier series and estimated via the calculation of the Fourier coefficients by taking into account the cyclic characteristics of the driven machine. The other method is based on harmonic speed control that aims to mitigate specific harmonics in the speed error. The design procedure of the harmonic speed controller is presented in detail, providing a full insight into the use of the harmonic controller. Experiments were used to verify and compare the effectiveness of the two proposed methods.