A New Wavelet-based Speed Controller for Induction Motor Drives

This article presents a novel speed controller based on multi-resolution decomposition analysis of the discrete wavelet transform for vector-controlled induction motor drives. The field-oriented control principle is used to decouple the flux and torque components of the induction motor dynamics. In the proposed controller, the discrete wavelet transform is used to decompose the speed error between the actual and command speeds at various scales. The control signal is generated using the wavelet-transformed coefficients of speed error of different scales. It has been found that these coefficients can represent the cumulative effect of motor drive uncertainties such as parameter variations, measurement noise, frictional variation, and external torque disturbances. The performance of this controller is evaluated in both simulation and experiments. The complete vector-control scheme incorporating the proposed controller is successfully implemented in real time using the ds1102 digital signal processor board (dSPACE, GmbH, Paderborn, Germany) for the laboratory 1-hp induction motor. The experimental results validate the robustness and, hence, justify the applicability of the proposed controller for the induction motor drive to be used in high-performance drive applications. In order to prove the superiority of the proposed controller, a comparison between the proposed and the conventional proportional-integral and proportional-integral-derivative controller-based systems is made at different dynamic operating conditions.