Real-time implementation of a wavelet based speed controller for induction motor drives

This paper presents a real-time implementation of a wavelet-based multiresolution proportional-integral-derivate (PID) controller for accurate speed control of an induction motor drive under system uncertainties. A field oriented induction motor drive model is used to decouple the flux and torque components of the motor dynamics. The discrete wavelet transform is used to decompose the error signal between the actual and estimated speed into different frequency components at various scales. The wavelet-transformed coefficients of different scales, which represent many underlying phenomena such as process dynamics, measurement noise, and effects of external disturbances, are scaled by its respective gain and then added together to generate the control signal. The performance of this newly devised wavelet controller is evaluated by simulation results as well as by experimental results. The complete vector control scheme incorporating the proposed controller is successfully implemented in real-time using the ds1102 digital signal processor board for the laboratory I-hp induction motor. In order to prove the superiority of the proposed controller over the conventional controllers, a comparison between the proposed and the conventional proportional-integral (PI) controller based systems is made at different dynamic operating conditions.