Intelligent control for linear ultrasonic motor system with H∞ robust performance

The linear ultrasonic motor (LUSM) has much merit, such as high precision, fast control dynamics and large driving force, etc., however, the dynamic characteristics of the LUSM are nonlinear and the precise dynamic model of the LUSM are nonlinear and the precise dynamic model of the LUSM is difficult to obtain. To tackle this problem, this study presents a robust intelligent control (RIC) system for the LUSM system to track periodic reference trajectories with H^∞ robust tracking performance. The developed RIC system is comprised of a recurrent neutral network controller and a robust controller. The neural network controller investigated to mimic an ideal controller is adopted to achieve H^∞ robust tracking performance. The robust controller is designed to achieve an arbitrarily small attenuation level. Finally, experimental results show that the developed RIC system can achieve favorable tracking and robust performances with unknown LUSM model.