As the pioneer of model reference adaptive control (MRAC) method, MIT control strategy is still used in various practical applications. In this paper, MIT is applied to the speed control of ultrasonic motor, trying to use a relatively simple control method to obtain good control performance. However, MIT control strategy only adjusts the gain, so it is difficult to achieve a large correction of the system's dynamic characteristics, which limits the actual performance. To solve this problem, two improved MIT control strategies based on iterative learning are proposed in this paper to enhance the control performance. Both methods adopt the P-type iterative learning control (P-ILC) strategy with simplest structure. One is to connect the P-ILC controller with the MIT controller in series to adjust the given value of the MIT controller in real time. The other is to use the P-ILC controller to adjust the adaptive gain of the MIT controller in real time, so as to enhance its control freedom and adaptive ability to deal with complex objects. The experimental results show that the proposed control strategies have their own advantages and can significantly improve the control performance after finite iterative learning processes.
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