Feedback-Aided Iterative Learning Control With Its Implementation In A Linear Motor System

Iterative learning control (ILC) is a versatile control technique for systems which perform repetitive tasks over a finite interval. The control performance of the systems gradually improves on the basis of previous actual operation data. The final output trajectory meets the requirements. In general ILC algorithms, it is assumed that the initial state value of the plant is equal to that of desired trajectory for perfect tracking. However, due to the limitation of positioning accuracy, it is hard to set the initial state value of the plant to that of the desired trajectory exactly.This thesis presents feedback-aided PD-type ILC strategies. Sufficient conditions of convergence for the learning algorithms are derived, and the converged output trajectory is given. The initial rectifying actions are applied to eliminate the effect of initial shifts. Experiment results of permanent magnet linear synchronous motor are presented to demonstrate effectiveness of the proposed algorithms.The main work and contributions of this thesis are summarized as follows:1. In order to improve the traditional PD-type ILC algorithms, feedback-aided ILC strategies are proposed. The control methods are applied to linear time-invariant and nonlinear systems. The algorithms accelerate the convergence speed and improve the system stability. Sufficient conditions of convergence for the learning algorithms are obtained.2. Two initial rectifying actions are applied to eliminate the effect of fixed initial shifts. Sufficient conditions of the control strategies are given for linear systems and nonlinear systems. Systems finial output converges to the desired one in a given finite time.3. Feedback-feedforward ILC strategies are proposed for both linear time-invariant and nonlinear systems. The feedback controller stabilizes the systems and reduces interference from the noise/uncertainty. Initial rectifying actions are applied for perfect tracking in a given finite time.4. The proposed algorithms are applied to position control of the linear motor servo systems. Experiment results are presented to demonstrate effectiveness of the proposed algorithms.