Research On Time-varying Periodic Disturbance Rejection Based On Iterative Learning

In real-world rotational motion servo systems,there widely exists time-varying periodic disturbance.This paper proposes iterative learning control methods for the timevarying disturbance control problem.Investigated on the pitch axis of a dual-axis rate turntable system,spatial iterative learning control is introduced,of which the parameter tuning principles are derived and design procedures are demonstrated.Simulation and experimental verifications illustrates the effectiveness of the proposed methods.The main work of this article is as follows.Firstly,the mechanism model of rate turntable is analyzed,and a numerical model of the pitch axis plant is fitted.The possible disturbances in the axis are analyzed theoretically.Experimental investigation and spectral analysis indicates that periods of the disturbances are time-varying but position-fixed.As a result,a spatial periodic disturbance model is set up for simulation.Secondly,iterative learning control is introduced,and a sort of algorithm with a lowpass filter is selected specifically for the turntable servo system.Then,a spatial feedforward iterative learning algorithm is proposed,and the convergence is analyzed by means of the contracting mapping principle.Parameter tuning principles and design procedures are derived from a convergence and performance point of view.Next,a spatial feedback iterative learning algorithm is proposed,and a equivalent feedforward structure is deduced.Based on the structure,the analysis and parameter tuning of the feedback algorithm is carried out,and the steps are provided.Thirdly,simulation studies states that the proposed methods are effective and superior to the time-domain iterative learning methods.Meanwhile,the validity of the design principles and procedures are verified.Finally,experimental investigations of both feedforward and feedback methods,which aims at time-varying disturbance control based on iterative learning,are conducted.Implemented on the pitch axis of the dual-axis rate turntable,the practicability of both methods and the corresponding parameter tuning are verified from the angle of pragmatism.