High Order Feedback-Feedforward Iterative Learning Control Scheme with a Variable Forgetting Factor

Hongbin Wang,Jian Dong,Yueling Wang

doi:10.5772/63936

Abstract

In this work, we present a new iterative learning control (ILC) scheme for a class of non-linear systems with uncertain and non-repetitive disturbances, in order to achieve perfect tracking by proposing a high order feedback-feedforward ILC algorithm with a variable forgetting factor. The high order feedback-feedforward iterative learning controller can fully apply the previous control data to the system, which allows the system to track expectations more rapidly and precisely. Introducing a variable forgetting factor can weaken the former control output and its variance in the control law, while strengthening the robustness of the ILC. Through rigorous analyses, we demonstrate that uniform convergence of the state tracking error is guaranteed under this new ILC scheme. Simulation examples are also included to demonstrate the feasibility and effectiveness of the proposed learning controls.

Highlights

iterative learning control (ILC) is effective for handling repeated control processes
A class of non-linear timevarying systems without uncertainty, disturbance and initialization error was discussed in previous studies for high order ILC algorithms
In this paper, we propose a high order feedback-feedforward ILC algorithm with a variable forgetting factor

Summary

Introduction

ILC is effective for handling repeated control processes. It has been widely used in industries for the control of repetitive motion, such as robotic manipulators, hard disk drives and chemical plants, because of its structural simplicity and effective learning ability in the controller design process [1,2,3]. Learning per‐ formance can be expected to improve more as a greater number of previous iterations are used This is called high order ILC, which was first proposed [7] for the tracking control of repetitive systems. A class of non-linear timevarying systems without uncertainty, disturbance and initialization error was discussed in previous studies for high order ILC algorithms. To overcome this problem, feedback-feedforward high order ILC [8] was proposed in the control system, despite uncertainties and disturbances. In this paper, we propose a high order feedback-feedforward ILC algorithm with a variable forgetting factor. The contribution of this paper is the combination of high order feedback-feedforward ILC and a variable forgetting factor.

Problem Statement

Designed Controller and Variable Forgetting Factor

Convergence Analysis

Simulation

Conclusion