A Model-Free Loop-Shaping Method based on Iterative Learning Control

TL;DR

This paper introduces a model-free loop-shaping control design method using iterative learning control, enabling improved performance without relying on an accurate plant model, validated through simulations.

Contribution

It develops a novel model-free loop-shaping approach by converting the problem into trajectory tracking and applying ILC, eliminating the need for plant modeling.

Findings

Successful convergence of the ILC algorithm in simulations

Enhanced loop-shaping performance without plant model

Validated effectiveness on a third-order plant

Abstract

Many techniques have been developed for the loop-shaping method in control design. While most loop-shaping methods apply a model of the open-loop controlled plant, the resulting performance depends on the accuracy of the dynamical model. This paper aims to develop a model-free loop-shaping technique. The core idea is to convert the model matching problem to a trajectory tracking problem. To achieve the desired loop gain, we need to determine the control input such that the system output tracks the impulse response of the loop gain function. In this paper, a model-free iterative learning control (ILC) algorithm is applied to solve this tracking problem. Once the ILC converges, the feedback controller that meets the desired loop gain can then be constructed. This method does not require the model of the controlled plant; hence it provides better performance of loop-shaping control design. The proposed method is validated through numerical simulation on a third order plant.