'Constant in gain Lead in phase' element - Application in precision motion control

TL;DR

This paper introduces a nonlinear reset-based control element called CgLp to enhance PID controllers in precision motion systems, overcoming fundamental linear control limitations and improving tracking and bandwidth.

Contribution

It proposes a novel CgLp element using reset techniques, with detailed frequency domain analysis and integration with PID for improved precision motion control.

Findings

Enhanced tracking accuracy and steady-state precision

Increased bandwidth of the control system

Demonstrated performance improvements in experimental setup

Abstract

This work presents a novel 'Constant in gain Lead in phase' (CgLp) element using nonlinear reset technique. PID is the industrial workhorse even to this day in high-tech precision positioning applications. However, Bode's gain phase relationship and waterbed effect fundamentally limit performance of PID and other linear controllers. This paper presents CgLp as a controlled nonlinear element which can be introduced within the framework of PID allowing for wide applicability and overcoming linear control limitations. Design of CgLp with generalized first order reset element (GFORE) and generalized second order reset element (GSORE) (introduced in this work) is presented using describing function analysis. A more detailed analysis of reset elements in frequency domain compared to existing literature is first carried out for this purpose. Finally, CgLp is integrated with PID and tested on one of the DOFs of a planar precision positioning stage. Performance improvement is shown in terms of tracking, steady-state precision and bandwidth.