Analysis of Settling Response to Deterioration of Ball Bearings in Galvanometer Scanners

Abstract

This paper presents a method for analyzing the settling response to the deterioration of ball bearings, such as fretting damage, of a galvanometer scanner. A galvanometer scanner is a type of swaying motor used in laser-drilling machines. It is able to position a laser at more than 2400 points per second with a positioning error of less than 3μm. Analysis of the settling response is important to the precise positioning of galvanometer scanners. The settling response of the galvanometer scanner was decoupled into each vibration-mode component through Prony analysis. This experimental modal analysis method was used to detect modal parameters from the time series data. The vibration modes from the pole-zero configuration of a closed-loop system where normalized frequencies was near the first torsion mode were caused by changing the frequency response characteristics of the controlled object. A galvanometer scanner with fretting damage to its ball bearings was analyzed using this method, and the relationship between the position error of the settling responses and the deterioration of the ball bearings was quantified by focusing on the initial amplitudes of the overdamping modes.