Design and Control of an Active Stage for Suppressing Motion Induced Vibration in Optical Inspection Systems

Abstract

Along with the development of industrial technologies in various manufacturing and metrology applications fast positioning and vibration suppression play important roles in virtually all tasks requiring high speed of maneuvers with sufficient motion accuracy One typical example is on the optical inspection system it performs numerous product defect inspections by fast moving to the desired inspection locations and take images for defect evaluation Due to the inherent structural compliance and the inertial force generated during fast movement residual vibrations will be inevitable for the point-to-point movement and this implies that additional settling time would be required for avoiding blurred images Obviously mounting a controllable stage on machine can effectively reduce residual vibration thereby improving inspection efficiency Therefore this work develops an active stage with rubber bearings and flexible structure equipping with a CCD camera designs the corresponding controller and verifying the vibration suppression capability of the active stage system under the action of the linear motor In terms of stage design the four sets of rubber-bonded aluminum blocks form rubber bearing which provide stiffness of the stage and a flexible beam is mounted on stage for imitating the camera-support structure of the real machine The model parameters are identified by dynamic testing and the mathematical model of the active stage is obtained In terms of controller design this work adopts both loop transmission (L T ) shaping and input shaping methods Through the L T method two schemes called A and B have been developed successively to handle the positioning and vibration suppression On the issue of stage positioning the overshoot and settling time of the A scheme are 9 2% and 0 16s Once it cooperating with input shaping scheme the corresponding performance can be further reduced to 7 1% and 0 09s On the vibration suppression issue the residual vibration and settling time of the A scheme are originally 154 1% and 1 3s and are improved to 31 0% and 0 60s with input shaping schemes Therefore the shaping-control integration can effectively improve the system controlled performance in comparison with the results from control only Meanwhile in order to further improve the vibration suppression in feedback control we also develop the B scheme and it successfully reduces residual vibration and settling time to 30 4% and 0 25s Finally essential AOI inspection experiments are carried Based on captured image the active stage employ above schemes can indeed reduce the blur level to achieve a faster inspection This work successfully confirmed that the active stage control system can effectively reduce residual vibration during optical inspection thereby improving inspection efficiency

Date of Award	2019
Original language	English
Supervisor	Kuo-Shen Chen (Supervisor)