Extrinsic calibration and kinematic modelling of a laser line triangulation sensor integrated in an intelligent fixture with 3 degrees of freedom

Abstract

This article presents the kinematic modelling for the extrinsic calibration of a laser line profile sensor integrated in an intelligent fixture. It aims to characterize the real 3D shape of flexible parts when they are clamped to ensure suitable stiffness for machining processes, aiding to define the machining path to improve the precision of the process. This tool consists of two linear axes and a rotary axis (3 DOF) which enables scanning the area of the part to be processed automatically. In order to carry out the accuracy evaluation of the intelligent fixture, some methods present in the state of the art have been considered and compared. Moreover, in order to design and identify the most suitable calibration procedure a previous simulation process is carried out based on sensitivity analysis. To complete the study, a test piece has been scanned with the intelligent fixture and compared with an external metrological frame employed as a ground truth. In addition, a characterization of the geometric performance of the fixture's linear actuators is carried out to check the geometric performance and its influence on the extrinsic calibration process accuracy. The results of this article show the importance of performing simulation processes in order to define the best measurement scenario for extrinsic calibration. Besides, it demonstrates the influence of the method used to perform extrinsic calibration in order to obtain good precision in the measures, where the geometric performance of the drives have a decisive influence.