The Error Analysis And Research Of On-line Inspection System

With higher level of CIMS and automation, on-line Inspection system is highlighted. It can monitor machining process of work piece with complex surfaces. The system in MC (Machining Center) using a high accuracy trigger probe to verify the quality of work piece has integrated machining and detecting functions. But because of the wok environment and moving accuracy of carrier, the lack of measuring accuracy confines the wide applications. The paper investigates the measuring accuracy of the system, and the following works are done:1. By analyzing the measurement theory of the on-line Inspection system, the factors that influence measuring uncertainty were reported. The causes of surface measuring error were discussed from hardware, software and operation, and the measures for decreasing error were provided. The expression of uncertainty in space ellipsoid form was given.2. Design of Experiments method were made to investigate the influence of detection range, measuring speed and advance angle on the measuring accuracy of the system. And the measuring accuracy along the Machining Center axis was tested.3. Least squares method was used to select a calculation model for calibration of measuring a ball, and the strategy of probe calibration test was given.4.The establishment of measuring coordinate system and alignment transformation were discussed. For work piece with reference elements such as planes and cylinder surfaces, the least squares method was used to fit reference elements which are used construction of the measuring coordinate system, and then the axes were aligned by resolving axes and translation. For the establishment of coordinate system without reference elements, First, the ICP (Iterative closest point) method was employed to search the corresponding points of the point set on surface, and the mapping of point set to point set was obtained. Then the SVD (singular value decomposition) method based on non-iterative calculation was used to solve the matrix of space transformation, iteration stop until iterative condition is fulfilled. so that the two coordinate systems were aligned.