Grid Distance Method in Three-Dimensional Measuring Path Planning and Collision-Free Analysis

• Main Author: 歐榮年
• Other Authors: 林榮慶
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/86811723025759578227

碩士 === 國立臺灣科技大學 === 機械工程系 === 88 === The main objective of this study is to increase the measuring speed of coordinate measuring machines (CMM) and analyze the shortest measuring path and define the barrier-free path under different measuring conditions. Three types of workpiece are defined in this paper. The simulated annealing method is proposed for path planning, while the grid distance method is used for planning the barrier-free path in this paper in order to improve the measuring speed of CMM. The first workpiece defined in this paper is a flat workpiece, on which there is a simple spherical protrusion object as defined in the paper. Though the minimum of 4 measuring points are required for the flatness of a flat surface, the authors decided to use 6 measuring points due to the dimensions of the flat surface. First, the simulated annealing method is used to plan the shortest measuring path. Then the grid distance method is used to conduct barrier-free analysis on the interference path of the protrusion object on the workpiece surface in order to obtain the optimal barrier-free path. Next, a flat surface workpiece plus a fixture are considered in this paper. Generally speaking, only the fixture dimensions are known after the fixture is designed. Thus, homogeneous coordinate transformation is adopted in this paper to transform fixture dimensions (relative to the original point of fixture), i.e. the so-called local coordinates, into the global coordinates relative to the mechanical original point. Thus, the simulated annealing method can be adopted to plan the shortest path, while the grid distance method can be used to plan the barrier-free path involving the protrusion object on the workpiece surface. Finally, a workpiece with free-form surfaces is studied. In this paper, a simple feature device is added as a protrusion object on the workpiece flat surface. First, the workpiece is projected onto a 2D surface (denoted as xy flat surface in this paper). Then, the simulated annealing method is used to plan the shortest path on the 2D surface. Next, the grid distance method is used to plan the barrier-free path involving the protrusion object on the projected surface. Finally, an equation derived in this paper is used to obtain the free-form curves of all paths including the barrier-free path. In this case, CMM can follow the free-form curves and enable the measuring probe to move quickly to the location of measuring points along the contour of free-form surfaces to execute measurement.