Virtual prototyping for a parallel-link coordinate measuring machine

Abstract

Compared with the conventional coordinate measuring machine (CMM), the parallel-link CMM has a simple structure, a higher measuring accuracy, a flexible probe posture, etc. However, the design for a physical prototype of the parallel-link CMM is very difficult because there is a non-linear relationship between the probe position and the actuating variables applied through three parallel links. For this reason, the paper reports an approach by constructing the virtual prototype for a parallel-link CMM. Firstly, the structure and the working theory of the parallel-link CMM are introduced, and then the kinematic model of it is established. On the basis of that, the three-dimensional geometric model for the virtual prototype is constructed on computer screen, and the realistic visual effect is achieved by using the strong colouring process function available in the OpenGL graphic library. After that, the kinematic simulation for the virtual prototype is realized in the virtual environment by combining organically the spatial kinematic mechanics and the graphic transformation functions, such as rotation and translation, included in OpenGL. Finally, an example of measurement simulation is given. Thereby, the correctness of the kinematic model is further verified in a virtual environment. This research lays the foundation for manufacturing the real prototype of the parallel-link CMM.