Research On Surface Measuring Path At CMM Based On PRM

In modern manufacturing industry the product has two manifestations as material object and information model. The latter contains most creative and valuable part in the product manufacturing, especially for free-form surface parts, which are widely used in modern industry. To extract three-dimensional characteristic information which precisely reflects material object directly influences the verisimilitude of material object model as well as the effect of reverse engineering follow-up data processing and final modeling. Therefore, effective three-dimensional geometric figure measurement for free-form surface part has practical significance in mathematical modeling as well as numerical control and product surface quality evaluation.Based on the literature review of studies home and abroad, combining the college's purpose of using and developing advanced manufacturing equipment, the thesis discusses measurement path planning of three-coordinate measuring machine (CMM) from the perspective of free-form surface, which is of great difficulty in complicated surface measurement in reverse engineering. The fundamental idea of coordinate measuring for surface measurement, as well as its key technology-measurement path planning, is investigated in the thesis. Based on accurate description of measurement path planning, the study makes a synthesized analysis of existing solutions to complicated curved surface measurement path planning from the angle of hardware and software and points out the shortcomings of existing solutions. The originality of the study lies in its dialectical and effective application of probabilistic roadmaps method (PRM) of space path planning for eluding obstacle movement in movement planning area into measurement path planning of CMM. Combining the frame of PRM, the study divides the measurement process into pre-measuring and on-line measuring. In pre-measuring stage, probe in measuring environment as well as objects to be measured are projected to the point, side and object to be measured zone in probabilistic roadmaps of C-space, which effectively avoids the necessary impact detecting in on-line stage and minimizes searching space in traditional method. In on-line stage, a reasonable measurement to free curved part of unknown CAD model is produced according to probabilistic roadmaps. Thus, path planning and predicating can be realized. Moreover, probe and its path following problem can be solved. In this way, probe path can follow the change of surface timely, which makes the measurement feasible, safe and effective. Besides, the thesis makes an elementary analysis of measuring software construction.