Research On Reverse Design For Autobody Parts Based On Engineering Rationality

The Reverse-engineering is an important mean in the automobile body and the development of spare part. The reversion of the automobile body parts and the surface is also a time-consuming manual process, which requires repeated evaluation and modification by engineers using human-computer interaction approach.In this paper, it describes the general approach of the curves and the surfaces of the automobile body parts and points out the deficiencies of the existing methods. The existing reverse tools are mainly connected with concrete curves and surfaces which are just parts of the whole complex body models. In fact, there are complex relation between these ones and others. Besides, concrete curves and surfaces also must meet the functional requirements. The existing function cares about the single curve and surface and it neglects the requesting and restraint. Besides, the evaluation indicator is unitary. To some extent, it affects the rationality of reverse results more or less. In order to restore the rationality, the engineer repeated adjustments in the curves and surfaces based on comprehensive consideration of the various factors in the later.In this paper, what have been discussed is that optimization technique will be applied in the reverse process of the automobile body and auto parts, and to various internal, external association and requirement into design constraints, to make the curve, surface and cloud point data matching through the optimization process. The introduction of more constraints will help to maintain the rationality and availability of the result. Meanwhile, as parameters optimization results, curve and surface will be a parameterized model which is very beneficial for the editor to modify.Based on these ideas on above, it starts the research and completes the basic process using secondary development in CATIA platform.1. Hole optimization based on the probability statistical principleIn the auto-body measurement, it doesn't need high scanning density in surface expression, but the exact expression of the hole's border needs to maximize the density scanning density in order to describe the hole's border. This is a contradiction, denser cloud point lead to efficiency and thinner cloud point lead to boundary of the bole. According to this problem, this paper analyze the hole near the boundary and meet the established accuracy based on statistical theory, and find that for some certain size holes always have enough cloud point near the border in the thin scanning density. As a result, it is possible to get high hole precision in thin scanning density. The paper completes the reverse module of the hole in the CATIA platform.2. Optimization base on profileAs a part of the profile, there are various geometric constraints between various lines, such as vertical, parallel, symmetry and so on. The current reverse function often discussed on the line, take seriously in part and ignore the holistic. This paper s tarts research on the contour angle, prevention at parameterized contour model that include internal constrained level, replace the curve reversion to profile revere in order to maintain the intrinsic rationality.3. Surface optimization based on technology templateCATIA, Imageware and other soft wares only offer surface reconstruction capabilities, however only considering the precision and smooth, it will not adapt the complexity model of automobile body. Reverse engineer often to give up these functions, complete reverse design using the way close to conventional design, which can adapt to the requirements of the auto-body design except time-consuming. According to the above, this paper put forward surface optimization based on technology template to various function of conventional design and constructing relevant parametric model. To aim to specifically cloud points, engineer define different model to match the cloud points by optimization. On the one hand improve the ability of engineers to the control surface; on the other hand reduce the time of manual editing.