Reverse Remodeling For Automobile Body Surface With Multiple Constraints Based On Siemens NX

Automobile body surface reconstruction which based on point cloud data is the key content in automobile body modeling and reverse design. The existing commercial reverse software can quickly realize surface automatic reconstruction that based on point cloud data, reduce the product development cycle of new products, significantly improve the efficiency of reverse design. On the contrary, the corresponding automatic surface reconstruction has not been widely accepted in the process of body surface reverse reconstruction, in many cases, the designer still had to use a time consuming manual modeling method to finish surface reconstruction.Making some analysis of this phenomenon, the reason mainly has two aspects:on the one hand, a lot of reverse CAD software developers want to perform complex surface fitting through the analytic method, this kind of method is difficult to achieve due to different surface types in the practical engineering; on the other hand, reverse software can automatically construct the corresponding surface for the segmentation point cloud data, and make the surface satisfies the requirement of certain accuracy and smooth. But it cannot carry out effective control in the surface geometry and the connection between adjacent surfaces. However, auto-body is complex geometry that composed of a large number of different forms of surface, the surfaces have different kinds of geometric constraints and design requirements, the conventional automatic surface reconstruction based on point cloud data is insufficient to meet the complex requirements.According to the above problem, this paper attempts to introduce the optimization method into auto-body surface reverse process, turning a variety of evaluation index and design constraints into optimization constraints, embedding the complex geometric rules in parametric model, and optimizing the parametric model with the cloud point as reference. Using optimization iteration instead of the repeated manually modify, eventually generate the parametric surface that satisfy a variety of engineering requirements, and that parameterized feature also facilitate the later editing and post-modification.This article is based on the second development platform which provided by the Siemens NX system, taking the relatively typical auto-body surface reverse as example. Introduced the parametric modeling approach in different body surfaces, added a variety of constraints on the model and then expressed the diverse restraints with the corresponding parameters. Through the parameterized design, the knowledge that embedded in model to ensure the surface can be automatically updated in optimization process, making the model match the point cloud data. The result show that the method and train of thought have certain reference value, the parameterized inverse method that based on optimization ensures the model "rationality", at the same time reduces the time which reverse used, the parametric results easy to later modification and improve the efficiency of auto-body design.