飞机外形和结构件反求建模技术研究

Reverse Engineering of Aircraft Contours and Structural Parts

探讨了基于特征的飞机外形和结构件反求建模策略,并给出曲面特征和实体特征的定义,该方法支持具有完整特征表达的模型快速重建。提出了大规模散乱数据k-近邻的空间球搜索算法,其逐步增大搜索范围的策略可有效提高搜索效率。研究了结构件与外形相关曲面特征的重建方法,当贴合面较窄、外形线接近于直线时,采用直纹面逼近,否则由蒙皮曲面等距间接求取。研究了基于工程约束的曲面形状修改算法,以B样条曲面需满足的点、线、面几何约束为目标约束,通过最小化形状修改前后差曲面的弯曲能得到精确满足目标约束的光滑曲面,推导了曲面弯曲能和曲线约束的表达式。最后,以飞机翼肋模型反求为例验证了所提方法的可行性。

A feature-based model reconstruction strategy of aircraft contours and structural parts is discussed systematically in this article,and the definition of infrastructural surfaces and solid features is given. The proposed method enables rapid CAD model reconstruction with comprehensive feature representation,which is beneficial to design improvement or modification. A spatial sphere algorithm by gradually widening the search range is developed for searching the k-nearest neighbors of a measured point in a massive scattered point set,which improves the search efficiency greatly. Then,an approach to rebuild the surface feature of a structural part conjoint with the aircraft contour is proposed. That is,if the surface feature conjoins a skin with a narrow area,it is approximated by a ruled surface;otherwise it is deduced by offsetting the aircraft contour. Surface shape modification based on engineering constraints is also investigated,and a smooth surface satisfying a given point,curve,and surface constraints can be derived by minimizing the bending energy of the different surfaces between pre-and post-shape modification. Also the expressions of the bending energy and curve constraint for a B-spline surface are given. Finally,model reconstruction of a certain wing rib is provided to illustrate the validity of the proposed method.