鞋楦定制CAD系统中NURBS特征曲线的弧长约束变形  

Arc-length constrained deformation of characteristic NURBS curves for customized shoe-last CAD system

作　　者：任怀艺[1] 王伯雄[1] 罗秀芝[1] 

机构地区：[1]清华大学精密仪器系,精密测试技术及仪器国家重点实验室,北京100084

出　　处：《清华大学学报（自然科学版）》2014年第2期217-222,共6页Journal of Tsinghua University(Science and Technology)

基　　金：国家自然科学基金资助项目(11274199)

摘　　要：为实现无鞋楦数据库的数字化量足制鞋,提出了基于足楦NURBS特征曲线变形的个性化鞋楦定制CAD系统,通过足楦特征曲线在弧长等特征信息约束下变形成新楦特征曲线进行设计定制。建立足楦舒适度匹配规则,根据变形方式、次序及约束情况不同,将特征曲线分为4种类型。给出4种曲线的约束变形技术路线,其中带弧长约束的II型曲线可采用正向、逆向和双向3种变形路线。双向约束变形中,采用改进的顶点替换算法和变参数4点细分算法,引入弧长损失因子和关节链模型,在母版鞋楦基础上对曲线依次进行采样离散、级放、分段、简化、优化变形、插值细分和NURBS拟合,生成定制的鞋楦特征曲线。以跖趾围轮廓线为例进行了双向约束变形试验,弧长改变量为1.0mm。该系统可在480s内给出男款鞋楦个性化量足定制结果。结果表明:该CAD系统精度较高,可实现无鞋楦数据库条件下的量足制鞋,且定制鞋楦的二次设计利用率显著提高。A customized shoe-last system is developed based on the deformation of characteristic NURBS curves for feet or shoe-lasts to enable customized shoes without a shoe-last database. Deformations of the feet or shoe-lasts characteristic curves are used to make new shoe-lasts with constraints of the arc-lengths. The system uses comfort matching rules between the feet and the shoe-lasts with the characteristic curves divided into four types according to their different deformation ways, orders, and constraints. Deformation roadmaps are then given with forward, reverse and bidirectional deformation roadmaps for the Ⅱ-type curves with are length constraints. The bidirectional deformation uses an improved vertex substitution algorithm and a modified variable-parameter 4 point interpolatory subdivision scheme with a new arc-｜ength loss actor and a rigid joint chain model. Customized shoe-last curves are produced from a mother shoe-last through sampling, grading, sectioning, simplifying, deforming, subdividing, and NURBS fitting. For the metatarsoplaalangeal contour curve, a bidirectional deEormation test gives an arc length change of 1.0 mm. With this system, a man＇s shoe-last can be customized in less than 480 s to give accurate, practical customized shoes without a shoe-last database. This method greatly increases the redesign for customized shoe-lasts.

关 键 词：CAD鞋楦定制 NURBS特征曲线 弧长约束变形 舒适度匹配规则 

分 类 号：TP391.7[自动化与计算机技术—计算机应用技术] TS943.2[自动化与计算机技术—计算机科学与技术]