共查询到19条相似文献,搜索用时 912 毫秒
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面向虚拟装配的零部件精确定位技术研究 总被引:5,自引:0,他引:5
针对基于几何约束自动识别的零部件精确定位技术中存在的识别效率和准确性不高的问题,提出了一种分层的几何约束自动识别方法。该方法通过装配意图获取、约束优先级判断、约束类型匹配、约束参数匹配、约束位置匹配和约束有效性检查等分层判断机制,有效地提高了几何约束自动识别的效率和准确性。相关方法已经在虚拟装配工艺规划系统中进行了验证,并已应用到航天产品的虚拟装配工艺规划中。 相似文献
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采用等价性分析方法消除三维几何约束系统中的伪约束闭环,并将几何约束图分解为单边子图、独立闭环子图和耦合闭环子图;采用螺旋理论识别出装配几何约束组合对应的运动副约束,将约束闭环子图映射为运动副约束图;通过分析运动副约束图的拓扑结构选择切除约束,建立装配几何约束闭环系统的相对坐标表达,将约束闭环系统的整体迭代求解转换为切除部分约束与相对坐标的迭代求解。该方法降低了数值迭代求解的规模,考虑了约束方向对求解结果的影响,既提高了约束求解的效率和稳定性,又保证了约束求解结果的正确性。 相似文献
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用双层重建法实现单幅图像的超分辨率重建 总被引:1,自引:0,他引:1
针对现有基于稀疏编码的单幅图像超分辨率重建算法易导致重建图像中出现不正确几何结构的现象,提出一种字典非相关性约束和稀疏系数非局部自相似性约束结合的稀疏编码方法。为解决引入这种自相似性约束造成的重建图像边缘过度平滑、模糊的问题,提出了基于平滑层和纹理层的双层重建框架。该方法运用一种全局非零梯度数目约束重建模型重建平滑层;通过提出的稀疏编码方法重建高分辨率纹理图像。最后,利用一个全局和局部优化模型进一步提升重建图像的质量。实验结果表明,与一些具有代表性的重建方法相比,该方法得到的峰值信噪比(PSNR)和结构相似度(SSIM)平均值分别提高了0.798 7~3.242 4dB和0.018 6~0.083 5,不仅主观视觉效果上取得了明显的改进,鲁棒性得到增强,而且重建出了更加准确的结构和边缘,取得了更好的重建效果。 相似文献
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研究参数化方法中经常遇到的多解问题。首次提出了约束元和约束组的概念,从拓扑及空间关系的角度研究了解的标识方法和约束组求解的几何算法。该算法具有几何语义直接、精确度高、计算量小等优点。 相似文献
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本文对汽门弹簧的优化设计,采用了约束正定式几何规划迭代法。该法是求解广义的约束正定式几何规划问题的一种迭代算法。当问题因目标函数的项数较多而引起困难度很大时,用迭代法求解比用其它优化方法更为简便,而且易学易懂,便于掌握,尤其当初始点选择比较恰当时,经几次迭代,就可收敛,取得满意的最优解。因此,该法是求解广义的几何规划问题的一种较好途境。 相似文献
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优化法求解几何约束的问题 总被引:3,自引:1,他引:2
几何约束的求解对于变量设计系统是最为关键的问题,提出用优化求解的方法来求解循环约束,一定程度上克服了Newton-Raphson算法的不稳定性,且可较容易地求解欠约束和过约束的问题。 相似文献
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Y. Wang L. Chen Z. Huang J. Wu Y. Zhong 《The International Journal of Advanced Manufacturing Technology》2005,25(3-4):334-342
History-independent modelling systems are more flexible than history-based ones. They let designers manipulate the model in a more associative, rather than prescribed, way. In this paper, an approach based on 2D geometric constraint solving and a topological entity naming mechanism (TENM) is presented to solve the geometric constraints between features in 3D space. Firstly, in order to break the unidirectional dependency between features in a history-based modelling system, a data structure named feature constraint graph(FCG) is adopted to represent the geometric constraints between features in 3D space. Then a solving sequence is obtained using degree-of-freedom (DOF) based graph analysis. And finally, during the evaluation of the solving sequence, the dimensions in 3D space are mapped to 2D space, the dimensions in 3D space are satisfied indirectly by solving the corresponding 2D geometric constraint system. An example is given to illustrate the process of our approach. 相似文献
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几何约束等价性及等价迭代研究 总被引:1,自引:0,他引:1
针对几何约束系统中不可构造的柔性复合顶点的求解问题,引入等价约束,分裂部分约束以打破柔性复合顶点的强耦合性,形成只包含简单顶点的求解序列。基于等价约束的性质和结构拓扑,研究了求解序列顶点存在与不存在实数解情况下,雅可比矩阵的求解方法,从而以少量分裂约束方程组对等价约束变量的等价迭代,或者柔性复合顶点的局部迭代,取代柔性复合顶点的整体数值迭代求解,降低迭代的维数,算法实现于几何约束求解引擎CBA(constraint broadcast automa-tion)中。 相似文献
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Zhi-Liang Shi Li-Ping Chen 《The International Journal of Advanced Manufacturing Technology》2007,32(3-4):366-377
In this paper, a novel approach for solving angular constraints based on spherical geometry is presented. This method can
determine the orientation of a set of parts given the mating constraints between them with the decoupled property of the angular
and distance constraints. The combination of angular constraints can be categorized into two cases: operable and un-operable.
The former can be solved efficiently by introducing simple spherical surface reasoning. The latter is solved by employing
spherical surface four-linkage mechanism. In this way, the rotation transformation matrix of the dependent rigid body is worked
out. This new method has the advantages over numerical approach and symbolic approach of clear geometric solubility, geometric
operability, and avoiding simultaneously solving all the constraint equations in the model. Moreover, it is an easy and efficient
way to determine whether there exist redundant constraints. The presented algorithm has been successfully implemented in our
assembly prototype system, InteVue. 相似文献
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