并联机构的结构降耦原理及其设计方法*

机构学的难题之一是寻找机构拓扑结构学与运动学、动力学之间的映射规律。前期研究表明，降低机构的结构耦合度可直接降低机构运动学、动力学求解的难度，这揭示了机构拓扑结构学与运动学、动力学之间的关系之一，因此，如何降低机构的结构耦合度已成为机构拓扑结构优化的重要内容，但目前国内外研究很少。研究并联机构的结构降耦原理、设计方法及其应用。定义并联机构结构降耦的概念，澄清并揭示机构结构降耦与机构运动解耦之间的内在区别与联系。从并联机构支链本身的拓扑结构以及支链在动/静平台之间布置的拓扑结构两方面，提出保持并联机构自由度和方位特征不变而降低机构耦合度的两个结构降耦原理，据此，进一步提出了基于设计混合支链的、基于运动副复合的、基于方位特征支链主动化的三种结构降耦设计方法，并分别给出设计例子，得到相应的自由度和方位特征保持不变但耦合度降低的新机构，为其应用研究提供了优选机型。提出的机构结构降耦原理与设计方法，适用于所有的复杂平面和空间平面。

Principle and Design Method for Structure Coupling-reducing of Parallel Mechanisms

One of the difficult issues is to discover the mapping laws among the topological structure, kinematics and dynamics of mechanisms. The previous work shows that reducing the structure coupling degree can reduce the complexity of solutions of kinematics and dynamics, which reveals one of the relations among topological structure characteristics, kinematics and dynamics. Therefore how to reduce the structure coupling-degree will become an important issue for topological structure optimization of mechanism but is little being studied so far. The principle, design methods and application of the structure coupling-reducing (SCR) are studied. A concept of the SCR is defined. The differences and connections between the SCR and motion decoupling are also revealed. From analyzing topological structures both branched chain itself and branched chains layout between the moving and the static platform of parallel mechanism, two principles and three methods for the SCR are proposed. These three methods are hybrid branched chains method, superposing kinematic joints method, and changing position and orientation characteristics branched chains into driving branched chains method, respectively. Corresponding examples of the SCR are given and some novel mechanisms with low coupling degrees are obtained. The principles and methods for the SCR can be applied to all complex planar mechanisms and spatial mechanisms.