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针对四面体构架式可展天线机构的多环耦合特性,提出了一种空间多环耦合机构的自由度分析方法——拆杆等效法。首先拆除四面体基本可展单元机构的耦合约束链,将剩余部分视为一个并联机构,然后应用螺旋理论分析各输出节点的自由度数目及性质,进而构造各输出节点与定节点之间的等效串联运动链,最后复原拆除的耦合约束链得到四面体基本可展单元的等效机构,应用修正的G-K公式计算等效机构的自由度数目,并基于反螺旋理论分析等效机构的自由度性质,从而获得四面体基本可展单元的运动特性。根据四面体基本可展单元的等效机构及其组合方式对最小组合单元及大尺寸构架式可展天线机构的结构进行了化简,并根据其几何特征约束方程推导了最小组合单元及大尺寸构架式可展天线机构的自由度。建立了由27个四面体基本可展单元组成的构架式可展天线机构的仿真模型,对该机构的自由度进行了验证,结果表明提出的拆杆等效法求得的自由度正确,为进一步分析此类天线机构的运动学和动力学奠定了基础,同时为其他类型的空间多环耦合机构的自由度分析提供了一种新的思路。
Aiming at the characteristics of multi-ring coupling of tetrahedral body-mountable antenna, a free-space analysis method of multi-ring space coupling mechanism is proposed. Firstly, the coupling constraint chain of the tetrahedral basic expandable unit mechanism is disassembled and the remaining part is regarded as a parallel mechanism. Then, the number and the nature of the degrees of freedom of each output node are analyzed by using the spiral theory. Then the relations between the output nodes and the fixed nodes The effect of the series kinematic chain is studied. Finally, the coupled constrained chain is removed and the equivalent mechanism of the tetrahedral basic expandable element is obtained. The modified GK formula is used to calculate the number of degrees of freedom of the equivalent mechanism and the degree of freedom of the equivalent mechanism is analyzed based on the anti-helix theory Nature, thus obtaining the tetrahedral basic expandable unit kinematics. Based on the equivalent mechanism of the tetrahedral basic expandable unit and its combination, the structure of the smallest unit and the large size frame-extendable antenna are simplified and the minimum combination unit and large size Frame-type antenna structure of the degree of freedom. A simulation model of a frame-type extendable antenna mechanism consisting of 27 tetrahedral basic expandable units is established and the freedom degree of the mechanism is verified. The results show that the proposed degree-of-freedom of the split-rod equivalent method is correct, Analyze the kinematics and dynamics of the antenna mechanism laid the foundation for the other types of spatial polycyclic coupling mechanism for freedom analysis provides a new way of thinking.