剪叉式过约束双环桁架可展天线机构的构型设计与自由度分析

Configuration Design and Mobility Analysis of the Scissors Overconstrained Double-Ring Truss Deployable Antenna Mechanism

基于过约束剪叉机构单元,构造了一种剪叉式过约束双环桁架可展天线机构作为星载天线支撑机构.首先,分析了剪叉式过约束双层环形桁架机构的构型机理及过约束特征,并对整体桁架机构进行了单元划分;考虑节点连接件的尺寸,推导出了此剪叉式过约束双环桁架机构的组环几何条件.然后,将双层环形桁架机构进行单元分解,基于图论和螺旋理论绘制了分解后机构单元的旋量约束拓扑图,进而分析了闭环可展开机构单元和整体双层环形桁架机构的自由度,结果表明,双层环形桁架机构的自由度和闭环可展开机构单元的自由度数相同,均只有1个自由度.最后建立了双层环形桁架可展开天线机构的仿真模型,模拟了整个机构的展开过程,验证了整体的可展性.该剪叉式过约束双环桁架可展天线机构所含运动副均为转动副,且整个机构仅具有单个自由度,运动形式简单.

Based on the overconstrained scissors mechanism unit, a scissors overconstrained double-ring truss deployable antenna mechanism is constructed as a support mechanism for the satellite antenna. Firstly, the configuration mechanism and overconstraint characteristics of the scissors overconstrained double-ring truss mechanism are analyzed, and the units of the whole truss mechanism are decomposed. Then, the geometric conditions for the ring structure of the scissors overconstrained double-ring truss mechanism are derived in consideration of the effects of joint size. Furthermore, the screw constraint topology of the decomposed mechanism units is drawn based on the graph theory and screw theory, and the mobilities of the closed-loop deployable mechanism unit and the double-ring truss mechanism are analyzed. The result shows that the mobility of the whole double-ring truss mechanism is the same as that of the closed-loop deployable mechanism, with only one mobility. Finally, a simulation model of the double-ring truss deployable antenna mechanism is built, the deploying process of the whole double-ring truss is simulated, and the deployable feature is verified. The proposed scissors overconstrained double-ring truss deployable antenna mechanism has only one mobility, its kinematic joints are all revolute joints, and the movement form is simple.