基于直线驱动的空间可展机构运动分析

Motion Analysis of Spatial Deployable Mechanism Driven in Straight Line

将直线机构与折纸机构相结合,设计出一种新型空间可展机构,并对其进行运动分析。运用抽象思维将筝形纸板的四条边线抽象为构件,将相邻边线间的拐点抽象为转动副,提出一种二自由度筝形七杆机构,采用几何证明的方式,对机构执行构件实现直线运动的条件进行研究,结合运动支链为末端执行构件提供约束的本质,通过引入平行约束的方式,设计得到多种单自由度筝形直线机构。以筝形直线机构为基础构造可展单元,阐述模块化组成筝形直线可展机构的原理和过程。根据三浦折纸机构的运动几何特性和面对称性,在运动学分析的基础上,提出一种通过改变对称面上共线等距点的间距来实现机构折展的驱动方式,经由筝形直线可展机构予以实现后,建立整体空间可展机构的虚拟样机模型,研究机构的运动干涉问题及其影响因素,绘制折展率性能图谱,得到了该空间可展机构的折展率随着板厚h的减小和切除长度c的增大而增大的结论,为机构的结构设计和工程应用提供参考依据。

Combining linear mechanism with origami mechanism, a new type of space developable mechanism is designed and its motion is analyzed. When four edges of kite-shaped cardboard are abstracted as components and vertexes are abstracted as revolute joints by using abstract thinking theory, a two-DOF kite-shaped mechanism with seven bars is proposed. By means of geometric method, the conditions of realizing straight-line motion of the executive component are studied and parallel restriction is introduced to design the single-DOF kite-shaped linear mechanism. Based on the straight-line mechanism, two types of modules named external module and internal module are constructed and modular principle of the kite straight-line deployable mechanism is explained. According to the kinematic geometric characteristics and face symmetry of Miura-origami mechanism, a new driving method of this origami mechanism is proposed by changing the distance between collinear equidistant points on the symmetrical plane which can be realized by the kite-shaped straight-line developable mechanism. Corresponding virtual prototype model of the spatial developable mechanism is established, and the movement interference and its influencing factors are studied. The performance atlas of folding ratio is drawn and it shows that the folding rate of the space expandable mechanism increases with the decrease of the thickness h and increase of the removal length c which can provide reference for structural design and engineering application of the mechanism.