面向空间应用的3-R(SRS)RP多环机构操作臂结构设计及逆运动学分析

Structural Design and Inverse Kinematics Analysis of a 3-R(SRS)RP Multi-loop Mechanism Manipulator for Space Application

针对空间在轨操作任务需求,为了得到高刚度、高强度、多活动度和大工作空间的操作臂,将多个3-R(SRS)RP多环机构模块串联组成多环机构操作臂。基于多环机构构型,提出一种空间操作臂整机结构设计方案:包含SRS复合铰链结构设计、多环机构模块结构设计、多环机构系统结构设计。SRS复合铰链的结构设计是基于一种改进的球副机构展开,该球副构型可复合双球副及额外转动副,且所有运动轴线相交于一点,提高了运动精度并简化了运动学模型。模块及系统结构设计主要表现在多环机构模块之间的连接平台和连接杆件的结构规划,以保证动、静平台上转动副轴线重合,满足折展和弯曲等运动需求,并解决了运动链耦合时的结构干涉问题。此外,建立了多环机构模块及系统的逆运动学模型,并进行了逆运动学分析。通过数值求解其工作空间发现,三模块操作臂在工作空间即可实现大的可达工作空间及弯曲角度。这一结论为后续样机的研制提供了理论基础。

Multiple 3-R(SRS)RP multi-loop mechanisms are used as modules to integrate a manipulator for obtaining high rigidity, high intensity, high mobility, and large workspace, thereby satisfying the requirements of space on-orbit tasks. Based on the configuration of the multi-loop mechanism, a whole structure design scheme of the space manipulator, including structural designs of SRS compound hinge, multi-loop mechanism module, and multi-loop mechanism system, is proposed. The SRS compound hinge is designed on the basis of an improved spherical joint mechanism. Two spherical and one additional revolute joints are combined, and all the motion axes intersect at one point, thereby improving the motion accuracy and simplifying kinematics model. Then, one connection method between platforms of different modules is developed for constructing the space manipulator system. Each module of the system is designed by planning its connecting links. Thus, the axes of the revolute joints on moving and base platforms are coincident, thereby meeting the requirements of folding and bending motion process. This design strategy eliminates the structural interference of coupling kinematic chains. In addition, the inverse-kinematics models of the multi-loop mechanism module and system are established thus inverse-kinematics analyzing. Based on the kinematics model and analysis, the numerical analysis of the workspace of multi-modular manipulators is conducted. It turns out that the three-modular manipulator achieves a large reachable workspace and bending angle, which provides theoretical basis for manufacture of the prototype.