Research On Joint Fast Exchange Interface Of Experimental Module Manipulator

Space station is an outpost of human space exploration, as well as a symbol of a country’s economic, scientific and technological strength. Space station serves as space laboratory which provides ideal experimental conditions for physics and a stronomy research. Large space manipulator is the key equipment for construction and maintenance of space station. With the development of Chinese space station project, China has made constant progress on space manipulator technology. In o rder to ensure long term stable operation of large space manipulator, core comp onents of manipulator joint need redundant backup. In consideration of the harsh space environment, joint should be replaced in orbit when it completely breaks down. On-orbit service technology can dramatically reduce maintenance costs and shorten the development cycle. Joint fast exchange interface is the crux of on-orbit service technology. Through analysis and study of internal and external literatures, this paper expounds the development of a space manipulator joint fast exchange i nterface which is convenient for astronaut extravehicular operation.According to the characteristics and requirements of astronaut extravehicular activities, the design of fast exchange interface is explicitly emphasis on its feature of easy replacement and small driving force, while ensuring rigi dity and load capacity of space manipulator at the same time. According to the design index and oper ational procedures of astronaut, this paper puts forward a general design scheme of joint fast exchange interface in which mechanical interface and electric al interface are actuated independently and separately. Fast exchange interface consists of to lerance docking mechanism, preliminary locking device, mechanical conne ction/locking device and pushing mechanism of electrical connector, four functional modules in total.According to tolerance parameter, a pair of male/female tolerance docking mechanism based on dual-cone fit is designed. In order to calculate the interface tolerance and modify design parameters, a mathematical model is built considering that the successful docking conditions are divided into geometrical and frictional conditions based on the feature of docking. This paper determinates parameters of docking mechanism by tolerance range obtained theoretically through MATLAB software. Through the ADAMS software, the tolerance range and the correctness of mathematical model are verified in simulation.According to the requirements of astronaut extravehicular operations, this p aper select an electrical connector with planar floating feature and design a floating device to make the electrical connector with over-travel. This paper designed a slider-crank mechanism to convert rotary motion of operation tool to linear motion of electrical connector, making electrical interface compact and reducing inse rtion/withdrawal force, thus making EVA operations easier. The parameters of the slider-crank mechanism are set based on the target of smallest driving torque. F inally, Through the ADAMS software, the variation of driving torque of electrical connector is obtained in simulation including friction and insertion/withdrawal force.A preliminary locking device is designed to remain interface docked after docking and before mechanical connection. The spring in the preliminary locking device provides locking force. Based on expandable fastener, this paper designs a mechanical connection/locking device, selects its material& dimension and analyzes the relationship between expansive deformation& extrusion stress and thrust force. This paper designs a self-locking screw jack, and computes the tightening torque of the mechanical connection/locking device and loading capacity of fast exchange i nterface based on the strength of screw thread. In the mechanical connection/locking device, an anti-off limit device is designed and analyzed as well.Based on the simplified stiffness model of expandable pin, lightweight design of fast exchange interface is achieved within constraints of structural strength and stiffness. Analysis of the impacts of decrease in preload on connection stiffness is achieved. Finally, this paper develops a six-dimensional rigidity testbed for fast exchange interface, measures stiffness of the fast exchange interface under different pre-tightening torques of expandable pin and analyzes measurement error of the testbed in addition.