Research On Dynamic Characteristics For Space Robot System With Gravity Effect And Clearance Consideration

Space manipulator has got more and more wide application in aerospace engineering. Along with the increase of the difficulty of mission, higher requirements are called for the movement precision of space manipulator. The space manipulator is often developed and debugging on the ground, and working in space, changes of gravity directly affect the dynamic characteristics of the space manipulator, whether space manipulator that works well on the ground can operate normally in space has become a hot topic of researchers.In previous studies, the scholars simulated the movement of space manipulator and obtained the dynamic characteristic parameters of space manipulator through the establishment of micro-gravity environment on the ground.However, with the interference of ground gravity field, the real dynamic characteristics of the space manipulator under micro-gravity condition can not be fully reflected by space manipulator dynamic characteristic parameters obtained by simulating micro-gravity environment. This article studies space manipulator from the perspective of gravity, through the analysis of the effect of gravity on the dynamic characteristics of the space manipulator, guidance for manipulator simulation in micro-gravity space is given, and suggestion is also put forward for the physical mechanism of motion behavior of space mechanism effected by gravity and the forecast for dynamic characteristics of the space manipulator under micro-gravity condition.In the research of effect of gravity on the dynamic characteristics of the space manipulator, two factors are mainly considered.Firstly,in the process of space manipulator debugging on the ground, dynamic characteristic parameters of the joint will change accordingly as the angle between the direction of the gravity field and manipulator’s joint angular velocity changes, Secondly, under the coupled action of gravity and clearance existing in the joint, it is different between the dynamic characteristics of the space manipulator and that clearance existed under the micro-gravity condition.Based on the above, taking the space manipulator for the research object, dynamics simulation of the space manipulator is carried out with modern simulation method, main contents are as follows:First of all, based on Pro/e, space manipulator three-dimensional entity model with six degrees of freedom is established, virtual prototype is imported into ADAMS, dynamic simulation model of the space manipulator is established on the basis of the dynamics modeling theory of ADAMS and actual quality parameters, physical characteristics, space manipulator and relative motion of the space manipulator.Secondly, space manipulator dynamic characteristics without hinge clearance are analyzed in the different orientation of the gravity field. Space manipulator dynamics parameters are compared as the angle between the direction of the gravity field and manipulator’s joint angular velocity changes, and the influence of gravity on the dynamic characteristics of the space manipulator is summarized.Finally, the dynamic characteristics of the space manipulator with joint clearance in the different orientation of the gravity field are analyzed. By comparing space manipulator dynamics parameters under the condition of different orientation of the gravity field and different clearance values, the influence law that the coupling of gravity and motion pair clearance on dynamic characteristics of the space manipulator is summarized. Guidance is given for the control of space manipulator trajectory tracking and the stability of motion.