Research On The Three Dimensional Dynamic Behavior Of Rod-cone Collision With On-orbit Replacement Unit

On-orbit Replacement Unit,is a kind of modular components used in space station or large and medium-sized on orbit spacecraft.When oru reaches its design life or fails,it can be easily replaced in orbit to complete the update and maintenance of spacecraft components.Limited by the volume,mass and other factors,the positioning and guiding mechanism of oru to the target spacecraft mostly adopts the simple rod cone structure.In the low damping microgravity environment,oru is affected by rigid motion in the process of rough positioning with the conical hole of the target spacecraft through its ball nose rod type guidance system.When the ball nose rod reaches a certain position,it will contact and collide with the conical hole of the target spacecraft,resulting in velocity mutation,which makes them bear a certain impact load and difficult to dissipate,The attitude stability of oru and target spacecraft is seriously affected.Therefore,this paper will focus on the dynamic modeling and nonlinear contact collision behavior characteristics of the positioning and guiding process of the on orbit replacement unit equipped with the rod cone guiding mechanism.The dynamic modeling of early guidance and positioning motion between oru and target spacecraft belongs to the problem of three-dimensional large-scale motion and contact collision of rigid body system.In this paper,according to the geometric characteristics of the positioning and guidance system structure,the vector analysis method is applied to study the cone rod collision detection method in three-dimensional space for different contact conditions.Based on the Newton method of rigid body dynamics,the kinetic equations of oru and target spacecraft system are established,and the influence of stiffness and damping is comprehensively considered in the part of contact mechanics model.The dynamic model covers the geometric structure and material nonlinear relationship of the positioning and guiding mechanism.On the one hand,it improves the traditional collision detection method of the rod cone positioning and guiding mechanism,on the other hand,it overcomes the difficulty of solving the contact dynamic equation when the guiding process is highly nonlinear,and has good applicability for the guidance and docking process of spacecraft with similar structure.According to the established dynamic equation of spacecraft collision and the positioning requirements of oru before mechanical connection,the contact collision of oru under typical positioning and guidance conditions is numerically simulated,and the dynamic simulation results of two spacecraft in the guidance simulation process are given.By comparing the simulation results with the LS-DYNA simulation results and the literature model,the correctness of the dynamic model is verified.It provides a theoretical basis for the contact collision and attitude stability adjustment of oru in the process of positioning guidance or docking in space on orbit service.An equivalent physical model is built to simulate the motion of oru in orbit and realize the contact collision with the target spacecraft.The dynamic behavior characteristics of oru and the target spacecraft are tested and analyzed.The simulation data and experimental results show that the theoretical model can effectively solve the dynamic problems of oru in orbit positioning and guidance process;At the same time,it is verified that the designed oru structure meets the expected performance index.Then the influence of initial attitude and initial velocity on the impact force is studied.It provides a reference for dynamic behavior analysis and attitude control of ORU in orbit positioning and guidance.