Design And Research Of The Interface Mechanism Of The Back-end Module Of The Space Telescope Based On On-orbit Maintenance

On-orbit maintenance technology is a frontier subject in the development of space science and technology.With the advancement of spacecraft's modular design concept,the study of on-orbit replaceable interfaces has become an important part of on-orbit maintenance.When the space telescope is working,the interface mechanism should ensure the stability and accuracy of long-time imaging of the space telescope on-orbit,and secondly,it must meet the corresponding repeated positioning accuracy.This article relies on major national engineering projects and takes the space telescope on-orbit repairable interface as the research object.With the goal of on-orbit thermal stress release,spatial disturbance dynamic stability,high repeated positioning accuracy,and high rigidity,in-depth research on the interface mechanism is carried out through theoretical analysis,mathematical modeling,structural design,simulation analysis,and experimental verification.Firstly,the goal is to achieve high stability and high positioning of the space telescope's on-orbit imaging,while satisfying the high rigidity of the interface structure.Finally,it is determined that the 3-2-1 kinematic principle is used as the positioning and the electric drive lock is used as protection,a new on-orbit maintenance interface scheme that takes into account both positioning and locking functions is formed.Secondly,analyze the stability of the on-orbit maintenance interface.The influence of temperature changes on the positioning of the interface mechanism is studied.Based on the 3-2-1 kinematic principle,the mathematical expressions of temperature change and interface point layout to the on-orbit positioning accuracy of the back-end module are derived.Then analyze the disturbing moment generated by the space telescope,establish a mathematical model,and derive the mathematical expressions of the pre-tightening force and anti-interference torque of the A positioning point.It is solved that under a given safety factor,the back-end module interface can resist a resistance torque not less than 16.74N·m,it can ensure the stability of on-orbit imaging.Then,the repeated positioning accuracy of the back-end module with the interface mechanism is studied.According to the spatial homogeneous coordinate transformation,the mathematical expressions of the interface point gap and repeated positioning accuracy are deduced under the rotation of a small angle.Through the reasonable distribution of gaps,theoretical calculations show that the angle repeated positioning accuracy of the back-end module is better than ±15.1",and the repeated positioning accuracy of the translation is better than ±0.01 mm.Immediately afterward,two sets of interface mechanism were designed in detail under the guidance of the theoretical interface scheme,which is the positioning-locking separate type of interface mechanism and the positioning-locking integrated type of interface mechanism.The separate interface mechanism can be applied to an on-orbit maintenance environment that is not limited by space resources,and the integrated interface mechanism is more suitable for occasions with limited structural dimensions,especially for compact space telescope systems.And check the strength of the integrated interface mechanism,the unlocking torque of the interface is about0.065N·m,and the locking accuracy is better than 0.022 mm.Then,a complete finite element simulation model of the back-end module interface mechanism was established,the simulation data show that the overall fundamental frequency of the interface mechanism reaches 139 Hz.Static overload analysis,dynamic low-frequency sinusoidal analysis and high-frequency random analysis results show that the interface stress under various working conditions is far less than the material yield strength,the interface structure has a high safety factor,strong reliability,meets the index design criteria.Finally,the machining of the principle prototype and test piece is completed.The temperature test results prove that the interface can realize kinematics positioning and complete the on-orbit thermal stress release.The results of the repeated positioning accuracy test show that the maximum deviation from the theoretical repeated positioning accuracy is less than 12%.The dynamic acceleration frequency sweep test verifies the accuracy of the finite element model simulation.The overall fundamental frequency of the back-end module is 136 Hz,which proves that the interface mechanism has good dynamic characteristics and meets the requirements of use.Multiple test results prove that the design scheme proposed in this paper is reasonable and the design structure is reliable,which provides a certain reference for the interfaces of other on-orbit maintenance modules.