Research On Thermal Distortion Of Space High Precision Motion Mechanism And Control Technology

Space high-precision motion mechanism refers to two-axis motion mechanism supporting optical system or other precise system.It is widely used in space free optical communication,space radar scanning,space early warning,precise pointing mechanism required by space astronomy,deep space exploration and other fields.It can achieve target acquisition,tracking and aiming.It requires high tracking accuracy and tracking stability.The coupling effect and thermal deformation between the support structure and shafting of the motion mechanism seriously affect the accuracy of the motion mechanism.At the same time,the complex space environment of the motion mechanism such as high vacuum,temperature alternation,high and low temperature and radiation have a great impact on the working performance and life of the motion mechanism,which may lead to the"stuck"of the motion mechanism and lead to the failure of the space mission.From the point of view of theory and practical application,this paper studies the mechanism of influence factors of thermal deformation on high reliability and long life of space motion mechanism,reveals the coupling thermal deformation between main support structure and shafting system of space motion mechanism,and the relationship between Hertz contact stress in shafting system and working performance and life of motion mechanism.On this basis,it puts forward measures and methods to improve working performance and life of shafting system.In this paper,the structure-thermal deformation and shafting reliability and longevity of space two-dimensional motion mechanism are studied.The main research contents are as follows:According to the working environment and characteristics of space high-precision motion mechanism,the mechanism of structure-thermal deformation affecting the tracking performance of"precision"motion mechanism is revealed.The characteristics and lubrication mechanism of solid lubrication film are studied.The effects of load,temperature and other factors on the solid lubrication performance are explored.Aiming at the characteristics of U-shaped structure and shafting of motion mechanism,based on the theory of space heat transfer,heat conduction and heat radiation,the temperature field calculation model and thermal resistance model of motion mechanism and motion shafting are established.Based on thermoelasticity and thermostatics,the mathematical models of main structure,coupling of semi-closed U-shaped structure and shafting and temperature-stress field in shafting are established.Finite element simulation and theoretical analysis are used to study the load change of shafting caused by thermal deformation.The correctness of the mathematical model and the feasibility of the analysis method are verified by ground and on-orbit tests.For the highly reliable space solid lubrication"precision"motion shafting,the influence mechanism of temperature,pre-tightening force,temperature difference and speed on multi-physical quantity and friction moment is revealed,and the coupling network of friction moment and multi-physical quantity is established.The friction moment of shafting under different temperature,temperature gradient,pre-tightening force and speed conditions is measured quantitatively through a large number of experimental results.The variation rule between friction moment and multi-physical quantity is revealed,which provides theoretical and experimental data basis for high reliability of"precision"motion shafting of space motion mechanism.The thermal characteristics of MoS₂ solid lubricated bearings under vacuum condition were quantitatively tested,and the thermal resistance model of shafting was verified.The experimental results were used to modify the thermal model of shafting,which provided theoretical support and data support for temperature field analysis and control of space motion mechanism.Aiming at the inherent mechanism that the change of the pre-tightening force of the shafting affects the life of the moving mechanism,and considering the working performance of the shafting assembly in the moving mechanism,the whole machine is analyzed and tested.The relationship between the wear of MoS₂-based composite film bearings and the alternation of launching environment,high and low temperatures is revealed,and the wear model of the film layer is established.The accelerated life test of the whole machine of the moving mechanism is designed.EDS analysis results of solid lubrication film on raceway and ball after test verify the wear theory of film layer and predict the service life of moving mechanism.Based on the research of the influence of the preload of the motion mechanism on the life of the motion mechanism,based on the theory of thermoelasticity and Hertz contact,supported by the reliability test of the shafting system,the relationship between the preload of the shafting system and the contact stress of Hertz is revealed,and a scheme of adjustable preload of the space shafting system,the design of temperature control and the implementation of the technology are proposed,which realizes the preload of the motion mechanism.The optimum control ensures that the space shafting works reliably on orbit.The thermal control technology of space load is introduced,and a feasible thermal control scheme is put forward.The rationality of the design of thermal control system is verified by thermal balance test and on-orbit application.This paper mainly focuses on technological progress and innovation as follows:1)On the basis of thermoelasticity and thermostatics,the mathematical models of temperature-stress field of the relationship between inner and outer rings of bearings and the relationship between semi-enclosed U-shaped structure and shafting are established.The thermal resistance models of inner and outer rings of bearings are established.The accuracy of the structural-thermal coupling mathematical model and thermal resistance model is verified by the measured data of on-orbit and ground environmental tests.The research provides the theoretical basis and data support for temperature field analysis and thermal control of space motion mechanisms.2)The influence of temperature,temperature gradient,pre-tightening force and speed on the friction moment of shafting is studied.Systematic experimental measurements of the friction moment of shafting under different temperature,temperature gradient,pre-tightening force and speed conditions are carried out.The variation law between the friction moment and the above-mentioned multi-physical quantities is obtained,which provides a theoretical basis for setting the temperature index of space motion mechanisms.3)A control method of pre-tightening force of space Shafting Based on temperature control is proposed,which realizes on-orbit control of pre-tightening force of motion mechanism,and provides a novel technical way to improve on-orbit motion life of shafting.The above achievements have been successfully applied to the project of Innovation Satellite 3 and Chang'e Satellite-based Optical Telescope 3.