Dynamic Modeling And Anaysis Of Flexible Spacecraft With Magnetic Bearings

With the development of China's space technology,the resolution of remote sensing satellites has evolved from the past tens of meters to the current sub-meter level,greatly improving the quality of acquired image information of the earth.Normally,the camera and the satellite body are connected by bearings,but the conventional bearings have clearances.When the satellite is maneuvered and stable,the camera will shake,which affects the image quality of the camera.In this paper,the magnetic suspension bearing is used to connect the camera and the satellite body.The magnetic suspension bearing uses the magnetic force to suspend the camera shaft in space.It has the characteristic s of no contact,adjustable bearing stiffness and damping,which can effectively reduce the camera shake and improve the imaging quality of the camera.This has important engineering significance for improving the resolution of remote sensing satellites.The model of the magnetic suspension bearing was built and simulated.The calculation formula of electromagnetic force of electromagnet is derived by field energy theory,and the mathematical model of magnetic levitation force in each degree of freedom is established by combining the specific conditions of axial bearing and radial bearing.The control system of the magnetic suspension bearing is established,and the suspension characteristics of the rotor are simulated and analyzed.The results show that the rotor can be quickly stabilized in the equilibrium position.The flexible satellite dynamic model with magnetic suspension bearing is further established by using the obtained magnetic levitation force model.Analyzing the structural characteristics of the satellite,the magnetic suspension bearing can be considered as a space hinge with clearance and the binding force is magnetic levitation force.Using the variational principle,a complete set of satellite dynamics equations is built and assembled into a matrix form,namely the dynamic model of the satellite.The model has not been simplified in the establishment process,and can fully and accurately describe the dynamic characteristics of the satellite.The modeling process has certain versatility and is suitable for modeling any tree multi-body dynamic system.The dynamic simulation model of the satellite is established and the attitude dynamics of the satellite is analyzed.The dynamic simulation program was programmed by Matlab/Simulink and the virtual prototype model was built by ADAMS.The simulation results were consistent under different working conditions,and the correctness of the established dynamic model was proved.The dynamic analysis model of the satellite is used to simulate the attitude dy namics of the satellite,including the coupling analysis between the translation and rotation of the satellite,the coupling analysis between the satellite attitude channels,the influence of the disturbance on the attitude of the satellite and a comparative analysis of the effects of different camera connection schemes on satellite attitude.These analysis results can provide guidance for the design of satellite attitude control systems.The camera's attitude response is simulated and analyzed.The simulation of satellites with magnetic bearings and satellites with mechanical bearings is carried out under the conditions of satellite maneuver and satellite stabilization.The simulation results show that the magnetic suspension bearings can isolate the vibration and reduce the disturbance well,thus reducing the attitude shake of the camera.