Research On The Mechanics Performance Of Magnetic Flux Pinning Interface And Its Application In Segmented Mirror

Segmented structure is the development trend of large aperture space telescope in the future.The mechanical segmented mechanism used in space optical system has problems such as lubrication,thermal expansion coefficient matching and complex structure.Using the flux pinning effect of the type II of non-ideal superconductor can form a stable non-contact interface between the superconductor and the magnet,which can provide a new technical path for the development of the mirror segmented mechanism.Flux pinning effect has the advantages of passive stability,adaptability,damping and rigidity.Besides,it does not need extra power consumption except for cooling the superconducting system.It has a good prospect in the field of close-proximity spacecraft maneuver and connection.In this paper,the flux pinning interface(FPI)which can be used in space segmented structure is studied in depth.The main research contents are as follows:Based on the frozen image model,the mathematical model for flux pinning of rigid body is derived and established.Than discusses the flux pinning interface,magnetic source,flux pinning mechanism and six freedom constrained flux pinning interface of different magnet superconductors.The structure and application of flux pinning interface are studied.The flux pinning interface,magnetic field source,flux pinning mechanism and 6DOF constrained flux pinning interface of different magnet superconductors are discussed.The magnetic field method is used to calculate the leviation force and connection stiffness of the single magnet single superconductor flux pinning interface.The calculation results are highly consistent with the experimental data,and the connection stiffness of the interface under different eccentricities is further obtained.The single magnet single superconductor flux pinning stiffness single pendulum experiment is designed to verify the validity of the calculation model.In this paper,the 6-DOF nonlinear dynamic performance of flux pinning interface of modular single superconductor multi magnet for space segmented structure mirror is analyzed,which provides the basis for the design and control of flux pinning interface.Based on the dynamic equation of flux pinning connection of spacecraft,the 6-DOF nonlinear dynamic performance of flux pinning interface of modular single superconductor and multi-magnet for space segmented structure mirror is analyzed.The results show that the flux pinning interface in passive state can achieve stable state;by powering up the actuator,the spacecraft can achieve stable state.The relative attitude and position can reach the balance state,and the balance attitude,balance position and natural frequency of the vehicle can be adjusted by the control voltage,which provides the basis for the design and control of flux pinning interface.The stability of FPI of single magnet and single superconductor is analyzed.This is the premise of its application in space,and provides the basis for further research on the control method of flux pinning system.The linear model of the system proves that the uncontrolled FPI system is passive,and the Lyapunov function of the system is obtained by using the energy method.It is proved by mathematical derivation that the function satisfies three criteria of Lyapunov stability at the stable point.Considering the resistance force,the system is gradually stable,and the uncontrolled single magnet single superconductor flux pinning system is established.This conclusion is verified by the dynamic model of the FPI.Then,the system response of the FPI of single magnet and single superconductor with PID active control is discussed,and the performance of the system response under different magnetic moment values and different control modes is compared.The Lyapunov function of the active FPI is obtained by adding the control force term to the Lyapunov function of the non-control system,and the condition that the system satisfies the stability is obtained.A simplified model of two rigid bodies flying along a circular orbit with flux pinning connection array is established.For the spatial application of flux pinning system,in addition to the interaction force of the interface itself,the influence of other disturbances such as gravity should also be considered.Through the simulation,two equilibrium positions of the flux pinning connection aircraft are obtained.In the first equilibrium state,the equilibrium position of the system is very close to the field cold distance,and the vehicle spacing is gradually stable,but the motion of the vehicle is in a state of edge stability in some attitudes.This stability characteristic is similar to the rigid body motion under the action of gravity gradient.In the second equilibrium state,the equilibrium position of the system is far from the field cooling position,and the system is unstable without control.In this state,the stability can be achieved at large intervals by adding linear state feedback control.The above analysis process and the mathematical framework established by derivation provide the basis for more complex array flight system and system analysis.Based on the optical design of a space-camera,the on orbit assembly of large aperture main mirror is studied by using flux pinning technology,and two designs of reconfigurable flux pinning interface are given.The fundamental frequency of segmented mirror with flux pinning interface is calculated to evaluate the influence of interface stiffness on the overall rigidity of the mirror.Based on the analysis of the mechanical properties of the segmented mirror with flux pinning connection mechanism,the RMS of the mirror are calculated.The technological progress and innovation of this paper are as follows:1)A pinning magnet superconductor interaction model is established,and the leviation force and connection stiffness of the pinning interface between single-magnet and single-superconductor are calculated.In the experiment of single magnet single superconductor flux pinning stiffness single pendulum,when the interval is 10 mm,the error between the measured value of lateral stiffness and the theoretical value is less than 5%,which verifies the validity of the theoretical model.2)The dynamic model of multi-magnet flux pinning interface in equilibrium state is established,and its dynamic performance is analyzed.The results show that the interface is stable.The position and attitude of the interface can be adjusted by controlling the voltage.The amount of translation around the y-axis can reach 20 mm,and the amount of rotation around the x-axis can reach 0.6 rad.3)The asymptotic stability of flux pinning interface is proved by Lyapunov function.The flight model of two rigid bodies along circular orbit array is established under flux pinning connection.The numerical simulation shows that the system can a stability under gravity.4)A scheme of flux pinning interface for on-orbit mirror assembly and reconstruction is proposed.The fundamental frequency and connection stiffness of 6-meter-diameter segmented mirror are simulated and calculated.The influence of external disturbance on the shape accuracy is analyzed.The RMS of the mirror can be kept in the order of 10-8 m,which can meet the needs of high-precision segmented of on-orbit mirror in space.