Investigation On Dynamical Modelling And Attitude-vibration Cooperative Control For The Spacecraft With Flexible Solar Arrays

With the development of space technology and the diversification of space missions,the new generation of spacecraft should meet the strong function,long life and high precision requirements,which makes the spacecraft tend to become more flexible and larger gradually.For a large-scale flexible spacecraft(LSFS)which is composed of large-scale flexible structures such as hinged multi-panel solar arrays,the property of inertia of the flexible components may exceed that of the spacecraft platform significantly.The coupling effect of attitude motion and structural vibration is very prominent for LSFS,and the nonlinear dynamic characteristics of the hinges have a great influence on the in-orbit operation of LSFS.Therefore,how to obtain the global mode and the low-dimensional and high-precision nonlinear dynamics model of the LSFS have become the key problems to be solved in the design of modern spacecraft.This dissertation considers a LSFS with hinged multi-panel solar arrays as the research object.Based on the global mode method,the rigid-flexible coupling dynamic characteristics of the LSFS is conducted from two aspects of theoretical analysis and experimental verification.Then,according to the low-dimensional and high-precision dynamic model of the system,the coordinated control technology of attitude maneuver and structural vibration suppression is applied on the LSFS system.The main research contents and achievements in this dissertation are listed as following:The global mode method of rod and beam composite structures is extended to hinged multi-panel composite structures,and a general method for solving the rigid-flexible coupling global mode of hinged multi-panel composite structures is developed.For the hinged multi-panel composite structures,the simulation and characterization methods of the contact stiffness of hinge connections between panels are determined.Hinges are modeled by torsional springs with variable stiffness,and mode functions of multi-point constrained panels and matching conditions of hinge connections are constructed.Then,the eigen equation of the system is given.The natural frequencies and the analytical rigid-flexible coupling global modes reflecting the dynamic characteristics of the system are obtained,and the dense modes and mode exchange phenomena of the system are studied.A general method of establishing a low-dimensional and high-precision nonlinear dynamic model for multi-panel composite structures with nonlinear hinges is proposed,and the nonlinear dynamic responses of the hinged honeycomb sandwich multi-panel solar array are studied.For the amplitude of external excitation within a certain range,the nonlinear dynamic model of the hinged multi-panel composite structure only needs to take the first two global modes for discretization to satisfy the accuracy of nonlinear vibration analysis,which reflects the advantages of low dimension and high precision in establishing dynamic model by global mode method.Furthermore,the multi-scale method is used to solve the vibration responses of the two-degree-of-freedom nonlinear dynamic model for the system,and the complex nonlinear phenomena are analyzed.The global mode method of hinged multi-panel composite structure is extended to the LSFS with multi-panel solar arrays,and the rigid-flexible coupling global modes of rigid motions and structural vibrations of the system are obtained.On this basis,the dense modes and mode exchange phenomena of the LSFS are studied under the variations of the geometrical parameters of the solar panels and the stiffness of the hinges.For the LSFS with hinged multi-panel solar arrays,the discrete dynamic model of the system is established by using the system analytical global mode.The rigidflexible coupling dynamic responses of the spacecraft under external excitation such as attitude adjustment torques are studied,and the influence of hinge flexibility on the rigid attitude motion of the spacecraft are analyzed.The LQR controller is designed based on the discrete dynamic model of the system,and the input shaper is designed based on the global mode of the system.Then it is combined with PD control to design PD+IS controller.Through a typical example of spacecraft maneuvering from a known attitude angle to an expected attitude angle,the results of LQR controller,PD controller and PD+IS controller are compared,and the control effects,and advantages of the three cooperative controllers designed in this paper are summarized.For the in-orbit LSFS with hinged multi-panel solar arrays,the typical mathematical models of various kinds of excitation(such as attitude control pulse torques,periodic pulse torques and periodic disturbance torques generated by external environment)are extracted.Based on the global mode method and multiple degrees of freedom nonlinear dynamic model establishing method,considering the effects on the spacecraft of various incentives,and the wing base plate hinge nonlinear stiffness,damping factors such as structure,build large the multi degree of freedom of flexible spacecraft orbiting the coupled nonlinear dynamic model.The nonlinear rigid-flexible coupling dynamic response of the system under typical excitation is studied,and the resonance characteristics of spacecraft such as primary resonance and secondary resonance are analyzed.Finally,the nonlinear vibration response of the flexible structure and the attitude motion of the spacecraft platform are studied.In order to verify the effectiveness of the global mode dynamic modeling method,the overall design schemes of global mode testing,nonlinear dynamic response testing and rigid-flexible coupling global mode testing of spacecraft are proposed.The vibration platform of hinged multi-panel structure is built,and its mode test and dynamic response test are carried out.Further considering the microgravity mechanical state of the spacecraft in orbit,the ground experimental model of the spacecraft with hinged multi-panel solar arrays is designed by using a single degree of freedom air floating hub,and the rigid-flexible coupling global mode test and dynamic response test platform of the single axis stable flexible spacecraft is built.Through the simulation and experiment results,the difference between constrained mode and unconstrained mode are compared,and the effectiveness of the global mode dynamic modeling method of hinged multi-panel structure and flexible spacecraft are verified.