Research On Coupled Dynamics And Control For Multi-rigid-flexible Bodies Of Spacecraft With Flexible Solar Arrays

Solar arrays track the sun to keep the largest area towards it,which ensures the the maximum conversion efficiency of energy.The spacecraft with large flexible solar arrays is a typical multi-rigid-flexible bodies coupled dynamical system.The rotation of solar arrays may result in the disturbance of the spacecraft attitude.Therefore,maintaining the stability of spacecraft attitude during the driving pro cess of solar arrays is an urgent problem to be solved.It is necessary to develop the method for multi-rigid-flexible coupled modelling of spacecraft.On this basis,it has important theoretical guiding significance and engineering practical values to do research on attitude motion,solar arrays driving and linear vibration of the structure.In this thesis,the dynamic modelling and attitude analysis for the spacecraft with lateral solar arrays are studied.Then multi-rigid-flexible bodies coupled modes are obtained based on the concept of global modes by analytical derivation and numerical simulation.On this basis,the dynamic characteristics,modal analysis and the response under different exciations are analyzed.According to the comparison of numerical simulation results,the validation and accuracy of the analytical model have been veryfied.The proposed control method is feasibility in engineering.The detailed research content is as follows:Rigid-flexible coupled dynamic equations,which describe the “hub-beams” system of a rigid shaft with flexible solar arrays and contain the effects of dynamic stiffening,are established by using Hamilton principle.The natrual frequency and modal shapes of the linearized model are obtained by the global mode meth od.Dynamic equations can be decoupled by the modal orthogonality,and then independent equations of the rigid body motion and each mode are obtained.The decoupled equations are more convenient for dynamic response analysis and control design,which are the advantages that the assumed mode method and finite element method do not have.Furthermore,the influence of the critical speed on the response stability of the system is discussed.Then applicability conditions of the linearized and first approximation model are given.The general applicability of the first approximation model is demonstrated from the analysis of frequency and response characteristics.Solar arrays are driven by the driving assembly to face the sun.Due to the influence of the complex internal structure and external disturbance,the driving speed may not be stable.In this thesis,the solar array driving model is installed on the platform,which is assumed to be fixed or large enough.Under the slow rotation,the linearized dynamic model is obtained.Effects of variations for the system stiffness and flexibility parameters on vibration modes are discussed by considering the rigid-flexible coupling effect of flexible solar arrays driven by the rigid shaft.The electromechanical integral model of the driving system is established,where the stepper motor is contained.Then effects of the subdivision driving scheme for the stepper motor on eliminating electromagnetic oscillation are analyzed.Aiming at the disturbance on rotational speed caused by harmonic and friction torques,a control strategy based on the combination of sliding mode control and input shaping is proposed.The rotation fluctuation and structure vibration can be suppressed by the cooperate control scheme simultaneously.Finally,the accuray of the load dynamic model and the validity of the cooperative controller are veryfied by numerial simulations.This thesis investigates the multi-rigid-flexible bodies coupled dynamic model of spacecraft with slender solar arrays.The three-axis stabilized dynamic model of the spacecraft with large lateral solar arrays is established,where there is the relative motion between the rigid platform and solar arrays.The particularity of spacecraft inherent characteristics due to the structural symmetry is discussed.Based on the concept of the global mode method,the reduced and discrete model of the spacecraft is obtained.Multi-rigid-flexible bodies coupled characteristics of the spacecraft are analyzed from parameters variation and the responses of different torques.Finally,the cooperative controller is designed for attitude motion and structure vibration when solar arrays are being driven,which is relied on multi-rigid-fleixble bodies coupled modes.Numerical simulation results demonstrate the validation of the proposed controller.In fact,the driving shaft cannot be absolutely rigid.The elastic deformation of the driving shaft can be caused by the motion of solar arrays as their rotary inertia is large.This thesis firstly studies dynamic characteristics and vibration suppression of the T-shaped structure,which can be considered as the component of spacecraft.The piezoelectric patches bonded to the surface of the structure are used as actuators to provide modal control torque.In order to optimize actuator configurations,the input energy criterion is proposed.Then the dynamic model of the flexible spacecraft with solar arrays driven by the flexible shaft is established.Considering the coupling of attitude motions and elastic vibration,distributed piezoelectric patches are used to suppress the vibration of solar arrays during the attitude maneuver of spacecraft.Numerical simulations demonstrate that the distributed control scheme performs better than the attitude-vibration integrated controller.