Investigation On The Nonlinear Characteristics Of Whole-spacecraft Vibration Isolation Systems Based On Volterra Series Theory

Along with the development of space technology, human beings are no longersatisfing with a short travel to space, and a growing number of new satellites andspace station are constantly lunched into space. Spacecraft suffers complex andharsh kinetic environment during launch stage. At the same time, a large stiffness ofconical shell adapter is employed to connect the launch vehicle and payloads totransfer thrust effectively, which leads to a variety of vibration loads and shockloads acting on satellites. Intense vibration will cause satellite structure fatiguedamage and failure of sensitive components. In order to reduce or inhibit the role ofthese loads to satellite and its components, reinforcing the satellite structure orisolating the components independently which can not meet the performance indexare usually employed by experts in the field of space at home and abroad. But thesemeasures will increase the useless mass and occupy the weight and space of thelaunch vehicle. Whole-spacecraft vibration isolation(WSVI) technology wasproposed to isolate all kinds of vibration loads and shock loads transmitted intosatellites from launch vehicle in the1990s.The viscoelastic constrained damping truss whole-spacecraft passive vibrationisolator (VCDTPVI) and nonlinear characteristics of the whole-spacecraft vibrationisolation system are investigated systematically based on the theory of Volterraseries. The main research contents involve the following aspects:In this dissertation, a new substitutional viscoelastic constrained damping trussvibration isolator (SVCDTVI) is presented on account of traditional payload adapter.The dynamic behavior of the viscoelastic damping structure is investigated and aviscoelastic material performance testing device is designed. The parameters of themodel are identified by the experiment and the laws of stiffness of dampingstructure changing with the frequency and the damping area are derived, these lay asolid foundation for further study of the SVCDTVI.Based on the theory of Volterra series, five order generalized frequencyresponse function is derived for the nonlinear system with nonlinear stiffnesscharacteristics according to the actual model parameters of the SVCDTVI and thefrequency response characteristics are analyzed. The output frequency responsecharacteristics of the nonlinear vibration system are investigated with differentinputs. The frequency response derived by Volterra series are compared with that ofby harmonic balance method(HBM), in which the correctness of the theoreticalanalysis results are verified.The relative displacement output response of nonlinear vibration isolation system with nonlinear stiffness and nonlinear damping are investigated by the outputfrequency response function(OFRF) under base displacement excitation. The effectsof nonlinear damping parameters on the output response are analyzed, and thetheoretical proofs are given by Volterra series. On this basis, the analysis of theinfluence of nonlinear stiffness and nonlinear damping parameters on the absolutedisplacement transmissibility from the bottom of whole-spacecraft to the top ofwhole-spacecraft are conducted.The nonlinear dynamic model of whole-spacecraft vibration isolation system isestablished, and the transmissibility from the bottom of the SVCDTVI to the massof whole-spacecraft at the first order and the second order resonants and othernon-resonant regions is investigated with nonlinear characteristic parameters ofnonlinear system based on OFRF under base displacement excitation. The structureparameters of the SVCDTVI are optimized based on improved adaptive ant colonyoptimization algorithm, and the vibration isolation performance of the SVCDTVIare analyzed by the finite element(FEM), at the same time, the dynamiccharacteristics of the coupled rocket-spacecraft system are simulated after theSVCDTVI is applied.The SVCDTPVI are designed and manufactured, and the experiments areperformed on the prototype vibration isolation platform. The simulation results arecompared with the experimental data to verify the validation of the presentedSVCDTPVI. The nonlinear influence factors of the output response and resonantfrequency are analyzed through the WSVI experimental system, which also verifiesthe correctness of theoretical analysis by the Volterra series in this dissertation.