Integration Of Quasi-Zero Stiffness Isolation And Energy Harvesting For Six-DOFS Vibration

Vibration control has always been one of the hot issues in engineering practice.Six-degree-of-freedom micro-vibrations are widely present in spacecraft,and these low-frequency micro-vibrations can seriously affect the imaging resolution of those high-precision remote sensing satellites.However,the traditional passive vibration isolation cannot meet the requirements of low-frequency vibration isolation and system bearing stability at the same time.Therefore,for the six-degree-of-freedom vibration isolation,the system needs to be isolated with a negative stiffness structure to achieve a quasi-zero stiffness isolation platform with high static and low dynamic stiffness to meet the high load carrying capacity under low frequency vibration isolation.In this paper,a negative stiffness magnetic spring(NSMS)structure composed of mutually attracted magnets is designed and statically analyzed.The energy harvesting structure is also connected in parallel to this basic structure,and then it is introduced into the two-degree-of-freedom vibration isolation platform and the six-degree-offreedom vibration isolation platform respectively,and its dynamic characteristics are studied by theoretical analysis,numerical validating and vibration test.The main contents of this paper are as follows:(1)The designed negative stiffness magnetic spring(NSMS)structure is introduced into the two-degree-of-freedom vibration isolation platform.The platform is divided into two layers,upper and lower.The negative stiffness magnetic springs and energy harvesting coils in the lower layer convert mechanical energy into electrical energy while suppressing vibration,and the electrical current is fed into the piezoelectric material in the upper layer to achieve variable stiffness to improve the vibration isolation performance of the system.Starting from the vibration equation obtained from the steady-state equilibrium,the frequency response function of the transmissibility and output power under simple harmonic excitation is obtained by using the harmonic balance method.The vibration isolation band is extended to the lower frequency and the two resonance peaks are reduced to the lower frequency.The numerical results verify the correctness of the analytical solution.Then the performance is measured by the absolute displacement ratio,relative displacement ratio and absolute acceleration ratio under the action of circular step displacement and circular pulse displacement,respectively.The numerical calculation results show that the introduction of high static low dynamic stiffness improves the vibration isolation performance of the double-layer vibration isolation system.(2)An electromagnetic Stewart stage with high static low dynamic stiffness is investigated to suppress spatial six-component microvibrations while allowing energy harvesting.Each leg in the Stewart stage contains a moving electromagnet suspended between two fixed permanent magnets.This arrangement allows the magnetic springs to have negative stiffness and soft nonlinearity,and also allows each leg to achieve quasi-zero stiffness(QZS).The harmonic balance method based on rigid body dynamics and nonlinear elasticity theory is used to obtain the frequency response functions of the force transmissibility and output power of the system at the first main resonance,and the effects of different mechanical and electrical parameters on the transmissibility and power of the system are analyzed.The agreement between the numerical simulation results and the analytical results indicates that the vibration isolation performance of this QZS vibration isolation platform in six directions is significantly better than that of the corresponding linear system.(3)The six-degree-of-freedom vibration isolation and energy harvesting integration experimental research was conducted: the designed six-degree-of-freedom vibration isolation platform was manufactured;through the use of electromagnetic three-axis shaker,harmonic sweep frequency excitation test is conducted;the acceleration transmissibility and displacement transmissibility of the platform and the induced electric potential of the legs were studied and analyzed,and the results showed that the designed vibration isolation platform has good vibration isolation performance and energy harvesting effect,which validated that the strengthening of nonlinear stiffness can optimize the vibration isolation efficiency of the platform.