Study On Mechanical Property And Damping Mechanism Of A New Isolator With Ouasi-zero-stiffness

As a kind of nonlinear vibration isolation, the quasi-zero-stiffness isolator has excellent performance when dealing with the low frequency vibration isolation problems and is a hot issue in the field of vibration isolation. Based on related theory, a self-adjusting quasi-zero-stifness vibration isolation system is designed through the positive and negative stiffness parallel mechanism. At the static equilibrium position, zero stiffness of the vibration isolation platform is achieved, and during the small amplitude vibration the design goals of high-static-low-dynamic stiffness is reached, which ensures the vibration isolator has high load capacity and low natural frequency at the same time, achieving the low-and-ultralow frequency vibration isolation and verifying the perfect vibration performance of the vibration isolator. The detailed content of this paper is showed as follows:First, the principle of quasi-zero-stifness is introduced. The mechanical model in the vertical direction of a three oblique spring mechanism was deduced, and the model characteristic of the force-displacement and the stiffness are studied. Then based on the studied mechanism, a novel quasi-zero-stifness vibration isolator is achieved and its mathematical model is established too. The force-displacement and the stifness-displacement curve characteristic of the isolator are deduced in detail. The relation between zero stiffness the system parameters is thoroughly analysed. Near the static equilibrium position, using the error analysis a reasonable simplified force-displacement expression of the isolator is achieved.Second, compared to the force transmission characteristics of a linear system, the amplitude frequency characteristics and force transfer characteristics of the quasi-zero-stiffness vibration isolator is studied. The jumping-up and jumping-down frequency and their influencing factors are analyzed. Using the harmonic balance method, the force transfer characteristics of the quasi-zero-stiffness isolator is discussed under harmonic excitation; using the average method, the displacement transfer characteristics of the isolation is discussed under foundation displacement excitation.The results show that the quasi-zero-stiffness isolator can realize low frequency vibration isolation.Third, as the excitation frequency is higher than the jump-down frequency, the quasi-zero-stiffness isolator has perfect performance in vibration attenuation. When the excitation frequency lies in the jumping frequency domain, the solution of system dynamics equations is uncertainty. A kind of increasing damping control method is proposed to solve this problem. When the system damping increased to a certain value, the jumping-down frequency will be smaller than the excitation frequency, and the system response can be transferred from the resonance branch to the non-resonance branch. The timing of control withdrawnness can be judged by the Von der Pol Plane. Finally, the mathod realizes that its effective vibration isolation frequency is enhanced to the jumped-up frequency Ωu, overcomes the problem of vibration isolation during the jumping frequency domain of the quasi-zero-stiffness system, and improves the vibration isolation effect of this isolator.