Dynamic Characteristics And Experimental Study Of A Quasi-zero Stiffness Vibration Isolation System

Mechanical vibration mainly comes from the external interference and the vibration generated by mechanical equipment.Mechanical vibration is a serious hazard,which reduces the machining accuracy,damages the mechanical equipment,causes environmental noise pollution and even endangers the life safety of the operators.Aiming at the problem that linear isolators have poor isolation effect for low and ultra-low frequency vibration,the in-depth study on the nonlinear system vibration isolation performance is the key to eliminate the harm of mechanical vibration.According to the principle of parallel vibration isolation with positive and negative stiffness,the static and dynamic characteristics analysis,vibration isolation performance as well as the experimental study of the quasi-zero stiffness vibration isolation system are carried out in this paper.Firstly,The dynamic model of quasi-zero stiffness vibration isolation system is established.Then,based on the average method,the dynamic characteristics of the quasi-zero stiffness vibration isolation system are analyzed theoretically and simulated numerically.The main contents of this paper include:?1?The model and static characteristics of quasi-zero stiffness isolator are analyzed.The principle of parallel vibration isolation with positive and negative stiffness is detailedly discussed,through static analysis,the relationship between Mechanical parameters and system stiffness is studied,and thus the zero stiffness condition is obtained.The expression of restoring force-displacement is expanded by Taylor's formula,the quantitative analysis shows,in the small displacement range x?27?0.2,the error rate of using approximate expression instead of exact expression is less than 1.76%.?2?Dynamic characteristics and isolation performance of the quasi-zero stiffness vibration isolation system are studied.The dynamic equation of quasi-zero stiffness vibration isolation system is established,based on the average method,the analytical formulas of the system dynamic response and transmissibility are derived theoretically,and the derivation process and results are verified by Runge-Kutta method.Then the effects of nonlinear coefficient,excitation amplitude,vertical damping and horizontal damping on the system dynamic characteristics are numerically analyzed,and compared with an equivalent linear system.The results indicate that the values of transmissibility peak and initial isolation frequency of quasi-zero stiffness vibration isolation system are smaller.When the vertical damping ratio is 0.01,compared with the linear system,the peak force transmissibility of quasi-zero stiffness system decreases by 49.0%,the peak absolute displacement transmissibility drops by 55.7%,under force and displacement excitations,the initial isolation frequency decreases by79.7%and 74.8%,respectively.?3?Based on dynamic vibration absorption principle,dynamic optimization of the quasi-zero stiffness vibration isolator is carried out.Based on the principle of dynamic vibration absorption,the dynamic model of the coupled system is established,the analytical solution of dynamic response and the expression of force transmissibility are deduced by the averaging method.The effects of the mass,stiffness and damping of the absorber on the dynamic response and force transmissibility characteristics of the coupled system are numerically analyzed.The research finds that when the excitation frequency is equal to the natural frequency of the absorber,the amplitude of the primary system decreases sharply to a minimum of2×10^-4.Thus,rational design of the natural frequency of the absorber can significantly suppress the vibration intensity of the primary system.?4?Experimental study of the quasi-zero stiffness isolator is actualized.An experimental platform is built to study the dynamic characteristics of the quasi-zero stiffness vibration isolation system and the coupled system.The experimental results reveal that when the excitation acceleration decreases from 3.0g to 2.0g,the initial isolation frequency of quasi-zero stiffness system reduces from 13 Hz to 6 Hz,and the isolation frequency bandwidth enlarges.For half-sinusoidal impact with pulse width less than 10 ms and acceleration less than 13.0g,sinusoidal harmonic excitation with acceleration of 2.0g,frequency of 30 Hz and 50 Hz,the quasi-zero stiffness isolation system has excellent isolation and cushioning performance.The dynamic response experiment of the coupled system proves that the vibration isolation performance of quasi-zero stiffness isolator can be further improved by introducing dynamic vibration absorber to reduce the amplitude of the primary system in a certain frequency domain.