Dynamic Characteristics Analysis Of Nonlinear Damping Vibration Isolation System

Linear passive vibration isolators are widely used in engineering fields due to their advantages of simple structure and no need for external energy input.However,due to their fixed stiffness and damping parameters,there are two main defects: one is the contradiction between large damping to suppress resonance and the vibration isolation effect in high frequency,and the other is that it is difficult to combine low natural frequency with large bearing capacity.These disadvantages of linear vibration isolation system can be avoided by using nonlinear damping and nonlinear stiffness.By controlling the damping and stiffness in different frequency bands,the nonlinear vibration isolator makes the vibration isolation system have better vibration isolation effect and wider vibration isolation frequency band.In this thesis,based on the moving cam mechanism,the realization method of nonlinear damping is proposed,the nonlinear damping vibration isolation model is established,and the dynamic characteristics of the nonlinear damping vibration isolation system are studied.The main research contents are as follows:(1)A variable damping device based on the moving cam is designed.According to the principle of equal damping energy consumption,the damping characteristics(piecewise damping and continuous variable damping)of two different cam profiles are analyzed.The piecewise damping device is applied to the vibration isolator.According to the different external excitation,the dynamic model of the piecewise damping active vibration isolation and passive vibration isolation system is established.The equivalent linear system is obtained according to the principle of energy equivalence.The theoretical solution of the equation is further obtained and the correctness of the theoretical solution is verified by the numerical solution.According to the theoretical solution,the influence of system parameters on the dynamic characteristics of the vibration isolation system is analyzed.(2)The dynamic model of continuous variable damping active vibration isolation and passive vibration isolation system is established.The model is solved and the correctness of the theoretical solution is verified by numerical solution.The influence of the main parameters of the system on the amplitude-frequency response is studied.The vibration isolation characteristics of continuous variable damping system are explored with force transfer rate/displacement transfer rate as the evaluation index.The advantages of continuous variable damping system over linear system are compared and analyzed.(3)Based on the introduction of quasi-zero stiffness into the moving cam mechanism,the quasi-zero stiffness device is designed,the characteristics of quasi-zero stiffness are analyzed,and the contour curve of the moving cam is designed.Combining the quasi-zero stiffness device with the continuous variable damping system,the dynamic model of the quasi-zero stiffness continuous variable damping vibration isolation system under the excitation of simple harmonic force is established.The vibration equation is solved according to the principle of energy equivalence and the harmonic balance method,and the amplitude-frequency characteristics and force transmissibility characteristics of the system are studied.The innovation of this thesis lies in the application of passive variable damping device based on moving cam in vibration isolation,which can provide important reference for the design and optimization of new nonlinear vibration isolation system.