| An important area of vibration engineering is vibration isolation.The effective isolation of harmful vibration has always been the focus of research.The medical equipment,optical equipment and aerospace detection precision instruments need strict vibration isolation to ensure the normal operation of the equipment.Therefore,the research on the new vibration isolator has important engineering practical significance.The existing vibration isolators generally have the problems of narrow frequency band and low precision of vibration isolation,while the multi-link mechanism has strong nonlinearity,which is conducive to the isolation of small vibration.In this paper,a Z-type connecting rod system is proposed,and the system is analyzed theoretically,simulated and experimentally studied.The results show that it has a wide vibration isolation frequency band and a small vibration transmission rate,and has a good performance of low frequency vibration isolation under active control.The main research work is as follows:(1)A Z-type connecting rod system is proposed.The kinematics and dynamics are modeled,and the dynamics is simulated by ADAMS,a multi-body dynamics simulation software.The results show that the amplitude-frequency response curves of the theoretical dynamics model and the simulation dynamics model basically coincide,and the error of the two models is less than 1%,which verifies the correctness of the established dynamics model.At the same time,it is found that the quasi-zero stiffness can be obtained by installing torsion spring at the joint Angle of Z-type connecting rod system(2)The passive vibration isolation performance of Z-type connecting rod system is studied.Firstly,the effects of connecting rod mass ratio and spring stiffness on the amplitude-frequency response of the vibration isolation system are studied.Secondly,the stiffness of the vibration isolation system is optimized.Single objective optimization and multi-objective optimization are carried out for the Z-type connecting rod system respectively.The optimization objective of the single objective optimization is the widest vibration isolation frequency band at the end point of the system in the y direction(vertical direction),while the optimization objective of the multi-objective optimization is to minimize the comprehensive response amplitude of the end point in the x direction(horizontal direction)and y direction at a specific frequency.The results show that the optimized vibration isolator has wider frequency band and better vibration isolation effect.(3)The experimental bench of Z-type connecting rod system was designed and built for vibration experiment.Firstly,the displacement transfer characteristics of Z-type connecting rod system under harmonic excitation are analyzed experimentally,and compared with the theoretical analysis results.The results show that the simulation results match well with the experimental results,which verifies that the proposed Z-type connecting rod system has good vibration isolation performance.Secondly,the quasi-zero stiffness characteristics of Z-type connecting rod system obtained by installing torsion spring at joint Angle are verified by statics experiments.Finally,the displacement transmission characteristics of Z-type quasi-zero stiffness system are tested,and compared with the original Z-type connecting rod system,the results show that the Z-type quasi-zero stiffness system has wider vibration isolation frequency band,smaller natural frequency,and higher vibration isolation accuracy than the Z-type connecting rod system.(4)The active vibration isolation performance of Z-type connecting rod vibration isolation system is studied.The Backstepping control algorithm is used to design the active vibration isolation controller of the Z-type connecting rod system,and the stability of the system is analyzed based on the Lyapunov stability theory.Then,the effectiveness of the proposed active vibration isolation controller based on Backstepping is verified by numerical simulation.The results show that when the system is excited at 4.5Hz,the displacement response amplitude of the end point in the x direction is 6×10-5m,and the response amplitude of the end point in the y direction is 8×10-4m,and the system isolation rate reaches 80.0%.Compared with passive vibration isolation,the vibration isolation rate of Z-type connecting rod system is improved by 42.5%under active vibration isolation strategy.It can be concluded that under the action of Backstepping control algorithm designed in this paper,Z-type connecting rod system has good vibration isolation effect. |
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