Design Of An Isolation Device For Multi-dimensional Low Frequency Vibration And Its Performance Analysis Based On A 3-PCR Parallel Mechanism

Human activities are inseparable from vibrations.The sound is transmitted through the vibration of the air,and the hearts beat and pump the blood.It’s common to find the vibration in engineering,such as the bridges and buildings are shaken by the wind,the work piece vibrates when they are processed.Different types of vibrations make different influence to the human beings.The approach of vibration utilization and vibration reduction are developed,as people making a deeper understanding of the vibration.The spring,rubber and varieties of absorbers are used in different occasion to isolate the vibration.The parallel mechanism is selected with the advantage of high-rigidity,high precision and multi-dimension,which can be used in vibration reduction by installing the damping element like spring-damp.The method has made great progress,which becomes one of the active research fields.The thesis is supported by the National Science Foundation of China(No.51675306)and(No.51275275).The 3-PCR parallel mechanism’ analysis of kinematic and dynamic are completed,and the parameters are optimized.Then the multi-dimensional and low-frequency vibration reduction is established by combining the quasi-zero stiffness system with the 3-PCR parallel mechanism and the vibration reduction preformation were analyzed.Firstly,the 3-PCR parallel mechanism is selected as the main structure of the vibration mitigation device for the most common three translational vibrations in production and life,and the original mechanism is modified to have better mechanical properties.The closed-loop vector method is used to investigate the kinematics of the mechanism,and the correctness of the ADAMS model is compared and verified with the theoretical model.The coordinate searching method is used to draw the working space of the mechanism.Based on the actual situation,the spherical space centered on the equilibrium position is selected as the research goal,the influence of the institutional parameters on the size of the spherical space are analyzed.Secondly,the dynamic model of 3-PCR parallel mechanism is established by using Lagrange equation.The influence of upper and lower platform radius,rod length,installation angle,spring stiffness and upper platform mass parameters on the natural frequency of the mechanism are analyzed.The natural frequencies and modes obtained in Matlab which are analyzed by ADAMS.Taking the 3-PCR parallel mechanism as the main body,according to the concept of equivalent stiffness which was proposed by some scholars,the equivalent stiffness of the vibration isolation system of the parallel mechanism is obtained.The effect of different spring on the modality is analyzed..Thirdly,the quasi-zero stiffness principle is briefly introduced.A quasi-zero stiffness structure is implemented and analyzed.The static characteristics of the quasi-zero stiffness structure are analyzed.The acceleration response analysis is obtained under the harmonic excitation,and the conditions that need to be satisfied to obtained the quasi-zero stiffness is analysis.The innovative use of a combination of a prismatic pair and a quasi-zero stiffness structure can be used to reduce the multidimensional low-frequency vibration;the natural frequency of the 3-PCR parallel mechanism are compared which with the quasi-zero stiffness structure or without the quasi-zero stiffness structure.The frequency response curve of the harmonic excitation device before and after the installation of the quasi-zero stiffness device is analyzed,and the equivalent stiffness value of the vibration reduction platform with the quasi-zero stiffness structure is calculated.The distribution of equivalent stiffness is analysis.Fourthly,the parameters such as upper and lower platform radius,rod length and included angle are used as variables to analyze the influence of single parameter on the equivalent stiffness,and then the evenly distributed of equivalent stiffness values in the working space are set as the goal,a variety of parameters were optimized by the genetic algorithm,and the equivalent stiffness distribution in the space obtained after optimization was analyzed.Then,the equivalent stiffness of the 3-PCR damping platform with quasi-zero stiffness structure was optimized,and the equivalent stiffness distributions optimized are compared with the result before the optimization.