Research On The Characteristics Of A Nonlinear Torsional Vibration Isolator With Positive And Negative Stiffness Parallel Mechanism

As industrial robots and other equipment widely used in manufacturing have higher and higher requirements for the stability of the working environment,and because vibration is one of the important indicators to measure stability,so it is particularly important to suppress or isolate the low frequency micro vibration brought by the working environment.The vibration can be divided into translational vibration and torsional vibration according to the direction of motion.All of these vibration can cause interference to the equipment,especially the sensitive low-frequency microvibration.Therefore,it is especially significant to suppress or isolate the low-frequency micro-vibration brought about by the working environment.In this paper,a nonlinear torsional vibration isolator with simultaneous transmission of static drive torque and isolated low-frequency torsional vibration is designed based on the positive and negative stiffness parallel mechanism,and the performance of which is analyzed.The main contents of this paper are as follows:Firstly,a nonlinear torsional vibration isolator with a positive and negative stiffness parallel mechanism is proposed.Positive rigidity components use round crosssection flexible rods,and negative stiffness components use torsion electromagnetic springs based on the hybrid electromagnetic-permanent magnet structure proposed in this paper.And a three-dimensional model of the non-linear torsional vibration isolator is built using Solidworks 3D drawing software based on the schematic diagram of a nonlinear torsional vibration isolator with a positive and negative stiffness parallel mechanism.In addition,the static and transient dynamics finite element analysis of its main components is performed using Ansys Workbench software.Then,the static characteristics of the nonlinear torsional vibration isolator with a positive and negative stiffness parallel mechanism designed in this paper are studied.The equivalent magnetic circuit method and the virtual displacement method are used to establish the static model of the torsion electromagnetic spring.The electromagnetic stiffness characteristics and the range of negative stiffness are obtained,and the influence of different parameters on the electromagnetic stiffness is analyzed.And The cantilever beam model is used to analyze the static characteristics of a flexible rod with a circular cross section,and the effect of effective length on its output torque,bending moment and potential energy is studied.Based on the research results of the static characteristics of the torsion electromagnetic spring and flexible rod,according to the superimposed nature of the stiffness of the parallel mechanism,Taylor formula is used to establish the sixth-order polynomial of the nonlinear torsional vibration isolator static model.Next,based on the research of static characteristics,the research on the dynamic characteristics of nonlinear torsional vibration isolator is carried out.A dynamic model is established,and the torque transfer rate and amplitude-frequency response characteristic functions are obtained by using the harmonic balance method.For the possible jumping phenomenon,the method of introducing small disturbances is used to analyze and derive the stability conditions of the system solution.Furthermore,the MATLAB software and the classical fourth-order Runge-Kutta method was used to perform numerical simulation of the nonlinear torsional vibration isolator,and its response characteristics under single-frequency,multi-frequency and shock torque excitation were studied to fully grasp the nonlinear torsional vibration isolation Dynamic characteristics.Finally,a prototype of the nonlinear torsional vibration isolator with positive and negative stiffness parallel mechanism is produced,the experimental parameters were determined,an experimental test platform was set up,and an experimental study on the nonlinear torsional vibration isolator was carried out.Through the static characteristic experiment,the actual torque-relative angular displacement characteristic curve is obtained,and the correctness of the static characteristic theoretical analysis is verified.And by carrying out dynamic characteristic experiments and comparing with linear vibration isolation systems,it is verified that the nonlinear torsional vibration isolator proposed in this paper has good vibration isolation performance.The results of this research have promoted the application of this type of torsional vibration isolator,and laid a foundation for the realization and development of the efficient,safe and stable operation of industrial robots.