Design And Performance Research Of Magnetic Negative Stiffness Vibration Isolator For Car Suspension

As people’s demand for car ride comfort has increased,the car suspension has developed from passive suspension to semi-active suspension and active suspension.In China,semi-active and active suspensions are difficult to popularize due to technical requirements and manufacturing costs,while passive suspensions are more widely used.Passive suspension because of constant suspension parameters,vibration isolation performance under different excitation is poor.In order to solve this problem on the basis of low cost,this paper integrates the magnetic spring,which is capable of generating negative stiffness,into the passive suspension of a car to build a magnetic suspension,and investigates and verifies the performance change of the magnetic suspension compared with the passive suspension through simulation and experimentation,and compares and analyses the performance superiority of the magnetic suspension.The details of the study are as follows:(1)A magnetic suspension isolator is designed based on the operating principle of a high static and low dynamic stiffness vibration isolator.Based on the design of suspension positive stiffness spring,in order to make the passive suspension have high static and low dynamic stiffness characteristics to improve the suspension performance,the negative stiffness magnetic spring is introduced into the automobile passive suspension,and the adaptive variable stiffness is realized by paralleling with the positive stiffness spring.Four vibration isolator solutions are briefly designed based on the magnetic spring,and the isolator design is selected based on the advantages and disadvantages of each solution and the application environment.The preliminary design of the vibration isolator dimensions and structure is carried out on the basis of this scheme,while the material properties of the magnetic spring are analysed to provide a theoretical basis for subsequent performance studies and the design of vibration isolator models under different car suspension parameters.(2)Based on MATLAB/Simulink,a simulation model of the dynamics of the magnetic suspension and passive suspension system is established and a comparative simulation analysis of the magnetic suspension performance is carried out.In the process of investigating the driving smoothness of the magnetic suspension,a time-domain analysis was carried out using the vertical acceleration of the reeded mass as the evaluation index,and a frequency-domain analysis was carried out using the displacement transfer rate between the reeded mass and the road surface as the evaluation index.The results show that in the time domain,the ride comfort of the magnetic suspension is better than that of the passive suspension and the degree of improvement of the ride comfort increases with the increase of the road excitation,from 8.8 % of the C level road to 38.9 % of the H level road.In the frequency domain,the smoothness advantage of the magnetic suspension is mainly in the relatively low frequency range of 0 to 3 Hz,while it is largely consistent in the relatively medium to high frequency range of 3 to 30 Hz.In addition,the presence of variable stiffness results in multiple peaks in the displacement transfer rate curve of the magnetic suspension.The suspension resonance interval,peak displacement transfer rate and starting vibration isolation frequency are significantly reduced.(3)In order to analyse the performance of the magnetic suspension in various aspects,the stability of the magnetic suspension is analysed using the dynamic load variation of the wheels and the difference in the phase trajectory curve of the system as evaluation indicators,and the suspension is evaluated comprehensively using functions.The results of the dynamic load variation show that the presence of the magnetic spring reduces the handling stability of the suspension and that the degree of deterioration of stability performance increases with the increase of road excitation,from 2.5% of the C level road to 14.1% of the H level road.The results of the phase diagram analysis show that the presence of the magnetic springs improves body stability while reducing wheel stability.Through the comprehensive analysis of the ride comfort and stability of the suspension,it can be seen that the performance of the magnetic suspension is better than that of the passive suspension except based on the limit performance weight ratio.(4)In order to verify the correctness of the simulation results of the magnetic suspension performance.An experimental rig for a two-degree-of-freedom 1/4 magnetic suspension was built,and the variation of spring load acceleration and wheel displacement under different excitations was tested using a dynamic signal test system.The experimental results show that,the addition of magnetic springs in the passive suspension improves the ride smoothness of the suspension system,but also reduces the handling stability of the suspension system,and the magnitude of the change in suspension performance varies with different excitations.