Research On Active Shifting Mechanism Of An Isolated Body Based On Asymmetric Damping And Simulation Applications

Vibration-isolation systems are widely used in many fields,such as automotive engineering,transportation,aerospace,and civil engineering.The vibration equilibrium position of the isolated body in a vibration-isolation system with asymmetric damping characteristics shows a shift,inspired by this physical phenomenon,a method of actively shifting an isolated body based on asymmetric damping is proposed in this paper.The specific idea is to change the vibration equilibrium position of the isolated body by controlling the damping asymmetry ratio of vibrationisolation systems(the ratio of the damping during the extension stroke to that during the compression stroke),and then control the height of the isolated body.This method can be applied in fields where the height of the isolated body is needed to be adjusted,such as vehicle attitude control,etc.Based on the project “Research on mechanism and control of automobile active tilt based on vibration utilization of strongly nonlinear systems(No.51975299)” supported by the Natural Science Foundation of China,in this paper,the mechanism and law of actively shifting an isolated body based on asymmetric damping are explored,and the proposed method of shifting an isolated body actively is applied to vehicle height control and vehicle tilt control by simulation.Specific studies are as follows:(1)The method of shifting an isolated body actively based on asymmetric damping is proposed,and the shifting mechanism and laws of the isolated body are explored by some methods such as analytical method and energy method.A piece-wise linear single-layer vibration-isolation systems model is established,to clearly and intuitively reflect the relationship between the system parameters and the height shift of the isolated body,the explicit function relationship between the system response and the parameters is derived by the harmonic balance method.Aiming at the strong nonlinearity and discontinuity of the established system,in order to solve it flexibly and improve the accuracy,the homotopy analysis method is used to solve the high order analytical solution,and the convergence accuracy of the series solution is improved by combining the idea of iterative method,the accuracy of this method is verified by comparing the obtained results with the numerical results produced by the fourth-order Runge-Kutta method(RKM).Based on the highorder analytical solution,the influences of some key parameters on the vibration responses of the system are analyzed,and the shifting principle of the isolated body in a vibration-isolation system is explained from the perspective of energy conservation.In the study,the applying range of the homotopy analysis method is expanded,the HAM is applied to solve the piece-wise linear differential equation,In the HAM,the non-smooth terms of differential equations are handled using Fourier series expansion,and the zeroth-order deformation and high-order deformation equations were constructed to solve the series solution of the piece-wise smooth system by selecting auxiliary linear operators and nonlinear operators.Moreover,the iterative methods are applied,and the results of the iteration are taken as the initial guess solution of the next iteration to improve the convergence accuracy of the series solution.The research results show that the method of actively shifting an isolated body based on asymmetric damping is feasible in theory and reveal its inherent laws.(2)The inherent laws of actively shifting an isolated body in a double-layer vibration isolation system based on asymmetric damping are explored by analytical method.A piece-wise linear double-layer vibration-isolation system model is established,and the explicit function relationship between system response and parameters is solved by the harmonic balance method.The steadystate responses of the two-degree-of-freedom coupled system under simple harmonic excitation are solved by the incremental harmonic equilibrium method and the homotopy analysis method,respectively,and the analytical results are verified by the fourth-order RKM,the results show that both analytical methods are effective methods for solving two-degree-of-freedom coupled piecewise linear differential equations,and the HAM has higher accuracy.Based on the analytical solution solved by the HAM,the effects of key parameters on the shifting height of the isolated body are explored.The research results provide theoretical basis and guidance for the application of the proposed active shifting isolated body method in the automotive field.(3)The proposed active shifting isolated body method is applied to vehicle height control by simulation.The single-wheel vehicle height control system is established.Based on the proposed method of actively shifting the isolated body with asymmetric damping,the model predictive controller(MPC)and the linear active disturbance rejection controller(LADRC)are designed,respectively,and simulation results show that both controllers can shift the vehicle body to the desired height quickly and accurately.On this basis,the whole vehicle height control system model is established,and the whole vehicle body height controller is designed based on the model predictive control theory.The results show that the designed vehicle height controller can control the vehicle body to the desired height quickly and accurately without deteriorating the vehicle pitch angle and roll angle.The proposed vehicle height control method makes it possible to adjust the vehicle height by a semi-active actuator,which tries a new method and approach for vehicle height control under specific conditions,such as high-speed steering,emergency avoidance,and rollover prevention.(4)The proposed active shifting isolated body method is applied to vehicle tilt control by simulation.The vehicle roll dynamics model and vehicle steering model are established.Based on the active shifting isolated body method,the linear active disturbance rejection controllers are designed(LADRC)to control the vehicle height on the left and right sides,respectively,and then control the vehicle body to tilt towards the inside of the curve,so that the torque generated by the gravity force can completely or partially offset the centrifugal torque generated by the centrifugal force,thus improving the handling stability and anti-rollover capability of the vehicle during turning.The results show that the proposed tilt control method can significantly reduce the lateral acceleration experienced by passengers and the lateral load transfer rate(LTR),thus improving the handling stability and driving safety of the vehicle.(5)The test platform of vibration-isolation system is built,and the active shifting control test of the isolated body is conducted with a ordinary magnetorheological damper as the actuator,the feasibility of the proposed method of actively shifting an iaolated body is verified.Firstly,the external characteristics of the classic RD-1005-3 magnetorheological damper produced by LORD Company is tested by the shock absorber performance test system.Based on the experimental data,the parameters of the Bouc-Wen model are identified by the least square method,and the mechanical model of the magnetorheological damper is established.The isolated body height controller is designed based on the proposed active shifting isolated body method,the feasibility of shifting an isolated body actively with a ordinary magnetorheological damper as actuator is proved by simulation calculation.Then,based on the NI-PXI hardware platform and Lab VIEW software platform,the real-time measurement and control test platform for shifting an isolated body actively is developed,the proposed active shifting the isolated body method is tested and studied with the RD-1005-3 magnetorheological damper as the actuator,the test results verify the feasibility of the active shifting isolated body method based on the asymmetric damping.