Multi-objective Optimization Of Multi-mode Magneto-rheological Mount Structure Based On Vehicle Vibration Control

With the development of modern society and economy,cars have entered thousands of households.At the same time,people have higher and higher requirements for the economy and comfort of the car.Due to the influence of road roughness,Vehicle Powertrain vibration and torque excitation on vehicle NVH performance,there is a certain contradiction between vehicle lightweight and ride comfort.Therefore,in the current development trend of vehicle lightweight,in order to attenuate the vibration and torque excitation transmitted by the powertrain to the vehicle body and reduce the impact of road impact on the powertrain,the vibration isolation performance of the powertrain mounting system needs to be further improved.The vibration isolation effect of passive hydraulic mount is better,but it can not be adjusted in real time according to the vibration isolation requirements of vehicle powertrain mount system.Active mount can achieve the ideal vibration isolation requirements,but its large-scale application is limited by its complex structure,large energy consumption and high cost.The semi-active hydraulic mount has been applied in advanced passenger cars for its ideal vibration isolation effect,relatively simple structure and low energy consumption.It is of great significance to study the semi-active mounting of powertrain for the improvement of NVH performance.As an intelligent industrial material,magnetorheological fluid(MRF)can change its rheological properties significantly in millisecond under the action of external magnetic field,and only needs a small energy input.In this paper,MRF was used as working fluid to design the magnetorheological(MR)mount in the mixed mode of flow and squeeze,and to optimize its structure,so that the MR mount can more effectively attenuate the vibration excitation transmitted from the automotive powertrain to the vehicle body.It provides theoretical basis and technical support for the optimal design of semi-active MR mount.The main research contents are as follows:(1)The working principle of MRF and the vibration isolation principle of powertrain mount were described.After the structure parameters of the rubber main spring were determined,the hardness of the rubber main spring was calculated by the finite element method.On the basis of the simulation,the output damping force and the adjustment coefficient of the MR mount were calculated.(2)Using ISIGHT software,the sensitivity analysis platform of magnetic circuit structure was built.Taking viscous damping force and controllable damping force of flow and squeeze mode as optimization objectives,the optimization model of magnetic circuit was established.According to the sensitivity analysis results and magnetic circuit optimization model,combined with the multi-disciplinary optimization simulation platform,the NSGA-II algorithm was used to optimize the magnetic circuit of the MR mount,and the simulation analysis of the optimization results was carried out;(3)Based on the principle of bond graph diagrams,a lumped parameter model and a bond diagram model of mixed-mode MR mount were established,and the theoretical model of the dynamic characteristics of the MR mount was derived.The dynamic characteristics of the MR mount in the mixed-mode mode were analyzed using MATLAB;(4)The optimization of MR mount cannot directly reflect its vibration isolation performance in the whole vehicle model.Based on the whole vehicle dynamics model,the optimization design method of structure parameters of MR mount was proposed.Firstly,the influence of vibration excitation of in-line four cylinder engine and road impact excitation on vehicle vibration was analyzed.Based on the dynamic characteristic model of MR mount,a 10 DOF dynamic model of vehicle including MR mount was established.Secondly,a multi-objective optimization model were established under the conditions of starting and stopping,constant speed of 60km/h and low speed of vehicle passing through the speed bumps.The root mean square values of vibration acceleration at the seat guide rail were taken as the optimization objectives.Finally,by using ISIGHT,ANSYS parametric design language(APDL)and MATLAB/Simulink software,a collaborative simulation optimization platform was built to optimize the structure of the magnetic circuit of the MR mount based on the vehicle dynamics model.Through the simulation and comparative analysis,the results showed that the isolation effect of MR mount based on the vehicle vibration control optimization was better.