| An automotive powertrain mounting system refers to the elastic connection system between the powertrain and the vehicle frame or body. It is an important part of vehicle vibration control system and it has great influence on improving automotive riding-comfort and performance of NVH (Noise, Vibration and Harshness). With advantages such as adjustable damping force, simple structure and less energy consumption, the MR (magnetorheological) mount has become the main development direction of powertrain mounting system in recent years. In order to improve the comprehensive performance of vehicle, the study of interrelationship between powertrain mounting system and suspension system, and how to take integrated control between powertrain mounting system and suspension system are considered to become the major trend. Under such background, the paper studied the dynamic characteristics of hydraulic engine mount, the dynamic characteristics of MR mount, the control strategy of MR semi-active mounting system and the integrated control of powertrain mounting system and suspension system.The hydraulic engine mount is the basis of MR mount, and the study of hydraulic engine mount working mechanism is important to the study of MR mount. Based on the consideration of the mixed features of hydraulic engine mount with decoupler, switched system model was established on the basis of linear model of hydraulic engine mount with decoupler according on the switched system theory. Dynamic characteristics simulation of hydraulic engine mount with decoupler according to the two typical conditions was carried out respectively. Compared the test results, the validity of switched system model was verified. Switched system model was used to simulate the work process of mount with sinusoidal excitation of low frequency with large amplitude or high frequency with small amplitude respectively, study the switching mechanism in double channel flow model and single channel flow model, and discusses the relationship of liquid flows in inertia channel and in decoupling channel. By characteristic test of the self-developed hydraulic engine mount with decoupler, the effect to the dynamic characteristics of hydraulic engine mount of preload, excitation amplitude and excitation frequency was discussed, which provide a theoretical basis for reveal working mechanism and structure design of hydraulic engine mount. Structure and working mechanism of MR mount based on extrusion model is analyzed. According to the operation mode and design principles of the MR fluid and the structure characteristics of mount components, the magnetic circuit of MR mount is designed by using the electro-magnetic field theory. The simulation analysis of MR mount’s magnetic circuit and magnetic field is made by using finite element method, and then the magnetic induction intensity distribution of MR fluid located at the plate gap is concluded. The numerical fitting method fitted out the relation between the control current and controllable damping force, which is used as a theoretical model in the application of the MR mount’s control. According to the MR fluid Bingham model and fluid dynamics theory, the mechanics model of MR mount was established, and the simulation was taken in Matlab. Then the results of experiment and simulation were compared, which showed that the simulation data and experimental data is similar and verify the correctness of the mechanics model of MR model mount.Two degrees of freedom model of MR semi-active mounting system was established and the equivalent stiffness and equivalent damping of suspension was considered in this model. According to the principle of linear quadratic optimal control, the optimal controller was designed, and the optimal control was taken in the MR semi-active mounting system, which can effectively reduce the body acceleration. Due to the optimal control can not adapt to the uncertainty of system parameters, the Fuzzy-PID switching control strategy established based on the Fuzzy control and the PID control was used in the simulation research of vibration isolation performance of MR semi-active mounting system under different working conditions. The simulation results showed that the Fuzzy-PID switching control effectively reduces the body heritability force, and have advantages of small system overstrike, high steady state precision and good robustness, which is suitable for the modeling and control of complex nonlinear systems such as the powertrain mounting system.After analyzing mutual influence and mutual restriction of the powertrain mounting system and suspension system, the integrated system model with13degrees of freedom contains these two systems is established. An analyzing method is proposed based on the modal coupling of energy, which is used to calculate the vibration coupling degree of the vehicle powertrain mounting system and the suspension system, and provides theoretic basis for integrated control of the vehicle powertrain mounting system and the suspension system. After establishing the integrated system model with 13degrees of freedom, the integrated controller of the MR semi-active mounting system and the MR semi-active suspension system is designed by using the principle of linear quadratic optimal control, and the integrated controller’s weights coefficient was optimized with the PSO algorithm. The simulation research for passive control, independent control and integrated control of the MR semi-active mounting system and the MR semi-active suspension system has been done, and results shows that the vehicle comprehensive performance using integrated control in MR semi-active mounting system and the MR semi-active suspension system is absolutely advanced than those using passive control or independent control. |
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