| With the development of the times,high demand has been put on the safety,comfort,handling,and lightweight in the vehicle industry,and then the high requirement of NVH(Noise,Vibration,Harshness)performance.Traditional suspensions cannot satisfy the multiple requirements of vehicles under various working conditions.Therefore,the controllable suspensions,which have the potential to satisfy multiple requirements subjected to various road conditions,operation modes,and loading conditions,are paid more attention by researchers and industries.The Hydropneumatic Interconnected Suspension(HIS),which can provide cooperative control between different wheels,has the potential to balance both ride comfort and handling performance demands compared with the independently controlled suspension.Considering the above,through extensive experimental study and analysis,this research mainly focuses on the semi-active Hydro-pneumatic Interconnected Suspension(HIS)based on the controllable damping of connection pipes.Besides,to meet the requirement of large flow rate,fast response and wide damping modifying range of the connection pipes,a Magneto-rheological(MR)valve designed based on the Magnetic Gradient Pitch Mode,named MGPMR valve,is proposed in this research to achieve the semi-active HIS system.Overall,this research focused on the design,modelling,and practical application of a novel semi-active HIS designed based on the pipe-installed MGPMR valve.The main contents of this study are summarized as following:(1)Based on the mathematical and experimental analysis,the model of HIS is established to predict the dynamic properties of HIS reasonably.The proposed model considers the gas state described by ideal gas law with Energy Equation,the damping of the connection pipes described by the fluid inertial model with the laminar flow model,and seal frictions described by the hyperbolic tangential hysteresis friction model.Based on the comprehensive comparisons between the model-predicted and experimental data under the in-phase and out-of-phase excitations,the comparison results show that the proposed model can significantly improve the model’s accuracy,compared with the traditional HIS model.Besides,the proposed model can describe the complex hysteresis phenomenon observed from the experimental data.Furthermore,the effect of the gas temperature and oil inertial on the dynamic performance of HIS is analyzed based on the proposed model.The simulation results show that the significant oil inertia forces in the connected pipe make the HIS stiffness performance worse,and even cause negative stiffness under high-frequency conditions.Besides,the temperature variations during the gas working process make the hysteresis and frequency dependency of the HIS’s stiffness.(2)The cavitation phenomenon of HIS is described and analyzed based on the proposed theoretical model.Firstly,the cavitation phenomenon process in HIS is analyzed based on the single bubble dynamics described by Rayleigh-Plesset model.Secondly,the HIS model considering the switch between the continuous and discontinuous fluid flow modes caused by the cavitation phenomenon is established,and its validity is verified by the laboratory test.Based on the established model,the dynamic performance of HIS in a roll-plane off-road vehicle is simulated under both the transient bump and twisted bump road excitation.The simulation results show that the negative effects on HIS dynamic performance,including the acceleration jumping and the separation of the tire from the road,are associated with the cavitation phenomenon.From the parametric analysis,the results suggest that(a)decreasing the loss coefficient of connected pipe and increasing the initial charging pressure are the effective method to avoid the cavitation phenomenon;(b)during the process of optimizing and controlling the connected pipe’s damping of HIS,the effect of the connected pipe’s damping on the cavitation and suspension vibration isolation performance should be considered simultaneously.(3)The model of MGPMR valve is established based on the experimental data.Firstly,the working principle of the round-hole type MGPMR valve is firstly investigated through the derivation of the mathematical model.Secondly,based on the experiments,the performance of the MGPMR valve with different numbers of the nonmagnetic ring and different diameters of flow path is compared to confirm the MGPMR valve configuration for the modelling work.The MGPMR valve model is then established based on the hyperbolic tangential hysteresis model and the model parameters are identified through the experimental data.The comparisons between the test and model-predicted data of pressure difference-flow rate characteristics indicate that the established model can describe the dynamic properties of the MGPMR valve,including the hysteresis characteristics,the correlation between viscous friction and current,and the inertia of the MR fluid in the flow channel.Besides,compared to the Bingham model,the established model can improve the model’s accuracy significantly.Finally,an inverse model of the MGPMR valve is developed using the neural network algorithm.(4)A 7 Degree of Freedom model of the full car equipped with the proposed semiactive HIS with multiple interconnected modes is established and a coordinated controller based on state recognition is designed.Based on the simulation results,the performance of the proposed semi-active HIS based on the MGPMR valve is verified under various excitation conditions,including random road disturbance,steering,braking,and combined operating conditions.The results show that the proposed semiactive HIS based on the MGPMR valve can effectively improve the comfort and smoothness of the vehicle,compared to the passive HIS.Compared to independent semi-active hydro-pneumatic suspension,the proposed semi-active HIS based on MGPMR valve effectively suppresses the movements of vehicle body under steering,braking and steering-braking conditions,and then improves the vehicle’s handling stability and driving safety.As a result,the proposed semi-active HIS based on the MGPMR valve can improve both the ride comfort and the anti-roll/anti-pitch performance. |
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