Modeling And Dynamic Analysis Of Interconnected Hydra-pneumatic Suspension Based On Integrated Struts

Interconnected hydro-pneumatic suspension(IC HPS)can achieve the collaboration between different suspensions in each wheel station,through using the connecting hydraulic pipes between different suspensions.Its key component is the interconnected hydro-pneumatic suspension strut(IC HPS strut),which is consisted of several hydro-pneumatic suspension struts(HPS strut)and connecting hydraulic pipes.Comparing with the traditional mechanical interconnected suspension,the IC HPS has more flexibility to interconnect the suspensions on roll plane,pitch plane and whole car.Moreover,the IC HPS can improve the anti-roll/pitch stiffness,and then maintain the soft bounce/warp-modes stiffness.Therefore,such coupled suspensions have the potential to provide good compromise design between the handling and ride dynamic performances.Considering the above,this study is focused on the modelling and dynamic analysis of the IC HPS struts based on the established experimental set-up.The fundamental strut of IC HPS is designed based on one type of novel compacted HPS,which is integrated the gas chamber within the rod,and the oil and gas is separated through a floating piston.The main contents in this study are following:1.The dynamic model of novel compact HPS strut integrating the gas chamber is established based on the experimental data applied on the designed prototype.A comprehensive experiment is designed to characterize the spring,damping and friction characteristicsof the prototype under broad ranges of excitations.Based on the analysis of the spring,damping and friction characteristics through the experiment,the dynamic model of HPS strut is established.Especially,in this study,a novel friction force model is proposed,which is combined by a hyperbolic tangential friction model and hyperbolic hysteresis operator.This model can predict the complex friction properties of HPS strut,which shows the combination of Coulomb friction,Stribeck friction,viscous friction,hysteresis,and the strong dependence of strut velocity and operating pressure.Finally,the validity of the proposed model,especially the friction model,is demonstrated through comparisons of force-displacement and force-velocity responses of the model with the corresponding measured data under broad ranges of excitations.2.Two types(Type 1 and Type 2)of IC HPS strut are analyzed through prototype experimental set-up and established simulation model based on the AMEsim software.Comparing with Type 1 IC HPS strut,Type 2 IC HPS strut has the orifices between main and annular oil chamber.Detailed analysis of the dynamic properties has been posted on the experimental data including the in-phase and out-of-phase tests.Special emphasis has been placed on the analysis of some unusual phenomenon shown in the experiment,such as the negative pressure in annular chamber,output force distortion,and small stiffness.And then the dynamic models of two types of IC HPS strut based on the AMEsim software,in which the validity of the established models have been verified through the experiment,are established.Finally,the detailed sensitivity analysis of the structural parameters,which include the length/diameter of the interconnected pipes and the number of orifices between main and annular oil chamber,to the dynamic properties,especially to the unusual phenomenon shown in the experiment,are discussed through the established AMEsim model.The results show that the Type 2 IC HPS may be more suitable for the practical application.3.Considering the above,the mathematical model of Type 2 IC HPS strut,which has the orifices between main and annular oil chamber,is established.The developed mathematical model considers ideal gas polytropic process,turbulent flows through piston orifices,laminar flows through the coupling pipes,frictions in rod and friction in floating piston.The relationships of fluid pressure between chambers are determined by the pressure balance and flow conservation.Finally,the validity of the established model is verified through the comparisons of force-displacement and force-velocity responses between the model and measured data under different types of excitations,including in-phase,out-of-phase and single-side harmonic excitations.4.The dynamic properties of roll-plane IC HPS in small vehicle model,which is equipped with the Type 2 IC HPS strut are investigated.Ignoring the damping of the tire,a simplified four-degree-of-freedom half-car model is established.Considering the friction of HPS strut,the dynamic model,which can be used to obtain not only the vertical movement of the vehicle body,but also the rotational movement of the vehicle body about the mass center,is established on AMEsim software.The relationship between the body mass center,suspension motions,and roll angle with different damping parameters is investigated based on the established AMEsim model,under the typical long-slope bump excitations.