| With the advancement of global science and technology,the vehicle industry has been witnessed a rapid growth in which the pursuit of vehicle driving performance and user experience is becoming increasingly higher.As traditional passive suspensions have been difficult to meet the comfort requirements of new vehicles emerged in recent years,the development of new suspension types and suspension system control methods,which are effective ways to optimize driving comfort and handling stability,has been the hotspot in the research field of vehicle dynamics which has very important practical value.In this paper,the nonlinear characteristic modeling method and semi-active control strategy of a single-chamber oil-gas non-separated hydro-pneumatic suspension(HPS)are studied.This paper is assembled as follows:At first,the specific composition and working principle of the HPS under investigation are introduced.The VOF model is used for CFD calculation of HPS.The transient simulation of the HPS is carried out in Fluent and the flow characteristic in HPS is analyzed through post-processing.The method of calculating the stiffness and damping of the HPS according to the pressure of the internal flow field is discussed,which lays the foundation for the following mathematical modeling of the nonlinear dynamic characteristics of HPS.Then the influence factors of nonlinear characteristics of HPS are analyzed.The effects of oil temperature,oil viscosity,gas dissolution rate,and suspension vibration speed on the HPS nonlinear characteristics are taken into consideration as the modeling parameters of the stiffness and damping characteristics of HPS.The latin hypercube sampling method is used for sampling within the design space of the four factors.A limited number of sample points with different combinations of values for the four factors are suggested.The sample points are then utilized to perform transient simulation experiments of HPS and the corresponding stiffness and damping of each group sample points are suggested.The simulation data is then approximated by the Kriging model.The Kriging model demonstrates excellent accuracy to describe the mathematical relationship between the four factors and the nonlinear characteristics of HPS.The ride comfort test of the mining dump truck is carried out on a random road.The acceleration data of the upper and lower measurement points of the four suspensions are measured and then used in the simulation of a seven degrees of freedom model of the vehicle,and the accuracy of the Kriging model for the stiffness and damping characteristics of the hydro-pneumatic suspension is verified by comparing the experimental and simulation results.Finally,the road excitation model and the vibration model of the passive suspension and semi-active hydro-pneumatic suspension are established by Matlab/Simulink,and the structure of semi-active control system is suggested.The PSO-PID control strategy of semi-active hydro-pneumatic suspension is designed to optimize the comfort evaluation indexes of semi-active hydro-pneumatic suspension.The simulation results indicate that the designed PSO-PID control strategy effectively optimizes the vibration mitigation properties of the suspension.The establishment of high-precision dynamic characteristics model is the premise of the control and performance optimization of the hydro-pneumatic suspension.The effects of oil temperature,oil viscosity,gas dissolution rate,and suspension vibration speed on the HPS nonlinear damping and stiffness characteristics are taken into consideration in the dynamic characteristics modeling method proposed in this paper.And a high-precision mathematical model between them is established.The prediction error of the model is less than 5%.This modeling method can effectively improve the accuracy of semi-active and active control of hydro-pneumatic suspension on the basis of combining suspension control method,and provide certain practical and guiding significance in the research field of hydro-pneumatic suspension. |
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