Nonlinear Modeling And Adaptive Conrtol Of Active Hydropneumatic Suspension

As one of the crucial components of the vehicle,the suspension is the link between the body and the wheel,which has a very significant impact on the vehicle.Hydro-pneumatic suspension is a classification of the suspension from the medium used,but from the perspective of control force,Hydro-pneumatic suspension is generally classified as passive suspension because hydro-pneumatic suspension generally does not involve control forces,primarily accumulator and structural changes.In order to further strengthen and coordinate the performance of hydro-pneumatic suspension and enhance its adaptability,the development of active hydro-pneumatic suspensions has received more and more attention,which has gradually become the emphasis of suspensions.Based on the patent of suspension(CN109050192A),the paper focuses on the non-linearity of the damping hole and the stiffness uncertainty among the transformation.Thus,the nonlinear dynamic model of the suspension is established and controlled.Furthermore,different adaptive control strategies are adopted according to different actual conditions in the control process.After theoretical deduction and the simulation analysis,the control of active hydro-pneumatic suspension was observed.First of all,according to the typical nonlinear stiffness and damping characteristics of hydro-pneumatic suspension,the nonlinear mathematical model of hydro-pneumatic suspension is established,and the dynamic model of active hydro-pneumatic suspension is established considering the non-linearity of damping hole in the process of mode change.Then the evaluation index of the suspension is introduced,and the mathematical modeling and simulation of the random pavement and the bump pavement are carried out.The data processing methods of vertical acceleration,suspension travel and tire dynamic load in the time response and frequency response are given.Secondly,based on the establishment of the active hydro-pneumatic suspension model,the input error saturation amplification method is adopted for the actuator saturation problem existing in the actual vehicle.The method achieves the goal of anti-saturation by introducing a stable auxiliary system,and the proposed adaptive back stepping control method effectively solves the influence of parameter uncertainty on the system and improves the operational safety,ride comfort and stability.Finally,for the characteristics of electro-hydraulic servo valves and the application of unknown disturbances,adaptive sliding mode control is adopted based on the nonlinear suspension model.The method can effectively solve the problem of uncertain parameters on the system by adaptively controlling the stiffness.The sliding mode control especially switching control is used to improve the system's suppression of interference,and the saturation function is used instead of the symbol function to reduce the adverse effects of system chattering.Finally,through the simulation comparison,the vertical acceleration,suspension travel and tire dynamic load of the active suspension have been greatly improved compared with the passive hydro-pneumatic suspension.