Study On Vertical And Lateral Dynamic Performances Of Vehicle With Active Hydropneumatic Suspension

Suspension is an important vehicle sub-system because its performances greatly affect vehicle ride comfort and handling stability. It is difficult for passive suspension to satisfy the desired vehicle performances in different conditions when vehicle runs in changeable environments. Thus, in recent years, taking electronic control technology as core, and according to road and vehicle running conditions, the active suspension have been developed.Based on the practical projects sponsored by'General Armament Department of China'and'Specialized Research Fund for Doctoral Program of Higher Education', the study on the vertical and lateral dynamic performances of vehicle with active hydropneumatic suspension is presented in this dissertation.By taking into account the compressibility of oil, nonlinear characteristics of spring stiffness, and the dynamic friction between hydraulic piston and cylinder wall, the nonlinear mathematical model of hydropneumatic spring is built. The simulations are performed in different excitation frequencies and amplitudes. The accuracy of mathematical model is verified by comparing the simulation curves and the experimental data. Based on the established mathematical model, the spring stiffness, the damping characteristics in different speeds and the pressure drop between the import and the export of damping valve with different flow are respectively investigated. By using the Taylor expansion and the non-dimensional method, the stability of the established nonlinear spring model is analyzed with cycle signal excitation. The result shows that the system is stable.The nonlinear damping valve and the accumulator of the hydropneumatic spring are linearly simplified based on the stability analysis, and a linear quarter vehicle model with active hydropneumatic suspension is built. According to robust control theory, a H_∞controller is designed based on the vehicle model with consideration of parameter uncertainty and unmodel dynamics, and the design procedure is described. The effectiveness of the designed controller is verified by the simulations in frequencies domain and time domain and...