Modelling and analysis of full-vehicle hydro-pneumatic suspension system considering real-gas polytropic process

Hydro-pneumatic suspension models built on the ideal-gas (IG) state equation or the traditional Benedict-Webb-Rubin (BWR) real-gas (RG) model cannot accurately predict the variation of gas pressure during suspension movement because the influence of gas hysteresis is ignored. This leads to incorrectly reflecting the properties of suspension and limiting the effect of control methods on the actual suspension system. In this study, the RG multivariate index model considering gas hysteresis is identified and applied. Based on this model, the output force of the suspension cylinder is deduced. Then, the general motion-force models of full-vehicle suspension are derived by applying a vector method based on a six suspension cylinders' test platform. Further, the stiffness and damping property formulas under different working conditions are discussed. The model's accuracy was verified through sinusoidal excitation tests on a full-vehicle test platform under different frequencies and amplitudes. The maximum discrepancy of gas pressure between prediction results and test data was 0.9%; whereas the maximum discrepancy of roll moment was 0.85%. The results indicate that the full-vehicle suspension models can accurately reflect the influence of gas hysteresis on the performance of a full-vehicle suspension system and be applied in confidence.

Automated summary

This study developed a hydro-pneumatic suspension model considering gas hysteresis, deduced the motion-force models of full-vehicle suspension, and verified the accuracy of the model in reflecting the influence of gas hysteresis on suspension system performance.