Experimental measurement and identification of mechanical characteristics for hydropneumatic suspension based on the improved friction model

The output characteristics of the hydropneumatic suspension (HPS) are critical to its performance. The friction force, as a component of the suspension's output characteristics, is often non-negligible. This article conducts both experimental and theoretical studies on the output characteristics of a single-chamber HPS system. Considering the viscoelastic hysteresis effect of the O-ring, the traditional LuGre model is modified using a hyperbolic tangent function to obtain a more precise friction model. The HPS output characteristic testing platform is established to capture the internal chamber pressure variations under different excitation frequencies, thereby characterizing the relationship between friction force, excitation displacement, and velocity. Using genetic algorithm, key parameters in the modified friction model are identified based on experimental data. These identified parameters are then fitted to determine their functional relationships with excitation velocity and initial working pressure, followed by verification. The results show that the error between the friction force computed by the modified model and the experimental data is approximately 6%–8%, demonstrating the accuracy of the proposed model. This model provides more precise theoretical guidance for further calculations of HPS output characteristics.