## 5 Experimental Results
### Active Suspension Control Effect  
To validate the performance of the HOA-FSMC active hydropneumatic suspension, it was compared with the FSMC active hydropneumatic suspension, SMC active hydropneumatic suspension, and passive hydropneumatic suspension. Simulation tests were set at a 10 km/h driving speed, and simulation data from 10 s of driving on various road grades were used for the evaluation. The specific RMS values of the evaluation indicators are shown in Tables 10-12, and the vehicle's dynamic performance simulation results for each road grade are shown in Figures 14-16, where \"Passive\" refers to a suspension system operating without active control. \"SMC\" represents an actively controlled suspension system employing sliding-mode control technology. The term \"FSMC\" indicates an enhanced version utilizing fuzzy-logic-based sliding-mode control for improved performance. Finally, \"HOA-FSMC\" describes the most advanced configuration, featuring fuzzy-logic-based sliding-mode control that has been further refined through HOA optimization techniques. Figure 14: Simulation results of Class B road vehicle dynamics: (**a**) body acceleration; (**b**) suspension dynamic deflection; (**c**) tire dynamic load. Figure 13: Road surface grade classification results: (**a**) mining truck road; (**b**) cement road. Figure 15: Simulation results of Class D road vehicle dynamics: (**a**) body acceleration; (**b**) suspension dynamic deflection; (**c**) tire dynamic load. The data clearly demonstrate that compared to the conventional passive hydro-neumatic suspension, the HOA-FSMC-, FSMC-, and SMC-based active hydropneumatic suspensions excel in reducing the body's acceleration, suspension's dynamic deflection, and tires' dynamic load. This suggests that the use of active suspension technology substantially enhances a vehicle's performance across different types of road surfaces. Compared to the SMC active hydropneumatic suspension, the FSMC active hydroropneumatic suspension provides further optimization of these evaluation indicators, demon  
Figure 16: Simulation results of Class F road vehicle dynamics: (**a**) body acceleration; (**b**) suspension dynamic deflection; (**c**) tire dynamic load. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{4}{c}{**Control Strategy**} \\ \cline{2-5}  & **Passive** & **SMC** & **FSMC** & **HOA-FSMC** \\ \hline Body’s Acceleration (m/s\({}^{2}\)) & 0.3570 & 0.3288 & 0.3066 & 0.2813 \\ Improvement (\%) & 0 & 7.90 & 14.12 & 21.20 \\ \hline Suspension’s Deflection (m) & 0.0029 & 0.0028 & 0.0027 & 0.0026 \\ Improvement (\%) & 0 & 3.45 & 6.90 & 10.34 \\ \hline Tires’ Dynamic Load (N) & 2458.457 & 2371.3612 & 2311.268 & 2232.1124 \\ Improvement (\%) & 0 & 3.54 & 5.97 & 9.21 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: RMS values of Class B pavement evaluation indices. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{4}{c}{**Control Strategy**} \\ \cline{2-5}  & **Passive** & **SMC** & **FSMC** & **HOA-FSMC** \\ \hline Body’s Acceleration (m/s\({}^{2}\)) & 1.1840 & 1.0765 & 1.0369 & 0.9607 \\ Improvement (\%) & 0 & 9.10 & 12.42 & 18.86 \\ \hline Suspension’s Deflection (m) & 0.0077 & 0.0074 & 0.0071 & 0.0068 \\ Improvement (\%) & 0 & 3.89 & 7.80 & 11.55 \\ \hline Tires’ Dynamic Load (N) & 8177.5675 & 7754.0977 & 7528.6590 & 7188.3891 \\ Improvement (\%) & 0 & 5.18 & 7.93 & 12.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: RMS values of Class D pavement evaluation indices.