## 3 Experimental Results and Analysis
### Analysis of Climbing Characteristics of Pure Electric Heavy-Duty Vehicles  
Existing research primarily focuses on conventional fuel-powered vehicles and analyzes their speed variation during the climbing process. This section will compare the speed variation patterns of conventional fuel-powered and pure electric heavy-duty vehicles during climbing. Specifically, this study will conduct simulation tests of vehicles at design speeds of 80 km/h (with grades ranging from 1.0% to 5.0%), 100 km/h (with grades ranging from 1.0% to 4.0%), and 120 km/h (with grades ranging from 1.0% to 3.0%) to gain a deeper understanding of the climbing characteristics of pure electric heavy-duty vehicles. A simulation test was conducted on the vehicle's performance at a design speed of 80 km/h on a road with grades ranging from 1.0% to 5.0%. As shown in Figure 7, the horizontal axis at \(-\)100 marks the starting point of the test road, 0 marks the beginning of the vertical curve, and 170 m marks the starting point of the graded section. A simulation test was conducted on the vehicle's performance at a design speed of 100 km/h on a road with grades ranging from 1.0% to 4.0%. As shown in Figure 8, the horizontal axis at \(-\)100 marks the starting point of the test road, 0 marks the beginning of the vertical curve, and 210 m marks the starting point of the graded section. A simulation test was conducted on the vehicle's performance at a design speed of 120 km/h on a road with grades ranging from 1.0% to 3.0%. As shown in Figure 9, the horizontal axis at \(-\)100 marks the starting point of the test road, 0 marks the beginning of the vertical curve, and 250 m marks the starting point of the graded section. From Figure 7, it can be observed that there are significant differences in the speed variation of heavy-duty vehicles under different longitudinal slope conditions. When the slope is 1.0% and 1.5%, heavy-duty vehicles can accelerate from the starting point to 3000 m, but their longitudinal acceleration gradually decreases. When the slope is between 2.0% and 5.0%, heavy-duty vehicles accelerate on the horizontal road segment and enter the vertical curve segment. However, due to the influence of slope resistance, the longitudinal acceleration of the vehicle begins to decrease until the power is insufficient to balance the slope resistance, at which point the vehicle begins to decelerate. After traveling a \begin{table}
\begin{tabular}{c c c} \hline \hline
**Input/Output** & **Variable Name** & **Physical Description** \\ \hline \multirow{4}{*}{Input} & IMP\_MYUSM\_L1 & Torque on left front wheel \\  & IMP\_MYUSM\_L2 & Torque on left rear wheel \\  & IMP\_MYUSM\_R1 & Torque on right front wheel \\  & IMP\_MYUSM\_R2 & Torque on right rear wheel \\ Output & Throttle & Electronic throttle \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Input/output interface settings for co-simulation of TruckSim and Simulink. of traditional fuel-powered heavy-duty vehicles requires a certain amount of time to respond to the action of the accelerator pedal, necessitating a shift from a high gear to a low gear and increasing torque to overcome slope resistance. The gear shifting is particularly noticeable when driving on steep slopes, as shown in Figure 7a, where the acceleration and deceleration processes of traditional fuel-powered heavy-duty vehicles are unstable with a noticeable jerkiness, and the speed at which they reach a stable state is relatively low. In addition to the lateral comparison of the climbing speed variations of traditional fuel-powered and pure electric heavy-duty vehicles under the same design speed road conditions, it is also necessary to conduct a vertical study on the climbing speed characteristics of pure electric heavy-duty vehicles under different design speed road conditions. As depicted in Figures 7-9, under different design speed road conditions, the speed variation trend of pure electric heavy-duty vehicles at the same slope shows a distinct similarity.