# Design and Mechanical Behavior Research of Highway Guardrail Patrol Robot
## 3 Analysis of Robot Obstacle-Crossing Behavior
### The Influence of Different Parameters on Obstacle-Crossing Behavior  
The obstacle-crossing height is influenced by numerous parameters, making it challenging to study and analyze effectively. Parameters such as the distance \(a\) from the rear end of the corrugated beam guardrail to the theoretical contact line, the wheelbase \(l\), the radius \(r\) of the auxiliary wheel, and the theoretical contact circle radius \(R\) of the contact line between the rubber-coated wheel and the guardrail are affected by the structure. Research on the impact of these parameters on the obstacle-crossing performance is relatively well established and is not the primary focus of this study. Therefore, in line with the requirements for compactness and coordination of the mechanical structure, fixed values are assigned to the parameters not under investigation, as shown in Table 3. Although the influence of the adhesion coefficient \(\varphi\) on the obstacle-crossing performance has also been extensively studied, this article includes an analysis of \(\varphi\) due to its strong independence from the specific structural configurations. Regarding the coefficient of adhesion \(\varphi\), the spring stiffness \(k_{1}\) on the active wheel side, and the spring stiffness \(k_{2}\) on the passive wheel side, the control variable method is employed to analyze the influence of these parameters on the obstacle-crossing height. When analyzing the influence of a certain parameter on the obstacle-crossing performance, the other parameters are held constant at fixed values (\(\varphi=0.8\), \(k_{1}=2\), \(k_{2}=0.5\)). The results of the theoretical analysis, as shown in Figure 4a, indicate that as the adhesion coefficient \(\varphi\) increases, the obstacle-crossing height \(h\) for the front and rear auxiliary wheels, non-driven rubber-coated wheels, and driven rubber-coated wheels improves. Among these, the driven rubber-coated wheel exhibits the lowest obstacle-crossing height. This is due to the robot's single-sided driving mechanism: when the sole driving wheel crosses an obstacle, the spring consumes a significant amount of energy, resulting in the lowest obstacle-crossing height. When the adhesion coefficient \(\varphi\) reaches 0.8, the obstacle-crossing height of the driven rubber wheel can reach approximately 10 mm, satisfying the obstacle-crossing requirements (Through investigation, we have preset 10 mm as the reference value for the height of the guardrail obstacle, which is indicated in the green area of Figure 4). As shown in Figure 4b, it is evident that as the stiffness \(k_{1}\) of the active wheel side spring increases, the obstacle-crossing height of the rear auxiliary wheel and the non-driven rubber-coated wheel also increases. Conversely, when the stiffness \(k_{2}\) of the passive wheel side spring increases, the obstacle-crossing performance of the rear auxiliary wheel and the non-driven rubber-coated wheel gradually decreases. This occurs because the non-driven rubber-coated wheel does not contribute to the robot's propulsion. Increasing the stiffness of the driven wheel side spring introduces additional resistance to the robot's movement. From the above analysis, it can be concluded that to ensure an obstacle-crossing height greater than 10 mm, the stiffness \(k_{2}\) of the non-driven wheel side spring should be minimized, while the stiffness \(k_{1}\) of the driven wheel side spring should be maximized. However, these selections must also comply with the detachment conditions and the safety requirements of the guardrail. Therefore, while ensuring that the robot neither detaches \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Distance between edge of guardrail & 80 mm \\ and theoretical contact line \(a\) & 30 mm \\ Auxiliary wheel radius \(r\) & 35 mm \\ Theoretical contact circle radius for rubber-coated wheels \(R\) & 55 mm \\ Wheelbase \(l\) & 180 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Fixed-value parameter values.