# Research on Shoveling Position Analysis and Recognition of Unmanned Loaders for Gravel Piles
## 3 Joint Simulation Analysis to Preliminarily Determine Location Features
### Discrete Element Modeling and Coupled Simulation of Bulk Materials
During the coupling simulation process, EDEM calculated the force of particles on the mechanical structure and transmitted it to Adams. Adams calculated the motion state of the mechanical structure and fed it back to EDEM. This coupling simulation can fully and realistically simulate the complex working conditions involving the interaction between granular materials and mechanical systems. EDEM-Adams coupling simulation conducts comprehensive functional verification and optimization to reduce the cost and time of actual prototype development. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Collision Restitution** & **Static Friction** & **Rolling Friction** \\  & **Coefficient** & **Coefficient** & **Coefficient** \\ \hline Crushed stone & 0.42 & 0.478 & 0.23 \\ Steel & 0.62 & 0.734 & 0.055 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Contact property parameters for crushed stone and steel. Figure 4: Crushed stone particle model. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Density (kg/m3)** & **Shear Modulus (pa)** & **Poisson’s Ratio** \\ \hline Crushed stone & 2600 & \(5\times 10^{7}\) & 0.2 \\ Steel & 7800 & \(8\times 10^{10}\) & 0.28 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Material property parameters for crushed stone and steel. When the loader is shoveling, especially when facing an uneven material surface, there may be increased resistance, tire slippage, and engine speed reduction. According to the \"Safety Technical Operation Regulations for Loaders\", shoveling operations should be stopped when encountering these situations. A forced operation could lead to the loader losing its balance and toppling over. Therefore, it is necessary to analyze the lateral force of the loader bucket based on the surface morphology of the pile to ensure the loader is produced safely during the shoveling process. The loader's shoveling process can be divided into two key stages: bucket horizontal insertion and bucket lifting [14]. In these two stages, the force on the side of the loader bucket is crucial. Relevant verification was carried out through EDEM simulation, as shown in Figure 5.  
The force acting on the side of the bucket is extracted by the EDEM post-processing, as shown in Figure 6, where 0-3 s is the scooping phase, 3-6 s is the lifting phase, and after 6 s the bucket retracts. It can be seen from Figure 6 that during the insertion phase, the position of the convex part exerts a much lower lateral force on the bucket's than the concave part. Therefore, the convex area of the bucket can effectively prevent the bucket from being subjected to excessive lateral forces during operation, ensuring safety during the working process and laying the foundation for subsequent evaluation of the bucket's contact point position. Figure 5: Modeling convex and concave areas of shoveling gravel in a coupled EDEM and Adams simulation, among them: (**a**) is the simulation of shoveling the convex part of gravel; (**b**) simulation of shoveling concave part of gravel. Figure 6: The lateral force of crushed stone on the bucket.