# 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  
EDEM has demonstrated significant effectiveness in the field of research on material loading by loaders. First, EDEM can accurately simulate the physical properties of materials. For all types of materials handled by loaders, whether they are loose gravel or other materials with different particle sizes, densities, and friction coefficients, EDEM can accurately model them through its powerful parameter setting function. This accurate \begin{table}
\begin{tabular}{c c c} \hline \hline
**Connection Type** & **Kinematic Pair** \\ \hline Arm, frame & & \\ Hydraulic cylinder of the arm, frame & & \\ Swing cylinder, frame & & \\ Arm, rocker arm & & \\ Rocker arm, linkage & & \\ Linkage, bucket & & \\ \hline Frame, ground & & \\ Swing cylinder, swing hydraulic rod & Sliding pair & \\ Arm hydraulic cylinder, arm hydraulic rod & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Set the motion constraints of the loader actuator. Figure 3: Loader bucket tip trajectory. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Motion State** & **Frame Drive Function (s)** & **Boom Drive Function (s)** & **Bucket Drive Function (s)** \\ \hline Insertion phase & STEP (time, 0, 0, 6, 2, 0.38) & None & None \\ Rising phase & STEP (time, 2, 1, 0, 4, \(-\)0.38) & STEP (time, 2, 0, 6, 0.25) & STEP (time, 2, 0, 3.3, 0.1) \\ Lifting phase & STEP (time, 2, 1, 0, 4, \(-\)0.38) & STEP (time, 2, 0, 6, 0.25) & STEP (time, 2, 0, 3.3, 0.1) \\ Resetting phase & -STEP (time, 6, 0, 7, 0.285) & None & None \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Loader actuator drive function settings. material model construction makes the simulation of the interaction between the loader bucket and the material more realistic. Second, EDEM is highly effective in simulating the kinematics and dynamics of the loader. It can accurately reproduce the various actions of the loader during loading, including bucket insertion, lifting, and turning. By setting the motion parameters of each joint and component of the loader, EDEM can calculate the forces acting on the loader during different loading stages, which provides reliable data support for studying the selection of the loader's loading position. If the particles are filled according to the shape of real particles, the results will be more accurate, but the simulation time cost will increase and a large amount of data will be generated, which is not conducive to subsequent post-processing and result analysis. Therefore, according to the outer contour of the actual gravel particles, spherical particles are used in the EDEM 2023 software to fill, and the size and shape are adjusted. The resulting gravel particle model is shown in Figure 4. Using spherical particles to represent gravel has advantages in computational efficiency and practicality and is a simplified method. Even though this simplified method does not fully capture the microscopic limitations caused by the angular properties of real gravel, we are more interested in the overall stability when figuring out where the unmanned loader should shovel from a macro perspective, so the inaccurate microscopic behavior caused by the simplification of spherical particles does not have a big effect on the simulation results. Given the relatively stable material properties, they are not affected by external variables. The contact parameters for materials primarily consist of the static friction coefficient, rolling friction coefficient, and collision restitution coefficient, which are assessed by sliding plate and drop tests [13]. The material property characteristics and contact property parameters for crushed stone and steel are presented in Table 3 and Table 4, respectively. The above process established a pile of crushed stone particles in EDEM and determined the motion trajectory of the loader model in Adams. A specific coupling interface enables bidirectional data transmission between the two.