# Autonomous Loading System for Load-Haul-Dump (LHD) Machines Used in Underground Mining
## 3 Proposed Autonomous Loading System
### Positioning and Charging
 \tag{5}\]  
then, if \(0<S_{1}<1\) or \(0<S_{2}<1\), the circular path intersects the segment \(\overline{E_{L}E_{R}}\). Otherwise, if \(\min(\left|S_{1}\right|,\left|S_{2}\right|)<\min(\left|S_{1}-1\right|,\left|S_ {2}-1\right|)\), the circular path passes to the right of the segment \(\overline{E_{L}E_{R}}\). If none of the previous conditions is met, then the path passes to the left of segment \(\overline{E_{L}E_{R}}\). The above process is executed for the circular paths defined by the left and right side of the LHD. If one of them does not intersect the pile, the steering angle is adjusted in the appropriate direction until both paths land within the rock pile limits. During this steering adjustment, a simple collision check is computed periodically over a bounding box for each body of the LHD. Figure 13 shows a diagram of the collision check for the front body of the LHD. A bounding box is defined for the front body. Then, vectors going from the bottom left corner to the top left corner (\(\overset{\rightharpoonup}{S_{f}}\)) and to the bottom right corner (\(\overset{\rightharpoonup}{B_{f}}\)) are defined. Figure 12: Intersection of the predicted trajectory with the detected pile limits. Left and right pile limit points denoted as \(\text{E}_{L}\) and \(\text{E}_{R}\), respectively (with the face of the pile between them in a red segmented line). LHD’s left side circular trajectory center and curvature radius denoted with C and R, respectively. In a blue dotted line both sides of the predicted LHD’s trajectory is presented. In order to check if point \(P\) of the detected tunnel wall is inside the bounding box (and hence causing a collision), the following condition is evaluated:  
\[0<\overset{\rightarrow}{S_{f}}\cdot\overset{\rightarrow}{d_{f}}<\left|S_{f} \right|^{2}\ \wedge 0<\overset{\rightarrow}{B_{f}}\cdot\overset{ \rightarrow}{d_{f}}<\left|B_{f}\right|^{2} \tag{6}\]  
where \(\overset{\rightarrow}{d_{f}}\) is the vector going from the bottom left corner of the bounding box to point \(P\). If the condition is true, then point \(P\) is inside the collision bounding box. Once the machine's steering angle has been adjusted so that its projected path lands within the rock pile limits, the bucket of the LHD is lowered using the tilt hydraulic cylinder. The tilt cylinder is commanded to extend until the pressure in its hydraulic line rises over a predefined threshold, signaling a tight contact between the bucket tip and the ground. An example from full-scale experimental data is shown in Figure 14, where a threshold of 23 bars was selected. Figure 14: Cylinder pressure increase as the bucket is tightly pressed against the ground in preparation for the charging maneuver. Figure 13: Simple collision check between the front body of the LHD and point \(P\) of the detected tunnel wall. Vectors Sf and Bf (in blue) of the collision bounding box are used alongside vector df (in red) to determine if point \(P\) is inside the bounding box. If the above positioning process is not completed within a predefined time limit (in the experiments, a threshold of 30 s was used), an operator assistance request is generated, effectively putting the system in the positioning assistance state from Figure 6. Otherwise, once the vehicle is in position and with the bucket down, it is commanded to drive forward in first gear. The transition to the excavation phase occurs as the collision with the rock pile is detected by a patented method that analyzes the machine's transmission pressure (engine load) and a skidding factor, estimated from the LIDAR odometry and the machine's tachometer data [18].