**4. Experiments and Analysis**

Full-scale experiments with a GHH LF11H model LHD (see picture in Figure 1) were carried out in a production tunnel of a sublevel stoping mine located in the Coquimbo Region (Chile), facilitated by the Chilean mining company, CMSG. Pictures of the mine site and the LHD inside its tunnel are shown in Figure 20. Figure 20a shows the mechanical workshop just outside the mine's main entrance, and Figure 20b shows the LHD during surface tests. Figure 20c shows the LHD outside the test tunnel with an almost fully loaded bucket.

Figure 21 shows the layout of the tunnel where experiments were carried out. The LHD traveled from the "start–end point" shown in the figure to the end of the red line, where the stope was originally located. A stope is a large open underground space that is produced by the sublevel stoping mining method. The LHDs load ore inside the stope from a large pile of material, also sometimes referred to as the loading point or draw point. Once the LHD has a fully loaded bucket, it has to travel back to the "start–end point" to dump the ore.

**Figure 20.** LHD machine and mining facility. (**a**) Mechanical workshop just outside the mine's main entrance; (**b**) LHD during surface tests; (**c**) LHD outside the test tunnel with an almost fully loaded bucket.

**Figure 21.** Layout of the mine's tunnel where experiments were carried out.

The experiments reported here were carried out in a fully functional tunnel of the mine, i.e., a tunnel used for extracting mineral. In fact, the experiments took place during day hours, while the mine's night shift used the LHD in manual mode for production. As a result of this, the shape and location of the stope and the draw point changed every day (as the ore runs out, the inner wall of the stope is blasted as part of the mining process).

Because of this, and since in situ experimentation was time-limited, experiments were separated in two parts. First, the field trial experiments regarding charging and collision detection of the LHD and the pile, and the LHD's excavation and payload weighing, are reported in Section 4.1. Then, pile identification experiments from an offline processing of the collected field data are presented in Section 4.2.

The mining tunnel was narrower than recommended by the LHD manufacturer, so the LHD's positioning was more complex than initially expected. This also contributed to dividing the experiments into the two groups described above. Figure 22 shows a picture of the draw point as seen from the teleoperation system cameras.

**Figure 22.** Operator's point of view of the loading point used for onsite experiments.
