# Topological Navigation and Localization in
## 5 Results and Discussion
The autonomous navigation tests showed that the system allowed tramming along a 180 [m] tunnel from its entrance to the loading point. The LHD took approximately 2 [min] to go from one point to another, which is comparable to the performance achieved by an experienced human operator. Some of the difficulties that were found included the tunnel being too narrow for the LHD (sized according to the manufacturer's specifications), and the floor having a large number of irregularities, pot holes, and varying inclinations. Of these factors, only the narrowness of the tunnel was included in the simulated environment. A view of the operator's control interface is shown in Figure 14.  
Because of time constraints in the mine, testing, development and parameter tuning were done simultaneously. Because of this, most datasets of the tests in the mine are from a work-in-progress version of the navigation system. Results presented in this section are from 14 datasets (labeled 1, 2, 3, etc. ), taken on a single afternoon two weeks before the end of on-site tests. 4 manual operation datasets (labeled M1, M2, M3, and M4) are also presented to have a reference for the performance of an experienced human LHD operator. These manual operation datasets were compiled a week later than the autonomous navigation datasets. An important problem during tests was roaming between different Wi-Fi access points inside the tunnel. For safety reasons, the system stops accelerating the LHD if communication with the operation station becomes unstable, generating an emergency stop if the loss of communications is longer than a few seconds. Because of this, and a wireless network that did not have fast roaming capabilities, the system often stopped when switching from one access point to another. This can be seen in Figure 15, where stops produced by roaming, and by unstable communications, are shown. The Figure 15 also shows the instant speed of the vehicle (in km/h), the operation mode (with a value of 10 for autonomous navigation, 0 for idle, and \(-\)10 for tele-operation), distance traveled (in decameters), the Wi-Fi channel of the access point, at which the LHD is connected (different channels are used for faster roaming), and, finally, the RSSI and Noise values reported by  
Figure 14: Operator’s graphical interface of the navigation system. the wireless modem of the vehicle. All the scales have been selected to fit in a single figure, to show the relation better between these variables. Another consideration for these datasets, since the navigation map was still being tuned, is the intervention of the operator through tele-operation (or assisted teleoperation) to help the LHD go through some narrow passages, or to get back and try again to pass autonomously through a given part of the tunnel. This is shown in Figure 16, as the vehicle needed to stop, then go back a couple of meters (with teleoperation assistance), to later reengage in the autonomous navigation mode, this time getting to the desired destination without further intervention. Taking these factors (stops because of communication problems and tele-operation) into account, a series of performance indicators were computed for all the datasets. The mean and max speed of the LHD are presented in Table 3. When analyzing the results, it is important to consider that some datasets were compiled with the LHD having a fully loaded bucket, and others with an empty bucket. In some of these datasets, the LHD is moving forward, towards the draw point of the tunnel, and in others, it is moving backward, towards the dump point of the tunnel. To better understand the performance of the system, and the effects of roaming and tele-operation, other indicators are presented, such as the length of the dataset, the total distance of the movement, and the total distance that the LHD was driven by the autonomous system. With an empty bucket, the seasoned operator drove through the tunnel at an average speed of 6.4 [km/h], while the autonomous system did the same at 5.8 [km/h], thus slightly underperforming.