# Precise Positioning of Autonomous Vehicles Combining UWB Ranging Estimations with On-Board Sensors
## 5 Experiments and Results
### Real Tests Setup  
The positioning solution presented in Section 4 has been tested in the \"Multilane Road\" of Astazero proving ground in Sweden. During the different tests, an UWB ranging system formed by 6 UWB anchor nodes and 1 UWB tag node has been used. The location of the UWB anchor nodes is the same as the one used in the final demonstration of the PRoPART project. On the one hand, two UWB anchor nodes were located in a gantry pole at a height of 4 m every 200 m covering a total path for testing of around 600 m (see Figure 7). In each gantry pole as the one in Figure 8, one UWB anchor node had the antenna oriented looking forward, at the direction of the movement, and the antenna of the other UWB anchor node was oriented at the opposite direction of the movement, see Figure 9. Note that, the position of these nodes was well-known due to the fact that each RSU was equipped with a GNSS module. Furthermore, a 3D scan of each RSU was carried out for computing the real position of the UWB nodes with regard to the position of the GNSS antenna. Figure 6: PRoPART use case. Figure 8: A couple of UWB anchor nodes installed at one gantry pole in the Astazero proving ground. Figure 7: PRoPART scenario. On the other hand, an UWB tag node was attached to the RC car presented in Section 3.4. This node has been equipped with an external antenna at 0.7 m of height attached to a plastic structure and oriented looking forward, see Figure 10. The main idea behind using the external antenna is to emulate as far as possible the setup used on the PRoPART UWB solution, see Section 5.1. It is important to highlight that the location of the UWB anchors have been determined to enhance the visibility and accuracy of the UWB system for the real demonstration of the PRoPART project. As previously mentioned, a real truck was used as vehicle within this project. Meaning that, the UWB tag was located higher than in the case of the RC car. Due to the height difference between the UWB anchors and the UWB tag located on the RC car, the elevation angle between these nodes was higher. This angle increased when the RC car approached the RSUs, as the distance between the UWB tag and UWB anchors was reduced. Moreover, the antennas of the different UWB nodes were not omnidirectional. Meaning that, there was a limitation in terms of the opening angle of the antennas. Due to these two facts, the spatial orientation between the UWB anchors and the UWB tag located  
Figure 10: UWB mobile node attached to the RC car. Figure 9: Representation of the testing scenario. in the RC car was not the optimal one for the used setup. However, it was not possible to change this location as the mentioned tests were carried out in parallel with the ones of the PRoPART project. Despite this fact, the obtained results have been accurate enough, as will be discussed in Section 5.3. The UWB system, which is based on the DW1000 chip of Decawave [21], was configured with the parameters presented in Table 2 as the basic configuration to comply with the PRoPART requirements. Furthermore, the UWB tag node was calibrated to work properly using an external antenna connected through a cable of 91.44 cm (36'') as can be seen in Figure 10.  
The trajectory followed by the RC car during the real test has been a straight line within the testing track. As previously mentioned, the idea behind these tests was to validate the positioning and accuracy continuity of the developed positioning solution within the whole trajectory. During these tests, the speed of the RC car was variable, being its maximum speed 20 km/h. Figure 9 shows a graphic representation of the testing scenario and the direction of movement of the RC car. In the performed tests, the RTK-SN position of the RC car has been recorded and used as ground truth. Note that, the RTK-SN position of the RC car does not correspond with its real position.