# BIZON-UGV for Airport Pavement Testing: Mechanics and Control
## 3 Modelling and Control
### Experiment and Measurement  
To demonstrate the effectiveness and usefulness of the proposed unmanned device in the context of trajectory tracking by autopilot and drives, as well as the designed mechanics, the mobile robotic platform BIZON was tested in real working conditions on the airport board, as shown in Figure 10.  
Figure 9: The PID-FF controller. The airport is located a few kilometers from Warsaw (the capital of Poland). The average elevation of the airport above sea level is 104 m. The basic element of the airport infrastructure is a runway made of asphalt concrete with concrete thresholds of a total length of 2500 m and a width of 45 m, with geographical directions 261\({}^{\circ}\) and 081\({}^{\circ}\) where the tests were performed. To check the correctness of the mechanics and control system of the device, a waypoint trajectory was applied on autopilot and tested considering two cases:  
1. typical PID-FF trajectory control;
2. the PID-FF with tightening to the trajectory. For testing purposes, the UGV is equipped with proprietary electronics and software. The only off-the-shelf components are the inverters. The navigation systems of the BIZON platform are based on GNSS RTK working differentially, allowing for the determination of the deviation angle even in static conditions (without movement). The state observer is based on inertial sensors and an extended Kalman filter, where data fusion utilizes information from the GNSS receiver, as well as encoders mounted in the propulsion system. The platform communicates with the command post using encrypted wireless communication. Data acquisition and recording occur both on board and at the command post. BIZON has an extensive telemetry system, and the applied communication with a bandwidth of up to 6 Mb/s allows for the transmission of a large amount of data for real-time and subsequent analysis. The realized trajectory was compared to a simulation of the vehicle behavior considering models (11)-(12) and control law (13). Table 1 presents the most important BIZON parameters. The included parameters are defined in Section 3, which describes modelling and control technique. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value [Quantity]** \\ \hline \(m_{b}\) & 2000 [kg] \\ \hline \(m_{wt}\) & 200 [kg] \\ \hline \(r\) & 0.6 [m] \\ \hline \(d\) & 0.5 [m] \\ \hline \(l_{zxb}\) & 21.2 [kg.m\({}^{2}\)] \\ \hline \(l_{zzw}\) & 0.02 [kg.m\({}^{2}\)] \\ \hline \(l_{yyw}\) & 0.27 [kg.m\({}^{2}\)] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: BIZON parameters. Figure 10: UGV BIZON on the airport board. Reference trajectory data were inserted into the autopilot as a waypoint. This way, lines that connect via inserted points define a trajectory. For this purpose, using the GNSS RTK module mounted on the robotic platform determined its geographic coordinates, which are presented in Table 2.  
The data can also be stored in the Remote Control Station (RCS) until the radio wireless connection works. The autopilot connecting with the RCS has implemented a special diagnostic algorithm to check the performance of the automatic control mode (full autonomy mode). In critical situations, the algorithm may not be able to work in fully automatic mode, in which case a checklist of failures and inefficient elements is generated. Before the experiment, the trajectory coordinates were introduced to the platform device via a special software package of RCS 6.8 and visualized using the Google Earth tool. Visualization is presented in Figure 11,b with numbered waypoints and indicated waypoint distance, where subfigure b to the right shows a zoomed-in view. Red and yellow line show reference trajectory. In addition, the distance between waypoints is indicated above yellow path. Firstly, the control system simulations and waypoint trajectory realization were examined. For tests, the device model described in Section 3.1 was considered. The device model started from point no. 1 with assumed zero initial position and zero initial speed: \(\mathbf{q}(0)=