## 4 Movement and Navigation Control Subsystem  
### Integration, Control, and Testing of BLDC Wheels  
From the rolling resistance values given in Table 2, the load to which the wheel motors will be subjected can be estimated using Equation (12):  
\[R~{}=~{}(\text{RRC}\cdot P)+(P\cdot\sin{(\partial)}) \tag{12}\]  
where:  
\(R\) is the platform wheels' resistance force (N).  
RRC is the rolling resistance coefficient (0.02 for bituminous).  
\(P\) is the gravitational attraction force due to the mass of the platform (637 N).  
\(\partial\) is the slope angle of the surface (0\({}^{\circ}\)).  
This results in \(R~{}=~{}12.74\) N. Working according to this value, six commercial wheels were used, extracted from a commercial skateboard, the Hoverboard X1s from SmartGyro (Madrid, Spain) (see Figure 12).  
The wheels were integrated into the robotic platform; Figure 12 (left) shows the interior of the wheel after removing the outer casing. Each wheel has an independent circuit that operates based on the movement detected by a hall effect sensor (Figure 12 (right)). By accessing the motor's internal winding mechanism (1 in Figure 12 (right)), it was observed that the wheel had 3 hall effect sensors (2 in Figure 12 (right)), which indicate the exact position of the wheel at any given moment, facilitating precise control of the wheel.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Component** & **Model** & **Component** & **Model** \\ \hline PEMFC + BoP controller & FCS-H2000 (Horizon Fuel Cell technologies, Bizkaia, Spain) & H2 bottle & MyH2–2000 (H2 Planet, Puertollano, Spain) \\ \hline PR-01 & Insert Deal PS 3 MPa (Insert Deal, Villasanta, Italy) & Battery Pack & 10s1p 36 V 6 Ah (SmartGyro, Madrid, Spain) \\ \hline SOV-01 & NC 2/2 7 W solenoid valve (WIKA, Barcelona, Spain) & BMS & Developed by authors \\ \hline FT-01 & Cs-Instruments VA-521 (Cs-Instruments, Zindelsteiner Strasse, Germany) & DC/AC converter & BLDC motor controller (Shenzhen Renhao Weiye Technology Electronics Co., Ltd., Donnguan, China) \\ \hline SOV-02 & NO 2/2 7W solenoid valve (WIKA, Barcelona, Spain) & DC/DC converter & DC/DC converter W (RS Group, London, UK) \\ \hline RLY-01 & Finder Alpes, Italy & Finder Alpes, Italy & CT-01 & LXSR 6-NPS (Farnell, Madrid, Spain) \\ \hline RLY-02 & Finder Alpes, Italy & FT-01 & Developed by authors \\ \hline INT-01 & Siemens 25 A 1P+N 4.5 KA (Siemens, Munich, Germany) & MOSFET & N-Channel MOSFET (RS Group, London, UK) \\ \hline Microcontroller & Arduino Mega 2560 Pro (Adafruit Industries, New York, NY, USA) & Brake resistance & 4 \(\Omega\) power resistor (RS Group, London, UK) \\ \hline \hline \end{tabular}
\end{table}
Table 5: Fact data for those components that integrate the hydrogen–battery hybrid power system.  
After identifying the necessary control and power electronics for the proper functioning of the wheels, a commercial brushless DC (BLDC) motor controller was used. This included hall sensor monitoring and allowed for the turning on and off of the motors, as well as the regulation of their power (affecting both the rotational speed and torque) and the direction of rotation. Additionally, in accordance with the power of the wheels, heat sinks with high heat dissipation capacity were used to prevent overheating of the transistors that make up the controller. The motors and controller connection schematic are shown in Figure 13.  
After testing the system's operation when connected to a power supply, with the speed manually regulated using a potentiometer, current consumption values ranging from 0 A to 1.5 A at 36 V were recorded, depending on the torque exerted by the wheel.