# Bio-Inspired Model-Based Design and Control of Bipedal Robot
## 4 Realization of a Physical Model of a Bipedal Robot
### Control Hardware  
An Arduino Mega 2560 Rev3 device [23] was chosen to control the operation of the bipedal robot. This device has 14 PWM channels and thus can control all joints of the robot. The advantage of the Mega 2560 Rev3 model compared to other models is mainly a significantly larger number of I/O pins and PWM channels. In general, Arduino products are considered suitable for prototyping systems due to the low price, the large number of hardware accessories, and especially the open and freely distributable hardware architecture. To ensure simple remote control, the control interface was supplemented with Raspberry Pi Zero W [24]. The advantage of this device is the relatively large computing capacity and thus the extensive possibilities of expanding control from the current state to a robust system. Very small dimensions and low weight are also a big advantage of the device.  
The communication linkage between the Raspberry Pi Zero W and the Arduino Mega 2560 Rev3 is possible using the I2C link, as both components contain the necessary bus. There are two positions in communication: master and slave, while I2C also supports multi-master mode. In this case, the Arduino microcontroller was chosen as the master.  
The simulation model contains a measuring device for the orientation of a material object in space (Internal Measurement Unit--IMU), which in our case detects the translational movement of the robot in three axes. This sensory device is standard in stability control for biped and other mobile robots and forms the basis of the system's feedback. In this case, it is used as a sensor to detect the fall of the robot, when the robot terminates the ongoing process prematurely. In the physical model, this block is represented by the MEMS system Bosch BNO055, which contains the three mentioned sensors and its own microcontroller. The device has the ability to send output data to the master device in the form of quaternions which are normally used in robotics when calculating direct and indirect kinematic tasks. The BNO55 was calibrated in the automatic NDoF FMC mode [14; 25].  
Due to the fact that the mobile robot carries the power source directly on its structure, a solution was proposed that is ensured by a source with the smallest possible weight for the longest possible operating time. Since the energy sources are structurally located on the first floor of the robot frame, it was necessary that they be rechargeable, and recharging was possible without the need to disassemble the frame. Because the selected servomotors  
Figure 13: Final shape of the effector.  
have a different working voltage than the Arduino and Raspberry devices, the decision to divide the robot power supply into two parts was made. A possible solution is to connect a voltage stabilizer to 6 V, but in this case the servomotors overheat. Therefore, the first power source will power all the servo motors and the second power source will power the rest of the control hardware.  
Based on the analysis of the available options, the BH Power 2S 6000 mAh Li-po battery was chosen to power the servomotors. In order to power the rest of the control interface, it was necessary to ensure the power supply of the Arduino Mega device, through which the remaining devices will also be powered. The use of an external battery for smartphones appeared to be the simplest solution from the point of view of recharging, dimensions, and weight, and for this reason the AVACOM PWRB-8001K external battery was chosen.