Vicenza Thunders Team
The Thunder Robot was built by the team Vicenza Thunders and is a derivative of the robot that they used to participate at the Robocup.
This robot is controlled by a Arduino MEGA2560 and three ATmega328 all intercommunicating between them via serial communication.
The Arduino Mega2560 has the task of managing the whole general system, so the motors, the display, the keyboard, the bluetooth connection and the communication with other microcontrollers.
Simultaneously two of the three ATmega328 mounted on the robot are used to read the data from the 24 infrared receivers placed along the perimeter of the robot and used to locate the target to follow.
The second ATmega, however, has the function of identifying the position in space of the robot controlling the four ultrasonic distance sensors and the compass sensor.
Basic operation of the omnidirectional wheels
For movements are used four DC motors, each independent of the other, ranging in the move of the omnidirectional wheels and offset by 90 °.
In the picture you can see a wheel of the robot which was produced with a 3D printer.
The omnidirectional wheels, as seen in the picture, do not differ much from the normal wheels, they just have in addition a lot of small rollers which rotate freely, having their axis perpendicular to the one of the wheel, and this allows the wheel to slide in other directions too.
The figure below explains the combinations of the speed of the motors to get the most basic movements.
You can notice how each motor must turn back and forth independently from the others, speaking electrically, this means that each motor needs an H bridge and to do that they used four VNH2SP30, which are a kind of very powerful integrated H bridges. The schematic below is represents the circuit to control a single motor, with this you can manage the speed and the direction of rotation of each motor.
Movements of the Omnidirectional Wheels
H-Bridge Schematic for a single motor