Soccer Electronics
From controlling to measuring
Max Känner
Timo de Vries
Felix Lesch
Robin Kai Kurzydym
At the Soccer Electronics team we develop and design our own PCBs. We also test and iterate these designs, which are custom built for our robots. To create the circuits and PCBs we use KiCad and LTspice. Many of our circuits are fairly complex, so that we have to test them very meticulously. For that we like to use our oscilloscopes.
ESP32 Module
We are using an ESP32-Wroom Module to control most of the robots functions. The via the connection module incoming velocity commands are converted to motor speeds and passed to the ESC Modul. In return the ESP-Module sends encoder data and data from the imu to our server. Besides, driving the kicking and dribbling devices have to be controlled by the ESP32.
Kicker
The Concept
In the soccer small size league, the robots are playing with a standard golf ball, which may be accelerated up to a speed of 6.5 m/s, representing a total kinetic energy of roughly 1 joule. From a variety of options to do so, we have chosen to use an electromagnetic kicking-device, because it meets several crucial requirements like a high reliability and a sufficient „firing-rate“.
Transformation
Through a flybacktransformer energy is stored in a capacitor. While kicking, this energy is dumped into a coil within milliseconds and the coil is attracting a ferromagnetic plunger, which then hits and accelerates the ball.
In the Future
Our current focus of optimization is to choose a good ferromagnetic material allowing for a high flux-density and low eddy-currents and to develop a high speed, low noise capacitor charging circuit, which also meets high safety standards.
Network Module
Since the Robocup Competitions are held in different countries around the globe, the available radio frequencies may vary. To be more flexible we are using a seperate Network Module which can be switched with other modules to use different frequency areas.
User Interface
To interact with our robots we need a user-friendly interface which can be accessed even if the robot is assembled and shell is mounted. We decided to use a removeable UI which can be plugged in at the interface module on the right side of our dribbling device. When the external UI is plugged in, the ESP32 gets notified and shows internal data on the display. Furthermore, robots can be controlled thru a rotatory encoder mounted on the external UI.
ESC
Task of the ESC Module is to control the BLDC-Motors of our robots. Since BLDC motors are relatively new in this speed region, there aren’t any prebuild speed controllers in our form factor, so we decided to design our own module. In order to safe space, we split the module in half and arrange them on top of each other, forming a pcb sandwich. That way every board has circuits and connectors for two motors. The communication between all boards is realised with our Main Hub.
TMC4671
Main component of the ESC-Modul is the TMC4671 Chip which is controlling one motor each. Controller loops for position controlling are already integrated in the chip, nevertheless it needs some additional circuits for power sensing and voltage switching.
Current sensing
In order to accurately control the motors, the controlling chip needs to know how much current is going through the motor. We are achieving this by adding Shunt Resistors in line of the three phases of the Motor. The current in each phase is proportional to the voltage over the resistor.
Molex Micro-Fit 3.0
We are using Molex Micro-Fit connectors to connect all power electronics on the robot. The connectors can deliver up to 10.5A which is just right for our purpose.