We are the TU Dresden Robotik AG (TURAG), a robotics club at TU Dresden University of Technology from Germany. Since 2006, we have been participating in the Eurobot competition every year. Our goal is not only to be successful in the competition, but also for our members to have a place to learn and thrive. We mostly consist of students in electrical engineering, mechanical engineering, mechatronics and computer science.
This year we participated in the German and international competition of Eurobot with the theme “Winter is Coming”. The teams had to move wooden blocks - “nut crates” - around, turn them and place them with the correct side up in different zones.
For this, we built a Robot with three or optionally four arms, which were used to pick up blocks using pneumatics and flip them using a sliding mechanism. Our team’s success, gaining 1st place in Germany and 4th place in the international competition, was partly due to building reliable PCBs for the different actuators and sensors in our bot.
Our robot contains several kinds of PCB assemblies. One of the most important PCBs is our motor control, which is used to move the robot. The motor assembly is reused and improved every year and contains the controls for the motors, allowing our bot to drive along paths, together with control of the odometry wheels and laser integration for precise position control. We also integrated PCBs for TOF sensors (ST VL53L5CX), pneumatics and servo motor control, color sensing for the blocks, breakout board for a Raspberry PI and power distribution.
Let’s have deeper look at the pneumatics PCB:
We want to present one PCB essential for our bot’s functionality, which is the pneumatics PCB controlling the pumps, valves and measures the pressure of the pneumatic system. Our robot contains four of these PCBs, each controlling two vacuum pumps, four valves and four pressure sensors. The PCB contains an STM32 microcontroller (STM32F051) for implementing the control, which is addressed via a custom protocol on top of RS485 (via an ST3485 transceiver). For the power supply we used the MCP1755T ldo to regulate the 5V to the needed 3.3V for the microcontroller. To switch the valves and pumps, we mostly used the Infineon IRLML2030 MOSFETs.
The PCB design was done using KiCad, where we used a simple 2-Layer board. We positioned the microcontroller in the middle to have short traces to the peripherals and segmented the PCB into different areas for communication, valve control, sensor readings and servo motor control. For simple soldering, we also tried to keep the amount of components on the back as small as possible. For routing, we tried to keep the traces on the top layer for as long as possible and trying to avoid long paths for data lanes. The servo motor control was an optional feature which we implemented in case we found some need for additional motors in our bot as actors. Thanks to AISLER, we could build on reliable PCBs and make soldering easy using the provided stencil.
Our favorite AISLER feature is definitely the blitz service - It gives us access to fast PCB revisions that we needed urgently for the competition.
Sometimes not everything goes works according to plan on the first try: During commissioning and testing, we observed that we could not control the valves and pumps correctly. Our design for the pneumatics PCB needed another revision and this was due to a simple problem which beginners might make in PCB design. In our design, we picked the wrong footprint and symbol for transistors, so we needed to solder some of the transistors upside-down in order for the board to work. So we recommend checking against the datasheet one more time than one might think is needed, specially with elements that may have different pin assignments.
How long did the valves refuse to cooperate until you figured out what’s the problem?