Participating at ‘Explore Science’

Date: June 20, 2018

Members Attending: Alexis, Eylert, Lynn, Sylvia

Mechanism:

Todo:

Functionality:

Project: Build an autonomous collector robot for a student competition

‚Explore Science‘ is a competition in Mannheim, Germany where students can participate and try to solve science and engineering tasks. The competition is organized by the Klaus-Tschira-Stiftung, a foundation from Klaus Tschira, one of the founders from SAP.

One of the tasks this year was collecting as many of 100 Ping-Pong-balls (each ball equals a point) as possible from a square wooden field with a side length of 1m and a 5cm high border. The robot had to fit completely on a DIN A3 paper, could not extend and had no height limitations. You can radio control the robot, however autonomously collected balls count twice for your score.

Some members of our team decided to participate and build a robot. We wanted to build a precise robot that could move in every direction and collect and store the balls reliably.

As hardware, we used nema 17 stepper motors to drive the robot. We went with classic omniwheels as they allow omnidirectional movement and we had some available from FTC. For the collector, it is built using a REV core hex motor and an axle from our FGC-robot from last year. The battery is a classic ten-cell 12V NiMH from FTC. For the electronics we used an Arduino mega with a Ramps-shield to be able to drive the steppers properly and program the robot in C++. Both the steppers and the Arduino with the Ramps-shield originate from an old 3D-printer. To build the mechanical parts, we mainly used 3D-printed parts as well as wood and a piece of acrylic to be able to see the balls when they are collected.

On the software site we used no sensors, so programming was quite easy. As we use steppers we can drive very precisely as long as we do not lose any steps. Controlling those steppers was quite easy, as the drivers for them (polulo a4988) only need a step and a direction signal to drive the robot. We used the walls of the field to orient ourselves. Unfortunately, we had no time to program acceleration for the steppers, so we sometimes lose steps when driving too fast.

At the competition, our robot worked quite well. We were able to collect almost all balls within the three minutes. The last eight balls were not collected because of our robot losing steps. With some more programming effort, our robot would have worked better. However, we were happy with the result. In the rankings, we scored second, some other team was able to collect two more balls, but as the results were quite close, we were awarded with a first place.

To our surprise there also were FTC- and FRC- members from the US and from another school from Germany, from Kaiserslautern. We knew the German team, ‘Halo World’ from our FTC-invitational event in Stuttgart. The US-team, ‘Combustible Lemons’, we knew from the FIRST championship 2017 in St. Louis. It’s always nice to meet other members of the FIRST-community around the world, especially when you don’t expect it. Team ‘Combustible Lemons’ ironically used the same REV expansion hub we use for FGC. Here is a picture of their robot with the REV hub.

Watch our robot on YouTube: https://youtu.be/9fQYZfYA_xQ

2 Replies to “Participating at ‘Explore Science’”

  1. When the robot is picking up the ping pong balls, are you using zip ties on your rotating rod? Also, for the ramp part at the bottom of the robot did you 3D print that part? If so, how were you able to 3D print on a curve with such a high angle?

    1. Yes, we are using regular zip ties on the rotating rods to collect the balls. The ramp part is 3-D-printed, as are the drive base and the other blue and white connection parts. The high angle is not an issue as long as you print it without overhangs. Basically it is a quarter circle in its profile. The part was printed with the face connected to the wall of the robot being on the build plate, as there were screw holes in that parts. Otherwise support would have been needed. The printer used was a Prusa i3 mk3. We can provide further files or pictures if you are interested.

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