Published: Dec 18, 2022 by Liz Metzger

(MAX, Computer Vision, 3D Printing)

I contributed to this project during an internship where we took the first iteration of this robot and improved its design to be more robust and reliable for the 2021 BattleBots filming. Axis is a five fingered robot that can balance uniformly shaped objects on its fingers and rotate them. For Battlebots we needed to make it so it could hold a pretty heavy trophy called the “Golden Bolt” on a clear acrylic plate and be able to be left with minimal supervision for filming.

The first step was that we wanted to replace the servos that were currently being used for stronger ones so that it would be better able to handle the acrylic plate and the trophy since we had never used the robot to balance something that heavy. We also replaced all of the 3D printed parts for each finger to ones that were printed with a higher resolution so they looked better and the seams between the parts were less visible. Some of the wires were also worn down to the copper so I remade some custom wiring of the appropriate length for the different parts of the finger – from the distal servo to the proximal one and from the proximal servo to the core servo. An example of what each of the fingers looked like can be seen below.

After we rebuilt Axis it was time to start tuning the software. In the video below Axis is working pretty well as the camera in the center tracks a dot on the acrylic plate and dynamically adjusts the finger’s steps to keep it centered, but for a while it was over correcting and actually walking the plate off of one of the sides. The fingers would also contact the plate at different heights so sometimes the hand-off between fingers had a bump where the plate either dropped to a finger that was lower or was pushed up by a finger that was higher. We spent a lot of time fiddling with offsets to account for super small mechanical differences in how the fingers were printed, the servos were calibrated, and even just how the base was set. This helped to get rid of the bump in the plate during hand-offs. I also helped to rewrite the computer vision program in MAX that was tracking the center of the plate and trying to keep it in the center of the frame so that the plate would not fall off. By filming we had a program and a robot that we were confident in and it filmed great!