Bridge Building Robot
Objective
I worked with three students to design and build a remotely-controlled robot to pick up foam, aluminum, and PLA materials and assemble a bridge from these materials. We also participated in a class competition to assemble a bridge in eight minutes, with as little of the provided materials as possible.
Technical Details
There was an assigned list of materials we were allowed to use for this project; anything else would have been against competition rules. Most of our robot ended up being made from 3D printed PLA parts and laser-cut birch plywood and acrylic pieces.
We were provided with foam and PLA blocks, as well as aluminum plates, which we could use to assemble the bridge. Our first course of action was to choose the best configuration for the bridge. We tried many different configurations by placing weights on them, and seeing which collapsed. We decided the best was configuration was one with two foam blocks at the bottom, a PLA block on top, and the 3 aluminum pieces laid out across the 'canyon'. As seen in the video, we built this configuration by using a gripper to pick up and place the foam blocks, and then an electromagnet to place the PLA and aluminum pieces. Unlike the foam, the PLA blocks and aluminum plates had magnets attached to them.
I designed the electromagnet holder and the final version of the gripper. We initially started with a lead-screw design for the gripper, which my and I then teammates then assembled. It was able to pick up the pieces, but there were problems: it was too heavy and too fragile. After more sketching and prototyping, I settled on a rack and pinion design (shown in slides above), which was lighter and way more robust. The electromagnet holder needed to be about the height and weight as the gripper to maintain balance, and avoid the bridge falling over.
I also designed the arm which holds the gripper and electromagnet holder. It moves transversely using a rack and pinion system, and vertically using a pulley system. The gearbox for the pulley system is shown in the slides above. I modelled all these designs in SolidWorks.
Results
As seen in the video above, we beat our opponents in both laps, completing the bridge in about half of the allowed eight minutes. Our bridge was also able to survive the sturdiness test of allowing a RC car to cross the canyon. Our robot placed third in the contest.
You can find our final report (which contains drawings for all the parts we fabricated) here and my design notebook (which contains all my sketches and calculations for this project) here.