Locomotion: Duck // Konrad Krawczyk
The idea Bishka and I worked on was to build a two-legged robot moving similarly to a duck.
The way ducks move can be well illustrated with this video:
In short, ducks move on their flexible two feet by putting their bodies in a bounce-like movement between left and right side, while also rotating their backs to the opposite side of their stepping foot. This is how they keep their balance despite having only two feet. What also helps them is the relative lightness of their bodies, especially the inner bone structure.
We started working on the duck without having reflected on these observation. This is perhaps why our first attempt was less than successful. We tried attaching two legs onto a heavy steel body of the Kittenbot. The legs, hastily made out of Lego brick and paper, were too long and fragile, and the robot fell every time we tried to add balance to it.
Later, we gave up and attached two extra legs of support to the robot, ending with a ball berry. This could at least stand on its (four) feet, but could not make any moves, as the servo would get blocked on the spot. We realised there was a bigger problem with our mechanism itself.
We assembled one of the robots in the pre-ordered set of simple robots. The robot would stand on two feet and make the bouncing move with just one motor. Our robot, however, was different in a sense that it was supposed to be a bit shorter and wider, which requires a different kind of balance.
On the Web, Bishka found an image of a mechanism that we eventually decided to recreate. The key difference here was that the part attached to the servo would be a Reuleaux triangle with rounded edges.
We quickly user a laser cutter to make the robot, and then assembled it with a new arrangement.
First problem we ran into was the leg movement. The ones made of wood got stuck immediately due to friction. The pieces of metal that we found were to tiny and frail to even stick to the trianglular wheel. With great help of prof. Cossovich, we assembled legs with bigger and more sturdy pieces of wire, three washers and a nut. The legs finally kept the balance at least slightly, however the robot would still fall forward.To decrease friction, we added a ball berry at the front, which caused the robot to move forward
One thing I would hope to accomplish with more time is definitely a greater balance for the legs, so that in can actually walk solely on its own two feet. This could be accomplished with changing the structure a little bit, perhaps by making it even lighter, and also adding extra power to the motors (both ran on the same two batteries).