MiniRHex Climbs 55 Degrees on Cork Board
I picked up this project from another undergraduate student for the spring semester of 2021.
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MiniRHex is a hexapod robot that uses whegs (the combination of wheels and legs) to traverse rough terrain. By inserting microspines (tiny fishhooks) into the ends of the legs, it allows the legs to latch onto random small impurities in the surfaces the robot tries to climb.
Primarily, I focused on implementing code on the existing MiniRHex platform that would allow the robot to use a tail to help itself climb. A tail helps climb steeper angles because it provides a moment that prevents the robot from tipping off surfaces.
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You can see a video of my tail code working. The legs of the robot move on periodic times, and the tail moves to discrete positions in sync with certain waypoints of the legs.
Working Tail Code
After successfully implementing the tail code, I focused on optimizing gaits and the designs of the legs for climbing. This involved gait design iteration and testing. In the videos below, you can see the progress the improvement in the ability of the robot to climb at an angle on brick. Ultimately, the brick seen in these videos were not porous enough to work well with the microspines, so the robot failed at higher angles. Ultimately, I successfully tuned the gaits to climb a 55 degree angle on cork board.
Gait Failure
Gait Improvement
Bed of Leg Slices
The design of the legs have a large impact on MiniRHex's ability to climb slopes. I iterated through many leg designs. The legs were 3D printed. Each of the 6 legs are comprised of multiple slices. The number of slices on each leg would depend on the thickness of each slice, based on the design. For example, for a design requiring 3 slices per leg, the robot would need 18 3D printed slices for a full leg set. The legs are designed this way so that there can be a fishhook in each slice, and so each slice will have individual compliance. This allows for a higher chance that at least one slice per leg can latch onto the surface. The fishhooks are inserted into the leg by pausing the print in the middle and manually adding the fishhoks. A bed of 3D printed legs can be seen here.
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