For the latter two thirds of my Intro to Engineering Design class, teams of 6-8 students work together for about 10 weeks on a final project. Unlike the mini project, most of the challenges aren’t open-ended competitions, but rather specific problems that need to be solved in some way. However, one of the teams gets to compete with local high schoolers in a competition using a Vex robot and custom 1v0 game. Guess which one I’m in?

The rules are pretty open ended and the tasks are pretty simple, so there’s not much strategy to the game since each task basically leads to the next. Navigating through a tunnel autonomously gets bonus points. 10 points are made for getting halfway through the tunnel, and 20 points are scored for autonomously completing the tunnel (about 72 inches of driving with 2 turns). Once past the tunnel, a set of small stairs must be climbed to get to the main portion of the field. Once on the field, various objects must be retrieved from various places (behind a door, on a shelf) and brought to within arm’s reach of a sitting human player for additional points. 20 points for a soda can behind a door, 10 points for an accessible soda can or a plastic bowl, 5 points for a juice box or some utensils. Field photos will be around in a week or so.

For build constraints, you get to use $200 of Vex parts, a Starter kit, and whatnot basically. This is kind of flexible and donated parts don’t count (guess who gets to use their Cortex?) so as long as we don’t spend too much of RPI’s money they don’t seem to care.

In our analysis and prototyping so far, the game is deceptively difficult. The big challenge is the stair set. The stairs are 4 inches tall, 4 inches deep, and you have to step up two of them. This means that the diagonal is about as long as the wheelbase (you won’t touch the floor and flat top at the same time) so you can’t just hop over a single step or gap, but you have to really climb up the stairs. In addition, the size constraints make stuff like tri-wheels and PackBot-style treads very hard to use. Stairs are a “must solve” problem; if you can’t get over the stairs you can only score about 25% of the game’s points. Our first prototype was to see how well tank treads could climb the stairs.

It looked more successful than it was.

Unfortunately actually climbing up the side of a step is actually not really easy or fun, so we had to place it on the edge of the first step to start it climbing. From there, the robot could pull itself onto the second step and get oh so close to making it on top. We played around with various ideas for arms to assist the robot at various parts of the climb. We’ll see how that goes. Moving our manipulator around to play with the CG during the ascent could also help.

Can we just turn this in as our robot?

Luckily manipulator prototyping was a lot easier. We grabbed a Vexplorer robot from RPI’s stock and saw if the claw could grab everything. Indeed it can. The utensils were easily pinched, the soda can even more easily pinched, and the only thing that was even remotely difficult was the styrofoam bowl. We tried placing objects at different heights to see what angle the claw should be at for easiest pickup (parallel to the ground won), and we’ll place the arm on a very compact four bar linkage for compactness and ease of use.

After a few days of prototyping and learning what looks hard / is easy and what is hard / looks easy, we have a fairly concrete plan of action for the next few weeks. The manipulator should be nearly problem free as four bar link arms and claws are very easy to do, but the drivetrain will be a real challenge that we will have to refine over time to get right. We still can’t decide on a team name and theme, but one of the last ideas looks promising…

Team Robot Unicorn Attack?

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