The 2018 FRC challenge, Power Up, had a retro 8-bit theme centered around the manipulation of a power cube. These cubes could be placed on scales to tip them in favor of an alliance or they could be stacked in a vault to unlock power ups. In the end game, teams could climb atop a rung designed to be small enough to make it difficult for two robots to hang on simultaneously. This year saw many teams building elevators and “lift” mechanisms which could assist friendly robots with a climb.
Going into the season our main goal was to do well in either the Hudson Valley or New York City regionals so that we might qualify for nationals. Our analysis of the game led us to conclude that if we had a consistent autonomous and a speedy elevator we would almost be guaranteed to rank highly (this was because a good auto gained us a ranking point). Building a climber was an exciting prospect but ultimately unnecessary for our goals. Due to the weight of our swerve drive and a desire to avoid the tippiness of “giraffe” robots we wanted to build our elevator as light as possible to lower our CG. This meant experimenting with carbon fiber, laser cut acrylic, and a variety of other plastics. To maximize our efficiency we wanted to build a touch-it-own-it intake which could bring cubes securely into our possession the moment our robot touched one.
Our final robot, Milkman, turned the scoring process into three stages. First, two deployable arms lined with a pair of wheels would suck the cube in. Afterwards a grabber would secure the cube by clamping on the sides with a linear piston. The grabber then rode along an elevator composed of stages of carbon fiber rods held together by plastic bushings and polycarbonate.
Two major problems came to haunt us throughout the whole competition season. Our robot lacked stability and synchronization. In our pursuit to build mechanisms as light as possible we added an extra layer of complexity to our elevator by choosing to use stages of carbon fiber rods instead of the more popular metal framework. Connecting each stage through an intricate design of plastic bushings and laser cut acrylic meant our elevator was a lot shakier than ideal. A shaky elevator meant a shaky grabber which stopped us from picking up cubes effectively and severely hindered our cycle times. The inaccuracies of the cube transfer from one mechanism to the next was avoided by many teams who simply put their intake on the elevator which doubled as an outtake once the mechanism was at its desired height. Another problem with synchronization occurred within the elevator itself. Continuing with the theme of lightness we chose to use belts to drive the elevator instead of chains or winches. Though we originally thought the teeth of the belt would stop it from skipping on the pulleys, at longer distances this precision became harder to manage. Because we had belts running on both sides of the elevator the lack of synchronicity meant the elevator was slightly tilted which would have completely jammed had it been made of metal. But because we used softer materials the elevator still rode up and down albeit at a slower pace due to the extra friction. Compounded with the natural shakiness of our elevator the effects of this problem multiplied and we found ourselves trying to add more motors for greater torque.
In both our regionals we were eliminated in the quarterfinals of playoffs so unfortunately we did not make nationals but the year served as a strong learning experience about the kinds of mechanisms and skills we needed to work on.
A Milkman prototype showing off our cube intake and swerve drive:
Milkman using its elevator to score pieces on the scale and tip the game in our favor in Qualification Match 23 at Hudson Valley Regional: