• Sajiv Shah

FRC 2021 Infinite Recharge @ Home Strategy Part 1(Ball Pickup)

Although official kickoff date for the 2021 Robotics season is during the first week of January, FIRST has announced that this year's game will be a replay of last year's Infinite recharge game, but there will be no in person tournaments for regional competitions but rather challenges that can be done at home.

Our team decided to treat the season as normal, with the same intensity as a 6-week build period, but start a little early since we had more work to do including trainings. With this strategy discussion, we assumed the game was as normal (played with opponents) in order to give newer members a look into what strategy discussions look like and allow them to offer their ideas. The goal of this strategy discussion that occurs at the beginning of each season is t list out the exact goals our robot needs to meet and from those goals develop specific subsystem requirements.

After reviewing the scoring methods and the structure of the game, including the stages and the endgame, we covered some basic discussion points.

Ranking points vs scoring points. Scoring points in different parts of some games leads to a different amount of ranking points, which makes a difference in strategy for qualification and playoff matches. What we found for this game is that the overall robot design does not pertain to the different gameplay type, whether it be qualification or playoff, as the robot still needed to carry out the same basic tasks, meaning the only thing that would be effected is our actual in-game strategy, which is a different discussion to have.

In the 2020 game, the most important scoring method is the ball cycle. The ball cycle is defined to be the process of intaking up to 5 robots, driving to a viable shooting location, and shooting the balls into one of the targets. Based on the point system, it was clear that the team that could cycle the quickest and maximize points/second with an accurate shot would win the game. In order to do so, our robot needed to have all 3 steps of a cycle optimized for time, so we started with the ball pickup.

From the field view from the game manual, we know that the game starts with 20 balls located on the field, 10 in each teams designated space. These starting balls are likely to be picked up during autonomous periods and within the first 10 seconds of tele-op considering 4-6 robots are attempting to store 5 balls and shoot them. Once the balls are picked up and shot, balls that are made into your teams power port are dropped out by the opposing alliance into the opposing loading zone, meaning that the balls are more likely to be picked up by your opponent since they are in a defended zone. This means that in playoff matches, the most common robot path will require a robot to travel back to it's alliance station side to get balls from its loading station.

The loading station has 2 different heights where balls can be dropped from. Although often overlooked, the high loading port is something our team identified to be a major advantage. Picking up 5 balls off the ground requires far more time and robot coordination in comparison to lining a robot up against a loading port and dropping balls into it. Considering that close to 60% of a cycle time is intaking balls according to our estimations, cutting this time down by picking up balls from the loading station will be a huge advantage for reducing cycle time.

So what does this specifically mean for robot design? Not all feeder/hopper mechanisms allow balls to be added from above, so we need to accommodate our design to have an area of open space where multiple 7 inch balls can drop through into a hopper, in an orderly and predictable fashion. Likely designs that we came up with have never been used before by our team, so the prototyping process for this feeder will be especially important.

Lastly on this topic, our team realized that having our shooter mounted on the opposing side of our intake would be beneficial in some scenarios and harmful in others (these specific scenarios will be discussed in other posts) , which brought up the idea of a dual sided intake. This again directly impacts the feeder/hopper design, which needs to be able to accept balls from both sides.