Catapult vs Wheeled Shooter

[M217]

Catapults had one big advantage this year that my team discussed in the early build season: typically, the vast majority of a catapult's variance is up-down (largely because of small inaccuracies in distance reading) while they are incredibly consistent left-right. The shape of this years goal allows for a little up-down inconsistency, since that's the longer dimension. I remember a lot of the catapult's I've seen hit a little lower than dead center from the outerworks (for example, 359's balls in tech valley seemed to touch the lower lip of the goal fairly often) but they still went in fine. For this reason, I think catapults were a lot more viable this year than they have been in previous years, and I would applaud any team that built one for making a sound strategic choice.

That being said, the packaging of a wheeled shooter and the flat linear trajectory (at least when you shoot as hard as we do) seemed to offer enough advantages that we decided to go with that. We didn't think defense would be too much of an issue because we planned for a fast release, and we'd already began work on a swerve drive that would make us much harder to pin and block.

The catapult is definitely a good choice this year, more so than I think it was in rebound rumble, but I think there are still advantages to having a wheeled shooter that make the decision nontrivial.

[sspoldi]

At team 230, we were concerned about the variability of the ball as it impacts either a spinning wheel or linear punching style shooter. In addition, we were inspired by the extremely accurate catapult used by our friends at team 177 in 2014, that was not only accurate, but extremely hard to block.

We got around the lack of adaptability of a traditional catapult by going electric, with 2 mini CIMS and a 28:1 reduction (or something like that). We found we could adapt the command profile to get pretty much any trajectory we wanted. If we went spring or bungee powered it would have been far less adaptable.

We had a lot of people comment that they couldn't believe we could shoot with a fully electric catapult. We did a fair amount of simulation to optimize the gear ratio to maximize energy delivered to the ball. A lot of teams don't do this and as a result don't get the most energy out of their device.

We lean pretty heavily on simulation written in Octave (a MATLAB like language) running on a Linux OS. It's all open source, so if anyone want's some more info please stop by our pit in champs and ask for Henry (or the drive team coach if he's off somewhere).

Cheers,
Steve S.

[marccenter]

Originally Posted by sspoldi

. We found we could adapt the command profile to get pretty much any trajectory we wanted. If we went spring or bungee powered it would have been far less adaptable.

We had a lot of people comment that they couldn't believe we could shoot with a fully electric catapult. We did a fair amount of simulation to optimize the gear ratio to maximize energy delivered to the ball. A lot of teams don't do this and as a result don't get the most energy out of their device..

Can you provide a little more information:

1) About your command profile adjustments

2) What your simulation revealed about getting the most energy out of your device (speed?).

[Gdeaver]

Puncher, catapult, or wheels. Many teams had actuate launchers. Auto aim seamed to be what separated the good from the great.

[domi]

I agree with Citrus, wheedle shooters are better to track and there is better control of speed and trajectory. Catapults are cool but, they easy to use because you have to think about the speed or rotation of the motor. Then after dealing with that, then you about vision tracking which is a problem because it will be 100 percent so there is a lot to deal with. But, at the end of the day, it's down to which one you are familiar with or comfortable with.