Shooter Calibration

I’ve noticed that many people have fairly low accuracy on shots, even bots like 973 and 1678, I was wondering if anyone has been having problems with calibration, and if so what were/are they

Balls are in horrible shape! Tips and years everywhere. As soon as one gets a significant tear it compresses soooooo much easier leading to less pressure on the shooter wheel. Shots come up alot shorter that a new ball. Teams are tuneing their shots in with those crappy balls then shooting new balls out of the arena


I think our failure modes were pretty unique, but I’ll post anyway.

Our biggest variance has been due to ball quality. We have two sets of tunes, one for well worn balls, and one for brand new ones. We only swapped out the setpoint RPM for our very last match.

We had one or two vision mis-acquisitions at Miami valley, and two cases of freak 10x execution time on our slow software loop for about a 30s stretch of the match. Multiple smoking guns, still investigating…

I think overall, unless there shiny or green things behind the target, the failure modes will be fairly unique to each team…

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When it’s the high-end teams having consistency problems, it’s almost certainly ball variation. In addition to the problems with torn skin on the balls, the other problem that develops is that the skin separates from the foam or whatever the interior material of the ball would be called. With new balls, we’re at about 95% outer port accuracy on the far side of the control panel. With less than a week of practice on the balls and not a tear to be found, we’re lucky to get 40% accuracy.

For less experienced or skilled teams, some other things that will cause inaccuracies are:

  • Lack of speed control or inadequate speed recovery on the shooter wheel(s)

  • Inconsistent ball entry speed into the shooter

  • Inconsistent ball alignment coming into the shooter


I’ve got another question about the PCs besides wear and tear. Our robot was designed at 7300 ft above sea level. Pool noodles in the bumpers get noticeably smaller (resulting in saggy bumpers) at sea level. Anyone have any experience with the balls having different sizes at high altitude and at low altitude?

The two main challenges with shooter calibration. Limelight tracking other things other than the target and degraded balls.
If you planned long court shots, I retract what I said earlier, abandon it now. You’ll feel less frustrated.
The struggle is real.

You just got me thinking with this. Arizona North Regional is at 7800 ft. When we opened the truck last year and saw the size of the cargo balls that had come from a plains state regional was quite impressive, and that was at sub-freezing temps. We had several volunteers with inflation needles just letting air out for hours to get them down to the nominal 13" size.

We fight this every year, sometimes the altitude difference had a bigger effect. Balls bounce differently at sea level and altitude. This year the Powercells seem to be pretty much the same at 3000 (El Paso, Amarillo) vs 7000 ft (here), probably because they’re made of open cell foam. But a pool noodle (closed cell foam) circumference shrinks from 7.5 in here down to 7.25 in down in El Paso. We noticed that right away in Houston last year, our bumpers had been nice and tight and were pretty “saggy” down at sea level.

Our bumpers get saggy from existing, not from elevation change. The foam “settles” over time, even from the pressure of the taut fabric on them.

The PCs are vented,so it’s not likely that they are changing size from air pressure changes due to elevation differences.

We live at 4500 ft and compete at Flagstaff (over 7000) and Phoenix (just over 1000), and are quite familiar with the elevation change thing.

Our biggest problem (in shooting) is that we didn’t get the lidar’s on for week 1. We’ll do better in week 5.

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