Consistent shooter

[Jeffrafa]

Originally Posted by Ether

and near the bottom of the list would be a) motor-powered kickers and b) motor-powered wheel shooters.

The sample size for wheeled shooters seems to be pretty small this year. We have a wheeled shooter consisting of 2 8" Colson wheels in a vertical orientation, shooting from fairly low. Each has independent closed-loop pwm control, to make sure the speed is consistent no matter the battery state (on the practice field we are making the same auto shot for a battery just used in a match as a fresh one). Also having the wheels above and below the ball lets us control the amount of back/top spin the ball has (currently tuned for backspin, although the effects of top spin on the ball trajectory are interesting and not quite intuitive - I am fairly confident we could increase our sweet spot range with top spin, but only the longest shot distance would improve. We have only done enough testing to demonstrate the spin effects I calculated, but not enough to justify a change.)

So far in our 1st day of qualifying matches we are 8/10 in auto mode (shooting from behind the white line), and have the 2nd highest cumulative auto score in our district (2nd to a 2-ball auto, but not by a lot). The 2 misses could likely be attributed to human error, as auto wheel speed was being read from an analog knob on the drivers station, now it's a set calibrated value.

Scoring high in teleop has not been as consistent as auto, but I am confident that will improve with more driver practice. We will see how things pan out in day 2 of this district, and at our second district in 2 weeks.

[Ether]

Originally Posted by Jeffrafa

on the practice field we are making the same auto shot for a battery just used in a match as a fresh one

What about ball inflation?

Have you tried making the exact same shot with a slightly overinflated ball and a slightly underinflated one?

[Ether]

Teams with wheeled shooters:

Have you tried making the exact same shot with a slightly overinflated ball and a slightly underinflated one?

[AustinH]

Speaking of adventures in consistency...

We couldn't for the life of us figure out why we had about a 75% accuracy rate in autonomous mode on the field as opposed to near 100% on the practice field. We controlled for starting position, angle, battery voltage, air pressure, etc. We even added a sizable delay between our "charge" forward and when our catapult fired in order to let the ball fully settle.

One of our four batteries had a terminal lug that was perpendicular to the rest. As a result, the battery power cable protruded *ever so slightly* into the catapult bucket, preventing the ball from seating properly in the bucket. Thus, every few matches (namely when the aforementioned battery was installed), we would miss our auto shot.

Needless to say, the fix was applied the moment we got back and is ready for Mount Vernon this weekend.

[Kevin Leonard]

From what I've seen of matches thus far this season, a high-pivot catapult with springs resistant to wear seems the most consistent.

We have a low-pivot catapult, and from our testing, we've discovered a few different things affect the variability of our shot (some controllable, some not).

• Where the ball seats itself in the catapult
• How far we pull the catapult back
• The thickness of our catcher panels (we generally shoot with our side-panels for catching retracted. This helps to:
  a)center the ball, and
  b)avoid breaking our catchers when they are under defense. They are filled with a padding to help deaden the ball when we catch, but the padding slides down our catchers over time, changing the effect of the catchers)
• Ball Inflation and Ball Condition-
  This is a very small effect, but it can change our accuracy if we're shooting from either end of our sweetspot. If the zipper of the ball sits right on one of the two prongs of the catapult, it can also change our shot.
  
  Our springs were custom made to be extremely resistant to wear. So even after hours and hours of drive practice, we still shoot very well.

[IronicDeadBird]

Originally Posted by Ether

Teams with wheeled shooters:

Have you tried making the exact same shot with a slightly overinflated ball and a slightly underinflated one?

Are you talking about making a shot with one angle from one point as being the same. Or are you talking about getting the ball to target consistently?

[Ether]

Originally Posted by IronicDeadBird

Are you talking about making a shot with one angle from one point as being the same. Or are you talking about getting the ball to target consistently?

The former.

[IronicDeadBird]

Originally Posted by Ether

The former.

I will ask the team I work with (1339) I don't believe we tested different ball size but I will ask and see if we have any information at all on it. Another team that might have the info is Robotknights they have a pretty intense wheeled shooter so if I can get a hold of them I'll see if I can find anything out.

[Mike Norton]

How about 100% in auto mode. 14-0 at WPI and 18-0 at Bryant. We use surgical tubing cross bow style.

We use extrude aluminum 1"x1" as the launcher with two rollers at the very top. This give the ball a slight backward spin to keep it floating.

[Johnnybukkel]

Our robot doesn't fit any of the shooter catagories... We are very consistent in the high goal (when our pit checks are done right).

[dodar]

Originally Posted by Johnnybukkel

Our robot doesn't fit any of the shooter catagories... We are very consistent in the high goal (when our pit checks are done right).

Your category of shooter is Scary.

[Johnnybukkel]

Originally Posted by dodar

Your category of shooter is Scary.

Nah, Howie's great! Definitely a robot that the kids can play with.

[Kevin Leonard]

Originally Posted by dodar

Your category of shooter is Scary.

Quoted for truth. And spotlighted.
See you guys tomorrow!
#repeat?

[seg9585]

At the LA Regional, our pneumatic catapult shooter had a 100% scoring percentage in both autonomous and teleop from our 2nd through 10th qual round and had 1 miss in elims amongst heavy defense (scored 6 in elims QF).
Note in the first round we missed shots due to a pneumatics leak which was fixed shortly after.

I was impressed with how consistent our shooter ended up performing.

We shoot between 6-8 feet away when stopped, and 8-10 feet while in motion (we use sensors, indicator LED lights, and telemetry to determine shot attempt distance)

[DampRobot]

Originally Posted by dodar

Your category of shooter is Scary.

Uhh... So how exactly does it work?