Re: Shooters: What have you learned?
 

Agreed.

Re: Shooters: What have you learned?
 

In terms of shooter this year, I think a big factor that seemed less important when compared the rpm & torque of your motors, the angle at which you shoot, or the horizontal distance from bot to basket was shooter contact time (the amount of time that the wheels, lexan or any other material used to guide or propel the ball is in contact with the ball). During the LA regional, we practically tripled the size of the lexan guide on our shooter and drastically changed the angle so that we could get an easy, consistent shot on the middle basket versus a high arching shot that was mildly less reliable for middle and high baskets.

Re: Shooters: What have you learned?
 

I think 33 did quite a few things correctly on our shooter this year due to experience with 2006 and 2009.

Absolutely 100% #1 most important thing is feeding consistancy. You can have the most consistant, perfect shooter in the world, but if it has 1 inch of tolarance side to side its not actually going through the shooter the same way each time. We took a lot of care to get this right. We made our shooter turret at the bottom. We found from 2006 that with the lazy susan mounted higher it was basically impossible to put the ball in the shooter the same way every time. We also went with a three point contact within the tower, two pieces being adjustable plastic skids one being a gates belt. This ensured that the balls are entering the gun at the same place as there is no room for lateral movement in the tower. We also have "kicker" wheels which basically push the ball up into the gun eliminating any potential dead spot between the gun and gates belt. Finally, our programming sequence is such that each ball stops just before going into the gun so every ball enters the gun at exactly the same speed from the same place within the tower.

Shooter design-wise we have almost 150 degrees of wrap around the gun before the ball exits. This assists considerably with ensuring that each ball accelerates to gun speed before exiting. We have done an enormous amount of calculated and dynamic shooter work to ensure that we have the least amount of variation in shooting as possible.

Of course, I can't share too much before worlds. Perhaps after.
Regards, Bryan

Re: Shooters: What have you learned?
 

Assuming we're talking one-wheeled-hooded shooters:

#1 - Make sure your shooter is sturdy. For us, this was probably the most important factor in ensuring repeatability. A janky shooter will Wobble and warp, affecting the ball's trajectory significantly.

#2 - Use as LITTLE compression as possible. We found that high compression caused big variations depending on balls' squishiness and how new/old they were. To make up for the force you lose to create the necessary friction, it's good to use a surface like grip tape on your shooter hood and wheels. this increases friction force with the friction coefficient rather than the normal force, so to speak. (Grip tape is great on both the wheel and the hood!)

#3 - Make sure the ball enters the shooter the exact same way every time. We found that changing the speed at which the balls are fed also can significantly impact their trajectory.

#4 (This goes with #3) - Surfaces in the shooter must be flat in the direction perpendicular to the balls' motion. This means that your hood should be one smooth "plate" rather than a set of rails. (It can still be curved around the wheel, so long as it curves with the wheel and not across it). It might also be worth looking into to make the shooter wheel a "drum". The reason for this is that you want the shooter to be tolerant to any side-to side error the ball might have upon entering.

With all that and a good control loop for wheel speed, you have a shooter that will fire almost exactly the same shot every single time.

Re: Shooters: What have you learned?
 

What I learned from shooter designs:

Back spin shooters are great due to the fact that they cause the ball to fly straight down after hitting the backboard.

.5 inch compression is the most decent amount of compression for foam balls. any tighter, the ball would rip apart. looser would cause the ball to shoot out with low power.

curved backplate for a backspin shooter helps get more traction on the ball.

rapid fire causes each ball after the first one to lose a small fraction of power.

the angle of fire can easily be adjusted by the motor for the wheel on the launcher without the backplate having to move if it ends at a 45 degree angle.

the best wheels are the ones with smooth rubber on it.

Re: Shooters: What have you learned?
 

One thing i noticed this year is that when you have multiple balls being fired, if they are fired in quick sequence it may not give the motors time to spin back up to the required speed thus reducing range/accuracy.
From what we saw with out robot this year that can be solved two ways. The first is to ramp up the shooters power to a point where a shot doesn't slow the wheel speed a noticeable amount. The problem with this is that it really prevents you from putting serious compression on the ball which may or may not be a problem depending on the shooter style you choose. Also lots of power may require transmissions or multiple motors which adds weight. If it is a fixed shooter this may not be a problem but on turreted shooters it may.
The other option is a mechanical feature designed around the idea to not feed multiple balls through in a line but only let them go through when the wheel was back up to speed. This was the option our team chose in the form of a pneumatic powered lever arm that pushed the balls into the shooter only when the trigger was pulled. This enabled us to shoot only when the speed was where it was needed. Hope this helps!

Re: Shooters: What have you learned?
 

We went 10 straight matches (starting with our 3rd match and continuing through SF's) and hit 18/20 balls in auton. Here's how we did it:

1.) Pick a point on the key that can be utilized every time as a reference. There are 4 such points: 2 corners and 2 edges where the middle line meets.
2.) Make a shooter than has insane backspin, such that a ball can be shot up at 60 degrees under full speed, hit a wall a few feet in front of the robot while still ascending, and still come back down to the hit robot.
3.) Make a sighting mechanism consisting of a hole and a narrow slit. Calibrate the slit to where the ball hits the wall.
4.) Make an adjustable autonomous where the driver's station can delay both balls such that they fire anywhere between 3 and 12 seconds.
5.) Make an adjustable autonomous where the driver's station has a "hard ball" and "soft ball" setting for both balls that fire. Calibrate. This is the hard part.
6.) We set the bot down with the front right wheel on the left front corner of the key. Then I sighted the direction of the bot to either the left or right bolt on the back of the rim: right for hard balls, left for soft balls. The shots would be off a degree or so depending on which we had.
7.) If the balls are ROCK HARD, I had to make a manual adjustment, moving the bot around the back of the key by 6-12". This is why we missed the 2 that we did, but they were in different matches.
8.) Pick 2 balls that are similar to the balls that were calibrated with, if at all possible.
9.) Profit.

Re: Shooters: What have you learned?
 

Pay close attention to the varriations between other balls that really killed us this year, one second we are shooting perfect when we get on the field and use there balls boom all is diffrent.

Re: Shooters: What have you learned?
 

When you have a 2lb aluminum pseudoflywheel that works going 3000 rpm, don't use a roll of duct tape as a makeshift brake pad. Things just go down hill from there...the roll itself got shredded, then the adhesive residue drastically changed our shooter grip. From needing to fire at 110% power, we had to drop it all the way down to <30% power.

Re: Shooters: What have you learned?
 

When coaching on the Curie field I remember picking through the available balls on the coop bridge. After seeing the stark differences between them we started "racing" the other alliance every time we got onto the field to procure the best balls for hybrid.

Re: Shooters: What have you learned?
 

I've written a quasi-successful swerve program in LabVIEW. In that the robot drives, but doesn't turn. Our team's analyses, however, state that the turning problem is mechanical (too heavy, swerve drive treads on carpet produce high coefficient of friction). pm me for source code.

Re: Shooters: What have you learned?
 

? Was this accidentally posted here?