1918 NC GEARS 2012 Robot

[JABot67]

How were you lining up to shoot? My team was under the impression that a robot would need some sort of vision targeting or driver station camera feed (for manual targeting) in order to shoot accurately. But it doesn't look like you have a camera...

[biancs15]

This is an awesome robot. Excellent job guys !!

[lynca]

My favorite robot of the season so far !

The roller arm has a hypnotic effect, What motor gearbox do you use for the roller arm ?

[jblay]

Yet another 1918 robot with a design that I hate myself for not thinking of. Can't wait to see it play.

[Gerdee]

This looks amazing, great job on making another awesome bot!

[Akash Rastogi]

Really great stuff from 1918 yet again. This robot is legit.

[flippy147852]

Originally Posted by lynca

My favorite robot of the season so far !

The roller arm has a hypnotic effect, What motor gearbox do you use for the roller arm ?

IIRC, we use a single BB P60 for the roller arm at a 64:1 reduction ratio. The extended arm is driven by a pneumatics tube (the orange thing) being powered by the roller claw inside the frame perimeter.

[Zach O]

How tall is the robot at it's highest point?

[flippy147852]

Originally Posted by Zach O

How tall is the robot at it's highest point?

29" with the arm down, 36" with it up. He's short lol

[ChristopherSD]

Word has it that we won't see you guys at Traverse again.

[flippy147852]

That is correct, unfortunately. We didn't want back to back events, so we switched to Gull Lake instead. Will you guys be at Troy?

[ChristopherSD]

Originally Posted by flippy147852

That is correct, unfortunately. We didn't want back to back events, so we switched to Gull Lake instead. Will you guys be at Troy?

Nah--Traverse and Wayne (back to back). I'm also not a fan of two consecutive competitions.

In regards to Troy, I'll probably come watch like I always do. It's a tough competition.

[Wayne TenBrink]

It is about 36" tall. (edit: already been answered)

The primary roller in the frame and the arm roller in the arm are both powered by the same FP motor. The roller motor/sprocket axis is in line with the arm pivot, so the urethane belt tension doesn't change with arm position. The arm roller does a decent job picking balls out of corners, etc., when the chassis isn't moving too fast, but for open field pickup we generally keep the arm up.

Our alignment is simple, but seems to work well. Mostly its just the drivers eyeballing it. We also use the camera when needed. We don't expect to win any Rockwell Automation Awards.

We have seen the same distance spread due to ball variation that most others have reported, and have taken steps to minimize its magnitude and impact. We did some studies and found that the "sweet spot" for scoring for a given wheel speed combination was quite deep. (We run the bottom wheel wide open and throttle the top wheel to control distance, which improves backspin). Shooting straight on, we could hit about 5/6 from within a distance tolerance of +/- 1 foot from the "ideal" distance thanks to backspin and the backboard. It dropped off to about 1/2 at 2 feet from "ideal". Once we figured this out, we changed our approach. We quit worrying about adjusting wheel speed as a direct function of distance and set up a few standard speeds for shots we expect to be taking often (short, medium, and long, etc.). Now, we just concentrate on the aim (azimuth) and get in the ballpark for distance, something the drivers can judge at a distance or quickly see from the camera. With a bit of practice, they were able to line up and shoot in a couple of seconds. We expect to miss a few, but that is likely to happen anyway because of ball variation. We'll just pick 'em up and shoot again.

We learned a lot about shooters this year (starting from nothing, it didn't take much!). The main thing we learned (thanks to some help from my brother) is that the motor doesn't really power the ball to the target. The kinetic energy in the ball comes from the stored energy in the spinning wheel (flywheel). A bigger motor (or more of them) doesn't throw the ball farther, it just improves the recovery time between shots. What you need is a good flywheel(s) with some decent grip (texture and compression) on the ball. We went from two 775's per wheel to one, and redesigned our wheels.

We chose early on to concentrate on shooting from the key and closer. Not only is the scoring percentage better from up close, but it lets us gear the shooter wheels for faster recovery between shots and keeps us in or near the protected zone. We also made ball collection and ball handling reliability a priority. Collecting from one side and shooting from the other allows for a straight ball flow. We also wanted a very low CG. This approach works well for that.

We saved a few new balls to recalibrate the wheel speeds prior to competition. The new ones go a lot farther than the well used ones.

Special thanks to whoever it was that came up with the trajectory calculator. It was a priceless tool in our design process. We used it to determine ball speed and launch angle, which drove amost every other detail of the ball feeder/shooter.

Edit: I hope the GDC offers their wisdom on the <R35> obscured number issue. This will come up again and again this year and in the future. IMHO, the intent of the rule is met if you can read the numbers while in the starting configuration. People don't come to events to check out the sleek lettering on the bumpers. They come to watch what the robots can do. It would be a bummer if this became a significant design constraint for manipulators. IMHO, putting numbers on the arm wouldn't satisfy a lawyer, either. Numbers get obscured in the course of playing the game by other robots, field elements, etc. I'm neither a lawyer or a GDC member, so I'll deal with whatever happens.

We will miss TC. We have many fond memories and hope to return soon. It just didn't work with our schedule this year.

[Akash Rastogi]

Originally Posted by Wayne TenBrink

Special thanks to whoever it was that came up with the trajectory calculator. It was a priceless tool in our design process. We used it to determine ball speed and launch angle, which drove amost every other detail of the ball feeder/shooter.

Which calculator? (link?)

Thanks

[Wayne TenBrink]

Originally Posted by Akash Rastogi

Which calculator? (link?)

Thanks

I'll post a link when I find it. One of our students found it.

I believe this is the one - from 2151 "Monty Pythons". Thanks to the "engunneer"

http://engunneer.com/content/blog/fi...ry-spreadsheet