Panthrobotics (FRC 3337) - First Teaser Video

[MysterE]

Enjoy!!

http://youtu.be/3ztPUkXHkns

[Trez]

That shooter looks almost too powerful!

[Akash Rastogi]

Sick! That's the farthest shot I've seen on video so far.

[Andrew Lawrence]

How far is it?

[MysterE]

Originally Posted by SuperNerd256

How far is it?

To answer that question, I must refer you to our distance teaser. http://www.chiefdelphi.com/forums/sh...hreadid=100913

[JamesCH95]

Is there any point to such an incredible range? How consistent is it?

[JesseK]

Originally Posted by JamesCH95

Is there any point to such an incredible range?

Yes.

[Akash Rastogi]

Originally Posted by JamesCH95

Is there any point to such an incredible range? How consistent is it?

Think about having an alliance partner who may be able to stand at your Inbounder station, take in the basketballs, and then just launch them over to your side of the field to alliance partners. At least, that's how I see it being useful.

[Andrew Lawrence]

Originally Posted by Akash Rastogi

Think about having an alliance partner who may be able to stand at your Inbounder station, take in the basketballs, and then just launch them over to your side of the field to alliance partners. At least, that's how I see it being useful.

And if they're lucky, make a basket or two. Worst thing that'll happen is you miss and your alliance partner will get the ball and score it for you.

[JesseK]

Originally Posted by SuperNerd256

And if they're lucky, make a basket or two. Worst thing that'll happen is you miss and your alliance partner will get the ball and score it for you.

No, the worst thing is that you miss and your alliance partner has to go chasing a ball that's rolling 15-20 ft/second. If it rolls towards the alley, your alliance partners should think twice about getting it. And that's after your opponents scored a ball (thus the reason you get it from the slot).

Put some true thought into what WILL happen, even in the rare cases, else you'll dismiss any negative tradeoffs that are based on assumptions you don't know you're making.

[Andrew Lawrence]

Originally Posted by JesseK

No, the worst thing is that you miss and your alliance partner has to go chasing a ball that's rolling 15-20 ft/second. If it rolls towards the alley, your alliance partners should think twice about getting it. And that's after your opponents scored a ball (thus the reason you get it from the slot).

Put some true thought into what WILL happen, even in the rare cases, else you'll dismiss any negative tradeoffs that are based on assumptions you don't know you're making.

The point of the post was to say that it's a good idea to feed your alliance members from your alley. I understand what WILL happen, but there are more variables going into that that you're not thinking of. I could, say shoot it over at the minimum required speed, so if it misses, it looses most of its velocity from hitting the backboard, falls on the fender, rolls down, and is on my alliance's scoring side. If you want to be more precise about it, you could shoot with enough power so the ball just gets over the bump in the center of the field.

[MysterE]

What I do find amusing in all of this is that as far as I can tell, there has been no one that has discussed testing a shooter of this magnitude in regards to its accuracy in making goals. We have a lot of 'nah, can't happen', but not a lot of 'we've tried it and it didn't work'. Now, we haven't gotten to the point of accuracy testing yet - and when we do, I'm not quite sure we will post the results. Consider this though - when we see any of you in Archimedes, Curie, Galileo, or Newton - would you bet your score that we won't be able to make more than 'two or three baskets'?

We have a number of tricks up our sleeves after all.

[JamesCH95]

Originally Posted by JesseK

No, the worst thing is that you miss and your alliance partner has to go chasing a ball that's rolling 15-20 ft/second. If it rolls towards the alley, your alliance partners should think twice about getting it. And that's after your opponents scored a ball (thus the reason you get it from the slot).

Put some true thought into what WILL happen, even in the rare cases, else you'll dismiss any negative tradeoffs that are based on assumptions you don't know you're making.

The pessimist in me thinks that it'll hit the alliance station, bounce into the opposing ally, and continue down the alley until it bounces back onto the defensive side and you're back at square 1.

My point merely being that it may seem cool to be able to shoot really far, but I don't think it will be practical to shoot much more than half field. It will be very difficult to shoot consistently at those ranges as +/-1degree of alignment will cause you to miss the hoop, not to mention range variations. If you miss, the ball will probably have enough energy to bounce far, far, away from the hoops (out of bounds, in the opposing alley, or across the field) on a bad rebound.

I realize that the motors can be controlled to the right speed, but I would rather see smaller diameter wheels to control speed because they're smaller and lighter and will recover after a shot more quickly which will improve consistency.

[JesseK]

Originally Posted by JamesCH95

... but I would rather see smaller diameter wheels to control speed because they're smaller and lighter and will recover after a shot more quickly which will improve consistency.

Not exactly true. Conservation of energy: Power In = Power Out + Losses. Then there's angular momentum and the flywheel effect. I'll describe it from a software control perspective. The two greatest factors in controlling a shooter wheel are (1) Ball Contact Time and (2) Power Available.

Greater contact time = greater Tau for your PID, meaning your software has more cycles to aggressively ramp up the motor. Smaller diameter = less contact time. Combined with angular momentum concepts, your wheel has to spin much faster than you think to start with because it will lose more speed %-wise than a greater diameter wheel.

Greater power = less time that your software needs to ramp up the motors because they give more output per time. This simply means that small diameter wheels and recovery time will be on par with a large-diameter flywheel, because if you put the same amount of power into each, then each will return to their respective speeds at the same time. The flywheel lost less speed than the smaller wheel.

The rest is just angular momentum and how you engineer the wheel itself (entry point, entry speed, entry angular velocity, tread characteristics of the wheel, moment of inertia of the wheel, etc). These have more effect on the ball than wheel diameter.

[JamesCH95]

Originally Posted by JesseK

Not exactly true. Conservation of energy: Power In = Power Out + Losses. Then there's angular momentum and the flywheel effect. I'll describe it from a software control perspective. The two greatest factors in controlling a shooter wheel are (1) Ball Contact Time and (2) Power Available.

Greater contact time = greater Tau for your PID, meaning your software has more cycles to aggressively ramp up the motor. Smaller diameter = less contact time. Combined with angular momentum concepts, your wheel has to spin much faster than you think to start with because it will lose more speed %-wise than a greater diameter wheel.

Greater power = less time that your software needs to ramp up the motors because they give more output per time. This simply means that small diameter wheels and recovery time will be on par with a large-diameter flywheel, because if you put the same amount of power into each, then each will return to their respective speeds at the same time. The flywheel lost less speed than the smaller wheel.

The rest is just angular momentum and how you engineer the wheel itself (entry point, entry speed, entry angular velocity, tread characteristics of the wheel, moment of inertia of the wheel, etc). These have more effect on the ball than wheel diameter.

I can see your point, and it is valid. I would still rather see smaller, lighter rollers/wheels rather than a speed-controller-limited shooter with bigger, heavier wheels.

FWIW we've never used closed-loop control on shooters and have achieved quite repeatable results in past years and with our prototype using super-light thin-walled aluminum rollers with some carpet no-slip rubber-cemented on.