Car Nack Predicts 3/06
 

FIRST will have problems handling the numerous claims that robots are exceeding the ball shooter intial velocity of 12meters per second.

Car Nack has spoken.

Re: Car Nack Predicts 3/06
 

Agreed.

Re: Car Nack Predicts 3/06
 

I certainly hope Car Nack is wrong, but I'm pretty sure he's right. We shall see.

Re: Car Nack Predicts 3/06
 

I am 99% sure that he is right!

Re: Car Nack Predicts 3/06
 

It's going to be pretty difficult to judge how fast the balls are coming out.

Re: Car Nack Predicts 3/06
 

I think that Car Nack will be wrong on this one _IF_ FIRST adopts one simple policy. In NASCAR, if Team A believes Team B has put a car with prohibited modifications on the track, they can request a tear down inspection by the authorities. If they are right and Team B has an illegal car, then Team B is penalized appropriately (up to and including having a "win" rescinded). However, if Team A is wrong and the challenged car is perfectly legal, then Team A has to pay for the tear down and rebuild. This is their penalty for filing a false charge. A similar policy could be instituted at the competitions if excessive spurious "they are shooting too fast!" charges become a problem.

-dave

Re: Car Nack Predicts 3/06
 

But what does team A pay? Krispy Kremes?

Re: Car Nack Predicts 3/06
 

I definitely agree with Car Nack, and completely disagree with Dave. (Sorry, Dave :))

Although it is a fantastic solution, I feel that the desire for low match turnaround time at a FIRST event will overpower any "checks" such as Dave proposed, or any other additional "check" than the inspection at the beginning. I can imagine that after the first time a team overturns a decision based on ball speed, teams will be more attune to the problem and thus request a check more often than if the issue was nipped in the bud even before the event begins.

Teams need to trust that every team is keeping within the rules set out by FIRST. I know they don't all the time, but I think the only way to stick to the idea of "referees calls are final" is by not allowing an overturn. Poor match calls can make-or-break the team perspective of an event, and thus referees should be chosen for their experience, so that if a situation arises it can be handled quickly and correctly. Selecting experienced referees also cuts down on the amount of issues missed, and decreases the amount of overturns.

Bottom Line? Which would you rather have, more matches while trusting your opponents are keeping within the same rules that you stuck to, or less matches and distrust of every team out there? I think we've come too far as the FIRST Community to regress to the latter decision.

Side note: If it is not addressed in the season, I think FIRST will be overwhelmed in the team forums about this particular point. And, it's not like that hasn't happened before!

Re: Car Nack Predicts 3/06
 

Since FIRST is incorporating an UL person to help with Safety Inspection, they should incorporate a State Trooper with a speed gun to check the exit velocity of the Poofballs.
The team is issue a speeding ticket and require to appear in front of the Robot Inspector again- 3 times and you're DQ. :ahh:

Seriously, maybe a speed gun can be used to check the speed of the balls?
Has anyone try it?
:confused:

Re: Car Nack Predicts 3/06
 

I apologize for not following every Q&A thread, but didn't FIRST say that the ball exit velocity was going to be judged based on going X distance when fired at Y angle?

It seems to me that this should be the test.

A team is supposed design robots that meet this test.

There are 100's of ways to cheat, but we don't plan on teams cheating.

Teams could sneak in extra fix it window hours or fudge accounting or or or.

I think that most teams will try to follow this rule if they are given a way to know if they are in violation.

A simple rule that is easy to verify seems to me to be the best friend of folks who want to see teams play by the rules.

Joe J.

Re: Car Nack Predicts 3/06
 

Negative. That was given in the rules as a guide, however someone asked Q&A(I think a search through the Rules/Strategy forum should turn up a few threads on this) and recieved an answer to the effect of, "we're still trying to decide which one or combination of the following (list of methods)". Using this method as a test is also risky because you need to account for shooter height when you do it, otherwise tall shooters will complain that short shooters can shoot faster.

Re: Car Nack Predicts 3/06
 

I think i like Dave's Idea, play it like Football you ask for a play to be reviewed and you are wrong you pay the consequences, If redabot says that blueabot's balls were being shot too fast and redabot was wrong, then Redabot should either get a 10 point penalty or possibly even a DQ for the soul reason of causing a hold up
and it shouldnt be just one team, if there are 3 teams in an alliance then the 3 teams should agree upon the review of the robot if they dont then no go,

Re: Car Nack Predicts 3/06
 

We've used a radar gun to measure ball speed. It can be very inaccurate if the ball is not traveling in/close to the same plane in which the gun is pointing.

Re: Car Nack Predicts 3/06
 

Perhaps the simpler solution is to use a nice and natural part of the planet to our advantage: gravity.

If you can tilt a robot so that it shoots vertically and measure the height from floor to shooter in centimeters, you can have it fire a ball and time how long it's airborne. Throw in some simple math, and bada-bing, you can tell in about ten seconds whether it's legal on the velocity side.

In fact, I'm sure Kevin Watson has been hiding in his workshop doing some black magic with an old RC, some limit switches, and a piece of string cheese to accomplish just that. ;)

Re: Car Nack Predicts 3/06
 

you can't be sure that 100% of the teams are going to be able to fire straight up, there are alot of teams with gravity feeds.

I am personally a fan of the radar gun. We had an officer come in and test ours yesterday and it seemed fairly accurate based on our calculations. The main thing is FIRST just needs to make it a standard for each comp. If a radar gun is used the same person set up in the same way for every team, so even if the gun is off everyone will be on the same playing field.

I was also thinking maybe we could make a custom poof ball with a build in accelerometer and a tiny micro processor. Then the teams would have to shoot that ball and whatever it says goes. just like these for baseballs. http://www.lillianvernon.com/catalog....jsp?pdId=2877


Now that i think about it i might go buy one of those baseballs and transplant it into a poof ball to see how it works.

Re: Car Nack Predicts 3/06
 

Car Nack is wise and I agree.
Certainly there will be many complaints about teams that exceed the 12 m/s rule.
Resolving the complaints will be interesting to watch and I am not even sure how or why they would consider doing it.
You know that resolving the complaint WILL NOT slow the throughput by testing the accused on the field of play.
Post inspection of the accused is possible if a method and location is readily available to resolve the accusation - but I can't believe that 10 -20 minutes after a match AND the accusation is resolved - the scores would be revised.
The NASCAR example is fine except it takes them TIME to resolve the complaint and they do it back in the garage - AFTER the race.
This is an issue that needed a clear methodology defined and included in the inspection process. It would be nice to be informed what that method will be in advance so we can validate using the same methodology before hand.
We used the guideline that was included at kickoff to validate, as we don't have access to a radar gun or other sophisticated equipment. We compensated the distance to include for being a certain distance from the horizontal (the ground).
Our design drives the motors through a speed controller so if we do exceed the velocity rule we will dial down until we meet it - but that does kill all our pre-work establishing the correct autonomous settings for the controls.
What does 12 m/s look like anyways?

Re: Car Nack Predicts 3/06
 

well, just drive a car at about 43 km/h (roughly 27mph) and you'll find out ;)

Re: Car Nack Predicts 3/06
 

This seems to me to be unfortunate. It does two bad things.

#1 It continues the uncertainty. What FIRST teams need more than anything is a quick ruling that they know they can trust to not change. Uncertainty causes delay or forces teams to go with a safer but less optimal solution. In both cases teams are justified in being upset with FIRST.

#2 It takes away an easily repeated test method from team. 30 Degrees is easily measured. The height of the shooter from the ground is easily measured. The distance a ball flies is easily measured. Seems as good of a method as anyone could have hoped for.

Does anyone have any insight into why there has not been a clear ruling on this? The only thing I can think if is that the folks in CO may have less air resistance than they have at Altanta, but I think teams can deal with that.

I don't think that the robots will be significantly more dangerous if balls exit the robot at 12+delta m/s in Altanta and 12-delta m/s in Denver especially if they fly the same distance.

As for me, I hope FIRST rules in favor of the Angle, Height, Distance method.

Joe J.

Re: Car Nack Predicts 3/06
 

From what I have been told wouldn't spin on the ball effect the distance the ball where to travel?

We used a photogate like sensor system to measure our shooter velocity on our prototype and got different measurements then when we used a radar gun.

Re: Car Nack Predicts 3/06
 

I think you missed my point, but thanks for converting it to mph for me.
I wanted to get a feel for what it looks like as an observer - if I drove, the perspective would be different than if I were stationary, watching something fly out at 12 m/s. I think that an object moving at a constant velocity may not "look the same" as an object moving at an instantaneous velocity.
If accusations are based on what something "looks" like - we could be surprised to find out that we were wrong.

Re: Car Nack Predicts 3/06
 

Jon got it right. The problem with the simple "height, angle, distance" method is that it is a very basic analysis of the actual flight dynamics of the ball that does not account for several (legal) variables that can significantly affect the distance traveled. For example, the distance guideline given in the manual is based on the initital constraint of no spin on the ball when it exits the robot. During some experimentation, we found that putting a serious backspin on the ball - while keeping all other performance parameters the same, including the 12m/s exit speed - could increase the distance traveled by up to 30%. If FIRST were to rely on just the "height, angle, distance" analysis, they would incorrectly classify a shooter that put a lot of backspin on a ball, and thereby got increased range, as an illegal solution.

-dave

Re: Car Nack Predicts 3/06
 

has anyone here played paintball? If you have then there is your answer. Paintballs are only allowed to travel about 300-350 ft per second. Before you enter the feild you have to get your gun clabrated and you shoot your paintball gun though a small barrle that tells you how fast you are shooting. I will see if i can find a pic.


shaun

Re: Car Nack Predicts 3/06
 

but I believe that the paintball chronographs only work with faster velocity's (300 mph! *edit 200 mph*). I am pretty sure that 12 m/s would not measure on a paintball chronograph.

Re: Car Nack Predicts 3/06
 

nope its 300 feet a sec



http://www.ehow.com/how_8414_calibra...tball-gun.html

shaun

Re: Car Nack Predicts 3/06
 

yeah, i know its 300 ft/sec. I accidentally typed a 3 instead of a 2

300 ft/ 1 sec * 3600 sec/1hr * 1mi/5280 = 204.5 mi/hr

I play tournament paintball, and usually shoot around 280 fps, but mph is so much easer to understand to the average person

whoops :o, but its still far faster than the 12 fps of a poof ball

Re: Car Nack Predicts 3/06
 

its 12 meters per sec
that about 38.4 fps
or 27 mph

shaun

Re: Car Nack Predicts 3/06
 

whoops! wow, i am just full of mistakes today, sorry

Re: Car Nack Predicts 3/06
 

I agree that there are going to be difference due to spin. And I appreciate that FIRST is trying to do the right thing.

My thoughts are basically this. Safety is the main concern. There are 2 aspects to safety: If the balls are exiting too fast, someone could get hurt from a short range direct hit. If the balls go too far, unsuspecting folks will take a hit.

If we classify the exit speed by range, we only take care of the second but not the first.

Or have we?

I don't think there is anything magical about getting hit with a 12m/s Poof ball vs a 15m/s Poof ball (which is 25% higher than the "true" limit). I realize that it would have 56% more energy, but I don't think there is a bright line between what will hurt a human and what won't. Robots are dangerous things as are the machines we use to make them. I don't think even a 15m/s Poof ball is among the more significant risks associated with building and competing FIRST robots.

There is also something to be said for a limit that all teams can easily test for themselves.

I would urge FIRST to go with the angle, height, distance method, knowing that it is going to be wrong in some cases but that an obviously flawed standard that is easily implemented & understood is better than an improved standard that is less easy to implement & yet to be defined in Week 6 of the design/build cycle.

Joe J.

Re: Car Nack Predicts 3/06
 

I point to the answer given on the Q & A when the official answer asked the team if they would provide a complete cover for the entire field ( wording was like that).

How about if all teams brought a piece of Poly carb and we covered the entire field after attaching them all together?

I make light (humor) because the real issue is not being addressed even as we approach the end of build.


What is the EXACT way the rule will be applied - MEASURED -TESTED or whatever. The Game committee better have an answer or there will be many unhappy teams.

Re: Car Nack Predicts 3/06
 

I wasn't particularly worried about hanging in 2004 (1293 had bigger concerns, like moving...), but how were the hangers with their 10-feet-per-second limit enforced? I don't have a 2004 manual in front of me, but I seem to recall the basic requirement being that teams had to prove through math or testing or black magic voodoo that their hanger was within the requirements.

If I'm right, what's stopping us from implementing a similar thing this year?

Re: Car Nack Predicts 3/06
 

You forgot about the flux-capacitor that warps local space-time <grin>.

-Kevin

Re: Car Nack Predicts 3/06
 

i agree but how are they going to check that? are they going to take some radar guns and test the speeds before each match i think its going to take to much work to stop that

Re: Car Nack Predicts 3/06
 

From Q&A: http://forums.usfirst.org/showthread.php?t=725

Re: Car Nack Predicts 3/06
 

Just out of curiosity, couldn't FIRST ask an organization like the USTA or MLB to donate some ball-speed measuring devices? Think about it, in almost every tennis or baseball event you see on tv (and probably a few other sports as well, I just can't think of them offhand) they give the speed that the ball was served or pitched at. If those guns can record speeds up to 150+ mph, they certainly must be able to handle 26.8 mph, right?

And it is a bit of an off-season for both sports, so...

Re: Car Nack Predicts 3/06
 

Umm, what about a beam-break sensor? Super simple to build, just as easy to calibrate, portable, battery-powerable, and will work with any shooter.

In case the idea isn't clear: Think of a tube a few inches (maybe a foot) long. Have someone shoot their ball through the tube. In the tube is an emitter (of light) and a sensor (on the sother side of the tube). Simply measure the time that a 7" ball breaks the beam (a few milliseconds) and you have a speed. Of course, the exact size of the ball needs to be measured, and an accurate timer needs to be used.

On the other hand, ask any experienced police officer, they will tell you they can judge the speed of a car to within 2 or 3 miles per hour, just from experience. I'd bet the referees develop a similar feel for speed, and will send teams back to the inspectors often.

Don

Re: Car Nack Predicts 3/06
 

You've been reading people's minds/posts, haven't you? :eek:

Vince Wilczynski in this post proposed the very same thing. Vince's setup uses 2 IR sensors (Emitter/Sensor combo, I recognized it as having been shipped in FRC kits sometime in the past 2 years), one at the start of a "tube" and the other at the end, and uses LabVIEW and a USB-DAQ device to measure the speed of the ball traveling through the tube (measures the time between the normally-low digital response from the sensors go "high"). It's not battery powered to my knowledge, but could be. And it's very effective, Vince said his tests worked out fairly well at a "mini-meet" he tried it out at. ;)

-Danny

Re: Car Nack Predicts 3/06
 

Danny,
The official word is it will be a setup like the one you describe, or something similar. I recall seeing it on CD, in fact, it's referenced higher up in this thread.

Re: Car Nack Predicts 3/06
 

Aha! So it is, I don't know how I missed that gem. It would be nice if NI Pilot Program teams (with the means to do so) would build one of these for people to use for spot-testing at their regional. If anyone wants "general" plans for one of these or the LabVIEW program I'd be happy to help out...

-Danny

Re: Car Nack Predicts 3/06
 

I have it on good authority that devices are under construction as we speak and will be shipped to each event.

Re: Car Nack Predicts 3/06
 

First question...is everybodies shooter shoot the same speed with every different ball in various states or destruction...i know we sure dont

Second question...unless a robot lines up to the edge of the field and delibertly shoots a few balls off into the crowd would the impact of a ball that most likely was lobbed into the crowd be that much of a safety hazard to the normal person (i say this because there may be some special cases where it could be dangerous such as an infant etc.) but how many of these cases do you see in the typical crowd.

just some things to think about