Balls bouncing out of goal
 

In viewing the proceedings at VCU I noticed that quite a large number of balls would hit the chains and bounce OUT of the high goal..... Obviously these balls should have counted but could not be seen by the automatic scoring mechanism.. I do not feel that FIRST designed the chains to be an obstacle but rather something that would allow the balls to drop easily.
It is apparent that the inertia of the chains (mass) is too great for the poof balls to move easily.

Can anyone shed any light on this problem?
Any possible solutions? How was this handled at your regional?

thanks

Re: Balls bouncing out of goal
 

FIRST has said that while the chains are up to prevent bounce out it is still a design obstacle needing to be overcome.

Re: Balls bouncing out of goal
 

Myself and other members of my team attended the BAE GSR in NH this past weekend. I also noticed this. Unfortunately, those balls were not counted either.

It is unfortunate for the teams who can shoot 10 or more balls effectively into the goal but some of the balls are not counted because they do not fall down and get counted by the automatic ball counter.

Teams like 1276 and 296 were some notable teams that I can remember distinctly not having all of the balls which crossed the plane of the top goal and did not have all of the balls scored.

Re: Balls bouncing out of goal
 

I noticed this as well.

I would think that FIRST would want to examine this and maybe modify the chain/netting to try and make it so that balls that are correctly scored through the opening would stay in better.

But, maybe they did and this is the best they can do. But, I was disappointed when I saw some robots do a great job battling into position with a bunch of balls, only to have them all shoot and score, but the last 3-5 bounce out...

Re: Balls bouncing out of goal
 

I also noticed this but it has to do with the way the balls are shot. If the balls are shot too fast the chains gain more inertia and force the balls back out of the goal. If the ball has too much spin in any certain direction it will skip on the chins and wither fly up into the goal or down. If the ball flies up it then falls down out of the goal because of the slanted face of the goal. If the ball flies down it has a greater retention rate but it may still bounce off the platform in the goal and come out. A soft shot into the goal with little spin would be ideal, but then the problem then becomes getting the ball to the goal. These where just my observations from the regional mixed with some physics knowledge. With the amount of shooters that were blatantly shooting over the muzzle velocity, i could see why may shots where falling out.

Re: Balls bouncing out of goal
 

What I saw watching the VCU webcast was balls getting impeded by the chains hanging down in the goals. I saw a ball take atleast 10 seconds to roll past the chains at the bottom of the goal. If this happens during the autonomous mode or before that team goes on defense or the match ends, there's no way that ball is going to score. I realize there's a large technical challenge involved here, but having the scoring system so physically seperated from the goal in this game format means that teams are getting denied 3-pointers simply because the goal is slowing down the balls. However, since the only solutions involve changing the chains or covering the goal instead of turning off the counter, this isn't going to change this year. So I'll be planning on last second shots not counting for anything.

Re: Balls bouncing out of goal
 

I would just like to highlight rule G05, since it was a design constraint on all teams.

So this is something that should not really be that big of a thing. We all knew that balls would bounce out.

Re: Balls bouncing out of goal
 

Actually, any balls that are on the bottom plane when the buzzer goes off will trigger the system to wait and count them even if the period is over.

Re: Balls bouncing out of goal
 

BoyWithCape is right, but also they had field personnel with long sticks moving the balls to the chute to get them there faster and to free them if they became stuck. I didn’t see any problem with them getting counted, it was just a matter of them staying in the goal.

Re: Balls bouncing out of goal
 

I agree... I guess I just didn't think they would bounce out as much as they do.

We will correct. Maybe "upper shelf" our shots into the upper corner of the center goal...

Re: Balls bouncing out of goal
 

The worst is when a ball bouncing out blocks a ball on the way in...
Happened once or twice to 222.

Re: Balls bouncing out of goal
 

I assume a ball bouncing out of the goal is akin to rimming out of a basketball goal or hitting of the uprights in a football kick. Just part of the game.

Re: Balls bouncing out of goal
 

The make up of the goal sensor array is as follows. There are 6 sensors in the center goal (made in arrays of 2) . one array at the far left of the goal, this one shoots a beam down the slant of the goal and is the senor that keeps the goal "active" during auto and the offence periods at the end if there are still balls in the goal. The next array is in the goal right above the hole, this senor is dual purpose dependent on what period you are in but it's main function is to be the first counter of balls. The last array is directly below the second one but is out of the goal looking at the shoot, this is the final counter for balls.

on each player station side there is a desktop computer which is responsible for interpreting the counting senors (both cameras, and the center goal arrays). That computer communicates with the scoring table computer which projects the scores.

Basically don't worry about balls in the goals not counting.

Re: Balls bouncing out of goal
 

The worst balls for falling out of the chains appear to be those with lots of backspin, which unfortunately described most of those at PNW, especially those shooting with a lot of arc. The spinning motion of the ball is slowed by contact with the chain, and converted to downward motion, pushing it down towards the floor. It's why you want backspin on a basketball -- if it hits the backboard, it tends to go down into the hoop.

I wish we had thought of this before designing a shooter with a ton of backspin... :(

Re: Balls bouncing out of goal
 

Greg's close, but really there are two types of sensors in the center goal:
Two parallel through-beam sensors which look for balls on the ramp and also validate balls which enter the goal within 2 sec. after the end of a goal-active period. Two are needed to provide coverage of the whole ramp width.

The balls are counted by the through-beam just below the hole in the ramp where the ball drops into the hose.

These through beams are connected to a data acquisition box which talks to the ball counting computer (the PC under the drivers station). The corner goal cameras also connect to this PC. A LabView app. does the all the heavy lifting to figure out whether the signals are valid ball counts and sends the results to the scoring computer.

And we thought making the robots' autonomous work was complex!

Re: Balls bouncing out of goal
 

Ultimately, its just another design challenge...

But, the way out that I see is to shoot closer, slower, and higher. This alone seems to fix much of the problem. But again, another challenge...:rolleyes:

Re: Balls bouncing out of goal
 

I don't see any mention of the balls being deflected back out after they have entered the center goal.
I didn't hear any mention of this possibility at the kick off event. Did I miss a memo? If it had been mentioned we could have allowed for it with our shooter.
I was under the impression that the balls would remain in the center goal after they have entered it.
Is it because the chains are too long and hang down into the bottom of the opening?
Would it help if the chains were behind the mesh? This way they would still slow down the momentum of the balls.

Re: Balls bouncing out of goal
 

I have a few questions for you:

1.) Did your team build a center goal? If so why didn't you test things on it? Did you notice that it was also tilted down (10 degrees from vertical)?
2.) Did you think about spin on the ball when it hits a surface? If so did you account for it being chains, and chains giving back on the ball?

Re: Balls bouncing out of goal
 

I feel that FIRST could have done a much better job with this, (yes its a design challenge and all..). But I feel that the chains should be replaced with a mesh type material, I saw a practice scrimmage which used this and worked beautifully. I haven't seen the game in person yet, But from all the video shots and web casts that I have watched there are a good percentage of the balls bouncing out. It is already tough enough to score in the center with all the defense being played, and having 30+% of your balls bounce out just makes it that much unnecessarily harder. I hope FIRST deals with this problem before there are too many people complaining.

Re: Balls bouncing out of goal
 

Alternately, perhaps a whole bunch of people might hold off on complaining until they actually go back, read the rules, re-examine the field drawings, build a goal, build a robot, practice the shots, and understand that this has been a part of the whole challenge since the very day that the game was announced. Nothing has changed, nothing is different. Perhaps those that are just chomping at the bit to complain might realize that a whole lot of teams figured out that controlling backspin, controlling the azimuth angle of the shot, and controlling the elevation of the shot are all factors in minimizing the probability of the ball bouncing back out, and they were able to do something about it. This is not an issue that FIRST has created, it is something that a few teams failed to recognize as part of the problem. So perhaps those that are so eager to complain might realize that if they spent a little less time complaining and a little more time analyzing the problem and developing solutions, then they might have a little less to complain about.

-dave

Re: Balls bouncing out of goal
 

In our entire day of playing, we only had three or four shots bounce out. I'd propose that those of you who are having 50% bounce out should shoot a bit slower or tone down the spin a bit... we're right at the 12m/s line and have a great deal of spin on the balls. If that's what's causing it, you might be a bit too far on either one of those two things. Then again, maybe it's something else...

Re: Balls bouncing out of goal
 

In the first weeks I was convinced that back spin would be best. After our shooter proto type was finished, the students spent hours testing it and came to the conclusion that top spin was best. The magic angle works with top spin but, not with back spin. And the balls seem to stay in with top spin. It's that poofy ball dynamics thing. They just will not behave the way you want them to.

Re: Balls bouncing out of goal
 

If you are playing foozball and your ball bounces back out of the goal, do you expect the table's manufacturer to fix it? No - you groan and keep playing! Nothing's different here. Like Dave said, it's part of the challenge of playing the game.

Re: Balls bouncing out of goal
 

More and more I'm becoming a big Dave fan :) CD won't let me give him any more rep points though, lol. Back on topic, Dave is absolutely right. Getting upset because you didn't fully understand the challenge of making 3-pt goals isn't going to help your team solve the problem. Our little tiny team quickly realized that there were many variables inherent in scoring high that we probably would not be able to overcome. Shooting the balls in the right direction is the LEAST difficult part of the problem. The downward angled goal looks enticingly easy to score in. As it turns out, it makes it a little easier for the balls to come back out. We opted to concentrate on shooting low, the logic being that we could make 4 1 pointers faster than 1 3 pointer. I have a lot of admiration for the teams shooting high. Just keep working the problem. Those chains are probably staying there so figure out how to make the balls stay in and quit wasting time shaking your fist at them. Reduce shooter speed, change ball spin (really at 12m/s spin doesn't have much effect on trajectory, but with high friction poof balls, spin seems to have a large effect on surface interaction), anyone thought of side spin?, change trajectory, do something to score more reliably! But please wait until after your match against our alliance to fix it! :D

Re: Balls bouncing out of goal
 

Let's look at it as a goal. The chains are the goalie. This goalie is not very good but sometimes you shoot at him/her and the ball is returned to the field. That's the way it goes when playing games. As has been stated earlier, FIRST did tell us about the chains and told us about the scoring procedure.

This may not be the correct place, BUT, my feeling is that FIRST did a great job on this years game, rules and consistency and they should be applauded for it.

Re: Balls bouncing out of goal
 

When we were setting the field up in NJ and tested the goals we found that if you put the right spin on the ball and hit the chain just right, the ball would ride the chain down, catch in the loop at the bottom and hook right out of the goal. Pretty neat. Not easy to repeat, though.

Re: Balls bouncing out of goal
 

Not so hard at all. About a third of our clean hits did (more or less) that. It sure changes the calculus away from backspin shooters.

Re: Balls bouncing out of goal
 

Guess I should've figured: repeatability is one of the hallmarks of good automation.

Re: Balls bouncing out of goal
 

David -
a point of clarification is in order.
The center goal chain drawing was added as New 1-31-06 to the FIRST website for low cost field

I do not recall seeing chains on the field pieces at the kickoff at Kettering University on the very day the game was announced, it was a low cost field element - but then again as every year I am overwhelmed on that Saturday with all that is going on.

Just for clarity sake - we do build alot of the field elements and frankly we totally missed the chains - but, thats our fault and we will figure out how to deal with it by adjusting the way we shoot the balls so that we limit how many bounce out.

I was concerned in another similar thread to this one that the chains could be installed such that they were closer to the opening than designed - as the chain frame is not symetrical according to the drawing for the low cost field. Where as, the official field drawings for the chain installation added 2/9 this year, make it appear to be symmetrical - so I don't know what to think - is the Low cost field drawing for the chain frame correct? I'd like to hang the chains and want them in the same place as the official field elements.

Re: Balls bouncing out of goal
 

the chains were on the Manchester Kickoff field and were visible during the webcast, if i remember correctly.

Re: Balls bouncing out of goal
 

The chains were most definitely in place at Kickoff in Manchester. Here's the proof these pictures have been up on our website since the day after Kickoff. :cool:

By the way, has anyone considered that these chains are another way to ensure that robots aren't shooting "hot" (faster than allowed)? The chains act as energy dampers to dissipate the balls energy, but if the ball is traveling too fast it will bounce back off the chains. In the web cast from VCU it sure looked like there were a few robots shooting too fast and they paid the price. There was a lot of traffic earlier on how FIRST would enforce the speed limits. By having clearly defined limits on shooting speed, do you really think that enforcing it was overlooked?

You should know by now that the games are designed very carefully and EVERY detail is probably well thought out and for a reason. What looks like an easy game or task may very well have some difficult problems to overcome.

Afterall, this is The Hardest Fun You'll Ever Have. :)

Re: Balls bouncing out of goal
 

Good - the chains were definately on the centergoal at the Kickoff in Manchester. That was built just as an official one was meant to be built.
No one is disagreeing with that.

Yes - I agree that the chains are there to deter balls from flying straight into the goal - hitting the screen and bouncing back out. I also witnessed the same thing at the VCU webcast as far as ball velocity (too fast). Someone in the other thread similar to this one mentioned that balls shot too slow also bounced back out - so it is obvious that a number of factors may cause the balls to bounce back out.

Yes - this is something that everyone should have considered as part of the challenge. Just as lighting conditions and the use of the camera in poorly lit venues were, last year.

"Everything" can be said is part of the challenge - everything that you can think of that is.

So, if I have this right, the chains are the conditions for entry into the goal that needs to be considered along with the aximum 12m/s exit velocity - which is primarily for safety purposes.