All About Ball Control

[BJC]

So after week 1 regionals its pretty clear that ball control is just as or more important then actully kicking (see 910 for great example)...

It is also clear that many teams underestimated the importance of ball control.

Here is a list from the least to most effective ball controlers that I saw this week. (these are on average, there were of course teams that used each of these methods to great effect.)

1. Nothing: I was very suprised by the amount of teams that bothered to build a fully functioning kicker but did not consider a device to hold the ball in place in order to use them effectively. I am sure that these teams will have some sort of device at their next compitition

2. A single roller: This was what most teams had and was also probably the most diverse. The concept behind this being to spin the ball towards the robot fast enough that when backing up or turning the ball would follow, basicly the faster you could spin the ball the more effective you were. Many of the robots with this type of ball control had to move slowly to avoid having the ball roll away although there were several very effective ones that I saw.

3. A vacuum: I did not see very many vacuums this week. However I believe they proformed very well for the teams that choose to use them. The concept being to suck the ball to the robot by maximizing the surface area the vacuum(s) had on the ball, more surface equals more hold on the ball. With this device teams generally had to move up to the ball slowly to aquire it, but then had quite a bit of control over it once it was possessed.

4. A double roller (pincher): I did not see that many double rollers this week either. However, they are in my opinion the most effective of all the devices I have seen yet. The concept being to pinch the ball with one roller on top and a second roller on the bottem reducing the force of the ground against the ball to as close to zero as possible while still maintaining contact. The only problem with this method is that it tends to draw penalties for pulling the ball slightly off the ground especially around the goals and bumps. This means that the slighest bump from another robot may move the ball into an illegal position if this device is not designed exactly right.

What type did your team have?
How effective was it?

Please elaborate!

[pfreivald]

We used a double-roller, but it wasn't at all a pinch. It had two small wheels, the centers of which are slightly lower than the center of the ball, and they are spaced pretty far out. It gives the ball a lot of backspin, which gives us a lot of control.

I'd post a .jpg of the CAD drawing, but I'm at home and it's on my work PC... But I did post it somewhere on one of these threads already.

You can find video of it in action here: http://www.facebook.com/profile.php?...=1212242513708

[Chris is me]

My team originally went with a very 1726 like ball magnet, but we made the mistake of assuming it was trivial to get to work. After ship, we made an impeller with an FP and two suction cups in order to hold the ball. It does moderately well in the shop, we'll see how well it works mounted tomorrow.

If that fails, 80/20 should make for a simple pinch prototype.

[Drivencrazy]

Team 1730 used a double roller design.

Initially we had just one top roller. Our top roller was a powered roller with radiator tube functioning as the actual contacting surface. We found that when we zero-degree turned or drove sideways (crab drive) too fast we would lose the ball because the normal force of the ground was too great and caused the balls to roll to the outside of the robot.

To fix this we added a bottom roller.

We used a non-powered bottom roller. The roller itself was an idler roller for a conveyor belt. We mounted the roller on a hinge so that we were able to clear the bump. The mounting bracket for the roller had plastic sliders attached that rode along the floor. The roller applied an upward force on the ball to dramatically lessen the normal force of the ground.

The added roller gave us much more maneuverability when we had a ball and were then able to maximize our scoring potential.

[BJC]

Of course, I'm sorry. If anyone has a method that is not one of the four listed Please explain how it works in addition to the other things. Sorry for my short sightedness

In addition:

my team, team 33, is using a single 2" or 2.5" diameter (I can't remember which) roller that has maby a quarter inch of float (able to move up and down) that is covered in roughtop which contacts the ball at the highest point possible without violating the 3" rule.

It was very effective controling the ball while going forward or backward however we probably lose the ball 50% of the time when making a sharp turn.
Overall, however, one of the most effective single rollers I have seen (and I saw a lot because I pit scouted at Kettering)

[pfreivald]

We can strafe and do zero-degree turns with no problems on ours, with no loss of ball control. The only real issue with it is if we get rammed hard... but that wasn't much of an issue, because we generally didn't have a reason to hold on to a ball for more than a second or two.

[ttldomination]

Team 1261 used suction cups in week 1 and here's how I felt.

- Forming a seal is tough. It takes a great deal to line up everything properly, and then grab the ball. It took a lot out of us to form a seal. 1771 had to use their camera to line up and properly form a seal, and they are generally the best at sucking.

- It was generally pretty hard to play against defense. Lining up takes so much effort, that robots can easily mess up the alignment process.

But when defense wasn't that much and everything was aligned, they worked great. At our best, we made 4-5 goals, and we could've definitely made more.

But, we were not satisfied with the suction cups, and we will be working with rollers for our second regional.

- Sunny

[=Martin=Taylor=]

We use a hinged ball magnet. When the ball starts to roll away, the roller hinges down maintianing contact with the ball. This helps us accelerate better without losing control of the ball.

We designed our robot to turn around its front end, so we can pivot around the ball without losing control of it.

We have a bit of trouble gathering a ball, but it works pretty well once we've got it.

[dtengineering]

We've got a 2" single roller covered in roughtop on our practice bot, powered by the FP running a 26:1 banebots P60 and contacting the ball at a point about 6.5-6.75" above the ground.

We can slowly back up and turn without losing the ball, but have also found that we need to make sure that we come to a stop slowly if we want to keep control of the ball.

We're going to try changing the gear ratio... to 20:1 and then to 16:1 to see if that works better, as the ball does seem to be spinning a bit too slow at the moment.

I think this was the right year to build a practice bot... we've still got a couple weeks until Seattle to get everything worked out, and then we can bolt it all on when we get there.

Jason

P.S. BJC... I'm pleased to see our approach has been the same as yours. Your team might not remember it, but you were our very first ever alliance partners back in 2004 in Toronto. Your robot was totally awesome that year... although not, unfortunately, awesome enough to compensate for our penalty-inducing rookie ineptness. In any case, I don't think we've played with... or against... you since, but I still hold your team in very high regard.

[DonRotolo]

Our single roller was a shaft, drilled crosswise every inch or so, with loops of latex tubing extending about 2". It was one long piece of tubing, threaded through all the holes, eliminating any problems with holding it in place.

We found that at times the tubing would collapse against the shaft, turning it into just a shaft with a grippy covering (which did not work as well). So, we added 4" long pieces of 1/8" pneumatic tubing through the same holes, these provide the 'keep-it-away" factor enough so that balls couldn't get too close to the shaft.

We use a FP motor and 2/3 of the gearbox, about 600RPM, via a belt that slips (so the FP doesn't stall). Works pretty well, but drive or turn fast enough and it's possible to lose the ball. It is very effective against the wall though.

[EgROS]

We have a double roller design which sounds very similar to 1730's as described above.

We also initially had only one roller. We played around with various positions but eventually settled on placing it a little bit above half way between the middle and top of the ball. It worked pretty well but we would lose the ball when we backed up to fast, pivoted on our axis or moved sideways (mecanum drive). We realized that the source of the problem was that the roller, while pulling the ball toward the robot, was also smashing the ball into the ground with considerable force (we put the robot on blocks, put a scale under the ball and measured it to be over 20 pounds!) The amount of friction between the ball and the ground prevented it from staying with us when we moved.

The solution: a double "roller" system to take most of the downward force of the ball off the ground allowing it to stay with us wherever we go. The bottom "roller" is actually just a 1/2 inch square aluminum bar which sits about a 3/4 of an inch off the ground. The bar rides up and down 7 inches on linear bearings so that it can clear the bump. Our kicker/ roller is on the long side of the robot but when we go over the bump we turn 90 degrees so that the short side is facing forward.

I can’t wait till next week to try it out in competition!

[Lowfategg]

The best ball control I have seen during week one was team 25's wind tunnel. It was able to hold the ball during all movement and able to grab or recover the ball from a little over 4-6" away.

Rollers seem to be most common and can work well when done properly.

[pfreivald]

Found it! http://www.chiefdelphi.com/forums/sh...ad.php?t=84014

We ran this with 2/3 of a FP gearbox, and the beauty of it -- besides the fact that it worked really well (see the video linked in my original post in this thread) is that there is no chance of it ever stalling, because it never, ever puts any downward force on the ball (aside from the torque to give it the backspin).

I was truly shocked at how many teams seemed to have considered ball control a sort of add-on, last-minute engineering decision. This is one of the first things we built, and we went through several iterative designs before settling on this one. (Good thing every part of our robot is modular, eh?)

[Alex Cormier]

Originally Posted by Lowfategg

The best ball control I have seen during week one was team 25's wind tunnel. It was able to hold the ball during all movement and able to grab or recover the ball from a little over 4-6" away.

Rollers seem to be most common and can work well when done properly.

Do you have any pictures of this for the people who were not at NJ? This sounds pretty amazing!

[falconmaster]

here is our vacuum ball sucker system. Prototype
http://www.youtube.com/watch?v=Xmmq1_JuQo0