All About Ball Control
 

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!

Re: All About Ball Control
 

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

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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)

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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!

Re: All About Ball Control
 

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.

Re: All About Ball Control
 

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?)

Re: All About Ball Control
 

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

Re: All About Ball Control
 

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

Re: All About Ball Control
 

here's a pic of the front of our robot showing our ball control mechanism... i don't want to share all of it's secrets... but yes those are rubber bands on the roller. It works pretty well.

http://www.oregonfirst.org/wp/wp-upl...6-DSC_3468.jpg

you can see video of it in action at the Oregon regional here
http://frcstream.com/main.php (click search for events, event name: Autodesk Portland Regional - 2010)

Re: All About Ball Control
 

I don't have any pictures, but I can describe the overall idea pretty well.

There's a Tunnel down the center of the robot that's slightly smaller than the ball. At one end of this tunnel are a series of small fan blades attached to a motor. When the motor is turned on, the fans move such a high volume of air that it creates a suction force that can draw balls in from about a half a foot away.

Re: All About Ball Control
 

Here's a video showing our competition robot with a lot of footage of our ball control mechanism. As you can see the primary components are rwo FP motors coupled to two Banebot 20:1 gearboxes powering two Banebot 3 7/8 wheels. The mechanism also has a way (ram light) of telling the driver when he is in control of a ball. The driver controls the mechanism via a second stick (left) on the control box. That stick also spins the robot left or right to aim. We have a practice robot with the same mechanism installed. The past few days the driver has been practicing ball control by keeping a person from being able to take the ball away from the robot. The mechanism works very well and we're anxious to see it in action on the playing field. Here's the video http://rambotics.com/video5.html

Re: All About Ball Control
 

Avast anti-virus reports a Trojan JS Downloader-LQ [Trj] at your link.

Perhaps this is a false positive, but I thought you should know.


~

Re: All About Ball Control
 

1918 uses a pool noodle on a 3/4" aluminum tube spindle that rotates at about 600 rpm. The noodle slips on the spindle with a few in-lb of torque. The noodle height is adjusted so that the ball contacts the noodle about 3/4 inch before it hits the 3" setback stop. The noodle slips on the spindle when we have a ball. It can pick up a ball with the robot moving at full speed withoug bouncing off. It holds during turns, and we can back up at partial speed. The bore of the noodle wears out, so we need to replace it every dozen matches or so.

Depending your design, many teams can make a very simple, limited ball collector with no moving parts. Install a piece of soft foam rubber at the the top of the 3" ball penetration zone (on the underside of the top of the ball opening), flush with the front of the robot. The bottom of the foam should be set so that the ball compresses the foam by about an inch before it hits the 3" backstop. This won't hold a ball while backing up, and has limitations during turns, but it does a decent job when you are pushing a ball. Basically, it just puts some friction between the robot and the rolling ball that holds it against the robot while driving forward.

Re: All About Ball Control
 

639 doesn't actually use an active ball control mechanism, however our kicker is also quite different from the "average" team's kicker.

First of all, we placed memory foam over the majority of our kicking area, allowing us to herd balls easily without them running away the moment touch them.

Also, our kicker is pneumatic powered, but it is also a spinner, using a clutch against a dual-FP motor gearbox to allow us to slide out the actual kicker without the ramming of the motors. Behind the memory foam, our kicker gets to target speed, then when we are ready to kick the pneumatic pistons fire, releasing the motors so the kicker spins on momentum. Since it is constantly moving, we have a 1-2 second window where the ball can be kicked with a good amount of force after we tell it to actually kick, removing the major need to possess balls

Anyways, we only have .5 pounds to spare. How can we not use it on cool LEDs?

P.S. image of our kicker here, and on the overall robot here