Suction as a method for possessing balls
 

I did a quick search for suction-related topics and didn't see anything, so here I go.

According to the rules possession is "Controlling the position and movement of a BALL." G43 allows robots to be in possession of 1 ball as long as G44-46 are not violated. G44 ensures that the ball must be touching the ground. G45 restricts mechanisms above the bumper zone. G46 allows balls to extend 3" into the frame perimeter. I see no restriction then on using suction (or some other holding device) to provide a firm grip on the ball. Thoughts?

Re: Suction as a method for possessing balls
 

Sounds like it's legal, though I have only seen one good suction device in FIRST (1771 in 2008) and video of several bad suction devices.

Re: Suction as a method for possessing balls
 

The thing I first thought of was suction, but conceivably it is possible to come up with other methods of grabbing the ball with just a three-inch grip. The trident from the field comes to mind, that gets a pretty good grip on the ball with very little contact area.

Re: Suction as a method for possessing balls
 

My only worries would be whether or not the ball comes off the ground at all and whether or not the seams of the ball might cause suction to be lost. Other than that, it seems reasonable.

Re: Suction as a method for possessing balls
 

It would be very hard to implement, because of the seams in the balls. You would need multiple small suction cups, to ensure at least some of them grab. But then they probably wouldn't be able to hold on if there were any reasonable bumps to the ball.

EDIT: Ah he beat me. And i trident wouldn't really work because the ball would need to be more than three inches under the bumper to grab the ball in that manner

Re: Suction as a method for possessing balls
 

We came to a similar conclusion, but after looking at the seams of the soccer ball we felt that it would be difficult to maintain suction. Remember the ball must maintain contact with the floor and there will be friction between the ball and the floor trying to pull the ball away. I say run a few tests and see what happens.

Re: Suction as a method for possessing balls
 

I did some tests of this todayt using a vacuum cleaner and a soccer ball. It's not effective as a mechanism for "aquiring" a ball, becausebut it did seem to do the amount of energy required to have a substantial radius where it sucks enough is enormous, but it did seem to do a .ecent job of holding the ball in place

Re: Suction as a method for possessing balls
 

I have to agree with you hear. We thought about the idea of using suction, as we used it back in 2007. However, the seams of the ball make it very difficult to get good suction. So we abandoned the idea after several attempts of trying to make it work.

Re: Suction as a method for possessing balls
 

If I understand correctly, <G30> would not allow this because your suction device would probably have to extend to where the ball is.

~DtD

Re: Suction as a method for possessing balls
 

<G30-A> allows it to go out to the bumper perimeter for 2 seconds every 2 seconds; <G46> allows a 3-inch penetration into the frame perimeter for the ball. You could do it legally in those constraints.

Re: Suction as a method for possessing balls
 

I think teams might be writing this off to easily. There are many kinds of suction devices which are used in the manufacturing industries. I would like to point you all to this one site which I found doing an easy google search and I am sure there are plenty of other things like this. http://www.anver.com/document/company/vacuum_cups.htm


I am not saying suction is a good solution I just think that there are ways to make it work.

Re: Suction as a method for possessing balls
 

We tried this today. We were at a sponsor's building, and did not have access to our usual array of building materials. But, we took a mini shop-vac and taped a paper bowl to it as a suction cup using blue painter's tape. It was easily able to hold the ball upside-down and through some pretty violent shaking. Did the same thing again this afternoon at home with a cut juice container that was skinnier than it was tall, to leave room for a kicking mechanism. It also worked as well.

I think it works well this year because the balls are essentially undeformable. The tubes in 07 deformed a lot, and most teams tried using very small suction cups and very low airflow, thus relying on a near-perfect seal. Team 190 picked up trackballs in 08 with a suction cup. They are more similar to this year's game piece than the tubes.

The key is to remember physics: First, the more airflow you have, the more leaks you can have. A fan will move much more air than, say, a vacuum pump that uses a piston. Since more air moves faster, the system is able to "fill in" the leaks and maintain a greater negative-pressure on the inside of the suction cup. Second, negative-pressure is pounds per square inch. Surface area varies with the square of the radius of your suction cup, so sucking force varies with the square of your suction cup's radius. These two things are what allowed our highly primitive device to work.

I suggest everyone try it out before discounting it, it doesn't take any materials and no more than 10 minutes.

Re: Suction as a method for possessing balls
 

This is an awesome thread.

I was having a discussion on the phone with a friend of mine about this (In a more hypothetical tense as to not reveal ideas :P) last night, and she and I determined that it would be a legal option assuming that the ball always is in contact with the ground...

The biggest unknown for me was the stitching of the ball and it's effect on creating a seal. Now that it sounds like it is possible, I'll have to do some more digging.

Re: Suction as a method for possessing balls
 

We talked about using air for possibly bringing the balls in from a distance, but with an air grab, you need to make sure the seal is tight or else holding the ball and driving might go to well.

We're pretty comfortable with the idea of a physical grab, although we haven't ruled air out, yet.

Re: Suction as a method for possessing balls
 

We found the opposite to be true. Trying to pull the ball in from farther than 1/2" away was futile, but once it gets within about a quarter of an inch, it is immediately sucked on and is very hard to break loose. This is with a mini shop-vac and a paper bowl.

Re: Suction as a method for possessing balls
 

well i believe that it is legal...the only problem i would really have is trying to get it past the bumps if the robot cant fit through the tunnel, isnt it a penalty for a robot picking up a ball?

Re: Suction as a method for possessing balls
 

As long as the ball stays on the ground it is considered POSSESION which is perfectly legal. If the ball comes off the ground that is considered HOLDING which is a penalty.

Re: Suction as a method for possessing balls
 

the key is that any ball on the ground can be in possession of the robot.
Any ball OFF the ground and in possession would be CARRIED... that is a penalty.
Carrying can occur ANYWHERE on the robot... the key is that the ball MUST stay in contact with the ground.

Any vacuum system would have to be designed to keep the ball on the ground...

Re: Suction as a method for possessing balls
 

So a robot that is controlling a ball via suction goes over a bump. At some point, that ball is going to lose contact with the ground. Would this be a carry?
edit: I realize this should be an official Q&A but I'd like to see what you fine folks think.

Re: Suction as a method for possessing balls
 

How would this not be a penalty? The rules explicitly state you cant be in control of a ball thats not in contact with the ground.

Re: Suction as a method for possessing balls
 

It's not intentional, and probably momentary. It's like having the ball bounce off your hand in soccer--the refs probably won't call that, especially if you don't make any move to control the ball or your hand is against your body, but they can if they think it's intentional on your part.

Yes, definitely one for Q&A.

Re: Suction as a method for possessing balls
 

IDK the fact that you know you designed your robot so that it violates that rule whenever you go over a bump sounds pretty intentional. I agree its definitely not an easy thing to work around but so far it seems pretty explicit.

Re: Suction as a method for possessing balls
 

in overdrive 1986 (Team Titanium) used a suction cup to move the track balls, it worked extremely well compared to initial thoughts.

Re: Suction as a method for possessing balls
 

Suction... hadnt thought about that yet but it seems fun!

to answer the bump problem... as long as the vaccuum suction is turned off when you go over the bump so its not holding the ball would it still be possession if it "happened" to go over the bump with you even tho you had no hold on it at that time?

i will put this idea to my team tho >.>

Re: Suction as a method for possessing balls
 

Suction may work, but it seem that the ball needs to drag on the ground, and not roll.

Re: Suction as a method for possessing balls
 

I don't see why using a suction method would be illegal. But like others have said, it doesn't seem like it would be the most efficient way to hold a ball.

Re: Suction as a method for possessing balls
 

My team has been considering this option, and our tests with a shop vac proved sufficient for further investigation. But what to use for suction? I guess I would use a house vacuum's fan attached to a Fisher Price motor?

Re: Suction as a method for possessing balls
 

At least the field includes the bumps. If you can manage to keep the ball in contact with the carpet, no penalty. But I bet that ends up being difficult.

Re: Suction as a method for possessing balls
 

we tried this method today with success, it was able to hold the ball as it slid along the carpet. it is a viable option for maintaining control.
good luck all!
-Rich Little

Re: Suction as a method for possessing balls
 

dude epic win XD were gonna post the video on youtube, it was strong, but as said, if the ball comes off the ground when going over a ramp it will be considered a penalty...which is why they have the tunnels XD and if a team was smart ehy would have a piston or some sort of way to hit the ball...

Re: Suction as a method for possessing balls
 

Can you elaborate? Not as to how you did it, but by "viable" did you mean you were able to come up with enough suction, within the constraints of the rules, to possess a ball effectively?

Re: Suction as a method for possessing balls
 

Our team also tried the shop vac + paper bowl method today and we shook the ball extremely hard before it went flying off. As long as the suction cup does not extend past the frame perimeter, does not allow the ball to protrude more than 3 inches into the frame perimeter, and has the ball touching the floor, I see no problem in keeping a firm grip on the ball.

Re: Suction as a method for possessing balls
 

For anyone planning to use suction and potentially go up the ramps to score or go under the tunnel, I would caution that there are little bumps in the carpet on either side of the tunnel that might cause you to lose contact with the ground (they are about 1" high). They are metal plates that hold up the tower underneath the rug. I dont believe they are mentioned in the rules, havent checked the field drawings, but they are there and you will need to be VERY careful of these...

Re: Suction as a method for possessing balls
 

A question I'll ask the Q&A if it isn't horribly obvious:

If a device (suction or otherwise) holds the ball, and another robot pushes you up the bump, and the ball becomes CARRIED, is that a penalty?

Re: Suction as a method for possessing balls
 

In the rules it states that another robot cannot cause another robot to get a penalty, so I would say that they would not throw a flag on the situation

Re: Suction as a method for possessing balls
 

After a lot of team discussion, I haven't seen a way that could control the ball more effectively than a vacuum could, given the design constraints. After reading about people's promising tests here, we are definitely going to attempt suction.

It seems like multiple people here want to use suction and drag the ball from zone to zone. Has anyone given any thought to using suction just to grab the ball, then have the robot align itself to the target and propel the ball over the bumps and into the goal, as opposed to dragging the ball over the bumps and placing it in the goal?

Re: Suction as a method for possessing balls
 

our suction was simple, a shop vac with basiclly a funnel on the front. we dont plan on actually dragging it over ther may be too much deal with a penalty. we would release the suction and push it over and then follow with the robot...

Re: Suction as a method for possessing balls
 

If the ball comes off the ground while you are in possesion of it AT ALL whether it is intentional or not IS a pentalty. The point of these rules is so that you can design a mechanism which does not all this to happen. You need to think of these problems preemptively and that is what the rules intend. Whether or not you were pushed over the bump or get a ball stuck on the top of your robot is not a factor. The rules are the rules, just like a hand ball in real soccer.

Re: Suction as a method for possessing balls
 

You might go back to read Law 12 about deliberate handling (not handball) if you're going to use a soccer comparison.

Re: Suction as a method for possessing balls
 

We made a prototype using nothing more than one of the 3 inch cooling fans provided in the kit, tape and paper (crude I know) and we were able to effectively control the ball. It would roll in any direction you moved the rig providing you didn't move it too fast. Granted a robot would never move so slowly while in possession of the ball, but the rig showed promise. We figured if we could find a fan that rotated at a much higher velocity, therefore sucking more air, the idea could be worth looking more into. However you would not be able to travel over the humps at all. Limiting the robots to the tunnel bottlenecks. I can't say that this is the plan we are going to use, but it would be awesome to see this idea used effectively at a regional! I just had fun rolling the ball with air.

Re: Suction as a method for possessing balls
 

i don't think a suction idea will work. It is not practical and uses to much energy to do a simple task.

Re: Suction as a method for possessing balls
 

3 things to think on:
1.Bumps are going to be nasty, requiring that you let go as you go over.
2.The ball's going to need to take more that a few hits, and if a robot were to, say, hit the soccerball, would it be able to still hold on?
3. Once you've got it, how are you going to shoot it? If you plan on having a light grip, #2 comes in. If it's strong enough or too strong, you'll need to let it go before you hit it, meaning it may roll.

We haven't gone through the gauntlet of design ideas, but it seems suction hasn't stood up to testing.

Re: Suction as a method for possessing balls
 

Cprrect me if i am wrong, i have only seen people testing this with shop vacs, but has anyone attempted this with the vacuum kits provided in previous years kits (Not exactly sure which year they were provided, 2007?) ?

Re: Suction as a method for possessing balls
 

I'm not an expert at pneumatics, but I believe those vacuum kits require a compressor/regulator/storage tanks/etc (basically alot of weight). Whereas a shop vac operates off of a motor. I was shocked at the simplicity in design when I tore apart a shop vac......

Re: Suction as a method for possessing balls
 

I think its almost impossible to cross the bump while possessing a ball. If you try to go up the bump with the ball in front of you, the ball will raise off of the surface as you reach the flat of the bump and thats saying the ball doesn't jam you up at the bottom of the incline and possibly causing you to climb on top of the ball. If you try to drag the ball behind you as you climb up the ramp, it will again come off of the surface as you level out on the flat and as you descend down the bump.

Although, what usually happens is I get proved wrong......

Re: Suction as a method for possessing balls
 

You would violate the rule if the ball was held static to the robot. However, if your vacuum end effector was on a articulated member such that the weight of the ball at the end always held it against the ground (no matter the angle of your robot) I could see this working.

Re: Suction as a method for possessing balls
 

Incorrect. You would be in POSSESSION of a ball, which you are alowed to do as long as the ball is in contact with the floor.

If the ball came off of the carpet then you would be CARRYING the ball, which is a penalty.

Re: Suction as a method for possessing balls
 

We tried suction and it did not work at all. We were dissapointed at the fact that it did not work and tried many different ways, but just could not come up with a way to keep hold of the ball effectively

Re: Suction as a method for possessing balls
 

What exactly did you try to do?

Re: Suction as a method for possessing balls
 

We tested with a SMALL 1 hp shopvac and had great SUCKsess. Going forward with it. Testing with 2 CIMs driving the impeller we got very close to the same RPM as the original 110 AC motor. Just need to figure the right gear ratios.
Bruce

Re: Suction as a method for possessing balls
 

Has anyone made an effective suction rig that does not involve using a CIM motor? With the limit on 5 CIM motors, we were looking at using four on the wheels and the last one on a propulsion mechanism. But if the vacuum requires a CIM motor, then we would have to re-design something.

Re: Suction as a method for possessing balls
 

This might help some people, I took a video last night of a standard home vacuum cleaner hose onto a soccer ball, and it works well. You get a good suction, and the ball stays with the hose unless you move it side to side really fast, which is a problem, but overall it works well. And the seams of the soccer ball have no effect at all. It can even pick up the ball straight into the air when it is directly on a corner seam.

EDIT: Here is the video link:

http://www.youtube.com/watch?v=2yDn6rXIlMI

--Ben

Re: Suction as a method for possessing balls
 

Try incorporating the FP motor with various transmissions, including the AM Planetary. Output torque, speed, etc. is dependent on the particular setup, so experiment and calculate.

Re: Suction as a method for possessing balls
 

I gave this idea a run. It holds some water, but it doesn't have as much power as i thought with a standard vacuum cleaner. I used a hose with a ~1" diameter and it held the ball relatively well. If your expecting to navigate the turns while holding the ball. your going to need a drive system that has excellent steering. Don't get me wrong though, I still believe this is one of the best ways to manipulate the ball once you get it in your grasp. which will be easier said than done.

http://www.youtube.com/watch?v=HzmdW2CcaXU

Re: Suction as a method for possessing balls
 

Which is exactly why what I described does not incur a penalty. If the ball always remains in contact with the floor then you are not carrying.

Others seem to suggest a vacuum system which is rigidly attached to the frame. If they did this and if they went over a bump the ball would lift in the air (because their robot would lift into the air) and they would incur a carrying penalty. Utilizing an articulated vacuum mechanism the ball will always remain in contact with the floor.

Re: Suction as a method for possessing balls
 

The power rating on shop vacs is very misleading. I have a shop vac at home that claims "5 PEAK HORSEPOWER". Is this a real number? If we assume that the machine is 100% efficient (violating several physical laws). 5 HP is equivalent to ~3750 Watts. Since power is defined as V*A, and my vac runs on 110 volts, it would require 33 amps to run the vac. In reality, these really cheap universal motors are horribly inefficient, so the actual current draw for a motor that produces 5 HP would be over 40 Amps. My vac runs fine when plugged into a 15 amp circuit.

The power number on the vac is only sales hype. The real power is closer to 1/2 HP, if that. A single CIM or two Fischer Price motors will work just fine. In 2008, 1771 powered a very large, two stage shop vac impeller with two Fischer Price motors with excellent results. In fact, we had to reduce the speed with the speed controller to get the ball off the manipulator. Also keep in mind that power requirements go down when you choke off the flow. So, once you acquire, and are holding the ball, the impeller will speed up, generating more vacuum.

As for manipulators, the holding force is dependent on two things: pressure differential, and area of the low pressure zone. In 2008, we had a 20" circular zone, so with a delta P of 1 PSI, we had 300 lb.s of holding force. This year, the balls are smaller. The maximum size for the holding area would be about 8" in diameter. so with 1 PSI delta, you would generate about 50 lb.s of holding force.

You don't need a perfect seal, vacuum cleaners are designed to flow a lot of air, so even with big leaks, you can get decent delta P.

In conclusion, a vacuum is an excellent method of manipulation a spherical object. For more force, go with the largest circular opening you can fit within the rules, and look for a vacuum device. that generates a high static pressure differential.

Re: Suction as a method for possessing balls
 

I believe that most of what everyone is saying is going against the rule. Under the definition of possession it says

"A Ball shall be considered in possession if, as the robot moves or changes oreintation ( e.g. backs up or spins in place), the ball remains in approximately the same position relative to the robot."

If you use suction then when you back up or spin the ball would come with you, which is the same position relative to the robot. Therefore I think the suction idea is out altogether. Unless you plan on sucking it up and then never moving.

Re: Suction as a method for possessing balls
 

POSSESSION is not a bad thing - it is explicitly allowed through <G43> as long as you only do this to one ball at a time.

Re: Suction as a method for possessing balls
 

Yes, by using suction you would be possessing the ball. How does this violate any rule? Just because there is a definition of an action, it does not imply that that action is illegal, in fact, if you read rule <G43> you will see that possession is defined as a legal action, if you are only doing it to one ball.

Re: Suction as a method for possessing balls
 

It's kind of like the power ratings of air compressors. Apparently some marketing genius, in the 1980s, discovered that a motor produces it's peak power when it's starting up the compressor, and had their company base their HP ratings on this number, instead of the HP being used in constant running.

It could be that the vacuums are rated the same way.

Anyways, this looks like an excellent use for a Fisher Price motor--you can run the fan at very high speed and you won't have to worry about the motor smoking since it's not mechanically connected to anything that can jam (if you build it well).

One potential problem with the vacuum idea is that the ball has to be in the right spot on the robot to get the vacuum to stick, so you probably need a good funnel system to get it there, and with only 3" of ball ingress that will be tricky on a 28" wide robot.

Re: Suction as a method for possessing balls
 

Maybe they should attach just a few Ball Magnets :)

Re: Suction as a method for possessing balls
 

So we could use FP motors, maybe attached to the 3 inch computer fan to speed it up?

Re: Suction as a method for possessing balls
 

I doubt the computer fan blades are what you want...they are designed to move air gently out of a computer case. The suction fan in a shop vac is quite different, you might see about getting some type of inexpensive vacuum cleaner and taking it apart and seeing if you can adapt the FP motor to it. Consider the RPM that the original motor runs at, though, and see if it's a good match for the FP motor.

Re: Suction as a method for possessing balls
 

No, an axial flow fan is not designed to create much delta P, only flow. You need an radial flow device, like a vacuum impeller. As a rule of thumb when looking at impellers, flow is proportional to the impellers' width, while pressure is proportional to its diameter. So, for max holding power, use a large diameter, narrow impeller, or better yet, a 2-stage impeller system.

Re: Suction as a method for possessing balls
 

I've seen discussions of Shop Vacs on Vacuum forming boards. According to them a decent shop vac will pull 3 inches of mercury or about 1.47psi. They didn't seem to think that a second shop vac in line with it provided a significant improvement, but they're looking for significantly lower pressure than a shop vac can provide. They might have discounted double the "delta P" as not significant.

I've seen a lot of people say fan for this idea, but an impeller is the fan-like device inside a shop vac. It is designed to work better for this type of application. I'm amazed with the performance people are saying they are getting with a 1" hose. That's only 0.785 square inches. Assuming 1.47 psi, then the holding force is 1.15 pounds. The ball weighs about 1 pound so I'd expect it to barely be able to pick up the ball. A 2" hose would bring the force up to 4.62 pounds and should provide a pretty good grip. Of course a larger grip surface will make that much stronger. In fact is seems very plausable that a suction cup mounted inside the frame could get a good grip.

I'd recommend that you don't plan to go over the bump while possessing a ball. I cannot think of a configuration that will work where the ball does not get wedged under the bumpers. Teams always seem to find a way to do what I think is impossible so I'll be watching for it at the regionals. I guess a 6 wheeled robot with an actuated center wheel could do it. Still, I think it's unlikely.

Andy

Re: Suction as a method for possessing balls
 

I hadn't thought of hooking two shop vacs in series, but I guess that could work. I was talking about two stage impeller designs. The vac unit we used in 2008 was a two stage impeller, it had two impellers on one shaft, separated by a flow straightener. Some vacs have wide single impellers for max flow, some have two narrow impellers for max delta P.


Choose wisely grasshopper.

(my cultural references are way out of date:D )

Re: Suction as a method for possessing balls
 

how would you suggest hooking the fisher price motor to the shop vac impeller?

Re: Suction as a method for possessing balls
 

We are currently in the process of replacing the AC motor from a Husky shop vac. with either an RS-555SH Mabuchi motor or an FP. The results of testing with the Mabuchi will tell us if we need to go to the FP.

By the way, we will most likely be gearing up which ever motor we decide to use. We currently are estimating we need something in the neighborhood of 18K RPM.

We had to custom build a shaft to replace the one that is part of the AC motor. If direct driving with either motor works, we will post up pics later tonight or tomorrow. If we need to gear up, that will take another day or so to complete.

Re: Suction as a method for possessing balls
 

Has anyone considered drawing a vacuum using a pneumatic piston? I would think the suction force from the piston would be much greater than from a shop vac. Down side is that if you have a small leak, once the piston reaches the end of it's stroke, you've lost your suction.

Just a thought that I want to tryout myself.

-Chip Tucker

Re: Suction as a method for possessing balls
 

Is anyone actually putting a suction mechanism on their robot? The gray area in the rules makes it seem like a judge could possibly rule it illegal and DQ the robot. And, if the mechanism is too strong and the robot accidentally goes over a bump with the ball, it would be a penalty.

Re: Suction as a method for possessing balls
 

On a suggestion from another teams mentor, I just cannibalized my 18v dewalt vaccum. It took me about 10 minutes to swap the motor in it for a fp. I think we will be using it on the robot.

Re: Suction as a method for possessing balls
 

Phenomenal idea. Too bad we didn't have one of those to use, it would have made this process a little easier.

So far we have determined that using a 1:2 gearing increase and a FP motor on a 6 in diameter impeller from a $20.00 Husky shop vac. will do the trick. We just need to make an adapter plate and assemble the whole thing tomorrow. Heck, we might even put the vac back together when we are finished. That way we will protect the impeller from damage due to field debris and might pick up a coin or two to boot.:yikes:

Re: Suction as a method for possessing balls
 

Which dewalt vac did you use, the DC500 or the DC515?

Re: Suction as a method for possessing balls
 

the dc 515
I just looked at a parts diagram for the 500 and it looks like pretty much the same motor & impeller.

Re: Suction as a method for possessing balls
 

What gray area? What part of the rules would indicate it is disallowed?