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.