Kicking System Design Considerations
 

A kicking system can be described as a mechanical manipulator used to accelerate a ball to a desired velocity to a desired trajectory. This can be achieved in many different ways with various actuators. Check out this research paper Segway CMBalance Robot Soccer Player. http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf
The paper presents information necessary to design and implement a soccer ball manipulation system for a mobile robot such as ours. We used to concepts in this paper to design the pneumatic kicking system we are going to use.

Re: Kicking System Design Considerations
 

Don't you think that the maximum pressure is not enough to use the pneumatic system the times we need? :confused:

Re: Kicking System Design Considerations
 

That probably depends on how far you think you need to kick the ball.

Re: Kicking System Design Considerations
 

We are testing the pneumatic and see if we can use it to throw the ball into the goal or make the ball cross the bumper, but I think that we are going to lose so much pressure in only one shoot trying to cross the ball.

Re: Kicking System Design Considerations
 

We had a mechanism last night going with pnuematics that was kicking the ball just fine over a bump. Not enough for the field, but a bump just fine. Going to try tonight to see if we can make it kick any further, but at least gettting the ball from zone to zone or pushing a ball into a goal should not be a problem. Im sure some teams will be launching it the length of the field with pnuematics. (remember levers are your friend)

Re: Kicking System Design Considerations
 

If I may ask, how did you have the pneumatics set up?
We had compressor -> two tanks -> regulator -> two tanks -> switch -> piston and the hit was rather wimpy. The piston was a 1.5" OD x 2" stroke. Thanks.

Re: Kicking System Design Considerations
 

842 is using a 2" bore by 12" stroke piston....

http://www.youtube.com/watch?v=QLH-XqNyQ-0

takes a lot of power to move that ball fast, so you need a pretty big cylinder

Re: Kicking System Design Considerations
 

1583's design uses several 1 1/2 inch x 2 inch stroke cylinders and yes they are levered to the kicking plate. We are building a full size prototype now. Don't forget you need some type of ball control mechanism to hold the ball against the kicking plate. We're prototyping one of those now also.

Re: Kicking System Design Considerations
 

and the key to getting a 2" cylinder to fire quickly is to pre-load it. If you watch the video you will see them manually releasing the mechanism, not just cycling the valve.

Re: Kicking System Design Considerations
 

The problem with pneumatics is that the bigger you go the slower the piston fires.

There are many ticks to speed up pistons. Preloading is a good option.

One idea I had was to use a mechanism like the pedal on a base drum to "gear up" the piston, allowing it to swing quickly.

We were able to get about 14' of range and about 18" of height with a simple 1.5" bore piston.

Re: Kicking System Design Considerations
 

i dont like a kicking design my self i look at the desing like a rotary vs a piston engin the rotary spins with no starting and stoping while the pistion engin has to start and stop all the time

Re: Kicking System Design Considerations
 

That is what our basic design will be when we full start building things. Right now we are using a 1.5 bore 8 inch stroke that has been in the KOP before. We are going right from the schools shop 120 psi tanks to a regulator to 60 psi, then the 2 small tanks we can use, then the valve and piston. Right now we just have some wood rigged up to get a prototype going. We are going to get some smaller diameter pistons to see if kick faster/further or not, hopefully get them in next week, or else we know the 1.5 bore works fine.

Right now we have the piston attached a little over half way up a 13 or so inch bar, then a 'foot' at the end of that bar that kicks the ball. We had the ball consistently going over 14 or so feet in the air, enough to get from one section to the next. I think our max was over 17 feet with one of the configurations we tried. We even put a ball about 2-3 feet in front of our kicker to simulate starting positions of the balls and it went right up and over.

Just out of curiosity, what are other teams doing to return their piston to the starting point. Right now are are planning on using some surgical tubing, because if you keep the exit valve open when you kick you can get more speed from the piston.

Re: Kicking System Design Considerations
 

If you need to increase the force coming from your piston, and/or speed it up you could always consider adding a spring or tying some surgical tubing in a way that it will assist the firing mechanism(up to doubling the power of a single piston stroke), however if you lose too much pressure, you may not be able to retract the pneumatics quick enough to abide by the rules.

I though id throw this power and thought generating idea out for you to kick around.

Re: Kicking System Design Considerations
 

My team has been trying to figure out how to do it our selfs. We tried 3 or 4 tanks with a 1.5 inch bore with an approximate 5 inch stroke. We managed to get the ball about half way up the bump when we were about 5 feet away. BTW, does anyone know how many balls we're allowed to kick at once?

Re: Kicking System Design Considerations
 

Only one that is in your possession...

Re: Kicking System Design Considerations
 

Well, what if you have one in your possesion and you're about to kick it. And out of nowhere a ball gets close enough to be affected by one of your kickers and you end up kicking two at once. Is that a penalty?

Re: Kicking System Design Considerations
 

Agreed, 397 did this PART of the year in 2008 to throw the Trackball and it worked pretty good. We eventually switched to using just 4 1/5" diameter 12" stroke cylinders to lob the ball the length of the field (Kettering Kickoff and WMRI) If you are curious about the arrangement of these I can find it and send you a picture. We were able to shoot it over the overpass from ~12 feet at 30psi. (In competition we ran at 60psi)

You may also want to consider the kinetic energy of a moving object is 1/2 * m * v^2. In a perfect world (which this is not) in a collision the energy from the kicker would be transferred to the object being kicked. Therefore you will get a lot more omph if you increase your speed. Consider using a lever to increase your speed.

Re: Kicking System Design Considerations
 

Its really an 8 " stroke, it was a type on the video

Re: Kicking System Design Considerations
 

To my knowledge there is no rule against kicking multiple balls, only possessing more than one.

Re: Kicking System Design Considerations
 

Thank you for the information on the pistons and on the kicking rules.

Re: Kicking System Design Considerations
 

BTW, does anyone know if the ball is allowed to come off of the ground for a split-seconde before a kick so that we can get the ball over the bump? You see, with our design, we managed to get the ball over the bump, but it needs to be a little bit off of the ground to make it. So, can anyone help with this problem?

Re: Kicking System Design Considerations
 

Without seeing more of your design, it's hard to say....but there is a rule that says you can't CARRY the ball.

Sounds like fun!

Re: Kicking System Design Considerations
 

Try hitting the ball in an upward motion from low. Look at 842's kicker video for an example of this. A version I saw was hitting them ~40 feet accurately. The only problem is fine tuning it to get the right amount of loft and not just blasting away at it.

Re: Kicking System Design Considerations
 

Just to clear this up, it was deemed legal to kick multiple balls at once on the FIRST Q&A: http://forums.usfirst.org/showthread.php?t=13900

Re: Kicking System Design Considerations
 

It is better, when possible, to use cylinders-pistons in TENSION than in COMPRESSION, but if this requires cables, then it becomes nore complicated
Tension loading tends to keep the forces aligned along axis of rod, which is where cylinder has most strength. Compression force tends to initiate torque and bending forces at an angle to the piston as objects try to "roll" around and past each other.

Since a hinged kicker rotates and moves away from cylinder, angle of force on kicker changes. Max acceleration happens, with a hinged kicker, with cylinder's force applied at 90 degrees to a line out from kicker pivot point to where cylinder is attached during the arc of the kick. As kicker moves away, this change the 90 degrees force angle, and applied force drops off. So, the cylinder should be oriented such that the force applied stays close to 90 degrees during critical acceleratiom range of the kick arc. This is easier to achieve when the piston's attach point stays closer to the pivot point -- but. this also reduces the leverage of the cylinder for accelerating kicker, so a larger bore is needed to gain more force.

There is also the issue of rate of pressure build up inside cylinder. Since the energy delivered to the kicker (then to ball) is the force times the distance over which it gets applied, reaching maximum force early in the stroke is important, since there are only so many inches of travel in which to apply it.
Having piston connect nearer to pivot point (low leverage) means force builds up faster in the cylinder. So having a stronger cylinder that pushes a shorter stroke on a spot nearer the pivot point can deliver more energy early in the stroke than a weaker cylinder attached further away from pivot having better leverage, but also building up force more slowly.
Finding the sweet spot between these two extremes is the key to a good kicker design.

-RRLedford


stance traveled during by point that piston connects to kicker is short.

Re: Kicking System Design Considerations
 

my team is working on our kicker design, we are using a 5" stroke-9/16" bore(I think) piston, mounted to the bottom of our hinged plate(which is hinged at the top, so we get the most leverage) we get about 20" hight and about 5ft of distance in the air. this is enough to kick the ball over the bump from about 4ft away, but we need it to go further and higher, we could use a bigger piston but we dont really have the space. how could we make it kick farther?(I've thought about surgical tubing and springs already, but i was wondering if there was any other way?)

Re: Kicking System Design Considerations
 

I didn't say carry. I was wondering if, when the robot is stationary, the ball can be lifted so that it can get more air when kicked.

Re: Kicking System Design Considerations
 

It doesn't matter if the robot is stationary or moving. Look at the definitions quoted above. If you lift the ball, it's not in contact with the field. If you are possessing the ball - controling its position - you can't lift it off the ground or you are carrying it.

Re: Kicking System Design Considerations
 

Double your bore and connect at 1/2 way up the swing arc (not at bottom).
Four times more force plus faster pressure build up will reach higher much higher velocity before kicker contacts ball.
-RRLedford

Re: Kicking System Design Considerations
 

To clarify my original quote...It would be clearer if I had said "Only one [b]if it's[b]in your possession", sorry if I mislead.