can we control the amount of air to control the speed of the cylinder?

[Team2339]

any suggestion or answers are highly welcomed.....thank you:D

[Matt H.]

Well technically you can't control the speed, but you can control the acceleration which gives you a little control over the speed. Here are some things my team discovered last year. By placing a needle valve (they have a small screw and locking ring and come in the KOP) on the venting end of the cylinder it will slow the cylinders extension based upon how fully closed it is.
If you want a cylinder to extend faster you must dump more air into by using multiple valves etc (see 39 last year).

Changing cylinder speed during a match would be more difficult, but is definitely possible.

[Fred Sayre]

In the past, my team has used 3 valves to control the speed of a piston. The first valve was a on/off valve to change the direction of the piston, and the other two valves had flow limiting exhausts on them. You send the output air from the first valve and then "T" it to the other two valves giving you the cases: both off, one venting, or two venting. This can give you a custom slow and fast speed for your piston, and if you wanted to you could add a number of valves to get a finer resolution, given that you can get each one to limit the air flow that much.

[EricH]

any suggestion or answers are highly welcomed.....thank you:DYes. There are commercially available, 125 PSI rated flow-control fittings that can go into a cylinder. They aren't in the KOP this year, though.

[Team2339]

Thank you.. and one more question, can we use three different regulators to the same cylinder?

[Matt H.]

Yes. There are commercially available, 125 PSI rated flow-control fittings that can go into a cylinder. They aren't in the KOP this year, though.

Oops My apologies,
I stated the valves were in the KoP, but I believe Eric is correct--this year they are not.

[Al Skierkiewicz]

Merle,
There are needle valves that are available that can control the volume of air that enters/leaves the cylinder. However, they are not designed to control the speed at which a cylinder operates. Teams have experimented with lower working pressures by adding a second pressure regulator downstream from the 60 PSI working regulator as described in the pneumatics manual. Please be advised that the valves do not seal much below 30PSI and so they become unreliable at reduced pressure.
There are many threads here that discuss this problem for the price of a search. The discussions will give you an insight to some of the team experience from past years.

[Bob Steele]

This brings me to ask the question...
Why do we have so many less pneumatic components in the KOP this year??

We don't have any of the hose connectors and flow regulators we have always had in the past. We also only have one solenoid. In the past we had several.

We still have the compressor and its associated fittings and gauges and such but we don't have the final fittings to move the air around.

I wonder if FIRST lost that supplier ??

We really enjoy using pneumatics and they are easy for rookie teams to put together... or at least they USED to be easy... now they will have to purchase their own components to handle this.

I DID see that we can use cylinders that are NOT Bimba this year.
They just have to comform to the size/length requirements...

Interesting...
I have fittings left over from other years so I can proceed...

We should all support rookie teams by sharing these older fittings and information with them... Perhaps we should start a clearing house for the
pneumatically disadvantaged (IE Rookie Teams) and donate some of the fittings they will need (and old solenoids that were never used...)

?????

[Chris_Elston]

The ultimate solution would be to purchase an analog output card for the cRIO. Though I dunno if it would be legal.

Purchase a 9263 4-channel analog output 0-10V output module to control a pneumatic analog regulator.

Next you'll need a 12VDC version of an analog regulator.

Last you'll need an external piloted valve because most KOP valves are internal pilot and won't trip the spool below 30PSI if you want to control PSI down to 1 PSI use an external pilot valve and vary the regulator with an analog 0-10V control signal with a full scale of 60 PSI is equal to 10volts.

You'll have to post some questions to make sure all the above is legal though...

Attached is a spec sheet on something I was checking into.

[Kevin Sevcik]

There's another, option that's quite likely to be legal, though it's largely insane. You could get a standard 12V, high frequency, low response time solenoid valve and wire it to the pneumatics bumper just like you would any other valve. Then laugh maniacally while telling your programming team that you want to duty-cycle control your solenoid valve. It's marginally nutty, as it hasn't been done in FRC before, but I think it'd work fairly brilliantly if you got a valve with a good enough response time and maximum operating frequency. Festo makes some rather fast valves, but they're 24VDC operated. Still, I think it'd be interesting if someone tried this in FRC.

[CDH Jeff]

This brings me to ask the question...
Why do we have so many less pneumatic components in the KOP this year??


I think the reason is because we can't extend outside of our starting area, so any pneumatics are going to be extremely limited in length, and usage. our team on day three just decided that we couldn't think of a way that we could use pneumatics in a better way than we could use a motor or a servo, it would just have been a waste of space to put that stuff on there for one or two small pistons that would need tons of equipment to use (compressor, air tanks, hose) compared to 2 wires per motor, and a spike.

[Racer26]

1075 in the past has built a multi-position pneumatic arm. To control the speed of your pneumatics, teams typically use the flow control fittings that came in the kit (at least in previous years). To build our multiposition arm, we have 3 valves, 1 to control direction, and 2 to control the flow of air to and from the direction valve. by switching the source and exhaust lines, you can make the piston stop at any point along its travel.

[Team2339]

Multi position would work. Do you have a scematic of what you described?:confused:

[Integral]

We are using the Festo to switch between a high and low pressure. Seems to be working pretty well. The hard part was writing a latch circiut in Labview to lock the Festo in the powered position. We also found that we had to have the high pressure in the correct port, to provide the internal pilot pressure.

[ZInventor]

valves do not seal much below 30PSI and so they become unreliable at reduced pressure

I've worked with the SMC solenoids (that used to be in the kit) for a coupple of years, and was able to run them very reliably at pressures down to 5 psi, which we used last year in competition (frcteam2002)

this year, we're running an SMC at 20psi, and have not had any problems yet...

-Z

[Al Skierkiewicz]

I've worked with the SMC solenoids (that used to be in the kit) for a coupple of years, and was able to run them very reliably at pressures down to 5 psi, which we used last year in competition (frcteam2002)

this year, we're running an SMC at 20psi, and have not had any problems yet...

-Z

Just so you remember this when and if you have problems.

[JesseK]

Here's a question on a related note:

We will only have a working pressure of 45 psi for the entire system as well, which we know how to implement. However we would also like to slow the air flow down to the entire pneumatics system (passed the 45 psi regulator) on our robot. We also need all four of the pistons on our linkage drive train to kick in/out at the same speeds (this is more important than anything).

How would we achieve a lower flow rate without putting independent flow control valves on the pistons themselves? I'm sure there's a flow rate regulator somewhere, but everything I look at is somewhat confusing, and somewhat expensive. If we can do this we would be able to fully automate all four independent linkages without running out of air in a 2:15 match :cool:.

[Team2339]

Sounds like you need a series of reduction regulators to each distinct cylinder. The balancing act is the hardest. Maybe make a test pressure dongle to a T and check each leg, then tune it up.

We learned more about pneumatics in 5 weeks than we ever knew. Our robot works with one speed going up and a different speed going down.

Thanks to everyone for their info:D

[Mark McLeod]

However we would also like to slow the air flow down to the entire pneumatics system (passed the 45 psi regulator) on our robot.

Look at the SMC in-line speed controllers on this catalog page (http://www.alliedelec.com/Catalog/pf.aspx?FN=1515.pdf).

[JesseK]

Look at the SMC in-line speed controllers on this catalog page (http://www.alliedelec.com/Catalog/pf.aspx?FN=1515.pdf).

Ah, I see. So we already had the answer staring us in the face, yet we assumed you had to put the elbow flow control valves directly on the piston ... silly us :rolleyes:. I'll look tomorrow and see if the ones we already have fit the brass t-junctions. Thanks a ton!

[artdutra04]

This brings me to ask the question...
Why do we have so many less pneumatic components in the KOP this year?I'm guessing that either SMC isn't sponsoring FRC as much this year, or the pneumatic fittings were eliminated as a cost-saving measure. Push-to-connect fittings cost anywhere from about $2-$10 each for 1/4" OD tubing and either 1/8" or 1/4" NPT thread. So that entire bag of fittings from previous years cost around $150-$200 dollars.

However, I'm really concerned about rookie teams not knowing these connectors exist and not using pneumatics because they don't know how to connect them. If this continues, existing FRC teams probably have enough of these fittings to last two or three years, but after that most teams will have run out of them. I certainly hope these are included in future years and in rookie team KoP.

In case anyone was wondering where to get more of these, you can buy more push to connect fittings at MSC Direct (http://www1.mscdirect.com/CGI/N2DRVSH?PACACHE=000000084490797) or McMaster. If you are looking on McMaster, search for "push-to-connect" (without quotes), then select the type of fitting, then select "For Use with Air", then select "For Use with Polyurethane tubing".

[Mark McLeod]

...yet we assumed you had to put the elbow flow control valves directly on the piston ...
All the world's a piston...:)

[Tom Line]

I wonder if you couldn't use one of the flow control valves with a servo...