3 position cylinders

Technical Pneumatics
1

Rule <R74> says that

Each commanded motion of a pneumatic cylinder or rotary actuator must be accomplished via the flow of compressed air through only one approved pneumatic valve.
Does this illlegalize 3 position cylinders, or are 3 position cylinders legal because they are technically 2 cylinders put together?

2

You should ask the GDC officially.

3

Has anyone asked the GDC yet?

4

not from my quick hour of looking, but don’t limit yourself to the “Pneumatics” section. Pneumatics can be found all over the “the Robot” section of the
Q & A.

5

Ty,
Can you provide a link to the actuator you are asking about?

6

It seems to me that one valve means one valve.

Here’s how you plumb a 2-port 3-position cylinder with a single 5/3 valve.

This 3-port arrangement probably wouldn’t work for you, unless you found an appropriate valve.

7

Here is a Bimba 3 position. We may use one. I have posted in the Q+A.

http://bimba.com/pdf/catalogs/FL_OriginalLine.pdf#page=67

Here is a pdf explaining how they work.

http://www.bimba.com/pdf/catalogs/TRD_3P_Series.pdf

I don’t know what the GDC will say, but I would say these are safer than connecting multiple cylinders together at the clevis or foot end, because these are built as a joined pair.

8

Here is a link to the 3 position cylinders. My only worry is that it’s a violation of <R74>. http://www.bimba.com/Products/OriginalLineCylinders/ThreePositionCylinders/

9

<R74> Each commanded motion of a pneumatic cylinder or rotary actuator must be accomplished via the flow of compressed air through only one approved pneumatic valve. Plumbing the outputs from multiple valves together into the same input on a pneumatic cylinder is prohibited.

I posted the question.

My interpretation is that the three position cylinders are legal, as long as you only have one solenoid connected to each input. The rule does not say one solenoid connected to each cylinder.

I will post the response from the GDC when I see it.

10

I can’t post a link (immediately) because a moderator has to approve it, but These cylinders from Bimba are the ones I’m talking about. I worry about <R74>, because it’s technically one cylinder, with multiple solenoids, but it’s also technically two cylinders together.

11

Ty,
I do not see that the use of this cylinder and multiple solenoids would violate R74. R74 specifically is written to prevent more than one valve to feed the same input on a cylinder in an attempt to make the cylinder react faster. I must abide by by the ruling of the GDC and I have been wrong before. Please standby until they respond.

12

Will do. Thanks for checking!

13

http://forums.usfirst.org/showthread.php?t=17069

Re: 2 Stage Bimba Cylinders

As long as <R74> is followed and “each commanded motion of a pneumatic cylinder is accomplished via the flow of compressed air through only one approved pneumatic valve” and these cylinders meet the requirements of <R66>, the cylinders are allowed.

14

Interesting note: Does <R74> as written outlaw the design 1075 used in 2004 and 2007 for stopping a pneumatic cylinder mid-stroke?

By passing the exhaust ports of a valve into the P port of another valve, with a looped hose connecting A and B, plugging EA. This seems like TWO valves controlling the flow through that ONE cylinder, though only ONE valve is DIRECTLY connected to the cylinder.

15

No clue if it’s just a negative externality of the pneumatics rules this year, but position control with multiple solenoids or even a single 3 position, normally closed solenoid seems to have been outlawed.

Check the official Q&A… our team asked about what you’re describing as did a few others and the answers point to a violation of <R74>.

16

3 port center port closed solenoid valves were illegal because they trapped pressure and would not allow the full pressure to be relieved. Why can’t you add addition pressure relief surge valves to the line to the cylinder and accomplish the same thing? Might be a good question to ask the GDC…

17

Which is odd, because a center-closed valve doesn’t trap any usable pressure. If you closed off a center-stop solenoid (trapping the air in the cylinder to keep the cylinder locked in one position), removed the air pressure from the P port (ie. open the dump valve) and then simultaneously open both sides to atmosphere, nothing will happen, except that gravity might take over, and actuate the cylinder. I think this is another case of the GDC being closed minded and limiting innovation they’ve allowed in the past, citing a rule intended to provide safety, when their rule arguably makes things less safe.

Center closed solenoid valve would keep a pneumatically actuated arm locked wherever it is, even if robot power or pneumatic pressure is removed. Any other configuration of valves results in a robot appendage that can move when solenoid power is lost (breaker, or field disabled), or when air pressure is lost (dump valve opened). I’m certain many teams can attest to needing to teach their students to be aware of robot actions that can occur when the pneumatic system gains and loses power.

18

This was my thought process as well. I have taken the approach that I need to expend my energy working on a solution rather than railing at the lack of sense the GDC is making. Rules are rules after all. My team would have been much better off if we had read the rules better at the beginning of the year. Oh, well…

19

Is it legal, per rule <R74>, to use Bimba’s 3 position cylinder, shown in the link below, on the robot this year? http://www.bimba.com/pdf/catalogs/FL…ne.pdf#page=67
2011FRC2484

GDC:
As long as <R74> is followed and “each commanded motion of a pneumatic cylinder is accomplished via the flow of compressed air through only one approved pneumatic valve” and these cylinders meet the requirements of <R66>, the cylinders are allowed.

So… Does that mean it’ legal to use them, or not? Would a three-position valve have to be used, instead of 3 open-or-closed solenoids, to make it legal? Is there such a thing as a three-position valve? The GDC isn’t cryptic on this one at all, are they?

20

center blocking/locking valves have been deemed illegal.