Pneumatics Question

[mrmatheou]

Hi,

I'm a team mentor for team 2603 and we have one of our Pneumatics experts proposing an idea and wanted to make sure it was legal. Here are his comments below with a diagram explaining. Any feedback on it's feasibility would be greatly appreciated!

Here is what I am proposing.



Control of a pneumatic cylinder:



Use a 4 way 2 Position single solenoid valve for directional control of an air cylinder. At each port on the cylinder use a blocking single solenoid valve would be used to turn air on or off. The default of this valve would be passing so that when the robot is in E-stop no air is trapped. The use of these multiple valves to control a cylinder would be done in series. (Thus the flow of .3 Cv would not be exceeded)

[scottydoh]

I'm having a hard time understanding the need for a third solenoid.

[DonRotolo]

I am speculating that the intent is to control the cylinder's piston so it stops in places other than the end stops.

If so, then you can get a single 3-way valve to do this, very much simplifying the setup.

What is shown appears legal to me.

But, from personal experience, trying to do this with pneumatics will be disappointing. Precision is difficult, and if the load changes the position changes as well. Search Chief Delphi for several dozen threads in the past 6 years on this topic.

[Mark McLeod]

It doesn't appear legal this year.

<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.

[Chris Fultz]

Originally Posted by Mark McLeod

It doesn't appear legal this year.

<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 believe it would be legal. There is only one solenoid connected to the input on the cylinder. The fist solenoid is connected to the input of the second solenoid.

My belief is that the intent of R74 it to limit a team having multiple solenoids feeding directly into one cylinder inlet, which woud significantly increase the flow rate into the cylinder.

IF you choose to go with this, it would be worth a question to the GDC.