Closed Loop Pneumatic Cylinders with Servo Valves - Any Experience?

Technical Technical Discussion
#1

Has anyone ever used a closed-loop pneumatic cylinder with a servo valve like these from Bimba?

https://www.bimba.com/Global/Library/Brochures/SPCS_2_Setup_Manual_10_14_13.pdf

I am pretty sure they’d be legal (valves still have 1/4" NPT inlet), but I don’t know if the legal compressor would provide enough flow to be useful. Still, the idea of an actuator with the accurate positioning of a servo, but the “soft touch” and overload capacity of a pneumatic cylinder is really attractive. I would love to hear any experience teams (or professional mentors) have with them.

#2

I believe you’d run afoul of R35 this year (a perennial rule)

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And possibly R60 (another perennial rule)

Essentially, the control for the solenoid valve has to come directly from the RIO through a relay module or PCM, and cannot be managed through an external device.

#3

This is one I would have to call Big Al on in order to make a ruling. My first thought in looking through that is R82. Where does a “Servo Pneumatic Control System” fall into the list of permitted pneumatic components? My second thought was R94 - does that thing fully vent when pressure is released, or can it trap air in part of it? I’m clear enough on how it functions to know just from what I read (fortunately, it’s an easy enough test to do in a team’s pit).

GeeTwo’s considerations follow on those ones, I think. We first need to figure out how a device like this is classified within the existing robot rules. If it connects to pneumatics, that’s the place to start.

It definitely looks like it would be pretty useful… but something like that would definitely need to be Q&A’d during the season, I would think.

#4

Or frcteams’d about now. That way it’s already been flagged for review so Q&A can just say “refer to Update X” as a pre-written rule/blue box slides in.

#5

Whatchu talkin’ 'bout, Willis?

#6

Oh, just the official runaround: “If you have suggestions about parts that you think should be legal, email frcteams@…”. (Usually seen when someone Q&A’s “We think this part should be legal”.)

Figger if frcteams has been made aware, the GDC will at least be aware someone’s likely to ask, and might even write the rules to make it obviously one way or t’other. Or have something ready to go when someone asks.

#7

A servo valve may not be legal but a servo and a valve was :smiley: https://scontent.fybz1-1.fna.fbcdn.net/v/t1.0-9/12919755_1139744022711495_3121225385749858335_n.jpg?oh=9419e73f0329abaa2dbf4c4ab001d1df&oe=5A6D8538

#8

I think you got a free ride on that one, especially if it did not vent to the atmosphere.

#9

It’s not a pressure vent plug. Just because it’s the same valve doesn’t mean it would count as one. Adding additional flow controls valves was legal as long as the pneumatics still drain fully and it wasn’t a year that disallowed flow control valves (I can’t remember which years but they ended up banning them in the q&a). This case wasn’t on one of my bots but the LRI passed it at the time and while it probably wouldn’t hold up to a Q&A ruling I believe they made the correct decision to pass it at the time. There are plenty of valves on a FRC that vent to atmosphere besides a pressure vent plug.

#10

Somewhat off topic:

This is where I note the irony that in my job many times closed center solenoid valves are required for safety, as when solenoid power drops (safety controls, etc), we want things to stop roughly where they happen to be rather than keep going (so people don’t have the full plant air supply trying to crush them via a pnumatic clamp or the like). Then again, I work on sub-assembly manufacturing lines (robots, automation, and welding jigs) so it’s a different situation with a completely different safety design and set of “rules”.

I do think it would be nice if up to X of non-exhausting solenoids were allowed if easily accessible exhaust valves were provided for the circuit. Idea being, for example, a closed center 3-position solenoid circuit would have exhaust valves one each side of the output plumbing, and opening both would exhaust all pressure. I mention this because at work we have a couple of welding jig/turntable assemblies that are plumbed that way (bank of exhaust valves in addition to the main air lockout point supplying the solenoid manifold) to allow easy pneumatic servicing and repair.

#11

Sorry; something about the post or picture made me think this was from the past two years, but I can’t find that now. At least since 2014 (first time I read the pneumatics rules looking for loopholes to launch yoga balls), the pneumatics rules have started out with certain devices required, another itemized set allowed, and everything else disallowed. In recent years, if that was somehow not a vent plug, you would have to identify which of the allowed devices it was (and convince the inspector that’s what it was).