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  • Pneumatics Question

    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)
    Attached Files

  • #2
    Re: Pneumatics Question

    Originally posted by team2603 View Post
    The default of this valve would be passing so that when the robot is in E-stop no air is trapped.
    This is what I first thought of. Most of the solenoid valves I've used don't have a "default" position, so air would not necessarily be released. If you have found an alternate legal valve that has this feature, than there shouldn't be a problem here.

    The rule I would be worried about, though, is <R74>:

    Originally posted by 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 think the intention of this rule is to prevent valves to be connected in parallel (you allude to this), but, as the rule is written, it would appear to prevent your idea as well. I would definitely post a question to the GDC before selecting this design.

    --Ryan

    Comment


    • #3
      Re: Pneumatics Question

      We have used this in the past. Each input on the cylinder is connected to one valve. The valves are connected to other valves in series, but that's not outlawed in <R74>. The main advantage of this approach is that you can move a cylinder out with pressure, hold at any point with pressure on both sides, release the pressure on both sides to make it move more quickly in either direction, or vent safely at the end.

      Comment


      • #4
        Re: Pneumatics Question

        Thanks to everyone for their posts. I'm new at posting questions but I guess I need a 'final' answer from the GDC. Do I just wait for them to respond and it eventually happens or do I somehow need to get their attention?

        Comment


        • #5
          Re: Pneumatics Question

          Note that "in the past" is not this year; new set of rules, though many are similar or the same as in past years.

          To post a question to the GDC, talk to your team leader to get the forum login for your team (available on TIMS), then post this question in the Q&A forum (labeled "Submit your questions here!" on the main page for the FIRST Robotics Competition forums). Then keep an eye on the "Find the answers to your questions here" subforum for the GDC's response.

          Not trying to discourage your idea (I've actually considered similar things in the past), just making sure you don't have more headaches than necessary when going through robot inspection.

          --Ryan

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          • #6
            Re: Pneumatics Question

            Thanks for the tips on posting to the GDC...

            I posted on Monday and have yet to hear back... What is the typical turnaround time for questions to be answered? I actually posted to postings. (The first time, I forgot to check the 'email notification' box so I submitted a 2nd post explaining.

            Thanks....

            Comment


            • #7
              Re: Pneumatics Question

              Thanks to all in giving me your input. I tried to reach out to the GDP and finally got an answer 5 days later: "We will not review specific designs for efficacy or legality. "

              Again, I'm new at posting but from the few topics I've seen posted before, it seems like a lot of other teams are asking to see if their designs / proposed ideas are legal too.

              Oh well, thanks anyway...

              Comment


              • #8
                Re: Pneumatics Question

                5 days is fairly usual, in my experience; I do sympathize with the waiting period, though. My understanding is the GDC usually conferences a couple times a week to discuss rulings.

                The trick with asking questions of the GDC is you have to reduce your query to a more generalized form that can be addressed with only a handful of rules. If I understand your design correctly, I would ask something like "is it permissible to control a pneumatic cylinder using multiple solenoids connected in series, if provisions are made to so air is released upon loss of control signal" or something like that, perhaps including a note that you have considered <R74>, but did not feel that your design violated the intent of the rule.

                I believe they enforce this policy so that people don't essentially post pictures of robots or CAD drawings and ask the GDC to rule on the legality of the entire design. Now, what you asked is somewhat removed from this extreme, but I think the GDC views it as a "slippery slope." There also does appear to be some variation in this - I suspect it depends on who actually responds to the question.

                Best,
                --Ryan

                Comment


                • #9
                  Re: Pneumatics Question

                  Originally posted by rcahoon View Post
                  ...The trick with asking questions of the GDC is you have to reduce your query to a more generalized form that can be addressed with only a handful of rules...

                  This Q&A thread
                  might answer your question.
                  Mike Betts

                  Alumnus, Team 177, Bobcat Robotics, 1995 - 2010

                  As easy as 355/113...

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