Just curious what the CD brain trust thinks of the idea – and whether it is a legitimate method of interfacing with pneumatics components. The rules don’t seem to outlaw it, but pneumatics have always been something of a sacred cow and so I’m nervous about pushing the envelope too much.
In short – we’d like to vary the force a pneumatic actuator exerts by varying its operating pressure. In order to do that, we’re imagining that we’ll mechanically drive a pressure regulator. There’ll still be a 60psi regulator as required, but this secondary regulator will allow us to reduce the working pressure to one or more actuators dynamically.
Thoughts on its legality? Has anyone tried this before? Are we insane? Yes is an okay answer.
You could have multiple one way solenoids, each with its own regulator. Any weirdness could be fixed in code.
The way it would work is that you use multiple single function solenoids (or just a standard two way with one output blocked) to feed air into the solenoid and one solenoid as an exhaust. This setup would have to be repeated per function (in, out, etc). It would be ugly, but it would work.
If you find a way to reliable change air pressure I would like to know
We did exactly this in 2010 to vary our kicker distance. We used a window motor with the black plastic connector that comes in the kit to control a secondary black Norgren regulator remotely via the drivers. We had a pressure transducer connected to report the pressure back to the drivers station which had a graph calibrated in distance. The coupling between the black plastic window motor thingy and the black Norgren regulator was a simple piece of automotive heater hose about 2" long. It worked great and required no modifications to any pneumatic components. We coded safety stops in the software to stop the window motor at something like 20PSI one way and 55PSI the other way so a trigger happy driver couldn’t break the knob off the regulator. Photos available upon request…
Madison,
There is currently no rule that would prevent it. When this discussion came up a few years ago, we all did some searching and found several electrically operated regulators. Unfortunately most were designed for AC 24 volt controls. While we expected many teams to jump on the band wagon, we actually saw very few in inspections. I don’t remember seeing any on the robots I inspected. I am going to guess that was due to either cost, complexity of control or additional weight. I know one team showed a servo attachment but the servo was not legal under FRC rules at the time. Please remember that all other rules still apply and one of those is the ability to release all stored pressure through one pressure relief valve.
[R77]
The pressure vent plug valve must be connected to the pneumatic circuit such that, when manually operated, it will
vent to the atmosphere to relieve all stored pressure. The valve must be placed on the Robot so that it is visible
and easily accessible. If the compressor is not used on the Robot, then an additional vent valve must be obtained
and connected to the high-pressure portion of the pneumatic circuit off board the Robot with the compressor (see
Rule [R73]).
I would setup the adjustable regulator downstream of the fixed 60psi Norgren regulator, to ensure nothing cause your pneumatic components to operate over 60psi.
If you are trying to vary the force / speed of cylinders, there is a trick involving multiple cylinders. Instead of one large cylinder, use several small cylinder in parallel, each connected to its own valve.
To vary speeds: Connect all cylinders to the valves in the normal fashion. High force kick, extend all cylinders. Lower force, extend some cylinders, keep some in retract, these retracting cylinders will “fight” the extending ones, reducing the force and speed. A cylinder has more force in extend than it does in retract, so as long as you have as many or more cylinders extending than retracting, it will extend. If you use four cylinders, that will give you three different extend speeds / forces. We did this in 2010 (we also used surgical tubing to help extend, so we could actually extend with all but one cylinder in retract)
All the cylinders that we have used in the past have an adjustable valve that allows you to adjust actuation speed/force manually. You should be able to design a servo- operated link to this valve knob to adjust the applied pressure. The servo has a built in encoder, and use a continuous rotation type. Some years we were only allowed to use certain servos, all of which had limited rotational capability (180 DEG. or less). check this year’s rules on servos that are allowed. they are usually very specific on maximum torque and capability specs.
I believe you’re describing fittings with needle valves built in. (They’re not part of an ordinary non-repairable cylinder, they’re part of the fitting.)
Isn’t there the possibility that the regulator controlling the variable air pressure could cause a violation if the motor control malfunctioned and adjusted all the way high. If the cylinder was then mechanical compressed then the pressure could go above 60 PSI and the regulator would not relieve. A pressure relief valve set at 60 psi would take care of this down stream from the variable regulator. Then I would be happy with it. Don’t Know about First take on it.
G,
R71
D. Solenoid valves that are rated for a maximum working pressure that is less than 125 psi rating mandated
above are permitted, however if employed, an additional pressure relief valve must be added to the low
pressure side of the main regulator. The additional relief valve must be set to a lower pressure than the
maximum pressure rating for the solenoid valve.
Is that what you were thinking?
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