Hi, I was wondering if anyone knew if using multiple pressure regulators was legal and possible? My reasoning behind this is that if you had say three of them you could have multiple working pressures such as 20psi, 40psi, and 60psi to conserve air where it is needed or frequently used. I attempted to do this last year but put it aside for a lack of results and due to the fact that we decided to just utilize a lower pressure on every mechanism.
Note the key part of that Q&A - everything passes through a single primary regulator set to 60PSI or less. If you want one or more secondary regulators after that to give you additional pressures, that is legal (as long as all other pneumatics rules are met, such as the pressure rating of the components).
If you look at rule 8.9 in the Game Manual it specifically stakes “One” compressor, but doesn’t set a limit on any of the other pneumatic components. So you’re good.
Lower pressure is a good way to save air. Another way is to use single acting (spring return) cylinders. Or if you can use gravity or external springs, elastic, etc. for the return, any double acting cylinder can become single-acting.
Such is also a great way to get intermittent jams in mechanisms. I’m not going to say it doesn’t work (obviously teams do it every year) but I will say that I’ve been taught (and have seen from experience in and out of FRC) that passive mechanisms are generally less reliable. I do know of cases where an inherently passive mechanism failed and cost an alliance a finals win. For example (as I mentioned in another thread) 71 and 461 just by chance had similar ramp designs in 2007. Both were passive (sprung folding lexan/aluminum ramps) that both jammed at the worst time possible. For 461, it was Finals 3 at Boilermaker Regional. For 71, it was Finals 2 on Einstein (forced a 3rd match which they lost, cost 71 a 5th championship win). Both lost to an alliance with an actively powered/controlled ramp/lift system.
In the end it’s all a trade off… just a point to keep in mind when designing things.
Ok so now we know it is possible. My next question is how do we do it? Like I said before I tried last year but all the pressure would justvleak out of the lowest pressure regulator until it equalized. Does anyone have a image or video explanation? Anything really would help!
Im not sure if this applies to this thread but can you supply different PSI’s to the same piston during the same match? like say at one point in the match you gave the piston 10 psi and then you wanted it to be stronger so you gave it 40 during a different part of the match.
Interesting question! I’m not currently sure if pneumatic component manufacturers produce such a device, and if they do, it may not be compliant with the manual. The only way I could see this being done would be to put pressure regulators on each output of the solenoid, but simply connecting those with a T-connector risks sending pressure through the wrong direction, damaging one of the regulators.
If it’s speed your worried about, you could try a flow rate regulator? Seems like an interesting problem!
I’m not 100% sure of the FRC legality of pneumatic check valves (as long as they’re rated for the PSI I think it would be accepted).
What you would could do is have two regulators feeding to two separate solenoids. The output of the solenoids would go through their own check valves (makes sure that air only flows in one direction and the air from one solenoid won’t flow to the other) and then combine via a wye connector (or Tee connector) to a single tube that connects to the piston.
Based on which solenoid you actuate, it will get a different pressure.
This will only work with single-acting pistons. For double-acting pistons you’d have to get a bit more clever, or end up with 4 solenoids.
I don’t see many applications where you’d want two different forces coming from the same piston, but I won’t limit you to the level of my own creativity. As someone else said, if you’re worried about how fast the piston actuates, you want to add a flow control valve, not a different pressure.
Then please, check the rules before giving advice.
R83 part G specifically allows check valves, provided R95 is still met. It’s possible to create a pneumatic system with check valves that does not vent all pressure from a single pressure vent plug, and this will be closely looked at by your inspector.
Also that arrangement would take 3 solenoids because a check valve on each solenoid output would prevent exhausting the cylinder, so you’d need a separate solenoid for the exhaust.
I know Q91 seems to suggest electronic pressure regulators are legal, but I can’t see how you square the actual operating principles with the suggested rules. I think they’re mostly solenoid valves with fancy electronics to pressurize a pilot chamber inside an otherwise normal regulator. Which means the valves would need to be controlled by Spikes or a Pneumatic Control Module, but that’s not possible. Or if it’s an internal servo, the internal servo would have to be controlled by a PWM port, which isn’t possible… Basically, I think Q91 means that while it’s potentially legal, you’re not going to be able to connect a COTS one to the control system legally.
Here’s some ways I think are more certainly legal and less reliant on mildly vague Q&As:
Two secondary regulators, low pressure one to a check valve, high pressure one to a 2-way normally open solenoid valve. For high pressure, leave the solenoid valve open. Otherwise pressure’s only supplied through the low pressure one. This is dicey on R95, since you’d have to power down AND open the dump valve to exhaust everything. (Actually, looking at #2 below, I think a 3-way valve with a check valve gets you past this.)
Do something like 488’s 2012 Gojira Catapult. They basically home-rolled an electronic pressure regulator using legal solenoid valves and a pressure sensor. Madison may have opinions on whether this solution was reasonable and worth it.
Spin the knob of a pressure regulator with an RC-servo. Use a pressure sensor on the output to turn it into a closed loop system.
#2 above, but use much smaller valves to drive a pilot controlled pressure regulator which is what actually feeds your system.
I’ve seen a team do this before. keep in mind that pneumatic parts cannot be modified (R82). The team that did this created a 3D printed mold that had a friction fit around the knob of the regulator. As such, the actual regulator wasn’t modified. Hook a servo up to the mold to spin it, and in turn it spun the regulator knob. Possibly the easiest way to go about it, and there’s actually no need for a pressure transducer - do some testing on it in your shop and find the set points you want, and figure out what angle that is for the servo. You basically create a hardcoded lookup table that matches pressure to angle, and lets you get right where you need without a PID loop.
I was assuming you couldn’t get the necessary adjustment out of the standard 270*-ish stroke of a servo. But if there’s a regulator, gearing, and servo option that gets you the range you need with absolute positioning, then sure. There might be some hysteresis, so you might need a routine for turning it too far down then up to get a more accurate pressure out of it or something.
The last time we did this we built our own “servo” using a window motor.
But we did it based on a transducer feedback, rather than fixed position.
The drivers liked to adjust on the fly based on how the balls were flying.