Varying Regulator Pressure Using Mechanical Device

[Madison]

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.

[AdamHeard]

I see no reason as to why it'd be illegal.

[Tristan Lall]

http://www.chiefdelphi.com/forums/sh...ad.php?t=80658
http://www.chiefdelphi.com/forums/sh...ad.php?t=72464
http://forums.usfirst.org/showthread.php?t=11220

As for this year, I don't see anything that would make it illegal, as long as you could show that the upper limit was always respected.

[Garrett.d.w]

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

A bit of googleing (yes... google as a verb) found these (http://www.smcetech.com/CC_host/page...6669613456b3f5)
They are electronic regulators, don't know if they are good for a robotics aplication, but it would be interesting to try.

[RoboDawg]

I agree with Tristan, I see no rule violation if you keep everything under the 60psi rule. Bummed we wont see X bot at Portland. Good luck, 2130)

[hocman22]

Originally Posted by Garrett.d.w

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

A bit of googleing (yes... google as a verb) found these (http://www.smcetech.com/CC_host/page...6669613456b3f5)
They are electronic regulators, don't know if they are good for a robotics aplication, but it would be interesting to try.

So with the link you posted..... is it possible to program it to fire a cylinder at different pressures?

Can we take a shot at 60 psi, then go to 55psi on the next one then drop to 30psi?

[Retired Starman]

Originally Posted by Garrett.d.w

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

A bit of googleing (yes... google as a verb) found these (http://www.smcetech.com/CC_host/page...6669613456b3f5)
They are electronic regulators, don't know if they are good for a robotics aplication, but it would be interesting to try.

I think Rule R78 would pretty much put this scheme out to pasture:

R78--The outputs from multiple valves may not be plumbed together into the same input on a pneumatic cylinder.

As an inspector, I would take a careful look at anything like you suggest.

Dr. Bob

Chairman's Award is not about building the robot. Every team builds a robot.

[Teched3]

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.

[Tristan Lall]

Originally Posted by Teched3

All the cylinders that we have used in the past have an adjustable valve that allows you to adjust actuation speed/force manually.

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.)

[IndySam]

Originally Posted by Teched3

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.

The adjustable valve will vary speed but not force.

[Al Skierkiewicz]

You know this might be a good use for the VEX motors.

[Gdeaver]

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.

[Al Skierkiewicz]

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?

[jreuter]

Here's how 1073 did this in 2010 for our variable pressure ball kicker.

Put a valve between the regulator and the pressure tank.
Put a pressure sensor on the pressure tank.
Pulse the valve, in roughly 1 ms increments until you get the pressure you want.

I also recommend putting a 2nd valve on the pressure tank side, which vents the tank. You can pulse this valve to drop the pressure.

This seemed to be repeatable within a couple PSI.

You will need to have two manual vents, one on each side of the first valve, to completely depressurize the system. Or, you can wire the 2nd valve to automatically vent when you lose power.

This system can also be used to pre-charge a cylinder that is restrained half way. In this case, the automated venting is vital for safety, since you do not want that stored energy in the robot when it is disabled.

Now, I am fully aware that these valves were probably not meant to be used this way, but our system was very reliable. We used the large plastic Festo valves.

Hope this helps.
-Jeff

[Al Skierkiewicz]

J.
[R72]
If pneumatic components are used on the Robot, the following items are required as part of the pneumatic system
and must be connected in accordance with this section.

D. An easily visible and accessible pressure vent plug valve to manually relieve the stored pressure (see Rule
[R77]).

[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.

One only, sorry.