Motorizied flow control
 

Hello
I came up with an idea to control the speed of a piston and use it with precision and i wanted to make sure its legal.
we bought 5 ports - 3 position valves so we could stop the piston at any position we want, but we had a problem, the piston is moving too fast for the drivers to control it well.
so i attached flow control tubes to the relief ports in the valve
http://www.andymark.com/product-p/am-2690.htm
its worked well but if we wanted to open the pistons fast we couldn't do so.
so i connected a hobby servo with a gear ratio to the screw on the flow control tubes so i can control the speed of piston with driving.
is this legal?

tnx in advance :D

Re: Motorizied flow control
 

To be honest, while I cannot recall a rule against doing so, a setup like that would have me asking the LRI for advice.

If you have a reason to use such a setup in the regular season, please ask the official Q&A as early as possible--and then bring the answer to your events, just in case your LRI hasn't read that particular Q&A.

Re: Motorizied flow control
 

I don't understand why this would invite any rules scrutiny at all. What rule does it even potentially violate?

Re: Motorizied flow control
 

as written in rule R77-F in this year's game:
"F. Pressure transducers, pressure gauges, passive flow control valves (specifically “needle
valve”), manifolds, and connecting fittings"

as u see its written passive flow control valves, so i dont know if it counts as an active or passive one.

Re: Motorizied flow control
 

We had a team pass with something similar at Waterloo, the LRI and I couldn't find anything illegal about it. As long as the pneumatic fitting remain unmodified It should be fine. I would still consult the Q&A as the ruling of inspectors could vary and It could potentially save some time during inspection.

Re: Motorizied flow control
 

The valve itself is passive, a custom system actuates the passive control, that is completely separate from the pneumatic system. The pneumatic components are, presumably, unmodified. Seems like it should be good. It's just unconventional.

Re: Motorizied flow control
 

When you use your 5 port 3 position valves to stop the piston half way, does your pneumatic system comply with R89?

Re: Motorizied flow control
 

The rules problem isn't with the throttle valve, it's with the 3 position solenoid valve. AFAIK, the pneumatic system is supposed to completely depressurize when you open the vent valve. A 3 position valve in the "locked" position would prevent that.

Edit: or what Joe said

Re: Motorizied flow control
 

Dare I ask what this was for?

Re: Motorizied flow control
 

The team wanted to have a 3rd position for their air cylinder. I think the plan was to actuate the cylinder with the solenoid and use the servo to let out air until it was the right height. I don't think they ever got it functioning.

Re: Motorizied flow control
 

As already mentioned the problem with your system is not the flow controls, but the 3-position valve.The question of using a 3-position valve to achieve intermediate cylinder positions has come up many times. If the center valve position is both-ports-closed, this technique is illegal because it creates closed, pressurized lines that are not vented when the system is vented. If the center valve position is both-ports-exhausted, this should be legal, but would have no ability to hold its position on its own.

Re: Motorizied flow control
 

It is a little Rube Golbergish, but there is a way to make a closed center 3 position valve legal under 2016 rules. You use check valves to allow both sides of the cylinder to flow back the working pressure side of the system. They won't do anything when the system is pressurized, but they will vent the cylinder when the system is depressurized.

Re: Motorizied flow control
 

Attached is a sketch on how to use check valves to make using a closed center 3 position valve legal under FRC rules (at least for 2016) :]

Re: Motorizied flow control
 

It is important to note that you connect the check valve to your working pressure, not your stored.

Re: Motorizied flow control
 

Oh very cool, thanks! With a setup like that you could create a pneumatic position control system (like http://www.bimba.com/Products-and-Ca...ntrol-System/). Add a pneumatic rod lock (http://www.bimba.com/Products-and-Ca...Line-Rod-Lock/) and you could move and hold actuators with very few mechanics.

The downside is the limited compressor size means you wouldn't be able to move a cylinder bigger than ~1" more than a few cycles a match.