Controling Pnumatics with joystick.
 

'ello, how’s life
I am the main programmer and trying to do what seems impossible. My team wants me to program the pneumatics with the joystick so when you push up on the handle so when Y axis moves from zero point, the pneumatic cylinder moves up and down relative to the joystick.

Yhea I don’t know if it’s even possible

Re: Controling Pnumatics with joystick.
 

I've never done this, but have always wanted to try it out (like in the off season). You use a 3-position, Center closed, Solenoid Valve such as an SMC SY3340, with Flow Control elbow fittings to limit how fast the piston moves, and power the two valve coils from the outputs of a Spike (tie both coils negative leads to ground)[this also prevents the dreaded powering of both coils at the same time]. When the joystick is centered (null) have the Spike Off (no current to either coil) this will close both the extend and retract valve output ports, holding the piston still (mostly). When the joystick is pushed forward, power the solenoid that extends the piston. When the joystick is pulled backward power the solenoid that retracts the piston. I recommend that you use meter-out flow control elbows and put them on the valve manifold ouput ports. How well this holds a mid stroke position will depend on the load and probably whether the Driver was extending or retracting the piston prior to trying to stop it. It'll work better in the direction that is pressurizing the cylinder against the applied load.

Good Luck,

Re: Controling Pnumatics with joystick.
 

yes, it is possible, your joysticks + the speed controllers create the variables -1 through 1... you can either set your joystick variable 1 to true and set it so that if it isnt "1" then it is false or you can set forward to true and backwards to false. hope this helps (:

Re: Controling Pnumatics with joystick.
 

Just attach a motor to drive the piston instead of air...:eek:

Re: Controling Pnumatics with joystick.
 

We were looking at a similar approach until last week when another thread pointed out this ruling: http://forums.usfirst.org/showthread.php?t=16642

Our 3-position, center closed solenoid is in the mail, but we don't see a way to release all stored pressure when a single relief valve is opened, therefore making the setup illegal.

Re: Controling Pnumatics with joystick.
 

I assume you are looking for true analog control. This can be done with an I/P transducer. Unfortunately, these devices are not legal competition parts. You should do some research on these control devices (in the off season) as an opportunity to learn about other control devices. All control system programmers need to be familiar with the control system components and machinery they control to be effective.

Re: Controling Pnumatics with joystick.
 

What is the difference between 2-position solenoid and a 3-position center closed solenoid when the power is off. The solenoid will only move when power is applied. The "working pressure" will be stored in the cylinder and cannot be released by the pressure release valve located at the compressor unless you release it at the solenoid. I don't see how this can be an illegal valve.

Re: Controling Pnumatics with joystick.
 

Don't forget single solenoids where the piston will move to the home position after the power is cut.

Re: Controling Pnumatics with joystick.
 

you can slow down the rate the cylinder with adjustable orifices . but the way the valves work is they pressurise one side of the cylinder and vent the other to atmosphere. there is no way to stop the cylinder mid-stroke with the avalable first hardware.

Re: Controling Pnumatics with joystick.
 

I believe 1075 did it in 2004 and 2007.

Re: Controling Pnumatics with joystick.
 

that's great it would be nice to see how they did it.

Re: Controling Pnumatics with joystick.
 

Correct me if I’m wrong, but there is no rule in the pneumatic section for the robot build that states that the valves must fail open so the pressure in the cylinder is released after the power is off. The rules do not restrict the 3 position center blocked valve. If you go for the strict interpretation of the rules then all 2 position valves are illegal because the "working pressure" cannot be relieved at the pressure relief valve.

Re: Controling Pnumatics with joystick.
 

The valves must be open when the power is off so the vent valve can relieve all stored pressure. See rule R73.

<R73> 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.

Re: Controling Pnumatics with joystick.
 

if they use a doubble-acting valve for the cylender and 2 single-acting valves to stop the exhaust they would fail open and allow the whole system to purge

Re: Controling Pnumatics with joystick.
 

That's very close to the test we ran prior to ordering the 3-way solenoid.

This document shows a way to control position that appears to comply with <R73> and <R74> after adjusting the single-acting solenoid to fail open (not closed like they specify):
http://www.chiefdelphi.com/media/papers/1476

It would be nice to use a 3-way, center closed solenoid, but my team hasn't seen a way to do it that is less complex than the above design and complies with both <R73> and <R74>.