FRC488 2012 -- Gojira

[PAR_WIG1350]

All the pneumatics rules seem to be satisfied. I'm definitely impressed, it is much more complex than any system I have ever built*. You might be able to cut down on time by using a servo actuated (relieving?) regulator in between the orange and blue parts of the system just after the solenoid. This would completely eliminate the need to have a bleed valve hooked up to a flow control which seems to be the bottleneck in efficiency. This would also conserve pressure since you are no longer bleeding away air. A good regulator and servo should be precise enough to be simple to program.






*Mostly because I have not had a chance to build this, yet.

[AllenGregoryIV]

I think I just got more ideas for how to use pneumatics in future robots that I have in the past 2-3 years. Thank you very much for writing this up and I can't wait to see this on Thursday.

P.S. I think your Double/Single labeling in the red zone is flipped.

[Madison]

Originally Posted by PAR_WIG1350

All the pneumatics rules seem to be satisfied. I'm definitely impressed, it is much more complex than any system I have ever built*. You might be able to cut down on time by using a servo actuated (relieving?) regulator in between the orange and blue parts of the system just after the solenoid. This would completely eliminate the need to have a bleed valve hooked up to a flow control which seems to be the bottleneck in efficiency. This would also conserve pressure since you are no longer bleeding away air. A good regulator and servo should be precise enough to be simple to program.

We also tested a system with a servo-driven regulator, but were unhappy with the reliability. We waste a bit more air this way, but we're able to get very consistent firing results from it as a consequence, so it's an okay trade.

Originally Posted by AllenGregoryIV

I think I just got more ideas for how to use pneumatics in future robots that I have in the past 2-3 years. Thank you very much for writing this up and I can't wait to see this on Thursday.

P.S. I think your Double/Single labeling in the red zone is flipped.

Come by our pit and see it. I'm not sure what state of affairs things with the robot are currently in since I've been buried at work and haven't made it to a few meetings this season, but I'm sure you can grab someone to give you the guided tour if you're so inclined.

Also, I'll see about getting our pneumatics mentor to post more about the solenoid choices; he says they're not mislabeled, but that's all I know about that

[Kevin Sevcik]

Thaaaat's a fancy pneumatic system. Very impressive. The only thing I can think of that would make it more impressive an responsive would be PWM control of your catapult solenoid valves. If you have fast enough solenoid valves, you can actually send a PWM signal to them to modulate the flow rate. So 100% duty cycle when you're first loading up the pressure, then you reduce the duty cycle as you approach your setpoint. If you do it right, you hit your setpoint and don't need any bleed-off. You could PWM the bleeder as well, obviously.

Granted, if you get your tuning wrong, you'll overshoot just as bad as you are now and take longer doing it. Or restrict things too early and take forever getting to your setpoint. But the plus side is you might not need any new hardware to implement it, just fancier programming.

[bleclerc]

About the Single/Double solenoids, this is something that is often confused, and I think I've gotten it figured out how best to explain it.

The solenoids control a valve that will let air come out of port A or port B. The solenoids should be called "Single with Spring" and Double. The valve has 2 positions it can be in, and the solenoids (and spring) are what switch the valves positions.

Starting with the Double, each solenoid is going to push the valve to one of the two positions, so we'll label them A and B for which port they push to. If you fire solenoid A, air will come out of port A. Once the valve has been pushed into one of the positions, the only way to change it is to fire the other solenoid (assuming you have removed power from the first). So the valve will stay in the last position you left it in (critical for our brakes to remain... broke? braked? after the match has ended and we lose power)

So the difference with the Single is that you only have one solenoid. There is a default position, lets say A for this. So the spring is always pushing the valve to A. The solenoid thus is what will change the valve to output to B. The difference here is that you must continue applying power to hold it there. As soon as you let go of the power, the spring will move it back to the default. The Double just needs a quick amount of energy to switch, and then you can stop powering the solenoid.

So the confusion often happens when you see varying amount of hosing coming out of solenoids. This is because the hosing come out of the valve portion. These are technically called solenoid valves, so it has two parts to it. All of our valves (and likely 90%+ of all teams) are 5 port 2 position valves. That maps to 1 input (P), 2 outputs (A and B), and 2 exhausts (EA and EB).

There are different types of valves you can use, but this does not change how the Single and Double solenoids work.

So the fact that the one solenoid we have marked as 2 only has one hose coming out of it is a result of the fact that we're using pistons that have a spring return, thus we don't need to power output B to retract them, and is independent of the type of solenoid and valve that we have there.

I hope that explains everything sufficiently

-Ben

[Sean Raia]

This is just my first impression but it doesn't seem as though you've taken the KISS route

Interesting design to say the least, that drive train looks solid.

Good luck Xbot!

[dtengineering]

Actually, it looks pretty KISS to me... but then again we used something similar on our ball "launcher" in 08 and our "kicker" in 2010. Of course neither year required the precision that this year does. Judging from the videos... you've achieved it, though. Nicely done.

Hope I'm assigned to inspection on your field... I want to get a closer look!

Jason