Pneumatics Resources

[Daniel Bathgate]

Whoa, another team that tried mid positions their rookie year! And to the best of my (limited) knowledge, you need to use two solenoids. One controls the direction of the movement, and an upstream solenoid with the exhausts blocked either lets air into the piston or holds it in place. But learn from our mistake - you really don't want to. The pneumatics are designed to be either all the way in or all the way out. What we forgot is that air will compress, and so if you try and hold a piston in the middle, any changing forces on the piston will cause the position to change. We made an articulated arm using only pneumatics last year that we had to remove due to massive weight problems, but it was entirely uncontrollable. I'm sure others could do a much better job, but pneumatics are really not the best choice if you want any positions other than all the way in or all the way out.

As for resources? The FIRST pneumatics manual is the best starting place, which you already found. You should also look at Bimba, the supplier for pistons for FIRST. Speifically, look at the Original Line Cylinders catalog. Only certain piston sizes are FIRST legal, but it should give you an idea of what is available and how to choose pistons. The force provided is a function of the bore size and line pressure, which is regulated to 60 psi on FIRST robots. Therefore, knowing the force required and the required stroke length should be all you need to know to choose a cylinder.