Roller test on the Raptor's Claw

In preparation for the last off-season event CowTown ThrowDown, Team 148 has been kind enough to lend us their claw, with a follow-up challenge to make it work in time for this event.

Click Here to see test of the rollers on the Raptor's claw.

I think one thing to be aware of is how much work goes in to doing something as simple as adding a few buttons. It is something that is not quite so obvious, we simply cannot apply full voltage when a button is pressed. When the button is pressed the voltage has to ramp up and down. The other thing is that I now have enough functionality to create a claw class which manages the pneumatic as well as the rollers. When a button is pressed, it applies an angular acceleration of 112 radians per second, which works out to a quarter of second to ramp to full velocity. If you notice I kept pressing the buttons back and forth to demonstrate that I never exceed 112 radians when switching directions.

The properties of the rollers has been estimated with an angular velocity of approximately 4-5 revolutions per second.
^{RS-550 motor with 64:1 BaneBots transmission, so this is spec at 19300 rpm free, and 17250 peak efficiency 17250 / 64 = 287.5 = rps of motor / 64 reduction = 4.492 rps * 2pi = 28.22524}
What is creepy about this is that the motor at peak efficiency is claimed to rotate at 287 revolutions per second! Therefore, the Robo-Wranglers switched from the 16:1 to the 64:1 transmission. You can tell by the sound of the motor that it is fast, it reminds me of a dentist's drill. To take the physics a bit further the rollers are about 2 inches in diameter so this means the linear velocity x = pi(2) * 4 = 25.13 inches per second. With this speed it would take about 200ms (milliseconds) to go 5 inches. 200ms is a magic number where Grant Imahara once stated that this is the time for an average person to respond to a stimulous. In this test the actual ramp-up time is 250ms, so this adds about another 100ms to the 200ms and should be quick enough to pick up the tube, and slow enough to not put strain on the motor. We can adjust this as necessary.

One other small side note is that it was fun to wire this thing up myself, and going through this exercise it clicked for me how the pieces work together! It reminds me of the electric kits we use to do when we were kids. I think all software developers for FRC should go through this exercise eventually to have a better understanding of the interfaces that you are working on.