Three joint arm

[Peter Matteson]

Originally Posted by pfreivald

That's why our 2011 robot had a two-joint arm: reaching the floor and the top peg while fitting within the starting configuration. There were of course other ways to do that -- single-joint arm with an extender or forklift-type mechanism, but I don't know that they were in fact any easier or more elegant than what we came up with. (Some were faster, which mattered far, far too much! )

In 2011 we had both an extender to aid in picking up off the floor and a forklift style lift to reach the upper row. We thought this enabled the best and simplest driver control.

The driver drove the arm into a hard stop to go to the down position, to pickup he extended the claw out, as soon as he had the tube he released the extension and could rotate the arm up and raise the list to position at the same time without haveing to adjust to rotational joints. The extension had multiple effects, it kept the arm as short as possible so it wouldn't sway bounce or move as far during adjustments, it gave us a quick move to steal tubes if was were going at the same one as an opponent, protected the claw by keeping it inside the robot perimeter most of the time, and allowed us to hang middle row without raising the lift.

In my experience the easier it is for the driver to understand the movements the better they drive. 2 rotational joints allow multiple ways to get to the same position and creates many possible combinations. of how to get there. Which violates the very solid design rules that JVN outlined above.