Drivetrain Control Systems

[z_beeblebrox]

Just curious and looking for ideas:

How does your team control your drivetrain? Tank, arcade or something different? What is your OI? Any feedback or closed-loop control? Extra features like automatic shifting, etc.? How do you control it in autonomous? Why did you do it like you did? How well does it work?

About my team:

Last year, we used the default arcade drive code with the turn and drive rate controls divided between the sticks of a gamepad. We had no autonomous driving or sensor feedback. Our control system worked OK, given the limitations (terrible turning) of the 4-wheel drive we built.
This year, we are using a 6-wheel dropped center wheel drivetrain with shifting transmissions. Based on the experience of our mentors and other successful Arizona teams, we decided to modify an RC pistol grip controller for our OI. (After driving it for a while, I never want to go back to gamepads) At first, we tried the same sort of arcade drive code as last year. It worked well enough to control the robot, but made it difficult to do smooth, fast movements (although lack of driver practice may have contributed to that).
Now, our control system is based on the pseudocode that a 254 mentor posted here. This system lets you control turn radius instead of turn rate, making the robot behave more like a car. Everyone who drives the robot is impressed by its smooth, precise turning at high speeds.
Over the next few days, we plan on implementing PID speed control with left and right encoders to make the robot drive straight without operator corrections. We are also working on driving to pick up discs in the autonomous period. This will use a trapezoidal speed profile generator and a speed PID controller for each side.