Controlling a Mecanum drive with two joysticks?

[MrForbes]

I think it really isn't too difficult to make it work, you can use one 2-axis joystick to move the robot in the 4 directions or diagonally, and another single axis joystick to rotate the robot. The one's we've played with here were done that way, this thread

http://www.chiefdelphi.com/forums/sh...ad.php?t=50030

has some information about it and a link to the code for a vex controller. Both of the mecanum robots used the vex controllers, not FRC, although the big one did use the big drive motors and Victor speed controllers. Our big one is shown here

http://www.chiefdelphi.com/forums/sh...ad.php?t=59027

[Jeff K.]

We did this last year only using 3 axes. On the left joystick, it was overall translation, with x and y. It also controlled strafing sideways, forward, and diagonal. The right joystick just had the x axis, and it was for rotation. It was relatively easy to drive.

Programming it was another story. We used another person's code that wasn't a part of FIRST and worked off of that. You can find code for how to do it on the vex platform, and base it off that.

To prototype though, do it on VEX with a holonomic drive using omni wheels in the offseason. Same code and it's definitely cheaper.

Good luck

[AdamHeard]

Originally Posted by Jeff K.

We did this last year only using 3 axes. On the left joystick, it was overall translation, with x and y. It also controlled strafing sideways, forward, and diagonal. The right joystick just had the x axis, and it was for rotation. It was relatively easy to drive.

Programming it was another story. We used another person's code that wasn't a part of FIRST and worked off of that. You can find code for how to do it on the vex platform, and base it off that.

To prototype though, do it on VEX with a holonomic drive using omni wheels in the offseason. Same code and it's definitely cheaper.

Good luck

I've heard/seen this is a good way to do it.

If i remember right, a team even used a turntable type input and were rather pleased with that.

[UrsaMNet]

Team 1540 did this for the 2007 season. We too, spent a LOT of time trying to figure out how to get it to work best. Once we figured it out, we were astounded at how simple it can be.

Our robot had two joysticks. One controlled planar motion (pushing the joystick forward, moved the robot forward. Moving it sideways meant that the robot moved straight sideways). The other joystick controlled rotation (we only used the x-axis). Our team members picked this up pretty quickly, and it's a blast to drive.

Control wise, you can break the problem into two parts. We figured out how to control planar motion using one joystick, and wrote a function for it. Then we figured out how to do rotation, and wrote another function for that. Both of these easier problems can be easily figured out with a pen and paper to diagram out what inputs you have, and what outputs you'd want in that situation.

Then all we had to do was combine them! We started out simply averaging the values (weighted averages, actually). There are better ways to do this, but this gets you going quickly and easily. Once you've gotten that up and working, you can try to figure out optimizations which can dramatically increase the maximum speed/performance.

Mecanum drive is a lot of fun, I'm glad to see another team taking it on.

As a side note, you can setup the wheels on your base in two ways. In one arrangement, the rollers on the wheels will form an 'x' on the bottom of the robot. In the other arrangement, they'll form an 'o'. You can program both to work, but it's worth taking the time to think through what the advantages/disadvantages to each are, as the two aren't interchangeable.

I hope that's helpful. I'll admit I haven't looked at the whitepaper. Good luck!