Mecanum Wheel Confusion

[nickcvet89]

Hey, I am a little confused about the mecanum wheels program, specifically the difference between the Cartesian and Polar option. I am having a hard time understanding the differences between the two and why you would choose one over the other. If someone would be able to explain the differences of the two, it would be greatly appreciated.

[Alan Anderson]

Both polar and cartesian varieties have a "rotation" parameter. That determines how the robot spins around its center of rotation.

The difference is in how the translational motion is specified. Cartesian control has separate X (left/right) and Y (forward/backward) parameters. Polar control uses a vector with a direction and a magnitude, saying how fast to move in the specified direction. Polar also has an optional parameter that can make the robot move in absolute field directions instead of relative to the robot's "front" side, if you implement a gyro properly.

[j.cole]

We use cartesian just because its easier and it works for what we need so I suggest you use cartesian for that reason. If you really want to use polar go ahead the only advantage is that you can wire a gyro into it.

[Ether]

Originally Posted by j.cole

If you really want to use polar go ahead the only advantage is that you can wire a gyro into it.

Last year's LabVIEW had a gyro input on the Cartesian. Did they remove it in 2011? If so, anybody know why??

(I'd look it up myself but I don't have 2011 FRC LabVIEW installed here)

[Alan Anderson]

Originally Posted by Ether

Last year's LabVIEW had a gyro input on the Cartesian. Did they remove it in 2011?

My mistake -- the gyro input is present in the Cartesian version, and is absent from the Polar version.

(I was going from outdated memory and hearsay. When we first used the holonomic drive vi, the gyro support had not yet been added.)

[nickcvet89]

Ahh, OK thanks for the feedback. I decided to go with Cartesian just like most of the teams.