6-wheel rover controller

[sees1]

I realize a six-wheel controller (6 x 4) for lunar rover on ros2_controller base now and maybe it relevant for this repo.
I can modify steering controller library or write controller from scratch.

[christophfroehlich]

Can you outline the kinematics of such a rover? It isn't a skid steer, you think of a rocker-bogie suspension system?

[sees1]

yeah, like rocker-bogie with front, middle and rear pair of wheel, where front and rear wheels are steerable and turn in the same direction.

[christophfroehlich]

Do you need other kinematic equations like described here?
If yes, please start with a PR updating the docs.

Then: we could implement this by refactoring the steering_controllers_library by not implementing the resulting vehicle-kinematics in the lib, but only axis-specific kinematics and the composition is done in the respective controller implementations. This would also help here #692. But this is a bigger change as what you are asking for.