The Hardest Drive System To Program:

[Ether]

Originally Posted by Siri

I'd say Unicorn drive is up there. There's so many modes available: tank (uncommon if snake works), full crab (all wheels pointed same direction), snake (front & back point opposite directions), center spin, arbitrary center spin, each potentially with x and y-orientation.

You left out the most interesting one: full 3-degree-of-freedom control, like a mecanum or omni.

Originally Posted by rahilm

There are other types of swerves, including ones where each wheel is rotated independently (allows greater maneuverability and less skidding and much more complicated programming)

A swerve with four-wheel independent steering and wheel speed control allows the vehicle to be programmed to behave much like a mecanum, but without the traction limitations.

The procedure for calculating the wheel speed and steering angle for each of the 4 wheels is presented here.

For those who like to have a deeper understanding, the derivation of those equations is given here.