paper: Bomb Squad Swerve Steering Code

[Jefferson]

Originally Posted by Ether

The spreadsheet implements Unicorn drive (four wheel independent unlimited steering and four wheel independent drive).

The spreadsheet does exactly that for a given set of inputs. Those inputs will be interpreted as operator interface inputs by most people. Given that mindset, I was trying to explain that the two sets of equations (spreadsheet and code) do not implement the same robot motion.

Originally Posted by Ether

So no matter what your operator interface is (4 wheel steering, Ackermann steering, or even tank-style steering), if you convert those operator-interface steering commands to the equivalent 3-degrees-of-freedom commands then you can duplicate it with the tester spreadsheet.

If you have to do significant calculations to describe your intended robot motion in the terms of the spreadsheet (FWD, STR, RCW), I don't see the utility of the spreadsheet to check your calcs. I would hate to describe the robot motion created by the Steer class in those terms. It is much more intuitive to consider the operator interface directly. The three degrees of freedom within those calcs are the steering angle, the point in Y on the robot where the turning radius exists (usually not varied in real-time), and the throttle.
So, for example, the robot's orientation only changes when the throttle is non-zero. The wheel angles can all change without any robot movement.

Originally Posted by Ether

Four-wheel-steering is what you get if you set cell A7 (strafe) equal to 0, and just play with cells A6 & A8 (forward/reverse & rotate). Try it and see.

This is not what I would describe as 4-wheel steering, nor is it what the Steer class implements. Our driver has a steering wheel and a joystick in hand. The steering wheel changes the steering angle and the joystick runs the throttle. Look at the code and see.