[Russ Beavis]

There's no easy relationship between PWM command -> voltage across the motor (which is very linear for the Jaguar but not quite so linear for a Victor) -> output torque.

I encourage you to search the CD threads for similar posts. I know that you'll find a few white papers and embedded spreadsheets and tools to help understand DC brush motor modeling.

Without going into too much detail, a DC brush motor can be very accurately modeled as a series combination of 3 elements - winding resistance (R), winding inductance (L) and back EMF (E). The voltage across the motor (V) is given by the following.

V = E + iR + Ldi/dt = constant*PWM command (for a Jaguar)

The only other equations that you need to know are -

E=k*speed with k in Volts per radian/second
torque=k*i where k is the same # as above but in Newton*meters per Amp

(it's actually very interesting that the proportionality constant "k" is the same # in both V/(rad/sec) and Nm/A)

Happy math-ing!

Russ