regarding torque biasing for an electronic differential, I tried something that actually worked quite well:
I built a little circuit with two potentiometer inputs, each 0-5V
One potentiometer is the "steering" or "bias" adjustment. It immediately goes into a simple inverting op-amp circuit with 1:1 gain.
The second potentiometer is the "throttle"
The output from the steering potentiometer goes into another op-amp circuit arranged as a differential amplifier with 1:1 gain. The second input for the differential amplifier is the throttle.
A second differential amp takes the inverted steering output and the throttle .
Basically, the outputs track up and down together when adjusting the throttle, or opposite from each other when using the steering.
While this is a very simple proof of concept, it shows that two different motor controls could get the outputs from the op-amp circuits described above to accomplish adjustable torque control:
1) right-left torque biasing using steering position as input
2) fore - aft torque biasing using a user adjustable knob (like WRC rally cars)
I'm working out some safety/bypass circuits, but this looks really promising.
