Hans Christiansene invented differential torque control to improve a
car's controllability when a driver is faced with radical steering
maneuvers or begins to skid or spin out of control. This comprises an
electronic sensor at the rear wheels that feed data to an onboard
computer. This computer control corrective torque applied to these
wheels to control spinout and skid. The torque control differential governs the torque balance on each propeller and provides some roll control of the vehicle. A bipolar control signal is applied to the integrator and then to the amplifier where it is added to the feedback signal. The speed of each motor is governed by a combination of speed demand and torque differential demand. The speed control circuits maintain a constant average speed of the two rotors under all conditions, while any speed is controlled by the torque control differential.
Standard power chairs use differential torque control with two wheels powered and two wheels cas-toring. They are also used in railways and many other industries.
