A vehicle steering device may include a rotatable input shaft, a motor in
communication with an input augmentation shaft, the input augmentation
shaft and the input shaft sharing a longitudinal axis, and the motor
further having a stator stationary with respect to rotation of the input
shaft. The vehicle steering device may further include a differential
mechanism for providing variable ratio steering to the steering device.
The differential mechanism may be a harmonic drive differential or a
planetary gearing system. In one embodiment, an external wave generator
may be used within the harmonic drive differential gearing mechanism. The
vehicle steering device may include a sensorless synchronous machine.