Development of a rotating-shaft torque sensor for automotive applications

The Ford Motor Company has supported work at Southampton University with the aim of producing a rugged noncontract shaft torque sensor, at a cost which will allow its use for automotive applications. The system described uses a novel capacitive torque sensor, which is attached to the rotating shaft. The capacitive sensor forms part of a rotating resonant circuit, which is excited across an airgap by means of inductive coupling. Variations in torque cause changes in the resonance frequency of the tuned circuit. The resonance frequency is detected as a change in referred impedance at the exciting coil.