Steering-torque sensor: Notes

The steering-torque sensor digitally senses the steering torque applied by the driver. The operating range is 4 steering wheel turns (corresponds to 1440°).

Fig 1: Identifying Steering-Torque Sensor

Courtesy of BMW OF NORTH AMERICA, INC.

The steering torque sensor contains 2 sensors (redundancy). Both sensors use the principle of the Hall effect (Hall effect sensor with magnetic wheel).

The steering torque causes the torsion bar spring to twist. In doing so, the torsion bar transfers the steering momentum to the pinion. Both sensors deliver a sine-wave signal and cosine-wave signal. The steering torque applied by the driver is determined from the signals. The two sensors work independently of one another. The 2nd sensor is present due to the higher availability of the system (redundancy). The sensors digitize the determined data. The signals are transferred across a redundant twin-wire connection. Both sensors are supplied with voltage by the EPS control unit.

The following other control units communicate with the electromechanical power steering:

Fig 2: Steering-Torque Sensor Communication Diagram

Courtesy of BMW OF NORTH AMERICA, INC.