Electric power assisted steering systems

摘要

An electric power assisted steering system is disclosed which comprises a steering shaft connected at one end to the handwheel and at its other end to at least one roadwheel, while an electric motor is connected to the steering a gearbox having a non-integer reduction gear ratio. Two sensors are also provided with one sensing the angular position of the motor rotor and the other sensing the angular position of the steering shaft. The presence of the non-integer gear ratio produces a beat frequency between the output of the two sensors from which an unambiguous measurement of the angular position of the steering shaft over a range of greater than one complete revolution can be made. The sensors may comprise either absolute position sensors or index-type sensors.