Trw Limited

Trw Automotive Gmbh

Trw Lucasvarity Electric Steering Limited

Angel Luis Andres Fernandez

George Thomas Dibben

Kevin M McLaughlin

Andrew James Stephen Williams

An electric power assisted steering system comprises a steering mechanism which operatively connects a steering wheel to the road wheels of the vehicle, an electric motor operatively connected to the steering mechanism; a torque signal generator adapted to produce a torque signal indicative of the torque carried by a portion of the steering mechanism, a column velocity signal generator for producing a column velocity signal indicative of the angular velocity of the steering wheel or steering column and a signal processing unit adapted to receive the output signals from the sensing means and to produce therefrom a torque demand signal representative of a torque to be applied to the steering mechanism by the motor. The signal processing means includes a processing means which generates a torque damping component which is representative of the sum of a first column velocity term which is a linear function of column velocity and a second column velocity term which is a function of the square of column velocity, or a higher order factor and in which the torque demand signal is dependent upon the value of the torque damping component.

Electrical power assisted steering system

An electric power assisted steering system for a vehicle, comprising: a steering mechanism which operatively connects a steering wheel to road wheels of the vehicle, a torque sensor arranged to, in use, produce a torque signal indicative of the torque carried by a portion of the steering mechanism, an electric motor operatively connected to the steering mechanism, a signal processing unit arranged to, in use, produce from the torque signal a torque demand signal representative of a torque to be applied to the steering mechanism by the motor, the signal processing unit comprising a first calculating unit arranged to calculate an initial torque demand signal dependent on the torque signal, and a second calculating unit arranged to, in use, calculate a torque damping signal indicative of an amount the initial torque signal is to be damped in order to generate the torque demand signal, and a motor drive stage arranged to provide, in use, a drive current to the motor responsive to the torque demand signal, in which the second calculating unit comprises an input for a signal dependent upon the torque demand signal, a differentiator, arranged to, in use, differentiate the input signal dependent upon the torque signal and a high pass filter arranged to filter the input signal to reduce low frequency components thereof.

An electric power assisted steering apparatus for a vehicle, comprises a steering mechanism, which operatively connects a steering wheel to the road wheels of the vehicle, an electric motor operatively connected to the steering mechanism, a torque sensing means adapted to produce a first output signal indicative of the torque carried by a portion of the steering mechanism, a vehicle speed sensing means for producing a second output signal indicative of the speed of the vehicle, a signal processing unit adapted to receive the first and second signals and to produce a torque demand signal representative of a torque to be applied to the steering mechanism by the motor; and a motor drive stage adapted to provide a drive current to the motor responsive to the torque demand signal. The apparatus includes torque limiting means, arranged to limit the magnitude of the torque to be applied to the steering mechanism to a maximum of a value that increases in time from a first value to a second value at a rate that is dependent on the second signal. Additionally or alternatively, it may be arranged to limit the maximum torque to a value that increases from a first to a second value at a rate that varies with time.

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Rochester, MI, United States of America

Angel Luis Andres Fernandez