Electrical Power Assisted Steering System

a technology of electric power and steering system, which is applied in the direction of steering initiation, instruments, vessel construction, etc., can solve the problems of typical vehicle plus eps dynamic system being under damped in its free rotational response, and called “fishing” of the vehicl

US20140088835A1Active Publication Date: 2014-03-27TRW LIMITED
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2014-03-27
Patent Text Reader

Abstract

An electric power assisted steering assembly comprises a steering mechanism which operatively connects a steering wheel to the roadwheels of a vehicle, a torque sensing means adapted to produce a first output signal indicative of the torque carried by a portion of the steering mechanism, a means for producing a second output signal indicative from a signal indicative of the angular velocity of the portion of the steering mechanism, an electric motor operatively connected to the steering mechanism, a signal processing unit adapted to receive the two output signals and to produce therefrom an overall 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 overall torque demand signal includes a damping component that is dependent upon the second output signal. The means for producing the yaw damping component includes a filter having one pole and one zero, and in use the second signal is passed through the filter to produce the damping component, the frequency of the pole and zero being selected such that the filter provides a band between the pole and zero within which the phase of the filtered second signal and the velocity signal are further out of phase or in phase than within the band.
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Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a national stage of International Application No. PCT / GB2011 / 051988 filed Oct. 13, 2011, the disclosures of which are incorporated herein by reference in entirety, and which claimed priority to Great Britain Patent Application No. GB 1017893.7 filed Oct. 22, 2010, the disclosures of which are incorporated herein by reference in entirety.BACKGROUND OF THE INVENTION

[0002] This invention relates to electrical power assisted steering systems of the kind in which an electrical motor is adapted to apply an assistance torque to a steering component such as a steering column so as to reduce the driver effort required to control the vehicle.

[0003] In a simple electric power assisted steering system a torque sensor is provided which is arranged so that the level of torque in a steering column is measured. From this measurement a controller calculates the value of an assistance torque demand signal that is indicative of the torque ...

Examples

Embodiment Construction

[0031]A typical electric power assisted steering system is illustrated in FIG. 1 of the accompanying drawings. The system comprises an electric motor 1 which acts upon a portion of a steering column 2 through an (optional) gearbox 4. The electric motor 1 may act upon a different part of a steering gear such as a rack and pinion that connects the steering column to the road wheels. The steering column is connected at one end to a steering wheel 3 which can be turned by a driver to turn the road wheels and hence steer the vehicle. Of course, this is not to be taken as limiting to the scope of protection we are seeking, and other power assisted steering systems are envisaged to which the invention has application.

[0032]The steering column 2 carries a multiple output sensor 5 that is adapted to measure the torque carried by the steering column 2 that is produced by the driver of the vehicle as the steering wheel (not shown) and hence steering column is turned against the resisting force...