Trw Lucasvarity Electric Steering Limited

Andrew James Stephen Williams

Anthony Walter Burton

Russell Wilson Jones

Simon David Stevens

John M Ironside

John Nicholas Cheel

Russell Wilson-Jones

Kevin M McLaughlin

Steven John Horton

George Thomas Dibben

Angel Luis Andres Fernandez

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.

Electric power assisted steering apparatus

An electric power assisted steering system is disclosed in which a torque demand signal ( ) is generated and applied to an electric motor ( ) operatively connected to a steering mechanism ( ) in order to assist a driver of the vehicle when steering the vehicle. The torque demand signal ( ) includes a damping component that is dependent upon a measurement of torque T carried by the steering mechanism and a measurement of the angular velocity &ohgr; of the steering mechanism. The torque produced by the motor ( ) is not obtrusive during &ldquo;hands-on&rdquo; maneuvers but provides enhanced damping in other maneuvers such as a steering flick.

Electrical power assisted steering systems

An electric power assisted steering system is disclosed in which a torque demand signal ( ) is generated and applied to an electric motor ( ) operatively connected to a steering mechanism ( ) in order to assist a driver of the vehicle when steering the vehicle. The torque demand signal ( ) includes a damping component that is dependent upon a measurement of torque T carried by the steering mechanism and a measurement of the angular velocity &ohgr; of the steering mechanism. The torque produced by the motor ( ) is not obtrusive during &ldquo;hands-on&rdquo; manoeuvers but provides enhanced damping in other manoeuvers such as a steering flick.

Relating to electrical power assisted steering systems

An apparatus and method for controlling an electric steering assist system, which system provides assist in response to a steering control signal, the apparatus comprising: torque sensing means ( ) operatively connected to a vehicle hand wheel ( ) for providing a torque signal (Ts) indicative of applied steering torque, blending filter means connected to the torque sensing means ( ) for providing a blended filtered torque signal having a first functional characteristic at torque frequencies less than a blending frequency and a second functional characteristic at torque frequencies greater than the blending frequency, the blending filter means including a low pass filter ( ) which passes all frequencies below the blending frequency and a high pass filter ( ) which passes all frequencies above the blending frequency, steering assist means for providing steering assist in response to a control signal, control means operatively connected to the blending filter means for providing said control signal to the steering assist means in response to the blended filtered torque signal, and means ( ) whereby high frequency gain of the steering assist system is arranged to be low for on-center operation of the hand wheel and relatively higher for off-center operation.

Method and apparatus for controlling an electric powered assisted steering system using an adaptive blending torque filter

A method of calculating the position of the rotor of a motor ( ) in for example an electrical power assisted steering assembly is disclosed. The method comprises the steps of measuring the output shaft ( ) (i.e. steering column) position, and scaling the measured value to produce an estimated motor rotor position value. This estimated value will be relative to an arbitrary datum point, and so the method further includes steps of adding an offset value derived from low resolution measurements of rotor position obtained using Hall effect sensors provided on the motor. Offsets for compensating for backlash and (in a second embodiment) compliance can also be included. Thus, the method allows high resolution information from an output shaft sensor (e.g. a torque sensor with a position dependent output) to be combined with the low resolution output from the Hall effect sensors to produce a high resolution rotor position signal. A correction is also made to allow for &ldquo;staleness&rdquo; in the Hall effect sensor output when calculating the offsets by monitoring rotor speed.

Position sensing in brushless motor systems

A motor control strategy for use in combination with an electric motor ( ) having a number of phase windings ( ) is disclosed, the motor ( ) being adapted to produce an output torque in response to current in the windings comprising the steps of during normal operation generating a motor torque demand signal indicative of the output torque required from the motor ( ), applying a first set of currents to the windings of the motor in response to the motor torque demand signal to produce a first output torque from the motor and during a test operation to enable diagnostics to be performed generating a motor current demand signal indicative of the total current required in the motor windings ( ) and adjusting the currents applied to one or more of the windings in response to both the torque demand signal and the motor current demand signal, whereby the adjusted currents produced in the windings are substantially equal to the total current demanded by the motor current demand signal regardless of the value of the motor torque demand signal and the motor ( ) produces a second output torque substantially equal to the first output torque produced during normal operation.

Method of controlling an electric motor having a number of phase windings

A method of monitoring the operation of a brushless motor is disclosed. The method comprises the steps of monitoring the current flowing into or out of the windings of the motor using a current measurement circuit to produce an output signal indicative of the current; measuring the output of the current measurement circuit when the instantaneous current flow through the current measurement circuit is known to be substantially zero; and producing a modified output signal which is compensated for any differences between the actual measured output signal value and an ideal output signal value. The method enables any drift in the output signal to be compensated &ldquo;on-line&rdquo; whilst the is running.

Motor control

An electrical power assisted steering system is disclosed having a boost curve which has inverse symmetry about a zero input torque value, each half of the boost curve comprising a first portion defined by a first polynomial equation between a zero value and a first value, and a second portion defined by a second polynomial between a second value and a third value, in which the gradient of the first portion of the curve at the first value is equal to the gradient of the second portion of the curve at the second value. By storing values for the first, second and third values and the gradient of each polynomial at those values a smooth boost curve can be defined by storing only a small amount of parameters.

Growing community of inventors

West Midlands, United Kingdom

Andrew James Stephen Williams