Trw Lucasvarity Electric Steering Limited

Trw Limited

Anthony Walter Burton

Andrew James Stephen Williams

Russell Wilson Jones

Simon David Stevens

Russell Wilson-Jones

John M Ironside

John Nicholas Cheel

Kevin M McLaughlin

Adam John Heenan

Steven John Horton

Andrew Dennis Barton

Marie Saunier

Tom Michael Richard Ernest Roberts

A method of controlling an electric motor in an electric power assisted steering system, the motor being arranged so as to apply a force to part of a steering mechanism of a vehicle, in which the method comprises calculating a force demand indicative of an assistance force dependent upon the torque applied by a user (T) to the steering mechanism that it is to be applied to the steering mechanism to reduce the exertion required by the user to steer the vehicle; combining the force demand with an overlay force demand (T) indicative of a force which it is desired to overlay over the assistance force, to generate a combined assistance force (T); and controlling the motor according to the combined assistance force, such that together with the force applied by the user, a total force is applied to the steering mechanism, in which, in order to generate the combined assistance force the torque applied by the user is subjected to a non-linear boost function and in which the overlay force demand is combined with the force demand such that, for an arbitrary change in the overlay force demand the change in the total force is independent of the torque applied by the user over a range of torques applied by the user.

Controlling motors in electric power assisted steering systems

An electric assisted steering control strategy for a steering system for a vehicle is arranged to assist the driver in controlling the vehicle during a split mu braking operation. The steering is provided with assistance being based on at least one operational variable representing a corrective steer angle for the vehicle which is added to a main assistance torque via a driver feedback controller, and the strategy is adapted to employ an estimate of yaw moment of the vehicle as the operational variable, the yaw moment being determined by processing the speed of wheels on opposite sides of the vehicle.

Steering control during split mu braking

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

An electric power assisted steering system of the kind in which an electric motor is operatively connected to a steering assembly through a gearbox to apply an assistance torque to the steering assembly and in which the steering assembly includes a steering column coupled at one end to a driver's handwheel and at the other end to steerable wheels, a means being provided for generating a signal representative of the velocity of rotation of the steering column. The system includes a high pass filter which is adapted to generate, for frequencies below a prescribed threshold, a signal at least approximately proportional to steering column acceleration and representative of the inertia of the rotor of the electric motor, the latter signal being arranged to be used to compensate for the motor rotor inertia in an overall assistance torque demand as developed by the system.

Compensation for motor inertia in electric power assisted steering systems

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.

Growing community of inventors

Birmingham, United Kingdom

Anthony Walter Burton