Abstract: An angular position sensor (1) suitable for use in combination with the rotor of an electric motor comprising both absolute and incremental encoders (3) where a first signal of the absolute encoder produces a period corresponding to an electric revolution of the motor and less than a mechanical revolution of the rotor, a second output of the incremental encoder varies periodically over a complete revolution of the rotor, where the two signals provide sufficient information to determine the absolute mechanical position of the rotor. Typically, transitions in the first output signal combined with the state of the second output signal provide such information.

Abstract: An optical displacement senor includes a source of optical radiation, a two-dimensional array of radiation detectors, and at least one modulating element disposed between the source and detector. The modulating element has alternating first and second modulating regions circumfrentially spaced around a central axis thereof. The modulating element is displacement relative to the array of detectors so that the detector array forms a two-dimensional image of the first and second regions of the modulating element of array. A data processor is connected to the detector array and is adapted to indentify the orientation of at least two different radially extending edges of regions on the modulating element from the two-dimensional image and also to determine the position of the centre of the element from the determined orientation of the edges.

Abstract: An optical displacement sensor includes a source of optical radiation, a two-dimensional array of radiation detectors, and at least one modulating element disposed between the source and detector. The modulating element has alternating first and second modulating regions circumferentially spaced around a central axis thereof. The modulating element is displaceable relative to the array of detectors so that the detector array forms a two-dimensional image of the first and second regions of the modulating element of the array. A data processor is connected to the detector array and is adapted to identify the orientation of at least two different radially extending edges of regions on the modulating element from the two-dimensional image and also to determine the position of the centre of the element from the determined orientation of the edges.

Abstract: A motor control strategy for use in combination with an electric motor (1) having a number of phase windings (201, 202, 203) is disclosed, the motor (1) 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 (1), 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 (201, 202, 203) 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 regardl

Abstract: In an electric power assisted steering system, the output signal from a motor position sensor (9) comprising a number of Hall effect devices (A,B,C) or the like is combined with an index signal from a sensor (108) connected to the steering column shaft (1) or the rack (6) or a yaw sensor or other angular position dependent device to produce an accurate measure of steering angle relative to the straight ahead position. In a preferred arrangement, transitions in the Hall effect sensor output are used to drive a counter (106) which is reset whenever the index signal is produced to ensure it does not drift out over a period of time. Most conveniently, the index signal corresponds to the steering gear straight ahead position.

Abstract: 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.

Abstract: An electrical power-assisted steering system is disclosed comprising a brushless electric motor (1) which has a plurality of phase windings connected at a start point and in which a switching means (13) such as a relay is provided in at least one phase of the motor, the switching means being movable between a closed position in which current is able to flow in the phase winding and an open position which prevents current flowing in the respective phase in the event of a fault. Also disclosed is a substantially rigid connector assembly (19) onto which is mounted the switching means (13), conductors (20) for connecting the motor phase windings and a motor position sensor (21) to an associated motor control means (6), the connector acting as a support for the motor stator, which simplifies the steps involved in assembly.

Abstract: An electrical power-assisted steering system comprising a brushless electric motor which has a plurality of phase windings connected at a star point and in which a switching device such as a relay is provided in at least one phase of the motor, the switching device being movable between a closed position in which current is able to flow in the phase winding and an open position which prevents current flowing in the respective phase in the event of a fault.

Abstract: An optical displacement sensor is used to measure the rotary displacement between two shafts which rotate together. By connecting the shafts together by means of a torsion bar, the sensor may be used to measure transmitted torque. The sensor comprises first and second coaxial discs mounted on the shafts and having slots formed therein. A light source directs light through the slots onto an array of photodetectors and a data processor determines the displacement or torque from the positions on the array of images of the slot edges.

Abstract: An optical displacement sensor is used to measure the rotary displacement between two shafts which rotate together. By connecting the shafts together by means of a torsion bar, the sensor may be used to measure transmitted torque. The sensor comprises first and second coaxial discs mounted on the shafts and having slots formed therein. A light source directs light through the slots onto an array of photodetectors and a data processor determines the displacement or torque from the positions on the array of images of the slot edges.