Abstract: A method of calculating the position of the rotor of a motor (1) in for example an electrical power assisted steering assembly is disclosed. The method comprises the steps of measuring the output shaft (2) (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.

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: A circuit is provided for testing a drive stage of an actuator, such as a motor of an EPAS system. A power supply circuit comprises a contact for supplying normal drive stage current and a resistor for supplying reduced drive stage current before the normal current is supplied. A measuring circuit measures a drive stage electrical parameter such as supply voltage and a comparator compares this with an acceptable value. If the measured parameter corresponds to a current through the drive stage which is different from an expected value, a fault is signaled and the contact is prevented from closing.

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: A gearbox monitoring apparatus is disclosed for use in combination with a gearbox (4) which provides a connection between an input shaft (3) driven by a motor (1) and an output shaft (2), said gearbox monitoring apparatus comprising a first position sensing means (11) and a second position sensing means (12), said first and second position sensing means generating a respective first and second output signal, said first output signal being representative of the angular position of the input shaft and said second output signal being representative of the angular position of the output shaft, a torque signal generating means (6) which generates a third output signal representative of the torque carried by the gearbox (4), and signal processing means (15) adapted to receive said output signals and to process said output signals to produce one or more modified output signals representative of the wear in the gearbox.

Abstract: A control system comprises a controller for controlling an actuator, for instance of an electrically power assisted vehicle steering system. An unstable circuit, such as first and second cascade connected integrators has an input connected to the controller and an output connected to a detector, which signals an error when the output signal of the unstable circuit is outside an acceptable range. During normal operation, the controller supplies a signal to the unstable circuit such that its output signal remains within the acceptable range. The error signal may be used to disable the actuator, for instance so as to remove power assistance from steering system.