Abstract: 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 (20) operatively connected to a vehicle hand wheel (12) for providing a torque signal (TS) indicative of applied steering torque, blending filter means connected to the torque sensing means (20) 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 (70) which passes all frequencies below the blending frequency and a high pass filter (71) 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 s

Abstract: 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.

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: An electrical power-assisted steering system is disclosed comprising an electric motor connected through a gearbox to act on a steering mechanism of the vehicle, the electric motor having a plurality of phase windings connected to a star point and switching means 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 windings, and an open position which prevents current flowing in a respective phase winding, The system incorporates a safety circuit operative when a fault develops to smooth out the transition between the presence and absence of servo support in assisting and not assisting by providing a prescribed period of damped operation as part of a shut-down phase.

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 electric power assisted steering system is disclosed in which a torque demand signal (8) is generated and applied to an electric motor (1) operatively connected to a steering mechanism (5) in order to assist a driver of the vehicle when steering the vehicle. The torque demand signal (8) 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 (1) is not obtrusive during “hands-on” maneuvers but provides enhanced damping in other maneuvers such as a steering flick.

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 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.

Abstract: A controller for an electric power assisted steering system comprises a drive circuit (2) for controlling current to a motor (1) and a data processor (8) for controlling the motor current and hence assistance torque. A circuit (9) generates a current limit which is a monotonically decreasing function of vehicle speed. A comparator (6) compares motor current with the current limit and switches off the drive circuit (2) if the current limit is exceeded.

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 control strategy for a multiple phase brushless motor (1) is disclosed in which the top (2, 3, 4) and the bottom (5, 6, 7) switching devices in two arms of the motor bridge are driven using complementary pulse width modulated waveforms, so that the top device (2, 3, 4) in one of the arms is in the ON state while the bottom device (5, 6, 7) is in the OFF state and vice versa. In an alternative arrangement, the control strategy described hereinbefore is used at high motor speeds while at low motor speeds a conventional modulation scheme is used in which a top switching device (2, 3, 4) in one arm of the bridge is in the ON state and a bottom device (5, 6, 7) in a different arm of the bridge is pulse width modulated. In another aspect, a method of calculating the position of the motor rotor is disclosed.

Abstract: A control strategy for a multiple phase brushless motor (1) is disclosed in which the top (2, 3, 4) and the bottom (5, 6, 7) switching devices in two arms of the motor bridge are driven using complementary pulse width modulated waveforms, so that the top device (2, 3, 4) in one of the arms is in the ON state whilst the bottom device (5, 6, 7) is in the OFF state and vice versa. In an alternative arrangement, the control strategy described hereinbefore is used at high motor speeds whilst at low motor speeds a conventional modulation scheme is used in which a top switching device (2, 3, 4) in one arm of the bridge is in the ON state and a bottom device (5, 6, 7) in a different arm of the bridge is pulse width modulated. In another aspect, a method of calculating the position of the motor rotor is disclosed.

Abstract: A video camera or equivalent sensor is mounted on a vehicle and used to detect the lane markings on the road (usually the white painted lines). An associated signal processor (11) estimates the vehicle's lateral position in relation to the lane markings. An electric motor (4) coupled to the steering mechanism (1) is used to provide a torque input to the steering which may either assist or oppose the steering torque from the driver. The processor (11) is designed to assist the driver to maintain the vehicle's lane position by holding the vehicle at a set-point using a biasing torque. This simulates the effect of the lane being cambered upwards towards the lane edges. However the driver is able to override or cancel the effect if the driver applied steering torque exceeds a prescribed torque threshold.