Trw Limited

Trw Automotive U.S. LLC

Trw Automotive Gmbh

Trw Lucasvarity Electric Steering Limited

Kevin M McLaughlin

Joseph D Miller

Engelbert Lu

Stuart Walter Parker

Russell Wilson Jones

Anthony Walter Burton

Andrew James Stephen Williams

Simon David Stevens

Mark William Gluch

Angel Luis Andres Fernandez

Paul H Kahler

Hristos K Mantjios

An electric power assisted steering system for a vehicle, comprising: a steering mechanism which operatively connects a steering wheel to road wheels of the vehicle, a torque sensor arranged to, in use, produce a torque signal indicative of the torque carried by a portion of the steering mechanism, an electric motor operatively connected to the steering mechanism, a signal processing unit arranged to, in use, produce from the torque signal a torque demand signal representative of a torque to be applied to the steering mechanism by the motor, the signal processing unit comprising a first calculating unit arranged to calculate an initial torque demand signal dependent on the torque signal, and a second calculating unit arranged to, in use, calculate a torque damping signal indicative of an amount the initial torque signal is to be damped in order to generate the torque demand signal, and a motor drive stage arranged to provide, in use, a drive current to the motor responsive to the torque demand signal, in which the second calculating unit comprises an input for a signal dependent upon the torque demand signal, a differentiator, arranged to, in use, differentiate the input signal dependent upon the torque signal and a high pass filter arranged to filter the input signal to reduce low frequency components thereof.

Electrical power assisted steering system

A method for controlling an electric motor includes the step of determining multi-phase voltage demand values. The method also includes the steps of determining a star voltage (vstar) of the electric motor and determining multi-phase voltage output command values as a function of the star voltage (vstar) and the multi-phase voltage demand values. The method further includes the step of supplying multi-phase voltage to the electric motor in accordance with the multi-phase voltage output command values energize the electric motor.

Method and apparatus for controlling an electric motor using star voltage modulation

A method and apparatus for determining a fault in an electric motor () determines a calculated star voltage (V) of the electric motor. The calculated star voltage (V) is compared to a measured star voltage (V) of the electric motor () to determine a star voltage error (V). The fault in the electric motor () is determined when the star voltage error (V) exceeds a predetermined maximum star voltage error (V).

Method and apparatus for determining faults in an electric assist steering system

The steering angle of a vehicle is monitored using position sensors of an electric motor of an electric power assisted steering (EPAS) system. A position of the electric motor corresponding to the straight-ahead, center position of the steering system is stored in non-volatile memory during a steering calibration procedure, such as an end-of-line calibration in a vehicle assembly plant. Following power loss due to a dead battery, a steering angle zeroing procedure performed in a vehicle stability control (VSC) system generates a center position with enough accuracy to be within one electrical cycle of the motor. The pre-stored electric motor position is then used to determine the electrical cycle where the center position was located, and accurate monitoring of steering angle is resumed.

Recovery of calibrated center steering position after loss of battery power

A method for controlling an electric assist motor ( ) for providing steering assist in response to a sensed torque signal (&tgr; ) includes the step of filtering the sensed torque signal to provide a low frequency torque signal (&tgr; ) and a high frequency torque signal (&tgr; ). A low frequency assist torque signal (&tgr; ) is determined as a function of the low frequency torque signal (&tgr; ). A high frequency assist gain signal (K ) is determined as a function of the sensed torque signal (&tgr; ) and a sensed vehicle speed (&ngr;). The high frequency assist gain signal (K ) is applied to the high frequency torque signal (&tgr; ) to determine a high frequency assist torque signal (&tgr; ) A torque command signal (&tgr; ) is determined as a function of the low frequency assist torque signal (&tgr; ) and the high frequency assist torque signal (&tgr; ) The electric assist motor ( ) is commanded to provide steering assist in accordance with the torque command signal (&tgr; ).

Method and apparatus for controlling an electric assist motor using a modified blending filter

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 assist steering system ( ) includes a torque sensor ( ) that provides an applied torque signal ( ) indicative of applied steering torque. A motor position sensor ( ) provides a motor position signal ( ) indicative of the relative position between the rotor and the stator of an AC permanent magnet electric assist motor ( ). A first controller ( ) controls energization of the electric assist motor and a second controller ( ) calculates a DQ vector value in response to applied steering torque and motor position. The second controller ( ) also transforms the monitored motor current and position into DQ values. The second controller ( ) compares the DQ values responsive to applied steering torque with the DQ value from monitored motor current and position. The electric assist motor ( ) is disabled if the comparison indicates inconsistent results.

Apparatus and method for controlling an electric motor

A motor controller includes a summing circuit (186) for summing a motor current command signal (i.sub.rcmd) with a motor current feedback signal (i.sub.s) and for providing an error current command signal (.DELTA.i.sub.cmd) having a value functionally related to the difference between the motor current command signal and the motor current feedback signal. A notch filter (200) filters the error current command signal and provides a filtered current command signal. The notch filter (200) is adapted to notch out frequencies from the error current command signal about the resonant frequency of a motor (28). A drive circuit (120, 204) energizes the motor (28) in response to the filtered current command signal. A motor current sensor (97) is used for sensing motor current and providing the motor current feedback signal (i.sub.s).

Electric assist steering system having an improved motor current

A motor controller controls the operation of an electric motor (28). The motor controller includes sensors (30, 97, 102) for sensing at least one dynamic operating characteristic of the motor and for providing a signal indicative of the at least one sensed dynamic motor operating characteristic. A variable gain regulator (190) receives a current command request signal having a value and provides a motor current control signal having a value functionally related to the value of the received current command request signal and a gain control value. A gain scheduler (196) is operatively coupled to the variable gain regulator (190) and to the sensor (30, 97, 102) for providing the gain control value to the variable gain regulator (196) in response to the sensed at least one dynamic motor operating characteristic to thereby control the amount of gain of the variable gain regulator (190). The motor controller further includes a drive circuit (204, 120) operatively connected to the variable gain regulator (190) and the motor (28) for energizing the motor in response to the motor current control signal.

Current control values are established for an electric motor including providing a table of motor current control values as a function of motor operating angle, providing a torque request signal indicative of the desired amount of torque to be supplied by the motor, and providing a torque command signal having a value functionally related to the torque request signal and a feed-forward torque signal. The motor operating angle is monitored and the motor is energized using current control values from the table in response to the torque command signal. The amount of torque ripple experienced by the motor is measured when the motor is energized. The measured torque ripple is filtered using a time domain filter and a time domain filtered torque ripple signal is provided. The time domain filtered torque ripple signal is then averaged and the averaged time domain filtered torque ripple signal is then filtered using a spatial domain filter, the spatially filtered averaged time domain filtered torque ripple signal is the used as the feed-forward torque signal. The current control values output to the motor is stored as a function of motor operating angle for the provided torque request value when the torque ripple value is less than a predetermined value.

Method and apparatus for reducing torque ripple in an electric motor

A control arrangement for an electric assist steering system having a variable reluctance motor (26) includes a motor position sensor (54) and an applied steering torque sensor (110). A controller determines a desired motor torque assist value in response to the applied steering torque. The controller modifies the desired torque assist value to linearize the gain relationship between the desired torque assist value and motor torque output. A plurality of look-up tables have a plurality of motor current values versus motor position values stored therein. The controller selects a first (T1) look-up table corresponding to a torque value less than the modified motor torque assist value and a second (T2) look-up table corresponding to a torque value greater than the modified motor torque assist value. A first motor current value (I1) and second motor current value (I2) are determined by interpolation. A final motor current value (ICMD) is determined by interpolating between the first and second determined motor current values. A motor control signal is provided in response to the determined final motor current value.

Method and apparatus for controlling an electric assist steering sysem

A steering assist system (10) providing assist in response to a steering control signal includes a vehicle speed sensor (150) for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed and a torque sensor (110) operatively connected to a vehicle hand wheel (12) for providing a torque signal indicative of applied steering torque. A controller (120) is connected to the vehicle speed sensor (150) and to the torque sensor (110). The controller (120) includes a first set of torque-in vs. torque-out assist values (132) associated with a first vehicle speed and a second set of torque-in vs. torque-out assist values (130) associated with a second vehicle speed. The controller (120) provides the steering control signal in response to applied steering torque and having a value functionally related to (i) the vehicle speed signal and (ii) both the first set and second set of torque-in vs. torque-out assist values.

Method and apparatus for controlling an electric assist steering system

A steering assist system (10) providing assist in response to a steering control signal includes a vehicle speed sensor (56) for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed and a torque sensor (44) operatively connected to a vehicle hand wheel (12) for providing a torque signal indicative of applied steering torque. A blending filter (70, 71) is connected to the torque sensor and provides a blended filtered torque signal having a non-linear characteristic at torque frequencies less than a blending frequency and a linear characteristic at torque frequencies greater than the blending frequency. The blending filter establishing the blending frequency at a value functionally related to vehicle speed. Steering assist motor (28) provides steering assist in response to a control signal. The control signal is provided in response to the blended filtered torque signal. The blending filters filtering the torque signal so as to maintain a selectable system bandwidth during system operation.

A control arrangement for an electric assist steering system having a variable reluctance motor (26) includes sensing (54) motor position and sensing (110) applied steering torque. A controller determines a desired motor torque assist value in response to the applied steering torque. A plurality of look-up tables are provided having a plurality of motor current values versus motor position values stored therein. The stored motor current values are functionally related to motor position values. The controller selects a first (T1) and second (T2) torque look-up table from the plurality of look-up tables. The first look-up table corresponds to a torque value less than the desired motor torque assist value. The second look-up table corresponds to a torque value greater than the desired motor torque assist value. A first motor current value (I1) is determined by interpolating between two current values corresponding to two motor positions stored in the first look-up table closest to the sensed motor position. A second motor current value (I2) is determined by interpolating between two current values corresponding to two motor positions stored in the second look-up table closest to the sensed motor position. A final motor current value (ICMD) is determined by interpolating between the first and second determined motor current values. A motor control signal is provided in response to the determined final motor current value.

A steering assist system (10) providing assist in response to a steering control signal includes a vehicle speed sensor (56) for sensing vehicle speed and for providing a speed signal having a value indicative of the sensed vehicle speed and a torque sensor (44) operatively connected to a vehicle hand wheel (12) for providing a torque signal indicative of applied steering torque. A controller is connected to the vehicle speed sensor (56) and to the torque sensor (44). The controller includes an adaptive torque filter (80) that maintains a selectable system bandwidth independent of gain changes and vehicle speed changes. The adaptive filter (80) recovers any gain reduction by increasing the frequency of a filter pole.

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Troy, MI, United States of America

Kevin M McLaughlin