Electric power steering control with torque ripple and road dist

Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control

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Details

318432, 318433, 180 62, 180 624, 180234, 180400, 180412, 180446, B62D 504

Patent

active

061225797

ABSTRACT:
An electric power steering control for a motor vehicle reduces motor torque ripple and road generated disturbances communicated to the vehicle handwheel while promoting system stability. In deriving an output command torque signal to the EPS motor, the control (1) derives an electric motor speed signal, (2) differentiates the electric motor speed signal, (3) stores a schedule of gain as an increasing function of electric motor torque, (4) modifies the differentiated estimated electric motor speed signal in response to the gain to provide a damping correction value and (5) derives the output command signal responsive to the damping correction. In a preferred embodiment, the control (1) stores power assist torque data as a function of handwheel torque and vehicle velocity, (2) provides a vehicle velocity signal, (3) provides a handwheel torque signal, (4) modifies the handwheel torque signal in response to the damping correction value, (5) derives a power assist torque value from the stored power assist torque data in response to the vehicle velocity signal and the modified handwheel torque signal and (6) derives the output command signal from the power assist torque value. The control may use an electric motor voltage signal as an estimate of electric motor speed and, for high torque loads, may use the pulse on-time parameter in a pulse width modulated, current switching control to represent the voltage of the controlled electric motor, and therefore the estimate of electric motor speed, so that no additional sensor is needed. The control may use separate stored relationships between the pulse width on-time and electric motor voltage for different commutation modes of the pulse width modulated, current switching control.

REFERENCES:
patent: 5444622 (1995-08-01), Takeshima et al.
patent: 5448482 (1995-09-01), Yamamoto et al.
patent: 5668721 (1997-09-01), Chandy
patent: 5668722 (1997-09-01), Kaufmann et al.
patent: 5704446 (1998-01-01), Chandy et al.
patent: 5719766 (1998-02-01), Bolourchi et al.
"Development of Electric Power Steering", Yasuo Shimizu and Toshitake Kawai, Honda R&D Co., Ltd., #910014, pp. 105-119, Date Unknown.
"The Next Generation of Vehicle Power Steering" NSK-RHP, Apr., 1997, pp. 1-7.
"Electric Power Steering (EPS)", Honda Accord Brochure, Japan, 1998, pp. V-6 thru V-12, No Month.

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