Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1999-04-05
2001-04-17
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S051000, C701S061000, C180S444000, C180S446000, C180S068100, C180S068400, C318S432000, C388S829000, C388S831000
Reexamination Certificate
active
06219603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering control apparatus for vehicle provided with a transmission ratio varying mechanism for varying a transmission ratio between a steering angle of a steering handle and a turn angle of wheels by driving force of an actuator.
2. Related Background Art
There are conventionally known steering control apparatus for vehicle provided with the transmission ratio varying mechanism capable of varying the transmission ratio between the steering angle of the steering handle and the turn angle of the wheels. For example, Japanese Laid-open Patent Application No. Sho 63-227472 discloses a mechanism capable of changing the transmission ratio by such structure that a prescribed gear mechanism connects an input shaft connected to the steering handle side to an output shaft connected to the tie rod side and this gear mechanism is driven by a motor as an actuator to vary the transmission ratio of rotations between the input shaft and the output shaft. On this occasion, a rotational angle position of the motor is detected and used in feedback control, whereby control of rotational angle position of the motor is carried out so as to match the rotational angle position of the motor with a target rotational angle position.
SUMMARY OF THE INVENTION
For carrying out the control of rotational angle position of motor as described above, it is common practice to set a high control gain so as to enhance the accuracy of position control. In a hand-off state where the driver keeps the hands off the steering handle, however, the steering handle side does not catch reaction of the driving force generated by the motor of the transmission ratio varying mechanism; in that state, the feedback control system becomes unstable and the steering handle might vibrate in the circumferential direction in certain cases.
The present invention has been accomplished in order to solve this problem and an object thereof is to provide a steering control apparatus for vehicle that can adequately suppress the circumferential vibration of the steering handle even in the hand-off state where the driver keeps the hands off the steering handle.
A steering control apparatus for vehicle is a steering control apparatus for vehicle comprising a transmission ratio varying mechanism for varying a transmission ratio between a steering angle of a steering handle and a turn angle of a wheel by driving force of an actuator, the steering control apparatus comprising: steering angle detecting means for detecting the steering angle of the steering handle; turn angle detecting means for detecting the turn angle of the wheel; target turn angle setting means for setting a target turn angle of the wheel according to the steering angle, based on a transmission ratio set according to a running condition of a vehicle; first control means for controlling a torque produced by the actuator, according to a deviation between the target turn angle and the turn angle detected by the turn angle detecting means; and second control means for controlling the magnitude of the torque produced by the actuator with respect to the deviation to a smaller value than that by the first control means when it is determined that the steering handle is in a handoff state.
In the normal steering state where the driver firmly grips the steering handle, the torque produced by the actuator is controlled according to the deviation under control of the first control means, whereupon the position control of the actuator is carried out with high accuracy, for example, by setting a high control gain.
On the other hand, in the hand-off state in which the driver keeps the hands off the steering handle or in which the force exerted on the steering handle is too small to stop the circumferential vibration of the steering handle, the second control means controls the magnitude of the torque produced by the actuator against the deviation to a smaller value than that by the first control means, thereby suppressing the circumferential vibration of the steering handle in the hand-off state.
In the steering control apparatus for vehicle, the second control means is adapted to estimate a force exerted on the steering handle by a driver, based on the torque produced by the actuator and the steering angle, and to determine whether the steering handle is in the hand-off state, based on the magnitude of the force thus estimated.
This configuration permits the force exerted on the steering handle by the driver to be estimated from the relation between the torque produced by the actuator and the steering angle of the steering handle which catches the reaction of this torque produced. The second control means determines that the steering handle is in the hand-off state where the steering handle can vibrate in the circumferential direction, for example, when the force thus estimated is smaller than a predetermined criterion for determination.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5423391 (1995-06-01), Shimizu
patent: 5513720 (1996-05-01), Yamamoto et al.
patent: 5568389 (1996-10-01), McLaughlin et al.
patent: 5887671 (1999-03-01), Yuki et al.
patent: 5913913 (1999-06-01), Okanoue et al.
patent: 5979587 (1999-11-01), Liubakka et al.
patent: 6072293 (2000-06-01), Shimizu et al.
patent: 63-227472 (1988-09-01), None
patent: 9-202252 (1997-08-01), None
Kojo Takahiro
Yamamoto Takashi
Cuchlinski Jr. William A.
Mancho Ronnie
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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