Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
1999-10-12
2001-11-27
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S041000, C701S071000, C303S146000
Reexamination Certificate
active
06324445
ABSTRACT:
This application claims priority under 35 U.S.C. Sec. 119 to No.10-307825 filed in Japan on Oct. 13, 1998, the entire content of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a yaw rate detecting system for a vehicle, and more particularly to an apparatus and method for detecting the yaw rate of the vehicle for use in a vehicle motion control system.
2. Description of the Related Arts
Recently, a system for controlling a vehicle motion characteristic, particularly a turning characteristic of a vehicle, has been noted, and a vehicle motion control system which is adapted to directly control a rotating moment by controlling a difference of braking force applied to left and right wheels, is now on the market. For example, when it is determined that the excessive oversteer occurs during cornering, the braking force will be applied to a front wheel located on the outside of the curve in the vehicle's path for example, to produce a moment for forcing the vehicle to turn in the direction toward the outside of the curve, i.e., an outwardly oriented moment, in accordance with an oversteer restraining control which may be called as a vehicle stability control. When it is determined that the excessive understeer occurs while a vehicle is undergoing a cornering maneuver, for example, the braking force will be applied to force the vehicle to turn in the direction toward the inside of the curve, i.e., an inwardly oriented moment, in accordance with an understeer restraining control, which may be called as a course trace performance control. The above described oversteer restraining control and understeer restraining control as a whole may be called as a steering control by braking. Accordingly, irrespective of brake pedal operation, the braking force applied to each wheel is controlled in response to a comparison of a desired yaw rate and an actual yaw rate, for example.
In the vehicle motion control system as described above, a sensor for detecting a vehicle yaw rate is employed, as described in Japanese Patent Laid-open Publication No.5-314397, for example. It is stated in that Publication that a prior apparatus for processing a signal output from a sensor neglects compensation for drift component included in the signal output from the sensor, so that an apparatus for processing the sensor signal has been proposed so as to calculate an accurate yaw rate irrespective of the drifted amount of the yaw rate sensor. In practice, a zero point signal of the yaw rate sensor is renewed to provide such a relationship that each value of steering angle of positive or negative value within a certain time period and each value of yaw rate of positive or negative value within a certain time period will coincide with each other, under a certain running condition. Also proposed is such a method that an output of the yaw rate sensor is renewed to be zero, in the case where an estimated generating yaw rate estimated in response to the output of the yaw rate sensor, e.g., steering angle, speed in the longitudinal direction, and vehicle characteristic, is smaller than a predetermined allowable yaw rate error, under such a running condition that the yaw rate is not generated, as in the case where the vehicle is running on a straight road at a low speed.
According to the apparatus for processing the sensor signal, however, an output of a steering angle sensor with low resolution is directly used for renewing the zero point. Therefore, it is impossible to set or renew the zero point signal accurately for the yaw rate sensor. Particularly, in calculating a vehicle side slip angle for use in the steering control by braking, errors in the output of the steering angle are accumulated to cause a large error. Furthermore, the process for correcting the error of the zero point by means of the apparatus for processing the output of the sensor as disclosed in the Publication is complicated, so that a relatively long processing time is needed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to set a zero point of a yaw rate sensor accurately, to detect a yaw rate of a vehicle on the basis of the zero point.
In accomplishing the above and other objects, an apparatus for detecting the yaw rate of the vehicle is adapted to include a yaw rate sensor for measuring a yaw rate of the vehicle, a stoppage determining device for determining a stopped state of the vehicle, a zero point setting device for setting a zero point at the yaw rate measured by the yaw rate sensor when the stoppage determining device determines the stopped state of the vehicle, and an actual yaw rate calculating device for calculating an actual yaw rate in response to an output of the yaw rate sensor, on the basis of the zero point set by the zero point setting device. According to the actual yaw rate calculating device, the actual yaw rate can be calculated by subtracting the yaw rate at the zero point from the yaw rate measured by the yaw rate sensor.
Preferably, the apparatus may further include a vehicle speed detecting device for detecting a vehicle speed of the vehicle, a steering angle detecting device for detecting a steering angle of the vehicle, a desired yaw rate setting device for setting a desired yaw rate on the basis of the vehicle speed detected by the vehicle speed detecting device and the steering angle detected by the steering angle detecting device, and a zero point correcting device for correcting the zero point set by the zero point setting device in response to a comparison of the desired yaw rate set by the desired yaw rate setting device and the actual yaw rate calculated by the actual yaw rate calculating device. The stoppage determining device may be constituted by the vehicle speed detecting device and a parking switch activated in response to a state of a parking brake of the vehicle, and adapted to determine the stopped state of the vehicle, when it is determined that the parking brake is activated on the basis of an output of the parking switch, and that the vehicle speed is lower than a predetermined speed on the basis of the output of the vehicle speed detecting device.
It may be so arranged that the zero point setting device includes a temporary zero point setting device for setting a temporary zero point in response to the result determined by the stoppage determining device, and the zero point correcting device includes a deviation calculating device for calculating a deviation between the desired yaw rate set by the desired yaw rate setting device and the actual yaw rate calculated by the actual yaw rate calculating device in response to the output of the yaw rate sensor, on the basis of the temporary zero point set by the temporary zero point setting device, and the zero point correcting device is adapted to correct the zero point on the basis of the temporary zero point, in response to the deviation calculated by the deviation calculating device and the vehicle speed detected by the vehicle speed detecting device. The actual yaw rate calculating device may be adapted to calculate the actual yaw rate by subtracting the yaw rate at the temporary zero point from the yaw rate measured by the yaw rate sensor.
The zero point correcting device may be adapted to renew the zero point by the temporary zero point, when the deviation calculated by the deviation calculating device is lower than a predetermined value, and such a state that the vehicle speed detected by the vehicle speed detecting device exceeds a predetermined speed has continued for a period longer than a predetermined time period. Furthermore, the zero point correcting device may be prohibited from correcting the zero point, when such a state that the deviation calculated by the deviation calculating device exceeds a predetermined value has continued for a period longer than a predetermined time period.
REFERENCES:
patent: 5369580 (1994-11-01), Monji et al.
patent: 5524079 (1996-06-01), Ishida et al.
patent: 5719790 (1998-02-01), Lohrenz et al.
Nishio Akitaka
Tozu Kenji
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Nguyen Tan
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