Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-11-28
2002-09-24
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S001000, C303S140000
Reexamination Certificate
active
06456920
ABSTRACT:
This application claims priority under 35 U.S.C. Sec. 119 to No.11-337603 filed in Japan on Nov. 29, 1999, the entire content of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for estimating a vehicle side slip angle, and more particularly to the apparatus for estimating the vehicle side slip angle by properly selecting one of the vehicle side slip angle estimated by integration and the vehicle side slip angle estimated on the basis of a vehicle motion model.
2. Description of the Related Arts
As a system for controlling a vehicle motion characteristic, especially a turning characteristic of the vehicle, an apparatus for controlling a difference between the braking force applied to right and left wheels to directly control a turning moment has been noted, and it is now on the market. For example, Japanese Patent Laid-open Publication No.9-301147 discloses a motion control apparatus which estimates an amount indicative of a motion state of a vehicle when the vehicle turns, and controls a hydraulic braking pressure control apparatus so as to correct a yaw moment of the vehicle to make the vehicle in motion to be stable, when the amount indicative of the motion state of the vehicle exceeded a threshold level for starting the control. In that publication, in order to change a range of the amount of the motion state of the vehicle for starting the control in accordance with a coefficient of friction, is proposed the motion control apparatus, wherein the lower the coefficient of friction is, the smaller the threshold level for starting the control is set.
In the vehicle motion control system as described above, various detectors for detecting signals indicative of the motion state of the vehicle have been provided. For example, Japanese Patent Laid-open Publication No.9-311042 proposes a detector for detecting a vehicle side slip angle through steering inputs and quantity of monitored motion state (e.g., yaw rate or lateral acceleration), wherein in order to deal flexibly with a variable parameter of a vehicle and estimate a side slip angle of a vehicle body with good accuracy, the vehicle side slip angle is estimated on the basis of an equation of motion indicative of the vehicle motion. Accordingly, it is described in the Publication that it is possible to deal flexibly with the nonlinearlity of a tire and with a change in the characteristic of the vehicle due to the vehicle speed, and enhance the estimated accuracy by correcting the estimated value of the vehicle side slip angle by means of a sensor signal.
It is disclosed in the Publication No.9-301147 that a vehicle side slip angular velocity D&bgr; (=Gy/Vso−&ggr;) is calculated on the basis of a vehicle lateral acceleration Gy, a vehicle speed Vso and a yaw rate &ggr;, and the vehicle side slip angular velocity D&bgr; is integrated to obtain a vehicle side slip angle &bgr; (=∫D &bgr;dt). Also, it is disclosed in the Publication No. 8-40232 that a vehicle lateral acceleration Gy, vehicle speed V and yaw rate &ggr;are detected to obtain a deviation (Gy−V·&ggr;), which is integrated by a predetermined integral time to obtain a vehicle side slip velocity Vy. Thus, proposed is a vehicle turning motion control apparatus which estimates a vehicle turning motion at least on the basis of the vehicle side slip velocity, and controls the vehicle turning motion on the basis of the estimated turning motion.
In the case where the vehicle side slip angle is estimated on the basis of the vehicle motion model, as described in the aforementioned Publication No.9-311042, it is possible to do with the nonlinearlity of the tire, or do with a change in the characteristic of the tire due to a road surface condition, for example. It is, however, limited to a single kind of tire, and it is difficult to do with them in the case where various kinds of tires are changed to be used, or where air pressure of the tire is changed to cause an extremely large difference, and the like. In these cases, it is preferable to estimate the vehicle side slip angle by integration. According to this estimation, however, there will be caused such problems that an error is accumulated as described in the Publication No.8-40232, and a robust characteristic of the vehicle on a slope or the like is still affected. The vehicle side slip velocity Vy used as a reference value for determining the vehicle turning motion in the Publication No.8-40232 corresponds to a value obtained by multiplying the vehicle side slip angular velocity D&bgr; (=Gy/Vso−&ggr;) disclosed in the Publication No.9-301147, with the vehicle speed V, so that it corresponds to the vehicle side slip angle.
Although the apparatus may be adapted to select properly one of the vehicle side slip angle estimated by integration and the vehicle side slip angle estimated on the basis of the vehicle motion model, as described above, so as to estimate the vehicle side slip angle, other problems will be caused. For instance, if changing the estimation is not executed properly, the vehicle motion control will be complicated to cause a delay in processing speed, so that it will be difficult to achieve a smooth motion control by using the vehicle side slip angle.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an apparatus for estimating a vehicle side slip angle by properly selecting one of the vehicle side slip angle estimated by integration and the vehicle side slip angle estimated on the basis of a vehicle motion model, through rapid and easy change of the estimation of the vehicle side slip angle.
In accomplish the above and other objects, the apparatus for estimating a vehicle side slip angle is arranged to include a monitor for monitoring quantity of motion state of a vehicle including such signals as a vehicle speed, a vehicle lateral acceleration, a yaw rate and a steering angle, and includes a motion model memory for storing therein a vehicle motion model. A first estimation device is provided for estimating a vehicle side slip angle by calculating a vehicle side slip angular velocity on the basis of the vehicle speed, vehicle lateral acceleration and yaw rate monitored by the monitor, and integrating the vehicle side slip angular velocity in a predetermined calculating cycle. Also, a second estimation device is provided for estimating the vehicle side slip angle on the basis of the quantity of motion state monitored by the monitor, and the vehicle motion model stored in the motion model memory. A tire load determination device is provided for determining a lateral load to each tire of the vehicle on the basis of the result monitored by the monitor. And, a changing device is provided for changing between the estimation of the vehicle side slip angle made by the first estimation device and the estimation of the vehicle side slip angle made by the second estimation device, in accordance with the result of determination of the tire load determination device.
Preferably, the tire load determination device is adapted to determine the lateral load to each tire of the vehicle, on the basis of a variation of at least one of the vehicle lateral acceleration and the yaw rate monitored by the monitor.
In the apparatus, the monitor may include a vehicle speed detector for detecting the vehicle speed, a lateral acceleration detector for detecting the vehicle lateral acceleration, a yaw rate detector for detecting the yaw rate, a steering angle detector for detecting the steering angle. Then, the first estimation device may be adapted to calculate the vehicle side slip angular velocity on the basis of the vehicle speed, the vehicle lateral acceleration and the yaw rate detected by the detectors respectively, and estimate the vehicle side slip angle by integrating the vehicle side slip angular velocity, and the second estimation device may be adapted to estimate the vehicle side slip angle on the basis of the vehicle speed, the vehicle lateral accele
Nishio Akitaka
Tozu Kenji
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Chin Gary
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