Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-07-08
2001-04-24
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S069000, C701S071000, C701S073000, C701S074000, C701S090000, C303S140000, C303S146000, C180S197000
Reexamination Certificate
active
06223116
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wheel slip angle detecting system for a vehicle, designed to determine a slip angle of each of wheels (an angle formed by the direction of movement of the wheel with respect to the orientation of the wheel) to grasp a road surface contact situation of each wheel, and more specifically, a lateral force itself of each wheel, in order to increase the accuracy in the control of the motion, e.g., of the turning movement of the vehicle.
2. Description of the Related Art
For example, there is conventionally known a technique of detecting a slip angle of each of wheels in the control of the motion of a vehicle (e.g., in the traction control, the antilock brake control and the like), such as the one disclosed in Japanese Patent Application Laid-Open No. 9-142280.
In Japanese Patent Application Laid-Open No. 9-142280, to determine the slip angle of the wheel, a lateral slip angle of a vehicle body (an angle formed by the direction of movement of the vehicle with respect to the orientation of the vehicle) must be calculated. It is a conventional practice to calculate a lateral slip angle &bgr; of a vehicle body by integrating a differentiated value of lateral slip angle determined according to a differential equation based on a linear two-wheel vehicle's motion model. More specifically, a differentiated value d&bgr;/dt of lateral slip angle &bgr; is calculated according to the differential equation {d&bgr;/dt=(AY/V)−&ggr;}, and a lateral slip angle &bgr; is determined by integrating the differentiated value d&bgr;/dt, wherein AY represents a lateral acceleration of a vehicle body; &ggr; represents a yaw rate; and V represents a vehicle speed.
However, when the vehicle is in a state traveling straightforwardly at a low speed, detected values of the lateral acceleration AY, yaw rate &ggr; and vehicle speed V are small. In a system designed so that a lateral slip angle &bgr; is determined by integrating such detected values, a sensor noise (a mounting error noise) of detector means for detecting a lateral acceleration AY, a yaw rate &ggr; and a vehicle speed V and a travel noise are accumulated in the course of integral calculation, resulting in poor lateral slip angle calculation accuracy and in reduced wheel slip angle detecting accuracy.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a wheel slip angle detecting system for a vehicle, wherein a lateral slip angle of a vehicle body is calculated with good accuracy using an appropriate calculating equation suitable for a travel state of the vehicle, and a wheel slip angle is determined with good accuracy using the lateral slip angle having high accuracy.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a wheel slip angle detecting system for a vehicle, comprising a vehicle speed detecting means for detecting a vehicle speed; a yaw rate detecting means for detecting a yaw rate, a lateral acceleration detecting means for detecting a lateral acceleration; a steering angle detecting means for detecting a steering angle; a slip rate calculating means for calculating a slip rate of each of wheels; a tire characteristic establishing means in which tire characteristics are previously determined based on actual travel data; a travel-state detecting means for detecting a travel state of the vehicle based on the vehicle speed, the yaw rate, the lateral acceleration and the steering angle which are detected by the detecting means, respectively; a lateral acceleration presuming means for determining a presumed lateral acceleration of a vehicle body; a first lateral slip angle calculating means for calculating a lateral slip angle of the vehicle body as a first lateral slip angle by integrating a differentiated value of lateral slip angle determined based on a non-linear four-wheel vehicle's motion model using the vehicle speed detected by the vehicle speed detecting means, the yaw rate detected by the yaw rate detecting means and the presumed lateral acceleration determined by the lateral acceleration presuming means; a second lateral slip angle calculating means for calculating a lateral slip angle of the vehicle body as a second lateral slip angle based on a linear two-wheel vehicle's motion model using the vehicle speed, the yaw rate, the lateral acceleration and the steering angle detected by the detecting means, respectively; a selecting means operable to select the second lateral slip angle calculated in the second lateral slip angle calculating means upon the detection by the travel-state detecting means of a state in which the vehicle is traveling straightforwardly at a low speed, and to select the first lateral slip angle calculated in the first lateral slip angle calculating means in other states; and a slip angle calculating means for calculating a slip angle of each wheel based on the lateral slip angle selected in the selecting means, wherein the lateral acceleration presuming means being operable to presume a presumed lateral acceleration of the vehicle body based on at least one of the slip angle calculated in the slip angle calculating means and the slip rate calculated in the slip rate calculating means, and based on the tire characteristics established in the tire characteristic establishing means.
As used herein, the term “linear two-wheel vehicle's motion model” means a motion model in which cornering forces for the front and rear wheels are varied linearly with respect to the slip angle on the assumption that the cornering forces for the left and right front wheels are equal to each other and the cornering forces for the left and right rear wheels are equal to each other. The term “non-linear four-wheel vehicle's motion model” means a motion model in which cornering forces for the front and rear wheels are varied non-linearly with respect to the slip angle in a state in which it is not on the assumption that the cornering forces for the left and right front wheels and for the left and right rear wheels are equal to each other.
With the arrangement of such first feature, when it is detected by the travel-state detecting means that the vehicle is in a state traveling straightforwardly at a low speed, the slip angle of each wheel is calculated based on the second lateral slip angle calculated in the second lateral slip angle calculating means. However, the second lateral slip angle is calculated using detected values of the vehicle speed, yaw rate, lateral acceleration and steering angle and is not calculated by integration. Therefore, even if the detected values of the vehicle speed, yaw rate, lateral acceleration and steering angle are small due to a low-speed traveling state near a state traveling straightforwardly, a sensor noise (a mounting error noise) and a travel noise cannot be accumulated and hence, the lateral slip angle can be calculated with good accuracy. On the other hand, except for the case where the vehicle is in the state traveling straightforwardly at a low speed, the slip angle of each wheel is calculated based on the first lateral slip angle calculated in the first lateral slip angle calculating means. However, among the vehicle speed, the yaw rate and the lateral acceleration used to calculate the first lateral slip angle, the detected values of the vehicle speed and the yaw rate are relatively large, and the proportion of the noise magnitude with respect to the detected values is relatively small. Moreover, the lateral acceleration is presumed using the tire characteristics previously established from actual travelings and at least one of the slip angle calculated in the slip angle calculating means and the slip rate calculated in the slip rate calculating means so that the presuming accuracy can be increased. Even if the first lateral slip angle is determined by integrating a differentiated value of the lateral slip angle, the error accumulation due to the noise in the c
Kin Keiyu
Urabe Hiroyuki
Armstrong Westerman Hattori McLeland & Naughton LLP
Arthur Gertrude
Cuchlinski Jr. William A.
Honda Giken Kogyo Kabushiki Kaisha
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