Data processing: vehicles – navigation – and relative location – Relative location – Collision avoidance
Reexamination Certificate
1999-06-10
2001-03-13
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Relative location
Collision avoidance
C701S096000, C367S098000, C340S435000
Reexamination Certificate
active
06202027
ABSTRACT:
TECHNICAL FIELD
This invention relates to motor vehicle collision warning (CW) and/or intelligent cruise control (ICC) systems, and more particularly to an automatic calibration of a measured radius of curvature of the vehicle travel path.
BACKGROUND OF THE INVENTION
Collision warning and intelligent cruise control systems generally employ a forward looking radar, laser or ultrasonic sensor (FLS) mounted at the forward end of the host vehicle for acquiring data corresponding to the range, range rate, and the azimuth angle of a target vehicle or other object. The range is the distance between the host vehicle and the target, the range rate is the rate of change of range, and the azimuth angle is the angle in a horizontal plane between the target and the direction of travel (the path or trajectory) of the host vehicle. A microprocessor receives and analyzes the sensor data along with other data corresponding to the vehicle velocity and yaw rate and/or lateral acceleration, and predicts the likelihood of an impending collision. In a collision warning system, the primary function of the system is to warn the operator of a potentially unsafe operating condition, or possibly to initiate a corrective action, whereas in an intelligent cruise control system, the primary function is to adjust the vehicle speed to maintain a desired headway or following distance. Such systems require an accurate determination of the target location relative to the path of travel of the host vehicle. This, in turn, requires precise alignment of the FLS viewing axis, and accurate detection of the yaw or lateral acceleration of the host vehicle.
In practice, precise alignment of the FLS sensor is difficult to achieve in a factory environment, and even more difficult to maintain in subsequent usage of the vehicle due to changes in wheel alignment, for example. Additionally, yaw or lateral acceleration sensors which are used to determine the travel path radius of curvature typically exhibit a certain amount of temperature-related drift. Even when differential wheel speeds are used to estimate travel path curvature, differences in tire pressure and wear, or road surface variations, can introduce significant error. As a result, it is difficult to accurately assess if a detected target is in the travel path of the host vehicle.
SUMMARY OF THE INVENTION
The present invention is directed to an improved system for accurately determining the travel path of a host vehicle and the azimuth angle of a target vehicle through an automatic calibration that detects and compensates for FLS mis-alignment and curve sensor drift. Selected FLS tracking data (range and azimuth angle) are transformed to cartesian coordinates and characterized by a second order curve fitting technique to determine both FLS misalignment and curve sensor bias. Successively determined FLS misalignment and curve sensor bias values are averaged and used to correct subsequently supplied azimuth angle and curve sensor data, thereby compensating an underlying control for both FLS misalignment and curve sensor bias.
REFERENCES:
patent: 5572428 (1996-11-01), Ishida et al.
Alland Stephen William
Searcy James Fredrick
Delphi Technologies Inc.
Funke Jimmy L.
Nguyen Tan
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