Optics: measuring and testing – Range or remote distance finding – With photodetection
Reexamination Certificate
1998-09-17
2001-02-27
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
With photodetection
C180S169000
Reexamination Certificate
active
06195157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distance sensor for a vehicle for detecting the distance from a vehicle to an object ahead of the vehicle, based on the time from the transmission of an optical signal to the reception of a reflected optical signal by means of transmitting the optical signal ahead of the vehicle and receiving the optical signal reflected from the object, and particularly, a process for determining an abnormality of detection in the distance sensor.
2. Description of the Relevant Art
An auto-cruising system is conventionally well-known, which is designed to allow a vehicle to travel following a target vehicle, by detecting the distance between the vehicle and the target vehicle traveling ahead of the vehicle using a radar device having a laser beam, and controlling the speed of the vehicle, so that the vehicle—vehicle distance is maintained at a predetermined value. In such an auto-cruising system, when a rear portion of the target vehicle is soiled which decreases the magnitude of the reflected signal of the laser beam, or when the target vehicle has raised a large amount of water or snow from a road surface, the state of reception of the reflected signal is deteriorated and as a result, the distance between the vehicle and the target vehicle may not be properly detected, resulting in the possibility that although the target vehicle actually exists, it is mis-determined that the target vehicle does not exist.
There is already proposed in Japanese Patent Application 9-199568, an auto-cruising system in which when the deterioration of the receiving environment is detected based on the magnitude of the signal reflected from the target vehicle and on interrupted or discontinuous supply of data on the distance between the vehicle and the target vehicle, the auto-cruise control is discontinued, or a warning is emitted to a driver.
In the previously proposed system, however, when the reception of the signal is started again after the interruption of the reception of the reflected signal from the target vehicle, the deterioration of the receiving environment is detected. For this reason, it is desirable that the deterioration of the receiving environment can be detected earlier.
SUMMARY OF THE INVENTION
The present invention has been accomplished with the above circumstance in view, and it is an object of the present invention to immediately detect the deterioration of the environment of the reception of the reflected signal from the target vehicle.
To achieve the above object of the present invention, there is provided a process for determining an abnormality of detection in a distance sensor for a vehicle which detects the distance from the vehicle to an object ahead of the vehicle, based on the time from the transmission of an optical signal to the reception of the reflected optical signal by means of transmitting the optical signal ahead of the vehicle and receiving the optical signal reflected from the object. When the variation in magnitude of the signal received from the object before the object falls into a non-detected state, becomes equal to or larger than a reference value which indicates the deterioration of the environment of reception of the signal, the abnormality of the detection is determined.
With the above feature, if the magnitude of the signal received is decreased, the variation in the magnitude of the signal received is increased, and the abnormality of the detection is determined when the variation in the magnitude of the signal received becomes equal to or larger than a reference value. Therefore, it is possible to immediately determine the deterioration of the receiving environment as soon as the object falls into a non-detected state. The reference value may be a value for enabling the deterioration of the receiving environment to be determined, and is a selected value which is set properly.
The variability is a standard deviation or a dispersion, and thus the extent of the variation in the magnitude of the signal received can be properly determined.
There is also provided a process for determining an abnormality of detection in a distance sensor which detects the distance from a vehicle to an object ahead of the vehicle, based on the time from the transmission of an optical signal to the reception of the reflected optical signal by means of transmitting the optical signal ahead of the vehicle and receiving the optical signal reflected from the object. When the average value of the magnitude of the signal received from the object before the object falls into a non-detected state, becomes equal to or smaller than a reference value which indicates the deterioration of the environment of the reception of the signal, the abnormality of the detection is determined.
Thus, if the magnitude of the signal received is decreased, the average value of the magnitude of the signal received decreases, the abnormality of the detection is determined when the average value of the magnitude of the signal received becomes equal to or smaller than the reference value. Therefore, it is possible to immediately determine the deterioration of the receiving environment as soon as the object falls into a non-detected state. The reference value may be a value for enabling the deterioration of the receiving environment to be determined, and is a selected value which is set properly.
In addition, when the object is within a predetermined distance from the vehicle, the determination of the abnormality of the detection is carried out. Therefore, it is possible to avoid a mis-determination of the abnormality of the detection due to a decrease in the magnitude of the signal received with the movement of the object away from the vehicle. The predetermined distance is set at 60 m in the embodiment, but may be varied depending upon the performance of the distance sensor.
When the deviation between the distance from the vehicle to the object when the object falls into a non-detected state, in the current cycle and the distance from the vehicle to the object when the object falls into the non-detected state, in the prior cycle is within a predetermined distance, the determination of the abnormality of the detection is carried out.
When a different object has been detected after the object falls into the non-detected state, the deviation between the distances from the vehicle to the respective objects becomes equal to or larger than the predetermined distance, whereby the determination of the abnormality of the detection is not carried out. Therefore, it is possible to prevent the determination of the abnormality of the detection from being carried out based on data from different objects. The predetermined distance is set at 10 m in the embodiment, but may be varied depending upon the performance of the distance sensor.
REFERENCES:
patent: 4639129 (1987-01-01), Hullein et al.
patent: 5321490 (1994-06-01), Olson et al.
patent: 5633705 (1997-05-01), Asayama
patent: 5633706 (1997-05-01), Cho et al.
patent: 9199568 (1999-02-01), None
Ogino Shigenori
Sugiyama Akira
Yamashita Kazuo
Arent Fox Kintner & Plotkin & Kahn, PLLC
Buczinski Stephen C.
Honda Giken Kogyo Kabushiki Kaisha
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