Method for detecting an obstacle around a vehicle
If the maximum time width Lt of the intensity of received light of reflected waves from a vehicle ahead is smaller than a reference time width, it is judged that the vehicle ahead is positioned in proximity to the detection limit distance of an obstacle detection device for vehicle. Thus, there is no problem, for example, even if a cut-in vehicle is present in reality between the vehicle ahead and the vehicle of interest and nevertheless, the distance to the cut-in vehicle cannot be detected. It can be judged whether the vehicle ahead is positioned in proximity to the detection limit distance of the device by judging the magnitude relation between Lt and the reference time width. As a result, the detecting capability of the device can be judged with accuracy.
1. A method for detecting an obstacle around a vehicle, comprising the steps of:
radiating transmitted waves outside the vehicle, the transmitted waves being radiated by a radar;
detecting reflected waves of the transmitted waves, the reflected waves being detected by the radar;
sensing a distance to an obstacle around the vehicle based on a result of detection of the reflected waves by the radar, including judging a signal level of the reflected waves;
determining a limit distance within which the distance can be sensed, wherein the determining step determines the limit distance based on certain waves of the detected reflected waves, the certain waves having the signal level lower than a preset level; and
comparing the limit distance determined by the determining step with a preset sensing reference distance, and thereby determining whether the obstacle can be detected.
2. The obstacle detection method according to claim 1 ,
wherein the transmitted waves are light waves,
wherein the signal level is judged by judging a time width in which a voltage value corresponding to an intensity of light in the reflected waves is over a predetermined value, and
wherein the limit distance is determined based on a result of detection of reflected waves whose time width is smaller than a preset reference time width.
3. The obstacle detection method according to claim 2 ,
further comprising presetting as the preset reference time width, a time width in which a voltage value corresponding to an intensity of light in given reflected waves is over the predetermined value, wherein the given reflected waves are reflected by an obstacle positioned in proximity to the limit distance.
4. The obstacle detection method according to claim 2 ,
wherein the sensing step includes recognizing a position of an obstacle as a segment formed of unified dots that gather adjacently, wherein the segment of unified dots are a subset of discontinuous dots that are obtained based on a result of detection of reflected waves, and
wherein the determining step determines the limit distance based on a result of detection of reflected waves of a given dot included in the segment, wherein the given dot has a time width in which the predetermined value is exceeded is largest among the dots included in the segment.
5. The obstacle detection method according to claim 1 ,
further comprising judging that the operating state has degraded when the limit distance becomes less than the preset sensing reference distance.
6. The obstacle detection method according to claim 1 ,
wherein, when the sensing step continuously senses a given obstacle for a predetermined time or longer after the sensing step senses the given obstacle for a first time, the determining step determines the limit distance based on a distance at which the sensing step senses the given obstacle for the first time.
7. The obstacle detection method according to claim 1 ,
wherein, when the sensing step continuously senses a certain obstacle for a predetermined time or longer and then becomes incapable of sensing the certain obstacle, the determining step determines the limit distance based on a distance at which the sensing step becomes incapable of sensing the certain obstacle.