By a News Reporter-Staff News Editor at Journal of Transportation -- A patent by the inventors Minemura, Akitoshi (Nishio, JP); Ogata, Yoshihisa (Chiryu, JP); Yokoyama, Takahisa (Anjo, JP), filed on March 27, 2014, was published online on July 12, 2016, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.
Patent number 9390624 is assigned to DENSO CORPORATION (Kariya, Aichi-pref., JP).
The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to an intersection judgement apparatus and program, for judging when an object located ahead and to one side of a vehicle is moving laterally to intersect with the motion path of the vehicle.
"Types of pre-crash safety system (abbreviated in the following to PCS) are known for installation on a vehicle (referred to in the following as the host vehicle). Such a system can detect a target object such as another vehicle, obstacle, pedestrian, etc., based on information obtained from a radar apparatus and/or an imaging (camera-based) system. The system can for example calculate the TTC (time to collision), i.e., the time remaining until the host vehicle will collide with the target object, by dividing the distance between the host vehicle and the target object by their relative speed. If it is judged based on the TTC that there is a high risk of collision, the PCS can take actions such as generating warnings to the driver of the host vehicle, executing automatic braking of the vehicle, etc., for attempting to prevent the collision.
"It is necessary for a PCS to take such actions when a target object is located directly ahead of the host vehicle. However such actions are also necessary when an object such as a pedestrian is positioned ahead of the host vehicle, outside the travel path of the host vehicle, but is becoming successively displaced along a lateral intersection direction (a direction oriented towards and at right angles to the advancement direction of the host vehicle).
"The PCS may be configured to detect such a circumstance. However when the host vehicle is being driven for example along a city street where there are many pedestrians, the following problem may arise with the prior art. If the PCS attempts to obtain TTC values for all of the nearby pedestrians who are located ahead of the host vehicle, at the left and right sides of the vehicle travel path, then even when a detected pedestrian moves only momentarily along a lateral intersection direction for a short distance, the PCS may take actions such as generating warning indications, executing automatic braking, etc., which are unnecessary. Hence in such a case, the pedestrians may become obstructions to the progress of the vehicle.
"There is thus a requirement for a type of PCS having increased reliability of judging whether a target object such as a pedestrian is actually becoming significantly displaced along a lateral intersection direction, for ensuring that the PCS does not take actions such as generating warning indications, etc., when these actions are unnecessary. Such an improvement of a PCS is referred to in the following as an 'improvement of the off performance'.
"As a measure for improving the off performance of a PCS, it has been proposed for example in Japanese patent publication No. 2008-197720 as described referring to a second embodiment, that amounts of lateral displacement of a pedestrian towards the advancement direction of the host vehicle are successively detected. If a detected amount of lateral displacement exceeds a threshold value TH1, a warning indication is generated. Each amount of lateral displacement is calculated as an absolute value of a displacement vector, oriented towards and at right angles to the advancement direction of the host vehicle.
"Although a radar apparatus or camera apparatus of such a prior art PCS may momentarily detect a target object such as a pedestrian moving in a lateral intersection direction, in many cases it is not possible to continuously detect the motion of the target object. This can occur for example when the object enters a blind spot (i.e., a position at which the field of view of the radar apparatus and/or camera apparatus of the host vehicle becomes partially or completely obstructed by some obstacle, etc.). In such a case, the PCS may not take necessary actions such as generating warning indications, etc., when required.
"However if it is attempted to reduce that danger, by relaxing the conditions which must be satisfied before the PCS takes actions such as generating warning indications (e.g., by lowering the threshold value used to judge the magnitudes of obtained values of lateral displacement) there is an increased possibility that the PCS will take such actions unnecessarily, so that the off performance of the PCS will deteriorate."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "Hence it is desired to overcome the above problem, by providing an intersection judgement apparatus and program for installation on a host vehicle, which provide increased reliability and accuracy of judgement as to whether a target object such as a pedestrian positioned ahead of the host vehicle, at one side of the motion path of the host vehicle, is moving laterally to intersect with the advancement of the host vehicle.
"An intersection judgement apparatus according to the present invention basically comprises distance measurement circuitry, direction angle measurement circuitry, displacement amount calculation circuitry, and intersection judgement circuitry. A target object detection apparatus periodically derives target object information (i.e., repetitively obtains updated target object information, with a fixed period between successive updatings) relating to target objects located within regions at either side of the host vehicle, ahead of the vehicle. The distance measurement circuitry periodically calculates the distance between the host vehicle and each target object based on the target object information, and the direction angle measurement circuitry periodically calculates the direction angle of the target object relative to the host vehicle based on the target object information. The displacement amount calculation circuitry periodically calculates an amount of lateral displacement of the target object (i.e., displacement along a direction towards and at right angles to the advancement direction of the host vehicle) based upon the calculated values of distance and direction angle of the target object. The intersection judgement circuitry utilizes the calculated lateral displacement amounts to judge whether the target object is moving along the displacement direction.
"The invention is characterized in that the intersection judgement circuitry employs one or more threshold condition groups, in judging the lateral displacement amounts. Each threshold condition group is associated with a corresponding lower displacement threshold and a corresponding count threshold. With respect to a specific target object and a specific threshold condition group, the intersection judgement circuitry counts the number of times that successively calculated lateral displacement amounts obtained for the target object exceed the lower displacement threshold corresponding to the threshold condition group, and judges that the threshold condition group is satisfied when the counted number of times attains the corresponding count threshold.
"Preferably, it is judged that the threshold condition group is satisfied only when the counted number of times attains the corresponding count threshold within a predetermined count range (i.e., predetermined number of consecutive lateral displacement calculation operations) having a value greater than the count threshold.
"A plurality of threshold condition groups are preferably utilized, having respectively different values of the lower displacement threshold and of the corresponding count threshold. In that case, the intersection judgement circuitry judges the probability that the target object is moving along the intersection direction based upon the respective statuses (i.e., satisfied or not satisfied) of the plurality of threshold condition groups.
"Preferably, the intersection judgement circuitry judges that the target object is moving along the intersection direction only if all of the plurality of threshold condition groups become satisfied. However alternatively, the intersection judgement circuitry may be configured to make that judgement if at least one of the plurality of threshold condition groups becomes satisfied.
"In assigning the respective values of count threshold and lower displacement threshold for such a plurality of threshold condition groups, the lower is made the value of the count threshold corresponding to a threshold condition group, the higher is made the value of the corresponding lower displacement threshold.
"Furthermore preferably a value of a displacement limit threshold is predetermined as being higher than each of the values of lower displacement threshold, i.e., each of the threshold condition groups is assigned a corresponding displacement amount range, extending between the corresponding lower displacement threshold and the (fixed) displacement limit threshold.
"The displacement limit threshold is set in accordance with the type of target object that is to be judged, e.g., based on an assumed maximum value of motion speed of that type of object, such as the highest walking speed that would be expected for a pedestrian. When a calculated displacement amount exceeds the displacement limit threshold, that occurrence is not counted.
"The target object detection apparatus may be implemented as a radar apparatus, with the distance and direction angle of a target object being obtained from radar information supplied from the radar apparatus.
"Alternatively, the target object detection apparatus may be implemented as an imaging apparatus, i.e., a combination of a camera which captures successive images of an external scene as respective frames of data, and circuitry for processing the images to derive image information, with the distance and direction angle of a target object being obtained from the image information.
"However preferably a radar apparatus and an imaging apparatus are used in combination, with each position of a target object being obtained as a fusion (combination) position, i.e., expressed by a distance value and a direction value respectively derived from radar information and from image information.
"In that case, the radar apparatus and the imaging apparatus are configured for enabling a position of a target object to be obtained based on the radar information alone and also based on the image information alone. A fusion position is selected as valid (for use in calculating an updated lateral displacement amount) only if there is at least some overlap between a first position error region and a second position error region. The first position error region is derived by adding estimated image measurement error amounts to a position for the target object that is obtained based only on the image information, while the second position error region is derived by adding estimated radar measurement error amounts to a position for the target object that is obtained based only on the radar information."
URL and more information on this patent, see: Minemura, Akitoshi; Ogata, Yoshihisa; Yokoyama, Takahisa. Vehicle-Installation Intersection Judgment Apparatus and Program. U.S. Patent Number 9390624, filed March 27, 2014, and published online on July 12, 2016. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=9390624.PN.&OS=PN/9390624RS=PN/9390624
Keywords for this news article include: DENSO CORPORATION, Auto Part Companies.
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