JP2014149741A - Collision determination device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly reliably determine collision with an approaching object which approaches an own vehicle even during the stoppage or low speed traveling of the own vehicle.SOLUTION: An approaching object detection part 11 detects an approaching object, and an approaching object distance calculation part 12 calculates the lateral distance and traveling direction distance of the approaching object. Then, a lateral collision prediction time calculation part 13 calculates a lateral collision prediction time TTCR from the lateral distance and relative speed of the approaching object, and a traveling direction collision prediction time calculation part 14 calculates a traveling direction collision prediction time TTC from the traveling direction distance and relative speed of the approaching object. Furthermore, when an own vehicle is traveling at a set vehicle speed or less, a prediction time correction part 14a corrects a traveling direction collision prediction time TTC0 of a time when the lateral collision prediction time TTCR is turned into 0 on the basis of acceleration. Afterwards, a collision determination part 15 determines whether or not the traveling direction collision prediction time TTC0 of the time when the lateral collision prediction time TTCR is turned into 0 satisfies collision determination conditions. Thus, the intervention of an alarm output or avoidance control is performed in accordance with the determination result.

Description

  The present invention relates to a vehicle collision determination device that determines a collision between an approaching object approaching the host vehicle and the host vehicle.

  In recent years, in vehicles such as automobiles, when an object approaching the host vehicle (approaching object) is detected and it is determined that there is a possibility that the approaching object and the host vehicle collide with each other, an alarm to the driver or automatic braking is performed. Control systems have been developed.

  In order to avoid a collision with an approaching object, generally, the time until the approaching object reaches the front of the host vehicle is predicted, and an alarm is issued or forced braking is performed according to the size of the predicted time. To avoid collisions. In particular, in order to avoid a collision accident with an approaching object approaching the host vehicle from the side, such as at an intersection, it is necessary to grasp the lateral movement.

For example, Patent Document 1 discloses a collision determination by calculating a time (collision prediction time) until a collision between a laterally moving object that moves in a direction crossing the traveling direction of the own vehicle and the own vehicle and comparing it with a threshold value. Techniques for performing are disclosed. In this prior art, the collision prediction time TTC is calculated from the relative distance Y in the traveling direction of the moving object with respect to the own vehicle and the relative speed Vy (TTC = Y / Vy), and the collision prediction time TTC is calculated as the relative distance X in the lateral direction. When the condition of the following equation (a) determined from the relative speed Vx and the vehicle width W is satisfied, it is determined that a collision has occurred.
−W / 2 <X + Vx × TTC <W / 2 (a)

Japanese Patent No. 4814928

  However, in the technique disclosed in Patent Document 1, when a moving object approaches when the host vehicle is about to start from a stop or is traveling at an extremely low speed, the predicted collision time TTVC is a very large value. Therefore, the condition of the formula (a) is not satisfied, and there is a possibility that alarm / control is not performed. If the vehicle does not move, there is no problem because the vehicle does not collide, but if the vehicle moves after that, the possibility of a collision increases.

  The present invention has been made in view of the above circumstances, and provides a vehicle collision determination device that can reliably determine a collision with an approaching object approaching the host vehicle even when the host vehicle is stopped or traveling at a low speed. The purpose is to do.

  A vehicle collision determination apparatus according to the present invention calculates a lateral collision prediction time from an approaching object detection unit that detects an approaching object approaching the host vehicle, and a relative distance and a relative speed of the approaching object with respect to the host vehicle in the lateral direction. A lateral collision prediction time calculation unit, a traveling direction collision prediction time calculation unit that calculates a traveling direction collision prediction time from a relative distance and a relative speed in the traveling direction of the approaching object with respect to the host vehicle, and the lateral collision prediction time And a collision determination unit that determines a collision between the host vehicle and the approaching object based on the traveling direction collision prediction time, and the traveling direction collision prediction time calculation unit, when the host vehicle is below a set vehicle speed, The traveling direction prediction time when the lateral collision prediction time becomes zero is corrected based on the acceleration of the host vehicle.

  According to the present invention, even when the host vehicle is stopped or traveling at a low speed, a collision with an approaching object approaching the host vehicle can be determined with high reliability.

Configuration diagram of collision determination device Flow chart showing the entire process of the collision determination device Explanatory drawing showing an example of input image Explanatory drawing which shows the position of the own vehicle and approaching object in real space coordinates Explanatory diagram showing the frequency distribution of acceleration when starting Explanatory diagram expressing the collision area in the predicted time coordinate system Illustration of alarm area

Embodiments of the present invention will be described below with reference to the drawings.
A collision determination apparatus 1 shown in FIG. 1 is mounted as a part of a collision prevention system for a vehicle such as an automobile, and mainly determines a collision at the time of encounter between a moving object such as another vehicle and the own vehicle in an intersection such as an intersection. To do. Specifically, the collision determination device 1 detects a moving object (approaching object) such as another vehicle that approaches the host vehicle from the side (left and right direction) at an intersection such as an intersection, and the detected approaching object is the host vehicle. The time to reach the position is predicted, and the possibility of collision between the host vehicle and the approaching object is determined.

  The collision determination between the own vehicle and the approaching object is based on the predicted time (lateral collision prediction time) TTCR from the lateral direction until the approaching object reaches the own vehicle position and the traveling direction until the approaching object reaches the own vehicle position. And the predicted time (traveling direction collision predicted time) TTC. In other words, the predicted lateral collision time TTCR is the time until the approaching object crosses the host vehicle. In addition to the case where the approaching object collides with the host vehicle, the host vehicle crosses the front of the host vehicle (the approaching object passes first). Therefore, by adding the predicted time TTC in the traveling direction, the accuracy of the collision determination is increased and unnecessary alarms and control interventions are avoided.

  At that time, when the collision determination is performed based on the value of the traveling direction collision prediction time TTC when the predicted lateral collision time TTCR becomes 0, that is, when the approaching object reaches the lateral position of the own vehicle, When starting from a stop, or when traveling at an extremely low speed, the traveling direction collision prediction time TTC becomes a very large value, and there is a possibility that warning / control of collision avoidance will not be executed. If the host vehicle does not move, there is no problem because the vehicle does not collide, but if the host vehicle moves thereafter, the possibility of a collision increases.

  For this reason, the collision determination apparatus 1 corrects the value of the traveling direction collision prediction time TTC when the lateral collision prediction time TTCR becomes 0 in consideration of the acceleration of the own vehicle when the own vehicle is below the set vehicle speed. Then, the collision determination is performed based on the corrected collision prediction time. This suppresses unnecessary alarms when there is no possibility of a collision, and avoids an unalarmed alarm / alarm delay when the driver intends to start even when the host vehicle is stopped (at extremely low speed). be able to.

  In this embodiment, a moving object approaching the host vehicle uses a monocular wide-angle camera (for example, a fish-eye camera with an angle of view of 180 °) 2 as a device for recognizing the external environment of the host vehicle. To detect. The collision determination device 1 is configured by the camera 2 and a single computer or a plurality of computers connected to each other for processing the image captured by the camera 2 to determine the collision between the host vehicle and an approaching object. .

  The functional units of the collision determination apparatus 1 include an approaching object detection unit 11, an approaching object distance calculation unit 12, a lateral collision prediction time calculation unit 13, a traveling direction collision prediction time calculation unit 14, a collision determination unit 15, an alarm / Further, the traveling direction collision prediction time calculation unit 14 includes a prediction time correction unit 14a that corrects the traveling direction collision prediction time below the set vehicle speed as an additional function. Below, first, the flow of the whole process of the collision determination apparatus 1 shown to the flowchart of FIG. 2 is demonstrated, and the detail of the process of each part is demonstrated after that.

  In the entire process shown in the flowchart of FIG. 2, first, a wide-angle image G (a 180-degree image by a fisheye lens) as shown in FIG. 3 is input from the camera 2 in step S1, and the camera image G automatically starts in step S2. A moving object (approaching object) approaching the vehicle and its position are detected. For example, a motion (optical flow) on the image between frames of the camera image G is obtained, and a moving object approaching the host vehicle is detected from the optical flow. FIG. 3 shows an example in which another vehicle CRo approaching the host vehicle from the right side is detected as an approaching object.

Next, in step S3, a lateral collision prediction time TTCR is calculated from the lateral position (lateral distance) X of the approaching object relative to the host vehicle and the relative speed Vx, and the approaching direction position (progression of the approaching object relative to the host vehicle). The traveling direction collision prediction time TTC is calculated from the directional distance Z and the relative speed Vz. Here, since the collision prediction time is distance / relative velocity, the lateral collision prediction time TTCR and the traveling direction collision prediction time TTC are obtained from the following equations (1) and (2), respectively.
TTCR = X / Vx (1)
TTC = Z / Vz (2)

  Thereafter, in step S4, when the vehicle speed of the host vehicle is equal to or lower than the set vehicle speed, the traveling direction collision prediction time TTC ((TTC0)) when the lateral collision prediction time TTCR becomes 0 is set as an estimated value of the acceleration of the host vehicle. Then, in step S5, a collision determination is performed using the traveling direction collision prediction time TTC when the lateral collision prediction time TTCR becomes 0, and in step S6, a warning is given to the driver according to the determination result of the collision determination. And whether or not control intervention such as brake control for collision avoidance is possible.

Next, processing of each functional unit in the above overall processing will be described in detail.
The approaching object detection unit 11 extracts and tracks the approaching object region from the image based on the motion information (optical flow) on the image, based on the motion information. For example, when the size of the input image G as shown in FIG. 3 is 640 × 60 pixels, the optical flow between temporally continuous frames is obtained by block matching or the like for each 8 × 8 pixel block, and the image Check the movement toward the center (movement toward the vehicle). Then, blocks moving toward the center of the image, that is, blocks moving toward the host vehicle are collectively cut out as an approaching object region, and the approaching object region is tracked in time series. In the example of FIG. 3, a rectangular area AR including the other vehicle CRo is detected as an approaching object moving in the image center direction.

  Next, the approaching object distance calculation unit 12 sets the position of the approaching object region on the image coordinates to the lateral distance from the host vehicle CRs to the approaching object (other vehicle) CRo, as shown in FIG. Then, the distance in the traveling direction is converted to a position on the real space coordinates with Z as the distance. The conversion from the position on the image to the position on the real space is performed using a distance conversion table prepared in advance, and each of the distances X and Z is determined from the image coordinates (i, j) of the approaching object region by referring to the table. Ask for.

  When referring to the distance conversion table, first, the contact point Po closest to the host vehicle in the approaching object region is obtained. Specifically, the ground point Po is set at the lower right of the approaching object region in the left half of the image and at the lower right of the approaching object region in the right half. In the example of FIG. 3, the lower left point of the area AR enclosed in a rectangular shape is the ground point Po.

  Next, the position of the ground point Po is referred to in the distance conversion table. The distance conversion table is a table representing which distance (X, Z) each pixel on the image corresponds to from the installation position and angle of the camera. Since the camera 2 in the present embodiment is a stereoscopic projection type fisheye camera, a table is created in advance using a model obtained by combining a stereoscopic projection camera model and a projection model onto the ground surface. At that time, the camera parameters are set by calibration from an actual camera image.

  The distances X and Z converted at the current time t by the distance conversion table are stabilized by applying a time series filter. Ideally, it is desirable not to apply time-series filters, but in reality, the resolution of the image (especially the resolution becomes worse at far distances), the approaching object area, tracking, and other processing accuracy are insufficient. The error may increase. For this reason, by applying a time series filter, the distance data handled for calculating the collision prediction times TTCR and TTC is stabilized in time series.

  The distances X and Z obtained by the approaching object distance calculation unit 12 are sent to the lateral collision prediction time calculation unit 13 and the traveling direction collision prediction time calculation unit 14, respectively. The lateral collision prediction time calculation unit 13 obtains the lateral relative speed Vx of the approaching object with respect to the host vehicle by the amount of change in the optical flow of the approaching object or the position differentiation by tracking, and the lateral collision prediction time based on the equation (1). TTCR is calculated. Similarly, the traveling direction collision prediction time calculation unit 14 obtains the traveling direction relative velocity Vz of the approaching object with respect to the host vehicle based on the optical flow change amount of the approaching object or the position differentiation by tracking, and the traveling direction collision is calculated based on the equation (2). A predicted time TTC is calculated.

Further, when the speed of the host vehicle is 0 or less than the set vehicle speed (for example, 3 km / h), the predicted time correction unit 14a sets the traveling direction predicted collision time TTC0 at the time when the lateral collision predicted time TTCR becomes zero. It is corrected assuming that the vehicle will accelerate after this. Specifically, assuming that the current time is t = 0 and the acceleration of the host vehicle is A, the traveling direction distance Z (t) and the traveling direction relative speed Vz (t) at time t are expressed by the following (3), It is obtained by the equation (4).
Z (t) = Z0-A * t * t / 2-Vzo * t (3)
Vz (t) = A × t + Vzo (4)
Where Z0: Distance in the direction of travel at the current time
Vz0: Current direction relative speed

  Since the time t at which the lateral collision prediction time TTCR becomes 0 is t = TTCR, that is, the value of the current lateral collision prediction time TTCR, the traveling direction distance Z at t = TTCR from the equations (3) and (4) Then, the traveling direction relative speed Vz is obtained and substituted into the equation (2). The traveling direction collision prediction time TTC0 obtained thereby becomes the prediction time corrected by the acceleration A of the host vehicle.

  Here, the acceleration A may be a general acceleration at the time of starting (for example, A = 0.2G), or may be an estimated value considering a difference for each driver. When considering the difference for each driver, it is possible to use a value obtained by storing the acceleration at the start of the past driver and performing an averaging process.

  Further, in order to improve the prediction accuracy of future acceleration and make the correction of the prediction time TTC0 more appropriate, a plurality of accelerations may be assumed. Specifically, when a plurality of candidates for the predicted time TTC0 at different accelerations are calculated and the collision determination unit 15 described below satisfies one of the plurality of candidates, the collision occurs. Judge that.

  For example, as shown in FIG. 5, the plurality of acceleration candidates is a first frequency located at a higher frequency (for example, upper 30%) using a frequency distribution created from a history of acceleration at the time of starting of the past driver. Prediction with a higher acceleration and prediction with a lower acceleration may be performed based on the candidate acceleration A1, the second candidate acceleration A2 located at a lower frequency (for example, lower 30%), and the like.

  However, in this case, there is a possibility that an alarm is generated even when the driver does not intend to start. Therefore, unnecessary warnings can be avoided by applying a plurality of accelerations only when it is estimated that there is an intention to start from the driving operation of the driver. Specifically, refer to the brake pressure of the driver and apply multiple accelerations assuming that the driver has a willingness to start when the differential value of the brake pressure is negative (the direction in which the brake is released) or when the brake pressure is zero To do.

The above-described lateral collision prediction time TTCR and traveling direction collision prediction time TTC are sent to the collision determination unit 15, and a collision between the host vehicle and an approaching object is determined based on the lateral collision prediction time TTCR and the traveling direction collision prediction time TTC. Is done. It is determined that the collision between the host vehicle and the approaching object occurs when the traveling direction collision prediction time TTC0 at the time when the lateral direction collision prediction time TTCR becomes 0 enters the range indicated by the following conditions. This collision determination condition is given by the following equation (5) using the width Ws and length Ls of the host vehicle and the width Wo and length Lo of the approaching object.
-(Wo + Ls) / Vz <TTC0 <(Ws + Lo) / Vx (5)

Here, when there is a correction due to the acceleration A of the host vehicle, the traveling direction relative speed Vz changes. Therefore, specifically, the condition of the equation (5) is a progression in which t = TTCR in the equation (4). It can be expressed by the following equation (5 ′) expressed using the directional relative velocity Vz. When the predicted time TTC0 satisfies the determination condition of the equation (5 ′), it is determined that the host vehicle and an approaching object collide.
− (Wo + Ls) / (A × TTCR + Vz0) <TTC0 <(Ws + Lo) / Vx (5 ′)

  The above collision determination conditions can be shown in a TTCR-TTC space with the horizontal collision prediction time TTCR and the traveling direction collision prediction time TTC shown in FIG. 6 as axes. In FIG. 6, when the host vehicle is at the current position Ps at the current time t = 0, as the time advances from the present time, the predicted lateral collision time TTCR is reduced as shown by the curve Pt in the figure, while the host vehicle The traveling direction relative speed Vz is increased by the acceleration of the traveling direction, and the traveling direction collision prediction time TTC is decreased. When the traveling direction collision prediction time TTC0 at the time when the lateral direction collision prediction time TTCR finally becomes 0 enters the region between the lines Lu and Ld indicated by the broken line in FIG. It is determined that there is a collision.

  Specifically, in FIG. 6, a line Lc passing through the coordinate origin of the TTCR-TTC space indicates a collision line where the host vehicle and an approaching object are represented by representative points (TTCR = 0). When TTC = 0). The upper broken line Lu with respect to the line Lc indicates the (Ws + Lo) / Vx line that is the upper limit of the collision range when the size of the host vehicle and the approaching object is taken into account, and the lower broken line Ld Indicates a (Wo + Ls) / Vz line that is the lower limit of the collision range, and is corrected by the acceleration of the host vehicle.

  The upper area of the line Lu indicates that the approaching object passes the front of the host vehicle without colliding first, and the area between the lines Lu and Lc indicates a situation where the host vehicle hits the approaching object. Yes. Conversely, the area between the lines Lc and Ld represents a situation in which the host vehicle is hit by an approaching object, and the area below the line Ld passes through the vehicle without colliding with the approaching object ( The approaching object passes behind the host vehicle.

  The alarm / avoidance control determination unit 16 determines that the alarm is issued or the avoidance control intervention is performed when the collision determination unit 15 determines that the collision occurs and the lateral collision prediction time TTCR is equal to or less than a threshold Th_war (for example, Th_war = 3 sec). FIG. 7 shows an alarm area on the TTCR-TTC space. In FIG. 7, area K_TTCR in FIG. 7A shows a conventional alarm range when the determination is made only under the condition of predicted lateral collision time TTCR, and area K_TTC0 in FIG. The alarm range when the determination is made under the condition of the predicted collision times TTCR and TTC0 is shown.

  From FIG. 7, in the conventional method in which the alarm determination is performed only by the lateral collision prediction time TTCR, an alarm is issued even in an area where no collision is predicted to occur. On the other hand, according to this method, it is understood that an alarm is not issued in an area where a collision is predicted not to occur, and an unnecessary alarm can be suppressed.

  Further, as described above, as a form of collision between the own vehicle and the approaching object, a collision form of which of the two contacts the opponent first, that is, when the own vehicle hits the approaching object, You may be hit by. When the host vehicle hits an approaching object, avoidance by deceleration is desirable. However, when the host vehicle is hit from an approaching object, acceleration may be avoided to avoid a collision. Therefore, the collision determination unit 15 performs a collision determination including the collision type, and changes the warning or control intervention method according to the collision type, thereby prompting the driver to avoid a safe accident.

  Thus, in the present embodiment, the possibility that the host vehicle and an approaching object meet and collide with each other is determined based on the collision prediction time in the lateral direction and the collision prediction time in the traveling direction, and the host vehicle is below the set vehicle speed. In this case, the collision prediction time in the traveling direction when the predicted collision time in the lateral direction becomes zero is corrected based on the acceleration of the host vehicle. As a result, even when the host vehicle is about to start from a stop or is traveling at an extremely low speed, the reliability of collision determination can be improved and erroneous determination can be avoided. It is possible to suppress unnecessary warnings when there is no warning and to avoid unalarmed / alarm delays when the driver intends to start even when the vehicle is stopped.

DESCRIPTION OF SYMBOLS 1 Collision determination apparatus 11 Approaching object detection part 12 Approaching object distance calculation part 13 Lateral direction collision prediction time calculation part 14 Travel direction collision prediction time calculation part 14a Prediction time correction part 15 Collision determination part 16 Alarm / avoidance control determination part A Acceleration TTC Traveling direction collision prediction time TTC0 Traveling direction collision prediction time when the lateral collision prediction time becomes zero TTCR Lateral collision prediction time X Lateral distance Z Traveling direction distance Vx Lateral relative speed Vz Traveling direction relative speed

Claims (5)

An approaching object detection unit for detecting an approaching object approaching the host vehicle;
A lateral collision prediction time calculation unit that calculates a lateral collision prediction time from the relative distance and relative speed of the approaching object in the lateral direction with respect to the host vehicle;
A traveling direction collision prediction time calculation unit that calculates a traveling direction collision prediction time from the relative distance and relative speed in the traveling direction of the approaching object with respect to the host vehicle;
A collision determination unit for determining a collision between the host vehicle and the approaching object based on the lateral collision prediction time and the traveling direction collision prediction time;
The traveling direction collision prediction time calculation unit corrects the traveling direction prediction time when the lateral collision prediction time becomes zero when the host vehicle is less than or equal to a set vehicle speed based on the acceleration of the host vehicle. A vehicle collision determination device.   The traveling direction prediction time calculation unit estimates the driver's intention to start based on the brake pressure when the host vehicle is stopped, and calculates the traveling direction prediction time only when it is estimated that there is an intention to start. The vehicle collision determination device according to claim 1, wherein the vehicle collision determination device is corrected.   The vehicle collision determination device according to claim 1, wherein the traveling direction prediction time calculation unit estimates the acceleration of the host vehicle based on a frequency distribution created based on a history of acceleration at the time of starting in the past. The advancing direction prediction time calculation unit calculates a plurality of prediction time candidates by setting a plurality of values for the acceleration of the host vehicle and correcting the advancing direction prediction time at each acceleration,
2. The vehicle collision determination device according to claim 1, wherein the collision determination unit determines that a collision has occurred when at least one of the plurality of prediction time candidates satisfies a collision determination condition.   The vehicle collision determination according to claim 1, wherein the collision determination unit determines a collision between the host vehicle and the approaching object, including a collision mode in which one of them first contacts the opponent. apparatus.