JP2010137803A - Vehicular drive assistance system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular drive assistance system for performing an own vehicle's braking operation of prompting a rear obstacle to perform a braking operation for alleviating a risk of a rear end collision when there is the risk that the rear end may collide with the rear obstacle due to the own vehicle's braking operation. <P>SOLUTION: The vehicular drive assistance system includes a braking necessity determination means 9 for determining whether the own vehicle needs to perform braking processing, an own vehicle's state detection means for detecting an own vehicle's motion state, a succeeding vehicle detection means for detecting a vehicle traveling at the rear side of the own vehicle, and an own vehicle braking force determination means 10 for implementing an own vehicle's braking force to prompt the succeeding vehicle to perform the braking operation without contacting the succeeding vehicle based on the information of the own vehicle and the succeeding vehicle when the braking necessity determination means 9 determines that the own vehicle needs to perform the braking processing. In this structure, when the rear end may collide with the rear obstacle due to the own vehicle's braking operation, the own vehicle's braking operation is performed to prompt the rear obstacle to perform the braking operation, thereby alleviating the risk of the rear end collision. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle driving support device, and more particularly to a vehicle driving support device that can reduce the risk of a rear-end collision by a following vehicle.

Conventionally, as a vehicle driving support device, when it is assumed that the vehicle touches both the preceding vehicle and the rear obstacle when there is a risk of contact with either of the preceding vehicle and the rear obstacle, the own vehicle An invention relating to a device that performs braking adjustment so as to minimize the sum of contact energies received is known (for example, see Patent Document 1).
JP 2006-160205 A

  However, in the invention disclosed in Patent Document 1, when it is assumed that the host vehicle contacts both the preceding vehicle and the rear obstacle, the braking control amount is determined so that the contact energy received by the host vehicle is small. is doing. That is, such a conventional apparatus performs a braking control for the minimum damage contact. This control method can be an effective method when the vehicle actually touches, but it is not a braking control for avoidance, so there is a high probability that contact can be avoided depending on how the vehicle is braked. However, there is a problem of trying to make the least damage contact.

  The present invention has been made in order to solve such a conventional problem, and its purpose is to apply a braking operation to a rear obstacle when there is a risk of rear-end collision with the rear obstacle due to braking of the host vehicle. An object of the present invention is to provide a driving support device for a vehicle that can perform such vehicle braking and reduce the risk of rear-end collision.

  Therefore, a feature of the present invention is a vehicle driving support device, a braking necessity determination unit that determines whether or not the vehicle is in a braking situation, and a host vehicle state detection unit that detects a motion state of the host vehicle. And the following vehicle detecting means for detecting a vehicle traveling behind the own vehicle, and the information on the own vehicle and the following vehicle when it is determined by the braking necessity determining means that the own vehicle needs to be braked. The gist of the present invention is that the vehicle braking force determination means for realizing the vehicle braking force that does not contact the succeeding vehicle and urges the succeeding vehicle to brake is provided.

  Here, the own vehicle braking force determination means includes a following vehicle model that expresses the braking characteristics of the following vehicle, and at least the relative position between the own vehicle and the following vehicle, the relative speed, and the braking force that the own vehicle tries to apply. It is preferable to use any one of the above as an input of the following vehicle model.

  Further, in the present invention, the following vehicle braking characteristic expressed by the following vehicle model can calculate at least one of the reaction time until the braking of the following vehicle and the braking amount of the following vehicle.

  Furthermore, in the present invention, the parameter of the following vehicle model can use at least one of the own vehicle or the following vehicle, the road surface condition, and the subsequent vehicle absolute speed.

  Further, in the present invention, the braking force determining means includes own vehicle forward environment recognizing means for detecting the environment ahead of the own vehicle, and when there is a high urgency to brake the own vehicle from the environment ahead of the own vehicle, the following vehicle It is preferable to perform a strong action such as braking the vehicle by braking the vehicle.

  Further, the own vehicle braking force determining means is based on the result of the sequential calculation of the braking force range based on the information on the own vehicle, the following vehicle, and the front environment newly acquired at predetermined time intervals. The optimum braking amount may be determined.

  According to the present invention, when there is a risk of rear-end collision with a rear obstacle due to braking of the own vehicle, the host vehicle is braked so that a braking operation is applied to the rear obstacle, and the rear obstacle is urged at an early stage. Thus, the rear-end collision risk can be reduced. In particular, according to the present invention, it is possible to effectively perform the braking operation to the succeeding vehicle by determining the braking force of the own vehicle based on the succeeding vehicle model representing the braking characteristics of the following vehicle.

  In addition, according to the present invention, it is possible to calculate at least one of the braking reaction time or the braking amount, which is an important braking characteristic of the rear obstacle, so that the accuracy of the movement prediction of the rear obstacle by the own vehicle braking is calculated. Can be improved.

  Furthermore, according to the present invention, by adopting a configuration that calculates the braking reaction time and the braking amount, which are important braking characteristics of the succeeding vehicle, it is possible to improve the accuracy of the motion prediction of the succeeding vehicle by the own vehicle braking.

  In addition, according to the present invention, by adopting a configuration in which the rear obstacle braking characteristic is changed according to the rear obstacle or the rear obstacle traveling state, the detailed characteristic that cannot be expressed only by the relative position and speed with the own vehicle. Can also be expressed.

  Furthermore, according to the present invention, since the vehicle determines the necessity of braking from the environment ahead of the host vehicle, the action to the rear obstacle can be changed according to the urgency of the host vehicle.

  In addition, according to the present invention, the vehicle braking amount is updated based on the latest information such as the own vehicle, the rear obstacle, the front environment, etc. It is possible to cope with changes as appropriate.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a vehicle driving support apparatus according to an embodiment of the present invention will be described with reference to the drawings. 1 to 5 show a vehicle driving support apparatus according to an embodiment of the present invention.

  FIG. 1 is a layout diagram illustrating a vehicle driving support apparatus according to the present embodiment and a device configuration necessary for the vehicle driving support apparatus.

  In FIG. 1, two stereo cameras 2 are arranged in front of a vehicle 1 in a vehicle 1 facing forward. These cameras 2 detect a front obstacle and a road environment ahead. By arranging the two stereo cameras 2 in this way, it is possible to detect the relative speed and the relative distance from the front object.

  A millimeter wave radar 3 is attached to the rear part of the vehicle 1 toward the rear. By using the reflected millimeter wave emitted from the millimeter wave radar 3, the relative speed and relative distance to the rear obstacle can be detected.

  The rotary encoder 4 detects the number of rotations of each wheel from a pulse signal generated according to the wheel rotation of each wheel, and uses it when calculating the speed in the traveling direction of the vehicle and the slip ratio of each wheel.

  The acceleration sensor 5 detects acceleration in a specific direction generated in the vehicle using a known device configured using a piezoelectric element or the like. Here, the structure which detects the acceleration which generate | occur | produces in the vertical direction of the vehicle 1 is assumed.

  The microprocessor 6 is an integrated circuit including an A / D conversion circuit, a D / A conversion circuit, a central processing unit, a memory, and the like, and processing information of signals detected by various sensors according to a program stored in the memory. Based on the above, the driving support algorithm of the present invention is calculated, and the calculation result is transmitted to the brake controller 7. The brake controller 7 includes a microprocessor 6 for control calculation and an actuator-driven booster circuit, and operates the brake actuator 8 using a braking torque signal output from the microprocessor 6 as a command value. The brake actuator 8 plays a role of automatically and independently moving each wheel braking system by adjusting the braking / driving force of each wheel according to the output signal from the brake controller 7.

  FIG. 2 is a block diagram expressing the apparatus configuration shown in FIG. First, information representing the motion state of the host vehicle is obtained by integrally processing detection signals from the wheel speed sensor and the acceleration sensor 5 as the host vehicle state detection means. Further, as a method for detecting the relative position and speed of a front obstacle existing ahead of the host vehicle as a front environment recognition means, a stereo camera 2 installed in front of the vehicle is connected to a rear obstacle detection means (following vehicle inspection). A method of detecting the relative position and speed of a rear obstacle traveling behind the host vehicle as the exit means) uses each millimeter wave radar 3 installed behind the vehicle.

  In addition to these sensor information processing functions, the microprocessor includes a vehicle braking necessity determining means 9 for determining whether or not the vehicle should perform braking, and the vehicle does not come into contact with a front obstacle. In addition, the vehicle has a vehicle braking force determining means 10 for determining a vehicle braking force that does not collide with an obstacle behind the vehicle.

  This own vehicle braking necessity determining means 9 determines the necessity of braking according to the degree of approach with the front obstacle. Further, the host vehicle braking force determining means 10 determines the braking characteristics of the rear obstacle based on the degree of approach to the rear obstacle, etc., when it is determined that the host vehicle braking necessity determining means 9 needs to perform braking. Determine the effective vehicle braking amount in consideration.

  By driving the brake actuator 8 mounted on the vehicle based on the braking amount calculation result, the driver can realize the time series operation amount output from the vehicle braking force determination means 10. In the present embodiment, it is assumed that an intervention operation in the braking system is performed, and the rotary encoder 4, the brake controller 7, and the brake actuator 8 are configured. Since a known control technique can be used for the brake control system, the description thereof is omitted.

  The calculation procedure in the microprocessor 6 will be described below based on the flowchart shown in FIG. In addition, in order to make the present embodiment specific, each processing content will be described assuming the scene shown in FIG. In FIG. 4, the host vehicle travels on a straight road with one lane on one side, and there are moving obstacles in front and rear of the host vehicle. In the state shown in FIG. 4, the vehicle is moving in the same direction along the road, but it is assumed that the host vehicle needs to perform an avoidance operation as the front obstacle is decelerated.

First, detection signals from the stereo camera 2, the millimeter wave radar 3, and each sensor are read, and the signal information is stored in a memory (not shown) in the microprocessor 6. Then, in order to describe the movement state by associating the information of the own vehicle, the front obstacle, and the rear obstacle with the unified coordinate values, the coordinate system is determined from the image captured from the stereo camera 2 (step) S1). In the present embodiment, as shown in FIG. 4, the X axis is set in the traveling direction of the road, and the Y axis is set in the direction perpendicular to the X axis. The coordinate origin is set such that the current value of the vehicle is the X coordinate origin and the center of the road is the Y coordinate origin.

On the coordinates set in this way, the position information of the center of gravity of the vehicle is calculated based on the information of (Xv, Yv) front obstacle and rear obstacle based on the information of the stereo camera 2 and the millimeter wave radar 3, These are respectively expressed as (X _F , Y _F ) (X _R , Y _R ). Further, the road boundary is detected from the information of the camera image, the Y coordinate of the road left boundary is expressed as y _L , and the Y coordinate of the road right boundary is expressed as y _R. Then, each moving speed and moving deceleration in the determined coordinate system are calculated.

In this embodiment, since both the own vehicle and each obstacle are traveling in the X-axis direction, the own vehicle speed is (V _V , 0) from the rotary encoder 4, and the speed of the front obstacle and the rear obstacle is the previous time. Based on the difference from the acquired absolute position information, (V _F , 0) and (V _R , 0) are set. And since the front obstacle is decelerating, deceleration _V'F is calculated based on the time change information of (V _F , 0). Further, the deceleration of the host vehicle is acquired from an onboard acceleration sensor.

Next, it is determined whether there is a space for avoiding a front obstacle by steering (step S2). First, from the camera image, and compares the parameter delta _D is set at a distance D _R, detects the D _L, width or more values of the vehicle between the front obstacle and the right road boundary.
D _R > Δ _D , D _L > ΔD (1)
When any of the conditions shown in the above equation (1) is satisfied, it is considered that a space for avoiding steering is present ahead, and steering avoidance control or steering avoidance as disclosed in, for example, JP-A-2002-293226 is disclosed. Switch to support device. If neither is established, it is necessary to avoid by braking, and the process proceeds to step S3.

In step S3, the host vehicle braking necessity determination means 9 determines whether or not there is a need for deceleration from the environmental information ahead of the host vehicle. If there is a need for deceleration, how much deceleration is necessary. Estimate. Now, running at (Xv, Yv) position and the vehicle running at _{V V} in the X-axis direction _{is, (X} F, _{Y F)} located in the X-axis direction speed _{V F,} deceleration V _'F In order to avoid contact with the front obstacle, it is necessary to decelerate by braking larger than the deceleration shown below.
^{_{a min = (Vv-V F}} ) 2/2 (Xv-X F) + V 'F ...... (2)
To step 4.

In step S4, the following two determinations are made based on the current host vehicle deceleration V′v. First, the first determination is a determination as to whether or not there is a high possibility that the vehicle is in contact with a front obstacle, and is compared with the minimum braking reference amount a _min calculated in step S2.
V′v <a _min a (3)
If the above expression (3) is not satisfied, step S4 is interrupted and the process proceeds to step S5. If the above equation (3) is satisfied, it is estimated what kind of braking operation is performed by the rear obstacle detected by the device in accordance with the braking motion of the own vehicle, and based on the estimated result, It is determined whether the rear-end collision risk is high. Here, as an estimation mainly, in this embodiment, a reaction time until braking of the rear obstacle and a braking amount after the reaction are assumed.

First, an example regarding reaction time estimation will be described. Generally, a driver notices braking of a preceding vehicle based on visual information, and a change in the visual size of the preceding vehicle can be considered as an example of the visual information. As a method of estimating the brake timing based on this visual change, a method of estimating the reaction time until the brake operation using a variable called the obstacle change rate calculated based on the camera information, for example, “Time-To -Collision can use the method described in "Do you decide the brake timing (Kazumoto Morita, Masafumi Ohno, Michiaki Sekine, 4th ITS Symposium)". This reaction time will be expressed as Tac.

Next, after the reaction time Tac calculated by the rear obstacle, the brake operation margin is estimated. Here, the following two estimation method examples are shown.

First, the first method calculates the minimum amount of braking required on the assumption that the rear obstacle decelerates after Tac seconds. First, assuming that the host vehicle decelerates at V′v by a certain amount, the relative distance and relative speed after Tac seconds are expressed as follows.
Dre = (Xv−X _R ) + (V _V− V _R ) · Tac + V′vT ² ac / 2 (4) Vre = (V _V− V _R ) + V′vTac (5)
Using the above two formulas (4) and (5), the minimum reduction speed a _R when assuming constant deceleration after Tac seconds required by the rear obstacle is shown as follows.
aR = V ² re / 2Dre−V′v (6)
With a _R calculated by the equation (6), it performs the following determination.
a _R ≦ a _th (7)
a _th represents the deceleration criterion is deemed braking margin, if aR is less than this value, considered V'v are vehicle deceleration can afford to rectangular obstacle, the Brake control is not performed by the device, and driver operation is given priority. If the above equation (7) is not satisfied, it is possible to avoid the rear-front obstacle, but it is considered that there is a possibility that the rear-end obstacle may collide, and the process proceeds to step 5. The above is the first method for estimating the braking amount of the rear obstacle.

The second method of estimating the amount of rear obstacle braking is that the rear obstacle has a time-series deceleration characteristic as shown in the following equation in accordance with the braking at the deceleration V′v of the vehicle traveling ahead. Assume that
V′v = (V _V −V _R ) (8)
The braking characteristics of the rear obstacle are such that even if the speed of the host vehicle changes, the speed of the host vehicle and the rear obstacle is adjusted so as to maintain the same speed, and the vehicle travels constantly at the same speed. At that time, if Xv ≦ X _R even temporarily before the vehicle and the rear obstacle enter the running state at the same speed, the vehicle will collide with the rear obstacle when the host vehicle decelerates. . Further, a parameter k ₁ is representative of a follow-up characteristic with respect to the vehicle of the rear obstacle in (8). After this if parameter k ₁ is greater rearward obstacle against deceleration of the vehicle braking reaction time, make the rapid deceleration and will align quickly to the same speed, also the deceleration of the vehicle smaller parameters k ₁ On the other hand, the rear obstacle performs gentle braking. Therefore, if the host vehicle deceleration V′v is such that contact avoidance is possible and k ₁ can be reduced, contact is made when viewed from the rear obstacle. It can be regarded as a deceleration of the vehicle with a margin of avoidance. Now, to calculate whether at the time of the current vehicle deceleration V'v, k ₁ can be reduced much.

Specifically, the following determination is made.
k1 <K (9)
K indicates the reference value of the deceleration characteristic parameters k ₁ of the rear obstacle, such as not to rear-end deceleration a and the vehicle has a margin. That is, if the own vehicle deceleration V′v satisfies the above equation (9), it is considered that the current deceleration V′v by the own driver operation is appropriate, and the braking control in this device is not performed. Give priority to driver operation. If equation (9) does not satisfy the determination equation, it is possible to avoid the front obstacle, but it is considered that there is a possibility of being collided with the rear obstacle, and the process proceeds to step S5. The above is the description of the second method for estimating the deceleration of the rear obstacle.

Here, a _th or K can be made variable according to the situation. For example, by installing a camera in the vehicle that can capture the back of the vehicle, the type of obstacles behind the vehicle can be determined. As a result, the inertia of a truck is large and sudden braking cannot be performed. it is possible to change the reference value K in accordance with the type, such as to set the lower the a _th or K, the braking performance is high if the sports car is set to enhance the a _th and K. In addition, by installing a means for estimating the road surface friction coefficient on the road, if the road surface friction coefficient is high, such as on dry asphalt roads, _ath and K are set higher, depending on the road surface condition. Can change the reference value. The above is the description of the processing in step S4.

In step S5, the own vehicle deceleration intervention amount with less risk of being collided with a rear obstacle is calculated. First, the target command value for own vehicle deceleration is temporarily placed as a _min calculated in step 3. Then, when the host vehicle deceleration is a _min , the same processing as the method of estimating the rear obstacle braking characteristic used in step S4 is performed. At this time, as long as satisfying the above expression (7) or (9) to indicate such a determination formula, and controls the temporary was a _min as the target command value of the vehicle deceleration. Also, if not satisfy the judgment formula, again temporarily placed as deceleration a _min -Δa stronger slightly than a _min, a determination is again. Here, Δa is a positive value. When this is repeated N times, when the own vehicle deceleration a _min −Δa · N satisfies the determination formula for the first time, this a _min −Δa · N can suppress the possibility of contact with the rear obstacle. Determine as vehicle deceleration.

  Next, the process proceeds to step S6. In step S6, the own vehicle target deceleration determined in step S5 is output to the braking force controller. Based on this signal, the braking force of each wheel is determined in the braking force controller and transmitted to each wheel to actually perform vehicle braking control. With respect to each wheel braking control based on the target deceleration, it is assumed that a known technique of brake control (for example, Japanese Patent Application Laid-Open No. 2007-55583) is used, and therefore detailed description in this embodiment is omitted.

  The above is the flow of processing in the microprocessor shown in FIG. Further, in the present embodiment, the latest information of each sensor, camera, and radar is acquired at regular intervals after the own vehicle braking necessity determination unit operates, and the above-described processing is performed based on this information, and the braking control amount is obtained. Update. As a result, it is possible to compensate for sudden changes in the environment and insufficient estimation of the rear obstacle braking characteristics.

  Further, in the present embodiment, the vehicle braking necessity determining means here detects a deceleration operation of a front obstacle using a stereo camera and determines whether or not braking of the own vehicle is necessary. If you can get information about the shape of the road ahead where your vehicle is traveling, etc., you can turn around a curved road as shown in Fig. 5 or turn left after slowing down an intersection. The host vehicle braking amount can be determined in consideration of the braking characteristics of the rear obstacle.

  An example of the vehicle braking necessity determination means when applied to curved roads and intersections is shown below. First, when applying to a curve road, the curvature radius of the curve is acquired by car navigation, and a target speed suitable for the curve approach is calculated from the curve information and road surface information. The idea of the calculation method here is that, as shown in FIG. 6, the approach speed decreases as the radius of curvature decreases, and the approach speed decreases as the road surface friction decreases. Using this target speed and the curve approach position, and the current host vehicle position and host vehicle speed, the minimum deceleration that the host vehicle should apply is calculated. The braking necessity determining unit is configured in this way. Next, when applying to an intersection, the driver will determine which intersection the vehicle will turn from the turn signal operation and car navigation information of the vehicle, and the minimum reduction that the vehicle should take from the distance to the intersection. Calculate the speed.

  Needless to say, the present invention is not limited to the above-described embodiment, and various design changes accompanying the gist of the configuration are possible.

1 is a configuration diagram of a vehicle including a vehicle driving support device according to an embodiment of the present invention. 1 is a block diagram of a vehicle driving support apparatus according to an embodiment of the present invention. It is a flowchart which shows the flow of a process of the driving assistance device for vehicles which concerns on embodiment of this invention. It is explanatory drawing which shows the condition which applies the driving assistance device for vehicles which concerns on embodiment of this invention. (A) And (B) is explanatory drawing which shows the situation which can apply the driving assistance device for vehicles which concerns on embodiment of this invention. It is a figure which shows the relationship between the curvature radius used by the own vehicle braking amount determination means at the time of applying the vehicle driving assistance device which concerns on embodiment of this invention to a curve road, and approach speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Stereo camera 3 Millimeter wave radar 4 Rotary encoder 5 Acceleration sensor 6 Microprocessor 7 Brake controller 8 Brake actuator 9 Own vehicle braking necessity determination means 10 Own vehicle braking force determination means

Claims (6)

Braking necessity determining means for determining whether or not the vehicle is in a braking situation;
Own vehicle state detection means for detecting the movement state of the own vehicle;
Subsequent vehicle detection means for detecting a vehicle traveling behind the host vehicle;
When it is determined by the braking necessity determining means that the host vehicle needs to be braked, based on the information on the host vehicle and the following vehicle, the vehicle that does not contact the following vehicle and urges the following vehicle to brake. Own vehicle braking force determining means for realizing vehicle braking force;
A vehicle driving support apparatus comprising: The host vehicle braking force determination means includes a following vehicle model that expresses the braking characteristics of the following vehicle,
2. The vehicle according to claim 1, wherein at least one of a relative position between the own vehicle and the following vehicle, a relative speed, and a braking force that the own vehicle is to apply is used as an input of the following vehicle model. Driving support device.   3. The vehicle-use vehicle according to claim 2, wherein at least one of a reaction time until braking of the subsequent vehicle and a braking amount of the subsequent vehicle is calculated as the subsequent vehicle braking characteristic expressed by the subsequent vehicle model. Driving assistance device.   4. The vehicle driving support apparatus according to claim 2, wherein at least one of a vehicle type, a road surface condition, and a subsequent vehicle absolute speed is used as the parameter of the subsequent vehicle model. The own vehicle braking force determination means includes own vehicle forward environment recognition means for detecting an environment ahead of the own vehicle,
5. The vehicle according to any one of claims 1 to 4, wherein when the vehicle is highly urgent to brake the vehicle from the environment in front of the vehicle, a strong action such as braking the following vehicle is performed by the vehicle braking. The vehicle driving support device according to one item.   The own vehicle braking force determination means is based on the results of the sequential calculation of the braking force range based on the information of the own vehicle, the following vehicle, and the front environment newly acquired at predetermined time intervals. The vehicle driving support device according to any one of claims 1 to 5, wherein an optimum braking amount is determined.

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