JP2999652B2 - Vehicle Recognition Method Using Scanning Laser Radar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recognizing a preceding vehicle by a scan laser radar for recognizing whether an object is a preceding vehicle traveling on the same lane when measuring a distance by a scan laser radar mounted on an automobile. .

[0002]

2. Description of the Related Art Conventionally, a laser radar is mounted on an automobile as an on-vehicle distance measuring apparatus, and an object is illuminated from an own vehicle based on a time required for irradiating the object with laser light and receiving reflected light from the object. In some cases, the distance to an object is calculated by an arithmetic circuit.However, in the case of such a laser radar, even if it is possible to detect the presence of an object in front, it is determined whether or not the preceding vehicle is traveling ahead. It is difficult to identify, and it is conceivable to recognize whether the target object is a preceding vehicle based on the relative speed to the own vehicle, that is, based on a change in distance per unit time, but the vehicle data is characterized by the distance. For example, at short distances, continuous data over the vehicle width is obtained, whereas at long distances, one point data is obtained. Thus, it is difficult to accurately recognize the presence of the vehicle regardless of the distance to the preceding vehicle. That.

Therefore, as a method of improving recognition accuracy, for example, as described in Japanese Patent Application Laid-Open No. 3-92436, a laser beam is scanned at a predetermined angle and a distance to an object is calculated for each irradiation point. A method has also been proposed for more accurately determining and recognizing whether or not the vehicle is a preceding vehicle from the pattern of the irradiation point data.

[0004] By the way, among the vehicles recognized using the laser as described above, a vehicle traveling on another lane or a shoulder on the same lane besides a preceding vehicle traveling on the same lane as the own vehicle. Although vehicles that are stopped are also included, vehicles that are traveling on these other lanes or vehicles that are stopped on the shoulder of the same lane have a lower risk of rear-end collision than vehicles that are traveling on the same lane. Even if the distance between the vehicle and the vehicle is short, the necessity of avoiding a rear-end collision is extremely small.

[0005]

However, in the conventional method, it is clearly distinguished between a vehicle traveling on the same lane, a vehicle traveling on another lane, and a vehicle stopping on the shoulder of the same lane. Unnecessary collision avoidance operation is performed in response to excessively stopped vehicles at the shoulder of the road, etc., so it is necessary to accurately determine whether the vehicle is traveling on the same lane and to travel on the same lane. Otherwise, it is necessary to perform a risk reduction process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to accurately determine whether a vehicle is traveling on the same lane.

[0007]

A method for recognizing a preceding vehicle by a scan laser radar according to the present invention irradiates a laser beam to a target object ahead by a scan laser radar mounted on an automobile, and reflects reflected light from the target object. A scan laser radar for recognizing whether the target is a preceding vehicle on the same lane when performing distance measurement by calculating the distance between the vehicle and the target based on the time until the light is received by the calculation means; A preceding vehicle recognition method according to the above, wherein the scanning laser radar scans the laser beam at a predetermined angle in a direction orthogonal to the traveling direction of the vehicle, and calculates the distance to the target object for each irradiation point, The calculated distance for each irradiation point is stored in each storage area of the storage means, and a plurality of measurement points having substantially the same distance over the vehicle width are present in the stored data. A candidate vehicle is detected based on whether the vehicle is moving or not, and a fitness function that is a function such as a difference between the own vehicle speed and the relative speed of the preceding vehicle candidate and a displacement amount of the preceding vehicle in the vehicle width direction with respect to the own vehicle is calculated. Is used to calculate the certainty factor representing the certainty of being the preceding vehicle, and calculate the coordinates of the position of the preceding vehicle candidate and the relative speed in a coordinate system using the scanning direction of the laser beam and the traveling direction as coordinate axes. Repeats the calculation of the certainty factor, and determines whether or not the sum of the differences between the certainty factor and the reference value is larger than another reference value. It is characterized in that it is determined that the vehicle is traveling on the same lane, and it is determined that the vehicle is not on the same lane when it is large.

[0008]

According to the present invention, the calculation of the certainty factor representing the certainty of the preceding vehicle using the fitness function is repeated for each calculation of the position coordinates and the relative speed of the preceding vehicle candidate.
A cumulative vehicle adds the difference between the certainty factor and the reference value, and determines that the preceding vehicle traveling on the same lane when the total sum is smaller than the other total value. It is possible to accurately distinguish a vehicle traveling on another lane, a vehicle stopped on the shoulder of the same lane, and the like.

[0009]

FIG. 1 is a flowchart for explaining the operation of an embodiment of a method for recognizing a preceding vehicle using a scanning laser radar according to the present invention, FIG. 2 is a block diagram of a distance measuring apparatus, and FIGS.

First, the configuration of the distance measuring device will be described. As shown in FIG. 2, a laser radar 1 composed of a semiconductor laser or the like is driven by a laser control ECU 2, and a laser beam from the laser radar 1 is reflected by a mirror 3. Is projected ahead of the vehicle.

At this time, the stepping motor 4 is controlled by the ECU.
The mirror 3 is rotated by the driving control of the mirror 2, and
The rotation angle of the mirror 3 is detected by the mirror angle sensor 5, and the motor 4 is controlled so that the rotation angle becomes a constant angle. The laser beam projected forward by the rotation of the mirror 3 is rotated by a predetermined angle such as 1 °. Each is scanned in one direction.

A reflected light from an object such as a preceding vehicle in front is received by a light receiving element such as a phototransistor. The host ECU 6 as a calculating means performs a process from irradiation of laser light to reception of the reflected light. The distance from the vehicle to the target object is calculated based on the time and the speed of light.

The speed of the vehicle is detected by the wheel speed sensor 7 and a detection signal is output to the host ECU 6. Similarly, the steering angle is detected by the steering angle sensor 8 and a detection signal is output to the host ECU 6. .

Reference numeral 9 denotes a danger avoidance control unit which performs vehicle control such as braking for avoiding danger in accordance with a command from the host ECU 6.

By the way, the distance for each irradiation point calculated by the host ECU 6 is stored in each storage area of a storage means such as a built-in memory of the ECU 6, and the stored distance data is processed to travel on the same lane. It is determined whether the vehicle is the preceding vehicle or not, but the processing of the host ECU 6 is performed as follows.

That is, the host ECU 6 detects some preceding vehicle candidates based on whether or not there are a plurality of data of measurement points having substantially the same distance over the vehicle width in the data stored in the storage means. Furthermore, in order to select an approaching vehicle other than the oncoming vehicle from these preceding vehicle candidates,
The magnitude of the own vehicle speed vector Vs and the magnitude of the relative velocity vector Vk of the preceding vehicle candidate are compared, and 0 <| Vk |
Only the preceding vehicle candidate Ck satisfying ≦ | Vs | is extracted,
The relative speed vector Vk of the extracted preceding vehicle candidate Ck is examined.

Now, as shown in FIG. 4, the vehicle Cj and the preceding vehicle Ck ₁ on the same lane and the vehicle Ck ₂ on the other lane.
, The relative speed vector Vk ₁ of the vehicle Ck ₁ on the same lane goes in the direction of the own vehicle Cj, but the relative speed vector Vk ₂ of the vehicle Ck ₂ on the other lane goes to other than the own vehicle Cj. It is determined whether the positional deviation amount | Lk | of the preceding vehicle with respect to the own vehicle in the vehicle width direction satisfies Expression 1, and if it is, it is determined that there is a high possibility that this vehicle is not on the same lane.

[0018]

(Equation 1)

In Equation 1, Xk and Yk are coordinate values on the X and Y axes indicating the position of the preceding vehicle in a coordinate system having the scanning direction and the traveling direction of the laser beam as coordinate axes, and Vk.
x and Vky are components of the relative speed Vk of the preceding vehicle in the X-axis direction,
The component in the Y-axis direction, β, is a vehicle width dimension.

Further, in order to check the certainty of the above-mentioned judgment, a fitness degree which is a function of a difference between the own vehicle speed and the relative speed of the preceding vehicle candidate, a positional deviation amount of the preceding vehicle with respect to the own vehicle in the vehicle width direction, and the like. A function is used to calculate a certainty factor indicating the certainty of the preceding vehicle, and to calculate the coordinates of the position of the preceding vehicle candidate and the relative speed in a coordinate system using the scanning direction and the traveling direction of the laser beam as coordinate axes. Then, the calculation of the certainty factor is repeated.

At this time, the fitness function used for the calculation of the certainty factor is, as shown in FIG.
The difference Vsk between s and the relative speed vector Vk of the preceding vehicle candidate
F1 (Vsk), and a function F2 (| Lk |) of the displacement | Lk | of the preceding vehicle in the vehicle width direction with respect to the own vehicle as shown in FIG. 3B, and these functions F1 (Vs)
k), F2 (Lk) is used to calculate the certainty factor Wsk by the calculation of Expression 2.

[0022]

(Equation 2)

The operation of equation (2) is the preceding vehicle candidate Ck.
Is repeated each time the position coordinates Ck (Xk, Yk) and the relative speed are calculated, and the difference between the certainty factor Wsk and the reference value Wrf is cumulatively added. It is determined whether the value is greater than the value Wnrf. When the value is smaller than the value Wnrf, the target preceding vehicle is determined to be traveling on the same lane. When the value is greater, the target vehicle is determined not to be on the same lane. Is not done.

[0024]

(Equation 3)

Next, a series of operations will be described with reference to the flowcharts of FIGS.

First, as shown in FIG. 1, it is determined whether all preceding vehicle candidates have been checked (step S).
1) If the determination result is NO, it is determined whether or not the relative speed of the preceding vehicle candidate is known (step S).
2), if the result of this determination is NO, step S described later
7 and if the determination result is YES, calculation of the certainty factor Wsk by Expression 2 is performed (step S3).

Then, the cumulative addition of the difference between the certainty factor Wsk obtained in step S3 and the reference value Wrf is performed (step S4), and it is determined whether or not the total sum ΣW is smaller than "0". If the result of the determination is NO (step S5), the process proceeds to step S7, which will be described later. If the result of the determination is YES, the addition total value ΣW is left at “0” (step S6), and the next data waits. (Step S7), returning to step S1.

On the other hand, if the decision result in the step S1 is YES, all of the detected preceding vehicle candidates are collided based on the relative speed, the inter-vehicle distance, the own vehicle speed and the like in the same manner as in the known collision danger judgment processing. A risk check process is performed (step S8), and it is determined whether there is a preceding vehicle candidate whose rear-end collision risk level has reached a predetermined level at which the danger avoidance control unit 9 should be operated (step S9). If the result of the determination is NO, the danger avoidance control section 9 is controlled to a non-operation state (step S10).

If the decision result in the step S9 is YES, it is determined whether or not the cumulative addition sum ΣW of the difference between the certainty factor Wsk of the target preceding vehicle candidate and the reference value Wrf is larger than the evaluation reference value Wnrf. A determination is made (step S
11), if the result of this determination is YES, step S10
If the result of the determination is NO, the danger avoidance control unit 9 is actuated to take an action to avoid a collision with the preceding vehicle (step S12), and then returns to the start after the processing of step S10.

Therefore, certainty factor Wsk using the fitness function
And the reference value Wrf are cumulatively added.
When W is smaller than the collision risk evaluation reference value Wnrf, it is determined that the vehicle is traveling ahead on the same lane, so that the vehicle traveling on the same lane and the vehicle traveling on other lanes are It is possible to accurately distinguish a vehicle or the like stopped at the shoulder of the road on the same lane, and it is possible to prevent unnecessary unnecessary collision avoiding operation as in the related art.

The relationship between the elapsed time and the above-mentioned total sum 合計 W was experimentally obtained under the condition that the own vehicle speed Vs = 40 km / h and the inter-vehicle distance at the start is 50 m, as shown in FIG. , The sum total value ΔW for vehicles on other lanes is equal to the evaluation reference value W before 5 seconds have elapsed since the start.
Since nrf is exceeded, it can be understood that a vehicle traveling on the same lane as the own vehicle and a vehicle traveling on another lane can be accurately distinguished.

Note that the fitness function is F1 (Vs
k) and F2 (| Lk |).

[0033]

As described above, according to the present invention, a preceding vehicle traveling on the same lane, a vehicle traveling on another lane, a vehicle stopped on the shoulder of the same lane, and the like are provided. Accurate distinction is possible, which is extremely effective as an aid for safe driving.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining the operation of one embodiment of a method for recognizing a preceding vehicle by a scanning laser radar according to the present invention.

FIG. 2 is a block diagram of an apparatus applied to the present invention.

FIG. 3 is an operation explanatory diagram of one embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of one embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of one embodiment of the present invention.

[Explanation of symbols]

 1 laser radar 2 laser control ECU 6 host ECU

Claims (1)

(57) [Claims] 1. A distance between a host vehicle and the target object based on a time required for irradiating a target object ahead with laser light by a scanning laser radar mounted on the vehicle and receiving reflected light from the target object. Is used by a scanning laser radar to recognize whether the target object is a preceding vehicle on the same lane. The distance to the object is calculated for each irradiation point by scanning at a predetermined angle in a direction orthogonal to the traveling direction of the vehicle, and the calculated distance for each irradiation point is stored in each storage area of the storage means. The preceding vehicle candidate is detected based on whether or not there are a plurality of measurement points having substantially the same distance over the vehicle width in these stored data, and the own vehicle speed and the relative speed of the preceding vehicle candidate are detected. Is calculated using a fitness function that is a function such as a difference between the vehicle and the position deviation of the preceding vehicle in the vehicle width direction with respect to the own vehicle. The calculation of the certainty factor is repeated each time the coordinates of the position of the preceding vehicle candidate and the relative speed in the coordinate system using the direction and the traveling direction as coordinate axes are calculated,
The difference between the certainty factor and the reference value is cumulatively added to determine whether or not the added total value is larger than another reference value.If the sum is smaller, it is determined that the preceding vehicle is traveling on the same lane. A method for recognizing a preceding vehicle using a scanning laser radar, which sometimes determines that the vehicle is not on the same lane.