JP2000009842A - Measuring method for relative speed in transverse direction of preceding vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method for relative speed in the transverse direction, in which the relative speed in the transverse direction of a vehicle which precedes its own vehicle is measured with high accuracy on the basis of the reflection intensity pattern of a laser radar. SOLUTION: From a laser radar 2 which is carried on its own vehicle 1, a laser beam LB is radiated toward the front of the vehicle, a reflected beam from a preceding vehicle A is detected, and a reflection intensity pattern is prepared. By using a previously prepared reflection intensity pattern and a recently prepared reflection intensity pattern, the movement amount in the transverse direction of the preceding vehicle A is computed by a pattern matching operation. On the basis of the computed movement amount in the transverse direction and on the basis of the time difference between the previously prepared reflection intensity pattern and the recently prepared reflection intensity pattern, the relative speed in the transverse direction of the preceding vehicle A is computed. Thereby, the relative speed in the transverse direction of the preceding vehicle A can be measured with high accuracy and stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the relative speed of a preceding vehicle in the lateral direction for measuring the relative speed of the preceding vehicle in the lateral direction.

[0002]

2. Description of the Related Art In recent years, a travel control device having an inter-vehicle distance control device for pursuing a preceding vehicle has been put into practical use in order to reduce the driving operation of an automobile. A travel control device provided with this inter-vehicle distance control device, based on information from a front recognition device such as a camera or a laser radar, for example, can control a vehicle (hereinafter, referred to as “own vehicle”) and a preceding vehicle (hereinafter, “preceding vehicle”).
) Is detected, and the vehicle speed is adjusted by adjusting the engine output and the like so that the inter-vehicle distance becomes a preset target inter-vehicle distance, and the preceding vehicle is tracked. .

In the automatic tracking system, the preceding vehicle is the closest vehicle traveling on the own vehicle traveling lane, and when the own vehicle is traveling on the traveling lane and another vehicle is traveling on the overtaking lane, The other vehicle must not be regarded as a preceding vehicle, and only a vehicle within the traveling lane of the own vehicle must be recognized as a preceding vehicle. Therefore, when performing automatic tracking of the preceding vehicle,
It is important to accurately detect the positional relationship between the preceding vehicle and the own vehicle, and to detect the distance between the preceding vehicle (inter-vehicle time) and the moving speed of the preceding vehicle in the lateral direction (lateral relative speed). It is necessary to.

In order to detect the inter-vehicle distance, a laser radar is usually mounted on the front of the own vehicle to emit laser light forward, and this laser light is reflected by a preceding vehicle located in front of the own vehicle and returned. The received reflected light is received, and the inter-vehicle distance between the own vehicle and the preceding vehicle is calculated based on the round-trip time (delay time) from emission to light reception.

In order to measure the relative speed in the lateral direction, a laser radar is mounted on the front of the own vehicle, and the average of the position coordinates of each reflected light from the rear positions (detection points) of the preceding vehicle is calculated. The so-called difference method that measures the lateral relative speed of the preceding vehicle using the time difference between the center position of the preceding vehicle at the previous measurement and the center position of the preceding vehicle at the current measurement as the relative speed vector is adopted as the center position of the vehicle. Have been. Usually, the inter-vehicle distance and the lateral relative speed are measured by a laser radar.

[0006]

However, in the measurement of the relative speed in the lateral direction of the preceding vehicle by the above-mentioned conventional difference method,
Regarding the reflection from the rear part of the preceding vehicle, the reflection level of the laser beam is not sufficient due to the shape of the rear part of the preceding vehicle, so that it may not be possible to detect a portion having a low reflection level, and the number of detection points varies. If the number of detection points fluctuates, the center position of the preceding vehicle fluctuates accordingly, increasing noise.There is a limit in the accuracy of the calculation of the relative speed, and the lateral relative speed between the host vehicle and the preceding vehicle increases. There is a problem that measurement cannot be performed with high accuracy.

For this reason, the present invention provides a method for measuring the relative speed of the preceding vehicle in the lateral direction of the preceding vehicle, which measures the relative speed of the vehicle preceding the own vehicle with high accuracy based on the reflection intensity pattern of the laser radar. It is intended to be.

[0008]

To achieve the above object, according to the first aspect of the present invention, a laser beam is emitted from a laser radar mounted on an own vehicle toward the front of a vehicle, and a reflected beam from a preceding vehicle is emitted. Detect and create a reflection intensity pattern. Then, the lateral movement amount of the preceding vehicle is calculated by pattern matching using the reflection intensity pattern created last time and the reflection intensity pattern created this time. Then, the lateral relative speed of the preceding vehicle is calculated based on the calculated lateral movement amount and the time difference between the previously generated reflection intensity pattern and the currently generated reflection intensity pattern. This makes it possible to measure the relative speed of the preceding vehicle in the lateral direction with high accuracy and stability.

According to the second aspect of the present invention, the reflection intensity pattern is created by the laser radar at every distance measurement cycle of the inter-vehicle distance to the preceding vehicle, and the pattern matching of the reflection intensity pattern between the previous time and the current time is performed each time. This makes it possible to always accurately measure the lateral relative speed of the preceding vehicle.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a traveling system for implementing a method for measuring a relative speed of a preceding vehicle in a lateral direction according to the present invention.

In FIG. 1, a laser beam LB is emitted forward to a front portion of a vehicle 1 (hereinafter referred to as “own vehicle”) as a host vehicle, and the laser beam LB is applied as shown in FIG. By scanning left and right in the horizontal direction, the preceding vehicle A as an object located in front of the own vehicle 1 is recognized,
Further, a scanning laser radar 2 capable of measuring the distance to the preceding vehicle A is mounted. A CCD camera 4 for capturing an image of the front of the own vehicle 1 is attached to a roof portion in the vehicle compartment, and an object located in front and a lane (white line) are provided.
Etc. can be recognized.

The engine 6 is provided with a throttle valve 8 for controlling the amount of intake air to the engine 6 to adjust the engine output. The throttle valve 8 is capable of automatically adjusting the throttle valve opening based on an operation signal output from an electronic control unit (ECU) 50, which will be described later, according to the opening of an accelerator pedal (not shown) or the like. An actuator 12 is provided.

Each of the left and right front wheels (drive wheels) 20 and each rear wheel (driven wheels) 22 is provided with a service brake (braking device) 24 such as a hydraulic disc brake. It is connected to a brake pedal 28 via a brake master cylinder 26 having a negative pressure booster. The brake master cylinder 26 is provided with a negative pressure type brake actuator 30 that can automatically operate the service brake 24 in response to an operation signal from the electronic control unit 50 regardless of an input from the brake pedal 28.

A wheel speed sensor 32 is provided near each of the left and right rear wheels 22 as driven wheels, and detects a right wheel speed VSR and a left wheel speed VSL. Each of these wheel speed sensors 32 functions as vehicle speed detecting means for detecting the vehicle speed Ve.

The steering column 36 of the steering wheel 34 is provided with a tracking travel changeover switch 38 for switching the travel control device of the vehicle 1 between a normal traveling state and a traveling state by tracking control. When the tracking travel changeover switch 38 is operated to the set side, the tracking travel control, that is, the inter-vehicle distance control is started, and when it is operated to the reset side, the inter-vehicle distance control is released.

The electronic control unit 50 is a main control unit for controlling each control unit of the vehicle 1. On the input side, a scanning laser radar 2, a CCD camera 4, each wheel speed sensor 32, a tracking switch 38, etc. The various sensors and switches are connected, and driving devices such as the throttle actuator 12 and the brake actuator 30 are connected to the output side.

Hereinafter, control contents of the traveling control device will be described with reference to a flowchart shown in FIG.

When the tracking travel changeover switch 38 is operated to the set side to start the tracking travel control, the laser beam LB is moved in the right and left directions at a predetermined distance measurement cycle from the laser radar 2 of the own vehicle 1 as shown in FIG. , And a preceding vehicle candidate determination process is executed (step S1). In addition, preceding car A
The previous measurement position is indicated by a thin line, and the current measurement position is indicated by a thick line. This preceding vehicle candidate determination processing is executed by a subroutine shown in FIG. The electronic control unit 50 determines whether or not there is a preceding vehicle by the scanning laser radar 2 in step S20 of FIG.
, The inter-vehicle distance L from the preceding vehicle A to the preceding vehicle A is measured, the reflection intensity data for each reflected beam reflected by the rear part of the preceding vehicle A is read, and the reflection intensity data at each detection point is interpolated at regular intervals to perform each measurement. A reflection intensity pattern of the preceding vehicle A is created for each distance cycle (step S21).

FIG. 5 shows an example of this reflection intensity pattern. In FIG. 5, the reflection intensity pattern of the preceding vehicle A at the previous measurement position is indicated by a thin line, and the reflection intensity pattern of the preceding vehicle A at the current measurement position is indicated by a thick line. The reflection intensity of the laser beam is strong in the reflector portions provided on the left and right sides of the rear portion of the vehicle, weak in the vehicle body portion, and provided between the reflectors provided on the left and right sides in each distribution pattern and between these reflectors It is maximum at each detection point such as a decorative panel (neither is shown) and is minimum at the vehicle body.

Next, the reflection intensity pattern is normalized based on the inter-vehicle distance between the vehicle 1 and the preceding vehicle A (step S2).
2), as shown in FIG. 6, the lateral movement amount D of the preceding vehicle A is calculated by pattern matching between the previous reflection intensity pattern and the current reflection intensity pattern (step S23).
Next, the lateral relative speed of the preceding vehicle A is calculated based on the lateral movement amount D and the time difference between the previous reflection intensity pattern creation and the current reflection intensity pattern creation (step S2).
4). The calculation of the lateral relative velocity is performed by using the laser beam LB.
Is performed for all the vehicles ahead (vehicles in front of the vehicle) reflected by the vehicle. This is to deal with a vehicle interruption or the like. Then, it is determined whether or not the calculation of the lateral relative velocities of all the preceding vehicles has been completed (step S25). If the calculation has not been completed, the process returns to step S21. If the calculation has been completed, the routine ends.

As an example, FIG. 8 shows the relationship between the inter-vehicle distance and the lateral relative speed when another vehicle B interrupts before the own vehicle 1 as shown in FIG. In FIG. 8, a thick line indicates a measurement result by the measurement method of the present invention, and a thin line indicates a measurement result by the conventional difference method. The arrow indicates the initial stage of the interruption of the interruption vehicle B in a state where only a part of the vehicle body can be detected by the scanning laser radar 2. As is apparent from FIG. 8, the measurement method using the pattern matching of the present invention reduces the variation including the initial stage of the interruption of the vehicle B in which only a part of the vehicle body can be detected, as compared with the measurement method using the conventional difference method. The measurement accuracy of the relative speed in the direction is stable.

Returning to FIG. 3, the vehicle speed Ve of the own vehicle 1 is calculated by the following equation based on the information from each wheel speed sensor 32 (step S2).

Ve = (VSR + VSL) / 2 Next, the relative speed between the own vehicle 1 and the preceding vehicle A is calculated based on the following distance L (step S3). The relative speed is calculated based on a change amount ΔL between the previously measured inter-vehicle distance and the currently measured inter-vehicle distance. If the change amount ΔL is positive, it can be considered that the own vehicle 1 is moving away from the preceding vehicle A, and if the change amount ΔL is negative, the own vehicle 1 is approaching the preceding vehicle A.
Next, the vehicle speed Va of the preceding vehicle A is calculated from the vehicle speed Ve of the own vehicle 1 and the relative speed ΔL (step S4).
The differential processing of _{a is performed} to calculate the deceleration α _a of the preceding vehicle A. This deceleration α _a is calculated from the change amount ΔVa between the vehicle speed of the preceding vehicle A calculated last time and the vehicle speed calculated this time.

Next, it is determined whether or not the vehicle 1 should be decelerated (step S6). That is, it is determined whether or not the change amount ΔL is negative and the vehicle 1 is approaching the preceding vehicle A, and it is necessary to decelerate the vehicle 1. If it is determined that there is no need to decelerate, the throttle actuator 12 is driven to open the throttle valve 8 so that the inter-vehicle distance L becomes the target inter-vehicle distance to perform acceleration control (step S7).

When it is determined that the own vehicle 1 should be decelerated, the target deceleration is calculated to calculate an auxiliary braking force to be added (step S8), and the throttle actuator 12 is driven based on this to drive the throttle valve 8 Is closed (step S9), and the brake actuator 30 is operated in accordance with the auxiliary braking force to apply the braking force by the service brake 24 (step S10). In this case,
Even if the driver does not operate the brake pedal 28, the vehicle 1
Travels well following the preceding vehicle A. This allows
When an automatic brake is introduced into the inter-vehicle distance control, deceleration control by the automatic brake due to erroneous recognition is suppressed, and the driver's discomfort is reduced.

[0027]

According to the present invention, according to the first aspect, the reflection intensity of the laser beam reflected from the preceding vehicle is detected to create a reflection intensity pattern, and the reflection intensity pattern is calculated from the previous reflection intensity pattern and the current reflection intensity pattern. The lateral movement amount of the preceding vehicle is calculated by pattern matching, and the lateral movement amount is calculated as follows:
By calculating the lateral relative speed based on the time difference between the previous and current reflection intensity patterns, the lateral relative speed of the preceding vehicle can be measured with high accuracy and stably.

According to the second aspect of the present invention, a reflection intensity pattern is created by the laser radar in each distance measurement cycle of the inter-vehicle distance to the preceding vehicle, and pattern matching of the reflection intensity pattern between the previous time and the current time is performed each time. This makes it possible to always accurately measure the lateral relative speed of the preceding vehicle.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a traveling control device of a vehicle for implementing a method of measuring a relative speed of a preceding vehicle in a lateral direction according to the present invention.

FIG. 2 is an explanatory diagram of a method for measuring a lateral position of a preceding vehicle.

FIG. 3 is a flowchart showing a traveling control procedure according to the present invention.

FIG. 4 is a flowchart showing a procedure for determining a preceding vehicle candidate in FIG. 3;

FIG. 5 is a diagram showing previous and current reflection intensity patterns formed by reflected beams from a preceding vehicle in FIG. 2;

FIG. 6 is an explanatory diagram for calculating a lateral movement amount by a pattern matching method from the previous and current reflection intensity patterns of FIG. 5;

FIG. 7 is an explanatory diagram in a case where a preceding vehicle is interrupting.

8 is an explanatory diagram illustrating a relationship between a relative speed in a lateral direction with respect to the interrupted vehicle and a distance between vehicles in FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 own vehicle (own vehicle) 2 scanning laser radar 50 electronic control unit A preceding vehicle (preceding vehicle)

Continued on the front page F term (reference) 3D046 BB18 EE01 HH20 HH22 5H180 AA01 CC03 CC04 CC14 CC24 LL01 LL02 LL04 5J070 AB01 AC02 AC06 AD01 AE01 AF03 AK22 5J084 AA02 AA05 AA07 AB01 AC02 AD01 AD03 BA03 BA11 CA03 CA31

Claims (2)

[Claims] 1. A laser radar mounted on a host vehicle emits a laser beam toward the front of a vehicle, detects a reflected beam from a preceding vehicle, creates a reflection intensity pattern, and generates a reflection intensity pattern of a previous reflection and a reflection intensity of a current reflection. A lateral movement amount is calculated by pattern matching with the intensity pattern, and a lateral relative speed of the preceding vehicle is measured based on the lateral movement amount and a time difference between the previous time and the current time. Direction relative speed measurement method. 2. The method for measuring a relative speed of a preceding vehicle in a lateral direction according to claim 1, wherein the reflection intensity pattern is created for each distance measurement cycle of an inter-vehicle distance to the preceding vehicle.