JP2000131436A - Curve estimation method and vehicle speed controlling device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a curve at an early stage by emitting laser beams using a scanning-type sensor, estimating the advance angle of a preceding vehicle according to the time difference information of a plurality of reflection beams being obtained after the laser beams hit the preceding vehicle, and estimating a curve in the road ahead. SOLUTION: A sensor (scanning-type laser radar) DT incorporates a laser oscillator and a light reception lens controller and applies a laser beam outputted from the laser oscillator in the forward direction (a preceding vehicle FC). Data such as the presence or absence of the preceding vehicle FC on a driver's own lane, the distance to the preceding vehicle FC, and a relative speed is outputted to a control device CT according to such data as time when a radar beam is reflected by a reflector or the like at the rear portion of the preceding vehicle FC returns to a light reception lens provided in the sensor after it is emitted, a relative speed, a reflection intensity, and an incidence angle. The control device CT performs following driving while retaining the distance to the preceding vehicle FC at a constant when the preceding vehicle FC exists in front of the driver's own vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curve estimating method for estimating a curve ahead using a preview sensor, and controlling the vehicle speed of the own vehicle to match the curve before the curve when the curve is estimated. The present invention relates to a vehicle speed control device that performs the control.

[0002]

2. Description of the Related Art In recent years, vehicle technology has been developed in vehicles, and the vehicle automatically drives (automatically drives) while recognizing a white line on the road surface by a preview sensor such as a camera or a laser radar, or there is a preceding vehicle ahead. ACC that follows the vehicle while keeping a certain distance from the preceding vehicle
(Adaptive Cruise Control) system has been proposed.

[0003] Among them, when estimating a forward curve using a radar laser or the like, a method of irradiating a laser beam forward and estimating a curve based on a state of reflected light reflected on a guardrail has been adopted. In this method, the front is scanned with the laser beam of the scanning radar laser, and the characteristic that the state of the light reflected on the guardrail and reflected at a constant interval is detected.

Further, a radar cruise control system having a function of detecting a preceding vehicle by a sensor such as a radar laser and performing a following operation while maintaining an inter-vehicle distance proportional to the vehicle speed is disclosed in the Toyota Progure New Car Manual (19).
5-124 of May 1998 Toyota Motor Corporation)
Pp. 131.

In this vehicle, a function of recognizing a curve ahead and performing vehicle control in accordance with the curve state (navigation cooperative shift control) is added. The navigation cooperative control includes road information from navigation and current position information. Is compared, and the gears are shifted down and decelerated during curve running based on the road shape to be driven, the running state of the vehicle, and driver's operation information.

[0006] Also in the above-mentioned vehicle, regarding the laser cruise control, when the state of the preceding vehicle is detected by a laser radar or the like during the following running, the state of the preceding vehicle is detected by using a steering sensor to detect the steering angle of the own vehicle. Detected.

Japanese Patent Laid-Open Publication No. Hei 5-203746 similarly detects the steering angle of the vehicle using a steering sensor, and uses the information from the steering sensor to calculate the radius of curvature of the circuit when the vehicle is running. The detection range of the laser beam is changed according to the condition.

[0008]

However, in the method in which the front is scanned by the laser beam of the scanning radar laser and the curve is estimated from the light reflected on the guardrail, the curve ahead is estimated if there is no guardrail ahead. It will not be possible.

Japanese Patent Laid-Open Publication No. Hei 5-203746, which performs speed control from the state of a preceding vehicle, discloses that if the own vehicle is traveling straight and the preceding vehicle is on its own lane, Can be recognized, but the car is still straight ahead,
Under the condition that the preceding vehicle turns a curve and is out of the sensor detection range, the detection range of the laser beam in the own vehicle does not change until the driver turns the steering wheel,
It may happen that the preceding vehicle is lost before the curve.

In this case, the point at which the vehicle recognizes that the vehicle is a curve is delayed, and if the vehicle speed is high to some extent before the curve, the deceleration timing before the curve is delayed. Curved curve detection is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to detect a forward curve at an early stage without using a steering sensor other than a laser beam. It is a technical subject to facilitate speed control from when the vehicle reaches a curve.

[0012]

The first technical means taken to solve the above-mentioned problem is that a scanning type sensor emits a laser beam, and the laser beam impinges on a preceding vehicle. The traveling angle of the preceding vehicle is estimated from the time difference information, and the forward curve is estimated based on the traveling angle.

According to this, since the curve ahead is estimated from the advancing angle of the preceding vehicle obtained from the time difference information of the plurality of reflected lights reflected by the preceding vehicle, the curve can be estimated only by the laser light. There is no need for a conventional steering sensor. In this method, it is possible to estimate a curve from information on reflected light based on the state of the preceding vehicle.

In this case, a regression line is calculated from information of a plurality of reflected lights obtained from the preceding vehicle, and a turning state of the preceding vehicle is estimated based on an angle between the regression line and a reference axis based on the own vehicle. If the curve is estimated from the state, the turning state of the preceding vehicle can be easily obtained from the angle formed between the regression line and the reference axis based on the own vehicle, and the curve can be estimated by a simple method.

If the regression line is determined based on the reflected light from the rear and side surfaces of the preceding vehicle, the regression line can be determined from the information on the reflected light from the two surfaces of the preceding vehicle, ie, the rear and side surfaces. Since the state of the advancing angle of the preceding vehicle can be reliably obtained, the reliability of curve detection based on the state of the preceding vehicle is improved.

A second technical means taken to solve the above problem is to provide a vehicle speed control device for estimating a curve ahead and performing speed control just before the curve when there is a curve. The laser beam is emitted using the laser beam, the traveling angle of the preceding vehicle is estimated based on the time difference information of the plurality of reflected lights reflected by the preceding vehicle, the forward curve is estimated based on the traveling angle, and the speed control is performed before the curve. That's what we did.

According to this, a forward curve is estimated from the advancing angle of the preceding vehicle obtained from the time difference information of a plurality of reflected light beams reflected by the preceding vehicle, and the state of the preceding vehicle is always represented by the information from the reflected light. Therefore, the detection of the curve is not delayed, and even when the vehicle speed of the own vehicle is high to some extent before the curve, the deceleration timing before the curve is not delayed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a speed control device according to an embodiment of the present invention. In FIG. 1, the state of the preceding vehicle FC is detected by a scanning preview sensor (referred to as a sensor) DT. The sensor DT used here adopts a method of scanning and detecting within a detection range using a scanning laser radar.
The present invention is not limited to this, and any device capable of detecting a forward object can be used, and a microwave laser or a millimeter wave can also be used.

This sensor (scanning laser radar) D
T incorporates a laser oscillator and a light-receiving lens controller, and irradiates a laser (detection range: 20 °, detection distance: about 100 m) output from the laser oscillator to the front (for example, a preceding vehicle). The vehicle travels from the data such as the time, the relative speed, the reflection intensity, and the angle of incidence from when the laser beam is emitted to when the radar reflected by the reflector behind the preceding vehicle returns to the light-receiving lens provided in the sensor. Data (data train) such as the presence or absence of a preceding vehicle on the line, the distance to the preceding vehicle, and the relative speed are output to a control device (controller) CT.

The control device CT controls the following running with the preceding vehicle FC when the following driving switch (not shown) is pressed by the driver.
When there is a vehicle, the vehicle follows the vehicle while maintaining a constant inter-vehicle distance with the preceding vehicle FC. Sensor D
An acceleration / deceleration command is output to the acceleration / deceleration device AT based on information on the reflected light from T, reflection intensity, and the like. In this case, the acceleration / deceleration device AT may be any device that accelerates or decelerates the vehicle CA to perform an acceleration / deceleration operation, such as a throttle device, a brake device, or an automatic transmission.
Further, information about the vehicle, for example, the vehicle speed of the own vehicle is input to the control device CT from the vehicle CA, and the control device CT
In this system, the running state of the vehicle can be monitored by feedback.

Next, the processing of the control device CT will be described with reference to FIG. When an ignition switch (not shown) is inserted into the key cylinder of the control device CT and the vehicle key is turned and the ignition is turned on, power is supplied from a battery. When power is supplied from the battery, the control device CT performs a predetermined constant cycle (for example, a 50 msec routine).
The main program shown in FIG. 2 is executed.

Therefore, the processing of the control device CT will be described. In step S101, initial processing is first executed. In this initial process, the state of the memory is checked, and after initial values are set in the RAM required for this process, it is checked whether the system operates normally. Thereafter, in step S102, data input processing is performed. In this data input processing, when laser light is emitted from the sensor DT, time difference information of a plurality of reflected lights reflected by the preceding vehicle FC when the laser light hits the preceding vehicle FC (transmitted in a data string). ), Reflection intensity, and vehicle CA as vehicle speed data.
The vehicle speed is input from the controller and stored in a necessary memory in the control device.

Next, in step S103, it is checked whether a curve presence flag is set forward (curve ahead). If there is no curve ahead (the forward curve presence flag is not set), step S104 and subsequent steps are performed. If there is a curve ahead (the front curve presence flag is set), step S107 is performed.

If there is a curve ahead in step S103, then in step S104, the distance between the own vehicle and the front curve is calculated. Here, when it is determined that there is a curve ahead, the traveling speed dm of the own vehicle is calculated by integrating the own vehicle speed from the time when it is recognized that there is a curve, and the deceleration start distance Ds is obtained from a map based on the own vehicle speed. . The deceleration start distance Ds is set to be long so that the deceleration control is not delayed at the point where the deceleration control is started when the own vehicle speed is high, but is linearly set to be short when the own vehicle speed is low. I have. In addition, this Ds is Ds = Vs ² /
It can also be obtained from 2G (G: maximum deceleration).

In step S105, a difference between the distance dc from the point (t = 0) at which the curve is recognized to the entrance of the curve and the travel distance dm after the curve recognition obtained by integrating the vehicle speed is calculated. dc-dm) corresponds to step S104.
It is checked whether or not the vehicle has reached the deceleration start distance Ds determined in step (1). Here, if the difference (dc−dm) has not reached the deceleration start distance Ds, the process returns to step S102, and the same processing from step S102 is repeated. On the other hand, if the difference (dc−dm) has reached the deceleration start distance Ds, deceleration control is performed before the curve in step S106, and a deceleration command is output to the acceleration / deceleration device AT to perform deceleration control. The front curve presence flag is cleared, and the process returns to step S102.

The deceleration control performed here is a brake control for decelerating by applying a brake to a wheel, a throttle control for restricting the amount of air supplied to the cylinder of the engine by reducing the throttle opening of the throttle device, Any type of shift control may be used in which the speed of the vehicle is reduced by lowering the gear of the automatic transmission to a lower gear.

On the other hand, based on the state where the forward curve presence flag is not set in step S103, step S103 is executed.
At 107, it is checked whether there is a preceding vehicle FC.
Here, whether or not the preceding vehicle FC exists is determined based on data sent from the sensor DT to the control device CT (calculating the distance to the object reflected by the time difference of the reflected light, relative speed) under a predetermined condition (for example, relative speed). The change in speed is small, and the change in relative speed is the same in the data sequence), and the grouped shape is a fixed shape (shape indicating the rear of the vehicle)
Is established, a known preceding vehicle recognition method is assumed to be a preceding vehicle, but the present invention is not limited to this.

Here, when the preceding vehicle FC does not exist ahead, vehicle speed control is performed in step S108 according to the road surface condition, and the process returns to step S102. On the other hand, when it is determined in step S107 that the preceding vehicle FC exists ahead, the curve is estimated in step S109. In this curve estimation, scanning is performed by scanning the preceding vehicle FC with the scanning laser radar DT, and the xy coordinates of the reflected waves from each part (particularly, reflectors, etc.) of the preceding vehicle are received as a data train, and The state of the curve ahead is estimated based on the running state of the FC.

In the curve estimation shown in FIG. 3, first, from the data sequence from the reflected light received in step S201, the contour behind one preceding vehicle, that is, one behind the preceding vehicle FC (backward on the turning side). Is estimated (L-shape estimation). In this L-shaped estimation, the radar oscillation unit of the own vehicle is set as the origin of the xy plane coordinate system (see FIG. 4), the width direction of the own vehicle is set as the reference axis x, and the entire length direction of the own vehicle is set as the reference axis y. First, a data sequence (xi, yi) having n data from the reflected light is first divided into two regions by a straight line x = P (see FIG. 5). Here, i is an integer of 1 to n.

Thereafter, an approximation straight line (that is, a regression line) is obtained by approximating the data string satisfying x ≧ P by the least square method.
11 and a data sequence (x
Let the squared integrated value of the error of the y coordinate of (i, yi) be f1.
Note that one end of the straight line 11 obtained at this time is a half line ending with x = P.

Next, a regression line 11 and a straight line (normal line) 12 which intersects at right angles at x = P, and a data sequence of x <P
Similarly, the square integration value f2 of the error of the y coordinate is obtained. One end of the straight line 12 obtained at this time is also a half line ending with x = P. Thereafter, the sum f (f = f1 + f2) of the squared cumulative value f1 of the error obtained from the straight line 11 and the squared cumulative value f2 of the error obtained from the straight line 12 is calculated. Next, a regression line is obtained from the data string satisfying x <P for the same data string, and the sum f ′ of the squared cumulative values of the errors obtained by the same method as described above is calculated. At this time, f ′ is compared with the previously obtained f, and the sum of the two half-lines when the value is small and the squared cumulative value of the error is used as the result at this time. P that minimizes the sum f of the squared cumulative values of the errors obtained by such a procedure is obtained by a one-dimensional optimization method (for example, the golden section method), and the two half-lines 11 and 12 at that time are determined at the rear of the vehicle. Of L
The minimum f at this time is stored in the memory.

Then, of the two straight lines 11 and 12 constituting the L-shape obtained in step S202, the one behind the preceding vehicle FC is specified by the reflection intensity. The information of the reflected wave intensity between the data strings is compared, and the straight line 11 in the region where the data with the strongest reflected intensity exists is defined as the rear of the vehicle. That is, focusing on the fact that the intensity of the reflected light from the reflector attached to the rear part of the vehicle is the strongest, the straight line (here, the straight line 1) in the area where the data having the strongest reflected intensity exists.
Let 1) be the rear part of the vehicle. After that, when the rear portion of the vehicle is specified by the reflection intensity, the half-line 11 specified as the rear portion of the vehicle in step S203 and the x-axis which is the reference axis of the own vehicle (coincides in the width direction of the own vehicle). The angle formed is determined, and the angle is defined as the inclination angle α of the preceding vehicle FC with respect to the traveling direction (y direction) of the own vehicle, and the inclination a of the semi-straight line 11 specified as the rear part of the vehicle (see FIG. 6). And the inclination angle α are obtained from the relational expression of α = tan ⁻¹ | a |.

After that, the value obtained by dividing the square root of the squared cumulative value f of the error of the data sequence obtained first by the total number of data n is defined as the average error e (= f / n). In this case, threshold values are set in advance for the inclination angle α and the average error e of the preceding vehicle FC, and the threshold value of the inclination angle of the preceding vehicle is αs, and the threshold value of the accumulated error is Es.

Next, in step S110, the own vehicle is traveling on a straight road (when the vehicle speed is determined, at least 2
When the brake control such as anti-skid control and stability control is not performed under the condition that the wheel speed sensor that detects the speed of the wheel above the wheel is used, the difference between the left and right driven wheels is less than a predetermined value. In the case where it hardly occurs, when the predetermined condition (α ≧ αs and e ≦ Es) is satisfied, it is determined that the preceding vehicle FC is starting to turn a curve, and it is assumed that there is a curve ahead of the own vehicle. Here, e ≦ Es is set to prevent a malfunction in the speed control in consideration of the influence of the error, and the inter-vehicle distance dc to the preceding vehicle at this time is stored in the memory. The threshold value αs of the inclination angle is a value obtained by experimentally obtaining the state of inclination of the vehicle when the preceding vehicle FC makes a curve with a radius of curvature R. The threshold value Es of the error is set when the radar light normally catches the vehicle. Is an experimentally obtained value of the squared integrated value of the error of.

When it is determined in step S110 that there is a curve ahead, in step S111, a forward curve presence flag is set and the process returns to step S102. When it is determined that there is no curve ahead, in step S112, the forward curve presence flag is set. The curve presence flag is cleared, and the normal inter-vehicle distance control is executed in the next step S113. In other words, the inter-vehicle distance control here is such that when the inter-vehicle distance with the preceding vehicle FC becomes dc-dm ≦ Ds with respect to the threshold value Ds of the deceleration start distance determined by the current own vehicle speed, the own vehicle accelerates. If so, the acceleration is terminated, and if the current vehicle speed is higher than the predetermined threshold value Vs, the vehicle is decelerated.

This is because, as shown in FIG. 7, when it is recognized that there is a curve from the information on the preceding vehicle FC when t = 0,
The state in which deceleration is started at t = T is shown. Where D
s is a distance that is possible to reduce the vehicle speed from the current vehicle speed to the vehicle speed threshold value Vs, and is determined by a reduction gear mounted on the vehicle. Vs is a theoretical value of the vehicle speed for turning a curve having a radius of curvature R. , An experimentally determined value.

[0038]

According to the first aspect, the curve ahead is estimated from the traveling angle of the preceding vehicle obtained from the time difference information of a plurality of reflected lights reflected by the preceding vehicle by the laser light, so that the curve is estimated only by the laser light. This eliminates the need for a conventional steering sensor, and in this method, a curve can be estimated from information on reflected light based on the state of the preceding vehicle.

In this case, a regression line is calculated from information of a plurality of reflected lights obtained from the preceding vehicle, and a turning state of the preceding vehicle is estimated based on an angle formed between the regression line and a reference axis based on the own vehicle. If the curve is estimated from the state, the turning state of the preceding vehicle can be easily obtained from the angle formed between the regression line and the reference axis based on the own vehicle, and the curve can be estimated by a simple method.

If the regression line is determined based on the reflected light from the rear and side surfaces of the preceding vehicle, the regression line can be determined from the information on the reflected light from the two surfaces of the preceding vehicle, ie, the rear and side surfaces. Since the state of the advancing angle of the preceding vehicle can be reliably obtained, the reliability of curve detection based on the state of the preceding vehicle is improved.

According to the second aspect, a curve ahead is estimated from the advancing angle of the preceding vehicle obtained from the time difference information of a plurality of reflected lights in which the laser light hits the preceding vehicle, and the state of the preceding vehicle is always reflected by the reflected light. Since the information can be monitored based on the information from the vehicle, the curve detection is not delayed, and even when the vehicle speed of the host vehicle is high to some extent before the curve, the deceleration timing before the curve is not delayed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a vehicle speed control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating processing of a control device according to an embodiment of the present invention.

FIG. 3 is a flowchart of the curve estimation shown in FIG. 2;

FIG. 4 is a diagram illustrating a detection range of a sensor that detects a preceding vehicle according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram in the case of estimating a straight line (regression line) from data of reflected light from a preceding vehicle in one embodiment of the present invention.

FIG. 6 is an explanatory diagram in a case where an inclination angle α of a preceding vehicle is obtained from a regression line in one embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between a preceding vehicle and a host vehicle according to an embodiment of the present invention.

[Explanation of symbols]

 FC preceding vehicle DT scanning sensor (scanning laser laser) CT controller AT acceleration / deceleration device CA vehicle

Claims (4)

[Claims] A laser beam is emitted using a scanning sensor,
A curve estimating method comprising: estimating a traveling angle of a preceding vehicle from time difference information of a plurality of reflected lights of the laser light hitting the preceding vehicle, and estimating a forward curve based on the traveling angle. 2. A regression line is calculated from information of a plurality of reflected lights obtained from a preceding vehicle, and a turning state of the preceding vehicle is estimated from an angle formed by the regression line and a reference axis with respect to the own vehicle.
The curve estimating method according to claim 1, wherein the curve is estimated from the turning state. 3. The curve estimation method according to claim 2, wherein the regression line is obtained based on light reflected from the rear and side surfaces of the preceding vehicle. 4. A vehicle speed control device for estimating a curve ahead and performing speed control in front of a curve when there is a curve, emits a laser beam using a scanning sensor, and the laser beam hits a preceding vehicle and is reflected. A vehicle speed control device for estimating a traveling angle of a preceding vehicle from time difference information of a plurality of reflected lights, estimating a forward curve based on the traveling angles, and performing speed control just before the curve.