JPH0717345A - Obstacle detecting device - Google Patents

Abstract

PURPOSE:To reduce the number of expensive parts and achieve cost reduction by realizing the constitution in which an obstacle at the front is detected by irradiating the light beams supplied from two light emitting elements in parallel, as for an obstacle detecting device which emits light beams forwardly. CONSTITUTION:An obstacle detectign devices is equipped with a light emitting means which emits ligh beams and a means for receiving the irradiated light beams, and is constituted so as to calculate the distance between an object at the front and the own vehicle by extracting the received light signal. Two laser diodes 55 and 56 are installed as light emitting means, in pair for the vehicle center axis, and each optical axis is set so as to be parallel and overlapped and cover the whole road width. Further, the laser diodes 55 and 65 are driven in a certain order by an LD selecting driver 57, and each light beam is irradiated in a pulse form. With this constitution, the necessity of using three laser diodes and the LD decice in the conventional is obviated, and cost reduction is ahcieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on a front end portion of a vehicle to detect a front target such as an obstacle in front of the vehicle.
The present invention relates to an obstacle detection device used to prevent the occurrence of a collision accident.

[0002]

2. Description of the Related Art As a conventional obstacle detecting device, there is one shown in FIG. 3, for example. In the figure, reference numeral 1 denotes a distance detection unit that detects a distance between a vehicle and an obstacle (front target) using a laser beam (light beam) emitted from a laser diode (hereinafter, LD).

Reference numeral 3 designates the own vehicle based on the distance information returned to the distance detection unit 1 in response to the distance detection command and the own vehicle speed information detected by a vehicle speed sensor 31 described later. Calculates the relative speed with the obstacle such as the vehicle in front and judges whether the obstacle is a stationary object or a moving object, and also determines the vehicle speed, the relative speed, and the idle running time until the driver brakes The signal processing unit determines the possibility of collision between the own vehicle and an obstacle according to a distance setting or the like set according to an individual difference.

4 is based on the information from the signal processing unit 3,
It is an alarm notification unit that displays the distance between the host vehicle and the obstacle, and also issues an alarm when the signal processing unit 3 determines that there is a possibility of collision with the obstacle.

Next, the operation will be described. The vehicle speed signal of the own vehicle detected by the vehicle speed sensor 31 is sent to the arithmetic circuit 41,
When the vehicle speed calculated based on the vehicle speed signal is, for example, 35 Km / h or more, the arithmetic circuit 41 sends a distance detection command signal to the distance detection unit 1.

In the distance detecting section 1, a signal corresponding to the distance detection command signal is sent from the arithmetic circuit 41 to the drive signal generating circuit 11
And the drive signal generation circuit 11 receives the LD shown in FIG.
The light emission signal is sent to the LD switching driver 12. The LD switching driver 12 sends out the signals shown in FIGS. 4B, 4C and 4D based on the received LD light emission signal (a),
LD-L, LD- of the LD array 13 as a light emitting means
C, LD-R (these three laser light-emitting elements are arranged in an array) are caused to constantly flash with the same intensity.

The laser beam from the LD-L of the LD array 13 forms a detection range B to the front left of the host vehicle as shown in FIG. 6, and the laser beam from the LD-C has a detection range C ahead. So that the laser beam from the LD-R forms the detection range A toward the front right side,
The laser beam of LD-C is emitted from the light-projecting lens 14, the laser beam of LD-C interrupts the front obstacle, the laser beam of LD-L interrupts the vehicle from the left lane, and the laser beam of LD-R interrupts the right lane. Used to detect vehicles.

The reflected light from the obstacle is condensed by the light receiving lens 15 and is received by the photodiode (hereinafter referred to as PD) 16. This received light signal is sent to the amplification circuit 17, which amplifies it and outputs the extraction signal of FIG. This extracted signal is a reflection signal B from an obstacle.
And a reflection signal A from a short distance road surface and the like are mixed.

The threshold generation circuit 18 is based on the LD light emission signal (a) output from the drive signal generation circuit 11 and is shown in FIG.
The threshold signal shown in FIG.
Output to. The comparator 19 compares the level of the output signal (e) of the amplifier circuit 17 with the threshold value signal (f) to extract only the reflected signal from the obstacle, and the obstacle shown in FIG. The object detection pulse signal (extraction signal) is output.

The counter 20 has an L level as shown in FIG.
At the rising edge of the D emission signal (a), the reference pulse generation circuit 21
Starts counting the clock pulse signal supplied from, stops counting at the rising edge of the obstacle detection pulse signal (g) based on the reflection signal from the obstacle, and counts from the count-up time and the speed of light to the obstacle. Seeking distance information,
It is sent to the arithmetic circuit 41 of the signal processing unit 3. In addition,
In the case of the distance information based on the laser beam from the laser diode indicated by LD-L and LD-R, the counter 20 cancels the value when it exceeds a predetermined value L1 shown in FIG. To do. Thereby, only the front target object located in the shaded portion shown in FIG. 7 is extracted.

Next, a method of determining the possibility of collision in the arithmetic circuit 41 of the signal processing unit 3 will be described with reference to the flowchart shown in FIG. First, when the power is turned on, S
Proceeding to the TART step, the CP forming the arithmetic circuit 41
U, RAM, etc. are initialized. Next, step S
At T11, a pulse having a predetermined pulse width is output to the drive signal generating circuit 11 in a predetermined cycle, and the next step ST12
At a predetermined cycle, the counter 20 of the distance detecting unit 1 outputs a distance signal indicating information on the distance R to the obstacle, and the vehicle speed sensor 31 of the traveling state detecting unit 2 outputs a vehicle speed signal indicating information on the own vehicle speed V _f. It is taken into the arithmetic circuit 41.

Then, in step ST13, the distance signal R is converted into a display signal and sent to the distance display 51 for display.
Next, in step ST14, the inter-vehicle distance R is differentiated to determine the relative speed (d / dt) R between the obstacle such as the preceding vehicle and the host vehicle.
Is calculated using a calculation method such as the least squares method, and the vehicle speed V _{a of the} preceding vehicle is relative to the own vehicle speed V _f (d / dt).
It is calculated by the sum with R.

In this calculation, (d / dt) R <0
In the case of (d / dt) R> 0, the distance is decreasing, and the distance is decreasing, and (d / dt) R = 0. In the case of, it shows that there is no change in the distance.

In determining the possibility of collision with an obstacle, the initial speed of the vehicle is V _f (m / s) and the initial speed of the obstacle (preceding vehicle) is V _a (m / s). Deceleration performance is α (m /
s ² ), the difference between the stop distance V _f ² / 2α of the host vehicle and the stop distance V _a ² / 2α of the preceding vehicle is set to the time T until the host vehicle sets the brake by the distance setting switch 42. _The distance R shown in the equation 1, which is the _sum of the free running distance V _f · T _{d due} to _d , becomes the reference for collision judgment.

[0015]

[Equation 1]

Therefore, first, in step ST15, the relative speed (d / dt) R and the vehicle speed V _f are compared, and-(d /
dt) In the case of R≈V _f , that is, when the obstacle is regarded as a road stop, the process proceeds to step ST16, and since V _a = 0 in Formula 1, the collision law is calculated by the following formula 2 Determine the risk.

[0017]

[Equation 2]

When the equation 2 is satisfied, there is a risk of collision with an obstacle, and the process proceeds to step ST19 to generate an alarm signal and send it to the alarm notifying unit 4, and the alarm device 52 causes a danger. A warning for avoidance is issued.

On the other hand, as a result of the judgment in step ST15,
When − (d / dt) R≈V _f is not satisfied, the obstacle is a preceding vehicle traveling on the road ahead, and the danger judgment should be originally made according to Equation 1. However, the relative velocity (d /
Since the calculation accuracy of dt) R cannot be strictly obtained, there is a risk of a false alarm in the calculation error. Therefore, in the case of a preceding vehicle in which an obstacle moves, the relative speed − (d / d
t) First, it is determined whether R is equal to or higher than a predetermined speed C (m / sec).

As a result, when-(d / dt) R≥C, the relative speed is fast and the vehicle is approaching rapidly. Therefore, the preceding vehicle is regarded as infinitely close to the stopped object, and the process proceeds to step ST16. Thereafter, the same logic as that of the stop obstacle is used to determine the alarm output by the discriminant of the equation (2).

Further, the determination result of step ST17 is −
When (d / dt) R <C, the relative speed is slow, and it is considered that the vehicle is normally following the vehicle at a constant inter-vehicle distance, and the own vehicle speed V _f and the preceding vehicle speed V _a are substantially equal to each other. Becomes the following expression 3, and in step ST18 the risk of collision is determined by this expression 3, and if this expression 3 holds similarly, an alarm is issued in step ST19.

[0022]

[Equation 3]

[0023]

However, in such a conventional obstacle detection device, three laser diodes (denoted by LD-R, LD-C, and LD-L) are used.
In order to cover the entire lateral width of the lane in which the vehicle is traveling and to detect as far as possible, the detection range by the three detection areas A (portion indicated by a set of a plurality of points), B (a plurality of points) shown in FIG. Part indicated by a set of x), C
(Diagonally shaded portion), the front target is set by dividing the distance from the LD array 13 to the front L1 for the detection areas A and B, and LD for the detection area C. It is set so that each of the front targets within the distance from the array 13 to the front L2 is detected, that is, the portion M shown by the diagonal lines in FIG. 7 is within the detection range. Therefore, three expensive laser diodes must be used, and an LD array must be used for miniaturization, resulting in a high price.

The present invention has been made in view of these problems, and an object thereof is to provide a low-cost device which requires only two light emitting elements.

[0025]

SUMMARY OF THE INVENTION An obstacle detecting device according to the present invention comprises a light emitting means for emitting a light beam toward the front in a pulsed form, and a light emitting means for emitting the light beam and reflecting it at a target located in front. Receiving means for receiving a light beam, a signal extracting means for extracting a pulsed electric signal corresponding to the light beam based on a light receiving signal received by the light receiving means, and an extraction signal from the signal extracting means In the obstacle detection device comprising a distance calculation means for calculating the distance between the front target and the own vehicle based on, the light emitting means is provided in pairs with respect to the central axis of the vehicle, In addition, the optical axes thereof are set in parallel with each other.

[0026]

The obstacle detecting device according to the present invention detects the front target by emitting the light beams from the two light emitting elements in parallel toward the front target, so that the cost can be reduced and the power consumption can be reduced. Less is required.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the present invention. First, the configuration will be described with reference to FIG. 1, but the same or equivalent components as those of the conventional example shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, 55 and 56 are laser diodes (denoted by LD-R and LD-L), respectively, so that one light beam is directed so that their optical axes N1 and N2 are parallel. And they are set so that they overlap each other and cover the entire road width.

Each of the laser diodes 5 is
The LDs 5 and 56 are sequentially driven by the LD switching driver 57 as shown in FIG. 4, and each emits a light beam in a pulse shape. Further, 61 and 62 are light projecting lenses, X is the own vehicle, and Y is a road.

[0030]

As described above, according to the present invention, the number of high-priced parts can be reduced, so that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an obstacle detection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a detection range of FIG.

FIG. 3 is a circuit block diagram of a conventional obstacle detection device.

FIG. 4 is a timing chart showing a time relationship of signals of respective parts in the conventional distance detecting part.

5 is a flowchart showing a flow of processing in the arithmetic circuit of FIG.

FIG. 6 is an explanatory diagram of a detection range formed by each light beam.

FIG. 7 is a diagram showing a detection range of a conventional obstacle detection device.

[Explanation of symbols]

 13 Light emitting means (LD array) 55, 56 Laser diode 57 LD switching driver

Claims (1)

[Claims] 1. A light emitting means for emitting a light beam toward the front in a pulse form, a light receiving means for receiving a light beam emitted from the light emitting means and reflected by a target located in front, and the light receiving means. A signal extracting means for extracting a pulsed electric signal corresponding to the light beam based on the received light receiving signal, and a signal between the front target and the own vehicle based on the extraction signal from the signal extracting means. In an obstacle detection device including distance calculating means for calculating a distance, the light emitting means are provided as a pair with respect to a central axis of the vehicle, and the optical axes thereof are set in parallel with each other. An obstacle detection device comprising: