JPH0330117B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vehicle laser radar device that is installed in a vehicle and measures an inter-vehicle distance to a preceding vehicle.

[Technical background of the invention and its problems] In recent years, optical radar devices have been installed on vehicles to detect the distance between the vehicle in front and the own vehicle, to maintain a safe distance between vehicles at all times, and to adjust the speed of the vehicle to ensure safe driving. Control devices have been proposed (for example, in JP-A-Sho
58−203524).

Incidentally, in order to properly control such a device, it is a prerequisite that the inter-vehicle distance can be detected efficiently and reliably. For this reason,
The performance of the optical radar device is related to the quality of the device. As an optical radar device used for such a purpose, for example, one using the scanning method disclosed in Japanese Patent Application Laid-open No. 134589/1983 can be considered. In an optical radar device using this scanning method, for example, a flat laser beam spread in the vertical direction of the vehicle is emitted at a fixed swing angle θ.
The laser beam is configured to detect a preceding vehicle in front of the vehicle while continuing to wave at a constant cycle, and the scanning direction of the laser beam is reversed after a certain period of time has elapsed after receiving the reflected pulse from the preceding vehicle. The scanning angle can be narrowed. That is, according to this optical radar device, since the laser beam scans only the vicinity of the preceding vehicle, highly efficient inter-vehicle distance detection can be performed with less wasted scanning time.

However, while an optical radar device that uses such a scanning method can efficiently detect the distance between vehicles, in reality there are various objects on the road in front of the vehicle other than the preceding vehicle, such as roadside guardrails. If a reflected pulse from an object other than the preceding vehicle is mistakenly detected as a reflected pulse from the target preceding vehicle, the laser beam will scan only in the vicinity of the object other than the preceding vehicle. , there is a risk that the distance to this distance may be mistakenly measured as the inter-vehicle distance to the preceding vehicle. Therefore, in order to efficiently and reliably detect the inter-vehicle distance, it is important as a premise that the preceding vehicle can be reliably identified from various objects present in front of the host vehicle.

[Object of the Invention] The present invention has been made in view of the above, and its object is to provide an optical radar device for a vehicle that can reliably identify a preceding vehicle.

[Summary of the Invention] In order to achieve the above object, the present invention scans and radiates light, and also generates a radiation signal indicating the radiation and a scanning angle signal indicating the scanning angle at the time of radiation. The light emitting means 1 outputs light and receives reflected light from a reflector of the emitted light, and when the intensity of the reflected light reaches a set intensity determined according to the reflectance of a reflex reflector, for example, a light receiving signal is output. A light receiving means 3 for outputting light, and a distance calculating means 5 for calculating the distance to the reflector based on the propagation delay time from the input of the radiation signal to the input of the light reception signal.
When the light receiving signal is input multiple times while the scanning angle of the light emission reaches the set angle based on the scanning angle signal, and the difference in the distance calculated from the light receiving signals for these multiple times is within a predetermined value, the Inter-vehicle distance determining means 7 that outputs the distance determined as the inter-vehicle distance to the preceding vehicle.
The gist is that the configuration has the following.

[Embodiments of the Invention] Examples of the present invention will be described below with reference to the drawings.

FIG. 2 shows a vehicle optical radar device according to an embodiment of the present invention. The vehicle optical radar device shown in the figure has a clock generator 21 that generates a clock signal at regular time intervals.
3 is driven, and a flat laser beam Lt spread in the vertical direction is output from the light transmitter 23 to the front of the vehicle. This output laser light hits a reflector such as a preceding vehicle located in front of the vehicle and is reflected, and this reflected light Lr is received by a light receiver 25 having a light receiving viewing angle φ. The reflected light received by the light receiver 25 is converted into an electrical signal, amplified by an amplifier 27, and then supplied to a distance detection circuit 29. The distance detection circuit 29 is further supplied with a clock signal from the clock generator 21.
The distance detection circuit 29 detects the time when this clock signal is supplied, that is, the time when the laser beam Lt is output from the light transmitter 23, and the time when the laser light Lt is outputted from the light transmitter 23, and the time when the laser light Lt is output from the light transmitter 23,
Measure the optical propagation delay time td between the time when the reflected optical electrical signal is supplied from the
Substitute into the following equation to calculate the distance l to the reflector.

l=C×td/2 Here, C is the speed of light (3×10 ⁸ m/sec).

The microcomputer 31 digitally converts the scanning angle control signal of the digital signal so that the vertically elongated flat laser beam that is spread in the vertical direction from the light transmitter 23 scans the front of the vehicle in the horizontal direction within the swing angle θ. - converted into an analog signal via an analog converter 35 and supplied to the scanning device 33; The scanning device 33 is controlled by a scanning angle control signal from the microcomputer 31 to drive and control the light transmitter 23 within the range of swing angle θ. This swing angle θ is the swing angle between leftward swing angle θ _L and rightward swing angle θ _R with respect to the front center line of the vehicle, that is, θ _L < θ < θ _R
It is. Note that this scanning control is performed by the clock generator 2.
The microcomputer 31 includes a clock generator 21 in order to match the timing of the clock signal 1.
clock signal is supplied. Further, the microcomputer 31 is supplied with the amplified voltage V from the amplifier 27, thereby inputting the magnitude of the reflected light intensity to the microcomputer 31.
The microcomputer 31 is, for example, a CPU,
It is composed of ROM, RAM, input/output interface (not shown), etc., and the processing functions of the flowchart shown in FIG. 3 are realized by the program stored in the ROM.

The operation will be explained below with reference to the flowchart of FIG.

The process of the flowchart shown in FIG.
It is executed at predetermined intervals by interrupt processing every sec.

First, as an initial state, it is assumed that the direction of the light beam emitted from the light transmitter 23 is oriented at a position of θ=0°, that is, directly in front of the vehicle. Then, the light beam moves from the position directly in front of this θ = 0° to the right to the angle of θ = θ _R ° in increments of △θ = 0.1°, and after reaching the maximum scanning angle θ = θ _R ° at the right end. △
The angle is decreased by θ=0.1° (△θ=−0.1°) and returned to the position directly in front of θ=0°. After returning to the front position of θ = 0°, further reduce the scanning angle △θ = 0.1° each time (△θ = -0.1°) and move θ to the left from the front position.
= θ _L ° (θ = θ _L °). After reaching the maximum scanning angle θ=θ _L゜ at the left end, the scanning angle △θ=
The angle increases by +0.1° and returns to the front direction of θ=0° (steps 100 to 150). Hereafter, while repeating this operation, scan the front direction of the vehicle to the right at the scanning angle θ.
A light beam is emitted in the range from = θ _R ° to a leftward scanning angle θ = θ _L ° via a digital-to-analog converter 35, a scanning device 33, and a light transmitter 23 under the control of a microcomputer 31. Then, the reflected light of this emitted light beam is received by the light receiver 25.

The signal received by the light receiver 25 is amplified as an electric signal by the amplifier 27, and is supplied to the distance detection circuit 29 to calculate the distance l to the reflector, and this distance l and the amplified voltage V amplified by the amplifier 27 are It is input to the microcomputer 31. (step
160).

By the way, there is a preceding vehicle 41 on the road ahead of the own vehicle at approximately the center of the road, as shown in FIG. There is also a traffic sign 4 on the left end of the road.
Consider the case where 7 is provided. Furthermore, two reflex reflectors 49 and 51 are provided at the rear end of the preceding vehicle 41 with a distance of 2d between them. Now, if the distance from the own vehicle to the preceding vehicle 41 is l, and the angle from the own vehicle to the preceding vehicle 41 with respect to the reflex reflectors 49, 51 is 2α, then the angle α is expressed by the following equation.

α=tan ⁻¹ d/l In step 170, this angle α is calculated. As will be described later, when scanning the front of the vehicle with a light beam to detect a preceding vehicle, the reflector that has the highest probability of identifying the preceding vehicle, that is, the target object, is placed at the rear end of the preceding vehicle. This is because the reflection reflectors 49 and 51 are provided. That is, the light beam 5 is directed toward the front of the vehicle as shown in FIG. 4a.
3, the amplified voltage V for the reflected light reflected from each front reflector is as follows:
As shown in FIG. 4b, the amplified voltage Va for the traffic sign 47, the amplified voltage Vb for the reflex reflector 45 of the guardrail 43, and the amplified voltage Vb for the reflection reflector 45 of the guardrail 43,
than any of the amplified voltage Vc for the body of
Reflex reflectors 49, 51 of the preceding vehicle 41
The amplified voltages Vd and Ve have the largest amount of reflected light among the front reflectors, and the distance 2d between them is almost constant. Therefore, by detecting the reflection pattern of this reflex reflector, it is possible to reliably identify the preceding vehicle.
is being calculated. Therefore, in order to identify the reflex reflectors 49 and 51,
What is necessary is to detect a pair of reflectors that have a relatively large amount of reflected light and are approximately the same distance apart, and to detect that the angle of both reflectors when viewed from the own vehicle is within a predetermined angle, that is, 2α. For this purpose, first, in step 170, the angle α with respect to the distance l to the preceding vehicle is calculated in advance.

Next, in step 180, in order to detect a reflex reflector with a large amount of reflected light, the amplified voltage V inputted from the amplifier 27 in step 160 is compared with a predetermined reference amplified voltage Vth, and the
Check whether it is larger than Vth (V>Vth). The reference amplified voltage Vth is the inter-vehicle distance l from the preceding vehicle.
This is a predetermined reference amplified voltage obtained by amplifying a signal corresponding to a predetermined reference amount of light reflected from the preceding vehicle, which is determined according to the distance l, as shown in FIG. , Vth=10 ⁸ Vo/l ⁴ . Here, the amplified voltage is the amplified voltage obtained by amplifying the light reflected by one reflex reflector of a vehicle 100 meters ahead by the light receiver 25 and then by the amplifier 27, and the light emission output of the light transmitter 23, It is determined in advance based on the spread angle of the light beam, the light receiving sensitivity of the light receiver 25, and the like. Therefore, it is considered that there is a strong possibility that a reflector having an amplified voltage V larger than the reference amplified voltage Vth determined for each distance l in the graph of FIG. 5 is a vehicle reflex reflector. Therefore, in step 180, the reference amplified voltage Vth determined for the distance l measured in step 160 from the graph of FIG. 5 is compared with the amplified voltage V input in step 160. As a result, if the amplified voltage V is not greater than the reference amplified voltage Vth, the vehicle is not in front, so step 240 is performed.
Then proceed to ``0'' and reset the preceding vehicle flag to ``0''.

Also, in the determination at step 180, the amplified voltage V is larger than the reference amplified voltage Vth (V>Vth).
In this case, the process proceeds to step 190, and it is checked whether the distance lp detected and measured in the previous process is not "0". If the distance lp detected and measured in the previous process is not "0", the step
Proceeding to step 200, it is checked whether the distance l just detected is approximately equal to the distance lp detected in the previous process (l=lp). The fact that the distance l just detected is almost equal to the previously detected distance lp means that, for example, the fourth
As shown in the figure, it is considered that one of the reflex reflectors 49 and 51 of the preceding vehicle 41 was detected in the previous process, and the other reflex reflector was detected in the current process. Therefore, the program proceeds to step 210 and calculates the difference between the scanning angle θ of the reflector at the distance l just detected and the scanning angle θp of the reflector at the previously detected distance lp. The angle between the two (|θ-θp|) when ) or not.

As a result, in step 210 |θ−θp|<
2α, that is, as a result of the checks in steps 180 to 210, the amplified voltage V is larger than the reference amplified voltage Vth, lp is not “0”, l≈lp, and |θ−θp|<2α. It is clear that the reflex reflectors 49 and 51 of the preceding vehicle are detected, so proceed to step 220 and prepare for the next processing by setting the just detected l and θ as lp and θp, respectively, and change △θ to -△ The scanning direction is reversed by setting θ and the process proceeds to step 250.

Note that if lp=0 in step 190,
If l≒lp is not found in step 200, and |θ−θp|<2α is not found in step 210, both reflectors are not the same in distance,
The angle is also a predetermined angle, and it is thought that it is not a reflex reflector of the preceding vehicle, so the step
Proceed to 230 and find the distance l and angle θ of the reflector just detected.
are set as lp and θp, respectively, and in preparation for the next process, proceed to step 240 and set the leading vehicle flag to "0".
and proceed to step 250.

At step 250, the leading vehicle flag is "1".
Check whether it is. If the preceding vehicle flag is “0”, there is no preceding vehicle (step
250), if the preceding vehicle flag is "1", the measured distance lp is set as the inter-vehicle distance lp and the process ends.

By detecting a pair of reflectors, that is, reflex reflectors, in which the amplified voltage V is greater than the predetermined reference amplified voltage Vth, the distance l is approximately the same, and the angle between them is a predetermined angle, as described above,
Even if there are traffic signs, guardrails, etc. in front, it is possible to reliably detect the preceding vehicle, and if a pair of reflex reflectors of the preceding vehicle are detected, the light beam can be compared without waste using only this reflex reflector. It can repeatedly scan within a narrowed range and constantly monitor the distance between vehicles in front while shining a light beam on them.

[Effects of the Invention] As explained above, according to the present invention, attention is paid to the reflection pattern of, for example, a pair of reflex reflectors provided at the rear end of the preceding vehicle, and the amount of reflected light is larger than a predetermined amount of reflected light. A pair of reflectors is detected, and the distance to both reflectors is approximately equal,
If the difference in scanning angle for both reflectors is less than a predetermined angle, this reflector is identified as the preceding vehicle, that is, the preceding vehicle's reflex reflector, and the following distance is calculated. Even if there are other objects such as traffic signs or guardrails, the preceding vehicle can be reliably identified and the inter-vehicle distance can be precisely measured without interfering with the calculation of the inter-vehicle distance. Furthermore, when a preceding vehicle is detected in this way, it is possible to repeatedly scan a narrowed range while reversing the scanning direction of the light beam between, for example, a pair of reflex reflectors of the preceding vehicle, so there is no waste in scanning. It can constantly monitor the distance between vehicles in front while shining a light beam only on the vehicle in front.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to claims of the present invention, Fig. 2 is a block diagram of an optical radar device for a vehicle showing an embodiment of the invention, and Fig. 3 is a flowchart showing the operation of the optical radar device for a vehicle shown in Fig. 2. Chart, Figure 4a shows various objects on the road ahead of the own vehicle, preceding vehicles, etc. Figure 4b corresponds to the reflected light when the light beam scans the front shown in Figure 4a. FIG. 5 is a graph showing the reference amplified voltage Vth corresponding to the reflected light from the vehicle ahead versus the distance l to the vehicle. 1... Light emitting means, 3... Light receiving means, 5... Distance calculating means, 9... Inter-vehicle distance determining means.

Claims (1)

[Scope of Claims] 1. A light emitting means that scans and emits light and outputs a radiation signal indicating that the light has been emitted and a scanning angle signal indicating the scanning angle at the time of emission, and light reflected by a reflector of the emitted light. and a distance for determining the distance to the reflector based on the propagation delay time from the input of the radiation signal to the input of the reception signal. When the light receiving signal is inputted multiple times while the scanning angle of the light emission reaches the set angle based on the scanning angle signal, and the difference in the distance obtained from the plurality of light receiving signals is within a predetermined value. 1. An optical radar device for a vehicle, comprising: inter-vehicle distance determining means for outputting the determined distance as an inter-vehicle distance to a preceding vehicle. 2. Claims characterized in that the light receiving means outputs a light receiving signal when the intensity of the reflected light reaches a set intensity determined according to the reflectance of a reflex reflector provided at the rear of the vehicle. The vehicle optical radar device according to item 1.