JPS61145474A - Range finder for vehicle - Google Patents

Abstract

PURPOSE:To certainly measure the distance between cars, by calculating the distance up to a reflector by the propagation delay time from transmission to reception and discriminating the forward car on the basis of the change in the relative relation of each reflector to the own car by using distance data. CONSTITUTION:Pulse laser beam emitted from a beam emitter 1 through a beam emitting trigger generator 2 is reflected from a target and the reflected beam is received by a beam receiver to be converted to an electric signal by a photoelectric converter circuit 4 while the electric signal is further amplified by an amplifier 5 to be inputted to a comparator 6. The comparator 6 outputs a high level pulse when the input signal is equal to or more than a predetermined value and this output signal is added to the clock signal preliminarily outputted from a microcomputer (MC)17 to be inputted to a counter through an OR gate 8. The output signal counted by the counter 16 is inputted to the reset input of FF7 and the output signal thereof is inputted to a counter 10 along with the clock signal from a clock 8 through an AND circuit 9. The output of a monostable multivibrator 11 and the latch data of a latch circuit 12 are inputted to MC17 and receives operational processing to perform the output of a distance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a distance measuring device for a vehicle that can reliably measure the inter-vehicle distance from one's own vehicle to a preceding vehicle.

[Technical aspects of the invention and its problems] In recent years, as vehicles have been equipped with constant-speed running devices that allow the vehicle to run at a constant set speed, improvements have been made to prevent rear-end collisions with preceding vehicles and improve driving operability. The purpose is to measure the distance between the own vehicle and the vehicle in front and control the vehicle speed according to the detection results.
2. Description of the Related Art Vehicle travel control devices have been proposed that cause the own vehicle to follow a preceding vehicle. Along with this, in order to improve the control reliability of the vehicle travel control device, there is a current demand for a device that can measure inter-vehicle distance with high reliability.

FIG. 7 shows an example of a device that measures distance using electromagnetic waves such as laser light as a medium. In the same figure, 31 is a light transmitter, and the light transmitter transmits light using a trigger pulse, which is a light transmitting trigger signal from the generator 31. 33 is a light receiver, which transmits light from the light transmitter 31. The pulsed light is reflected by the target object and the reflected light is received. 34 is a photoelectric conversion circuit that converts the reflected light received by the light receiver 3 into an electrical signal, and 35 is an amplifier that amplifies the electrical signal. A comparator 36 outputs a high level (H) pulse as a comparator output signal when the input signal from the amplifier 35 is equal to or higher than a predetermined value Vth. 37 is an R-S flip-flop, which receives the light transmission trigger signal as a set (S) input and receives the comparator output signal as a reset (R) input. That is, R
-S flip 70 knob 37 outputs a pulse having a time width corresponding to the propagation time of pulsed light traveling back and forth between targets. 38 is a clock, for example, clock frequency Io=15
A clock signal of about 0 MHz is generated. The clock signal and the output pulse signal of the R-S flip-flop 37 are input to an AND gate 39, and the output signal of the AND gate 39 is input to a clock terminal (CL) of a counter 40. Further, the light transmission trigger signal from the light transmission trigger generator 32 is input to the clear terminal (C) of the counter 40.

On the other hand, the monostable multivibrator 41 transmits pulsed light between targets (for example, 150n+) every time the light transmission trigger signal is input.
A pulse having a time width τ1, which is sufficiently longer than the propagation time for reciprocating, is output.

Further, the latch circuit 42 latches the count signal from the counter 40 at the falling edge of the pulse from the monostable multivibrator 41 (at the end of counting). Finally, the distance converter 43 converts the latched data into distance data according to equation (1) below and outputs it.

1=n -0/ 2fo ・-= (1) 吏
... Distance value n ... Counter output (latch data) C...
Speed of light, fo... Clock frequency By the way, in such conventional distance measuring devices,
A configuration in which the distance to the reflective target of the reflected light, that is, the closest reflective target, is measured by counting the propagation delay time of the reflected light that first exceeds the threshold of the comparator 36 using the only counter 4o. It is. However, when this distance measuring device is applied to the vehicle travel control device described above, the following problems occur. That is,
As shown in FIG. 8, for example, when traveling on a curved road 21, the preceding vehicle 44, which should originally be distanced, is illuminated within the pulsed light (which has a spread angle of several 101+1 rad to ensure that the preceding vehicle does not deviate from the beam area even on a somewhat curved road). Even if there is a flex reflector 45 (hereinafter referred to as a reflector) arranged at a predetermined interval on a roadside guardrail or located closer than the preceding vehicle 44 within the pulsed light,
The distance to the reflector 45, which does not originally need to be measured, is measured, and as a result, the inter-vehicle distance to the preceding vehicle 44 cannot be measured. This is not limited to when traveling on a curved road, but also when traveling on a straight road, there is a possibility that the inter-vehicle distance to the preceding vehicle cannot be reliably measured due to the presence of roadside objects, pedestrians, etc.

[Object of the Invention] The present invention has been made in view of the above, and an object thereof is to provide a distance measuring device for a vehicle that can reliably measure the distance from the host vehicle to the preceding vehicle.

[Summary of the Invention] In order to achieve the above object, the present invention includes a wave transmitting means 51 for transmitting electromagnetic waves, and a receiver for receiving reciprocal waves caused by a reflector of the transmitted electromagnetic waves, as shown in FIG. a wave means 53, a distance calculation means 55 for calculating the distance from the own vehicle to each reflector based on the propagation delay time from transmission to delivery of the electromagnetic wave for each received reflected wave; The main feature is to include a preceding vehicle determining means 57 for determining a preceding vehicle from among the reflectors based on a change in the relative relationship of each reflector with respect to the own vehicle and outputting the distance to the preceding vehicle.

[Embodiment of the invention j Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 shows a circuit of a vehicle ranging device according to an embodiment of the present invention. In the figure, 1 is a light transmitter composed of, for example, a laser oscillator, and a light transmitter trigger generator 2
A light transmitting bird supplied at regular intervals T receives a signal and outputs a pulsed laser. On the other hand, this light transmitting trigger oscillator 2 has an output of the R-S flip-flop 7.
The set terminal (S) of , and the high level (
1-1) Monostable multivibrator 11 that outputs a signal
and is connected to the clear terminal (C) of the counter 10. The monostable multivibrator 11 has its output connected to the microcomputer 17 and is also connected to the latch circuit 12 to control its latch action. The counter 10 has its clock terminal (CL) connected to the clock 8 outputting a clock signal of a constant frequency IO via the input terminal a of the AND circuit 9, and its output connected to the latch circuit 12. ing. In addition, AND
The input terminal of the circuit 9 is connected to the output of the R-S flip-flop 7. Therefore, in the counter 10, the output of the R-S flip-flop 7 is at a high level (
)-1), the clock signal supplied from the clock 8 via the AND circuit 9 is counted and output to the latch circuit 12. The latch circuit 12 detects the fall of the pulse signal from the monostable multivibrator 11, latches the counted output value at this time, and outputs it to the microcomputer 17.

On the other hand, 4 is a photoelectric conversion circuit that charges and converts the light received through the light receiver 3, and the output of this photoelectric conversion circuit 4 is connected to an input terminal a of a comparator 6 via an amplifier 5. The input terminal of this comparator 6 is connected to a predetermined power supply voltage vth, and the output is connected to the OR circuit 1.
The clock terminal of the counter 16 (
CL). The counter 16 has a 4-bit binary output, of which the output with a weight of 23 is connected to the reset terminal (R>) of the R-S flip 70 block 7. Note that the input of the OR circuit 18 The terminal and the clear terminal (C) of the counter 16 are connected to the microcomputer 17. Therefore, the comparator 6 has a predetermined value for all the signals photoelectrically converted from the light received by the photoreceptor 3 by the photoelectric conversion circuit 4. By comparing with the voltage vth, only the pulse signal related to the reflected light of the pulsed laser outputted by the pre-distributing optical device 1 is extracted from the light received by the light receiver 3 and is supplied to the counter 16. performs counting on this supplied pulse signal, and when the count reaches a predetermined value, that is, when the weight output 23 switches to high level (H), a signal is sent from the light transmission trigger generator 2 when the pulse laser is output. This high level (H) signal is supplied to the reset terminal (R) of the R-S flip-flop 7 whose output is in the high level (H) state due to the output light transmission trigger signal, and the output of the R-8 flip-flop 7 is This will reset the output to a low level <1). Regarding the timing of outputting the signal to the reset terminal (R) of the R-S flip 70 knob 7 in the counter 16, the microcomputer 17 clears the count value of the counter 16 before counting, and then outputs the OR circuit 18. Preset adjustments can be made by supplying several pulses in advance through the oscilloscope.

Next, the operation of this embodiment will be explained with reference to FIGS. 3, 4, and 5.

Figure 3 shows a time chart of each point in the configuration diagram of Figure 2,
FIG. 4 shows a flow chart of the microcomputer 17.

First, the operation of time-divisionally measuring distances to a plurality of reflective targets having different distances will be described.

First, in step 100 of Fig. 4, 1=j-1゜1i
-+11i=-0 and initialization processing is performed. Here, register i represents the i-th closest target, and register j
is the number of samples when calculating the average distance. now,
Assuming that the period of the light emission trigger is 200 μsec, i = 1
．． 2.3.・, 8 (because the counter 16 is a 4-bit counter), j = 1.2, 3°..., 500 (that is, distance output cycle = 200 x 10' x 500 = O-1se
c).

Next, after this initialization process, the process proceeds to step 110, where it is determined whether the output of the monostable multivibrator 11 is at a low level (L), and while it is at a high level (H), step 110 is performed.
When it stops and becomes low level (L), step 120
Proceed to.

In step 120, the count output n of the counter 10 is input, and the process proceeds to step 130. In step 130, mouth≧
It is determined whether or not τfO holds true, that is, there is no received pulse of a reflected wave from a reflective target existing within a certain distance. If it holds true, the process proceeds to step 180, and if it does not hold, the process proceeds to step 140. . Further step 18
In the case of 0 (when there is no received light pulse, for example, corresponding to i = 4 in Fig. 3), step 1 is performed after resetting i - Q.
The process advances to 90 and outputs a clear signal to the counter 16. In step 200, after outputting a clear signal to the counter 16,
(7-i) clock pulses are output to the counter 16 until the next light emission trigger signal is issued. i.e. i
When = Q, there are 7 pulses, when i -1 there are 6 pulses, when i -2 there are 5 pulses, when i = 3 there are 4 pulses, and when i = 4 there are no received light pulses, so i = O, and as shown in Figure 3. As shown in (G), there are 7 pieces. In step 210, the register i is incremented (i = i +1>) and the process returns to step 110.

In addition, if the latter 0≧τfO does not hold (if a received light pulse exists), the count value n is converted into a distance hair according to the above formula (1), and then the distance calculated by adding the i-th closest distance is determined in step 150. Add the current distance hair to sum l (
hair °1 - love 1 tenshi) or the number of distance data added m
is repeatedly increased by increments (1lli = Ii +1).

Next, in step 160, after incrementing the number of samples j when calculating the average distance (j = j + 1),
In step 170, it is determined whether j≧500. As a result, if the determination of j≧500 is YES (every 100+1 sec), in step 220, L+
−ILI/I + , L2=IL2/m 2 , 13
= 3/I3..., and in step 230, the distance LX to the preceding vehicle is determined by the preceding vehicle identification process, which will be described later.
(identify and remove the others), and further in step 240 LX
Outputs as a distance value.

As is clear from the above explanation, according to the process of this flowchart, in the case of measuring the first target object from a distance close to the own vehicle, the value of the counter 16 is set to 7 in advance, and the value of the second target object is measured from a distance close to the host vehicle. By adding 6 for the distance and 5 for the third, the values are sequentially 1, 2, 3, etc. ...If the distance measurement for the i-th target object cannot be performed because there is no received light pulse, the distance measurement for the i-th target object is repeated from the next time, starting from the first object distance measurement at regular intervals. It can be seen that it is averaged.

Next, the operation of each part of the configuration diagram of the embodiment shown in FIG. 2 will be explained using the time chart of FIG. M3.

Note that i=1, 2, 3, 4, . . . shown in FIG. 3 each indicate a cycle corresponding to a light transmission pulse corresponding to the distance to the i-th nearest target.

First, in FIG. 2, a light transmitting trigger signal (FIG. 3 (A)) from a light transmitting trigger signal is inputted to the light transmitting device 1 to cause the pulsed laser to transmit light. Now, this transmitted pulsed laser light is reflected by the target object, and the reflected light is received by the optical receiver 3, converted into an electrical signal by the photoelectric transformer circuit 4, further amplified by the amplifier 5, and sent to the comparator 6. is input. The comparator 6 outputs a high level ( ) ( ) pulse when the input signal is greater than or equal to a predetermined value vth (see
In the case of B), it indicates that the received light pulses were received by reflected light from three targets). This output signal is a preset clock signal output from the microcomputer 17 in advance (in the case of FIG. 3 (G), each (7-i) clock pulses are output, here +-1, 2, 3). In addition to this, the signal is input to the counter 16 via the OR gate 18.

The counter 16 counts the input pulse signals in this manner, and outputs 23 weighted bits out of 8 counted values, that is, 4 bits of binary output, to a high level (
H), this is reset inputted to the R-S flip 70 knob 7. This R-, S flip-flop 7 inputs the light transmission trigger signal (FIG. 4(A)) as a set <S> input, and inputs the output signal of the counter 16 as a reset (R) input. It outputs a pulse corresponding to the propagation time for light to travel back and forth between targets, and it time-divides the distances to multiple reflective targets having different distances in order of distance from the own vehicle using one counter 10. A pulse is output to enable distance measurement (Fig. 4 (D)). This pulse output signal is input to the AND circuit 9 together with the clock signal (for example fo -150M)-1z) output from the clock 8, and the output signal is input to the clock terminal (CL) of the counter 10 (fourth Figure (E)). Next, the latch circuit 12 latches the count signal from the counter 10 at the falling edge of the single pulse from the single-shot multivibrator 11 (when the counter ends) (FIG. 4(F)). Finally, the microcomputer 17 inputs the output pulse of the single-shot multivibrator 11 and the latch data of the latch circuit 12, performs the process shown in FIG. 4 described above, and outputs the distance.

Next, the time-divisionally measured distance values L1. L2, L3...
5 and 6, a description will be given of a preceding vehicle identification process in which, for example, when the vehicle is traveling on a curved road, the distance value of the roadside slope flap is removed and only the distance measurement signal of the preceding vehicle is output.

Distance value L+ when traveling on curved road 21 as shown in FIG.

L2. The state of L3... is shown in the distance value relationship diagram when traveling on a curved road in FIG. Here, the distance value of [=to just indicates the distance m value in the situation shown in FIG. In addition, in Fig. 5, the symbols ○, △9, and O represent the 1st, 2nd, and 3rd positions, respectively.
The fourth closest distance value L+, 12, L3
, L4 [indicates IR]. Also straight line 11.12. I
L3...2 magazine 6 is a distance signal from a roadside reflector, and the slope kc of each straight line is almost the same, as shown in the following equation 2), and the interval Δ and [1] between adjacent straight lines are also almost the same. This is expressed by the following equation (3).

kC-1''17''a... (2) ΔL'':D
...... (3) However,? a is the own vehicle speed [rA/5eCj, and D is the distance between the lifters installed on the roadside and D = 20 to 30 Il.
It is l.

On the other hand, the straight line ILo is a distance signal from the preceding vehicle, and the slope kO of the straight line is different from kc and is expressed by the following equation (4).

ko−−′υ−a −1−V b −・= (4)
However, yb is the preceding vehicle speed [m/sec:l.

By focusing on this difference in slope, the distance signal (distance value on the straight line ILo) from the preceding vehicle can be identified.

FIG. 6 is a flowchart of the preceding vehicle identification process,
This corresponds to step 220 in the flowchart of FIG.

In step 2200 of the flowchart, time t
The measured distance value is +t * 12t, *L3shi,...
and input these into step 2300 of the flowchart corresponding to step 230 in FIG. 4. For example, for L+6 (corresponding to LX in FIG. -1,... will be compared.

Now, step 2310GC, L I? =L
If te, -1 holds true, add L + z to the set G1 of points on the straight line that includes L + t-1.Step 23
20), further calculate the slope k by linearly approximating the set G1 of points, and [in the determination of k valve kcJ (step 2370), if k=kc holds, the measured distance value L17 is removed as being due to the roadside reflector. Step 239Q), k=
If kC does not hold, the distance measurement value Let, is output as the distance value by the preceding vehicle (step 2380).

For L2t, a comparison operation is performed in the same way as for L+-p (Step 2400), and for L3i, 6L+
t (step 2500), and the following 4 ships:
The same process is performed for Lst, . . . . Then, in the subsequent step 2600, the time register t
are incremented by 10QfflSeG respectively.
As the time passes, the microcomputer 17 outputs the averaged distance value to the preceding vehicle at each fixed period.

[Effects of the Invention] As explained above, according to the present invention, the reflected wave of the transmitted electromagnetic wave by the reflector is received, and the reflected wave is determined based on the propagation delay time from the transmission to the delivery. The distances to all the reflectors for which the distance was obtained are determined, and the distance data thus determined is used to identify the preceding vehicle based on changes in the relative relationship of each reflector to the host vehicle. Since the distance to the preceding vehicle is output, it is possible to reliably measure the inter-vehicle distance from the own vehicle to the preceding vehicle.

By applying the distance measuring device according to the present invention to a vehicle travel control device, it is possible to obtain high control reliability.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to complaints, Fig. 2 is a configuration diagram of a vehicle distance measuring device according to an embodiment of the present invention, Fig. 3 is a time chart of the number points in Fig. 2, and Fig. 4 is a diagram of the above-mentioned vehicle distance measuring device. A flowchart explaining the operation of the microcomputer constituting the distance device, - Figure 5 is a distance value relationship diagram when traveling on a curved road, Figure 6 is a flowchart of preceding vehicle identification processing which constitutes a part of Figure 4, Figure 7 This figure is a configuration diagram of a conventional example, and FIG. 8 is a diagram for explaining the operation of the conventional example of FIG. 7 when traveling on a curved road. 51... Wave transmitting means 53-... Wave receiving means 55.
... Distance calculation means 57 ... Leading vehicle discrimination means Fig. 1

Claims (1)

[Claims] A transmitting means for transmitting electromagnetic waves, a receiving means for receiving reflected waves from a reflector of the transmitted electromagnetic waves, and a propagation delay time from transmitting to receiving the electromagnetic waves for each received reflected wave. a distance calculating means for calculating the distance from the own vehicle to each reflector based on the calculated distance; A distance measuring device for a vehicle, comprising a preceding vehicle determining means that outputs a distance to a preceding vehicle.