JP3531515B2 - Obstacle warning device for vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle obstacle warning device for detecting the position of an obstacle with respect to a vehicle and notifying a driver of the presence or approach of the obstacle.

[0002]

2. Description of the Related Art JP-A-57-66372 discloses a method for calculating the position up to an obstacle by utilizing the difference in ultrasonic wave reflection time.
The technology disclosed in Japanese Patent Publication has been proposed. In this conventional technique, the one-shot multivibrator is used as a part of the means for obtaining the reception time of the reflected waveform from the obstacle. The reception waveform of the ultrasonic pulse signal generally has a rising waveform as shown in FIG. 15, and in the prior art, when the amplitude of the reception waveform exceeds the threshold level of the one-shot multivibrator, a high level for a fixed time is obtained. A signal is output, and the distance is calculated using the rising time of this output signal as the reception time of the reflected waveform. In FIG. 15, the horizontal axis represents time and the vertical axis represents voltage.

However, the actual received waveform of ultrasonic waves is
Since the amplitude fluctuates due to various factors such as wind, temperature distribution fluctuations, movement of obstacles, and vibration of ultrasonic wave transmitter / receiver, a constant threshold value like the one-shot multivibrator and other comparators mentioned above. In the method of detecting the rising edge of the received waveform by the level, the output (shaped waveform) after the level comparison is shifted by about one cycle due to the amplitude fluctuation of the received waveform near the threshold level V11 as shown in FIGS. Sometimes. That is, as shown in FIG. 16 (a), the original shaped waveform becomes high level at time t51, whereas when the amplitude of the received waveform fluctuates, the shaped waveform becomes as shown in FIG. 16 (b). It goes high at time t51 '. 16A and 16B, the upper part shows the received waveform at the center voltage Vc11, and the lower part shows the shaped waveform.

As a result, the accuracy of detecting the distance to the receiver or the accuracy of detecting the reception time of the reflected wave includes an error of one cycle of the received waveform, and the error from the obstacle required by the plurality of receivers. The value of the angle with respect to the obstacle obtained from the difference in distance will include an error corresponding to the sum of the errors generated by the respective receivers. That is, improving the detection accuracy of the position and (distance, angle) of the obstacle results in improving the accuracy of measurement of the arrival time of the reflected wave.

A sensor 50 for detecting the position of the obstacle.
18 (a) and 18 (b), when one transmission / reception device 52 and one reception only device 51 are used, if the distance Ls between the transmission / reception device 52 and the reception only device 51 is increased. , Even if the same obstacle position (distance and angle from the center of the sensor 50), the time until the receiver far from the obstacle receives, that is, the reception-only device 51 in FIG. In (b), since the time required for the transmission / reception device 52 to receive increases, the time difference Δt between the reflected wave reception times of the transmission / reception device 52 and the reception only device 51 becomes larger than that when the distance Ls is small.

As will be described later, the angle between the sensor 50 and the obstacle is obtained from the time difference Δt, but the influence of the angle change due to the change in the time difference Δt is reduced, and the angle detection accuracy is improved. However, by increasing the distance between the transmission / reception device 52 and the reception-only device 51, downsizing becomes difficult, which results in adverse effects such as increased cost and poor appearance of the sensor 50.

For the above reasons, it is possible to improve the detection performance of the obstacle position without increasing the distance between the transmission / reception device 52 and the reception exclusive device 51, that is, to improve the measurement accuracy of the arrival time of the reflected wave. It becomes important.

In order to solve such a problem, a technique described in Japanese Utility Model Laid-Open No. 60-74071 has been proposed as a method for accurately obtaining the rising time of a reflected waveform. This method is a method in which the received waveform is full-wave rectified to suppress the rise detection deviation to a half cycle.
Since the threshold level V12 is fixed to one as shown in (b), the rising time of the shaped waveform is time t52 shown in FIG. 17 (a) due to fluctuations in the amplitude of the reflected wave.
From time t52 ′ shown in FIG. 17 (b),
As a result, the output after level comparison is shifted by half a period. In each of FIGS. 17A and 17B, the upper part shows a waveform obtained by full-wave rectifying the received waveform of the center voltage Vc12, and the lower part shows a shaped waveform shaped by the threshold level V12.

Further, as a method of detecting the presence or absence of a reflected waveform by using a detection circuit having a plurality of threshold levels, Japanese Patent Laid-Open Nos. 63-311190 and 63-311191,
A technique described in Japanese Patent Laid-Open No. 63-111192 has been proposed, but this method aims to detect the presence or absence of a reflected waveform from the signal buried in the reverberation part of the transmitted signal. It is not for obtaining the reception time of the reflected waveform with the accuracy of the wavelength level of.

[0010]

As described above, the conventional technique is easily affected by the amplitude fluctuation of the reflected waveform of the ultrasonic wave reflected by the obstacle and has a problem in the accuracy of measuring the position of the obstacle.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the position measurement accuracy of an obstacle by accurately obtaining the reception time of a reflected wave without being affected by the amplitude fluctuation of the reflected waveform. An object is to provide a good vehicle obstacle warning device.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 is one or more transmitters mounted on a vehicle for transmitting ultrasonic signals, and ultrasonic waves mounted on the vehicle and transmitted. Based on two or more receivers that receive reflected waves from signal obstacles, amplification means that amplifies the ultrasonic signal received by the receiver, and the received signal amplified by the amplification means. From the transmission start time of ultrasonic waves from the transmitter,
Time measuring means for measuring the elapsed time until the reflected wave from the obstacle is received by each receiver, and distance calculating means for calculating the distance to the obstacle based on the time measured by the time measuring means. , The angle calculation means for calculating the difference between the measurement times for each receiver measured by the time measurement means, and the angle with the obstacle, from the value calculated by the distance calculation means and the angle calculation means Measure the position of obstacles,
In a vehicular obstacle warning device for alerting a driver to the presence and approach of an obstacle, the time measuring means sets a predetermined signal for each signal after being amplified by the amplifying means of the signal received by each receiver. includes a plurality of waveform shaping means for outputting a shaping signal in comparison with the threshold level, the threshold level of the plurality of waveform shaping means to be different, respectively, wherein
Of the plurality of shaped signals obtained from the plurality of waveform shaping means
Binarized sampling is performed at fixed time intervals, and
Data corresponding to each shaped signal obtained by sampling
Reflected waves only when a specific pattern is detected in the row
Of the rising amplitude of
Shaped signal waveform Pulse rising data measurement time
Is determined as the reception time of the reflected wave .

Further, the invention of claim 2, wherein the waveform shaping means in the invention according to the first includes a said central value and to Rukoto received signal waveform threshold level of one of the waveform shaping means according to each receiver To do.

According to a third aspect of the present invention, in the first and second aspects of the present invention, the waveform shaping means has a threshold level that is larger than a central value of a signal waveform received by each receiver and smaller than the central value. Is used.

[0015]

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The basic operation of the vehicle obstacle warning system of the present invention will be described based on the system configuration diagram shown in FIG. The transmission signal generation means 1 generates a transmission signal for transmitting the ultrasonic signal, and the transmitter 2 mounted on the vehicle transmits the ultrasonic signal to the outside based on the transmission signal. The ultrasonic wave signal transmitted to the outside is reflected by the obstacle 12 and received by the receivers 3 and 4 mounted on the vehicle, and the received signal received by the receivers 3 and 4 is amplified by the amplifying means 5. And is sent to the time measuring means 6.

The time measuring means 6 has an elapsed time (reflection time tn) from the generation time of the transmission signal from the transmission signal generation means 1, that is, from the transmission start time to the reception time of the reflected wave by each of the receivers 3 and 4. , N: the number of receivers) and sends the measurement result to the distance calculating means 7 and the angle calculating means 8. In the distance calculating means 7, the reflection time t measured by the time measuring means 6
From n, the distance value L between the obstacle 12 and each of the receivers 3 and 4 is calculated using the sound velocity C0 of the ultrasonic wave by the method described later. The angle calculation means 8 forms the obstacle 12 and the receivers 3 and 4 based on the arrangement of the transmitter 2 and the receivers 3 and 4 based on the difference in the reflection times tn obtained by the receivers 3 and 4. Calculate the angle value φ. From each of the receivers 3 and 4 thus obtained, the obstacle 1
From the distance value L to 2 and the angle value φ, the obstacle position calculation means 9 calculates the positions of the vehicle and the obstacle 12, and sends the result to the position indicator 10 for display, and the existence of the obstacle 12 or When the approach is detected, the alarm buzzer 11 is sounded to warn the driver.

Here, a method of calculating the distance and angle between the sensor transmitting and receiving the ultrasonic signal and the obstacle will be described with reference to FIGS. 18 (a) and 18 (b). FIG. 18 is a plan view showing the positional relationship between the sensor 50 and the reflected wave W from the obstacle,
The sensor 50 is a transmitter / receiver 52 for both transmitting and receiving ultrasonic signals.
And a reception-only device 51 dedicated to reception. Here, the transmission / reception device 52 corresponds to one having the functions of the transmitter 2 and the receiver 3 in FIG. 2, and the reception only device 51 corresponds to the receiver 4.

The distance between the sensor 50 and an obstacle (not shown) is L, the normal line of the sensor 50 is V, the angle between the normal line V of the sensor 50 and the obstacle (not shown) is φ, and the center of the sensor 50 is O. The distance between the transmission / reception device 52 and the reception only device 51 is Ls, and the angle between the reflected wave W from the obstacle and the sensor 50 is θ. FIG.
(A) and (b) respectively show the case where the obstacle is in the right direction and the left direction from the normal line V of the sensor 50, and the reflected wave from the obstacle from the time when the ultrasonic wave signal is transmitted from the transceiver 52. Is the reflection time ta until the time when the transmission / reception device 52 receives it, and the reflection time t is the time difference between the transmission time of the ultrasonic signal from the transmission / reception device 52 and the reception time of the reception-only device 51.
b.

As shown in FIG. 18A, when the obstacle is on the right side of the normal line V of the sensor 50, Δt = (tb-t
If a) / 2, the reception-only device 51 receives the reception signal later than the transmission / reception device 52, so Δt> 0. If a perpendicular line is drawn from the transmission / reception device 52 to the reflected signal W to the reception-only device 51 and the distance between the intersection and the reception-only device 51 is Lx, θ = cos ⁻¹ (Lx / Ls) = cos ⁻¹ (| Δt | /
A) φ = 90 ° −θ L = tb × C0 / 2 At this time, A = Ls / (2 × C0), and C0 is a sound velocity of 340 m.
/ S and the angle φ> 0.

On the other hand, when the obstacle is on the left side of the normal line V of the sensor 50 as shown in FIG. 18B, Δt = (tb
If -ta) / 2, the transmission / reception device 52 receives the reception signal later than the reception-only device 51, so Δt <0. Reflection signal W to the transmission / reception device 52 to receive only device 51
If a perpendicular line is drawn and the distance between the intersection and the transmitter / receiver 52 is Lx, θ = cos ⁻¹ (Lx / Ls) = cos ⁻¹ (| Δt | /
A) φ = − (90 ° −θ) L = tb × C0 / 2 At this time, A = Ls / (2 × C0), and C0 is a sound velocity of 340 m.
/ S and the angle φ <0. In this way, the distance L and the angle φ between the sensor 50 and the obstacle are calculated. At this time, since the distance Ls (about 3 cm) between the transmission / reception device 52 and the reception-only device 51 is sufficiently short with respect to the distance between the sensor center O and the obstacle, the distance is calculated from the reflection time tb of the reception-only device 51. Is approximated as the distance L between the sensor 50 and the obstacle.

Next, the details of the vehicle obstacle warning device of the present invention will be described with reference to the circuit block diagram of FIG. 1 and the circuit diagram of FIG. A part of the transmitted signal generating means 1 and the time measuring means 6 and the distance calculating means 7, the angle calculating means 8 and the obstacle position calculating means 9 described with reference to FIG. Consists of
Control processing such as transmission signal generation control, time / distance / angle / obstacle position calculation, generation / transmission of an obstacle position display signal, and ringing of an alarm buzzer is performed based on a program executed by the CPU 15. . The CPU 15 is composed of, for example, a general-purpose 8-bit type one-chip microcomputer, and a program for ultrasonic signal control and obstacle position calculation processing is recorded in an internal ROM.

As the ultrasonic wave transmitter 2 and receivers 3 and 4 shown in FIG. 2, in FIG. 1, a transmission / reception transmission / reception device 16 having a transmission / reception function and a reception-only reception dedicated device 17 are provided.
It is composed of two units and is placed at a predetermined position. In this embodiment, as shown in FIG. 16, the respective centers are arranged on the same plane with a center interval of 3 cm.

From the CPU 15, a rectangular pulse signal of, for example, 41.7 kHz is output as a transmission instruction signal every 25 ms.
During the period of 00 μs, the signal is applied to the transmission drive circuit 18 forming a part of the transmitted signal generating means 1, and the center frequency 4 is accordingly applied.
An ultrasonic signal of 1.7 kHz is transmitted from the transmission / reception device 16. The transmitted ultrasonic signal is reflected by an obstacle, if any, and is received by the transmission / reception device 16 and the reception-only device 17. Transmission / reception device 16 and reception-only device 1
The reception signals VA and VB received by 7 are amplified by the reception signal amplification circuit 19 which is amplification means,
It is sent to the comparison circuit 20 which constitutes a part of the time measuring means 6.

The comparison circuit 20 is constructed as shown in FIG. 3, and each of the reception signals VA and VB is the reception signal V.
Three comparators 21A and 2A, in which A is a waveform shaping means
Two threshold levels Vac, Va2 by 2A, 23A
The shaping signal VAC, which is compared with Va1 and binarized into a low level or a high level depending on the magnitude of each threshold level,
VA2, VA1 are generated, the received signal VB is compared with three threshold levels Vbc, Vb2, Vb1 by three comparators 21B, 22B, 23B, and similarly binarized shaping signals VBC, VB2, VB1 are generated, and the CPU is generated.
15 is input.

At this time, in the comparators 21A and 21B, the threshold levels Vac and Vbc generated by resistance division by the resistors R11 and R12 of the power supply Vcc are input from the positive side, and the reception signals VA and VB are input from the negative side. Further, in the comparators 22A and 22B, the threshold levels Va2 and Vb2 generated by resistance division by the resistors R31 and R32 of the power supply Vcc are input from the negative side, and the reception signals VA and VB are input from the positive side. In addition, the comparator 23
In A and 23B, the resistors R41 and R of the power source Vcc are connected from the positive side.
Threshold levels Va1 and V generated by resistance division by 42
b1 is input, and the reception signals VA and VB are input from the negative side.

In this example, the threshold levels Vac and Vb are
Although c, Va2 and Vb2, and Va1 and Vb1 are the same, they may be different from each other. Also,
Although the threshold levels are set to three in FIG. 3, the threshold levels may be set to three or more.

The position indicator 10, the alarm buzzer 11, and the obstacle 12 in FIG. 1 are the same as those in FIG.

The CPU 15 performs a series of ultrasonic wave transmission, wave reception, obstacle position calculation, signal transmission to a display, and buzzer alarm processing by the method described below. The contents of these processes are shown in the timing chart of FIG. 4 and the flowcharts of FIGS.

First, the main routine of the processing of the CPU 15 will be described with reference to FIGS. 4 and 5, the same processes are given the same reference numerals. First, initialization processing step S0 of internal registers and input / output terminals is performed at power-on or by user reset.
At 1, the timing control for waiting the transmission start timing is performed.

After a certain period of time has passed, ultrasonic wave signal transmission processing is performed in step S2, and then, in step S3, received signal sampling processing of the reception signal of the reflected wave from the obstacle, which will be described later, is performed. After the sampling process is completed, the distance value L and the angle value φ of the obstacle are calculated in step S4, and the data to be transmitted to the position indicator 10 in steps S5 and S6 is created, and the created data is also created. The transmission process is performed. Then, in step S7, according to the detection result of the obstacle, ringing control of the alarm buzzer 11 for alerting the driver to the presence and approach of the obstacle is performed, and a series of processes is ended, and the timing of step S1 is again set. Return to control. After the power is turned on, a series of wave transmission and detection processes from step S1 to step SS7
After the initialization processing by, it is repeated at regular intervals.

The time is measured by a timer counter, and the timer counter is set to a predetermined value, and when the set time elapses, a timer interrupt process as shown in the series of processes in FIG. 6 is performed. This timer interrupt processing is "disable interrupt" → "timer stop" → "save register value before interrupt" → "reset timer counter" → "clear timer interrupt request" → "restart timer" → It is performed in the order of "setting of sampling end flag"->"restoration of register before interrupt"->"interrupt occurrence permission"->"interruptend".

In this way, the interval of the wave transmission process, the sampling process duration, the buzzer sounding period, etc. are managed, and a series of processes from the wave transmission to the display output are performed at a constant interval.
In this embodiment, from the start of wave transmission in step S2 to step S3
The time until the end of the reception sampling of 4.2 ms is 4.2 ms, then the timer interrupt processing is performed 4 times every 5 ms, and the transmission is restarted after the waiting time of 0.8 ms. The detection process is being performed.

As shown in FIG. 1, the CPU 15 receives the following three shaping signals for each of the received signals VA and Vb from the comparison circuit 20 described above. The reception signals VA and VB are compared with threshold levels Vac and Vbc corresponding to the center voltage which is the center value of the waveforms of the reception signals VA and VB.
Shaped signals VAC, V whose waveforms are shaped so that
BC and the received signals VA and VB are set to threshold levels Vac and Vb.
Upper threshold levels Va1 and Vb1 which are values larger than c
Compared with, the shaped signals VA1 and VB1 and the received signals VA and VB whose waveforms are shaped to have a high level (1 notation) when they are large and a low level (0 notation) when they are small, and threshold levels Vac and Vbc. Compared to the lower threshold levels Va2 and Vb2, which are smaller values, a low level (0 notation) when larger, a high level (1 notation) when smaller
Shaped signals VA2 and VB2 whose waveforms are shaped so that

The received wave sampling method described above will be described. The above-mentioned shaped signal is binarized at high level and low level from the input terminal of the CPU 15 at regular intervals and stored in the internal memory. The sampled data is recorded in a predetermined memory location in time series,
The time corresponding to the sampled data can be converted from the address value of the memory. For example,
When the data address at the start of sampling is A0 and the data of the next sampling data is recorded as A1 ..., The time of the data stored at the address An (n: 0, 1, 2 ...) It can be calculated by the start time + (n × sampling interval).

The vibration center frequency of the ultrasonic signal is 41.7 kHz as described above, and the sampling interval is 4.8 μs.
There is. In the case of the frequency of the ultrasonic signal and the sampling interval, three points of sampling data are obtained per half cycle (12 μs). FIG. 8 shows a reception signal from the transmission / reception device 16 (hereinafter referred to as a sensor P), waveforms of each shaping signal VA1, VA2, VAC, a shaping signal according to the conventional method, and a sampling time. FIG. A device 17 (hereinafter referred to as a sensor Q) is also shown in the same manner. FIG. 11 shows a comparison example of the present invention and the conventional sampling results of the sensors P and Q. The upper three columns are values relating to the sensor P, the middle three columns are values relating to the sensor Q, and the lower two columns are conventional. The value by each sensor is shown.

In this way, the sampling data obtained is examined in time series to determine the reception time of the reflected wave from the obstacle. The procedure will be described with reference to the flowchart of FIG. First, in step S11, the reception time of the reflected wave, that is, the rising time is initialized to the out-of-range value, and the step S11
The data address value for retrieving data in 12 is initialized to the sampling start address, the sampled data is sequentially examined for one sensor P from the oldest one, and the time when the shaping signal VA2 becomes 1 is detected first. To do. If the sampled data ends without being detected, the rising time remains the out-of-range value. That is, it is checked whether or not the data to be searched in step S13 has ended. If the data has ended, the process moves to step X described later, and the rising time remains the out-of-range value. If the data has not ended, the process goes to step S14 to check whether or not the data of the shaping signal VA2 is 1, and if the data of the shaping signal VA2 is not 1,
The process proceeds to step S16, the data address is updated to check the next data, and the process proceeds to step S13.

If the shaping signal VA2 is 1 in step S14, the process proceeds to step S15. In step S15, the sampling time when the shaping signal VA2 is 1 is T
As 1 is checked whether or not the shaping data VA1 and VA2 have the following patterns with the sampling data for one time before and five times after the time T1.

Sampling time: T0 T1 T2 T3 T4 T5 T6 Shaped signal VA1: · 0 0 0 0 1 1 1 0 Shaped signal VA2: 0 1 1 · 0 0 · (・ is 0 or 1) This pattern is obtained by shaped signal VA2 It is obtained when the upper amplitude appears after the lower amplitude that has fallen below the threshold level, and when it matches the above pattern, the time T4 is regarded as the rising amplitude of the waveform of the received signal. In the example shown in FIG. 11, the rising amplitude corresponds to the above pattern at time t5. (See FIG. 13A) If the pattern does not correspond to the above pattern, the process proceeds to step S16, the data address is updated, and the pattern matching is performed with the time when the shaping signal VA2 becomes 1 as T1.

On the other hand, in the case of the above pattern, the shaping signal VAC is used to obtain the time (zero cross position) at which the rising amplitude rises from the center voltage of the received signal.
Find out. That is, the process proceeds to step S17, and it is checked whether or not the shaping signal VAC is 1. Shaped signal VAC is 1
If it is, the process proceeds to step S18, the data address time is added to the rising time, the data address for searching the data is set to the previous value in step S19 to check the previous data, and the step S17 is performed. The shaped signal VAC is examined, and step S17 → step S18 → step S19 → step S17 is repeated until the value becomes a value other than 1 and moves to step X. Thus, the rising time at which the data of the waveform pulse of the shaping signal VAC to which the rising amplitude at the previous time of the rising amplitude t5 belongs changes from the 0 to 1 is the reception time of the reflected wave. In the example shown in FIG. 11, the shaped signal V at time t4
Since AC has changed from 0 to 1, the reception time of the reflected wave received by the sensor P is determined as t4. (See FIG. 13B) Similarly, for the sensor Q, the rising amplitude and the reception time of the reflected wave are determined by the procedure described in FIG. 7. In the example of FIG. 11, the time of the rising amplitude for the sensor Q is t11.
Then, the reception time of the reflected wave also becomes t11. In FIG. 7, the rising waveform of the received signal is detected in steps S13 to S16, and the reception time of the received signal is detected in steps S17 to S19.

In the above example, the data sampling interval is set to 4.8 μs, but the data sampling interval is not limited to this value as long as the process of vibration can be obtained by a plurality of thresholds within the vibration period of the ultrasonic signal. The detection pattern can also be changed according to the sampling interval and the set value.

In step X of FIG. 7, the rising time stores the out-of-range value or the detected rising time, that is, the data address value corresponding to the reception time, and the reception time of the reflected wave received by the sensors P and Q. Is required.

When the reception time of the reflected waves received by the sensors P and Q, that is, the rising time is obtained in this manner, the reflection time (ta, tb) from the start of transmission to the reception of the reflected waves is calculated by the above method. Then, the distance value L is calculated, and the angle φ between the normal line of the sensor including the sensor P and the sensor Q and the obstacle is calculated.

In this embodiment, the sensor P and the sensor Q are arranged on the same plane with a distance of 3 cm, and the distance is the distance between the sensor and the obstacle (tens of cm to m order).
Sufficiently short, and the distance difference (mm order) due to the difference in the reception time of the sensor P and the sensor Q (μs order)
Is short enough for the distance between the sensor center and the obstacle,
The distance between the sensor Q and the obstacle is approximated to the distance L.
Therefore, the distance value is calculated from the reflection time tb of the sensor Q.

Here, the sampling start time is t0, and the elapsed time from the start of ultrasonic wave transmission to time t0 is T.
If it is off, the reflection time tb from the start of transmission of the ultrasonic signal to the reception time t11 of the sensor Q is obtained by tb = Toff + (Ts × 11) (Ts: sampling interval, 4.8 μs), and the distance is as described above. The value can be calculated. The difference (ΔT) between the rising times of the sensors P and Q is ΔT = t11−t4 = 7Ts = 33.6 μs in this example. When calculated by the method shown in FIG. 18 from this time difference, the angle of the obstacle is about 22 degrees on the sensor P side.

At this time, in order to reduce the calculation processing time,
The distance value and the angle value are calculated in advance by the above formulas and are recorded in the ROM as a table, and the value is obtained by searching the corresponding distance value and angle value from the obtained reception time value and time difference. You may use the method of calculating. Further, when the waveform does not continue for a certain period of time or more after the reflected wave reception time detected by the above method, it may be regarded as a reflected wave and a process of removing external noise may be performed.

Next, the processing when the amplitude of the waveform of the received signal of the sensor P fluctuates to become as shown in FIG. 10 will be described. FIG. 10 shows an example in which the amplitude on the sensor P side is smaller than that shown in FIG. 8 and the amplitude waveform from time t0 to t1 does not exceed the threshold level Va1.
The sensor Q side does not change.

The result of sampling the waveform is shown in FIG. Similar to FIG. 11, FIG. 12 shows a comparative example of the present invention of the sampling results of the sensors P and Q, and the upper three columns are values relating to the sensor P, the middle three columns are values relating to the sensor Q, The lower two columns show the values obtained by each conventional sensor. The same time t5 is obtained when the rising amplitude is obtained for the sensor P by the same method as described above, and the time t4 is obtained when the rising time of the reception signal of the reflected wave is obtained from the shaping signal VAC, and even if the amplitude fluctuation of the reception waveform occurs. The detection result of the rising time does not change.

A method using a one-shot multivibrator or a comparator output signal with one threshold value as in the conventional example is shown in the lower part of each of FIGS. 8, 9, 10, 11, and 12 for comparison. is there. In these methods, a shaping signal that becomes a high level when the threshold values Va1 and Vb1 are exceeded is generated, and the rising time of this shaping signal is used as the reception time of the reflected wave of each sensor P, Q.

FIG. 14 shows a comparison of the measurement results of the reception time of the reflected wave between the conventional method and the method of the present invention for the reflected signals shown in FIGS. 8, 9 and 10. In the reception result (waveform example 1) when the reception waveforms shown in FIGS. 8 and 9 are normal, the rising time of the sensor P is t1 in the conventional example.
Therefore, in the reception result (waveform example 2) shown in FIGS. 10 and 9 which is an example when the amplitude of the waveform of the received signal fluctuates, in the conventional example, the rising time of the sensor P is t5. As a result, the angle value calculated from the time difference between the rising times changes from 33 degrees to 15 degrees due to the amplitude fluctuation of the waveform of the received signal.

As described above, in the conventional technique, the reception time of the reflected wave fluctuates due to the amplitude fluctuation of the reception waveform, and as a result, the angle value calculated from the difference between the reception times of the sensors P and Q fluctuates. According to the invention, the fluctuation can be eliminated as described above.

In this embodiment, a general-purpose 8-bit one-chip CPU is used for calculating distances and angles, a position indicator, and alarm processing control. However, a 16-bit one-chip CPU is used.
It is also possible to speed up the process by using a dedicated DSP (digital signal processor). In addition, although the configuration is such that two receivers for receiving ultrasonic signals are used, one additional dedicated wave receiving device is added to form a three-sensor configuration to calculate a three-dimensional position from three reception time values. Is also possible. The receivers are not necessarily arranged on the same plane, but may be arranged along the curved shape of the vehicle body.

[0053]

As described above, according to the invention of claim 1,
One or more transmitters mounted on the vehicle for transmitting ultrasonic signals, two or more receivers mounted on the vehicle for receiving reflected waves from obstacles of the transmitted ultrasonic signals, and receiving by the receivers Based on the amplification means for amplifying the generated ultrasonic signal and the reception signal amplified by the amplification means, each receiver receives the reflected wave from the obstacle from the transmission start time of the ultrasonic wave from the transmitter. Time measuring means for measuring the elapsed time until being measured, distance calculating means for calculating the distance to an obstacle based on the time measured by the time measuring means, and each receiver measured by the time measuring means The angle calculation means calculates the difference between the measurement times for each of them, and the angle calculation means for calculating the angle with the obstacle, and the position of the obstacle is measured from the value calculated by the distance calculation means and the angle calculation means, and the existence of the obstacle. And alert driver to approach In the vehicle obstacle alarm device, the time measuring means is a waveform shaping circuit that outputs a shaping signal to each signal after amplification by the amplifying means of the signal received by each receiver and comparing the signal with a predetermined threshold level. A plurality of means, the threshold levels of the plurality of waveform shaping means are different from each other, and the plurality of waveform shaping means
The binarized sampling of the obtained plurality of shaped signals is performed.
Obtained by sampling at each fixed time interval
Specific pattern from the data sequence corresponding to each shaped signal
Is detected as the rising amplitude of the reflected wave only when
Waveform pulse of the shaping signal to which the rising amplitude belongs
The measurement time of the rising data of is set as the reception time of the reflected wave.
To constant, it will be able to accurately determine the reception time of the reflected wave without being affected by the amplitude fluctuation of the reflected wave,
It is possible to obtain an obstacle warning device for a vehicle with improved position measurement accuracy.

[0054] Further, the invention of claim 2, wherein the waveform shaping means in the invention according to the first, the center value of the received signal waveform threshold level of one of the waveform shaping means by the receiver and to order, claim The same effect as 1 can be obtained.

The third aspect of the present invention is the method of the first and second aspects, wherein the waveform shaping means has a threshold level that is larger than a central value of a signal waveform received by each receiver and smaller than the central value. As a result, the same effect as that of claim 1 is obtained.

[0056]

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an obstacle warning device for a vehicle according to the present invention.

FIG. 2 is a configuration diagram showing a system configuration of an obstacle warning device for a vehicle of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a comparison circuit of the vehicle obstacle warning device of the present invention.

FIG. 4 is a timing chart showing the processing of the CPU of the vehicle obstacle warning device of the present invention.

FIG. 5 is a flowchart showing the main processing of the CPU of the vehicle obstacle warning device of the present invention.

FIG. 6 is a flowchart showing a timer interrupt process of the CPU of the vehicle obstacle warning device of the present invention.

FIG. 7 is a flowchart showing a reception time detection process of the CPU of the vehicle obstacle warning device of the present invention.

FIG. 8 is a waveform diagram showing the waveform of each signal in the sensor P.

9 is a waveform diagram showing the waveform of each signal in the sensor Q. FIG.

FIG. 10 is a waveform diagram showing the waveform of each signal when the amplitude of the received signal varies.

FIG. 11 is a state diagram showing a state in which a received signal is binary-sampled.

FIG. 12 is a state diagram showing a binary-sampled state of the received signal when the amplitude of the received signal varies.

13A is a relationship diagram showing a relationship between a shaping signal VA1, a sampling value and a sampling time, and FIG. 13B is a relationship diagram showing a relationship between a shaping signal VAC, a sampling value and a sampling time.

FIG. 14 is a relationship diagram showing the difference between the angle calculation results of the present invention and the conventional example in the case where the amplitude fluctuation of the received signal occurs and the case where it does not.

FIG. 15 is a waveform diagram showing a received waveform of a reflected wave from an obstacle.

16A and 16B are waveform diagrams showing a received waveform of an ultrasonic wave and a shaped waveform thereof, where FIG. 16A is a waveform diagram at a normal time and FIG. 16B is a waveform diagram at a time of amplitude fluctuation.

FIG. 17 is a waveform diagram showing a received waveform that has undergone full-wave rectification and its shaped waveform. FIG. 17A is a waveform diagram during normal operation, and FIG.
[Fig. 3] is a waveform diagram when the amplitude changes.

FIG. 18 is a plan view showing a positional relationship between a sensor and a reflected wave from an obstacle, where (a) shows the obstacle to the right of the sensor normal and (b) shows the obstacle with the sensor normal. FIG. 4 is a plan view in the left direction of FIG.

[Explanation of symbols]

10 Position indicator 11 Alarm buzzer 12 obstacles 15 CPU 16 Dual-purpose device 17 Receiver only 18 Transmission drive circuit 19 Received signal amplification circuit 20 Comparison circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-92265 (JP, A) JP-A-53-135369 (JP, A) JP-A-9-184883 (JP, A) JP-A-57- 207882 (JP, A) JP-A-57-122372 (JP, A) JP-A-4-291124 (JP, A) Actual development 1-135378 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S 1/72-1/82 G01S 3/80-3/86 G01S 5/18-5/30 G01S 7/52-7/64 G01S 15/00-15/96 G01R 29/02 G01F 23/28 H03K 5/153

Claims (3)

(57) [Claims] 1. One or more transmitters mounted on a vehicle for transmitting ultrasonic signals, and two or more receivers mounted on the vehicle for receiving reflected waves from obstacles of the transmitted ultrasonic signals. Based on the amplification means for amplifying the ultrasonic signal received by the receiver and the reception signal amplified by the amplification means, from the transmission start time of the ultrasonic wave from the transmitter, from the obstacle at each receiver Time measuring means for measuring the elapsed time until the reflected wave is received, distance calculating means for calculating the distance to an obstacle based on the time measured by the time measuring means, and measurement by the time measuring means The difference between the measured time for each receiver is calculated, and the angle calculation means for calculating the angle with the obstacle, and the position of the obstacle is measured from the value calculated by the distance calculation means and the angle calculation means. , Against the presence and approach of obstacles In the vehicle obstacle warning device for warning a transfer person, the time measuring means compares each signal after amplification by the amplifying means of the signal received by each receiver with a predetermined threshold level and adjusts the shaping signal. It includes a plurality of waveform shaping means for outputting, to the threshold level of the plurality of waveform shaping means to be different each of the plurality of waveforms
Binarization sun of the plurality of shaped signals obtained from the shaping means
Sampling is performed at regular intervals.
From the data sequence corresponding to each shaped signal obtained by
Only when a specific pattern is detected, the reflected wave rises
Shaped signal to which the rising amplitude belongs
Waveform pulse rise time measurement time of the reflected wave
An obstacle warning device for a vehicle, characterized in that it is determined as a reception time . Wherein said waveform shaping means includes a central value of the received signal waveform threshold level of one of the waveform shaping means according to each receiver
To Rukoto vehicle obstacle alarm system according to claim 1, wherein. Wherein said waveform shaping means is greater than the center value of the received signal waveform due to the receiver as a threshold level and any one of claims 1 or 2, characterized by using a smaller value than the center value The obstacle warning device for vehicles according to .