JPS6195267A - Ultrasonic object confirmation apparatus - Google Patents

Abstract

PURPOSE:To enhance the confirmation accuracy of an obstacle by reducing the effect of the multiple reflection of an ultrasonic wave, by setting two or more kinds of exciting powers of an ultrasonic oscillation element to cyclically changeover the same and providing a definite exciting stop period. CONSTITUTION:In an apparatus wherein the ultrasonic reflected wave from an object is detected and the distance to the object is measured from the detection time thereof, two or more kinds of exciting powers 30a, 30b different in magnitude are set and said exciting powers are cyclically changed over to be applied to ultrasonic oscillation elements. Then, an exciting stop period 30c is provided between the exciting pulses of these oscillation elements. By this method, the correspondence to objects at short and long distances can be performed by the magnitude of exciting powers and, because the stop period 30c is provided, a multiple reflected wave 32c is not detected even if generated and the adverse effect of multiple reflection can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an object recognition device using ultrasonic waves, and particularly to a device for reducing measurement errors due to multiple reflections.

[Background of the invention]

Conventionally, some devices of this kind split a part of the reflected ultrasound wave, perform processing such as delay and attenuation, and then perform processing such as addition or subtraction with the other signal to obtain the necessary signals. There is a method that extracts only the signal (Japanese Patent Laid-Open No. 58-20699)
0 Public IP) = In an environment where multiple reflections are likely to occur, ImQ may be high, such as making it difficult to adjust the delay time.

[Purpose of the invention]

An object of the present invention is to provide an ultrasonic distance measurement system that can reduce the negative effects of multiple reflections on object recognition accuracy even in environments where multiple reflections from objects are relatively likely to occur in object recognition using ultrasonic waves. The goal is to provide equipment.

[Summary of the invention]

In order to achieve the above object, the present invention periodically controls the excitation power of an ultrasonic heating element, and divides object recognition into two types: short-range and long-range, and performs long-range measurement and measurement. A certain pause period is provided between the measurement and the short-distance measurement to reduce the negative effects of multiple reflections. ′ [Embodiments of the invention]・.

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an antenna including an ultrasonic 1 oscillation element, 2 is a rotary joint and a motor for driving the antenna, 5 is a rotation detector for measuring the rotation angle of the antenna, and 4 is an ultrasonic probe for excitation. The part (A) surrounded by a broken line in Oq, which is the transmitter and reception signal processing circuit (hereinafter abbreviated as transmission and reception processing circuit), is the anti-transmission circuit.
・A circuit that measures the distance from station 1 to an obstacle.
□ Mainly reference signal generator 5. Pulse counter6. It consists of a D' type flip-flop (D-FF) 7 and a latch 8. Also, the part (B) surrounded by the broken line is a circuit that measures the rotation angle of the antenna 1, and mainly consists of the rotation detector 6. The aforementioned D type furi.

011 is a switching circuit for the transmission/reception processing circuit 4, which is composed of a block flop 7, a pulse counter 9, and a latch 10.
Controls the excitation power to the ultrasonic oscillator and switches the transmission/reception processing circuit. Reference numeral 12 indicates a central processing unit, and 13 indicates a storage unit, which controls the excitation of the ultrasonic excavator, and calculates and corrects the position of an obstacle from distance data and angle data.

In distance measurement, the ultrasonic probe is excited for about 1 ms and at the same time the D-FF 7 and pulse counter 6 are reset. At this time, the Q output of r)-FF7 becomes LOW and the launch is canceled.

In addition, when the ultrasonic oscillator is excited, the switching circuit 11 switches the transmitting/receiving geographic circuit 4 to one on the transmitting side, and then switches the receiving circuit to one on the transmitting side.
0 and waits for the reflected wave to return. Here, r, and logarithm return to 0. If the logarithm returns to Song, the signal amplified and shaped by the transmitting/receiving processing circuit 4 enters CLK of D-F''F7. Q output is set to HIGH 0 At this time, latches 8 and 10 hold the values of pulse counters 6 and 97. That is, latch 8 holds the distance data, latch 10 holds the ridge angle data, and the latch terminal is LOW'. (until the next ultrasonic excitation pulse is emitted).Then, the central processing unit @12 reads each data, excites the ultrasonic oscillator again, and repeats the same operation.

Figure 2 shows the antenna 1 and the obstacle 15. In the diagram showing the relationship with '16, it is assumed that the antenna 1' recognizes obstacles while rotating counterclockwise. 'In the figure, 1-5& schematically shows the propagation path of the ultrasonic wave toward the obstacle 15:
It's a good thing. 16g towards □ is 16g against 16 obstacles.
b~i6d are 17 against the obstacle 16 and the wall 17.
A to '17c show propagation paths to the wall 17.

FIG. 3 is a time chart showing excitation pulses of the ultrasonic oscillator and reflected waves from obstacles.

20-22 are the excitation pulses of the ultrasonic oscillator, 23-2
6 indicates a reflected wave from an obstacle, and the distance measurement from antenna 1 to the obstacle is measured from the end of excitation of the ultrasonic oscillator until the first return of the anti-sealing liquid. Time TI
- Calculate each from time T4.

Further, the direction of the antenna 1 can be determined by reading the rotation detector 3 when the reflected wave returns.

Next, we will briefly explain the negative effects when multiple reflections occur in object recognition as described above.

In FIG. 2, suppose that the antenna 1 is facing toward the obstacle 1 and 6. When the antenna 1 is facing the obstacle 1 and 6, the excitation of the ultrasonic oscillator shows a time island at 20 in FIG. route to 16af
This can be seen by the reflected wave 28. Furthermore, if the nantenna 1 is stationary, the path of the ultrasonic wave passes through 16a in the next cycle as well.

Therefore, the reflected wave from the obstacle 16 corresponding to the excitation pulse 21 is shown at 214, and the time (Tl and T2) until the antistatic sealing liquid returns shown at 23.24 is the same time, and the obstacle is correctly measured. be done.

However, since the antenna 1 is rotating counterclockwise, at the time when the ultrasonic oscillator is excited, the path of the ultrasonic wave passes through 16b and 16c, and the path of the ultrasonic wave passes through the wall 17.
It may be reflected at the corner of , and come back through the path 16d. In this way, when the reflected wave returns through the path 16b=16d, it becomes longer than the path 16a, so
As shown in the reflected wave 27 shown in FIG. 3, a time period of Ts has elapsed since the excitation pulse 21. However, since distance measurement is repeatedly performed at a certain period, the reflected wave 27 enters into the next repetition period as shown in the figure.

As a result, the measured distance data becomes the time indicated by T4, which is different from the values measured at T1 to T3, and the obstacle is recognized at a wrong position.

4 and 5 are detailed explanatory diagrams of the present invention. Fourth
The excitation pulse waveform shown at 50 in the figure represents the excitation power applied to the ultrasonic oscillator in terms of amplitude, and the horizontal axis represents time.

Waveforms 51 to 34 are reflected waves of ultrasonic waves, and the intensity of the reflected waves is represented by amplitude, and the horizontal axis represents time. Reference numeral 35 indicates a reference value of the comparator of the transmission/reception processing circuit 4, and anything that exceeds this level is treated as an effective reflected wave.

FIG. 5 is a flowchart for explaining the present invention in detail, which will be explained hereinafter with reference to FIGS. 1 to 4. In FIG. Detect reference points. When the reference point is detected, first, the excitation power applied to the ultrasonic oscillator oscillates for short distance (waveform 60a). Now, in FIG. 2, if the antenna 1 is facing toward the obstacle 15, the reflected wave 51a will return after a certain period of time. At this time, multiple reflections shown at 31b and 31c may return, but there is no problem in 31b because the repetition period of the excitation pulse is within the same period. Further, although 31c is in the next repetition period, the ultrasonic output is small because the excitation power is used for short distances, and the level of the reflected wave does not exceed the reference value of the comparator and has no adverse effect. Therefore, in (e) to (g) of the flowchart, the distance data indicated by T6 and the angle data at that time are stored in MEMOI.

Next, when ultrasonic waves for long and short distances (waveform 60b) are oscillated, the reflected wave from the obstacle 15 is 32a%! There may be multiple reflections like +20. At this time, the recognized distance data corresponds to T7. In the flowchart (in Figures ~ (branch)),
Because it targets long-distance data ~t FJvo
Nothing is stored in u. Next, if we provide an excitation pause period for the ultrasonic oscillator as shown in 5[]c, the distance and angle data will not be read during this period, so there will be no misidentification of multiple reflections as shown in 32c. 1. Now, if excitation and data reading were performed during this period, the factor of multiple reflections in the next repetition period would increase, and the erroneous reflected wave shown at 32c' would be recognized, and the distance corresponding to T8 would be increased. There is a risk that data will be imported.

Next, assuming that the antenna 1 is facing the obstacle 16,
In the flowchart (/2~(g)), the excitation power of the ultrasonic oscillator is small, so the reflected wave is indicated by 53a and is not recognized.In the flowchart (~(, F), the excitation power is large and the reflected wave is returns as shown at 54a and corresponds to the distance data I/iT+o. This data is (
Stored in IVI E M OH in power.

As described above, the short-distance obstacle 15 is recognized in cycle flowcharts 09 to (g) with small excitation power, and the MEM
Stored in OI.

A long-distance obstacle 16 is recognized by periodic flowcharts (a) to (tactile) with large excitation power and stored in the MFEMOI.In addition, the adverse effects due to multiple reflections that tend to occur when excitation power is large are recognized as shown in flowchart (a). rj) to) and distance 1. This can be reduced by pausing the acquisition of angle data.・Therefore, the obstacle is M
By performing calculations from the data of EMOI and MEM OII, recognition is possible without the influence of multiple reflections.

〔Effect of the invention〕

From the above, according to the present invention, the short-distance excitation power of the ultrasonic oscillator is used to recognize short-distance obstacles, and the long-distance excitation power is used to recognize long-distance obstacles. , long-distance excitation 1. By providing a certain rest period after force oscillation, the adverse effects of multiple reflections of ultrasonic waves can be reduced, and the accuracy of recognizing obstacles can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram of an embodiment of the present invention, Fig. 2 is a diagram of the relationship between the antenna and an obstacle, and Figs. 3 and 4 are timing diagrams showing the excitation pulse of the ultrasonic oscillator and the reflected wave from the obstacle. chart,
FIG. 5 is an explanatory flowchart of the present invention. 1... Antenna 4... Transmission and reception processing circuit 6
．． 9...Counter 8, 10...Latch 11...
・Switching circuit 12...Central processing unit 15, 16
... Obstacle 50 ... Excitation pulse breeding 1 Fig. 1゜ 2nd concave M 3 4th Fig. 5 Fig.

Claims (1)

[Claims] 1. In an object recognition device that measures a distance to an object by emitting ultrasonic waves and measuring the time until a reflected wave from the object returns, at least a first Exciting the ultrasonic oscillator periodically with two or more types of excitation power as described in 2.
and an object recognition device using ultrasonic waves having a first excitation rest period and a second excitation rest period for a certain period of time. 2. An object recognition period in which the first excitation power of the ultrasonic oscillator is for short distance use, an object recognition period in which the second excitation power of the ultrasonic oscillator is used for long distance use, and an excitation rest period of a certain period. An ultrasonic object recognition device according to claim 1, comprising: