JPH01187485A - Ultrasonic distance measuring method - Google Patents

Abstract

PURPOSE:To decide a short distance and a long distance effectively within the same range by outputting ultrasonic waves of different frequencies in the same direction at the same time, measuring the amplitude differences of their reflected waves, and calculating a measured distance from whether the level is large or small. CONSTITUTION:Exciting circuits 21, 22...2n are excited by a timing output circuit 100 to output signals of different frequencies F1, F2...Fn. Further, an ultrasonic wave sending means 1 outputs the ultrasonic waves of different frequencies in the same direction successively by being excited by the circuits 21, 22...2n. A changeover switch 1A is provided between this means 1 and circuits 21, 22...2n. A receiving means 3 which receives the reflected waves of the ultrasonic waves outputted by the means 1 is arranged nearby the means 1. This means 3 is provided successively with receiving circuits 41, 42...4n which convert the respective ultrasonic waves received by the means 3 into level signals corresponding to reception levels by the frequencies and a distance arithmetic part 6 which finds the level differences according to the outputs of the circuits 41, 42...4n to calculate the measured distance. The outputs of the circuits 41, 42...4n are supplied to an amplitude difference detector 5 to find the level difference of the respective signals, which are sent to an arithmetic part 6.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ultrasonic distance measuring method.

[Conventional technology]

Conventionally, ultrasonic waves have been relatively often used to measure distances underwater and in the air. Particularly underwater, ultrasonic waves are indispensable for acoustic sounders, sonar devices, and underwater communication equipment. When measuring distance using ultrasonic waves in these acoustic devices, it is common to calculate an approximate distance by multiplying the elapsed time from transmission to reception by the speed of sound in water.

FIG. 5 shows the time interval of the ultrasonic transmission output (pulse wave). As shown in this figure, normally the next transmission is performed after waiting for the time elapsed from the transmission until the maximum range of reflected sound is received. In FIG. 5, A indicates reflected sound.

[Problem to be solved by the invention]

However, in the conventional example described above, several inconveniences occur when setting the maximum range. For example, when trying to obtain a large amount of measurement information at short or medium distances that are 1/4 of the maximum range, the ultrasonic output repetition time should be set to output ultrasound at a transmission interval that is approximately 1/4 of the maximum range L. Must.

As a result, as shown in Fig. 6, there is the inconvenience that it is unclear whether the reflected sound A, , A, obtained during measurement is the reflected sound of the transmitted ultrasonic waves ■, ■, ■, or ■. be.

For this reason, in the conventional method described above, it is necessary to set the interval between transmitting waves according to the maximum range to be received, and if the target is also a long distance, the interval between transmitting waves becomes longer and it becomes necessary to The drawback was that the number of times the reflected sound was received from a target at a distance was reduced, resulting in poor measurement accuracy.

[Purpose of the invention]

The purpose of the present invention is to improve the disadvantages of the conventional example and, in particular, to effectively measure short and long distances in the same range regardless of the time interval of repeated output of ultrasonic pulses. The object of the present invention is to provide an ultrasonic distance measuring method that can perform ultrasonic distance measurement.

[Means to solve the problem]

The present invention employs a configuration in which ultrasonic waves of different frequencies are simultaneously output in the same direction, the amplitude difference of the reflected waves is measured, and the measured distance is calculated based on the magnitude of the level. This aims to achieve the above-mentioned purpose.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the embodiment of FIG. 1, the timing output circuit 100 is energized to output different frequencies F I + F 2+ F 3+ .
・A plurality of excitation circuits 2I each outputting a signal of FA,
2□, 23°..., 2. l, and each of these excitation circuits 2I,
2°, 23. ..., 2. The ultrasonic transmitting means 1 is energized by the ultrasonic wave transmitter 1 and sequentially outputs ultrasonic waves having at least different frequencies in the same direction. Ultrasonic wave transmitting means 1 and excitation circuit 2
A changeover switch IA is provided between 0, 2□, 23°, . . . , 27.

In the vicinity of the ultrasonic wave transmitting means 1, a wave receiving means 3 for receiving reflected waves of the ultrasonic waves outputted from the ultrasonic wave transmitting means 1 is arranged. This delivery means 3 includes a receiving circuit 4 which converts each reflected ultrasonic wave received by the wave receiving means 3 into a level signal corresponding to the reception level for each frequency. ．． 4□, 4
3. ..., 4ゎ, and each receiving circuit 41+4214
A distance calculating section 6 is provided which calculates the measured distance by determining the level difference based on the output of 3+...l4fi.

Receiving circuits 4I, 4□, 43. . . , 4 are the aforementioned excitation circuits 23, 2□, 28. ..., equipped corresponding to 2A, each frequency F l + F 21 F
31, . . . , a filter circuit section and an amplification circuit section that individually pass the signals of F7 and amplify them with a constant amplification factor. This receiving circuit 41+
4g+ 431..., 41, the level difference of each signal is determined by the amplitude difference detector 5. The output of this amplitude difference detector 5 is sent to a distance calculation section 6.

FIG. 2 shows an example of propagation loss at frequencies F, . . . F2, and FIG. 3 shows the relationship between the change in the level difference of the reflected reception wave of the signal and the propagation distance at each frequency. As shown in Figure 3, the difference in propagation loss due to ultrasonic waves of different frequencies roughly follows the difference in absorption loss (a function proportional to distance), so the received signal is reflected from near and medium distances. is long distance (
By determining whether the sound is a reflected sound from the first convergence zone or the second convergence zone, it is possible to perform distance measurement by sufficiently covering a long distance at the transmission interval for short and medium-range objects. In the distance calculating section 6, for example, F is sent from the amplitude difference detector 5.
, , F2, the calculation shown in FIG. 3 is performed to calculate the propagation distance of the reflected ultrasound. The calculation performed by the distance calculation section 6 is displayed on the display section 7.
It is now displayed as =4-.

FIG. 4 shows another embodiment. The embodiment shown in FIG.
It has one wave transmitting means 10.11 and two wave receiving means 20.21. The wave transmitting means 10 and the wave receiving means 2° both have the function of transmitting or receiving ultrasonic waves of frequency F1. On the other hand, both the transmitting wave means 11 and the wave receiving means 21 have the function of transmitting or receiving ultrasonic waves of frequency F2.

Each of the wave transmitting means 10.11 is equipped with an excitation circuit 13.14 which outputs excitation signals of different frequencies.

These excitation circuits 13 and 14 operate at the same timing and have different frequencies Fl and F2 (however, Fl<Fz
) is designed to output an excitation signal of the same level.

On the other hand, each of the wave receiving means 20.21 includes the receiving circuit 4.2 shown in FIG. ．． 4□, 43. ...4. Receiving circuits 22 and 23 that function in the same manner as the above, and an amplitude difference detector 25 and a distance calculation section 26 that also function in the same manner are each equipped as shown in FIG. The calculation results are displayed on the display section 27.

The embodiment shown in FIG. 4 has the advantage that signal processing can be carried out quickly because reflected received waves can be detected simultaneously.

Note that the above embodiment can be used not only for distance measurement in the air, but also for distance measurement in the air.
It can also be applied to underwater active sonar, etc.

〔Effect of the invention〕

Since the present invention is configured and functions as described above, it is possible to effectively measure short and long distances in the same range regardless of the measurement range, and there is no need to switch measurement ranges, and multiple measurement ranges can be measured effectively. By transmitting and receiving ultrasonic waves with different frequencies at a predetermined timing, it is easy to capture reflected waves, and in this respect, it provides an excellent ultrasonic distance measurement method that is unprecedented in that it can reduce measurement errors. can do.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the propagation loss of ultrasonic waves in water, and Fig. 3 is a diagram showing the propagation loss of ultrasonic waves with different frequencies in water. FIG. 4 is a block diagram showing another embodiment, and FIGS. 5 and 6 are explanatory diagrams showing the state of distance measurement in the conventional example. 1.10.11... Ultrasonic wave transmitting means, 21-2
A, 13゜14... Excitation circuit, 3, 20.21
・・・・・・Wave receiving means, 4° to 4 degrees, 20.21...
...Receiving circuit, 5,25...Excitation width difference detector,
6, 26... Distance calculation section.

Claims (1)

[Claims] (1) An ultrasonic distance measuring method characterized by emitting ultrasonic waves of different frequencies in the same direction at the same time, measuring the amplitude difference of the reflected waves, and calculating the measured distance based on the magnitude of the level.