JPH0436351B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ultrasonic azimuth sensor that detects azimuth using ultrasonic waves.

[Background technology]

Generally, this type of ultrasonic azimuth sensor uses a plurality of transducers to convert ultrasonic waves into electrical signals, detects the phase difference between these signals, and detects the propagated azimuth.

4 to 7 are diagrams showing a conventional example, in which an upper surface 6 which is a detection surface of two vibrators 1a and 1b having sensor bodies 8a and 8b having a cylindrical shape is shown.
a, 6b are arranged in the same plane, one of the two output terminals 7a, 7b protruding from the lower part of the sensor bodies 8a, 8b is grounded, and a cable is connected to the other amplifier 2a, 2b, respectively. It is connected at 5. Therefore, the upper surface 6a of the vibrator 1a, 1b,
The ultrasonic waves incident on 6b are converted into electrical signals by transducers 1a and 1b, respectively, and the respective electrical signals are amplified by amplifiers 2a and 2b. Here, the outputs of the amplifiers 2a and 2b are V ₀₁ and V ₀₂ , and when ultrasonic waves are incident from the front direction as shown by the solid arrow in FIG. 4, the outputs of the amplifiers 2a and 2b are V ₀₁ and V ₀₂ . As shown in FIG. 5, the waveforms have the same phase. Next, from the direction tilted by α degrees from the front direction, the fourth
When an ultrasonic wave is incident as indicated by a broken line arrow in the figure, the output V ₀₂ lags behind the output V ₀₁ in phase as shown in FIG. 6, and a phase difference φα occurs. Here, as shown in the top view _of FIG.
b are in contact. ), and the difference in the distance traveled by the ultrasonic waves is Δl, then the azimuth α is simα≈Δl/l ₀ . However, the phase difference φα can only be detected within the range of ±π (for example, a phase advanced by 2/3π and a phase delayed by π/3 cannot be distinguished), so if the wavelength of the ultrasound is λ, then Δl<|λ /2｜ must satisfy the following conditions.

Therefore, the maximum detectable azimuth αmax′ is sin(αmax′)≒|λ/2l ₀ |. That is, when detecting the azimuth as described above, the maximum detectable azimuth angle αmax' is determined by the wavelength λ of the ultrasonic wave and the distance l ₀ between the centers of the transducers 1a and 1b, and the wavelength λ of the ultrasonic wave If is constant, the disadvantage is that the maximum detectable azimuth αmax' is limited by the distance l ₀ between the centers of the vibrators 1a and 1b.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide an ultrasonic azimuth sensor that can widen the maximum detectable azimuth angle.

[Disclosure of the invention]

1 to 3 are diagrams showing embodiments of the present invention. In this embodiment, as shown in FIG. 1, a vibrator 1 has cylindrical sensor bodies 8a to 8c with the same radius.
Using three pieces of a to 1c, each vibrator 1a to 1c
The upper surfaces 6a to 6c are arranged in the same plane, and the transducer 1a is placed at the midpoint O between the centers b and c of the transducers 1b and 1c in a direction perpendicular to the direction in which the transducers 1b and 1c are to be detected.
They are arranged so that the center a is on a horizontal straight line containing the . Here, the straight line connecting the midpoint O and the center a of the vibrator 1a becomes the direction to be detected. Two output terminals 7a to 7c are protruded from the lower part of the sensor bodies 8a to 8c of these vibrators 1a to 1c, respectively.
The respective output terminals 7a to 7c are connected via cables 5 to amplifiers 2a to 2c, which will be described below. FIG. 2 is a schematic block diagram of the direction detection circuit. First, the outputs of ultrasonic waves converted into electrical signals by the transducers 1a to 1c are input to amplifiers 2a to 2c and amplified, respectively. Here, the output voltages of these amplifiers 2a to 2c are V _A , V _B , and V _C , respectively, as shown in Fig. 3 a to c.
The waveform is shown in . Next, the output voltages Vb and Vc of the amplifiers 2b and 2c are determined by the phase in the direction to be detected by the 1/2 phase generation circuit 3, that is, the midpoint O in FIG.
Create a voltage V _BC according to the phase at the position of
The waveform is shown in Figure d. This voltage V _BC and amplifier 2
The azimuth detection circuit 4 compares the output voltage V A of the output voltage V _A with the output voltage V A of the output voltage V A of the output voltage V A of the output voltage a. The output V ₀ of this direction detection circuit 4 becomes the direction output. Here, the azimuth detection circuit 4 has two gates _G1 to _G3 , and each gate _G1 to _G3 operates only for a period of ⅓ of the half cycle of the output of the amplifier 2a.

In this operating state, as shown in Fig. 3e to g, gate _G1 is turned on at the same time as the output of amplifier 2a rises, gate _G2 is turned on when gate _G1 is turned off, and gate _G3 is turned on when gate _G2 is turned off. Turn on at the same time. This gate G ₁
~ _G3 , the phase difference φα depends on which on period of the gates _G1 to _G3 the rising position of the output voltage V _BC of the 1/2 phase generation circuit 3 belongs to, and the phase difference φα is a half period of the output voltage V _A of the amplifier 2a. It is possible to detect within which range of π the phase is, and to detect whether the phase is behind or ahead.

As mentioned above, in this embodiment, three vibrators 1a
By using ~1c, it is the same as having a vibrator whose center is at the midpoint O of the vibrator 1a in the 1/2 phase creation circuit of the output of the vibrators 1b and 1c in the direction perpendicular to the detection direction. Since the phase can be detected, the distance between the vibrators can be substantially reduced. Therefore, it is possible to widen the maximum detectable azimuth αmax on one side. For example, the distance between the vibrators
l ₁ is 8 [m/m], and the ultrasonic frequency is 25KHz.
(Wavelength λ = 13.3 m/m), αmax≒sin ^-1 13.3/2×8≒56°. Note that the angular range of the gate _G2 under the above conditions is approximately 18° to 37°.

〔Effect of the invention〕

As described above, the present invention includes at least three transducers that convert incident ultrasonic waves into electrical signals, and all the transducers are arranged so that their detection surfaces are included in the same plane. 2 transducers are arranged at intervals from each other, and the center of the detection surface is located on a line perpendicular to the line at the midpoint on the line connecting the centers of the detection surfaces of the first and second transducers, and , a third vibrator is arranged such that the distance between the midpoint and the center of the detection surface is at least less than the outer dimension;
Using the outputs of the first and second vibrators, create a 1/2 phase signal having a phase that is half the phase of the outputs of the first and second vibrators, and place the center of the detection surface at the midpoint position. 1/2 phase signal generating means for calculating the output of a virtual fourth transducer when the virtual fourth transducer is placed; Since it is equipped with an azimuth detecting means that calculates the difference and detects the azimuth in which the ultrasonic wave arrives from this path difference and the distance between the centers of the virtual fourth and third oscillators, the first and a virtual fourth vibrator whose center is at the midpoint of the second vibrator and a third vibrator.
The azimuth can be detected between the oscillators, and the actual distance between the oscillators can be made smaller than the external dimensions, which has the effect of widening the maximum detectable azimuth angle αmax.

[Brief explanation of drawings]

FIG. 1a is a top view of an embodiment of the present invention, FIG. 1b is a side view, FIG. 2 is a schematic circuit block diagram of the main parts of the same, FIG. 6 to 6 are explanatory diagrams of the operation of the conventional example, FIG. 7a is a top view of the conventional example, and FIG. 7b is a side view. 1a-1c
is the vibrator, 6a to 6c are the top surfaces, a to c are the center, O
is the midpoint.

Claims (1)

[Claims] 1 Equipped with at least three transducers that convert incident ultrasonic waves into electrical signals, all the transducers are arranged so that their detection surfaces are included in the same plane, and the first
and a second vibrator are arranged at a distance from each other, and the center of the detection surface is positioned on a line perpendicular to the line at the midpoint on the line connecting the centers of the detection surfaces of the first and second vibrators. At the same time, a third vibrator is arranged so that the distance between the midpoint and the center of the detection surface is at least less than the outer dimension, and the outputs of the first and second vibrators are used to generate the first and second vibrations. Create a 1/2 phase signal with a phase half that of the child's output,
1/2 phase signal generation means for obtaining an output of a virtual fourth vibrator when the center of the detection surface is placed at the midpoint position; Determine the ultrasonic path difference from the output phase difference,
An ultrasonic azimuth characterized by comprising: azimuth detecting means for detecting the azimuth in which the ultrasonic waves arrive from this path difference and the distance between the centers of the virtual fourth and third oscillators. sensor.