JPH08292254A - Method and apparatus for measuring speed of moving object - Google Patents

Abstract

PURPOSE: To provide a speed-measuring apparatus which measures a speed of an object approaching to the apparatus. CONSTITUTION: A part of an ultrasonic wave transmitter/receiver 19 having a plurality of elements arranged is vibrated by a signal from a driving signal source 20, thereby to generate ultrasonic waves in a target area. A receiving signal detected by the transmitter/receiver 19 from a reflecting body is amplified by an amplifier 21, digitized by an analog-digital converter 22 and input to a speed-operating part 23. The speed-operating part 23 operates/calculates a speed. The presence/absence of a colliding object or a relative speed is displayed by hues, luminance or numerals at a display part 24. A two-dimensional receiving signal in an arranging direction of the plurality of elements of the receiving means and a time series direction which is obtained by repeating the transmitting and receiving operations a plurality of number of times is subjected to two-dimensional Fourier transformation to measure a moving speed of the object towards the receiving means 19. Accordingly, only a truly dangerous object can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a normal velocity measuring device for detecting an approaching object using a wave signal.

[0002]

2. Description of the Related Art A method for measuring the velocity component in the normal direction of a target object by the Doppler effect of ultrasonic waves is known (Jp.
n. J. Appl. Phys. Vol. 34 (199
5) pp. 2515-2518, Pt. 1, No. 5
B). Further, the method by the present inventor capable of measuring the velocity component in the direction orthogonal to the traveling direction of the ultrasonic wave includes the operation of transmitting the ultrasonic wave to the target object and receiving the reflection signal from the specific direction by the plurality of elements. This is a method of measuring the vectorial motion velocity by performing the Fourier transform of the received signal corresponding to the specific depth in the array direction multiple times and considering the resulting time change as a two-dimensional signal and performing the radial Fourier transform (1
992 IEEE ULTRASONICS SYMPO
SIUM 1187-1190).

[0003]

When considering an automobile collision prevention device using the ordinary Doppler effect, a stationary object such as a utility pole or a street tree on a sidewalk has a velocity component in the normal direction, and therefore approaches the automobile. Detected as an object
It is not practical because false alarms are always generated.

The object of the present invention is to solve this problem and to provide a target object that comes in the direction of itself (in other words, a near object detecting device for detecting an object approaching the vehicle, which is arranged in the vehicle). An object of the present invention is to provide an object speed measuring device that detects and measures a truly dangerous target object by measuring the relative speed.

[0005]

[Means for Solving the Problems] Wave signals such as radio waves or ultrasonic waves are transmitted toward a target object by a plurality of elements,
The operation of receiving the reflected signal from the target object by the plurality of elements is performed a plurality of times, and the received signal of each element is obtained in time series. By performing a two-dimensional Fourier transform on this received signal, the relative velocity of the vectorial motion of the target object approaching to itself is measured.

The transmission / reception operation of the present invention will be described with reference to FIG. 1 by taking the case of using an ultrasonic wave as a wave. First, an ultrasonic signal Tp (p = p = p = p) with a time interval T in a relatively wide range 2 from the transmitting element 1 for transmitting ultrasonic waves shown in FIG.
-P, -P + 1, ..., P-1, + P) are sequentially transmitted (p indicates a transmission number). Here, a signal from a reflector (target object) that moves in the circumferential direction is received by the array type transducer 3, and the curvature of the wavefront depending on the distance to the reflector is corrected by the concave delay circuit 4. To do. The received signal R (n, m, p) thus obtained changes as indicated by 5, 6, and 7 in FIG. 1 corresponding to the position of the reflector that changes with time. Here, m represents the element number of the array type transducer 3, and n represents the sample number. The received signal R ₀ (m, p) = R (n ₀ , m, p) of such a received signal at a specific time (sample number n0) corresponding to the target distance is 8, 9, 1 in FIG.
It changes like 0.

Therefore, the spatial frequency of the received signal R ₀ (m, p) changes with time corresponding to the movement of the reflector in the azimuth direction, as shown in FIG. 2 (a). Fourier transform (Fm) of such a signal in the array direction of the elements of the array-type transducer 3
Then, as shown in FIG. 2B, the signal R is displayed on the inclined straight line 11.
₁ (ω, p) is obtained. Here, R ₁ (ω, p) is given by (Equation 1), where d is the element spacing of the array type transducer 3. Where ω is the spatial frequency.

[0008]

## EQU1 ## R ₁ (ω, p) = ΣR ₀ (m, p) exp (-jmωd) (Equation 1) is given (j is an imaginary unit, and addition is m
= M to m = M). Where this R
The gradient of the straight line 11 in which ₁ (ω, p) appears corresponds to the azimuth direction velocity of the reflector. Further, when the reflector (target object) moves in the circumferential direction, the distance between the center of the reflector and the central element of the array type transducer 3 is constant, so that
Output of Fourier transform (R ₁ (ω, p)) in the array direction of the elements of the received signal R ₀ (m, p) indicated by the arrow in (b)
2 is constant as shown in FIG. 2B (the following FIG. 3B, FIG. 4B, FIG. 5A, FIG. 6A, FIG.
The arrow in (b) indicates the received signal R ₀ , as in FIG.
The output of the Fourier transform (representing the phase of R ₁ (ω, p)) in the array direction of the (m, p) elements is shown.

Here, when the reflector simultaneously has a velocity component in the distance direction, the phase of the received signal changes as shown in FIG. 3 (a), and the signal R as shown in FIG. 3 (b).
The phase of ₁ (ω, p) rotates. This phase rotation speed corresponds to the speed of the reflector in the distance direction. Therefore, when the reflector is moving in a constant direction with respect to the array type transducer 3, R ₀ (m, p) shows a constant spatial frequency as shown in FIG. , Its phase rotates according to the approaching speed of the reflector. Therefore, R ₁ (ω, p) is output as R ₁ (ω ₀ , p) on a vertical straight line of ω = ω ₀ as shown in FIG. 4B. Here, ω ₀ corresponds to the movement direction of the reflector, and the phase of R ₁ (ω ₀ , p) rotates with respect to the transmission time p.

Since this phase rotation speed corresponds to the speed of the reflector in the distance direction, the signal R ₁ (ω, p) is shown on each line such as aA, bB, ... Shown in FIG. 5A. When the Fourier transform (Fp) is performed on the transmission time p in, the R ₂ (ω, η) corresponding to the position of each line is as shown in FIG. 5B. Here, R ₂ (ω, η) is given by (Equation 2) (addition is performed in the range of p = −P to p = P). η is the normal velocity of the reflector.

[0011]

## EQU2 ## R ₂ (ω, η) = ΣR ₁ (ω, p) exp (-jηpT) (Equation 2) This output is obtained as a large value at the position corresponding to the phase rotation speed. On the other hand, when the azimuth of the target object is changed, R ₁ (ω, p) is because it is inclined as shown in FIG. 3 (b), the results of Fourier transform with respect to transmit times p this R ₂ (Ω, η) has a small value. From the above, according to the method of the present invention, the velocity of motion in the radial direction is measured only for the target object whose direction from the array type transducer is constant. This configuration is shown in FIG.

Further, in the case of a relatively stationary target object in which the distance from the array type transducer is not changed, R
₁ (ω, p) is the signal on the left side in FIG. 6 (a),
With respect to p, the signals always have the same phase. On the other hand, in the case of the target object whose distance is relatively changing, the signal on the right side of FIG. 6A is generated and the phase is rotated. Therefore, by calculating the difference between R ₁ (ω, p) between adjacent values of p (for example, the difference, {R ₁ (ω, p) −R ₁ (ω, p +
1)}), and the in-phase signal disappears as shown in FIG. 6B, and only the signal from the moving target object can be obtained. It is also effective to calculate R ₂ (ω, η) by performing Fourier transform on p with respect to the signal subjected to the process (MTI) of selecting the moving target object.
This R ₂ (ω, η) is given by, for example, (Equation 3) (addition is performed in the range of p = P to p = P).

[0013]

R ₂ (ω, η) = Σ {R ₁ (ω, p) −R ₁ (ω, p + 1)} exp (−j ηpT) ... (Equation 3) The received signal is Fourier-transformed in the array direction, It is known that the Fourier transform of the resulting two-dimensional signal in the time series direction is equivalent to the two-dimensional Fourier transform of the received signal. Therefore, the relative velocity of the vectorial motion of the target object is similarly obtained by performing the operation of transmitting the wave signal and receiving the reflected signal by the plurality of elements a plurality of times, and performing the two-dimensional Fourier transform of the resulting two-dimensional signal. Can be measured.

Since the two-dimensional Fourier transform does not depend on the order of conversion, first the received signal is Fourier-transformed in the time series direction (Fp, (Equation 2)), and then the resulting two-dimensional signal is arranged in the array direction. Similar processing can be performed by performing Fourier transform (Fm, (Equation 1)). This configuration is shown in FIG. Note that R1 ′ is the result of Fourier transform of the received signal in the time series direction.

It is known from the Fourier projection theorem that the projection process and the one-dimensional Fourier transform of the projection signal are equivalent to the two-dimensional Fourier transform. Therefore, the projection process (PJ)
An equivalent configuration is possible by the one-dimensional Fourier transform (Fr) of the projection signal. This structure is shown in FIG. Note that R ″ is the result of the projection process (PJ).

Since the operation ((Equation 1)) of Fourier transforming the received signal in the array direction is equivalent to the directivity synthesis, the directivity synthesis process (BF) transfers the received signal from each direction to the transmitter / receiver. An equivalent configuration is possible by converting (decomposing) the received signal to be incident and performing a Fourier transform (Fp, (Equation 2)) in the time series direction as a two-dimensional signal with the converted (decomposed) result. This structure is shown in FIG.
Here, the process of performing Fourier transform ((Formula 2)) in the time series direction is generally equivalent to performing frequency analysis (FA). A configuration using frequency analysis (FA) is shown in FIG. In the two-direction Fourier transform in the two-dimensional Fourier transform, the result of the two-dimensional Fourier transform does not depend on the order of the transforms. Therefore, the received signal R ₀ (m, p) is first subjected to the Fourier transform in the time series direction ((Equation 2)). ) Or frequency analysis, and then Fourier transform ((Equation 1)) this conversion result in the array direction.
By doing so, equivalent processing can be similarly performed.

According to the present invention, an operation of transmitting a wave signal and receiving a reflection signal from a target object by a plurality of elements is performed a plurality of times, and a two-dimensional signal (reception signal) obtained as a result is subjected to a two-dimensional Fourier transform. The velocity measuring device for measuring the relative velocity of the vectorial motion of the target object is characterized by the two-dimensional Fourier transform, in which the received signal is Fourier-transformed in the array direction and the resulting two-dimensional signal is Fourier-transformed in the time-series direction. The received signal is transformed or the received signal is Fourier transformed in the time series direction and the resulting two-dimensional signal is Fourier transformed in the array direction. The above Fourier transform in the time series direction can be performed by correcting the previously performed Fourier transform in the time series direction.

The two-dimensional Fourier transform is performed by the projection process of the received signal and the one-dimensional Fourier transform of the projected signal. The two-dimensional Fourier transform operation is a means for converting (decomposing) a received signal at a specific time into a received signal that is incident on the transducer from each direction, and Fourier transforming the result of this conversion (decomposition) in the time series direction. Means, or means for frequency analysis, or Fourier transform in the time series direction, or conversion by means for frequency analysis, and means for Fourier transforming the conversion result in the array direction.

Further, the detection result of the relative velocity of the vectorial motion of the target object may be an acoustic signal (language, a specific meaning, for example, a sound expressing a warning, etc.) or an optical signal (specified on the entire surface of the display means). It indicates that an object approaches by the color of), and is output by.

As the wave signal, an ultrasonic wave signal or a radio wave signal is used. The above speed measuring device is mounted on, for example, an automobile, a ship that sails over a river, a submarine that sails in the sea, an aircraft, etc., and is used for their safe operation.

[0021]

FIG. 7 shows the configuration of an apparatus according to the present invention. An electric signal from the wave transmission signal source 20 is applied to the wave transmitter / receiver 19. This transmitter / receiver is an antenna array in a configuration using radio waves, and is a piezoelectric vibrator array in a configuration using ultrasonic waves. A wave signal such as a radio wave or an ultrasonic wave is transmitted from a partial element (element) of the wave transmitter / receiver within the range of the observation field of view (usually about 30 degrees forward in the traveling direction). The reflected signal of the transmitted signal from the object is received by all the elements of the transmitter / receiver. Such a transmission / reception operation is performed a plurality of times, and the reception signal by each element is obtained in time series.
The received signal is converted into discrete numerical values by the analog-digital converter 22 and stored as a two-dimensional signal relating to the position of the receiving element and the transmission time. By subjecting this two-dimensional received signal to two-dimensional Fourier transform by the speed calculator 23,
The vectorial velocity of motion is measured only for the object that faces the user, and the display units 17, 18 and 2 are displayed in various display formats.
The determination result of the motion velocity of the object is displayed in 4. INDUSTRIAL APPLICABILITY The device of the present invention can be applied to various fields such as safety devices in automobiles, torpedo detection, and missile detection.

An apparatus for detecting the moving speed of a moving object using ultrasonic waves will be described below. As shown in FIG. 7, an array type ultrasonic transducer 19 in which a plurality of elements are arrayed.
An ultrasonic wave is generated in the target area 2 by vibrating a part of the above by a signal from the drive signal source 20. The signal from the reflector is received by the transceiver 19. This received signal is amplified by the amplifier 21, digitized by the analog-digital converter 22, and the speed calculator 23
To enter. This speed calculation unit performs speed measurement processing according to the present invention, and determines the presence or absence of a collision object or the relative speed,
The display unit 24 displays the hue, brightness, and numbers. Further, the sound output unit 17 outputs a sound signal in which the speed of the target is made to correspond to the frequency or a language voice such as "abnai". As the output of the sound output unit 17, it is also possible to set and control a threshold value relating to the distance or speed of the target, and output it. In addition, the acoustic output unit 17 has a stereo configuration and R corresponding to the approaching direction of the collision object.
It is also possible to make ω in ₂ (ω, η) correspond to the phase difference between the signals coming into both ears and the direction in which the target object exists to correspond to the sound source localization position of the auditory stereo sound image. Further, the result is output by the vibration of the vibration exciter 18. Naturally, other general processing for the normal wave signal is also used.

A typical array type ultrasonic wave transmitter / receiver constituting a near object detecting device used in an automobile has a total length of about 1 m, an element pitch of about 3 cm, and a driving frequency. Is about 10 KHz to several tens KHz.
When using radio waves, it is desirable to use radio waves of 10 GHz to 30 GHz.

In the above description, measurement in a two-dimensional space has been described. However, measurement of three-dimensional vector velocity can be performed by expanding one-dimensional processing of all Fourier transforms such as one-dimensional Fourier transform in two dimensions. It is possible. That is, it is possible to detect a target object approaching oneself in the three-dimensional space.

The two-dimensional Fourier transform used here may have an ordinary arithmetic structure by batch processing, or an arithmetic structure for accelerating by a simple method shown in FIG. 8 for sequentially processing new received signals. R ₀ (m, p) is obtained corresponding to each transmission time p, and Fourier transform is sequentially performed for m to obtain R ₁
(Ω, p). The part from the p = 1 to p = P, is performed a Fourier transform with respect to p shown in FIG. 8 R ₂
(Ω, η). Here, R ₁ (ω, p) and R ₂ (ω, p
η) is represented by (Equation 4) and (Equation 5).

[0026]

[Equation 4] R ₁ (ω, p) = ΣR ₀ (m, p) exp (jmω) (Equation 4)

[0027]

R ₂ (ω, η) = ΣR ₁ (ω, p) exp (jpη) (Equation 5) The addition in (Equation 4) is performed in the range of m = 1 to m = M by The addition in 5) is performed in the range of p = 1 to p = P.

Next, a new received signal R ₀ (m, P + 1) corresponding to p = P + 1 is obtained. This signal is Fourier transformed to be R ₁ (ω, P + 1). This p = 2 to p
A new R2 (ω, η) is obtained by Fourier transforming the part up to = P + 1 with respect to p.
_{If 2} '(ω, η) ((Equation 6), (7))

[0029]

## EQU6 ## R ₂ ′ (ω, η) = ΣR ₁ (ω, p) exp (jpη) (Equation 6)

[0030]

Equation 7] _{R 2 '(ω, η)} = ΣR 1 (ω, p) exp (jpη) -R 1 (ω, 1) exp (jp) + R 1 (ω, p + 1) exp {j (p + 1) η } = R ₂ (ω, η) -R ₁ (ω, 1) exp (jη) + R ₁ (ω, p + 1) exp {j (p + 1) η} ... (Equation 7) and old R ₂ (ω, Since R ₂ ′ (ω, η) is obtained by adding and subtracting R ₁ (ω, p) to η), p 2
The Fourier transform with respect to is unnecessary and the calculation is greatly simplified. The addition in (Equation 6) is performed from p = 2 to p = P
In the range of +1, the addition in (Equation 7) is p = 1 to p = P
Perform within each range.

[0031]

According to the present invention, it is possible to measure only the speed of a target object toward itself (for example, a near object detection device for detecting an object approaching an automobile arranged in a car), and a truly dangerous target object. It can detect and measure only.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a receiving operation according to the present invention.

FIG. 2A is a diagram for explaining a received signal from a target object that makes a circumferential motion in the present invention, and FIG. 2B shows a target signal that makes a circumferential motion in the present invention. For explaining the phase change of the output of the one-dimensional Fourier transform of the received signal in the element array direction.

FIG. 3A is a diagram for explaining a received signal when a target object according to the present invention has a velocity component in a distance direction; FIG.
FIG. 4 is a diagram for explaining a phase change of the output of the one-dimensional Fourier transform in the element array direction of the received signal when the target object in the present invention has a velocity component in the distance direction.

FIG. 4A is a diagram for explaining a received signal from a target object that is moving in a certain direction with respect to the array type transducer according to the present invention; and FIG. 4B is an array type according to the present invention. The figure explaining the phase change of the output of the Fourier transform in the element arrangement direction of the received signal from the target object which is moving in a fixed direction with respect to the transmitter / receiver.

FIG. 5A illustrates a phase change of an output of a Fourier transform in an element array direction of a reception signal from a target object moving in a fixed direction with respect to the array type transducer according to the present invention. FIG. 5B is a diagram for explaining the output of the Fourier transform regarding the transmission time of FIG.

6A and 6B are diagrams for explaining a process of detecting a moving object with respect to the array type transducer according to the present invention.

FIG. 7 is a block diagram of an embodiment of the present invention.

FIG. 8 is a diagram illustrating sequential calculation processing according to an embodiment of the present invention.

9A to 9E are diagrams for explaining the arithmetic processing procedure in the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmitting element, 2 ... Transmission range of ultrasonic waves, 3 ... Array type transducer, 4 ... Concave delay circuit 5, 6, 7 ... Received signal,
8, 9, 10 ... Received signal at a specific time corresponding to the target distance, 11 ... Straight line, 17 ... Acoustic output section, 18 ... Vibration output section, 19 ... Transducer, 20 ... Transmitted signal source, 21 ... Amplifier, 22 ... Analog-digital converter, 23 ... Velocity calculation part, 24 ... Display part.

Claims (13)

[Claims] 1. A step of (1) transmitting a wave signal by a transmitting means composed of a plurality of elements, (2) a step of receiving a reflected signal from a target object by a receiving means composed of a plurality of elements, and (3) the step. (1) and (2) are repeated a plurality of times, and (4) a two-dimensional Fourier transform of the two-dimensional received signal obtained in step (3) in the arrangement direction of the plurality of elements of the receiving means and the time series direction is performed. And a speed measuring method for measuring the motion speed of the target object toward the receiving means. 2. A transmission means composed of a plurality of elements for transmitting a wave signal, a reception means composed of a plurality of elements for receiving a reflection signal from a target object, and the transmission and reception operations are repeated a plurality of times. Velocity measurement that has a Fourier transform unit that performs a two-dimensional Fourier transform of a two-dimensional received signal in the array direction of a plurality of elements of the receiving unit and a time-series direction, and measures the moving velocity of the target object toward the receiving unit. apparatus. 3. The apparatus according to claim 2, wherein the two-dimensional Fourier transforming means includes first means for Fourier transforming the two-dimensional received signal in the array direction and two-dimensional signal obtained by the first means. A velocity measuring device comprising second means for performing Fourier transform in the time series direction. 4. The speed measuring apparatus according to claim 3, wherein the first means obtains the Fourier transform in the time series direction by correcting a result of the Fourier transform in the time series direction which has been previously executed. 5. The apparatus according to claim 2, wherein the two-dimensional Fourier transform means performs third Fourier transform on the two-dimensional received signal in the time series direction, and two-dimensional signal obtained by the third means. And a fourth means for performing a Fourier transform on the array direction. 6. The apparatus according to claim 2, wherein the two-dimensional Fourier transforming means comprises projection processing means for projecting the two-dimensional received signal, and means for one-dimensional Fourier transforming the projection signal obtained by the projection processing means. Speed measuring device. 7. The apparatus according to claim 2, wherein the two-dimensional Fourier transform means outputs the two-dimensional received signal at a specific time,
A velocity measuring device comprising: a conversion unit that converts a reception signal incident on the reception unit from each direction; and a unit that performs a Fourier transform of a result obtained by the conversion unit in the time series direction. 8. The apparatus according to claim 2, wherein the two-dimensional Fourier transform means outputs the two-dimensional received signal at a specific time,
A velocity measuring device comprising: a conversion means for converting into a reception signal incident on the reception means from each direction; and a means for frequency-analyzing the result obtained by the conversion means. 9. The apparatus according to claim 2, wherein the two-dimensional Fourier transforming means comprises an analyzing means for frequency-analyzing the two-dimensional received signal and a means for Fourier transforming a result obtained by the analyzing means in the array direction. Speed measurement device. 10. The velocity measuring device according to claim 2, wherein the movement velocity of the target object is output as an acoustic signal. 11. The velocity measuring device according to claim 2, wherein the velocity of movement of the target object is output by an optical signal. 12. The velocity measuring device according to claim 2, wherein the wave signal is an ultrasonic signal. 13. The velocity measuring device according to claim 2, wherein the wave signal is a radio wave signal.