JP2007017309A - Target detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a target detector capable of reducing alarm error probability when a target is detected, and accurately calculating a target azimuth, a target distance, and a target speed. <P>SOLUTION: The target detector comprises a transducer 12 for receiving a wave signal from a target to which wave is radiated with a predetermined period, a device 14 for forming a plurality of directional beams including a split beam from a received signal, a target detection processing device 15 that converts the output signal of each of the plurality of taken directional beams into a frequency region and determines the target using a level threshold and azimuth dispersion threshold from a signal level and signal azimuth corresponding to each frequency on the obtained frequency region, and a device 16 for calculating a distance to the target on the basis of the time from wave radiation to arrival of the wave signal after target determination and calculating the target speed of the detected target from the target azimuth, target distance, and the predetermined period of the same detected target obtained by previous and present transmissions in the predetermined period. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a target detection apparatus that irradiates a target moving and stationary object with a wave and detects a target from a wave signal including a reflected component from the target. The present invention relates to a target detection apparatus that displays a calculation result on a screen.

  In order to detect the target, a wave signal including a reflection component from the target is usually used. In particular, as a method for calculating a target azimuth, there is a split beam method in which two reception beams are formed. The azimuth is calculated from the phase difference of each received signal by the split beam. Patent Document 1 discloses an example of a sonar display device that uses two sets of split beams in a split beam system and selects either of the two sets depending on whether the signal-to-noise ratio is good or bad to increase detection accuracy. ing.

JP 2000-147096 A

  Conventionally, as a method for detecting a target from a wave signal including a reflection component from the target, there is a method for detecting from a target likelihood based on a target level and duration in the wave signal. Further, the above-described split beam method for calculating the target azimuth is frequently used because it can be realized with a relatively small apparatus configuration. However, with this method, there is a problem that the azimuth calculation error occurs due to the difference between the target azimuth and the directional beam center azimuth and the influence of noise, and the same target is detected in different directional beams, and signals other than the target azimuth are There is a possibility of detection, and reducing the false alarm probability becomes a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the probability of false alarm when detecting a target, and to calculate a target azimuth, target distance, and target speed with high accuracy. It is to provide a detection device.

  In order to achieve the above object, a target detection apparatus of the present invention irradiates a target object with a wave at a predetermined first period, and further receives a wave signal including a reflection component from the target. And means for forming a plurality of directional beams including split beams from the received signal received by the means; and means for capturing each output signal of the plurality of directional beams at a predetermined second period. It has. In addition to the above, the target detection apparatus of the present invention corresponds to means for converting the captured output signal into the frequency domain, means for detecting a signal level corresponding to each frequency in the frequency domain, and corresponding to each frequency in the frequency domain. Means for calculating the signal direction to be performed, means for aligning the signal level corresponding to each detected frequency in the time direction, means for aligning the signal direction corresponding to each calculated frequency in the time direction, aligned signal levels, and Means for capturing a signal direction for a predetermined period; means for calculating an average value of signal levels acquired during the predetermined period; means for calculating a variance value of signal directions captured during the predetermined period; and a calculated average value Means for determining as a detection target a target whose signal is higher than the level threshold and whose calculated dispersion value is lower than the azimuth dispersion threshold becomes a wave signal. In addition to the above, the target detection apparatus of the present invention further includes means for calculating the distance to the detection target as the target distance based on the time from the irradiation of the wave until the arrival of the wave signal that has reached the target determination. The signal direction that has reached the target determination is set as the target direction, and the target distance and the target direction are output as target detection information. Since the detection target is determined using the level threshold value and the azimuth distribution threshold value, the false alarm probability can be reduced, and the target azimuth, the target distance, and the target speed can be calculated with high accuracy.

  According to the present invention, a signal with an average value of the calculated signal level higher than the threshold value and a calculated azimuth variance value lower than the threshold value is determined as the target, so that the false alarm probability can be reduced. It is possible to calculate the target distance and the target speed with high accuracy.

  Hereinafter, the target detection apparatus according to the present invention will be described in more detail with reference to embodiments shown in the drawings. In this embodiment, a mode when applied to sonar will be described.

  FIG. 1 shows the overall configuration of the present embodiment.

  In FIG. 1, a transmitter 11 generates and outputs an electrical signal to be transmitted. The transmitter / receiver 12 converts the electrical signal output from the transmitter 11 into a sound wave and transmits it into the water, and receives an incoming sound wave from the water and converts it into an electrical signal. The sound wave is transmitted for a period of time t1 with a period Δt (predetermined first period). Reception is repeatedly performed in a period shorter than the period Δt, that is, a predetermined second period Δt2 during a time (Δt−t1) in which no sound wave is transmitted. That is, reception is performed k times (where k = (Δt−t1) / Δt2} until the next transmission is performed.

  The receiver 13 amplifies the electric signal output from the transmitter / receiver 12 for each reception, further performs digital conversion on the amplified electric signal, and outputs the converted signal. The converted signal becomes a signal sequence by receiving k times.

  In reception, a reception angle is provided for each narrow angle obtained by dividing the transmission angle of the sound wave transmitted by the transducer 12 into a plurality of angles, and a plurality of directional beams having narrow reception angles are formed. That is, the beam forming device 14 reads each azimuth of a plurality of directional beams to be formed in advance, and performs a process of forming directional beams by the number of azimuths read from the signal sequence output from the receiver 13. Each signal sequence for the number of beams is output. The directional beam is formed based on a split beam method.

  The target detection processing device 15 inputs each signal sequence for the number of directional beams and performs target detection processing. FIG. 2 shows the configuration of the target detection processing device 15. The target detection processing device 15 includes a frequency conversion processing unit 151, an azimuth calculation processing unit 152, a target detection processing unit 153, and the same target integration processing unit 154.

  The frequency conversion processing unit 151 converts the output data from the beam forming device 14 into the frequency domain. The azimuth calculation processing unit 152 calculates a signal azimuth corresponding to each frequency on the frequency domain. The signal direction is represented by θ (t) at each time point t.

The signal azimuth θ (t) is obtained by calculating the phase difference φ (t) between split beams, the distance between split beams is d (m), the sound speed is C (m / s), and the transmission frequency is F _s (Hz). , Calculated by equation (1).

  The target detection processing unit 153 inputs the calculated signal direction and performs target determination. FIG. 3 shows the configuration of the target detection processing unit 153. The target detection processing unit 153 includes a signal level alignment processing unit 1531 for aligning signal levels corresponding to each frequency on the frequency domain in the time direction, and a frequency for aligning the calculated signal orientation corresponding to each frequency in the time direction. Each azimuth alignment processing unit 1532, a signal level average processing unit 1533 that takes in the aligned signal level and signal azimuth for a certain period, calculates an average value of the acquired signal level, and a signal azimuth that calculates a variance value of the acquired signal azimuth A variance value calculation processing unit 1534. The above-described fixed period for obtaining the average, that is, the predetermined period is represented by jΔt2 where j <k.

  In the target determination processing unit 1535, a signal whose calculated average value is higher than the level threshold value and whose calculated variance value is lower than the azimuth variance threshold value is determined as the target. After the target determination, the facing speed calculation processing unit 1536 calculates the facing speed from the detected frequency determined as the target.

When the detection frequency is F ₀ (Hz), the facing speed V _d (m / s) is calculated by the equation (2).

  Next, even if the same target integration processing unit 154 includes a plurality of (n) directional beam output signals at the same time in the reflected signal from the target, the same target integration target 154 The same target determination unit that performs the determination and the azimuth average calculation unit that calculates the weighted azimuth average based on the signal level in the case of the same target, uniquely specify the target detection information.

The only specific azimuthal theta _a goal, a theta _n from orientation theta ₀ of the same target a plurality of (n), the signal level is assumed to be A _n from A _0, is calculated by the equation (3) .

  After the target is detected as described above, the distance to the target and the moving speed of the target are calculated by the target distance and target speed calculating device 16. FIG. 4 shows the configuration of the target distance and target speed calculation device 16. The target distance and target speed calculation device 16 includes a target distance calculation processing unit 161, an identical target determination processing unit 162, and a target speed calculation processing unit 163.

The target distance calculation processing unit 161 calculates the target distance from the time from when the wave is irradiated until the output signal is captured for each directional beam. The same target determination processing unit 162 starts from the target speed opposing component when the previous transmission time before the time Δt is the first detection, and, if not the first detection, as shown in FIG. The same target determination distance range 1622 set from (to be described later) and the same target determination azimuth range 1623 set in advance from the target exercise ability are set around the target movement direction 1621 indicated by the target speed, and the distance range The same target determination range surrounded by 1622 and the azimuth range 1623 is set. The same target determination processing unit 162 determines that the target detected this time is the same as the previous time when the direction and distance of the target at the time of the current transmission are within the set same target determination range. When the target speed or the target speed opposing component is V _d (m / s) and the transmission cycle is Δt (s), the same target determination distance range 1622ΔR is calculated by Expression (4).

The target speed calculation processing unit 163 calculates a target speed from the target position of the target determined to be the same as the previous time by the same target determination processing unit 162 among the targets detected at the time of transmission this time. As shown in FIG. 6, the direction of the target 1631 detected at the previous transmission is θ ₁ (deg), the distance is r ₁ (m), and the direction of the target 1632 detected at the current transmission is θ ₂ (deg), If the distance is r ₂ (m), the target speed 1633 is calculated by the equation (5).

  The display device 17 displays the target azimuth and target distance detected by the target detection device 15 and the target distance and target speed calculation device 16 on a screen having a distance on the vertical axis and an orientation on the horizontal axis, and the target speed is written in characters. indicate.

  As described above, according to the present embodiment, since the average level value and the azimuth variance value of a plurality of signals captured at regular time intervals are used for target determination, the false alarm probability can be reduced, and the target azimuth, target distance, and target The speed can be calculated with high accuracy.

The block diagram for demonstrating embodiment of the target detection apparatus which concerns on this invention. The block diagram for demonstrating the target detection processing apparatus used for this embodiment. The block diagram for demonstrating the target detection process part used for this embodiment. The block diagram for demonstrating the target distance and target speed calculation apparatus used for this embodiment. The figure for demonstrating the same target determination azimuth | direction range and the same target determination distance range. The figure for demonstrating calculation of target speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Transmitter, 12 ... Transmitter / receiver, 13 ... Receiver, 14 ... Beam forming device, 15 ... Target detection processing device, 16 ... Target distance and target speed calculation device, 151 ... Frequency conversion processing unit, 152 ... Direction calculation processing 153 ... Target detection processing unit, 154 ... Same target integration processing unit, 161 ... Target distance calculation processing unit, 162 ... Same target determination processing unit, 163 ... Target speed calculation processing unit, 1531 ... Signal level alignment processing unit for each frequency , 1532... Azimuth alignment processing unit for each frequency, 1533... Signal level average processing unit, 1534... Signal orientation dispersion value calculation processing unit, 1535... Target determination processing unit, 1536.

Claims (5)

Means for irradiating a target object with a wave at a predetermined first period, and further receiving a wave signal including a reflection component from the target;
Means for forming a plurality of directional beams including split beams from the received signal received by the means;
Means for capturing an output signal of each of the plurality of directional beams at a predetermined second period;
Means for converting the captured output signal into the frequency domain;
Means for detecting a signal level corresponding to each frequency on the frequency domain;
Means for calculating a signal orientation corresponding to each frequency on the frequency domain;
Means for aligning signal levels corresponding to each detected frequency in a time direction;
Means for aligning the signal direction corresponding to each calculated frequency in the time direction;
Means for capturing the aligned signal level and signal orientation for a predetermined period of time;
Means for calculating an average value of the signal levels captured during the predetermined period;
Means for calculating a variance value of the signal orientation captured during the predetermined period;
Means for determining, as a detection target, a target whose calculated average value is higher than a level threshold and whose calculated dispersion value is lower than an azimuth dispersion threshold is a wave signal;
And a means for calculating the distance to the detection target as a target distance based on the time from irradiating the wave until the arrival of the wave signal that has reached the target determination.
A target detection apparatus characterized in that a signal azimuth reaching a target determination is set as a target azimuth, and the target distance and the target azimuth are output as target detection information. In claim 1,
Means for calculating the target opposing speed from the frequency on the frequency domain that has led to the target determination;
When the target detection information is obtained from at least two directional beams included in the plurality of directional beams, detection is obtained from the at least two directional beams from the target azimuth and the opposing speed. It is determined whether or not the targets are the same. When the targets are determined to be the same, the target directions from the at least two directional beams are weighted by the signal level, and the average of the weighted target directions is the average target direction. And means for calculating as
A target detection apparatus characterized in that the calculated average target direction is set as a target direction of the target detection information. In claim 1,
Means for determining whether the detection target obtained by the previous transmission in the predetermined first period and the detection target obtained by the current transmission are the same;
From the target distance and target direction of the detection target obtained by the previous transmission, the target distance and target direction of the detection target obtained by the current transmission, and the first cycle when determined to be the same, the detection target Means for calculating the target speed of
A target detection apparatus characterized in that the target speed is included in the target detection information and output. In claim 3,
A target detection apparatus comprising: a display device that displays the target distance, the target direction, and the target speed as the target detection information. A transducer for irradiating a target object with a wave at a predetermined first period and further receiving a wave signal including a reflection component from the target;
A beam forming device for forming a plurality of directional beams including split beams from the received signal received by the transducer;
From the signal level and the signal direction corresponding to each frequency on the frequency domain obtained by capturing each output signal of the plurality of directional beams in the second period and converting the captured output signal to the frequency domain, A target detection processing device that performs target determination using a level threshold value and an azimuth dispersion threshold value, and determines a signal azimuth leading to the target determination as a target azimuth;
Based on the time from the irradiation of the wave until the arrival of the wave signal that has reached the target determination, the distance to the target determined by the target determination is calculated as the target distance, and the predetermined first From the target orientation and target distance of the detection target obtained by the previous transmission in the cycle, the target orientation and target distance of the same detection target obtained by the current transmission, and the first cycle, the detection target A target distance and target speed calculation device for calculating a target speed;
The target detection comprising: a display device for displaying the target azimuth determined by the target detection processing device and the target distance and target speed calculated by the target distance and target speed calculation device. apparatus.

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