JP2004301737A - Simple substance echo detection method with hull vibration compensation, simple substance echo sensing device, and echo-tracking method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple substance echo sensing device, an echo tracking method and a simple substance echo detection method with hull vibration compensation that can more precisely obtain reflective echoes of simple substance fish, by means of transmitting and receiving echoes at an optimal timing taking into consideration the hull vibration. <P>SOLUTION: The method is provided with a hull vibration sensing means for detecting hull vibration, a sound wave transmitting means for transmitting sound wave to the seabed, a sound wave receiving means for receiving sound wave, and a simple substance echo sensing means for analyzing the signal from the sound wave receiving means and for detecting the simple substance echoes. When the output signal from the hull vibration sensing means lies within the range of the predetermined value, the sound wave transmitting means transmit the sound wave to the seabed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

である。ローパスフィルタの場合には基本式（１）のｓにｓ／ωを代入し、ハイパスフィルタではｓにω／ｓを代入する。なお、ωは角周波数を示す。
２次のバタワース型のハイパスフィルタの伝達関数は（２）で示される。
【００２４】
【数２】

なお、振動ジャイロは角速度出力時に微分要素を既に持っているので、最終的な伝達関数は（３）となる。
【００２５】
【数３】

次に、２次のＩＩＲ型のデジタルフィルタを作成するために、ｓＺ変換を行う。
【００２６】
【数４】

を代入すれば
【００２７】
【数５】

となり、漸化式から
【００２８】
【数６】

が得られる。なお、ａ０からａ２，ｂ０からｂ２は係数である。
【００２９】
動揺計３は、角速度計３ａからの角速度にローパスフィルタおよびハイパスフィルタのデジタル処理を行って、ロールおよびピッチの傾斜角のデータを出力する。
【００３０】
次に、ロールおよびピッチの傾斜角のデータから、動揺計３による方位角および地頂角の算出について説明する。以後、ロールおよびピッチの傾斜角をそれぞれロール角、ピッチ角と記す。図５に示すように、方位角φおよび地頂角θは、船に装備している送受波器５の法線ベクトル方向に対する基準軸（Ｘ，Ｙ，Ｚ）からの角度を示す。方位角φおよび地頂角θより、送受波器５から送受波されるビームの方向を知ることができる。
【００３１】
方位角φおよび地頂角θへの変換は、図５に示すロール角βおよびピッチ角αのデータから、図３に示すマイクロコンピュータ３ｃの方位角、地頂角変換の処理プログラムを実行して行われる。なお、ロール角およびピッチ角から方位角および地頂角への変換については、説明を省略すが、ピッチ角または、およびロール角が０度のときには、以下に示す事項に対する注意が必要となる。
１）ピッチ角またはロール角が０度の時は、次のような場合分けが必要である。
▲１▼ピッチ角が０度の時、方位角はロール角の符号により＋９０度（ロール角：負符号）もしくは−９０度（ロール角：正符号）になる。地頂角はロール角の絶対値になる。
▲２▼ロール角が０度の時、方位角はピッチ角の符号により０度（ピッチ角：正符号）もしくは１８０度（または−１８０度、ピッチ角：負符号）になる。地頂角はピッチ角の絶対値になる。
２）ピッチ角およびロール角とも０度のとき、地頂角は０度であるが、方位角は規定不可能となる。
【００３２】
以上により、動揺計３により船のロール角およびピッチ角の検出が行われる。なお、動揺計３は、ロール角およびピッチ角から演算により方位角および地頂角を出力することも可能となっている。
【００３３】
なお、ローパスフィルタ、ハイパスフィルタは、ソフトウエア処理によるデジタルフィルタであるが、ローパスフィルタ、ハイパスフィルタをアナログ回路で構成するようにしてもよい。しかしながら、アナログフィルタは、フィルタ特性が固定されるためフィルタ特性を容易に変更すことができない。デジタルフィルタは、カットオフ周波数などのフィルタ特性の変更を容易に行えるなどの利点を有している。
【００３４】
以下に、動揺計３を使用した動揺補正付き単体エコー検出方法について説明する。単体エコーとは、受信波の受信レベルから抽出した単体魚で反射されたエコーをいう。単体エコーを検出することにより魚体長の推定を行うことができる。
【００３５】
図６に単体エコーの検出、魚体長の推定までの手順をフローチャートを示す。なお、単体エコーの検出はスプリットビーム法を使用して行われる。図６に示すように、受信波の受信レベルからの単体エコーの検出は、最初に、動揺計３により船のピッチ角およびロール角の検出を行う（ステップＳ１）。ピッチ角およびロール角が予め設定した角度０度を含む設定値の範囲内であるかを動揺計３でチェックする（ステップＳ２）。ピッチ角およびロール角が設定値の範囲外のときには、ステップＳ１に移行する。ピッチ角およびロール角が設定値の範囲内のときに、送受波器５より音波の送信を行う（ステップＳ３）。
【００３６】
図７（ａ）に、動揺計３からのピッチ角およびロール角の時系列変化を示す。図７（ａ）に示すように、動揺計３からのピッチ角およびロール角が設定値の範囲内のときに（図７（ｂ）に示す時間Ｔ１からＴ５）、デジタル信号処理部１０から送信増幅器７への発振指令（図７（ｂ）に示す）が出力される。また、図８（ａ）に示すように、ピッチ角およびロール角から演算された地頂角が予め設定した角度０度を含む設定値の範囲内のときに（図８（ｂ）に示す時間Ｔ１０からＴ１４）、送信増幅器７に発振指令（図８（ｂ）に示す）を発するようにしてもよい。なお、送信の周期は、音響的に有効な周期以下にならないように制御されている。
【００３７】
ピッチ角およびロール角、または地頂角が予め設定した角度０度を含む設定値の範囲内のときに音波の送信を行うことにより、音波の指向軸は常に一定したものとなる。
【００３８】
ターゲット（魚体）からの音波の反射波を送受波器５で受信する（ステップＳ４）。ターゲットからの反射波（ビーム）の受信信号は、受信増幅器８で増幅、整流を行いレベル情報となる。また、送受波器５の前ビーム、後ビーム、左ビーム、右ビームの受信信号から受信位相検出器９で増幅、変調を行って位相情報を検出する。
【００３９】
次に、受信増幅器８からの信号より単体エコーの検出を行う（ステップＳ５）。受信増幅器８で得られたレベル情報を測定レンジ分の時間に対し所定のサンプリング間隔でＡＤ変換を行い、ＡＤ変換したデータを演算して、受信レベルＥ_Ｒに変換する。受信レベルＥ_Ｒの中から、単体魚から反射された単体エコーのみを抽出する。受信レベルＥ_Ｒと単体魚から得られるＴｓの関係は、送受信係数をＴ_Ｒ、距離をｒ、吸収減水係数をβ、円形送受波器５の指向性関数をＤ（θ）とすれば、単体エコーのソナー方程式より、
【００４０】
【数７】

と表せる。式（４）の受信レベルＥ_Ｒに距離減衰を考慮した受信レベルＥ_Ｔとすれば、
【００４１】
【数８】

と表せる。式（５）の左辺に示された値のデータ列より、単体エコーを検出する。図９に単体エコーの規準となる１／２レベル、１／２レベルパルス幅、ベースレベル、ベースレベルパルス幅を示す。また、図９の●印で示される部分は、単体エコー検出の処理で使用されるＥ_Ｔ ^２／Ｔ_Ｒデータである。レベル、パルス幅の規準を満たし、単体エコーと判定されたパルスの極大値を求め、浅いデータに向かいｎ個分のデータの平均処理を行った値がＤ（θ）^４・Ｔｓとなる。
【００４２】
次に、ターゲットの位置角の検出を行う（ステップＳ６）。受信位相検出器９からの位相情報を測定レンジ分の時間に対し所定のサンプリング間隔でＡＤ変換を行い、電気角δｘ、δｙに変換する。受信レベルＥ_Ｒの極大値に相当する受信位相検出器９から得られたタイミングの電気角δｘ，δｙに対し、浅いデータに向かってｍ個分のデータを検出する。この時、ｍ個の範図内でδｘ、およびδｙの最大値−最小値の値をそれぞれ△δｘ、Δδｙとした場合に、これらが規準の変化量以下であるか判定する。条件を満たす場合、ｍ個の範図内のδｘ、およびδｙに対し、平均処理を行なう。この平均結果を式（６）を用い、位置角θを算出する。
【００４３】
【数９】

ただし、ｄは波数、ｋは送受波器の位相ビーム用アレイの中心距離を示す。
【００４４】
（６）で検出された位置角θにより、送受波器５の指向性関数Ｄ（θ）が求まり、（５）よりＴｓが算出される。ＴＳとＴｓとの関係を示す式
ＴＳ＝１０ｌｏｇ_１０Ｔｓ
からＴＳ値を算出する（ステップＳ７）。
【００４５】
次に、魚体長の推定を行う（ステップＳ８）。魚体長（Ｌ）の推定は、式（７）にＴＳ値を代入することで求まる。
【００４６】
ＴＳ＝２０ｌｏｇ_１０（Ｌ）＋ＴＳｃｍ （７）
なお、式（７）中のＴＳｃｍとした部分は、規準化ＴＳと呼ばれ、ユーザが設定する値である。規準化ＴＳを設定することにより、多魚種に対して魚体長の推定が可能となっている。
【００４７】
以上述べたように、単体エコーの検出は、動揺計３により船の傾きをチェックして、船の傾きが設定値範囲内のときに音波を送波して行う。このため、音波の指向軸が一定して、単体エコーの検出精度が向上する。また、魚体長の推定は、単体エコーのレベルを使用して行うため、魚体長の推定値の精度も向上する。
【００４８】
次に、魚の遊泳方向、遊泳軌跡の解析を行うエコートレース解析について述べる。エコートラッキングによりエコートレース解析を行うためには，まず単体エコーを識別する必要がある。エコーのトラッキングは、自船からみた魚の３次元位置をスプリッドビーム法より求め使用している。
【００４９】
図１０にエコートレース解析の手順をフローチャートで示す。図１０に示すように、ステップＳ１１からＳ１５までは、図６に示すステップＳ１からＳ６と同一の内容であるため説明を省略する。図１０に示すステップＳ１６のエコートラッキングについて詳述する。
【００５０】
図１１に魚のエコートラッキングの原理を示す。図１１に示すように，魚の位置ベクトルをｘで表し，音波の送波順番を示す添字ｉ（以後、ピングという）をつけて，ｘｉは，ｉピングでの魚の位置ベクトルを表すものとする。なお、音波の送信は、動揺計３のピッチ角およびロール角の出力信号が予め設定した設定値の範囲内のときに、行われるようになっている。
【００５１】
ｉピングで得られるｎｉ個の単体エコーとｉ＋１ピングで得られるｎｉ＋１個の単体エコーについて，ｉピングのｊ番目（１≦ｊ≦ｎｉ）の単体エコーとｉ＋１ピングでのｋ番目（１≦ｋ≦ｎｉ＋１）の単体エコーの距離を計算する。最大（ｎｉ）×（ｎｉ＋１）個の組み合わせの中で，あらかじめ設定した第１の予測最大半径Ｒ０以下でかつ最短のものを同じ魚から帰ってきたエコーの候補とし，この２点から決まる直線上でｉ＋２ピングでの推定位置ベクトルＸｐを求める。
【００５２】
ｉ＋２ピングで得られたエコーのうち，第２の予測最大半径Ｒ内で推定位置にもっとも近いものを同じ魚から得られたエコーとして，魚に番号をつける。この番号は，ｉピングの魚にすでに番号があれば，その番号を付け，なければ，既存の番号＋１とする。ｉ＋２ピング目で，第２の予測最大半径Ｒ内にエコーがなければ，ｉ，ｉ＋１ピングで候補とされたエコーは捨てる。第２の予測最大半径Ｒは，ｉピングとｉ＋１ピングの間の移動距離Ｌとパラメータ積αＬとし，Ｌが大きければ，第２の予測最大半径も大きくなる。このような処理を繰り返すことによりトラツキングを行っていく。また，第１の予測最大半径Ｒ０は，パラメータとしてあらかじめ与える魚の最大遊泳速度と送信周期の積で与える。
【００５３】
エコートレースは、単体エコーの検出を行ってトラッキングを行うため、船の動揺によりトラッキングの検出精度が低下することがあるが、本発明によるエコートラッキング方法では、動揺計３により船の傾きをチェックして、船の傾きが設定値範囲内のときに音波を送波するため、音波の指向軸が変動することなく、常に一定しているため、安定したトラッキングが可能となる。
【００５４】
【発明の効果】
以上述べたように本発明によれば、送受波器の機構を変えることなく、船の動揺の影響を最小限に抑えた送受信動作を行うことにより、単体魚からの反射エコーをより高精度に得ることが可能とる。
【００５５】
また、本発明は、船体に動揺計を設置することにより安定した送受信動作を行うことができるため、送受波器を船の動揺に追従した機械的なジンバル構造にする必要がなく、装置のコストを低く抑えることが可能となる。
【図面の簡単な説明】
【図１】単体エコー検出装置の構成を示す図である。
【図２】動揺計の構成を示す図である。
【図３】動揺計のマイクロコンピュータのメモリに記憶されたプログラムの構成を示す図である。
【図４】積分演算の伝達関数のブロック線図を示す図である。
【図５】ロール角、ピッチ角と方位角および地頂角との関係を示す図である。
【図６】単体エコーの検出および魚体長の推定までの手順を示すフローチャートである。
【図７】（ａ）は、動揺計からのピッチ角およびロール角の時系列変化を示し、（ｂ）は、デジタル信号処理部から送信増幅器への発振指令のタイミングを示す図である。
【図８】（ａ）は、動揺計からの地頂角の時系列変化を示し、（ｂ）は、デジタル信号処理部から送信増幅器への発振指令のタイミングを示す図である。
【図９】単体エコーの検出の判定規準を示す図である。
【図１０】エコートレース解析の手順を示すフローチャートである。
【図１１】単体エコーからのトラッキングの原理を説明した図である。
【図１２】（ａ）は、ターゲットが送受波器の中心軸付近に存在する場合、（ｂ）は中心軸より離れた位置に存在する場合のターゲットの位置と受信レベルとの関係を示す図である。
【符号の説明】
１ 単体エコー検出装置
３ 動揺計（動揺検出装置）
３ａ 角速度計（圧電型振動ジャイロ）
３ｂ ＡＤ変換器
３ｃ デジタルフィルタ（マイクロコンピュータ）
３ｄ 出力部
５ 送受波器
６ 送信受信切替器
７ 送信増幅器
８ 受信増幅器
９ 受信位相検出器
１０ デジタル信号処理部
１５ 中央処理装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a single echo detection method with a motion correction, a single echo detection device, and an echo tracking method capable of obtaining a reflected echo from a single fish with high accuracy without being affected by the motion of a hull.
[0002]
[Prior art]
Fish finder is used for fisheries resource survey and grasping fish length before putting fishing gear into the sea. The weighing fish finder detects a single echo reflected from a single fish, estimates the fish length from the single echo, and outputs information such as the fish length to the outside.
[0003]
The weighing fish finder transmits a sound wave through the entire transducer and receives a reflected wave from the target. Since sound waves have directional characteristics, the target shown in FIG. 12A exists near the directional axis of the transmitter / receiver 5, and the target shown in FIG. 12B exists at a position away from the directional axis. In FIG. 12A and FIG. 12B, there is a difference between the magnitudes of the reception levels. Since the difference in the reception level causes an error when estimating the fish length, it must be corrected so as to eliminate the influence of the directivity. As the correction means, there are a method of obtaining the position angle of the target, and a method of transmitting and receiving waves which are not affected by the directivity.
[0004]
As a method for detecting the position angle θ of a single fish (target) with respect to the directional axis of the transducer 5 shown in FIG. 12B, a split beam method is known (for example, see Patent Document 1). The split beam method is a method in which four reception beams (a front beam, a rear beam, a left beam, and a right beam) are formed, and a time difference between reflected echoes from a single fish is detected to obtain a position angle θ. As a method for removing the influence of directivity, a dual beam method is known (for example, see Patent Document 1). The dual beam method is a method in which two narrow beams and wide receiving beams are used to remove the influence of directivity from the intensity of the reflected echoes of the narrow and wide beams from a single fish.
[0005]
However, when the ship shakes, the pointing axis of the transducer 5 fluctuates, and an error occurs in the detected position angle. Therefore, it is necessary to transmit and receive sound waves by correcting the beam in accordance with the motion of the ship. To correct the beam, a method of configuring a transducer in which a plurality of transducers are arranged, controlling the phase of each transducer to form directivity corresponding to the fluctuation, and stabilizing the directional axis of the transducer ( For example, there is a method in which the transducer is made to have a mechanical gimbal structure so that the transducer follows the fluctuation of the ship.
[0006]
It is important not only to estimate the fish length but also to know the behavior of the fish such as the swimming direction and the swimming speed of the fish in a natural state. In order to know the behavior of the fish, observation is performed with an underwater camera,
1) Since it is difficult to fix the camera, an error occurs in estimating the tilt angle of the target.
2) Lighting may be required in the sea, and observation in a natural state is not possible.
3) Observation is possible only at a short distance.
For this reason, a single echo is detected by the split beam method, and the behavior of the fish is observed by echo tracing.
[0007]
[Patent Document 1]
Japanese Patent No. 2620983 [Patent Document 2]
JP-A-6-201818
[Problems to be solved by the invention]
The split beam method and the dual beam method are effective for detecting the position of the fish with respect to the directional axis of the transducer. However, when the hull oscillates, the directional axis of the transducer fluctuates and the angle of the beam incident on the fish is not constant, so the detection directivity of a single fish is affected by the reflection directivity of the fish. Gets worse. Therefore, as described above, it is necessary to correct the beam in accordance with the sway of the hull.
[0009]
However, the method of stabilizing the directional axis by a transducer having a plurality of transducers arranged increases the size of the transducer and complicates the control of the transmitted and received waves. Also, the method in which the transducer is made to have a mechanical gimbal structure so that the transducer follows the sway of the ship requires a special mechanism in the device, and the configuration becomes complicated and large, and the device becomes large. There is a problem that it becomes expensive.
[0010]
Accordingly, the present invention provides a single echo detection method with a motion compensation, a single echo detection device, and an echo tracking method that transmit and receive at an optimal timing in consideration of the motion of a ship and can obtain a reflected echo of a single fish with higher accuracy. The purpose is to provide.
[0011]
[Means for Solving the Problems]
The method for detecting a single echo with the sway correction according to the present invention includes the steps of detecting the sway of the hull with a tilt angle, and determining whether the detected tilt angle is within a set value range including a preset 0 degree, Transmitting the sound wave to the sea floor when the inclination angle is within the range of the set value, receiving the sound wave, and determining whether the reception level of the sound wave is within a predetermined reference range; Detecting as a single echo when the level is within the standard range.
[0012]
In addition, the single echo detection device according to the present invention includes a hull motion detection unit that detects sway of the hull at an inclination angle, a sound wave transmission unit that transmits a sound wave to the sea floor, a sound wave reception unit that receives a sound wave, and a sound wave reception unit. A single echo detection unit for analyzing a signal from the unit and detecting a single echo, when the inclination angle from the hull sway detection unit is within a set value range including a preset 0 degree. , Wherein the sound wave transmitting means transmits a sound wave to the sea floor.
[0013]
Further, the hull sway detection means of the single echo detection device according to the present invention comprises a sway detection device which detects the sway of the hull by the inclination angle and outputs the detected inclination angle to the outside.
[0014]
Also, the echo tracking method according to the present invention includes a step of detecting the motion of the hull as a tilt angle, a step of determining whether the detected tilt angle is within a set value including a preset 0 degree, and a step of determining the tilt angle. Transmitting a sound wave to the sea floor when is within a set value range, receiving the sound wave, and determining whether or not the reception level of the sound wave is within a preset range every time the sound wave is received. A step of detecting as a single echo when the reception level is within a reference range; a step of calculating a target position vector from the single echo; a single echo obtained from the n-th transmission and an (n + 1) -th Calculating the distance between the single echoes obtained from the transmissions of the same, and determining the single echo located within the first predicted circle set in advance and having the shortest distance as the same target. And calculating the estimated position of the target on a straight line determined by the position vectors of the two single echoes determined to be the same target. The simple echo obtained from the (n + 3) th transmission is used to calculate the estimated position from the estimated position. Detecting a single echo closest to the estimated position within the second predicted circle set in advance as the same target.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, with reference to the drawings, embodiments of a single echo detection method, a single echo detection device, and an echo tracking method according to the present invention will be described. FIG. 1 is a diagram showing the configuration of a single echo detection device, FIG. 2 is a diagram showing the configuration of an oscillometer, FIG. 3 is a diagram showing the configuration of a program stored in a memory of a microcomputer of the oscillometer, and FIG. FIG. 5 is a diagram showing a block diagram of a transfer function of an integral operation, FIG. 5 is a diagram showing a relationship between a roll angle, a pitch angle and an azimuth and a zenith angle, and FIG. It is a flowchart which shows the procedure until an estimation.
[0016]
As shown in FIG. 1, a single echo detection device 1 includes a rocker 3 for detecting a roll angle and a pitch angle of a ship, a transducer 5 for transmitting a sound wave and receiving a reflected wave from a target, A transmission / reception switch 6 for switching between a transmission signal and a reception signal with the wave filter 5, a transmission amplifier 7 for oscillating at a predetermined frequency and amplifying the signal, and a reception amplifier 8 for amplifying the reception signal from the transmission / reception switch 6 And a reception phase detector 9 for detecting a phase from a reception signal from the transmission / reception switch 6, and an oscillation command is issued to the transmission amplifier 7 by a signal from the fluctuation meter (motion detection device) 3, and the reception amplifier 8 and the reception phase It comprises a digital signal processing unit 10 for digitally processing a signal from the detector 9 to detect a single echo or the like, and a central processing unit 15 for storing, storing, and processing data from the digital signal processing unit 10. .
[0017]
The oscillating meter 3 detects the roll and pitch inclination angles of the ship. As shown in FIG. 2, an gyro 3a composed of a piezoelectric vibrating gyroscope and an analog signal from the gyro 3a are converted into digital signals. And a microcomputer 3c for performing digital filter processing and the like, and an output unit 3d for outputting roll and pitch tilt angle data to the outside. Note that the fluctuation meter 3 includes an angular velocity meter 3a for detecting rolls and an angular velocity meter 3a for detecting pitch.
[0018]
FIG. 3 shows a configuration of the digital filter processing of the microcomputer 3c. The low-pass filter and the high-pass filter shown in FIG. 3 are stored in a memory of the microcomputer 3c as a program, and the program is executed to perform the filter processing.
[0019]
The piezoelectric vibrating gyroscope of the oscillometer 3 vibrates by utilizing the piezoelectric characteristics of piezoelectric ceramics, and when a rotational angular velocity Ω is applied to the vibration, a Coriolis force is generated and the force is converted into a voltage. The generated Coriolis force is proportional to the angular velocity Ω. Since the output is a value proportional to the angular velocity Ω, the output value is integrated to calculate the angle. In calculating the angle, the output voltage from the gyro 3a is converted into digital data by the AD converter 3b. Note that the sampling frequency of the AD converter 3b is 20 Hz. Next, filtering is performed by a low-pass filter including the microcomputer 3c. The low-pass filter is for cutting noise included in a signal output from the gyro 3a. Next, the signal from the low-pass filter is processed by a high-pass filter as an integrator including the microcomputer 3c.
[0020]
Hereinafter, the low-pass filter and the high-pass filter incorporated in the oscillometer 3 will be described. Assuming that the output signal of the angular velocity from the vibrating gyroscope is h (t) = A · e (jωt), the angle is calculated by integrating the angular velocity. Assuming that the angle is H (t), H (t) = A / (jω) · e (jωt).
[0021]
Simple time integration of the discretized angular velocity h (t) gives:
H (t) = Δt · h (t) + H (t−1). However, due to the drift and nonlinearity of the piezoelectric vibrating gyroscope, the simple time integral diverges. For this reason, the low frequency component is removed by feeding back the result of integration a plurality of times and subtracting it from the input. FIG. 4 is a block diagram of a transfer function of the integral operation. As shown in FIG. 4A, the integration of the input signal is performed twice, and the signal is fed back after each integration. FIG. 4B is a block diagram showing the transfer function shown in FIG. 4A as one transfer function.
[0022]
In order to remove the low frequency component of the signal, the integration processing shown in FIG. 4 is performed by a high-pass filter. As the high-pass filter, a Butterworth filter is used. The basic expression (1) of the second-order Butterworth filter is given by
(Equation 1)

It is. In the case of a low-pass filter, s / ω is substituted for s in the basic equation (1), and in the case of a high-pass filter, ω / s is substituted for s. Note that ω indicates an angular frequency.
The transfer function of the second-order Butterworth high-pass filter is shown by (2).
[0024]
(Equation 2)

Since the vibrating gyroscope already has a differential element when the angular velocity is output, the final transfer function is (3).
[0025]
[Equation 3]

Next, sZ conversion is performed to create a second-order IIR digital filter.
[0026]
(Equation 4)

By substituting
(Equation 5)

From the recurrence formula,
(Equation 6)

Is obtained. Note that a0 to a2 and b0 to b2 are coefficients.
[0029]
The oscillating meter 3 performs digital processing of a low-pass filter and a high-pass filter on the angular velocity from the gyro 3a, and outputs roll and pitch inclination data.
[0030]
Next, calculation of the azimuth angle and the apex angle by the rocker 3 from the data of the roll and pitch inclination angles will be described. Hereinafter, the roll and pitch inclination angles are referred to as a roll angle and a pitch angle, respectively. As shown in FIG. 5, the azimuth angle φ and the zenith angle θ indicate angles from a reference axis (X, Y, Z) with respect to a normal vector direction of the transducer 5 mounted on the ship. From the azimuth angle φ and the apex angle θ, the direction of the beam transmitted and received from the transducer 5 can be known.
[0031]
The conversion into the azimuth angle φ and the zenith angle θ is performed by executing the azimuth and zenith angle conversion processing program of the microcomputer 3c shown in FIG. 3 from the data of the roll angle β and the pitch angle α shown in FIG. Done. Note that the description of the conversion from the roll angle and the pitch angle to the azimuth angle and the apex angle is omitted, but when the pitch angle or the roll angle is 0 degrees, attention must be paid to the following matters.
1) When the pitch angle or the roll angle is 0 degrees, the following cases are required.
{Circle around (1)} When the pitch angle is 0 degree, the azimuth is +90 degrees (roll angle: negative sign) or -90 degrees (roll angle: positive sign) depending on the sign of the roll angle. The vertex angle is the absolute value of the roll angle.
{Circle around (2)} When the roll angle is 0 degree, the azimuth angle is 0 degree (pitch angle: positive sign) or 180 degrees (or -180 degrees, pitch angle: negative sign) depending on the sign of the pitch angle. The vertex angle is the absolute value of the pitch angle.
2) When both the pitch angle and the roll angle are 0 degrees, the apex angle is 0 degrees, but the azimuth angle cannot be specified.
[0032]
As described above, the roll angle and the pitch angle of the ship are detected by the motion meter 3. The oscillating meter 3 can also output the azimuth angle and the apex angle by calculation from the roll angle and the pitch angle.
[0033]
Although the low-pass filter and the high-pass filter are digital filters formed by software processing, the low-pass filter and the high-pass filter may be configured by analog circuits. However, since the filter characteristics of an analog filter are fixed, the filter characteristics cannot be easily changed. The digital filter has an advantage that a filter characteristic such as a cutoff frequency can be easily changed.
[0034]
Hereinafter, a method of detecting a single echo with the motion compensation using the motion meter 3 will be described. A single echo is an echo reflected by a single fish extracted from the reception level of a received wave. The length of the fish can be estimated by detecting a single echo.
[0035]
FIG. 6 is a flowchart showing the procedure from the detection of a single echo to the estimation of the fish length. The detection of a single echo is performed using the split beam method. As shown in FIG. 6, for detecting a single echo from the reception level of a reception wave, first, the pitch angle and the roll angle of the ship are detected by the motion meter 3 (step S1). It is checked by the oscillometer 3 whether the pitch angle and the roll angle are within a set value range including a preset angle of 0 degree (step S2). When the pitch angle and the roll angle are out of the range of the set values, the process proceeds to step S1. When the pitch angle and the roll angle are within the set values, the sound wave is transmitted from the transducer 5 (step S3).
[0036]
FIG. 7A shows a time series change of the pitch angle and the roll angle from the oscillometer 3. As shown in FIG. 7A, when the pitch angle and the roll angle from the oscillometer 3 are within the range of the set values (time T1 to T5 shown in FIG. 7B), transmission from the digital signal processing unit 10 is performed. An oscillation command (shown in FIG. 7B) is output to the amplifier 7. Further, as shown in FIG. 8A, when the zenith angle calculated from the pitch angle and the roll angle is within a range of a set value including a preset angle of 0 degree (the time shown in FIG. 8B). From T10 to T14), an oscillation command (shown in FIG. 8B) may be issued to the transmission amplifier 7. The transmission cycle is controlled so as not to be shorter than the acoustically effective cycle.
[0037]
By transmitting a sound wave when the pitch angle and the roll angle or the apex angle are within a set value including a preset angle of 0 degree, the directivity axis of the sound wave is always constant.
[0038]
The reflected wave of the sound wave from the target (fish body) is received by the transducer 5 (step S4). The reception signal of the reflected wave (beam) from the target is amplified and rectified by the reception amplifier 8 to become level information. Further, a reception phase detector 9 amplifies and modulates the reception signals of the front beam, rear beam, left beam, and right beam of the transmitter / receiver 5 to detect phase information.
[0039]
Next, a single echo is detected from the signal from the receiving amplifier 8 (step S5). Level information obtained by the receiving amplifier 8 performs AD conversion to measurement range fraction of time at a predetermined sampling interval, and calculates the data obtained by AD conversion, converts the reception level E _R. From the received level E _R, to extract only a single echo reflected from the single fish. Relationship Ts obtained from the reception level E _R and single fish is a reception coefficient T _R, the distance r, the absorption water reducing coefficient beta, if the directivity function of the circular transducer 5 and D (theta), alone From the echo sonar equation,
[0040]
(Equation 7)

Can be expressed as If the reception level E _T in consideration of attenuation of the reception level E _R of formula (4),
[0041]
(Equation 8)

Can be expressed as A single echo is detected from the data string of the value shown on the left side of Expression (5). FIG. 9 shows the 、 level, レ ベ ル level pulse width, base level, and base level pulse width that are the criteria for a single echo. Also, a portion indicated by the symbol ● in Fig. 9 is a E _{T 2} ^/ _{T R} data used in the processing of a single echo detection. D (θ) ⁴ · Ts is a value that satisfies the criteria of the level and the pulse width, finds the maximum value of the pulse determined to be a single echo, and averages n pieces of data toward shallow data.
[0042]
Next, the position angle of the target is detected (step S6). The phase information from the reception phase detector 9 is subjected to A / D conversion at a predetermined sampling interval for a time corresponding to the measurement range, and converted into electrical angles δx and δy. Reception level E reception phase detector 9 of a timing obtained from the electrical angle δx corresponding to the maximum value of _R, .delta.y to detect the m pieces of data toward the shallow data. At this time, when the values of the maximum value-minimum value of δx and δy in the m models are △ δx and Δδy, respectively, it is determined whether or not these values are smaller than the reference variation. If the condition is satisfied, the averaging process is performed on δx and δy in the m models. Using this average result, the position angle θ is calculated using Expression (6).
[0043]
(Equation 9)

Here, d indicates the wave number, and k indicates the center distance of the phase beam array of the transducer.
[0044]
The directivity function D (θ) of the transducer 5 is obtained from the position angle θ detected in (6), and Ts is calculated from (5). Equation TS = 10log ₁₀ Ts showing the relationship between TS and Ts
Is calculated from (step S7).
[0045]
Next, the fish length is estimated (step S8). The estimation of the fish length (L) is obtained by substituting the TS value into equation (7).
[0046]
TS = 20 log ₁₀ (L) + TScm (7)
Note that the part of TScm in the equation (7) is called a standardized TS and is a value set by the user. By setting the standardized TS, it is possible to estimate the fish length for multiple fish species.
[0047]
As described above, the detection of the single echo is performed by checking the inclination of the ship with the motion meter 3 and transmitting a sound wave when the inclination of the ship is within the set value range. For this reason, the directivity axis of the sound wave is constant, and the detection accuracy of a single echo is improved. Since the estimation of the fish length is performed using the level of the single echo, the accuracy of the estimation value of the fish length is also improved.
[0048]
Next, an echo trace analysis for analyzing a swimming direction and a swimming locus of a fish will be described. In order to perform echo trace analysis by echo tracking, it is first necessary to identify a single echo. The echo tracking uses the three-dimensional position of the fish as seen from the own ship using the split beam method.
[0049]
FIG. 10 is a flowchart showing the procedure of the echo trace analysis. As shown in FIG. 10, steps S11 to S15 have the same contents as steps S1 to S6 shown in FIG. The echo tracking in step S16 shown in FIG. 10 will be described in detail.
[0050]
FIG. 11 shows the principle of fish echo tracking. As shown in FIG. 11, the position vector of the fish is represented by x, and a subscript i (hereinafter referred to as ping) indicating the transmission order of the sound waves is added, and xi represents the position vector of the fish at i-ping. The transmission of the sound wave is performed when the output signals of the pitch angle and the roll angle of the oscillating meter 3 are within the range of preset values.
[0051]
Of the ni single echoes obtained by the i-ping and the ni + 1 single echoes obtained by the i + 1 ping, the j-th (1 ≦ j ≦ ni) single echo of the i-ping and the k-th (1 ≦ k ≦) of the i + 1 ping The distance of the single echo of (ni + 1) is calculated. Among the maximum (ni) × (ni + 1) combinations, the shortest one that is less than or equal to the first predicted maximum radius R0 and that is the shortest is set as a candidate for an echo returned from the same fish, and on a straight line determined from these two points. To obtain an estimated position vector Xp at i + 2 ping.
[0052]
Among the echoes obtained by the i + 2 ping, those closest to the estimated position within the second predicted maximum radius R are numbered as echoes obtained from the same fish. This number is assigned to the i-ping fish if it already has a number, otherwise the existing number + 1. At the (i + 2) th ping, if there is no echo within the second predicted maximum radius R, the echo set as a candidate in the i, i + 1 ping is discarded. The second predicted maximum radius R is a moving distance L between i-ping and i + 1-ping and a parameter product αL. If L is large, the second predicted maximum radius is also large. Tracking is performed by repeating such processing. Further, the first predicted maximum radius R0 is given by the product of the maximum swimming speed of the fish previously given as a parameter and the transmission cycle.
[0053]
In the echo trace, since tracking is performed by detecting a single echo, the accuracy of tracking detection may decrease due to the motion of the ship. However, in the echo tracking method according to the present invention, the tilt of the ship is checked by the motion meter 3. Since the sound wave is transmitted when the inclination of the ship is within the set value range, the directional axis of the sound wave does not fluctuate and is always constant, thereby enabling stable tracking.
[0054]
【The invention's effect】
As described above, according to the present invention, the reflected echo from a single fish can be more accurately reflected by performing the transmitting / receiving operation while minimizing the effect of the motion of the ship without changing the mechanism of the transducer. It is possible to get.
[0055]
Further, according to the present invention, since a stable transmission / reception operation can be performed by installing an oscillating meter on the hull, there is no need to use a mechanical gimbal structure that follows the sway of the ship, thereby reducing the cost of the apparatus. Can be kept low.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a single echo detection device.
FIG. 2 is a diagram showing a configuration of a wobble meter.
FIG. 3 is a diagram showing a configuration of a program stored in a memory of a microcomputer of the oscillometer.
FIG. 4 is a diagram showing a block diagram of a transfer function of an integral operation.
FIG. 5 is a diagram illustrating a relationship among a roll angle, a pitch angle, an azimuth angle, and a vertex angle.
FIG. 6 is a flowchart showing a procedure up to detection of a single echo and estimation of a fish body length.
FIG. 7A is a diagram illustrating a time series change of a pitch angle and a roll angle from an oscillating meter, and FIG. 7B is a diagram illustrating a timing of an oscillation command from a digital signal processing unit to a transmission amplifier.
FIG. 8A is a diagram showing a time series change of a zenith angle from an oscillometer, and FIG. 8B is a diagram showing a timing of an oscillation command from a digital signal processing unit to a transmission amplifier.
FIG. 9 is a diagram showing criteria for detecting a single echo.
FIG. 10 is a flowchart illustrating a procedure of an echo trace analysis.
FIG. 11 is a diagram illustrating the principle of tracking from a single echo.
12A is a diagram illustrating a relationship between a target position and a reception level when the target is located near the central axis of the transducer, and FIG. It is.
[Explanation of symbols]
1 Single echo detector 3 Shaking meter (shaking detecting device)
3a Angular velocity meter (piezoelectric vibration gyro)
3b AD converter 3c Digital filter (microcomputer)
3d output unit 5 transmitter / receiver 6 transmission / reception switch 7 transmission amplifier 8 reception amplifier 9 reception phase detector 10 digital signal processing unit 15 central processing unit

Claims (4)

Detecting the motion of the hull based on the tilt angle; determining whether the detected tilt angle is within a set value range including a preset 0 degree; and detecting the sound wave when the tilt angle is within the set value range. Transmitting the sound wave to the sea floor, receiving the sound wave, and determining whether the reception level of the sound wave is within a predetermined reference range, and as a single echo when the reception level is within the reference range Detecting the single echo with shaking correction. Hull motion detection means for detecting the motion of the hull at an angle of inclination, sound wave transmission means for transmitting sound waves to the sea floor, sound wave reception means for receiving sound waves, and analysis of signals from the sound wave reception means to detect a single echo A single echo detecting device that transmits a sound wave to the sea floor when the inclination angle from the hull fluctuation detecting device is within a set value including a preset 0 degree. A single echo detection device characterized by being made to wave. The single echo detection device according to claim 2, wherein the hull motion detection means is a motion detection device that detects the motion of the hull based on a tilt angle and outputs the detected tilt angle to the outside. Detecting the motion of the hull based on the tilt angle; determining whether the detected tilt angle is within a set value range including a preset 0 degree; and detecting the sound wave when the tilt angle is within the set value range. Transmitting the sound wave to the sea floor, receiving the sound wave, and determining whether the reception level of the sound wave is within the range of a preset standard every time the sound wave is received, and the reception level is within the range of the standard. The step of detecting as a single echo at the time of, the step of calculating the position vector of the target from the single echo, and the step between the single echo obtained from the nth transmission and the single echo obtained from the (n + 1) th transmission. Calculating the same target, and determining the single echo located within the first predicted circle set in advance and having the shortest distance as the same target. Calculating the estimated position of the target on a straight line determined by the position vector of the single echo of the point; and obtaining the single echo obtained from the (n + 3) th transmission in the second predicted circle set in advance from the estimated position. Detecting a single echo close to the estimated position as the same target.

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