JP2017156303A - Water bottom altitude detection device, underwater sailing body, and water bottom altitude detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an underwater sailing body to be controlled with high followability to the undulation of a water bottom.SOLUTION: An FLS provided on a UUV 1 transmits a transmission wave beam in a transmission wave angular range including directly below and front downward of the UUV 1 relative to the travel direction of the UUV 1, and receives a reflection wave about which the transmission wave beam was reflected by a sea bottom as a plurality of reception wave beams with different directions. Then, on the basis of the received reflection wave, it calculates sea bottom altitude in front of the UUV 1. The UUV 1 autonomously navigates by feed-forward control on the basis of the calculated front sea bottom altitude.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a water bottom altitude detecting device, an underwater vehicle, and a water bottom altitude detecting method.

An unmanned underwater vehicle (UUV) emits ultrasonic waves (acoustic beams) to the sea floor (water bottom) by a sonar, and receives echoes reflected from the sea floor to investigate the depth of the sea area. May search for sinking objects.
Since these sonars have an appropriate seabed altitude, an underwater vehicle equipped with a sonar must maintain a seabed altitude within an appropriate range for sonar operation.
Further, as shown in FIG. 14, in order to increase the investigation efficiency by minimizing the duplication of the search range for each lane 102 with respect to the investigation area 101 by the underwater vehicle 100, it is necessary to maintain the search width by the sonar. . For this purpose, the underwater vehicle needs to perform altitude control following the undulations of the seabed.

  In order to control the seabed altitude of the underwater vehicle (UUV), it is necessary to measure the seabed altitude of the underwater vehicle. One of the methods for measuring the seabed altitude is a method of measuring the current altitude in the downward direction using a single beam echo sounder (Single-Beam Echo Sounder) or a DVL (Doppler Velocity Log). The method of measuring the altitude directly below the underwater vehicle is generally reliable and accurate because the intensity of the reflected wave from the seabed is strong. However, if feedback control is performed on the underwater vehicle based on the measurement of the current altitude immediately below the underwater vehicle, the control is delayed when the water depth changes in the traveling direction of the underwater vehicle. For this reason, it is preferable to measure the sea floor altitude in front of the underwater vehicle and perform feedforward control using the result.

  As a method for measuring the forward altitude of an underwater vehicle, for example, an altimeter such as a single-beam echo sounder that launches a very thin pencil beam on the sea floor is installed in front of and under the underwater vehicle. To measure the altitude ahead.

  Patent Document 1 discloses an underwater vehicle including a plurality of distance sensors (single beam echo sounders) and an altitude estimation unit. In this underwater vehicle, the plurality of distance sensors measure the distance between the airframe and the seabed in each of a plurality of directions having different depression angles with respect to the horizontal direction. Further, the altitude estimation unit estimates the altitude from the seabed of the aircraft at each of the plurality of forward positions based on the distances and depression angles measured in each of the plurality of directions.

  Further, there is a method using a two-dimensional image sonar. For example, a two-dimensional image sonar is installed in a vertical plane with respect to the underwater vehicle, and the sea bottom is detected by image processing or the like to calculate the front sea bottom altitude. In addition, a two-dimensional image sonar is installed to be tilted downward with respect to the horizontal plane with respect to the underwater vehicle, and the sea bottom is detected by image processing or the like to calculate the front sea bottom altitude.

JP, 2014-121927, A

However, in altitude measurement using a single beam echo sounder or the like, the echo level decreases as the angle of incidence of the acoustic beam on the seabed becomes shallower, that is, the lower front of the underwater vehicle, the farther downward. For this reason, the measurable horizontal distance to the bottom of the sea floor is short (about 1 to 2 times the altitude), and the followability of the underwater vehicle is particularly poor when the sea bottom is large.
In addition, since the underwater vehicle disclosed in Patent Document 1 has a large number of distance sensors, a large mounting space is required inside the underwater vehicle.
Further, in the two-dimensional image sonar, the measurement accuracy is low because the seabed is detected based on the density of the image, and it is difficult to use the control for autonomous navigation such as UUV.

  The present invention has been made in view of such circumstances, and it is possible to control the underwater vehicle with high followability with respect to the undulation of the bottom of the water. The purpose is to provide an altitude detection method.

  In order to solve the above problems, the water bottom height detecting device, the underwater vehicle and the water bottom height detecting method of the present invention employ the following means.

  The water bottom altitude detecting device according to the first aspect of the present invention is provided in an underwater vehicle that travels underwater, and is located directly below and in front of the underwater vehicle with respect to the traveling direction of the underwater vehicle. A transmitting means for transmitting a transmission beam in a predetermined angle range, a receiving means for receiving a reflected wave reflected from the bottom of the water by a plurality of receiving beams having different directions, and the reflection received by the receiving means. Processing means for calculating bottom elevations in a plurality of directions ahead of the underwater vehicle based on the wave.

  According to this configuration, the transmission beam is transmitted in a predetermined angle range including directly under and under the underwater vehicle with respect to the traveling direction of the underwater vehicle. And since the wave bottom height in front of the underwater vehicle is calculated based on the reflected wave reflected by the bottom of the transmitted beam, this configuration uses the calculated water height to make the underwater vehicle undulate. The followability can be controlled to a high level.

  In the first aspect, the processing means sets a non-calculation range according to the bottom height calculated based on the reflected wave from directly below the underwater vehicle, and the reflected wave beyond the non-calculated range is set. The bottom height may be calculated based on

  Since the intensity of the reflected wave of the direct component of the transmitted beam transmitted in a predetermined angle range including directly under and under the underwater vehicle is strong, the received beam in front of other than directly below is reflected directly under the seabed by the side lobe. Waves may be received, leading to false detection of the water level at the front. According to this configuration, the range that may be affected by the reflected wave from directly under the underwater vehicle is set, and the water bottom height ahead of the underwater vehicle is calculated based on the reflected wave beyond this range. As a result, erroneous detection of the bottom height can be suppressed.

  In the first aspect, the processing means may calculate the water bottom altitudes at a plurality of points within a predetermined angle range as a front lower part of the underwater vehicle.

  According to this configuration, since the bottom height is calculated only in a meaningful direction for controlling the altitude of the underwater vehicle, the calculation time required for the calculation can be shortened and the power consumption of the bottom height detector can be reduced.

  In the first aspect, the bottom height may be averaged for each of the plurality of bottom heights calculated based on the reflected wave having the same depression angle.

  According to this configuration, it is possible to reduce an error in the calculated bottom height.

  The underwater vehicle according to the second aspect of the present invention provides a selected one depression angle among the above-mentioned water bottom altitudes calculated based on the above-described water bottom height detection device and the reflected waves reflected at a plurality of depression angles. Control means for feedforward controlling the underwater vehicle using the corresponding bottom height.

  According to this configuration, the followability of the underwater vehicle can be controlled with respect to the undulation of the bottom of the water.

  In the second aspect, the altimeter that measures the bottom height of the underwater vehicle and the measured value by the altimeter and the bottom height by the bottom height detection device are compared to compare the bottom height by the bottom height detection device. An accuracy determining means for determining the accuracy of the water bottom altitude, and when the accuracy of the water bottom altitude used in the control means is low, the water bottom altitude used in the control means is determined based on the reflected wave having a deeper depression angle. When the water bottom altitude used in the control means is high, the water bottom altitude used in the control means is calculated based on the reflected wave at a shallow depression angle. You may switch to.

  According to this configuration, the accuracy of the pre-reading water bottom altitude is determined by comparing the current water bottom height with the current water bottom height pre-read by the water bottom altitude detecting device in the past. The angle of the reflected wave used to calculate the water bottom altitude used for the feedforward control is switched so that the control of the underwater vehicle can be optimized automatically. As the altimeter, for example, a single beam echo sounder, a Doppler velocimeter (DVL), or the like is applicable.

  In the second aspect, when the underwater vehicle performs a rapid infiltration, the bottom height detecting device performs a bottom detection detection process for determining whether or not a bottom has been detected, and the bottom is detected by the bottom detection determination process. When detected, the water bottom altitude detecting device may end the water bottom detection determination process and perform a process of calculating the water bottom altitude in front of the underwater vehicle.

  According to this configuration, it is possible to prevent the water bottom altitude detecting device from performing the process of calculating the water bottom altitude and erroneously detecting the water bottom even though the water bottom is so deep that the water bottom altitude detecting device cannot measure the water bottom.

  In the second aspect, when the water bottom altitude at which the ground speed can be measured by the ground speed meter is reached, the aircraft pitch angle of the underwater vehicle is raised, and even if the transition from rapid infiltration to gentle infiltration is made. Good.

  According to this configuration, the underwater vehicle can easily shift from the rapid infiltration state to the gentle infiltration.

  In the second aspect, in the state in which the underwater vehicle is infiltrated and the bottom of the water is detected by the bottom detection detection process, the bottom of the sea level detector detects the bottom height in order from the reflected wave having a deep depression angle. If the straight line distance to the measured bottom position exceeds the maximum detection distance, the bottom height may not be calculated at a shallower depression angle.

  According to this configuration, although the depression angle is shallow and the bottom of the water cannot be measured, the bottom of the sea level detection device can perform a process of calculating the bottom of the water to prevent erroneous detection of the bottom of the water.

  The underwater altitude detection method according to the third aspect of the present invention includes a transmitting means provided in an underwater vehicle that travels underwater, and a position immediately below the underwater vehicle with respect to the traveling direction of the underwater vehicle. And a first step of transmitting a transmission beam in a predetermined angle range including the front and lower sides, and a second step of receiving a reflected wave reflected from the bottom of the water by a receiving means with a plurality of reception beams having different directions. And a third step of calculating bottom heights in a plurality of directions in front of the underwater vehicle based on the reflected wave received by the receiving means.

  ADVANTAGE OF THE INVENTION According to this invention, it has the effect that followability can be controlled highly with respect to the undulation of a bottom of water.

It is a side view which shows the structure of UUV which concerns on embodiment of this invention. It is a schematic diagram which shows the shape of the transmission beam transmitted from FLS which concerns on embodiment of this invention. It is a figure which shows the operation state of UUV which concerns on embodiment of this invention. It is a functional block diagram which shows the control structure of UUV which concerns on embodiment of this invention. It is a functional block diagram which shows the function of FLS which concerns on embodiment of this invention. It is the schematic diagram which showed the example of the search by FLS which concerns on embodiment of this invention. It is a flowchart which shows the flow of the search process which concerns on embodiment of this invention. It is a schematic diagram which shows the outline | summary of the averaging process of the FLS depth value which concerns on embodiment of this invention. It is a schematic diagram which shows the outline | summary of the depth value switching process which concerns on embodiment of this invention. It is a functional block diagram which shows the function of the UUV controller which concerns on the seabed altitude control which concerns on embodiment of this invention. It is the figure which showed the state which UUV which concerns on embodiment of this invention transfers from a rapid infiltration to a gentle infiltration. It is the figure which showed the state in which UUV which concerns on embodiment of this invention is performing gentle infiltration. It is the figure which showed the other state where UUV which concerns on embodiment of this invention is performing rapid infiltration. It is the schematic diagram which showed the example of the search path | route for every voyage line with respect to the investigation area by an underwater vehicle.

  EMBODIMENT OF THE INVENTION Below, one embodiment of the water bottom altitude detection apparatus, underwater navigation body, and water bottom altitude detection method which concern on this invention is described with reference to drawings.

  FIG. 1 is a side view showing the configuration of the underwater vehicle according to the present embodiment. In the present embodiment, as an example of an underwater vehicle, an unmanned underwater vehicle (UUV) that autonomously travels by inertial navigation is used. Moreover, although this embodiment demonstrates as an example that UUV navigates in the sea, it is not restricted to this, UUV may sail a river, a lake, etc.

  The UUV 1 according to this embodiment includes a fuselage 2, a propulsion unit 3, a front horizontal rudder 4, a rear horizontal rudder 5, a front vertical rudder 6, a rear vertical rudder 7, a DVL (Doppler Velocity Log) 8, and an FLS (Forward Looking Sonar). 9 is provided.

  The airframe 2 includes a driving source for driving the propulsion unit 3, the front horizontal rudder 4, the rear horizontal rudder 5, the front vertical rudder 6, and the rear vertical rudder 7. Examples of the drive source include a battery that stores electric power and an electric motor that is driven by electric power from the battery, but may be other types of drive sources. The airframe 2 has a substantially circular cross-sectional shape in a plane orthogonal to the airframe axis A1. In addition, each rudder does not necessarily need to be provided at the front and back, and may be provided only at the rear.

  The UUV 1 travels underwater with a propulsive force obtained by rotating the propeller provided in the propulsion device 3 with a driving source inside the airframe 2 with the direction indicated by the arrow in FIG.

  The front horizontal rudder 4 and the rear horizontal rudder 5 are elevators and are plate-shaped members having a cross-sectional view airfoil shape. The front horizontal rudder 4 is provided one by one on the left and right along a horizontal axis (not shown) extending in the left-right direction (width direction) of the body 2 at the front of the body 2. Similarly, the rear horizontal rudder 5 is provided one by one on the left and right along a horizontal axis (not shown) extending in the left-right direction (width direction) of the body 2 at the rear of the body 2.

  The front vertical rudder 6 and the rear vertical rudder 7 are rudder and are plate-like members having a cross-sectional wing shape, and are provided one above and below the body 2 respectively.

  The front vertical rudder 6 is configured to rotate around a front horizontal axis by a drive motor provided inside the machine body 2. Further, the rear vertical rudder 7 is configured to be rotated around the rear horizontal axis by a drive motor provided in the body 2. By controlling the front vertical rudder 6 and the rear vertical rudder 7, the left and right traveling directions of the UUV 1 can be arbitrarily controlled.

  The DVL 8 is a ground speed meter that is provided on the lower side of the airframe 2 and has a transducer that transmits and receives 3 to 6 acoustic beams and measures the ground speed by the Doppler effect with respect to the seabed. The DVL 8 also measures the altitude directly below the UUV 1 by averaging the direction cosine of the linear distance to the seabed measured with 3 to 6 acoustic beams simultaneously with the ground speed.

The FLS 9 is a forward sonar provided near the tip of the UUV 1 and functions as a seabed altitude detection device.
The FLS 9 transmits a transmission beam (acoustic beam) in a predetermined angle range (hereinafter referred to as a “transmission angle range”) including directly under and under the UUV1, and a reflected wave (“submarine echo” reflected from the bottom of the water). Is also received by a plurality of receiving beams having different directions. Then, the FLS 9 processes the reception signals of the respective reception beams and measures the reception beam direction in front of the UUV1, that is, the sea level in a plurality of directions.

  FIG. 2 is a schematic diagram showing the shape of a transmission beam transmitted from the FLS 9 according to the present embodiment. 2A is a top view, and FIG. 2B is a side view (vertical surface). Note that the surface in the vertical direction with respect to the body axis A1 of UUV1 is referred to as a vertical surface. Also, the upward angle with respect to the horizontal axis is called the elevation angle, and the downward angle with respect to the horizontal axis is called the depression angle. When the airframe pitch angle is 0 °, the airframe axis A1 and the horizontal axis coincide.

  As shown in FIG. 2A, the transmission beam transmitted from the FLS 9 has a relatively small spread in the left-right direction of the UUV1. On the other hand, as shown in FIG. 2 (B), the transmitted beam has a spread in an angular range including directly under and under UUV1 with respect to the vertical plane.

Specifically, the mounting direction of the FLS 9 (hereinafter referred to as “FLS machine shaft”) B is set to a depression angle of about 30 ° when the roll angle of the UUV 1 is 0 °. Then, the transmission beam is transmitted in the form of a sheet within a transmission angle range of ± 60 ° with the FLS mechanical axis B as the central axis, and a transmission fan beam surface is formed. The surface of the transmitting fan beam coincides with the vertical plane. The transmission angle range is an example of ± 60 ° and is not limited thereto.
As shown in FIG. 2 (B), the transmission beam transmitted toward −60 ° (when the upward direction of the transmission angle range is positive) with the FLS mechanical axis B as the central axis. Will measure the seafloor height just below UUV1. The received beam obtained by reflecting directly under UUV1 has the highest intensity, and can be used as a reference for detecting the seabed altitude. In other words, the FLS machine axis B is determined so that the FLS machine axis B of the FLS 9 can transmit a transmission beam from directly under UUV1 to the front. In the present embodiment, as an example of this, the FLS machine axis B is set to a depression angle of 30 °.
Here, the relationship between the transmitted beam and the received beam will be described more specifically by taking the case where the airframe pitch angle is 0 ° as an example.
For example, among the transmission beams transmitted continuously and widely in the transmission angle range ± 60 °, the component in the −60 ° direction is reflected by the seabed directly under UUV1 and received by the received beam directed in the direct downward direction. . The FLS 9 processes the received beam signal to measure the seabed height just below UUV1. Similarly, the component of the transmitted beam whose FLS mechanical axis B is in the direction of 0 ° propagates in the direction of the depression angle of 30 ° and is reflected on the seabed in that direction. The FLS 9 receives this as a received beam with the FLS machine axis B directed in the direction of 0 ° (= a depression angle of 30 °), processes the received beam signal, and measures the forward altitude in the depression angle of 30 ° direction.

  As described above, the FLS 9 transmits the transmission beam in the transmission angle range including the position immediately below and the front lower side of the UUV 1 with respect to the traveling direction of the UUV 1. The FLS 9 receives the reflected wave reflected from the seabed by the plurality of received beams having different directions, and calculates the seabed altitude detection process in front of the UUV1 for each received beam signal. I do.

In other words, the FLS 9 has the same function as the MBES (Multi-Beam Echo Sounder) that is a sounding instrument, but is provided in the vicinity of the tip of the UUV1 and is used for measuring the seabed height in front of the UUV1. In general, the mechanical axis of the MBES provided in the UUV or the like is in a direction directly below the UUV (a depression angle of 90 °), and thus is not used for measuring the front altitude of the UUV.
Even if a single beam echo sounder generally used as an altimeter is provided in front of and under UUV1, only one transmitted beam is transmitted, and therefore only one point in front can be measured. On the other hand, the FLS 9 according to the present embodiment transmits a transmission beam in a sheet shape within a transmission angle range, and electrically forms a necessary number of reception beams in a necessary direction, thereby requiring the front and lower sides. It becomes possible to measure the sea level in the direction.

Next, the operating state of the UUV 1 will be described with reference to FIG.
FIG. 3A shows a state in which UUV1 is cruising around the seabed at a substantially constant altitude. 3B and 3C show a state in which the UUV 1 is infiltrated. That is, the operation state of UUV1 is roughly classified into two operation states in which UUV1 is cruising near the seabed and invading.

  As shown in FIG. 3 (A), when UUV1 is cruising near the seabed at a substantially constant altitude, the depression angle is not more than a certain level within the maximum detection distance that is the maximum distance measurable by FLS9. There is always a seabed. For this reason, measurement of the seafloor altitude by FLS9 is possible.

  As shown in FIG. 3 (B), when UUV1 infiltrates a sea area that is shallow enough to measure the ground speed with DVL8, UUV1 has a gentle aircraft pitch that allows ground speed to be measured with DVL8. Infiltrate at the corner. Also in this case, within the maximum detection distance of the FLS 9, there is always a seabed in the direction where the depression angle is a certain degree or more, and the seabed altitude can be measured by the FLS9.

As shown in FIG. 3 (C), when UUV1 infiltrates a sea area where the ground speed cannot be measured by DVL8, UUV1 has a steep aircraft pitch until ground speed can be measured by DVL8. Infiltrate at an angle (for example, depression angle of 60 ° or more)
This is because the pure inertial navigation tends to diverge the navigation error compared to the speed hybrid inertial navigation using the measurement result of the ground speed by DVL8. This is because the divergence of navigation errors is suppressed by infiltration. In this case, the seabed may not exist within the maximum detection distance of the FLS 9, and the seafloor height may not be measured by the FLS9.

  FIG. 4 is a block diagram showing a control configuration of UUV1.

  The UUV controller 30 is a control unit that controls the entire UUV 1, and includes, for example, a CPU (Central Processing Unit). The UUV controller 30 reads a program stored in a program storage unit 31 such as a ROM (Read Only Memory) into a RAM (Random Access Memory) 32 and executes it. Based on the program, the UUV controller 30 calculates a feedback control amount corresponding to the direct altitude measured by the DVL 8 and a feedforward control amount corresponding to the forward altitude measured by the FLS 9, and outputs a control signal to each elevator. Generate. Note that transmission of control signals from the UUV controller 30 to each unit and transmission of signals from each unit to the UUV controller 30 are performed via the control bus 50.

  The buffer unit 33 includes a plurality of buffers for storing the seabed altitude calculated based on the information acquired by the UUV controller 30 from the DVL 8 and the FLS 9, the aircraft depth detected by the aircraft depth sensor 34, and the like.

  The body depth sensor 34 is a sensor that detects the depth of the UUV1 from the water surface as the body depth. When the UUV controller 30 instructs the aircraft depth sensor 34 to acquire the aircraft depth, the aircraft depth sensor 34 detects the aircraft depth and notifies the UUV controller 30 of it.

  The body posture sensor 35 is a sensor that detects the posture of the UUV1. The airframe attitude sensor 35 includes an airframe axis A1 that passes through an angle (airframe pitch angle) of the airframe axis A1 with respect to the horizontal direction, a rotation angle (roll angle) of the airframe 2 around the airframe axis A1, and a center position C of the UUV1. It is possible to detect the angle (yaw angle) of the body axis A1 with the center axis A2 orthogonal to the center.

  The propeller drive unit 36 controls a drive motor that rotates the propeller included in the propulsion device 3. The UUV controller 30 controls the drive motor that rotates the propeller included in the propulsion device 3 by transmitting a control signal to the propeller drive unit 36.

  The front horizontal rudder drive unit 37 controls a drive motor that rotates the front horizontal rudder 4. The UUV controller 30 controls a drive motor that rotates the front horizontal rudder 4 by transmitting a control signal to the front horizontal rudder drive unit 37.

  The rear horizontal rudder drive unit 38 controls a drive motor that rotates the rear horizontal rudder 5. The UUV controller 30 controls a drive motor that rotates the rear horizontal rudder 5 by transmitting a control signal to the rear horizontal rudder drive unit 38.

  The front vertical rudder drive unit 39 controls a drive motor that rotates the front vertical rudder 6. The UUV controller 30 controls a drive motor that rotates the front vertical rudder 6 by transmitting a control signal to the front vertical rudder drive unit 39.

  The rear vertical rudder drive unit 40 controls a drive motor that rotates the rear vertical rudder 7. The UUV controller 30 controls a drive motor that rotates the rear vertical rudder 7 by transmitting a control signal to the rear vertical rudder drive unit 40.

  The DVL 8 notifies the UUV controller 30 of the measured ground speed and seafloor altitude and stores it in the buffer unit 33.

  The FLS 9 notifies the UUV controller 30 of the measured seabed altitude and stores it in the buffer unit 33.

FIG. 5 is a functional block diagram illustrating functions related to the seabed altitude detection process.
The FLS 9 includes a transmitter 20, a receiver 21, and a signal processing unit 22.

The transmitter 20 transmits a transmission beam in a transmission angle range (−60 ° to + 60 °).
The receiver 21 is a phased array antenna as an example, receives the reflected wave reflected by the transmitted beam, and adjusts and adds the phase of the reflected wave received by each antenna element, thereby increasing the phase adjustment amount. A receiving beam with an appropriate angle is used. The receiver 21 outputs a received beam signal indicating the intensity and phase of the received beam to the signal processing unit 22. Note that numbers corresponding to the angles are sequentially given to the received beam signals.

  The signal processing unit 22 calculates the seabed altitude in front of the UUV1 in order from the position immediately below the UUV1 (90 ° depression angle) based on the received received beam signal, and outputs it to the UUV controller 30. Further, the signal processing unit 22 outputs the calculated seafloor altitude to the buffer unit 33 and stores it in the buffer unit 33.

  The UUV controller 30 feed-forward-controls UUV1 based on the measured seabed altitude.

The UUV 1 performs signal processing on various information necessary for calculating the sea bottom altitude, such as information on the aircraft pitch angle, sea bottom altitude measured by the DVL 8 (hereinafter referred to as “DVL measurement value”), transmission angle range, and the like. The signal processing unit 22 calculates the seafloor altitude using these input various information.
For example, the airframe pitch angle is used to correct the correspondence between the FLS mechanical angle and the depression angle of the received beam.
Since the DVL measurement value is the seafloor height immediately below UUV1, the signal processing unit 22 determines whether the seabed height measured by FLS9 is appropriate by comparing the DVL measurement value with the seafloor height measured by FLS9. It becomes possible.

  With such a configuration, the FLS 9 transmits a transmission beam in a transmission angle range including directly under and under the UUV1 with respect to the traveling direction of the UUV1, and receives a reflected wave reflected from the seabed. Then, the FLS 9 calculates the seabed altitude in front of UUV1 based on the received reflected wave. The UUV 1 autonomously navigates itself by feed-forward control based on the calculated forward seabed altitude.

Next, details of the seabed altitude detection process will be described.
In the following description, a series of processes for transmitting a transmission beam from the FLS 9 and receiving a reflected wave (seafloor echo) to measure the seafloor height is also referred to as searching (ping). Moreover, the measurement of the seafloor height by FLS9 is also called depth measurement, and the result is also called FLS depth measurement value.

First, processing for each search will be described with reference to FIGS.
FIG. 6 is a schematic diagram showing a search by the FLS 9, and as an example, shows a state in which the UUV 1 is cruising around the seabed at a substantially constant altitude. FIG. 7 is a flowchart showing the flow of the search process.

In FIG. 6, the z-axis direction that is also directly under UUV1 is a depression angle of 90 °, and the x-axis direction that is also the traveling direction of UUV1 is a depression angle of 0 °. The depression angle 30 ° corresponds to the FLS machine axis B (also referred to as “FLS attachment depression angle”), and the received beam steering angle with respect to the FLS machine axis B is 0 °. The depression angle of 90 ° is a received beam steering angle of −60 °, and the depression angle of −30 ° is a reception beam steering angle of + 60 °.
The aircraft pitch angle is positive upward, and the received beam steering angle is positive on the elevation side.

  When the FLS 9 transmits a transmission beam (S100) and receives a reflected wave (S102), the seabed altitude immediately below UUV1 is calculated as processing 1 (S104).

In the processing 1, the signal processing unit 22 calculates the received beam number closest to the depression angle 90 ° with reference to the airframe pitch angle, and calculates the depth measurement value directly below which is the seafloor height immediately below the UUV1 based on the received beam. . The depression angle of the received beam in absolute space (hereinafter referred to as “received beam depression angle”) is calculated based on the following equation (1).
Received beam depression angle = FLS installation depression angle-body pitch angle-received beam steering angle
... (1)

Next, in step 106, as a process 2, a range gate (hatched area in FIG. 6) that is a range corresponding to the directly measured depth value is set. The range gate is a value obtained by adding a certain margin to the depth measurement value (the time from when the transmitted beam is transmitted directly below UUV1 until the reflected wave is received).
This range gate is for using only the received beam signal beyond the range gate when calculating the seafloor height based on other received beam signals.

The reason for setting such a range gate is as follows.
The intensity of the reflected wave (underwater echo level) of the component directly below the transmitted beam is the highest compared to the others, so this leaks from the side lobes of other received beams in the vicinity and is based on the other received beams. May cause false detection of the seabed altitude calculated by
Therefore, the range that may be affected by the reflected wave from directly under UUV1 is set as a non-calculated range (range gate) in which the seabed altitude is not calculated. For this reason, since the FLS 9 calculates the seabed altitude in front of the UUV1 based on the reflected wave beyond the range gate, it is possible to suppress erroneous detection of the seabed altitude due to sidelobe leakage.
In addition, the range gate is determined based on the depth measurement value immediately below, but usually there is no sea bottom on a concentric circle having the radius of UUV1 and the sea floor directly below. For this reason, even if the inside of the range gate is excluded from the depth measurement, the detection of the seabed altitude is not affected.

In the next step 108, as process 3, the seabed altitude below UUV1 before the range gate is calculated.
In the present embodiment, depth measurement is performed at a plurality of points within an angle range (hereinafter referred to as “depth measurement angle range”) predetermined as the front lower side of UUV1. The depth measurement range is, for example, a depression angle of 10 ° to a depression angle of 45 °, and depth measurement is performed at a pitch of 5 °.

Here, if the depth is measured at equal angular intervals in the entire transmission angle range as in the case of a normal MBES that is not used as a seafloor altitude detecting device, the depth just below UUV1 is also measured closely. On the other hand, as the seafloor height detection of UUV1, it is not necessary to measure the depth directly under UUV1, so a depth measurement range is set.
As described above, in the present embodiment, the underwater altitude is calculated only in the depth measurement angle range as a meaningful direction for the UUV1 undersea altitude control. Thereby, the signal processing load of the FLS 9 is reduced, the calculation time required for the calculation can be shortened, and the power consumption of the FLS 9 can be reduced.

  In particular, for calculating the seabed altitude in a direction with a shallow depression, for example, a method using a phase difference between two received beam signals having different acoustic center positions in the altitude direction (for example, Lurton, X., An Introduction to Underwater Known methods such as Acoustics Principles and Applications, Praxis Publishing Ltd, Chichester, UK, 2002. P.274-275) are used.

  In the next step 110, FLS sounding values immediately below and in front of UUV1 are output to the UUV controller 30, and the process returns to step 100 to perform the next sounding.

Next, an averaging process for averaging FLS sounding values of a plurality of consecutive probes will be described with reference to FIG.
The averaging process is performed by the UUV controller 30 as an example, but is not limited thereto, and may be performed by the signal processing unit 22 included in the FLS 9 and the averaged FLS sounding value may be output to the UUV controller 30. .

  As shown in FIG. 8A, an error (range error) is included in the FLS depth value for each probe. For this reason, the averaging process reduces the influence of errors that the UUV1 seafloor height control receives. By reducing the influence of the error, it is possible to prevent the UUV 1 from reacting sensitively to the error of the FLS sounding value and unnecessarily changing the altitude and pitch angle of the airframe 2.

In the averaging process according to the present embodiment, averaging is performed for each of a plurality of FLS depth measurement values of the same depression angle.
Specifically, in the averaging process, the slant range obtained by sounding (straight line distance from the FLS9 to the seafloor position measured by the FLS9) is transformed into the fixed earth local coordinates O-xy, and then the same depression angle. Addition averaging is performed in the x direction (R _{FLS (θ)} ) and y direction (H _{FLS (θ)} ) to obtain an averaged FLS depth measurement value.
The reason why the FLS depth values are averaged for each same depression angle is that the magnitude of the error of the received beam differs for each depression angle. In general, the deeper the depression angle, the smaller the error of the FLS depth measurement value, and the shallower the depression angle, the larger the error of the FLS depth measurement value. In addition, since UUV1 is searching while moving, a plurality of FLS sounding values having the same depression angle have different measured seabed positions. That is, the averaging process according to the present embodiment reduces the influence of errors and also averages the measured seabed space, so that the control of the aircraft 2 is less affected by the seafloor altitude, and the control of the UUV1 is more stable. To do.

FIG. 8B shows five FLS depth measurement values for every five pitches at a depression angle of 15 ° to 45 °, and FIG. 8C is a schematic diagram showing an average of these values.
In the example of FIG. 8, the FLS sounding values are averaged every five searches, and when a new search is performed, the FLS sounding values in the new search and the past four searches are averaged. That is, since the averaging process according to the present embodiment calculates the moving average of the FLS depth measurement values for each search, an error in the calculated seabed altitude can be reduced.

Here, an example of UUV1 seabed altitude control using feedforward control by the UUV controller 30 will be described with reference to FIG.
The seafloor altitude control uses FLS sounding values with a depression angle of 15 °, which will measure the seafloor altitude farther within the sounding angle range. That is, the pre-read front seafloor altitude H _{FLS (15)} and pre-read horizontal distance R _{FLS (15),} seabed altitude control is performed using a direct seabed altitude H ₀ in the current UUV1 measured by DVL8 or other altimeter .
Thus, the UUV controller 30 feed-forward-controls UUV1 using the seabed altitude corresponding to one selected depression from the seabed altitude calculated based on the reflected waves reflected at a plurality of depressions.

  Next, a depth measurement value switching process for switching the FLS depth measurement value used for UUV1 seafloor height control will be described.

  In general, the reflected wave (seafloor echo) reflected by the seabed received by FLS9 decreases in intensity as the incident angle (received beam depression angle) of the transmitted beam to the seabed becomes shallower, and the accuracy of the calculated FLS depth measurement value Decreases. However, as the FLS depth value at a shallow depression is used for seabed altitude control, UUV1 performs control in which the seabed altitude farther away is read ahead, and thus the followability to the seabed altitude is improved. That is, there is a trade-off relationship between the accuracy of the FLS depth measurement value and the distance of prefetching.

FIG. 9 is a functional block diagram showing functions of the UUV controller 30 related to seabed altitude control including depth measurement switching processing.
The UUV controller 30 includes a feedforward control unit 25, an averaging processing unit 26, and an accuracy determination unit 27.

  As described above, the feedforward control unit 25 performs feedforward control using the measured value (hereinafter referred to as “currently lower altitude”) by the DVL8, the FLS depth measurement value, and the like as the seabed altitude control.

The averaging processing unit 26 performs the above-described averaging process, and outputs the averaged FLS sounding value to the buffer unit 33 for storage.
That is, by repeating the above-described seafloor height detection process and averaging process, the forward seabed height H _{FLS (15)} calculated based on the received beam with a depression angle of 15 ° was calculated based on the received beam with a depression angle of 20 °. Forward seafloor height H _{FLS (20)} , forward seafloor height _{HFLS (25)} , forward seafloor height _{HFLS (30)} , forward seafloor height _{HFLS (35)} , forward seafloor height _{HFLS (40)} , forward seabed The altitude H _{FLS (45)} is generated as time-series data and stored in the buffer unit 33.
In addition, the averaging processing unit 26 outputs an FLS depth measurement value corresponding to a preselected depression angle used for feedforward control to the feedforward control unit 25 and the accuracy determination unit 27.

  The DVL 8 outputs the current direct altitude obtained by measuring the seabed altitude immediately below the UUV 1 to the feedforward control unit 25 and the accuracy determination unit 27.

  The accuracy determination unit 27 determines the accuracy of the FLS depth measurement value obtained by the FLS 9 by comparing the current direct altitude obtained by the DVL 8 and the FLS depth measurement value obtained by the FLS 9.

  And the averaging process part 26 switches the depression angle of the FLS depth measurement value used by feedforward control according to the determination result of the precision determination part 27. FIG.

The depth measurement value switching process will be described more specifically with reference to FIG.
When UUV1 is at position A, the FLS 9 performs seabed altitude detection processing and obtains FLS depth measurement values for every five pitches at depression angles of 15 ° to 45 °. The position B is a position corresponding to the FLS depth measurement value corresponding to the depression angle 45 °, and the position C is a position corresponding to the FLS depth measurement value corresponding to the depression angle 15 °.
When the UUV1 passes the position B, the accuracy determination unit 27 reads the FLS depth measurement value (the FLS depth measurement value of the local point previously read) according to the depression angle 45 ° from the time-series data stored in the buffer unit 33. And the precision determination part 27 compares the water depth of the local point read ahead based on the FLS sounding value according to the depression angle 45 degrees, and the current water depth based on the current direct height by DVL8, and whether the difference is less than a predetermined threshold value. Determine whether. When it is less than the predetermined threshold, it is determined that the accuracy of the FLS depth measurement value is high, and when it is equal to or greater than the predetermined threshold, it is determined that the accuracy of the FLS depth measurement value is low.
The accuracy determination unit 27 performs such determination for each FLS depth measurement value of each depression until UUV1 passes through position C.
In addition, the water depth of the local point read ahead and the current water depth are calculated by the following formula.
Pre-reading water depth at the local point = FLS sounding value pre-read in the past + past UUV1 travel depth Current water depth = current bottom height + current UUV1 travel depth

When it is determined that the accuracy of the FLS depth measurement value used by the feedforward control unit 25 is low, the averaging processing unit 26 receives the FLS depth measurement value used (output) by the feedforward control unit 25 at a deeper depression angle. The wave beam is switched to an FLS depth value calculated based on a received beam having sufficient accuracy for use in feedforward control.
On the other hand, when it is determined that the accuracy of the FLS depth measurement value used by the feedforward control unit 25 is high, the averaging processing unit 26 receives the FLS depth measurement value used (output) by the feedforward control unit 25 at a shallower depression angle. Switch to the FLS depth value calculated based on the wave beam.

  The averaging processing unit 26 may not switch the depression angle of the FLS depth measurement value output to the feedforward control unit 25 when the accuracy of the FLS depth measurement value used in the feedforward control unit 25 is sufficient.

  In this way, the depth measurement switching process determines the accuracy of the FLS depth measurement value by comparing the FLS depth measurement value of the local point prefetched in the past with the current direct altitude, and uses it for feedforward control of UUV1 according to the accuracy. Since the depression angle of the receiving beam for calculating the FLS depth value is switched, the control of the UUV 1 can be automatically optimized.

  Next, the control when the UUV 1 infiltrates as shown in FIGS. 3B and 3C will be described.

FIG. 11 is a diagram showing a state in which UUV1 shifts from rapid infiltration to gentle infiltration.
When the UUV 1 performs rapid infiltration, the signal processing unit 22 according to the present embodiment performs sea bottom detection determination processing for determining whether or not the water bottom is detected based on the received beam. Then, when the seabed is detected by the seabed detection determination process, the signal processing unit 22 ends the seabed detection determination process and performs a seabed height detection process for calculating the seabed altitude in front of the UUV1.

Here, when the seabed can be reliably detected by the FLS 9 as shown in FIG. 3A and the like, for example, with respect to the received beam signal, the seabed from a range closer to a farther range by TVG (Time Valuable Gain). In a state where the echo level is substantially smoothed, a range in which the intensity of the received beam signal takes a peak is detected, and this is set as an FLS depth measurement value (thrust range).
On the other hand, the rapid infiltration state is a state in which the FLS 9 is infiltrating deeply into the seabed so that the seabed cannot be measured. In such a state, there is no seabed within the maximum detection distance which is the maximum value of the measurement distance of FLS9. Therefore, the signal processing unit 22 performs the seabed detection determination process without performing the seabed altitude detection process in the rapid infiltration state. Thereby, even though the sea bottom is so deep that the FLS 9 cannot measure the sea bottom, the FLS 9 can perform a process of calculating the sea bottom altitude to prevent erroneous detection of the sea bottom.

  Specifically, when the aircraft pitch angle exceeds a predetermined threshold (for example, 60 °), the signal processing unit 22 determines that the state is a rapid infiltration state. Alternatively, a rapid infiltration flag may be provided in the control command from the UUV controller 30 to the FLS 9, and when the rapid infiltration flag is on, the signal processing unit 22 may determine that it is in the rapid infiltration state.

  In the rapid infiltration state (state A in FIG. 11), the signal processing unit 22 refers to the airframe pitch angle, calculates the received beam number closest to the depression angle 90 ° (directly below UUV1), and receives the received wave. Seabed detection processing is performed based on a plurality of received beams including the beam number. Note that the plurality of received beams may be at least two in the direction of the machine axis A1 (machine axis direction) immediately below the UUV1 and the UUV1.

  In the seabed detection determination process, when the intensity of the received beam is equal to or lower than a preset threshold, a signal indicating that the seabed has not been detected is output, and when the intensity of the received beam exceeds the threshold, the seabed detection is performed. A signal indicating is output. Note that this threshold value may be a fixed value or may be included in a control command from the UUV controller 30 to the FLS 9 and may be changed according to the bottom sediment of the UUV1 operating sea area.

When the seabed is detected (state B), the signal processing unit 22 switches the seabed detection determination process to the seabed altitude detection process, and measures the seabed altitude using the FLS 9.
When it is determined by the seafloor height detection processing that the seafloor height directly below UUV1 or the seafloor height in the axial direction can be measured by the DVL8 (state C), the UUV controller 30 sets the aircraft pitch angle of UUV1. Wake up and shift from rapid infiltration to gradual infiltration, and continue gradual infiltration.
As a result, the UUV 1 can quickly shift from a rapid infiltration state to a gentle infiltration where the ground speed can be measured by the DVL 8, and the divergence of the navigation error can be minimized.

FIG. 12 is a diagram illustrating a state in which UUV1 performs a gentle infiltration.
Slow infiltration is a state in which the aircraft pitch angle is about 10 ° to 15 °, for example, and the current seafloor height of UUV1 does not reach the target seafloor height.

  In such infiltration, the distance to the sea floor is longer than the maximum detection distance of the FLS 9 in the direction where the depression angle is shallow, and there is a possibility that the sea floor altitude cannot be measured.

  Therefore, the signal processing unit 22 according to the present embodiment calculates the seabed altitude in order from the received beam with the deep depression angle in the state where the UUV1 is infiltrated and the seabed is detected by the seabed detection determination process, and the measurement is performed. If the measured slant range exceeds the maximum detection distance of FLS9, the seabed altitude at a shallower depression angle is not calculated.

Specifically, when a gentle infiltration state is reached, first, the seafloor height is measured by a received beam in the direction directly below UUV1, and a range gate for other received beams is set based on this depth measurement value.
Then, when the seafloor height is measured in order from the received beam with the deep depression angle, and the measured slant range to the seabed is less than the set detectable detectable distance, which is a value obtained by subtracting a predetermined margin from the maximum detectable distance of FLS9. Then, the measurement of the seabed altitude is completed up to the received beam. In the example of FIG. 12, since the slant range is less than the set detectable distance at a depression angle of 25 °, measurement of the seabed altitude at a depression angle shallower than that is not performed.

  Thereby, although the depression angle is shallow and the seabed cannot be measured, the FLS 9 can perform the process of calculating the seabed altitude and prevent the seabed from being erroneously detected.

When the measurement of the sea bottom altitude is terminated halfway, for example, the front sea bottom altitude is defined by one of the following methods, used in feedforward control, and infiltrated until UUV1 reaches the target altitude.
1. Among the measured seafloor altitudes, the seabed altitude is based on the shallowest receiving beam. 2. Average measured seafloor height 3. The lowest seafloor height among the measured seafloor altitudes. If the seafloor height is measured based on the received beam in the axial direction, the seafloor height

FIG. 13 is a diagram illustrating another state in which the UUV 1 performs rapid infiltration.
As shown in FIG. 13, UUV1 is in a state of rapid infiltration (state D). However, the seabed in the direction of travel of UUV1 rises and the seabed altitude is high. In such a case, even if the seafloor height just below UUV1 does not reach the altitude at which the ground speed can be measured by DVL8, the seafloor height in the direction of the axis of UUV1, that is, the traveling direction of UUV1, can measure the ground speed by DVL8 If so, the aircraft pitch angle of UUV1 is raised (state E).

  As mentioned above, although this invention was demonstrated using the said embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which the changes or improvements are added are also included in the technical scope of the present invention. Moreover, you may combine the said embodiment suitably.

  In addition, the flow of the seabed altitude detection process described in the above embodiment is also an example, and unnecessary steps are deleted, new steps are added, or the processing order is changed within a range not departing from the gist of the present invention. Or you may.

1 UUV (underwater vehicle)
8 DVL (altimeter)
9 FLS (water bottom altitude detector)
20 Transmitter (Transmission means)
21 Receiver (Receiving means)
22 Signal processing unit (processing means)
25 Feedforward controller (control means)
27 Accuracy determination unit (accuracy determination means)
30 UUV controller (control means)

Claims (10)

A transmission means provided in an underwater vehicle that travels underwater, and that transmits a transmission beam in a predetermined angle range including directly under and under the underwater vehicle with respect to a traveling direction of the underwater vehicle; ,
Receiving means for receiving the reflected wave reflected by the water bottom with a plurality of received beams having different directions;
Based on the reflected wave received by the receiving means, processing means for calculating the bottom height in a plurality of directions ahead of the underwater vehicle,
Water bottom altitude detecting device.   The processing means sets a non-calculation range corresponding to the bottom height calculated based on the reflected wave from directly under the underwater vehicle, and the bottom height based on the reflected wave beyond the non-calculated range. The water bottom altitude detecting device according to claim 1 which calculates   The water bottom height detecting device according to claim 1, wherein the processing means calculates the water bottom height at a plurality of points within an angle range predetermined as a front lower part of the underwater vehicle.   The water bottom height detecting device according to any one of claims 1 to 3, wherein the water bottom height is averaged for each of the plurality of water bottom heights calculated based on the reflected wave having the same depression angle. The water bottom altitude detecting device according to any one of claims 1 to 4,
Control means for feedforward controlling the underwater vehicle using the bottom height corresponding to one selected depression among the bottom elevations calculated based on the reflected waves reflected at a plurality of depressions;
Underwater vehicle equipped with. An altimeter that measures the bottom height of the underwater vehicle,
An accuracy determination means for determining the accuracy of the water bottom height by the water bottom height detection device by comparing the measurement value by the altimeter and the water bottom height by the water bottom height detection device;
With
When the accuracy of the bottom height used in the control means is low, the bottom height used in the control means is switched to the bottom height calculated based on the reflected wave of a deeper depression angle, and used in the control means. The underwater vehicle according to claim 5, wherein when the accuracy of the water bottom altitude is high, the water bottom altitude used by the control means is switched to the water bottom altitude calculated based on the reflected wave at a shallow depression angle. When the underwater vehicle makes a quick infiltration, the water bottom altitude detection device performs a water bottom detection determination process for determining whether or not the water bottom is detected,
6. The water bottom altitude detection device, when detecting a water bottom by the water bottom detection determination process, ends the water bottom detection determination process and performs a process of calculating the water bottom altitude in front of the underwater vehicle. The underwater vehicle according to claim 6.   The underwater cruising according to claim 7, wherein when the water bottom altitude at which the ground speed can be measured by a ground speedometer is reached, the aircraft pitch angle of the underwater vehicle is raised to shift from rapid infiltration to gentle infiltration. body. In the state where the underwater vehicle is infiltrated and the bottom is detected by the bottom detection determination process,
The water bottom height detection device calculates the water bottom height in order from the reflected wave having a deep depression angle, and when the measured straight line distance to the bottom position exceeds the maximum detection distance, the water bottom height calculation at a shallow depression angle is performed. The underwater vehicle according to claim 7 or 8, wherein the underwater vehicle is not operated. A transmission beam is transmitted from a transmission means provided in the underwater vehicle that travels underwater in a predetermined angle range including directly under and under the underwater vehicle with respect to the traveling direction of the underwater vehicle. A first step of
A second step of receiving the reflected wave reflected from the bottom of the water by the receiving means with a plurality of received beams having different directions;
A third step of calculating a bottom height in a plurality of directions ahead of the underwater vehicle based on the reflected wave received by the receiving means;
Water bottom altitude detection method.

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