JP6755677B2 - Underwater altitude detection device, underwater vehicle, and underwater altitude detection method - Google Patents

Description

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

An unmanned underwater vehicle (UUV) emits ultrasonic waves (acoustic beams) to the seabed (underwater) by a sonar and receives echoes reflected from the seabed to investigate the depth of the sea area or to the seabed. May search for submerged objects.
Since these sonars have an appropriate seafloor altitude, the underwater vehicle equipped with the sonar must maintain an appropriate seafloor altitude for sonar operation.
Further, as shown in FIG. 14, in order to minimize the overlap of the search range for each line 102 with respect to the search area 101 by the underwater vehicle 100 and improve the search efficiency, it is necessary to maintain the search width by the sonar. .. For this reason as well, the underwater vehicle needs to perform altitude control by following the undulations of the seabed.

In order to control the seafloor altitude of the underwater vehicle (UUV), it is necessary to measure the seafloor altitude of the underwater vehicle. One of the methods for measuring the seafloor altitude is to measure the current altitude in the direct direction using a single-beam echo sounder (Single-Beam Echo Sounder) or DVL (Doppler Velocity Log). The method of measuring the altitude directly below the underwater vehicle is generally highly accurate because the intensity of the reflected wave from the seabed is strong. However, if the underwater vehicle is feedback-controlled based on the measurement of the current altitude directly under the underwater vehicle, the control will be delayed when the water depth changes in the traveling direction of the underwater vehicle. Therefore, it is preferable to measure the seafloor altitude in front of and below the underwater vehicle and use the result for feed forward control.

As a method of measuring the forward altitude of the underwater vehicle, for example, an altimeter such as a single-beam echo sounder that emits a very fine pencil beam to the seabed is installed in front of and below the underwater vehicle. There is a method of measuring the altitude ahead.

Further, Patent Document 1 discloses an underwater vehicle including a plurality of distance sensors (single beam echo sounder) 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 the plurality of directions having different depression angles with respect to the horizontal direction. In addition, the altitude estimation unit estimates the altitude of the aircraft from the seabed 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 on a vertical surface with respect to an underwater vehicle, the seabed is detected by image processing or the like, and the seafloor altitude in front is calculated. Further, the two-dimensional image sonar is installed by tilting the underwater vehicle downward with respect to the horizontal plane, and the seabed is detected by image processing or the like to calculate the altitude of the seabed ahead.

Japanese Unexamined Patent Publication No. 2014-121927

However, in the altitude measurement by 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, as the distance from directly below the underwater vehicle becomes lower in front and lower. Therefore, the measurable horizontal distance to the front and lower seabed is short (about 1 to 2 times the altitude), and the followability of the underwater vehicle is inferior especially when the seabed has large undulations.
Further, since the underwater vehicle disclosed in Patent Document 1 requires a large number of distance sensors to be arranged, a large mounting space is required inside the underwater vehicle.
Further, the two-dimensional image sonar has low measurement accuracy because it detects the seabed by the shading of the image, and it is difficult to use it for control for autonomous navigation such as UUV.

The present invention has been made in view of such circumstances, and is capable of controlling the underwater vehicle with high followability to the undulations of the water bottom, a water bottom altitude detection device, an underwater vehicle, and a water bottom. The purpose is to provide an altitude detection method.

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

The submersible altitude detection device according to the first aspect of the present invention is provided on the underwater navigating body that is navigating underwater, and is directly below and forward and downward of the underwater navigating body with respect to the traveling direction of the underwater navigator. A transmitting means for transmitting a transmitting beam in a predetermined angle range including the receiving means, a receiving means for receiving a reflected wave reflected by the transmitting beam on the bottom of the water with a plurality of receiving beams having different directions, and the reflection received by the receiving means. A processing means for calculating the bottom altitude in a plurality of directions in front of the underwater vehicle based on the wave is provided , and the processing means calculates based on the reflected wave from directly below the underwater vehicle. is the set of water bottom highly non calculated range corresponding with, you calculate the water bottom altitude based only on the reflected wave of the non-calculation range beyond.

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

Since the intensity of the reflected wave of the component in the direction directly below the wave transmitted beam transmitted in the predetermined angle range including directly below and below the underwater vehicle is strong, the received beam in front other than directly below is reflected directly below the seaflobe by the side lobe. It may receive waves and lead to false positives of the seafloor altitude ahead. According to this configuration, a range that may be affected by the reflected wave from directly under the underwater vehicle is set, and the water bottom altitude in front of the underwater vehicle is calculated based on the reflected wave beyond this range. Therefore, false detection of water bottom altitude 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 the front and lower parts of the underwater vehicle.

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

In the first aspect, the bottom altitude may be averaged for each of a plurality of bottom altitudes calculated based on the reflected waves having the same depression angle.

According to this configuration, the error of the calculated bottom altitude can be reduced.

The underwater vehicle according to the second aspect of the present invention has a depression angle selected from the water bottom altitude detection device described above and the water bottom altitude calculated based on the reflected waves reflected by a plurality of depression angles. A control means for feed-forward controlling the underwater vehicle using the corresponding bottom altitude is provided.

According to this configuration, the underwater vehicle can be highly controlled to follow the undulations of the bottom of the water.

In the second aspect, the altitude meter for measuring the altitude of the water bottom directly under the underwater vehicle, and the measured value by the altitude meter and the water bottom altitude by the water bottom altitude detection device are compared with each other to obtain the above-mentioned by the water bottom altitude detection device. An accuracy determining means for determining the accuracy of the bottom altitude is provided, and when the accuracy of the bottom altitude used by the control means is low, the bottom altitude used by the control means is determined based on the reflected wave having a deeper depression angle. When the accuracy of the bottom altitude used by the control means is high by switching to the calculated bottom altitude, the bottom altitude used by the control means is calculated based on the reflected wave having a shallower depression angle. You may switch to.

According to this configuration, the accuracy of the pre-reading water bottom altitude is determined by comparing the water bottom altitude of the local point pre-read by the water bottom altitude detector in the past with the current water bottom altitude, and the underwater vehicle is determined according to the accuracy. Since the depression angle of the reflected wave that calculates the bottom altitude used for the feed forward control of is switched, the control of the underwater vehicle can be automatically optimized. As the altimeter, for example, a single beam echo sounder, a Doppler speedometer (DVL), or the like can be applied.

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

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

In the second aspect, when the ground speed reaches the ground altitude at which the ground speed can be measured by the ground speedometer, even if the aircraft pitch angle of the underwater vehicle is raised and the rapid infiltration is changed to the gentle infiltration. Good.

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

In the second aspect, in a state where the underwater vehicle is infiltrating and the water bottom is detected by the water bottom detection determination process, the water bottom altitude detection device performs the water bottom altitude in order from the reflected wave having a deep depression angle. If the linear distance to the measured bottom position exceeds the maximum detection distance, it is not necessary to calculate the bottom altitude at a shallower depression angle.

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

In the method for detecting the height of the bottom of the water according to the third aspect of the present invention, the transmission means provided on the underwater vehicle traveling underwater is directly below the underwater vehicle with respect to the traveling direction of the underwater vehicle. A transmission step of transmitting a wave- transmitting beam in a predetermined angle range including the front and lower parts, a reception step of receiving the reflected wave reflected by the wave-transmitting beam at the bottom of the water by a plurality of receiving beams having different directions, and the above-mentioned. on the basis of the reflective wave received by the receiving means, have a, a process of calculating the forward plurality of directions of the water bottom altitude of the underwater vehicle, said processing step is from immediately below the underwater vehicles the set non-calculation range, wherein the corresponding in water bottom altitude calculated on the basis of the reflected wave, he calculates the water bottom altitude based only on the reflected wave of the non-calculation range beyond.

According to the present invention, there is an effect that the underwater vehicle can be controlled with high followability to the undulations of the water bottom.

It is a side view which shows the structure of the UUV which concerns on embodiment of this invention. It is a schematic diagram which shows the shape of the wave transmission beam transmitted from FLS which concerns on embodiment of this invention. It is a figure which shows the operational state of the UUV which concerns on embodiment of this invention. It is a functional block diagram which shows the control structure of the 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 a schematic diagram which showed the example of the detection by FLS which concerns on embodiment of this invention. It is a flowchart which shows the flow of the detection process which concerns on embodiment of this invention. It is a schematic diagram which shows the outline of the averaging process of FLS sounding value which concerns on embodiment of this invention. It is a schematic diagram which shows the outline of the sounding value switching process which concerns on embodiment of this invention. It is a functional block diagram which shows the function of the UUV control device which concerns on the seafloor altitude control which concerns on embodiment of this invention. It is a figure which showed the state which the UUV which concerns on embodiment of this invention shifts from rapid infiltration to slow infiltration. It is a figure which showed the state which the UUV which concerns on embodiment of this invention is slowly infiltrating. It is a figure which showed the other state which the UUV which concerns on embodiment of this invention performs rapid infiltration. It is a schematic diagram which showed the example of the search route for each navigation line with respect to the investigation area by an underwater vehicle.

Hereinafter, an embodiment of the water bottom altitude detection device, the underwater vehicle, and the water bottom altitude detection method according to the present invention will be described with reference to the 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 the underwater vehicle, an unmanned underwater vehicle (UUV) that autonomously navigates by inertial navigation is used. Further, in the present embodiment, as an example, the UUV will be described as traveling in the sea, but the present invention is not limited to this, and the UUV may navigate a river, a lake, or the like.

The UUV1 according to the present embodiment includes an airframe 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 body 2 includes a propulsion unit 3, a front horizontal rudder 4, a rear horizontal rudder 5, a front vertical rudder 6, and a drive source for driving the rear vertical rudder 7. Examples of the drive source include a battery for storing electric power, an electric motor driven by electric power from the battery, and the like, but other types of drive sources may be used. Further, the airframe 2 has a substantially circular cross-sectional shape in a plane orthogonal to the airframe axis A1. It should be noted that each rudder does not necessarily have to be provided in the front and rear, and may be provided only in the rear.

The UUV1 travels in water with propulsive force obtained by rotating the propeller included in the propeller 3 by a drive source inside the airframe 2, with the direction indicated by the arrow in FIG. 1 as the traveling direction.

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

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

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 a rear horizontal axis by a drive motor provided inside the machine body 2. By controlling the front vertical rudder 6 and the rear vertical rudder 7, the traveling direction of the UUV 1 in the left-right direction can be arbitrarily controlled.

The DVL 8 is a ground speedometer provided on the lower side of the airframe 2, which has a transmitter / receiver for transmitting / receiving 3 to 6 acoustic beams, and measures the ground speed with respect to the seabed by the Doppler effect. The DVL8 also measures the altitude directly below the UUV1 by averaging the directional cosine of the linear distance to the seabed measured by 3 to 6 acoustic beams at the same time as the ground speed.

The FLS 9 is a front sonar provided near the tip of the UUV 1 and functions as a seafloor altitude detection device.
The FLS 9 transmits a wave transmission beam (acoustic beam) in a predetermined angle range (hereinafter referred to as “wave transmission angle range”) including directly below and in front of and below UUV1, and the reflected wave (“seafloor echo”) reflected by the transmission beam on the water bottom. ”) Is received by a plurality of receiving beams having different directions. Then, the FLS 9 processes the received signal of each received beam and measures the received beam direction in front of the UUV 1, that is, the seafloor altitude in a plurality of directions.

FIG. 2 is a schematic view showing the shape of the wave transmission beam transmitted from FLS 9 according to the present embodiment. FIG. 2 (A) is an upward view, and FIG. 2 (B) is a lateral view (vertical face). The surface of the UUV1 in the vertical direction with respect to the body axis A1 is referred to as a vertical plane. 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 with each other.

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

Specifically, the mounting orientation of the FLS 9 (hereinafter referred to as "FLS mechanical shaft") B is set to a depression angle of about 30 ° when the roll angle of the UUV1 is 0 °. Then, the transmission beam is transmitted in a sheet shape in a transmission angle range of ± 60 ° with the FLS mechanical axis B as the central axis, and a transmission fan beam surface is formed. This wave fan beam plane coincides with the vertical plane. The transmission angle range is ± 60 ° as an example, and the present invention is not limited to this.
As shown in FIG. 2B, the transmission beam transmitted toward −60 ° (when the upward direction of the transmission angle range is positive) about the FLS mechanical axis B as the central axis. Will measure the seafloor altitude directly 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 seafloor altitude. In other words, the FLS mechanical axis B of the FLS 9 is determined so that the transmitted beam can be transmitted from directly below the UUV1 toward the front. In the present embodiment, as an example of this, the FLS mechanical shaft B has 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, of the wave transmission beams continuously and widely transmitted in the wave transmission angle range of ± 60 °, the component in the -60 ° direction is reflected on the seabed directly below UUV1 and is received by the wave reception beam facing directly below. .. The FLS9 processes this received beam signal to measure the seafloor altitude directly below UUV1. Similarly, a component of the transmitted beam in which the FLS mechanical axis B is in the 0 ° direction propagates in the direction of a 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 mechanical axis B facing in the direction of 0 ° (= depression angle 30 °), processes the received beam signal, and measures the forward altitude in the depression angle 30 ° direction.

In this way, the FLS 9 transmits a transmission beam in a transmission angle range including directly below the UUV 1 and below the front and the bottom with respect to the traveling direction of the UUV 1. Then, the FLS 9 receives the reflected wave reflected by the transmitted beam on the seabed with a plurality of received beams having different directions, and calculates the seafloor altitude in front of the UUV1 for each received beam signal. I do.

In other words, the FLS9 has the same function as the MBES (Multi-Beam Echo Sounder), which is a sounding instrument, but it is provided near the tip of the UUV1 and is used for measuring the seafloor altitude in front of the UUV1. In general, the mechanical axis of the MBES provided in the UUV or the like is in the direction directly below the UUV (depression angle of 90 °), and therefore is not used for measuring the forward altitude of the UUV.
Further, even if a single beam echo sounder generally used as an altimeter is provided in front of and below the UUV1, only one transmitting beam is transmitted, so that only one point in front can be sounded. On the other hand, the FLS 9 according to the present embodiment transmits the transmitted beam in a sheet shape within the transmitted angle range, and electrically forms the required number of received beams in the required direction, thereby requiring the front and lower directions. It becomes possible to measure the seafloor altitude in the direction.

Next, the operating state of UUV1 will be described with reference to FIG.
FIG. 3A shows a state in which UUV1 is cruising near the seabed at a substantially constant altitude. FIGS. 3 (B) and 3 (C) show a state in which UUV1 is infiltrating. That is, the operating state of the UUV1 is roughly divided into two operating states: a state in which the UUV1 is cruising near the seabed and a state in which the UUV1 is infiltrating.

As shown in FIG. 3A, when the UUV1 is cruising near the seabed at a substantially constant altitude, the depression angle is in the direction of a certain degree or more within the maximum detection distance which is the maximum distance that can be measured by the FLS9. There is always a seabed. Therefore, it is possible to measure the seafloor altitude by FLS9.

As shown in FIG. 3 (B), when the UUV1 infiltrates a sea area where the water depth is shallow enough to measure the ground speed with the DVL8, the UUV1 has a gentle aircraft pitch so that the ground speed can be measured by the DVL8. Infiltrate at the corner. In this case as well, the seabed always exists in the direction in which the depression angle is above a certain level within the maximum detection distance of the FLS9, and the seafloor altitude can be measured by the FLS9.

As shown in FIG. 3C, when the UUV1 infiltrates a sea area where the ground speed cannot be measured by the DVL8, the UUV1 has a steep aircraft pitch until the ground speed can be measured by the DVL8. Infiltrate at an angle (for example, a depression angle of 60 ° or more).
This is because, compared to speed hybrid inertial navigation using the measurement result of the ground speed by DVL8, navigation error is more likely to occur in pure inertial navigation, so if the ground speed cannot be measured by DVL8, it will be rapidly shortened for a short time. This is because the divergence of navigation error is suppressed by infiltrating with. In this case, the seabed may not exist within the maximum detection distance of FLS9, and it may not be possible to measure the seafloor altitude by 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 is composed of, for example, a CPU (Central Processing Unit) or the like. 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 the feedback control amount according to the direct altitude measured by the DVL8 and the feedforward control amount according to the forward altitude measured by the FLS9, and outputs a control signal to each elevator. Generate. The transmission of the control signal from the UUV controller 30 to each unit and the transmission of the signal 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 by the UUV controller 30 based on the information acquired from the DVL 8 and the FLS 9, the airframe depth detected by the airframe depth sensor 34, and the like.

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

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

The propeller drive unit 36 controls a drive motor for rotating the propeller included in the propeller 3. The UUV controller 30 controls a drive motor for rotating the propeller included in the propeller 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 the 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 the 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 the 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 the 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 them in the buffer unit 33.

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

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

The transmitter 20 transmits a transmitter beam in a transmitter angle range (−60 ° to + 60 °).
The receiver 21 is a phased array antenna as an example, and receives the reflected wave reflected by the transmitted beam, adjusts the phase of the reflected wave received by each antenna element, and adds the phase to the phase adjustment amount. The receiving beam has a corresponding angle. The receiver 21 outputs a received beam signal indicating the intensity and phase of the received beam to the signal processing unit 22. The received beam signal is sequentially assigned a number according to the angle.

Based on the input received beam signal, the signal processing unit 22 calculates the seafloor altitude in front of the UUV1 in order from directly below the UUV1 (depression angle 90 °) 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 the UUV1 based on the measured seafloor altitude.

The UUV1 signals various information necessary for calculating the seafloor altitude, for example, information and commands such as the aircraft pitch angle, the seafloor altitude measured by DVL8 (hereinafter referred to as "DVL measurement value"), and the transmission angle range. It is output to the unit 22, and the signal processing unit 22 calculates the seafloor altitude using the various input 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 seabed altitude directly below UUV1, the signal processing unit 22 determines whether the seabed altitude measured by FLS9 is appropriate by comparing the DVL measurement value with the seabed altitude measured by FLS9. It will be possible.

With such a configuration, the FLS 9 transmits a wave transmission beam in a transmission angle range including directly below and in front of and below the UUV1 with respect to the traveling direction of the UUV1, and receives the reflected wave reflected by the transmitted beam on the seabed. Then, FLS9 calculates the seafloor altitude in front of UUV1 based on the received reflected wave. The UUV1 autonomously navigates itself by feed forward control based on the calculated seafloor altitude in front of it.

Next, the details of the seafloor altitude detection process will be described.
In the following description, a series of processes for transmitting a wave transmission beam from FLS9, receiving a reflected wave (seafloor echo), and measuring the seafloor altitude is also referred to as detection (ping). Further, the measurement of the seafloor altitude by FLS9 is also referred to as bathymetry, and the result is also referred to as bathymetry value.

First, the processing for each detection will be described with reference to FIGS. 6 and 7.
FIG. 6 is a schematic view showing the detection by FLS9, and as an example, shows a state in which UUV1 is cruising near the seabed at a substantially constant altitude. FIG. 7 is a flowchart showing the flow of the detection process.

In FIG. 6, the z-axis direction, which is also directly below the UUV1, is a depression angle of 90 °, and the x-axis direction, which is also the traveling direction of the UUV1, is a depression angle of 0 °. The depression angle of 30 ° corresponds to the FLS mechanical axis B (also referred to as “FLS mounting depression angle”), and the receiving beam steering angle with respect to the FLS mechanical axis B is 0 °. Further, a depression angle of 90 ° has a receiving beam steering angle of −60 °, and a depression angle of −30 ° has a receiving beam steering angle of + 60 °.
The aircraft pitch angle is positive in the upward direction, and the receiving beam steering angle is positive in the elevation angle side.

When the FLS9 transmits a wave transmission beam (S100) and receives a reflected wave (S102), the seafloor altitude directly below UUV1 is calculated as process 1 (S104).

In process 1, the signal processing unit 22 calculates the received beam number closest to the depression angle of 90 ° with reference to the aircraft pitch angle, and calculates the bathymetric value, which is the seafloor altitude directly below UUV1, based on this 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 mounting depression angle-Aircraft pitch angle-Received beam steering angle
... (1)

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

The reason for setting such a range gate is as follows.
Since the intensity of the reflected wave (seafloor echo level) of the component directly below the transmitted beam is the highest compared to the others, it leaks from the side lobes of other received beams in the vicinity and is based on the other received beams. It may lead to false detection of the seafloor altitude calculated by.
Therefore, the range that may be affected by the reflected wave from directly under UUV1 is set as a non-calculation range (range gate) that does not calculate the seafloor altitude. Therefore, since the FLS9 calculates the seafloor altitude in front of the UUV1 based on the reflected wave beyond the range gate, it is possible to suppress erroneous detection of the seafloor altitude due to sidelobe leakage.
Further, the range gate is determined based on the bathymetric value directly below, but usually, the seabed does not exist on the concentric circle whose radius is UUV1 and the seabed directly below this. Therefore, excluding the inside of the range gate from the bathymetry does not affect the detection of seafloor altitude.

In the next step 108, as the process 3, the seafloor altitude in front of and below the UUV1 beyond the range gate is calculated.
In the present embodiment, a plurality of points are measured within a predetermined angle range (hereinafter referred to as “depth sounding angle range”) as the front and lower parts of the UUV1. As an example, the sounding angle range is from a depression angle of 10 ° to a depression angle of 45 °, and the sounding is performed at a pitch of 5 °.

Here, if the depth is measured at equal angle intervals over the entire wave transmission angle range as in the normal MBES that is not used as a seafloor altitude detection device, the depth directly below the UUV1 is also measured densely. On the other hand, in order to detect the seafloor altitude of the UUV1, it is not necessary to measure the depth directly under the UUV1 densely, so a sounding angle range is set.
As described above, in the present embodiment, the undersea altitude is calculated only in the bathymetric angle range as a meaningful direction for controlling the seafloor altitude of UUV1. As a result, the signal processing load of the FLS 9 can be reduced, the calculation time required for the calculation can be shortened, and the power consumption of the FLS 9 can be reduced.

In order to calculate the seafloor altitude in the direction in which the depression angle is particularly shallow, for example, a method using the phase difference between two received beam signals having different acoustic center positions in the altitude direction (for example, Lurton, X., An Introduction to Underwater). Conventionally known methods such as Acoustics Principles and Applications, Praxis Publishing Ltd, Chichester, UK, 2002. P.274-275) are used.

In the next step 110, the FLS sounding values directly below and in front of the UUV 1 are output to the UUV controller 30, and the process returns to step 100 to perform the next bathymetry.

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

As shown in FIG. 8A, the FLS sounding value for each detection includes an error (range error). Therefore, the averaging process reduces the influence of the error on the seafloor altitude control of UUV1. By reducing the effect of the error, it is possible to prevent the UUV1 from reacting sensitively to the error of the FLS sounding value and unnecessarily fluctuating 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 sounding values having the same depression angle.
Specifically, in the averaging process, the slant range (straight line distance from FLS9 to the seafloor position measured by FLS9) obtained by sounding is converted into the local coordinates O-xy fixed to the earth, and then for each same depression angle. Add and average in the x direction (R _{FLS (θ)} ) and y direction (H _{FLS (θ)} ) to obtain the averaged FLS sounding value.
The reason for averaging the FLS sounding values for the same depression angle is that the magnitude of the error of the received beam differs for each depression angle. Generally, the deeper the depression angle, the smaller the error in the FLS sounding value, and the shallower the depression angle, the larger the error in the FLS sounding value tends to be. Since UUV1 is performing detection while moving, the measured depth positions of the seabed are different for a plurality of FLS sounding values having the same depression angle. That is, the averaging process according to the present embodiment reduces the influence of the error and also averages the measured seabed space, so that the control of the airframe 2 is less affected by the seafloor altitude and the control of the UUV1 is more stable. To do.

FIG. 8B shows the FLS sounding values for 5 times for every 5 pitches at a depression angle of 15 ° to 45 °, and FIG. 8C is a schematic diagram showing the average of these sounding values.
In the example of FIG. 8, the FLS sounding value is averaged every 5 detections, and when a new detection is performed, the FLS sounding value in the new detection and the past 4 detections is averaged. That is, since the averaging process according to the present embodiment calculates the moving average of the FLS bathymetric value for each detection, the calculated error of the seafloor altitude can be reduced.

Here, an example of seafloor altitude control of UUV1 using feed forward control by the UUV controller 30 will be described with reference to FIG. 8C.
The seafloor altitude control uses a FLS bathymetric value with a depression angle of 15 °, which measures the seafloor altitude farther within the sounding angle range. That is, the seafloor altitude control is performed using the pre-reading forward seafloor altitude H _{FLS (15)} , the pre-reading horizontal distance R _{FLS (15),} and the current seafloor altitude H ₀ of UUV1 measured by DVL8 or another altimeter. ..
As described above, the UUV controller 30 feed-forward controls the UUV1 by using the seafloor altitude corresponding to one selected depression angle among the seafloor altitudes calculated based on the reflected waves reflected by the plurality of depression angles.

Next, a bathymetric value switching process for switching the FLS bathymetric value used for controlling the seafloor altitude of the UUV1 will be described.

In general, the intensity of the reflected wave (seafloor echo) reflected by the FLS9 on the seafloor decreases as the angle of incidence of the transmitted beam on the seafloor (received beam depression angle) decreases, and the accuracy of the calculated FLS sounding value decreases. Decreases. However, the more the FLS bathymetric value with a shallow depression angle is used for the seafloor altitude control, the more distant seafloor altitude is pre-read for the UUV1, and the followability to the seafloor altitude is improved. That is, there is a trade-off between the accuracy of the FLS sounding value and the look-ahead distance.

FIG. 9 is a functional block diagram showing the functions of the UUV controller 30 related to the seafloor altitude control including the bathymetry value switching process.
The UUV controller 30 includes a feed forward control unit 25, an averaging processing unit 26, and an accuracy determination unit 27.

As the seafloor altitude control, the feed forward control unit 25 performs feed forward control using the measured value by the DVL 8 (hereinafter referred to as “current altitude directly below”), the FLS sounding value, and the like as described above.

The averaging processing unit 26 performs the averaging processing described above, outputs the FLS sounding value after averaging to the buffer unit 33, and stores it.
That is, by repeating the above-mentioned seafloor altitude detection process and averaging process, the seafloor altitude H _{FLS (15)} calculated based on the received beam with a depression angle of 15 ° and the received beam with a depression angle of 20 ° were calculated. Forward seafloor altitude H _{FLS (20)} , similarly forward seafloor altitude H _{FLS (25)} , front seafloor altitude H _{FLS (30)} , front seafloor altitude H _{FLS (35)} , front seafloor altitude H _{FLS (40)} , front seafloor The altitude H _{FLS (45)} is generated as time series data, and this is stored in the buffer unit 33.
Further, the averaging processing unit 26 outputs the FLS sounding value corresponding to the depression angle selected in advance used for the feed forward control to the feed forward control unit 25 and the accuracy determination unit 27.

The DVL 8 outputs the current altitude directly below the seabed obtained by measuring the altitude directly below the UUV 1 to the feed forward control unit 25 and the accuracy determination unit 27.

The accuracy determination unit 27 determines the accuracy of the FLS sounding value by FLS 9 by comparing the current altitude directly below the DVL 8 with the FLS sounding value by FLS 9.

Then, the averaging processing unit 26 switches the depression angle of the FLS sounding value used in the feed forward control according to the determination result of the accuracy determination unit 27.

The sounding value switching process will be described more specifically with reference to FIG.
When UUV1 is at position A, FLS9 performs seafloor altitude detection processing to obtain FLS bathymetric values every 5 pitches at depression angles of 15 ° to 45 °. Position B is a position corresponding to the FLS sounding value corresponding to the depression angle of 45 °, and position C is a position corresponding to the FLS sounding value corresponding to the depression angle of 15 °.
When the UUV1 passes the position B, the accuracy determination unit 27 reads out the FLS sounding value (FLS sounding value of the local point read ahead in the past) according to the depression angle 45 ° from the time series data stored in the buffer unit 33. Then, the accuracy determination unit 27 compares the water depth of the pre-reading local point based on the FLS bathymetric value corresponding to the depression angle 45 ° with the current water depth based on the current altitude directly below by DVL8, and whether or not the difference is less than a predetermined threshold value. Is determined. If it is less than the predetermined threshold value, it is determined that the accuracy of the FLS sounding value is high, and if it is more than the predetermined threshold value, it is determined that the accuracy of the FLS sounding value is low.
The accuracy determination unit 27 makes such a determination for each FLS sounding value of each depression angle until the UUV1 passes the position C.
The pre-read water depth at the local point and the current water depth are calculated by the following formula.
Pre-reading local point water depth = previously pre-read FLS sounding value + past UUV1 cruising depth Current water depth = current seafloor altitude + current UUV1 cruising depth

Then, when it is determined that the accuracy of the FLS sounding value used by the feed forward control unit 25 is low, the averaging processing unit 26 receives the FLS sounding value used (output) by the feed forward control unit 25 to receive a deeper depression angle. The wave beam is switched to the FLS sounding value calculated based on the received beam having sufficient accuracy for feed forward control.
On the other hand, when it is determined that the accuracy of the FLS sounding value used by the feed forward control unit 25 is high, the averaging processing unit 26 receives the FLS sounding value used (output) by the feed forward control unit 25 with a shallower depression angle. Switch to the FLS sounding value calculated based on the wave beam.

The averaging processing unit 26 does not have to switch the depression angle of the FLS sounding value output to the feed forward control unit 25 when the accuracy of the FLS sounding value used by the feed forward control unit 25 is sufficient.

In this way, the sounding value switching process determines the accuracy of the FLS sounding value by comparing the FLS sounding value of the local point read in the past with the altitude directly below the present, and is used for the feed forward control of the UUV1 according to the accuracy. Since the depression angle of the received beam for calculating the FLS sounding value is switched, the control of UUV1 can be automatically optimized.

Next, the control when the UUV1 infiltrates as shown in FIGS. 3B and 3C described above will be described.

FIG. 11 is a diagram showing a state in which UUV1 shifts from rapid infiltration to slow infiltration.
When the UUV1 rapidly infiltrates, the signal processing unit 22 according to the present embodiment performs a seabed detection determination process 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 the seabed altitude detection process for calculating the seabed altitude in front of the UUV1.

Here, when the seabed can be reliably detected by FLS9 as in FIG. 3A described above, for example, the seabed from a range closer to the TVG (Time Valuable Gain) to a range farther from the received beam signal. With the echo level substantially smoothed, the range in which the intensity of the received beam signal peaks is detected, and this is defined as the FLS sounding value (thrust range).
On the other hand, the rapid infiltration state is a state in which FLS9 infiltrates toward the seabed so deep 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 seafloor detection determination process without performing the seafloor altitude detection process in the rapid infiltration state. As a result, even though the seabed is so deep that the FLS9 cannot measure the seabed, the FLS9 can perform a process of calculating the seabed altitude to prevent erroneous detection of the seabed.

Specifically, when the airframe pitch angle exceeds a predetermined threshold value (for example, 60 °), the signal processing unit 22 determines that it is in 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 the rapid infiltration state.

Then, in the rapid infiltration state (state A in FIG. 11), the signal processing unit 22 calculates the received beam number closest to the depression angle 90 ° (directly below the UUV1) with reference to the aircraft pitch angle, and receives the received beam. The seafloor detection process is performed based on a plurality of received beams including the beam number. It should be noted that the plurality of received beams may be at least two in the direction directly below the UUV1 and in the direction of the body axis A1 of the UUV1 (axis direction).

Then, in the seabed detection determination process, when the intensity of the received beam is equal to or less than a preset threshold value, a signal indicating that the seabed has not been detected is output, and when the intensity of the received beam exceeds the above threshold value, the seabed is detected. Outputs a signal indicating. This threshold value may be a fixed value, or may be included in the control command from the UUV controller 30 to the FLS9 and may be changed according to the seabed sediment in the operating sea area of the UUV1.

Then, 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 by FLS9.
When it is determined by the seafloor altitude detection process that the seafloor altitude directly below UUV1 or the seafloor altitude in the axial direction can measure the ground speed by DVL8 (state C), the UUV controller 30 determines the aircraft pitch angle of UUV1. Wake up, shift from rapid infiltration to gradual infiltration, and continue gradual infiltration.
As a result, the UUV1 can quickly shift from the rapid infiltration state to the gentle infiltration where the ground speed can be measured by the DVL8, and the divergence of the navigation error can be minimized.

FIG. 12 is a diagram showing a state in which UUV1 is slowly infiltrating.
The gentle infiltration is a state in which the airframe pitch angle is, for example, about 10 ° to 15 °, and the current seafloor altitude of UUV1 does not reach the target seafloor altitude.

In such an infiltration, the distance to the seafloor is longer than the maximum detection distance of FLS9 in the direction of shallow depression angle, and there is a possibility that the seafloor altitude cannot be measured.

Therefore, the signal processing unit 22 according to the present embodiment calculates and measures the seafloor altitude in order from the receiving beam having the deepest depression angle in a state where the UUV1 is infiltrating and the seafloor is detected by the seafloor detection determination process. If the slant range exceeds the maximum detection distance of FLS9, the seafloor altitude at a shallower depression angle will not be calculated.

Specifically, when a gentle infiltration state is reached, first, the seafloor altitude is measured by the receiving beam in the direction directly below the UUV1, and a range gate for another receiving beam is set based on this bathymetric value.
Then, the seafloor altitude is measured in order from the receiving beam with the deepest depression angle, and the slant range to the measured seafloor is equal to or less than the set detectable distance, which is the value obtained by subtracting the predetermined margin from the maximum detection distance of FLS9. At the same time, the measurement of seafloor altitude is completed up to the receiving beam. In the example of FIG. 12, since the slant range is equal to or less than the set detectable distance at a depression angle of 25 °, the seafloor altitude is not measured at a depression angle shallower than that.

As a result, even though the depression angle is shallow and the seafloor cannot be measured, the FLS9 can perform a process of calculating the seafloor altitude to prevent erroneous detection of the seafloor.

When the measurement of the seafloor altitude is completed in the middle, for example, the seafloor altitude in front is defined by one of the following methods, used in the feed forward control, and infiltrated until the UUV1 reaches the target altitude.
1. 1. Of the measured seafloor altitudes, the seafloor altitude based on the receiving beam with the shallowest depression angle 2. Average value of measured seafloor altitude 3. 4. The lowest seafloor altitude measured. If the seafloor altitude is measured based on the receiving beam in the axial direction, the seafloor altitude

FIG. 13 is a diagram showing another state in which UUV1 is rapidly infiltrating.
As shown in FIG. 13, UUV1 is in a rapid infiltration state (state D). However, the seafloor in the direction of travel of UUV1 is rising, and the seafloor altitude is high. In such a case, even if the seafloor altitude directly below UUV1 does not reach the altitude at which the ground speed by DVL8 can be measured, the seafloor altitude in the axial direction 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).

Although the present invention has been described above using the above-described embodiment, the technical scope of the present invention is not limited to the scope described in the above-described embodiment. Various changes or improvements can be made to the above embodiments without departing from the gist of the invention, and the modified or improved forms are also included in the technical scope of the present invention. Moreover, you may combine the said embodiment as appropriate.

Further, the flow of the seafloor 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 deviating from the gist of the present invention. You may do it.

1 UUV (underwater vehicle)
8 DVL (altimeter)
9 FLS (Underwater Altitude Detection Device)
20 Transmitter (transmission means)
21 Receiver (Receiving means)
22 Signal processing unit (processing means)
25 Feed forward control unit (control means)
27 Accuracy determination unit (accuracy determination means)
30 UUV controller (control means)

Claims (9)

A transmitting means provided on an underwater vehicle that navigates underwater and transmitting a wave beam in a predetermined angle range including directly below and below the front of the underwater vehicle with respect to the traveling direction of the underwater vehicle. ,
A receiving means for receiving the reflected wave reflected by the transmitting beam on the bottom of the water with a plurality of receiving beams having different directions.
A processing means for calculating the bottom altitude in a plurality of directions in front of the underwater vehicle based on the reflected wave received by the receiving means, and a processing means.
Equipped with a,
The processing means sets a non-calculation range according to the water bottom altitude calculated based on the reflected wave from directly below the underwater vehicle, and the water bottom is based only on the reflected wave beyond the non-calculation range. It calculates advanced underwater altitude sensing device. The water bottom altitude detecting device according to claim 1 , wherein the processing means calculates the water bottom altitude at a plurality of points within a predetermined angle range as the front and lower parts of the underwater vehicle. The water bottom altitude detecting device according to claim 1 or 2, wherein the water bottom altitude is averaged for each of a plurality of the water bottom altitudes calculated based on the reflected waves having the same depression angle. The water bottom altitude detection device according to any one of claims 1 to 3 ,
A control means for feed-forward controlling the underwater vehicle using the bottom altitude corresponding to one selected depression angle among the bottom altitudes calculated based on the reflected waves reflected by a plurality of depression angles.
An underwater vehicle equipped with. An altimeter that measures the altitude of the bottom of the water directly under the underwater vehicle,
An accuracy determination means for determining the accuracy of the water bottom altitude by the water bottom altitude detection device by comparing the measured value by the altimeter with the water bottom altitude by the water bottom altitude detection device.
With
When the accuracy of the water bottom altitude used by the control means is low, the water bottom altitude used by the control means is switched to the water bottom altitude calculated based on the reflected wave having a deeper depression angle, and the water bottom altitude is used by the control means. The underwater vehicle according to claim 4 , wherein when the accuracy of the bottom altitude is high, the bottom altitude used by the control means is switched to the bottom altitude calculated based on the reflected wave having a shallower depression angle. When the underwater vehicle performs rapid infiltration, the water bottom altitude detection device performs a water bottom detection determination process for determining whether or not the water bottom has been detected.
When the water bottom is detected by the water bottom detection determination process, the water bottom altitude detection device ends the water bottom detection determination process and performs a process of calculating the water bottom altitude in front of the underwater vehicle according to claim 4 or The underwater vehicle according to claim 5 . The underwater navigation according to claim 6, wherein when the altitude reaches the bottom of the water where the ground speed can be measured by the ground speedometer, the aircraft pitch angle of the underwater vehicle is raised to shift from rapid infiltration to gentle infiltration. Running body. In a state where the underwater vehicle is infiltrating and the water bottom is detected by the water bottom detection determination process.
The water bottom altitude detection device calculates the water bottom altitude in order from the reflected wave having a deep depression angle, and when the linear distance to the measured water bottom position exceeds the maximum detection distance, the water bottom altitude is calculated at a shallower depression angle. The underwater vehicle according to claim 6 or 7, wherein the above is not performed. From the transmitting means provided in the underwater vehicle traveling underwater, the wave transmitting beam is transmitted in a predetermined angle range including directly below and in front of and below the underwater vehicle with respect to the traveling direction of the underwater vehicle. Transmission process and
A receiving process in which the reflected wave reflected by the transmitting beam at the bottom of the water is received by a receiving means with a plurality of receiving beams having different directions.
A processing step of calculating the bottom altitude in a plurality of directions in front of the underwater vehicle based on the reflected wave received by the receiving means, and a processing step.
Have a,
In the processing step, a non-calculation range corresponding to the water bottom altitude calculated based on the reflected wave from directly below the underwater vehicle is set, and the water bottom is based only on the reflected wave beyond the non-calculation range. water bottom altitude detecting how to calculate the altitude.

Images