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EP 3 388 327 A1

EUROPEAN PATENT APPLICATION(12)published in accordance with Art. 153(4) EPC(51) Int Cl.:

(43) Date of publication:

B63C 11/00 (2006.01)

17.10.2018 Bulletin 2018/42(86) International application number:(21) Application number: 16873112.3

PCT/JP2016/086723(22) Date of filing: 09.12.2016(87) International publication number:
WO 2017/099219 (15.06.2017 Gazette 2017/24)(84) Designated Contracting States:(71) Applicant: National Institute of Maritime, Port and

AL AT BE BG CH CY CZ DE DK EE ES FI FR GB
GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO
PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
MA MD(30) Priority: 09.12.2015 JP 2015240252

Aviation
Technology
Tokyo 181-0004 (JP)(72) Inventor: KIM Kangsoo
Mitaka-shi
Tokyo 181-0004 (JP)(74) Representative: Balder IP Law, S.L.
Paseo de la Castellana 93
5ª planta
28046 Madrid (ES)(54)

ROUTE SETTING METHOD FOR UNDERWATER VEHICLE, UNDERWATER VEHICLE
OPTIMUM CONTROL METHOD USING SAME, AND UNDERWATER VEHICLE

EP 3 388 327 A1(57)

The present invention enables navigation control of an underwater vehicle by setting an optimum underwater navigation route with respect to a reference.
The route setting method is provided with: an underwater
waypoint input step S12 for inputting underwater waypoints of the underwater vehicle; a target value setting
step S 14 for setting initial target values at the underwater
waypoints; an underwater navigation simulation step S22
for simulating an underwater navigation route of the underwater vehicle by using water bottom topography data
and the target values on the basis of a dynamics modelof the underwater vehicle; and a target value update step
S28 for updating the target values on the basis of an
objective function which is calculated on the basis of theunderwater navigation route obtained through the simulation in the underwater navigation simulation step S22.
Optimum target values are derived by repeating the underwater navigation simulation step S22 and the target
value update step S28.

Printed by Jouve, 75001 PARIS (FR)1

EP 3 388 327 A1

Description

CITATION LISTTECHNICAL FIELDPATENT LITERATURE[0001] The present invention relates to a route setting
method for an underwater vehicle, an optimum control
method for an underwater vehicle using the same, andan underwater vehicle.

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BACKGROUND

10[0002] In recent years, the underwater bottom is drawing attention as a supply source of all resources ranging
from mineral resources. Accordingly, there has been an
increasing necessity for inspecting the underwater bottom. In the inspection of the underwater bottom, a remotesensing method using signals such as sonic waves, lasers, visible light, and electromagnetic waves is normallyemployed. However, since these signals suffer a propagation loss, these signals are used at positions as close
as possible to the underwater bottom in order to obtain
information of high resolution and high accuracy. Therefore, there is a need for a technology that enables anunderwater vehicle (for example, a submersible vessel)
to navigate (sails) on a desired route and in a desired
attitude near the underwater bottom.
[0003] There is disclosed a technique that the underwater vehicle is provided with a depth setting unit to set
a depth thereof, and performs control on driving of stern
steering on the basis of a predetermined depth (Patent
Document 1). Herein, a limit circuit is provided between
the depth setting unit and a depth control unit such thatthe underwater vehicle is controlled so as not to comeinto contact with the underwater bottom.
[0004] In relation to an automatic pilot of the underwater vehicle, there is disclosed a technique that an estimation accuracy of a dynamic state quantity is improved
using a dynamic model to trace a dynamic characteristicof the underwater vehicle in order to estimate its dynamic
state (Patent Document 2). In addition, there is disclosed
a technique of controlling the steering of the underwater
vehicle in consideration of an influence of tidal currents(Patent Document 3).
[0005] In addition, there is a need to acquire an accurate position of the underwater vehicle to control the navigation of the underwater vehicle. Moreover, there is disclosed a positioning technique in which the depths aremeasured at a plurality of positions using a multi-beam
depth sounder to specify the position of the underwater
vehicle (Patent Document 4). There is disclosed a technique in which the vehicle state information such as aspeed, a depth, a height, and an attitude of the underwater vehicle is acquired, a safety region for a safe navigation is set on the basis of the state information, andthe underwater vehicle is controlled to navigate in thesafety region (Patent Document 5).

2[0006]
Patent Document 1: JP 63-273797 A
Patent Document 2: JP 05-016878 A
Patent Document 3: JP 2003-127983 A
Patent Document 4: JP 2007-292729 A
Patent Document 5: JP 2015-063181 A
SUMMARY

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TECHNICAL PROBLEM[0007] A reflection intensity of an inspection signal
such as a sonic wave is in inverse proportion to an incident angle to the underwater bottom. In other words, thereflection intensity is remarkably weakened compared toa normal incidence (an incident angle of "0") when theincident angle is large at a region which is shallow withrespect to the underwater bottom. Therefore, in a casewhere a submarine topography has complicate ups anddowns, an intensity of a reflection signal is correlated tothe topography and is weak compared to a case where
the submarine topography is flat. Further, in a complicated submarine topography the problem of multipath is remarkable compared to a flat underwater bottom. As aresult, a height of a vehicle measured by a height indicator is lowered in reliability.
[0008] For such a reason, a height-based vertical control of a vehicle is rarely employed in view of the safe
navigation except a case where information of the heightis stably obtained with high accuracy similarly to the flat
underwater bottom, but a depth-based vertical control ofa vehicle is employed in many cases.
[0009] In an actual situation, when the depth control isapplied to underwater vehicle navigation, a target depth
is set such that the underwater vehicle is controlled to besafe from the bottom collision. However, a relation between a submarine topography and the dynamics of anunderwater vehicle is extremely difficult to be evaluatedin setting the target depth. Further, in a rough submarine
topography there is a concern of bottom collision. On theother hand, when the target depth is set to make theunderwater vehicle separated from the underwater bottom by a sufficient distance in order to avoid bottom collision, the quality of data obtained from the underwaterbottom and the resolution are remarkably degraded.
Therefore, in practice, the target depth is set to make theunderwater vehicle appropriately separated from the underwater bottom on the basis of experience and intuition.
In addition, the underwater vehicle may take a specificattitude (for example, an attitude parallel to the underwater bottom) according to a type of sensor used in theinspection of the underwater bottom. In this case, it isdesirable that the underwater vehicle navigate on a route3

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approximating most to the slopes of the underwater bottom while avoiding collision with the underwater bottom.
[0010] There is no consideration in all of Patent Documents 1 to 5 about a configuration that an underwater
waypoint is determined in order to obtain an optimum
underwater navigation route which can make the underwater vehicle approach the underwater bottom while preventing collision with the underwater bottom.
[0011] The invention has been made in view of at least
one of the above problems, and an object thereof is toprovide a route setting method for an underwater vehicle,
an optimum control method for an underwater vehicle
using the same, and the underwater vehicle, so that an
optimum route is set with respect to a reference to makethe underwater vehicle controlled to navigate.

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SOLUTION TO PROBLEM[0012] A route setting method for an underwater vehicle according to the present invention includes: inputting
an underwater waypoint of an underwater vehicle; setting
an initial target value in the underwater waypoint; simulating an underwater navigation route of the underwater
vehicle with respect to the target value on the basis of a
dynamic model of the underwater vehicle using data ofa submarine topography as a reference and the target
value; and updating the target value on the basis of an
objective function which is calculated on the basis of theunderwater navigation route obtained in the simulatingof the underwater navigation, wherein the target value is
optimized by repeatedly performing the simulation of theunderwater navigation and the updating of the target value.
[0013] Here, the target value is preferably a target
depth in the underwater waypoint.
[0014] Furthermore, the route setting method for anunderwater vehicle preferably further includes: setting aminimum allowable height of the underwater vehicle, andin the simulation of the underwater navigation, a calculated underwater navigation height of the underwater vehicle with respect to the target depth is preferably simulated on the basis of the dynamic model of the underwater
vehicle using the data of the submarine topography andthe target depth, and the calculated underwater navigation height and the minimum allowable height are preferably compared to derive the optimum target depth.
[0015] Furthermore, in the updating of the target value,
the target depth is preferably updated such that a minimum value of the calculated underwater navigation
height approaches the minimum allowable height in acase where there is a difference between the minimum
value of the calculated underwater navigation height andthe minimum allowable height.
[0016] Furthermore, a value of the objective function
is preferably a total sum of absolute values of differences
between the calculated underwater navigation heights at
a plurality of the underwater waypoints and the minimum
allowable height, or a total sum of squares of the differ-

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ences, and in the updating of the target value, the target
depth is preferably updated such that the value of theobjective function is decreased.
[0017] Furthermore, the target value is preferably a target height at the underwater waypoint.
[0018] Furthermore, the route setting method for anunderwater vehicle preferably further includes: setting aminimum allowable height of the underwater vehicle, andin the simulation of the underwater navigation, a calculated underwater navigation height of the underwater vehicle with respect to the target height is preferably simulated on the basis of the dynamic model of the underwater vehicle using the data of the submarine topography
and the target height, and the calculated underwater navigation height and the minimum allowable height are preferably compared to derive the optimum target height.
[0019] Furthermore, in the updating of the target value,
the target height is preferably updated such that a minimum value of the calculated underwater navigation
height approaches the minimum allowable height in acase where there is a difference between the minimum
value of the calculated underwater navigation height andthe minimum allowable height.
[0020] Furthermore, a value of the objective function
is preferably a total sum of absolute values of differences
between the calculated underwater navigation heights at
a plurality of the underwater waypoints and the minimum
allowable height, or a total sum of squares of the differences, and in the updating of the target value, the target
height is preferably updated such that the value of theobjective function is decreased.
[0021] Here, the target value is preferably a target reference attitude of the underwater vehicle at the underwater waypoint.
[0022] Furthermore, the route setting method for anunderwater vehicle preferably further includes: setting aminimum allowable height of the underwater vehicle, andin the simulation of the underwater navigation, a calculated underwater navigation height of the underwater vehicle with respect to the target reference attitude is preferably simulated on the basis of the dynamic model ofthe underwater vehicle using the data of the submarine
topography and the target reference attitude, and the calculated underwater navigation height and the minimum
allowable height are preferably compared to derive theoptimum target reference attitude.
[0023] Furthermore, in the updating of the target value,
the target reference attitude is preferably updated suchthat a minimum value of the calculated underwater navigation height approaches the minimum allowable heightin a case where there is a difference between the minimum value of the calculated underwater navigation
height and the minimum allowable height.
[0024] Furthermore, a value of the objective function
is preferably a total sum of absolute values of differences
between the calculated underwater navigation heights at
a plurality of the underwater waypoints and the minimum
allowable height, or a total sum of squares of the differ-

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ences, and in the updating of the target value, the target
reference attitude is preferably updated such that the value of the objective function is decreased.
[0025] Furthermore, the number of repetitions of thesimulation of the underwater navigation and the updatingof the target value is preferably set in advance.
[0026] Furthermore, a reference route is preferably
used instead of the data of the submarine topography.
In addition, a reference attitude of the underwater vehicle
at the underwater waypoint is preferably used instead ofthe data of the submarine topography. Furthermore, reference attitude angles of the underwater vehicle at theunderwater waypoint are preferably used instead of thedata of the submarine topography.
[0027] An optimum control method for an underwater
vehicle according to the present invention includes controlling the underwater vehicle using the optimum target
value obtained in the route setting method for an underwater vehicle described above.
[0028] Furthermore, the optimum target value and aposition of the underwater vehicle are preferably compared to control a motion control system of the underwater vehicle according to a comparison result.
[0029] Furthermore, the underwater vehicle preferably
surfaces urgently in a case where the optimum target
value and the position of the underwater vehicle deviate
from a predetermined condition.
[0030] Furthermore, an observation control is preferably performed to observe a submarine topography.
[0031] An underwater vehicle according to the present
invention preferably includes: a target value acquisition
unit which acquires the optimum target value acquired in
the route setting method for an underwater vehicle described above; a storage unit which stores the acquired
target value; and a motion control unit which controls adrive unit using the target value stored in the storage unit.
[0032] Here, the underwater vehicle preferably further
includes: at least one of a depth measuring unit, a heightmeasuring unit, and a attitude measurement unit, andthe motion control unit preferably compares a measurement value of at least one of the depth measuring unit,
the height measuring unit, and the attitude measurement
unit with the target value stored in the storage unit tocontrol the drive unit.
[0033] Furthermore, the underwater vehicle preferably
further includes: an obstacle detection unit, and the motion control unit preferably controls the drive unit according to a detection result of the obstacle detection unit.
[0034] Furthermore, the underwater vehicle preferably
further includes: an inertial navigation unit, and the motion control unit preferably controls the drive unit on thebasis of an output of the inertial navigation unit.
[0035] Furthermore, the underwater vehicle preferably
further includes: an observation unit which observes asubmarine topography.

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ADVANTAGEOUS EFFECTS OF INVENTION

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[0036] A route setting method for an underwater vehicle according to claim 1 includes inputting an underwater
waypoint of an underwater vehicle, setting an initial target
value in the underwater waypoint, simulating an underwater navigation route of the underwater vehicle with respect to the target value on the basis of a dynamic modelof the underwater vehicle and the data of a submarine
topography as a reference and the target value, and updating the target value on the basis of an objective function which is calculated on the basis of the underwaternavigation route obtained in the simulation of the underwater navigation. The target value is optimized by repeatedly performing the simulation of the underwater navigation and the updating of the target value. Therefore, it ispossible to set an optimum target value which is optimized to the submarine topography at the underwater
waypoint. With this configuration, the underwater vehicle
can navigate underwater with an optimum target value
at the underwater waypoint. Further, it is possible to set
a route which can realize the navigation in an optimum
navigation state according to a purpose.
[0037] Herein, the target value is a target depth at theunderwater waypoint. Therefore, it is possible to set an
optimum target depth which is optimized to the submarine topography at the underwater waypoint. With thisconfiguration, the underwater vehicle can navigate to be
the optimum target depth at the underwater waypoint.
Further, it is possible to set a route which can realize thenavigation of the optimum depth according to a purpose
such as observation.
[0038] In addition, the route setting method for an underwater vehicle includes setting a minimum allowableheight of the underwater vehicle. In the simulation of theunderwater navigation, a calculated underwater navigation height of the underwater vehicle with respect to thetarget depth is simulated on the basis of the dynamic
model of the underwater vehicle using the data of thesubmarine topography and the target depth, and the calculated underwater navigation height and the minimum
allowable height are compared to derive the optimum
target depth. Therefore, it is possible to set a route inwhich the underwater vehicle navigates underwater tobe the optimum target depth at the underwater waypoint
while avoiding the underwater vehicle from approaching
the underwater bottom below the minimum allowableheight.
[0039] In addition, in the updating of the target value,
the target depth is updated such that a minimum valueof the calculated underwater navigation height approaches the minimum allowable height in a case where there
is a difference between the calculated underwater navigation height and the minimum allowable height. Therefore, it is possible to set the optimum target depth suchthat the underwater vehicle approaches the underwaterbottom as close as possible at the underwater waypoint
while avoiding the underwater vehicle from approaching

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EP 3 388 327 A1

the underwater bottom below the minimum allowableheight.
[0040] In addition, the objective function is a total sumof absolute values of differences between the calculated
underwater navigation heights at a plurality of the underwater waypoints and the minimum allowable height, or a
total sum of squares of the differences. In the updatingof the target value, the target depth is updated such thatthe objective function is decreased. Therefore, it is possible to set the optimum target depths at the plurality ofunderwater waypoints such that a total sum of absolutevalues of differences between the calculated underwaternavigation heights at the plurality of underwater waypoints and the minimum allowable height, or a total sumof squares of the differences is minimized.
[0041] In addition, the target value is a target height at
the underwater waypoint. Therefore, it is possible to set
an optimum target height which is optimized to the submarine topography at the underwater waypoint. With thisconfiguration, the underwater vehicle can navigate to be
the optimum target height at the underwater waypoint.
Further, it is possible to set a route which can realize thenavigation of the optimum underwater navigation heightaccording to a purpose such as observation.
[0042] In addition, the route setting method for an underwater vehicle includes setting a minimum allowableheight of the underwater vehicle. In the simulation of theunderwater navigation, a calculated underwater navigation height of the underwater vehicle with respect to thetarget height is simulated on the basis of the dynamic
model of the underwater vehicle using the data of thesubmarine topography and the target height, and the calculated underwater navigation height and the minimum
allowable height are compared to derive the optimum
target height. Therefore, it is possible to set a route inwhich the underwater vehicle navigates underwater tobe the optimum height at the underwater waypoint while
avoiding the underwater vehicle from approaching theunderwater bottom below the minimum allowable height.
[0043] In addition, in the updating of the target value,
the target height is updated such that a minimum valueof the calculated underwater navigation height approaches the minimum allowable height in a case where there
is a difference between the calculated underwater navigation height and the minimum allowable height. Therefore, it is possible to set the optimum target height suchthat the underwater vehicle approaches the underwaterbottom as close as possible at the underwater waypoint
while avoiding the underwater vehicle from approaching
the underwater bottom below the minimum allowableheight.
[0044] In addition, the objective function is a total sumof absolute values of differences between the calculated
underwater navigation heights at a plurality of the underwater waypoints and the minimum allowable height, or a
total sum of squares of the differences. In the updatingof the target value, the target height is updated such thatthe objective function is decreased. Therefore, it is pos-

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sible to set the optimum target heights at the plurality ofunderwater waypoints such that a total sum of absolutevalues of differences between the calculated underwaternavigation heights at the plurality of underwater waypoints and the minimum allowable height, or a total sumof squares of the differences is minimized.
[0045] Herein, the target value is a target reference
attitude of the underwater vehicle at the underwater waypoint. Therefore, it is possible to set an optimum target
reference attitude which is optimized to the submarine
topography at the underwater waypoint. With this configuration, the underwater vehicle can navigate to be theoptimum target reference attitude at the underwater waypoint. Further, it is possible to set a route which can realize the navigation of the optimum underwater navigation attitude according to a purpose such as observation.
[0046] In addition, in the simulating of the underwaternavigation, a calculated underwater navigation height of
the underwater vehicle with respect to the target reference attitude is simulated on the basis of the dynamic
model of the underwater vehicle using the data of thesubmarine topography and the target reference attitude,
and the calculated underwater navigation height and theminimum allowable height are compared to derive theoptimum target reference attitude. Therefore, it is possible to set a route in which the underwater vehicle navigates underwater to be the optimum target reference attitude at the underwater waypoint while avoiding the underwater vehicle from approaching the underwater bottom below the minimum allowable height.
[0047] In addition, in the updating of the target value,
the target reference attitude is updated such that a minimum value of the calculated underwater navigation
height approaches the minimum allowable height in acase where there is a difference between the minimum
value of the calculated underwater navigation height andthe minimum allowable height. Therefore, it is possible
to set the optimum target reference attitude such that theunderwater vehicle approaches the underwater bottom
as close as possible at the underwater waypoint while
avoiding the underwater vehicle from approaching theunderwater bottom below the minimum allowable height.
[0048] In addition, a value of the objective function isa total sum of absolute values of differences between thecalculated underwater navigation heights at a plurality of
the underwater waypoints and the minimum allowableheight, or a total sum of squares of the differences. In
the updating of the target value, the target reference attitude is updated such that the value of the objective function is decreased. Therefore, it is possible to set the optimum target reference attitude at the plurality of underwater waypoints such that a total sum of absolute valuesof differences between the calculated underwater navigation heights at the plurality of underwater waypoints
and the minimum allowable height, or a total sum ofsquares of the differences is minimized.
[0049] In addition, the number of repetitions of the simulating of the underwater navigation and the updating of9EP 3 388 327 A1

the target value is set in advance. Therefore, it is possible
to complete an underwater navigation simulation an appropriate number of times.
[0050] In addition, a reference route is used instead ofthe data of the submarine topography. Alternatively, reference attitude angles of the underwater vehicle in theunderwater waypoint are used instead of the data of thesubmarine topography. Therefore, it is possible to optimize the target value such that the underwater vehicle
approaches the reference route or the reference attitude
angles at the underwater waypoint.
[0051] An optimum control method for an underwater
vehicle according to the present invention preferably controls the underwater vehicle using the optimum target
value obtained in the route setting method for the underwater vehicle. Therefore, it is possible that the underwater vehicle navigates underwater with the optimum target
value which is optimized to the submarine topography at
the underwater waypoint. Further, it is possible to set aroute which can realize the navigation in an optimum navigation state according to a purpose.
[0052] Herein, the optimum target value and a positionof the underwater vehicle are compared to control a motion control system of the underwater vehicle according
to a comparison result. Therefore, it is possible to specifically realize the optimum control method for the underwater vehicle.
[0053] In addition, the underwater vehicle urgently ina case where the optimum target value and the positionof the underwater vehicle deviate from a predetermined
condition. Therefore, it is possible to avoid a risk such asa case where the underwater vehicle is about to collidewith an obstacle.
[0054] In addition, an observation control is performed
to observe a submarine topography. Therefore, it is possible to perform observation while navigating in the underwater navigation state which is appropriate to the observation.
[0055] An underwater vehicle according to the present
invention preferably includes a target value acquisition
unit which acquires the optimum target value acquired in
the route setting method for the underwater vehicle, astorage unit which stores the acquired target value, anda motion control unit which controls a drive unit using thetarget value stored in the storage unit. Therefore, it ispossible to perform the underwater navigation with the
optimum target value which is optimized to the submarine
topography at the underwater waypoint. Further, it is possible to set a route which can realize the navigation in an
optimum navigation state according to a purpose.
[0056] Herein, the underwater vehicle includes at least
one of a depth measuring unit, a height measuring unit,
and an attitude measurement unit. The motion control
unit compares a measurement value of at least one ofthe depth measuring unit, the height measuring unit, andthe attitude measurement unit with the target value stored
in the storage unit to control the drive unit. Therefore, it
is possible to specifically realize the optimum control

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method for the underwater vehicle which obtains the optimum target value.
[0057] In addition, the underwater vehicle includes an
obstacle detection unit. The motion control unit controls
the drive unit according to a detection result of the obstacle detection unit. Therefore, it is possible to avoid arisk such as a case where the underwater vehicle is about
to collide with an obstacle.
[0058] In addition, the underwater vehicle includes aninertial navigation unit. The motion control unit controls
the drive unit on the basis of an output of the inertial
navigation unit. Therefore, it is possible to set the optimum target value which is optimized to the submarine
topography at the underwater waypoint only by the subject vehicle without acquiring the position informationfrom the outer side.
[0059] In addition, the underwater vehicle includes anobservation unit which observes a submarine topography. Therefore, it is possible to perform observation whilenavigating in the underwater navigation state which isappropriate to the observation.
BRIEF DESCRIPTION OF DRAWINGS

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[0060]
Fig. 1 is a conceptual diagram illustrating a configuration of an underwater vehicle according to an embodiment of the invention.
Fig. 2 is a diagram illustrating a configuration of aroute setting device of the underwater vehicle according to the embodiment of the invention.
Fig. 3 is a flowchart of a route setting method for theunderwater vehicle according to the embodiment of
the invention.
Fig. 4 is a functional block diagram of the route setting device of the underwater vehicle according to
the embodiment of the invention.
Fig. 5 is a diagram for describing a route setting process of the underwater vehicle according to the embodiment of the invention.
Fig. 6 is a flowchart of an optimum navigation controlof the underwater vehicle according to the embodiment of the invention.
Fig. 7 is a functional block diagram of the underwater
vehicle according to the embodiment of the invention.
Fig. 8 is a diagram illustrating an observation systemof a submarine topography using the underwater vehicle according to the embodiment of the invention.
DESCRIPTION OF EMBODIMENTS<System Configuration>

55[0061] Fig. 8 is a diagram illustrating an observation
system of a submarine topography using an underwater
vehicle according to an embodiment of the invention. The

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observation system is configured by an underwater vehicle 100 which submerges into the water, a route setting
device 200, and a support ship 300 on the water, on which
the route setting device is mounted. The underwater vehicle 100 navigates along an optimum underwater navigation route which is set to make a closest approach tothe underwater bottom while preventing collision in orderto observe a submarine topography 400 at an underwater
waypoint. The support ship 300 receives a GPS signal
from a satellite 500 to determine its own geographicalposition. Therefore, a geographical position of the underwater vehicle 100 can be known. In the support ship 300,
an acoustic positioning device 310 is mounted, so that a
relative position of the underwater vehicle 100 in the water from the support ship 300 can be ascertained. In addition, the underwater vehicle 100 can detect the relative
position to the support ship 300 using a position detection
unit mounted in the underwater vehicle 100. The support
ship 300 and the underwater vehicle 100 both can ascertain the relative position through an acoustic communication device 320. Therefore, the geographical positionof the underwater vehicle 100 can be ascertained in the
support ship 300 and/or the underwater vehicle 100 by
combining the geographical position obtained in the support ship 300 and the relative position obtained in the
acoustic positioning device 310 or the position detection
unit of the underwater vehicle 100.

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<Configuration of Underwater Vehicle>
30[0062] As illustrated in a conceptual diagram of Fig. 1,
the underwater vehicle 100 according to the embodimentof the invention is configured by a hull 10, a main propeller
12, a main propeller drive motor 14, a vertical rudder 16,
a vertical rudder drive motor 18, a horizontal rudder 20,
a horizontal rudder drive motor 22, a depth indicator 24,
a height indicator 26, an obstacle sensor 28, an observation sensor 30, an inertial navigation device 32 which
is a position detection unit, a control device 34, an acoustic communication device 36, and an acoustic positioning
device 38. The underwater vehicle 100 is, for example,
an autonomous underwater vehicle (AUV), but the invention is not limited thereto.
[0063] The hull 10 is a sealable structure which makes
spaces such as cabins. The hull 10 is configured by ametal or reinforced plastic material, and also serves tomechanically support components of the underwater vehicle 100.
[0064] The main propeller 12 is a component which
generates a driving force to propel the underwater vehicle
100. The main propeller 12 is configured by a propeller
and a rotation shaft, for example. The main propeller drive
motor 14 is a motor to apply the driving force to the main
propeller 12. The main propeller drive motor 14 receives
a drive control signal from the control device 34 to rotatably drive the rotation shaft of the main propeller 12 bypower from a battery 14a at the rotation number andtorque according to the drive control signal. With this con-

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figuration, the propeller connected to the drive shaft isrotated, and applies a propulsive force to the underwater
vehicle 100.
[0065] The vertical rudder 16 is a rudder to turn (revolve) the hull 10 in the right and left direction. The hull
10 can be revolved to the left or right side by inclining thevertical rudder 16 to the right or left side with respect tothe hull 10. The vertical rudder drive motor 18 is a motor
to generate a driving force to rotate the vertical rudder
16. The vertical rudder drive motor 18 receives a verticalsteering control signal from the control device 34 to rotatably drive the vertical rudder 16 to form attitude angles
corresponding to the vertical steering control signal.
[0066] Further, the hull 10 may be configured to turn(revolve) in the right and left direction such that the main
propellers 12 are individually provided on the right andleft sides to balance the propulsive force of the right andleft main propellers 12 without depending on the verticalrudder 16.
[0067] The horizontal rudder 20 is a rudder to raise andfall the hull 10. The hull 10 can pitch up or down by inclining up or down the horizontal rudder 20 with respect
to the hull 10. The horizontal rudder drive motor 22 is a
motor to generate a driving force to rotate the horizontal
rudder 20. The horizontal rudder drive motor 22 receives
a horizontal steering control signal from the control device 34 to rotatably drive the horizontal rudder 20 to form
attitude angles corresponding to the horizontal steering
control signal.
[0068] The depth indicator 24 is a device which measures a distance (depth) from the water surface of theunderwater vehicle 100 and outputs the distance. The
depth indicator 24 measures a depth from a water pressure applied to the hull 10 of the underwater vehicle 100
for example. The depth indicator 24 outputs the measured depth to the control device 34. The height indicator
26 is a device which measures a distance (height) fromthe underwater bottom to the underwater vehicle 100,and outputs the distance. The height indicator 26 outputs
sonic waves to the lower side of the hull 10 for example,
and measures the height on the basis of a time taken
until the sonic waves reflected on the underwater bottom
are received. The height indicator 26 outputs the measured height to the control device 34.
[0069] The obstacle sensor 28 is a sensor to detect an
obstacle which exists in an advancing direction (frontside) of the underwater vehicle 100. The obstacle sensor
28 outputs the sonic waves to the front side (or in a slightly
lower direction on the front side) of the hull 10, for example. The obstacle sensor measures the presence of an
obstacle and a distance thereto on the basis of a time
taken until the sonic waves reflected on the obstacle on
the front side are received. The obstacle sensor 28 outputs a detection result of the obstacle to the control device
34.
[0070] The observation sensor 30 is a sensor for theobservation of the underwater vehicle 100. The observation sensor 30 may be configured by various sensors

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according to the purpose of the observation. The observation sensor 30 may be configured by a sonic wave
sensor, an electromagnetic wave sensor, an optical sensor, a pressure sensor, and a thermal sensor, for example. The observation sensor 30 outputs an observed result to the control device 34.
[0071] The inertial navigation device 32 includes anacceleration sensor and a gyro sensor which measure
an acceleration when the hull 10 moves. Position information of the hull 10 is obtained by twice integrating theaccelerations measured by these sensors with respect
to time. The position information of the underwater vehicle 100 obtained by the control device 34 is output to thecontrol device 34.
[0072] The control device 34 receives information fromthe depth indicator 24, the height indicator 26, the obstacle sensor 28, the observation sensor 30, and the inertial
navigation device 32, and controls the navigation of theunderwater vehicle 100 on the basis of the information.
The control device 34 controls the main propeller 12, thevertical rudder drive motor 18, and the horizontal rudder
drive motor 22 on the basis of the position informationfrom the inertial navigation device 32, the depth from thedepth indicator 24, and height information from the heightindicator 26. Therefore, the hull 10 approaches a predetermined underwater waypoint and a target value (a target depth, a target height, a target attitude, a target attitude angle, etc.) which is set by a route setting method(described below). Navigation control of the control device 34 will be described below.
[0073] The acoustic communication device 36 is a device which communicates with the outer side of the underwater vehicle 100 through the sonic waves. The
acoustic communication device 36 receives information
about the results and the navigation from the control device 34 which are measured by the depth indicator 24,
the height indicator 26, the obstacle sensor 28, the observation sensor 30, and the inertial navigation device
32. The acoustic communication device 36 transmits theinformation to the outer side of the underwater vehicle
100 (for example, a ship on the sea). In addition, theacoustic communication device receives an absolute position which is measured by a GPS in the outer side (forexample, a ship on the sea).
[0074] The acoustic positioning device 38 receives therelative position between the underwater vehicle 100 anda ship on the outer side. When being provided in a shipon the sea, the acoustic positioning device 38 acquires
information of the relative position of the underwater vehicle 100. The relative position information is input to thecontrol device 34. The control device 34 acquires information of an absolute position of the ship on the sea
which is acquired by the acoustic communication device
36. The control device can obtain an absolute positionof the underwater vehicle 100 from the absolute positionof the ship and the relative position of the underwater
vehicle 100. The control device 34 can correct the position information acquired from the inertial navigation de-

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vice 32 using the absolute position information of the underwater vehicle 100 thus acquired. For example, thecontrol device 34 corrects the position of the inertial navigation device 32 using the position of the acoustic positioning device 38 in a case where a difference between
the position calculated from the relative position information acquired from the acoustic positioning device 38 andthe position acquired from the inertial navigation device
32 is larger than a predetermined value. The inertial navigation device 32 keeps estimating the position of theunderwater vehicle 100 using the corrected position asa new initial value.
<Route Setting Method for Underwater Vehicle>

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[0075] A route setting process of the underwater vehicle 100 according to this embodiment will be described
below. In this embodiment, the description will be given
about a case where the route setting is performed by theroute setting device 200 separated from the underwater
vehicle 100. In this case, the invention is not limited tothe above configuration, and the route setting device 200
may be mounted in the underwater vehicle 100.
[0076] As illustrated in Fig. 2, the route setting device
200 is a computer which includes a processing unit 40,
a storage unit 42, an input unit 44, and an output unit 46.
The processing unit 40 is configured by a CPU. The
processing unit 40 performs the route setting process(described below) by executing a route setting program
which is stored in the storage unit 42 in advance. The
storage unit 42 is a storage device to store the routesetting program, a hull motion calculation model, and various types of data. The storage unit 42 may be a semiconductor memory and a hard disk, for example. The
input unit 44 includes a device which inputs information
to the route setting device 200 to perform the route setting
process. The input unit 44 may be a keyboard, a mouse,
and a touch panel. In addition, the input unit 44 may acquire information from other devices through a network
interface. The output unit 46 includes a device to output
information of a route obtained by the route setting device
200. The output unit 46 may be a display and a printer.
In addition, information may be output to the control device 34 of the underwater vehicle 100 through the output
unit 46 as the network interface.
[0077] The route setting process is performed along a
flowchart of Fig. 3. The route setting device 200 serves
as the respective units illustrated in a functional block
diagram of Fig. 4 by executing the route setting process.
[0078] In step S10, an initial setting is performed. In
this process, the route setting device 200 serves as an
initial setting unit 50. In the initial setting, information of
the submarine topography 400 is input, the maximum
number of repetitions (Ne) is set, and a minimum allowable height (ha) is set as a reference using the input unit
44. The information of the submarine topography 400 is
information indicating a height of topography at every
coordinate of the underwater bottom in a navigation tar-

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EP 3 388 327 A1

get region of the underwater vehicle 100 as illustrated
with a thick solid line of Fig. 5. The maximum number ofrepetitions (Ne) is a maximum number of repetitions in
the route setting process. The minimum allowable height(ha) is a minimum allowable height from the underwaterbottom to set a route so that the underwater vehicle 100
does not come into contact with the underwater bottom.
[0079] In step S12, an input process of the underwater
waypoint is performed. In this process, the route setting
device 200 serves as an underwater waypoint setting
unit 52. The underwater waypoints are information indicated by discrete coordinates on a navigation route of
the underwater vehicle 100 in a plane (the water surface;a surface parallel to the sea surface). In other words, theunderwater waypoints are sequentially connected to obtain a two-dimensional navigation route of the underwater
vehicle 100. The underwater waypoints are set according
to an entire underwater navigation route plan based on
an observation plan in advance.
[0080] In step S14, initial target values at the respective
underwater waypoints are set. In this process, the routesetting device 200 serves as a target value setting unit
54. In this embodiment, the target value is a target depthof the underwater vehicle 100. In other words, as illustrated in Fig. 5, an initial value (illustrated as a white triangle in the drawing) of a target depth of the underwaternavigation route of the underwater vehicle 100 is set forevery the underwater waypoint which is input in step S12.
[0081] In step S16, the hull dynamic model is set. In
this process, the route setting device 200 serves as ahull dynamic model setting unit 56. The hull dynamic
model is also called AUV dynamics in which the motionof the hull 10 (or the underwater vehicle 100) in the water
is obtained on the basis of calculation. Equations of motion represented by differential equations in a time domain are a typical example. As a general solution, a
speed and an angular speed component as unknown
quantities in the equations of motion are found using aforce applied to an object and a moment component as
inputs. In many cases, an initial condition is given by ananalytic procedure to obtain a general solution, and anumerical procedure is used to obtain a time sequenceof speeds and angular speeds as time passes. Specifically, the solution is determined on the basis of response
characteristics of the main propeller 12, the vertical rudder 16, and the horizontal rudder 20, and a movement
characteristic of the hull 10. When an optimum target
value (the depth and the height) in the invention is obtained, there is used a procedure of updating the target
value by a sequential method as illustrated in Fig. 3. However, the hull dynamic model is used as a tool for obtaining a behavior of the hull 10 (AUV) in a numerical mannerby an underwater navigation simulation in the procedure.
A coefficient term in the equations of motion is a functionof a fluid force operating on the hull 10, and is frequently
called a hydrodynamic coefficient. The hydrodynamic coefficient can be obtained by a tank test using a scalemodel of the hull or a numerical calculation using a pro-

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cedure of a computational fluid dynamics. In the equations of motion, items other than the hydrodynamic coefficient are variables and an external force item, so thatthe equations of motion are completed by obtaining thehydrodynamic coefficient.
[0082] In steps S18 to S32, there are performed theunderwater navigation simulation in which the underwater navigation route of the underwater vehicle 100 withrespect to the target value is simulated on the basis of
the dynamic model of the underwater vehicle 100 using
data and the target depth of the submarine topography
400, and an optimization analysis in which a target value
updating process is repeatedly performed to update thetarget depth and the target value (target depth) at theunderwater waypoint is optimized on the basis of an objective function which is calculated on the basis of theunderwater navigation route obtained in the underwaternavigation simulation.
[0083] In step S18, a counter ie is set to an initial value"0." The counter ie is used to count the number of repetitions of the simulation. In step S20, "1" is added to thecounter ie.
[0084] In step S22, the underwater navigation simulation is performed. In this process, the route setting device
200 serves as a target value following simulation unit 58.
The processing unit 40 simulates the underwater navigation route of the underwater vehicle 100 using the information of the submarine topography 400 input in step
S10, the underwater waypoint input in step S12, and thetarget depths of the current underwater waypoints suchthat the hull 10 approaches the submarine topography
400 at each underwater waypoint on the basis of the hull
dynamic model set in step S16. In addition, the underwater navigation route of the underwater vehicle 100 may
be simulated such that the hull 10 approaches the minimum allowable height (ha). With the simulation, there are
obtained a new underwater navigation route of the underwater vehicle 100; that is, an underwater navigation
depth (a distance from the water surface to the hull 10,
hereinafter, referred to as a calculated underwater navigation depth), and an underwater navigation height (adistance from the underwater bottom to the hull 10, hereinafter, referred to as a calculated underwater navigation
height) at each underwater waypoint.
[0085] In step S24, it is determined whether a distance(calculated underwater navigation height) from the underwater bottom at each underwater waypoint in the newunderwater navigation route obtained in the simulationin step S22 is larger than the minimum allowable height(ha). In this process, the route setting device 200 serves
as an underwater navigation height confirming unit 60.
In a case where there is an underwater waypoint where
the calculated underwater navigation height is lower thanthe minimum allowable height (ha), the simulation is ended and the process proceeds to step S30. In a case where
there is no underwater waypoint where the calculated
underwater navigation height is lower than the minimum
allowable height (ha), the process proceeds to step S26.

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EP 3 388 327 A1[0086] In step S26, it is determined whether the counterie is equal to the maximum number of repetitions (Ne).
In this process, the route setting device 200 serves as arepetition count confirming unit 62. In a case where thecounter ie is less than the maximum number of repetitions(Ne), the process proceeds to step S28 and, if not, theprocess proceeds to step S30.
[0087] In step S28, an optimization procedure is applied on the basis of the objective function to update thetarget depth at each underwater waypoint. In this process, the route setting device 200 serves as a target value
updating unit 64. The objective function is set with respect
to a specific target in the navigation of the underwater
vehicle 100. For example, in a case where the hull 10 isintended to submerge from the water surface as deep as
possible, a total sum of the calculated underwater navigation depths of the hull 10 in the entire underwater navigation route is set to the objective function. Then, theprocessing unit 40 updates the target value at each underwater waypoint such that the value of the objectivefunction is minimized. Thereafter, the process returns tostep S20 to repeat the simulation of the underwater navigation route again using the new target value.
[0088] In a case where the process proceeds to step
S30, an optimum target value (optimum target depth) isset. In this process, the route setting device 200 serves
as an optimum target value setting unit 66. In step S32,
the processing unit 40 sets and outputs the current target
depth as the optimum target depth (depicted with a black
circle in the drawing) as illustrated in Fig. 5. In this process, the route setting device 200 serves as an optimum
target value output unit 68. The optimum target depth isa target depth at each underwater waypoint to take theunderwater navigation route as deep from the water surface as possible while keeping the minimum allowableheight (ha) so as not to come into contact with the underwater bottom when the underwater vehicle 100 navigates underwater.
[0089] With the above process, when a navigation control of the underwater vehicle 100 is performed, the target
depth (target depth) at each underwater waypoint is optimized. Therefore, the underwater vehicle 100 can navigate underwater in an appropriate underwater navigation route by controlling a motion control system of theunderwater vehicle 100 such that the target depth at eachunderwater waypoint is optimized.
[0090] Further, in a case where the hull 10 is intended
to approach the underwater bottom as close as possible,
a total sum of the calculated underwater navigation
heights of the hull 10 in the entire underwater navigationroute may be set to the objective function in step S28.
Then, the processing unit 40 updates the target value ateach underwater waypoint such that the value of the objective function is minimized. Thereafter, the process returns to step S20 to repeat the simulation of the underwater navigation route again using the new target value.
Then, in a case where the process proceeds to step S30,
an optimum target value (optimum target height) is set.

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[0091] With the above process, when the navigation
control of the underwater vehicle 100 is performed, thetarget depth at each underwater waypoint is optimized.
Therefore, the underwater vehicle 100 can navigate underwater in an appropriate underwater navigation routeby controlling the motion control system of the underwater vehicle 100 such that the target height at each underwater waypoint is optimized. Further, when the speed of
the underwater vehicle 100 is lowered, the inertial influence becomes smaller. Therefore, it is considered thatthe underwater navigation route may be taken deep fromthe water surface while avoiding the collision with theunderwater bottom. However, when the speed is lowered, the vertical rudder 16 and the horizontal rudder 20
are degraded in effectiveness. Further, efficiency in inspection on the underwater bottom is also degraded, andthus there is a limitation. In addition, if the speed is increased excessively, there occur a limitation in the control system and problems in resolution and accuracy at
the time of observation. Therefore, there is an appropriate speed range for every underwater vehicle 100.
[0092] In addition, in this embodiment, the objectivefunction has been set to a total sum of the depths or theheights of the hull 10 in the entire underwater navigationroute, but the invention is not limited thereto. For example, in a case where the hull 10 is intended to approacha reference route (a reference depth and a reference
height) as a predetermined reference instead of approaching the underwater bottom on the basis of the submarine topography 400, a total sum of absolute valuesof differences between the depths of the hull 10 in theentire underwater navigation route and the reference
route (the reference depth and the reference height) ora total sum of squares of the differences is set to theobjective function. The target value (the target depth andthe target height) may be optimized on the basis of theobjective function.
[0093] In addition, in a case where the hull 10 is intended to be controlled in its attitude, an attitude (for example,
an angle of the hull to make the hull 10 parallel to an
inclined angle of the underwater bottom) at each underwater waypoint is set in advance as a reference. In step
S28, a total sum of absolute values of differences between the attitudes (angles of the hull) of the hull 10 in
the entire underwater navigation route and the reference
attitude or a total sum of squares of the differences may
be set to the objective function. Then, the processing unit
40 updates the target value at each underwater waypointsuch that the value of the objective function is minimized.
Then, in a case where the process proceeds to step S30,
an optimum target value is set.
<Optimum Navigation Control of Underwater Vehicle>

55

10[0094] Hereinafter, the navigation control of the underwater vehicle 100 will be described on the basis of the
optimum target value which is set in the route setting
process of the underwater vehicle 100.

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EP 3 388 327 A1[0095] A navigation control process is progressedalong a flowchart of Fig. 6. The respective units of theunderwater vehicle 100 serve as the respective units illustrated in a functional block diagram of Fig. 7 so as torealize the navigation control.
[0096] In step S40, the optimum target value (optimum
target depth) is input and set. In this process, the control
device 34 of the underwater vehicle 100 serves as an
optimum target value input unit 70. The optimum target
value (optimum target depth) set by the route setting
method for the underwater vehicle 100 is input to thecontrol device 34 through an input unit (not illustrated) of
the control device 34, and is stored in a storage unit 72
of the control device 34. Herein, the input to the underwater vehicle 100 may be performed using an input device which is laid on the control device 34, or may be
performed by an external interface such as the acoustic
communication device 36. Further, the optimum target
value is derived along a flowchart of Fig. 3 normally by
the support ship 300 or according to an observation plan
before the support ship 300 puts out to sea, and the optimum target value is input to the control device 34. However, the optimum target value may be derived by performing the route setting method when the control device
34 of the underwater vehicle 100 starts the underwaternavigation.
[0097] In a case where the underwater vehicle 100 is
applied to the autonomous underwater vehicle (AUV),
the underwater vehicle 100 may receive a predetermined
optimum target value (optimum target depth) and conditions from a ship on the sea, and submerge into the sea
to autonomously navigate. As a merit on the control of
the underwater vehicle 100 by inputting the predetermined optimum target value (optimum target depth), theunderwater vehicle 100 can be accurately controlled
without being affected by a delay on time taken when theunderwater navigation route is repeatedly simulated.
[0098] In step S42, the position of the underwater vehicle 100 is measured by the inertial navigation device
32 and the acoustic communication device 36. The control device 34 acquires the position information of theunderwater vehicle 100 which is obtained by the inertial
navigation device 32. In this process, the underwater vehicle 100 serves as a subject vehicle motion detection
unit 76. As described above, the control device 34 may
be configured to correct the position information of theunderwater vehicle 100 which is obtained by the inertial
navigation device 32 on the basis of the position information obtained from the acoustic communication device
36. In this process, the underwater vehicle 100 serves
as a subject vehicle position calculation unit 78.
[0099] In step S44, the underwater navigation of theunderwater vehicle 100 is controlled. The control device
34 controls the navigation of the underwater vehicle 100
to sequentially trace the optimum target values (optimum
target depths) at the underwater waypoints from the current position of the underwater vehicle 100 using the position information acquired in step S42. The control de-

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vice 34 outputs a drive control signal, a vertical steering
control signal, and a horizontal steering control signal tothe main propeller drive motor 14, the vertical rudder drive
motor 18, and the horizontal rudder drive motor 22 respectively so as to control the driving thereof. Thus, themain propeller 12, the vertical rudder 16, and the horizontal rudder 20 move to control the behavior of the hull
10. In addition, the motion of the hull 10 is detected by
the acceleration sensor and the gyro sensor of the inertial
navigation device 32 to obtain the position informationfrom the behavior of the hull 10. With such a process,the control device 34 controls the motion of the underwater vehicle 100 such that the hull 10 has the optimum
target values (optimum target depth) at each underwater
waypoint. In this process, the underwater vehicle 100
serves as a hull motion control unit 74.
[0100] In step S46, a necessary observation is performed by the observation sensor 30. In other words,
there is performed, for example, the observation of thesubmarine topography 400 which is the purpose of theunderwater navigation of the underwater vehicle 100.
The control device 34 may transmit an observation result
to the outer side of the hull 10 through the acoustic communication device 36. In this process, the underwater
vehicle 100 serves as an observation execution unit 80.
[0101] In step S48, it is determined whether there is aneed for emergency surfacing. In a case where the obstacle sensor 28 detects an obstacle against the navigation of the underwater vehicle 100, the control device 34
causes the process proceed to step S50 to float the hull
10 urgently and ends the underwater navigation. On theother hand, in a case where no obstacle is detected, theprocess proceeds to step S52. With this process, theunderwater vehicle 100 serves as an emergency surfacing determination unit 82. Further, the emergency surfacing may be performed by a command from a ship on
the sea through the acoustic communication device 36.
[0102] In step S52, it is determined whether the hull
reaches a final underwater waypoint. The control device
34 determines whether the hull 10 reaches the final underwater waypoint of the underwater navigation route
among the predetermined underwater waypoints. If thehull reaches the final underwater waypoint, the processproceeds to step S54 to normally float the underwater
vehicle 100, and the underwater navigation is ended. If
the hull 10 does not reach the middle underwater waypoint, the process returns to step S44 to keep the navigation control toward the next underwater waypoint.
[0103] As described above, the underwater vehicle
100 can navigate along an underwater navigation routeand in an underwater navigation attitude which are appropriate to a purpose by performing the navigation control of the underwater vehicle 100 to realize the underwater navigation route (the target values at the respective
underwater waypoints) set by the route setting method
for the underwater vehicle. With this configuration, an
observation of the underwater vehicle 100 can be realized in an optimum state. Further, Fig. 5 illustrates a di-

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EP 3 388 327 A1

agram for describing the route setting process of the underwater vehicle according to the embodiment of the invention, which is an example when the route setting
method and the underwater vehicle 100 of this embodiment are applied to a real sea area. Submarine resourceswere surveyed at Myojin knoll caldera located in the sea
near the Izu islands of Japan in June, 2015 using theunmanned underwater vehicle "URASHIMA" for navigation (developed by Japan Agency for Marine-Earth Science and Technology) as the underwater vehicle 100.
The "URASHIMA" navigated in the entire underwaternavigation area at an average height of 67 m and a minimum height of 39 m (a minimum setting height was 40m). The "URASHIMA" is a large underwater vehicle(AUV) having an overall length of 8 m. Assuming Myojinknoll caldera has an extremely rugged underwater bottom which has a steep slope of 53 degrees at maximum,
the result shows that an extremely high degree of difficulty has been cleared. When an appropriate route point
is derived, an initial depth at each route point is set at
120 m above from the underwater depth of the corresponding coordinates (latitude/longitude), and an appropriate depth (optimum target value) at each route point
is derived using the route setting method of the embodiment. In this way, according to the route setting method
for the underwater vehicle 100 of this embodiment, it ispossible to reduce the height (increase the target depth)
to an average of 67 m down to 39 m at minimum withrespect to the initial target value of 120 m. Further, it isproved that the navigation along a predetermined underwater navigation route can be made even in the navigation of a real sea area.

22

28: obstacle sensor
30: observation sensor
32: inertial navigation device
34: control device
36: acoustic communication device
38: acoustic positioning device
40: processing unit
42: storage unit
44: input unit
46: output unit
50: initial setting unit
52: underwater waypoint setting unit
54: target value setting unit
56: hull dynamic model setting unit
58: target value following simulation unit
60: underwater navigation height confirming unit
62: repetition count confirming unit
64: target value updating unit
66: optimum target value setting unit
68: optimum target value output unit
70: optimum target value input unit
72: storage unit
74: hull motion control unit
76: subject vehicle motion detection unit
78: subject vehicle position calculation unit
80: observation execution unit
82: emergency surfacing determination unit
100: underwater vehicle
200: route setting device
300: support ship
400: submarine topography
500: satellite

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INDUSTRIAL APPLICABILITY
35[0104] The invention is able to be applied to a routesetting and a navigation control of an underwater vehicle
as well as a movement route and a movement control ofa moving body according to a predetermined condition
such as topography data and a reference attitude. For
example, the invention is able to be applied to a movement route setting and a movement control of an airplane
and a drone.
REFERENCE SIGNS LIST

1.

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[0105]
10: hull
12: main propeller
14: main propeller drive motor
14a: battery
16: vertical rudder
18: vertical rudder drive motor
20: horizontal rudder
22: horizontal rudder drive motor
24: depth indicator
26: height indicator

Claims50

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A route setting method for an underwater vehicle,
comprising:
inputting an underwater waypoint of an underwater vehicle;
setting an initial target value on the underwater
waypoint;
simulating an underwater navigation route of theunderwater vehicle with respect to the target value on the basis of a dynamic model of the underwater vehicle using data of a submarine topography as a reference and the target value;
andupdating the target value on the basis of an objective function which is calculated on the basisof the underwater navigation route obtained in
the simulating of the underwater navigation,
wherein the target value is optimally derived byrepeatedly performing the simulation of the underwater navigation and the updating of the target value.

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the data of the submarine topography and thetarget height, and the calculated underwaternavigation height and the minimum allowableheight are compared to derive the optimum target height.

The route setting method for an underwater vehicleaccording to claim 1,
wherein the target value is a target depth on the underwater waypoint.
5

3.

The route setting method for an underwater vehicleaccording to claim 2, further comprising:setting a minimum allowable height of the underwater vehicle,
wherein, in the simulation of the underwater navigation, a calculated underwater navigation
height of the underwater vehicle with respect tothe target depth is simulated on the basis of the
dynamic model of the underwater vehicle using
the data of the submarine topography and thetarget depth, and the calculated underwaternavigation height and the minimum allowableheight are compared to derive the optimum target depth.

4.

5.

6.

7.

The route setting method for an underwater vehicleaccording to claim 3,
wherein, in the updating of the target value, the target
depth is updated such that a minimum value of thecalculated underwater navigation height approaches the minimum allowable height in a case where
there is a difference between the minimum value ofthe calculated underwater navigation height and theminimum allowable height.
The route setting method for an underwater vehicleaccording to claim 3 or 4,
wherein a value of the objective function is a totalsum of absolute values of differences between thecalculated underwater navigation heights at a plurality of the underwater waypoints and the minimum
allowable height, or a total sum of squares of thedifferences, andin the updating of the target value, the target depth
is updated such that the value of the objective function is decreased.
The route setting method for an underwater vehicleaccording to claim 1,
wherein the target value is a target height at the underwater waypoint.
The route setting method for an underwater vehicleaccording to claim 6, further comprising:setting a minimum allowable height of the underwater vehicle,
wherein, in the simulation of the underwater navigation, a calculated underwater navigation
height of the underwater vehicle with respect tothe target height is simulated on the basis of the
dynamic model of the underwater vehicle using

8.

The route setting method for an underwater vehicleaccording to claim 7,
wherein, in the updating of the target value, the target
height is updated such that a minimum value of thecalculated underwater navigation height approaches the minimum allowable height in a case where
there is a difference between the minimum value ofthe calculated underwater navigation height and theminimum allowable height.

9.

The route setting method for an underwater vehicleaccording to claim 7 or 8,
wherein a value of the objective function is a totalsum of absolute values of differences between thecalculated underwater navigation heights at a plurality of the underwater waypoints and the minimum
allowable height, or a total sum of squares of thedifferences, andin the updating of the target value, the target height
is updated such that the value of the objective function is decreased.

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10. The route setting method for an underwater vehicleaccording to claim 1,
wherein the target value is a target reference attitudeof the underwater vehicle at the underwater waypoint.
11. The route setting method for an underwater vehicleaccording to claim 10, further comprising:setting a minimum allowable height of the underwater vehicle,
wherein, in the simulation of the underwater navigation, a calculated underwater navigation
height of the underwater vehicle with respect tothe target reference attitude is simulated on thebasis of the dynamic model of the underwater
vehicle using the data of the submarine topography and the target reference attitude, and thecalculated underwater navigation height and theminimum allowable height are compared to derive the optimum target reference attitude.

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12. The route setting method for an underwater vehicleaccording to claim 11,
wherein, in the updating of the target value, the target
reference attitude is updated such that a minimum
value of the calculated underwater navigation heightapproaches the minimum allowable height in a casewhere there is a difference between the minimum
value of the calculated underwater navigation height25

EP 3 388 327 A1

and the minimum allowable height.
13. The route setting method for an underwater vehicleaccording to claim 11 or 12,
wherein a value of the objective function is a totalsum of absolute values of differences between thecalculated underwater navigation heights at a plurality of the underwater waypoints and the minimum
allowable height, or a total sum of squares of thedifferences, andin the updating of the target value, the target reference attitude is updated such that the value of theobjective function is decreased.
14. The route setting method for an underwater vehicleaccording to any one of claims 1 to 13,
wherein the number of repetitions of the simulationof the underwater navigation and the updating of thetarget value is set in advance.

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15. The route setting method for an underwater vehicleaccording to claim 1,
wherein a reference route is used instead of the dataof the submarine topography.
25

16. The route setting method for an underwater vehicleaccording to claim 1,
wherein reference attitude angles of the underwater
vehicle at the underwater waypoint is used insteadof the data of the submarine topography.
17. An optimum control method for an underwater vehicle comprising:
controlling the underwater vehicle using the optimum
target value obtained in the route setting method for
an underwater vehicle according to any one of claims
1 to 16.
18. The optimum control method for an underwater vehicle according to claim 17, wherein the optimum
target value and a position of the underwater vehicle
are compared to control a motion control system of
the underwater vehicle according to a comparison
result.

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19. The optimum control method for an underwater vehicle according to claim 18,
wherein the underwater vehicle surfaces urgently ina case where the optimum target value and the position of the underwater vehicle deviate from a predetermined condition.
20. The optimum control method for an underwater vehicle according to any one of claims 17 to 19,
wherein an observation control is performed to observe a submarine topography.

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21. An underwater vehicle, comprising:

14

26
a target value acquisition unit which acquires
the optimum target value acquired in the routesetting method for an underwater vehicle according to any one of claims 1 to 16;
a storage unit which stores the acquired target
value; anda motion control unit which controls a drive unit
using the target value stored in the storage unit.

22. The underwater vehicle according to claim 21, further comprising:at least one of a depth measuring unit, a heightmeasuring unit, and a attitude measurement
unit,
wherein the motion control unit compares ameasurement value of at least one of the depth
measuring unit, the height measuring unit, andthe attitude measurement unit with the target
value stored in the storage unit to control thedrive unit.
23. The underwater vehicle according to claim 21 or 22,
further comprising:an obstacle detection unit,
wherein the motion control unit controls the drive unit
according to a detection result of the obstacle detection unit.
24. The underwater vehicle according to any one ofclaims 21 to 23, further comprising:an inertial navigation unit,
wherein the motion control unit controls the drive
unit on the basis of an output of the inertial navigation unit.
25. The underwater vehicle according to any one ofclaims 21 to 24, further comprising:an observation unit which observes a submarine topography.

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REFERENCES CITED IN THE DESCRIPTIONThis list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European
patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be
excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description
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•
•

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JP 63273797 A [0006]
JP 5016878 A [0006]
JP 2003127983 A [0006]

24

JP 2007292729 A [0006]
JP 2015063181 A [0006]