U.S. patent application number 15/498936 was filed with the patent office on 2018-04-12 for underwater mobile body.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Motofumi BABA, Tsutomu KIMURA, Yoshihiko NEMOTO, Masahiro SATO, Kengo TOKUCHI, Akihito YAMAUCHI.
Application Number | 20180102854 15/498936 |
Document ID | / |
Family ID | 61829164 |
Filed Date | 2018-04-12 |
United States Patent
Application |
20180102854 |
Kind Code |
A1 |
KIMURA; Tsutomu ; et
al. |
April 12, 2018 |
UNDERWATER MOBILE BODY
Abstract
An underwater mobile body includes: a communication unit that
has a plurality of communicators adopting different communication
systems and that performs underwater wireless communication with
another device using one of the plurality of communicators; an
acquisition unit that acquires information on depth or information
varying with depth; and a control unit that controls the
communication unit to switch, between the plurality of
communicators and based on the acquired information, the one
communicator used for underwater wireless communication
Inventors: |
KIMURA; Tsutomu; (Kanagawa,
JP) ; BABA; Motofumi; (Kanagawa, JP) ; SATO;
Masahiro; (Kanagawa, JP) ; NEMOTO; Yoshihiko;
(Kanagawa, JP) ; YAMAUCHI; Akihito; (Kanagawa,
JP) ; TOKUCHI; Kengo; (Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
61829164 |
Appl. No.: |
15/498936 |
Filed: |
April 27, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 13/02 20130101 |
International
Class: |
H04B 13/02 20060101
H04B013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2016 |
JP |
2016-198244 |
Claims
1. An underwater mobile body comprising: a communication unit that
has a plurality of communicators adopting different communication
systems and that performs underwater wireless communication with
another device using one of the plurality of communicators; an
acquisition unit that acquires information on depth or information
varying with depth; and a control unit that controls the
communication unit to switch, between the plurality of
communicators and based on the acquired information, the one
communicator used for underwater wireless communication.
2. The underwater mobile body according to claim 1, wherein when
communication is not possible with any of the plurality of
communicators, the control unit moves the underwater mobile body to
a predetermined position and attempts to establish
communication.
3. The underwater mobile body according to claim 2, wherein when
communication is not possible with the plurality of communicators
even after the movement to the predetermined position, the control
unit causes a failure signal transmitter to transmit a failure
signal.
4. The underwater mobile body according to claim 1, wherein the
control unit selects a communicator having a faster communication
speed from the plurality of communicators in a case where the depth
is smaller.
5. The underwater mobile body according to claim 4, wherein in an
area where the depth is small, the control unit selects a
communicator that uses radio waves from the plurality of
communicators, and in an area where the depth is large, the control
unit selects a communicator that uses sound waves from the
plurality of communicators.
6. An underwater mobile body comprising: a communication unit that
has a plurality of communicators adopting different communication
systems and that performs underwater wireless communication with
another device using one of the plurality of communicators; and a
control unit that, when depth is changed, controls the
communication unit to switch the one communicator to another one of
the plurality of communicators.
7. An underwater mobile body comprising: a communication unit that
performs underwater wireless communication with another device; and
a state detection unit that detects a state of the underwater
wireless communication performed by the communication unit, wherein
depth is changed according to a result of the detection by the
state detection unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2016-198244 filed Oct.
6, 2016.
BACKGROUND
Technical Field
[0002] The present invention relates to an underwater mobile
body.
SUMMARY
[0003] According to an aspect of the invention, there is provided
an underwater mobile body including: a communication unit that has
multiple communicators adopting different communication systems and
that performs underwater wireless communication with another device
using one of the multiple communicators; an acquisition unit that
acquires information on depth or information varying with depth;
and a control unit that controls the communication unit to switch,
between the plurality of communicators and based on the acquired
information, the one communicator used for underwater wireless
communication.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Exemplary embodiments of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 is a diagram illustrating a configuration example of
an underwater drone according to a first exemplary embodiment;
[0006] FIG. 2 is a block diagram illustrating an example of a
functional configuration of a controller according to the first
exemplary embodiment;
[0007] FIG. 3 is an illustration conceptually explaining switching
between communication systems performed by a communication
controller according to the first exemplary embodiment;
[0008] FIG. 4 is a flowchart illustrating an example of processing
steps executed by the controller according to the first exemplary
embodiment;
[0009] FIG. 5 is a diagram illustrating a configuration example of
an underwater drone according to a second exemplary embodiment;
[0010] FIG. 6 is a block diagram illustrating an example of a
functional configuration of a controller according to the second
exemplary embodiment;
[0011] FIG. 7 is an illustration conceptually explaining switching
between communication systems performed by a communication
controller according to the second exemplary embodiment;
[0012] FIG. 8 is a flowchart illustrating an example of processing
steps executed by the controller according to the second exemplary
embodiment;
[0013] FIG. 9 is an illustration for explaining the concept of
control performed by a communication controller according to a
third exemplary embodiment;
[0014] FIG. 10 is a flowchart illustrating an example of processing
steps executed by the communication controller according to the
third exemplary embodiment;
[0015] FIG. 11 is an illustration for explaining the concept of
control performed by a communication controller according to a
fourth exemplary embodiment;
[0016] FIG. 12 is a flowchart illustrating an example of processing
steps executed by the communication controller according to the
fourth exemplary embodiment.
[0017] FIG. 13 is a conceptual illustration of control operations
in a fifth exemplary embodiment;
[0018] FIG. 14 is a flowchart illustrating an example of processing
steps executed by the communication controller according to the
fifth exemplary embodiment;
[0019] FIG. 15 is a conceptual illustration of control operations
in a sixth exemplary embodiment; and
[0020] FIG. 16 is a flowchart illustrating an example of processing
steps executed by the communication controller according to the
sixth exemplary embodiment.
DETAILED DESCRIPTION
[0021] Hereinafter, exemplary embodiments of the present invention
will be described in detail with reference to the accompanying
drawings.
First Exemplary Embodiment
[0022] <Configuration of Underwater Drone>
[0023] FIG. 1 is a diagram illustrating a configuration example of
an underwater drone 1 according to a first exemplary embodiment.
The underwater drone 1 is an example of an underwater mobile body,
and more specifically, is a type of unmanned underwater mobile
body. The underwater drone is classified into an autonomous
navigation type and a remote-control type. In this exemplary
embodiment, the underwater drone is assumed to be remote-control
type. However, the details of the control described later may be
applied to an autonomous navigation underwater drone.
[0024] In the underwater drone 1 according to this exemplary
embodiment, functional units are connected to a controller 10 which
is as an example of a control unit. The functional units including
the controller 10 are basically housed in a housing which adopts a
waterproof structure. Power is supplied from a battery 22 to the
functional units including the controller 10. The battery 22 is an
example of a power source, and uses, for instance, a primary
battery, a secondary battery and/or a fuel cell. It is to be noted
that an internal combustion engine may be used as the power
source.
[0025] The controller 10 controls the units that configurate the
underwater drone 1. The controller 10 is configurated by a central
processing unit (CPU) 11, a read only memory (ROM) 12, and a random
access memory (RAM) 13. The ROM 12 stores programs to be executed
by the CPU 11. The CPU 11 reads a program stored in the ROM 12, and
executes the program using the RAM 13 as a work area. The CPU 11
controls the functional units that configurate the underwater drone
1, by the execution of the program.
[0026] The underwater drone 1 is equipped with multiple
communicators adopting different communication systems. In the case
of this exemplary embodiment, the underwater drone 1 is equipped
with two types of communicator: a radio wave communicator 15 and a
sound wave communicator 16. The radio wave communicator 15 is a
communicator that transmits and receives radio waves, and the sound
wave communicator 16 is a communicator that transmits and receives
sound waves. The radio wave communicator 15 and the sound wave
communicator 16 are examples of a communicator that configurates
the communication unit.
[0027] The radio wave communicator 15 in this exemplary embodiment
uses radio waves with a wavelength of 10 to 100 km, called very low
frequency radio waves for communication. In this case, the
transmission distance underwater is 10 m. It is to be noted that
when radio waves with a wavelength of 100 to 1,000 km, called
extremely low frequency radio waves is used for communication, the
transmission distance underwater is 100 m. However, the
transmission distance varies depending on whether communication is
performed in fresh water or sea water, and is affected by the
presence of wave on the surface of water, the presence of turbidity
and a water temperature.
[0028] The sound wave communicator 16 in this exemplary embodiment
uses sound waves for communication. In general, the transmission
distance underwater of sound waves is several 100 to several 1,000
m, and may reach 10,000 m. In the case of this exemplary
embodiment, the radio wave communicator 15 is selected for shallow
water area, and the sound wave communicator 16 is selected for a
deep water area.
[0029] An illuminator 17 is provided to illuminate an operating
range. As the illuminator 17, for instance, a halogen lamp, a white
light emitting diode (LED) or a color LED is used. An imaging
camera 18 is provided to capture an image of the operating range.
The imaging camera 18 may be a camera that captures a still image
or a camera that captures a dynamic image. A captured image is
stored in the RAM 13, for instance.
[0030] A depth sensor 19 detects a depth utilizing a water
pressure. The depth sensor 19 converts a detected water pressure to
a depth, and outputs the depth to the controller 10. The accuracy
of measurement of and resolution of the depth depend on the depth
sensor 19.
[0031] A steerer 20 is used to change the direction of movement.
The direction of movement is controlled by remote control or a
program executed by the controller 10. The direction of movement
includes not only a direction in a horizontal plane, but also a
vertical direction (a surfacing direction and a descending
direction). A propeller 21 is configurated by, for instance, a
propeller and a motor that rotates the propeller. The motor has a
watertight structure to protect the inside from rusting.
[0032] <Functional Configuration of Controller>
[0033] Next, the functional configuration of the controller 10 will
be described. FIG. 2 is a block diagram illustrating an example of
the functional configuration of the controller 10 according to the
first exemplary embodiment. The controller 10 has a depth acquirer
101 and a communication controller 102. The depth acquirer 101 is
an example of the acquisition unit, and the communication
controller 102 is an example of the control unit.
[0034] The depth acquirer 101 acquires a depth D from the depth
sensor 19, and stores the depth D, for instance, in the RAM 13. The
communication controller 102 compares the acquired depth D with a
threshold Th_D, and determines a communication system (specifically
communicator) to be used for underwater wireless communication. In
the case of this exemplary embodiment, the threshold Th_D is set to
10 m. The value of the threshold Th_D depends on the wavelength and
application of radio waves to be used.
[0035] FIG. 3 is an illustration conceptually explaining switching
between communication systems performed by the communication
controller 102 according to the first exemplary embodiment. The
depth D here is the distance from a water surface 200 to the
underwater drone 1, and is given as a value measured by the depth
sensor 19.
[0036] The communication controller 102 compares the measured value
of the depth D with the threshold Th_D, and determines a
communication system to be used according to a result of the
comparison. In the case of this exemplary embodiment, the
communication controller 102 uses a water depth area shallower than
the threshold Th_D as a radio wave communication area 201, and uses
a water depth area deeper than the threshold Th_D as a sound wave
communication area 202. This is because radio waves have a shorter
underwater transmission distance and a higher transmission speed
compared with sound waves.
[0037] Use of radio waves with a relatively high transmission speed
increases the responsiveness of the underwater drone 1 to a user
operation. Therefore, in a shallow water area (radio wave
communication area 201), the operability of a user is improved
compared with the case where only sound waves are used for
underwater wireless communication. In addition, the use of radio
waves is also advantageous for achieving real-time transmission of
image data captured by the imaging camera 18 because of the high
transmission speed.
[0038] In contrast, in an area where it is difficult for radio
waves to reach or an area where radio waves do not reach (sound
wave communication area 202) due to the large depth of water,
remote control of the underwater drone 1 is continued by using
sound waves. Although the transmission speed of sound waves is
lower than the transmission speed of radio waves, remote control is
also continued due to a longer transmission distance of sound
waves. It is to be noted that the current image format may be
switched to an image format having a higher compression rate at a
timing when the communication system is switched to the sound wave
system.
[0039] The communication controller 102 outputs a switching signal
when detecting satisfaction of switching conditions. Specifically,
the communication controller 102 outputs a signal to switch the
communicator used for communication from the radio wave
communicator 15 to the sound wave communicator 16, or a signal to
switch the communicator used for communication from the sound wave
communicator 16 to the radio wave communicator 15.
[0040] <Processing Steps Executed by Underwater Drone 1>
[0041] Next, the processing steps executed by the underwater drone
1 according to this exemplary embodiment will be described. FIG. 4
is a flowchart illustrating an example of processing steps executed
by the controller 10 (the communication controller 102) according
to the first exemplary embodiment. The controller 10 repeatedly
executes the processing of the flowchart illustrated in FIG. 4. In
the case of this exemplary embodiment, the flowchart illustrated in
FIG. 4 is executed every time a predetermined time elapses.
[0042] First, the communication controller 102 measures the depth D
(step 101). In the case of this exemplary embodiment, as the depth
D, the value measured by the depth sensor 19 is used as it is.
[0043] Next, the communication controller 102 determines whether or
not the depth D has become larger than the threshold Th_D (step
102). The determination here is made based on whether or not the
relationship of D.ltoreq.Th_D has changed to the relationship of
D>Th_D. For instance, it is determined whether or not the
measured depth D is switched from a state of being smaller than 10
m to a state of being larger than 10 m.
[0044] When an affirmative result is obtained in step 102, the
communication controller 102 switches the communication system from
the radio wave communication system (the radio wave communicator
15) to the sound wave communication system (the sound wave
communicator 16) (step 103). Although the transmission speed is
basically decreased due to the switching to the sound wave
communication system, even after a depth D, which does not allow
communication by the radio wave communication system, is reached,
remote control and transmission of image data are continued. It is
to be noted that when communication by the sound wave communication
system is selected, decrease in the transmission speed may be
reduced by enhancing the image compression rate or increasing the
number of communications channels. After the switching here, the
flow for the communication controller 102 returns to step 101.
[0045] When a negative result is obtained in step 102, the
communication controller 102 determines whether or not the depth D
has become smaller than the threshold Th_D (step 104). The
determination here is made based on whether or not the relationship
of D.gtoreq.Th_D has changed to the relationship of D<Th_D. For
instance, it is determined whether or not the measured depth D is
switched from a state of being larger than 10 m to a state of being
smaller than 10 m.
[0046] When an affirmative result is obtained in step 104, the
communication controller 102 switches the communication system from
the sound wave communication system (the sound wave communicator
16) to the radio wave communication system (the radio wave
communicator 15) (step 105). The switching to the radio wave
communication system makes the transmission speed higher than the
transmission speed in the sound wave communication system. After
the switching here, the flow for the communication controller 102
returns to step 101. It is to be noted that when a negative result
is obtained in step 104, the communication controller 102 does not
switch the communication system, that is, maintains the
communication system and the flow returns to step 101.
[0047] As described above, the controller 10 of the underwater
drone 1 according to this exemplary embodiment is equipped with the
radio wave communicator 15 and the sound wave communicator 16, and
switching between communication using these two types of
communicators is done based on whether or not the depth D of the
drone 1 has changed across a predetermined threshold Th_D.
Specifically, in an area where the depth is smaller than the
threshold Th_D, radio waves are used for communication, and in an
area where the depth is larger than the threshold Th_D, sound waves
are used for communication. Therefore, the operability of a user is
improved compared with the case where only sound waves are used for
underwater wireless communication.
[0048] For instance, for fishing, inspection of marine facilities
or leisure, remote control application of the underwater drone 1 in
a shallow water area is assumed. As described above, due to a
higher transmission speed of radio waves, the operability of a user
is improved compared with the case where the underwater drone 1 is
remotely controlled using only sound waves regardless of the depth.
Meanwhile, for the purpose of avoiding an underwater obstacle such
as a structure or a terrain, or due to the effect of stream of
water, the underwater drone 1 may be moved to a deep water area
where radio waves do not reach.
[0049] However, when the underwater drone 1 is moved to a deep
water area, the communication system is switched to the sound wave
communication system having a long transmission distance, and thus
remote control is continued. For this reason, the operability of a
user is not reduced compared with the case where wireless
communication is performed using radio waves only. It is to be
noted that switching between the communication systems may be
performed not only when the transmission distance increases in the
depth direction, but also when the transmission distance increases
in a horizontal direction. Consequently, the operating range of the
underwater drone 1 is increased, and the operability of a user is
improved.
[0050] Although the determination processing by the communication
controller 102 is repeatedly executed at a predetermined execution
interval in this exemplary embodiment, when the depth D is close to
the threshold Th_D, the execution interval for the determination
processing may be reduced. In this case, the execution interval is
increased when the depth D is away from the threshold Th_D, and
thus the consumption of a battery is reduced. In addition, since
the frequency of execution of the determination processing
increases in the vicinity of the threshold Th_D where the necessity
of switching between the communication systems is high, the timing
of changing the depth D across the threshold Th_D approaches the
timing of switching between the communication systems.
[0051] Although determination as to switching between the
communication systems is done at a predetermined time interval in
this exemplary embodiment, the execution interval may be changed
according to the movement speed in the depth direction, that is,
the surfacing speed or the descending speed of the drone 1. For
instance, when the movement speed is low, the execution interval
may be increased because the change in the depth is small, and when
the movement speed is high, the execution interval may be decreased
because the change in the depth is large.
[0052] Although the communication system is switched after
detecting a change of the measured depth D across the threshold
Th_D in this exemplary embodiment, the depth D may be simply
compared with the threshold Th_D and according to the magnitude
relationship, a signal for switching to the radio wave system or
the sound wave system may be outputted. Although the case is
assumed where the underwater drone 1 communicates with a
communication device (not illustrated) that is operated by a user
for remote control in this exemplary embodiment, the underwater
drone 1 may communicate with a communication device mounted on a
ship or a buoy, or may autonomously navigate without communicating
with the outside.
[0053] Although the same value is used as the threshold Th_D for
determination as to switching between the communication systems for
both cases where the depth D increases and the depth D decreases in
this exemplary embodiment, as in the case of a second embodiment
described later, different values may be used for the cases where
the depth D increases and the depth D decreases.
Second Exemplary Embodiment
<Configuration of Underwater Drone>
[0054] FIG. 5 is a diagram illustrating a configuration example of
an underwater drone 1A according to a second exemplary embodiment.
The underwater drone 1A according to the second exemplary
embodiment does not use information on the depth D for switching
between the communication systems, and differs from the
above-described underwater drone 1 according to the first exemplary
embodiment in that the transmission speed V is used.
[0055] In this exemplary embodiment, attention is focused on that
the underwater transmission speed V is changed under the effect of
the depth D. It is to be noted that the transmission speed V is
affected by not only the depth D but also a wave height or
transparency (turbidity), and when the wave height is high or when
the transparency is low, the transmission speed V is reduced. Thus,
in contrast to the case where a fixed threshold Th_D for the depth
D is given, in this exemplary embodiment, selection of a
communication system based on a change in the communication state
is achieved.
[0056] As far as switching between communication systems in this
exemplary embodiment is concerned, the depth sensor 19 is not
required. For this reason, the depth sensor 19 is not mounted on
the underwater drone 1A illustrated in FIG. 5. However, the depth
sensor 19 may be mounted for a purpose other than switching between
communication systems.
[0057] <Functional Configuration of Controller>
[0058] Next, the functional configuration of a controller 10A will
be described. FIG. 6 is a block diagram illustrating an example of
the functional configuration of the controller 10A according to the
second exemplary embodiment. The controller 10A has a transmission
speed acquirer 103 and a communication controller 104. The
transmission speed acquirer 103 is an example of the acquisition
unit, and the communication controller 104 is an example of the
control unit.
[0059] The transmission speed acquirer 103 acquires a transmission
speed V based on the amount of data exchanged between a
communicator in use (that is, either one of the radio wave
communicator 15 and the sound wave communicator 16) and another
communication device (mounted on, for instance, a ship or a buoy).
The transmission speed V is calculated as the amount of data
transmitted per unit of time.
[0060] The communication controller 104 compares the acquired
transmission speed V with a threshold Th_V, and determines a
communication system (specifically, a communicator) used for
underwater wireless communication. The value of the threshold Th_V
depends on the wavelength and application of radio waves to be
used.
[0061] FIG. 7 is an illustration conceptually explaining switching
between communication systems performed by the communication
controller 104 according to the second exemplary embodiment. FIG. 7
illustrates an example in which another communication device
serving as a communication partner is mounted on a ship 300. As
described above, the transmission speed V is calculated by the
transmission speed acquirer 103. The communication controller 104
compares the transmission speed V with the threshold Th_V, and
determines a communication system to be used according to a result
of the comparison. In the case of this exemplary embodiment, the
communication controller 104 uses an area with the transmission
speed higher than the threshold Th_V as a radio wave communication
area 203, and uses an area with the transmission speed lower than
the threshold Th_V as a sound wave communication area 204. This is
because radio waves have a shorter underwater transmission distance
and a higher transmission speed compared with sound waves.
[0062] In the radio wave communication area 203, use of radio waves
with a relatively high transmission speed increases the
responsiveness of the underwater drone 1A to a user operation.
Therefore, in an area where the depth is small (the radio wave
communication area 203), the operability of a user is improved
compared with the case where only sound waves are used for
underwater wireless communication. In addition, the use of radio
waves is also advantageous for achieving real-time transmission of
image data captured by the imaging camera 18 because of the high
transmission speed.
[0063] In contrast, sound waves are used in the sound wave
communication area 204, and thus, in spite of a lower transmission
speed, remote control of the underwater drone 1A is continued.
Although the transmission speed of sound waves is lower than the
transmission speed of radio waves, remote control is also continued
due to a longer transmission distance of sound waves. It is to be
noted that the current image format may be switched to an image
format having a higher compression rate at a timing when the
communication system is switched to the sound wave system.
[0064] The communication controller 104 outputs a switching signal
when detecting satisfaction of switching conditions. Specifically,
the communication controller 104 outputs a signal to switch the
communicator used for communication from the radio wave
communicator 15 to the sound wave communicator 16, or a signal to
switch the communicator used for communication from the sound wave
communicator 16 to the radio wave communicator 15. In FIG. 7,
although the communication area is set in the depth direction,
switching between the communication systems according to this
exemplary embodiment may be used when the transmission distance
increases in a horizontal direction, and the transmission speed V
changes.
[0065] <Processing Steps Executed by Underwater Drone 1A>
[0066] Next, the processing steps executed by the underwater drone
1A according to this exemplary embodiment will be described. FIG. 8
is a flowchart illustrating an example of processing steps executed
by the controller 10A (the communication controller 104) according
to the second exemplary embodiment. The controller 10A repeatedly
executes the processing of the flowchart illustrated in FIG. 8. In
the case of this exemplary embodiment, the flowchart illustrated in
FIG. 8 is executed every time a predetermined time elapses.
[0067] First, the communication controller 104 acquires a
transmission speed V from the transmission speed acquirer 103 (step
201). Subsequently, the communication controller 104 determines
whether or not the transmission speed V has become slower than the
threshold Th_V1 (step 202). The determination here is made based on
whether or not the relationship of V.gtoreq.Th_V1 has changed to
the relationship of V<Th_V1. The threshold Th_V1 is a threshold
that is used when switching from radio waves to sound waves is
done, and that is defined based on the transmission speed of radio
waves.
[0068] When an affirmative result is obtained in step 202, the
communication controller 104 switches the communication system from
the radio wave communication system (the radio wave communicator
15) to the sound wave communication system (the sound wave
communicator 16) (step 203). Although the transmission speed is
basically decreased due to the switching to the sound wave
communication system, even after a post-change communication state
disconnects communication in the radio wave communication system
(for instance, even after the depth exceeds the transmission
distance of radio waves), remote control and transmission of image
data are continued. It is to be noted that in communication by the
sound wave communication system, decrease in the transmission speed
may be reduced by enhancing the image compression rate or
increasing the number of communications channels. After the
switching here, the flow for the communication controller 104
returns to step 201.
[0069] When a negative result is obtained in step 202, the
communication controller 104 determines whether or not the
transmission speed V has become higher than the threshold Th_V2
(step 204). The determination here is made based on whether or not
the relationship of V.ltoreq.Th_V2 has changed to the relationship
of V>Th_V2. The threshold Th_V2 is a threshold that is used when
switching from sound waves to radio waves is done, and that is
defined based on the transmission speed of sound waves. It is to be
noted that although two types of thresholds Th_V1 and Th_V2 are
used in the description here, a common threshold may be used for
both cases where switching from radio waves to sound waves is done
and switching from sound waves to radio waves is done.
[0070] When an affirmative result is obtained in step 204, the
communication controller 104 switches the communication system from
the sound wave communication system (the sound wave communicator
16) to the radio wave communication system (the radio wave
communicator 15) (step 205). In the case of sound waves, the
transmission speed V is higher in a shallow water area than in a
deep water area. The communication controller 104 detects this
change. Switching the communication system to the radio wave
communication system makes the transmission speed higher than the
transmission speed in the sound wave communication system.
[0071] After the switching here, the flow for the communication
controller 104 returns to step 201. It is to be noted that when a
negative result is obtained in step 204, the communication
controller 104 does not switch the communication system, that is,
maintains the communication system and the flow returns to step
201.
[0072] As described above, the controller 10A of the underwater
drone 1A according to this exemplary embodiment is equipped with
the radio wave communicator 15 and the sound wave communicator 16,
and switching between communication using these two types of
communicators is done based on whether or not the transmission
speed V measured at the time of determination has changed across a
predetermined threshold Th_V (Th_V1 or Th_V2).
[0073] Specifically, when the underwater drone 1A is in
communication through radio waves, in a water area where the
transmission speed V is higher than the threshold Th_V1,
communication via radio waves is maintained, and in a water area
where the transmission speed V is lower than the threshold Th_V1,
sound waves are used for communication. On the other hand, when the
underwater drone 1A is in communication through sound waves, in a
water area where the transmission speed V is lower than the
threshold Th_V2, communication via sound waves is maintained, and
in a water area where the transmission speed V is higher than the
threshold Th_V2, radio waves are used for communication.
[0074] In other words, when the operating water range of the
underwater drone 1A is changed to a shallow area, switching to the
communication via radio waves with a higher transmission speed is
done, and when the operating water range of the underwater drone 1A
is changed to a deep area and the transmission speed is reduced,
switching to the communication via sound waves with a longer
transmission distance is done. Therefore, the operability of a user
is improved compared with the case where only sound waves are used
for underwater wireless communication.
[0075] For instance, for fishing, inspection of marine facilities
or leisure, remote control application of the underwater drone 1 in
a shallow water area is assumed. As described above, due to a
higher transmission speed of radio waves, the operability of a user
is improved compared with the case where the underwater drone 1 is
remotely controlled using only sound waves regardless of the depth.
Meanwhile, for the purpose of avoiding an underwater obstacle such
as a structure or a terrain, or due to the effect of stream of
water, the underwater drone 1 may be moved to a deep water area
where radio waves do not reach.
[0076] However, when the underwater drone 1 is moved to a deep
water area and the transmission speed V is reduce, the
communication system is switched to the sound wave communication
system having a long transmission distance, and thus remote control
is continued. For this reason, the operability of a user is
improved compared with the case where wireless communication is
performed using radio waves only. It is to be noted that switching
between the communication systems is not limited to when the
transmission distance increases in the depth direction. For
instance, also when the transmission distance increases in a
horizontal direction, switching between the communication systems
causes the operating water range of the underwater drone 1 to
increase, and thus the operability of a user is improved.
[0077] Although the determination processing by the communication
controller 102 is repeatedly executed at a predetermined execution
interval in the above-described exemplary embodiment, when the
transmission speed V is close to the threshold Th_V1 or Th_V2, the
execution interval for the determination processing may be reduced.
In this case, the execution interval is increased when the
transmission speed V is away from the threshold Th_V1 or Th_V2, and
the consumption of a battery is reduced. In addition, since the
frequency of execution of the determination processing increases in
the vicinity of the threshold Th_V1 or Th_V2 where the necessity of
switching between the communication systems is high, the timing of
changing the transmission speed V across the Th_V1 or Th_V2
approaches the timing of switching between the communication
systems.
[0078] Although determination as to switching between the
communication systems is made at a predetermined time interval in
the above-described exemplary embodiment, the execution interval
may be changed according to the movement speed in the depth
direction, that is, the surfacing speed or the descending speed of
the drone 1. For instance, when the movement speed is low, the
execution interval may be increased because the change in the depth
is small, and when the movement speed is high, the execution
interval may be decreased because the change in the depth is
large.
[0079] Although the communication system is switched after
detecting a change of the measured transmission speed V across the
threshold Th_V1 or Th_V2 in the above-described exemplary
embodiment, the transmission speed V may be simply compared with
the threshold Th_V1 or Th_V2 and according to the magnitude
relationship, switching to the radio wave system or the sound wave
system may be done.
Third Exemplary Embodiment
[0080] The underwater drone 1 in the above-described first
exemplary embodiment switches between the communication systems
when the depth D of the drone 1 is changed across the threshold
Th_D. However, in this exemplary embodiment, a new function of
placing priority to the transmission speed is added to the
communication controller 102. Thus, the underwater drone 1 in this
exemplary embodiment uses the underwater drone 1 in the first
exemplary embodiment as it is.
[0081] FIG. 9 is an illustration for explaining the concept of
control performed by the communication controller 102 according to
the third exemplary embodiment. As seen from FIG. 9, in the case of
this exemplary embodiment, even when the underwater drone 1 arrives
at an area deeper than the threshold Th_D, the radio wave
communication system is maintained as the communication system
(from time T1 to time T2).
[0082] However, when the depth D continues to descend with the
radio wave communication system maintained, communication becomes
impossible, and thus the communication controller 102 in this
exemplary embodiment controls the steerer 20 controls the steerer
20 to forcedly surface the underwater drone 1 (from time T2 to time
T3). Thus, the underwater drone 1 continues to work in an area
shallower than the threshold Th_D, and consequently, communication
via radio waves with a relatively high transmission speed is
maintained. In this exemplary embodiment, the depth sensor 19
functions as an example of the state detection unit.
[0083] Next, the processing steps executed by the underwater drone
1 according to this exemplary embodiment will be described. FIG. 10
is a flowchart illustrating an example of processing steps executed
by the communication controller 102 according to the third
exemplary embodiment. In the case of this exemplary embodiment,
after the measurement (step 101) of the depth D, the communication
controller 102 determines whether or not the current mode is a
high-speed communication mode (step 111). The high-speed
communication mode is a communication mode that places priority to
the communication via radio waves with a transmission speed higher
than the transmission speed of sound waves, and a user specifies
the high-speed communication mode in advance.
[0084] The operation to be performed when a negative result is
obtained in step 111 is the same as what has been described in the
first exemplary embodiment. When an affirmative result is obtained
in step 111, the communication controller 102 determines whether or
not the depth D has become larger than the threshold Th_D (step
112). In other words, as in the first exemplary embodiment, it is
determined whether or not a phenomenon, which triggers switching of
the communication system to the sound wave communication system,
has occurred. As long as a negative result is obtained in step 112,
communication via radio waves is continued, and the communication
controller 102 repeats the determination processing.
[0085] When an affirmative result is obtained in step 112, the
communication controller 102 controls the steerer 20 in the
surfacing direction (step 113). Thus, the underwater drone 1 is
controlled and forcedly moved in a direction in which the depth D
decreases. Since the control is performed when the depth D is
detected to be larger than the threshold Th_D, communication via
radio waves is not interrupted.
[0086] Next, the communication controller 102 determines whether or
not the depth D has become smaller than the threshold Th_D (step
114). In the determination, whether or not the depth has returned
to a depth in the radio wave communication area 201 is determined.
As long as a negative result is obtained in step 114, surfacing of
the underwater drone 1 has to be continued, and the communication
controller 102 repeats the determination processing.
[0087] When an affirmative result is obtained in step 114, the
communication controller 102 controls the steerer 20 to stop the
surfacing (step 115). This is because the underwater drone 1 has
returned to the radio wave communication area 201 where the
transmission speed is high. It is to be noted that since the
control is autonomously performed in consideration of the
transmission speed, the subsequent control is again remote control
by a user.
[0088] In this exemplary embodiment, as described above, the
underwater drone 1 is assumed to be equipped with the radio wave
communicator 15 and the sound wave communicator 16 as the
communicators. However, the invention is applicable to an
underwater drone equipped with only one communicator. This is
because communication in the radio wave communication area 201 is
continued without switching between communication systems.
Fourth Exemplary Embodiment
[0089] The underwater drone 1A in the above-described second
exemplary embodiment switches between the communication systems
when the transmission speed V has changed across the threshold
Th_V1 or Th_V2. However, in this exemplary embodiment, a new
function of placing priority to the transmission speed is added to
the communication controller 104. Thus, the underwater drone 1A in
this exemplary embodiment uses the underwater drone 1A in the
second exemplary embodiment as it is. In this exemplary embodiment,
the transmission speed acquirer 103 functions as an example of the
state detection unit.
[0090] FIG. 11 is an illustration for explaining the concept of
control performed by the communication controller 104 according to
the fourth exemplary embodiment. As seen from FIG. 11, in the case
of this exemplary embodiment, even when the underwater drone 1A
arrives at a depth of water where the transmission speed V of the
underwater drone 1A is lower than the threshold Th_V1, the radio
wave communication system is maintained as the communication system
(from time T1 to time T2).
[0091] However, when the depth D continues to descend with the
radio wave communication system maintained, communication becomes
impossible, and thus the communication controller 104 in this
exemplary embodiment controls the steerer 20 controls the steerer
20 to forcedly surface the underwater drone 1A (from time T2 to
time T3). Thus, the underwater drone 1A continues to work in an
area where the transmission speed V is lower than the threshold
Th_V1, and consequently, communication via radio waves with a
relatively high transmission speed is maintained.
[0092] Next, the processing steps executed by the underwater drone
1A according to this exemplary embodiment will be described. FIG.
12 is a flowchart illustrating an example of processing steps
executed by the communication controller 104 according to the
fourth exemplary embodiment. In the case of this exemplary
embodiment, after the measurement (step 201) of the transmission
speed V, the communication controller 104 determines whether or not
the current mode is a high-speed communication mode (step 211).
[0093] The operation to be performed when a negative result is
obtained in step 211 is the same as what has been described in the
second exemplary embodiment. When an affirmative result is obtained
in step 211, the communication controller 104 determines whether or
not the transmission speed V has become slower than the threshold
Th_V1 (step 212). In other words, as in the second exemplary
embodiment, it is determined whether or not a phenomenon, which
triggers switching of the communication system to the sound wave
communication system, has occurred. As long as a negative result is
obtained in step 212, communication via radio waves is continued,
and the communication controller 104 repeats the determination
processing.
[0094] When an affirmative result is obtained in step 212, the
communication controller 104 controls the steerer 20 in the
surfacing direction (step 213). Thus, the underwater drone 1A is
controlled and forcedly moved in a direction in which the depth D
decreases. Since the control is performed when the transmission
speed V is detected to be lower than the threshold Th_V1,
communication via radio waves is not interrupted.
[0095] Next, the communication controller 104 determines whether or
not the transmission speed V has become higher than threshold Th_V2
(step 214). In the determination, whether or not the underwater
drone 1A has returned to the radio wave communication area 203 is
determined. As long as a negative result is obtained in step 214,
surfacing of the underwater drone 1A has to be continued, and the
communication controller 104 repeats the determination
processing.
[0096] When an affirmative result is obtained in step 214, the
communication controller 104 controls the steerer 20 to stop the
surfacing (step 215). This is because the underwater drone 1A has
returned to the radio wave communication area 201 where the
transmission speed is high. It is to be noted that since the
control is autonomously performed in consideration of the
transmission speed, the subsequent control is again remote control
by a user.
[0097] In this exemplary embodiment, as described above, the
underwater drone 1A is assumed to be equipped with the radio wave
communicator 15 and the sound wave communicator 16 as the
communicators. However, the invention is applicable to an
underwater drone equipped with only one communicator. This is
because communication in the radio wave communication area 201 may
be continued without switching between communication systems.
Fifth Exemplary Embodiment
[0098] In this exemplary embodiment, a function to be used in
combination with the above-described first to fourth exemplary
embodiments will be described. FIG. 13 is a conceptual illustration
of control operations in a fifth exemplary embodiment. In the case
of this exemplary embodiment, when communication is impossible with
any of the radio wave communicator 15 and the sound wave
communicator 16, the communication controller 102 or 104 performs
control to move the underwater drone 1A to a predetermined position
and to attempt to establish communication by the radio wave
communicator 15 and the sound wave communicator 16.
[0099] FIG. 13 illustrates a water surface as an example of the
predetermined position. The predetermined position may be on a
water surface or in water as long as the position is for
re-establishing communication. The movement here may be movement in
a horizontal direction, or movement in the surfacing direction or
the descending direction. For instance, when a communication device
as a communication destination is installed at the bottom of water
or at a position deeper than the underwater drone, the underwater
drone may be moved in the descending direction for the purpose of
reducing the communication distance to the underwater drone. The
predetermined position is not necessarily one position.
[0100] Next, an example of the detail of the control performed by
the communication controller 102 or 104 will be described. FIG. 14
is a flowchart illustrating an example of processing steps executed
by the communication controller according to the fifth exemplary
embodiment. Hereinafter, the communication controller 102 will be
described as an example. The communication controller 102 executes
the processing illustrated in FIG. 14 in parallel with the
above-described switching control for communication system.
[0101] First, it is determined whether or not communication is
impossible with any of the radio the wave communicator 15 and the
sound wave communicator 16 (step 301). As long as a negative result
is obtained in step 301, the communication controller 102 executes
the operation which has been explained in one of the exemplary
embodiments described above. When an affirmative result is obtained
in step 301, the communication controller 102 controls the steerer
20 and the propeller 21 to move the underwater drone 1 to a
predetermined position (step 302). For the movement, various
sensors mounted on the underwater drone 1 and information on
movement path, and position information from a position detection
system are used.
[0102] The movement operation in step 302 is continued until
arrival to a predetermined position is checked (until an
affirmative result is obtained) in step 303. When an affirmative
result is obtained in step 303, the communication controller 102
stops the movement and attempts to establish communication by the
communicator (either one of the radio wave communicator 15 and the
sound wave communicator 16 in this exemplary embodiment) (step
304). In other words, even when communication becomes impossible
due to a sudden change in the underwater environment or the like,
in this exemplary embodiment, the communication controller 102
moves the underwater drone 1 to a predetermined position and
attempts to establish communication by the communicator. After step
304, the flow for the communication controller 102 returns to step
301, and when communication is resumed, the underwater drone 1
returns to remote control.
[0103] It is to be noted that in this exemplary embodiment, the
underwater drone 1A is assumed to be equipped with the radio wave
communicator 15 and the sound wave communicator 16 as the
communicators. However, the movement to a predetermined position
and a function of trying communication in the case of impossible
communication may applied to an underwater drone equipped with only
one communicator.
Sixth Exemplary Embodiment
[0104] In this exemplary embodiment, a function provided in case
communication is not resumed in the above-described fifth exemplary
embodiment will be explained. FIG. 15 is a conceptual illustration
of control operations in a sixth exemplary embodiment. In the case
where impossible communication is caused by the communicator, even
when the underwater drone 1 is moved to a predetermined position,
communication is not recoverable as described above.
[0105] Thus, in this exemplary embodiment, a failure signal
transmitter (not illustrated) is mounted on the underwater drone 1,
and when communication is impossible even after the underwater
drone 1 is moved to a predetermined position, a failure signal is
transmitted. The failure signal is a one-way signal that is
transmitted from the underwater drone 1, for instance, a
beacon.
[0106] FIG. 16 is a flowchart illustrating an example of processing
steps executed by the communication controller according to the
sixth exemplary embodiment. After execution of the processing (FIG.
14) from step 301 to step 304, the communication controller 102
determines whether or not communication is impossible after a trial
of communication (step 305). When a negative result is obtained in
step 305, communication is resumed, and thus the flow for the
communication controller 102 returns to step 301. On the other
hand, when an affirmative result is obtained in step 305, the
communication controller 102 commands a failure signal transmitter
(not illustrated) to transmit a failure signal (step 306). Although
the flow returns to step 301 after transmission of a failure signal
in this exemplary embodiment, transmission of a failure signal may
be continued.
[0107] In this exemplary embodiment, as described above, the
underwater drone 1 is assumed to be equipped with the radio wave
communicator 15 and the sound wave communicator 16 as the
communicators. However, the invention is applicable to an
underwater drone equipped with only one communicator.
Other Exemplary Embodiments
[0108] In the above-described exemplary embodiments, the underwater
drone 1 or 1A equipped with the radio wave communicator 15 and the
sound wave communicator 16 has been explained. However, the
communicator mounted on the underwater drone 1 or 1A is not limit
to these. For instance, an optical communicator that uses light for
communication may be used. The optical communicator is configurated
by a light emitter and a light receiver, and for instance, visible
light is used. As the light emitter, for instance, an LED, which
emits blue light absorbed less underwater, is used.
[0109] In consideration of optical communicators, there are three
combinations of communicators: a combination of the radio wave
communicator and the optical communicator, a combination of the
sound wave communicator and the optical communicator, and a
combination of the radio wave communicator, the sound wave
communicator, and the optical communicator. A threshold used for
switching between communication systems is set for each of the
combinations. A threshold used for a combination of or switching
between communicators may be determined comprehensively from the
viewpoint of the application, the communication distance, the
transmission speed, and the environment, for instance. Switching
between multiple types of communication systems based on the depth
or information varying with the depth causes the operability of a
user to be improved compared with the case where wireless
communication is performed only using a single communication
system.
[0110] Although the illuminator 17 and the imaging camera 18 are
mounted on the underwater drone 1 or 1A according to the
above-described exemplary embodiments, these components may not be
mounted. The underwater drone according to the above-described
exemplary embodiments may include, for instance, a robot arm, a
fixing tool, or equipment needed depending on the application.
[0111] Although a depth measured by the depth sensor 19 is used for
switching between the communication systems in the above-described
exemplary embodiments, a water pressure measured by a pressure
gauge or a water temperature measured by a temperature gauge may be
outputted to the controller 10. When a value indicating the ambient
environment or the usage environment is used, the control unit 10
compares a water pressure instead of a depth with a threshold to
switch between the communication systems, or compares a water
temperature instead of a depth with a threshold to switch between
the communication systems. It is sufficient that each threshold be
set to a value that achieves the switching as in the case where a
depth is used.
[0112] Although a transmission speed is measured in the
above-described exemplary embodiments, a communication situation
may be checked using the intensity of a signal received and
switching between the communication systems may be done. This is
because the transmission speed is affected by the intensity of
communication. Although the imaging camera 18 is mounted on the
underwater drone 1 in the above-described exemplary embodiments, an
underwater microphone may be mounted along with the imaging camera
18 or instead of the imaging camera 18. When an imaging camera is
not used, the illuminator 17 does not have to be mounted.
[0113] Although each one of the radio wave communicator 15 and the
sound wave communicator 16 is disposed as the communicator in the
above-described exemplary embodiments, multiple units of each
communicator may be disposed. Multiple units of a communicator may
be prepared for one communication system so that an alternative
communicator may be used as a replacement for a failed
communicator, or multiple units of a communicator may be used to
increase the amount of communication per unit time.
[0114] Although the underwater wireless communication in the
underwater drone as an unmanned underwater mobile body has been
described as an example in the above-described exemplary
embodiments, the invention is applicable to underwater wireless
communication in a manned underwater mobile body, for instance, a
mobile body to be boarded by one to three crews.
[0115] Although the case where the underwater drone changes the
moving direction by the steerer has been explained in the
above-described exemplary embodiments, in the case of a robot for
underwater work, the moving direction may be changed by a
caterpillar or another drive unit.
[0116] Although the exemplary embodiments of the invention have
been described so far, the technical scope of the invention is not
limited to the range described in the exemplary embodiments. It is
apparent from the description of the claims that embodiments
obtained by making various modifications or improvements to the
exemplary embodiments are also included in the technical scope of
the present invention.
[0117] The foregoing description of the exemplary embodiments of
the present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiments were chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
* * * * *