Subminiature unmanned submarine comprising rotary artificial muscle motor and operating method thereof

Abstract

Provided are a propulsion device and a propulsion method of a subminiature unmanned submarine using an artificial muscle and a paddle. The propulsion device of the subminiature unmanned submarine may be actively utilized to implement a subminiature unmanned submarine by driving a paddle coupled to a rotary-type artificial muscle that generates a rotational force through repeated twisting and untwisting depending on whether a voltage is applied, and may reduce noise generation, thereby minimizing the likelihood of detection.

Description

CLAIM FOR PRIORITY

[0001] This application claims priority to Korean Patent Application No. 2024-0131470 filed on Sep. 27, 2024 in the Korean Intellectual Property Office (KIPO), the entire contents of which are hereby incorporated by reference.BACKGROUND1. Technical Field

[0002] Example embodiments of the present invention relate to a propulsion device for submarines, and more particularly, to a propulsion device and a propulsion method of a subminiature unmanned submarine using an artificial muscle and a paddle.2. Related Art

[0003] A submarine refers to a vessel that operates while submerged in water, and is mostly used for military purposes. Submarine propulsion devices mainly employ a method of generating a propulsive force using rotational motion obtained by supplying power to a motor, with power sources mainly including diesel-electric propulsion and nuclear-powered propulsion.

[0004] In particular, unmanned submarines are increasingly in demand because they can stealthily perform underwater operations, such as surveillance, reconnaissance, mine detection, and mine removal, without being detected by the enemy, and can be deployed in dangerous waters, such as very shallow waters or enemy ports, which are difficult for manned submarines to access or are heavily mined.

[0005] However, conventional unmanned submarines have limitations in miniaturization due to mechanical motor-based devices, such as power sources and buoyancy control mechanisms, and are highly likely to be detected by the enemy because of operational noise. As a result, research is actively being conducted to address these issues.SUMMARY

[0006] Example embodiments of the present invention are directed to providing a propulsion device and a propulsion method of a subminiature unmanned submarine using an artificial muscle and a paddle, which enable easy implementation of miniaturization of an unmanned submarine.

[0007] Example embodiments of the present invention are also directed to providing a propulsion device and a propulsion method of a subminiature unmanned submarine using an artificial muscle and a paddle, which are capable of reducing noise generation.

[0008] It should be noted that technical objects of the present invention are not limited to the above-described technical objects, and other technical objects of the present invention will be apparent to those skilled in the art from the following descriptions.

[0009] In some example embodiments, a propulsion device of a subminiature unmanned submarine includes an outer frame formed to extend from a submarine pressure hull and disposed to surround a seawater inflow space, fixing members coupled to an inner wall of the outer frame and provided to face each other, an artificial muscle motor part disposed in the seawater inflow space, having one end portion fixed by one of the fixing members, and configured to generate a rotational force by repeated twisting and untwisting, an artificial muscle return part disposed apart from the artificial muscle motor part and having one end portion fixed by the other of the fixing members, an insulating member having opposite end portions respectively attached to the other end portion of the artificial muscle motor part and the other end portion of the artificial muscle return part, and configured to connect the artificial muscle motor part and the artificial muscle return part to each other, a paddle coupled to the insulating member and configured to perform a paddling function of pushing water by receiving rotational forces from the artificial muscle motor part and the artificial muscle return part, a counter electrode disposed apart from the artificial muscle motor part and provided to be partially exposed in the seawater inflow space, and a battery part electrically connected to the artificial muscle motor part and the counter electrode.

[0010] Each of the artificial muscle motor part and the artificial muscle return part may include a mono-filament yarn having a single filament or a multi-filament yarn having a plurality of filaments.

[0011] The artificial muscle motor part may include a conductive material yarn.

[0012] The conductive material yarn may include a carbon nanotube yarn.

[0013] Each of the artificial muscle motor part and the artificial muscle return part may have one of a Z-twist twisted in a clockwise direction and an S-twist twisted in a counterclockwise direction.

[0014] The artificial muscle motor part and the artificial muscle return part may have the same twist.

[0015] The propulsion device may further include a first paddle guide and a second paddle guide, each having opposite end portions coupled to the inner wall of the outer frame and disposed apart from each other within a region in which the paddle is positionable.

[0016] In other example embodiments, a propulsion method of a subminiature unmanned submarine includes providing the propulsion device of the subminiature unmanned submarine, applying a driving voltage derived from the battery part to the artificial muscle motor part and the counter electrode, rotating the artificial muscle motor part and the artificial muscle return part, to which the voltage is applied, in one direction, allowing the paddle to perform a paddling function of pushing water in the one direction by transmitting the rotational forces of the artificial muscle motor part and the artificial muscle return part, which rotate in the one direction, to the paddle, rotating the artificial muscle motor part and the artificial muscle return part in the other direction when the voltage applied to the artificial muscle motor part and the counter electrode is removed or a reference voltage lower than the driving voltage is applied, and allowing the paddle to perform a paddling function of pushing water in the other direction by transmitting the rotational forces of the artificial muscle motor part and the artificial muscle return part, which rotate in the other direction, to the paddle.

[0017] When the driving voltage is applied to the artificial muscle motor part and the counter electrode, an ion, either a cation or an anion, in seawater may be adsorbed onto the counter electrode, and an ion having a charge opposite to that of the ion adsorbed onto the counter electrode may penetrate into the artificial muscle motor part, thereby causing the artificial muscle motor part to expand in volume, rotate in a direction opposite to a twisting direction, and transition into an untwisted state, and when the artificial muscle motor part rotates in the untwisted state, the artificial muscle return part may also rotate in the direction opposite to the twisting direction and may be further twisted.

[0018] No voltage may be applied to the artificial muscle return part, so that the ion in the seawater does not penetrate into the artificial muscle return part.

[0019] When the voltage applied to the artificial muscle motor part and the counter electrode is removed or the reference voltage lower than the driving voltage is applied, the expanded artificial muscle motor part may contract, and the artificial muscle motor part, which had been untwisted, may rotate in the original twisting direction, and when the artificial muscle motor part rotates in the twisted state, the artificial muscle return part may also rotate in the twisting direction.

[0020] When a fully-ON voltage and an OFF voltage are alternately applied to the artificial muscle motor part and the counter electrode, the submarine may operate in a forward mode.

[0021] When a half-ON voltage and an OFF voltage are alternately applied to the artificial muscle motor part and the counter electrode, the submarine may operate in a left-turn mode.

[0022] When a half-ON voltage and a fully-ON voltage are alternately applied to the artificial muscle motor part and the counter electrode, the submarine may operate in a right-turn mode.BRIEF DESCRIPTION OF DRAWINGS

[0023] Example embodiments of the present invention will become more apparent by describing in detail example embodiments of the present invention with reference to the accompanying drawings, in which:

[0024] FIG. 1 is an isometric view of a propulsion device of a subminiature unmanned submarine according to one example embodiment of the present invention;

[0025] FIG. 2 is a cross-sectional view taken along line A-A′ of FIG. 1, showing an enlarged view of the propulsion device;

[0026] FIG. 3 is a rear view of the propulsion device of the subminiature unmanned submarine according to one example embodiment of the present invention;

[0027] FIG. 4 is an enlarged cross-sectional view of portion B of FIG. 2, showing an enlarged view of an artificial muscle motor part, an artificial muscle return part, and an insulating member;

[0028] FIGS. 5A and 5B are schematic views illustrating changes in the artificial muscle motor part depending on whether a voltage is applied, according to one example embodiment of the present invention;

[0029] FIGS. 6 and 7 are schematic views illustrating a paddle performing a paddling function of pushing water, according to one example embodiment of the present invention;

[0030] FIGS. 8A and 8B are schematic views illustrating the paddle whose movable range is limited by a first paddle guide and a second paddle guide according to one example embodiment of the present invention;

[0031] FIG. 9 is a schematic view illustrating traveling directions of the subminiature unmanned submarine provided with the propulsion device according to one example embodiment of the present invention; and

[0032] FIG. 10 is a set of schematic diagrams illustrating propulsion modes of the subminiature unmanned submarine according to a voltage applied to the propulsion device according to one example embodiment of the present invention.DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0033] Hereinafter, example embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0034] The present invention can undergo various modifications and variations, and specific embodiments thereof are exemplified with reference to the drawings and will be described in detail. However, this is not intended to limit the present invention to the particular forms disclosed, and it is to be appreciated that the present invention includes all changes, equivalents, and substitutes compatible with the spirit or scope of the present invention defined by the appended claims.

[0035] When an element, such as a layer, region, or substrate, is described as being “on” another element, the element can be directly on another element, or there can be one or more elements between the element and another element.

[0036] It will be understood that although terms such as “first” and “second” may be used herein to describe various elements, components, areas, layers, and / or regions, the elements, components, areas, layers, and / or regions should not be limited by these terms.

[0037] In the present example embodiment, the phrase “A and B are connected” means that A and B are physically directly connected or mechanically indirectly connected via other components or the like.

[0038] In the present example embodiment, the term “hull” refers to a body portion of a submarine, the term “bow” refers to a front portion of the submarine in a forward direction of travel during normal navigation, and the term “stern” refers to a rear portion of the submarine, which is opposite to the bow with respect to the hull.Embodiment

[0039] According to one aspect of the present invention, a propulsion device of a subminiature unmanned submarine using an artificial muscle and a paddle is provided. The propulsion device of the subminiature unmanned submarine according to the present invention may be a device configured to provide propulsive force to the submarine to operate the submarine. The submarine may incorporate all conventional unmanned submarine (or submersible) devices.

[0040] FIG. 1 is an isometric view of a propulsion device of a subminiature unmanned submarine according to one example embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-A′ of FIG. 1, showing an enlarged view of the propulsion device, FIG. 3 is a rear view of the propulsion device of the subminiature unmanned submarine according to one example embodiment of the present invention.

[0041] Referring to FIGS. 1 to 3, the propulsion device of the subminiature unmanned submarine may include an outer frame 10 that is formed to extend from a pressure hull 20 of the submarine and disposed to surround a seawater inflow space 30, fixing members 100 that are coupled to an inner wall of the outer frame 10 and provided to face each other, an artificial muscle motor part 210 that is disposed in the seawater inflow space 30, has one end portion fixed by one of the fixing members 100, and is configured to generate a rotational force by repeated twisting and untwisting, an artificial muscle return part 220 that is disposed apart from the artificial muscle motor part 210 and has one end portion fixed by the other of the fixing members 100, an insulating member 230 that has opposite end portions attached to the other end portions of the artificial muscle motor part 210 and the artificial muscle return part 220, respectively, and is configured to connect the artificial muscle motor part 210 and the artificial muscle return part 220 to each other, a paddle 300 that is coupled to the insulating member 230 and configured to perform a paddling function of pushing water while receiving rotational forces from the artificial muscle motor part 210 and the artificial muscle return part 220, a counter electrode 400 that is disposed apart from the artificial muscle motor part 210 and provided to be partially exposed in the seawater inflow space 30, and a battery part 500 electrically connected to the artificial muscle motor part 210 and the counter electrode 400.

[0042] The submarine may include the pressure hull 20, the seawater inflow space 30 located at a stern of the pressure hull 20, and the outer frame 10 formed to extend from the pressure hull 20 and disposed to partially surround the seawater inflow space 30. The shapes and functions of the outer frame 10, the pressure hull 20, and the seawater inflow space 30 may be based on conventional submarine structures and designs.

[0043] The seawater inflow space 30 may have an open region at one side that is not sealed by the outer frame 10, through which seawater may flow in and out. The seawater inflow space 30 may have various shapes and may be disposed at different positions depending on the shape of the submarine. In FIGS. 1 to 3, the pressure hull 20 is illustrated as being disposed from the bow to the stern of the submarine, and the seawater inflow space 30 is illustrated as being disposed at the stern of the pressure hull 20. However, the present invention is not limited thereto, and in some example embodiments, the seawater inflow space 30 may additionally be provided at the bow of the pressure hull of the submarine or at a side portion of the pressure hull of the submarine.

[0044] As shown in FIGS. 1 to 3, a protruding structure may be provided on an outer side of the submarine. Specifically, the protruding structure may include, for example, vertical rudders 11 and 12 and horizontal rudders 13 and 14, but the present invention is not limited thereto. According to example embodiments, the number and shape of the vertical rudders 11 and 12 and the horizontal rudders 13 and 14 may be configured in various ways. In the present example embodiment, a cross (+)-shaped protruding structure is illustrated, including the vertical rudders 11 and 12 vertically disposed in an up-down direction on an outer side of the stern of the submarine, and the horizontal rudders 13 and 14 laterally disposed in a left-right direction of the hull on the outer side of the stern of the submarine. However, the present invention is not limited thereto, and the vertical rudders 11 and 12 and the horizontal rudders 13 and 14 may be configured in an X-shape. Alternatively, the protruding structure may be a rudder or a skeg that is typically disposed on an outer side of an unmanned submarine.

[0045] Referring to FIGS. 1 and 2, the fixing members 100 may be coupled to an inner wall of the outer frame 10 and may mechanically fix the artificial muscle motor part 210 and the artificial muscle return part 220. As an example, the fixing members 100 may include an upper fixing member 110 and a lower fixing member 120. The upper fixing member 110 may be disposed in an upper region of the inner wall of the outer frame 10, and the lower fixing member 120 may be disposed in a lower region of the inner wall of the outer frame 10. Specifically, the fixing members 100 may fix end portions of the artificial muscle motor part 210 and the artificial muscle return part 220. The fixing members 100 and end portions of the artificial muscle motor part 210 and the artificial muscle return part 220 may be bonded and fixed using an adhesive or the like. Since the fixing members 100 are coupled to the inner wall of the outer frame 10, the fixing members 100 may be supported by the outer frame 10, and thus may securely fix the artificial muscle motor part 210 and the artificial muscle return part 220.

[0046] The upper fixing member 110 and the lower fixing member 120 may be provided to face each other. Specifically, one end portion of the artificial muscle motor part 210 is fixed to the upper fixing member 110, and one end portion of the artificial muscle return part 220 is fixed to the lower fixing member 120 disposed at a position facing the upper fixing member 110, so that the artificial muscle motor part 210 and the artificial muscle return part 220 may be disposed across the seawater inflow space 30. Accordingly, each of the artificial muscle motor part 210 and the artificial muscle return part 220 may function as a shaft of the paddle 300.

[0047] The fixing members 100 may employ fixing devices that are typically used in submarines. As an example, the fixing members 100 may be formed of a polymer material such as SU-8 in consideration of durability and weight. In addition, the fixing members 100 may have a weight of 120 to 150 μg. In this case, a diameter and a height of the propulsion device of the subminiature unmanned submarine and the subminiature unmanned submarine including the same may each be configured to be smaller than 10 cm. However, the present invention is not limited thereto.

[0048] Referring to FIGS. 1 to 3, the artificial muscle motor part 210 is a twisted linear structure, specifically, a yarn, which may generate a rotational force by repeated twisting and untwisting. The yarn may be a mono-filament yarn having a single filament or a multi-filament yarn having a plurality of filaments.

[0049] Specifically, the artificial muscle motor part 210 may include a conductive material yarn. The conductive material yarn may be formed by twisting a conductive material. Specifically, the conductive material yarn may be a conductive nanomaterial yarn. The nanomaterial may be a carbon-based nanomaterial such as a carbon nanotube (CNT) or graphene. More specifically, the artificial muscle motor part 210 may be a carbon nanotube yarn.

[0050] The carbon nanotube yarn may be formed by twist spinning a carbon nanotube sheet, on which carbon nanotubes are arranged in substantially the same direction and which is obtained from a carbon nanotube forest in which carbon nanotubes are grown on a substrate in almost the same direction, into an Archimedean or dual-Archimedean structure. However, the twisted shape is not limited thereto. In one example embodiment, the carbon nanotube yarn may have a height of 250 to 350 μm and a density of 40 to 70 mg / cm3. Specifically, the carbon nanotube yarn may have a twisted form, and may exhibit different properties depending on the direction and number of twists.

[0051] Referring to FIGS. 1 to 3, the artificial muscle return part 220 is a twisted linear structure, specifically, a yarn, which may generate a rotational force by repeated twisting and untwisting. The yarn may be a mono-filament yarn having a single filament or a multi-filament yarn having a plurality of filaments. Specifically, the artificial muscle return part 220 may include a conductive material yarn or a non-conductive material yarn. For example, the conductive material yarn may be a carbon nanotube yarn, and the non-conductive material yarn may be a polymer fiber yarn.

[0052] In one example embodiment, the artificial muscle motor part 210 and the artificial muscle return part 220 may each have one of a Z-twist, which is twisted in a clockwise direction, and an S-twist, which is twisted in a counterclockwise direction. Generally, the Z-twist refers to twisting in a leftward direction, i.e., in the clockwise direction, whereas the S-twist refers to twisting in a rightward direction, i.e., in the counterclockwise direction. In this case, the artificial muscle motor part 210 and the artificial muscle return part 220 may have the same twist. As an example, when the artificial muscle motor part 210 has a Z-twist, the artificial muscle return part 220 may also have a Z-twist.

[0053] Each of the artificial muscle motor part 210 and the artificial muscle return part 220 may have a twist of 3,000 TPM or more. Here, TPM refers to the number of twists per meter. In another example embodiment, the artificial muscle motor part 210 and the artificial muscle return part 220 may be in a coiled state, in which the twisted yarns are further twisted such that the twisted yarns overlap and form coils. However, the artificial muscle motor part 210 and the artificial muscle return part 220, which are in an uncoiled state, may be more advantageous in terms of generating rotational forces.

[0054] As described above, in one example embodiment, by using the artificial muscle motor part 210 and the artificial muscle return part 220 each having a twist of 3,000 TPM or more, an appropriate level of repeated twisting and untwisting can be achieved to generate rotational forces, thereby effectively driving the propulsion device of the subminiature unmanned submarine. When the number of twists of each of the artificial muscle motor part 210 and the artificial muscle return part 220 is less than 3,000 TPM, a rotational force sufficient to drive the propulsion device of the subminiature unmanned submarine may not be generated, and thus the subminiature unmanned submarine may not operate normally. In another example embodiment, the artificial muscle motor part 210 and the artificial muscle return part 220 may each have a twist in a range of 3,000 to 10,000 TPM.

[0055] In one example embodiment, the artificial muscle motor part 210 and the artificial muscle return part 220 may each have a length of 5 to 10 mm, an average diameter of 50 to 100 μm, and a weight of 20 to 100 μg, but the present invention is not limited thereto. In addition, the maximum rotation angle of each of the artificial muscle motor part 210 and the artificial muscle return part 220 may be in a range of 70 to 90° / mm, the maximum rotational speed may be in a range of 8,000 to 12,000 RPM, and the maximum output torque may be in a range of 6 to 9 Nm / kg, but the present invention is not limited thereto. Furthermore, the artificial muscle motor part 210 and the artificial muscle return part 220 may each have a high electrical conductivity of 400 S / cm or less, but the present invention is not limited thereto.

[0056] Specifically, the linear artificial muscle motor part 210 and the linear artificial muscle return part 220 may be disposed apart from each other. The artificial muscle motor part 210 may be a yarn that is electrically connected to the battery part 500. The artificial muscle return part 220 may be disposed apart from the artificial muscle motor part 210 in a longitudinal direction and may be a yarn that is not electrically connected to the battery part 500.

[0057] The artificial muscle motor part 210 and the artificial muscle return part 220 may have a size ratio ranging from 9:1 to 5:5. When the artificial muscle motor part 210 and the artificial muscle return part 220 are configured such that the size of the artificial muscle return part 220 is smaller than that in a 9:1 size ratio, it may be difficult for the artificial muscle motor part 210 to rapidly return to its twisted state by the force of the artificial muscle return part 220, resulting in reduced stability during repeated twisting and untwisting. When the artificial muscle motor part 210 and the artificial muscle return part 220 are configured such that the size of the artificial muscle return part 220 is larger than that in a 5:5 size ratio, the length of the artificial muscle motor part 210 may be reduced, resulting in a decrease in the rotational force generated by repeated twisting and untwisting. The sizes of the artificial muscle motor part 210 and the artificial muscle return part 220 shown in the drawings are schematic and may be different from the actual size ratio.

[0058] Referring to FIGS. 1 to 3, the insulating member 230 may be provided, which is attached to the artificial muscle motor part 210 and the artificial muscle return part 220 to connect the artificial muscle motor part 210 and the artificial muscle return part 220 to each other.

[0059] That is, by disposing the artificial muscle motor part 210 and the artificial muscle return part 220 sequentially in a spaced-apart manner in the longitudinal direction and positioning the insulating member 230 that connects the artificial muscle motor part 210 and the artificial muscle return part 220 in the center, the transition of the artificial muscle motor part 210 and the artificial muscle return part 220 from a twisted state to an untwisted state and from an untwisted state to a twisted state can be more effectively achieved.

[0060] Specifically, one end portion of the artificial muscle motor part 210 may be fixed by the upper fixing member 110, and the other end portion of the artificial muscle motor part 210 may be fixed by the insulating member 230. The artificial muscle motor part 210 may be electrically connected to the battery part 500 via the upper fixing member 110. By being supported and protected by the outer frame 10 and disposed within the seawater inflow space 30, the artificial muscle motor part 210 may operate safely.

[0061] One end portion of the artificial muscle return part 220 may be fixed by the lower fixing member 120, and the other end portion of the artificial muscle return part 220 may be fixed by the insulating member 230. As the artificial muscle return part 220 is disposed apart from the artificial muscle motor part 210, the artificial muscle return part 220 may not be in direct contact with the artificial muscle motor part 210 and may also not be electrically connected to the battery part 500. That is, since no electric field is applied to the artificial muscle return part 220 and the artificial muscle return part 220 performs only a mechanical role, the durability of the artificial muscle return part 220 may be improved.

[0062] The insulating member 230 may be disposed between the artificial muscle motor part 210 and the artificial muscle return part 220, such that one end portion of the insulating member 230 is coupled to one end portion of the artificial muscle motor part 210, and the other end portion of the insulating member 230 is coupled to one end portion of the artificial muscle return part 220. Accordingly, the insulating member 230 may connect the artificial muscle motor part 210 and the artificial muscle return part 220, which are disposed apart from each other, and may fix their respective end portions. As the artificial muscle motor part 210 and the artificial muscle return part 220 are connected through the insulating member 230, the artificial muscle return part 220 may act as a return spring while remaining in a state without an electric field. Any typical insulating material may be used for the insulating member 230.

[0063] FIG. 4 is an enlarged cross-sectional view of portion B of FIG. 2, showing an enlarged view of the artificial muscle motor part, the artificial muscle return part, and the insulating member.

[0064] Referring to FIG. 4, as an example, the insulating member 230 may be provided with a structure having a hollow interior. Accordingly, an outer end portion of the artificial muscle motor part 210 and an outer end portion of the artificial muscle return part 220 may be inserted into the hollow interior of the insulating member 230 and coupled thereto. The outer end portion of the artificial muscle motor part 210 and the outer end portion of the artificial muscle return part 220 may be coupled and fixed to the insulating member 230 using an adhesive or the like.

[0065] Referring to FIGS. 1 to 3, the paddle 300 may be coupled to the insulating member 230 and may generate a propulsive force by pushing and stirring water with the artificial muscle motor part 210, the artificial muscle return part 220, and the insulating member 230 acting as an axis. The submarine may be propelled by a fluid flow generated by the paddling function of the paddle 300. The paddle 300 may refer to a “row,” and various shapes of commonly used paddles can all be applied. In the present example embodiment, a fan-shaped paddle is illustrated, but the present invention is not limited thereto.

[0066] Specifically, the paddle 300 may be bonded to a portion of the insulating member 230 using an adhesive. Since the paddle 300 is coupled to the insulating member 230, no electric field flows through the paddle 300, and thus the rotational forces generated by the repeated twisting and untwisting of the artificial muscle motor part 210 and the artificial muscle return part 220 can be stably transmitted to the paddle 300. The paddle 300 may perform a paddling function by reciprocating left and right to push water, according to rotational directions of the artificial muscle motor part 210 and the artificial muscle return part 220. In the present example embodiment, an example will be described, in which the artificial muscle motor part 210 and the artificial muscle return part 220 are disposed vertically, as illustrated in FIG. 1, and the paddle 300 rotates by reciprocating left and right. However, depending on example embodiments, when the artificial muscle motor part 210 and the artificial muscle return part 220 are disposed horizontally, the paddle 300 may reciprocate in the up-and-down direction.

[0067] Referring to FIGS. 1 to 3, the counter electrode 400 may assist the artificial muscle motor part 210 in generating a rotational force through an electrochemical reaction with the artificial muscle motor part 210 in seawater. To this end, the counter electrode 400 may be disposed apart from the artificial muscle motor part 210. At the same time, the counter electrode 400 may be provided to be partially exposed within the seawater inflow space 30 and may be in contact with seawater. Further, the counter electrode 400 may be provided to have a large surface area to increase the rotational force generation efficiency of the artificial muscle motor part 210. In the present example embodiment, the counter electrode 400 may be fixedly disposed on the outside of the pressure hull 20, but a position thereof may vary depending on the example embodiment. Any electrically conductive electrode material may be used for the counter electrode 400. Specifically, for example, the counter electrode 400 may be formed of a material having a high specific surface area and high conductivity, such as carbon nanotubes or a carbon nanotube- platinum (Pt) composite.

[0068] Referring to FIGS. 1 to 3, the battery part 500 may be disposed inside the pressure hull 20. The battery part 500 may be electrically connected to the artificial muscle motor part 210 and the counter electrode 400. Specifically, one side of the battery part 500 may be electrically connected to the uppermost end portion of the artificial muscle motor part 210, and the other side of the battery part 500 may be electrically connected to the counter electrode 400. The battery part 500 may use high-output and high-safety battery materials, such as a lithium titanate (LTO) battery, a lithium iron phosphate (LFP) battery, or a nickel-cadmium (NiCd) battery, but the present invention is not limited thereto.

[0069] Referring to FIG. 2, a pulse generator 510 may be disposed on one side of the battery part 500. The pulse generator 510 may be electrically connected to the battery part 500 and may generate a voltage pulse wave using power received from the battery part 500. The pulse generator 510 may also be electrically connected to the artificial muscle motor part 210 in order to transmit the generated voltage pulse wave to the artificial muscle motor part 210.

[0070] To this end, the propulsion device of the present invention may further include a first circuit 520, which is derived from the battery part 500, embedded in the pressure hull 20 and the outer frame 10, and electrically connected to one end portion of the artificial muscle motor part 210, and a second circuit 530, which is derived from the battery part 500, embedded in the pressure hull 20, and electrically connected to the counter electrode 400. That is, since the battery part 500, the pulse generator 510, the first circuit 520, and the second circuit 530 are embedded in the pressure hull 20 and the outer frame 10, the battery part 500, the pulse generator 510, the first circuit 520, and the second circuit 530 are not exposed to seawater and can operate effectively and stably even underwater.

[0071] Further, a wireless signal transceiver (not shown) may be embedded in the submarine. The wireless signal transceiver may be provided to transmit and receive wireless signals, thereby allowing a user to remotely control the propulsion device of the subminiature unmanned submarine according to the present invention. Materials used in typical wireless signal transceivers may be applied to the wireless signal transceiver.

[0072] Referring to FIGS. 1 to 3, the propulsion device of the subminiature unmanned submarine may further include a first paddle guide 610 and a second paddle guide 620, each of which has opposite end portions coupled to the inner wall of the outer frame 10 and is disposed apart from each other within a region in which the paddle 300 can be located. Specifically, the first paddle guide 610 and the second paddle guide 620 may be provided within the seawater inflow space 30 to limit a range in which the paddle 300 moves left and right with respect to the bow with the insulating member 230 as an axis. Through the first paddle guide 610 and the second paddle guide 620, the paddle 300 may be controlled to reciprocate within a specified range, thereby allowing the repeated twisting and untwisting of the artificial muscle motor part 210 and the artificial muscle return part 220 to occur more smoothly and preventing damage to the paddle 300 caused by excessive reciprocating motion. In addition, any form capable of minimizing damage caused by contact with the paddle 300 and easily controlling the left-right movement range of the paddle 300 may be applied to the first paddle guide 610 and the second paddle guide 620.

[0073] Another aspect of the present invention may provide a propulsion method of the subminiature unmanned submarine.

[0074] Referring to FIGS. 1 to 3, the propulsion method of the subminiature unmanned submarine may include applying a driving voltage, which is derived from the battery part 500, to the artificial muscle motor part 210 and the counter electrode 400 of the propulsion device of the subminiature unmanned submarine described above, rotating the artificial muscle motor part 210 and the artificial muscle return part 220, to which the voltage is applied, in one direction, allowing the paddle 300 to perform a paddling function of pushing water in the one direction by transmitting rotational forces of the artificial muscle motor part 210 and the artificial muscle return part 220, which rotate in the one direction, to the paddle 300, rotating the artificial muscle motor part 210 and the artificial muscle return part 220 in the other direction when the voltage applied to the artificial muscle motor part 210 and the counter electrode 400 is removed or a reference voltage lower than the driving voltage is applied, and allowing the paddle 300 to perform a paddling function of pushing water in the other direction by transmitting rotational forces of the artificial muscle motor part 210 and the artificial muscle return part 220, which rotate in the other direction, to the paddle 300.

[0075] Hereinafter, the propulsion method of the subminiature unmanned submarine according to the present invention will be described in detail as follows.

[0076] FIGS. 5A and 5B are schematic views illustrating changes in the artificial muscle motor part depending on whether a voltage is applied according to one example embodiment of the present invention, FIGS. 6 and 7 are schematic views illustrating the paddle performing a paddling function of pushing water according to one example embodiment of the present invention, and FIGS. 8A and 8B are schematic views illustrating the paddle whose movable range is limited by the first paddle guide and the second paddle guide according to one example embodiment of the present invention.

[0077] Referring to FIGS. 1 and 2, a user may start or stop the operation of the battery part 500 through the wireless signal transceiver (not shown) provided in the submarine. When the operation of the battery part 500 begins, the battery part 500 supplies power to the pulse generator 510 electrically connected thereto, and the pulse generator 510 may apply a potential to the artificial muscle motor part 210 and the counter electrode 400 by generating a voltage pulse wave. In addition, when the operation of the battery part 500 is stopped, the potential applied to the artificial muscle motor part 210 and the counter electrode 400 may be removed.

[0078] Referring to FIGS. 5A and 5B together with FIGS. 1 and 2, when a driving voltage is applied to the artificial muscle motor part 210 and the counter electrode 400, specifically, when a positive (+) potential is applied to the artificial muscle motor part 210 and a negative (−) potential is applied to the counter electrode 400 such that a potential difference therebetween becomes the driving voltage, cations among the ions in the seawater accommodated in the seawater inflow space 30 may be adsorbed onto the counter electrode 400, and anions may penetrate into the artificial muscle motor part 210. In another example embodiment, when a negative (−) potential is applied to the artificial muscle motor part 210 and a positive (+) potential is applied to the counter electrode 400 such that a potential difference therebetween becomes the driving voltage, anions may be adsorbed onto the counter electrode 400, and cations may penetrate into the artificial muscle motor part 210. Accordingly, as shown in FIGS. 5A and 5B, a diameter d2 of the artificial muscle motor part 210 after the application of a potential having a potential difference greater than or equal to the driving voltage may become larger than a diameter d1 before the application of the potential. At the same time, since no potential is applied to the artificial muscle return part 220, ions may not penetrate into the artificial muscle return part 220.

[0079] The seawater may serve as an electrolyte for the electrochemical driving method of the propulsion device of the subminiature unmanned submarine of the present invention. During electrochemical driving, it is necessary to appropriately set the driving voltage so that the seawater acting as the electrolyte is not electrolyzed. As an example, the driving voltage may be less than 1.8 V, and specifically, less than 1.2 V.

[0080] Hereinafter, an example will be described, in which the artificial muscle motor part 210 and the artificial muscle return part 220 have a Z-twist twisted in the clockwise direction. In another example embodiment, when the artificial muscle motor part 210 and the artificial muscle return part 220 have an S-twist twisted in the counterclockwise direction, rotation directions thereof and the corresponding movement of the paddle may be performed in the opposite manner.

[0081] Referring to FIGS. 6 and 8A together, due to the above-described ion penetration, the artificial muscle motor part 210 may expand in volume, rotate in a direction opposite to a twisting direction, specifically in the counterclockwise direction, and transition into an untwisted state.

[0082] Since the total number of twists of the artificial muscle motor part 210 and the artificial muscle return part 220 must be maintained, the artificial muscle return part 220 may become further twisted when the artificial muscle motor part 210 rotates and untwists.

[0083] In other words, when a potential is applied to the artificial muscle motor part 210 and a volume of the artificial muscle motor part 210 increases as ions penetrate into the artificial muscle motor part 210, the artificial muscle motor part 210 may rotate in a direction opposite to the twisting direction to become less twisted, the artificial muscle return part 220 may also rotate in the direction opposite to the twisting direction to become further twisted, and the insulating member 230 connected to the artificial muscle motor part 210 and the artificial muscle return part 220 may also rotate in the direction opposite to the twisting direction. Accordingly, as shown in FIG. 8A, the paddle 300 may perform a paddling function of pushing water in the direction opposite to the twisting direction of the artificial muscle motor part 210 and the artificial muscle return part 220, specifically, from left to right with respect to the bow. The paddle 300 may push fluid, such as seawater, toward the stern by the paddling function of pushing water, thereby propelling the subminiature unmanned submarine.

[0084] Referring to FIGS. 7 and 8B together, when the potential applied to the artificial muscle motor part 210 and the counter electrode 400 is removed or when the potential difference therebetween becomes a reference voltage lower than the driving voltage, the artificial muscle motor part 210, which had been untwisted, may rotate in the twisting direction, specifically in the clockwise direction as the anions that had penetrated into the artificial muscle motor part 210 are desorbed and the artificial muscle motor part 210 contracts.

[0085] At the same time, the artificial muscle return part 220, which had been further twisted by rotating in the direction opposite to the twisting direction, specifically in the counterclockwise direction, may rotate in the twisting direction, specifically in the clockwise direction, thereby allowing the artificial muscle motor part 210 to rotate in the twisting direction more rapidly as the artificial muscle return part 220 is untwisted to restore the original number of twists. This operation of the artificial muscle return part 220 is different from that of the artificial muscle motor part 210 because the artificial muscle return part 220 is not electrically connected to the battery part 500, is disposed apart from the artificial muscle motor part 210, and is connected thereto by the insulating member 230, and thus no voltage is applied to the artificial muscle return part 220.

[0086] In this case, the insulating member 230 connected to the artificial muscle motor part 210 and the artificial muscle return part 220 may also rotate in the twisting direction, specifically in the clockwise direction. As a result, as shown in FIG. 8B, the paddle 300 coupled to the insulating member 230 may perform a paddling function of pushing water in the twisting direction, specifically from right to left with respect to the bow.

[0087] As described above, when the potential applied to the artificial muscle motor part 210 and the counter electrode 400 is removed, or when the potential difference therebetween becomes a reference voltage lower than the driving voltage, the rotational force stored in the artificial muscle return part 220 may be transmitted to the artificial muscle motor part 210 as the artificial muscle motor part 210 returns to its original twisted state, thereby enabling the twist recovery of the artificial muscle motor part 210 to occur more rapidly.

[0088] Further, as shown in FIGS. 8A and 8B, when the paddle 300 performs a paddling function of pushing water in one direction (e.g., in the direction opposite to the twisting direction of the artificial muscle motor part, specifically in the counterclockwise direction with respect to the bow) or in the other direction (e.g., in the twisting direction of the artificial muscle motor part, specifically in the clockwise direction with respect to the bow), the range of positional movement of the paddle 300 may be limited by the first paddle guide 610 and the second paddle guide 620. Specifically, as shown in FIG. 8A, before the propulsion device of the submarine is driven, the paddle 300 may be located adjacent to the first paddle guide 610 on the left with respect to the bow. When a potential is applied to the artificial muscle motor part 210 (see FIG. 6) and the counter electrode, and a potential difference therebetween becomes the driving voltage, the insulating member 230 may rotate by the artificial muscle motor part 210 (see FIG. 6), and the paddle 300 may perform a paddling function of pushing water in the rightward direction with the insulating member 230 as a central axis. In this case, the positional movement of the paddle 300 to the right may be limited by the second paddle guide 620 provided on the right side of the paddle 300, and thus the paddling function is performed only within a specified range on the right side.

[0089] Subsequently, as shown in FIG. 8B, when the potential applied to the artificial muscle motor part 210 and the counter electrode is removed, or when the potential difference therebetween becomes a reference voltage lower than the driving voltage, the paddle 300, which is located on the right side with respect to the bow, may perform a paddling function of pushing water to the left with the insulating member 230 as a central axis, as the insulating member 230 rotates. In this case, the positional movement of the paddle 300 to the left may be limited by the first paddle guide 610 provided on the left side with respect to the bow, and thus the paddling function may be performed only within a specified range on the left side.

[0090] As described above, the propulsion device of the subminiature unmanned submarine according to the present invention may generate a propulsive force as the paddle 300 reciprocates left and right by performing a paddling function of pushing water to the left or right. In addition, the propulsion device of the subminiature unmanned submarine of the present invention may allow a user to control the propulsive force of the propulsion device by modulating a frequency and a width of the voltage pulse wave applied to each of the artificial muscle motor part 210 and the counter electrode 400 through the wireless signal transceiver and the pulse generator.

[0091] Specifically, referring again to FIG. 2, a voltage pulse wave of 0.01 to 1.0 V / mm may be applied to the artificial muscle motor part 210 and the counter electrode 400 from the first circuit 520 and the second circuit 530 connected to the pulse generator 510. When the voltage pulse wave exceeds 1.0 V / mm, electrolysis may occur, which may prevent the above-described operation from being smoothly implemented. The voltage pulse wave may have a frequency of 5 to 15 Hz, and either pulse width modulation (PWM) or pulse frequency modulation (PFM) may be applied to the artificial muscle motor part 210 and the counter electrode 400 depending on navigation conditions of the propulsion device of the subminiature unmanned submarine of the present invention.

[0092] Further, the propulsion device of the subminiature unmanned submarine of the present invention may allow a user to control the submarine to move forward, turn left, or turn right by modulating the frequency and width of a pulse-type voltage applied to each of the artificial muscle motor part 210 and the counter electrode 400 through the wireless signal transceiver and the pulse generator 510.

[0093] FIG. 9 is a schematic view illustrating traveling directions of the subminiature unmanned submarine provided with the propulsion device according to one example embodiment of the present invention, and FIG. 10 is a set of schematic diagrams illustrating propulsion modes of the subminiature unmanned submarine according to a voltage applied to the propulsion device according to one example embodiment of the present invention.

[0094] Referring to FIGS. 9 and 10, the propulsion modes of the subminiature unmanned submarine according to the propulsion device of the present invention may be broadly classified into a forward mode (Case 1), a left-turn mode (Case 2), and a right-turn mode (Case 3).

[0095] The propulsion modes of the submarine may be controlled by adjusting the magnitude of the potential difference applied between the artificial muscle motor part 210 and the counter electrode 400. The potential difference applied between the artificial muscle motor part 210 and the counter electrode 400 may be described based on the driving voltage and the reference voltage. Here, a threshold voltage may refer to the minimum potential difference required to drive the artificial muscle motor part 210 and the counter electrode 400.

[0096] Specifically, when a potential difference applied between the artificial muscle motor part 210 and the counter electrode 400 is greater than the threshold voltage, the artificial muscle motor part 210 and the counter electrode 400 may be driven, and such a potential difference may be referred to as a driving voltage. In the present example embodiment, the driving voltage may be described as being classified into a fully-ON voltage and a half-ON voltage. The fully-ON voltage may refer to a voltage at which ions in seawater have fully penetrated into the artificial muscle motor part 210. At the same time, the fully-ON voltage may also refer to the maximum voltage that does not cause electrolysis of seawater (water), and, for example, may be a voltage of 1.0 V or less. The half-ON voltage may refer to a voltage at which ions in seawater have penetrated into the artificial muscle motor part 210 to a certain extent. For example, the half-ON voltage may mean 0.4 to 0.6 times, and specifically, approximately half, of the fully-ON voltage at which ions in seawater can fully penetrate into the artificial muscle motor part 210.

[0097] Further, when a potential difference applied between the artificial muscle motor part 210 and the counter electrode 400 is lower than the threshold voltage, or when the potential applied to the artificial muscle motor part 210 and the counter electrode 400 is removed, the operation of the artificial muscle motor part 210 and the counter electrode 400 may be stopped, and such a potential difference may be referred to as a reference voltage. In the present example embodiment, the reference voltage may be described as an OFF voltage.

[0098] The OFF voltage may refer to a state in which no potential is applied to the artificial muscle motor part 210 and the counter electrode 400, or in which the applied potential is removed. That is, the OFF voltage may refer to a voltage at which the ions that had penetrated into the artificial muscle motor part 210 are released and move back into the seawater.

[0099] In the left-turn mode and the right-turn mode, the propulsive force may increase as the difference between pulse levels applied at the fully-ON voltage or the half-ON voltage decreases, and the degree of rotation may increase as the difference between the pulse levels increases.

[0100] Referring also to FIGS. 8A and 8B, the paddle 300 may perform a paddling function of pushing water between two positions at which the paddle 300 are respectively in contact with the first paddle guide 610 and the second paddle guide 620, i.e., between an outermost left position L located on the left side of the bow and an outermost right position R located on the right side of the bow. A center position C, which faces the center of the bow, may be present between the outermost left position L and the outermost right position R. An example will be described in which an initial position of the paddle 300 is the outermost left position L when no voltage is applied to the propulsion device of the subminiature unmanned submarine.

[0101] As in case 1, when the fully-ON voltage and the OFF voltage are alternately applied to the artificial muscle motor part 210 and the counter electrode 400, the submarine may operate in the forward mode. Specifically, when a fully-ON voltage of 1 V is applied to the artificial muscle motor part 210 and the counter electrode 400 at the same pulse level as the driving voltage, ions in the seawater may fully penetrate into the artificial muscle motor part 210, and the paddle 300 may perform a paddling function of pushing water in the rightward direction with respect to the bow due to the resulting rotation.

[0102] Thereafter, when the OFF voltage is applied to the artificial muscle motor part 210 and the counter electrode 400, to which the fully-ON voltage had been applied, the ions that had penetrated into the artificial muscle motor part 210 may be released, and due to the resulting rotation, the paddle 300 may perform a paddling function of pushing water in the leftward direction with respect to the bow. By alternately applying the fully-ON voltage and the OFF voltage in this manner, the paddle 300 may reciprocate between the outermost left position L and the outermost right position R, thereby enabling the forward mode of the submarine.

[0103] As in case 2, when the half-ON voltage and the OFF voltage are alternately applied to the artificial muscle motor part 210 and the counter electrode 400, the submarine may operate in the left-turn mode. Specifically, when a half-ON voltage of 0.5 V is applied to the artificial muscle motor part 210 and the counter electrode 400 at the same pulse level as the driving voltage, ions in the seawater may penetrate into the artificial muscle motor part 210 to a certain extent, and due to the resulting rotation, the paddle 300 may perform a paddling function of pushing water in the rightward direction with respect to the bow. In this case, the paddle 300 may perform the paddling function from the outermost left position L to the center position C.

[0104] Thereafter, when the OFF voltage is applied to the artificial muscle motor part 210 and the counter electrode 400 to which the half-ON voltage had been applied, the ions that had penetrated into the artificial muscle motor part 210 may be released, and due to the resulting rotation, the paddle 300 may perform a paddling function of pushing water leftward from the center position C toward the outermost left position L. When the half-ON voltage and the OFF voltage are alternately applied in this manner, the paddle 300 may reciprocate between the outermost left position L and the center position C, thereby enabling the submarine to operate in the left-turn mode.

[0105] As in case 3, when the half-ON voltage and the fully-ON voltage are alternately applied to the artificial muscle motor part 210 and the counter electrode 400, the submarine may operate in the right-turn mode. Specifically, when a half-ON voltage of 0.5 V is applied to the artificial muscle motor part 210 and the counter electrode 400 at the same pulse level as the driving voltage, ions in the seawater may penetrate into the artificial muscle motor part 210 to a certain extent, and due to the resulting rotation, the paddle 300 may perform a paddling function of pushing water in the rightward direction with respect to the bow. In this case, the paddle 300 may perform the paddling function from the outermost left position L to the center position C. Thereafter, when the fully-ON voltage is applied to the artificial muscle motor part 210 and the counter electrode 400 to which the half-ON voltage had been applied, a greater amount of ions in seawater may further penetrate into the artificial muscle motor part 210, and the ions may infiltrate to a maximum extent. Due to the resulting rotation, the paddle 300 may perform a paddling function of pushing water rightward from the center position C toward the outermost right position R. When the half-ON voltage and the fully-ON voltage are alternately applied in this manner, the paddle 300 may reciprocate between the center position C and the outermost right position R, thereby enabling the submarine to operate in the right-turn mode.

[0106] As described above, the present invention can propose a novel type of rotary artificial muscle motor based on a subminiature and ultra-lightweight conductive material yarn, specifically a carbon nanotube yarn, which may replace conventional electric motors that cannot be miniaturized.

[0107] According to the present invention described above, a motor structure for driving a propulsion device of a subminiature unmanned submarine can be simplified by using an artificial muscle motor part and an artificial muscle return part that generate rotational forces through repeated twisting and untwisting, thereby significantly reducing the size and weight of the unmanned submarine.

[0108] Accordingly, the subminiature unmanned submarine can be implemented with a size of 10 cm or less.

[0109] In addition, since electric motor noise is eliminated in the present invention, the likelihood of detection in military reconnaissance applications can be minimized.

[0110] Furthermore, according to the present invention, a user can easily control a propulsion device of a subminiature unmanned submarine by controlling whether a voltage is applied and adjusting the frequency of the applied voltage through a pulse generator connected to a wireless signal transceiver.

[0111] It should be noted that technical effects of the present invention are not limited to the above-described technical effects, and other technical effects of the present invention will be apparent to those skilled in the art from the following descriptions.

[0112] While the present invention has been described in detail with reference to preferred example embodiments, the present invention is not limited to these example embodiments, and various modifications and changes may be made by those skilled in the art within the technical spirit and scope of the present invention.

Claims

1. A propulsion device of a subminiature unmanned submarine, comprising:an outer frame formed to extend from a submarine pressure hull and disposed to surround a seawater inflow space;fixing members coupled to an inner wall of the outer frame and provided to face each other;an artificial muscle motor part disposed in the seawater inflow space, having one end portion fixed by one of the fixing members, and configured to generate a rotational force by repeated twisting and untwisting;an artificial muscle return part disposed apart from the artificial muscle motor part and having one end portion fixed by the other of the fixing members;an insulating member having opposite end portions respectively attached to the other end portion of the artificial muscle motor part and the other end portion of the artificial muscle return part, and configured to connect the artificial muscle motor part and the artificial muscle return part to each other;a paddle coupled to the insulating member and configured to perform a paddling function of pushing water by receiving rotational forces from the artificial muscle motor part and the artificial muscle return part;a counter electrode disposed apart from the artificial muscle motor part and provided to be partially exposed in the seawater inflow space; anda battery part electrically connected to the artificial muscle motor part and the counter electrode.

2. The propulsion device of claim 1, wherein each of the artificial muscle motor part and the artificial muscle return part includes a mono-filament yarn having a single filament or a multi-filament yarn having a plurality of filaments.

3. The propulsion device of claim 1, wherein the artificial muscle motor part includes a conductive material yarn.

4. The propulsion device of claim 3, wherein the conductive material yarn includes a carbon nanotube yarn.

5. The propulsion device of claim 2, wherein each of the artificial muscle motor part and the artificial muscle return part has one of a Z-twist twisted in a clockwise direction and an S-twist twisted in a counterclockwise direction.

6. The propulsion device of claim 5, wherein the artificial muscle motor part and the artificial muscle return part have the same twist.

7. The propulsion device of claim 1, further comprising a first paddle guide and a second paddle guide, each having opposite end portions coupled to the inner wall of the outer frame and disposed apart from each other within a region in which the paddle is positionable.

8. A propulsion method of a subminiature unmanned submarine, comprising:providing an outer frame formed to extend from a submarine pressure hull and disposed to surround a seawater inflow space, fixing members coupled to an inner wall of the outer frame and provided to face each other, an artificial muscle motor part disposed in the seawater inflow space, having one end portion fixed by one of the fixing members, and configured to generate a rotational force by repeated twisting and untwisting, an artificial muscle return part disposed apart from the artificial muscle motor part and having one end portion fixed by the other of the fixing members, an insulating member having opposite end portions respectively attached to the other end portion of the artificial muscle motor part and the other end portion of the artificial muscle return part and configured to connect the artificial muscle motor part and the artificial muscle return part to each other, a paddle coupled to the insulating member and configured to perform a paddling function of pushing water by receiving rotational forces from the artificial muscle motor part and the artificial muscle return part, a counter electrode disposed apart from the artificial muscle motor part and provided to be partially exposed in the seawater inflow space, and a battery part electrically connected to the artificial muscle motor part and the counter electrode;applying a driving voltage derived from the battery part to the artificial muscle motor part and the counter electrode;rotating the artificial muscle motor part and the artificial muscle return part, to which the voltage is applied, in one direction;allowing the paddle to perform a paddling function of pushing water in the one direction by transmitting the rotational forces of the artificial muscle motor part and the artificial muscle return part, which rotate in the one direction, to the paddle;rotating the artificial muscle motor part and the artificial muscle return part in the other direction when the voltage applied to the artificial muscle motor part and the counter electrode is removed or a reference voltage lower than the driving voltage is applied; andallowing the paddle to perform a paddling function of pushing water in the other direction by transmitting the rotational forces of the artificial muscle motor part and the artificial muscle return part, which rotate in the other direction, to the paddle.

9. The propulsion method of claim 8, wherein each of the artificial muscle motor part and the artificial muscle return part of the propulsion device of the subminiature unmanned submarine has one of a Z-twist twisted in a clockwise direction and an S-twist twisted in a counterclockwise direction,the artificial muscle motor part and the artificial muscle return part have the same twist,when the driving voltage is applied to the artificial muscle motor part and the counter electrode, an ion, either a cation or an anion, in seawater is adsorbed onto the counter electrode, and an ion having a charge opposite to that of the ion adsorbed onto the counter electrode penetrates into the artificial muscle motor part, thereby causing the artificial muscle motor part to expand in volume, rotate in a direction opposite to a twisting direction, and transition into an untwisted state, andwhen the artificial muscle motor part rotates in the untwisted state, the artificial muscle return part also rotates in the direction opposite to the twisting direction and is further twisted.

10. The propulsion method of claim 9, wherein no voltage is applied to the artificial muscle return part, so that the ion in the seawater does not penetrate into the artificial muscle return part.

11. The propulsion method of claim 9, wherein when the voltage applied to the artificial muscle motor part and the counter electrode is removed or the reference voltage lower than the driving voltage is applied, the expanded artificial muscle motor part contracts, and the artificial muscle motor part, which had been untwisted, rotates in the original twisting direction, andwhen the artificial muscle motor part rotates in the twisted state, the artificial muscle return part also rotates in the twisting direction.

12. The propulsion method of claim 8, wherein, when a fully-ON voltage and an OFF voltage are alternately applied to the artificial muscle motor part and the counter electrode, the submarine operates in a forward mode.

13. The propulsion method of claim 8, wherein, when a half-ON voltage and an OFF voltage are alternately applied to the artificial muscle motor part and the counter electrode, the submarine operates in a left-turn mode.

14. The propulsion method of claim 8, wherein, when a half-ON voltage and a fully-ON voltage are alternately applied to the artificial muscle motor part and the counter electrode, the submarine operates in a right-turn mode.

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