Variable stiffness flapping underwater robotic fish and method of operation thereof

Abstract

The application provides a variable stiffness flapping underwater robot fish and a working method thereof, and relates to the technical field of underwater robots.The variable stiffness flapping underwater robot fish comprises a flapping skeleton, a main body, a rotary driving mechanism and a variable stiffness connecting piece.The flapping skeleton comprises a plurality of fluctuation moving pieces.The plurality of fluctuation moving pieces are arranged in sequence along a first direction.Two adjacent fluctuation moving pieces are rotationally connected around a second direction.The first direction is perpendicular to the second direction.The rotary driving mechanism is installed on the main body and is drivingly connected to one end of the flapping skeleton along the first direction.The rotary driving mechanism is used to drive the flapping skeleton to rotate around the second direction.The variable stiffness connecting piece is made of raw material comprising a variable stiffness material and has a rigid state and a flexible state.The variable stiffness connecting piece is connected to the plurality of fluctuation moving pieces and is used to convert between the rigid state and the flexible state through external excitation.The variable stiffness of the variable stiffness connecting piece can improve the endurance of the underwater robot fish when running underwater.

Description

Technical Field

[0001] This invention relates to the field of underwater robot technology, and more specifically, to a variable stiffness flapping-wing underwater robotic fish and its working method. Background Technology

[0002] With the increasing emphasis on ocean development, more new requirements have been put forward for underwater operations. Existing underwater detection, operation, and transportation devices are no longer sufficient to meet the needs of complex underwater operations. Compared with ordinary underwater propulsion devices, underwater robotic fish, which have advantages such as high propulsion efficiency, good maneuverability, and good stealth performance, are being widely used.

[0003] Currently, underwater robotic fish are mainly propelled by tail fins and pectoral fins. When moving underwater, the drive mechanism drives the tail fin or pectoral fin to swing, providing power for propulsion. However, existing underwater robotic fish need to keep their tail fin or pectoral fins swinging constantly when moving underwater. This requires the drive mechanism to maintain a continuous power output, which causes the energy supplied by the underwater robotic fish to be consumed quickly, reducing the underwater robotic fish's endurance. Summary of the Invention

[0004] The problem addressed by this invention is how to improve the endurance of underwater robotic fish during underwater operation.

[0005] To address the aforementioned problems, this invention provides a variable stiffness flapping-wing underwater robotic fish and its operating method.

[0006] In a first aspect, the present invention provides a variable stiffness flapping-wing underwater robotic fish, comprising a flapping-wing frame, a main body, a rotary drive mechanism, and a variable stiffness connector. The flapping-wing frame includes multiple undulating moving parts arranged sequentially along a first direction, with adjacent undulating moving parts rotatably connected about a second direction, the first direction being perpendicular to the second direction. The rotary drive mechanism is mounted on the main body and is drivenly connected to one end of the flapping-wing frame along the first direction, the rotary drive mechanism being used to drive the flapping-wing frame to rotate about the second direction. The variable stiffness connector is made of a raw material including a variable stiffness material and has a rigid state and a flexible state. The variable stiffness connector is connected to all of the multiple undulating moving parts and is used to switch between the rigid state and the flexible state by external excitation.

[0007] Optionally, the variable stiffness material includes shape memory polymers, shape memory polymer composites, electromagnetic rheological materials, or shear thickening materials.

[0008] Optionally, the variable stiffness flapping-wing underwater robotic fish further includes a flexible cover that covers the flapping-wing frame and is connected to the variable stiffness connector and the undulating movement component, respectively.

[0009] Optionally, the variable stiffness connector extends along the outer surface of the plurality of undulating moving parts to form a skin covering the flapping wing frame.

[0010] Optionally, the flapping wing frame further includes a support connector and a damper. The support connector is connected between two adjacent undulating moving parts, and the support connector is rotatably connected to the undulating moving parts about the second direction through the damper.

[0011] Optionally, the rotary drive mechanism includes a rotary drive component, a damping structure, and a mounting base. The mounting base is mounted on the main body, the rotary drive component is mounted on the mounting base, and is drivenly connected to the flapping wing frame through the damping structure.

[0012] Optionally, the flapping wing frame further includes an undulating outer frame, and a plurality of undulating moving parts are arranged sequentially along the first direction to form an undulating inner frame. There are multiple undulating inner frames and multiple undulating outer frames. The multiple undulating inner frames are spaced apart along the second direction, and the multiple undulating outer frames are spaced apart along the first direction and are all connected to the variable stiffness connector. The multiple undulating moving parts spaced apart along the second direction are correspondingly connected to the same undulating outer frame.

[0013] Optionally, the flapping wing frame further includes a tail connector, which is located on the side of the undulating inner frame away from the rotary drive mechanism along the first direction, and is connected to multiple undulating inner frames.

[0014] Optionally, the undulating outer frame includes a ring frame and connecting rods. The ring frame is sleeved outside the undulating inner frame and connected to the variable stiffness connector. The connecting rods are connected to the undulating moving member and the ring frame respectively. In the first direction, the radial dimension of the ring frame closer to the rotary drive mechanism is greater than the radial dimension of the ring frame farther from the rotary drive mechanism.

[0015] Secondly, the present invention provides a method for operating a variable stiffness flapping-wing underwater robotic fish, based on the variable stiffness flapping-wing underwater robotic fish as described above, the method for operating the variable stiffness flapping-wing underwater robotic fish includes:

[0016] The propulsion method of the variable stiffness flapping-wing underwater robot fish is selected as the first method. The variable stiffness connector of the variable stiffness flapping-wing underwater robot fish is flexible. The flapping-wing frame of the variable stiffness flapping-wing underwater robot fish is driven to rotate by the rotation drive mechanism of the variable stiffness flapping-wing underwater robot fish.

[0017] When the propulsion method changes from the first method to the second method, the variable stiffness connector is driven to change from a flexible state to a rigid state by external excitation;

[0018] When the propulsion method changes from the second method to the first method, the variable stiffness connector is driven to change from the rigid state to the flexible state by the external excitation.

[0019] The beneficial effects of the variable stiffness flapping-wing underwater robotic fish of the present invention are as follows: The variable stiffness flapping-wing underwater robotic fish is composed of a flapping-wing frame, a main body, a rotary drive mechanism, and variable stiffness connectors. The flapping-wing frame has multiple undulating moving parts, which are arranged sequentially along a first direction, and adjacent undulating moving parts are rotatably connected around a second direction. The first direction is perpendicular to the second direction. Simultaneously, the rotary drive mechanism is mounted on the main body and driven by the flapping-wing frame, driving the flapping-wing frame to rotate around the second direction. With this configuration, when the variable stiffness flapping-wing underwater robotic fish performs underwater propulsion, the rotary drive mechanism outputs a rotary driving force, which in turn drives the flapping wings. The frame and rotary drive mechanism rotate around a second direction, thereby sequentially driving multiple undulating moving parts to oscillate around the second direction along the first direction. This creates undulating waves from a single moving part and alternating undulating waves from multiple moving parts arranged along the first direction, thus disturbing the water flow. This disturbance generates a propulsive force on the main body and the flapping wing frame, enabling the movement of the variable stiffness flapping wing underwater robotic fish. Therefore, underwater propulsion is achieved by simply swaying one end of the flapping wing frame at a small angle using the rotary drive mechanism. This method is simple to control, consumes little energy, and provides excellent propulsion. Furthermore, the system is constructed from materials including variable stiffness materials. The variable stiffness connector can switch between a rigid and a flexible state under external excitation. Simultaneously, it connects to multiple undulating moving parts. This configuration allows the variable stiffness flapping-wing underwater robot to move by disturbing the water flow through the rotation of the flapping wing frame. Under external excitation, the variable stiffness connector remains in a flexible state, deforming with the undulating moving parts to avoid restricting their movement and ensuring the stability of the flapping wing frame's rotation. When the variable stiffness flapping-wing underwater robot is positioned on the water flow path, the water flow propels it to slide underwater. When the variable stiffness connector is in a rigid state under external excitation, it prevents adjacent undulating moving parts from rotating relative to each other, thus keeping the overall shape of the flapping wing frame fixed. As the variable stiffness flapping wing underwater robot slides underwater, the fixed-shape flapping wing frame breaks through the water flow, reducing the resistance encountered by the variable stiffness flapping wing underwater robot during sliding and improving the propulsion effect. Moreover, at this time, there is no need for the rotary drive mechanism to output rotary drive force, which can effectively reduce the energy consumption of the variable stiffness flapping wing underwater robot and thus improve the endurance of the variable stiffness flapping wing underwater robot in underwater operation. Attached Figure Description

[0020] Figure 1 This is a partial structural schematic diagram of the variable stiffness flapping-wing underwater robotic fish from one perspective in the first embodiment of the present invention;

[0021] Figure 2 for Figure 1 An enlarged schematic diagram of A shown in the image;

[0022] Figure 3 This is a partial structural schematic diagram of the variable stiffness flapping-wing underwater robotic fish from another perspective in the first embodiment of the present invention;

[0023] Figure 4 This is a partial structural schematic diagram of the variable stiffness flapping-wing underwater robotic fish from another perspective in the second embodiment of the present invention;

[0024] Figure 5 This is a flowchart illustrating the working method of the variable stiffness flapping-wing underwater robotic fish in an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1. Flapping wing frame; 11. Irregular moving parts; 12. Support connecting parts; 13. Damper; 14. Irregular outer frame; 141. Ring frame; 142. Connecting rod; 15. Tail connecting parts; 2. Main body; 3. Rotary drive mechanism; 31. Rotary drive parts; 32. Mounting base; 4. Variable stiffness connecting parts; 5. Flexible covering parts. Detailed Implementation

[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0028] In the attached diagram, the Z-axis represents the vertical direction, i.e., up and down, with the positive direction of the Z-axis representing upward and the negative direction representing downward. The X-axis represents the horizontal direction and is designated as front and back, with the positive direction of the X-axis representing the front and the negative direction representing the back. The Y-axis represents the left and right direction, with the positive direction of the Y-axis representing the right and the negative direction representing the left. It should be noted that the aforementioned representations of the Z, Y, and X axes are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention.

[0029] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0030] It should be noted that the terms "one" and "more" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0031] In recent years, research on underwater robotic fish has shifted its focus to the exploration and development of biomimetic robotic fish, with tail fin and pectoral fin propulsion being the primary methods. Tail fin propulsion biomimetic fish are simple in design and can swim quickly and continuously, but their common drawback is instability. Pectoral fin propulsion biomimetic fish, on the other hand, rely on symmetrical pectoral fins for propulsion, offering higher stability, positioning ability, and maneuverability compared to tail fin propulsion, better meeting the requirements for ocean exploration. The manta ray, which propels itself by flapping its wings, is a representative example of fish using pectoral fin propulsion. However, the control system for the flapping wings of manta ray-inspired robotic fish is currently complex, with significant limitations on the flapping amplitude, spanwise, and chordal deformation, resulting in poor underwater propulsion. To ensure underwater propulsion, the wings need to constantly flap up and down, rapidly consuming the robotic fish's energy supply and reducing its underwater endurance.

[0032] To address the problems existing in the aforementioned related technologies, this embodiment provides a variable stiffness flapping-wing underwater robotic fish and its working method.

[0033] like Figure 1As shown in the figure, an embodiment of the present invention provides a variable stiffness flapping-wing underwater robotic fish, including a flapping-wing frame 1, a main body 2, a rotary drive mechanism 3, and a variable stiffness connector 4. The flapping-wing frame 1 includes multiple undulating moving parts 11, which are arranged sequentially along a first direction. Adjacent undulating moving parts 11 are rotatably connected around a second direction, and the first direction is perpendicular to the second direction. The rotary drive mechanism 3 is mounted on the main body 2 and is drivenly connected to one end of the flapping-wing frame 1 along the first direction. The rotary drive mechanism 3 is used to drive the flapping-wing frame 1 to rotate around the second direction. The variable stiffness connector 4 is made of raw materials including variable stiffness material and has a rigid state and a flexible state. The variable stiffness connector 4 is connected to all multiple undulating moving parts 11 and is used to switch between the rigid state and the flexible state by external excitation.

[0034] Specifically, such as Figure 1 As shown, the first direction is the Y-axis direction, and the second direction is the X-axis direction; Figure 1 The structure shown is half of a variable stiffness flapping-wing underwater robotic fish; the other half of the variable stiffness flapping-wing underwater robotic fish is the same as... Figure 1 The structure is the same as that in, and is similar to Figure 1 The structure is symmetrical about the X-axis. Variable stiffness material is a new type of material with two forms: a rigid state with high stiffness and a flexible state with low stiffness. Variable stiffness material can switch between the rigid and flexible states under external excitation, that is, the external excitation can adjust the stiffness of the variable stiffness material. The variable stiffness material can be a shape memory polymer, a shape memory polymer composite material, an electromagnetic rheological material, or a shear thickening material. The external excitation can be thermal, magnetic, or electrical. The main body 2 can be the body of an underwater robotic fish, while the flapping fin skeleton 1 can be the pectoral fin skeleton of the underwater robotic fish, or it can be the dorsal fin skeleton, pelvic fin skeleton, caudal fin skeleton, or anal fin skeleton. The rotary drive mechanism 3 is a rotary motor.

[0035] In this embodiment, a variable stiffness flapping-wing underwater robotic fish is constructed by a flapping-wing frame 1, a main body 2, a rotary drive mechanism 3, and a variable stiffness connector 4. The flapping-wing frame 1 has multiple undulating moving parts 11, which are arranged sequentially along a first direction, with adjacent undulating moving parts 11 rotatably connected around a second direction. The first direction is perpendicular to the second direction. Simultaneously, the rotary drive mechanism 3 is mounted on the main body 2 and driven by the flapping-wing frame 1, driving the flapping-wing frame 1 to rotate around the second direction. This configuration allows the variable stiffness flapping-wing underwater robotic fish to propel itself underwater by outputting a rotational driving force through the rotary drive mechanism 3, which in turn drives the flapping-wing frame 1 to rotate around the second direction. One end rotates around the second direction, thereby sequentially driving multiple undulating moving parts 11 to swing around the second direction along the first direction, forming the undulating ripples of a single undulating moving part 11 and the staggered undulating ripples of multiple undulating moving parts 11 arranged along the first direction, thereby disturbing the water flow. The disturbance of the water flow can generate a pushing force on the main body 2 and the flapping wing frame 1, and the movement of the variable stiffness flapping wing underwater robot fish can be achieved under the drive of this pushing force. Thus, by simply swaying one end of the flapping wing frame 1 at a small angle through the rotary drive mechanism 3, the flapping wing frame 1 can automatically flap to achieve underwater propulsion. Therefore, the variable stiffness flapping wing underwater robot fish of this embodiment is simple to control, consumes less energy, and has a good propulsion effect; on this basis, it includes The variable stiffness connector 4 is made from a variable stiffness material. Under external excitation, the variable stiffness connector 4 can switch between a rigid and a flexible state. Simultaneously, the variable stiffness connector 4 is connected to multiple undulating moving parts 11. This configuration allows the variable stiffness flapping-wing underwater robot to move when the undulating motion of the flapping-wing frame 1 disturbs the water flow. Under external excitation, the variable stiffness connector 4 can remain in a flexible state. In this flexible state, the variable stiffness connector 4 can deform with the undulating motion of the moving parts 11, avoiding any restriction on the undulation of the moving parts 11 and ensuring the stability of the flapping-wing frame 1's rotation. When the variable stiffness flapping-wing underwater robot is located on the water flow trajectory, the water flow can propel the variable stiffness flapping-wing underwater robot. As the underwater robot glides, the variable stiffness connector 4 remains rigid under external excitation. In this rigid state, the variable stiffness connector 4 prevents adjacent undulating moving parts 11 from rotating relative to each other, thus keeping the overall shape of the flapping wing frame 1 fixed. While the variable stiffness flapping wing underwater robot glides, the fixed-shape flapping wing frame 1 breaks through the water flow, reducing the resistance encountered by the variable stiffness flapping wing underwater robot gliding and improving its propulsion effect. Moreover, at this time, there is no need for the rotary drive mechanism 3 to output rotary drive force, which can effectively reduce the energy consumption of the variable stiffness flapping wing underwater robot gliding, thereby improving the underwater endurance of the variable stiffness flapping wing underwater robot gliding.

[0036] It should be noted that the external excitation applied to the variable stiffness connector 4 can be thermal excitation, magnetic excitation, or electrical excitation, or any combination of the above external excitation methods. For example, when using thermal excitation, the variable stiffness connector 4 can be heated by a heating element, which can be an embedded resistance wire, an embedded electric heating film, or an externally attached electric heating film. When using magnetic excitation, ferromagnetic materials, such as iron oxide particles, can be filled into the raw materials used to make the variable stiffness connector 4. When using electrical excitation, single-walled or multi-walled carbon nanotubes, graphene, carbon black, carbon nanopaper, carbon nanofibers, or mixed particles can be doped into the raw materials used to make the variable stiffness connector 4. If a combined driving method is used, the particles doped into the raw materials used to make the variable stiffness connector 4 should be two or more of the above combinations.

[0037] It should be noted that the main body 2 is a hollow structure, and is formed by two hollow structures with one open at one end connected together. The interior of the main body 2 is equipped with control elements such as circuit boards, which can receive control signals and control the rotary drive mechanism 3 to output driving force or stop outputting driving force.

[0038] Optionally, the variable stiffness material includes shape memory polymers, shape memory polymer composites, electromagnetic rheological materials, or shear thickening materials.

[0039] Specifically, the shape memory polymer is made of epoxy resin, cyanate ester resin, etc.; the shape memory polymer composite material is made by using shape memory polymer as the matrix material and adding reinforcing materials, including carbon fiber, glass fiber or aramid fiber, graphene or carbon nanotubes, etc., which can not only improve the fracture toughness of the variable stiffness connector 4, but also improve the driving force of the variable stiffness connector 4 during the flexible deformation process, thereby improving the propulsion effect of the flapping wing frame 1; the electromagnetic rheological material includes electromagnetic rheological fluid, electromagnetic rheological foam, electromagnetic rheological elastomer, etc., which has fast response, good reversibility and can continuously change the mechanical properties of the material by adjusting the magnetic field. By sealing the electromagnetic rheological material in silicone... A variable stiffness connector 4 is manufactured within the structure, and the stiffness of the silicone structure can be changed through electro / magnetic excitation. The shear thickening fluid is a suspension system with special properties, mainly composed of a dispersed phase and a dispersion medium of nano- to micron-sized particles. The dispersed phase particles can be divided into naturally occurring minerals and chemically synthesized polymers, such as silica, calcium carbonate, polystyrene, and polymethyl methacrylate. By sealing the shear thickening fluid within the silicone structure to manufacture the variable stiffness connector 4, the stiffness of the silicone structure can be changed through external force excitation. For example, the force on the variable stiffness connector 4 can be changed by changing the rotation amplitude and rotation frequency of the flapping wing frame 1 driven by the rotary drive mechanism 3 around the second direction.

[0040] In this optional embodiment, the variable stiffness material is a shape memory polymer, and the external excitation is thermal excitation. The shape memory polymer can be heated to a higher temperature under thermal excitation. When the temperature reaches above the glass transition temperature of the shape memory polymer, the stiffness of the shape memory polymer decreases and changes from a rigid state to a flexible state. However, by lowering the temperature of the shape memory polymer below the glass transition temperature, the stiffness of the shape memory polymer increases and changes from a flexible state to a rigid state.

[0041] Optionally, such as Figure 1 and Figure 3 As shown, the variable stiffness flapping-wing underwater robotic fish also includes a flexible cover 5, which covers the flapping-wing frame 1 and is connected to the variable stiffness connector 4 and the undulating movement component 11, respectively.

[0042] Specifically, the flexible cover 5 is made of a flexible and tough material, such as silicone.

[0043] In this optional embodiment, such as Figure 1 and Figure 3 As shown, a flexible cover 5 is placed on the flapping wing frame 1 and connected to the undulating moving member 11. This flexible cover 5 increases the contact area between the flapping wing frame 1 and the water, while reducing the water pressure on the flapping wing frame 1, thus resisting underwater pressure to ensure the structural stability of the flapping wing frame 1. Furthermore, the flexible cover 5 is connected to the undulating moving member 11. When the rotary drive mechanism 3 drives the flapping wing frame 1 to rotate around the second direction, the relative rotation of the undulating moving member 11 can cause the flexible cover 5 to deform, thereby achieving the desired effect through the deformation of the flexible cover 5. The disturbance of the water generates a water flow that propels the variable stiffness flapping-wing underwater robot fish. On this basis, the variable stiffness connector 4 is connected to the flexible cover 5. Thus, when the variable stiffness connector 4 is in a rigid state, it can increase the stiffness of the flexible cover 5 while keeping the shape of the flapping-wing frame 1 unchanged. This enhances the effect of the flapping-wing frame 1 in breaking through the water flow through the flexible cover 5, further reducing the resistance encountered by the variable stiffness flapping-wing underwater robot fish when sliding, and effectively improving the propulsion effect of the variable stiffness flapping-wing underwater robot fish.

[0044] Unlike the first embodiment, in the second embodiment of the present invention, as follows: Figure 4 As shown, the variable stiffness connector 4 extends along the outer surface of multiple undulating moving parts 11 to form a skin covering the flapping wing frame 1.

[0045] In this embodiment, as Figure 4As shown, the variable stiffness connector 4 in its flexible state is extended to cover all the undulating moving parts 11 of the flapping wing frame 1, forming a skin covering the flapping wing frame 1. When the rotary drive mechanism 3 drives the flapping wing frame 1 to rotate around the second direction, the relative rotation of the undulating moving parts 11 can cause the flexible cover variable stiffness connector 4 to deform. The deformation of the variable stiffness connector 4 can then disturb the water, generating a water flow that propels the variable stiffness flapping wing underwater robot fish. At the same time, when the variable stiffness connector 4 is in a rigid state, the shape of the entire skin remains unchanged. The flapping wing frame 1 can better break through the water flow through the variable stiffness connector 4, further reducing the resistance encountered by the variable stiffness flapping wing underwater robot fish during sliding and effectively improving the propulsion effect of the variable stiffness flapping wing underwater robot fish.

[0046] Optionally, such as Figure 1 and Figure 2 As shown, the flapping wing frame 1 also includes a support connector 12 and a damper 13. The support connector 12 is connected between two adjacent undulating moving parts 11. The support connector 12 is rotatably connected to the undulating moving parts 11 about a second direction through the damper 13.

[0047] Specifically, damper 13 is a damping gear.

[0048] In this optional embodiment, such as Figure 1 and Figure 2 As shown, the flapping wing frame 1 also has a support connector 12 and a damper 13. The support connector 12 is connected between two adjacent undulating moving parts 11 and is rotatably connected to the undulating moving parts 11 about a second direction. In this way, the support connector 12 maintains the stable transmission of the undulating driving force between the two adjacent undulating moving parts 11 while separating the two adjacent undulating moving parts 11. This avoids interference between the undulating ripples of one undulating moving part 11 and the adjacent undulating moving part 11 when the two adjacent undulating moving parts 11 are directly rotatably connected, thus improving the structural stability of the flapping wing frame 1. On this basis, the support connector 12 is rotatably connected to the undulating moving parts 11 through the damper 13. With this configuration, the damper 13 can reduce the impact of the undulating driving force on the undulating moving parts 11 or the support connector 12 when the undulating driving force is transmitted between the undulating moving parts 11 and the support connector 12. This improves the structural stability of the flapping wing frame 1 during operation and can effectively reduce the vibration and noise of the flapping wing frame 1 during undulation, thus improving the quietness of the variable stiffness flapping wing underwater robotic fish during underwater propulsion.

[0049] Optionally, such as Figure 1 and Figure 3As shown, the rotary drive mechanism 3 includes a rotary drive component 31, a damping structure, and a mounting base 32. The mounting base 32 is mounted on the main body 2, and the rotary drive component 31 is mounted on the mounting base 32 and is drivenly connected to the flapping wing frame 1 through the damping structure.

[0050] Specifically, the rotary drive component 31 is a drive motor. Adding a damping structure forms a damped motor. This damping structure can be a damping ring, a metal ring with a damping effect. Its function is to increase the motor's damping by generating friction with the rotor of the drive motor. The damping ring can be directly mounted on the motor rotor or installed via magnetic coupling. Alternatively, the damping structure can be an adhesive material coated on the rotor of the drive motor. Coating the rotor with an adhesive material increases damping; commonly used adhesive materials include glue and tape. Another option is a structure directly mounted on the rotor to increase its mass. Increasing the rotor's mass increases the drive motor's rotational inertia and damping, reducing vibration and noise. This can be achieved by mounting iron blocks or other materials on the rotor. Finally, the damping structure can be a damping component installed on the stator of the drive motor, such as a damping plate or damping spring, which increases the drive motor's damping and improves its accuracy and stability.

[0051] In this optional embodiment, such as Figure 1 and Figure 3 As shown, a rotary drive mechanism 3 is composed of a rotary drive component 31, a damping structure, and a mounting base 32. The mounting base 32 is mounted on the main body 2, while the rotary drive component 31 is mounted on the mounting base 32 to ensure the connection stability between the rotary drive component 31 and the main body 2. Based on this, the rotary drive component 31 is driven to the flapping wing frame 1 through the damping structure. With this configuration, while the rotary drive component 31 outputs driving force to drive the flapping wing frame 1 to undulate, the damping structure can reduce the impact of the driving force output by the rotary drive component 31 on the flapping wing frame 1, thereby improving the structural stability of the flapping wing frame 1 during operation. It can also effectively reduce the vibration and noise of the flapping wing frame 1 during undulation, and improve the quietness of the variable stiffness flapping wing underwater robotic fish during underwater propulsion.

[0052] Optionally, such as Figure 1 As shown, the flapping wing frame 1 also includes an undulating outer frame 14, and multiple undulating moving parts 11 are arranged sequentially along a first direction to form an undulating inner frame. Both the undulating inner frame and the undulating outer frame 14 are multiple. The multiple undulating inner frames are spaced apart along a second direction, and the multiple undulating outer frames 14 are spaced apart along the first direction and are all connected to the variable stiffness connector 4. The multiple undulating moving parts 11 spaced apart along the second direction are correspondingly connected to the same undulating outer frame 14.

[0053] Specifically, the undulating exoskeleton 14 can be a plate-like structure, a frame structure, or a ring-like structure, etc.

[0054] In this optional embodiment, such as Figure 1 As shown, multiple undulating moving parts 11 are arranged sequentially along the first direction to form an undulating inner frame. There are multiple undulating inner frames, which are spaced apart along the second direction. The multiple undulating inner frames arranged in parallel can effectively increase the area that the flapping wing frame 1 can cover, thereby increasing the driving force generated when the flapping wing frame 1 is driven by the rotary drive mechanism 3 to disturb the water, and improving the propulsion effect of the variable stiffness flapping wing underwater robot fish. On this basis, in order to ensure the structural stability of the flapping wing frame 1, multiple undulating outer frames 14 are also provided. The multiple undulating outer frames 14 are spaced apart along the first direction and are all connected to the variable stiffness connector 4. The multiple undulating moving parts 11 arranged in the second direction are connected to the same undulating outer frame 14, so that the undulating moving parts 11 arranged in parallel along the second direction are connected as a whole by the undulating outer frames 14, ensuring that the flapping wing frame 1 is a whole structure. Moreover, when the variable stiffness connector 4 turns to a rigid state, the shape of the entire flapping wing frame 1 can be kept unchanged by maintaining the relative stillness between adjacent undulating outer frames 14.

[0055] Optionally, such as Figure 1 As shown, the flapping wing frame 1 also includes a tail connector 15, which is located on the side of the undulating inner frame away from the rotary drive mechanism 3 along the first direction, and is connected to multiple undulating inner frames.

[0056] Specifically, the volume of the multiple undulating exoskeletons 14 gradually decreases along the direction away from the main body 2, and the volume of the tail connector 15 is smaller than the volume of the smallest undulating exoskeleton 14.

[0057] In this optional embodiment, such as Figure 1 As shown, in order to ensure the flapping wing frame 1's water-slapping effect, a tail connector 15 is also provided. The tail connector 15 is located on the side of the undulating inner frame away from the rotary drive mechanism 3 along the first direction, and is connected to multiple undulating inner frames. In this way, the tail connector 15 can further maintain the integrated setting of multiple undulating inner frames of the flapping wing frame 1, and when the rotary drive mechanism 3 drives the flapping wing frame 1 to rotate, the tail connector 15 can finally release the undulating driving force from the flapping wing frame 1, ensuring the flapping wing frame 1's water-slapping effect.

[0058] Optionally, such as Figure 1 and Figure 2 As shown, the undulating outer frame 14 includes a ring frame 141 and a connecting rod 142. The ring frame 141 is sleeved on the outside of the undulating inner frame and is connected to the variable stiffness connector 4. The connecting rod 142 is connected to the undulating moving member 11 and the ring frame 141 respectively. In the first direction, the radial dimension of the ring frame 141 closer to the rotary drive mechanism 3 is greater than the radial dimension of the ring frame 141 farther away from the rotary drive mechanism 3.

[0059] Specifically, the ring frame 141 can be a circular structure, an elliptical structure, or a polygonal structure.

[0060] In this optional embodiment, such as Figure 1 and Figure 2 As shown, an undulating outer frame 14 is formed by a ring frame 141 and a connecting rod 142. The ring frame 141 is connected to the variable stiffness connector 4, while the connecting rod 142 is connected to the undulating moving parts 11 and the ring frame 141 respectively. In this way, the variable stiffness connector 4 and the undulating moving parts 11 can be connected through the ring frame 141 and the connecting rod 142. At the same time, multiple undulating moving parts 11 along the second direction can be integrated through the ring frame 141. On this basis, the ring frame 141 is fitted on the undulating moving parts 11, which can support the structure covering the flapping wing frame 1 and keep the overall structure of the flapping wing frame 1 stable. At the same time, in the first direction, the radial dimension of the ring frame 141 closer to the rotary drive mechanism 3 is larger than the radial dimension of the ring frame 141 farther away from the rotary drive mechanism 3. That is, in the direction away from the main body 2 along the first direction, the area enclosed by the ring frame 141 gradually decreases, realizing the biomimetic design of the overall shape of the flapping wing frame 1 and improving the propulsion effect when the rotary drive mechanism 3 drives the flapping wing frame 1 to rotate.

[0061] like Figure 5 As shown, an embodiment of the present invention provides a method for operating a variable stiffness flapping-wing underwater robotic fish. Based on the aforementioned variable stiffness flapping-wing underwater robotic fish, the method includes: selecting a propulsion mode of the variable stiffness flapping-wing underwater robotic fish as a first mode, the variable stiffness connector 4 of the variable stiffness flapping-wing underwater robotic fish being in a flexible state, and driving the flapping-wing frame 1 of the variable stiffness flapping-wing underwater robotic fish to rotate through the rotation drive mechanism 3 of the variable stiffness flapping-wing underwater robotic fish; when the propulsion mode changes from the first mode to the second mode, the variable stiffness connector 4 is driven to change from a flexible state to a rigid state through external excitation; when the propulsion mode changes from the second mode to the first mode, the variable stiffness connector 4 is driven to change from a rigid state to a flexible state through external excitation.

[0062] Specifically, for the propulsion method of the variable stiffness flapping wing underwater robot fish, the first method is to move the variable stiffness flapping wing underwater robot fish by disturbing the water flow through the rotation and undulation of the flapping wing frame 1, and the second method is to move the variable stiffness flapping wing underwater robot fish by keeping the flapping wing frame 1 stationary and sliding in the water.

[0063] like Figure 5 As shown in S1 to S3, the beneficial effects of the working method of the variable stiffness flapping wing underwater robotic fish in this embodiment compared with the prior art are the same as those of the variable stiffness flapping wing underwater robotic fish described above, and will not be repeated here.

[0064] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A variable stiffness flapping underwater robotic fish, characterized in that, The flapping skeleton (1) includes a plurality of heave moving members (11), the plurality of heave moving members (11) are arranged in sequence along a first direction, and two adjacent heave moving members (11) are rotationally connected around a second direction, the first direction is perpendicular to the second direction; the rotation driving mechanism (3) is installed on the main body (2) and is drivingly connected with one end of the flapping skeleton (1) along the first direction, and the rotation driving mechanism (3) is used for driving the flapping skeleton (1) to rotate around the second direction; the variable stiffness connecting piece (4) is made of a raw material including a variable stiffness material and has a rigid state and a flexible state, and the variable stiffness connecting piece (4) is connected with the plurality of heave moving members (11) and is used for converting between the rigid state and the flexible state through external excitation. The variable stiffness connecting piece (4) extends along the outer surfaces of the plurality of heave moving members (11) to form a skin covering the flapping skeleton (1). The plurality of heave moving members (11) are arranged in sequence along the first direction, and the flapping skeleton (1) further includes a support connecting piece (12) and a damper (13), the support connecting piece (12) is connected between two adjacent heave moving members (11), and the support connecting piece (12) is rotationally connected with the heave moving member (11) around the second direction through the damper (13).

2. The variable stiffness flapping underwater anguifish robot of claim 1, wherein, The variable stiffness material includes a shape memory polymer, a shape memory polymer composite, an electromagnetic rheological material or a shear thickening material.

3. The variable stiffness flapping underwater anguifish robot according to claim 1 or 2, characterized in that, The rotation driving mechanism (3) includes a rotation driving member (31), a damping structure and a mounting seat (32), the mounting seat (32) is installed on the main body (2), the rotation driving member (31) is installed on the mounting seat (32) and is drivingly connected with the flapping skeleton (1) through the damping structure.

4. The variable stiffness flapping underwater anguifish of claim 1 or 2, wherein, The flapping skeleton (1) further includes a heave outer skeleton (14), the plurality of heave moving members (11) arranged in sequence along the first direction form a heave inner skeleton, the heave inner skeleton and the heave outer skeleton (14) both have a plurality of, the plurality of heave inner skeletons are arranged at intervals along the second direction, the plurality of heave outer skeletons (14) are arranged at intervals along the first direction and are all connected with the variable stiffness connecting piece (4), and the plurality of heave moving members (11) arranged at intervals along the second direction are connected with the same heave outer skeleton (14) correspondingly.

5. The variable stiffness flapping underwater anguifish of claim 4, wherein, The flapping skeleton (1) further includes a tail connecting piece (15), the tail connecting piece (15) is located on a side of the heave inner skeleton away from the rotation driving mechanism (3) along the first direction and is connected with the plurality of heave inner skeletons.

6. The variable stiffness flapping underwater anguifish robot of claim 4, wherein, The undulating exoskeleton (14) comprises a ring-shaped frame (141) and a connecting rod (142), the ring-shaped frame (141) is sleeved outside the undulating endoskeleton and connected with the variable stiffness connecting piece (4), the connecting rod (142) is connected with the undulating moving piece (11) and the ring-shaped frame (141) respectively, and in the first direction, the radial dimension of the ring-shaped frame (141) close to the rotary driving mechanism (3) is greater than the radial dimension of the ring-shaped frame (141) away from the rotary driving mechanism (3).

7. A method of operating a variable stiffness flapping underwater robotic fish, comprising: The working method of the variable stiffness flapping underwater robot fish based on any one of claims 1 to 6 comprises: Selecting the propulsion mode of the variable stiffness flapping underwater robot fish as a first mode, the variable stiffness connecting piece (4) of the variable stiffness flapping underwater robot fish is in a flexible state, and the rotary driving mechanism (3) of the variable stiffness flapping underwater robot fish drives the flapping skeleton (1) of the variable stiffness flapping underwater robot fish to rotate; When the propulsion mode is changed from the first mode to a second mode, the variable stiffness connecting piece (4) is driven by external excitation to change from the flexible state to a rigid state; When the propulsion mode is changed from the second mode to the first mode, the variable stiffness connecting piece (4) is driven by the external excitation to change from the rigid state to the flexible state.

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