Passive fish tail structure based on damping force and bionic robotic fish

Abstract

The application relates to the technical field of underwater robots, and provides a passive fish tail structure based on damping force and a bionic robotic fish. The passive fish tail structure based on damping force comprises a shell, a piston rod, a connecting rope and an elastic piece, the shell is filled with damping liquid, the first end of the piston rod penetrates through the shell and is connected with a fish body through the connecting rope, the piston rod is provided with an annular boss, the annular boss is located in the shell, the elastic piece is sleeved on the second end of the piston rod, the first end of the elastic piece is connected with the second end of the piston rod, when a tail fin swings from the body axis of the fish body to both sides, the elastic piece generates elastic force, when the tail fin swings, the piston rod reciprocates, the annular boss is configured as a damping structure, the damping liquid flows through the damping structure, and damping force is generated. The passive fish tail structure based on damping force can realize passive wide-range adjustment of the tail fin swing angle through adjustment of the damping force and the elastic force, so that the propelling performance of the tail of the robotic fish in a wide frequency band is improved.

Description

Technical Field

[0001] This invention relates to the field of underwater robot technology, and in particular to a passive fish tail structure based on damping force and a biomimetic robotic fish. Background Technology

[0002] In recent years, researchers have begun to focus on the development of biomimetic robotic fish, hoping that they can be applied to fields such as marine resource development. Biomimetic robotic fish achieve underwater propulsion by mimicking the swimming movements of fish, thus exhibiting advantages such as high efficiency and high maneuverability.

[0003] Improving the swimming performance of robotic fish is a crucial issue. Numerous studies have shown that the propulsion performance, such as speed, of biomimetic robotic fish depends on the tail's undulation pattern. When a robotic fish swims underwater, its tail interacts with the water flow; different tail undulation patterns produce different body waves, thus affecting its propulsion performance.

[0004] Some researchers have developed biomimetic robotic fish with passive flexible joints, which utilize elastic elements to passively adjust the tail's swaying pattern. However, these robotic fish can only achieve optimal swimming performance at a single frequency. Furthermore, some researchers have focused on biomimetic robotic fish with variable tail stiffness, which actively adjust tail stiffness online using a stiffness adjustment mechanism. Then, by utilizing the interaction between the tail and water flow, the tail's swaying pattern is adjusted to achieve optimal body waves, allowing the robotic fish to exhibit optimal swimming performance in different swimming states. However, biomimetic robotic fish with variable tail stiffness require an additional stiffness adjustment drive source for real-time adjustment of tail stiffness, which increases the weight, size, and power consumption of the robotic fish. Some biomimetic robotic fish with variable tail stiffness use hydraulic pressure or smart materials (such as shape memory alloys) to adjust tail stiffness, but their stiffness adjustment response is slow, making it difficult to achieve rapid response to control inputs, especially high-frequency control; and the adjustable stiffness range is small, making it difficult to achieve wide-range adjustment of the tail's swaying pattern across a broad frequency band.

[0005] For the reasons mentioned above, it is necessary to explore a fish-tail-inspired propulsion device that can achieve wide-range adjustment of the fish tail's oscillation pattern across a broad frequency band, thereby improving the robotic fish's swimming performance. Furthermore, its passive adjustment eliminates the need for an additional stiffness adjustment drive source, significantly reducing the robotic fish's power consumption and improving its endurance. Summary of the Invention

[0006] This invention provides a passive fish tail structure based on damping force and a biomimetic robotic fish to solve the shortcomings of existing biomimetic robotic fish tails, which can only adjust the angle within a small frequency range and are actively adjustable.

[0007] This invention provides a passive fishtail structure based on damping force, comprising: a drive mechanism, a fish body, a damping mechanism, and a tail fin. The drive mechanism is connected to the fish body and is used to drive the fish body to reciprocate. The damping mechanism is connected to a first end of the fish body, and the tail fin is rotatably connected to a second end of the fish body. When the fish body reciprocates, it can drive the damping mechanism and the tail fin to reciprocate. The damping mechanism comprises: a housing, a piston rod, a connecting rope, and an elastic element. The housing is filled with damping fluid. The first end of the piston rod passes through the housing and is connected to the fish body via the connecting rope. The piston rod has an annular boss located inside the housing. The elastic element is sleeved on the fish body. The second end of the piston rod is connected to the first end of the elastic element, which abuts against the housing. When the tail fin swings from both sides of the fish's body axis, the connecting rope pulls the piston rod towards the tail fin, and the elastic element is in a compressed state. When the tail fin swings from both sides towards the fish's body axis, the elastic element uses its elastic force to drive the piston rod away from the tail fin. During the reciprocating movement of the piston rod, the annular boss forms a damping structure, and the damping fluid flows through the damping structure to generate a damping force. Adjusting the damping force and the elastic coefficient of the elastic element can adjust the angle of rotation of the tail fin.

[0008] According to the present invention, a passive fishtail structure based on damping force is provided, wherein a gap is formed between the circumferential surface of the annular boss and the inner wall of the housing, and when the piston rod reciprocates, the damping fluid flows through the gap to generate a damping force.

[0009] According to the present invention, a passive fishtail structure based on damping force is provided, wherein the circumferential surface of the annular boss abuts against the inner wall of the housing, the annular boss is provided with at least one first through hole, and when the piston rod reciprocates, the damping fluid flows through the first through hole to generate damping force.

[0010] According to the present invention, a passive fishtail structure based on damping force is provided, wherein the housing includes: a sleeve; a pair of end caps respectively sleeved on both ends of the sleeve, the piston rod passing through the pair of end caps, and one end of the elastic element abutting against the end caps; and a pair of sealing structures, wherein the sleeve, the end caps and the piston rod are sealed together by the sealing structures.

[0011] According to the present invention, a passive fishtail structure based on damping force is provided, each of the sealing structures includes: a sealing cap disposed inside the sleeve, the sleeve and the end cap being sealed and connected by the sealing cap; a plurality of sealing rings embedded in the outer wall and the inner wall of the sealing cap, the sealing cap and the sleeve being sealed and connected by the sealing rings, and the piston rod and the sealing cap being sealed and connected by the sealing rings.

[0012] According to the present invention, a passive fishtail structure based on damping force is provided, wherein any of the sealing structures further includes a sealing element, and any of the end caps and the sealing caps are provided with a second through hole, the second through hole being used to drain excess damping fluid, and the sealing element being used to seal the second through hole.

[0013] According to the present invention, a passive fishtail structure based on damping force is provided, wherein the driving mechanism includes: a first mounting bracket; a servo motor disposed on the first mounting bracket; and a second mounting bracket connected to the output shaft of the servo motor and connected to the fish body, so that when the servo motor reciprocates, it can drive the fish body to swing back and forth.

[0014] According to the present invention, a passive fish tail structure based on damping force is provided, wherein the fish body includes: a third mounting frame connected to a second mounting frame; a fourth mounting frame connected to the third mounting frame; and a rotating joint, wherein both ends of the rotating joint are rotatably connected to the third mounting frame and the fourth mounting frame respectively, and the opposite sides of the rotating joint are connected to the connecting rope and the tail fin respectively.

[0015] According to the present invention, a passive fishtail structure based on damping force is provided, wherein the rotating joint includes: a rotating shaft, the two ends of which are rotatably connected to the third mounting bracket and the fourth mounting bracket respectively; a connecting plate, the two ends of which are connected to the rotating shaft and the tail fin respectively; and a connecting post, the connecting post and the connecting plate being respectively disposed on both sides of the rotating shaft, the two ends of which are connected to the rotating shaft and the connecting rope respectively.

[0016] The present invention also provides a biomimetic robotic fish, comprising: a fish head shell, a fish body shell, and a passive fish tail structure based on damping force as described above, wherein the fish head shell is sleeved outside the drive mechanism, and the fish body shell is sleeved outside the fish body and the damping mechanism.

[0017] The passive fish tail structure based on damping force provided by this invention can achieve passive wide-range adjustment of the tail fin angle by setting up a damping structure and elastic element, thereby improving the propulsion performance of the robotic fish tail in a wide frequency band. Moreover, it does not require setting up an additional stiffness adjustment drive source, reducing the power consumption of the bionic robotic fish and improving its endurance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the passive structure based on damping force provided by the present invention;

[0020] Figure 2 yes Figure 1 The diagram shows the structure of the drive mechanism and the fish body.

[0021] Figure 3 yes Figure 2 The diagram shows the structure of the rotating joint.

[0022] Figure 4 yes Figure 2 One of the cross-sectional views of the damping mechanism shown in the figure;

[0023] Figure 5 yes Figure 4 One of the schematic diagrams of the piston rod shown in the figure;

[0024] Figure 6 yes Figure 2 The second cross-sectional view of the damping mechanism shown in the figure;

[0025] Figure 7 yes Figure 6 The second schematic diagram of the piston rod structure shown in the figure;

[0026] Figure 8 This is a schematic diagram of the structure of the biomimetic robotic fish provided by the present invention;

[0027] Figure label:

[0028] 1: Drive mechanism; 2: Fish body; 3: Damping mechanism; 4: Tail fin; 5: Fish head shell; 6: Fish body shell; 11: Servo motor; 12: First mounting bracket; 13: Second mounting bracket; 21: Third mounting bracket; 22: Fourth mounting bracket; 23: Rotating joint; 31: Piston rod; 32: Sleeve; 34: Elastic element; 35: End cap; 36: Connecting rope; 37: Cavity; 38: Gap; 39: First through hole; 211: Third through hole; 221: Fourth through hole; 222: First plate; 223: Second plate; 224: Third plate; 231: Fifth through hole; 232: Connecting post; 233: Rotating shaft; 234: Connecting plate; 311: Annular boss; 312: Sixth through hole; 331: Sealing ring; 332: Sealing cap; 333: Linear bearing; 3321: Second through hole; 3322: Seal. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] The terms "first" and "second" in the specification and claims of this invention may explicitly or implicitly include one or more of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] The following is combined Figures 1-8 This invention describes a passive fish tail structure based on damping force and a biomimetic robotic fish.

[0032] like Figure 1 and Figure 4As shown, in an embodiment of the present invention, the passive fish tail structure based on damping force includes: a drive mechanism 1, a fish body 2, a damping mechanism 3, and a tail fin 4. The drive mechanism 1 is connected to the fish body 2 and is used to drive the fish body 2 to swing back and forth. The damping mechanism 3 is connected to the first end of the fish body 2, and the tail fin 4 is rotatably connected to the second end of the fish body 2. When the fish body 2 swings, it can drive the damping mechanism 3 and the tail fin 4 to swing. The damping mechanism 3 includes a housing, a piston rod 31, a connecting rope 36, and an elastic element 34. The housing is filled with damping fluid. The first end of the piston rod 31 passes through the housing and is connected to the fish body 2 via the connecting rope 36. The piston rod 31 has an annular boss 311 located inside the housing. The elastic element 34 is sleeved on the second end of the piston rod 31. The first end of the elastic element 34 is connected to the second end of the piston rod 31, and the second end of the elastic element 34 abuts against the housing. When the tail fin 4 swings from the body axis of the fish body 2 to both sides, the connecting rope 36 pulls the piston rod 31 towards the direction closer to the tail fin 4, and the elastic element 34 is in a compressed state. When the tail fin 4 swings from both sides towards the body axis of the fish body 2, the elastic element 34 uses elastic force to drive the piston rod 31 away from the tail fin 4. During the reciprocating movement of the piston rod 31, the annular boss 311 forms a damping structure, and the damping fluid flows through the damping structure, generating a damping force.

[0033] Specifically, in this embodiment, the drive mechanism 1 is used to drive the fish body 2 to swing back and forth. When the fish body 2 swings, it will cause the damping mechanism 3 and the tail fin 4 to also swing back and forth, realizing the imitation of a fish tail swinging. When the drive mechanism 1 rotates through an angle and holds, the fish body 2, the damping mechanism 3 and the tail fin 4 will also rotate through an angle and hold. Due to the combined effect of the water force on the damping mechanism 3 and the tail fin 4, the rotation angle of the tail fin 4 may be different from the rotation angle of the fish body 2 and the damping mechanism 3.

[0034] When the drive mechanism 1 drives the fish body 2 and tail fin 4 to swing back and forth, the tail fin 4 rotates relative to the fish body 2 under the action of hydrodynamics. When the tail fin 4 swings from both sides of the body axis of the fish body 2, the fish body 2 pulls the connecting rope 36, and the connecting rope 36 pulls the piston rod 31 to move closer to the tail fin 4, and the elastic element 34 is in a compressed state; when the tail fin 4 swings from both sides towards the body axis of the fish body 2, the elastic element 34 uses elastic force to drive the piston rod 31 to move away from the tail fin 4. During the reciprocating movement of the piston rod 31, the annular boss 311 is constructed as a damping structure, and the damping fluid flows through the damping structure to generate damping force.

[0035] A gap 38 exists between the annular boss 311 of the piston rod 31 and the inner wall of the housing. During the reciprocating movement of the piston rod 31, damping fluid flows through this gap 38, generating a damping force. Further, in embodiments of the present invention, the damping fluid can be a Newtonian fluid or a non-Newtonian fluid. The magnitude of the damping force is related to the size of the gap 38 and the viscosity of the damping fluid; the larger the gap 38, the smaller the damping force; the larger the viscosity coefficient, the larger the damping force. The greater the damping force, the slower the movement speed of the piston rod 31. Further, the elastic force can be adjusted by adjusting the elastic coefficient of the elastic element 34. When the elastic force is small, the speed at which the elastic element 34 drives the piston rod 31 to move is slow. By adjusting the damping force and the elastic coefficient of the elastic element 34, the angle of rotation of the tail fin 4 can be adjusted. Because the adjustable range of the damping force and the elastic force is large, the angle of rotation of the tail fin 4 can be adjusted over a wide frequency range.

[0036] Furthermore, such as Figure 5 As shown, the first end of the piston rod 31 is provided with a sixth through hole 312, which is used to thread the connecting rope 36. In this embodiment, the connecting rope 36 can be a steel wire rope. When the fish body 2 drives the tail fin 4 to swing, the connecting rope 36 can ensure the swing angle of the tail fin 4.

[0037] The passive fishtail structure based on damping force provided in this embodiment of the invention can achieve passive wide-range adjustment of the tail fin angle by setting up a damping structure and elastic elements, thereby improving the propulsion performance of the robotic fishtail in a wide frequency band. Moreover, it does not require setting up an additional stiffness adjustment drive source, reducing the power consumption of the bionic robotic fish and improving its endurance.

[0038] like Figure 4 As shown, in one embodiment of the present invention, a gap 38 is formed between the circumferential surface of the annular boss 311 and the inner wall of the housing. When the piston rod 31 reciprocates, the damping fluid flows through the gap 38 to generate a damping force.

[0039] Specifically, the housing is filled with damping fluid. When the piston rod 31 reciprocates, the damping fluid flows through the gap 38, generating a damping force. In this embodiment, the damping force is related to the size of the gap 38; the larger the gap 38, the smaller the damping force.

[0040] like Figure 6 and Figure 7 As shown, in another embodiment of the present invention, the circumferential surface of the annular boss 311 abuts against the inner wall of the housing. The annular boss 311 is provided with at least one first through hole 39. When the piston rod 31 reciprocates, the damping fluid flows through the first through hole 39 to generate a damping force.

[0041] Specifically, the housing is filled with damping fluid. When the piston rod 31 reciprocates, the damping fluid flows through the first through hole 39, generating a damping force. In this embodiment, the damping force is related to the number and size of the first through holes 39. The more first through holes 39 there are, the smaller the damping force; the larger the diameter of the first through hole 39, the smaller the damping force.

[0042] The passive fishtail structure based on damping force provided in this embodiment of the invention can adjust the damping force by adjusting the size of the gap or the size or number of the first through holes. At the same time, by adjusting the viscosity coefficient of the damping fluid and the elastic coefficient of the elastic element, a passive wide-range adjustment of the tail fin angle is achieved, thereby improving the propulsion performance of the robotic fishtail in a wide frequency band.

[0043] like Figure 4 and Figure 6 As shown, in an embodiment of the present invention, the housing includes: a sleeve 32, a pair of end caps 35, and a pair of sealing structures. The pair of end caps 35 are respectively fitted onto both ends of the sleeve 32, and the piston rod 31 passes through the pair of end caps 35. One end of the elastic member 34 abuts against the end caps 35. The sleeve 32, end caps 35, and piston rod 31 are connected by the sealing structures.

[0044] Specifically, both ends of the sleeve 32 are open, and a pair of end caps 35 are respectively fitted onto both ends of the sleeve 32 to close both ends. Each end cap 35 has a through hole in the center so that the piston rod 31 can pass through. Each sealing structure includes a sealing ring 331 and a sealing cover 332. The sealing cover 332 has a stepped structure, and the end face of the sleeve 32 also has a stepped hole. The small end of the sealing cover 332 is inserted into the small hole of the stepped hole, and the large end is inserted into the large hole of the stepped hole. The end cap 35 and the sealing cover 332 abut against each other, thereby achieving a sealed connection between the sleeve 32 and the end cap 35.

[0045] The sealing cap 332 also has a through hole to allow the piston rod 31 to pass through. The outer wall of the sealing cap 332 has an annular groove, and the sealing ring 331 is embedded in this annular groove to ensure a sealing connection between the sealing cap 332 and the sleeve 32. Simultaneously, the inner wall of the through hole of the sealing cap 332 also has an annular groove, and the sealing ring 331 is also embedded in this annular groove. The sealing ring 331 abuts against the piston rod 31 to ensure a sealing connection between the sealing cap 332 and the piston rod 31.

[0046] Furthermore, in an embodiment of the present invention, each sealing structure further includes a linear bearing 333, which is disposed at the through hole of the end cap 35, and the piston rod 31 passes through the linear bearing 333. The second end of the elastic member 34 abuts against the linear bearing 333. When the tail fin 4 swings from both sides of the fish body axis, the piston rod 31 moves towards the tail fin 4, and the elastic member 34 is in a compressed state. When the tail fin 4 swings from both sides towards the body axis of the fish body 2, the elastic force of the elastic member 34 can drive the piston rod 31 to move away from the tail fin 4.

[0047] like Figure 4 and Figure 6 As shown, in the embodiments of the present invention, any sealing structure further includes a sealing element 3322, and any end cap 35 and sealing cap 332 are provided with a second through hole 3321. The second through hole 3321 is used to drain excess damping fluid, and the sealing element 3322 is used to block the second through hole 3321.

[0048] Specifically, when assembling the damping mechanism 3, after fixing the sealing caps 332 on both sides to the sleeve 32, the excess damping fluid will flow out from the second through hole 3321. Then, the sealing element 3322 is inserted into the second through hole 3321 to achieve the sealing of the damping mechanism 3. This design can ensure that the damping fluid fills the cavity 37 of the sleeve 32, so that there is no air in the cavity 37, thus ensuring the stability of the damping mechanism 3.

[0049] like Figure 2 As shown, in an embodiment of the present invention, the drive mechanism 1 includes: a servo motor 11, a first mounting bracket 12, and a second mounting bracket 13. The servo motor 11 is mounted on the first mounting bracket 12, and the output shaft of the servo motor 11 serves as an active rotating joint. The second mounting bracket 13 is connected to the output shaft of the servo motor 11 and is also connected to the fish body 2. When the output shaft of the servo motor 11 reciprocates, it can drive the fish body 2 to swing back and forth. Optionally, in this embodiment, the servo motor 11 can be a waterproof servo motor, and the servo motor 11 can be controlled by a position or angle servo driver.

[0050] like Figure 2 As shown, in an embodiment of the present invention, the fish body 2 includes: a third mounting frame 21, a fourth mounting frame 22, and a rotating joint 23. The third mounting frame 21 is connected to the second mounting frame 13, the fourth mounting frame 22 is connected to the third mounting frame 21, the two ends of the rotating joint 23 are respectively connected to the third mounting frame 21 and the fourth mounting frame 22, and the opposite sides of the rotating joint 23 are respectively connected to the connecting rope 36 and the tail fin 4.

[0051] Specifically, the fourth mounting bracket 22 includes a first plate, a second plate, and a third plate connected in sequence. The first plate is parallel to the third mounting bracket 21, the second plate is perpendicular to the first plate, and the third plate is perpendicular to the second plate. The third plate is stacked and connected to the third mounting bracket 21, thus creating a certain space between the first plate and the third mounting bracket 21. The piston rod 31 passes through the second plate, and the connecting rope 36 is located in the space between the first plate and the third mounting bracket 21. The rotary joint, as a passive rotary joint, has its two ends rotatably connected to the first plate and the third mounting bracket 21, respectively.

[0052] The two ends of the connecting rope 36 are connected to the piston rod 31 and the rotating joint 23 respectively. When the tail fin 4 swings from the body axis of the fish body 2 to both sides, it drives the rotating joint 23 to rotate. The rotating joint 23 drives the connecting rope 36 to pull the piston rod 31 to move closer to the tail fin 4.

[0053] Correspondingly, when the tail fin 4 swings from both sides toward the body axis of the fish body 2, the piston rod 31 moves away from the tail fin 4 under the action of elastic force.

[0054] like Figure 3 As shown, in an embodiment of the present invention, the rotating joint 23 includes: a connecting post 232, a rotating shaft 233, and a connecting plate 234. The two ends of the rotating shaft 233 are rotatably connected to the third mounting bracket 21 and the fourth mounting bracket 22, respectively. The two ends of the connecting plate 234 are connected to the rotating shaft 233 and the tail fin 4, respectively. The connecting post 232 and the connecting plate 234 are respectively disposed on both sides of the rotating shaft 233. The two ends of the connecting post 232 are connected to the rotating shaft 233 and the connecting rope 36, respectively.

[0055] Specifically, the third mounting bracket 21 has a third through hole 211, and the first plate of the fourth mounting bracket 22 has a fourth through hole 221. The two ends of the rotating shaft 233 are respectively inserted into the third through hole 211 and the fourth through hole 221, so that the rotating shaft 233 can rotate relative to the third mounting bracket 21 and the fourth mounting bracket 22. One side of the rotating shaft 233 is connected to the connecting plate 234, and the other side of the rotating shaft 233 is connected to the connecting post 232. One end of the connecting post 232 has a fifth through hole 231, and the two ends of the connecting rope 36 pass through the sixth through hole 312 of the piston rod 31 and the fifth through hole 231 of the connecting post 232 to connect the piston rod 31 to the connecting post 232.

[0056] When the tail fin 4 swings from both sides of the fish's body axis, the tail fin 4 drives the rotating shaft 233 to rotate. The rotating shaft 233 drives the connecting rope 36 to pull the piston rod 31 towards the tail fin 4, and the elastic element 34 is in a compressed state. When the tail fin 4 swings from both sides towards the body axis of the fish 2, the elastic element 34 uses its elastic force to drive the piston rod 31 away from the tail fin 4. At this time, the elastic element 34 needs to overcome the damping force of the damping mechanism 3 and the tension that may exist in the connecting rope 36.

[0057] like Figure 8 As shown, this embodiment of the invention also provides a biomimetic robotic fish, including: a fish head shell 5, a fish body shell 6, and a passive fish tail structure based on damping force. The fish head shell 5 is sleeved on the outside of the drive mechanism 1, and the fish body shell 6 is sleeved on the outside of the fish body 2 and the damping mechanism 3.

[0058] Specifically, the fish head shell 5 is connected to the first mounting bracket 12 of the drive mechanism 1, and the fish head shell 5 encloses the drive mechanism 1. The fish body shell 6 is connected to the third mounting bracket 21 and the fourth mounting bracket 22. The fish body shell 6 is fitted outside the fish body 2 and the damping mechanism 3, so that the entire bionic robotic fish has a streamlined shape, thereby reducing the resistance of the bionic robotic fish when swimming and improving its swimming performance.

[0059] The biomimetic robotic fish provided in this embodiment of the invention, by setting a passive tail structure based on damping force, can achieve a passive wide-range adjustment of the tail fin angle by adjusting the damping force and elastic force, thereby improving the propulsion performance of the robotic fish tail in a wide frequency band.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive fishtail structure based on damping force, characterized in that, include: The fish includes a drive mechanism, a fish body, a damping mechanism, and a tail fin. The drive mechanism is connected to the fish body and is used to drive the fish body to swing back and forth. The damping mechanism is connected to the first end of the fish body, and the tail fin is rotatably connected to the second end of the fish body. When the fish body swings, it can drive the damping mechanism and the tail fin to swing. The damping mechanism includes: a housing, a piston rod, a connecting rope, and an elastic element. The housing is filled with damping fluid. The first end of the piston rod passes through the housing and is connected to the fish body via the connecting rope. The piston rod has an annular boss located inside the housing. The elastic element is sleeved on the second end of the piston rod. The first end of the elastic element is connected to the second end of the piston rod, and the second end of the elastic element abuts against the housing. When the tail fin swings from both sides of the fish's body axis, the connecting rope pulls the piston rod towards the tail fin, and the elastic element is in a compressed state. When the tail fin swings from both sides towards the fish's body axis, the elastic element uses elastic force to drive the piston rod away from the tail fin. During the reciprocating movement of the piston rod, the annular boss forms a damping structure, and the damping fluid flows through the damping structure to generate a damping force. Adjusting the damping force and the elastic coefficient of the elastic element can adjust the angle of rotation of the tail fin.

2. The passive fishtail structure based on damping force according to claim 1, characterized in that, A gap is formed between the circumferential surface of the annular boss and the inner wall of the housing. When the piston rod reciprocates, the damping fluid flows through the gap to generate a damping force.

3. The passive fishtail structure based on damping force according to claim 1, characterized in that, The circumferential surface of the annular boss abuts against the inner wall of the housing. The annular boss is provided with at least one first through hole. When the piston rod reciprocates, the damping fluid flows through the first through hole to generate a damping force.

4. The passive fishtail structure based on damping force according to claim 1, characterized in that, The housing includes: Sleeve; A pair of end caps are respectively fitted onto both ends of the sleeve, the piston rod passes through the pair of end caps, and one end of the elastic element abuts against the end caps; A pair of sealing structures are provided, through which the sleeve, the end cap, and the piston rod are sealed together.

5. The passive fishtail structure based on damping force according to claim 4, characterized in that, Each of the sealing structures includes: A sealing cap is disposed inside the sleeve, and the sleeve and the end cap are sealed together by the sealing cap. Multiple sealing rings are embedded in the outer wall and the inner wall of the sealing cover. The sealing cover and the sleeve are sealed together by the sealing rings, and the piston rod is sealed together by the sealing rings.

6. The passive fishtail structure based on damping force according to claim 5, characterized in that, Any of the sealing structures further includes a sealing element, and any of the end caps and the sealing caps are provided with a second through hole for draining excess damping fluid, and the sealing element is used to block the second through hole.

7. The passive fishtail structure based on damping force according to claim 1, characterized in that, The drive mechanism includes: First mounting bracket; The servo motor is mounted on the first mounting bracket; The second mounting bracket is connected to the output shaft of the servo motor and to the fish body, so that the fish body can be driven to swing back and forth when the servo motor reciprocates.

8. The passive fishtail structure based on damping force according to claim 7, characterized in that, The fish body includes: The third mounting bracket is connected to the second mounting bracket; The fourth mounting bracket is connected to the third mounting bracket; The rotating joint has two ends that are rotatably connected to the third mounting bracket and the fourth mounting bracket, respectively, and the opposite sides of the rotating joint are connected to the connecting rope and the tail fin, respectively.

9. The passive fishtail structure based on damping force according to claim 8, characterized in that, The rotary joint includes: A rotating shaft, the two ends of which are rotatably connected to the third mounting bracket and the fourth mounting bracket, respectively; A connecting plate, the two ends of which are respectively connected to the rotating shaft and the tail fin; A connecting column is provided on both sides of the rotating shaft, and the connecting column and the connecting plate are respectively disposed on both sides of the rotating shaft. The two ends of the connecting column are respectively connected to the rotating shaft and the connecting rope.

10. A biomimetic robotic fish, characterized in that, include: The fish head shell, the fish body shell, and the passive fish tail structure based on damping force according to any one of claims 1-9, wherein the fish head shell is sleeved on the outside of the drive mechanism, and the fish body shell is sleeved on the outside of the fish body and the damping mechanism.

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