A robotic fish bionic mechanical tail device with variable cross-sectional characteristics

Abstract

This invention discloses a biomimetic mechanical tail device for a robotic fish with variable cross-section features, including a tail peduncle mechanism and a tail fin mechanism connected to the fish body. This invention draws inspiration from the biological structure and propulsion mechanism of fish tails in nature. The tail fin mechanism is crescent-shaped and includes a push rod, an upper tail fin, and a lower tail fin. The left end of the push rod passes through the tail peduncle and is threadedly connected to a spring seat. The left end of the tail peduncle is connected to the tail fin mechanism. The spring is sleeved on the outside of the spring seat and placed between the tail peduncle and the spring. A hydraulic cylinder is installed inside the distal end of the tail peduncle. The piston is fixedly connected to the left side of the spring seat through a hydraulic oil line. An elongated hole is opened in the middle of the push rod. The upper and lower tail fins are symmetrically arranged on both sides of the push rod. The middle parts of the upper and lower tail fins are slidably and rotatably connected to the elongated hole through a rotating shaft. The upper and lower tail fins are rotatably connected to the push rod through connecting rod one and connecting rod two, respectively. The left side of the upper and lower tail fins overlaps the left side of the push rod.

Description

Technical Field

[0001] This invention belongs to the field of bionic engineering, and specifically relates to a bionic mechanical tail device for a robotic fish with variable cross-sectional features. Background Technology

[0002] The ocean covers most of the Earth's surface and possesses abundant natural resources, including mineral resources, seawater chemical resources, marine biological resources, marine dynamic resources, and marine space resources. With the increasing depletion of land resources, people are turning their attention to the ocean, which boasts rich natural resources and immense development value. Biomimetic robotic fish can play a vital role in complex underwater environments, underwater exploration, underwater salvage, marine life observation, and archaeology. Most fish in nature use a body / tail fin swimming pattern, relying primarily on body or tail fin undulations for propulsion, resulting in high swimming speed, high propulsion efficiency, and good maneuverability. Therefore, robotic fish employing this swimming pattern have been widely researched and applied.

[0003] Studies have shown that parameters such as the aspect ratio, sweep angle, and stiffness of the caudal fin affect the propulsion effect of the robotic fish's tail mechanism. The aspect ratio affects the magnitude of the propulsive force generated by the tail, while the sweep angle affects the magnitude of the drag experienced by the tail. The formula for calculating the aspect ratio is: In the formula l To lengthen the tail fin, S This refers to the area of ​​the tail fin. Existing robotic fish tails mostly employ a non-deformable, one-piece structure with an adjustable aspect ratio, providing the necessary thrust for forward movement with a fixed cross-section and shape. Researching a biomimetic mechanical tail device for robotic fish with a variable tail fin cross-section can ensure sufficient propulsion efficiency while adapting to more application scenarios and improving maneuverability. For example, during acceleration, increasing the area and decreasing the aspect ratio can increase the robotic fish's acceleration; during high-speed cruising, decreasing the area and increasing the aspect ratio can reduce drag and improve motion efficiency. Therefore, developing a biomimetic mechanical tail device for robotic fish with an adjustable aspect ratio has significant scientific importance.

[0004] Common robotic fish tail mechanisms typically possess a certain propulsion efficiency and operating speed, but their structural parameters and shapes often cannot be altered to meet specific needs. The biomimetic mechanical tail device in this invention, besides providing forward thrust for the robotic fish, is innovative primarily due to its deformable tail fin mechanism, which adapts to different usage conditions, thus enhancing the robotic fish's adaptability in various scenarios.

[0005] A similar technical solution to this invention is a deformable bionic tail fin propulsion device disclosed in patent number CN219884066U. The CN219884066U solution involves mounting two fin plates on a base, hinged together, with a skin attached to the corresponding fin plates on both sides. When the skin and fin plates are retracted, a protrusion exists in the folded area on the skin's side, increasing forward resistance. The bionic tail fin of this invention does not have a folded area when retracted, its thickness remains constant, and it does not generate additional resistance. Summary of the Invention

[0006] The purpose of this invention is to design a biomimetic mechanical tail device for a robotic fish with variable cross-section features, which can be applied to underwater robotic fish that use a body / tail fin propulsion mode to provide thrust and increase maneuverability.

[0007] A biomimetic mechanical tail device for a robotic fish with variable cross-section features includes a tail peduncle mechanism and a tail fin mechanism connected to the fish body. This invention draws inspiration from the biological structure and propulsion mechanism of fish tails in nature. The tail fin mechanism is crescent-shaped and includes a push rod, an upper tail fin, and a lower tail fin. The left end of the push rod passes through the tail peduncle and is threadedly connected to a spring seat. The left end of the tail peduncle is connected to the tail fin mechanism. The spring is sleeved on the outside of the spring seat and placed between the tail peduncle and the spring. A hydraulic cylinder is installed inside the distal end of the tail peduncle. The piston is fixedly connected to the left side of the spring seat through a hydraulic oil line. An elongated hole is opened in the middle of the push rod. The upper and lower tail fins are symmetrically arranged on both sides of the push rod. The middle parts of the upper and lower tail fins are slidably and rotatably connected to the elongated hole through a rotating shaft. The upper and lower tail fins are rotatably connected to the push rod through connecting rod one and connecting rod two, respectively. The left side of the upper and lower tail fins overlaps the left side of the push rod.

[0008] Furthermore, the upper and lower caudal fins can rotate around the same axis, allowing adjustment of the aspect ratio and sweep angle of the caudal fin mechanism.

[0009] Furthermore, the push rod can reciprocate along the fish's body axis, and its movement can make the edge of the caudal fin mechanism form a continuous curve, while filling the gap between the upper and lower caudal fins to keep the caudal fin mechanism intact.

[0010] Furthermore, when no hydraulic pressure is applied, the upper and lower caudal fins are offset by an angle α, where α is 30°.

[0011] Furthermore, the spring seat can adjust the preload of the spring in its initial state, thereby adjusting the minimum pressure required to drive the tail fin mechanism.

[0012] Furthermore, the piston pushes the liquid towards the tail, which reaches the tail fin mechanism through the hydraulic oil pipeline inside the tail shank mechanism. The hydraulic pressure acts on the spring seat and push rod. When the hydraulic pressure exceeds the spring force, the push rod moves to the right, driving the upper and lower tail fins to move, thus deforming the tail fin mechanism.

[0013] The beneficial effects of this invention are:

[0014] The biomimetic mechanical tail device consists of multiple parts that can move relative to each other. The deformation of the tail fin mechanism can be controlled by controlling the stroke of the hydraulic cylinder piston. The control process is simple and can quickly change the size of the tail fin cross section, thus improving the adaptability of the tail fin.

[0015] The biomimetic mechanical tail device's tail fin is divided into two parts: an upper tail fin and a lower tail fin. Both can rotate around the same axis, and the angles they rotate through are the same, which helps maintain the balance of the robotic fish. During the deformation of the tail fin mechanism, parameters affecting propulsion efficiency, such as the aspect ratio and sweep angle of the tail fin, will change accordingly, thus adjusting the robotic fish's propulsion efficiency and drag.

[0016] The gap between the upper and lower caudal fins allows them to rotate in the same plane, making them more symmetrical. The crescent-shaped push rod at the far end fills the gap between the caudal fins. During the rotation of the caudal fins, the push rod can maintain the shape of the caudal fins and improve their propulsion efficiency. Attached Figure Description

[0017] Figure 1 This is a three-dimensional view of the structure of the present invention installed on the robotic fish;

[0018] Figure 2 This is a front view of the robotic fish equipped with the present invention;

[0019] Figure 3 (A) is a front view of the present invention before modification;

[0020] Figure 3 (B) is a modified front view of the present invention;

[0021] Figure 4 This is a schematic diagram showing the connection between the hydraulic cylinder, hydraulic oil pipeline and spring seat of the present invention;

[0022] Figure 5 This is a 3D diagram of the upper caudal fin structure;

[0023] Figure 6 This is a 3D diagram of the lower tail fin structure;

[0024] Figure 7 This is a schematic diagram of the push rod. Detailed Implementation

[0025] Referring to the accompanying drawings, a biomimetic mechanical tail device for a robotic fish with variable cross-section features includes a tail shank mechanism 2 and a tail fin mechanism 3 connected to the fish body 1. This invention draws inspiration from the biological structure and propulsion mechanism of fish tails in nature. The tail fin mechanism 3 has a crescent-shaped structure and includes a push rod 6, an upper tail fin 4, and a lower tail fin 5. The left end of the push rod 6 passes through the tail shank 9 and is threadedly connected to a spring seat 14. The left end of the tail shank 9 is connected to the tail fin mechanism 3. A spring 10 is sleeved on the outside of the spring seat 14 and positioned between the tail shank 9 and the tail fin mechanism 3. Between the springs 10, a hydraulic cylinder 11 is installed inside the distal end of the tailstock 9. The piston 12 is fixedly connected to the left side of the spring seat 14 through the hydraulic oil line 13. An elongated hole is opened in the middle of the push rod 6. The upper tail fin 4 and the lower tail fin 5 are symmetrically arranged on both sides of the push rod 6. The middle parts of the upper tail fin 4 and the lower tail fin 5 are slidably and rotatably connected in the elongated hole through the pivot. The upper tail fin 4 and the lower tail fin 5 are rotatably connected to the push rod 6 through the connecting rod 1 7 and the connecting rod 2 8 respectively. The left side of the upper tail fin 4 and the lower tail fin 5 overlaps the left side of the push rod 6.

[0026] Furthermore, the upper caudal fin 4 and the lower caudal fin 5 can rotate around the same axis to adjust the aspect ratio and sweep angle of the caudal fin mechanism 3.

[0027] Furthermore, the push rod 6 can reciprocate along the fish's body axis, and its movement can make the edge of the tail fin mechanism 3 form a continuous curve, while filling the gap between the upper tail fin 4 and the lower tail fin 5 to keep the tail fin mechanism 3 intact.

[0028] Furthermore, when no hydraulic pressure is applied, the upper caudal fin 4 and the lower caudal fin 5 are offset by an angle α, where α is 30°.

[0029] Furthermore, the spring seat 14 can adjust the preload of the spring 10 in its initial state, thereby adjusting the minimum pressure required to drive the tail fin mechanism 3.

[0030] Furthermore, the piston 12 pushes the liquid towards the tail end, which reaches the tail fin mechanism 3 through the hydraulic oil line 13 inside the tail fin mechanism 2. The hydraulic pressure acts on the spring seat 14 and the push rod 6. When the hydraulic pressure exceeds the elastic force of the spring 10, the push rod 6 moves to the right, driving the upper tail fin 4 and the lower tail fin 5 to move, thereby deforming the tail fin mechanism 3.

[0031] Work process:

[0032] The working process of this invention is as follows Figure 3As shown, the piston 12 inside the hydraulic cylinder 11 moves backward, pushing the liquid and applying hydraulic pressure to the push rod 6, causing the push rod 6 to move backward. The movement of the push rod 6 causes the connecting rod 7 and connecting rod 8 to swing, thereby causing the upper tail fin 4 and the lower tail fin 5 to rotate, thus changing the cross-section and aspect ratio of the tail fin mechanism 3. At the same time, the movement of the push rod 6 compresses the spring 10. When the tail fin needs to return to its original shape, the piston 12 only needs to be returned to its original position, and the hydraulic pressure decreases. When the hydraulic pressure on the push rod 6 is less than the elastic force of the spring 10, the push rod 6 will move to the left, thereby causing the upper tail fin 4 and the lower tail fin 5 to rotate in the opposite direction.

[0033] By setting the lengths of connecting rod 7 and connecting rod 8 to be the same, it can be ensured that the upper tail fin 4 and lower tail fin 5 rotate through the same angle when the push rod 6 moves, maintaining the symmetry of the structure. During the deformation of the tail fin mechanism 3, the aspect ratio of the upper tail fin 4 and lower tail fin 5 changes accordingly. The deformation process is hydraulically driven, with the required hydraulic pressure provided by the hydraulic system inside the tail shank mechanism 2. When the tail fin mechanism 3 needs to deform, the piston 12 pushes the hydraulic oil, and the hydraulic pressure is applied to the spring seat 14 at the left end of the push rod 6 through the hydraulic oil line 13. The hydraulic pressure then drives the push rod 6 to move and the upper tail fin 4 and lower tail fin 5 to rotate. The detachable spring seat 14 and spring 10 installed at the left end of the push rod 6 can be used to reset the various parts of the tail fin mechanism 3.

[0034] like Figures 5 to 7 As shown, the upper caudal fin 4, the lower caudal fin 5, and the crescent-shaped structure at the distal end of the push rod 6 together form a complete fish caudal fin. The caudal fin adopts the crescent shape commonly seen in fish. The upper caudal fin 4 and the lower caudal fin 5 are fixed on the same pivot, which passes through an elongated hole on the push rod 6. The interiors of the upper caudal fin 4 and the lower caudal fin 5 have grooves to accommodate the push rod 6. The crescent-shaped curved surfaces on the right side of the upper caudal fin 4 and the lower caudal fin 5 and the right side of the push rod 6 have the same radius of curvature, which can form a complete arc in the initial state and a continuous curve after deformation.

Claims

1. A biomimetic mechanical tail device for a robotic fish with variable cross-section features, characterized in that: The fish includes a caudal peduncle mechanism (2) and a caudal fin mechanism (3) connected to the fish body (1). The caudal fin mechanism (3) has a crescent-shaped structure and includes a push rod (6), an upper caudal fin (4), and a lower caudal fin (5). The left end of the push rod (6) passes through the caudal peduncle (9) and is threadedly connected to a spring seat (14). A spring (10) is fitted outside the spring seat (14) and placed between the end of the caudal peduncle (9) and the end of the spring seat (14). A hydraulic cylinder (11) is installed inside the distal end of the caudal peduncle (9). A piston (12) is driven by a hydraulic cylinder. The oil pressure line (13) is fixedly connected to the left side of the spring seat (14). The middle part of the push rod (6) has an elongated hole. The upper tail fin (4) and the lower tail fin (5) are symmetrically arranged on both sides of the push rod (6). The middle parts of the upper tail fin (4) and the lower tail fin (5) are slidably and rotatably connected in the elongated hole through the rotating shaft. The upper tail fin (4) and the lower tail fin (5) are rotatably connected to the push rod (6) through the connecting rod one (7) and the connecting rod two (8) respectively. The left side of the upper tail fin (4) and the lower tail fin (5) overlaps on the left side of the push rod (6).

2. The biomimetic mechanical tail device of a robotic fish with variable cross-section features according to claim 1, characterized in that: The upper caudal fin (4) and the lower caudal fin (5) can rotate around the same axis to adjust the aspect ratio and sweep angle of the caudal fin mechanism (3).

3. The biomimetic mechanical tail device of a robotic fish with variable cross-section features according to claim 1, characterized in that: The push rod (6) can reciprocate along the fish's body axis. Its movement can make the edge of the tail fin mechanism (3) form a continuous curve, and at the same time fill the gap between the upper tail fin (4) and the lower tail fin (5) to keep the tail fin mechanism (3) intact.

4. The biomimetic mechanical tail device of a robotic fish with variable cross-section features according to claim 1, characterized in that: When no hydraulic pressure is applied, the upper caudal fin (4) and the lower caudal fin (5) are offset by an angle α, where α is 30°.

5. The biomimetic mechanical tail device of a robotic fish with variable cross-section features according to claim 1, characterized in that: The spring seat (14) can adjust the preload of the spring (10) in its initial state, thereby adjusting the minimum pressure required to drive the tail fin mechanism (3).

6. The biomimetic mechanical tail device of a robotic fish with variable cross-section features according to claim 1, characterized in that: The piston (12) pushes the liquid to the tail end, and through the hydraulic oil line (13) inside the tail fin mechanism (2) it reaches the tail fin mechanism (3). The hydraulic pressure acts on the spring seat (14) and the push rod (6). When the hydraulic pressure exceeds the elastic force of the spring (10), the push rod (6) moves to the right, driving the upper tail fin (4) and the lower tail fin (5) to move, thereby realizing the deformation of the tail fin mechanism (3).

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