A biomimetic robotic fish based on the principle of swept jet

Abstract

This invention relates to the field of underwater robotics, specifically to a biomimetic robotic fish based on the sweeping jet principle. The biomimetic robotic fish, based on the sweeping jet principle, includes a body with a water inlet at the front end and a water outlet at the rear end. A drive structure is located at the rear end of the water inlet, connected to a steering structure at the rear end of the drive structure, and a swinging structure at the rear end of the steering structure. The drive structure includes a water pump and a water delivery pipe. The water delivery pipe connects to the water inlet and splits into a left and a right water delivery pipe at the inlet. The left and right water delivery pipes merge at a rear connection point. Each of the left and right water delivery pipes contains a water pump, which enables water to flow from the water inlet to the connection point. This device utilizes the sweeping jet principle to create a periodic oscillating water flow to propel the robotic fish forward, overcoming the problems of low propulsion efficiency and short endurance of existing biomimetic robotic fish.

Description

Technical Field

[0001] This invention relates to the field of underwater robot technology, and more specifically to a biomimetic robotic fish based on a sweeping jet. Background Technology

[0002] The ocean is rich in biological and mineral resources, which urgently need human exploration and development. However, the harsh underwater environment, characterized by low temperatures, high pressure, and darkness, greatly increases the difficulty of ocean exploration. In recent years, with the development of underwater robots, some complex tasks in harsh and dangerous underwater environments can be performed by robots instead of humans, which greatly facilitates ocean exploration.

[0003] Currently, most robotic fish tails are driven by traditional electric motors, which is also the most mature driving method for biomimetic robotic fish. These include DC motors, servo motors, and servo motors. While these methods result in good swimming performance, they also lead to high noise levels, complex structures, and difficulties in further increasing the oscillation frequency of the tail fin after a certain point. To address the key issues of low propulsion efficiency and short endurance in existing robotic fish, a method based on swept jet-driven tail fin oscillation is proposed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a swinging device based on swept jet. This device uses the sweeped jet principle to form a periodic oscillating water flow to propel the robotic fish forward, thus overcoming the problems of low propulsion efficiency and short endurance of existing bionic robotic fish.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: a biomimetic robotic fish based on the principle of swept jet, comprising a fish body, the fish body comprising a front cavity, an inlet provided at the front end of the cavity, an outlet provided at the rear end of the cavity, a drive structure provided at the rear end of the inlet, a steering structure connected at the rear end of the drive structure, and a swing structure connected at the rear end of the steering structure.

[0006] The drive structure includes a water pump and a water supply pipe. The water supply pipe is connected to the water inlet and splits into a left water supply pipe and a right water supply pipe from the water inlet. The left water supply pipe and the right water supply pipe are located on the left and right sides of the fish body, respectively. The left water supply pipe and the right water supply pipe merge together at the rear connection port. Each of the left water supply pipe and the right water supply pipe is equipped with a water pump, which enables water to flow from the water inlet to the connection port.

[0007] The steering structure includes a steering hose connected to a connection port and branching into a left-turning hose and a right-turning hose. The left-turning hose and the right-turning hose are located on the left and right sides of the fish body, respectively. Openings are also provided on the left and right sides of the rear end of the cavity. The middle part of the left-turning hose and the right-turning hose protrudes from the openings outside the cavity to form an enlarged end. A rigid cavity is also connected to the connection port. The rigid cavity is located between the left-turning hose and the right-turning hose and is hollow inside. The left-turning hose and the right-turning hose are connected to the rigid cavity from the left and right sides, respectively. A drain outlet is provided at the bottom of the rigid cavity and is connected to the water outlet of the cavity. A fixing ring is provided on each of the left and right sides of the outer side of the rear of the cavity, and a steering rod is movably connected to the fixing ring.

[0008] The swing structure includes two parallel vertical swing plates, defined as the left swing plate and the right swing plate, which are connected by a horizontal connecting rod. The left swing plate and the right swing plate are respectively hinged and fixed to the left and right sides of the water outlet at the rear of the cavity. One end of the steering rod at the rear of the cavity is hinged to the expanded end of the steering hose 11, and the other end is hinged to the front end of the vertical swing plate.

[0009] The steering hose and rigid cavity in the drive structure and steering structure are both located inside the cavity, while the steering rod and swing structure in the steering structure are located outside the cavity.

[0010] Ideally, the drain outlet at the bottom of the rigid cavity is located precisely in the center of the water outlet at the tail of the fish's body cavity. Even more ideally, the drain outlet at the bottom of the rigid cavity is smaller than the water outlet at the tail of the fish's body cavity.

[0011] In the optimized configuration, the water pump in the water supply pipe is driven to rotate by a motor, and its rotation speed is controlled by a program.

[0012] In an optimized configuration, the water supply pipe, the steering hose, and the rigid cavity are all connected at the connection port and are interconnected.

[0013] In the optimized configuration, a fixed ring is symmetrically arranged on the left and right sides of the outer side of the rear of the cavity. The middle part of the steering rod passes through the fixed ring and is movably connected to the fixed ring. The steering rod on the left side of the cavity is defined as the left steering rod, and the steering rod on the right side of the cavity is defined as the right steering rod. The front end of the left steering rod is connected to the expanded end of the left-turn hose, and the rear end is connected to the left swing plate; the front end of the right steering rod is connected to the expanded end of the right-turn hose, and the rear end is connected to the right swing plate.

[0014] Ideally, the left-turn hose and the right-turn hose are connected to the tail of the rigid cavity from the left and right sides of the rigid cavity, respectively; even more ideally, the left swing plate and the right swing plate are connected to the tail of the cavity via a universal joint.

[0015] In the optimized configuration, the left and right swing plates are movably connected by a connecting rod, and the left and right swing plates can move in the same direction to the left and right.

[0016] The optimized design features a left and right sway plate with a triangular structure resembling a tail fin, where the width of the sway plate near the cavity is smaller than that of the sway plate away from the cavity.

[0017] In this invention, water is driven by a water pump to enter the left and right water pipes through the inlet. At the connection point, the water is split into the left and right turning hoses and the rigid cavity, and discharged from the drain outlet at the rear of the rigid cavity to the outlet at the rear of the cavity. By adjusting the working efficiency of the water pumps in the left and right water pipes, the size of the expansion at the left and right turning hoses is affected, thereby influencing the rotation angle of the left and right steering rods connected to the expansion ends. By setting the water pump control program, the water pumps on both sides periodically pump water, causing the swing plate at the rear of the cavity to periodically swing left and right, which effectively improves the swing efficiency and endurance.

[0018] Water enters the cavity under the action of the pumps and flows out from the connection point. When the left and right pumps operate at the same power, the water flow direction is consistent with the axial direction of the cavity; when the left and right pumps operate at different power, the water flow direction is inconsistent with the axial direction of the cavity, and the water flow will deflect. When the left pump has a higher power and the right pump has a lower power, the water flow in the left water pipe is greater. After merging, the water flow from the left water pipe to the right is greater, resulting in more water entering the right-turning hose. The bulging end of the right-turning hose also bulges more, causing the front end of the connected right-turning rod to push further to the right, and the end of the right-turning rod to push further to the left, causing the right swing plate to swing to the left, thus achieving the leftward swing of the entire swing plate. Similarly, when the right pump has a higher power, the swing plate can swing to the right. Therefore, by setting the pump program to periodically increase and decrease the power of the pumps, the left and right swing of the fish can be achieved.

[0019] The beneficial effects of this invention are as follows: it designs a method for driving the tail fin's oscillation based on the principle of swept jet, and on this basis, it designs a simple and reliable turning mechanism. Compared with the method of directly using a motor to drive the tail fin's oscillation, this method and structure are simpler, have a longer operating time, and better utilize the swimming characteristics of natural fish. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the external structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the internal structure of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure when swinging to the right in this invention;

[0023] Figure 4 This is a schematic diagram of the structure when swinging to the left in this invention.

[0024] Figure label:

[0025] 1. Fish body; 2. Cavity; 3. Inlet; 4. Outlet; 5. Drive structure; 6. Steering structure; 7. Swinging structure; 8. Water pump; 9. Water supply pipe; 91. Left water supply pipe; 92. Right water supply pipe; 10. Connecting port; 11. Steering hose; 111. Left turning hose; 112. Right turning hose; 113. Expanded end; 12. Rigid cavity; 13. Drain outlet; 14. Fixing ring; 15. Steering rod; 151. Left steering rod; 152. Right steering rod; 16. Vertical swing plate; 161. Left swing plate; 162. Right swing plate; 17. Connecting rod. Detailed Implementation

[0026] The present invention will now be further described with reference to the accompanying drawings. The following embodiments are only used to illustrate the structure of the present invention more clearly.

[0027] like Figure 1 and Figure 2 As shown, a biomimetic robotic fish based on the sweeping jet principle includes a fish body 1. The fish body 1 includes a front cavity 2. A water inlet 3 is provided at the front end of the cavity 2, and a water outlet 4 is provided at the rear end of the cavity 2. A drive structure 5 is provided at the rear end of the water inlet 3. A steering structure 6 is connected to the rear end of the drive structure 5, and a swing structure 7 is connected to the rear end of the steering structure 6.

[0028] The drive structure 5 includes a water pump 8 and a water supply pipe 9. The water supply pipe 9 is connected to the water inlet 3 and splits into a left water supply pipe 91 and a right water supply pipe 92 from the water inlet 3. The left water supply pipe 91 and the right water supply pipe 92 are located on the left and right sides of the fish body 1, respectively. The left water supply pipe 91 and the right water supply pipe 92 converge at the rear connection port 10. Each of the left water supply pipe 91 and the right water supply pipe 92 is equipped with a water pump 8, which enables water to flow from the water inlet 3 to the connection port 10.

[0029] The steering structure 6 includes a steering hose 11, which is connected to a connection port 10 and splits into a left-turning hose 111 and a right-turning hose 112 from the connection port 10. The left-turning hose 111 and the right-turning hose 112 are located on the left and right sides of the fish body 1, respectively. Openings are also provided on the left and right sides of the rear end of the cavity 2. The middle part of the left-turning hose 111 and the right-turning hose 112 protrudes from the opening to the outside of the cavity 2 to form an enlarged end 113. A rigid cavity 12 is also connected to the connection port 10. The rigid cavity 12 is located between the left-turning hose 111 and the right-turning hose 112 and is hollow inside. The left-turning hose 111 and the right-turning hose 112 are connected to the rigid cavity 12 from the left and right sides, respectively. A drain outlet 13 is provided at the bottom of the rigid cavity 12 and is connected to the water outlet 4 of the cavity 2. A fixing ring 14 is provided on each of the left and right sides of the outer side of the tail of the cavity 2, and a steering rod 15 is movably connected to the fixing ring 14.

[0030] The swing structure 7 includes two parallel vertical swing plates 16, defined as left swing plate 161 and right swing plate 162 respectively, and the left swing plate 161 and right swing plate 162 are connected by a transverse connecting rod 17. The left swing plate 161 and right swing plate 162 are respectively hinged and fixed to the left and right sides of the water outlet 4 at the tail of the cavity 2. One end of the steering rod 15 at the tail of the cavity 2 is hinged to the expanded end 113 of the steering hose 11, and the other end is hinged to the front end of the vertical swing plate 16.

[0031] The steering hose 11 and rigid cavity 12 in the drive structure 5 and steering structure 6 are both located inside the cavity 2, while the steering rod 15 and swing structure 7 in the steering structure 6 are located outside the cavity 2.

[0032] The drain outlet 13 at the bottom of the rigid cavity 12 is located at the center of the water outlet 4 at the tail of the fish body 1 cavity 2. More preferably, the size of the drain outlet 13 at the bottom of the rigid cavity 12 is smaller than that of the water outlet 4 at the tail of the fish body 1 cavity 2.

[0033] The water pump 8 in the water supply pipe 9 is driven to rotate by a motor, and its speed is controlled by a program. The water supply pipe 9, the steering hose 11 and the rigid cavity 12 are all connected at the connection port 10 and are interconnected.

[0034] A fixing ring 14 is symmetrically arranged on the left and right sides of the rear outer side of the cavity 2. The middle part of the steering rod 15 passes through the fixing ring 14 and is movably connected to the fixing ring 14. The steering rod 15 on the left side of the cavity 2 is defined as the left steering rod 151, and the steering rod 15 on the right side of the cavity 2 is defined as the right steering rod 152. The front end of the left steering rod 151 is connected to the expanded end 113 of the left turn hose 111, and the rear end is connected to the left swing plate 161; the front end of the right steering rod 152 is connected to the expanded end 113 of the right turn hose 112, and the rear end is connected to the right swing plate 162.

[0035] Left-turning hose 111 and right-turning hose 112 are connected to the tail of the rigid cavity 12 from the left and right sides, respectively. More optimally, the left swing plate 161 and right swing plate 162 are connected to the tail of the cavity 2 via a universal joint. The left swing plate 161 and right swing plate 162 are movably connected by a connecting rod 17, and can move in the same direction both left and right. The left swing plate 161 and right swing plate 162 have a triangular structure resembling a tail fin, with the width of the swing plate 161 closer to the cavity 2 being smaller than the width of the swing plate 161 further away from the cavity 2.

[0036] In this invention, water pump 8 drives water to enter the left and right water pipes 9 through inlet 3. At connection port 10, the water is split into left-turn hose 111, right-turn hose 112, and rigid cavity 12, and discharged from drain port 13 at the tail of rigid cavity 12 to outlet port 4 at the tail of cavity 2. By adjusting the working efficiency of water pump 8 in left and right water pipes 91 and 92, the size of the expansion end 113 of left-turn hose 111 and right-turn hose 112 is affected, which in turn affects the rotation angle of left steering rod 151 and right steering rod 152 connected to the expansion end 113. By setting the control program of water pump 8, the water pumps 8 on both sides periodically pump water, causing the swing plate 16 at the tail of cavity 2 to periodically swing left and right, which can effectively improve the swing efficiency and endurance.

[0037] Water enters the cavity 2 under the action of pump 8 and flows out from the connection port 10. When the two pumps 8 operate at the same power, the water flow direction is consistent with the axial direction of the cavity 2; when the two pumps 8 operate at different power, the water flow direction is inconsistent with the axial direction of the cavity 2, and the water flow will deflect. When the left pump 8 has a higher power and the right pump 8 has a lower power, the water flow in the left water pipe 91 is greater. After merging, the water flow from the left water pipe 91 to the right is greater, resulting in more water entering the right-turning hose 112. The expansion end 113 of the right-turning hose 112 also expands more, causing the front end of the connected right steering rod 152 to push further to the right, and the end of the right steering rod 152 to push further to the left, driving the right swing plate 162 to swing to the left, thus realizing the leftward swing of the entire swing plate 16. Similarly, when the right pump 8 has a higher power, the swing plate 16 can swing to the right. Therefore, by setting the program for water pump 8 to periodically increase and decrease its power, the fish body 1 can be made to sway left and right. This is the principle behind the fish body 1 mimicking natural swaying.

[0038] In practical applications, such as Figure 3As shown, the right-side pump 8 has greater power. Therefore, after the water flows converge at the connection port 10, the direction of the water flow will shift further to the left side of the rigid cavity 12. This results in more water entering the left-hand rotating hose 111 at the bottom left of the rigid cavity 12, causing the expanded end 113 of the left-hand rotating hose 111 to be larger. This pushes the left steering rod 151 to move further to the right, causing the swing plate 16 to swing to the right. Furthermore, the water flow at the drain port 13 at the bottom of the rigid cavity 12 also shifts to the right. Since the two swing plates 16 are located on either side of the outlet 4, the water flow sandwiched between the left and right swing plates 16 is shifted to the right, further pushing the swing plates 16 to swing to the right. During this process, a vortex is formed within the rigid cavity 12. This vortex causes the water flow in the middle and outlet of the rigid cavity 12 to gradually decrease the water flow entering the left-hand rotating hose 111, while the water flow entering the right-hand rotating hose 112 gradually increases, thus triggering the next water flow shift and creating a periodic oscillating water flow within the rigid cavity 12. In this process, by setting the program of water pump 8, the water flow of the left-turning hose 111 gradually decreases under the influence of the vortex, while the water flow of the right-turning hose 112 gradually increases. At the same time, the power of the right-side water pump 8 gradually decreases, while the power of the left-side water pump 8 gradually increases. This will produce a superimposed effect, improving the swaying efficiency of the fish body 1.

[0039] Similarly, such as Figure 4 As shown, the left pump 8 has greater power. Therefore, after the water flows converge at the connection port 10, the direction of the water flow will shift further to the right of the rigid cavity 12. This results in more water entering the right-hand rotating hose 112 at the bottom right of the rigid cavity 12, causing the expanded end 113 of the right-hand rotating hose 112 to be larger. This pushes the right steering rod 152 to move further to the left, causing the swing plate 16 to swing to the left. Furthermore, the water flow at the drain port 13 at the bottom of the rigid cavity 12 also shifts to the left. Since the two swing plates 16 are located on either side of the outlet 4, the water flow sandwiched between the left and right swing plates 16 shifts to the left, further pushing the swing plates 16 to swing to the left. During this process, a vortex is formed within the rigid cavity 12. This vortex causes the water flow in the middle and outlet of the rigid cavity 12 to gradually decrease, while the water flow into the left-hand rotating hose 111 gradually increases, triggering the next water flow shift and creating a periodic oscillating water flow within the rigid cavity 12. In this process, by setting the program of water pump 8, the water flow of the right-turn hose 112 gradually decreases under the influence of the vortex, while the water flow of the left-turn hose 111 gradually increases. At the same time, the power of the left water pump 8 gradually decreases, while the power of the right water pump 8 gradually increases. This will produce a superimposed effect, improving the swaying efficiency of the fish body 1.

[0040] The above describes the situation where the water flow direction is not the same as the axial direction of the fish body 1 when the left water pipe 91 and the right water pipe 92 merge at the connection port 10 due to the different power of the water pump 8. When the power of the water pump 8 is the same, after the left water pipe 91 and the right water pipe 92 merge at the connection port 10, the main direction of the water flow is the same as the axial direction of the fish body 1. The swing principle of the swing plate 16 is as follows: the water flows into the rigid cavity 12 from the connection port 10, and is discharged from the drain port 13 of the rigid cavity 12 into the outlet port 4 of the fish body 1 cavity 2. At this time, very little water will enter the left turning hose 111 and the right turning hose 112. However, once the water flow after entering the rigid cavity 12 is subjected to some small disturbances (because the bionic robotic fish is placed in the water and is affected by the buoyancy of the water, it drifts with the waves, and such small disturbances always exist), the direction of the water flow will deviate from the axis of the rigid cavity 12. Then the water flow in the rigid cavity 12 will not be discharged directly from the drain outlet 13, but will form a vortex in the rigid cavity 12. The water flow in the rigid cavity 12 will enter the left-turning hose 111 and the right-turning hose 112 from the bottom, and the water flow rate entering the left-turning hose 111 and the right-turning hose 112 will also be different. The water flow at the bottom of the left-turning hose 111 and the right-turning hose 112 will reverse and re-enter the rigid cavity 12 from the connection port 10 at the front end of the rigid cavity 12, further causing the direction of the water flow in the rigid cavity 12 to deviate.

[0041] For example, when the robotic fish 1 is floating in the water, it suddenly encounters a small disturbance to the right. The fish 1 shifts to the right, and due to inertia, the water at the connection port 10 of the cavity 2 is sprayed out to the left side of the rigid cavity 12. Obviously, more water enters the left-hand turning hose 111 at the bottom left of the rigid cavity 12. The enlarged end 113 of the left-hand turning hose 111 will increase, which will drive the left steering rod 151 to move, thereby causing the swing plate 16 to swing to the right. That is, the fish 1 will always maintain a left-right swinging state, even when the power of the water pumps 8 on the left and right sides is the same.

[0042] There are three main factors affecting the swaying of the fish body 1: (1) the power of the left and right water pumps 8. The power of the water pump 8 has the greatest impact on the swaying direction of the fish body 1. When the power of the left water pump 8 is high, the fish body 1 sways to the left; (2) the influence of the vortex in the rigid cavity 12. When the water flow is sprayed obliquely on the side wall of the rigid cavity 12, a vortex will be formed in the rigid cavity 12. The vortex will compress the water flow in the middle and bottom of the rigid cavity 12 and enter the hose on the opposite side, forming a periodic oscillating water flow. Its direction of action is: when the water flow in the left hose is large, the generated vortex will cause the water flow to gradually flow to the right hose, making the swaying amplitude of the fish body 1 to the left smaller and smaller. Its influence on the swaying direction of the fish body 1 swing plate 16 is smaller than that of the water pump 8; (3) random small disturbances in the water. Small disturbances that come suddenly in the water are everywhere, and their influence on the swaying direction of the fish body 1 swing plate 16 is minimal. The direction of the disturbance force received is consistent with the swing direction of its pendulum 16. When the power of the two water pumps 8 is different, the effect of water disturbance can be ignored. Only when the power of the two water pumps 8 is the same, the fish body 1 can still swing and will not remain stationary in the water.

[0043] It should be noted that the connection methods for the various components of the robotic fish are as follows: (1) The water pump 8 can be fixed in the water supply pipe 9 by adhesive, hook and loop fastener, screw, etc.; (2) The connection port 10 can be connected by a four-way connector to ensure the connection between the water supply pipe 9, the hose, and the rigid cavity 12; (3) The connection between the outer side of the tail of the cavity 2 and the steering rod 15 can be achieved by setting a fixing ring 14 on the outer side of the cavity 2, and the middle part of the steering rod 15 is movably connected to the fixing ring 14 by elastic rope or other components to ensure that the steering rod 15 can swing left and right. The connection between the front end of the steering rod 15 and the expanded end 113 of the hose can be achieved by adhesive, or by setting a groove on the expanded end 113 of the hose and engaging the steering rod 15 in the groove. As long as the connection between the front end of the steering rod 15 and the expanded end 113 of the hose is kept stable, and the expansion and contraction of the expanded end 113 of the hose will drive the steering rod 15 to swing left and right, it is acceptable. The connection between the rear of the steering rod 15 and the swing plate 16 is such that, since the swing plate 16 has a large area and the middle and front of the steering rod 15 have been firmly connected, the rear of the steering rod 15 only needs to have sufficient contact with the swing plate 16. The swing of the rear of the steering rod 15 is enough to drive the swing plate 16 to swing left and right. (4) The connection between the two vertically parallel swing plates 16 is through the horizontal connecting rod 17. In order to ensure that the two swing plates 16 can swing in the same direction at the same time, it is necessary to ensure that the swing plate 16 and the connecting rod 17 can move horizontally and be stably connected vertically. For example, a vertical pin can be set on the swing plate 16 and a vertical through hole can be set on the connecting rod 17 as a fixing hole. The fixing hole is fitted on the vertical pin, so that the two swing plates 16 can move horizontally and are relatively stably fixed vertically. (5) Connection between the swing plate 16 and the cavity 2: Since the swing plate 16 needs to swing left and right, the left and right swing plates 16 can be fixed on both sides of the outlet 4 of the cavity 2 by hinge.

[0044] The beneficial effects of this invention are as follows: it designs a method for driving the tail fin's oscillation based on the principle of swept jet, and on this basis, it designs a simple and reliable turning mechanism. Compared with the method of directly using a motor to drive the tail fin's oscillation, this method and structure are simpler, have a longer operating time, and better utilize the swimming characteristics of natural fish.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A biomimetic robotic fish based on the principle of swept jet, comprising a fish body, the fish body including a front cavity, an inlet at the front end of the cavity, and an outlet at the rear end of the cavity, characterized in that: A drive structure is provided at the rear end of the water inlet, a steering structure is connected to the rear end of the drive structure, and a swing structure is connected to the rear end of the steering structure. The drive structure includes a water pump and a water supply pipe. The water supply pipe is connected to the water inlet and splits into a left water supply pipe and a right water supply pipe from the water inlet. The left water supply pipe and the right water supply pipe are located on the left and right sides of the fish body, respectively. The left water supply pipe and the right water supply pipe merge at the connection port at the rear. Each of the left water supply pipe and the right water supply pipe is equipped with a water pump, which enables water to flow from the water inlet to the connection port. The steering structure includes a steering hose connected to a connection port and divided into a left-turning hose and a right-turning hose from the connection port. The left-turning hose and the right-turning hose are located on the left and right sides of the fish body, respectively. Openings are also provided on the left and right sides of the rear end of the cavity. The middle part of the left-turning hose and the right-turning hose protrudes from the opening to the outside of the cavity to form an enlarged end. A rigid cavity is also connected to the connection port. The rigid cavity is located between the left-turning hose and the right-turning hose and is hollow inside. The left-turning hose and the right-turning hose are connected to the rigid cavity from the left and right sides, respectively. A drain outlet is provided at the bottom of the rigid cavity and is connected to the water outlet of the cavity. A fixing ring is provided on each of the left and right sides of the outer side of the rear of the cavity, and a steering rod is movably connected to the fixing ring. The swing structure includes two parallel vertical swing plates, defined as the left swing plate and the right swing plate, which are connected by a horizontal connecting rod. The left swing plate and the right swing plate are respectively hinged and fixed to the left and right sides of the water outlet at the rear of the cavity. One end of the steering rod at the rear of the cavity is hinged to the expanded end of the steering hose, and the other end is hinged to the front end of the vertical swing plate. The steering rod on the left side of the cavity is defined as the left steering rod, and the steering rod on the right side of the cavity is defined as the right steering rod. The front end of the left steering rod is connected to the expanded end of the left-turn hose, and the rear end is connected to the left swing plate; the front end of the right steering rod is connected to the expanded end of the right-turn hose, and the rear end is connected to the right swing plate. The steering hose and rigid cavity in the drive structure and steering structure are both located inside the cavity, while the steering rod and swing structure in the steering structure are located outside the cavity. When the left water pump has a higher power and the right water pump has a lower power, the water flow in the left water pipe is greater. After the flow merges, the water flowing out of the left water pipe to the right is greater, resulting in more water entering the right-turning hose. The expansion end of the right-turning hose also expands more, causing the front end of the connected right-turning rod to push further to the right, and the end of the right-turning rod to push further to the left, causing the right swing plate to swing to the left, thus achieving the leftward swing of the entire swing plate. In addition, the water flow at the drain outlet at the bottom of the rigid cavity is also shifted to the left. Since the left and right swing plates are respectively set on both sides of the outlet, the water flow sandwiched between the left and right swing plates is shifted to the left, which will further push the swing plates to swing to the left. Similarly, when the right water pump has a higher power, the swing plate can swing to the right.

2. The biomimetic robotic fish based on the sweeping jet principle according to claim 1, characterized in that: The drain outlet at the bottom of the rigid cavity is located in the center of the water outlet at the tail of the fish's body cavity.

3. The biomimetic robotic fish based on the sweeping jet principle according to claim 2, characterized in that: The size of the drain outlet at the bottom of the rigid cavity is smaller than the water outlet at the tail of the fish's body cavity.

4. A biomimetic robotic fish based on the sweeping jet principle according to claim 1 or 3, characterized in that: The water pump in the water supply pipe is driven by a motor, and its speed is controlled by a program.

5. A biomimetic robotic fish based on the sweeping jet principle according to claim 4, characterized in that: A fixed ring is symmetrically arranged on the left and right sides of the rear of the cavity, and the middle part of the steering rod passes through the fixed ring and is movably connected to the fixed ring.

6. A biomimetic robotic fish based on the sweeping jet principle according to claim 5, characterized in that: The left-turn hose and the right-turn hose are connected to the tail of the rigid cavity from the left and right sides, respectively.

7. A biomimetic robotic fish based on the sweeping jet principle according to claim 6, characterized in that: The left and right swing plates are connected to the rear of the cavity via a universal joint.

8. A biomimetic robotic fish based on the sweeping jet principle according to claim 7, characterized in that: The left and right sway plates are triangular structures that mimic the tail fin, with the width of the sway plate closer to the cavity being smaller than the width of the sway plate further away from the cavity.

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