Fluid-structure interaction characteristic testing system and method of bionic flexible pectoral fin

Abstract

The invention discloses a fluid-solid coupling characteristic test system and method for a bionic flexible pectoral fin, and the system is characterized in that a test pool is used for providing a flow field environment required by a test, a bionic flexible pectoral fin test prototype is installed in the test pool, and a mechanical sensor is installed on the test prototype and is used for collecting the mechanical data of the test prototype; the underwater action capture system comprises a plurality of cameras distributed around the test model machine and is used for capturing and collecting actions of the test model machine by combining mark points arranged on flexible pectoral fins of the test model machine; the PIV test system is used for providing illumination for a to-be-observed area in the test pool in a test process and performing focusing observation on the to-be-observed area; the circuit control system is used for driving and controlling a driving steering engine of the test prototype, so that the test prototype simulates the motion form of the bionic underwater vehicle; and the test control unit is used for issuing a motion instruction to the test prototype and collecting mechanical data acquired by the mechanical sensor and motion data acquired by the underwater motion capture system.

Description

Technical Field

[0001] The invention relates to the field of underwater bionic flexible propulsion and experimental testing, and in particular to a fluid-solid coupling characteristic testing system and method for a bionic flexible pectoral fin. Background Art

[0002] Since the new era, unmanned underwater vehicles, as equipment that can autonomously perform underwater exploration missions, have shown great development potential in both the national defense and civilian fields. Among them, bionic underwater vehicles that imitate the propulsion mode of marine organisms have developed rapidly in recent years.

[0003] Bionic underwater vehicles usually rely on the propulsion force generated by the periodic flapping of bionic fins to maneuver. The common movement form of applied bionic underwater vehicles is that the internal motor drives the root of the bionic skeleton to rotate through periodic rotational motion, and the flexible material covering the bionic skeleton is bent and deformed under the dual action of the internal skeleton and the water body. The vehicle releases momentum into the water body to generate a reaction force to drive itself. Compared with traditional vehicles based on propeller propulsion, the driving structure of the bionic underwater vehicle has greater flexibility. During the propulsion process of periodic flapping, the bionic pectoral fin will show the characteristics of large bending deformation, that is, large deformation fluid-solid coupling. Studying the propulsion characteristics and flexible deformation characteristics of bionic flexible pectoral fins is the basis and performance evaluation standard for optimizing bionic propulsion structures. The simulation results of bionic fluid-solid coupling numerical technology show that flexible pectoral fins have better thrust characteristics and higher propulsion efficiency than rigid pectoral fins.

[0004] Most of the existing technologies focus on the simulation calculation of the fluid-structure coupling characteristics of bionic flexible pectoral fins, such as the patent application with publication number CN116374720A, which proposes a bidirectional fluid-structure coupling analysis method for the tail fin of a piezoelectric-driven bionic propeller, or a single hydrodynamic test system, such as the patent application with publication number CN112924138A, which proposes a multifunctional bionic hydrodynamic test platform. However, there is no complete fluid-structure coupling characteristic test system and test analysis method for bionic flexible pectoral fins. Summary of the invention

[0005] In response to the problem of lack of testing technology mentioned in the background technology, the purpose of the present invention is to propose a fluid-solid coupling characteristics testing system and method for bionic flexible pectoral fins, which can be used for mechanical testing, flow field testing and deformation testing of bionic flexible pectoral fins, thereby supporting the testing and analysis of underwater bionic flexible structures.

[0006] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0007] A fluid-solid coupling characteristic test system for a bionic flexible pectoral fin comprises a test pool, a bionic flexible pectoral fin test prototype, a circuit control system, an underwater motion capture system, a mechanical sensor, a PIV test system and a test control unit, wherein:

[0008] The test pool is used to provide the flow field environment required for the test. The bionic flexible pectoral fin test prototype is installed in the test pool, and the mechanical sensor is installed on the test prototype to collect the mechanical data of the test prototype; the underwater motion capture system includes a plurality of cameras distributed around the test prototype, which are used to realize the motion capture and collection of the test prototype in combination with the marking points arranged on the flexible pectoral fins of the test prototype; the PIV test system is used to provide lighting to the area to be observed in the test pool during the test, and to focus on the area to be observed; the circuit control system is used to drive and control the driving servo of the test prototype, so that the test prototype simulates the movement form of the bionic underwater vehicle; the test control unit is used to send motion instructions to the test prototype through the circuit control system, and collect the mechanical data obtained by the mechanical sensor and the motion data obtained by the underwater motion capture system.

[0009] Furthermore, the test water pool is a circulating water pool that provides a flow field environment. A position adjustment structure is installed on the upper part of the test water pool, and the position adjustment mechanism is an air floating guide rail or a sliding groove; the bionic flexible pectoral fin test prototype is assembled on the position adjustment structure through a fixed connecting rod, and the position of the test prototype underwater is adjusted by the position adjustment mechanism; the flow field velocity of the test water pool should match the swimming speed range of the full-size bionic underwater vehicle corresponding to the test prototype on the basis of satisfying the similarity criterion.

[0010] Furthermore, the biological prototype of the bionic flexible pectoral fin test prototype is a bionic underwater vehicle;

[0011] The test prototype includes a main structure, flexible pectoral fins and driving servos, among which: the main structure corresponds to the part of the biological prototype except the pectoral fins, and plays an overall supporting role; the flexible pectoral fins are symmetrically arranged on both sides of the main structure, and are composed of an internal hard bionic skeleton and a bionic muscle wrapped thereon, and the bionic muscle is made of flexible material; the driving servos are fixed inside the main structure and connected to the flexible pectoral fins through movable joints; the driving servos are arranged in one group at the front and back of the main structure, and the movements of the two groups of driving servos have a phase difference to realize the wave transmission on the surface of the flexible pectoral fins.

[0012] Furthermore, the main structure is formed by 3D printing of high-performance nylon material, the bionic skeleton is made by cutting carbon fiber composite material plates, and the bionic muscle is prepared by Shaw 0-degree silicone demolding; the output angle of the driving servo is determined by a PWM signal.

[0013] Furthermore, the marking points are on the flexible pectoral fins on both sides of the main structure of the test prototype; multiple rows of marking points are arranged in the span direction of the flexible pectoral fin on each side from the root to the tip, and multiple marking points are arranged in each row; the positions of some marking points should correspond to the bionic bones inside the flexible pectoral fin, and the remaining marking points are used as marking points for recording the movement characteristics of the bionic muscles.

[0014] Furthermore, the circuit control system includes a power supply part and a signal transmission part, wherein: the power supply part is used to provide power to the driving servo in the test prototype, the output waveform of the driving servo is given by the microcontroller and sent to the driving servo through the signal transmission part; the movement form of the flexible pectoral fin is controlled by the driving servo to be periodic reciprocating flapping.

[0015] Furthermore, the mechanical sensor is installed at the portion where the fixed connecting rod is connected to the test prototype, and the central axis of the mechanical sensor coincides with the vertical axis where the center of mass of the test prototype is located.

[0016] Furthermore, the underwater motion capture system includes a motion capture camera and an underwater video camera, wherein the motion capture cameras are distributed around the test prototype, and the underwater video camera is located in front of the test prototype in the incoming flow direction.

[0017] Furthermore, the PIV test system includes a light source, a high-speed camera and a test control unit; after the tracer particles are evenly spread in the test water pool according to a preset mass ratio, the area to be observed is calibrated using a high-speed camera; the light source is arranged at the bottom of the test water pool to illuminate the area to be observed; the high-speed camera is placed outside the observation window of the test water pool, the optical axis of the high-speed camera is perpendicular to the observation window, and is focused on the area to be observed, and the collected images are displayed in real time on the display of the test control unit.

[0018] A method for testing fluid-solid coupling characteristics of a bionic flexible pectoral fin, comprising:

[0019] Step 1, designing and manufacturing a corresponding bionic flexible pectoral fin test prototype for the bionic underwater vehicle, and after installing and debugging the test prototype, arranging marking points on the flexible pectoral fin of the test prototype;

[0020] Step 2, assemble the test prototype to be tested into the test water pool through a fixed connecting rod, and adjust the position of the test prototype so that the test prototype is located in the middle of the flow field of the test water pool, and the head of the test prototype faces the incoming flow direction;

[0021] Step 3, arranging an underwater motion capture system in the test pool, wherein the motion capture cameras of the underwater motion capture system are distributed around the test prototype, and the underwater video camera is arranged in front of the test prototype in the incoming flow direction;

[0022] Step 4, after evenly spreading the tracer particles in a preset mass ratio in the test pool, the flow-making function of the test pool is turned on to make the tracer particles evenly distributed in the pool;

[0023] Step 5, arrange the PIV test system, set a light source at the bottom of the test pool, illuminate the area to be observed with the light source, and calibrate the area to be observed with a high-speed camera;

[0024] Step 6, the test control unit sends a driving instruction to the driving servo in the test prototype through the circuit control system; wherein the output signal of the driving servo is obtained by modulating the duty cycle at the microcontroller port, and the physical parameters of the output signal include the amplitude and frequency of the output angle and the phase difference between the front and rear driving servos;

[0025] Step 7, the test control unit collects the output signal of the driving servo through the mechanical sensor, and turns on the shooting function of the high-speed camera of the PIV test system, so as to obtain the mechanical and flow field characteristics of the flexible pectoral fin of the test prototype when it moves on the continuous time axis;

[0026] Step 8, the test control unit performs motion capture through the motion capture camera of the underwater motion capture system, and uses the underwater camera to shoot at the same time, so as to obtain the displacement field of the marked points on the continuous time axis, and compares it with the displacement field calculated by the marked points under the rigid body condition, and obtains the relative displacement of the marked points, that is, the deformation characteristics;

[0027] Step 9, obtaining the fluid-solid coupling characteristics of the flexible pectoral fin based on the functional relationship between the deformation characteristics of the flexible pectoral fin and the mechanical and flow field characteristics through a regression analysis method.

[0028] Compared with the prior art, the present invention has the following technical features:

[0029] The fluid-solid coupling characteristics testing system of the bionic flexible pectoral fin provided by the present invention fills the gap in the testing field; the testing system can be used to carry out mechanical tests, flow field tests and deformation tests on the bionic flexible pectoral fin, and then the fluid-solid coupling characteristics of the bionic flexible pectoral fin when flapping can be obtained through experimental methods, which has guiding significance for the subsequent design and optimization of the flexible pectoral fin of the bionic underwater vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the fluid-structure coupling characteristics test system of the bionic flexible pectoral fin;

[0031] Figure 2 This is a schematic diagram of the bionic flexible pectoral fin test prototype;

[0032] Figure 3 This is a schematic diagram of the driving form of the test prototype;

[0033] Figure 4Schematic diagram of the marker point arrangement of the bionic flexible pectoral fin.

[0034] Explanation of the numbers in the figure: 1 motion capture camera, 2 underwater camera, 3 high-speed camera, 4 light source, 5 mechanical sensor, 6 test prototype, 61 main structure, 62 flexible pectoral fin, 63 bionic skeleton, 64 bionic muscle, 65 driving servo, 66 marking point, 7 fixed connecting rod, 8 air floating guide rail, 9 fixed connecting parts, 10 test control unit, 11 test pool. DETAILED DESCRIPTION

[0035] Referring to the accompanying drawings, the present invention provides a fluid-solid coupling characteristic test system for a bionic flexible pectoral fin, comprising a test pool 11, a bionic flexible pectoral fin test prototype 6, a circuit control system, an underwater motion capture system, a mechanical sensor 5, a PIV test system, and a test control unit 10, wherein:

[0036] The test pool 11 is used to provide the flow field environment required for the test. The bionic flexible pectoral fin test prototype 6 is installed in the test pool 11. The mechanical sensor 5 is installed on the bionic flexible pectoral fin test prototype 6 to collect mechanical data of the test prototype 6. The underwater motion capture system includes a plurality of cameras distributed around the test prototype 6, which are used to realize motion capture and collection of the test prototype 6 in combination with the marking points 66 arranged on the flexible pectoral fin 62 of the test prototype 6. The PIV test system is used to provide lighting to the area to be observed in the test pool 11 during the test, and to focus on the area to be observed. The circuit control system is used to drive and control the driving servo 65 of the test prototype 6, so that the test prototype 6 simulates the movement form of the bionic underwater vehicle. The test control unit 10 is used to issue motion instructions to the test prototype 6 through the circuit control system, and collect the mechanical data obtained by the mechanical sensor 5 and the motion data obtained by the underwater motion capture system.

[0037] The content of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0038] 1. Test pool

[0039] In this solution, the test pool 11 is a circulating water pool that provides a flow field environment. A position adjustment structure is installed on the upper part of the test pool 11. The position adjustment mechanism can be an air-floating guide rail 8 or a sliding groove. The bionic flexible pectoral fin test prototype 6 is assembled on the position adjustment structure through a fixed connecting rod 7. The horizontal position or depth of the test prototype 6 under water is adjusted by the position adjustment mechanism to meet different test requirements. The flow field velocity of the test pool 11 should match the swimming speed range of the full-size bionic underwater vehicle corresponding to the test prototype 6 on the basis of meeting the similarity criterion. The size of the observation window of the observation section of the test pool 11 should be large enough so that the backflow between the water surface and the pool wall can be ignored for the disturbance of the measurement process. According to different tests and related requirements, the test pool 11 can also be a still water pool.

[0040] Figure 1 In the given example, the test site is a large circulating water pool. Figure 1 What is shown is the observation section at the end of the pool; the observation window is a side wall of the pool, and the PIV test system focuses on the area of ​​interest to be observed through the observation window. In this embodiment, an air flotation rail 8 is installed on the upper part of the pool through a fixed connection component 9, and the test prototype 6 is connected to the air flotation rail 8 through a fixed connecting rod 7; by adjusting the air flotation rail 8, the test prototype 6 is placed in the middle of the flow field of the test pool 11. It should be noted that if a moored model test is to be carried out, the air pump of the air flotation rail 8 should be stopped.

[0041] 2. Bionic flexible pectoral fin test prototype

[0042] See also Figures 2 to 4 The bionic flexible pectoral fin test prototype 6 provided in this application has a biological prototype of a bionic underwater vehicle; the test prototype 6 includes a main structure 61, a flexible pectoral fin 62 and a driving servo 65, wherein: the main structure 61 corresponds to the part of the biological prototype except the pectoral fin, and plays an overall supporting role; the flexible pectoral fins 62 are symmetrically arranged on both sides of the main structure 61, and are composed of an internal hard bionic skeleton 63 and a bionic muscle 64 coated thereon, and the bionic muscle 64 is made of a large deformation flexible material; the driving servo 65 is fixed inside the main structure 61 and connected to the flexible pectoral fin 62 through a movable joint; in this embodiment, a group of driving servos 65 are arranged at the front and back of the main structure 61, respectively, for driving the bionic skeleton 63 of the front and back parts of the flexible pectoral fins 62 on both sides of the test prototype 6; the movement of the front and back two groups of driving servos 65 has a phase difference to realize the wave transmission on the surface of the flexible pectoral fin 62.

[0043] In this embodiment, the main structure 61 is formed by 3D printing of high-performance nylon material, the bionic skeleton 63 is made by cutting carbon fiber composite material plate, and the bionic muscle 64 is made by Shaw 0 degree silicone demoulding; the output angle of the driving servo 65 is determined by the PWM signal, and the PWM waveform is output by the pin of the development board STM32F103VET6. Figure 3 As shown, with a front group of driving servos 65 as a reference, a time phase difference is applied between a rear group of driving servos 65 and the reference driving servos 65 to achieve asynchronous output.

[0044] 3. Marking points

[0045] See also Figure 4 In this embodiment, the marking points 66 are on the flexible pectoral fins 62 on both sides of the main structure 61 of the test prototype 6; multiple rows of marking points 66 are arranged from the root to the tip of the flexible pectoral fin 62 on each side in the span direction, and multiple marking points are arranged in each row; the positions of some marking points 66 should correspond to the bionic skeleton 63 inside the flexible pectoral fin 62 (that is, the marking points 66 are outside the bionic skeleton 63), and the remaining marking points 66 are used as marking points 66 for recording the motion characteristics of the bionic muscles 64. The marking points 66 are used to cooperate with the underwater motion capture system to capture and collect the motion data of the flexible pectoral fin 62.

[0046] 4. Circuit control system

[0047] The circuit control system includes a power supply part and a signal transmission part, wherein: the power supply part is used to provide power to the driving servo 65 in the test prototype 6, the output waveform of the driving servo 65 is given by the microcontroller and sent to the driving servo 65 through the signal transmission part; the movement form of the flexible pectoral fin 62 is controlled by the driving servo 65 to be periodic reciprocating flapping.

[0048] 5. Mechanical sensors

[0049] The mechanical sensor 5 is used to measure and record the mechanical data of the test sample 6 in real time during the test. In this embodiment, the mechanical sensor 5 is installed at the part where the fixed connecting rod 7 is connected to the test sample 6, and the central axis of the mechanical sensor 5 coincides with the vertical axis where the center of mass of the test sample 6 is located.

[0050] 6. Underwater motion capture system

[0051] The underwater motion capture system includes a motion capture camera 1 and an underwater video camera, wherein the motion capture cameras 1 are distributed around the test prototype 6, and the underwater video camera is located in front of the test prototype 6 in the incoming flow direction (i.e., the underwater camera 2 is facing the head end of the test prototype 6). Through the cooperation of the motion capture camera 1, the underwater video camera and the marking points 66 on the test prototype 6, the frame images of the deformation of the flexible pectoral fin 62 of the test prototype 6 during the movement are recorded; in order to accurately depict the deformation of the flexible pectoral fin 62, the number of marking points 66 in the span direction and the chord direction should be sufficient.

[0052] 7.PIV test system

[0053] The PIV test system includes a light source 4 and a high-speed camera 3; after the tracer particles are evenly spread in the test pool 11 according to a preset mass ratio, the high-speed camera 3 is used to calibrate the area to be observed; during the test, the tracer particles are observed by the high-speed camera 3 to obtain the flow field characteristics of the area to be observed; the light source 4 is arranged at the bottom of the test pool 11 to illuminate the area to be observed; the high-speed camera 3 is placed outside the observation window of the test pool 11, the optical axis of the high-speed camera 3 is perpendicular to the observation window, and is focused on the area to be observed, and the collected images are displayed in real time on the display of the test control unit 10.

[0054] 8. Test control unit

[0055] The test control unit 10 is used to control the issuance of instructions and data collection during the test, including instruction control of the flow field environment in the test pool 11, instruction control of the PIV test system for lighting adjustment and focusing and display of the area to be observed, instruction control of the movement form of the test prototype 6, and collection of mechanical data obtained by the mechanical sensor 5 and motion data obtained by the underwater motion capture system.

[0056] Based on the above test system, the present invention further provides a method for testing the fluid-solid coupling characteristics of a bionic flexible pectoral fin, comprising:

[0057] Step 1, designing and manufacturing a corresponding bionic flexible pectoral fin test prototype 6 for the bionic underwater vehicle, after installing and debugging the test prototype 6, arranging marking points 66 on the flexible pectoral fin 62 of the test prototype 6;

[0058] Step 2, assemble the test sample 6 to be tested into the test water pool 11 through the fixing connecting rod 7, and adjust the position of the test sample 6 so that the test sample 6 is located in the middle of the flow field of the test water pool 11, and the head of the test sample 6 faces the incoming flow direction;

[0059] Step 3, arranging an underwater motion capture system in the test pool 11, wherein the motion capture cameras 1 of the underwater motion capture system are distributed around the test prototype 6, and the underwater video camera is arranged in front of the test prototype 6 in the incoming flow direction;

[0060] Step 4, after uniformly spreading the tracer particles in a preset mass ratio in the test water pool 11, the flow-making function of the test water pool 11 is turned on to make the tracer particles uniformly distributed in the water pool; in this embodiment, the preset mass ratio is 5g / kg.

[0061] Step 5, arranging the PIV test system, setting a light source 4 at the bottom of the test pool 11, illuminating the area to be observed with the light source 4, and calibrating the area to be observed with the high-speed camera 3, wherein the test prototype 6 is located in the area to be observed;

[0062] Step 6, the test control unit 10 sends a driving instruction to the driving servo 65 in the test prototype 6 through the circuit control system; wherein the output signal of the driving servo 65 is obtained by modulating the duty cycle at the microcontroller port, and the physical parameters of the output signal include the amplitude and frequency of the output angle and the phase difference between the front and rear driving servos 65;

[0063] Step 7, the test control unit 10 collects the output signal of the driving servo 65 through the mechanical sensor 5, and turns on the shooting function of the high-speed camera 3 of the PIV test system, so as to obtain the mechanical and flow field characteristics of the flexible pectoral fin 62 of the test prototype 6 when it moves on the continuous time axis; wherein the flow field characteristics refer to the velocity field of the tracer particles in the area to be observed;

[0064] Define the output angle of the front driving servo 65 as θ1, the output angle of the rear driving servo 65 as θ2, the maximum angle A, the angular frequency ω, the phase difference between the front and rear driving servos 65 t is the time parameter, which can be expressed as:

[0065] θ1=Asin(ωt)

[0066]

[0067] Step 8, the test control unit 10 performs motion capture through the motion capture camera 1 of the underwater motion capture system, and simultaneously uses the underwater camera 2 to shoot, thereby obtaining the displacement field of the marker point 66 on the continuous time axis, and compares it with the displacement field calculated using the marker point 66 under the rigid body condition, and obtains the relative displacement of the marker point 66, that is, the deformation characteristic;

[0068]

[0069] Among them, Δu i (t) is the relative displacement of the flexible pectoral fin 62 at time t, u i (t) is the displacement field of the i-th marker point 66 obtained in the experiment, is the calculated displacement field of the i-th marking point 66 , and N is the number of marking points 66 .

[0070] The displacement field calculated using the marker point 66 under the rigid body condition is:

[0071] The displacement field calculated when the test prototype 6 is not affected by water flow; the geometric parameters of the flexible pectoral fin 62 of the test prototype 6 are known, and the radius of the marked point 66 relative to the rotation position of the flexible pectoral fin 62 is known; therefore, it is only necessary to set the angular frequency ω to the same value as that during the test to calculate the displacement field of the marked point 66 on the continuous time axis under rigid body conditions.

[0072] Step 9: Obtain the fluid-solid coupling characteristics of the flexible pectoral fin 62 through regression analysis based on the functional relationship between the deformation characteristics of the flexible pectoral fin 62 and the mechanical and flow field characteristics.

[0073] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A fluid-solid coupling characteristics testing system for a bionic flexible pectoral fin, characterized in that: The device comprises a test pool (11), a bionic flexible pectoral fin test prototype (6), a circuit control system, an underwater motion capture system, a mechanical sensor (5), a PIV test system and a test control unit (10), wherein: The test pool (11) is used to provide a flow field environment required for the test. The bionic flexible pectoral fin test prototype (6) is installed in the test pool (11). The mechanical sensor (5) is installed on the test prototype (6) to collect mechanical data of the test prototype (6). The underwater motion capture system includes a plurality of cameras distributed around the test prototype (6) to realize motion capture and collection of the test prototype (6) in combination with marking points (66) arranged on the flexible pectoral fin (62) of the test prototype (6). The PIV test system is used to provide lighting to the area to be observed in the test pool (11) during the test, and to focus on the area to be observed. The circuit control system is used to drive and control the driving steering engine (65) of the test prototype (6) so that the test prototype (6) simulates the motion form of the bionic underwater vehicle. The test control unit (10) is used to send motion instructions to the test prototype (6) through the circuit control system, and collect mechanical data obtained by the mechanical sensor (5) and motion data obtained by the underwater motion capture system.

2. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The test water pool (11) is a circulating water pool that provides a flow field environment. A position adjustment structure is installed on the upper part of the test water pool (11), and the position adjustment mechanism is an air floating guide rail (8) or a sliding groove; the bionic flexible pectoral fin test prototype (6) is assembled on the position adjustment structure through a fixed connecting rod (7), and the position of the test prototype (6) underwater is adjusted by the position adjustment mechanism; the flow field speed of the test water pool (11) should match the swimming speed range of the full-size bionic underwater vehicle corresponding to the test prototype (6) on the basis of satisfying the similarity criterion.

3. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The biological prototype of the bionic flexible pectoral fin test prototype (6) is a bionic underwater vehicle; The test prototype (6) includes a main structure (61), a flexible pectoral fin (62) and a driving servo (65), wherein: the main structure (61) corresponds to the part of the biological prototype except the pectoral fin, and plays an overall supporting role; the flexible pectoral fin (62) is symmetrically arranged on both sides of the main structure (61), and is composed of an internal hard bionic skeleton (63) and a bionic muscle (64) coated thereon, and the bionic muscle (64) is made of flexible material; the driving servo (65) is fixed inside the main structure (61) and connected to the flexible pectoral fin (62) through a movable joint; the driving servo (65) is arranged in a group at the front and rear of the main structure (61), and the movement of the front and rear two groups of driving servos (65) has a phase difference, so as to realize the wave transmission on the surface of the flexible pectoral fin (62).

4. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The main structure (61) is formed by 3D printing of high-performance nylon material, the bionic skeleton (63) is made by cutting a carbon fiber composite material plate, and the bionic muscle (64) is prepared by Shaw 0-degree silicone demoulding; the output angle of the driving steering gear (65) is determined by a PWM signal.

5. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The marking points (66) are on the flexible pectoral fins (62) on both sides of the main structure (61) of the test prototype (6); multiple rows of marking points (66) are arranged from the root to the tip in the span direction of the flexible pectoral fin (62) on each side, and multiple marking points are arranged in each row; the positions of some marking points (66) should correspond to the bionic skeleton (63) inside the flexible pectoral fin (62), and the remaining marking points (66) are used as marking points (66) for recording the movement characteristics of the bionic muscles (64).

6. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The circuit control system comprises a power supply part and a signal transmission part, wherein: the power supply part is used to provide power to a driving servo (65) in a test prototype (6); the output waveform of the driving servo (65) is given by a microcontroller and sent to the driving servo (65) through the signal transmission part; the movement form of the flexible pectoral fin (62) is controlled by the driving servo (65) to be periodic reciprocating flapping.

7. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The mechanical sensor (5) is installed at the portion where the fixed connecting rod (7) is connected to the test sample (6), and the central axis of the mechanical sensor (5) coincides with the vertical axis where the center of mass of the test sample (6) is located.

8. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: The underwater motion capture system comprises a motion capture camera (1) and an underwater video camera, wherein the motion capture camera (1) is distributed around a test prototype (6), and the underwater video camera is located in front of the test prototype (6) in the incoming flow direction.

9. The fluid-solid coupling characteristic testing system of the bionic flexible pectoral fin according to claim 1, characterized in that: The PIV test system comprises a light source (4), a high-speed camera (3) and a test control unit (10); after tracer particles are evenly spread in a test pool (11) according to a preset mass ratio, the high-speed camera (3) is used to calibrate the area to be observed; the light source (4) is arranged at the bottom of the test pool (11) to illuminate the area to be observed; the high-speed camera (3) is placed outside the observation window of the test pool (11), the optical axis of the high-speed camera (3) is perpendicular to the observation window, and is focused on the area to be observed, and the collected images are displayed in real time on the display of the test control unit (10).

10. A method for testing the fluid-solid coupling characteristics of a bionic flexible pectoral fin, characterized in that: include: Step 1, designing and manufacturing a corresponding bionic flexible pectoral fin test prototype (6) for a bionic underwater vehicle, after installing and debugging the test prototype (6), arranging marking points (66) on the flexible pectoral fin (62) of the test prototype (6); Step 2, assembling the test sample (6) to be tested into the test water pool (11) through the fixing connecting rod (7), adjusting the position of the test sample (6) so that the test sample (6) is located in the middle of the flow field of the test water pool (11), and the head of the test sample (6) faces the incoming flow direction; Step 3, arranging an underwater motion capture system in the test pool (11), wherein the motion capture cameras (1) of the underwater motion capture system are distributed around the test prototype (6), and the underwater video camera is arranged in front of the test prototype (6) in the incoming flow direction; Step 4, after uniformly spreading the tracer particles in a preset mass ratio in the test water pool (11), the flow-making function of the test water pool (11) is turned on, so that the tracer particles are uniformly distributed in the water pool; Step 5, arranging the PIV test system, setting a light source (4) at the bottom of the test pool (11), irradiating the area to be observed with the light source (4), and calibrating the area to be observed with a high-speed camera (3); wherein the test prototype (6) is located in the area to be observed; Step 6, the test control unit (10) sends a drive instruction to the driving servo (65) in the test prototype (6) through the circuit control system; wherein the output signal of the driving servo (65) is obtained by modulating the duty cycle at the microcontroller port, and the physical parameters of the output signal include the amplitude and frequency of the output angle and the phase difference between the front and rear driving servos (65); Step 7, the test control unit (10) collects the output signal of the driving servo (65) through the mechanical sensor (5), and turns on the shooting function of the high-speed camera (3) of the PIV test system, so as to obtain the mechanical and flow field characteristics of the flexible pectoral fin (62) of the test prototype (6) when it moves on a continuous time axis; Step 8, the test control unit (10) performs motion capture using the motion capture camera (1) of the underwater motion capture system, and simultaneously uses the underwater camera (2) to shoot, thereby obtaining the displacement field of the marker point (66) on the continuous time axis, and compares it with the displacement field calculated using the marker point (66) under rigid body conditions, to obtain the relative displacement of the marker point (66), that is, the deformation characteristic; Step 9, obtaining the fluid-solid coupling characteristics of the flexible pectoral fin (62) through a regression analysis method based on the functional relationship between the deformation characteristics of the flexible pectoral fin (62) and the mechanical and flow field characteristics.

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