A fluid-structure coupling characteristic test system and method of a bionic flexible pectoral fin

Abstract

The application discloses a kind of fluid-structure coupling characteristics test system and method of bionic flexible chest fin, wherein test pool is used to provide the flow field environment required by test, bionic flexible chest fin test prototype is installed in test pool, and mechanical sensor is installed on test prototype, for collecting the mechanical data of test prototype;Underwater motion capture system includes multiple cameras distributed around test prototype, for realizing the motion capture and acquisition of test prototype in combination with the marker point arranged on the flexible chest fin of test prototype;PIV test system is used to provide illumination to the observation area to be observed in test pool during test, and focus observation is carried out on the observation area to be observed;Circuit control system is used to drive control the drive steering gear of test prototype, so that test prototype simulates the motion form of bionic underwater vehicle;Test control unit is used to issue motion instruction to test prototype, and collect the mechanical data obtained by mechanical sensor, the action data obtained by underwater motion capture system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underwater bionic flexible propulsion and test testing, and particularly relates to a fluid-structure coupling characteristic test system and method of a bionic flexible pectoral fin. BACKGROUND

[0002] Since the new era, as a device that can autonomously carry out underwater reconnaissance tasks, unmanned underwater vehicles have shown great development potential in the fields of national defense and civil use, among which 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 for maneuvering. The common application type of bionic underwater vehicles is that the internal motor drives the rotation of the bionic skeleton root through periodic rotary motion, and the flexible material covering the bionic skeleton produces bending deformation under the dual action of the internal skeleton and the water body, and the vehicle releases momentum to the water body to generate a reaction force to drive itself. Compared with traditional vehicles based on propeller propulsion, the driving structure of bionic underwater vehicles has greater flexibility, and the bionic pectoral fin will exhibit large bending deformation characteristics during the periodic flapping propulsion, i.e. large deformation fluid-structure coupling. Studying the propulsion characteristics and flexible deformation characteristics of bionic flexible pectoral fins is the basis for optimizing bionic propulsion structures and performance evaluation criteria. The simulation results of bionic fluid-structure coupling numerical technology show that the flexible pectoral fin has better thrust characteristics and higher propulsion efficiency than the rigid pectoral fin.

[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 perfect fluid-structure coupling characteristic test system and test analysis method for bionic flexible pectoral fins. SUMMARY

[0005] In view of the problem of the lack of test technology mentioned in the background art, the purpose of the present application is to propose a fluid-structure coupling characteristic test system and method of a bionic flexible pectoral fin, which is 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-mentioned task, the present application adopts the following technical solutions:

[0007] The fluid-structure coupling characteristic test system of the 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 for providing a flow field environment required by the test, the bionic flexible pectoral fin test prototype is installed in the test pool, the mechanical sensor is installed on the test prototype and is used for collecting mechanical data of the test prototype; the underwater motion capture system comprises a plurality of cameras distributed around the test prototype and is used for realizing motion capture and collection of the test prototype in combination with mark points arranged on the flexible pectoral fin of the test prototype; the PIV test system is used for providing illumination to a to-be-observed area in the test pool during the test, and is used for focusing on observing 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 a motion form of a bionic underwater vehicle; and the test control unit is used for issuing a motion instruction to the test prototype through the circuit control system, and collecting mechanical data acquired by the mechanical sensor and motion data acquired by the underwater motion capture system.

[0009] Further, the test pool is a circulating pool for providing a flow field environment, a position adjusting mechanism is installed on an upper portion of the test pool, the position adjusting mechanism is an air floating guide rail or a sliding groove; the bionic flexible pectoral fin test prototype is assembled on the position adjusting mechanism through a fixed connecting rod, and the position of the test prototype in water is adjusted through the position adjusting mechanism; and a flow field speed of the test pool should be matched with a swimming speed range of a full-size bionic underwater vehicle corresponding to the test prototype on the basis of satisfying a similarity criterion.

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

[0011] The test prototype comprises a main body structure, a flexible pectoral fin and a driving steering engine, wherein: the main body structure corresponds to a part of the biological prototype except the pectoral fin, and plays a role of overall support; the flexible pectoral fin is symmetrically arranged on both sides of the main body structure, is composed of an internal hard bionic skeleton and bionic muscles wrapped thereon, and the bionic muscles adopt a flexible material; the driving steering engine is fixed in the main body structure and is connected to the flexible pectoral fin through a movable joint; one set of driving steering engines is arranged in front of and behind the main body structure, and the movements of the driving steering engines in front of and behind the main body structure have a phase difference, so as to realize wave transmission on the surface of the flexible pectoral fin.

[0012] Further, the main body structure is formed by 3D printing of high-performance nylon material, the bionic skeleton is cut from a carbon fiber composite material plate, and the bionic muscles are prepared by demolding of a Shore 0 silicone rubber; and an output angle of the driving steering engine is determined by a PWM signal.

[0013] Further, the marker points are arranged on the flexible pectoral fins on both sides of the main body structure of the test prototype; a plurality of rows of marker points are arranged on each flexible pectoral fin from the root to the tip in the spanwise direction, and a plurality of marker points are arranged in each row; some of the marker points correspond to the internal bionic skeleton of the flexible pectoral fin, and the rest of the marker points are used to record the motion characteristics of the bionic muscles.

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

[0015] Further, the mechanical sensor is installed at the part 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] Further, the underwater motion capture system comprises motion capture cameras and an underwater camera, wherein the motion capture cameras are distributed around the test prototype, and the underwater camera is arranged in front of the test prototype in the direction of the incoming flow.

[0017] Further, the PIV test system comprises a light source, a high-speed camera, and a test control unit; after uniformly scattering tracer particles in the test pool according to a predetermined mass ratio, the high-speed camera is used to calibrate the observation area; the light source is arranged at the bottom of the test pool to irradiate the observation area; the high-speed camera is placed outside the observation window of the test pool, the optical axis of the high-speed camera is perpendicular to the observation window, and the high-speed camera is focused on the observation area; the collected pictures are displayed in real time on the display of the test control unit.

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

[0019] Step 1: design and manufacture a corresponding bionic flexible pectoral fin test prototype for a bionic underwater vehicle; after the test prototype is installed and adjusted, arrange marker points on the flexible pectoral fins of the test prototype;

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

[0021] Step 3: arrange 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 camera is arranged in front of the test prototype in the direction of the incoming flow.

[0022] Step 4, after uniformly spreading the tracer particles in the test pool at a preset mass ratio, the flow generating function of the test pool is started, so that the tracer particles are uniformly distributed in the test pool;

[0023] Step 5, the PIV test system is arranged, a light source is arranged at the bottom of the test pool, the light source is used to irradiate the to-be-observed region, and the to-be-observed region is calibrated through a high-speed camera;

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

[0025] Step 7, the test control unit collects the output signal of the driving rudder through the mechanical sensor, and starts 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 sample machine in 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 simultaneously performs shooting through the underwater camera, so as to obtain the displacement field of the marker points in the continuous time axis, and compare the displacement field calculated by the marker points under the rigid body condition, to obtain the relative displacement of the marker points, that is, the deformation characteristics;

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

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

[0029] The fluid-structure coupling characteristic test system of the bionic flexible pectoral fin provided by the present application fills the gap in the test field; the mechanical test, flow field test and deformation test of the bionic flexible pectoral fin can be carried out by using the test system, and then the fluid-structure coupling characteristics of the bionic flexible pectoral fin during flapping are obtained through the test method, which has guiding significance for the subsequent design and optimization of the flexible pectoral fin of the bionic underwater vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a schematic diagram of the fluid-structure coupling characteristic test system of the bionic flexible pectoral fin;

[0031] Figure 2 It is a schematic diagram of the test sample machine of the bionic flexible pectoral fin;

[0032] Figure 3 It is a schematic diagram of the driving form of the test sample machine;

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

[0034] Explanation of reference numerals 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 drive steering engine, 66 marker point, 7 fixed connecting rod, 8 air floatation guide rail, 9 fixed connecting part, 10 test control unit, 11 test pool. DETAILED DESCRIPTION

[0035] Referring to the drawings, the present application provides a fluid-structure coupling characteristic test system of 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 and is used to collect the mechanical data of the test prototype 6; the underwater motion capture system comprises a plurality of cameras distributed around the test prototype 6 and is used to realize the motion capture and collection of the test prototype 6 in combination with the marker points 66 arranged on the flexible pectoral fin 62 of the test prototype 6; the PIV test system is used to provide illumination to the to-be-observed area in the test pool 11 during the test and to focus on the observation of the to-be-observed area; the circuit control system is used to drive and control the drive steering engine 65 of the test prototype 6, so that the test prototype 6 simulates the motion form of the bionic underwater vehicle; and the test control unit 10 is used to issue a motion instruction to the test prototype 6 through the circuit control system and to collect the mechanical data acquired by the mechanical sensor 5 and the motion data acquired by the underwater motion capture system.

[0037] The content of the present application will be further described in detail below in combination with the drawings.

[0038] 1. Test pool

[0039] In the scheme, the test pool 11 is a circulating pool providing a flow field environment. A position adjusting mechanism is installed on the upper part of the test pool 11, which 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 adjusting mechanism through a fixed connecting rod 7. The horizontal position or depth of the test prototype 6 in water is adjusted through the position adjusting mechanism to meet different test requirements. The flow field speed of the test pool 11 should be matched with the cruising 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 of the water surface and the pool wall surface 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 embodiment, the test site is a large circulating pool, Figure 1 The observation section at the end of the pool is shown. The observation window is a side wall of the pool, and the PIV test system focuses on the observation area of interest through the observation window. In this embodiment, the air floating guide rail 8 is installed on the upper part of the pool through the fixed connecting part 9, and the test prototype 6 is connected to the air floating guide rail 8 through the fixed connecting rod 7. By adjusting the air floating guide rail 8, the test prototype 6 is located in the middle of the flow field of the test pool 11. It should be noted that if a mooring model test is to be performed, the air inflation pump of the air floating guide rail 8 should be stopped.

[0041] 2. Bionic flexible pectoral fin test prototype

[0042] Referring to Figures 2 to 4 The bionic flexible pectoral fin test prototype 6 provided in the present application has a biological prototype of a bionic underwater vehicle. The test prototype 6 includes a main body structure 61, a flexible pectoral fin 62, and a drive steering gear 65. The main body structure 61 corresponds to the part of the biological prototype except the pectoral fin and plays a role of overall support. The flexible pectoral fin 62 is symmetrically arranged on both sides of the main body structure 61 and is composed of an internal hard bionic skeleton 63 and a bionic muscle 64 wrapped thereon. The bionic muscle 64 is made of a large deformation flexible material. The drive steering gear 65 is fixed inside the main body structure 61 and connected to the flexible pectoral fin 62 through a movable joint. In this embodiment, one set of drive steering gears 65 is arranged in front of and behind the main body structure 61, respectively, and used to drive the bionic skeletons 63 of the front and rear parts of the flexible pectoral fins 62 on both sides of the test prototype 6. The movements of the two sets of drive steering gears 65 have a phase difference to realize the transmission of the undulation on the surface of the flexible pectoral fin 62.

[0043] In this embodiment, the main structure 61 is 3D printed with high-performance nylon material, the bionic skeleton 63 is cut from a carbon fiber composite material plate, and the bionic muscle 64 is prepared by demolding with a Shore 0 silicone rubber. 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. As shown in Figure 3 , a time phase difference is applied between the rear driving servo 65 and the reference driving servo 65 to realize asynchronous output.

[0044] 3. Marking points

[0045] Referring to 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. On each flexible pectoral fin 62, multiple rows of marking points 66 are arranged from the root to the tip in the spanwise direction, and multiple marking points 66 are arranged in each row. Some of the marking points 66 are located at positions corresponding to the bionic skeleton 63 inside the flexible pectoral fin 62 (i.e., the marking points 66 are outside the bionic skeleton 63), and the remaining marking points 66 are used to record the movement characteristics of the bionic muscle 64. The marking points 66 are used in cooperation 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. The power supply part is used to provide power to the driving servo 65 in the test prototype 6, and 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 sensor

[0049] The mechanical sensor 5 is used to measure and record the mechanical data of the test prototype 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 prototype 6, and the central axis of the mechanical sensor 5 coincides with the vertical axis where the center of mass of the test prototype 6 is located.

[0050] 6. Underwater motion capture system

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

[0052] 7. The PIV test system

[0053] The PIV test system comprises the light source 4 and the high-speed camera 3; after uniformly scattering the tracer particles in the test pool 11 according to the preset mass ratio, the high-speed camera 3 is used to calibrate the to-be-observed region; in the test process, the high-speed camera 3 is used to observe the tracer particles, so as to obtain the flow field characteristics of the to-be-observed region; the light source 4 is arranged at the bottom of the test pool 11 and irradiates the to-be-observed region; 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 the high-speed camera 3 is focused on the to-be-observed region; the collected pictures are displayed in real time on the display of the test control unit 10.

[0054] 8. The test control unit

[0055] The test control unit 10 is used to control the instruction issuing and data acquisition in the test process, including the instruction control of the flow field environment in the test pool 11, the instruction control of the light adjustment of the PIV test system and the focusing and display of the to-be-observed region, the instruction control of the movement form of the test prototype 6, and the acquisition of the mechanical data obtained by the mechanical sensor 5 and the motion data obtained by the underwater motion capture system.

[0056] On the basis of the above-mentioned test system, the application further provides a test method for the fluid-structure coupling characteristics of the bionic flexible pectoral fin, comprising:

[0057] Step 1, a corresponding bionic flexible pectoral fin test prototype 6 is designed and manufactured for the bionic underwater vehicle; after the test prototype 6 is installed and adjusted, the marking points 66 are arranged on the flexible pectoral fin 62 of the test prototype 6;

[0058] Step 2, the test prototype 6 to be measured is assembled into the test pool 11 through the fixed connecting rod 7; the position of the test prototype 6 is adjusted, so that the test prototype 6 is located in the middle of the flow field of the test pool 11, and the head of the test prototype 6 faces the incoming flow direction;

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

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

[0061] Step 5, arrange the PIV test system, set the light source 4 at the bottom of the test pool 11, use the light source 4 to irradiate the observation area, and calibrate the observation area through the high-speed camera 3, wherein the test prototype 6 is located in the observation area;

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

[0063] Step 7, the test control unit 10 collects the output signal of the driving rudder 65 through the mechanical sensor 5, and starts 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 when the test prototype 6 moves in the continuous time axis; wherein the flow field characteristics refer to the velocity field of the tracer particles in the observation area;

[0064] Define the output angle of the front driving rudder 65 as θ1, the output angle of the rear driving rudder 65 as θ2, the maximum angle A, the angular frequency ω, and the phase difference between the front and rear driving rudders 65 t is the time parameter, which is represented 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, so as to obtain the displacement field of the marker point 66 in the continuous time axis, and compare it with the displacement field calculated by the marker point 66 under the rigid body condition, to obtain the relative displacement of the marker point 66, i.e. the deformation characteristics;

[0068]

[0069] Wherein, 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 by the test, is the displacement field of the i-th marker point 66 calculated, and N is the number of marker points 66.

[0070] The displacement field calculated by the marker point 66 under the rigid body condition refers to:

[0071] The displacement field calculated by the test prototype 6 without the action of water flow; the geometric parameters of the flexible pectoral fin 62 of the test prototype 6 are known, and the radius of the marker point 66 relative to the rotating part of the flexible pectoral fin 62 is known; therefore, only the angular frequency ω is set to the same value as that in the test, and the displacement field of the marker point 66 on the continuous time axis under the rigid body condition can be calculated.

[0072] Step 9, through the 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, the fluid-solid coupling characteristics of the flexible pectoral fin are obtained.

[0073] The above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should 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 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 test prototype (6) to collect mechanical data of the test prototype (6). 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), flexible pectoral fins (62) and a driving steering gear (65), wherein: the main structure (61) corresponds to the part of the biological prototype except the pectoral fins, and plays the role of the whole 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 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 driving servo (65) groups has a phase difference, so as to realize the wave transmission on the surface of the flexible pectoral fin (62); The underwater motion capture system includes a motion capture camera (1) and an underwater video camera (2), wherein the motion capture camera (1) is distributed around the test prototype (6), and the underwater video camera (2) is located in front of the test prototype (6) in the incoming flow direction; the underwater motion capture system is used to realize the motion capture and collection of the test prototype (6) in combination with the marking points (66) arranged on the flexible pectoral fins (62) of the test prototype (6); the marking points (66) are on the flexible pectoral fins (62) on both sides of the main structure (61) of the test prototype (6), and 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 (66) are arranged at intervals in each row; the positions of some marking points (66) are It should correspond to the bionic skeleton (63) inside the flexible pectoral fin (62), and the remaining marking points (66) serve as marking points (66) for recording the movement characteristics of the bionic muscle (64); 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 send movement instructions to the test prototype (6) through the circuit control system, and collect the mechanical data obtained by the mechanical sensor (5) and the movement data obtained by the underwater motion capture system.

2. The fluid-solid coupling characteristics 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 floatation 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-scale bionic underwater vehicle corresponding to the test prototype (6) on the basis of satisfying the similarity criterion.

3. The fluid-solid coupling characteristics 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 carbon fiber composite material plates, and the bionic muscle (64) is prepared by Shore 0 degree silicone demoulding; the output angle of the driving servo (65) is determined by a PWM signal.

4. The fluid-structure coupling characteristics testing system of the bionic flexible pectoral fin according to claim 1 is characterized in that: 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 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 motion form of the flexible pectoral fin (62) controlled by the driving servo (65) is periodic reciprocating flapping.

5. The fluid-structure coupling characteristics 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 prototype (6), and the central axis of the mechanical sensor (5) coincides with the vertical axis where the center of mass of the test prototype (6) is located.

6. The fluid-structure coupling characteristics testing system of the bionic flexible pectoral fin according to claim 1 is 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).

7. A method for testing the fluid-structure coupling characteristics of a bionic flexible pectoral fin based on the test system according to any one of claims 1 to 6, characterized in that: include: Step 1, designing and manufacturing a corresponding bionic flexible pectoral fin test prototype (6) for a bionic underwater vehicle, installing and debugging the test prototype (6), and arranging marking points (66) on the flexible pectoral fin (62) of the test prototype (6); Step 2: Assemble the test prototype (6) to be tested into the test water pool (11) through the fixed connecting rod (7), and adjust the position of the test prototype (6) so that the test prototype (6) is located in the middle of the flow field of the test water pool (11) and the head of the test prototype (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 (2) 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-generating function of the test water pool (11) is turned on to make the tracer particles 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), illuminating 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) issues 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, thereby obtaining the mechanical and flow field characteristics of the flexible pectoral fin (62) of the test prototype (6) during the movement on the 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 the rigid body condition, 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) based on the functional relationship between the deformation characteristics and the mechanical and flow field characteristics of the flexible pectoral fin by regression analysis method.

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