Animal swimming three-dimensional force testing device and testing method

Abstract

The invention discloses an animal swimming three-dimensional force testing device and a testing method, and belongs to the technical field of biomechanical testing. The testing device comprises a water tank, a base, a force testing device with a three-dimensional force sensor, a camera shooting device with double high-speed infrared cameras and a suspension device composed of a fishing line, a reflective ball and a silk ribbon. The testing method comprises the steps of calibration, water animal processing, synchronous video and force data acquisition, data alignment triggering through knocking, and three-dimensional force decomposition based on a fishing line space vector. The two-dimensional limitation is broken through, the three-dimensional force can be measured in real time when the animal freely swims, the posture is synchronously captured, the precision is high, the method is suitable for crocodiles and other large aquatic animals, and data support is provided for bionic design.

Description

Technical Field

[0001] The present invention relates to the technical field of biomechanics testing, and more particularly to a device and method for testing the three-dimensional force of animal swimming. Background Art

[0002] Crocodiles, as important semi-aquatic reptiles, possess significant propulsion capabilities thanks to their tails. Their swimming behavior has served as an important inspiration for engineering systems such as biomimetic propulsion and biomimetic underwater robots. However, current research on the dynamics of large aquatic animals like crocodiles remains limited.

[0003] Traditional animal swimming research primarily uses videography to extract motion trajectories, and then indirectly calculates force responses through dynamic models. These methods are typically limited to two-dimensional planes and rely on assuming ideal animal motion under certain simplified conditions. This makes it difficult to accurately describe the complex fluid interactions between the tail and the water in three-dimensional space. Furthermore, existing studies often employ methods that constrain the animal's posture or impose external interference, resulting in distortions in the animal's motion behavior and failing to truly reflect its dynamic characteristics during natural swimming. Some studies have attempted to use methods such as PIV (particle image velocimetry) to observe the flow field around the animal. While this can capture vortex structure and velocity changes, it is difficult to accurately invert the location and magnitude of the animal's force, and the technology is expensive to manufacture and use.

[0004] Therefore, how to provide a three-dimensional force testing system and testing method for animals swimming, and perform real-time three-dimensional force measurement, synchronous posture capture and force visualization reconstruction when the animals are swimming freely, is an urgent problem that needs to be solved by technical personnel in this field. Summary of the Invention

[0005] In view of this, the present invention provides a three-dimensional force testing device and method for animal swimming, which can realize real-time measurement of three-dimensional force and synchronous capture of posture when the animal is swimming freely, solving the problems of insufficient measurement dimension, motion constraint interference and data asynchrony in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In one aspect, the present invention provides a three-dimensional force testing device for animal swimming, comprising a water tank, a base, a force testing device, a camera device, and a suspension device; The water tank is a hexahedral structure with an open top and closed other surfaces; The base includes a rectangular frame at the bottom, the water tank is placed in the rectangular frame, a vertical connecting rod is provided on each side of the rectangular frame, and the two vertical connecting rods are connected by a transverse connecting rod; A camera device is installed on the vertical connecting rod; The force testing device is installed on the transverse connecting rod; and the suspension device is installed at the bottom of the force testing device.

[0007] Preferably, a thermometer is installed inside the water tank, and a drainage pipe is provided at the bottom of the water tank.

[0008] Preferably, the force testing device includes a first fixing plate and a second fixing plate; the three-dimensional force sensor is installed between the first fixing plate and the second fixing plate, the first fixing plate is fixed on the transverse connecting rod, and a semicircular hole is provided at the bottom of the second fixing plate.

[0009] Preferably, the suspension device comprises a fishing line, two reflective balls and a ribbon; the two reflective balls are arranged at both ends of the fishing line; One end of the fishing line is fixed on the second fixing plate through the semicircular hole, passes through the two reflective balls through the through hole in the center of the reflective balls, and is connected to a ribbon at the tail end of the fishing line.

[0010] Preferably, the through hole is filled with glue to fix the position of the reflective ball.

[0011] Preferably, the vertical connecting rod includes a first connecting rod and a second connecting rod; The camera device includes a first high-speed infrared camera and a second high-speed infrared camera; The first high-speed infrared camera is installed on the first connecting rod through an adjustable connecting piece; the second high-speed infrared camera is installed on the second connecting rod through an adjustable connecting piece.

[0012] On the other hand, the present invention also provides a method for testing the three-dimensional force of animal swimming, which is applied to the above-mentioned three-dimensional force testing device for animal swimming, comprising the following steps: Calibrate the camera device and three-dimensional force sensor; Treat the water body and the aquatic animals to be tested; The camera is turned on to collect video data. The aquatic animal to be tested is placed in a water tank. A silk ribbon is tied around the animal while the water level is fine-tuned. As the animal swims in the water, the fishing line is tightened, thereby changing the spatial position of the reflective ball. Force data is then collected using a three-dimensional force sensor. Processing video data and force data, including alignment of video data and force data and decomposition and synthesis of force data.

[0013] Preferably, the alignment of the video data and the force data comprises: After clicking the acquisition button of the camera in the 3D force sensor and camera device, use a rod with a reflective ball fixed on one end to quickly tap the sensor's force measurement surface within the camera's field of view to form a peak in the force data; The frame where the wave peak is located and the frame where the ball contacts the force sensor in the video data are used as the common starting frame of the force data and the video data; The force data and the video data are interleaved according to the multiple relationship between the frame rate of the force sensor and the frame rate of the camera to complete the alignment of the force data and the video data.

[0014] Preferably, the decomposition and synthesis of force data includes: The spatial coordinates of the two reflective balls are obtained using a camera, and the spatial orientation of the fishing line is calculated. The swimming direction of the aquatic animal to be tested is the same as the spatial orientation of the fishing line. In the horizontal plane, the force measured on the three-dimensional force sensor is decomposed into a force in the same direction as the swimming direction of the aquatic animal to be tested, thereby obtaining the propulsion force of the swimming aquatic animal to be tested; the force on the three-dimensional force sensor is decomposed into a force perpendicular to the swimming direction of the aquatic animal to be tested, thereby obtaining the lateral force of the swimming aquatic animal to be tested; the force in the vertical direction on the three-dimensional force sensor is the vertical force of the swimming aquatic animal to be tested; The above decomposition process is performed on each frame of the video data to obtain the coherent three-dimensional force when the aquatic animal to be tested swims.

[0015] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a device and method for testing the three-dimensional force of animal swimming, which has the following beneficial effects: (1) Accurately collect three-dimensional force data: By setting up multiple high-sensitivity force sensors in the water, the three-dimensional force data generated by the crocodile's tail swimming in different postures can be collected in real time, including thrust, lateral force, and vertical force. The data has high accuracy and fast response speed, meeting the needs of dynamic modeling and swimming performance analysis. (2) Supporting the fusion of synchronized high-frame-rate video and force data: The test device is used in conjunction with a synchronized image acquisition system to achieve time synchronization between high-frame-rate video and three-dimensional force data, providing complete experimental data support for subsequent posture recognition, dynamic modeling, and bionic engineering research.

[0016] (3) The test method is standardized and suitable for scientific research and promotion: The test process proposed in this invention has clear experimental preparation, data collection and processing processes, and a high degree of standardization, which is convenient for wide promotion and application in related research fields such as animal behavior and underwater bionic engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0018] Figure 1 This is an overall schematic diagram of the animal swimming three-dimensional force testing device proposed by the present invention; Figure 2 This is a schematic diagram of the water tank structure of the present invention; Figure 3 This is a schematic diagram of the base structure of the present invention; Figure 4 Schematic diagram of the force testing device of the present invention; Figure 5 It is a schematic diagram of the suspension device of the present invention; Figure 6 This is a schematic diagram of the usage status of the three-dimensional force testing device for animal swimming.

[0019] In the figure, 1-water tank, 101-hexahedral water tank, 102-thermometer; 2-base, 201-rectangular frame, 202-first connecting rod, 203-second connecting rod, 204-lateral connecting rod; 3-camera device, 301-first high-speed infrared camera, 302-second high-speed infrared camera; 4-force testing device, 401-first fixed plate, 402-three-dimensional force sensor, 403-second fixed plate; 5-suspension device, 501-first reflective ball, 502-fishing line, 503-second reflective ball, 504-ribbon; 6-crocodile. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] On the one hand, the embodiment of the present invention provides a three-dimensional force testing device for animal swimming, such as Figure 1 As shown, it includes a water tank 1, a base 2, a force testing device 4, a camera device 3, and a suspension device 5. The water tank 1 is placed on a horizontal table, the base 2 surrounds the water tank 1, the camera device 3 and the force testing device 4 are fixed to the base 2, and the suspension device 5 is tied to the force testing device 4.

[0022] like Figure 2 As shown, the water tank 1 comprises a hexahedral tank 101. The upper end of the hexahedral tank 101 is open, with a thermometer 102 mounted inside. Drainage devices are installed at the bottom of the sidewalls. Both the length and width of the hexahedral tank 101 are less than 1.5 times the body length of the test subject. The tank is constructed of fully transparent glass, allowing for easy observation of the movement of the aquatic animal under test and the reading of the thermometer 102 from all angles. The thermometer 102 is secured at the lower end of the tank, ensuring that its probe is fully submerged in the water.

[0023] like Figure 3 As shown, the base 2 includes a rectangular frame 201 at the bottom, within which the water tank 1 is placed. A vertical connecting rod, a first connecting rod 202 and a second connecting rod 203, are disposed on either side of the rectangular frame 201. The two vertical connecting rods are connected by a transverse connecting rod 204. The base 2 is made of aluminum profiles, which are high in strength, lightweight, and easy to process and recycle.

[0024] The force testing device 4 is installed on the transverse connecting rod; specifically, refer to Figure 4 The force testing device 4 includes a first fixing plate 401 and a second fixing plate 403; the three-dimensional force sensor 402 is installed between the first fixing plate 401 and the second fixing plate 403, the first fixing plate 401 is fixed on the transverse connecting rod 204, and a semicircular hole with a diameter of 2 mm is provided at the bottom of the second fixing plate 403.

[0025] In this embodiment, the three-dimensional force sensor 402 has several threaded holes on the front and back. The back of the three-dimensional force sensor 402 is fixed to the transverse connecting rod 204 through the first fixing plate 401 using studs. The installation position is close to the center of the sink. The front of the three-dimensional force sensor 402 is connected to the second fixing plate 403 by bolts.

[0026] The suspension device 5 is installed at the bottom of the force testing device 4 .

[0027] like Figure 5 As shown, the suspension device 5 includes a fishing line 502, a first reflective ball 501, a second reflective ball 503 and a ribbon 504; the first reflective ball 501 and the second reflective ball 503 are balls with reflective tape wrapped around their surfaces, which can appear bright white under a high-speed infrared camera. The first reflective ball 501 and the second reflective ball 503 have through holes in their centers, and the fishing line 502 passes through the through holes and passes through the first reflective ball 501 and the second reflective ball 503 in turn. One end of the fishing line 502 passes through the second fixing plate 4 03 and tie a knot to secure it, tie the other end of the fishing line 502 to the ribbon 504 and secure it, adjust the position of the first reflective ball 501 so that the first reflective ball 501 is located on the end of the fishing line 502 close to the second fixed plate 403, adjust the position of the second reflective ball 503 so that the second reflective ball 503 is located on the end of the fishing line 502 close to the ribbon 504, and then fill the through holes of the first reflective ball 501 and the second reflective ball 503 with glue so that the two reflective balls cannot move on the fishing line.

[0028] Furthermore, the camera device 3 includes a first high-speed infrared camera 301 and a second high-speed infrared camera 302. The first high-speed infrared camera 301 is connected to the first connecting rod 202 via a connector, and the second high-speed infrared camera 302 is connected to the second connecting rod 203 via a connector. The positions of the high-speed infrared cameras 301 and 302 are adjusted so that both can see the first reflective ball 501 and the second reflective ball 503. The fields of view of the high-speed infrared cameras 301 and 302 intersect with each other, both pointing to the area around the ribbon 504, but neither can see the other's lens, thereby preventing the infrared light emitted by the lens from forming a bright spot in the camera image and affecting the shooting effect.

[0029] On the other hand, an embodiment of the present invention further provides a method for testing the three-dimensional force of animal swimming. The aquatic animal to be tested is a crocodile 6, for example. The method is applied to the above-mentioned animal swimming three-dimensional force testing device, including the following steps: S1. Calibrate the camera device and three-dimensional force sensor.

[0030] The camera device is calibrated using a calibration rod. First, adjust the exposure of the first and second high-speed infrared cameras 301 and 302 so that the reflective ball in the field of view is clearly imaged, the background is gray-black, and there are no obvious white spots. The camera frame rate is 50fps. Then, slowly swing the calibration rod in the center of the camera's field of view to record a 30-second video, recorded as Video 1. Place a calibration table on the floor of the sink, requiring the vertical axis of the calibration table to pass through the first reflective ball. Record one frame of the calibration table video, recorded as Video 2. Import Videos 1 and 2 into the calibration software for processing, completing the process of constructing a 3D camera using two high-speed infrared cameras.

[0031] The three-dimensional force sensor is calibrated using a spring dynamometer. Using a spring dynamometer that matches the force sensor's range, slowly pull the spring dynamometer in the ±X, ±Y, and +Z directions of the force sensor. Stop at 10%, 30%, 50%, 70%, and 90% of the force sensor's range, wait for the sensor to stabilize, and then take readings. Compare the force readings on the spring dynamometer and force sensor. If there is a significant difference, perform precision compensation on the force sensor until the reading matches the spring dynamometer's.

[0032] S2. Treat the water body and the aquatic animals to be tested.

[0033] Add enough water to the tank to cover the thermometer probe. Hold the second reflective ball at a distance above the water, so that the fishing line is at a 45-degree angle to the vertical and the second reflective ball is flush with the water. This allows the crocodile to fully contact the water without completely submerging. Add an appropriate amount of dechlorinator to the water. After letting it sit for 1 minute, heat the water in the tank with an electric heater until it reaches a temperature above 25°C.

[0034] Before the experiment, the crocodile's body should be rinsed to prevent the attachments on the crocodile's body from falling off during the experiment, contaminating the sink and affecting the camera's view.

[0035] S3. Turn on the camera to collect video data, place the aquatic animal to be tested in a water tank, tie a silk ribbon around the animal, and fine-tune the water surface height. When the aquatic animal to be tested swims in the water, tighten the fishing line, thereby changing the spatial position of the reflective ball. Force data is collected using a three-dimensional force sensor.

[0036] Click the acquisition buttons on the three-dimensional force sensor and the two high-speed infrared cameras to start data collection, and use a pole with a reflective ball fixed on one end to quickly tap the lower surface of the second fixed plate within the camera's field of view.

[0037] Then, flatten the flexible ribbon and tie it around the crocodile's neck, then place it steadily in the water. By adding or reducing water, fine-tune the water level so that the crocodile's nose can slightly float above the water when the fishing line is tightened (refer to Figure 6 Once in the water, the crocodile will swim forward, pulling on the fishing line. This will cause the reflective ball to change its position, and the 3D force sensor will collect force data. During the data collection process, the crocodile's movements should be constantly observed. When the crocodile becomes exhausted, a float should be placed in the tank for the crocodile to rest on. Click the "Stop Collection" button to complete the data collection.

[0038] S4. Processing the video data and the force data, including alignment of the video data and the force data and decomposition and synthesis of the force data.

[0039] The alignment of video data and force data includes: After clicking the acquisition button of the camera in the 3D force sensor and camera device, use a rod with a reflective ball fixed on one end to quickly tap the sensor's force measurement surface within the camera's field of view to form a peak in the force data; The frame where the wave peak is located and the frame where the ball contacts the force sensor in the video data are used as the common starting frame of the force data and the video data; The force data and the video data are interleaved according to the multiple relationship between the frame rate of the force sensor and the frame rate of the camera to complete the alignment of the force data and the video data.

[0040] The decomposition and synthesis of force data include: The spatial coordinates of the two reflective balls are obtained using a camera, and the spatial orientation of the fishing line is calculated. The crocodile's swimming direction is the same as the spatial orientation of the fishing line. In the horizontal plane, the force measured on the three-dimensional force sensor is decomposed into the force in the same direction as the crocodile's swimming, and the propulsion force of the crocodile's swimming is obtained; the force on the three-dimensional force sensor is decomposed into the force perpendicular to the crocodile's swimming direction, and the lateral force of the crocodile's swimming is obtained; the force in the vertical direction on the three-dimensional force sensor is the vertical force of the crocodile's swimming; The above decomposition process is performed on each frame of the video data to obtain the coherent three-dimensional forces when the crocodile swims.

[0041] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0042] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-dimensional force testing device for animal swimming, characterized in that: It includes a water tank, a base, a force testing device, a camera device and a suspension device; The water tank is a hexahedral structure with an open top and closed other surfaces; The base includes a rectangular frame at the bottom, the water tank is placed in the rectangular frame, a vertical connecting rod is provided on each side of the rectangular frame, and the two vertical connecting rods are connected by a transverse connecting rod; A camera device is installed on the vertical connecting rod; The force testing device is installed on the transverse connecting rod; and the suspension device is installed at the bottom of the force testing device.

2. The three-dimensional force testing device for animal swimming according to claim 1, characterized in that: A thermometer is installed inside the water tank, and a drainage pipe is provided at the bottom of the water tank.

3. The three-dimensional force testing device for animal swimming according to claim 1, characterized in that: The force testing device includes a first fixing plate and a second fixing plate; a three-dimensional force sensor is installed between the first fixing plate and the second fixing plate, the first fixing plate is fixed on the transverse connecting rod, and a semicircular hole is provided at the bottom of the second fixing plate.

4. The three-dimensional force testing device for animal swimming according to claim 3, characterized in that: The suspension device includes a fishing line, two reflective balls and a ribbon; the two reflective balls are arranged at both ends of the fishing line; One end of the fishing line is fixed on the second fixing plate through the semicircular hole, passes through the two reflective balls through the through hole in the center of the reflective balls, and is connected to a ribbon at the tail end of the fishing line.

5. The three-dimensional force testing device for animal swimming according to claim 4, characterized in that: The through hole is filled with glue to fix the position of the reflective ball.

6. The three-dimensional force testing device for animal swimming according to claim 1, characterized in that: The vertical connecting rod includes a first connecting rod and a second connecting rod; The camera device includes a first high-speed infrared camera and a second high-speed infrared camera; The first high-speed infrared camera is installed on the first connecting rod through an adjustable connecting piece; the second high-speed infrared camera is installed on the second connecting rod through an adjustable connecting piece.

7. A method for testing the three-dimensional force of animal swimming, characterized in that: A three-dimensional force testing device for animal swimming as described in any one of claims 1 to 6 comprises the following steps: Calibrate the camera device and three-dimensional force sensor; Treat the water body and the aquatic animals to be tested; The camera is turned on to collect video data. The aquatic animal to be tested is placed in a water tank. A silk ribbon is tied around the animal while the water level is fine-tuned. As the animal swims in the water, the fishing line is tightened, thereby changing the spatial position of the reflective ball. Force data is then collected using a three-dimensional force sensor. Processing video data and force data, including alignment of video data and force data and decomposition and synthesis of force data.

8. The method for testing the three-dimensional force of animal swimming according to claim 7, characterized in that: The alignment of video data and force data includes: After clicking the acquisition button of the camera in the 3D force sensor and camera device, use a rod with a reflective ball fixed on one end to quickly tap the sensor's force measurement surface within the camera's field of view to form a peak in the force data; The frame where the wave peak is located and the frame where the ball contacts the force sensor in the video data are used as the common starting frame of the force data and the video data; The force data and the video data are interleaved according to the multiple relationship between the frame rate of the force sensor and the frame rate of the camera to complete the alignment of the force data and the video data.

9. The method for testing the three-dimensional force of animal swimming according to claim 7, characterized in that: The decomposition and synthesis of force data include: The spatial coordinates of the two reflective balls are obtained using a camera, and the spatial orientation of the fishing line is calculated. The swimming direction of the aquatic animal to be tested is the same as the spatial orientation of the fishing line. In the horizontal plane, the force measured on the three-dimensional force sensor is decomposed into a force in the same direction as the swimming direction of the aquatic animal to be tested, thereby obtaining the propulsion force of the swimming aquatic animal to be tested; the force on the three-dimensional force sensor is decomposed into a force perpendicular to the swimming direction of the aquatic animal to be tested, thereby obtaining the lateral force of the swimming aquatic animal to be tested; the force in the vertical direction on the three-dimensional force sensor is the vertical force of the swimming aquatic animal to be tested; The above decomposition process is performed on each frame of the video data to obtain the coherent three-dimensional force when the aquatic animal to be tested swims.

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