Bionic underwater propulsion device based on tensegrity structure

Abstract

The application discloses a kind of bionic underwater propulsion devices based on tensegrity structure, including head, swing mechanism, tail fin and drive mechanism, head, swing mechanism and tail fin are sequentially connected along the axial direction, and drive mechanism is installed in head;Swing mechanism includes joint component, hinged shaft, transverse tension elastic component and connecting rod;Including a plurality of joint components that are arranged axially spaced;Joint component left and right side is provided with hinged shaft;Transverse tension elastic component is connected between hinged shaft;Connecting rod connects two adjacent joint components, and the hinged shaft of two joint components is connected at the both ends of connecting rod, and two connecting rods in X-shaped structure are arranged between two joint components;Drive mechanism includes axial sliding table, linear drive machine, swing drive machine and elastic stay wire;Linear drive machine drives axial sliding table to move axially;Elastic stay wire is connected with the side of joint component.This propulsion device is rigidly coupled, can change rigidity within a certain range, response speed is fast, swimming speed and efficiency are high, and maneuverability is strong.

Description

Technical Field

[0001] This invention belongs to the field of underwater robot technology, and in particular relates to a biomimetic underwater propulsion device based on a tensioned integral structure. Background Technology

[0002] Research on underwater propulsion devices is a key focus of underwater robotics technology. Currently, propeller propulsion and biomimetic propulsion are two important research directions. In nature, after hundreds of millions of years of evolution, fish have developed excellent swimming speed, efficiency, and agility, with their relative performance indicators surpassing those of man-made underwater vehicles. Building on this foundation, more and more researchers are dedicating themselves to the development of biomimetic robotic fish propulsion devices. These biomimetic fish propulsion devices possess excellent swimming performance and outstanding maneuverability, while also exhibiting low noise, resistance to entanglement, and strong environmental adaptability, offering advantages over propeller propulsion in certain specialized applications.

[0003] Fish swimming patterns can be broadly categorized into two types: body / tail fin oscillation propulsion (BCF) and intermediate fin / pair fin propulsion (MPF). Since most fish use the BCF mode for propulsion and exhibit high swimming performance, it is often used as the propulsion mode for biomimetic robotic fish. Currently, biomimetic robotic fish propulsion devices based on body / tail fin oscillation propulsion can be divided into two main categories based on structural characteristics: rigid structures and continuous flexible structures. Rigid structures include multi-servo series structures and crank-connecting rod reciprocating oscillation structures. These structures often fail to achieve optimal efficiency due to high friction between joints and the need for a large number of servos. Continuous flexible structures, driven by materials such as gas, liquid, and shape memory alloys, offer advantages such as continuous deformation and body waves closely resembling those of real fish. However, their disadvantages are also significant, namely, generally slow oscillation speed and slow swimming speed. Neither of these two structural types of biomimetic robotic fish propulsion devices can adjust stiffness, yet changes in stiffness are crucial for improving efficiency in fish swimming. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a biomimetic underwater propulsion device based on a tensioned integral structure, which solves the problems of poor biomimetic effect and swimming efficiency of current biomimetic robotic fish propulsion devices based on body / tail fin oscillation.

[0005] This invention is implemented as follows: a biomimetic underwater propulsion device based on a tensioned integral structure, characterized in that it includes a head, a swing mechanism, a tail fin, and a drive mechanism mounted on the head; the head, swing mechanism, and tail fin are sequentially connected along the axial direction, and the drive mechanism is mounted on the head; the swing mechanism includes joint components, hinge shafts, lateral elastic components, and connecting rods; it includes a plurality of joint components spaced axially, wherein the joint components located at the front end of the axial direction are connected to the head, and the joint components located at the rear end of the axial direction are connected to the tail fin; the axis of the hinge shaft is vertically arranged, and the hinge shafts are arranged on the left and right sides of the joint components; the lateral elastic components are connected between the hinge shafts, and the lateral elastic components... A spring force is applied to bring the two hinge axes closer together; the connecting rod connects two adjacent joint components, with each end of the connecting rod connected to the hinge axis of the two joint components respectively, and two connecting rods with an X-shaped structure are provided between the two joint components; the driving mechanism includes an axial slide, a linear drive gyroscope, a oscillating drive gyroscope, and an elastic cable; the axial slide is mounted on the head in a manner that allows it to move axially; the linear drive gyroscope is mounted on the head and drives the axial slide to move axially; the oscillating drive gyroscope is mounted on the axial slide; the elastic cable is connected to the side of the joint component, and the elastic cable is connected to the oscillating drive gyroscope and is tensioned by the oscillating drive gyroscope.

[0006] In the above technical solution, preferably, the joint component includes two symmetrically arranged joint assemblies and a transverse guide post disposed between the two joint assemblies; the transverse guide post is disposed on one of the two joint assemblies, and the other of the two joint assemblies is provided with a transverse guide hole that engages with the transverse guide post.

[0007] In the above technical solution, preferably, the upper and lower parts of the two joint components are respectively provided with the hinge shaft, and the upper and lower parts of the two adjacent joint components are respectively connected to the connecting rod with an X-shaped structure.

[0008] In the above technical solution, preferably, the lateral elastic component is a spring connected to the two joint assemblies.

[0009] In the above technical solution, preferably, the outer side of the joint assembly forms a curved surface with a ring axis, and the outer contour dimension of the joint component decreases sequentially from front to back.

[0010] In the above technical solution, preferably, the joint assembly is provided with a through hole for the elastic tension wire to pass through.

[0011] In the above technical solution, preferably, the head is provided with a vertical pivot shaft connected to the end of the connecting rod, and the upper and lower parts of the joint component at the axial front end are respectively connected to the head through the connecting rod with an X-shaped structure.

[0012] In the above technical solution, preferably, the head is equipped with an axial slide rail, and the axial slide table is fitted onto the axial slide rail.

[0013] In the above technical solution, preferably, the elastic tension wire includes a steel wire and a tension spring connected in series with the steel wire, and the tension springs connected in series with the steel wire are respectively provided on the side of the X-shaped connecting rod.

[0014] In the above technical solution, preferably, the output shaft of the oscillating drive gyroscope is mounted with a wire cam connected to the steel wire.

[0015] The advantages and effects of this invention application are:

[0016] The tensioned integral structure proposed in this application serves as a propulsion device for underwater vehicles. By incorporating elastic cables into the tensioned integral structure, the flexibility of the swing mechanism is achieved. A linear drive servo is incorporated, which can alter the axial spacing between joint components via the elastic cables. This allows the overall stiffness of the propulsion device to vary within a certain range, mimicking the adaptive functions of a real fish body and improving swimming efficiency. This propulsion device achieves both rapid response to tail fin swing and a degree of flexibility, reducing the driving force requirements of the servo, minimizing mechanical friction and wear, and resulting in high transmission efficiency. This biomimetic underwater propulsion device based on a tensioned integral structure can be applied to biomimetic robotic fish or other underwater vehicles, offering advantages such as flexible movement, resistance to entanglement with underwater debris, low noise, and high efficiency. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention;

[0018] Figure 2 This is a schematic diagram of the swing mechanism in this invention;

[0019] Figure 3 This is a schematic diagram of the joint component in this invention;

[0020] Figure 4 This is a schematic diagram of the joint assembly in this invention;

[0021] Figure 5 This is a schematic diagram of the drive mechanism in this invention;

[0022] Figure 6 This is a diagram showing the dimensional relationships of the swing mechanism in this invention;

[0023] Figure 7 This is a top view of the swing mechanism in the present invention in its non-swinging state;

[0024] Figure 8This is a top view of the swing mechanism in the swing state of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] To address the shortcomings of current biomimetic robotic fish propulsion devices based on body / tail fin oscillation propulsion, such as poor biomimetic performance and swimming efficiency, this invention provides a biomimetic underwater propulsion device based on a tensioned integral structure. This propulsion device features rigid-flexible coupling, allowing for adjustable stiffness within a certain range, rapid response, high swimming speed and efficiency, and strong maneuverability, thus meeting the propulsion requirements of underwater vehicles. For further illustration of the invention's structure, a detailed description is provided below in conjunction with the accompanying drawings:

[0027] Please see Figure 1 A biomimetic underwater propulsion device based on a tensioned integral structure includes a head 1, a swing mechanism 2, a tail fin 3, and a drive mechanism 4 mounted on the head. The head, swing mechanism, and tail fin are connected sequentially along the axial direction, and the drive mechanism is mounted on the head. The axial direction mentioned here can be understood as the forward direction of this propulsion device.

[0028] In this embodiment, the internal main body of the head is a support frame 101, and a head shell 102, mimicking the shape of a fish head, is installed on the outside of the support frame. The head shell is fixed to the support frame with screws. The head shell is made of tough resin and can be manufactured by 3D printing, mimicking the shape of a biological fish. The control module 103 of this propulsion device is located on the support frame inside the head shell. It integrates a microcontroller, a communication module, and a servo drive module. It is responsible for receiving control signals from the host computer, generating control waveforms, generating servo control commands, and transmitting feedback data back to the host computer.

[0029] Please see Figures 2-4 The swing mechanism is the intermediate structure of this propulsion device. It is the action mechanism that enables the propulsion device to move. The swing mechanism includes joint components, hinge shafts, horizontal elastic components and connecting rods.

[0030] The swing mechanism includes several joint components spaced apart axially. In this embodiment, there are three joint components. The joint component located at the front axial direction is connected to the head, and the joint component located at the rear axial direction is connected to the tail fin.

[0031] The joint component includes two symmetrically arranged joint assemblies 201 and a transverse guide post 202 disposed between the two joint assemblies. Under the action of the transverse guide post, the joint component forms a combined component with a variable transverse width and transverse expansion elasticity. The transverse guide post is located on one of the two joint assemblies, and the other joint assembly has a transverse guide hole that engages with the transverse guide post. The outer side of the joint assembly forms a curved surface around the axis, and the joint assembly has a through hole 203 for the passage of an elastic tension wire. Specifically, the joint assembly is a crescent-shaped component, with transverse guide posts integrally formed on the upper, middle, and lower parts of the inner end face of the joint assembly, and a corresponding guide hole on the end face of the other joint assembly. The outer contour dimensions of the joint components decrease sequentially from front to back, so that the outer skin of the three joint components can form an outer contour similar to a fish body, which is wider at the front and narrower at the back, simulating the cross-sectional structure of a real fish.

[0032] The axis of the hinge shaft 204 is vertically arranged, and hinge shafts are provided on the left and right sides of the joint component. Specifically, in this embodiment, two vertically coaxial rotating shafts are formed at the upper and lower parts of the joint component, which are integral with the joint component. Each joint component has two hinge shafts for connecting the connecting rod, which can provide good lateral support force.

[0033] A lateral elastic component is connected between the hinge shafts, applying a pulling force to the two hinge shafts. In this embodiment, the lateral elastic component is a spring 205 connected to the two joint assemblies. Opposing grooves are provided on the upper and lower parts of the opposite end faces of the joint assemblies, and the two ends of the spring are respectively connected to these grooves, i.e., two springs distributed vertically are provided between the two joint assemblies. The lateral elastic component can balance the lateral forces exerted on the two joint assemblies by the elastic tension wires on both sides.

[0034] Link 206 is a rigid rod with hinge holes at both ends. The link connects two adjacent joint components, with each end connected to the hinge shaft of one of the joint components. Two X-shaped link structures are arranged between the two joint components. Specifically, the upper and lower parts of two adjacent joint components are connected to X-shaped link structures. The head has a vertical pivot connected to the end of the link, and the upper and lower parts of the axially front-end joint components are connected to the head via X-shaped link structures.

[0035] Please see Figure 5 The drive mechanism is a combination of components that drive the movement of the swing mechanism. The drive mechanism includes an axial slide 401, a linear drive gyroscope 402, a swing drive gyroscope 403, and an elastic drawbar 404.

[0036] An axial slide is mounted on the head for axial movement. An axial slide rail is mounted on the head, and the axial slide is fitted onto the axial slide rail 405. Specifically, an upper slide rail and a lower slide rail are mounted on the head's support frame using screws. The upper slide rail is equipped with an upper slider, and the lower slide rail is equipped with a lower slider, enabling low-resistance sliding of the oscillating drive servo. A linear drive servo is mounted on the head, driving the axial slide for axial movement. The oscillating drive servo is mounted on the axial slide. In this embodiment, the slide is mounted on an oscillating drive servo bracket using screws, used to mount the oscillating drive servo. The oscillating drive servo bracket consists of three parts: an upper bracket, a lower bracket, and a rear bracket. The upper bracket is connected to the upper slider of the upper slide rail, the lower bracket is connected to the lower slider of the lower slide rail, and the rear bracket is connected to the linear drive servo, transmitting the thrust of the linear drive servo. The linear drive servo is fixed on the head's support frame, and its output shaft is connected to the oscillating drive servo bracket, driving the oscillating drive servo to move linearly.

[0037] The output shaft of the oscillating drive servo is mounted with a cable-operated cam connected to a flexible cable. The cable-operated cam is fixed to the oscillating drive servo with bolts, and the upper end of the cable-operated cam is connected to the oscillating drive servo bracket via a small bearing to ensure that the cable-operated cam can rotate normally. A flexible cable is fixed to the cam and wound around it. The other end of the flexible cable is connected to the corresponding part of the oscillating mechanism. The oscillating drive servo drives the cable-operated cam to rotate reciprocally, and the flexible cable drives the oscillating mechanism to oscillate.

[0038] The linear drive servo motor functions by altering the preload of the elastic cable. This change in preload causes the overall tensioned structure's tail fin to oscillate to a certain extent, and the variation in preload causes variations in the tail fin's stiffness within its respective segments. This simulates the changes in tail fin stiffness in real fish, thus improving their swimming efficiency. The radius of the cable-pulling cam is also designed to ensure that the extension and release strokes do not conflict.

[0039] Elastic tension cables connect both sides of the joint component, passing through the side of the joint component and connecting to the side of the axial tail-end joint component. The elastic tension cables pass through the perforation of the joint assembly of the joint component. The elastic tension cables are connected to the oscillating drive mechanism and are tensioned by the oscillating drive mechanism. The elastic tension cables include steel wires and tension springs connected in series with the steel wires. Tension springs connected in series with the steel wires are respectively provided on the side of the X-shaped connecting rod. In this embodiment, specifically, the first joint component at the axial front end is connected to the oscillating drive mechanism via two elastic tension cables arranged on the left and right sides; the second joint component is connected to the oscillating drive mechanism via two elastic tension cables arranged on the left and right sides passing through the first joint component; and the third joint component is connected to the second joint component via two elastic tension cables arranged on the left and right sides.

[0040] The joint components of this swing mechanism are designed as a two-parallel, three-unit system. The two parallel connections refer to the upper and lower connecting rods of the swing mechanism being connected in parallel by horizontal springs. The rods within the same series are connected by a pivot. Each joint component, along with the two connecting rods, forms a tensioned overall structure via three elastic wires. The X-shaped connecting rods and their corresponding elastic wire segments form elastic units, ensuring that each unit is flexible. The drive mechanism pulls the elastic wires to achieve the swinging motion of the mechanism. The rotational stiffness of each unit can be adjusted by changing the spring stiffness or the preload. Furthermore, to ensure the structure can stably form a specific configuration, the stiffness values ​​of the three tension springs in the three units must be in a specific ratio. The X-shaped connecting rods are installed between two adjacent joint components, forming three-stage axial joints between the head and the joint component, and between the joint components themselves. Please refer to [link / reference]. Figure 6 In this embodiment, the total length of the body is 262mm, of which the first joint is 77mm, the second joint is 89mm, the third joint is 96mm, and the two connecting rods of the first joint are connected to the head 1 with a shaft spacing of 75mm.

[0041] The swing mechanism forms a three-stage joint, in which the first joint is connected to the head, the third joint is connected to the tail fin, the first and second joints are directly connected to the drive mechanism through elastic wires, and the third joint is connected to the second joint through elastic wires.

[0042] In this embodiment, the control system obtains the target motion position of the oscillating servo by calculating the discrete CPG equation, and at the same time outputs a serial port signal to the servo driver. The servo driver can send control commands and read the feedback signal of the servo at the same time.

[0043] The specific working process of this embodiment is as follows:

[0044] Please see Figure 7 and Figure 8The oscillating servo, via a cable cam, drives two elastic cables to pull the first joint component, one on each side. Similarly, the cable cam drives two elastic cables to pull the second joint component. The cable cam has four slots, two of which connect to the first joint and have the same major and minor axes, and the two connecting to the second joint have the same major and minor axes. Thus, when the oscillating servo rotates to one side, the elastic cables tighten at one end and loosen at the other under the cam's influence. The two joints of the tail fin are pulled by the elastic cables and also rotate to one side. The third joint component, connected only to the second joint component, also oscillates to one side under the influence of the second joint component. Due to the interaction with the water flow, it forms a certain angle opposite to the oscillation direction, thus more closely resembling the waveform of a real fish swimming. Therefore, when the oscillating servo oscillates left and right according to the waveform output by the main control, the tail fin's oscillation mechanism also oscillates accordingly, achieving underwater biomimetic propulsion. When turning is needed, the underwater biomimetic propulsion device can be steered by changing the phase of the oscillation center point. When the linear drive servo propels forward, the entire oscillating drive servo mechanism moves towards the head, which lengthens the elastic cable, increases the preload of the elastic cable, changes the torsional stiffness of the tail fin, and improves the swimming performance of the bionic propulsion device.

[0045] From a structural perspective, the biomimetic underwater propulsion device based on a tensioned integral structure can be divided into a rigid head, a flexible swinging mechanism, and a flexible tail fin made of silicone. The rigid head conforms to the streamlined shape of a real fish head to reduce drag. Its internal shell houses the power supply and control system, while the tail fin is cast from silicone, making it simple to manufacture. The central tensioned integral structure unit consists of 3D-printed module units, elastic tension lines composed of steel wire and springs, and metal shafts and connecting rods. This tensioned integral structure forms a flexible series-parallel structure for the swinging tail fin. The elastic tension lines provide tension, while the rigid connecting rods provide kinetic energy, allowing the module units to rotate under the constraint of the elastic tension lines and the support of the connecting rods. The tension lines extending from the tension line cams connect the left and right sides of the first and second joint components, respectively. This is similar to the musculoskeletal system in animal joints; the rigid connecting rods are analogous to bones, while the elastic tension lines are analogous to muscles or ligaments. The tensioned integral structure is inspired by animal anatomy, reducing purely mechanical friction and wear, improving the mechanical stress state, and lowering the required driving force. The stiffness of each unit can be designed to mimic the stiffness distribution of real fish as much as possible, thereby achieving higher swimming efficiency.

[0046] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biomimetic underwater propulsion device based on a tensioned integral structure, characterized in that: It includes a head, a swinging mechanism, a tail fin, and a drive mechanism mounted on the head. The head, the swinging mechanism, and the tail fin are connected sequentially along the axial direction, and the drive mechanism is mounted on the head. The swing mechanism includes: The joint components include a plurality of said joint components arranged axially spaced apart, wherein the joint components located at the axially front end are connected to the head, and the joint components located at the axially rear end are connected to the tail fin; A hinge shaft, wherein the axis of the hinge shaft is vertically arranged, and the hinge shaft is arranged on the left and right sides of the joint component; A lateral elastic component is connected between the hinge shafts, and the lateral elastic component applies a spring force to the two hinge shafts to bring them closer together; A connecting rod connects two adjacent joint components, with both ends of the connecting rod connected to the hinge shafts of the two joint components respectively, and two connecting rods with an X-shaped structure are provided between the two joint components; The drive mechanism includes: An axial slide table is mounted on the head in a manner that allows it to move axially. A linear drive gyroscope, which is mounted on the head and drives the axial slide to move axially; A swing-drive gyroscope, which is mounted on the axial slide table; An elastic cable is connected to the side of the joint component and to the oscillating drive mechanism, which applies tension to the cable. The joint component includes two symmetrically arranged joint assemblies and a transverse guide post disposed between the two joint assemblies; the transverse guide post is disposed on one of the two joint assemblies, and the other of the two joint assemblies is provided with a transverse guide hole that engages with the transverse guide post.

2. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 1, characterized in that: The upper and lower parts of the two joint components are respectively provided with the hinge shaft, and the upper and lower parts of two adjacent joint components are respectively connected to the connecting rod with an X-shaped structure.

3. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 2, characterized in that: The lateral elastic component is a spring connected to the two joint assemblies.

4. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 3, characterized in that: The outer side of the joint assembly forms a curved face with a ring axis, and the outer contour dimensions of the joint components decrease sequentially from front to back.

5. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 4, characterized in that: The joint assembly is provided with a perforation through which the elastic tension wire passes.

6. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 5, characterized in that: The head is provided with a vertical pivot that is connected to the end of the connecting rod. The upper and lower parts of the joint component at the axial front end are respectively connected to the head via the connecting rod with an X-shaped structure.

7. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 6, characterized in that: The head is equipped with an axial slide rail, and the axial slide table is fitted onto the axial slide rail.

8. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 7, characterized in that: The elastic tension cable includes a steel wire and a tension spring connected in series with the steel wire. The tension springs connected in series with the steel wire are respectively provided on the sides of the X-shaped connecting rod.

9. The biomimetic underwater propulsion device based on a tensioned integral structure according to claim 8, characterized in that: The output shaft of the oscillating drive gyroscope is equipped with a wire cam connected to the steel wire.

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