A variable-stiffness manta ray-inspired flexible flapping wing propulsion device with chordwise movement function

Abstract

The present invention discloses a variable stiffness manta ray-like flexible flapping wing propulsion device with spanwise motion function, which belongs to the field of bionic underwater vehicles. The present invention includes a shell, a crankshaft drive device, a pectoral fin skeleton device, a drive servo device and a flexible skin. The present invention adopts a driver to realize complex spanwise flexible flapping wing motion, and the rotation of the servo is realized by cooperating with the bevel gear to realize the drive of the crankshaft, driving the entire device to move. The skeleton is connected with a leaf spring to realize the variable stiffness configuration of the skeleton part, so that the device can realize spanwise motion deformation through the action of water when swimming in the water; by optimizing the rotation radius, phase difference and number of the connecting rod neck of the crankshaft, the pectoral fins are divided to realize spanwise motion deformation; the skeleton device is combined with the airfoil to produce a support structure, which further supports and connects the flexible skin. The present invention can simplify the variable stiffness manta ray-like flexible flapping structure, simplify the control and achieve a high degree of bionics, and improve the aerodynamic performance of the variable stiffness manta ray-like flexible flapping wing.

Description

Technical Field

[0001] The invention relates to a variable-rigidity manta ray-like flexible flapping-wing propulsion device with aspect-wise motion function, belonging to the field of bionic underwater vehicles. Background Art

[0002] With the development of the times, underwater robots have great application value in marine resource exploration, underwater reconnaissance, and rescue work in harsh environments. Traditional underwater vehicles mainly use propellers for propulsion. To adapt to the complex marine environment and the diversity of missions, bionic propulsion technology has emerged.

[0003] Fish are the most common swimming animals in the ocean. Their low-drag shape and efficient, flexible swimming style offer valuable insights into biomimetic design. Fish can be categorized by the body parts they use for propulsion: BCF (body and / or caudal) and MPF (median and / or paired fin). The BCF mode utilizes body undulation propulsion and caudal fin oscillation, while the MPF mode utilizes pectoral fin oscillation and undulation propulsion. The BCF mode offers greater propulsion force and improved acceleration, but suffers from poor stability and controllability. The MPF mode offers lower propulsion force but greater maneuverability, stability, and controllability, offering broader practical application prospects.

[0004] Existing designs often employ motor-driven crankshafts, planetary gear trains, and rope propulsion systems. These methods present challenges such as heavy weight, space occupancy, structural complexity, and a lack of biomimetic control. Rope propulsion systems are not yet mature, making it difficult to control motion. From a structural perspective, the majority employ fin-ray-driven two-dimensional structures, with each fin directly configured with the same phase difference and amplitude. This simplistic approach ignores the biological characteristics and true motion of manta rays, simplifying their motion to simple fluctuations that are inconsistent with reality. Summary of the Invention

[0005] In order to solve the problems of existing underwater bionics such as complex structure, difficult control, low degree of biomimetic and poor aerodynamic performance, the main purpose of the present invention is to provide a variable stiffness manta ray-like flexible flapping wing propulsion device with aspect ratio motion function. The device can simplify the variable stiffness manta ray-like flexible flapping structure, simplify control and achieve a high degree of biomimetic, thereby improving the aerodynamic performance of the variable stiffness manta ray-like flexible flapping wing.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] The present invention discloses a variable-stiffness manta ray-like flexible flapping propulsion device with spanwise motion capabilities. This device utilizes a single driver to achieve complex spanwise flexible flapping motion. The steering gear rotates, coordinated with bevel gears, to drive the crankshaft, thereby driving the entire device. Leaf springs are used to connect the skeleton to achieve a variable-stiffness configuration, allowing the device to passively deform through the action of the water as it swims, thereby achieving spanwise motion deformation. The pectoral fins are divided by optimizing the rotation radius, phase difference, and number of the crankshaft's connecting rod necks to achieve spanwise motion deformation. The skeleton device is combined with the airfoil to create a support structure, which in turn supports and connects the flexible skin.

[0008] Preferably, the skeleton device is combined with a NACA0012 airfoil to produce a support structure, thereby supporting and connecting the flexible skin.

[0009] The invention discloses a variable-rigidity manta ray-like flexible flapping-wing propulsion device with aspect-wise motion function, comprising a shell, a crankshaft drive device, a pectoral fin skeleton device, a drive steering gear device and a flexible skin.

[0010] The housing structure includes a nacelle, a crankshaft retaining groove, and a frame retaining groove. Multiple recesses within the nacelle house the servo drive assembly and crankshaft drive mechanism, providing ample space for various sensors and the center of gravity adjustment mechanism. The crankshaft bearing retaining groove houses and secures the crankshaft bearing, while the frame bearing retaining groove houses and secures the frame bearing. The housing is constructed of a waterproof material, typically photosensitive resin.

[0011] The crankshaft drive assembly is secured within the crankshaft retaining slot of the housing and is connected to the pectoral fin frame assembly. The pectoral fin frame assembly is symmetrically arranged on either side of the housing. The drive servo assembly is secured to the housing and provides power. A flexible skin covers the pectoral fin frame assembly and accompanies its movement.

[0012] The crankshaft driving device includes a crankshaft, a crankshaft and housing fixing device, and a crankshaft and frame connecting device.

[0013] (1) Crankshaft optimization includes connecting rod necks, main journals, balancing blocks, and large bevel gears: By optimizing the number of connecting rod necks, the pectoral fins are divided along the chord direction; by optimizing the rotation radius and angle of the connecting rod necks, different movement amplitudes of different parts of the pectoral fin along the chord direction are achieved, thereby achieving chord-wise movement. There are multiple connecting rod necks. In theory, the more connecting rod necks there are, the more parts the pectoral fin is divided into along the chord direction, and the closer it is to the flexible pectoral fins of a manta ray. Gears are directly set on the crankshaft, and the servo drives the bearings through the bevel gears, which makes the transmission simple and takes up little space.

[0014] (2) The crankshaft and housing fixing device includes a crankshaft bearing fixing frame and a seat bearing.

[0015] (3) The crankshaft and frame connection device includes a connecting rod cap, a connecting rod body, and a primary frame. The connecting rod cap and the connecting rod body are connected by bolts, and the connecting rod body and the frame are connected using a telescopic structure to save space.

[0016] The two balancing blocks are connected by a connecting journal to form a U-shaped structure; multiple U-shaped structures are fixedly connected by a main journal to form a crankshaft; the large bevel gear is installed on the main journal; and the crankshaft is fixed to the housing through a seat bearing and a crankshaft bearing fixing frame.

[0017] The pectoral fin skeleton device includes a multi-stage skeleton, leaf springs, micro-seat bearings, skeleton bearing fixing frames, connecting rod bodies, and connecting rod covers. The multi-stage skeletons are connected by leaf springs, so that the flapping wings produce passive deformation when moving in the water. The one close to the shell is named the first-stage skeleton. A sleeve with an extension rod is fixed on one side of the first-stage skeleton for installing the connecting rod body. The other end of the connecting rod body is connected to the connecting rod neck through a fixed connecting rod cover. The skeleton bearing fixing frame is fixed to the shell, and the extension rod is fixed to the shell through a micro-seat bearing and skeleton bearing fixing frame. The surface of the multi-stage skeleton is provided with a skin support.

[0018] The multiple U-shaped structures have different sizes; the angles formed by the two balance blocks of each U-shaped structure are different; the movement amplitudes of the flapping wings of the bionic manta ray are different at different positions. By changing the size and angle of the U-shaped structure, the mechanism is made more consistent with the movement state of the flapping wings of the manta ray, thereby improving the degree of bionics.

[0019] Furthermore, the dimensions of the multiple U-shaped structures and the angle formed by the two balancing blocks of each U-shaped structure are obtained by the following method:

[0020] Construct the kinematic equations for the manta ray's pectoral fin:

[0021]

[0022] y(x f ,y f ,t)=y f

[0023]

[0024] f(y f ,t)=sin(ωt+Ky f / b)

[0025] Among them, (x f ,y f) is the neutral plane of the pectoral fin; (x, y, z) are the deformation coordinates of the fin at a certain time t; (K, m, n, ω) are the fitting parameters, with n = 0.1342 m² and K = 2.23. Observations show that manta ray motion has a period of approximately 2.4 seconds, or a normal flapping frequency of 0.4 Hz. The three key features of this kinematic model are: spanwise deformation of bending, near-zero spanwise strain during deformation, and chord-wise traveling waves.

[0026] The kinematic equations for the manta ray's pectoral fins are used to derive the trajectory of each point on the manta ray's wings, allowing us to determine the states of points, lines, and surfaces at any given moment. For a crankshaft-rocker mechanism, the simplified mechanism consists of a crank with a sleeve extending through one end of the rocker. The formulas for calculating angles and dimensions are:

[0027] make but

[0028] Where α = α0 + ωt, where α is the angle, R is the radius of rotation of the U-shaped structure, and L is the distance between the crankshaft and the rocker's rotational center. After obtaining the angle values for the flapping wings at different positions and times, the optimized parameters of the mechanism are determined by comparing the calculated β values with the angle values of the kinematic curve trajectory.

[0029] The analysis results show that the radius of rotation of the U-shaped structure increases from front to back along the flapping wing, and the angle formed by the two balance blocks of each U-shaped structure becomes increasingly larger. This is consistent with the movement patterns of manta rays, where the distal end of the manta ray deforms more significantly and the front end drives the rear end.

[0030] The pectoral fin skeleton device includes a primary skeleton and a secondary skeleton connection device, and a primary skeleton and a shell fixing device. Among them, the primary skeleton is close to the crankshaft skeleton, and the secondary skeleton is far away from the crankshaft skeleton. In the primary skeleton and the secondary skeleton connection device, the primary and secondary skeletons are connected by leaf springs to achieve a variable stiffness configuration, thereby realizing chord-wise motion deformation and achieving a large distal deformation effect when swimming in water; a skin support structure and a spring connection structure are provided on the skeleton to make the flexible skin more continuous during movement, wherein the skeleton support structure adopts a NACA0012 airfoil. The primary skeleton and the shell fixing device provide a rotation fulcrum for the pectoral fin movement, making the overall structure more stable.

[0031] Furthermore, the steering gear drive device includes a steering gear, a steering wheel, a small bevel gear, and a steering gear bracket. The steering gear bracket is fixedly connected to the housing, and the small bevel gear is connected to the steering gear through the steering wheel and cooperates with the large bevel gear on the crankshaft to realize the function of the steering gear driving the crankshaft.

[0032] Furthermore, the flexible skin is wrapped around the outside of the frame and is adhered and fixed to the supporting structure on the frame.

[0033] Furthermore, the rotation center of the crankshaft is flush with the surface of the housing, and both ends of the crankshaft are fixed to the housing through seat bearings.

[0034] Furthermore, the pectoral fin skeleton device is symmetrically placed in the shell, and the skeleton part is a rigid material, which is carbon fiber.

[0035] Furthermore, the flexible skin is cast by a mold.

[0036] The present invention discloses a variable-stiffness manta ray-like flexible flapping wing propulsion device with spanwise motion capability. The device operates as follows: a servo drives a crankshaft through a bevel gear; a connecting rod body is fixedly connected to a connecting rod cap, forming a telescopic structure with a frame having a sleeve at one end. The sleeve frame, which is fixed with an extension rod, is fixed to a housing via the extension rod and a miniature seat bearing, thereby forming a rotational fulcrum. The crankshaft transmits power to the frame through the telescopic structure, and the frame rotates around the rotational fulcrum, thereby driving the frame to move. Passive deformation of the flapping wing in water is achieved through the flexible connection of a leaf spring, thereby achieving spanwise passive deformation of the flapping wing. A flexible skin covers the entire frame device, making the overall motion more coherent. By controlling the rotational speed of the servo, the flapping frequency of the entire flexible flapping wing and the motion direction of the entire bionic robot can be controlled. By adjusting the number of crankshaft connecting rod necks, the rotation radius, and the angle, the motion of the manta ray-like flexible flapping wing can be simulated. Manta rays use the MPF movement mode, which has the following characteristics during movement: (1) the front end drives the pectoral fins to move, and the distal end deforms greatly; (2) when the pectoral fins flap from top to bottom, the distal end deforms upward; when they flap from bottom to top, the distal end deforms downward.

[0037] Beneficial effects:

[0038] 1. The present invention discloses a variable-stiffness manta ray-like flexible flapping-wing propulsion device with spanwise motion capability. By optimizing the number, rotation radius, and included angle of the crankshaft connecting rod necks, the device achieves different motion amplitudes for each part of a bionic fish's pectoral fin, thereby realizing spanwise motion. A variable-stiffness design is achieved by connecting the skeleton plates with leaf springs, thereby enabling spanwise deformation. The overall structural optimization ensures both a simple and stable structure and a high degree of biomimetic properties, thereby improving the reliability and practicality of the variable-stiffness manta ray-like flexible flapping-wing propulsion device.

[0039] 2. Compared with traditional propeller propulsion, the variable stiffness manta ray-like flexible flapping wing propulsion device with aspect-direction motion function disclosed in the present invention can generate lower noise and better concealment using both BCF and MPF propulsion modes. Manta rays use the MPF motion mode, which has the following characteristics during motion: (1) The front end drives the pectoral fins to move, and the distal end deforms significantly; (2) When the pectoral fins flap from top to bottom, the distal end deforms upward; when they flap from bottom to top, the distal end deforms downward.

[0040] 3. This invention discloses a variable-stiffness manta ray-like flexible flapping wing propulsion device with aspect-wise motion. The connecting rod cap and connecting rod body are connected by bolts, and the connecting rod body and frame are connected using a telescopic structure, which saves space. The frame support structure adopts a NACA0012 airfoil. The primary frame and shell fixing device provide a rotational fulcrum for the pectoral fin movement, making the overall structure more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a structural diagram of a variable-rigidity manta ray-like flexible flapping-wing propulsion device with aspect-direction motion function according to the present invention;

[0042] Figure 2 This is a structural diagram of a variable-rigidity manta ray-like flexible flapping-wing propulsion device with aspect-wise motion capability according to the present invention;

[0043] Figure 3 The housing of the present invention;

[0044] Figure 4 The crankshaft drive device of the present invention;

[0045] Figure 5 The crankshaft in the crankshaft drive device of the present invention;

[0046] Figure 6 This is an exploded view of the crankshaft and housing fixing device in the crankshaft drive device of the present invention;

[0047] Figure 7 This is an exploded view of the crankshaft and frame connection device in the crankshaft drive device of the present invention;

[0048] Figure 8 It is the pectoral fin skeleton device of the present invention;

[0049] Figure 9 This is an exploded view of the primary frame and the shell fixing device in the pectoral fin frame device of the present invention;

[0050] Figure 10 It is an exploded view of the driving steering gear device of the present invention.

[0051] Figure 11 A schematic diagram of the mechanism of the present invention.

[0052] 1-housing, 101-crankshaft fixing groove, 102-skeleton fixing groove, 2-crankshaft bearing fixing bracket, 3-bearing seat, 4-crankshaft, 401-connecting rod neck, 402-large bevel gear, 403-main shaft neck, 404-balance block, 5-first-stage skeleton, 6-leaf spring, 7-second-stage skeleton, 8-miniature bearing seat, 9-skeleton bearing fixing bracket, 10-connecting rod body, 11-connecting rod cover, 12-servo gear bracket, 13-servo gear, 14-flexible skin, 15-steering wheel, 16-small bevel gear. DETAILED DESCRIPTION

[0053] The following description with reference to the accompanying drawings is exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0054] See Figures 1 to 8 The present embodiment discloses a variable-stiffness manta ray-like flexible flapping wing propulsion device with aspect-wise motion function, comprising a housing 1, a crankshaft fixing slot 101, a frame fixing slot 102, a crankshaft bearing fixing bracket 2, a seat bearing 3, a crankshaft 4, a connecting rod neck 401, a large bevel gear 402, a main journal 403, a balancing weight 404, a primary frame 5, a leaf spring 6, a secondary frame 7, a miniature seat bearing 8, a frame bearing fixing bracket 9, a connecting rod body 10, a connecting rod cover 11, a servo bracket 12, a servo 13, a skin 14, a steering wheel 15, and a small bevel gear 16.

[0055] Combine Figure 1-10 The installation method of the mechanism is described as follows: the crankshaft drive device includes a crankshaft 4, a crankshaft and housing fixing device, and a crankshaft and frame connecting device; the housing 1 structure includes a cabin, a crankshaft fixing groove 101, and a frame fixing groove 102. The crankshaft 4 cooperates with the seat bearing 3, and the seat bearing 3 is fixed in the crankshaft fixing groove 101 through the crankshaft bearing fixing frame 2, thereby completing the fixation of the crankshaft 4; the connecting rod body 10 and the connecting rod cover 11 are combined with the crankshaft connecting rod neck 403 by bolts, and the connecting rod body 10 and the primary frame 5 form a telescopic Structure; the primary skeleton and shell fixing device consists of a primary skeleton 5, a micro-seat bearing 8, and a skeleton bearing fixing frame 9. The primary skeleton 5 cooperates with the micro-seat bearing 8, and the micro-seat bearing 8 is placed in the skeleton fixing groove 102 and fixed by the skeleton bearing fixing frame 9; the overall composition of the primary skeleton 5 and the secondary skeleton 7 conforms to the shape of the manta ray pectoral fin in a top view, and the supporting structure on the skeleton is made of a NACA0012 airfoil, which gradually decreases from the root to the distance; the flexible skin is attached to the skeleton.

[0056] The pectoral fin skeleton device includes a multi-stage skeleton, a leaf spring 6, a micro-seat bearing 8, a skeleton bearing fixing frame 9, a connecting rod body 10, and a connecting rod cover 11; the multi-stage skeletons are connected by leaf springs 6, so that the flapping wings produce passive deformation when moving in the water; the one close to the shell is named the first-level skeleton; a sleeve with an extension rod is fixed on one side of the first-level skeleton for installing the connecting rod body 10; the other end of the connecting rod body 10 is connected to the connecting rod neck 401 through a fixed connecting rod cover 11; the skeleton bearing fixing frame 9 is fixed to the shell, and the extension rod is fixed to the shell 1 through the micro-seat bearing 8 and the skeleton bearing fixing frame 9; the surface of the multi-stage skeleton is provided with a skin support,

[0057] The multiple U-shaped structures have different sizes; the angles formed by the two balance blocks 404 of each U-shaped structure are different; the movement amplitudes of the flapping wings of the bionic manta ray are different at different positions. By changing the size and angle of the U-shaped structure, the mechanism is made more consistent with the movement state of the flapping wings of the manta ray, thereby improving the degree of bionics.

[0058] The dimensions of the multiple U-shaped structures and the angle formed by the two balancing blocks 404 of each U-shaped structure are obtained by the following method:

[0059] Construct the kinematic equations for the manta ray's pectoral fin:

[0060]

[0061] y(x f ,y f ,t)=y f

[0062]

[0063] f(y f ,t)=sin(ωt+Ky f / b)

[0064] Among them, (x f ,y f ) is the neutral plane of the pectoral fin; (x, y, z) is the deformation coordinate of the pectoral fin at a certain time t; (K, m, n, ω) is the fitting parameter, and n is taken as 0.1342m 2 , K = 2.23. Manta ray motion has been observed to have a period of approximately 2.4 seconds, or a normal flapping frequency of 0.4 Hz. The three key features of this kinematic model are: spanwise deformation of the bend, near-zero spanwise strain during deformation, and chord-wise traveling waves.

[0065] The kinematic equations for the manta ray's pectoral fins are used to derive the trajectory of each point on the manta ray's wings, allowing us to determine the states of points, lines, and surfaces at any given moment. For a crankshaft-rocker mechanism, the simplified mechanism consists of a crank with a sleeve extending through one end of the rocker. The formulas for calculating angles and dimensions are:

[0066] make but

[0067] Where α = α i +ωt,α is the angle value, α i is the initial angle of the i-th fin ray, ω is the crankshaft angular velocity, R is the rotation radius of the U-shaped structure, and L is the distance between the crankshaft and the rocker's rotation center. After obtaining the flapping wing angle values at different positions and times, the optimized parameters of the mechanism are determined by comparing the calculated β values with the kinematic curve trajectory angle values.

[0068] Since the manta ray movement period T is 2.4s, By selecting appropriate values for d and α0, the angle β formed by the mechanism can be determined. Compare the calculated angle with the angle obtained from the kinematic equation and select the parameter with the smallest relative error. The calculated design parameters for this design are: d1 = 4.2, d2 = 3.6, d3 = 2.65, α1 = -100°, α2 = -122°, α3 = -140°. Taking L = 70mm, we obtain R1 = 16.67mm, R2 = 19.4mm, and R3 = 26.4mm.

[0069] The calculated results are characterized by a U-shaped structure whose rotation radius increases from front to back along the flapping wing, and an increasing angle between the two balance blocks of each U-shaped structure. This is consistent with the motion patterns of manta rays, where the distal end of the ray deforms more significantly and the front end drives the rear end.

[0070] Combine Figure 4 、 Figure 5 Analyze the chord-wise motion of the pectoral fins: Figure 5 The rotation radius of the connecting rod journal 401 of the crankshaft 4 shown increases from left to right, and the angles between the connecting rod journals are different, thereby achieving chord-wise movement of the pectoral fin.

[0071] Combine Figure 8 Analysis of the spanwise movement of the pectoral fins: The primary skeleton 5 and the secondary skeleton 7 are connected by a leaf spring 6. When the mechanism swims in the water, due to the resistance of the water, the secondary skeleton will produce corresponding passive deformation, and the deformation will increase as it is farther away from the root, thereby realizing the spanwise movement of the pectoral fins, which is consistent with the biological movement characteristics of manta rays.

[0072] This embodiment discloses a variable-stiffness manta ray-like flexible flapping wing propulsion device with spanwise motion. The device operates as follows: a servo 13 drives a crankshaft 4 through a bevel gear. A connecting rod 10 is fixedly connected to a connecting rod cap 11, forming a telescopic structure with a frame having a sleeve at one end. The sleeve frame, which is fixed with an extension rod, is fixed to a housing 1 via the extension rod and a miniature seated bearing 8, thereby forming a pivot point. The crankshaft 4 transmits power to the frame through the telescopic structure, and the frame rotates around the pivot point, thereby driving the frame's motion. The flapping wing is passively deformed in water through the flexible connection of a leaf spring 6, thereby achieving spanwise deformation. A flexible skin 14 covers the entire frame device, making the overall motion more coherent. By controlling the rotation speed of the servo 13, the flapping frequency of the entire flexible flapping wing and the movement direction of the entire bionic robot can be controlled. By adjusting the number, rotation radius, and angle of the crankshaft 4 connecting rod neck 401, the chord-wise movement of the flapping wing can be achieved, thereby imitating the movement mode of the flexible flapping wing of the manta ray. The manta ray adopts the MPF movement mode, which has the following characteristics during the movement process: (1) the front end drives the pectoral fin to move, and the distal end deforms greatly; (2) when the pectoral fin flaps from top to bottom, the distal end deforms upward; when it flaps from bottom to top, the distal end deforms downward.

[0073] The above specific description further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A variable stiffness manta ray-like flexible flapping wing propulsion device with aspect-wise motion capability, characterized by: By adopting a single driver to realize complex spanwise flexible flapping motion, the steering gear (13) rotates to realize the driving of the crankshaft (4) through the bevel gear, thereby driving the entire device to move; using a leaf spring (6) to connect the skeleton to realize the variable stiffness configuration of the skeleton part, so that the device can realize passive deformation through the action of water when swimming in the water, thereby realizing spanwise motion deformation; by optimizing the rotation radius, phase difference and number of the connecting rod neck (401) of the crankshaft (4), the pectoral fin is divided to realize spanwise motion deformation; the skeleton device is combined with the airfoil to make a support structure, thereby supporting and connecting the flexible skin (14); The variable stiffness manta ray-like flexible flapping wing propulsion device with aspect-wise motion function comprises a housing (1), a crankshaft drive device, a pectoral fin skeleton device, a drive steering gear device, and a flexible skin (14); The housing (1) includes a cabin, a crankshaft fixing groove (101), and a frame fixing groove (102); a plurality of grooves are provided inside the cabin for accommodating a driving steering gear device and a crankshaft driving device, and providing sufficient space for installing various sensors and a center of gravity adjustment structure; the crankshaft fixing groove (101) is used to place a seat bearing (3) and fix the bearing via a crankshaft bearing fixing frame (2); the frame fixing groove (102) is used to place a miniature seat bearing (8) and fix the bearing via a frame bearing fixing frame (9); the housing portion is made of waterproof material; The crankshaft drive device is fixed in the crankshaft fixing groove (101) of the housing (1) and is used to connect to the pectoral fin frame device; the pectoral fin frame device is symmetrically arranged on both sides of the housing; the driving steering gear device is fixed on the housing (1) and is used to provide power; the flexible skin (14) covers the pectoral fin frame device and moves with the frame; The crankshaft drive device comprises a crankshaft (4), a crankshaft and housing fixing device, and a crankshaft and frame connecting device; The crankshaft optimization includes a connecting rod neck (401), a main journal (403), a balancing block (404) and a large bevel gear (402), wherein the connecting rod neck (401) is provided in plurality; the large bevel gear (402) is directly provided on the crankshaft (4), and the steering gear (13) drives the crankshaft (4) through the bevel gear; The crankshaft and housing fixing device includes a crankshaft bearing fixing frame (2) and a seat bearing (3); The crankshaft and frame connecting device comprises a connecting rod body (10), a connecting rod cover (11), and a primary frame (5); the connecting rod cover (11) and the connecting rod body (10) are connected by bolts, and the connecting rod body (10) and the frame are connected by a telescopic structure; Two balancing blocks (404) are connected via a connecting rod neck (401) to form a U-shaped structure; a plurality of U-shaped structures are fixedly connected via a main shaft neck (403) to form a crankshaft (4); a large bevel gear (402) is mounted on the main shaft neck (403); and the crankshaft (4) is fixed to the housing (1) via a seat bearing (3) and a crankshaft bearing fixing frame (2); The pectoral fin skeleton device comprises a multi-stage skeleton, a leaf spring (6), a micro-seat bearing (8), a skeleton bearing fixing frame (9), a connecting rod body (10), and a connecting rod cover (11); the multi-stage skeletons are connected by the leaf spring (6), so that the flapping wing generates passive deformation when moving in water; the one close to the shell is named the first-stage skeleton; a sleeve with an extension rod is fixed on one side of the first-stage skeleton for mounting the connecting rod body (10); the other end of the connecting rod body (10) is connected to the connecting rod neck (401) through a fixed connecting rod cover (11); the skeleton bearing fixing frame (9) is fixed to the shell, and the extension rod is fixed to the shell (1) through the micro-seat bearing (8) and the skeleton bearing fixing frame (9); the surface of the multi-stage skeleton is provided with a skin support; The pectoral fin skeleton device comprises a primary skeleton and a secondary skeleton connection device, and a primary skeleton and a shell fixing device; wherein the primary skeleton (5) is close to the crankshaft skeleton, and the secondary skeleton (7) is far away from the crankshaft skeleton; in the primary skeleton and the secondary skeleton connection device, the primary and secondary skeletons are connected by a leaf spring (6) to realize a variable stiffness configuration, thereby realizing spanwise motion deformation; a skin support structure and a spring connection structure are provided on the skeleton, so that the flexible skin is more continuous when moving, wherein the skeleton support structure adopts a NACA0012 airfoil; the primary skeleton (5) and the shell fixing device provide a rotation fulcrum for the pectoral fin movement; The multiple U-shaped structures have different sizes; the angles formed by the two balancing blocks (404) of each U-shaped structure are different; the movement amplitudes of the flapping wings of a bionic manta ray are different at different positions; by changing the size and angle of the U-shaped structure, the mechanism is made more consistent with the movement state of the flapping wings of a manta ray.

2. The variable stiffness manta ray-like flexible flapping wing propulsion device with aspect ratio motion function according to claim 1, characterized in that: The driving steering gear device comprises a steering gear bracket, a steering gear (13), a steering wheel (15) and a small bevel gear (16); the steering gear bracket is fixedly connected to the housing (1), the small bevel gear (16) is connected to the steering gear (13) through the steering wheel (15), and cooperates with the large bevel gear (402) on the crankshaft (4), thereby realizing that the steering gear (13) drives the crankshaft (4).

3. The variable stiffness manta ray-like flexible flapping wing propulsion device with aspect ratio motion function according to claim 2, characterized in that: The flexible skin (14) is wrapped around the outside of the frame and is adhered and fixed to the supporting structure on the frame; The rotation center of the crankshaft (4) is flush with the surface of the housing, and both ends of the crankshaft (4) are fixedly connected to the housing (1) via seated bearings (3).

4. The variable stiffness manta ray-like flexible flapping wing propulsion device with aspect ratio motion function according to claim 3, characterized in that: The pectoral fin skeleton device is symmetrically placed in the shell (1), and the skeleton part is made of carbon fiber; The flexible skin is cast from a mold.

Images