A bionic pectoral fin with variable stiffness, a bionic manta ray robot and its control method

Abstract

The present invention belongs to the technical field related to underwater bionic robots and discloses a variable stiffness bionic pectoral fin, a bionic manta ray robot, and a control method thereof. The variable stiffness bionic pectoral fin includes a fin ray module and a flexible skin. The fin ray module includes an exoskeleton, a flapping servo, and a restraining structure. The flapping servo is used to drive the exoskeleton to rotate, thereby driving the flexible skin to oscillate up and down. The restraining structure is arranged along the span of the exoskeleton and is connected to the exoskeleton. It has an unconstrained state and a constrained state. When the restraining structure is in the unconstrained state, it does not constrain the rotation of the exoskeleton, causing the variable stiffness bionic pectoral fin to be in a rigid flapping mode. When the restraining structure is in the constrained state, it constrains the rotation of the exoskeleton. By restricting the rotation of the exoskeleton, the variable stiffness bionic pectoral fin is placed in a flexible warping mode. The present invention structurally expands the functions of the bionic pectoral fin, increases the diversity of movement, and achieves structural changes in the hydrodynamic performance of the flexible skin.

Description

Technical Field

[0001] The present invention belongs to the technical field related to underwater bionic robots, and more specifically, relates to a bionic pectoral fin with variable stiffness, a bionic manta ray robot and a control method thereof. Background Art

[0002] Manta rays belong to the order Rayiformes and are the largest of over 500 species of rays. Unlike conventional fish, which use a body / tail fin propulsion system, manta rays utilize a medial / opposed fin propulsion system. This propulsion system offers excellent stability, low-speed maneuverability, and high propulsion efficiency. Manta rays' exceptional swimming abilities have attracted the attention of numerous researchers both domestically and internationally, leading to the development of numerous biomimetic manta ray robotics.

[0003] Research has shown that the broad, flat pectoral fins of manta rays are key to their efficient swimming. However, the pectoral fins of existing bionic manta ray robots have a simple structural design and a single motion function. They are usually only used to support and drive the flexible skin to flap up and down, without the ability to structurally change the hydrodynamic performance of the flexible skin. To meet the complex underwater environment and diverse mission requirements, traditional pectoral fins usually require complex control algorithms to adjust variables such as the pectoral fin's flapping amplitude, flapping frequency, flapping phase difference, and flapping offset in real time, so that the flexible skin produces different motion states, increasing the complexity and instability of the system.

[0004] Existing bionic manta ray robots have the problems of simple pectoral fin structure design, single motion function, and lack of the ability to structurally change the hydrodynamic performance of the flexible skin. Summary of the Invention

[0005] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a variable stiffness bionic pectoral fin, a bionic manta ray robot and a control method thereof, which are used to solve the problems of the existing bionic manta ray robot, such as the simple pectoral fin structure design, single motion function, and the inability to structurally change the hydrodynamic performance of the flexible skin.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a variable stiffness bionic pectoral fin is provided for installation on both sides of a robot skeleton of a bionic fish robot, comprising a fin ray module and a flexible skin; the fin ray module comprises an exoskeleton, a flapping servo, and a restraining structure; the exoskeleton is rotatably arranged relative to the robot skeleton; the flapping servo is mounted on the robot skeleton and is transmission-connected to the exoskeleton; the flexible skin covers the exoskeleton; the flapping servo is used to drive the exoskeleton to rotate, thereby driving the flexible skin to achieve up and down oscillation;

[0007] The restriction structure is extended along the span direction of the exoskeleton and is connected to the exoskeleton. The restriction structure has an unconstrained state and a constrained state. When the restriction structure is in the unconstrained state, the rotation of the exoskeleton is not constrained, so that the variable stiffness bionic pectoral fin is in a rigid flapping mode; when the restriction structure is in the constrained state, the rotation of the exoskeleton is constrained. By limiting the rotation of the exoskeleton, the variable stiffness bionic pectoral fin is in a flexible warping mode.

[0008] According to the variable stiffness bionic pectoral fin provided by the present invention, the exoskeleton includes side panels extending along the span direction and a plurality of connecting panels arranged along the span direction, wherein the connecting panels are connected to the side panels; the limiting structure includes an inner core panel, a two-degree-of-freedom base, a fixed seat, and a stiffness-variable enabling servo, wherein the inner core panel extends along the span direction and is rotatably connected to the connecting panels about the span direction;

[0009] The inner core plate is rotatably connected to the two-degree-of-freedom base around a first direction, the two-degree-of-freedom base is rotatably connected to the fixed base around a second direction, the fixed base is fixed to the robot frame, and the stiffness change enabling servo is fixed to the robot frame and is transmission-connected to the two-degree-of-freedom base, and is used to drive the two-degree-of-freedom base to rotate around the second direction; wherein the first direction is perpendicular to the second direction, and the second direction is a span direction;

[0010] When the restriction structure is in an unconstrained state, the first direction is consistent with the rotation axis of the side plate; when the restriction structure is in a constrained state, the first direction intersects or is perpendicular to the rotation axis of the side plate.

[0011] According to the variable stiffness bionic pectoral fin provided by the present invention, the side panels include an upper side panel and a lower side panel correspondingly arranged above and below, the connecting panel is connected between the upper side panel and the lower side panel, and the inner core panel is located between the upper side panel and the lower side panel;

[0012] The upper side plate and the lower side plate are connected at the fin tip through a fin tip connecting block and are rotatably connected to a transmission mechanism at the fin root. The flapping servo is connected to the transmission mechanism and is used to simultaneously drive the upper side plate and the lower side plate to flap up and down through the transmission mechanism.

[0013] According to the variable stiffness bionic pectoral fin provided by the present invention, the transmission mechanism is a parallelogram transmission mechanism, the upper side plate and the lower side plate are rotatably connected to the upper and lower edges of the parallelogram transmission mechanism on the same side at the fin root, and support frames are respectively provided on both sides of the parallelogram transmission mechanism along the chord direction, and the support frames are connected to mounting pins, and the mounting pins pass through the transmission rod of the parallelogram transmission mechanism located between the upper and lower planes so that the parallelogram transmission mechanism is mounted on the mounting pins, and the support frames are fixed to the robot frame;

[0014] A tooth structure is provided on the transmission rod on at least one side of the parallelogram transmission mechanism along the chord direction, and a tooth structure is also provided on the output shaft of the flapping servo. The flapping servo drives the transmission rod to rotate around the mounting pin through the engagement of the tooth structure, so that the parallelogram transmission mechanism is deformed and then drives the upper side plate and the lower side plate to flap up and down synchronously.

[0015] According to the variable stiffness bionic pectoral fin provided by the present invention, the fixing seat is located inside the parallelogram transmission mechanism, and the fixing seat is fixedly mounted to the robot frame via the mounting pins.

[0016] According to the variable stiffness bionic pectoral fin provided by the present invention, the two-degree-of-freedom base is transmission-connected to the stiffness-variable enabling servo via a flexible shaft.

[0017] According to a second aspect of the present invention, a bionic manta ray robot is provided, comprising the variable stiffness bionic pectoral fin described in any one of the above items, and also comprising a robot frame, wherein the variable stiffness bionic pectoral fins are respectively provided on both sides of the robot frame.

[0018] According to the bionic manta ray robot provided by the present invention, the robot skeleton includes a bottom plate, a top plate, a connecting column and a buoyancy bottle, the bottom plate and the top plate are connected by the connecting column, and the buoyancy bottle is fixed on the top plate.

[0019] The bionic manta ray robot provided by the present invention also includes a tail fin module and a controller, wherein the tail fin module includes a left tail fin plate, a right tail fin plate, a left servo, a right servo, and a tail fin seat; the left tail fin plate is connected to the left servo, and the right tail fin plate is connected to the right servo; the left servo and the right servo are both fixed to the tail fin seat; and the tail fin seat is fixed to the tail of the robot frame;

[0020] The controller is installed at the front of the robot frame and is connected to the fin ray module and the tail fin module of the variable rigidity bionic pectoral fin through signal lines.

[0021] According to a third aspect of the present invention, a control method for a bionic manta ray robot is provided. Based on any of the above-mentioned bionic manta ray robots, the control method comprises:

[0022] When the movement speed needs to be increased, the variable stiffness bionic pectoral fins on both sides are controlled to be in the rigid flapping mode;

[0023] When the endurance performance needs to be improved, the variable stiffness bionic pectoral fins on both sides are controlled to be in the flexible warping mode;

[0024] When flipping or yaw is required, the variable stiffness bionic pectoral fin on one side is controlled to be in a rigid flapping mode, and the variable stiffness bionic pectoral fin on the other side is controlled to be in a flexible warping mode.

[0025] In general, compared with the prior art, the above technical solutions conceived by the present invention provide variable stiffness bionic pectoral fins, bionic manta ray robots and control methods thereof:

[0026] 1. A rotatable exoskeleton enables the exoskeleton to drive the flexible skin to flap up and down to capture hydrodynamic forces under the drive of flapping servos. A restraining structure is connected to the exoskeleton and is configured to have unconstrained and constrained states relative to the exoskeleton. This structurally achieves variable stiffness of the bionic robot's pectoral fins. The variable stiffness bionic pectoral fins produce two motion modes: rigid rotation and flexible warping, at different stiffness levels, mimicking the motion states of pelagic and benthic manta rays, respectively. Rigid rotation contributes to greater dynamic performance, while flexible warping improves motion efficiency and endurance. This structurally expands the functionality of the bionic pectoral fins, increases the diversity of motion, and achieves structural changes in the hydrodynamic performance of the flexible skin.

[0027] 2. The proposed exoskeleton includes an upper and lower plate configuration, resulting in a triangular cross-section and improved stability. A parallelogram transmission mechanism is proposed, enabling synchronous drive of the upper and lower plates, with a stable and reliable connection for ease of setup. The proposed restraining structure is an inner core plate, connected to a variable-stiffness-enabling servo via a two-degree-of-freedom base and a fixed seat. Switching between two modes of control can be achieved through the rotation of the inner core plate, resulting in a simple, reliable structure and easy control.

[0028] 3. The bionic manta ray robot's variable-stiffness bionic pectoral fin design not only allows the stiffness of both pectoral fins to be changed simultaneously to achieve different motion modes to meet mission requirements for high maneuverability and long endurance, but also allows the stiffness of only one pectoral fin to be changed to achieve differentiated dynamic performance on both sides, enhancing motion diversity.

[0029] 4. This design structurally expands the pectoral fin function of the existing bionic manta ray robot. It has a simple structure and is easy to manufacture, which helps it adapt to complex environments and multiple tasks under simple control algorithms. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 3D bottom-up structural diagram of a bionic manta ray robot with bionic pectoral fins with variable stiffness according to an embodiment of the present invention;

[0031] Figure 2 for Figure 1 A schematic diagram of the three-dimensional structure of the robot skeleton and tail fin module in the bionic manta ray robot shown;

[0032] Figure 3 for Figure 1 A top view of the layout of the bottom plate and fin modules in the bionic manta ray robot;

[0033] Figure 4 for Figure 1 Schematic diagram of the three-dimensional structure of the fin module in the bionic manta ray robot;

[0034] Figure 5 for Figure 1 The side view structural diagram of the fin module in the bionic manta ray robot shown;

[0035] Figure 6 for Figure 4 Schematic diagram of the local structure of the transmission connection between the parallelogram transmission mechanism and the flapping servo in the fin module shown;

[0036] Figure 7 for Figure 4 A schematic diagram of the partial structure of the transmission connection between the rotatable inner core and the stiffness-variable enabling servo in the fin ray module shown;

[0037] Figure 8 for Figure 7 Schematic diagram of the three-dimensional structure comparison under two stiffness modes in the rotatable inner core shown;

[0038] Figure 9 for Figure 4 Schematic diagram comparing the motion shapes of the fin module in the rigid rotation mode and the flexible warping mode;

[0039] Figure 10 for Figure 4 Schematic diagram of the specific installation of the parallelogram transmission mechanism and the fixing seat in the fin module shown;

[0040] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0041] 1. Robot skeleton; 2. Fin ray module; 3. Tail fin module; 4. Controller; 5. Flexible skin; 1-1. Bottom plate; 1-2. Top plate; 1-3. Connecting column; 1-4. Buoyancy bottle; 2-1. Exoskeleton; 2-2. Support frame; 2-3. Flapping servo; 2-4. Stiffness-variable enabling servo; 2-5. Mounting pin; 2-11. Upper side plate; 2-12. Lower side plate; 2-13. Fin tip connection block; 2 -14, connecting plate; 2-15, parallelogram transmission mechanism; 2-151, upper plane; 2-152, lower plane; 2-153, transmission rod; 2-16, flapping gear; 2-21, inner core plate; 2-22, two-degree-of-freedom base; 2-23, fixed seat; 2-24, flexible shaft; 3-1, left tail fin plate; 3-2, left servo; 3-3, right tail fin plate; 3-4, right servo; 3-5, tail fin seat. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0043] See also Figure 1 , this embodiment 1 provides a variable stiffness bionic pectoral fin for being installed on both sides of the robot skeleton 1 of a bionic fish robot, the variable stiffness bionic pectoral fin comprising a fin module 2 and a flexible skin 5; the fin module 2 comprises an exoskeleton 2-1, a flapping servo 2-3 and a restriction structure, the exoskeleton 2-1 is rotatably arranged relative to the robot skeleton 1, the flapping servo 2-3 is installed on the robot skeleton 1 and is transmission-connected to the exoskeleton 2-1, the flexible skin 5 covers the exoskeleton 2-1, and the flapping servo 2-3 is used to drive the exoskeleton 2-1 to rotate to drive the flexible skin 5 to oscillate up and down.

[0044] In this embodiment, the robot skeleton 1 serves as a support frame for the remaining structural components of the bionic fish robot. Two fin ray modules 2 are mounted on the left and right sides of the robot skeleton 1. These fin ray modules 2 drive the flexible skin 5 to flap up and down in the water, capturing hydrodynamic forces. The interaction between the flexible skin 5 and the water flow propels the robot forward. Flapping servos 2-3 are connected to the fin ray exoskeleton 2-1 to achieve this flapping motion.

[0045] This embodiment further considers that manta rays capable of ocean migration in nature have relatively rigid pectoral fins for greater dynamic performance, while benthic manta rays have relatively soft pectoral fins for higher movement efficiency. Based on this, it is proposed to design bionic pectoral fins with variable stiffness to enhance the diversity of movement. Specifically, a restriction structure is provided, which is arranged to extend along the span of the exoskeleton 2-1 and is connected to the exoskeleton 2-1. The restriction structure has an unconstrained state and a constrained state. When the restriction structure is in the unconstrained state, the restriction structure does not constrain the rotation of the exoskeleton 2-1. The exoskeleton 2-1, driven by the flapping servo 2-3, drives the flexible skin 5 to vibrate normally up and down, so that the bionic pectoral fin with variable stiffness is in a rigid flapping mode.

[0046] When the restriction structure is in the restriction state, the restriction structure constrains the rotation of the exoskeleton 2-1, forming resistance to the rotation of the exoskeleton 2-1. By restricting the rotation of the exoskeleton 2-1, a pulling force in the opposite direction is formed on the exoskeleton 2-1 when the flapping servo 2-3 drives the exoskeleton 2-1 to rotate, thereby making the variable stiffness bionic pectoral fin in a flexible warping mode, such as Figure 9 As shown in the figure, the side of the exoskeleton 2-1 is straight in the rigid flapping mode, while the side of the exoskeleton 2-1 is curved in the flexible warping mode. The variable stiffness fin ray module 2 helps to generate greater dynamic performance in rigid rotation, while in flexible warping, it helps to improve movement efficiency and endurance.

[0047] In some specific embodiments, reference Figure 3 and Figure 4 The exoskeleton 2-1 includes side panels extending along the span direction and multiple connecting panels 2-14 arranged along the span direction, and the connecting panels 2-14 are connected to the side panels; the limiting structure includes an inner core panel 1, a two-degree-of-freedom base 2, a fixed seat 3 and a stiffness change enabling servo 2-4, and the inner core panel 1 extends along the span direction and is rotatably connected to the connecting panels 2-14 around the span direction; the span direction is the direction in which the pectoral fin extends outward from the robot skeleton 1, and the chord direction is a direction perpendicular to the span direction. The exoskeleton 2-1 rotates around the chord direction at the root to achieve up and down flapping.

[0048] The inner core plate 1 is rotatably connected to the two-degree-of-freedom base 2 in a first direction, and the two-degree-of-freedom base 2 is rotatably connected to the fixed base 3 in a second direction, thereby enabling the inner core plate 1 to rotate in two directions with two degrees of freedom. The fixed base 3 is fixed to the robot frame 1, and the stiffness change enabling servo 2-4 is fixed to the robot frame 1 and is in transmission connection with the two-degree-of-freedom base 2, and is used to drive the two-degree-of-freedom base 2 to rotate in the second direction; wherein the first direction and the second direction are perpendicular, and the second direction is the span direction;

[0049] When the limiting structure is in a non-constrained state, the first direction is consistent with the rotation axis of the side panel, so that the inner core panel 1 can rotate around the direction consistent with the rotation axis of the side panel, i.e., the chord direction, so that it can rotate together with the side panel without constraining the rotation of the side panel; when the limiting structure is in a constrained state, the first direction intersects or is perpendicular to the rotation axis of the side panel, so that the rotation axis of the inner core panel 1 is inconsistent with the rotation axis of the side panel, thereby constraining the rotation of the side panel. When the side panel rotates, a flexible mode will be formed due to the limiting constraint of the inner core panel 1. The specific orientation of the inner core panel 1 is as follows: Figure 8 The change in stiffness enables the servo 2-4 to drive the inner core plate 1 to rotate, thereby changing the stiffness and structural constraint state of the fin exoskeleton 2-1.

[0050] Specifically, refer to Figure 4 and Figure 5 The side panels include an upper side panel 2-11 and a lower side panel 2-12 correspondingly arranged above and below, the connecting panel 2-14 is connected between the upper side panel 2-11 and the lower side panel 2-12, and the inner core panel 1 is located between the upper side panel 2-11 and the lower side panel 2-12; specifically, with reference to Figure 6 The connecting plate 2-14 is connected with the upper side plate 2-11 at the top, that is, the upper side plate 2-11 is connected through the top of the connecting plate 2-14 and the upper side plate 2-11 can slide relative to the connecting plate 2-14; the connecting plate 2-14 is connected with the lower side plate 2-12 at the bottom, that is, the lower side plate 2-12 is connected through the bottom of the connecting plate 2-14 and the lower side plate 2-12 can slide relative to the connecting plate 2-14; the inner core plate 1 can be rotatably connected to the connecting plate 2-14 through a rotating bearing; multiple connecting plates 2-14 arranged along the span direction constrain and limit the inner core plate 1 at multiple positions.

[0051] The upper side plate 2-11 and the lower side plate 2-12 are connected at the fin tip through the fin tip connecting block 2-13, and are rotatably connected to the transmission mechanism at the fin root. The flapping servo 2-3 is connected to the transmission mechanism and is used to drive the upper side plate 2-11 and the lower side plate 2-12 to flap up and down at the same time through the transmission mechanism.

[0052] The flexible skin 5 is connected to the top of the exoskeleton 2-1; specifically, a support rod can also be connected to the top of the connecting plate 2-14, and the flexible skin 5 can be connected and fixed to the support rod by bonding or other means.

[0053] Specifically, refer to Figure 4 、 Figure 5 、 Figure 6 and Figure 10The transmission mechanism is a parallelogram transmission mechanism 2-15, and the upper side plate 2-11 and the lower side plate 2-12 can be rotatably connected to the upper and lower sides of the parallelogram transmission mechanism 2-15 on the same side at the fin root. The parallelogram transmission mechanism 2-15 is provided with support frames 2-2 on both sides along the chord direction. The support frames 2-2 are connected with mounting pins 2-5. The mounting pins 2-5 pass through the transmission rod 2-153 of the parallelogram transmission mechanism 2-15 located between the upper and lower planes, so that the parallelogram transmission mechanism 2-15 is mounted on the mounting pin 2-5 and can rotate around the mounting pin 2-5. The support frame 2-2 is fixed to the robot skeleton 1; the parallelogram transmission mechanism 2-15 has an upper plane 2-151, a lower plane 2-152 and four transmission rods 2-153 connected between the upper and lower planes.

[0054] The parallelogram transmission mechanism 2-15 is provided with a tooth structure on the transmission rod 2-153 on at least one side along the chord direction, and the output shaft of the flapping servo 2-3 is also provided with a tooth structure, namely a flapping gear 2-16. The flapping servo 2-3 drives the transmission rod 2-153 to rotate around the mounting pin 2-5 through the engagement of the tooth structure, so that the parallelogram transmission mechanism 2-15 is deformed and then drives the upper side plate 2-11 and the lower side plate 2-12 to flap up and down synchronously.

[0055] Furthermore, the fixing base 3 is located inside the parallelogram transmission mechanism 2-15, and the fixing base 3 is fixed to the robot frame 1 via the mounting pins 2-5. The mounting pins 2-5 pass through the support frame 2-2 and the transmission rod, and are then connected and fixed to the fixing base 3 by bolts or other means, thereby achieving the installation of the fixing base 3 on the robot frame 1.

[0056] refer to Figure 4 and Figure 5 In this specific embodiment, the fin exoskeleton 2-1 includes: an upper side plate 2-11, a lower side plate 2-12, a fin tip connecting block 2-13, a fin connecting plate and a parallelogram transmission mechanism 2-15; one side of the upper side plate 2-11 and the lower side plate 2-12 are fixed by the fin tip connecting block 2-13 and connected in the middle by a connecting plate 2-14; the other side of the upper side plate 2-11 and the lower side plate 2-12 are connected to the parallelogram transmission mechanism 2-15, forming a triangular outline, and flapping up and down accordingly. The rotatable inner core is installed on the central axis of the fin exoskeleton 2-1 and can rotate 360° around the axis. The stiffness change enables the servo 2-4 to be connected to the rotatable inner core and control the rotation angle of the inner core, thereby controlling the stiffness of the rotatable inner core.

[0057] Among them, the function of the connecting plate 2-14 is to constrain the relative positions of the upper side plate 2-11 and the lower side plate 2-12 while ensuring that the upper side plate 2-11 and the lower side plate 2-12 can flexibly move relative to each other; at the same time, the rotatable inner core is constrained on the central axis of the fin exoskeleton 2-1; this embodiment does not make a unique limitation on the number of connecting plates 2-14.

[0058] Specifically, refer to Figure 4 and Figure 5 The rotatable inner core includes: an inner core plate 1, a two-degree-of-freedom base 2 and a fixed seat 3; the inner core plate 1 is constrained on the central axis of the fin exoskeleton 2-1 by the connecting plate 2-14; Figure 7 The inner core plate 1 and the two-degree-of-freedom base 2 are hinged together by pins, and can rotate around the thickness direction of the inner core plate 1, that is, around the first reverse direction; the two-degree-of-freedom base 2 is constrained on the center line of the fixed seat 3 by bearings and can rotate around the center line, that is, the second direction.

[0059] In this embodiment, the exoskeleton 2-1 and the inner core plate 1 are elastic structures, specifically, structures capable of warping. For example, the inner core plate 1 can be made of materials such as carbon fiber and metal. Furthermore, the inner core plate 1 should be thinner in thickness and wider in width to maximize the difference in the cross-sectional moments of inertia in the two directions.

[0060] Specifically, refer to Figure 6 The root of the fin exoskeleton 2-1 adopts a parallelogram transmission mechanism 2-15 to ensure stable flapping under different stiffness; the parallelogram transmission mechanism 2-15 has a tooth structure, and the flapping servo 2-3 and the parallelogram transmission mechanism 2-15 are engaged and transmitted through a flapping gear 2-16, which is used to improve the smoothness of the transmission and reduce the off-load torque during the transmission process, thereby reducing the off-load torque during the movement process.

[0061] In some specific embodiments, the two-degree-of-freedom base 2 is transmission-connected to the stiffness-variable enabling servo 2-4 via a flexible shaft 4. The flexible shaft 4 is transmission-connected to the output shaft of the stiffness-variable enabling servo 2-4, and the flexible shaft 4 and the two-degree-of-freedom base 2 can be transmission-connected via a key structure. This is used to control the rotation angle of the inner core plate 1 to change the stiffness mode of the fin ray module 2; the fin ray module 2 changes the bending stiffness and flapping constraint of the exoskeleton 2-1 through the rotation of the inner core plate 1, achieving switching between a rigid flapping mode and a flexible warping mode.

[0062] refer to Figure 7 and Figure 8 The change in stiffness enables the rotation angle output by the servo 2-4 to be transmitted to the two-degree-of-freedom base 2 through the flexible shaft 4, driving the two-degree-of-freedom base 2 and the inner core plate 1 to rotate relative to the fixed base 3.

[0063] In this embodiment, the rotation angle of the inner core plate 1 is controlled within a range of 0 to 90°; when the angle is 0°, the hinge axis between the inner core plate 1 and the two-degree-of-freedom base 2 and the rotation axis of the parallelogram transmission mechanism 2-15 are axially parallel, so that the variable stiffness fin module 2 swings up and down with a larger cross-sectional moment of inertia, which is called a rigid rotation mode; when the angle is 90°, the hinge axis between the inner core plate 1 and the two-degree-of-freedom base 2 and the rotation axis of the parallelogram transmission mechanism 2-15 are axially displaced and perpendicular, and the inner core plate 1 and the two-degree-of-freedom base 2 cannot rotate. Therefore, the inner core plate 1 bends under the drive of the fin exoskeleton 2-1, and the variable stiffness fin module 2 performs an up and down warping motion with a smaller cross-sectional moment of inertia, which is called a flexible warping mode.

[0064] Specifically, refer to Figure 9 The variable stiffness fin module 2 presents a straight rotation trajectory in the rigid rotation mode; and a curved warping trajectory in the flexible warping mode.

[0065] Furthermore, the second embodiment provides a bionic manta ray robot, comprising the variable stiffness bionic pectoral fins described in any one of the above items, and also comprising a robot skeleton 1, wherein the variable stiffness bionic pectoral fins are respectively provided on both sides of the robot skeleton 1.

[0066] This embodiment proposes a bionic manta ray robot with a variable stiffness fin mechanism. By giving the pectoral fins a structurally variable stiffness function, it simulates the two motion modes of manta rays and achieves performance switching between high thrust and high efficiency under a simple control method, thereby expanding the motion function of the bionic manta ray robot and improving control convenience and stability.

[0067] Specifically, refer to Figure 1 This embodiment provides a bionic manta ray robot with bionic pectoral fins of variable stiffness, comprising a robot frame 1, a fin ray module 2, a tail fin module 3, and a controller 4 fixed to the robot frame 1, and a flexible skin 5 covering the fin ray module 2. The robot frame 1 includes a bottom plate 1-1, a top plate 1-2, connecting columns 1-3, and a buoyancy bottle 1-4. The bottom plate 1-1 and the top plate 1-2 are connected by the connecting columns 1-3, and the buoyancy bottle 1-4 is fixed to the top plate 1-2.

[0068] refer to Figure 2The robot skeleton 1 includes a bottom plate 1-1, a top plate 1-2, connecting columns 1-3, and buoyancy bottles 1-4. The bottom plate 1-1 is secured with a variable-stiffness bionic pectoral fin and tail fin module 3 and a controller 4, and is connected to the top plate 1-2 via connecting columns 1-3. Buoyancy bottles 1-4 are secured to the top plate 1-2 to provide underwater buoyancy for the robot, counteracting its gravity underwater. The number of connecting columns 1-3 and buoyancy bottles 1-4 may vary depending on the size and weight of the robot, and are not intended to be exclusive to each other in this embodiment.

[0069] The bionic manta ray robot also includes a tail fin module 3 and a controller 4. The tail fin module 3 includes a left tail fin plate 3-1, a right tail fin plate 3-3, a left servo 3-2, a right servo 3-4, and a tail fin seat 3-5. The left tail fin plate 3-1 is connected to the left servo 3-2, and its rotation angle is controlled by the left servo 3-2. The right tail fin plate 3-3 is connected to the right servo 3-4, and its rotation angle is controlled by the right servo 3-4. The left servo 3-2 and the right servo 3-4 are both fixed to the tail fin seat 3-5. The tail fin seat 3-5 is fixed to the tail of the robot frame 1. The left servo 3-2 and the right servo 3-4 are fixed to the tail of the base plate 1-1 through the tail fin seat 3-5. The left servo 3-2 and the right servo 3-4 are both fixed to the tail fin seat 3-5. The tail fin seat 3-5 is fixed to the base plate 1-1.

[0070] The controller 4 is installed at the front of the robot skeleton 1 and is connected to the fin ray module 2 and the tail fin module 3 of the variable rigidity bionic pectoral fin through signal lines.

[0071] The tail fin module 3 is fixed to the rear end of the robot frame 1 and is used to assist in adjusting the robot's posture during swimming. The controller 4 is installed at the front end of the base plate 1-1 and is connected to the variable-stiffness bionic pectoral and tail fin modules 3 via signal cables. In this embodiment, the left and right tail fins 3-1 and 3-3 can adjust their angles relative to the base plate 1-1 in real time via the left and right servos 3-2 and 3-4, respectively, during the robot's swimming process, assisting in adjusting the robot's pitch, yaw, and roll angles during forward swimming.

[0072] Furthermore, this third embodiment provides a control method for a bionic manta ray robot. Based on any of the above-mentioned bionic manta ray robots, the control method includes:

[0073] When the movement speed needs to be increased, the variable stiffness bionic pectoral fins on both sides are controlled to be in the rigid flapping mode;

[0074] When the endurance performance needs to be improved, the variable stiffness bionic pectoral fins on both sides are controlled to be in the flexible warping mode;

[0075] When flipping or yaw is required, the variable stiffness bionic pectoral fin on one side is controlled to be in a rigid flapping mode, and the variable stiffness bionic pectoral fin on the other side is controlled to be in a flexible warping mode.

[0076] In this embodiment, the rigid rotational mode helps to provide greater propulsion force for the bionic manta ray robot, allowing it to maneuver at high speed in wide waters; while the flexible warping mode is conducive to providing higher propulsion efficiency at low energy consumption, allowing it to perform long-term endurance movement in a given target water area; the structural mode switching helps to meet diversified task requirements under a simple control algorithm.

[0077] In this embodiment, the switching of stiffness modes can also occur differently on the left and right sides of the bionic manta ray robot; for example, when the left side is in a rigid rotation mode and the right side is in a flexible warping mode, the flapping power on the left side is large while the flapping power on the right side is small, causing the robot to roll and yaw to the right, which helps to enhance the robot's maneuverability and agility.

[0078] This embodiment discloses a bionic manta ray robot driven by a variable stiffness fin ray mechanism, belonging to the field of underwater bionic robots, comprising a robot skeleton 1 and a variable stiffness fin ray module 2, a tail fin module 3, a controller 4 and a flexible skin 5 arranged on the skeleton; the variable stiffness fin ray module 2 is composed of a fin ray exoskeleton 2-1, a rotatable inner core, a flapping servo 2-3 and a stiffness change enabling servo 2-4, the root of the fin ray exoskeleton 2-1 is connected to the flapping servo 2-3 through a parallelogram transmission mechanism 2-15, and is driven by the flapping servo 2-3 to perform Oscillating motion; the rotatable inner core is installed on the central axis of the fin ray exoskeleton and is composed of an inner core plate 1 and a two-degree-of-freedom base 2; the stiffness change enables the servo 2-4 to drive the two-degree-of-freedom base 2 to rotate, thereby driving the inner core plate 1 to rotate to change the cross-sectional inertia moment and rotation constraint state of the fin ray exoskeleton 2-1, so as to realize the switching of the two stiffness modes of rigid rotation and flexible warping of the pectoral fins on both sides of the robot; the rigid mode of the variable stiffness fin ray module 2 can enhance the power brought by the flapping and increase the movement speed, while the flexible mode helps to reduce the movement energy consumption and improve the endurance. This embodiment structurally expands the movement mode of the bionic manta ray robot, which is conducive to bringing more movement strategies to the bionic manta ray robot.

[0079] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A bionic pectoral fin with variable stiffness, used to be installed on both sides of the robot frame of a bionic fish robot, characterized in that: The robot comprises a fin ray module and a flexible skin; the fin ray module comprises an exoskeleton, a flapping servo, and a restraining structure; the exoskeleton is rotatably arranged relative to the robot frame; the flapping servo is mounted on the robot frame and is in transmission connection with the exoskeleton; the flexible skin covers the exoskeleton; the flapping servo is used to drive the exoskeleton to rotate so as to drive the flexible skin to oscillate up and down; The restriction structure is extended along the span direction of the exoskeleton and is connected to the exoskeleton. The restriction structure has an unconstrained state and a constrained state. When the restriction structure is in the unconstrained state, the rotation of the exoskeleton is not constrained, so that the variable stiffness bionic pectoral fin is in a rigid flapping mode; when the restriction structure is in the constrained state, the rotation of the exoskeleton is constrained. By limiting the rotation of the exoskeleton, the variable stiffness bionic pectoral fin is in a flexible warping mode.

2. The variable stiffness bionic pectoral fin according to claim 1, characterized in that: The exoskeleton includes side panels extending along the span direction and a plurality of connecting panels arranged along the span direction, wherein the connecting panels are connected to the side panels; the restraining structure includes an inner core panel, a two-degree-of-freedom base, a fixing seat, and a stiffness-variable enabling servo, wherein the inner core panel extends along the span direction and is rotatably connected to the connecting panels about the span direction; The inner core plate is rotatably connected to the two-degree-of-freedom base around a first direction, the two-degree-of-freedom base is rotatably connected to the fixed base around a second direction, the fixed base is fixed to the robot frame, and the stiffness change enabling servo is fixed to the robot frame and is transmission-connected to the two-degree-of-freedom base, and is used to drive the two-degree-of-freedom base to rotate around the second direction; wherein the first direction is perpendicular to the second direction, and the second direction is a span direction; When the restriction structure is in an unconstrained state, the first direction is consistent with the rotation axis of the side plate; when the restriction structure is in a constrained state, the first direction intersects or is perpendicular to the rotation axis of the side plate.

3. The variable stiffness bionic pectoral fin according to claim 2, characterized in that: The side panels include an upper side panel and a lower side panel correspondingly arranged above and below, the connecting panel is connected between the upper side panel and the lower side panel, and the inner core panel is located between the upper side panel and the lower side panel; The upper side plate and the lower side plate are connected at the fin tip through a fin tip connecting block and are rotatably connected to a transmission mechanism at the fin root. The flapping servo is connected to the transmission mechanism and is used to simultaneously drive the upper side plate and the lower side plate to flap up and down through the transmission mechanism.

4. The variable stiffness bionic pectoral fin according to claim 3, characterized in that: The transmission mechanism is a parallelogram transmission mechanism, the upper side plate and the lower side plate are rotatably connected to the upper and lower edges of the parallelogram transmission mechanism on the same side at the fin root, support frames are respectively provided on both sides of the parallelogram transmission mechanism along the chord direction, and mounting pins are connected to the support frames. The mounting pins pass through the transmission rod of the parallelogram transmission mechanism located between the upper and lower planes so that the parallelogram transmission mechanism is mounted on the mounting pins, and the support frames are fixed to the robot frame; A tooth structure is provided on the transmission rod on at least one side of the parallelogram transmission mechanism along the chord direction, and a tooth structure is also provided on the output shaft of the flapping servo. The flapping servo drives the transmission rod to rotate around the mounting pin through the engagement of the tooth structure, so that the parallelogram transmission mechanism is deformed and then drives the upper side plate and the lower side plate to flap up and down synchronously.

5. The variable stiffness bionic pectoral fin according to claim 4, characterized in that: The fixing seat is located inside the parallelogram transmission mechanism, and the fixing seat is fixedly mounted on the robot frame via the mounting pins.

6. The variable stiffness bionic pectoral fin according to claim 2, characterized in that: The two-degree-of-freedom base is transmission-connected to the stiffness-variable enabling steering gear via a flexible shaft.

7. A bionic manta ray robot, characterized in that: The invention comprises the variable stiffness bionic pectoral fin according to any one of claims 1 to 6, and further comprises a robot skeleton, wherein the variable stiffness bionic pectoral fins are respectively provided on both sides of the robot skeleton.

8. The bionic manta ray robot according to claim 7, characterized in that: The robot frame comprises a bottom plate, a top plate, a connecting column and a buoyancy bottle. The bottom plate and the top plate are connected via the connecting column, and the buoyancy bottle is fixed on the top plate.

9. The bionic manta ray robot according to claim 7, wherein: The robot also includes a tail fin module and a controller, wherein the tail fin module includes a left tail fin plate, a right tail fin plate, a left servo, a right servo, and a tail fin seat; the left tail fin plate is connected to the left servo, and the right tail fin plate is connected to the right servo; the left servo and the right servo are both fixed to the tail fin seat; and the tail fin seat is fixed to the tail of the robot frame; The controller is installed at the front of the robot frame and is connected to the fin ray module and the tail fin module of the variable stiffness bionic pectoral fin through signal lines.

10. A control method for a bionic manta ray robot, characterized in that: Based on the bionic manta ray robot according to any one of claims 7 to 9, the control method includes: When the movement speed needs to be increased, the variable stiffness bionic pectoral fins on both sides are controlled to be in the rigid flapping mode; When the endurance performance needs to be improved, the variable stiffness bionic pectoral fins on both sides are controlled to be in the flexible warping mode; When flipping or yaw is required, the variable stiffness bionic pectoral fin on one side is controlled to be in a rigid flapping mode, and the variable stiffness bionic pectoral fin on the other side is controlled to be in a flexible warping mode.

Images