Variable-rigidity bionic pectoral fin, bionic manta ray robot and control method of bionic pectoral fin and bionic manta ray robot

Abstract

The invention belongs to the related technical field of underwater bionic robots, and discloses a variable-rigidity bionic pectoral fin, a bionic manta ray robot and a control method thereof, and the variable-rigidity bionic pectoral fin comprises a fin ray module and a flexible skin; the fin ray module comprises an exoskeleton, a flapping steering engine and a limiting structure; the flapping steering engine is used for driving the exoskeleton to rotate so as to drive the flexible skin to oscillate up and down; the limiting structure extends in the spanwise direction of the exoskeleton and is connected with the exoskeleton, the limiting structure has a non-constrained state and a constrained state, and when the limiting structure is in the non-constrained state, rotation of the exoskeleton is not constrained, so that the variable-rigidity bionic pectoral fin is in a rigid flapping mode; when the limiting structure is in the restrained state, rotation of the exoskeleton is restrained, and the variable-rigidity bionic pectoral fin is in the flexible warping mode by limiting rotation of the exoskeleton. According to the bionic pectoral fin, the function of the bionic pectoral fin is expanded structurally, the diversity of movement is expanded, and the hydrodynamic performance of the flexible skin is changed structurally.

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 the more than 500 species of rays. Unlike conventional fish that use the body / tail fin propulsion mode, manta rays use the middle fin / opposite fin propulsion mode. This type of propulsion mode has good motion stability and low-speed maneuverability, and high propulsion efficiency. The excellent swimming ability of manta rays has attracted the attention of many researchers at home and abroad, and various types of bionic manta rays have been successfully developed.

[0003] Studies have shown that the broad, flat pectoral fins of manta rays are the 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, and do not have the ability to structurally change the hydrodynamic performance of the flexible skin. In order to meet the complex underwater environment and diversified mission requirements, traditional pectoral fins usually need to be equipped with complex control algorithms to adjust the pectoral fins' flapping amplitude, flapping frequency, flapping phase difference, flapping offset and other variables in real time, so that the flexible skin produces different motion states, which increases the complexity and instability of the system.

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

[0005] In view of the above 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 having a simple pectoral fin structure design, a single motion function, and a lack of the ability to structurally change the hydrodynamic performance of the flexible skin.

[0006] To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided a bionic pectoral fin with variable stiffness, which is used to be installed on both sides of a robot frame of a bionic fish robot, and comprises a fin module and a flexible skin; the fin module comprises an exoskeleton, a flapping servo and a limiting structure, the exoskeleton is rotatably arranged relative to the robot frame, the flapping servo is installed on the robot frame and is transmission-connected to the exoskeleton, the flexible skin is covered on the exoskeleton, and the flapping servo is used to drive the exoskeleton to rotate so as to drive 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, and the variable stiffness bionic pectoral fin is in a flexible warping mode by limiting the rotation of the exoskeleton.

[0008] According to the variable stiffness bionic pectoral fin provided by the present invention, the exoskeleton comprises side plates extending along the span direction and a plurality of connecting plates arranged along the span direction, wherein the connecting plates are connected to the side plates; the limiting structure comprises an inner core plate, a two-degree-of-freedom base, a fixing seat and a stiffness-variable enabling steering gear, wherein the inner core plate extends along the span direction and is rotatably connected to the connecting plates around 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 limiting structure is in a non-constrained state, the first direction is consistent with the rotation axis of the side plate; when the limiting 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 plate comprises an upper side plate and a lower side plate which are arranged correspondingly up and down, the connecting plate is connected between the upper side plate and the lower side plate, and the inner core plate is located between the upper side plate and the lower side plate;

[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 drive the upper side plate and the lower side plate to flap up and down at the same time 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 sides of the parallelogram transmission mechanism on the same side at the fin root, support frames are respectively arranged on both sides of the parallelogram transmission mechanism along the chord direction, and mounting pins are connected to the support frames, 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 erected on the mounting pins, and the support frame is 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 on 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 steering gear via a flexible shaft.

[0017] According to a second aspect of the present invention, there is provided a bionic manta ray robot, comprising the variable stiffness bionic pectoral fin as 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 further 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 on the tail fin seat; the tail fin seat is fixed to the tail of the robot frame;

[0020] The controller is installed at the front part of the robot frame and is connected with 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 of a bionic manta ray robot is provided. Based on the bionic manta ray robot described in any one of the above items, 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 in a flexible warping mode.

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

[0026] 1. The exoskeleton is rotatably arranged so that the exoskeleton can drive the flexible skin to flutter up and down to capture the hydrodynamic force under the drive of the flapping servo. A restriction structure is arranged to be connected to the exoskeleton and the restriction structure is arranged to have an unconstrained state and a constrained state relative to the exoskeleton, thereby realizing the change of the stiffness of the pectoral fin of the bionic robot in structure. Among them, the variable stiffness bionic pectoral fin will produce two motion modes of rigid rotation and flexible warping under different stiffness, respectively imitating the motion states of the pelagic manta ray and the benthic manta ray; the variable stiffness bionic pectoral fin helps to produce greater power performance under rigid rotation, and is conducive to improving the efficiency of movement and endurance under flexible warping, thereby expanding the function of the bionic pectoral fin in structure, expanding the diversity of movement, and realizing the structural change of the hydrodynamic performance of the flexible skin;

[0027] 2. The proposed exoskeleton includes an upper side plate and a lower side plate, which makes the cross section of the exoskeleton triangular and improves stability; it is proposed to set a parallelogram transmission mechanism, which can realize the synchronous drive of the upper side plate and the lower side plate, and the connection is stable and reliable, which is easy to set; it is proposed to set the limiting structure as an inner core plate, and the inner core plate is connected to the stiffness change enabling steering gear through a two-degree-of-freedom base and a fixed seat, and the control switching of the two modes can be realized by the rotation of the inner core plate, and the structure is simple and reliable, which is easy to control;

[0028] 3. With the design of variable stiffness bionic pectoral fins, the bionic manta ray robot can not only change the stiffness of the pectoral fins on both sides at the same time to obtain different motion modes to meet the mission requirements of high maneuverability and long endurance, but also change the stiffness of only one side of the pectoral fin to obtain differentiated dynamic performance on the left and right sides, thereby improving the diversity of motion;

[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 a simple control algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of a three-dimensional upward-looking structure 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 shown;

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

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

[0035] Figure 6 for Figure 4 A 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 local structure of the transmission connection between the rotatable inner core and the stiffness variation enabling servo in the fin 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] Fig. 9 for Figure 4 A schematic diagram showing the comparison of motion shapes in the rigid rotation mode and the flexible warping mode in the fin module shown;

[0039] Fig.10 for Figure 4 A 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 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 change enabling servo; 2-5. Mounting pin; 2-11. Upper side plate; 2-12. Lower side plate; 2-13. Fin tip connecting 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 purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 can 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 installation on both sides of a robot skeleton 1 of a bionic fish robot, the variable stiffness bionic pectoral fin comprises 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, the flapping servo 2-3 is used to drive the exoskeleton 2-1 to rotate so as to drive the flexible skin 5 to oscillate up and down.

[0044] In this embodiment, the robot skeleton 1 is used as a support frame for fixing the other structural parts of the bionic fish robot; there are two fin modules 2, which are respectively installed on the left and right sides of the robot skeleton 1; the fin module 2 drives the flexible skin 5 to flutter up and down in the water to capture the hydrodynamic force, and the interaction between the flexible skin 5 and the water flow drives the robot to move. The flapping servo 2-3 is connected to the fin exoskeleton 2-1 to achieve the up and down flapping movement.

[0045] This embodiment further takes into account that the pectoral fins of manta rays with the ability to migrate over the ocean in nature are relatively rigid in order to obtain greater dynamic performance, while benthic manta rays have relatively soft pectoral fins in order to obtain 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, and the restriction structure is extended along the span direction 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 drives the flexible skin 5 to vibrate normally up and down under the drive of the flapping servo 2-3, so that the bionic pectoral fin with variable stiffness is in a rigid flapping mode.

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

[0047] In some specific embodiments, reference Figure 3 and Figure 4 The exoskeleton 2-1 includes side panels extending along the span direction and a plurality of 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 fixing 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 around a first direction, and the two-degree-of-freedom base 2 is rotatably connected to the fixed seat 3 around a second direction, so that the inner core plate 1 can rotate in two directions of two degrees of freedom. The fixed seat 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 transmission-connected to the two-degree-of-freedom base 2, and is used to drive the two-degree-of-freedom base 2 to rotate around the second direction; wherein the first direction is perpendicular to the second direction, 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 limiting 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 steering gear 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 plate includes an upper side plate 2-11 and a lower side plate 2-12 which are arranged correspondingly from top to bottom, the connecting plate 2-14 is connected between the upper side plate 2-11 and the lower side plate 2-12, and the inner core plate 1 is located between the upper side plate 2-11 and the lower side plate 2-12; specifically, refer 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 passes through the top of the connecting plate 2-14 to be connected 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 passes through the bottom of the connecting plate 2-14 to be connected 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 Fig.10The transmission mechanism is a parallelogram transmission mechanism 2-15, the upper side plate 2-11 and the lower side plate 2-12 are rotatably connected to the upper and lower sides of the parallelogram transmission mechanism 2-15 on the same side at the fin root, and support frames 2-2 are respectively arranged on both sides of the chord direction of the parallelogram transmission mechanism 2-15, and the support frames 2-2 are connected with mounting pins 2-5, and 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, and 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 seat 3 is located inside the parallelogram transmission mechanism 2-15, and the fixing seat 3 is fixedly mounted on the robot frame 1 through the mounting pin 2-5. The mounting pin 2-5 passes through the support frame 2-2 and the transmission rod and is connected and fixed to the fixing seat 3 by bolts or the like, thereby realizing the installation of the fixing seat 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 connection 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 is fixed by the fin tip connection block 2-13, and is 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 is connected to the parallelogram transmission mechanism 2-15, forming a triangular profile, 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 position 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 a bearing 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 elastic structures that can be warped. For example, the material of the inner core plate 1 can be selected from carbon fiber, metal and other materials; at the same time, the size of the inner core plate 1 should be thinner in the thickness direction and wider in the width direction, so as to expand the difference in the moment of inertia of the section in the two directions.

[0060] Specifically, refer to Figure 6 A parallelogram transmission mechanism 2-15 is used at the root of the fin exoskeleton 2-1 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 meshed and transmitted through a flapping gear 2-16, which is used to improve the stability of transmission and reduce the eccentric load torque during the transmission process, and reduce the eccentric load torque during the movement process.

[0061] In some specific embodiments, the two-degree-of-freedom base 2 is connected to the stiffness change enabling servo 2-4 through a flexible shaft 4. The flexible shaft 4 is connected to the output shaft of the stiffness change enabling servo 2-4 through a transmission connection, and the flexible shaft 4 and the two-degree-of-freedom base 2 can be connected through a key structure. It is used to control the rotation angle of the inner core plate 1 to change the stiffness mode of the fin module 2; the fin module 2 changes the bending stiffness and flapping constraint of the exoskeleton 2-1 through the rotation of the inner core plate 1, and realizes the switching between the rigid flapping mode and the 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 at 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 misaligned 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 up and down warping motion with a smaller cross-sectional moment of inertia, which is called a flexible warping mode.

[0064] Specifically, refer to Fig. 9 The variable stiffness fin module 2 presents a straight rotation trajectory in the rigid rotation mode; and presents 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 fin as 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] The present embodiment proposes a bionic manta ray robot with a variable stiffness fin mechanism, which simulates two motion modes of manta rays by giving the pectoral fins a variable stiffness function in structure, 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 The present embodiment provides a bionic manta robot with bionic pectoral fins with variable stiffness, comprising: a robot frame 1, a fin module 2, a tail fin module 3 and a controller 4 fixed on the robot frame 1, and a flexible skin 5 covering the top of the fin module 2. The robot frame 1 comprises a bottom plate 1-1, a top plate 1-2, a connecting column 1-3 and a buoyancy bottle 1-4, wherein the bottom plate 1-1 and the top plate 1-2 are connected via the connecting column 1-3, and the buoyancy bottle 1-4 is fixed on the top plate 1-2.

[0068] refer to Figure 2The robot skeleton 1 includes: a bottom plate 1-1, a top plate 1-2, a connecting column 1-3 and a buoyancy bottle 1-4; the bottom plate 1-1 is fixed with a variable stiffness bionic pectoral fin, a tail fin module 3 and a controller 4, and is connected to the top plate 1-2 through the connecting column 1-3; the buoyancy bottle 1-4 is fixed on the top plate 1-2 to provide underwater buoyancy for the robot and to balance the gravity of the robot underwater. Among them, the number of connecting columns 1-3 and buoyancy bottles 1-4 needs to be adjusted according to the size and weight of the robot, and the embodiment of the present invention does not limit the uniqueness.

[0069] The bionic manta ray robot also includes a tail fin module 3 and a controller 4, wherein 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 on the tail fin seat 3-5; the tail fin seat 3-5 is fixed to the tail of the robot skeleton 1; the left servo 3-2 and the right servo 3-4 are fixed to the tail of the bottom plate 1-1 through the tail fin seat 3-5. The left servo 3-2 and the right servo 3-4 are both fixed on the tail fin seat 3-5; the tail fin seat 3-5 is fixed to the bottom plate 1-1.

[0070] The controller 4 is installed at the front of the robot skeleton 1 and is connected to the fin 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 skeleton 1, and is used to assist the robot in adjusting its posture during swimming; the controller 4 is installed at the front end of the base plate 1-1, and the controller 4 is connected to the variable stiffness bionic pectoral fin and tail fin module 3 through a signal line. In this embodiment, the left tail fin plate 3-1 and the right tail fin plate 3-3 can adjust their angles relative to the base plate 1-1 in real time through the left servo 3-2 and the right servo 3-4 during the robot's swimming, and assist in adjusting the robot's pitch angle, yaw angle, and roll angle during the forward swimming process.

[0072] Furthermore, the third embodiment provides a control method for a bionic manta ray robot. Based on the bionic manta ray robot described in any one of the above items, 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 in a flexible warping mode.

[0076] In this embodiment, the rigid rotation mode helps to provide greater propulsion force for the bionic manta ray robot and perform high-speed maneuvers in wide waters; while the flexible warping mode is conducive to providing higher propulsion efficiency at low energy consumption and long-term endurance movement in a given target waters; 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 of the left side is large while the flapping power of 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] The present embodiment discloses a bionic manta ray robot driven by a variable stiffness fin mechanism, belonging to the field of underwater bionic robots, comprising a robot skeleton 1 and a variable stiffness fin module 2, a tail fin module 3, a controller 4 and a flexible skin 5 arranged on the skeleton; the variable stiffness fin module 2 is composed of a fin 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 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 change in stiffness 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 only 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 protection scope of the present invention.

Claims

1. A bionic pectoral fin with variable stiffness, used for installation on both sides of the robot frame of a bionic fish robot, characterized in that: It comprises a fin module and a flexible skin; the fin module comprises an exoskeleton, a flapping servo and a limiting structure; the exoskeleton is rotatably arranged relative to the robot frame; the flapping servo is installed on the robot frame and is transmission-connected to the exoskeleton; the flexible skin is covered on 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, and the variable stiffness bionic pectoral fin is in a flexible warping mode by limiting the rotation of the exoskeleton.

2. The variable stiffness bionic pectoral fin according to claim 1, characterized in that: The exoskeleton comprises side plates extending in the span direction and a plurality of connecting plates arranged in the span direction, wherein the connecting plates are connected to the side plates; the limiting structure comprises an inner core plate, a two-degree-of-freedom base, a fixing seat and a stiffness variation enabling steering gear, wherein the inner core plate extends in the span direction and is rotatably connected to the connecting plates around 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 limiting structure is in a non-constrained state, the first direction is consistent with the rotation axis of the side plate; when the limiting 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 plate comprises an upper side plate and a lower side plate which are arranged correspondingly up and down, the connecting plate is connected between the upper side plate and the lower side plate, and the inner core plate is located between the upper side plate and the lower side plate; 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 drive the upper side plate and the lower side plate to flap up and down at the same time 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 sides 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, 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 erected 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 through 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 arranged 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, wherein 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, characterized in that: It 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 on the tail fin seat; the tail fin seat is fixed to the tail of the robot frame; The controller is installed at the front part of the robot frame and is connected with the fin ray module and the tail fin module of the variable rigidity bionic pectoral fin through signal lines.

10. A control method of 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 comprises: 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 cruising range 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 in a flexible warping mode.

Images