Water-air amphibious bionic flapping-wing robot with chordwise dual modes

Abstract

The invention belongs to the related technical field of bionic flapping-wing robots, and discloses a water-air amphibious bionic flapping-wing robot with chordwise bimodal flapping wings, which comprises a main body, the chordwise bimodal flapping wings, an empennage, a cross-medium mechanism, a control unit and a flexible skin, the main machine body is a main supporting component of the robot, and the chordwise bimodal flapping wings are installed on the left side and the right side of the main machine body and oscillate up and down in a reciprocating mode to drive the flexible skin covering the chordwise bimodal flapping wings to generate power. The empennage is fixed to the rear end of the main fuselage to assist the robot in posture adjustment. The cross-medium mechanism is installed at the front end of the main machine body and used for providing impulsive force for cross-medium movement of the robot. And the control unit is connected with each component through a signal line. The bionic flapping-wing robot has an overwater motion mode and an underwater motion mode in the chordwise direction of the flapping wing, the overwater motion mode is beneficial to generation of lift force in the air, the underwater motion mode is beneficial to reduction of power consumption in water and concentration of power in the thrust direction, and the use environment and scene of the bionic flapping-wing robot are expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field related to bionic flapping-wing robots, and more specifically, relates to an amphibious bionic flapping-wing robot with chord-wise dual modes. Background Art

[0002] The inspiration of bionic flapping-wing robots comes from imitating the way creatures in nature flap their wings to achieve movement. Compared with traditional artificial propellers and other drive forms, flapping wings have higher movement efficiency, lower environmental noise and safer operation mode. In the water environment, the bionic flapping-wing robot imitates the wings of birds to achieve flight, while in the underwater environment, it imitates the pectoral fin propulsion of fish represented by manta rays to swim. However, the existing bionic flapping-wing robots are only designed for a single organism, which makes it difficult for flapping-wing robots designed for flying in the air to swim underwater, and flapping-wing robots designed for swimming underwater cannot fly in the air. Its application scenario can only adapt to a single medium environment, and cannot meet the flapping-wing motion needs of amphibious cross-medium scenarios in water and air. Summary of the invention

[0003] In response to the above defects or improvement needs of the prior art, the present invention provides a water-air amphibious bionic flapping-wing robot with chord-wise dual-mode. By designing chord-wise dual-mode flapping wings to imitate the behavioral differences between bird feathers and manta ray fin bones during movement, the bionic flapping-wing mechanism is endowed with more motion modes and functions, and the motion environment and application scenarios of the bionic flapping-wing robot are expanded, thereby solving the technical problem that the existing bionic flapping-wing robots cannot meet the flapping-wing motion requirements of water-air amphibious cross-media scenarios.

[0004] To achieve the above-mentioned object, according to one aspect of the present invention, there is provided a water-air amphibious bionic flapping-wing robot with chord-wise dual-mode, comprising a main body 1, chord-wise dual-mode flapping wings 2, a tail wing 3, a cross-medium mechanism 4, a control unit 5 and a flexible skin 6;

[0005] The main body 1 includes a main skeleton 1-1, a flapping gear set 1-2, a flapping motor 1-3, a flapping connecting rod 1-4 and a tail fixing rod 1-5; the main skeleton 1-1 is the core load-bearing structure of the robot, and is used to install the remaining components of the main body 1; the flapping gear set 1-2 is installed inside the main skeleton 1-1, and drives the flapping connecting rod 1-4 to flap back and forth under the drive of the flapping motor 1-3; the tail fixing rod 1-5 is installed at the rear end of the main skeleton 1-1;

[0006] The chord-wise bimodal flapping wing 2 is installed on the left and right sides of the main fuselage 1 and is connected to the flapping link 1-4; the flexible skin 6 is adhered to the top of the chord-wise bimodal flapping wing 2; the tail wing 3 is installed on the tail wing fixing rod 1-5; the cross-medium mechanism 4 is installed at the front end of the main frame 1-1; the control unit 5 is fixed on the main frame 1-1 and is connected to each component through a signal line;

[0007] Preferably, the chord-wise bimodal flapping wing 2 comprises a flapping mechanism 2-1, a chord-wise bimodal joint 2-2 and a mode switching mechanism 2-3; the flapping mechanism 2-1 is hinged on the left and right sides of the main skeleton 1-1, and flaps back and forth under the drive of the flapping link 1-4; the chord-wise bimodal joint 2-2 is installed on the flapping mechanism 2-1, and moves with the flapping mechanism 2-1; the mode switching mechanism 2-3 is fixed on the main skeleton 1-1, and controls the movement mode of the chord-wise bimodal joint 2-2 during the movement;

[0008] Preferably, the flapping mechanism 2-1 includes a wing root fixing seat 2-11, a flapping rod 2-12 and a wing tip fixing seat 2-13; the wing root fixing seat 2-11 is hinged on the left and right sides of the main skeleton 1-1, and is connected to the flapping connecting rod 1-4, and flaps back and forth under the drive of the flapping connecting rod 1-4; the flapping rod 2-12 is fixed on the wing root fixing seat 2-11.

[0009] Preferably, the chordal bimodal joint 2-2 includes a joint fixing seat 2-21, a joint movable seat 2-22, an upstroke torsion spring 2-23 and a downstroke torsion spring 2-24; the joint movable seat 2-22 is hinged on the joint fixing seat 2-21 and can rotate relative to the joint fixing seat 2-21; the upstroke torsion spring 2-23 and the downstroke torsion spring 2-24 are both constrained on the hinge axis of the joint movable seat 2-22 and the joint fixing seat 2-21; one end of the upstroke torsion spring 2-23 is fixed on the joint fixing seat 2-21, and the other end provides torque when the joint movable seat 2-22 rotates downward relative to the joint fixing seat 2-21; one end of the downstroke torsion spring 2-24 is fixed on the joint fixing seat 2-21, and the other end provides torque when the joint movable seat 2-22 rotates upward relative to the joint fixing seat 2-21.

[0010] Preferably, the mode switching mechanism 2-3 includes a mode switching servo 2-31, a mode switching connecting rod group 2-32, a transmission rope 2-33, a sawtooth plate 2-34 and a tension spring 2-35; the mode switching servo 2-31 is fixed on the tail wing fixing rod 1-5, and serves as the input end of the mode switching connecting rod group 2-32 to control its movement; the output end of the mode switching connecting rod group 2-32 is sleeved on the flapping rod 2-12, and can slide along the axial direction of the flapping rod 2-12; one end of the transmission rope 2-33 is fixed to the output end of the mode switching connecting rod group 2-32, and the other end is connected to the sawtooth plate 2-34; the sawtooth plate 2-34 passes through the interior of the joint fixing seat 2-21, and is connected to the wingtip fixing seat 2-13 through the tension spring 2-35.

[0011] Preferably, when the output end of the mode switching link group 2-32 slides toward the root of the flapping rod 2-12, the transmission rope 2-33 is pulled to drive the serrated plate 2-34 to slide; the serrated plate 2-34 has a plurality of bosses and grooves, and the pulling of the transmission rope 2-33 determines whether the boss or the groove is located inside the joint fixing seat 2-21; when the boss is located inside the joint fixing seat 2-21, the chord-wise bimodal joint 2-2 will produce an asymmetric rotation trajectory during the flapping process, imitating the movement state of bird feathers during the flapping process, which is an above-water mode; when the groove is located inside the joint fixing seat 2-21, the chord-wise bimodal joint 2 will produce a symmetrical trajectory similar to the manta ray fin bone during the flapping process, which is an underwater mode.

[0012] Preferably, the tail 3 includes a pitch wing 3-1, a yaw wing 3-2, a pitch servo 3-3, a yaw servo 3-4 and a tail servo fixing seat 3-5; the pitch servo 3-3 drives the pitch wing 3-1 to move, and is installed on the tail fixing rod 1-5 through the tail servo fixing seat 3-5; the yaw servo 3-4 is installed on the pitch wing 3-1 and follows the movement of the pitch wing; the yaw servo 3-4 is connected to the yaw wing 3-2 and drives it to rotate relative to the pitch wing 3-1.

[0013] Preferably, the cross-medium mechanism 4 includes a cross-medium motor 4-1, propeller blades 4-2 and a motor fixing seat 4-3; the cross-medium motor 4-1 is connected to the propeller blades 4-2 and is installed at the front end of the main skeleton 1-1 through the motor fixing seat 4-3; the cross-medium motor 4-1 drives the propeller blades 4-2 to rotate at high speed, driving the robot from underwater to air, realizing cross-medium movement, and turning off the cross-medium motor 4-1 after completely entering the aerial environment.

[0014] Preferably, a water-air amphibious bionic flapping-wing robot with chord-wise dual-mode swims in the water through the underwater mode of the chord-wise dual-mode flapping wing 2, and concentrates the power in the thrust direction and reduces the required power consumption during the flapping process through the symmetrical chord-wise trajectory; when crossing from the water environment to the air environment, the cross-medium motor 4-1 is turned on and drives the robot out of the water; when the robot completely enters the air, the cross-medium motor 4-1 is turned off and the chord-wise dual-mode flapping wing 2 is switched to the water mode, and the aerial flight is achieved through the asymmetric trajectory generated by the flapping.

[0015] In general, compared with the prior art, the above technical solution conceived by the present invention provides a water-air amphibious bionic flapping-wing robot with chord-wise dual-mode, which mainly has the following beneficial effects:

[0016] 1. The present invention provides a water-air amphibious bionic flapping-wing robot with chord-wise dual modes, which gives the flapping-wing structure two motion modes, above water and underwater, and imitates the motion state of bird feathers and manta ray fin bones to adapt to the water-air amphibious environment, thus solving the technical difficulty that the existing flapping-wing robots can only move in a single medium.

[0017] 2. The water-air amphibious bionic flapping-wing robot with chord-wise dual-mode provided by the present invention has a higher degree of flexibility than the traditional flapping-wing robot which only relies on the flexibility of carbon rods to produce chord-wise deformation when flying in the air.

[0018] 3. The present invention provides an amphibious bionic flapping-wing robot with chord-wise dual modes. When swimming in water, the underwater mode of the robot's flapping wings can release the chord-wise stiffness of the wing surface, reduce the projected area and flapping resistance during the flapping process, and enable a small brushless motor to drive a large-sized flapping wing to flap underwater.

[0019] 4. The water-air amphibious bionic flapping-wing robot with chord-wise dual mode provided by the present invention can also redirect the dynamics in the flapping process when swimming in the water, generate more power along the thrust direction, enhance the underwater propulsion efficiency of the flapping-wing robot, and reduce the oscillation of the robot in the lift direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 3D schematic diagram of the structure of a water-air amphibious bionic flapping-wing robot with chord-wise dual modes in an embodiment of the present invention;

[0021] Figure 2 It is a three-dimensional structural schematic diagram of a main body and a cross-medium mechanism in a water-air amphibious bionic flapping-wing robot with chord-wise dual modes in an embodiment of the present invention;

[0022] Figure 3It is a schematic diagram of the three-dimensional structure of the tail wing of a water-air amphibious bionic flapping-wing robot with chord-wise dual modes in an embodiment of the present invention;

[0023] Figure 4 It is a three-dimensional structural schematic diagram of a chord-wise dual-mode flapping wing and a mode switching mechanism in an amphibious bionic flapping wing robot with chord-wise dual-mode in an embodiment of the present invention;

[0024] Figure 5 1 is a schematic diagram of the three-dimensional structure of a chord-wise bimodal joint in a chord-wise bimodal flapping wing in an embodiment of the present invention;

[0025] Figure 6 is a top view of the structure of a chord-wise bimodal joint in a chord-wise bimodal flapping wing in an embodiment of the present invention;

[0026] Figure 7 It is a schematic diagram of the position of a mode switching mechanism in two modes in a water-air amphibious bionic flapping-wing robot with chord-wise dual modes in an embodiment of the present invention;

[0027] Figure 8 is the motion state of the dual-mode joint in two modes in the embodiment of the present invention;

[0028] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0029] 1. Main body; 2. Chord-wise dual-mode flapping wing; 3. Tail wing; 4. Cross-medium mechanism; 5. Control unit; 6. Flexible skin; 1-1. Main skeleton; 1-2. Flapping gear set; 1-3. Flapping motor; 1-4. Flapping connecting rod; 1-5. Tail wing fixing rod; 2-1. Flapping mechanism; 2-2. Chord-wise dual-mode joint; 2-3. Mode switching mechanism; 3-1. Pitch wing; 3-2. Yaw wing; 3-3. Pitch servo; 3-4. Yaw servo; 3-5. Tail wing Servo fixing seat; 4-1, trans-medium motor; 4-2, propeller blade; 4-3, motor fixing seat; 2-11, wing root fixing seat; 2-12, flapping rod; 2-13, wing tip fixing seat; 2-21, joint fixing seat; 2-22, joint movable seat; 2-23, upstroke torsion spring; 2-24, downstroke torsion spring; 2-31, mode switching servo; 2-32, mode switching connecting rod group; 2-33, transmission rope; 2-34, serrated plate; 2-35, tension spring. DETAILED DESCRIPTION

[0030] 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.

[0031] refer to Figure 1 The embodiment of the present invention provides a water-air amphibious bionic flapping wing robot with chord-wise dual-mode, comprising: a main body 1, a chord-wise dual-mode flapping wing 2, a tail wing 3, a cross-medium mechanism 4, a control unit 5, and a flexible skin 6.

[0032] In this embodiment, there are two chord-wise bimodal flapping wings 2, which are respectively installed on the left and right sides of the main body 1; the flexible skin 6 covers the top of the chord-wise bimodal flapping wings 2 and follows its flapping, capturing power to drive the robot to move; the tail wing 3 is installed at the tail of the main body 1; the cross-medium mechanism 4 is installed at the head of the main body; the control unit 5 is connected to the servos and motors in each component through signal lines.

[0033] refer to Figure 2 The main body 1 includes a main skeleton 1-1, a flapping gear set 1-2, a flapping motor 1-3, a flapping connecting rod 1-4 and a tail fixing rod 1-5; the main skeleton 1-1 serves as the core load-bearing component of the robot, connecting and installing the remaining structures; the flapping gear set 1-2 is installed inside the main skeleton 1-1, and a reduction gear box is formed by a multi-stage gear; the flapping motor 1-3 serves as the input end of the flapping gear set 1-2, driving the flapping gear set 1-2 to rotate; the flapping connecting rod 1-4 is connected to the output end of the flapping gear set 1-2 on the left and right sides and is driven by it; the tail fixing rod 1-5 is fixed to the rear end of the main skeleton 1-1 for installing the tail.

[0034] Among them, the number of reduction gears and the reduction ratio of the flapping gear set 1-2 need to be adjusted according to parameters such as the flapping torque and frequency of the robot, and the embodiment of the present invention does not make any unique limitation.

[0035] refer to Figure 2 The cross-medium mechanism 4 includes a cross-medium motor 4-1, propeller blades 4-2 and a motor fixing seat 4-3; the cross-medium motor 4-1 is installed on the head of the main skeleton 1-1 through the motor fixing seat 4-3; the propeller blades 4-2 are installed on the cross-medium motor 4-1 and driven to rotate thereby providing the robot with impulse when exiting the water.

[0036] refer to Figure 3The tail 3 includes a pitch wing 3-1, a yaw wing 3-2, a pitch servo 3-3, a yaw servo 3-4 and a tail servo fixing seat 3-5; the pitch servo 3-3 is fixed to the tail fixing rod 1-5 through the tail servo fixing seat 3-5, and controls the rotation angle of the pitch wing 3-1; the yaw servo 3-4 is installed on the pitch wing and rotates up and down with the pitch wing; the yaw wing 3-2 is connected to the yaw servo 3-4 and rotates under its drive.

[0037] In this embodiment, the pitch wing is used to assist the robot in adjusting the pitch angle during flying on water and swimming underwater, and the yaw wing is used to adjust the yaw angle of the robot in real time during movement.

[0038] refer to Figure 4 The chord-wise bimodal flapping wing 2 includes a flapping mechanism 2-1, a chord-wise bimodal joint 2-2 and a mode switching mechanism 2-3; the flapping mechanism 2-1 is hinged on the left and right sides of the main skeleton 1-1, and is connected to the flapping link 1-4, and performs up and down reciprocating motion under the drive of the flapping link 1-4; multiple chord-wise bimodal joints 2-2 are installed on the flapping mechanism 2-1 to provide two motion modes for the flapping wing; one end of the mode switching mechanism 2-3 is installed on the main skeleton 1-1, and the other end passes through the chord-wise bimodal joint 2-2, which is used to adjust the flapping mode of the robot.

[0039] Among them, the number and positions of the chord-wise dual-mode joints need to be adjusted according to the flapping wing size and structural strength requirements of the robot, and the embodiments of the present invention do not limit the uniqueness.

[0040] refer to Figure 5 and Figure 6 The chordal bimodal joint 2-2 includes a joint fixing seat 2-21, a joint movable seat 2-22, an upstroke torsion spring 2-23 and a downstroke torsion spring 2-24; the joint fixing seat 2-21 is fixed on the flapping rod 2-12; the joint movable seat 2-22 is hinged on the joint fixing seat 2-21 and can rotate relative to it; the upstroke torsion spring 2-23 and the downstroke torsion spring 2-24 are constrained on the hinge axis of the joint movable seat 2-22 and the joint fixing seat 2-21.

[0041] In this embodiment, each chordal bimodal joint has two upstroke torsion springs and two downstroke torsion springs, which are respectively installed on the left and right sides of the joint; the upstroke torsion spring is used to provide dynamic response for the joint moving seat during the process of flapping wings upward; the downstroke torsion spring is used to provide dynamic response for the joint moving seat during the process of flapping wings downward; the joint moving seat can rotate relative to the joint fixed seat in the range of -45° to 45°; in addition, the two sets of torsion springs constrain the initial position of the joint moving seat to 0°.

[0042] Among them, the stiffness and number of the upstroke and downstroke torsion springs need to be adjusted according to the dynamic flapping reaction force of the flapping wing size, and the rotation range of the joint moving seat relative to the joint fixed seat also needs to be adjusted according to the flapping parameters. The embodiment of the present invention does not make a unique limitation.

[0043] refer to Figure 4 The mode switching mechanism includes a mode switching servo 2-31, a mode switching connecting rod group 2-32, a transmission rope 2-33, a sawtooth plate 2-34 and a tension spring 2-35; the mode switching servo 2-31 is installed on the tail fixed rod 1-5, driving the mode switching connecting rod group 2-32 to move; the output end of the mode switching connecting rod group 2-32 is sleeved on the flapping rod 2-12, and can slide relatively along the axis of the flapping rod 2-12; the transmission rope 2-33 connects the output end of the mode switching connecting rod group 2-32 and one end of the sawtooth plate 2-34, and transmits the sliding of the mode switching connecting rod group 2-32 to the sawtooth plate 2-34; the other end of the sawtooth plate 2-34 is connected to the wing tip fixing seat 2-13 through the tension spring 2-35.

[0044] In this embodiment, the serrated plate 2-34 passes through the interior of the joint fixing seat 2-21 and has a plurality of boss and groove structures; the boss will constrain the rotation angle of the chord-wise dual-modal joint 2-2 to -45° to 0°, producing an asymmetric motion trajectory similar to that of bird feathers, which becomes an above-water mode; and the groove will release the angle of the joint to -45° to 45°, producing a symmetrical motion trajectory similar to that of the manta ray fin bone, which is called an underwater mode.

[0045] refer to Figure 7 , the mode switching servo 2-31 is in the initial position. At this time, the output end of the mode switching linkage group 2-32 is close to the wing tip on the flapping rod 2-12, the transmission rope 2-33 is in a relaxed state, and the position of the serrated plate 2-34 is maintained by the tension spring 2-35, and its boss is placed inside the chord-wise dual-mode joint 2-2, causing the entire flapping wing to be in the water mode; when the mode switching servo 2-31 rotates to the target position, the output end of the mode switching linkage group 2-32 slides toward the wing root direction on the flapping rod 1-12, pulling the transmission rope 2-33 and driving the serrated plate 2-34 to slide inward, placing the groove of the serrated plate 2-34 inside the chord-wise dual-mode joint 2-2, and at the same time the tension spring 2-35 is stretched and produces a pulling force tendency for the serrated plate 2-34 to return to its initial position, causing the entire flapping wing to be in the underwater mode.

[0046] In this embodiment, the back-and-forth rotation of the mode switching servo 2-31 between the initial position and the target position will produce a reversible switching between the above-water mode and the underwater mode for the chord-wise dual-mode joint 2-2.

[0047] refer to Figure 8In the water mode, the chord-wise bimodal joint 2-2 will be restricted by the boss on the serrated plate 2-34, causing the rotation angle to decrease to -45° during the upstroke and to 0° during the downstroke. This trajectory helps the flapping wing to increase the projected area to capture power when flapping down and reduce resistance when flapping up, which is beneficial to the generation of lift and thrust in the water environment; in the underwater mode, the groove on the serrated plate 2-34 releases the rotation angle during the downstroke to 45°, which is beneficial to releasing the projected area of ​​the flapping wing to reduce motion resistance and power consumption during underwater movement. At the same time, the symmetrical chord-wise trajectory helps to concentrate power in the thrust direction and increase underwater propulsion efficiency.

[0048] 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 water-air amphibious bionic flapping-wing robot with chord-wise dual modes, characterized in that: The robot comprises a main body (1), a chord-wise dual-mode flapping wing (2), a tail wing (3), a cross-medium mechanism (4), a control unit (5) and a flexible skin (6); wherein the main body (1) comprises a main skeleton (1-1), a flapping gear set (1-2), a flapping motor (1-3), a flapping connecting rod (1-4) and a tail wing fixing rod (1-5); the main skeleton (1-1) is the core load-bearing structure of the robot and is used to install the remaining components of the main body (1); The flapping gear set (1-2) is installed inside the main frame (1-1), and drives the flapping connecting rod (1-4) to flap back and forth under the drive of the flapping motor (1-3); the tail wing fixing rod (1-5) is installed at the rear end of the main frame (1-1); The chord-wise bimodal flapping wing (2) is mounted on the left and right sides of the main body (1) and is connected to the flapping connecting rod (1-4); the flexible skin (6) is adhered to the top of the chord-wise bimodal flapping wing (2); the tail wing (3) is mounted on the tail wing fixing rod (1-5); the cross-medium mechanism (4) is mounted on the front end of the main frame (1-1); the control unit (5) is fixed on the main frame (1-1) and is connected to each component through a signal line.

2. The water-air amphibious bionic flapping-wing robot with chord-wise dual-mode according to claim 1, characterized in that: The chord-wise bimodal flapping wing (2) comprises a flapping mechanism (2-1), a chord-wise bimodal joint (2-2) and a mode switching mechanism (2-3); the flapping mechanism (2-1) is hinged on the left and right sides of the main frame (1-1), and flaps back and forth under the drive of the flapping link (1-4); the chord-wise bimodal joint (2-2) is mounted on the flapping mechanism (2-1) and moves with the flapping mechanism (2-1); the mode switching mechanism (2-3) is fixed on the main frame (1-1), and controls the movement mode of the chord-wise bimodal joint (2-2) during the movement process.

3. The water-air amphibious bionic flapping-wing robot with chord-wise dual-mode according to claim 2, characterized in that: The flapping mechanism (2-1) comprises a wing root fixing seat (2-11), a flapping rod (2-12) and a wing tip fixing seat (2-13); the wing root fixing seat (2-11) is hinged on the left and right sides of the main frame (1-1), and is connected to the flapping connecting rod (1-4), and flaps back and forth under the drive of the flapping connecting rod (1-4); the flapping rod (2-12) is fixed on the wing root fixing seat (2-11).

4. The water-air amphibious bionic flapping-wing robot with chord-wise dual-mode according to claim 2, characterized in that: The chord-wise dual-mode joint (2-2) comprises a joint fixing seat (2-21), a joint movable seat (2-22), an upstroke torsion spring (2-23) and a downstroke torsion spring (2-24); the joint movable seat (2-22) is hinged on the joint fixing seat (2-21) and can rotate relative to the joint fixing seat (2-21); the upstroke torsion spring (2-23) and the downstroke torsion spring (2-24) are both constrained between the joint movable seat (2-22) and the joint fixing seat. One end of the up-stroke torsion spring (2-23) is fixed on the joint fixing seat (2-21), and the other end provides torque when the joint movable seat (2-22) rotates downward relative to the joint fixing seat (2-21); one end of the down-stroke torsion spring (2-24) is fixed on the joint fixing seat (2-21), and the other end provides torque when the joint movable seat (2-22) rotates upward relative to the joint fixing seat (2-21).

5. The water-air amphibious bionic flapping-wing robot with chord-wise dual-mode according to claim 3, characterized in that: The mode switching mechanism (2-3) comprises a mode switching servo (2-31), a mode switching connecting rod group (2-32), a transmission rope (2-33), a sawtooth plate (2-34) and a tension spring (2-35); the mode switching servo (2-31) is fixed on the tail wing fixing rod (1-5) and serves as the input end of the mode switching connecting rod group (2-32) to control its movement; the output end of the mode switching connecting rod group (2-32) is sleeved on the flapping rod (2-12) and can slide along the axial direction of the flapping rod (2-12); one end of the transmission rope (2-33) is fixed to the output end of the mode switching connecting rod group (2-32), and the other end is connected to the sawtooth plate (2-34); the sawtooth plate (2-34) passes through the interior of the joint fixing seat (2-21) and is connected to the wing tip fixing seat (2-13) through the tension spring (2-35).

6. The water-air amphibious bionic flapping-wing robot with chord-wise dual modes as claimed in claim 5, characterized in that: When the output end of the mode switching link group (2-32) slides toward the root of the flapping rod (2-12), the transmission rope (2-33) is pulled to drive the sawtooth plate (2-34) to slide; the sawtooth plate (2-34) is provided with a plurality of bosses and grooves, and the pulling of the transmission rope (2-33) determines whether the bosses or the grooves are located inside the joint fixing seat (2-21); when the bosses are located inside the joint fixing seat (2-21), the chord-wise bimodal joint (2-2) will generate an asymmetric rotation trajectory during the flapping process, imitating the movement state of bird feathers during the flapping process, which is an above-water mode; when the grooves are located inside the joint fixing seat (2-21), the chord-wise bimodal joint (2) will generate a symmetrical trajectory similar to the fin bones of a manta ray during the flapping process, which is an underwater mode.

7. The water-air amphibious bionic flapping-wing robot with chord-wise dual-mode according to claim 1, characterized in that: The tail wing (3) comprises a pitch wing (3-1), a yaw wing (3-2), a pitch servo (3-3), a yaw servo (3-4) and a tail wing servo fixing seat (3-5); the pitch servo (3-3) drives the pitch wing (3-1) to move, and is mounted on the tail wing fixing rod (1-5) through the tail wing servo fixing seat (3-5); the yaw servo (3-4) is mounted on the pitch wing (3-1) and moves with the pitch wing; the yaw servo (3-4) is connected to the yaw wing (3-2) and drives it to rotate relative to the pitch wing (3-1).

8. The water-air amphibious bionic flapping-wing robot with chord-wise dual modes as claimed in claim 1, characterized in that: The cross-medium mechanism (4) comprises a cross-medium motor (4-1), a propeller blade (4-2) and a motor fixing seat (4-3); the cross-medium motor (4-1) is connected to the propeller blade (4-2) and is installed at the front end of the main skeleton (1-1) through the motor fixing seat (4-3); the cross-medium motor (4-1) drives the propeller blade (4-2) to rotate at a high speed, driving the robot to rush from underwater to air to achieve cross-medium movement, and the cross-medium motor (4-1) is turned off after the robot completely enters the air environment.

9. The water-air amphibious bionic flapping-wing robot with chord-wise dual modes as claimed in claim 8, characterized in that: The robot swims in the water through the underwater mode of the chord-wise dual-mode flapping wing (2), and concentrates power in the thrust direction and reduces the required power consumption during flapping through a symmetrical chord-wise trajectory; when entering an aerial environment from an underwater environment, the cross-medium motor (4-1) is turned on and drives the robot to rush out of the water; when the robot completely enters the air, the cross-medium motor (4-1) is turned off and the chord-wise dual-mode flapping wing (2) is switched to an above-water mode, and aerial flight is achieved through an asymmetric trajectory generated by flapping.

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