Bionic robotic fish with tail self-sensing and tail swing curve optimization method thereof

Abstract

The present invention relates to a bionic robot fish with tail self-sensing and a tail swing curve optimization method thereof, wherein the bionic robot fish comprises a control system, a driving mechanism, and a bionic flexible fish tail; the bionic flexible fish tail comprises a flexible bionic fish tail bone plate, a plurality of joint pieces vertically fixed on the bionic fish tail bone plate at a set spacing, and two flexible sensors arranged on both sides of the bionic fish tail bone plate; when the bionic fish tail bone plate swings, one of the flexible sensors on both sides is stretched and the other is compressed, and the resistance value changes, and the control system uses a predetermined algorithm to control the swing angle of the bionic fish tail bone plate in real time according to the resistance difference of the flexible sensors on both sides to achieve the expected fish tail bending state, thereby realizing self-sensing correction. The present invention mathematically models a simplified fish tail structure, selects the area difference between the traveling wave curve of the croaker fish and the machine fish tail curve as the objective function, optimizes the bending posture of the machine fish tail by adjusting the distribution spacing of the sheet joints of the robot fish, and makes the robot fish conform to the swimming characteristics of the croaker fish, and the swimming ability indicators such as the straight swimming speed and the turning radius after the optimization are significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of bionic robots and relates to a bionic robot fish with tail self-sensing and a tail swing curve optimization method thereof. Background Art

[0002] After tens of thousands of years of natural selection, the body structure and movement of fish have been perfectly adapted to the complex underwater water flow environment. As an underwater robot designed to imitate the movement of fish, the robot fish has more outstanding movement performance than the traditional spiral-propelled underwater robot fish, and has an irreplaceable position in the future underwater environment detection, resource mining and other applications. In fish research, multiple studies have shown that the tail bending movement of the croaker fish is mainly concentrated in the rear half of the tail, which makes the movement efficiency of the croaker fish higher than that of other fish in the BCF mode. In the current robot fish research, the BCF (Body / Caudal Fin propulsion, referred to as BCF) swimming mode robot fish designed to imitate the croaker fish has the best comprehensive movement performance, but due to the complexity of the tail structure design and the difficulty in establishing a tail flexible bending posture model, the robot fish imitates the croaker fish tail bending concentrated in the middle and rear part of the tail. This makes the robot fish's movement ability still have a large gap with the croaker fish. In addition, due to the lack of self-perception of the movement state, it is difficult for the robot fish to adapt to the complex wild water flow environment like biological fish.

[0003] In the current research on robotic fish, researchers use a variety of driving methods to imitate the regular and frequent swinging of fish tails. Among them, the fish tail bending imitated by multi-servo series collaborative driving and wire driving is closer to biological fish, and changing the bending posture of the fish tail is easier than other methods. In the drive design and bending posture optimization design of robot fish, in 2007, Tan Ming et al. of the Chinese Academy of Sciences found in their research on multi-servo serial coordinated drive that the bending posture of the robot fish tail is more similar to that of biological fish as the size of the servo decreases from the head to the tail, and the robot fish has better comprehensive movement ability. However, due to the linear bending tail posture brought by this drive mode and the limitations of the servo manufacturing process, it is difficult for the robot fish to more perfectly fit the smooth bending posture of the biological fish tail. In order to design a fish tail structure with smoother bending, Du Ruxu and Zhong Yong et al. of South China University of Technology used wire drive to imitate the hinged coccyx joint designed by the tail bone of fish. In order to adjust the bending posture of the robot fish tail, they designed two hinged coccyx joints of different sizes and used two sets of pull wires to drive the two sets of coccyx joints respectively to achieve the C-shaped and S-shaped movement of the wire-driven fish tail. However, due to the complex coccyx design, it is difficult for the current wire-driven robot fish to establish a smooth robot fish tail bending posture and optimize the fish tail bending posture. Therefore, the bending posture of the wire-driven robot fish is still far from that of real fish.

[0004] In the design research of the perception ability of robot fish, researchers have used mature sensor robot fish to give robot fish the ability to perceive the external environment, which is already quite mature. However, how robot fish can further adapt to complex water flow environments still needs to rely on sensory organs such as the spinal cord of biological fish to perceive their own motion structure state. In 2023, Zhilin Zhang et al. improved the conductive polymer hydrogel to make the sensor have a higher fatigue resistance, which can adapt to the large-scale and frequent swinging tail movement, but the sensor did not show good perception of the bending state of the tail. In addition, there are few reports on the self-perception of the motion state of robot fish, and traditional bending strain gauges are difficult to perfectly fit with the tail bone. The sensor is easy to fall off or break during large-scale and frequent tail bending movements. Therefore, how to design a robot fish with better comprehensive motion ability and self-perception of motion state is of great value to the practical application of robot fish. Summary of the invention

[0005] In view of this, the purpose of the present invention is to solve the above-mentioned problem and provide a bionic robotic fish with tail self-sensing and a method for optimizing the tail swing curve thereof.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A bionic robot fish with tail self-sensing comprises a control system, a driving mechanism, and a bionic flexible fish tail; the bionic flexible fish tail comprises a flexible bionic fish tail bone plate, a plurality of joint pieces vertically mounted and fixed on the bionic fish tail bone plate at a set interval, and two flexible sensors arranged on both sides of the bionic fish tail bone plate; the driving mechanism comprises a steering gear, a turntable, and a pull wire; the joint piece is divided into left and right sides with the bionic fish tail bone plate as a boundary, a pull wire is connected to each side of the turntable, and the other ends of the two pull wires pass through the middle joint piece and are respectively connected to the left and right sides of the joint piece at the tail end; the steering gear is connected to the turntable to drive the turntable to rotate left and right, thereby driving the bionic fish tail bone plate to swing left and right through the pull wires on both sides;

[0008] The flexible sensor and the steering gear are both connected to the control system. The control system drives the bionic fishtail bone plate to swing through the steering gear. The flexible sensors on both sides of the bionic fishtail bone plate are stretched and compressed, and the resistance value changes. The control system collects the resistance change of the flexible sensor; the resistance values ​​of the flexible sensors on both sides are detected to be different, and the positive and negative values ​​of the difference are used to define the swing direction of the fishtail, and the size of the difference corresponds to the swing angle of the fishtail; the control system uses a predetermined algorithm to control the swing angle of the bionic fishtail bone plate in real time according to the resistance difference of the flexible sensors on both sides to achieve the expected fishtail bending state, thereby realizing self-sensing correction.

[0009] Furthermore, the flexible sensor is a LIG sensor, comprising a flexible substrate, a sensitive unit, a wire and a protective layer;

[0010] The flexible substrate is a composite film comprising at least two particles of polydimethylsiloxane (PDMS) and polyimide (PI), which is attached to the bionic fishtail bone plate;

[0011] The sensitive unit is laser-induced graphene formed by laser scanning on the flexible substrate and distributed linearly along the length direction of the bionic fishtail bone plate; the wire connects the two ends of the sensitive unit to the control system; the protective layer is a polydimethylsiloxane layer covering the surface of the flexible substrate and the sensitive unit.

[0012] Furthermore, the driving mechanism also includes a cable tie, which is arranged between the turntable and the bionic fishtail bone plate; there are multiple pull wires on both sides of the turntable, and the multiple pull wires pass through the joint plate and then merge into one strand through the cable tie and are connected to the turntable; the servo drives the turntable to rotate by rotating the angle, thereby tightening the pull wire on one side wrapped around the turntable, and at the same time loosening the pull wire on the other side by the same amount, so that the bionic fishtail bone plate bends to one side.

[0013] Furthermore, wire holes are provided on the joint pieces, and the distances from the wire holes on the same side of each joint piece to the bionic fishtail bone plate are equal; one end of the pull wire is connected to the tailmost joint piece, and the other end passes through the wire holes of the remaining joint pieces in turn and then gathers on the cable harness.

[0014] Furthermore, the turntable is provided with two upper and lower grooves, and the pulling wires on both sides are gathered into one strand through a wire tie device and then wound in the two grooves in opposite directions one by one.

[0015] Furthermore, it also includes a waterproof shell, the overall shape of which imitates the shape of a rainbow trout; the waterproof shell includes a fish head shell and a fish tail waterproof rubber film, the control system and the drive mechanism are arranged in the fish head shell; the bionic flexible fish tail is arranged in the fish tail waterproof rubber film.

[0016] Furthermore, the control system includes a control chip, a communication module, a power module, and a circuit module; the control chip receives the signal collected by the flexible sensor and controls the swing of the bionic flexible fishtail through a steering gear.

[0017] Furthermore, the fish head shell includes an upper half shell and a lower half shell, the antenna of the communication module is arranged on the upper half shell and partially extends out of the shell; the front of the lower half shell is provided with a charging port, and the side is provided with a main switch and a program burning port.

[0018] Furthermore, the bionic flexible fish tail also includes a bionic tail fin, which imitates the tail fin structure of a rainbow trout and has vertical protruding patterns on its surface. A slot is provided at one end of the bionic tail fin, and is connected to the tail end of the bionic fish tail bone plate through the slot.

[0019] A tail swing curve optimization method of a bionic robotic fish with tail self-sensing as described above, wherein the spacing between the joint pieces of the bionic flexible fish tail is determined by fitting the established bionic robotic fish tail bending posture curve with the tail bending posture curve of the croaker fish:

[0020] The effective force F of each joint piece on the bending of the bionic fishtail bone plate Oi for:

[0021]

[0022] in F is the tension of the cable on the end of the joint piece, θ maxi is the maximum rotation angle of the bionic fishtail bone plate between each joint piece;

[0023] The maximum rotation angle of the bionic fishtail bone plate between the joint pieces derived by combining the cantilever beam mechanical model θ maxi :

[0024]

[0025] in F Oi is the radial force of the tension wire on each joint piece, l i is the distance between the joint pieces, E is the Young's modulus of the bionic fishtail bone plate, I is the moment of inertia;

[0026] According to the cantilever beam mechanics model, the bionic fishtail plate is deduced to have a unilateral tensile F The bending curve under the action of Y ( x ):

[0027]

[0028] in, x is the independent variable between the joint piece spacing, F Oi is the radial force of the tension wire on each joint piece, l i is the distance between the joint pieces, E is the Young's modulus of the bionic fishtail bone plate, I is the moment of inertia;

[0029] Create the curved curve for the tail of the croaker:

[0030]

[0031] Establishing the bending curve of the bionic fishtail bone plate and the curved tail of the croaker fish The objective function S of the minimum geometric area difference between Lmin :

[0032]

[0033] when and When the geometric area difference between them is the smallest, the bionic flexible fish tail is most similar to the bending posture of the tail of the croaker fish. At this time, the corresponding spacing between the joint pieces is the optimal spacing distribution of the joint pieces, and the swing curve of the bionic flexible fish tail is optimal.

[0034] The beneficial effects of the present invention are:

[0035] 1. The bionic flexible fishtail in the present invention can realize the self-perception of the swing amplitude of the tail of the robot fish. The corresponding biological fish will adapt to the environment and present different swinging postures in different environments. The greater the impact of the water flow on the robot fish, the greater the difference between the actual swing amplitude of the fishtail and the expected swing amplitude. Flexible sensors are set on both sides of the bionic fishtail bone plate in the present invention, and their resistance value corresponds to the swing angle of the robot fishtail. By monitoring the resistance value to sense the swing amplitude of the tail, the self-perception correction can be achieved by compensating the error, which solves the problem that the bending angle error of the robot fishtail becomes larger when the wire-driven fishtail is impacted by faster water flow. And in previous studies, it was found that the swimming of biological fish presents a regularity: in still water, it swings with a large amplitude and a small frequency; in rapids, it swings with a small amplitude and a large frequency. The self-perception ability of the robot fish enables it to imitate the law of the swimming of biological fish and better adapt to environmental changes.

[0036] 2. The present invention improves the comprehensive swimming ability of the robot fish by imitating the swimming characteristics of the croaker fish. The simplified fish tail structure is mathematically modeled, and the area difference between the traveling wave curve of the croaker fish and the robot fish tail curve is selected as the objective function. By adjusting the distribution spacing of the robot fish's lamellar joints and optimizing the bending posture of the robot fish tail, the robot fish is made to conform to the swimming characteristics of the croaker fish. The optimized robot fish has significantly improved swimming ability indicators such as straight swimming speed and turning radius.

[0037] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0039] Figure 1It is a schematic diagram of the overall structure of the bionic robotic fish with tail self-sensing in the present invention.

[0040] Figure 2 It is a schematic diagram of the driving mechanism in the present invention.

[0041] Figure 3 It is a schematic diagram of the turntable in the present invention.

[0042] Figure 4 Schematic diagram of the bionic tail fin of the present invention.

[0043] Figure 5 It is a schematic diagram of the bionic fishtail bone plate in the present invention.

[0044] Figure 6 Schematic diagram of a fish head shell provided for an example of the present invention.

[0045] Figure 7 The figure is a flow chart of manufacturing the bionic fishtail bone plate of the present invention.

[0046] Figure 8 It is a schematic diagram of the flexible fishtail swing control in the present invention.

[0047] Fig. 9 This is a force analysis diagram of the flexible fishtail bending in the present invention.

[0048] Fig.10 This is the correspondence between the resistance value and the stretching length of the flexible sensor in the present invention.

[0049] Figure numerals: 1-fish head shell; 2-control main board; 3-battery; 4-counterweight; 5-communication module; 6-driving mechanism; 7-joint piece; 8-pull wire; 9-waterproof rubber film; 10-bionic flexible fish tail; 11-bionic tail fin; 12-cable harness seat; 13-turntable; 14-servo; 15-cable harness; 16-servo support; 17-side groove of turntable; 18-slot at the bottom of turntable; 19-texture; 20-slot; 21-bionic fish tail bone plate; 22-copper foil wire at the end of the tail; 23-copper foil wire at the head of the tail; 24-flexible substrate; 25-sensitive unit; 26-conductive paint; 27-lower half shell; 28-upper half shell; 29-communication module antenna; 30-charging port; 31-main switch; 32-program burning port. DETAILED DESCRIPTION

[0050] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0051] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0052] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0053] See also Figures 1 to 8 , which is a bionic robot fish with tail self-sensing, including a control system, a driving mechanism 6, a bionic flexible fish tail 10, and a waterproof shell. The bionic flexible fish tail 10 includes a flexible bionic fish tail bone plate 21 made of rubber, a plurality of joint pieces 7 vertically mounted and fixed on the bionic fish tail bone plate 21 at a set interval, and two flexible sensors arranged on both sides of the bionic fish tail bone plate 21; the driving mechanism 6 includes a steering engine 14, a turntable 13, and a pull wire 8; the joint piece 7 is divided into left and right sides with the bionic fish tail bone plate 21 as the boundary, and a pull wire 8 is connected to each side of the turntable 13, and the other ends of the two pull wires 8 pass through the middle joint piece 7 and are respectively connected to the left and right sides of the joint piece 7 at the tail end; the steering engine 14 is connected to the turntable 13 to drive the turntable 13 to rotate left and right, thereby driving the bionic fish tail bone plate 21 to swing left and right through the pull wires 8 on both sides.

[0054] The flexible sensor and the servo 14 are both connected to the control system. The control system drives the bionic fishtail bone plate 21 to swing through the servo 14. The flexible sensors on both sides of the bionic fishtail bone plate 21 are stretched and compressed, and the resistance value changes. The control system collects the resistance change of the flexible sensor; the resistance values ​​of the flexible sensors on both sides are detected to be different, and the positive and negative values ​​of the difference are used to define the swing direction of the fishtail, and the size of the difference corresponds to the swing angle of the fishtail; the control system uses a predetermined algorithm to control the swing angle of the bionic fishtail bone plate 21 in real time according to the resistance difference of the flexible sensors on both sides to achieve the expected fishtail bending state, thereby realizing self-sensing correction.

[0055] Among them, the overall shape of the waterproof shell imitates the shape of a rainbow trout; the waterproof shell includes a fish head shell 1 and a fish tail waterproof rubber film 9, and the control system and the driving mechanism 6 are arranged in the fish head shell 1; the bionic flexible fish tail 10 is arranged in the fish tail waterproof rubber film 9. The control system includes a control chip, a communication module 5, a battery 3, and a circuit module; the control chip, the communication module 5, and the circuit module are arranged on the control main board 2; the control chip receives the signal collected from the flexible sensor, and controls the bionic flexible fish tail 10 to swing through the steering gear 14. The fish head shell 1 includes an upper half shell 28 and a lower half shell 27, and the upper half shell 28 and the lower half shell 27 are tightly fitted and waterproofed. The communication module antenna 29 is arranged on the upper half shell 28 and partially extends out of the shell; the front of the lower half shell 27 is provided with a charging port 30, and the side is provided with a main switch 31 and a program burning port 32. The charging port 30 is used to charge the bionic robot fish, and the port needs to be sealed before entering the water; the main switch 31 is used to control the power supply of the control mainboard 2; and the program burning port 32 is used to update the internal program of the control mainboard 2.

[0056] A counterweight block 4 is also provided in the fish head shell 1, and the bionic robotic fish is controlled to suspend in the water by adjusting the weight.

[0057] See also Figure 7The flexible sensor in this embodiment is a LIG sensor, including a flexible substrate 24, a sensitive unit 25, a wire and a protective layer; the flexible substrate 24 is a composite film composed of two particles of polydimethylsiloxane (PDMS) and polyimide (PI), which is attached to the bionic fish tail bone plate 21; the sensitive unit 25 is a laser-induced graphene formed by scanning the flexible substrate 24 by a laser and distributed linearly along the length direction of the bionic fish tail bone plate 21; in this embodiment, the wire is a copper foil wire, and the copper foil wire 23 at the tail head is closely attached to the flexible substrate 24 and longitudinally bonded and led out to connect with the fish head control main board 2; the copper foil wire 22 at the tail end is closely attached to the flexible substrate 24 and led out by the end around the sensitive unit 25 to connect with the control main board 2, and its sticky side is bonded to one end of the sensitive unit 25; conductive paint 26 is applied at the connection between the copper foil wire and the sensitive unit 25; the protective layer is a polydimethylsiloxane layer covering the surface of the flexible substrate 24 and the sensitive unit 25.

[0058] The driving mechanism 6 also includes a cable harness 15, which is installed between the turntable 13 and the bionic fishtail bone plate 21. The steering gear 14 maintains a certain distance from the fishtail joint plate 7 through the steering gear support 16. The pull wire 8 is made of steel wire, and the pull wire 8 on both sides of the turntable 13 has two strands. After passing through the joint plate 7, the two strands of the pull wire 8 are merged into one strand through the cable harness 15 and then connected to the turntable 13; the steering gear 14 drives the turntable 13 to rotate by rotating the angle, thereby tightening the pull wire 8 on one side of the turntable 13, and at the same time, the pull wire 8 on the other side is loosened by the same amount, so that the bionic fishtail bone plate 21 bends to one side.

[0059] The bottom slot 18 of the turntable is connected to the steering gear 14, and the two sets of cables 8 on both sides of the fishtail are respectively fixed in the grooves 17 on the sides of the upper and lower turntables after being merged into one through the cable tie 15, and are wound around the turntable 13 in a clockwise or counterclockwise direction. When the steering gear 14 drives the turntable 13 to rotate, one side of the two sets of cables 8 wound around the turntable 13 in the opposite direction will be tightened, so that one side of the bionic fishtail bone plate 21 will be subjected to tension and bend, while the cables 8 on the other side will be relaxed, and will not hinder the bending deformation of the fishtail.

[0060] The joint piece 7 is provided with wire holes, and the distances from the wire holes on the same side of each joint piece 7 to the bionic fishtail bone plate 21 are equal; one end of the pull wire 8 is fixed to the last joint piece 7 of the fishtail through a wire harness seat 12, and the other end passes through the wire holes of the remaining joint pieces 7 in turn and then gathers on the wire harness 15.

[0061] The bionic flexible fish tail 10 also includes a bionic tail fin 11 , which imitates the tail fin structure of a rainbow trout, and has vertical protruding patterns 19 on its surface. A slot 20 is provided at one end of the bionic tail fin 11 , and is connected to the tail end of the bionic fish tail bone plate 21 through the slot 20 .

[0062] The spacing between the joint pieces 7 is determined by fitting the established bending posture of the fishtail of the bionic robot fish with the bending posture of the fishtail of the croaker fish.

[0063] like Figure 8 As shown, the bionic robot fish of the present invention has the functions of moving straight and turning, and its system control uses a steering gear 14 with a rotation range of 0-180°: the steering gear 14 rotates cyclically at a position of 45° to 135° to drive the tail to swing left and right, thereby realizing the control of the robot fish swimming straight. In the turning control of the bionic robot fish, the 90° tail swing is the main drive, and the turning radius of the robot fish is further reduced by swinging the tail 45° continuously and quickly. Taking the robot fish turning left as an example, the steering gear 14 completes the robot fish's 180° turn to the left through 6 consecutive rotations.

[0064] See also Fig. 9 , 10 , is a method for optimizing the tail swing curve of a bionic robotic fish with tail self-sensing in this embodiment, and the spacing between the joint pieces 7 of the bionic flexible fish tail 10 is determined by fitting the established bionic robotic fish bending posture curve with the tail bending posture curve of the croaker fish:

[0065] The effective force F of each joint piece 7 on the bending of the bionic fishtail bone plate 21 Oi for:

[0066]

[0067] in F is the pulling force of the pull wire 8 on the joint piece 7 at the end, θ maxi is the maximum rotation angle of the bionic fishtail bone plate 21 between the joint pieces 7;

[0068] The maximum rotation angle of the bionic fishtail bone plate 21 between the joint pieces 7 derived by combining the cantilever beam mechanical model θ maxi :

[0069]

[0070] in F Oi is the radial force of the pull wire 8 on each joint piece 7, l i is the distance between the joint pieces 7, E is the Young's modulus of the bionic fishtail bone plate 21, I is the moment of inertia;

[0071] According to the cantilever beam mechanical model, the bionic fishtail plate 21 is deduced to have a unilateral tensile force F The bending curve under the action of Y (x ):

[0072]

[0073] in, x is the independent variable between the joint pieces 7, F Oi is the radial force of the pull wire 8 on each joint piece 7, l i is the distance between the joint pieces 7, E is the Young's modulus of the bionic fishtail bone plate 21, I is the moment of inertia;

[0074] Refer to the relevant literature on biological fish motion posture curves to establish the tail bending curve of the croaker fish:

[0075]

[0076] Establishing the bending curve of the bionic fishtail bone plate 21 and the curved tail of the croaker fish The objective function S of the minimum geometric area difference between Lmin :

[0077]

[0078] when and When the geometric area difference between them is the smallest, the bionic flexible fish tail 10 is most similar to the bending posture of the tail of the croaker fish. At this time, the corresponding spacing between the joint pieces 7 is the optimal spacing distribution of the joint pieces 7, and the swing curve of the bionic flexible fish tail 10 is optimal.

[0079] The present invention establishes a mechanical model of the tail structure of the line-driven robot fish, and derives the bending curve of the tail of the robot fish from the mechanical model. The spacing between the joint pieces 77 is determined by fitting the bending posture of the tail of the robot fish with the bending posture of the tail of the croaker fish. A genetic algorithm is used in Matlab, and the minimum geometric area difference between the bending curves of the tails of the robot fish and the croaker fish is selected as the fitness function. The optimal result is the spacing length of each joint piece 7.

[0080] Referring to the movement posture of the tail of biological fish in different water flow environments, different controls are performed on the bionic robot fish swimming in different environments. In still water, the swing amplitude of the robot fish tail is the expected swing amplitude, and the controlled swing rule is large amplitude and small frequency; in rapids, the swing amplitude of the robot fish tail becomes smaller due to the impact of the water flow, and the controlled swing rule is small amplitude and large frequency.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A bionic robotic fish with tail self-sensing, characterized by: It comprises a control system, a driving mechanism, and a bionic flexible fishtail; the bionic flexible fishtail comprises a flexible bionic fishtail bone plate, a plurality of joint pieces vertically mounted and fixed on the bionic fishtail bone plate at a set interval, and two flexible sensors arranged on both sides of the bionic fishtail bone plate; the driving mechanism comprises a steering gear, a turntable, and a pull wire; the joint piece is divided into left and right sides with the bionic fishtail bone plate as a boundary, a pull wire is connected to each side of the turntable, and the other ends of the two pull wires pass through the middle joint piece and are respectively connected to the left and right sides of the joint piece at the tail end; the steering gear is connected to the turntable to drive the turntable to rotate left and right, thereby driving the bionic fishtail bone plate to swing left and right through the pull wires on both sides; The flexible sensor and the steering gear are both connected to the control system. The control system drives the bionic fishtail bone plate to swing through the steering gear. The flexible sensors on both sides of the bionic fishtail bone plate are stretched and compressed, and the resistance value changes. The control system collects the resistance change of the flexible sensor; the resistance values ​​of the flexible sensors on both sides are detected to be different, and the positive and negative values ​​of the difference are used to define the swing direction of the fishtail, and the size of the difference corresponds to the swing angle of the fishtail; the control system uses a predetermined algorithm to control the swing angle of the bionic fishtail bone plate in real time according to the resistance difference of the flexible sensors on both sides to achieve the expected fishtail bending state, thereby realizing self-sensing correction; The flexible sensor is a LIG sensor, comprising a flexible substrate, a sensitive unit, a wire and a protective layer; The flexible substrate is a composite film comprising at least two types of particles, polydimethylsiloxane and polyimide, and is attached to the bionic fishtail bone plate; The sensitive unit is laser-induced graphene formed by laser scanning on the flexible substrate and distributed linearly along the length direction of the bionic fishtail bone plate; the wire connects the two ends of the sensitive unit to the control system; the protective layer is a polydimethylsiloxane layer covering the surface of the flexible substrate and the sensitive unit.

2. The bionic robotic fish with tail self-sensing according to claim 1, characterized in that: The driving mechanism also includes a cable harness, which is arranged between the turntable and the bionic fishtail bone plate; there are multiple pull wires on both sides of the turntable, and the multiple pull wires pass through the joint plate and then merge into one strand through the cable harness and connected to the turntable; the servo drives the turntable to rotate by rotating the angle, thereby tightening the pull wire on one side wrapped around the turntable, and at the same time loosening the pull wire on the other side by the same amount, so that the bionic fishtail bone plate bends to one side.

3. The bionic robotic fish with tail self-sensing according to claim 2, characterized in that: The joint piece is provided with wire holes, and the distances from the wire holes on the same side of each joint piece to the bionic fishtail bone plate are equal; one end of the pull wire is connected to the joint piece at the tail end, and the other end passes through the wire holes of the remaining joint pieces in turn and then gathers on the wire harness.

4. The bionic robotic fish with tail self-sensing according to claim 2, characterized in that: The rotating disk is provided with two upper and lower grooves, and the pulling wires on both sides are gathered into one strand through a wire tie device and then wound in the two grooves in opposite directions one by one.

5. The bionic robotic fish with tail self-sensing according to claim 1, characterized in that: It also includes a waterproof shell, the overall shape of which imitates the shape of a rainbow trout; the waterproof shell includes a fish head shell and a fish tail waterproof rubber film, the control system and the drive mechanism are arranged in the fish head shell; the bionic flexible fish tail is arranged in the fish tail waterproof rubber film.

6. The bionic robotic fish with tail self-sensing according to claim 5, characterized in that: The control system includes a control chip, a communication module, a power module, and a circuit module; the control chip receives the signal collected by the flexible sensor and controls the swing of the bionic flexible fish tail through the steering gear.

7. The bionic robotic fish with tail self-sensing according to claim 6, characterized in that: The fish head shell includes an upper half shell and a lower half shell. The antenna of the communication module is arranged on the upper half shell and partially extends out of the shell. The front part of the lower half shell is provided with a charging port, and the side part is provided with a main switch and a program burning port.

8. The bionic robotic fish with tail self-sensing according to claim 1, characterized in that: The bionic flexible fish tail also includes a bionic tail fin, which imitates the tail fin structure of a rainbow trout and has vertical protruding patterns on its surface. A slot is provided at one end of the bionic tail fin, and is connected to the tail end of the bionic fish tail bone plate through the slot.

9. A method for optimizing the tail swing curve of a bionic robotic fish with tail self-sensing according to any one of claims 1 to 8, characterized in that: The spacing between the joint pieces of the bionic flexible fish tail is determined by fitting the established bionic robot fish tail bending posture curve with the tail bending posture curve of the croaker fish: The effective force F of each joint piece on the bending of the bionic fishtail bone plate Oi for: in F is the tension of the cable on the end of the joint piece, θ maxi is the maximum rotation angle of the bionic fishtail bone plate between each joint piece; The maximum rotation angle of the bionic fishtail bone plate between the joint pieces derived by combining the cantilever beam mechanical model θ maxi : in F Oi is the radial force of the tension wire on each joint piece, l i is the distance between the joint pieces, E is the Young's modulus of the bionic fishtail bone plate, I is the moment of inertia; According to the cantilever beam mechanical model, the bionic fishtail plate is deduced to have a unilateral tensile F The bending curve under the action of Y ( x ): in, x is the independent variable between the joint piece spacing, F Oi is the radial force of the tension wire on each joint piece, l i is the distance between the joint pieces, E is the Young's modulus of the bionic fishtail bone plate, I is the moment of inertia; Create the curved curve for the tail of the croaker: Establishing the bending curve of the bionic fishtail bone plate and the curved tail of the croaker fish The objective function S of the minimum geometric area difference between Lmin : when and When the geometric area difference between them is the smallest, the bionic flexible fish tail is most similar to the bending posture of the tail of the croaker fish. At this time, the corresponding spacing between the joint pieces is the optimal spacing distribution of the joint pieces, and the swing curve of the bionic flexible fish tail is optimal.

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