Multi-Joint Bionic Hairtail Robot and Method Based on BCF Propulsion Mode

Abstract

This is a multi-joint bionic hairtail robot and method based on the BCF propulsion mode, belonging to the field of robot technology applications. The multi-joint bionic hairtail robot consists of three main parts: a hairtail head, N body units, and a hairtail tail. Among them, there is a center of gravity adjustment structure inside the hairtail head. Through different movement modes of the configuration blocks in this mechanism, the multi-joint bionic hairtail robot can achieve movements such as swimming vertically forward, turning left or right, pitching vertically up and down, and flipping from vertical to horizontal in water. This robot has high flexibility, uses a wireless remote control method to perform hairtail-like swimming, and realizes rapid adjustment of the movement path. By simulating the BCF movement mode of the hairtail, it studies how to improve the propulsion efficiency while achieving maneuverability and stability. It has important research significance and application value for fields such as underwater pipeline quality inspection and water quality inspection.

Description

Technical Field

[0001] The invention belongs to the field of robot technology applications, and specifically relates to the mechanical structure and motion mode of a multi-joint bionic hairtail robot based on the BCF propulsion method. It can meet functions such as underwater obstacle avoidance and pipeline quality inspection, and can also be applied to observing wild biological activities in the natural environment, providing a new solution for field research. In addition, it can also be applied to other fields such as commerce and scientific research. Background Art

[0002] Robots that can adapt to various complex underwater environments are one of the most cutting-edge topics in the current field of robot research. They integrate multiple disciplines such as machinery, electronics, computer, materials, sensors, control technology, and artificial intelligence, reflecting a country's intelligent and automated research level. At the same time, they also serve as an important symbol of a country's high-tech strength. Developed countries have successively invested heavily in research in this field.

[0003] Body / caudal fin propulsion mode (BCF). BCF propulsion forms thrust through the telescopic undulation of the trunk and the swinging of the caudal fin. It has a fast swimming speed, high efficiency, and high quick-start performance, and is suitable for long-time, long-distance, high-speed swimming or occasions that require instantaneous acceleration or turning. In addition, according to the morphological characteristics of fish movement, BCF propulsion can be divided into two categories: undulatory propulsion and oscillatory propulsion. Undulatory fish generate propulsion waves through body undulation during swimming. The direction of the propulsion wave is opposite to the movement direction of the fish body, and the wave speed is faster than the movement speed of the fish body. Oscillatory fish rotate their fins or caudal peduncles around an axis or a base during swimming propulsion, and the movement does not generate a complete waveform. And the present invention belongs to the bionic robotic fish of undulatory propulsion.

[0004] Compared with the bionic fish robots with similar movements of some domestic institutions, the bionic fish structure CN202022538937.8 for environmental monitoring developed by Beijing Zhongke Unlimited Education Technology Co., Ltd. relies on the left output shaft of the motor to connect with the driving pulley. The outer diameter surface of the driving pulley rotates synchronously with the driven pulley through a synchronous belt, and a drive shaft is arranged in the middle of the driven pulley to realize bionic swing; A new type of machine bionic fish CN201320870892.1 of Wenzhou Vocational and Technical College can realize various underwater movements through the cooperation of pectoral fins and caudal fins. The pectoral fins are like the main wings or horizontal wings of an aircraft to control the rise and dive of the aircraft. When the fish swims at high speed, the pectoral fins act as elevators to control the rise and dive of the fish; Beijing Spei A bionic fish CN202122120426.9 for fish school monitoring and induction by De Culture Communication Co., Ltd. is driven by a servo motor to rotate the twisting arm, which is connected to the rotating rod through a U-shaped connecting frame, and can drive the rotating rod to swing back and forth, and is connected to the tail fin through a connecting rod, which can drive the tail fin to swing synchronously, thereby pushing the bionic fish body forward in the water; A smart ornamental bionic fish CN201420414492.4 by the School of Applied Technology of Soochow University is respectively fixed on two servo frames, and the two U-shaped frames are respectively connected to the output shafts of the front servo and the rear servo of the fish tail, and the two servo frames and the two U-shaped frames are respectively connected by two L-shaped frames, and the front servo and the rear servo of the fish tail are connected in series to form a relatively rotating joint. This type of bionic fish robot generally uses underwater servos, which are expensive, and bionic fish projects using ordinary servos are relatively rare. It achieves and reaches the experimental results of the same project at a relatively low cost, coupled with reasonable and effective waterproofing measures. This method has not been specifically studied in China. Summary of the invention

[0005] The purpose of the present invention is to utilize the appearance characteristics and swimming characteristics of hairtail, through modeling simulation, 3D printing, single-chip microcomputer control and underwater testing and other processes, to realize the production of a multi-joint bionic hairtail robot that can meet the functions of underwater obstacle avoidance and pipeline quality inspection, and ultimately effectively reduce the need for manual underwater operations.

[0006] A multi-joint bionic hairtail robot based on BCF propulsion mode, characterized by:

[0007] Including the head of the hairtail fish, N body units, and the tail of the hairtail fish;

[0008] The above-mentioned hairtail head is composed of an upper head shell, a lower head shell, a system board, a battery, a visual recognition module, and a center-of-gravity adjustment mechanism installed inside the lower head shell; the center-of-gravity adjustment mechanism is composed of a first built-in motor of the fish head, a moving configuration block of the fish head, a second built-in motor of the fish head, a guide rod, a screw rod, and a deflection configuration block of the fish head; among them, the screw rod is installed on the output shaft of the second built-in motor of the fish head, and the second built-in motor of the fish head and the above-mentioned guide rod are fixed inside the head shell; the moving configuration block of the fish head is installed on the screw rod and the guide rod, and the threaded hole of the moving configuration block of the fish head is screwed with the screw rod; the first built-in motor of the fish head is installed on the moving configuration block of the fish head, and the deflection configuration block of the fish head is installed on the output shaft of the first built-in motor of the fish head.

[0009] The above-mentioned body unit includes an upper body unit shell, a dorsal fin installed on the back of the upper body unit shell through a dorsal fin support frame, and a ventral fin installed on the lower body unit shell through a ventral fin support frame; it also includes a body unit servo motor, a body unit servo motor disk, a body unit output shaft, and a body unit bearing installed inside the lower body unit shell; among them, after the body unit output shaft is matched with the body unit bearing, it is fixed to the output rotating shaft of the body unit servo motor through the body unit servo motor disk, and the body unit servo motor is fixed inside the lower body unit shell; the end of the body unit output shaft extends out of the upper body unit shell;

[0010] The hairtail tail is composed of an upper tail shell, an upper tail shell, a tail servo motor, a tail servo motor disk, a tail output shaft, a bearing at the tail output shaft, and a thin sheet at the end of the tail; among them, after the tail output shaft is matched with the bearing at the tail output shaft, it is fixed to the output rotating shaft of the tail servo motor through the tail servo motor disk, and the tail servo motor is fixed inside the lower tail shell; the end of the tail output shaft extends out of the upper tail shell;

[0011] The above-mentioned upper head shell is connected to the first adjacent body unit output shaft, the upper body unit shell is connected to the body unit output shaft of the adjacent body unit behind it; the upper body unit shell of the last body unit is connected to the tail output shaft; each of the above-mentioned N body units and the inside of the hairtail tail is equipped with four configuration blocks, which are respectively located in the upper, lower, left, and right, and are symmetrically arranged.

[0012] The motion method of the above-mentioned multi-joint bionic hairtail robot based on the BCF propulsion method is characterized by including the following processes:

[0013] First, the posture when the dorsal fin and ventral fin of the multi-joint bionic hairtail robot are respectively directly above and directly below the horizontal plane is called the vertical posture, and the posture when both the dorsal fin and ventral fin of the multi-joint bionic hairtail robot are on the horizontal plane is called the horizontal posture. The angle between each body unit and the adjacent body unit in the direction close to the head of the hairtail is called the forward offset angle, and the angle between the body unit and the adjacent body unit in the direction away from the head of the hairtail is called the backward offset angle. A leftward deviation relative to the forward direction is positive, and a rightward deviation relative to the moving direction is negative; the symmetry line of the vertical symmetry plane of the body of the multi-joint bionic hairtail robot is called the body center line, and the positive direction of the body center line is from the tail of the hairtail to the head of the hairtail. When the head of the hairtail deviates above the horizontal plane, the angle between the positive direction of the body center line and the horizontal plane is called the elevation angle, and when the head of the hairtail deviates below the horizontal plane, the angle between the positive direction of the body center line and the horizontal plane is called the depression angle;

[0014] A center-of-gravity adjustment mechanism is configured at the head of the hairtail; four configuration blocks are configured inside the rear N body units and the tail of the hairtail. The four configuration blocks are divided into two each, upper and lower, left and right, and are symmetrically arranged. During installation, by adjusting the positions of the configuration blocks, the center of gravity and the center of buoyancy of each body unit or the tail of the hairtail are made to coincide with each other;

[0015] Overall horizontal-vertical conversion: There is a center-of-gravity adjustment mechanism at the head of the hairtail. During vertical or horizontal swimming, the head of the fish is rotated by the first built-in motor in the fish head to deflect the configuration block, adjusting the left-right movement of the center of gravity; since the center of gravity and the center of buoyancy are not on the same vertical line, a deflecting moment will be generated, causing the multi-joint bionic hairtail robot to gradually change from the vertical posture to the horizontal posture, or from the horizontal posture to the vertical posture;

[0016] Overall vertical forward swimming: The swing frequencies and amplitudes of all body units are exactly the same, but there is a fixed and equal phase difference, thus achieving a standard sine-wave motion;

[0017] Flexible dorsal fins and ventral fins are adopted. When swinging left and right, the vertical cross-sections of each body unit and the flexible surfaces of the dorsal fins and ventral fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the multi-joint bionic hairtail robot, realizing overall forward movement;

[0018] Overall vertical left or right turning swimming: A number of body units close to the head of the hairtail remain relatively stationary and have a fixed forward offset angle; the swing frequencies of a number of body units close to the tail of the hairtail are exactly the same, but there is a linearly increasing relationship in the swing amplitudes, and there is also a fixed phase difference;

[0019] By adopting flexible dorsal fins and ventral fins, when swinging left and right, the vertical cross-sections of each body unit and the flexible surfaces of the dorsal fins and ventral fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the robot;

[0020] When the current row offset angle is positive, the thrust on the right side by the water is greater than that on the left side, and the robot is subject to an unbalanced force, i.e., a left-turn torque, to achieve a left turn; when the current row offset angle is negative, the thrust on the left side by the water is greater than that on the right side, and the robot is subject to an unbalanced force, i.e., a right-turn torque, to achieve a right turn.

[0021] The motion method of the multi-joint bionic hairtail robot based on the BCF propulsion mode is characterized by including the following process:

[0022] Pitch conversion is achieved through the relevant motion of the center-of-gravity adjustment mechanism of the hairtail head, and the specific implementation is as follows: In the initial state, the fish head moving configuration block is located at the middle position of the guide rail, and the fish head deflection configuration block is located directly above the axis of the first built-in motor of the fish head; at this time, the center of gravity of the hairtail head coincides with the center of buoyancy, and the multi-joint bionic hairtail robot presents a vertical suspension state in water; the second built-in motor of the fish head drives the fish head moving configuration block to move forward towards the front of the hairtail head through the rotation of the screw. When the fish head moving configuration block reaches a certain position, the upper fish head deflection configuration block rotates 180 degrees from the upper part to the lower part, and the fish head deflection configuration block is located below the axis of the output shaft of the first built-in motor of the fish head. At this time, the center of gravity of the hairtail head is located at the front lower segment position of the hairtail head; during the entire movement process of the fish head moving configuration block, the center of gravity of the hairtail head gradually moves forward, and a torque is formed between gravity and buoyancy, thereby driving the body part of the multi-joint bionic hairtail robot to achieve a downward flipping motion. When the changed center of gravity and the center of buoyancy are again on the same vertical line, stop the downward flipping to reach the target downward-looking posture. The degree of this downward-looking, i.e., the size of the downward angle, is proportional to the magnitude of the forward displacement of the fish head moving configuration block; when the upward-looking posture is to be achieved, the second built-in motor of the fish head drives the fish head moving configuration block to move backward towards the rear of the hairtail head through the rotation of the screw. When the fish head moving configuration block reaches a certain position, the upper fish head deflection configuration block rotates 180 degrees from the upper part to the lower part, and the fish head deflection configuration block is located directly below the axis of the output shaft of the first built-in motor of the fish head. At this time, the center of gravity of the hairtail head is biased towards the rear lower segment position of the hairtail head; during the entire movement process of the fish head moving configuration block, the center of gravity of the hairtail head gradually moves backward, and a torque is formed between gravity and buoyancy, thereby driving the body part of the multi-joint bionic hairtail robot to achieve an upward flipping motion. When the changed center of gravity and the center of buoyancy are again on the same vertical line, stop the upward flipping to reach the target upward-looking posture. The degree of this upward-looking, i.e., the size of the upward angle, is proportional to the magnitude of the backward displacement of the fish head moving configuration block.

[0023] The present invention has the following advantages compared with the prior art:

[0024] 1. Compared with previous few-joint bionic fish, the fabrication of a multi-joint bionic hairtail robot is realized.

[0025] 2. A servo motor is arranged at each joint to realize the coordinated movement of a multi-joint bionic hairtail robot.

[0026] 3. The structure of the present invention is simple, the motion principle is clear, and the motion implementation is convenient.

[0027] 4. The present invention can realize the high-maneuverability swimming of a multi-joint bionic hairtail robot in water, and has the characteristics of high efficiency, low energy consumption and strong environmental adaptability.

[0028] 5. A center-of-gravity adjustment mechanism is installed inside the head of the hairtail, which can realize the transformation of postures including pitching up and down, horizontal rolling, etc.

[0029] The described multi-joint bionic hairtail robot is characterized in that: the main body of the body is composed of multiple similar body units; the structures of each abdominal fin and dorsal fin are the same. This symmetric structure design is simple in structure, clear in motion principle, and beneficial to the motion stability of the robot. Description of the Drawings

[0030] Figure 1 is the overall oblique view of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention;

[0031] Figure 2 is the schematic diagram of module decomposition of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention;

[0032] Figure 3 is the schematic diagram of head structure decomposition of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention;

[0033] Figure 4 is the schematic diagram of intermediate joint structure decomposition of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention;

[0034] Figure 5 is the schematic diagram of tail structure decomposition of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention;

[0035] Figure 6 is the motion schematic diagram of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention changing from vertical swimming to horizontal swimming in water;

[0036] Figure 7 is the motion schematic diagram of a multi-joint bionic hairtail robot and method based on the BCF propulsion mode of the present invention turning in an underwater pipeline;

[0037] Figure 8 It is a schematic diagram of the up-and-down pitching motion in water of a multi-joint bionic hairtail robot and method based on the BCF propulsion method of the present invention;

[0038] Figure 9 It is a schematic diagram of the left-and-right rolling motion in water of a multi-joint bionic hairtail robot and method based on the BCF propulsion method of the present invention;

[0039] Figure 10 It is a schematic diagram of the motion of a multi-joint bionic hairtail robot and method based on the BCF propulsion method of the present invention gradually changing from vertical swimming to horizontal swimming in water;

[0040] Figure 11 It is a schematic diagram of the distribution of internal configuration blocks for adjusting the center of gravity and the center of buoyancy to one point inside the body joint part (Z1~Z5) and the tail part (W1) of a multi-joint bionic hairtail robot and method based on the BCF propulsion method of the present invention;

[0041] Figures 1-11 Names of reference numerals in the figure: hairtail head T1; body unit Z1; body unit Z2; body unit Z3; body unit Z4; body unit Z5; hairtail tail W1; upper shell of the head A1; first built-in motor of the fish head A2; moving configuration block of the fish head A3; second built-in motor of the fish head A4; second motor fixing box of the fish head A5; fish head sealing ring A6; lower shell of the head A7; visual recognition module A8; model airplane battery A9; system board A10; guide rod 11; screw A12; fish head deflection configuration block A13; dorsal fin B1; dorsal fin support frame B2; upper shell of the body unit B3; first sealing ring B4; body unit bearing B5; first screw B6; body unit output shaft B7; second sealing ring B8; body unit servo steering wheel B9; body unit servo B10; lower shell of the body unit B11; abdominal fin B12; abdominal fin support frame B13; upper shell of the fish tail C1; sealing ring at the fish tail output shaft C2; bearing at the fish tail output shaft C3; fish tail output shaft C4; fish tail servo steering wheel C5; fish tail servo fixing screw C6; fish tail servo C7; fish tail sealing ring C8; lower shell of the fish tail C9; thin sheet at the end of the fish tail C10. Wherein X, Y, and Z are the corresponding three-dimensional space coordinate systems. Detailed implementation manners

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0043] Combined with Figures 1-8, this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion method, including a hairtail head T1; a body unit Z1; a body unit Z2; a body unit Z3; a body unit Z4; a body unit Z5; a hairtail tail W1; an upper head shell A1; a first built-in motor A2 in the fish head; a fish head movement configuration block A3; a second built-in motor A4 in the fish head; a second motor fixing box A5 in the fish head; a fish head sealing ring A6; a lower head shell A7; a visual recognition module A8; a model airplane battery A9; a system board A10; a guide rod 11; a screw A12; a fish head deflection configuration block A13; a dorsal fin B1; a dorsal fin support B2; an upper body unit shell B3; a first sealing ring B4; a body unit bearing B5; a first screw B6; a body unit output shaft B7; a second sealing ring B8; a body unit servo steering wheel B9; a body unit servo B10; a lower body unit shell B11; an abdominal fin B12; an abdominal fin support B13; an upper tail shell C1; a sealing ring at the tail output shaft C2; a bearing at the tail output shaft C3; a tail output shaft C4; a tail servo steering wheel C5; a tail servo fixing screw C6; a tail servo C7; a tail sealing ring C8; a lower tail shell C9; a thin sheet at the end of the tail C10.

[0044] Combined with Figure 1 , 2 , 3, this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion method, including a hairtail head T1; a body unit Z1; a body unit Z2; a body unit Z3; a body unit Z4; a body unit Z5; a hairtail tail W1. The upper surface concave hole and the lower surface concave hole at the rear connection of the lower head shell A7 are respectively matched with the upper front output shaft and the lower connection convex platform of the body unit Z1, showing a connection method of pairwise buckling. Figure 2 Only the body units Z1~Z5 of the multi-joint bionic hairtail robot are given in Figure 2 . In theory, there are Z1~ZN. So far,

[0045] Combined with Figure 6 , this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion method. The swing frequencies and swing amplitudes of all joints are exactly the same, but there is a fixed and equal phase difference, so as to achieve a standard sine wave motion; flexible dorsal fins and abdominal fins are adopted. When swinging left and right, the vertical cross-sections of each body unit and the flexible surfaces of the dorsal fins and abdominal fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the multi-joint bionic hairtail robot. To achieve overall forward movement.

[0046] Combined with Figure 7, this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion mode. The angle between each body unit and the adjacent body unit in the direction close to the head of the hairtail is called the forward offset angle, and the angle between it and the adjacent body unit in the direction away from the head of the hairtail is called the backward offset angle. A positive value indicates a left offset relative to the forward direction, and a negative value indicates a right offset relative to the movement direction. A number of joints close to the head of the hairtail remain relatively stationary and have a fixed forward offset angle. A number of joints close to the tail of the hairtail have exactly the same swing frequency, but there is a linearly increasing relationship in the swing amplitude, and there is also a fixed phase difference. Flexible dorsal fins and ventral fins are adopted. When swinging left and right, the vertical cross-section of each body unit and the flexible surfaces of the dorsal fins and ventral fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the multi-joint bionic hairtail robot. When the forward offset angle is positive, the thrust on the right side by the water is greater than that on the left side, generating an unbalanced force, that is, a left-turn torque, to achieve the overall left-turn movement.

[0047] Combined with Figure 7 , this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion mode. Through the reciprocating cyclic motion of each body unit, the multi-joint bionic hairtail robot can simulate a sinusoidal reciprocating swing underwater. By changing the forward offset angle of one or multiple body units alone or simultaneously to push the water flow, the movement thrust can be increased, the movement speed can be improved, the turning radius can be reduced at the same time, and the turning efficiency can be improved.

[0048] Combined with Figure 6 and Figure 7 , this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion mode. Through the reciprocating cyclic motion of each body unit, the multi-joint bionic hairtail robot can simulate a sinusoidal reciprocating swing in the water. By changing the reciprocating cyclic motion frequency and amplitude of the whole, and pushing the water flow, the movement thrust can be increased, the movement speed can be improved, and the movement maneuverability can be improved.

[0049] Combined with Figure 8 , this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion mode. There is a center-of-gravity adjustment mechanism at the head of the hairtail. During the vertical swimming process, by rotating the screw A12 of the second built-in motor A4 of the fish head, the fish head moving configuration block moves forward or backward, thereby adjusting the center of gravity to move forward or backward. Since the center of gravity and the center of buoyancy are not on the same vertical line, a deflection moment will be generated, so that the body center line of the multi-joint bionic hairtail robot forms a certain pitch angle with the horizontal plane, realizing the attitude adjustment of pitching up and down.

[0050] Combined with Figure 9, this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion method. There is a center-of-gravity adjustment mechanism in the hairtail head. During vertical swimming, by rotating the fish head deflection configuration block A13 forward or backward with the first built-in motor A2 in the fish head, since the center of gravity and the center of buoyancy are not on the same vertical line, a deflection moment will be generated, which can cause the multi-joint bionic hairtail robot to flip clockwise or counterclockwise. Thus, the attitude adjustment of left and right flips is achieved.

[0051] Combined with Figure 9 , 10 , this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion method. There is a center-of-gravity adjustment mechanism in the hairtail head. During vertical swimming, by rotating the fish head deflection configuration block A13 with the first built-in motor A2 in the fish head, the center of gravity of the hairtail head is adjusted. Since the center of gravity and the center of buoyancy are not on the same vertical line, a deflection moment will be generated, so that the multi-joint bionic hairtail robot gradually changes from a vertical posture to a horizontal posture during swimming in water.

[0052] Combined with Figure 11 , this embodiment is a multi-joint bionic hairtail robot and method based on the BCF propulsion method. Four configuration blocks are arranged inside the rear 5 body units (Z1~Z5) and the hairtail tail (W1). The four configuration blocks are divided into two upper and lower and two left and right, symmetrically arranged. When installed, by adjusting the positions of the configuration blocks, the center of gravity and the center of buoyancy of each body unit (Z1~Z5) or the hairtail tail (W1) are made to coincide with each other.

Claims

1. A multi-joint bionic hairtail robot based on the BCF propulsion method, characterized in that: It includes a hairtail head, N body units, and a hairtail tail; The above-mentioned hairtail head consists of an upper head shell (A1), a lower head shell (A7), and a system board (A10), a battery (A9), a visual recognition module (A8), and a center-of-gravity adjustment mechanism installed inside the lower head shell (A7); the center-of-gravity adjustment mechanism consists of a first built-in motor of the fish head (A2), a fish head moving configuration block (A3), a second built-in motor of the fish head (A4), a guide rod (A11), a screw rod (A12), and a fish head deflection configuration block (A13); among them, the screw rod (A12) is installed on the output shaft of the second built-in motor of the fish head (A4), and the second built-in motor of the fish head (A4) and the above-mentioned guide rod (A11) are fixed inside the head shell; the fish head moving configuration block (A3) is installed on the screw rod (A12) and the guide rod (A11), and the threaded hole of the fish head moving configuration block (A3) is screwed with the screw rod; the first built-in motor of the fish head (A2) is installed on the fish head moving configuration block (A3), and the fish head deflection configuration block (A13) is installed on the output shaft of the first built-in motor of the fish head (A2); The above-mentioned body unit includes an upper body unit shell (B3), a lower body unit shell (B11), a dorsal fin (B1) installed on the upper body unit shell (B3) through a dorsal fin support frame (B2), and a ventral fin (B12) installed on the lower body unit shell (B11) through a ventral fin support frame (B13); it also includes a body unit servo (B10), a body unit servo disk (B9), a body unit output shaft (B7), and a body unit bearing (B5) installed inside the lower body unit shell (B11); among them, after the body unit output shaft (B7) is matched with the body unit bearing (B5), it is fixed at the output rotating shaft of the body unit servo (B10) through the body unit servo disk (B9), and the body unit servo (B10) is fixed inside the lower body unit shell (B11); the end of the body unit output shaft (B7) extends out of the upper body unit shell (B3); using flexible dorsal fins and ventral fins, when swinging left and right, the vertical cross-section of each body unit and the flexible surfaces of the dorsal fins and ventral fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the multi-joint bionic hairtail robot to achieve overall forward movement; Among them, the hairtail tail consists of an upper tail shell (C1), a lower tail shell (C9), a tail servo (C7), a tail servo disk (C5), a tail output shaft (C4), a bearing at the tail output shaft (C3), and a tail end thin sheet (C10); among them, after the tail output shaft (C4) is matched with the bearing at the tail output shaft (C3), it is fixed at the output rotating shaft of the tail servo (C7) through the tail servo disk (C5), and the tail servo (C7) is fixed inside the lower tail shell (C9); the end of the tail output shaft (C4) extends out of the upper tail shell (C1); The upper shell of the above-mentioned head (A1) is connected to the adjacent first body unit output shaft (B7), the upper shell of the body unit (B3) is connected to the adjacent body unit output shaft (B7) behind it; the upper shell of the last body unit is connected to the fish tail output shaft (C4); four configuration blocks are respectively arranged inside each of the above-mentioned N body units (Z1~Z5) and the fish tail (W1), and the four configuration blocks are respectively located in the upper, lower, left, and right positions, and are symmetrically arranged.

2. The motion method of the multi-joint bionic hairtail robot based on the BCF propulsion method according to claim 1, characterized in that It includes the following processes: First, the symmetry line of the vertical symmetry plane of the body of the multi-joint bionic fish robot is called the body center line. When the body center line is in the horizontal plane, the postures when the dorsal fin (B1) and ventral fin (B12) of the multi-joint bionic fish robot are respectively directly above and directly below the horizontal plane are called the vertical postures, and the postures when the dorsal fin (B1) and ventral fin (B12) of the multi-joint bionic fish robot are both in the horizontal plane are called the horizontal postures; the angle between each body unit and the adjacent body unit in the direction close to the fish head is called the forward offset angle, and the angle between the adjacent body unit in the direction away from the fish head is called the backward offset angle, with a positive value for left deviation relative to the forward direction and a negative value for right deviation relative to the moving direction; among them, the positive direction of the body center line is from the fish tail (W1) to the fish head (T1). When the fish head (T1) deviates towards the upper part of the horizontal plane, the angle between the positive direction of the body center line and the horizontal plane is called the elevation angle, and when the fish head (T1) deviates towards the lower part of the horizontal plane, the angle between the positive direction of the body center line and the horizontal plane is called the depression angle; A center of gravity adjustment mechanism is configured in the fish head; four configuration blocks are respectively arranged inside the subsequent N body units (Z1~ZN) and the fish tail (W1), with two configuration blocks each in the upper and lower, and left and right positions, and are symmetrically arranged. During installation, by adjusting the positions of the configuration blocks, the center of gravity and the center of buoyancy of each body unit or the fish tail are made to coincide with each other; Overall horizontal-vertical conversion: There is a center of gravity adjustment mechanism in the fish head. During the process of vertical swimming or horizontal swimming, the fish head first built-in motor (A2) rotates the fish head deflection configuration block (A13) to adjust the left-right movement of the center of gravity; since the center of gravity and the center of buoyancy are not on the same vertical line, a deflection moment will be generated, thereby causing the multi-joint bionic fish robot to gradually change from the vertical posture to the horizontal posture, or from the horizontal posture to the vertical posture; Overall vertical forward swimming: The swing frequencies and swing amplitudes of all body units are exactly the same, but there are fixed and equal phase differences, so as to achieve a standard sine wave-like motion; Flexible dorsal fins and ventral fins are adopted. When swinging left and right, the vertical cross-sections of each body unit and the flexible surfaces of the dorsal fins and ventral fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the multi-joint bionic fish robot to achieve overall forward movement; Overall vertical left or right turning swimming: A number of body units close to the fish head remain relatively stationary and have a fixed forward offset angle at the same time; the swing frequencies of a number of body units close to the fish tail are exactly the same, but there is a linearly increasing relationship in the swing amplitudes, and there is a fixed phase difference at the same time; Flexible dorsal fins and ventral fins are adopted. When swinging left and right, the vertical cross-sections of each body unit and the flexible surfaces of the dorsal fins and ventral fins simultaneously generate a backward acting force on the water, and the water generates a forward thrust on the robot. When the current row offset angle is positive, the thrust of the water on the right side is greater than that on the left side, and the robot is subjected to an unbalanced force, that is, a left-turn torque, to achieve a left turn. When the current row offset angle is negative, the thrust of the water on the left side is greater than that on the right side, and the robot is subjected to an unbalanced force, that is, a right-turn torque, to achieve a right turn.

3. The motion method of the multi-joint bionic hairtail robot based on the BCF propulsion method according to claim 2, characterized in that It includes the following processes: Pitch conversion is achieved through the relevant movements of the center-of-gravity adjustment mechanism of the fish head. The specific implementation is as follows: In the initial state, the fish head movement configuration block (A3) is located at the middle position of the guide rail (A11), and the fish head deflection configuration block (A13) is located directly above the axis of the first built-in motor (A2) of the fish head; at this time, the center of gravity of the fish head coincides with the center of buoyancy, and the multi-joint bionic fish robot presents a vertical suspension state in water; the second built-in motor (A4) of the fish head drives the fish head movement configuration block (A3) to move forward towards the front of the fish head through the rotation of the screw (A12). When the fish head movement configuration block (A3) reaches a certain position, the fish head deflection configuration block (A13) rotates 180 degrees from the upper part to the lower part and is located below the axis of the output shaft of the first built-in motor (A2) of the fish head. At this time, the center of gravity of the fish head is located at the front lower segment position of the fish head; during the entire movement process of the fish head movement configuration block (A3), the center of gravity of the fish head gradually moves forward, and a torque is formed between gravity and buoyancy, thereby driving the body part of the multi-joint bionic fish robot to achieve a downward flipping movement. When the changed center of gravity and the center of buoyancy are again on the same vertical line, the downward flipping stops, and the target downward-looking posture is reached. The degree of this downward look, that is, the size of the downward angle, is proportional to the magnitude of the forward displacement of the fish head movement configuration block (A3). When the upward-looking posture is to be achieved, the second built-in motor (A4) of the fish head drives the fish head movement configuration block (A3) to move backward towards the rear of the fish head through the rotation of the screw (A12). When the fish head movement configuration block (A3) reaches a certain position, the upper fish head deflection configuration block (A13) rotates 180 degrees from the upper part to the lower part, and the fish head deflection configuration block (A13) is located directly below the axis of the output shaft of the first built-in motor (A2) of the fish head. At this time, the center of gravity of the fish head is biased towards the rear lower segment position of the fish head; during the entire movement process of the fish head movement configuration block (A3), the center of gravity of the fish head gradually moves backward, and a torque is formed between gravity and buoyancy, thereby driving the body part of the multi-joint bionic fish robot to achieve an upward flipping movement. When the changed center of gravity and the center of buoyancy are again on the same vertical line, the upward flipping stops, and the target upward-looking posture is reached. The degree of this upward look, that is, the size of the upward angle, is proportional to the magnitude of the backward displacement of the fish head movement configuration block (A3).

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