A high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish

Abstract

This invention relates to the field of underwater robot technology and discloses a highly maneuverable robotic fish with a high-torsion-resistant flexible shaft integrated drive. The flexible shaft, composed of a spring and a flexible constraint sleeve, serves as the power transmission medium. The flexible constraint sleeve restricts the radial expansion of the spring under torsion, thus forcing the spring's deformation to be primarily axial torsional deformation rather than radial expansion deformation. This enhances the overall torsional strength of the flexible shaft, ensuring that the output torque of the drive motor can be quickly transmitted to the tail body, providing continuous thrust for high-speed swimming. Furthermore, the propulsion power transmission path and steering drive path of the robotic fish are physically separated and do not interfere with each other. This allows the robotic fish to maintain high-frequency stable oscillation and achieve high-speed straight swimming while simultaneously completing large-angle, small-radius rapid turns, balancing high-speed propulsion and high-maneuverability, meeting the requirements of rapid response, flexible obstacle avoidance, and precise tracking in complex underwater environments.

Description

Technical Field

[0001] This invention relates to the field of underwater robot technology, and in particular to a highly maneuverable robotic fish with an integrated high-torsion flexible shaft drive. Background Technology

[0002] The demand for robotic fish in fields such as marine exploration, underwater monitoring, target tracking, and ecological observation is constantly increasing, with high-speed straight swimming and high-maneuverability turning being their core performance indicators. However, existing biomimetic propulsion technologies generally suffer from an underlying contradiction where high speed and high maneuverability are difficult to reconcile, becoming a key issue restricting their engineering applications.

[0003] Currently, robotic fish are mainly driven in two ways. The first type uses multi-joint body undulation drive, relying on multiple bends of the fish's body to achieve flexible turning and excellent maneuverability. However, it has many drive components and a large tail inertia, making high-frequency oscillation impossible and limiting swimming speed; it is characterized by high maneuverability but low speed. The second type uses single-joint tail oscillation drive, enabling high-speed straight swimming, but the fish's overall body is relatively rigid, resulting in a large turning radius and slow response; it is characterized by high speed but low maneuverability. Neither type of solution can simultaneously achieve high speed and high maneuverability on the same mechanism.

[0004] To balance speed and maneuverability, existing technologies attempt to use flexible steel wire shaft transmissions, placing the motor at the front to reduce tail inertia, allowing the fish body to bend flexibly while simultaneously driving the tail to swing. However, traditional flexible steel wire shafts have several inherent defects that are difficult to overcome, severely limiting robot performance. First, the flexible shaft is made of multiple strands of twisted steel wires, and during transmission, the internal steel wires continuously slide relative to each other, resulting in significant frictional losses and low energy transfer efficiency, especially at high speeds. Second, the overall torsional strength is insufficient, and significant torsional deformation easily occurs when transmitting torque, leading to tail swing phase lag and response delay. It is difficult to precisely match the motor output with the tail movement, resulting in poor stability under high-frequency conditions and difficulty in maintaining continuous high-speed swimming. Third, the internal steel wires are prone to fatigue damage under long-term rotational friction and alternating stress, resulting in problems such as wire breakage and loosening. With prolonged use, this gradually leads to transmission jamming and power interruption, resulting in short service life and insufficient long-term operational reliability. Fourth, the flexible shaft itself has nonlinear backlash and springback characteristics, resulting in low swing control accuracy and poor posture stability, directly affecting the robot's maneuverability.

[0005] While existing technologies include solutions that adjust the stiffness of the fish body by adding elastic elements, such structures can only change the passive posture and cannot solve the core problems such as high frictional loss of the steel wire flexible shaft, insufficient torsional strength, and easy fatigue failure. They do not substantially help improve speed and maneuverability, but instead increase the complexity of the structure.

[0006] Therefore, traditional steel wire flexible shaft transmissions cannot simultaneously meet the requirements of biomimetic robots for high speed, high maneuverability, high precision, and high reliability. The incompatibility between high speed and high maneuverability remains unresolved. Developing a novel integrated transmission mechanism with high torsional resistance, low friction, long lifespan, and stable transmission has become a key technical problem urgently needing to be solved in this field. Summary of the Invention

[0007] The main objective of this invention is to provide a highly maneuverable robotic fish with a high-torsion-resistant flexible shaft integrated drive, aiming to improve the shortcomings of the prior art and solve the problem of poor steering response of traditional bionic robots in high-speed swimming.

[0008] To achieve the above objectives, the present invention proposes a highly maneuverable robotic fish with a high torsion resistance integrated flexible shaft drive, comprising: Fish head body; The main body of the fish has a head connected to the head body at its head. The main body of the fish has multiple fish joints connected in series. The main body of the fish tail is connected to the end of the main body of the fish; A steering actuator, comprising a servo motor, a reel, and a drive rope, wherein the reel is mounted on the output shaft of the servo motor, one end of the drive rope is connected to the reel, and the other end of the drive rope passes sequentially through multiple fish body joints from the head end of the fish body and is connected to the fish body joint located at the end of the fish body. The propulsion actuator includes a drive motor, a transmission flexible shaft, a first transmission joint, and a second transmission joint; the transmission flexible shaft is connected to the drive motor through the first transmission joint, and the transmission flexible shaft is connected to the fish tail body through the second transmission joint. The transmission flexible shaft includes: spring; A flexible constraint sleeve is fitted over the outside of the spring, and the flexible constraint sleeve is configured to limit the radial expansion of the spring under torsional conditions.

[0009] Optionally, the first transmission joint includes: The speed reducer is connected to the output shaft of the drive motor; The first coupling is connected to the output shaft of the reducer; A first connecting pin, one end of which is connected to the first coupling, and the other end of which is connected to the spring.

[0010] Optionally, the second transmission joint includes: The second coupling has a sliding chamber inside, which extends along the axial direction of the second coupling, and the inner wall of the sliding chamber is provided with a spline groove. A sliding torque transmission element is installed in the sliding cavity. The sliding torque transmission element can move in the sliding cavity along the axial direction of the second coupling. The outer peripheral surface of the sliding torque transmission element is provided with spline teeth extending along its axial direction. The spline teeth and the spline groove mesh with each other. A rotary lever mechanism is connected to the second coupling, and the rotary lever mechanism is used to drive the fish tail body to swing back and forth.

[0011] Optionally, the rotary lever mechanism includes: A rotary dial is connected to the second coupling, and an eccentric lever is provided at the end of the rotary dial opposite to the second coupling; A rotating slotted seat is connected to the fish tail body. The rotating slotted seat has a slot, and the eccentric lever is at least partially inserted into the slot, and the eccentric lever can slide within the slot. When the rotary dial rotates, the eccentric lever rotates accordingly and slides back and forth in the slot to drive the fish tail body to swing back and forth.

[0012] Optionally, the main body of the fish tail includes: Caudal fin; The fish tail base has one end extending into the main body of the fish and connected to the fish body joint located at the end of the main body of the fish via the rotating groove seat. The other end of the fish tail base is connected to the tail fin.

[0013] Optionally, the fish tail body further includes: Tension spring; The fish tail base and the tail fin are movably connected by a first connecting shaft; The fish tail base is provided with a first hook, the tail fin is provided with a second hook, and the two ends of the tension spring are respectively connected to the first hook and the second hook.

[0014] Optionally, a through groove is provided inside the fish body joint, and the drive rope is threaded through the through groove.

[0015] Optionally, the fish body joint located at the head end of the main body of the fish is movably connected to the main body of the fish head via a second connecting shaft, and two adjacent fish body joints are movably connected via a third connecting shaft; The axial direction of the second connecting shaft and the axial direction of the third connecting shaft are both perpendicular to the length direction of the fish body.

[0016] Optionally, the fish head body includes: Fish head; A fixed fish body is connected to the fish head. The fixed fish body and / or the fish head are provided with an annular sealing groove. An annular sealing ring is provided in the annular sealing groove. The annular sealing ring is used to seal the fitting gap between the fixed fish body and the fish head. The fixed fish body and the fish head cooperate to form a sealed cavity. The drive motor, control unit and reducer are all installed in the sealed cavity.

[0017] Optionally, there is a movable gap between two adjacent fish-body joints, the movable gap being used to provide deflection space for the fish-body joints when turning.

[0018] Beneficial effects: The high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish proposed in this invention has the following beneficial effects: (1) The high-torsion flexible shaft integrated drive high-mobility robotic fish provided by the present invention uses a transmission flexible shaft composed of a spring and a flexible constraint sleeve as the power transmission medium. The flexible constraint sleeve restricts the radial expansion of the spring under torsion, thereby forcing the deformation of the spring to be mainly axial torsional deformation rather than radial expansion deformation, thereby improving the overall torsional strength of the transmission flexible shaft and ensuring that the output torque of the drive motor can be quickly transmitted to the fish tail body to provide continuous thrust for high-speed swimming.

[0019] (2) Compared with traditional steel wire flexible shafts, the transmission flexible shaft provided by the present invention adopts a combination of spring and flexible constraint sleeve. During the transmission process, there is no wear interface caused by the relative movement between steel wire strands. The structure is simple and there is no internal wear pair. It can reduce transmission friction, improve torque transmission accuracy and response speed, and maintain stable torque transmission performance under long-term continuous operation conditions. It reduces the frequency of downtime maintenance due to transmission component failure, making the robotic fish suitable for long-term autonomous operation in marine exploration, ecological observation and other scenarios.

[0020] (3) The high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish provided by the present invention uses a transmission flexible shaft as the power transmission medium in its propulsion actuator. The rotational motion output by the drive motor is transmitted to the main body of the fish tail through the first transmission joint, the transmission flexible shaft and the second transmission joint. Finally, the second transmission joint converts the rotational motion into driving the fish tail to swing back and forth. Moreover, the steering actuator is set relatively independently. The drive rope is wound and released by the servo motor driving the reel. The drive rope actively pulls and controls multiple fish body joints so that the main body of the fish can achieve lateral bending of a preset curvature. In addition, the transmission flexible shaft can bend passively when the fish body bends, avoiding jamming of the transmission chain and increased energy loss when bending. This design makes the propulsion power transmission path and the steering drive path of the robotic fish physically separated and do not interfere with each other. This allows the robotic fish to maintain high-frequency stable swing and achieve high-speed straight swimming while completing large-angle, small-radius rapid turning. It takes into account both high-speed propulsion capability and high-mobility operation capability, and meets the requirements of rapid response, flexible obstacle avoidance and precise tracking in complex underwater environments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a three-dimensional structural diagram of the highly mobile robotic fish disclosed in this application; Figure 2 This is one of the internal structural diagrams of the highly mobile robotic fish disclosed in this application; Figure 3 This is the second schematic diagram of the internal structure of the highly mobile robotic fish disclosed in this application; Figure 4 for Figure 3 A magnified view of a section at point A in the middle; Figure 5 for Figure 3 A magnified view of a section at point B in the middle; Figure 6 This is a schematic diagram of the tail swinging of the highly mobile robotic fish disclosed in this application; Figure 7 This is one of the schematic diagrams of the tail structure of the highly mobile robotic fish disclosed in this application; Figure 8 This is the second schematic diagram of the tail structure of the highly mobile robotic fish disclosed in this application; Figure 9 A schematic diagram of the highly maneuverable robotic fish disclosed in this application making a left turn; Figure 10This is a schematic diagram of the highly mobile robotic fish swimming in a straight line, as disclosed in this application. Figure 11 This is a schematic diagram of the highly mobile robotic fish disclosed in this application making a right turn.

[0023] Explanation of icon numbers: 1. Fish head body; 1a. Fish head; 1b. Fixing the fish body; 11. Annular sealing groove; 12. Sealed chamber; 2. Main body of the fish; 21. Joints of the fish body; 211. Through groove; 3. Tail body; 31. Tail fin; 311. Second hook; 32. Tail base; 321. First hook; 33. Tension spring; 34. First connecting shaft; 4. Steering actuator; 41. Servo motor; 42. Spool; 43. Drive rope; 5. Propulsion actuator; 51. Drive motor; 52. Transmission flexible shaft; 521. Spring; 522. Flexible constraint sleeve; 53. First transmission joint; 531. Reducer; 532. First coupling; 533. First connecting pin; 54. Second transmission joint; 541. Second coupling; 5411. Sliding chamber; 542. Sliding torque transmission element; 543. Rotary lever mechanism; 5431. Rotary dial; 5432. Eccentric lever; 5433. Rotary slot seat; 54331. Slot; 6. Second connecting shaft; 7. Third connecting shaft; 8. Control unit; 9. Movement clearance.

[0024] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0027] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the word "and / or" throughout the text means including three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0029] The demand for robotic fish in fields such as marine exploration, underwater monitoring, target tracking, and ecological observation is constantly increasing, with high-speed straight swimming and high-maneuverability turning being their core performance indicators. However, existing biomimetic propulsion technologies generally suffer from an underlying contradiction where high speed and high maneuverability are difficult to reconcile, becoming a key issue restricting their engineering applications.

[0030] Currently, robotic fish are mainly driven in two ways. The first type uses multi-joint body undulation drive, relying on multiple bends of the fish's body to achieve flexible turning and excellent maneuverability. However, it has many drive components and a large tail inertia, making high-frequency oscillation impossible and limiting swimming speed; it is characterized by high maneuverability but low speed. The second type uses single-joint tail oscillation drive, enabling high-speed straight swimming, but the fish's overall body is relatively rigid, resulting in a large turning radius and slow response; it is characterized by high speed but low maneuverability. Neither type of solution can simultaneously achieve high speed and high maneuverability on the same mechanism.

[0031] To balance speed and maneuverability, existing technologies attempt to use flexible steel wire shaft transmissions, placing the motor at the front to reduce tail inertia, allowing the fish body to bend flexibly while simultaneously driving the tail to swing. However, traditional flexible steel wire shafts have several inherent defects that are difficult to overcome, severely limiting robot performance. First, the flexible shaft is made of multiple strands of twisted steel wires, and during transmission, the internal steel wires continuously slide relative to each other, resulting in significant frictional losses and low energy transfer efficiency, especially at high speeds. Second, the overall torsional strength is insufficient, and significant torsional deformation easily occurs when transmitting torque, leading to tail swing phase lag and response delay. It is difficult to precisely match the motor output with the tail movement, resulting in poor stability under high-frequency conditions and difficulty in maintaining continuous high-speed swimming. Third, the internal steel wires are prone to fatigue damage under long-term rotational friction and alternating stress, resulting in problems such as wire breakage and loosening. With prolonged use, this gradually leads to transmission jamming and power interruption, resulting in short service life and insufficient long-term operational reliability. Fourth, the flexible shaft itself has nonlinear backlash and springback characteristics, resulting in low swing control accuracy and poor posture stability, directly affecting the robot's maneuverability.

[0032] While existing technologies include solutions that adjust the stiffness of the fish body by adding elastic elements, such structures can only change the passive posture and cannot solve the core problems such as high frictional loss of the steel wire flexible shaft, insufficient torsional strength, and easy fatigue failure. They do not substantially help improve speed and maneuverability, but instead increase the complexity of the structure.

[0033] Therefore, traditional steel wire flexible shaft transmissions cannot simultaneously meet the requirements of biomimetic robots for high speed, high maneuverability, high precision, and high reliability. The incompatibility between high speed and high maneuverability remains unresolved. Developing a novel integrated transmission mechanism with high torsional resistance, low friction, long lifespan, and stable transmission has become a key technical problem urgently needing to be solved in this field.

[0034] Based on this, this embodiment provides a highly maneuverable robotic fish with an integrated high-torsion flexible shaft drive, see [link to documentation]. Figures 1-3 As shown, the highly mobile robotic fish includes a head body 1, a body body 2, a tail body 3, a steering actuator 4, and a propulsion actuator 5.

[0035] In this embodiment, the head end of the fish body 2 is connected to the head body 1. The fish body 2 has multiple fish body joints 21, which are connected in series along the length of the robotic fish. The fish body 2 is not a single rigid body, so that the fish body 2 has the ability to actively bend after being equipped with the steering actuator 4. The tail body 3 is connected to the end of the fish body 2.

[0036] In this embodiment, the propulsion actuator 5 drives the tail body 3 to generate high-frequency reciprocating oscillations, providing forward thrust for the robotic fish to achieve high-speed straight swimming. The steering actuator 4 independently controls the lateral bending of the fish body 2, achieving maneuvering actions such as turning, obstacle avoidance, and tracking by changing the posture of the fish body 2. The propulsion actuator 5 and the steering actuator 4 operate independently without interfering with each other, ensuring complete decoupling of propulsion and steering actions, thereby enabling the robotic fish to simultaneously perform high-speed propulsion and large-angle turning.

[0037] The steering actuator 4 includes a servo motor 41, a reel 42, and a drive rope 43. The reel 42 is mounted on the output shaft of the servo motor 41. One end of the drive rope 43 is connected to the reel 42, and the other end of the drive rope 43 passes through multiple fish body joints 21 sequentially from the head end of the fish body 2 and is connected to the fish body joint 21 located at the end of the fish body 2. The propulsion actuator 5 includes a drive motor 51, a transmission flexible shaft 52, a first transmission joint 53, and a second transmission joint 54. The transmission flexible shaft 52 is connected to the drive motor 51 through the first transmission joint 53, and the transmission flexible shaft 52 is connected to the fish tail body 3 through the second transmission joint 54.

[0038] Specifically, one end of the first transmission joint 53 is connected to the transmission flexible shaft 52, and the other end of the first transmission joint 53 is connected to the output shaft of the drive motor 51; one end of the second transmission joint 54 is connected to the transmission flexible shaft 52, and the other end of the second transmission joint 54 is connected to the fish tail body 3. The second transmission joint 54 is configured to convert the rotational motion into the reciprocating swing of the fish tail body 3.

[0039] In this embodiment, the fish head body 1 includes a fish head 1a shell and a fixed fish body 1b. The fixed fish body 1b is connected to the fish head 1a. The fixed fish body 1b and / or the fish head 1a are provided with an annular sealing groove 11. An annular sealing ring is provided in the annular sealing groove 11. The annular sealing ring is used to seal the fitting gap between the fixed fish body 1b and the fish head 1a. The fixed fish body 1b and the fish head 1a cooperate to form a sealed cavity 12.

[0040] To achieve low inertia and high-frequency response swimming characteristics, the robotic fish provided in this embodiment centrally arranges the power components and mass components inside the head body 1. Specifically, the drive motor 51 that provides power to the propulsion actuator 5, the servo motor 41 that provides power to the steering actuator 4, the control unit 8 that manages the overall motion logic, and the power supply module that supplies power to each electrical component are all integrated and installed within the sealed chamber 12 of the head body 1. By adopting a forward-positioned center of gravity design, the rotational inertia of the rear of the robotic fish, especially the body 2 and the tail body 3, is reduced, thereby further increasing the swaying frequency of the tail. Secondly, the forward-positioned center of gravity helps improve the directional stability of the robotic fish when swimming in water and reduces self-rolling and yaw disturbances caused by tail swaying.

[0041] See Figure 1 As shown, the fish head 1a and the fixed fish body 1b adopt a streamlined design to reduce the resistance when the robotic fish swims in the water.

[0042] In this embodiment, since the robotic fish needs to operate in an underwater environment for extended periods, its internal electronic components, such as the drive motor 51, control unit 8, and power supply module, must be completely isolated from the external aquatic environment. An annular sealing ring is used to seal the gap between the fixed fish body 1b and the fish head 1a. After the fixed fish body 1b and the fish head 1a are assembled in place, the annular sealing ring is pressed between them, forming a static seal structure. This allows the fixed fish body 1b and the fish head 1a to cooperate and jointly enclose a closed, sealed chamber 12.

[0043] The annular sealing groove 11 can be set on the fixed fish body 1b, or on the fish head 1a, or both can be provided with mutually cooperating annular sealing groove structures, as long as the annular sealing ring can be effectively compressed.

[0044] The highly mobile robotic fish provided in this embodiment uses a transmission flexible shaft 52 composed of a spring 521 and a flexible constraint sleeve 522 as the power transmission medium. The flexible constraint sleeve 522 restricts the radial expansion of the spring 521 under torsion.

[0045] Specifically, when spring 521 is subjected to torque, in addition to torsional deformation around its axis, it also experiences radial expansion due to the geometric characteristics of the helix itself. When the torque is large enough, this expansion can easily lead to an increase in the diameter of the helix of spring 521, or even permanent deformation and instability. To overcome this problem, this embodiment provides a flexible constraint sleeve 522 around spring 521.

[0046] The flexible restraint sleeve 522 is a tubular component whose inner diameter matches the outer diameter of the spring 521, and the flexible restraint sleeve 522 and the spring 521 are in clearance fit. The flexible restraint sleeve 522 includes, but is not limited to, polyester fiber braided mesh tube, polytetrafluoroethylene (PTFE) thin-walled tube, and sleeve made of aramid fiber (Kevlar).

[0047] When the spring 521 tends to expand radially due to the transmission of torque, the flexible constraint sleeve 522 can apply a radial constraint force to the spring 521 to limit its radial expansion, thereby forcing the deformation of the spring 521 to be mainly axial torsional deformation rather than radial expansion deformation, which in turn improves the overall torsional strength of the transmission flexible shaft 52 and ensures that the output torque of the drive motor 51 can be quickly transmitted to the fish tail body 3 to provide continuous thrust for high-speed swimming.

[0048] Unlike traditional flexible shafts made of multiple strands of steel wire twisted together, the transmission flexible shaft 52 provided in this embodiment uses a cylindrical helical spring made of a single steel wire spirally wound. During transmission, when torque is applied to one end of the spring 521, the torque is transmitted to the other end along the helical path of the spring 521. At this time, since there is no relative sliding interface similar to that between multiple strands of steel wire inside the spring 521, the transmission flexible shaft 52 has low friction loss and high energy transmission efficiency. Moreover, it has a simple structure and no internal wear pairs, which can reduce transmission friction, improve torque transmission accuracy and response speed, and maintain stable torque transmission performance under long-term continuous working conditions. This reduces the frequency of downtime maintenance due to transmission component failure, making the robotic fish suitable for long-term autonomous operation in marine exploration, ecological observation and other scenarios.

[0049] The above structural design gives the transmission flexible shaft 52 high torsional resistance and low bending resistance, which can ensure efficient and stable torque transmission while allowing the robot fish's body to bend flexibly.

[0050] Specifically, the high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish provided in this embodiment uses a transmission flexible shaft 52 as the power transmission medium in its propulsion actuator 5. The rotational motion output by the drive motor 51 is transmitted to the fish tail body 3 via the first transmission joint 53, the transmission flexible shaft 52, and the second transmission joint 54. Finally, the second transmission joint 54 converts the rotational motion into driving the fish tail to swing back and forth. The steering actuator 4 is set relatively independently. The servo motor 41 drives the reel 42 to raise and lower the drive rope 43. The drive rope 43 actively pulls and controls multiple fish body joints 21, so that the fish body body 2 can achieve lateral bending of a preset curvature. Moreover, the transmission flexible shaft 52 can passively bend along with the fish body when it bends, avoiding the problems of transmission chain jamming and increased energy loss when bending. This design physically separates the propulsion power transmission path and the steering drive path of the robotic fish, preventing them from interfering with each other. This allows the robotic fish to maintain high-frequency stable oscillation and achieve high-speed straight swimming while simultaneously completing large-angle, small-radius rapid turns. It balances high-speed propulsion capability with high maneuverability, meeting the requirements of rapid response, flexible obstacle avoidance, and precise tracking in complex underwater environments.

[0051] In this embodiment, the steering action is driven by the servo motor 41. During the steering process, the transmission flexible shaft 52 only bends with the movement, without generating additional resistance or consuming propulsion torque, so that the propulsion action and the steering action are completely decoupled, and high-speed propulsion and large-angle steering can be achieved at the same time.

[0052] See Figure 4 As shown, the first transmission joint 53 includes a reducer 531, a first coupling 532, and a first connecting pin 533. The first transmission joint 53 is used to transmit the reduced torque of the drive motor 51 to the input end of the transmission flexible shaft 52.

[0053] The reducer 531 is connected to the output shaft of the drive motor 51; the first coupling 532 is connected to the output shaft of the reducer 531 and is used to transmit torque; one end of the first connecting pin 533 is connected to the first coupling 532 and the other end of the first connecting pin 533 is connected to the spring 521.

[0054] Specifically, in this embodiment, a reducer 531 is provided between the drive motor 51 and the transmission flexible shaft 52. The reducer 531 reduces the high speed of the drive motor 51 to a frequency suitable for the tail swing of the robotic fish. The reducer 531 can be any one of a planetary gear reducer 531, a harmonic reducer 531, or a worm gear reducer 531. The specific selection depends on parameters such as the required reduction ratio, output torque, and the size of the robotic fish. In actual production, those skilled in the art can select a suitable reducer 531 according to actual production needs.

[0055] To accommodate the bending of the fish body 2 and ensure continuous and reliable transmission, the flexible transmission shaft 52 adopts a connection method with one end fixed and the other end adaptively retractable. Specifically, the end of the flexible transmission shaft 52 connected to the first transmission joint 53 is the fixed end, realizing torque input and radial positioning; the end of the flexible transmission shaft 52 connected to the second transmission joint 54 is the driven end.

[0056] See Figure 5 As shown, the second transmission joint 54 includes a second coupling 541, a sliding torque transmission element 542, and a rotary lever mechanism 543.

[0057] The second coupling 541 has a sliding chamber 5411 inside, which extends along the axial direction of the second coupling 541. The inner wall of the sliding chamber 5411 is provided with a spline groove. The sliding torque transmission element 542 is installed in the sliding chamber 5411 and can move along the axial direction of the second coupling 541 within the sliding chamber 5411. The outer peripheral surface of the sliding torque transmission element 542 is provided with spline teeth extending along its axial direction, and the spline teeth and spline groove mesh with each other. The rotary lever mechanism 543 is connected to the second coupling 541 and is used to drive the fish tail body 3 to swing back and forth.

[0058] With the above structural design, when the steering actuator 4 drives the fish body 2 to bend laterally, the transmission flexible shaft 52 bends accordingly. Since the bending arc of the transmission flexible shaft 52 is greater than the straight distance between its two ends, the sliding torque transmission element 542 can slide in the sliding chamber 5411 to automatically adjust its position to adapt to the change in the straight distance between the two ends of the transmission flexible shaft 52, automatically adapt to the bending deformation of the fish body, and avoid jamming.

[0059] The structure employs a spline tooth and spline groove combination, allowing the sliding torque transmission element 542 and the second coupling 541 to transmit torque in the circumferential direction through keyway constraint, ensuring that the two can rotate synchronously. The second coupling 541 has a sliding chamber 5411 in the axial direction, which allows the sliding torque transmission element 542 to automatically extend and retract with the bending of the fish body 2, compensating for the length change of the transmission flexible shaft 52 caused by bending, avoiding problems such as jamming and binding, and ensuring that torque transmission can continue during the turning process.

[0060] In this embodiment, the drive motor 51 adopts a unidirectional continuous rotation working mode. The unidirectional rotational power of the drive motor 51 is transmitted to the tail of the robotic fish via the transmission flexible shaft 52, and is converted into high-frequency reciprocating oscillation through the rotary lever mechanism 543 to achieve high-speed propulsion. This design avoids problems such as forward and reverse rotation impact, increased energy consumption, and complex control. Secondly, the unidirectional continuous rotation working mode of the drive motor 51 eliminates commutation impact, resulting in low energy consumption, low noise, and simple control. The robotic fish has high integration, is easy to maintain, and has low sealing difficulty.

[0061] See Figure 7 As shown, the rotary lever mechanism 543 includes a rotary dial 5431 and a rotary slot seat 5433. The rotary dial 5431 is connected to the second coupling 541, and an eccentric lever 5432 is provided at one end of the rotary dial 5431 away from the second coupling 541. The rotary slot seat 5433 is connected to the fish tail body 3, and a slot 54331 is provided in the rotary slot seat 5433. The eccentric lever 5432 is at least partially inserted in the slot 54331, and the eccentric lever 5432 can slide in the slot 54331. When the rotary dial 5431 rotates, the eccentric lever 5432 rotates accordingly and slides back and forth in the slot 54331 to drive the fish tail body 3 to swing back and forth.

[0062] See Figure 6 As shown, when the transmission flexible shaft 52 drives the rotary dial 5431 to rotate continuously around the Y-axis through the second coupling 541, the eccentric lever 5432 fixed on it will also make circular motion. Since the eccentric lever 5432 is simultaneously constrained in the groove 54331 of the rotary dial seat 5433, its circular motion is decomposed into two components: reciprocating sliding along the direction of the groove 54331 and reciprocating swing perpendicular to the direction of the groove 54331. The swing component perpendicular to the groove 54331 can drive the rotary dial seat 5433 and the fish tail body 3 connected thereto to swing around a rotating shaft arranged along the Z-axis. By adjusting the eccentricity of the eccentric lever 5432, the swing amplitude of the fish tail body 3 can be controlled.

[0063] The fish tail body 3 includes a fish tail base 32 and a tail fin 31. One end of the fish tail base 32 extends into the fish body body 2 and is connected to the fish body joint 21 located at the end of the fish body body 2 via a rotating slot seat 5433. The other end of the fish tail base 32 is connected to the tail fin 31.

[0064] Specifically, the fish tail base 32 is a rigid component, with one end extending into the interior of the fish body 2 and connected to the aforementioned rotating slot seat 5433, so that the fish tail base 32 can swing synchronously with the rotating slot seat 5433.

[0065] See Figure 8 As shown, the tail fin 31 is crescent-shaped or forked. The other end of the fish tail base 32 is movably connected to the tail fin 31 through the first connecting shaft 34. One or more tension springs 33 are also provided between the fish tail base 32 and the tail fin 31.

[0066] Specifically, a first hook 321 is provided on the fish tail base 32, and a second hook 311 is provided on the tail fin 31. The two ends of the tension spring 33 are hooked onto the first hook 321 and the second hook 311 respectively.

[0067] See Figure 6 and Figure 8 As shown, the axial direction of the first connecting shaft 34 is Z. ， In terms of direction, when the tail base 32 is driven to swing, the water flow acts on the tail fin 31, causing the tail fin 31 to rotate in a Z-shape. ， The direction of the movement is deflected to overcome the preload of the tension spring 33. The tail fin 31 generates an additional passive rotation angle relative to the tail base 32. When the swing direction changes, the elastic potential energy stored in the tension spring 33 is released, which helps the tail fin 31 to quickly return to its original position and generate an instantaneous whip effect, thereby further improving the propulsion efficiency.

[0068] In this embodiment, a through groove 211 is provided in the fish body joint 21, and the drive rope 43 is passed through the through groove 211. The fish body joint 21 located at the head end of the fish body 2 is movably connected to the fish head body 1 through the second connecting shaft 6, and two adjacent fish body joints 21 are movably connected through the third connecting shaft 7. The axial direction of the second connecting shaft 6 and the axial direction of the third connecting shaft 7 are both perpendicular to the length direction of the fish body 2.

[0069] In this embodiment, there is a movable gap 9 between two adjacent fish body joints 21. The movable gap 9 is used to provide deflection space for the fish body joint 21 when turning. The movable gap 9 is used to limit the maximum deflection angle of the fish body joint 21 and provide the necessary physical space for the lateral bending of the fish body joint 21, so as to prevent rigid collision between adjacent fish body joints 21 when turning.

[0070] See Figure 10As shown, when the robotic fish needs to swim in a straight line at high speed, the control unit 8 sends a start command to the drive motor 51. The drive motor 51 rotates continuously in one direction at a preset speed. The rotational torque is transmitted to the beginning of the transmission flexible shaft 52 through the reducer 531, the first coupling 532, and the first connecting pin 533. The transmission flexible shaft 52 transmits the torque to its end and drives the sliding torque transmission element 542 to rotate. The sliding torque transmission element 542 converts the rotational motion into the reciprocating swing of the fish tail body 3 through the rotary lever mechanism 543, thereby propelling the robotic fish to swim forward in a straight line at high speed.

[0071] See Figure 9 and Figure 11 As shown, when the robotic fish needs to perform an emergency turn or a small-radius turn while swimming at high speed, the control unit 8, while maintaining the continuous operation of the drive motor 51, sends a steering command to the servo motor 41. The servo motor 41 drives the reel 42 to rotate, thereby releasing and retracting the drive rope 43. The tension of the drive rope 43 acts on the fish body joint 21, pulling the fish body 2 to bend in a predetermined direction. During this process, the transmission flexible shaft 52 located inside the fish body 2 is passively bent. Because the transmission flexible shaft 52 has low bending resistance, the external force required for its bending is minimal, and it will not cause additional load to the servo motor 41. At the same time, the sliding torque transmission element 542 undergoes axial displacement to compensate for the length change of the transmission flexible shaft 52 caused by bending, enabling the robotic fish to actively bend the fish body 2 without affecting the propulsion power, thus completing a maneuvering and turning action similar to that of a fish.

[0072] In summary, the present invention provides a highly maneuverable robotic fish with a high-torsion-resistance flexible shaft integrated drive, comprising a head body 1, a body body 2, a tail body 3, a steering actuator 4, and a propulsion actuator 5. The head end of the body body 2 is connected to the head body 1, and the body body 2 has multiple body joints 21 connected in series. The tail body 3 is connected to the tail end of the body body 2. The steering actuator 4 includes a servo motor 41, a reel 42, and a drive rope 43. The reel 42 is mounted on the output shaft of the servo motor 41. One end of the drive rope 43 is connected to the reel 42, and the other end of the drive rope 43 passes through multiple body joints 21 sequentially from the head end of the body body 2 and connects to the body joint 21 located at the tail end of the body body 2. The propulsion actuator 5 includes a drive motor 51, a transmission flexible shaft 52, a first transmission joint 53, and a second transmission joint 54. Shaft 52 is connected to drive motor 51 via first transmission joint 53, and flexible shaft 52 is connected to fish tail body 3 via second transmission joint 54. Flexible shaft 52 includes spring 521 and flexible constraint sleeve 522. Flexible constraint sleeve 522 is sleeved outside spring 521 and is configured to limit the radial expansion of spring 521 under torsion. By using flexible shaft 52, composed of spring 521 and flexible constraint sleeve 522, as the power transmission medium, the flexible constraint sleeve 522 limits the radial expansion of spring 521 under torsion, thus forcing the deformation of spring 521 to be mainly axial torsional deformation rather than radial expansion deformation. This improves the overall torsional strength of flexible shaft 52, ensuring that the output torque of drive motor 51 can be quickly transmitted to fish tail body 3, providing continuous thrust for high-speed swimming. Compared with traditional steel wire flexible shafts, the transmission flexible shaft 52 provided by this invention adopts a combination of spring 521 and flexible constraint sleeve 522. During the transmission process, there is no wear interface caused by the relative movement between steel wire strands. Moreover, the structure is simple and there are no internal wear pairs, which can reduce transmission friction, improve torque transmission accuracy and response speed, maintain stable torque transmission performance under long-term continuous operation conditions, reduce the frequency of downtime maintenance due to transmission component failure, and make the robotic fish suitable for long-term autonomous operation in marine exploration, ecological observation and other scenarios.

[0073] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A highly maneuverable robotic fish with an integrated high-torsion flexible shaft drive, characterized in that, include: Fish head body; The main body of the fish has a head connected to the head body at its head. The main body of the fish has multiple fish joints connected in series. The main body of the fish tail is connected to the end of the main body of the fish; A steering actuator, comprising a servo motor, a reel, and a drive rope, wherein the reel is mounted on the output shaft of the servo motor, one end of the drive rope is connected to the reel, and the other end of the drive rope passes sequentially through multiple fish body joints from the head end of the fish body and is connected to the fish body joint located at the end of the fish body. The propulsion actuator includes a drive motor, a transmission flexible shaft, a first transmission joint, and a second transmission joint; the transmission flexible shaft is connected to the drive motor through the first transmission joint, and the transmission flexible shaft is connected to the fish tail body through the second transmission joint. The transmission flexible shaft includes: spring; A flexible constraint sleeve is fitted over the outside of the spring, and the flexible constraint sleeve is configured to limit the radial expansion of the spring under torsional conditions.

2. The high-torsion-resistance flexible shaft integrated drive high-mobility robotic fish according to claim 1, characterized in that, The first transmission joint includes: The speed reducer is connected to the output shaft of the drive motor; The first coupling is connected to the output shaft of the reducer; A first connecting pin, one end of which is connected to the first coupling, and the other end of which is connected to the spring.

3. The high-torsion-resistance flexible shaft integrated drive high-mobility robotic fish according to claim 2, characterized in that, The second transmission joint includes: The second coupling has a sliding chamber inside, which extends along the axial direction of the second coupling, and the inner wall of the sliding chamber is provided with a spline groove. A sliding torque transmission element is installed in the sliding cavity. The sliding torque transmission element can move in the sliding cavity along the axial direction of the second coupling. The outer peripheral surface of the sliding torque transmission element is provided with spline teeth extending along its axial direction. The spline teeth and the spline groove mesh with each other. A rotary lever mechanism is connected to the second coupling, and the rotary lever mechanism is used to drive the fish tail body to swing back and forth.

4. The high-torsion-resistance flexible shaft integrated drive high-mobility robotic fish according to claim 3, characterized in that, The rotary lever mechanism includes: A rotary dial is connected to the second coupling, and an eccentric lever is provided at the end of the rotary dial opposite to the second coupling; A rotating slotted seat is connected to the fish tail body. The rotating slotted seat has a slot, and the eccentric lever is at least partially inserted into the slot, and the eccentric lever can slide within the slot. When the rotary dial rotates, the eccentric lever rotates accordingly and slides back and forth in the slot to drive the fish tail body to swing back and forth.

5. The high-torsion-resistance flexible shaft integrated drive high-mobility robotic fish according to claim 4, characterized in that, The main body of the fish tail includes: Caudal fin; The fish tail base has one end extending into the main body of the fish and connected to the fish body joint located at the end of the main body of the fish via the rotating groove seat. The other end of the fish tail base is connected to the tail fin.

6. The high-torsion-resistance flexible shaft integrated drive high-mobility robotic fish according to claim 5, characterized in that, The main body of the fish tail also includes: Tension spring; The fish tail base and the tail fin are movably connected by a first connecting shaft; The fish tail base is provided with a first hook, the tail fin is provided with a second hook, and the two ends of the tension spring are respectively connected to the first hook and the second hook.

7. The high-torsion-resistance flexible shaft integrated drive high-mobility robotic fish according to claim 1, characterized in that, A through groove is provided inside the fish body joint, and the drive rope is threaded through the through groove.

8. The high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish according to claim 7, characterized in that, The fish body joint located at the head end of the main body of the fish is movably connected to the main body of the fish head via a second connecting shaft, and two adjacent fish body joints are movably connected via a third connecting shaft; The axial direction of the second connecting shaft and the axial direction of the third connecting shaft are both perpendicular to the length direction of the fish body.

9. The high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish according to claim 2, characterized in that, The main body of the fish head includes: Fish head; A fixed fish body is connected to the fish head. The fixed fish body and / or the fish head are provided with an annular sealing groove. An annular sealing ring is provided in the annular sealing groove. The annular sealing ring is used to seal the fitting gap between the fixed fish body and the fish head. The fixed fish body and the fish head cooperate to form a sealed cavity. The drive motor, control unit and reducer are all installed in the sealed cavity.

10. The high-torsion-resistant flexible shaft integrated drive high-mobility robotic fish according to claim 1, characterized in that, There is a movable gap between two adjacent fish body joints, which is used to provide deflection space for the fish body joints when turning.

Images