An underwater snake-like robot posture stiffness composite control soft joint

Abstract

This invention provides a composite attitude and stiffness control soft joint for an underwater snake-like robot, belonging to the field of underwater robot joint technology. It consists of an execution module and a drive module. The execution module contains three independent soft units, each connected to the drive module for independent pressurization and depressurization control. A central spring with high axial stiffness and bending stiffness runs through the center of the execution module. During pressurization, this central spring antagonizes the drive units, enabling bending, extension, and wide-range stiffness adjustment. The drive module contains three independent hydraulic circuits that provide controllable water pressure to each soft unit via pump-controlled pressure regulation, achieving three-degree-of-freedom attitude control and overall stiffness adjustment. The soft joint of this invention is compact and energy efficient, significantly reducing impact forces during collisions or contact with the underwater environment, thus improving the reliability and environmental adaptability of the underwater snake-like robot.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underwater robot joints, in particular, especially relates to a posture stiffness composite control soft joint of an underwater snake-shaped robot. BACKGROUND

[0002] The underwater snake-shaped robot has become an important branch and research hotspot in the field of underwater robots in recent years due to its flexible body structure and excellent environmental adaptability. Compared with traditional underwater robots, the snake-shaped robot has smaller water resistance, higher maneuverability and superior passing ability, and can perform detection, cruising, search and rescue and other tasks in complex underwater environments, and has certain operation ability. The research on underwater serial robots has important engineering value and broad development prospects for realizing ocean resource exploration, underwater rescue support and other complex environment operations.

[0003] In the prior art, the underwater snake-shaped robots involved are all rigid robots, and their joint modules are mostly single-degree-of-freedom or two-degree-of-freedom hinge rigid structures, such as patent No. 202410422607.2 (a snake-shaped underwater search and rescue robot and a use method), 202311717781.1 (a propelling and driving multi-cabin section hinged underwater snake-shaped robot), 202110417425.2 (a modular underwater snake-shaped robot), and 202510735149.2 (an underwater bionic snake-shaped robot and a hybrid adaptive control method thereof). In complex underwater environments, the probability of collision between rigid robots and surrounding structures increases significantly, and a large impact force is generated, which can easily cause damage to the robot structure. In addition, the instantaneous acceleration caused by the collision can damage sensors and circuit systems, and in severe cases, it can even cause the robot to lose control or be unable to return.

[0004] Therefore, according to the above-mentioned problems existing in the prior art, it is necessary to provide a variable stiffness soft joint that can quickly absorb kinetic energy when a collision occurs. SUMMARY

[0005] According to the above-mentioned technical problems of the rigid joint snake-shaped robot that is prone to failure and has insufficient reliability when colliding with environmental structures, a posture stiffness composite control soft joint of an underwater snake-shaped robot is provided. The present application mainly utilizes the variable stiffness soft joint that can quickly absorb kinetic energy when a collision occurs, effectively reduces the impact force, and thus significantly improves the operation reliability of the robot.

[0006] The technical means adopted by the present application are as follows: A posture stiffness composite control soft joint of an underwater snake-shaped robot, comprising an execution module and a driving module. The execution module is cylindrical, comprising a lower end cover, an upper end cover, soft body units, a center spring, a plurality of retaining frames, a plurality of retaining springs, a bellows cover, and a threaded bolt; the three soft body units are independent cavities that can be pressurized, and the two ends of each soft body unit are fixed to the lower end cover and the upper end cover respectively; the center spring is arranged through the execution module in the axial direction, and the two ends of the center spring are fixed to the center holes of the lower end cover and the upper end cover; the small holes on the retaining frames are sleeved on the center spring, and the plurality of large holes on the retaining frames are respectively sleeved on the outside of the soft body units; the retaining springs are sleeved on the center spring, and are used to provide spacing and support between the lower end cover, the upper end cover, and the retaining frames. The driving module is connected with the execution module, and three independent hydraulic circuits are arranged in the driving module, each hydraulic circuit comprising a micro motor pump and a pressure sensor, and being used to provide independent water pressure to the soft body units.

[0007] Further, the soft body unit comprises a plug, a silica gel base body, an aramid sleeve, a nylon winding wire, and a connector; the silica gel base body is located in the interior of the soft body unit, the outer surface of the silica gel base body is provided with a threaded groove, the nylon winding wire is uniformly wound and arranged along the threaded groove of the outer surface of the silica gel base body, and is used to limit the radial expansion of the soft body unit when being pressurized; the two ends of the silica gel base body are connected with the plug and the connector; the aramid sleeve is sleeved on the outer layer of the soft body unit, and is used to improve the overall rigidity and strength of the soft body unit.

[0008] Further, one end of the silica gel base body is provided as a closed end, and the other end is provided as an open end, both ends of the plug are provided with external threads, one end with a large outer diameter is embedded in the closed end of the silica gel base body and is locked and fixed by a clamp, and one end with a small outer diameter is fixed to the upper end cover by a nut; the center of the connector is provided with a through hole, one end of the connector is locked with the soft body unit by a clamp, and the other end is installed and fixed on the lower end cover by a nut, so as to realize the stable connection of the soft body unit and the driving passage.

[0009] Further, the driving module comprises a sealed end cover, a lower adapter ring, a pressure-resistant sleeve, an upper adapter ring, a water pressure driving system tool, and an electric control system tool; the sealed end cover is fixedly connected with the lower adapter ring by a bolt, and is sealed by a sealing ring; the lower adapter ring and the pressure-resistant sleeve, and the upper adapter ring and the pressure-resistant sleeve are bonded by sealing glue; the upper adapter ring is connected with the lower end cover by a bolt with a sealing ring.

[0010] Furthermore, the water pressure drive system fixture includes three micro motor pumps, three pressure transmitters, and a mounting plate; the micro motor pumps and pressure transmitters are fixed on the mounting plate, the inlet end of the micro motor pumps is connected to the internal cavity of the execution module to draw water from the external water environment and pressurize it, and the outlet end of the micro motor pumps is connected to the corresponding software unit; the pressure transmitters are connected to the delivery pipeline of the corresponding software unit through a tee connector to monitor the pressure of the software unit.

[0011] Furthermore, the upper end cover is also provided with two wire holes and one water inlet. The wire holes are used for the threading of control cables and power cables, and the water inlet is used to connect the internal cavity of the execution module with the external water environment so that the drive module can draw water.

[0012] Furthermore, the central spring is a high-stiffness rectangular spring, fixed at the center hole of the lower end cover and the upper end cover, used to provide basic support when the soft unit is under low pressure, and to antagonize the expansion force of the soft unit to achieve stiffness adjustment.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The drive module of this invention provides controllable water pressure to each software unit. It has three independent hydraulic circuits, each consisting only of a micro motor pump and pipelines, resulting in a compact and small structure that saves internal space in the drive module. Because the hydraulic circuits are independent, mutual interference between circuits is effectively avoided. Simultaneously, the pump-controlled pressure regulation method precisely controls the pressurization and depressurization of each software unit, achieving not only multi-degree-of-freedom joint posture control and overall stiffness adjustment, but also improving energy efficiency and the underwater robot's endurance compared to valve-controlled pressure regulation.

[0014] 2. The execution module of the present invention is provided with a high-stiffness rectangular spring at its center, which can provide basic support for the soft unit under low pressure or no pressure, and maintain the necessary stiffness and structural stability of the soft joint; when the soft unit is pressurized, the central spring and the soft unit form an antagonistic effect, which can realize the combined control of attitude and stiffness.

[0015] 3. This invention uses water pressure drive and directly utilizes the surrounding water environment as the working medium, eliminating the need for gas storage devices or lengthy gas pipes, thus simplifying the system structure.

[0016] In summary, this invention achieves a wide range of attitude and stiffness control of soft joints by combining the antagonistic effect of the central spring and multiple soft units within the execution module with a pump-controlled independent hydraulic circuit, providing technical assurance for the high reliability and adaptability of underwater snake robots in complex environments. Attached Figure Description

[0017] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall structure in an embodiment of the present invention; Figure 2 This is a schematic diagram of the execution module structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of the software unit structure in an embodiment of the present invention; Figure 4 This is a schematic diagram of the drive module structure in an embodiment of the present invention; Figure 5 This is a schematic diagram of the tooling structure of the water pressure drive system in an embodiment of the present invention; Figure 6 This is a schematic diagram of the tooling structure of the electronic control system in an embodiment of the present invention.

[0019] In the diagram: 1. Execution module; 11. Lower end cover; 12. Software unit; 121. Plug; 122. Silicone substrate; 123. Aramid sleeve; 124. Nylon winding thread; 125. Connector; 13. Cage; 14. Bellows cover; 15. Center spring; 16. Nut; 17. Upper end cover; 18. Retaining spring; 19. Wire bolt; 2. Drive module; 21. Sealing end cover; 22. Lower adapter ring; 23. Pressure-resistant sleeve; 24. Upper adapter ring; 25. Hydraulic drive system fixture; 26. Electrical control system fixture; 261. Pneumatic module mounting plate; 262. Microcontroller; 263. Relay; 264. Step-down module; 265. PWM module. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0024] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0025] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0026] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0027] This invention provides a soft joint for attitude stiffness composite control of an underwater snake-like robot, such as... Figures 1-6 As shown, the design adopts an integrated drive-actuation system, mainly consisting of an execution module 1 and a drive module 2, both of which are cylindrical and connected together by multiple bolts. The execution module 1 can bend in different directions and adjust its stiffness, thereby changing the posture and stiffness of the underwater snake robot; the drive module 2 is used to drive the execution module 1 and control its bending angle and stiffness.

[0028] The actuator module 1 is cylindrical in shape and mainly includes a lower end cover 11, soft units 12, a retainer 13, a bellows cover 14, a central spring 15, a nut 16, an upper end cover 17, a retaining spring 18, and a wiring bolt 19. Both the lower end cover 11 and the upper end cover 17 are disc-shaped structures, each with three circular holes arranged in an equilateral triangle to define the mounting positions of the three soft units 12. In addition to the mounting holes for the soft units 12, the upper end cover 17 also has two wiring holes and one water inlet. The wiring holes are used for the introduction and transmission of control and power lines for the soft joints, and the water inlet connects the internal cavity of the actuator module 1 to the external water body. The drive module 2 can directly obtain water from inside the execution module. In addition, the outer cylindrical surface of the upper end cover 17 is provided with six countersunk holes as standardized interfaces for connection with other structural modules of the robot. The central spring 15 and the soft unit 12 constitute the core components of the execution module. The central spring 15 is a high-stiffness rectangular spring, and its two ends are fixed to the central holes of the lower end cover 11 and the upper end cover 17 with special resin, thus penetrating the entire execution module 1. When the soft unit 12 is pressed into high-pressure water and elongates, the central spring 15 generates a large restoring force in the opposite direction to achieve an antagonistic effect, so that the execution module 1 can obtain adjustable overall stiffness. The two ends of the three soft units 12 are fixed to the lower end cover 11 and the upper end cover 17 respectively, forming the main body of the execution module; the center of the retainer 13 has a small hole and three large holes are evenly arranged on the outer periphery. The small hole in the center is fitted onto the central spring 15, and the three large holes are fitted onto the three soft units 12 respectively, to maintain the stability of the soft units 12; the retaining spring 18 is fitted onto the outside of the central spring 15, to provide a uniform interval between each retainer 13 and the two end covers; several threaded bolts 19 are installed on the lower end cover 11, to provide fixing and sealing functions when various pipelines pass through the lower end cover 11; the two ends of the bellows cover 14 are fixed to the lower end cover 11 and the upper end cover 17 respectively, to protect the internal components of the execution module 1 and reduce the hydrodynamic resistance when the snake robot is navigating.

[0029] The working principle of the soft joint for attitude stiffness composite control of an underwater snake robot provided by this invention is as follows: After the soft unit 12 is filled with high-pressure water, the soft unit 12 undergoes axial elongation. By independently controlling the elongation of the three soft units 12, the bending direction and bending angle of the execution module 1 can be adjusted. Due to the antagonistic effect of the central spring 15, when the pressure of the soft unit 12 increases, the overall stiffness of the execution module 1 increases synchronously. In particular, when the same pressure is applied to the three soft units 12, the execution module 1 elongates slightly as a whole and exhibits significantly enhanced axial stiffness. Based on the above structure and principle, the soft joint provided by this invention can realize the composite control function of bending attitude control and stiffness adjustment.

[0030] Figure 3This is a schematic diagram of the soft unit structure; the soft unit 12, as the actuator of the execution module 1, consists of a plug 121, a silicone substrate 122, an aramid sleeve 123, a nylon winding thread 124, and a connector 125; the silicone substrate 122 is located inside the soft unit 12, formed by molding, with one end being a closed end and the other end being an open end, and the outer surface having threaded grooves; both ends of the plug 121 are provided with external threads, the end with the larger outer diameter is embedded into the closed end of the silicone substrate 122 and locked in place by a stainless steel clamp, while the end with the smaller outer diameter is fixed to the upper end cap 17 by a nut 16; the nylon winding thread 124... The silicone substrate 122 is evenly wound with threaded grooves on its outer surface to limit the radial expansion of the soft unit 12 under pressure, thereby enhancing its pressure resistance and maintaining structural shape stability. The connector 125 has a through hole in its center to provide working pressure to the inside of the soft unit 12. The large end of the connector 125 is reliably locked to the soft unit 12 by a stainless steel clamp, while the small end is installed and fixed to the lower end cover 11 by a nut 16, realizing a stable connection between the soft unit 12 and the drive channel. The aramid sleeve 123 is sleeved on the outer layer of the soft unit 12 to improve the overall rigidity and strength of the soft unit 12, thereby enhancing its load-bearing capacity and durability.

[0031] Figure 4 The diagram shows the structure of the drive module. The drive module 2 is also cylindrical, with the same outer diameter as the actuator module 1. It mainly consists of a sealing end cap 21, a lower adapter ring 22, a pressure-resistant sleeve 23, an upper adapter ring 24, a hydraulic drive system fixture 25, and an electrical control system fixture 26.

[0032] The sealing end cap 21 is located at the bottom of the drive module 2. Its outer edge is fixedly connected to the lower adapter ring 22 by 12 bolts with sealing rings. A sealing ring is set between the sealing end cap 21 and the lower adapter ring 22 to achieve a reliable seal. The sealing end cap 21 is equipped with two through bolts for passing through control cables and power cables, respectively. In addition, consistent with the upper end cap 17, the cylindrical surface of the sealing end cap 21 is also provided with 6 countersunk holes as a standardized interface for modular connection with other robot components. The lower adapter ring 22 has a stepped ring structure. The end with the smaller outer diameter is embedded in one end of the pressure-resistant sleeve 23 and is fixed by sealing silicone. The inner side of the end with the larger outer diameter is provided with a nut mounting groove to achieve a stable connection with the sealing end cap 21. The upper adapter ring 24 has the same structure as the lower adapter ring 22. It is also fixed to the pressure-resistant sleeve 23 by sealing silicone and connected to the lower end cover 11 by bolts with sealing rings, so as to achieve a stable assembly between the drive module 2 and the execution module 1. In addition, a sealing ring is also installed between the upper adapter ring 24 and the lower end cover 11 to ensure reliable sealing. The hydraulic drive system fixture 25 and the electrical control system fixture 26 are respectively set in the upper and lower parts inside the drive module 2. The hydraulic drive system fixture 25 is used to provide the required working pressure to the execution module 1 to drive the length and rigidity of the software unit 12. The electrical control system fixture 26 is used to control the action of the hydraulic drive system fixture 25 to achieve composite control of the attitude and rigidity of the execution module 1.

[0033] Figure 5 This is a schematic diagram of the tooling structure of the water pressure drive system. The water pressure drive system tooling 25 mainly consists of three micro motor pumps 251, three pressure transmitters 253, and a fixing plate 252. The fixing plate 252 is used to fix the micro motor pumps 251 and the pressure transmitters 253, and two additional round holes are provided on the plate for the passage of control cables and power cables, respectively. The micro motor pump 251 is used to transport water from the external water environment to the interior of the soft unit 12. Its inlet end is connected to the soft unit 1 via a hose and then introduced into the cavity of the execution module 1 via a threaded bolt 19. The cavity inside the execution module 1 is connected to the external water environment through a through hole provided in the upper end cover 17. Therefore, the micro motor pump 251 can directly draw water from the water environment and pressurize and transport it to the interior of the soft unit 12. The outlet end of the micro motor pump 251 is connected to the connector 125 of the soft unit 12 via a hose. The pressure transmitter 253 is connected to the delivery pipeline from the outlet of the micro motor pump 251 to the soft unit 12 via a three-way connector for real-time monitoring of the pressure inside the soft unit 12.

[0034] Figure 6This is a schematic diagram of the electrical control system fixture structure. To save internal space in the drive module 2, the electrical control system fixture 26 is designed as a flat plate, mainly composed of an electrical module mounting plate 261, an STM32 microcontroller 262, a relay 263, a step-down module 264, and a PWM module 265. The electrical module mounting plate 261 is used to fix and support each functional module. The STM32 microcontroller 262 serves as the control motherboard for the soft joint, receiving control commands sent from the host computer and controlling the posture and stiffness of the soft joint according to the commands. The relay 263 receives high and low level signals output by the STM32 microcontroller 262, controlling the forward and reverse rotation of the micro motor pump 251, thereby realizing the boost and depressurization regulation within the soft unit. Two step-down modules 264 are provided, used to convert the 24V power supply voltage to 12V and 5V respectively, providing stable power to the PWM module 265 and the STM32 microcontroller 262. The PWM module 265 is used to convert the PWM control signal output by the STM32 microcontroller 262 into a corresponding voltage signal to control the speed of the micro motor pump 251 and achieve fine adjustment of the charging speed of the software unit.

[0035] As can be seen, this invention provides a soft joint for the attitude stiffness composite control of an underwater snake-like robot, which significantly reduces impact force when the robot comes into contact or collides with the underwater environment, thereby improving the reliability and service life of the underwater snake-like robot. This soft joint achieves adjustable stiffness through the antagonism between a central spring and the soft unit, which can significantly improve the robot's load-bearing capacity. Simultaneously, the joint of this invention adopts a high-efficiency miniaturized drive architecture, facilitating multi-section integration and making it suitable for lightweight snake-like robot applications requiring long underwater endurance.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A soft joint for attitude stiffness composite control of an underwater snake-like robot, characterized in that, Includes execution modules and drive modules; The execution module is cylindrical and includes a lower end cover, an upper end cover, soft units, a central spring, multiple retainers, multiple retaining springs, a bellows cover, and threaded bolts. Each of the three soft units is an independent pressurizable cavity, with both ends fixed to the lower and upper end covers, respectively. The central spring extends axially through the execution module, with both ends fixed to the central holes of the lower and upper end covers. Small holes on the retainers are fitted onto the central spring, and multiple large holes on the retainers are fitted onto the outer sides of the soft units. The retaining springs are fitted onto the central spring and provide spacing and support between the lower end cover, the upper end cover, and each retainer. The drive module is connected to the execution module. The drive module has three independent hydraulic circuits inside. Each hydraulic circuit includes a micro motor pump and a pressure sensor, which are used to provide independent water pressure to the software unit.

2. The attitude stiffness composite control soft joint of the underwater snake robot according to claim 1, characterized in that, The software unit includes a plug, a silicone substrate, an aramid sleeve, a nylon winding wire, and a connector; The silicone substrate is located inside the soft unit. The outer surface of the silicone substrate is provided with threaded grooves. Nylon winding thread is evenly wound and distributed along the threaded grooves on the outer surface of the silicone substrate to limit the radial expansion of the soft unit under pressure. The two ends of the silicone substrate are connected to plugs and connectors. The aramid sleeve is sleeved on the outer layer of the soft unit to improve the overall rigidity and strength of the soft unit.

3. The attitude stiffness composite control soft joint of the underwater snake robot according to claim 2, characterized in that, One end of the silicone substrate is a closed end, and the other end is an open end. Both ends of the plug are provided with external threads. The end with the larger outer diameter is embedded into the closed end of the silicone substrate and locked in place by a clamp. The end with the smaller outer diameter is fixed to the upper end cover by a nut. The connector has a through hole in the center. One end of the connector is locked to the software unit by a clamp, and the other end is installed and fixed to the lower end cover by a nut, so as to achieve a stable connection between the software unit and the drive channel.

4. The attitude stiffness composite control soft joint of the underwater snake robot according to claim 1, characterized in that, The drive module includes a sealed end cap, a lower adapter ring, a pressure-resistant sleeve, an upper adapter ring, a hydraulic drive system fixture, and an electrical control system fixture. The sealed end cap is fixedly connected to the lower adapter ring by bolts and sealed by a sealing ring. The lower adapter ring and the pressure-resistant sleeve, as well as the upper adapter ring and the pressure-resistant sleeve, are bonded together with sealant. The upper adapter ring is connected to the lower end cap by bolts with sealing rings.

5. The attitude stiffness composite control soft joint of the underwater snake robot according to claim 4, characterized in that, The water pressure drive system fixture includes three micro motor pumps, three pressure transmitters, and a mounting plate. The micro motor pumps and pressure transmitters are fixed on the mounting plate. The inlet end of the micro motor pump is connected to the internal cavity of the execution module to draw water from the external water environment and pressurize it. The outlet end of the micro motor pump is connected to the corresponding software unit. The pressure transmitter is connected to the delivery pipeline of the corresponding software unit through a tee connector to monitor the pressure of the software unit.

6. The attitude stiffness composite control soft joint of the underwater snake robot according to claim 1, characterized in that, The upper cover is also provided with two wiring holes and one water inlet. The wiring holes are used for the wiring of control cables and power cables, and the water inlet is used to connect the internal cavity of the execution module with the external water environment so that the drive module can draw water.

7. The attitude stiffness composite control soft joint of the underwater snake robot according to claim 1, characterized in that, The central spring is a high-stiffness rectangular spring, fixed at the center hole of the lower end cover and the upper end cover. It is used to provide basic support when the soft unit is under low pressure and to counteract the expansion force of the soft unit, thereby achieving stiffness adjustment.

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