A buoyancy adjusting device and a buoyancy adjusting method based on a large-stretch-ratio seawater soft bag

Abstract

The application discloses a kind of based on big extension ratio seawater soft bag's buoyancy adjusting device, including integrated pressure cylinder, wind box type big extension ratio seawater soft bag, telescopic guide mechanism, integrated electric servo drive mechanism composition.Seawater soft bag separates the wet cabin and dry cabin in cylinder inner portion;Telescopic guide mechanism is supported ring through guide rod and soft bag wave crest cooperation, ensure that soft bag is stable and orderly telescopic under deep sea high pressure;Servo motor drives screw through speed reduction synchronous transmission mechanism, drive piston disc fixed with soft bag movable end to do linear motion, change soft bag volume reaches the purpose of adjusting buoyancy;Magnetostrictive position sensor real-time detects piston disc position and feedback to controller, realizes the high-precision closed-loop control of injection and discharge capacity.The application has the advantages of compact structure, large adjustment range, fast response, high reliability and low noise, and can better meet the needs of small and medium-sized underwater platform in deep sea environment for large range, high precision, high reliability, low noise and low power consumption.

Description

Technical Field

[0001] This invention belongs to the field of underwater equipment technology, and particularly relates to a buoyancy adjustment device and buoyancy adjustment method based on a seawater soft bladder with a large stretch ratio. Background Technology

[0002] The buoyancy adjustment device is the core system of an underwater platform that enables it to achieve constant depth navigation, precise hovering, long-term endurance, and attitude control by actively changing its buoyancy or gravity. Its performance directly affects the safety of the underwater platform and its overall mission performance.

[0003] Currently, mainstream buoyancy control technologies are mainly divided into two categories: adjustable ballast tank type and variable volume type. The main representatives of each are pump-valve ballast systems and oil bladder volume control systems. Both have inherent technical defects, making it difficult to meet the comprehensive performance requirements of small and medium-sized underwater platforms for buoyancy control devices, which demand lightweight, miniaturization, fast response, high efficiency, high reliability, low noise, low cost, and high adjustability. For example, pump-valve ballast systems control the injection and drainage of ballast tanks through seawater pumps, valves, and pipelines. Although they are stable and reliable with a large buoyancy adjustment range, they suffer from complex structures, high costs, large dry tank space requirements, slow response, high energy consumption, high vibration and noise, high seawater cleanliness requirements, and a high risk of corrosion for seawater-contacting components. While oil bladder volume control systems offer fast response and compact structures, the bladders are prone to disorganized folding and stress concentration, resulting in a short lifespan. Furthermore, their adjustment range and working depth are very limited, making it difficult to meet the needs of reliable buoyancy adjustment over a wide range. Summary of the Invention

[0004] This invention addresses the inherent shortcomings of existing buoyancy adjustment technologies in terms of structure, performance, power consumption, and cost. It proposes a buoyancy adjustment device based on a seawater soft bladder with a large stretch ratio that can meet the comprehensive performance requirements of "wide range, high precision, high reliability, fast response, low noise, and low power consumption" to satisfy the buoyancy adjustment needs of small and medium-sized underwater platforms in deep-sea environments.

[0005] One of the above-mentioned objectives of the present invention is achieved by the following technical solution: A buoyancy adjustment device based on a seawater soft bladder with a high stretch ratio, comprising: The integrated pressure-resistant cylinder is a horizontal cylindrical body that is directly immersed in seawater. One end is an open opening that connects to the outside seawater, and the other end is equipped with a sealed end cap. The seawater soft bag is bellows-shaped and made of multi-layer flexible composite material. The front end of the seawater soft bag is a fixed end, which is fixed to the open end of the cylinder by a flange. The rear end of the seawater soft bag is a movable end, which is sealed and fixed to the piston plate by a flange. The internal cavity of the seawater soft bag forms a wet chamber with variable volume. The outer wall of the seawater soft bag, the inner wall of the pressure-resistant cylinder and the sealing end cap form a dry chamber for installing electromechanical components. The telescopic guide mechanism includes three guide rods arranged parallel to the axial direction of the pressure-resistant cylinder and multiple crest support rings fixed at the crests of the seawater soft bag. The guide rods pass through guide positioning holes at corresponding positions of all crest support rings to provide radial constraint and axial guidance for the axial extension and retraction of the seawater soft bag. An integrated electric servo drive mechanism is arranged inside the dry chamber, including a servo motor, a reduction mechanism driven by the servo motor, a synchronous transmission mechanism connected to the output shaft of the reduction mechanism, and three lead screws driven to rotate synchronously by the synchronous transmission mechanism. The three lead screws and the corresponding nuts built into the piston disk form a helical pair, which is used to drive the piston disk to perform reciprocating linear motion along the axial direction. The control and detection system includes a magnetostrictive position sensor for detecting the absolute position of the piston disk and a controller, wherein the controller performs closed-loop control of the servo motor based on the feedback signal from the magnetostrictive position sensor.

[0006] Moreover, the seawater soft bag is a bellows-type flexible bag structure with continuous multi-segment annular folds along the axis, and its expansion ratio is not less than 10; the material of the seawater soft bag includes a high-strength fiber fabric base layer as a pressure-bearing skeleton and a functional coating to ensure water tightness.

[0007] Moreover, the crest support ring is a metal ring structure, which is fixed to the outer edge of the folded crest position of the seawater soft bag unit segment by hydraulic pressing; three guide positioning holes are evenly distributed around the edge of the crest support ring; and self-lubricating composite material thin-walled bushings are inlaid in the guide positioning holes.

[0008] Furthermore, the surfaces of the three guide rods are coated with a "nickel-phosphorus-polytetrafluoroethylene chemical composite plating" process; the guide rods and the guide holes on the wave crest support ring are fitted with a small clearance precision sliding fit using a hole-based H7 / g6 grade system.

[0009] Furthermore, the reduction mechanism adopts a planetary reduction gear pair, consisting of a sun gear, three planet gears, an internal gear ring, and a planet carrier; the synchronous transmission mechanism adopts a fixed-axis planetary splitter gear pair, consisting of a central gear and three circumferentially distributed planetary idler gears, each planetary idler gear being fixed to a lead screw.

[0010] Moreover, the three lead screws are arranged parallel to and evenly along the axial direction of the pressure-resistant cylinder within the annular dry compartment formed by the outer wall of the seawater soft bag and the inner wall of the cylinder.

[0011] Moreover, the magnetostrictive position sensor is characterized by a triple redundancy configuration, with its three non-contact probes respectively built into three hollow guide rods, and its detection end fixed to the piston disc, which is used to convert the actual position of the piston disc into real-time water volume information of the wet chamber.

[0012] One of the above-mentioned objectives of the present invention is achieved by the following technical solution: A buoyancy adjustment method based on the above-mentioned buoyancy adjustment device based on a large stretch ratio seawater soft bladder includes buoyancy increase adjustment and buoyancy decrease adjustment. When buoyancy needs to be increased, the servo motor is controlled to rotate forward, and the three lead screws are driven to rotate synchronously forward through the reduction mechanism and synchronous transmission mechanism. This pushes the piston disc to move toward the open end of the integrated pressure-resistant cylinder, compressing the seawater soft bag and expelling the seawater inside, thus achieving buoyancy. When buoyancy needs to be reduced, the servo motor is controlled to reverse, and the three lead screws are driven to reverse synchronously through the reduction mechanism and synchronous transmission mechanism, which pulls the piston disc toward the sealing end cap, stretches the seawater soft bag, draws in seawater, and achieves diving; Throughout the process, the absolute position of the piston disc is detected in real time by the magnetostrictive position sensor and fed back to the controller. The controller converts this into the actual injection / discharge volume, compares it with the commanded volume, and forms a closed-loop control to achieve precise and rapid adjustment of the injection / discharge volume. The advantages and positive effects of this invention are as follows: 1) The structure is highly simplified and integrated, resulting in a significant reduction in overall cost. By integrating the pressure-resistant cylinder and regulating device into a single unit, the complex water pump, valve group, pipeline and hydraulic components of the traditional split structure are eliminated, significantly reducing system complexity, space occupation, power consumption and manufacturing and maintenance costs.

[0013] 2) It has the dual advantages of wide-range regulation and fast response. By employing a bellows-type seawater soft bladder with a large expansion ratio (≥10), the challenge of instability due to large deformation of flexible bladders under high pressure has been overcome. Inheriting the advantages of direct volume adjustment and rapid response of variable-volume systems, it achieves a wide range of buoyancy adjustment capabilities comparable to ballast tank systems, exhibiting excellent comprehensive performance indicators, and is particularly suitable for the buoyancy adjustment needs of small and medium-sized underwater platforms. Furthermore, the adopted "expansion guide mechanism" design overcomes the technical bottleneck of instability during the expansion and contraction of traditional slender flexible bladders, providing a key mechanical guarantee for achieving the large expansion ratio of the soft bladder. The synergistic effect of the support ring and guide rod provides linearity constraint for the reciprocating expansion and contraction motion of the soft bladder, achieving radial constraint and shape maintenance. This solves the problems of easy deflection, instability, twisting, jamming, or disordered folding during expansion and contraction, ensuring that the seawater soft bladder can continuously, stably, and orderly complete large-scale axial deformation under deep-sea high pressure, thus improving the reliability and service life of the device.

[0014] 3) Dry and wet separation improves reliability and environmental adaptability. The innovative "dry-wet separation" structural design seals all precision electromechanical components within the dry chamber inside the cylinder, eliminating the need for additional watertight design. This fundamentally solves the problems of waterproofing, pressure resistance, and corrosion prevention for electromechanical components in seawater environments, significantly improving the overall reliability, maintainability, and service life of the system.

[0015] 4) A high-precision, high-dynamic, and low-noise servo drive and control system was constructed. The design adopts an "integrated electric servo drive and position detection" system. It uses a DC servo motor and a reduction synchronous transmission mechanism to drive the lead screw to achieve precise and quiet linear drive of the piston disc. Combined with a magnetostrictive position sensor, it completes non-contact absolute position detection, forming an integrated drive unit with "power-transmission-execution-feedback" full closed-loop control. It establishes closed-loop control of the axial length of the soft bladder, enabling rapid, accurate, and reliable adjustment of the injection and drainage volume.

[0016] 5) Possesses good engineering adaptability and scalability The device has a compact structure and a high degree of modularity. It can be standardized and mass-produced in series according to its buoyancy adjustment capability to adapt to small and medium-sized underwater platforms of different sizes. At the same time, it can also be parametrically designed and expanded according to different depth and adjustment requirements. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the buoyancy adjustment device based on a large stretch ratio seawater soft bladder of the present invention. Figure 2 This is a schematic diagram of the wave crest support ring structure of the present invention; Figure 3 This is a cross-sectional schematic diagram of the internal structure of the pressure-resistant cylinder of the present invention; Figure 4 This is a schematic diagram showing the installation position of the magnetostrictive position sensor of the present invention; In the diagram: 1. Integrated pressure-resistant cylinder; 1-1. Sealed end cap; 2. High-expansion-ratio seawater soft bladder; 3. Piston disc; 4. Wet chamber; 5. Sealed dry chamber; 6. Wave crest support ring; 6-1. Guide hole; 7. Guide rod; 8. Limiting block; 9. Synchronous transmission mechanism; 10. Reduction mechanism; 11. Servo motor; 12. Controller; 13. Lead screw; 14. Measuring rod; 15. Magnetic ring. Detailed Implementation

[0018] The structure of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that these embodiments are descriptive and not limiting.

[0019] This invention provides a buoyancy adjustment device for underwater platforms. Its core component is a bellows-type, high-expansion-ratio soft bladder fixed inside a pressure-resistant cylinder as a direct volume adjustment unit. An integrated electric servo drive system precisely controls the expansion and contraction of the soft bladder. An innovative telescopic guide mechanism ensures stable and orderly folding and expansion of the soft bladder under deep-sea pressure. The entire device meets the performance requirements of small and medium-sized underwater platforms for wide-range, high-precision, high-reliability, and low-noise buoyancy adjustment.

[0020] The technical solution adopted to achieve the above objectives is a buoyancy adjustment device based on a seawater soft bladder with a large expansion ratio. Please refer to [link / reference]. Figures 1-4 Its inventive points include: Integrated pressure-resistant cylinder 1: The integrated pressure-resistant cylinder 1 is designed to be directly immersed in seawater. The cylinder is precision-machined from high-strength, seawater-corrosion-resistant titanium alloy (such as TC4) and has a cylindrical structure. In this embodiment, the cylinder has an outer diameter of 300mm, a wall thickness of 8mm, and a length of 1500mm. One end of the cylinder is open, directly connected to the external seawater via a flange; the other end is sealed via a circular sealing end cap 1-1, which is equipped with a watertight electrical connector and an airtightness inspection interface. The cylinder is designed to withstand pressure at a depth of not less than 100 meters.

[0021] High stretch ratio seawater soft capsule 2: The high-extension-ratio seawater soft bladder 2 is installed inside the pressure-resistant cylinder. The soft bladder has a bellows-like corrugated tubular structure. It is a type of flexible structure with controlled deformation. Its high extension-ratio is achieved through the ordered deformation of its geometric topology design (folds) under a controlled mechanical environment (material + guiding mechanism), rather than relying on the material's inherent elasticity. The soft bladder employs an axially continuous multi-segment annular fold design, with each fold acting as an independent folding / unfolding unit. By optimizing the fold depth (the radial height difference between the crest and trough when compressed to its shortest length) and pitch (the maximum tensile length under pressure) parameters, the extension-ratio of the soft bladder unit is maximized within the material's strain limit. Multiple segments are then connected in series to achieve the overall volume adjustment capability of the soft bladder. The soft bladder material is a high-strength, low-elongation, fatigue-resistant flexible multilayer composite material. The base fabric layer is the pressure-bearing skeleton, made of high-strength, low-creep fiber fabric, which provides extremely high radial tensile strength to resist the pressure of seawater inside the bladder, thereby limiting radial expansion; the functional coating ensures water tightness, prevents seawater penetration, provides the necessary flexibility and resistance to folding fatigue, and has the ability to resist seawater corrosion.

[0022] In this embodiment, the soft capsule is composed of 10 soft capsule units with annular pleats connected in series along the axial direction. The pitch of the soft capsule unit is 10 mm and the wave depth is 60 mm at the ultimate compression position, and the pitch is 100 mm at the ultimate tension position. When the piston disk 3 moves from the ultimate compression position to the ultimate tension position, the axial length of the soft capsule can reach 1000 mm, achieving a stretch ratio of not less than 10, corresponding to a maximum adjustable seawater volume of approximately 60 liters.

[0023] The front end (fixed end) of the soft bladder is fixed and sealed to the open end of the cylinder via a flange; the rear end (movable end) is fixed and sealed to the piston disc via a flange. Thus, the inner cavity of the soft bladder forms a wet chamber 4, which is in direct contact with the outside seawater; the outer wall of the soft bladder, the inner wall of the cylinder, and the sealed end cap form a closed dry chamber 5.

[0024] At the crest position of each soft capsule unit, a crest support ring 6 made of titanium alloy (TC4) is externally fixed by a crest bonding process. The crest support ring is designed to act as a rigid skeleton to provide radial constraint and shape maintenance, resist the radial expansion force generated by the water pressure inside the soft capsule, and prevent excessive deformation and interference with the inner wall of the capsule and other components. On the other hand, the three guide holes 6-1 evenly distributed on the edge of the ring and the guide rod 7 form a telescopic guide mechanism.

[0025] In this embodiment, the outer diameter of the wave crest support ring is 280mm, the inner diameter is 200mm, and the thickness is 8mm. Three guide holes with a diameter of 18mm are evenly distributed on its circumferential edge.

[0026] Telescopic guide mechanism: The telescopic guide mechanism consists of three high-precision guide rods and the aforementioned wave crest support ring. The guide rods are made of precipitation-hardened stainless steel with an outer diameter of 15mm and the surface is treated with a "nickel-phosphorus-PTFE chemical composite plating" process. The three guide rods are arranged parallel to the axial direction of the cylinder and evenly in the circumferential direction within the annular dry chamber between the outer wall of the soft bladder and the inner wall of the cylinder.

[0027] One end of the guide rod is threaded to the back of the flange at the open end of the cylinder; the other end passes through the corresponding guide holes 6-1 of all the corrugated support rings and is locked by the limiting block 8 fixed to the cylinder wall. The guide rod has high straightness to provide accurate axial reference; at the same time, it must have sufficient bending stiffness to resist the lateral force during the expansion and contraction of the soft bladder and prevent the rod from deflecting. The guide rod and the guide holes on the support rings adopt a precision clearance fit. In this embodiment, the single-sided fit clearance between the guide rod and the guide hole of the support ring is 0.2mm, which ensures that the support ring can slide along the guide rod with low resistance during the expansion and contraction of the soft bladder, and effectively limits the radial sway and deflection of the soft bladder. In addition, the guide rod is made of high-strength, wear-resistant metal material, and the surface is treated with a low-friction coating to reduce frictional resistance and mechanical wear during guidance and ensure smooth long-term movement.

[0028] Integrated electric servo drive mechanism: The entire drive mechanism is integrated and installed inside the dry compartment. It includes a servo motor 11, a reduction gear 10, a synchronous transmission mechanism 9, and three sets of ball screws. The output end of the servo motor is connected to the input end of the reduction gear via gear meshing, and the output end of the reduction gear is connected to the input end of the synchronous transmission mechanism via gear meshing. The synchronous transmission mechanism is connected to the three sets of ball screws via three synchronous gears, respectively, to achieve synchronous drive of the three screws 13.

[0029] The servo motor serves as the power source, employing a 600W rated power DC brushless servo motor, mounted inside the circular sealed end cover via a bracket. The reduction mechanism utilizes a planetary gear reducer pair, consisting of a sun gear, three planet gears, an internal gear ring, and a planet carrier, with the planet carrier serving as the power output component. The synchronous transmission mechanism employs a fixed-axis planetary splitter gear pair, composed of a central gear and three circumferentially distributed planetary idler gears. The output shaft of the servo motor connects to the input end of the planetary gear reducer pair, with a reduction ratio of 15:1. The output shaft of the planetary gear reducer pair directly drives the central gear of the fixed-axis planetary splitter gear pair, which simultaneously meshes with three circumferentially distributed planetary idler gears (rotating only on their own axis, not around the sun), each planetary idler gear being fixed to a ball screw. The three ball screws (in this embodiment, 16mm in diameter and 5mm in lead) are parallel and evenly distributed within the annular dry chamber, their nuts integrated into the piston disc via bearing seats, forming a helical pair.

[0030] Control and detection system The detection employs magnetostrictive position sensors, with three sensor probes 14 mounted within three hollow guide rods. A non-contact magnetic ring 15 is mounted on the piston disc, coaxially fixed with the guide holes corresponding to the guide rods. The sensor has a measurement range of 0-1200 mm and a linear accuracy of ±0.05%FS, enabling real-time, non-contact detection of the absolute position of the piston disc.

[0031] Controller 12 is an embedded computer module integrating CAN communication, serial communication, and digital and analog signal acquisition functions. It receives water injection / discharge control commands from the aircraft control platform and feedback signals from displacement sensors, and drives the piston disc movement through a built-in PID control algorithm to form a closed-loop position control. The control system is equipped with multiple safety protection mechanisms: 1) Limit protection: The upper and lower limits are set by software according to the expansion and contraction limits of the soft capsule; mechanical limit switches are set at both ends of the dry chamber as hardware limits; 2) Motor protection: Real-time monitoring of motor speed, current, and temperature; immediately cuts off power in case of overspeed, overload, or overheating. 3) Monitoring and Alarm: The system detects water ingress into the dry compartment using sensors located at the bottom; it also determines the empty or full status of the soft bladder based on the piston disc position. The controller sends alarm information to the navigation management platform in real time. 4) Power-off memory: Upon power failure, the controller automatically stores the current piston disk position in non-volatile memory. After power is restored, the system reads this position and can immediately resume normal operation without needing to perform a "return to zero" operation, improving safety and operational efficiency. 5) Emergency buoyancy: Once a fatal malfunction is detected in the system, an alarm will be triggered immediately and the control motor can be started to rotate at full speed according to the strategy to carry out emergency drainage and buoyancy operation.

[0032] 1) The absolute position of the piston disc is directly detected by a magnetostrictive position sensor, which enables accurate calculation of the water volume in the ballast tank. This completely eliminates the cumulative error caused by the need for flow meters to calculate the injection and drainage volume in traditional ballast tank systems. It also overcomes the problem of inaccurate liquid level measurement due to liquid level fluctuations when a liquid level meter is installed on the tank. At the same time, the sensor detection value is used as a feedback signal to form a position closed-loop control, which enables accurate and rapid control of the water tank injection and drainage volume. 2) Reliability and safety design of the control system. The control system is designed with multiple safety protection mechanisms: software and hardware limits for the position of the piston disc; overspeed protection, overload protection, and overheat protection for the motor; monitoring of water ingress into the dry compartment and the empty / full status of the soft bladder and reporting alarm information; power failure memory and power-on recovery functions for system power failure handling; and automatic activation of emergency buoyancy function according to strategy in case of fatal failure.

[0033] The working principle of the buoyancy adjustment device based on a high-stretch-ratio seawater soft bladder of the present invention is as follows: When the underwater platform needs to surface, the control system outputs a discharge command, controlling the servo motor to drive the lead screw to rotate forward, pushing the piston disc to compress the soft bladder. The soft bladder's inner cavity shrinks, seawater is discharged, and the pressure tank's discharge volume increases. The underwater platform begins to surface due to increased remaining buoyancy. When the underwater platform needs to submerge, the control system outputs a water injection command, controlling the servo motor to drive the lead screw to rotate in reverse, pushing the piston disc to extend the soft bladder. The soft bladder's inner cavity expands, seawater is drawn in, the pressure tank's discharge volume decreases, and the underwater platform begins to submerge due to decreased remaining buoyancy. The control system receives piston disc position information detected by the magnetostrictive position sensor, converts it into the current water volume in the tank, calculates the actual water injection / discharge volume, compares it with the commanded water injection / discharge volume, and outputs the control command for the next cycle, forming a closed-loop control of the water injection / discharge volume.

[0034] The buoyancy adjustment device based on the high-stretch-ratio seawater soft bladder locks and fixes the pressure-resistant cylinder to the underwater platform mounting surface through three metal clamps that are axially evenly distributed on the outer surface of the pressure-resistant cylinder.

[0035] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A buoyancy adjustment device based on a seawater soft bladder with a large stretch ratio, characterized in that, include: The integrated pressure-resistant cylinder is a horizontal cylindrical body that is directly immersed in seawater. One end is an open opening that connects to the outside seawater, and the other end is equipped with a sealed end cap. The seawater soft bag is bellows-shaped and made of multi-layer flexible composite material. The front end of the seawater soft bag is a fixed end, which is fixed to the open end of the cylinder by a flange. The rear end of the seawater soft bag is a movable end, which is sealed and fixed to the piston plate by a flange. The internal cavity of the seawater soft bag forms a wet chamber with variable volume. The outer wall of the seawater soft bag, the inner wall of the pressure-resistant cylinder and the sealing end cap form a dry chamber for installing electromechanical components. The telescopic guide mechanism includes three guide rods arranged parallel to the axial direction of the pressure-resistant cylinder and multiple crest support rings fixed at the crests of the seawater soft bag. The guide rods pass through guide positioning holes at corresponding positions of all crest support rings to provide radial constraint and axial guidance for the axial extension and retraction of the seawater soft bag. An integrated electric servo drive mechanism is arranged in the dry chamber, including a servo motor, a reduction mechanism driven by the servo motor, a synchronous transmission mechanism connected to the output shaft of the reduction mechanism, and three lead screws driven by the synchronous transmission mechanism to rotate synchronously. The three lead screws and the corresponding nuts built into the piston disk form a helical pair, which is used to drive the piston disk to perform reciprocating linear motion along the axial direction. The control and detection system includes a magnetostrictive position sensor for detecting the absolute position of the piston disk and a controller, wherein the controller performs closed-loop control of the servo motor based on the feedback signal from the magnetostrictive position sensor.

2. The buoyancy adjustment device based on a large stretch ratio seawater soft bladder according to claim 1, characterized in that: The seawater soft capsule is a bellows-type flexible capsule structure with continuous multi-segment annular folds along the axis, and its expansion ratio is not less than 10; the material of the seawater soft capsule includes a high-strength fiber fabric base layer as a pressure-bearing skeleton and a functional coating to ensure water tightness.

3. The buoyancy adjustment device based on a large stretch ratio seawater soft bladder according to claim 1, characterized in that: The crest support ring is a metal ring structure, which is fixed to the outer edge of the folded crest position of the seawater soft bag unit segment by hydraulic pressing; three guide positioning holes are evenly distributed around the edge of the crest support ring; and self-lubricating composite material thin-walled bushings are inlaid in the guide positioning holes.

4. The buoyancy adjustment device based on a large stretch ratio seawater soft bladder according to claim 1, characterized in that: The surfaces of the three guide rods are coated with a "nickel-phosphorus-polytetrafluoroethylene chemical composite plating" process; the guide rods and the guide holes on the wave crest support ring are precision sliding fits with small clearances of H7 / g6 grade based hole system.

5. The buoyancy adjustment device based on a large stretch ratio seawater soft bladder according to claim 1, characterized in that: The reduction mechanism adopts a planetary reduction gear pair, which consists of a sun gear, three planet gears, an internal gear ring, and a planet carrier; the synchronous transmission mechanism adopts a fixed-axis planetary splitter gear pair, which consists of a central gear and three circumferentially distributed planetary idler gears, each of which is fixed to a lead screw.

6. The buoyancy adjustment device based on a large stretch ratio seawater soft bladder according to claim 1, characterized in that: The three lead screws are arranged parallel to and evenly along the axial direction of the pressure-resistant cylinder within the annular dry compartment formed by the outer wall of the seawater soft bag and the inner wall of the cylinder.

7. The buoyancy adjustment device based on a large stretch ratio seawater soft bladder according to claim 1, characterized in that: The magnetostrictive position sensor adopts a triple redundancy configuration, with its three non-contact probes respectively built into three hollow guide rods. Its detection end is fixed to the piston disc, and it is used to convert the actual position of the piston disc into real-time water volume information of the wet chamber.

8. A buoyancy adjustment method based on the buoyancy adjustment device of the seawater soft bladder with a large elongation ratio as described in any one of claims 1-7, characterized in that: This includes adjustments to increase buoyancy and adjustments to decrease buoyancy; When buoyancy needs to be increased, the servo motor is controlled to rotate forward, and the three lead screws are driven to rotate synchronously forward through the reduction mechanism and synchronous transmission mechanism. This pushes the piston disc to move toward the open end of the integrated pressure-resistant cylinder, compressing the seawater soft bag and expelling the seawater inside, thus achieving buoyancy. When buoyancy needs to be reduced, the servo motor is controlled to reverse, and the three lead screws are driven to reverse synchronously through the reduction mechanism and synchronous transmission mechanism, which pulls the piston disc toward the sealing end cap, stretches the seawater soft bag, draws in seawater, and achieves diving; Throughout the process, the absolute position of the piston disc is detected in real time by the magnetostrictive position sensor and fed back to the controller. The controller converts this into the actual injection and drainage volume, compares it with the commanded water volume, and forms a closed-loop control to achieve precise and rapid adjustment of the injection and drainage volume.

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