Passive buoyancy compensation method for profile buoys using gas-liquid mixing

Abstract

This invention discloses a passive buoyancy compensation method using gas-liquid mixing for profiling buoys, belonging to the field of buoyancy adjustment technology for marine observation buoys. This method constructs a passive buoyancy compensation system containing gas and liquid chambers, and adjusts the gas-liquid volume ratio to achieve linear and continuous adjustment of the system's equivalent compressibility coefficient, dynamically matching the compression characteristics of seawater at different depths. A mathematical model of the overall force on the buoy is established to determine system design parameters. Sensors are deployed to collect buoy depth and axial acceleration data, calculate motion parameters, predict and estimate the depth, and compare it with the target depth. When the deviation threshold is exceeded, an active fine-tuning judgment process is initiated. Active adjustment is disabled during the inertial-dominated phase, and during the non-inertial phase, the controller sends a fine-tuning command to the active buoyancy system to execute reverse buoyancy adjustment. The passive buoyancy compensation method using gas-liquid mixing provided by this invention can achieve low-power buoyancy control with passive adjustment as the primary method and active adjustment as a secondary method, effectively extending the underwater operational life of the buoy.

Description

Technical Field

[0001] This invention belongs to the field of buoyancy adjustment technology for marine observation buoys, and particularly relates to a passive buoyancy compensation method for profile buoys using gas-liquid mixing. Background Technology

[0002] With the ever-increasing demand for global ocean observation, profiling buoys, as the core devices of the "Global Ocean Observing Network," face the critical challenge of long-term, autonomous operation, which has become a key factor limiting system effectiveness. Currently, most mainstream profiling buoys employ active buoyancy control devices for ascent and descent. These devices typically consist of hydraulic pumps, solenoid valves, internal oil tanks, external bladders, and hydraulic pipelines, resulting in a complex structure and extremely high energy consumption, accounting for 60-80% of the total power consumption. Due to limited internal space, energy relies primarily on lithium batteries with limited capacity. This high-power active buoyancy control mechanism severely shortens the buoy's service life, making it difficult to meet the endurance requirements of long-term deep-sea observation missions.

[0003] Currently, passive buoyancy compensation technology is an effective method to reduce the burden on active systems. This is achieved by introducing airbags or multi-stage accumulators. However, the former's performance is highly dependent on accurate pre-modeling and the physical characteristics of the accumulators. In actual deployment, adjusting fluid needs to be injected and pre-pressurized individually, making the operation cumbersome and requiring stringent sealing. The latter uses a mixture of multiple liquids to regulate the overall compressibility coefficient, but even small deviations in the mixing ratio can lead to uncontrollable system compression behavior, resulting in high engineering difficulty and poor stability. Neither of these two approaches achieves continuous, linear, and adjustable control of the buoy's equivalent compressibility coefficient, making it difficult to dynamically match the compression characteristics of seawater as it changes with depth.

[0004] Furthermore, the fixed or nonlinear equivalent compression coefficient of the passive compensation unit in existing technologies leads to a mismatch between the overall compression characteristics of the buoy and the surrounding seawater. This forces the active buoyancy system to intervene frequently to correct buoyancy deviations, thus negating the energy-saving advantages of passive compensation. Simultaneously, the lack of a coordinated active-passive control mechanism based on the buoy's real-time motion status makes it impossible to maximize the dominant role of passive compensation while ensuring trajectory accuracy.

[0005] Therefore, there is an urgent need for a low-power buoyancy compensation method that can achieve linearly adjustable equivalent compressibility through a gas-liquid mixing structure and combine motion state perception for intelligent coordination of active and passive buoyancy, so as to effectively extend the underwater operating life of profile buoys. Summary of the Invention

[0006] In view of the shortcomings of the related technologies, the purpose of this invention is to provide a passive buoyancy compensation method for gas-liquid mixing for profile buoys, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for passive buoyancy compensation using gas-liquid mixing for profile buoys, wherein the profile buoy is equipped with a controller and an active buoyancy system, includes the following steps: S1. Construct a gas-liquid hybrid passive buoyancy compensation system, which includes a gas chamber with an actively adjustable volume and a liquid chamber that contains compressible liquid; by adjusting the volume ratio of the gas chamber to the liquid chamber, the equivalent compressibility coefficient of the system can be linearly and continuously adjusted to dynamically match the compressibility characteristics of seawater at different depths. S2. Establish a mathematical model of the overall force of the buoy, derive the maximum compensation volume that passive buoyancy compensation can provide based on the static equilibrium condition, and determine the design parameter boundary of the gas-liquid mixture passive buoyancy compensation system. S3. Deploy the sensor module, which includes a depth sensor and a triaxial MEMS accelerometer, to collect the buoy's current depth and axial acceleration in real time. S4. Calculate the current motion parameters of the buoy, calculate the average velocity based on the depth change within the first preset time window, and combine it with the real-time axial acceleration to predict the estimated depth that the buoy will reach within the second preset time window. S5. Compare the estimated depth with the preset target depth and calculate the depth deviation; when the absolute value of the depth deviation does not exceed the preset depth deviation threshold, maintain the current state and do not perform active adjustment; when the absolute value of the depth deviation exceeds the preset depth deviation threshold, enter the active fine-tuning judgment process. In the active fine-tuning judgment process, a preset speed threshold is set. When the current speed of the buoy is greater than the preset speed threshold and the acceleration direction is the same as the speed direction, it is determined that it is in the inertial-dominated motion stage and relies entirely on the gas-liquid mixture passive buoyancy compensation system to operate, and active adjustment is prohibited. When the current speed of the buoy is not greater than the preset speed threshold and the acceleration direction is opposite to the speed direction, the controller sends a fine-tuning command to the active buoyancy system. According to the buoy's upward or downward motion direction, the active buoyancy system performs buoyancy adjustment in the opposite direction of motion trend.

[0008] In some embodiments, in step S1, the controller monitors the changes in air pressure inside the buoy in real time. First, calculate the volume of the gas chamber based on the ideal gas law under isothermal conditions. Then calculate the equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. Based on this, the volume ratio of the gas chamber to the liquid chamber is adjusted to adjust the equivalent compressibility coefficient of the gas-liquid mixing passive buoyancy compensation system. The compressibility coefficient of compressible liquids With the effective compressibility coefficient of the gas chamber The linear and continuous adjustment between them is possible; Gas cavity volume The calculation formula is: in, This represents the amount of substance of the gas inside the gas chamber. Let be the ideal gas constant. The internal thermodynamic temperature of the buoy. This refers to the initial air pressure inside the buoy's pressure-resistant hull. This represents the real-time change in air pressure inside the buoy; When | When the air pressure change is less than the preset threshold, and They are inversely proportional; System equivalent compression coefficient The calculation formula is:

[0009] in, The equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. The compressibility coefficient of a compressible liquid. For the volume of a compressible liquid, The effective compressibility coefficient of the gas chamber. Let be the volume of the gas chamber.

[0010] In some embodiments, in step S2, based on the overall force mathematical model of the buoy, according to the static equilibrium condition:

[0011] in, For buoy mass, It is the acceleration due to gravity. The density of the surface seawater, The initial volume of the buoy body. The additional buoyancy of the buoy under normal pressure. pressure Seawater density at that location pressure The main volume of the buoy at that location, , The overall pressure coefficient of the buoy body. pressure Additional buoyancy of the buoy at that location; The total change in buoyancy is:

[0012] in, pressure The volume of the passive buoyancy compensation system for gas-liquid mixing at that location. , The equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. The initial volume of the gas-liquid mixture passive buoyancy compensation system; Ignore the initial buoyancy deviation and let The maximum effective compensation volume that passive buoyancy compensation can provide is:

[0013] in, For reference volume, the initial volume of the buoy body is taken. Initial volume of passive buoyancy compensation system with gas-liquid mixture The sum of is the seawater compressibility coefficient.

[0014] In some embodiments, in step S4, the estimated depth is obtained by calculating the corresponding estimated static pressure, and the corresponding calculation formula is:

[0015]

[0016] in, For the first preset time window, This represents the change in static pressure of the buoy within the first preset time window. The axial average velocity of the buoy. For the second preset time window, This represents the current static pressure of the buoy. This represents the real-time axial acceleration of the buoy. Estimate the static pressure for the buoy at the estimated depth.

[0017] In some embodiments, in step S5, when the fine-tuning command is executed, the adjustment range of the fine-tuning command executed by the active buoyancy system is limited, so that the gas-liquid mixture passive buoyancy compensation system undertakes the basic buoyancy adjustment function as the seawater pressure changes during the normal movement of the buoy, and the active buoyancy system only undertakes the prediction deviation compensation function caused by environmental disturbances and modeling errors.

[0018] In some embodiments, when the fine-tuning command is executed, the change in buoyancy adjustment volume of the active buoyancy system satisfies:

[0019] in, To adjust the volume change in real time for the active buoyancy system This represents the total volume change required for buoyancy adjustment under the current motion state of the buoy.

[0020] In some embodiments, in step S3, a triaxial MEMS accelerometer is mounted near the buoy's center of gravity and its sensitive axis is aligned with the buoy's central axis.

[0021] In some embodiments, in step S1, the volume injected into the liquid chamber is Compressible liquids, the compressibility coefficient of compressible liquids Greater than the compressibility coefficient of seawater Furthermore, the density of compressible liquids is less than that of seawater.

[0022] In some embodiments, in step S5, the preset depth deviation threshold is the deviation threshold corresponding to a static pressure of 50 dbar.

[0023] In some embodiments, the gas-liquid mixture passive buoyancy compensation method for profile buoys also includes an active-passive cooperative control logic priority mechanism. When the controller detects an emergency ascent command, it forcibly shuts down the adjustment function of the gas-liquid mixture passive buoyancy compensation system and switches to a fully active rapid response mode, driving the buoy to rise rapidly through the active buoyancy system.

[0024] Compared with the prior art, the beneficial effects of the present invention are: 1. The gas-liquid mixing passive buoyancy compensation method for profile buoys provided by the present invention can realize the linear and continuous adjustment of the equivalent compression coefficient of the system by constructing a gas-liquid mixing passive buoyancy compensation system, so that the buoy compression characteristics can be dynamically matched with the compression characteristics of seawater at different depths. This solves the limitations of nonlinear adjustment and fixed parameters of related passive compensation devices, and effectively reduces buoyancy drift caused by compression mismatch.

[0025] 2. The gas-liquid mixture passive buoyancy compensation method for profile buoys provided by the present invention, through active and passive coordinated control based on motion state perception, prohibits active adjustment when the buoy is in the inertial-dominated motion stage, giving full play to the basic buoyancy adjustment function of the gas-liquid mixture passive buoyancy compensation system, and significantly reducing the number of start-stop cycles and running time of the active buoyancy system.

[0026] 3. The gas-liquid mixing passive buoyancy compensation method for profiling buoys provided by the present invention predicts the depth by fusing depth and axial acceleration, and initiates active fine-tuning only when necessary based on deviation threshold and velocity criteria, and limits the adjustment range of the active buoyancy system so that it only undertakes the function of deviation compensation, which significantly reduces the power consumption of the active buoyancy system and effectively extends the underwater operation life of the profiling buoy. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a flowchart illustrating the method logic of one embodiment of the passive buoyancy compensation method for gas-liquid mixing for profile buoys according to the present invention. Detailed Implementation

[0028] The technical solutions in 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 a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and 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. Therefore, they should not be construed as limitations on this invention.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] See appendix Figure 1 This paper presents an illustrative embodiment of the gas-liquid mixing passive buoyancy compensation method for profiling buoys proposed in this invention. It can effectively solve the problems of excessive power consumption and short service life caused by the use of active buoyancy adjustment devices in mainstream profiling buoys, as well as the nonlinearity of related passive compensation technologies, difficulty in dynamically matching seawater compression characteristics, and lack of coordinated control strategies between active and passive systems.

[0032] The gas-liquid hybrid passive buoyancy compensation method in this embodiment relies on an integrated buoy control system, which includes a gas-liquid hybrid passive buoyancy compensation system, an active buoyancy system, a sensor module, and a controller. The gas-liquid hybrid passive buoyancy compensation system is the core of buoy buoyancy adjustment, while the active buoyancy system serves as an auxiliary fine-tuning tool. Both systems work collaboratively under the unified scheduling of the controller. The sensor module collects depth and acceleration information in real time, providing data support for motion state prediction and control decisions.

[0033] The passive buoyancy compensation method for profile buoys using gas-liquid mixing includes the following steps: S1. Construct a gas-liquid hybrid passive buoyancy compensation system. The gas-liquid hybrid passive buoyancy compensation system includes a gas chamber with an actively adjustable volume and a liquid chamber that contains compressible liquid. The volumes of both the gas chamber and the liquid chamber are variable. By adjusting the volume ratio of the gas chamber to the liquid chamber, the equivalent compressibility coefficient of the system can be linearly and continuously adjusted to dynamically match the compressibility characteristics of seawater at different depths. In this embodiment, the gas chamber is isolated from the buoy's pressure-resistant shell by a flexible diaphragm to prevent direct gas contact with electronic components. The flexible diaphragm is made of polyimide composite material with a thickness of 0.2 mm, possessing excellent resistance to pressure fatigue and gas barrier properties, effectively preventing high-pressure nitrogen or air from directly contacting internal electronic components and ensuring the electrical safety of the system. The gas chamber is connected to the buoy's internal gas path via a miniature air pump and a low-power air valve. The air pump adopts a piston structure driven by a miniature brushless DC motor, with a rated power of less than 1.5W (e.g., 1.2W), a maximum output pressure of 8MPa, and a start / stop response time of less than 50ms. The air valve is a low-power magnetically latched two-position three-way valve, requiring no holding current under normal conditions, and its switching energy consumption is less than 0.1J per action (e.g., 0.075J per action), significantly reducing standby power consumption. In addition, it includes a pressure sensor installed on the outlet pipe of the gas chamber, with a measurement range of 0~60 MPa, a resolution better than 0.01 MPa (reaching 0.008 MPa), and a sampling frequency of 10 Hz, used for real-time monitoring of changes in internal air pressure of the buoy. Ensure that Precise capture.

[0034] S2. Establish a mathematical model of the overall force of the buoy, derive the maximum compensation volume that passive buoyancy compensation can provide based on the static equilibrium condition, and determine the design parameter boundary of the gas-liquid mixture passive buoyancy compensation system. S3. Deploy the sensor module, which includes a high-precision depth sensor and a triaxial MEMS accelerometer, to collect the buoy's current depth value and axial acceleration in real time. S4. Calculate the current motion parameters of the buoy, calculate the average velocity based on the depth change within the first preset time window, and combine it with the real-time axial acceleration to predict the estimated depth that the buoy will reach within the second preset time window. S5, Estimated Depth With respect to the preset target depth The system compares and calculates the depth deviation. When the absolute value of the depth deviation does not exceed the preset depth deviation threshold, the current state is maintained and no active adjustment is performed. When the absolute value of the depth deviation exceeds the preset depth deviation threshold, the active fine-tuning judgment process is initiated. In the active fine-tuning judgment process, a preset speed threshold is set. When the current speed of the buoy is greater than the preset speed threshold and the acceleration direction is the same as the speed direction, it is determined that it is in the inertial-dominated motion stage and relies entirely on the gas-liquid mixture passive buoyancy compensation system. Active adjustment is prohibited and the active buoyancy system is prohibited from being started. When the current speed of the buoy is not greater than the preset speed threshold and the acceleration direction is opposite to the speed direction, the controller sends a fine-tuning command to the active buoyancy system. According to the buoy's upward or downward motion direction, the active buoyancy system performs buoyancy adjustment in the opposite direction of motion trend.

[0035] Specifically, if the buoy is in the process of diving ( If the buoyancy is reduced, the solenoid valve will open, allowing the hydraulic oil inside the outer bladder to flow back to the inner tank, reducing the displaced volume and thus reducing the positive buoyancy; if it is in the process of rising ( If the hydraulic pump is activated, it pumps hydraulic oil from the inner tank into the outer bladder, increasing the displaced volume and thus increasing positive buoyancy. The fine-tuning command is executed using pulse width modulation (PWM) to control the opening duration of the solenoid valve. The volume of oil discharged or returned for a single action is precisely controlled within 0.5~2mL. The adjustment step can be finely adjusted in increments of 0.1mL to ensure continuous and smooth buoyancy changes, avoiding step-like impacts that could cause buoy attitude oscillations and affect motion stability.

[0036] In step S1, the controller monitors the changes in internal air pressure of the buoy in real time using a pressure sensor. First, calculate the volume of the gas chamber based on the ideal gas law under isothermal conditions. Then calculate the equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. Based on this, the volume ratio of the gas chamber to the liquid chamber is adjusted to adjust the equivalent compressibility coefficient of the gas-liquid mixing passive buoyancy compensation system. The compressibility coefficient of compressible liquids With the effective compressibility coefficient of the gas chamber The linear and continuous adjustment between them is possible; Gas cavity volume The calculation formula is: in, This represents the amount of substance of the gas inside the gas chamber. The universal ideal gas constant is... This refers to the thermodynamic temperature (absolute temperature) inside the buoy. The initial air pressure (reference) inside the buoy's pressure-resistant shell. This represents the real-time change in air pressure inside the buoy; when changes in external seawater pressure cause... When smaller (usually) (|<0.5MPa), approximately considered and They are inversely proportional; When | When the air pressure change is less than the preset threshold, and They are inversely proportional; By adjusting the volume of the gas chamber With the volume of the liquid cavity The ratio of the system's overall equivalent compression coefficient Available and Achieving linear and continuous adjustment between them, the system's equivalent compression coefficient The calculation formula is:

[0037] in, The equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. The compressibility coefficient of a compressible liquid. For the volume of a compressible liquid, It is the effective compressibility coefficient of the gas chamber (which can be regarded as a constant in the small deformation range, and its value is determined by the initial inflation pressure and the geometry of the chamber). Let be the volume of the gas chamber.

[0038] In this embodiment, in step S1, before the actual deployment of the buoy, different data are obtained through laboratory calibration. : proportional Response curves are used to establish a lookup table-based control mapping relationship. During initial deployment, and The initial volume ratio is set to ,correspond Approximately 4.45 × 10 - ¹ 0 Pa - ¹, close to the typical seawater compressibility coefficient. The controller queries the seawater compressibility coefficient based on the real-time depth. (P) Automatically adjusts the operation of the air pump and air valve, selects the optimal ratio, and changes... This ensures that the relative error between the overall equivalent compressibility coefficient of the buoy and the compressibility coefficient of the local seawater is less than [a certain value]. ,Right now:

[0039] in, To correspond to seawater hydrostatic pressure Real-time equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system at (current depth); To correspond to seawater hydrostatic pressure The real-time compressibility coefficient of the seawater in the current area at (current depth). This accuracy ensures that buoyancy drift caused by compression mismatch is controlled within an acceptable range during free descent or ascent of the buoy, providing a physical basis for significantly reducing the load on the active system.

[0040] In step S2, a mathematical model of the overall forces acting on the buoy is established. Based on this model, and according to the static equilibrium condition:

[0041] in, For buoy mass, It is the acceleration due to gravity. The density of the surface seawater, This refers to the initial volume of the buoy body (excluding the gas-liquid mixture passive buoyancy compensation system) under normal pressure. The additional buoyancy of the buoy under normal pressure. pressure Seawater density at that location pressure The main volume of the buoy at that location, , The overall pressure coefficient of the buoy body (determined by the material and structure of the buoy body). pressure The additional buoyancy of the buoy at that location (mainly from the active system); Corresponding seawater static pressure The seawater depth at that location is The two satisfy an engineering approximation relationship. .

[0042] The total change in buoyancy is:

[0043] in, pressure The volume of the passive buoyancy compensation system for gas-liquid mixing at that location. , The equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. The initial volume of the gas-liquid mixture passive buoyancy compensation system under normal pressure; Ignore the initial buoyancy deviation and let The maximum effective compensation volume that passive buoyancy compensation can provide is:

[0044] in, For reference volume, the initial volume of the buoy body is taken. Initial volume of passive buoyancy compensation system with gas-liquid mixture The sum of The seawater compressibility coefficient is used to determine the boundary parameters of the system design.

[0045] Only when lie in and In between, A positive value indicates that the passive system can effectively compensate for the compression mismatch of the main body. This must be ensured during the design phase. (The buoy body is more difficult to compress than seawater), and by adjusting... Make it slightly larger This allows them to gain positive compensation capabilities. For example, if =4.0×10 - ¹ 0 Pa - ¹, =4.4×10 - ¹ 0 Pa - ¹, then It should be adjusted to 4.45×10 - ¹ 0 Pa - ¹Approximately, at this time The system has the ability to compensate for buoyancy upwards, making it suitable for maintaining buoyancy during descent.

[0046] In step S4, the current motion state of the buoy is calculated, and the controller calculates the average velocity based on the depth sequence within the first preset time window. The estimated depth is obtained through the corresponding estimated static pressure calculation, and the corresponding calculation formula is:

[0047]

[0048] in, For the first preset time window, The change in static pressure of the buoy within the first preset time window (unit: dbar, 1 dbar ≈ 1 meter water depth). The axial average velocity of the buoy. For the second preset time window, This represents the current static pressure of the buoy. This represents the real-time axial acceleration of the buoy. For acceleration to tend to stabilize (i.e.) When kept constant, the buoy in the future The estimated static pressure of the buoy at the corresponding estimated depth to be reached within the time window.

[0049] In this embodiment, Set the time window to 30 seconds. The time window is set to 60 seconds. This time window balances real-time response and data stability, avoiding misjudgments caused by instantaneous fluctuations. To improve data stability, the speed... and acceleration All data are processed using a moving average algorithm with a window length of 10 sampling periods to further smooth dynamic noise and generate smooth velocity and acceleration estimates for subsequent control logic judgment.

[0050] In step S5, a preset speed threshold is set. Set as This value is determined from the measured cruising speed distribution of a large number of profile buoys. When the buoy speed is higher than this threshold, it indicates that it has entered a stable motion phase. At this time, passive compensation is sufficient to maintain trajectory accuracy, and no active intervention is required. That is, when |v|>0.08m / s and the direction of acceleration a is the same as the direction of velocity v (i.e., a·v>0), the buoy is in a stable acceleration or deceleration phase dominated by inertia. At this time, the passive buoyancy compensation mechanism can effectively track the changes in seawater compression characteristics. The trajectory prediction deviation mainly stems from environmental disturbances rather than system mismatch. Therefore, it is completely forbidden to start the active buoyancy system to avoid unnecessary energy consumption. When |v|≤0.08m / s and the direction of a is opposite to the direction of v (i.e., a·v<0), it indicates that the buoy motion tends to stagnate or is about to reverse. At this time, passive compensation may not be sufficient to overcome the accumulated deviation, and the controller issues a fine-tuning command to the active buoyancy system.

[0051] In step S5, when the fine-tuning command is executed, the adjustment range of the active buoyancy system is limited. This allows the gas-liquid hybrid passive buoyancy compensation system to handle the basic buoyancy adjustment function as the buoy moves normally with changes in seawater pressure, while the active buoyancy system only compensates for prediction deviations caused by environmental disturbances and modeling errors. The controller estimates the total buoyancy adjustment requirement in real time. (based on (Calculated based on the current compressibility characteristics of the buoy), and ensuring the volume change induced by the active system intervention. No more than 20% of, that is: When the fine-tuning command is executed, the change in buoyancy adjustment volume of the active buoyancy system satisfies:

[0052] in, To adjust the volume change in real time for the active buoyancy system This is the total volume change required for buoyancy adjustment under the current motion state of the buoy, ensuring the realization of a coordinated control mode of "passive as the main component and active as the auxiliary component". This constraint forces the system to maintain the coordinated mode of "passive as the main component and active as the auxiliary component", and the active system is only used to compensate for short-term prediction deviations caused by changes in ocean internal waves, thermocline abrupt changes or modeling residuals, rather than undertaking the main buoyancy adjustment task.

[0053] In step S3, the depth sensor employs a quartz resonant pressure sensor with a measurement range of 0~60MPa, an accuracy better than ±0.05% of full scale, and a temperature drift of less than 0.01% / ℃. The range of the triaxial MEMS accelerometer is... With a noise density below 150 μg / √Hz (e.g., 120 μg / √Hz), the sampling frequency is set to 100 Hz. The raw acceleration data is processed by a digital low-pass filter to extract the axial component. The filter uses a second-order Butterworth structure with a cutoff frequency of 10 Hz, effectively eliminating high-frequency vibration interference (>10 Hz) caused by ocean currents, eddies, and internal mechanical vibrations, while retaining low-frequency signals reflecting the overall motion trend of the buoy, thus improving attitude recognition accuracy. The filtered axial acceleration 'a' and the current depth value 'Pcur' output by the depth sensor are synchronously transmitted to the controller, with a timestamp alignment accuracy better than 1 ms. A three-axis MEMS accelerometer is installed near the buoy's center of gravity, with its sensitive axis aligned with the buoy's central axis, to accurately acquire axial acceleration data and collect depth values ​​in real time. and acceleration It is used to analyze the motion state of buoys.

[0054] In step S1, the volume injected into the liquid chamber is Compressible liquids, the compressibility coefficient of compressible liquids Greater than the compressibility coefficient of seawater Furthermore, the density of compressible liquids is less than that of seawater. Under changes in external pressure, by adjusting... and The volume ratio achieves the system's equivalent compression coefficient. The linear continuous adjustment makes exist and The range is adjustable to match the compression behavior of seawater at different depths.

[0055] The compressible liquid selected is dimethyl silicone oil, which has a compressibility coefficient at a standard temperature of 25°C. 4.5×10 - ¹ 0 Pa - ¹, significantly higher than the typical seawater compressibility coefficient. (4.4×10 - ¹ 0 Pa - ¹), and its density is 776 kg / m³, which is lower than the average density of seawater 1025 kg / m³. Therefore, it can provide high compressibility while having a slight net buoyancy gain and contributing positive buoyancy. The liquid cavity is a sealed structure made of nitrile rubber and is specially vulcanized to effectively prevent the seepage and leakage caused by long-term immersion of dimethyl silicone oil in high water depth environments.

[0056] In step S5, the preset depth deviation threshold is the corresponding The deviation threshold for static pressure. Depth deviation is... The preset depth deviation threshold is Then when When the buoy's trajectory is determined to be within the normal fluctuation range, the current gas-liquid mixing system state is maintained, and no active adjustment is performed; when This indicates a significant risk of trajectory deviation, triggering the active fine-tuning judgment process. Correspondingly... The deviation threshold of static pressure corresponds to a change of approximately 50 meters in actual water depth. This value is set based on the statistical results of historical temperature and salinity profile data of global Argo buoys. It can cover the normal fluctuation range of most ocean internal wave and turbulence disturbance amplitudes, while effectively identifying significant trajectory deviations that require intervention.

[0057] The gas-liquid hybrid passive buoyancy compensation method for profile buoys also includes a priority mechanism for active-passive coordinated control logic. When the controller detects an emergency ascent command, it forcibly shuts down the adjustment function of the gas-liquid hybrid passive buoyancy compensation system (forcibly shuts down the air pump and air valve, and locks the current state of the gas-liquid hybrid passive buoyancy compensation system), switches to a fully active rapid response mode, and the hydraulic pump operates at maximum power to drive the buoy to rise rapidly through the active buoyancy system, ensuring safe recovery capability.

[0058] In the above illustrative embodiments, the profile buoy uses a gas-liquid mixing passive buoyancy compensation method, which couples a variable gas cavity with a highly compressible, low-density liquid cavity to achieve an overall equivalent compressibility coefficient for the buoy. This method possesses the advantages of linearity, continuity, and adjustability, overcoming the technical bottleneck of unadjustable and nonlinear compression characteristics caused by fixed materials or structures in related passive compensation devices. It enables the buoy's compression behavior to dynamically match the actual compression characteristics of seawater at different depths. Compared to related pure liquid or pure gas passive compensation schemes, this method effectively expands the overall compressibility adjustment range of the buoy, significantly improving buoyancy tracking accuracy and reducing depth drift caused by compression mismatch. Furthermore, it constructs a motion-state-aware active-passive coordinated control strategy. By fusing depth and acceleration data, it predicts the buoy's future depth in real time and intelligently determines whether to activate active fine-tuning based on velocity magnitude and acceleration direction. Limited active intervention is allowed only in the low-speed, non-inertial phase with reverse acceleration, fundamentally changing the traditional profiling buoy's reliance on an active system for regulation. Compared to traditional "timed and fixed-point" or "open-loop regulation" strategies, it reduces the number of ineffective active adjustments, effectively avoiding mechanical wear and energy waste caused by frequent start-stop cycles. An energy optimization architecture of "passive as the main component and active as the auxiliary component" was established. By strictly limiting the active system intervention threshold (deviation > 50 dbar), speed conditions (v ≤ 0.08 m / s), and adjustment range (≤ 20% of total demand), the power consumption of the active buoyancy system was reduced from 60%–80% in the traditional scheme to below 30%, effectively extending the buoy's endurance. At the same time, due to the significant reduction in the frequency of active system use, the overall failure rate was also significantly reduced, and the adaptability was enhanced.

[0059] 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 preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for passive buoyancy compensation using gas-liquid mixing in a profiling buoy, wherein the profiling buoy is equipped with a controller and an active buoyancy system, characterized in that, Includes the following steps: S1. Construct a gas-liquid hybrid passive buoyancy compensation system, which includes a gas chamber with an actively adjustable volume and a liquid chamber containing a compressible liquid; by adjusting the volume ratio of the gas chamber to the liquid chamber, the equivalent compressibility coefficient of the system can be linearly and continuously adjusted to dynamically match the compressibility characteristics of seawater at different depths. S2. Establish a mathematical model of the overall force of the buoy, derive the maximum compensation volume that passive buoyancy compensation can provide based on the static equilibrium condition, and determine the design parameter boundary of the gas-liquid mixture passive buoyancy compensation system. S3. Deploy the sensor module, which includes a depth sensor and a triaxial MEMS accelerometer, for real-time acquisition of the buoy's current depth value and axial acceleration. S4. Calculate the current motion parameters of the buoy, calculate the average velocity based on the depth change within the first preset time window, and combine it with the real-time axial acceleration to predict the estimated depth that the buoy will reach within the second preset time window. S5. Compare the estimated depth with the preset target depth and calculate the depth deviation; when the absolute value of the depth deviation does not exceed the preset depth deviation threshold, maintain the current state and do not perform active adjustment; when the absolute value of the depth deviation exceeds the preset depth deviation threshold, enter the active fine-tuning judgment process. In the active fine-tuning judgment process, a preset speed threshold is set. When the current speed of the buoy is greater than the preset speed threshold and the acceleration direction is consistent with the speed direction, it is determined that it is in the inertial-dominated motion stage and relies entirely on the gas-liquid mixed passive buoyancy compensation system to operate, and active adjustment is prohibited. When the current speed of the buoy is not greater than the preset speed threshold and the direction of acceleration is opposite to the direction of speed, the controller sends a fine-tuning command to the active buoyancy system. Based on the direction of the buoy's upward or downward movement, the active buoyancy system performs buoyancy adjustment in the opposite direction of the movement trend.

2. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, In step S1, the controller monitors the changes in air pressure inside the buoy in real time. First, calculate the volume of the gas chamber based on the ideal gas law under isothermal conditions. Then calculate the equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. Based on this, the volume ratio of the gas chamber to the liquid chamber is adjusted to adjust the equivalent compressibility coefficient of the gas-liquid mixing passive buoyancy compensation system. The compressibility coefficient of compressible liquids With the effective compressibility coefficient of the gas chamber The linear and continuous adjustment between them is possible; Gas cavity volume The calculation formula is: in, This represents the amount of substance of the gas inside the gas chamber. Let be the ideal gas constant. The internal thermodynamic temperature of the buoy. This refers to the initial air pressure inside the buoy's pressure-resistant hull. This represents the real-time change in air pressure inside the buoy; When | When the air pressure change is less than the preset threshold, and They are inversely proportional; System equivalent compression coefficient The calculation formula is: in, The equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. The compressibility coefficient of a compressible liquid. For the volume of a compressible liquid, The effective compressibility coefficient of the gas chamber. Let be the volume of the gas chamber.

3. The passive buoyancy compensation method for gas-liquid mixing for profile buoys according to claim 2, characterized in that, In step S2, based on the overall force mathematical model of the buoy, and according to the static equilibrium condition: in, For buoy mass, It is the acceleration due to gravity. The density of the surface seawater, The initial volume of the buoy body. The additional buoyancy of the buoy under normal pressure. pressure Seawater density at that location pressure The main volume of the buoy at that location, , The overall pressure coefficient of the buoy body. pressure Additional buoyancy of the buoy at that location; The total change in buoyancy is: in, pressure The volume of the passive buoyancy compensation system for gas-liquid mixing at that location. , The equivalent compressibility coefficient of the gas-liquid mixture passive buoyancy compensation system. The initial volume of the gas-liquid mixture passive buoyancy compensation system; Ignore the initial buoyancy deviation and let The maximum effective compensation volume that passive buoyancy compensation can provide is: in, For reference volume, the initial volume of the buoy body is taken. Initial volume of the passive buoyancy compensation system with gas-liquid mixture the sum of is the seawater compressibility coefficient.

4. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, In step S4, the estimated depth is obtained by calculating the corresponding estimated static pressure, and the corresponding calculation formula is: in, For the first preset time window, This represents the change in static pressure of the buoy within the first preset time window. The axial average velocity of the buoy. For the second preset time window, This represents the current static pressure of the buoy. This represents the real-time axial acceleration of the buoy. Estimate the static pressure for the buoy corresponding to the estimated depth.

5. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, In step S5, when the fine-tuning command is executed, the adjustment range of the active buoyancy system is limited, so that the gas-liquid mixture passive buoyancy compensation system undertakes the basic buoyancy adjustment function as the seawater pressure changes during the normal movement of the buoy, while the active buoyancy system only undertakes the prediction deviation compensation function caused by environmental disturbances and modeling errors.

6. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 5, characterized in that, When the fine-tuning command is executed, the change in buoyancy adjustment volume of the active buoyancy system satisfies: in, To adjust the volume change in real time for the active buoyancy system This represents the total volume change required for buoyancy adjustment under the current motion state of the buoy.

7. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, In step S3, the triaxial MEMS accelerometer is installed near the center of gravity of the buoy and its sensitive axis is aligned with the central axis of the buoy.

8. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, In step S1, the volume injected into the liquid cavity is A compressible liquid, wherein the compressibility coefficient of the compressible liquid is... Greater than the compressibility coefficient of seawater Furthermore, the density of the compressible liquid is less than that of seawater.

9. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, In step S5, the preset depth deviation threshold is the deviation threshold corresponding to a static pressure of 50 dbar.

10. The method for passive buoyancy compensation using gas-liquid mixing for profile buoys according to claim 1, characterized in that, It also includes a priority mechanism for active and passive coordinated control logic. When the controller detects an emergency buoyancy command, it forcibly shuts down the adjustment function of the gas-liquid mixed passive buoyancy compensation system and switches to a fully active rapid response mode, driving the buoy to rise rapidly through the active buoyancy system.

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