Autonomous leveling system and method for underwater base platform

Abstract

The invention provides an autonomous leveling system and method for an underwater base platform. The autonomous leveling system for the underwater base platform comprises a hydraulic control module, hydraulic telescopic supporting legs, an inertial navigation module and an autonomous leveling master control module. The hydraulic control module comprises a hydraulic sealed cabin and an external pressure compensation device, the hydraulic telescopic supporting legs are provided with displacement and pressure sensors, the inertial navigation module feeds back platform attitude data, and the autonomous leveling master control module achieves data interaction and instruction issuing through an industrial personal computer and a switch. According to the method, a platform coordinate system is established, front and back coordinate changes of the base are combined, the expansion amount of the supporting legs is calculated through a rotation translation matrix, and the state estimation precision is improved through adaptive robust control until the platform meets the angle, pressure and stability conditions. According to the invention, autonomous leveling of the unmanned underwater vehicle recovery platform under different working conditions can be realized, and stable docking of the unmanned underwater vehicle is ensured.

Description

Technical Field

[0001] This invention relates to the field of marine engineering equipment and automatic control technology, specifically to an autonomous leveling system and method for an underwater platform. More particularly, it relates to an underwater platform leveling system and method based on multimodal adaptive control. Background Technology

[0002] Underwater landing platforms are crucial foundational equipment for marine observation, resource exploration, and equipment deployment. They primarily ensure the energy supply for unmanned underwater vehicles (UUVs) and other equipment operating in open ocean areas. Therefore, the levelness of the platform's recovery mechanism directly affects the success rate of UUV deployment and recovery, thus impacting functions such as energy replenishment and data transmission. Due to the varying softness of the seabed and the impact of ocean currents, the platform often tilts after landing, necessitating precise leveling.

[0003] Existing platform leveling technologies (such as patent document CN106089862A) mostly employ a "highest point chasing" strategy combined with hydraulic drive. However, these methods are primarily designed for terrestrial environments and do not consider issues such as sealing, pressure resistance, and seawater corrosion in underwater hydraulic systems. Furthermore, their control algorithms have limited anti-interference capabilities. Moreover, current leveling methods are mainly designed for terrestrial environments and have the following shortcomings for complex underwater terrain: they do not consider the unique environmental issues such as underwater current disturbances and pressure; they do not consider the "soft leg" problem caused by uneven seabed geology; they lack precise control of multi-leg coordinated movement; and they are not robust enough to external disturbances. Therefore, there is an urgent need for an autonomous leveling system and method that can adapt to complex underwater environments, has strong anti-interference capabilities, and high reliability.

[0004] In his paper "Co-simulation Study on Leveling Methods for Heavy-Duty Platforms" (Hydraulics, Pneumatics & Seals, 2015, 35(04):39-42), Zhou Bo proposed a leveling method based on fuzzy adaptive PID control. By combining fuzzy control with PID control, intelligent control of the leveling process of heavy-duty platforms was achieved. This method adopts a "chasing" leveling strategy where the highest point remains stationary, and the control effect was verified through co-simulation using AMESim and Simulink. However, this method is based on co-simulation and does not address the specific challenges of land and underwater physical systems. Furthermore, the control object described in this invention is a 5-ton underwater hull-mounted platform, making the control process complex.

[0005] Patent document CN106437698A discloses an underwater platform for exploration, sampling, or in-situ testing, and its usage method. The control module of this underwater platform monitors at regular time intervals, intelligently and automatically leveling it continuously. The control module reads the tilt angle values ​​(X, Y) through a data acquisition module and employs a leveling algorithm that keeps the highest point stationary while adjusting the lowest point in one direction. Leveling is performed in the X direction at the lowest point, followed by leveling in the Y direction. If there are any false legs after leveling, leveling continues; otherwise, leveling ends. The drawback of patent document CN106437698A is that it does not use adaptive robust control technology to improve the accuracy of state estimation, making it difficult to cope with special environmental problems such as underwater flow disturbances and pressure, and thus failing to achieve the ideal leveling effect. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide an autonomous leveling system and method for underwater bottom platforms.

[0007] According to the present invention, an autonomous leveling method for an underwater platform includes a main platform and multiple hydraulically telescopic outriggers disposed on the side of the main platform. The autonomous leveling method includes the following steps: S1: After system initialization, start the power source to make the hydraulic drive module reach the preset working pressure; S2: Extend the hydraulic telescopic outriggers to contact the seabed and provide initial support for the mother platform; S3: The platform attitude data is collected in real time through the inertial navigation module to calculate the offset of the mother platform and the expected extension of each hydraulic telescopic outrigger. S4: Based on the desired extension amount, output control signal to adjust the flow and direction of hydraulic oil in the hydraulic drive module, drive each hydraulic telescopic outrigger to adjust the platform posture; S5: Determine if the platform attitude error is within the allowable range. If so, complete the leveling process; otherwise, proceed to the branch adjustment process until the attitude error meets the requirements.

[0008] Preferably, the specific process for calculating the expected extension / retraction amount of each hydraulic telescopic outrigger in step S3 includes: S3.1: Based on the right-hand rule, establish a coordinate system with the platform's center of gravity as the origin, and set the initial coordinates in front of the hydraulic telescopic outrigger base. And the coordinates behind the base of the hydraulic telescopic outrigger. The roll angle α, pitch angle β, bow angle γ, and vertical heave displacement Δz of the underwater platform around the coordinate axes were measured using the inertial navigation module, and a matrix was constructed:

[0009]

[0010]

[0011] in, M Rotx To make the initial coordinates The rotation matrix for rotating about the x-axis by an angle α; M Roty To make the initial coordinates The rotation matrix for rotating about the y-axis by an angle β; M T Initial coordinates The translation matrix for a distance Δz along the z-axis; S3.2: By multiplying the matrix obtained in S3.1 by the coordinate changes of the hydraulic telescopic outriggers before and after the base, the expected telescopic extension of each hydraulic telescopic outrigger is obtained.

[0012] Preferably, S3.2 includes: Construct M res =M Rotx M Roty M T M res To make the initial coordinates The rotation and translation matrix is ​​the matrix for rotating about the x-axis by an angle α, rotating about the y-axis by an angle β, and translating along the z-axis by a distance Δz. The rotation and translation matrix M res Left multiplication From the initial coordinate values, the coordinates behind the base of the hydraulic telescopic outrigger can be obtained. :

[0013] Extension range of each hydraulic telescopic outrigger The changes (i=1,2,3,4) can be obtained through the following expression:

[0014] The range of motion for the main platform and each hydraulic telescopic outrigger is 0m≤ ≤0.7m.

[0015] Preferably, the control signal in step S4 is an adaptive robust control signal based on Lyapunov stability theory, and the control law u of the control signal is:

[0016] in, For the proportional gain matrix, It is the differential gain matrix; , For the desired tilt angle, This is the actual tilt angle; The derivative of e represents the angular velocity; For adaptive parameter estimation vectors; The vector represents the regression function, where x represents state variables such as inclination angle, angular velocity, water depth, and ocean current. For robustness, it is used to suppress unmodeled dynamics and external disturbances; The adaptive law is:

[0017] in It is a positive definite adaptive gain matrix. yes The derivative of .

[0018] Preferably, adjusting the flow rate and direction of the hydraulic oil in step S4 specifically involves: controlling the opening of the proportional valve group by outputting a signal from the analog output module in the hydraulic drive module to adjust the hydraulic oil flow rate; The hydraulic control module in the hydraulic drive module outputs a signal to control the directional valve group, adjusts the direction of hydraulic oil, and thus controls the extension speed and direction of the hydraulic telescopic outriggers.

[0019] Preferably, the branch adjustment process in step S5 is as follows: check whether the hydraulic telescopic outrigger has reached its maximum extension. If so, perform single-cylinder precise fine adjustment for the hydraulic telescopic outrigger corresponding to the posture error until the posture error meets the requirements. Otherwise, return to step S4 to continue driving each hydraulic telescopic outrigger to coordinate and adjust the posture.

[0020] Preferably, the criterion for determining the allowable range of attitude error in step S5 is that the following conditions are met simultaneously: The platform's roll angle α and pitch angle β are both less than the set values; All hydraulic telescopic outrigger pressure values ​​are greater than the safety threshold and the difference between them is less than 10%; Within 3 consecutive seconds, the change in tilt angle of the mother platform was less than 0.02°.

[0021] Preferably, the system initialization in step S1 includes: completing the initialization of core electronic modules such as the autonomous leveling main control module and the inertial navigation module, and establishing data connections between the modules.

[0022] Preferably, in step S3, when calculating the offset of the mother platform, the displacement feedback data of the displacement detection component on the hydraulic telescopic outrigger is also combined, and the attitude data and displacement feedback data are fused by the Kalman filter algorithm to improve the accuracy of offset calculation. The displacement detection component is built into the hydraulic telescopic outrigger.

[0023] An autonomous leveling system for an underwater platform according to the present invention is used to implement the aforementioned autonomous leveling method for an underwater platform, comprising: An inertial navigation module is installed at the center of gravity of the underwater platform to collect attitude data of the underwater platform in real time. The hydraulic drive module includes a hydraulic control module and multiple sets of hydraulic telescopic outriggers. The hydraulic control module is used to adjust the flow and direction of hydraulic oil. The hydraulic telescopic outriggers are equipped with displacement detection components and pressure detection components to support the underwater base platform and provide feedback on the extension and pressure data of the hydraulic telescopic outriggers. The hydraulic control module also includes an external pressure compensation device, which includes an external oil bladder filled with hydraulic oil. The external oil bladder is connected to the hydraulic control module and is used to supplement the main oil circuit pressure of the hydraulic control module under the pressure of the underwater environment. The autonomous leveling main control module communicates with the inertial navigation module and the hydraulic drive module. It is used to perform system initialization, receive attitude data collected by the inertial navigation module, calculate the expected extension and retraction of each hydraulic telescopic outrigger, and output control signals to the hydraulic drive module to control the extension and retraction length of the hydraulic telescopic outrigger.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention obtains the desired control quantities of each hydraulic outrigger through inverse kinematics. By designing an adaptive control law and target data filtering algorithm, it can adaptively suppress underwater environmental interference, adapt to uneven seabed geology, and achieve excellent platform leveling accuracy and speed.

[0025] 2. The autonomous leveling system and method described in this invention are not only applicable to the recovery and deployment platform of unmanned underwater vehicles, but also to the attitude leveling of other bottom-mounted underwater observation platforms. It can meet the platform stability requirements when the operating platform is carrying different loads, and can also be applied to the platform stability leveling under unknown seabed conditions, including but not limited to the autonomous leveling of land platforms. Attached Figure Description

[0026] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram illustrating the structure of the autonomous leveling system for the underwater platform, which is the main feature of this invention. Figure 2 This is a schematic diagram illustrating the structure of the hydraulic control module, which is the main feature of this invention. Figure 3 This is a schematic diagram illustrating the principle of hydraulic circuitry, which is the main feature of this invention. Figure 4This is a top view schematic diagram illustrating the attitude coordinate system of the underwater platform. Figure 5 This is a schematic diagram illustrating the logic of the autonomous leveling, adaptive, and robust control of the underwater platform, which is the main feature of this invention. Figure 6 This is a schematic diagram illustrating the leveling process of the underwater platform, which is the main feature of this invention. Figure 7 This is a schematic diagram illustrating the attitude leveling result of the underwater platform after it has been seated.

[0027] As shown in the figure: Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0029] This embodiment provides an autonomous leveling system and method for an underwater landing platform. Addressing the challenges of varying seabed geology and the tendency for the landing platform to tilt, it enables autonomous leveling of the unmanned underwater vehicle (UUV) recovery platform under different operating conditions, ensuring stable docking and improving the success rate. The underwater landing platform includes a main platform and multiple hydraulically telescopic outriggers 2 mounted on its sides. The core of the autonomous leveling system is a hydraulic drive module, which includes a hydraulic control module 1 and multiple sets of hydraulically telescopic outriggers 2. The following detailed explanation uses the deployment of an underwater landing platform for UUV recovery as an example. This invention utilizes the landing platform and a platform leveling algorithm to achieve autonomous and precise leveling of the platform after it has landed. Figure 1 As shown, the system mainly includes a hydraulic control module 1, a hydraulic telescopic outrigger 2, an inertial navigation module 3, and an autonomous leveling main control module 4.

[0030] 1. Hydraulic control module The hydraulic control module 1 includes a hydraulic sealed chamber 5 and an external pressure compensation device 6, which are integrated within the hydraulic sealed chamber 5. The hydraulic sealed chamber 5 includes a hydraulic pump station, an analog output module 11, a digital output module 12, a proportional valve group 8, a directional valve group 9, and a relief valve group 10. The analog output module 11 belongs to the hydraulic drive module, and the digital output module 12 belongs to the hydraulic control module 1 within the hydraulic drive module. The hydraulic pump station maintains the main oil circuit pressure. The analog output module 11 connects to the proportional valve group 8 to control the oil flow of the hydraulic telescopic outrigger 2. The digital output module 12 connects to the directional valve group 9 to control the extension and retraction of the hydraulic telescopic outrigger 2. The relief valve group 10 maintains the set main oil circuit pressure. The external pressure compensation device 6 is embodied in the form of an external oil bladder filled with hydraulic oil and connected to the hydraulic sealed chamber 5, supplementing the insufficient pressure in the main hydraulic oil circuit under the pressure of external water. The autonomous leveling main control module 4 is fixedly installed in the lower front part of the middle of the platform. It receives the task instructions from the shore-side control and simultaneously issues extension and retraction instructions to the hydraulic control module 1 for the relevant mechanisms of the hydraulic telescopic outriggers 2.

[0031] like Figure 2 As shown, the hydraulic control module 1 is an integrated dry and wet compartment design. The external oil bladder of the external pressure compensation device 6 is connected to the hydraulic oil tank 7. The hydraulically sealed dry compartment includes a proportional valve group 8, a reversing valve group 9, an overflow valve group 10, an analog output module 11, a digital output module 12, and an oil pump motor 13, which are used for the reversing control of the hydraulic telescopic outrigger 2. The specific hydraulic circuit principle is as follows. Figure 3 As shown.

[0032] 2. Hydraulic telescopic outriggers The hydraulic telescopic outrigger 2 includes a primary hydraulic telescopic rod, a displacement detection component, a pressure detection component, and a ball joint chassis. The displacement detection component is specifically a displacement sensor, which is built into the hydraulic telescopic outrigger 2. The primary hydraulic telescopic rod supports the overall platform. The displacement detection component provides feedback on the telescopic extension / retraction of the hydraulic telescopic outrigger 2. The pressure detection component is specifically a pressure sensor, installed on the top of the hydraulic telescopic outrigger 2, used to monitor the internal pressure of the hydraulic telescopic outrigger 2 in real time.

[0033] The hydraulic telescopic outrigger 2 works in conjunction with the proportional valve group 8, the directional valve group 9, the analog output module 11, and the digital output module 12. The analog output module 11 is connected to the proportional valve group 8, and the digital output module 12 is connected to the directional valve group 9. This invention uses a designed adaptive robust control technology to control the valves such as the proportional valve group 8 and the directional valve group 9. A converter transforms the hydraulic cylinder displacement x detected by the displacement detection component into a feedback signal. Then calculate its relationship with the predetermined signal. The difference is used to obtain the deviation signal. Then, it is converted into a current signal I by a converter, which controls the valve core opening of the proportional valve group 8. By adjusting the valve core opening x of the proportional valve group 8... v The control equation for the hydraulic cylinder is shown below:

[0034] In the formula, the valve core opening degree of the proportional valve assembly 8 The transfer function between the input current I and the input current can be simplified to a proportional element. This is the amplification factor of the proportional valve; This represents the error value at the previous moment. It is a proportional gain matrix. This is the differential gain matrix.

[0035] 3. Inertial Navigation Module like Figure 1 The inertial navigation module 3 shown is installed at the platform's center of gravity. The inertial navigation module 3 includes an inertial navigation sensor and a navigation data processing module. The inertial navigation sensor can provide real-time feedback of the platform's attitude data, specifically measuring the rotation angles α, β, and γ of the underwater platform around the coordinate axes, as well as the vertical heave displacement Δz. The navigation data processing module analyzes this attitude data in real time and feeds it back to the autonomous leveling main control module 4.

[0036] By default, the platform's roll angle α and pitch angle β approach zero. Based on the fixed installation relationship between the inertial navigation module 3 and the platform, a coordinate system is established according to the right-hand rule. The roll and pitch directions of the inertial navigation module 3 are fixed in the same direction relative to the origin of this coordinate system. The origin of this coordinate system is the platform's center of gravity underwater. The x-axis represents the platform's forward / backward direction (vertical axis), the y-axis represents the platform's left / right direction (horizontal axis), and the z-axis represents the platform's height direction (vertical axis). The xy-plane is parallel to the plane containing the underwater platform base. The default coordinate system is... The coordinate system after the platform's bottom orientation changes is: During this state change, α is the roll angle generated by the platform rotating around the x-axis, β is the pitch angle generated by the platform rotating around the y-axis, and γ is the yaw angle generated by the platform rotating around the z-axis. A top view of the coordinate system relationship is shown below. Figure 4 As shown. In actual operation, the inertial navigation sensor is installed at the platform's center of gravity to monitor the platform's yaw, roll, and pitch angles in real time, and uses these as inputs for subsequent calculations.

[0037] 4. Autonomous Leveling Main Control Module like Figure 1As shown, the autonomous leveling main control module 4 is installed in the main control compartment. The autonomous leveling main control module 4 includes an industrial computer and a network switch. The industrial computer is used to run the autonomous leveling control method, receive attitude data from the inertial navigation module 3 in real time, and control the opening size of the proportional valve group 8 through the analog output module 11, thereby controlling the extension and speed of the hydraulic telescopic outrigger 2. The switch is used to connect the digital output module 12, the analog output module 11, and the hydraulic control module 1 for real-time data exchange.

[0038] The autonomous leveling main control module 4 is connected to the inertial navigation module 3 via a surface connector to acquire platform attitude data in real time. The autonomous leveling main control module 4 is connected to the hydraulic control module 1 via a watertight connector to exchange data via network communication. It receives task commands from the shore-based control system and simultaneously issues extension commands to the hydraulic telescopic outrigger 2 actuator of the hydraulic control module 1 to control the extension length of the hydraulic telescopic outrigger.

[0039] 5. Platform leveling control method Furthermore, in the schematic diagram of platform attitude coordinate transformation The center of gravity when the platform is in a seated position. As the initial coordinate system, Let the coordinate system be the coordinate system after platform adjustment. Assume the initial coordinates of the piston rods of the four hydraulic telescopic outriggers 2 in front of the base are: The coordinates of the bottom of the two hydraulic telescopic outriggers are: The roll angle α, pitch angle β, bow angle γ, and vertical heave displacement Δz of the underwater platform around the coordinate axes were measured using the inertial navigation module, and a matrix was constructed:

[0040] Among them, M Rotx To make the initial coordinates The rotation matrix for rotating about the x-axis by an angle α; M Roty To make the initial coordinates The rotation matrix for rotating about the y-axis by an angle β; M T Initial coordinates The translation matrix for translating a distance Δz along the z-axis.

[0041] Construct M res =M Rotx M Roty M T M res To make the initial coordinates The rotation and translation matrix is ​​the matrix that rotates by an angle α around the x-axis, rotates by an angle β around the y-axis, and translates by a distance Δz along the z-axis.

[0042] The rotation and translation matrix M res Left multiplication From the initial coordinate values, the coordinates behind the base of the hydraulic telescopic outrigger can be obtained. :

[0043] The range of motion for the main platform and each hydraulic telescopic outrigger 2 is 0m≤ ≤0.7m; When the platform reaches a certain posture and position after rotation and translation during its movement, the extension and retraction of the hydraulic cylinders of each hydraulic telescopic outrigger 2 is... The changes (i=1,2,3,4) can be obtained through the following expression:

[0044] Position closed-loop feedback control is achieved by calculating the extension and retraction of each hydraulic cylinder. This controls the opening angle of the proportional valve assembly 8, thereby controlling the flow of hydraulic oil through the valve body and further converting it into pressure to drive the actuator (hydraulic cylinder). Assuming the tracking error of the rotation angle around the x-axis after the mother platform moves is... The tracking error expression is:

[0045] In the formula, From the perspective of expectation, This represents the angle of rotation about the z-axis output by the inertial navigation sensor. This represents the extension / retraction of the hydraulic cylinder piston rod of each hydraulic telescopic outrigger 2, derived from the inverse kinematics solution of the platform. Displacement amount fed back by displacement detection component The difference between them.

[0046] Furthermore, based on the above inverse kinematics solution and control law calculation, an adaptive robust controller is designed, with the control logic as follows: Figure 5 As shown, closed-loop feedback control is implemented based on the extension and retraction of the hydraulic telescopic outrigger 2, employing an adaptive robust controller based on Lyapunov stability theory, such as... Figure 5 As shown, the control law u output by the adaptive robust controller to the servo valve is:

[0047] in: For the proportional gain matrix, The differential gain matrix is ​​statically adjusted using a fuzzy rule table. 'e' represents the deviation between the desired dip angle and the actual dip angle. For the desired tilt angle, This is the actual tilt angle; The derivative of e represents the angular velocity; For adaptive parameter estimation vectors; The vector represents the regression function, where x represents state variables such as inclination angle, angular velocity, water depth, and ocean current. For robustness, it is used to suppress unmodeled dynamics and external disturbances.

[0048] The adaptive law is:

[0049] in It is a positive definite adaptive gain matrix. yes The derivative of .

[0050] Furthermore, when calculating the offset of the mother platform, the Kalman filter algorithm is used to fuse the attitude data collected by the inertial navigation module 3 and the displacement data fed back by the displacement detection component to improve the accuracy of the offset calculation of the mother platform. The attitude of the platform and the pressure and displacement values ​​of the hydraulic telescopic outriggers 2 are repeatedly observed until the following conditions are met simultaneously: (1) Angle condition: the roll angle α and pitch angle β of the platform are both less than the set value; (2) Pressure condition: the pressure values ​​of all hydraulic telescopic outriggers 2 are greater than the safety threshold and the difference between them is less than 10%; (3) Stability condition: the change in the tilt angle of the mother platform is less than 0.02° within 3 consecutive seconds.

[0051] This invention also discloses a method for autonomous leveling of an underwater platform. Figure 6 The flowchart is shown. After the leveling process is started, S1 is executed first: the system powers on, completes the initialization of core electronic modules such as the autonomous leveling main control module 4 and the inertial navigation module 3, establishes data connections between modules, and ensures the successful issuance of subsequent attitude detection and commands.

[0052] Then proceed to S2: The power source is turned on, starting the hydraulic pump station in the hydraulic control module 1, so that the hydraulic drive module reaches the preset working pressure. At the same time, the external pressure compensation device 6 starts to respond, ensuring the stability of the hydraulic main oil circuit pressure.

[0053] Then, S3 is executed: the base support device is extended, driving the first-stage hydraulic telescopic rods of the four hydraulic telescopic outriggers 2 to extend until the outrigger ball joint chassis contacts the seabed and initially supports the mother platform, completing the initial deployment of the platform base.

[0054] Then, in S4: the attitude adjustment of the mother platform, the autonomous leveling main control module 4 collects attitude data such as the platform roll angle α and pitch angle β in real time through the inertial navigation module 3, calculates the offset of the mother platform, and combines the pressure and displacement feedback data of the hydraulic telescopic outriggers 2. The desired extension amount required by each hydraulic telescopic outrigger 2 is calculated through the rotation matrix. Then, the proportional valve group 8 and the reversing valve group 9 are controlled through the analog output module 11 and the digital output module 12 to drive the movement of each hydraulic telescopic outrigger 2 to adjust the attitude of the platform.

[0055] After attitude adjustment, the process proceeds to S5: The attitude error of the mother platform is assessed. The real-time attitude error (the difference between the actual attitude and the horizontal attitude) is compared with a preset allowable error range to meet the accuracy requirements for docking with the unmanned underwater vehicle (UUV). If the mother platform's attitude error is detected to be less than or equal to the allowable error range, it indicates that the platform has reached a horizontal state, and the process proceeds directly to S6: Mission preparation self-check. This involves a final verification of the working status of each module, hydraulic system pressure, data signal transmission lines, etc. After successful verification, the leveling process ends, and the platform enters the waiting state for UUV recovery and docking.

[0056] If the S5 judgment result is that the mother platform's attitude error is greater than the allowable error range, then the branch adjustment process begins: First, execute S5.1: Check if the hydraulic telescopic outrigger 2 has reached its maximum extension. If the test confirms that the hydraulic telescopic outrigger 2 has reached its maximum extension, it means that synchronous adjustment can no longer meet the leveling requirements, and S5.2: Perform single-cylinder precise fine-tuning on the hydraulic telescopic outrigger 2 corresponding to the attitude error to avoid insufficient stroke caused by multi-cylinder synchronous adjustment, until the attitude error meets the requirements. If the S5.1 detection result is that the hydraulic telescopic outrigger 2 has not reached its maximum extension, then return to step S4 to continue driving each hydraulic telescopic outrigger 2 to coordinately adjust the attitude. After completing the single-cylinder precise fine-tuning to make the attitude error meet the requirements, proceed to S6: Task preparation status self-check, and the process ends after the check is passed.

[0057] Based on this process, calculations show that the platform can quickly reach a level state within a short time, demonstrating excellent performance. The leveling results after the platform is seated are as follows: Figure 7 As shown.

[0058] In summary, the above are merely preferred embodiments of the present invention. The hydraulic control module included in the underwater docking platform and the internal layout of the unmanned underwater vehicle recovery platform are both within the scope of protection of the present invention. Furthermore, the attitude autonomous adjustment system and method described in the present invention are also applicable to other underwater working platforms, and their application on relevant platforms should also fall within the scope of protection of the present invention.

[0059] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "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 application 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 application.

[0060] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for autonomous leveling of an underwater platform, characterized in that, The underwater platform includes a main platform and multiple hydraulically telescopic outriggers disposed on the side of the main platform. The autonomous leveling method includes the following steps: S1: After system initialization, start the power source to make the hydraulic drive module reach the preset working pressure; S2: Extend the hydraulic telescopic outriggers to contact the seabed and provide initial support for the mother platform; S3: The platform attitude data is collected in real time through the inertial navigation module to calculate the offset of the mother platform and the expected extension of each hydraulic telescopic outrigger. S4: Based on the desired extension amount, output control signal to adjust the flow and direction of hydraulic oil in the hydraulic drive module, drive each hydraulic telescopic outrigger to adjust the platform posture; S5: Determine if the platform attitude error is within the allowable range. If so, complete the leveling process; otherwise, proceed to the branch adjustment process until the attitude error meets the requirements.

2. The underwater platform self-leveling method according to claim 1, characterized in that, The specific process for calculating the expected extension / retraction amount of each hydraulic telescopic outrigger in step S3 includes: S3.1: Based on the right-hand rule, establish a coordinate system with the platform's center of gravity as the origin, and set the initial coordinates in front of the hydraulic telescopic outrigger base. And the coordinates behind the base of the hydraulic telescopic outrigger. The roll angle α, pitch angle β, bow angle γ, and vertical heave displacement Δz of the underwater platform around the coordinate axes were measured using the inertial navigation module, and a matrix was constructed: in, M Rotx To make the initial coordinates The rotation matrix for rotating about the x-axis by an angle α; M Roty To make the initial coordinates The rotation matrix for rotating about the y-axis by an angle β; M T Initial coordinates The translation matrix for a distance Δz along the z-axis; S3.2: By multiplying the matrix obtained in S3.1 by the coordinate changes of the hydraulic telescopic outriggers before and after the base, the expected telescopic extension of each hydraulic telescopic outrigger is obtained.

3. The underwater platform self-leveling method according to claim 2, characterized in that, S3.2 includes: Construct M res =M Rotx M Roty M T M res To make the initial coordinates The rotation and translation matrix is ​​the matrix for rotating about the x-axis by an angle α, rotating about the y-axis by an angle β, and translating along the z-axis by a distance Δz. The rotation and translation matrix M res Left multiplication From the initial coordinate values, the coordinates behind the base of the hydraulic telescopic outrigger can be obtained. : Extension range of each hydraulic telescopic outrigger The changes (i=1,2,3,4) can be obtained through the following expression: The range of motion for the main platform and each hydraulic telescopic outrigger is 0m≤ ≤0.7m.

4. The autonomous leveling method for the underwater platform as described in claim 1, characterized in that, The control signal in step S4 is an adaptive robust control signal based on Lyapunov stability theory, and the control law u of the control signal is: in, For the proportional gain matrix, It is the differential gain matrix; , For the desired tilt angle, This is the actual tilt angle; The derivative of e represents the angular velocity; For adaptive parameter estimation vectors; The vector represents the regression function, where x represents state variables such as inclination angle, angular velocity, water depth, and ocean current. For robustness, it is used to suppress unmodeled dynamics and external disturbances; The adaptive law is: in It is a positive definite adaptive gain matrix. yes The derivative of .

5. The method for autonomously leveling an underwater platform as described in claim 1, characterized in that, In step S4, adjusting the flow rate and direction of the hydraulic oil specifically involves controlling the opening of the proportional valve group by outputting a signal from the analog output module in the hydraulic drive module, thereby adjusting the hydraulic oil flow rate. The hydraulic control module in the hydraulic drive module outputs a signal to control the directional valve group, adjusts the direction of hydraulic oil, and thus controls the extension speed and direction of the hydraulic telescopic outriggers.

6. The method for autonomously leveling an underwater platform as described in claim 1, characterized in that, The branch adjustment process in step S5 is as follows: check whether the hydraulic telescopic outrigger has reached its maximum extension. If so, perform single-cylinder precise fine adjustment for the hydraulic telescopic outrigger corresponding to the posture error until the posture error meets the requirements. Otherwise, return to step S4 to continue driving each hydraulic telescopic outrigger to coordinate and adjust the posture.

7. The underwater platform self-leveling method according to claim 2, characterized in that, The criterion for determining the allowable range of attitude error in step S5 is that the following conditions must be met simultaneously: The platform's roll angle α and pitch angle β are both less than the set values; All hydraulic telescopic outrigger pressure values ​​are greater than the safety threshold and the difference between them is less than 10%; Within 3 consecutive seconds, the change in tilt angle of the mother platform was less than 0.02°.

8. The method for autonomously leveling an underwater platform as described in claim 1, characterized in that, The system initialization in step S1 includes: initializing the core electronic modules such as the autonomous leveling main control module and the inertial navigation module, and establishing data connections between the modules.

9. The method for autonomously leveling an underwater platform as described in claim 1, characterized in that, In step S3, when calculating the offset of the mother platform, the displacement feedback data of the displacement detection component on the hydraulic telescopic outrigger is also combined. The attitude data and displacement feedback data are fused by the Kalman filter algorithm to improve the accuracy of offset calculation. The displacement detection component is built into the hydraulic telescopic outrigger.

10. An autonomous leveling system for an underwater platform, characterized in that, The method for autonomous leveling of an underwater platform according to any one of claims 1 to 9 includes: An inertial navigation module is installed at the center of gravity of the underwater platform to collect attitude data of the underwater platform in real time. The hydraulic drive module includes a hydraulic control module and multiple sets of hydraulic telescopic outriggers. The hydraulic control module is used to adjust the flow and direction of hydraulic oil. The hydraulic telescopic outriggers are equipped with displacement detection components and pressure detection components to support the underwater base platform and provide feedback on the extension and pressure data of the hydraulic telescopic outriggers. The hydraulic control module also includes an external pressure compensation device, which includes an external oil bladder filled with hydraulic oil. The external oil bladder is connected to the hydraulic control module and is used to supplement the main oil circuit pressure of the hydraulic control module under the pressure of the underwater environment. The autonomous leveling main control module communicates with the inertial navigation module and the hydraulic drive module. It is used to perform system initialization, receive attitude data collected by the inertial navigation module, calculate the expected extension and retraction of each hydraulic telescopic outrigger, and output control signals to the hydraulic drive module to control the extension and retraction length of the hydraulic telescopic outrigger.

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