High-efficiency drag reduction buoy system for unmanned hydrofoil vessel based on air film stability control

Abstract

The present invention belongs to the field of ship technology, and relates to an efficient drag reduction buoy system for unmanned hydrofoil vessels based on air film stabilization control. The system includes a buoy, an airflow conduction system, a sensor system, a control system and an actuator; the airflow conduction system includes an air supply system and an airflow conduction groove; a one-way exhaust hole is arranged at the bottom of the buoy, and is connected to the air supply system through a pipeline; the airflow conduction groove is V-shaped and distributed along the central axis of the buoy at the bottom of the buoy, and one end thereof is connected to the one-way exhaust hole; the sensor system is arranged at the bottom of the buoy; the control system includes a data acquisition module and a control mainboard; the data acquisition module is used to collect data from the sensor system and transmit it to the control mainboard; the control mainboard is used to execute an adaptive control algorithm and output a control signal to the actuator to adjust the output of the airflow in real time. The present invention can analyze the data fed back by the sensor in real time, adjust the airflow output, and realize adaptive adjustment of the air film under different water flow, speed, and pressure changes.

Description

Technical Field

[0001] The invention belongs to the technical field of ships and relates to an efficient drag reduction buoy system for an unmanned hydrofoil vessel based on air film stabilization control. Background Art

[0002] The friction resistance between the hull and the water is one of the key factors affecting the ship's speed, fuel consumption and operating efficiency. Traditional hull designs use streamlined shapes and surface coating technology to reduce the viscous resistance of the water to the hull. However, these methods have significant limitations when facing high speeds and complex sea conditions.

[0003] Traditional ship drag reduction technologies, such as hull streamline optimization, coating application or applying tiny structural features on the hull surface, can reduce hull resistance to a certain extent, but the effects of these technologies are not significant enough under high-speed navigation or complex water flow conditions, especially in long-term operation, the effect of the coating is easy to decay.

[0004] The friction resistance caused by the direct contact between the water and the hull surface is still large, especially on components such as buoys with large-area contact, the viscous resistance of the water is the main source of energy consumption.

[0005] Air film drag reduction technology proposes to form an air film between the hull and the water to reduce direct contact between the two, which can theoretically significantly reduce friction resistance. However, most existing air film technologies rely on fixed airflow discharge systems, making it difficult to dynamically adjust the thickness and stability of the air film. In practical applications, the air film is often unstable, especially when the speed changes or the external environment changes, which can easily lead to the air film rupture or fail to effectively cover the surface of the buoy, affecting the drag reduction effect.

[0006] At the same time, due to the lack of an effective real-time monitoring and feedback system, the existing air film generating device is unable to make adaptive adjustments according to external conditions such as water flow and speed, resulting in inconsistent drag reduction effects.

[0007] At present, most ship drag reduction technologies rely on passive systems and cannot make dynamic adjustments according to real-time navigation status. For example, the exhaust hole design is usually fixed and cannot automatically adjust the airflow output and the air film shape in response to environmental changes, resulting in significant fluctuations in the drag reduction effect under different navigation speeds and water flow conditions. Summary of the invention

[0008] In order to solve the problem in the prior art of stably maintaining the air film at high speed or in a changing hydrodynamic environment, resulting in unstable drag reduction effect, the present invention introduces sensors and automatic control systems to achieve real-time monitoring of the contact pressure between the buoy and the water body, and utilizes a mechanism for dynamically adjusting the airflow output to ensure the stability and consistency of the air film under different conditions, thereby effectively reducing the resistance fluctuation of the buoy and improving navigation efficiency.

[0009] The technical solution adopted by the present invention to solve its technical problems is: an unmanned hydrofoil ship high-efficiency drag reduction buoy system based on air film stable control, including a buoy, an airflow conduction system, a sensor system, a control system and an actuator; the airflow conduction system includes a one-way exhaust hole, an air supply system, and an airflow conduction groove; the one-way exhaust hole is arranged at the bottom of the buoy, and the one-way exhaust hole is connected to the air supply system through a pipeline; the airflow conduction groove is V-shaped and distributed at the bottom of the buoy along the central axis of the buoy, and one end thereof is connected to the one-way exhaust hole; the sensor system is arranged at the bottom of the buoy, and is used to detect the pressure change and the buoy posture in the contact area between the buoy surface and the water body; the control system includes a data acquisition module and a control mainboard; the data acquisition module is used to collect data from the sensor system and transmit it to the control mainboard; the control mainboard has a built-in adaptive control algorithm, which is used to execute the algorithm and output a control signal to the actuator, so as to adjust the output of the airflow in real time and adjust the thickness of the air film; the adaptive control algorithm includes a model predictive control algorithm and an adaptive PID control strategy.

[0010] Preferably, the model predictive control algorithm calculates the optimal control input based on the prediction of the system state, specifically including:

[0011] (1) Constructing a mathematical model of the system:

[0012] ;

[0013] in, is the state variable of the system, including the pressure of the buoy in contact with the water ,speed , servo or air flow control valve position ; is the control input, which refers to the signal that controls the airflow output; It is the output of the system, which refers to the actual measured value of pressure;

[0014] (2) Define the objective function: minimize the weighted sum of future errors and control inputs:

[0015] ;

[0016] in, is the expected output, is the control input penalty coefficient, is the prediction step size, i.e. the number of steps to be predicted and optimized in the future time window; From the current moment Start forecasting future time steps;

[0017] (3) Construction constraints:

[0018] ;

[0019] in, , are the lower and upper limits of the state variable, respectively. , are the lower and upper limits of the control input respectively;

[0020] (4) Solve the optimization problem: At each time step, solve the optimal control input through linear programming .

[0021] Preferably, the adaptive control algorithm also includes an adaptive PID control strategy, specifically including:

[0022] (1) According to the expected output of MPC and the actual output Calculation error,

[0023] ;

[0024] in, is the control error, describing the difference between the expected output and the actual output;

[0025] (2) Update the integral and calculus terms of the PID controller according to the PID formula:

[0026] ;

[0027] ;

[0028] in, is the time step used to calculate the integral and differential of the error, is the integral term representing the accumulated value of the error, is the differential term, which represents the rate of change of the error;

[0029] (3) Dynamic adjustment based on system performance , , :

[0030] ;

[0031] ;

[0032] ;

[0033] in, is the initial proportional gain, is the initial integral gain, is the initial differential gain, is the adjustment factor, is the absolute value of the current error;

[0034] (4) Output control signal, the calculated Converted into PWM signal to control the airflow output of the servo or airflow regulating valve.

[0035] Preferably, the actuator is a mechanical valve, a solenoid valve or a stepper motor control valve linked to a steering gear.

[0036] Preferably, the sensor system is arranged at the front end and both sides of the bottom of the buoy, and includes a thin film pressure sensor and a posture sensor.

[0037] Preferably, the airflow conducting groove has a depth of 2-5 mm and a width of 5-10 mm, and its inner wall has a bionic texture.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) By introducing a thin film pressure sensor and a dynamic control system, the present invention can monitor the pressure changes in the contact area between the buoy and the water in real time, and dynamically adjust the airflow output according to the navigation status to ensure that the air film is evenly and stably distributed on the surface of the buoy. Compared with the existing technology that relies on fixed airflow, the sustainability and stability of the air film are significantly improved, effectively avoiding the problem of air film rupture or uneven coverage;

[0040] (2) The present invention optimizes the formation and distribution of the air film through the design of the airflow conduction groove, reduces the direct contact area between the buoy and the water body, and significantly reduces the viscous resistance. Compared with the traditional hull surface coating or simple streamline design, the drag reduction effect of this solution is more excellent in a variety of complex hydrodynamic environments, and is particularly suitable for the drag reduction needs during high-speed navigation;

[0041] (3) The present invention adopts an automatic control system based on the MPC-PID adaptive algorithm, which can analyze the data fed back by the sensor in real time, automatically adjust the airflow output of the exhaust hole, and realize adaptive adjustment to different water flow, speed, and pressure changes. Compared with the fixed airflow discharge system in the traditional air film drag reduction technology, the present invention greatly improves the responsiveness to environmental changes and the accuracy of airflow control. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a bottom schematic diagram of a buoy in an embodiment of the present invention;

[0043] Figure 2 is a side view of a buoy in an embodiment of the present invention;

[0044] Figure 3 is a cross-sectional view of a buoy in an embodiment of the present invention;

[0045] Figure 4 Schematic diagram of the module composition of the control system in an embodiment of the present invention;

[0046] Figure 5 4 is a flow chart of the principle of the adaptive control algorithm in the embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with specific embodiments and the accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention is obviously capable of being implemented in a variety of other ways different from the description herein. For those skilled in the art, any substitution, improvement or change made to the embodiments of the present invention is within the protection scope of the present invention, and the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0048] The unmanned hydrofoil boat high-efficiency drag reduction buoy system based on air film stabilization control provided by the present invention realizes a stable air film between the buoy and the water body through an innovative air film generation system, combined with real-time pressure monitoring, attitude monitoring and automatic airflow adjustment, thereby reducing the contact area between the buoy and the water body, and thus reducing the viscous resistance during navigation. The system includes a buoy, an airflow conduction system, a sensor system, a control system, an actuator, and other parts. The following is a detailed introduction to each component in conjunction with the accompanying drawings.

[0049] 1. Structural design of buoy

[0050] The buoy is one of the core components of the present invention, and its main function is to support the hull and improve the sailing efficiency through the drag reduction design. Figure 1-3 As shown, in the present invention, the buoy adopts the following structural design:

[0051] 1.1 Streamlined design of buoy

[0052] The shape of the buoy 1 adopts a streamlined design that conforms to the principles of fluid dynamics to minimize the resistance caused by the direct contact between the buoy surface and the water body. There are multiple one-way exhaust holes in the area where the bottom of the buoy contacts the water body. The diameter, arrangement density and angle of these exhaust holes are optimized according to the parameters such as the navigation speed of the hull, buoyancy requirements, and contact area with the water body.

[0053] 1.2 One-way exhaust hole

[0054] The one-way exhaust hole 2 is arranged at the bottom of the buoy 1, and its function is to discharge airflow underwater through the air supply system to form an air film between the buoy 1 and the water body. The thickness and distribution of the air film depend on the design of the one-way exhaust hole. The aperture of the exhaust hole ranges from 0.5 to 2 mm, so that the flow rate of the gas can be accurately controlled and the airflow can be evenly distributed at the bottom of the buoy 1.

[0055] 1.3 Airflow guide groove

[0056] In order to promote the effective distribution of gas, a plurality of airflow conducting grooves 3 are designed at the bottom of the buoy 1. The shape of these airflow conducting grooves 3 is designed to be V-shaped, and the inner wall thereof has a bionic texture to simulate the surface characteristics of shark skin. These microscopic textures can reduce the viscous resistance of the water body, further optimize the stability of the airflow, and make the airflow smoothly conduct in the grooves, thereby forming a stable air film on the surface of the buoy.

[0057] 1.4 Material selection

[0058] The selection of buoy materials is crucial, and they need to be corrosion-resistant, wear-resistant and waterproof. The buoys are made of high-molecular polymer materials (such as glass fiber reinforced composite materials), which have light weight and high impact resistance, and can be used for a long time in harsh marine environments.

[0059] 2. Airflow system

[0060] The invention realizes uniform distribution and stable output of gas through reasonably designed air flow channels and exhaust holes. The system includes an air supply system, a one-way exhaust hole, an air flow conducting groove and a gas recovery system to ensure the generation and maintenance of an air film.

[0061] 2.1 Gas supply system

[0062] The air supply system is responsible for providing a stable airflow to the one-way exhaust hole at the bottom of the buoy. The air supply system in this system consists of an air pump and a gas storage bottle, which can provide sufficient air pressure to maintain the formation of the air film. The air supply system is connected to the gas pipeline inside the buoy, which is connected to the one-way exhaust hole and accurately adjusts the airflow through the control valve.

[0063] 2.2 Airflow guide groove

[0064] The design of the airflow conduction groove is to ensure that the airflow can quickly diffuse at the bottom of the buoy and form a stable air film on the water surface after flowing out of the one-way exhaust hole. Through the conduction effect of the airflow conduction groove, the gas can be evenly distributed in the entire area where the buoy contacts the water, avoiding the situation of insufficient air film or air film rupture in local areas.

[0065] The size and shape of the airflow conducting groove are optimized according to fluid dynamics simulation to achieve the best diffusion effect of the airflow. The depth of the airflow conducting groove is preferably 2-5 mm, and the width is between 5-10 mm. The inner wall of the groove adopts a bionic texture with a microstructure, which can reduce the turbulence of the airflow in the groove and improve the stability of the airflow.

[0066] 3. Sensor system

[0067] The sensor system is the key to achieving automatic airflow regulation. By monitoring the contact pressure between the buoy and the water body, it can provide real-time feedback to the control system, thereby dynamically adjusting the airflow output.

[0068] 3.1 Sensor

[0069] The present invention uses a thin film pressure sensor 4, whose high sensitivity and fast response performance can accurately detect the pressure change in the contact area between the buoy surface and the water body. These thin film pressure sensors 4 are arranged at multiple key positions, which can capture the water pressure in different areas and convert it into an electrical signal to send to the control system.

[0070] The MPU6050 attitude sensor 5 is used to measure the angle and acceleration information of the buoy.

[0071] The layout density of the sensors is determined according to the distribution of different pressure zones where the buoy contacts the water body. More sensors are arranged at the front end and both sides of the buoy to capture areas with large pressure changes under the impact of water flow.

[0072] Sensor performance parameters: The measuring range of the thin film pressure sensor is 0-200kPa, the response time is less than 1 millisecond, and it can quickly feedback the pressure changes at the bottom of the float.

[0073] 3.2 Data Collection and Transmission

[0074] The pressure data collected by the sensor is transmitted to the control system through the data acquisition module. The data acquisition module has multi-channel input capabilities and can process data from multiple sensors at the same time and transmit it to the control system in the form of digital signals.

[0075] 4. Control system

[0076] The control system of the present invention uses the Arduino control board as the core and adopts an intelligent control algorithm to achieve dynamic regulation of the airflow. The control system dynamically adjusts the airflow output of the one-way exhaust hole according to the real-time feedback data of the sensor system to ensure the stability of the air film.

[0077] 4.1 MPC-PID adaptive control algorithm

[0078] The MPC-PID adaptive control algorithm is the core control algorithm of the present invention. The adaptive PID control strategy can be adjusted in real time and respond quickly to changes, while MPC can focus on long-term optimization prediction. MPC ensures the stability of the overall control strategy by predicting future states; while the adaptive PID control strategy provides rapid local adjustments to further enhance the stability of the system.

[0079] The outer control of the present invention uses the model predictive control algorithm (MPC) as the main control strategy, which is responsible for long-term prediction and optimization. MPC will formulate a control strategy based on the prediction of the system state to achieve the overall goal (such as stabilizing the air film and reducing resistance). The inner control uses an adaptive PID control strategy, and an adaptive PID controller is used for fine-tuning in each control cycle of MPC. The adaptive PID control strategy is responsible for real-time processing of short-term fluctuations and instantaneous changes in the system to ensure that the system can quickly respond to external disturbances based on the MPC output.

[0080] The principle of MPC-PID adaptive control algorithm is as follows Figure 5 As shown, the specific implementation steps are as follows:

[0081] (1) Mathematical model of MPC-PID adaptive algorithm

[0082] Assume that the state variables of the system Including the pressure of the buoy in contact with the water ,speed , servo or air flow control valve position ; is the control input, which refers to the signal that controls the airflow output; It is the output of the system and refers to the real-time pressure value monitored.

[0083] The dynamic behavior of the system is modeled as:

[0084] .

[0085] Since the dynamic model is nonlinear, the initial state of the system and Linearization is performed at:

[0086] ;

[0087] in, ; ; , is the symbol for partial differential; is the state transition matrix, which describes how the current state transfers to the next state. is the control input matrix, describing the effect of the control input on the state, is the output matrix, describing how states are mapped to outputs.

[0088] Define the objective function: minimize the weighted sum of future errors and control inputs:

[0089] ;

[0090] in, is the expected output, is the control input penalty coefficient, is the prediction step size, that is, the number of steps for prediction and optimization in the future time window, and is the time range for system prediction and optimization; From the current moment Start forecasting future time steps.

[0091] Build constraints:

[0092] ;

[0093] in, , are the lower and upper limits of the state variable, respectively. , are the lower and upper limits of the control input respectively.

[0094] Solve the optimization problem: At each time step, solve the optimal control input through linear programming .

[0095] (2) Adaptive PID control steps

[0096] According to the expected output of MPC and the actual output Calculation error:

[0097] ;

[0098] in, is the control error, describing the difference between the expected output and the actual output.

[0099] Update the PID controller, the PID formula is:

[0100] ;

[0101] Update the integral and calculus terms according to the above PID formula:

[0102] ;

[0103] ;

[0104] in, is the proportional gain, the relationship between the control error and the control input, is the integral gain, controlling the cumulative effect of past errors, is the differential gain, the effect of the rate of change of the control error, is the time step used to calculate the integral and differential of the error, is the integral term representing the accumulated value of the error, is the differential term, which represents the rate of change of the error.

[0105] Adaptive mechanism: Dynamically adjust according to system performance , , :

[0106] ;

[0107] ;

[0108] ;

[0109] in, is the initial proportional gain, is the initial integral gain, is the initial differential gain, is the adjustment factor, is the absolute value of the current error.

[0110] Output control signal: The calculated Converted into PWM signal to control the airflow output of the servo or airflow regulating valve.

[0111] 4.2 Hardware Configuration of Control System

[0112] like Figure 4 As shown in the figure, the hardware configuration of the control system includes Arduino control mainboard, data acquisition module, memory module, etc. The control mainboard is responsible for processing sensor data, executing control algorithms and outputting control signals to actuators. The power of the control system is provided by a 12V battery, and the voltage regulation module maintains stable operation of the system.

[0113] 5. Executive Agency

[0114] The actuator is responsible for actually adjusting the output of the airflow according to the output signal of the control system. Specifically, the actuator includes a mechanical valve or an airflow regulating valve (solenoid valve or stepper motor control valve) linked to the steering gear.

[0115] 5.1 Servo linkage system

[0116] The servo is responsible for adjusting the opening of the mechanical valve according to the control signal, thereby changing the airflow output of the one-way exhaust hole. The rotation angle of the servo is proportional to the control signal, with high rotation accuracy and fast response speed, and can quickly complete the airflow adjustment.

[0117] 5.2 Air flow control valve

[0118] The air flow regulating valve is the core component for controlling the gas flow. It usually adopts a solenoid valve or a stepper motor control valve, and its accuracy can reach a flow adjustment range of 0.01 ml / s to ensure fine control of the gas film.

[0119] 6. Gas supply system and gas recovery system

[0120] The gas supply system and gas recovery system ensure the recycling of gas in the gas flow system, reducing gas consumption and improving energy utilization.

[0121] 6.1 Gas Recovery System

[0122] The gas recovery system sets micro air return holes at the bottom of the float and in the air flow conducting grooves to recover the unused gas into the gas circulation pipeline, and then re-enter the gas supply system to reduce gas consumption.

[0123] 6.2 Gas supply system

[0124] The gas is collected by the air pump and enters the gas storage bottle to ensure stable outlet pressure.

Claims

1. An efficient drag reduction buoy system for unmanned hydrofoil vessels based on air film stabilization control, characterized by: It includes a float, an air flow conduction system, a sensor system, a control system and an actuator; the air flow conduction system includes a one-way exhaust hole, an air supply system and an air flow conduction groove; the one-way exhaust hole is arranged at the bottom of the float and connected to the air supply system through a pipeline; the air flow conduction groove is V-shaped and distributed at the bottom of the float along the central axis of the float, and one end thereof is connected to the one-way exhaust hole; the sensor system is arranged at the bottom of the float, and is used to detect the pressure change in the contact area between the float surface and the water body and the float posture; the control system includes a data acquisition module and a control mainboard; the data acquisition module is used to collect data from the sensor system and transmit it to the control mainboard; the control mainboard has a built-in adaptive control algorithm, which is used to execute the algorithm and output a control signal to the actuator, so as to adjust the output of the airflow in real time and adjust the thickness of the air film; the adaptive control algorithm includes a model predictive control algorithm and an adaptive PID control strategy; The model predictive control algorithm calculates the optimal control input based on the prediction of the system state, specifically including: (1) Constructing algorithm mathematical model: ； in, is the state variable of the system, including the pressure of the buoy in contact with the water ,speed , servo or air flow control valve position ; is the control input, which refers to the signal that controls the airflow output; It is the output of the system, which refers to the actual measured value of pressure; (2) Define the objective function: minimize the weighted sum of future errors and control inputs: ； in, is the expected output, is the control input penalty coefficient, is the prediction step size, i.e. the number of steps to be predicted and optimized in the future time window; From the current moment Start forecasting future time steps; (3) Construction constraints: ； in, , are the lower and upper limits of the state variable, respectively. , are the lower and upper limits of the control input respectively; (4) Solving the optimization problem: At each time step, the optimal control input is solved through linear programming.

2. The unmanned hydrofoil vessel high-efficiency drag reduction buoy system based on air film stabilization control according to claim 1 is characterized in that: The adaptive PID control strategy specifically includes: (1) According to the expected output of MPC and the actual output Calculation error, ； in, is the control error, describing the difference between the expected output and the actual output; (2) Update PID controller: The PID formula is: ; in, is the proportional gain, the relationship between the control error and the control input; is the integral gain, which controls the cumulative effect of past errors; is the differential gain, which controls the effect of the rate of change of the error; Update the integral and differential terms according to the PID formula: ； ； in, is the time step used to calculate the integral and differential of the error, is the integral term representing the accumulated value of the error, is the differential term, which represents the rate of change of the error; (3) Adaptive mechanism: Dynamic adjustment based on system performance , , : ； ； ； in, is the initial proportional gain, is the initial integral gain, is the initial differential gain, is the adjustment factor, is the absolute value of the current error; (4) Output control signal: The calculated It is converted into a PWM signal and controls the air flow output through the actuator.

3. The unmanned hydrofoil vessel high-efficiency drag reduction buoy system based on air film stabilization control according to claim 1 or 2, characterized in that: The actuator adopts a mechanical valve, a solenoid valve or a stepper motor control valve linked with a steering gear.

4. The unmanned hydrofoil vessel high-efficiency drag reduction buoy system based on air film stabilization control according to claim 1 or 2, characterized in that: The sensor system is arranged at the front end and both sides of the bottom of the buoy, and includes a film pressure sensor and a posture sensor.

5. The unmanned hydrofoil vessel high-efficiency drag reduction buoy system based on air film stabilization control according to claim 1 or 2, characterized in that: The airflow conducting groove has a depth of 2-5 mm and a width of 5-10 mm, and its inner wall has a bionic texture.

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