Active suppression based air-sea amphibious unmanned aerial vehicle into horizontal stable transition method and system

Abstract

The application discloses an air-sea amphibious unmanned aerial vehicle horizontal stable transition method and system based on active inhibition, and the method comprises the following steps: hovering the air-sea amphibious unmanned aerial vehicle above a target sea area, constructing multi-source heterogeneous information, and performing sea surface motion state rolling prediction and solution to obtain the best water entry time point and the best water entry attitude angle; performing power pre-adjustment and active buffering on the air-sea amphibious unmanned aerial vehicle, and controlling the air-sea amphibious unmanned aerial vehicle to smoothly enter the sea surface; until the air-sea amphibious unmanned aerial vehicle completely enters the sea surface, performing PID control according to the current pitch angle, roll angle and angular velocity of the air-sea amphibious unmanned aerial vehicle, generating a restoring torque, and realizing the underwater six-degree-of-freedom motion of the air-sea amphibious unmanned aerial vehicle. The application can offset the attitude disturbance caused by the sea wave and the self micro-motion, so that the air-sea amphibious unmanned aerial vehicle can smoothly enter the water. The application can be widely applied to the field of unmanned aerial vehicle control technology.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) control technology, and in particular to a method and system for smooth transition of an air-sea amphibious UAV into water based on active suppression. Background Technology

[0002] The large-scale development of offshore wind power in deep-sea areas has driven technological exploration of amphibious unmanned aerial vehicles (UAVs), an emerging type of equipment aimed at overcoming the limitations of single-medium inspection and achieving integrated operations. However, the stability and reliability of this type of UAV during its transition from air to water, especially during the water entry phase, is a recognized technical bottleneck restricting its engineering application.

[0003] Existing water entry control strategies for cross-medium UAVs tend to be passive and simplistic, making them ill-suited for complex sea conditions. For example, some solutions employ inflatable floats for passive buffering, which can reduce some impact, but the entry process is slow and the attitude is uncontrollable, making it impossible to actively adapt to wave dynamics. Another solution attempts to reverse propeller power at the moment of water contact to resist the impact, but this strategy results in significant energy loss, a sharp reduction in underwater thrust, and the drastic power change can easily lead to instability. Still other solutions switch propulsion modes through mechanical structure changes, but their control mechanisms are complex, dynamic response is sluggish, and reliability is challenged.

[0004] The relevant technologies lack systematic and intelligent control over the core challenge of the water entry process: proactive perception and forward-looking decision-making regarding the dynamic wave environment. Most solutions fail to achieve optimal selection of the water entry timing and attitude relative to the wave phase, and also lack the ability to proactively and rapidly suppress impact loads and stabilize attitude at the moment of water contact. This results in high impact risk and an uneven transition during the water entry process, seriously affecting the platform's safety and subsequent operational efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method and system for a smooth water entry of an amphibious unmanned aerial vehicle (UAV) based on active suppression, which can counteract attitude disturbances caused by sea waves and the UAV's own micro-movements, thereby achieving a smooth water entry for the UAV.

[0006] The first technical solution adopted in this invention is: a method for smooth transition of an amphibious unmanned aerial vehicle (UAV) into water based on active suppression, comprising the following steps: The amphibious drone is hovered above the target sea area to construct multi-source heterogeneous information and perform rolling prediction and calculation of the sea surface motion state to obtain the optimal entry time and optimal entry attitude angle. By combining the optimal water entry time and optimal water entry attitude angle, and by performing power pre-adjustment and active buffering on the amphibious UAV, the amphibious UAV can be controlled to smoothly enter the sea surface. Until the amphibious drone fully enters the sea surface, PID control is performed based on the current pitch angle, roll angle and angular velocity of the amphibious drone to generate restoring torque and realize the underwater six-degree-of-freedom motion of the amphibious drone.

[0007] Furthermore, the step of hovering the amphibious UAV above the target sea area, constructing multi-source heterogeneous information, and performing rolling prediction and calculation of the sea surface motion state to obtain the optimal entry time and optimal entry attitude angle specifically includes: The amphibious drone is hovered above the target sea area to acquire sea wave data, sea wind speed, wind direction and micro-motion information of the amphibious drone itself, and to construct multi-source heterogeneous information. A unified environmental situation map is generated based on multi-source heterogeneous information and then calculated to obtain the dynamic environmental parameters of the current target sea area. The dynamic environmental parameters of the current target sea area include the effective wave height, wave period, wave propagation direction, wind speed, and wind direction. Based on a simplified wave motion model, the dynamic environmental parameters of the current target sea area are predicted in a rolling manner within a preset time period to obtain the phase and local slope distribution of sea surface elevation changes. A comprehensive evaluation function is constructed, and an optimization search is performed within the prediction time window based on the phase and local slope distribution of sea surface elevation changes to obtain the optimal entry time point. The global wave slope of the sea surface corresponding to the optimal entry time is obtained. Combined with the current yaw angle of the amphibious UAV, the optimal entry attitude angle is obtained by transforming it to the body coordinate system through a rotation matrix. The optimal entry attitude angle includes the target pitch angle and the target roll angle.

[0008] Furthermore, the expression for the comprehensive evaluation function is as follows: ; In the above formula, This represents the comprehensive evaluation function. This represents the predicted wavefront slope vector after coordinate transformation to the body coordinate system. Describes the Euclidean norm. This indicates the vertical descent speed command for the drone. and These represent normalized thresholds determined based on the structural strength and control performance of the aircraft, respectively representing the maximum permissible safe entry wavefront slope and the maximum permissible relative vertical velocity difference. and Indicates the weighting coefficient. This indicates the vertical velocity of the drone under the influence of waves.

[0009] Furthermore, the specific expression for calculating the optimal entry attitude angle is as follows: ; In the above formula, Indicates the target pitch angle. Indicates the target roll angle. This represents the slope of the local wavefront along the X-axis in the UAV's body coordinate system. This represents the slope of the local wavefront along the Y-axis in the UAV's body coordinate system. This represents the arctangent function.

[0010] Furthermore, the step of combining the optimal water entry time and optimal water entry attitude angle, and performing dynamic pre-adjustment and active buffering on the amphibious UAV to control its smooth entry into the sea surface, specifically includes: Control the amphibious drone to descend smoothly, and adjust the fuselage angle of the amphibious drone according to the optimal water entry attitude angle; By introducing wavefront prediction information, the altitude tracking error is defined to adjust the total lift of the air-sea amphibious UAV, thereby controlling the air-sea amphibious UAV to descend to the critical altitude above the sea surface. According to the smoothing function, the robotic arm of the amphibious drone deflects horizontally according to a predetermined law and performs thrust compensation, controlling the amphibious drone to enter the best ready state. Based on the optimal readiness state of the amphibious drone, and combined with the optimal water entry time, the drone body is controlled to make contact with the sea surface and enter the impact suppression mode. Define the vertical acceleration error, generate the vertical acceleration and feed it back to the robotic arm of the amphibious UAV to generate pulse thrust; Based on the generated pulse thrust, the current pitch angle, roll angle and angular velocity of the amphibious UAV are obtained in real time, and differential adjustment is performed to control the amphibious UAV to enter the sea surface smoothly.

[0011] Furthermore, the amphibious unmanned aerial vehicle (UAV) is equipped with a cross-shaped tilt-coaxial dual-propeller propulsion system, the specific expression of which is shown below: ; In the above formula, This represents the total lift control input for an amphibious unmanned aerial vehicle (UAV). This represents the roll control input for amphibious unmanned aerial vehicles (UAVs). This represents the pitch control input for an amphibious unmanned aerial vehicle (UAV). This represents the yaw control input for an amphibious unmanned aerial vehicle (UAV). , and These represent the roll angle, pitch angle, and yaw angle, respectively. , and These represent the accelerations of the drone along each axis. , and These represent the moments of inertia of each axis of the machine body. Indicates the quality of the drone. Represents gravitational acceleration. This indicates the distance from the center of the drone to the center of each propeller. , and These represent the three translational air drag coefficients. , and These represent the air resistance torque coefficients for the three rotations.

[0012] Furthermore, it also includes correcting the parameters of the simplified wave motion model and the parameters of the PID control based on the dynamic environmental parameters of the current target sea area, the optimal entry time, the optimal entry attitude angle, the vertical acceleration, and the convergence time required to control the amphibious UAV to achieve a stable state.

[0013] Furthermore, the modified expressions for the parameters of the simplified wave motion model are as follows: ; In the above formula, These represent the parameters of the modified, simplified wave motion model. Indicates the predicted wavefront elevation. Indicates the actual wavefront elevation. These represent the parameters of the initial simplified wave motion model. Indicates the first Each sampling time, Indicates the sequence number of the sampling point.

[0014] The second technical solution adopted in this invention is: a smooth transition system for amphibious unmanned aerial vehicles (UAVs) entering water based on active suppression, comprising: The first module is used to hover the amphibious UAV above the target sea area, construct multi-source heterogeneous information and perform rolling prediction and calculation of the sea surface motion state to obtain the optimal entry time and optimal entry attitude angle. The second module is used to combine the optimal water entry time and the optimal water entry attitude angle, and to perform power pre-adjustment and active buffering on the amphibious UAV to control the amphibious UAV to enter the sea surface smoothly. The third module is used to perform PID control based on the current pitch angle, roll angle and angular velocity of the amphibious UAV until it is fully in the sea. This generates a restoring torque and enables the amphibious UAV to move underwater with six degrees of freedom until it is fully in the sea.

[0015] The beneficial effects of the method and system of this invention are as follows: By hovering an amphibious UAV above the target sea area, constructing multi-source heterogeneous information and performing rolling prediction and calculation of the sea surface motion state, the optimal entry time and optimal entry attitude angle are obtained. This transforms the complex and random marine environment into a predictable and plannable controlled task, significantly reducing the impact risk of the entry process from the source. Furthermore, by combining the optimal entry time and optimal entry attitude angle with dynamic pre-adjustment and active buffering of the amphibious UAV, the system controls the amphibious UAV to smoothly enter the sea surface, coordinating the spatial position, speed, body attitude, and power system configuration to the optimal ready state. This creates the most favorable initial conditions for active buffering at the moment of water contact, and continuously monitors the impact attenuation index to generate an upward pulse thrust to offset part of the impact kinetic energy. When the vertical acceleration and attitude angular rate are both below the set threshold and remain stable, it is determined that active buffering is completed, and the UAV enters the water smoothly. Finally, until the amphibious UAV is fully in the sea, PID control is performed based on the current pitch angle, roll angle and angular velocity of the amphibious UAV to generate a restoring torque, realizing the underwater six-degree-of-freedom motion of the amphibious UAV. The controller unlocks the horizontal navigation degree of freedom, allowing underwater six-degree-of-freedom motion to be realized by coordinating the thrust vectors of the four tilt rotors. Attached Figure Description

[0016] Figure 1 This is a flowchart of the steps of the present invention for a smooth transition method for amphibious unmanned aerial vehicles entering water based on active suppression; Figure 2 This is a structural block diagram of the active suppression-based smooth water entry transition system for amphibious unmanned aerial vehicles (UAVs) of the present invention. Figure 3 This is a schematic diagram of the tilting unit structure provided in a specific embodiment of the present invention; Figure 4 This is a schematic diagram of surface navigation provided in a specific embodiment of the present invention; Figure 5 This is a schematic diagram of the multi-mode cross-medium motion control process provided in a specific embodiment of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0018] Reference Figure 1 and Figure 5 This invention provides a method for a smooth transition of an amphibious unmanned aerial vehicle (UAV) into water based on active suppression. The method includes the following steps: S100: Hover the amphibious UAV above the target sea area, construct multi-source heterogeneous information and perform rolling prediction and calculation of sea surface motion state to obtain the optimal entry time and optimal entry attitude angle. Specifically, the amphibious drone is hovered above the target sea area to acquire sea wave data, sea wind speed, wind direction and micro-motion information of the amphibious drone itself, and to construct multi-source heterogeneous information. A unified environmental situation map is generated based on multi-source heterogeneous information and calculated to obtain the dynamic environmental parameters of the current target sea area. The dynamic environmental parameters of the current target sea area include the effective wave height, wave period, wave propagation direction, wind speed, and wind direction. Based on a simplified wave motion model, the dynamic environmental parameters of the current target sea area are predicted in a rolling manner within a preset time to obtain the phase and local slope distribution of sea surface elevation changes. A comprehensive evaluation function is constructed, and an optimization search is performed within the prediction time window based on the phase and local slope distribution of sea surface elevation changes to obtain the optimal entry time point. The global wave surface slope of the sea surface corresponding to the optimal entry time point is obtained, and combined with the current yaw angle of the amphibious UAV, it is transformed to the body coordinate system through a rotation matrix for calculation to obtain the optimal entry attitude angle, which includes the target pitch angle and the target roll angle.

[0019] In this embodiment, once the UAV arrives above the predetermined water entry area and enters a stable hovering state, the system immediately initiates a high-precision environmental perception and intelligent decision-making process. The onboard sensor network begins to work collaboratively: external sensors detect waves in real time and generate corresponding wave data, while the inertial measurement unit and atmospheric data sensors synchronously collect wind speed, wind direction, and the UAV's own micro-motion information. The central controller integrates this multi-source heterogeneous information into a unified environmental situation map through a data fusion algorithm, and calculates the core dynamic parameters of the current water area in real time, including the effective wave height. Major wave cycles Wave propagation direction and wind speed and wind direction These parameters constitute the environment state vector at the current moment. This laid the data foundation for subsequent predictions and decision-making.

[0020] After acquiring real-time environmental information, the central controller initiates a wave prediction algorithm. This algorithm, based on a simplified wave motion model, uses the currently acquired wave characteristics as initial conditions to predict future waves. The system performs rolling predictions of water surface motion over a period of seconds (typically 3-5 seconds). The core of the prediction model is to calculate the phase and local slope of the water surface elevation change. Specifically, the system constructs a prediction model based on linear spectral theory, which characterizes the motion as a superposition of multiple simple harmonic waves. ; For the current moment By fitting parameters to the wavefront state estimated by sensor fusion, the model can extrapolate any future moment. water surface elevation wavefront slope and wave surface vertical velocity The wavefront slope is defined as follows: ; The controller performs an optimization search within the prediction time window, aiming to find an optimal water entry time. The selection criteria are based on an original comprehensive evaluation function. This function simultaneously quantifies two key indicators: wavefront flatness and the relative vertical velocity matching between the UAV and the wavefront. The comprehensive evaluation function is defined as follows: ; in, This is the predicted wavefront slope vector after coordinate transformation to the body coordinate system. It represents its Euclidean norm (i.e., the magnitude of the total slope); The vertical descent speed command (constant or slowly varying) for the drone. and These are normalized thresholds determined based on the structural strength and control performance of the machine body, representing the maximum permissible safe entry wave surface slope and the maximum permissible relative vertical velocity difference, respectively. and Let be the weighting coefficient, satisfying This is used to balance the relative importance of the two optimization objectives. The system solves this by... The optimal entry point was determined to minimize the impact risk. This optimization process ensured that the selected entry point was both a "window" when the wave surface was relatively flat and minimized the normal relative velocity of the UAV when it came into contact with the water surface.

[0021] After determining the optimal water entry time, the system further calculates the optimal water entry attitude angle that precisely matches it. The goal of attitude optimization is to ensure that the UAV body, especially its designed main water contact surface, is geometrically tangent to the local wave surface at the moment of contact, thereby achieving uniform load distribution and a smooth transition. Based on the predicted... Global wavefront slope at time t First, based on the current yaw angle of the drone Transform to the body coordinate system using a rotation matrix: ; in, This is the rotation matrix about the vertical axis. Then, the required target pitch angle is calculated using geometric relationships. and target roll angle : ; This embodiment incorporates environmental adaptability and fault tolerance mechanisms. When sensor data is abnormal or prediction confidence is insufficient, the system can automatically downgrade to a conservative strategy, such as selecting the nearest wave peak or trough as an alternative and adopting a preset safe attitude angle, thereby ensuring operational robustness under various uncertainties. Finally, this embodiment outputs a structured water entry decision command package, which precisely includes the optimal water entry time, target attitude angle sequence, and relevant expected environmental parameters. This command serves as the benchmark for all subsequent control actions and is sent to the flight control system via the bus, triggering a mode transition from hovering to controlled water entry. The entire environmental perception, prediction, and optimization decision-making process is typically completed within seconds, transforming the complex and random marine environment into a predictable and plannable controlled task, significantly reducing the impact risk of the water entry process from the source, and embodying the core idea of ​​the active suppression strategy of this invention.

[0022] The S200 combines the optimal water entry time and optimal water entry attitude angle, and performs dynamic pre-adjustment and active buffering on the air-sea amphibious UAV to control the air-sea amphibious UAV to smoothly enter the sea surface. Specifically, such as Figure 3 As shown, the system controls the amphibious drone to descend smoothly, adjusting its fuselage angle according to the optimal water entry attitude angle. Wave surface prediction information is introduced, and an altitude tracking error is defined to adjust the drone's total lift, controlling its descent to the critical altitude above the sea surface. Based on a smoothing function, the drone's robotic arm deflects horizontally according to a predetermined pattern and performs thrust compensation, controlling the drone to enter its optimal preparatory state. Based on this optimal preparatory state and the optimal water entry time, the drone's fuselage contacts the sea surface, entering impact suppression mode. A vertical acceleration error is defined, generating vertical acceleration and feeding it back to the drone's robotic arm to generate pulse thrust. Based on this generated pulse thrust, the drone's current pitch angle, roll angle, and angular velocity are obtained in real-time and differentially adjusted to ensure a smooth entry into the sea.

[0023] In this embodiment, when the UAV begins its operation based on the calculated optimal water entry plan, it enters the crucial descent and pre-adjustment phase. The controller first guides the UAV from a hovering state to a smooth descent along a preset trajectory, while simultaneously adjusting the fuselage angle to gradually approach the target pitch angle required for water entry. and roll angle To ensure the UAV can accurately track dynamic wavefronts, its altitude control loop incorporates wavefront prediction information, and the altitude tracking error is defined as: ; in This represents the current absolute altitude of the drone. The average still water level height, This is the predicted real-time wavefront elevation. The controller adjusts the total lift... To minimize this error, thereby ensuring the drone operates at the commanded speed Smoothly approaching the waves.

[0024] During the descent, when the altitude sensor detects that the drone has reached a preset critical altitude above the water surface... At this point, the system enters a more refined pre-adjustment phase of the power system. While maintaining a stable descent, the controller commands the robotic arms connected to the rotors to begin rotating synchronously, causing the rotation planes of all rotors to deflect from a vertical, upward position to a horizontal position according to a predetermined pattern. The deflection process follows a smoothing function: ; in, Prepare an angle for the target. The time constant is used to control the smoothness of the deflection. This deflection process causes a decrease in the vertical component of the rotor force, so the controller must synchronously increase the rotor speed for thrust compensation to ensure the total vertical thrust. Always matching the drone's gravity and descent acceleration requirements is a precise coordination process that requires real-time monitoring of altitude and attitude changes and dynamic adjustment of the power output of each rotor.

[0025] As the drone continued its descent and approached the water's surface, the system's preparations entered their final stage. The descent speed was further fine-tuned to ensure it matched the vertical velocity of the waves at the moment of impact. The aircraft's pitch and roll angles are finally calibrated. At this point, the rotors have rotated to the preset "preparatory angle," which allows them to provide sufficient vertical thrust for cushioning while also generating significant horizontal thrust and corrective torque. All rotor motors are maintained in a highly responsive standby state, ready to adjust power output rapidly and significantly upon command. Various sensors, especially the inertial measurement unit, prioritize their data update rate to the highest level, preparing for millisecond-level responses in the next stage of the impact detection procedure. The entire descent and pre-adjustment process is interconnected, with the core objective of coordinating the UAV's spatial position, speed, attitude, and power system configuration to an optimal standby state before it contacts the water, thereby creating the most favorable initial conditions for active cushioning at the moment of impact.

[0026] like Figure 4 As shown, once the contact between the UAV body and the water surface is detected by the triggering mechanism, the controller immediately enters the impact suppression mode. First, the controller instructs all rotor motors to increase their speed to peak value within a very short time, generating an upward pulse thrust to offset some of the impact kinetic energy. The vertical acceleration error is defined. The intensity of this pulse thrust is determined by the real-time feedback of vertical acceleration. Dynamic regulation, its control law can be expressed as: ; in, This is a preset safety acceleration threshold. The thrust output is designed to quickly converge the actual vertical acceleration to the target value, thereby smoothing out the impact load.

[0027] Meanwhile, the controller uses the pitch angle fed back in real time by the inertial measurement unit. Roll angle and angular velocity The data, through differential adjustment of the rotational speed and tilt angle of the front and rear, left and right rotors, generates a restoring torque opposite to the direction of the disturbance, suppressing the aircraft's attitude oscillations. Attitude stabilization control is achieved by calculating attitude errors. , ,based on The basic principle is to calculate the required corrective torque and then distribute it to each rotor actuator. For example, to compensate for a positive pitch angle error (nose pitching up), the control system will increase the thrust of the nose rotor or decrease its roll angle, and correspondingly decrease the thrust of the rear rotor or increase its roll angle, thereby generating a restoring torque that pushes the nose down. The entire process constitutes a fast closed-loop control based on real-time feedback from multiple sources. The system continuously monitors the impact attenuation indicators. When both the vertical acceleration and attitude angular rate are below the set thresholds and remain stable, the active buffering is considered complete, and then the system smoothly transitions to the control phase after full immersion.

[0028] The S300, until the amphibious UAV fully enters the sea surface, performs PID control based on the current pitch angle, roll angle and angular velocity of the amphibious UAV to generate restoring torque, thus realizing the underwater six-degree-of-freedom motion of the amphibious UAV.

[0029] In this embodiment, once the depth sensor confirms that the UAV is completely submerged in water, the central controller switches the system control mode from "water entry buffer mode" to "underwater stabilization mode." The core objective of this stage is to rapidly dissipate the residual kinetic energy and angular momentum from the water entry impact, allowing the aircraft to regain stability and complete the transition from aerial flight mechanism to underwater propulsion mechanism. In this mode, the left and right rotor arms have tilted to a near-horizontal position according to a preset program, forming the main horizontal thrusters. The controller immediately activates the pitch angle-based... Roll angle The PID (proportional-integral-derivative) control law, based on angular velocity feedback, differentially adjusts the rotational speeds of the left and right rotors to generate restoring torque, thereby rapidly suppressing attitude oscillations. The basic control variables are calculated as follows: ; in, For command torque, This represents the error between the current attitude angle and the target attitude angle (usually horizontal, i.e., 0°). This is the rate of change of error (i.e., angular velocity). and To control the gain, the command torque is mapped to the thrust difference between the left and right rotors through a control distribution algorithm. Meanwhile, the tilt angle and thrust of the front and rear rotors are used for depth control and fine-tuning of pitch attitude. The controller adjusts the vertical components of the front and rear rotors based on the depth error to achieve stable descent or depth maintenance.

[0030] The system continuously monitors the aircraft's angular velocity and rate of change of depth. When the pitch and roll angles stabilize within threshold ranges and the depth change tends to level off, it is determined to be in a "stable underwater hovering state." Subsequently, the controller unlocks the horizontal navigation degree of freedom, allowing for six-degree-of-freedom underwater motion by coordinating the thrust vectors of the four tilt rotors. At this point, the UAV has successfully transitioned into a fully controlled underwater vehicle, laying the foundation for subsequent underwater operations.

[0031] Furthermore, it should be noted that the dynamic model of the cross-shaped tilt-coaxial dual-propeller propulsion system upon which the UAV in this embodiment relies is the basis for achieving coordinated control in different media. This model can be described as follows: ; In the above formula, It is the total lift control input. It is the roll control input. It is the pitch control input. It is the yaw control input; , , and Each rotor generates lift; , and These are roll angle, pitch angle, and yaw angle, respectively. , and These represent the accelerations of the drone along each axis. , and These represent the moments of inertia of each axis of the machine body. Indicates the quality of the drone. Represents gravitational acceleration. This indicates the distance from the center of the drone to the center of each propeller. , and These represent the three translational air drag coefficients. , and These represent the air resistance torque coefficients for the three rotations.

[0032] During the flight phase, all four rotor arms remain in a vertical position, and the rotation planes of all rotors are in a horizontal state, just like a traditional multi-rotor aircraft. Attitude control is achieved by adjusting the rotation speed of each rotor to generate differential torque, and vertical altitude is controlled by changing the total thrust, thereby completing stable hovering, cruising and maneuvering.

[0033] As the drone enters the water entry transition phase, a crucial shift occurs in the system's control strategy. Based on the optimal water entry time and angle, the controller instructs the four rotors to begin synchronous or differential tilting, at which point the rotor thrust vector direction changes accordingly. This process is precisely controlled: in the final stage of descent, while providing some vertical lift to cushion the descent speed, the rotors begin to generate a horizontal component in their thrust vector. This component precisely counteracts attitude disturbances caused by wind or the drone's own minor movements, providing multi-dimensional force and torque guarantees for a smooth water entry.

[0034] At the moment of water contact and during the subsequent active buffering phase, the rotor response reaches its peak, the motor is driven to peak power output, and by rapidly adjusting the thrust magnitude and vector direction of each rotor, a powerful upward pulse force is generated to offset the impact, and a precise corrective torque is generated to suppress the pitch and roll oscillations of the fuselage, demonstrating the system's rapid response and precise distribution capability under transient high-intensity loads.

[0035] Once the drone enters the surface or underwater navigation phase, the versatility of this propulsion system is fully demonstrated. For surface navigation, the controller adjusts the front and rear rotors to a smaller tilt angle, ensuring that their thrust primarily provides buoyancy to maintain waterline stability. Simultaneously, the left and right rotors are tilted to near-horizontal positions, making their rotors the primary surface thrusters. Forward, backward, and turning are achieved by coordinating the left and right thrust. When the drone is fully submerged and enters underwater navigation mode, all four rotors are treated as independent vector thrusters. Based on an underwater six-degree-of-freedom motion model, the controller uses a control distribution algorithm to calculate the target rotational speed and tilt angle for each rotor based on the desired resultant force and torque commands. For example, to achieve horizontal forward movement, the system can coordinate all four rotors to generate forward thrust components; for depth control or pitch adjustment, the difference in the vertical thrust components of the front and rear rotors is primarily utilized; roll and yaw control are achieved through thrust differential or vector direction differential between the left and right rotors. The entire switching process is automatically determined and seamlessly connected by the central controller based on data from the depth sensor and inertial unit. The control parameters between each mode transition smoothly, avoiding sudden changes in power output, thereby ensuring the overall stability and maneuverability of the UAV during complex crossings of the air and sea interfaces.

[0036] In addition, after each water entry mission is completed, the system automatically packages and transmits the entire process data of the mission to the ground station. This data package contains the environmental state vector at the beginning of the mission. The optimal water entry time point obtained by calculation and target attitude angle and Measured vertical impact acceleration at the moment of water contact The time history curve, and the convergence time required for the body to reach a stable underwater state. .

[0037] The ground station's analysis system uses accumulated historical mission data to iteratively optimize key model parameters and control law gains. First, for the wave prediction model, it minimizes the predicted wavefront elevation. Compared with the actual wavefront elevation estimated during the mission inversion To correct the model parameters based on the error between them. Its optimization objective can be expressed as: ; Secondly, the gain of the proportional-derivative controller in the active buffer control loop is optimized. This control law aims to output buffering force. To track target acceleration. The optimization algorithm uses comprehensive performance metrics obtained from historical tasks. The objective function is a weighted index composed of peak impact acceleration and settling time. This index is solved using the gradient descent method. Minimize the next generation gain parameter and Its update rules follow ,in This is the learning rate.

[0038] After extensive data training and verification, a set of system parameters optimized for different sea state characteristics was formed. When the UAV performs a mission again, the central controller can match and load the optimal parameter set from this parameter library based on real-time perceived environmental information. This enables the system to learn from experience and adapt to complex and ever-changing marine environments, realizing the continuous evolution and self-optimization of the water entry control performance of this invention.

[0039] Reference Figure 2 A water entry smooth transition system for amphibious unmanned aerial vehicles (UAVs) based on active suppression includes: The first module 201 is used to hover the air-sea amphibious UAV above the target sea area, construct multi-source heterogeneous information and perform rolling prediction and calculation of sea surface motion state to obtain the optimal entry time and optimal entry attitude angle. The second module 202 is used to combine the optimal water entry time and the optimal water entry attitude angle, and to perform dynamic pre-adjustment and active buffering of the air-sea amphibious UAV to control the air-sea amphibious UAV to enter the sea surface smoothly. The third module 203 is used to perform PID control based on the current pitch angle, roll angle and angular velocity of the amphibious UAV until it is fully in the sea surface, generate restoring torque, and realize the underwater six-degree-of-freedom motion of the amphibious UAV.

[0040] The content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0041] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for smooth water entry transition of amphibious unmanned aerial vehicles (UAVs) based on active suppression, characterized in that, Includes the following steps: The amphibious drone is hovered above the target sea area to construct multi-source heterogeneous information and perform rolling prediction and calculation of the sea surface motion state to obtain the optimal entry time and optimal entry attitude angle. By combining the optimal water entry time and optimal water entry attitude angle, and by performing power pre-adjustment and active buffering on the amphibious UAV, the amphibious UAV can be controlled to smoothly enter the sea surface. Until the amphibious drone fully enters the sea surface, PID control is performed based on the current pitch angle, roll angle and angular velocity of the amphibious drone to generate restoring torque and realize the underwater six-degree-of-freedom motion of the amphibious drone.

2. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 1, characterized in that, The step of hovering the amphibious UAV above the target sea area, constructing multi-source heterogeneous information, and performing rolling prediction and calculation of sea surface motion state to obtain the optimal entry time and optimal entry attitude angle specifically includes: The amphibious drone is hovered above the target sea area to acquire sea wave data, sea wind speed, wind direction and micro-motion information of the amphibious drone itself, and to construct multi-source heterogeneous information. A unified environmental situation map is generated based on multi-source heterogeneous information and then calculated to obtain the dynamic environmental parameters of the current target sea area. The dynamic environmental parameters of the current target sea area include the effective wave height, wave period, wave propagation direction, wind speed, and wind direction. Based on a simplified wave motion model, the dynamic environmental parameters of the current target sea area are predicted in a rolling manner within a preset time period to obtain the phase and local slope distribution of sea surface elevation changes. A comprehensive evaluation function is constructed, and an optimization search is performed within the prediction time window based on the phase and local slope distribution of sea surface elevation changes to obtain the optimal entry time point. The global wave slope of the sea surface corresponding to the optimal entry time is obtained. Combined with the current yaw angle of the amphibious UAV, the optimal entry attitude angle is obtained by transforming it to the body coordinate system through a rotation matrix. The optimal entry attitude angle includes the target pitch angle and the target roll angle.

3. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 2, characterized in that, The expression for the comprehensive evaluation function is as follows: ； In the above formula, This represents the comprehensive evaluation function. This represents the predicted wavefront slope vector after coordinate transformation to the body coordinate system. Describes the Euclidean norm. This indicates the vertical descent speed command for the drone. and These represent normalized thresholds determined based on the structural strength and control performance of the aircraft, respectively representing the maximum permissible safe entry wavefront slope and the maximum permissible relative vertical velocity difference. and Indicates the weighting coefficient. This indicates the vertical velocity of the drone under the influence of waves.

4. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 3, characterized in that, The specific expression for calculating the optimal entry attitude angle is as follows: ； In the above formula, Indicates the target pitch angle. Indicates the target roll angle. This represents the slope of the local wavefront along the X-axis in the UAV's body coordinate system. This represents the slope of the local wavefront along the Y-axis in the UAV's body coordinate system. This represents the arctangent function.

5. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 4, characterized in that, The step of combining the optimal water entry time and optimal water entry attitude angle, and performing dynamic pre-adjustment and active buffering on the amphibious UAV to control its smooth entry into the sea surface, specifically includes: Control the amphibious drone to descend smoothly, and adjust the fuselage angle of the amphibious drone according to the optimal water entry attitude angle; By introducing wavefront prediction information, the altitude tracking error is defined to adjust the total lift of the air-sea amphibious UAV, thereby controlling the air-sea amphibious UAV to descend to the critical altitude above the sea surface. According to the smoothing function, the robotic arm of the amphibious drone deflects horizontally according to a predetermined law and performs thrust compensation, controlling the amphibious drone to enter the best ready state. Based on the optimal readiness state of the amphibious drone, and combined with the optimal water entry time, the drone body is controlled to make contact with the sea surface and enter the impact suppression mode. Define the vertical acceleration error, generate the vertical acceleration and feed it back to the robotic arm of the amphibious UAV to generate pulse thrust; Based on the generated pulse thrust, the current pitch angle, roll angle and angular velocity of the amphibious UAV are obtained in real time, and differential adjustment is performed to control the amphibious UAV to enter the sea surface smoothly.

6. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 5, characterized in that, It also includes the fact that the amphibious unmanned aerial vehicle has a cross-shaped tilt-coaxial dual-propeller propulsion system, the specific expression of which is shown below: ； In the above formula, This represents the total lift control input for an amphibious unmanned aerial vehicle (UAV). This represents the roll control input for amphibious unmanned aerial vehicles (UAVs). This represents the pitch control input for an amphibious unmanned aerial vehicle (UAV). This represents the yaw control input for an amphibious unmanned aerial vehicle (UAV). , and These represent the roll angle, pitch angle, and yaw angle, respectively. , and These represent the accelerations of the drone along each axis. , and These represent the moments of inertia of each axis of the machine body. Indicates the quality of the drone. Represents gravitational acceleration. This indicates the distance from the center of the drone to the center of each propeller. , and These represent the three translational air drag coefficients. , and These represent the air resistance torque coefficients for the three rotations.

7. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 6, characterized in that, It also includes modifying the parameters of the simplified wave motion model and the parameters of the PID control based on the dynamic environmental parameters of the current target sea area, the optimal entry time, the optimal entry attitude angle, the vertical acceleration, and the convergence time required to control the amphibious UAV to a stable state.

8. The method for smooth water entry transition of an air-sea amphibious unmanned aerial vehicle based on active suppression according to claim 7, characterized in that, The modified expressions for the parameters of the simplified wave motion model are as follows: ； In the above formula, These represent the parameters of the modified, simplified wave motion model. Indicates the predicted wavefront elevation. Indicates the actual wavefront elevation. These represent the parameters of the initial simplified wave motion model. Indicates the first Each sampling time, Indicates the sequence number of the sampling point.

9. A smooth water entry transition system for amphibious unmanned aerial vehicles (UAVs) based on active suppression, characterized in that: Includes the following modules: The first module is used to hover the amphibious UAV above the target sea area, construct multi-source heterogeneous information and perform rolling prediction and calculation of the sea surface motion state to obtain the optimal entry time and optimal entry attitude angle. The second module is used to combine the optimal water entry time and the optimal water entry attitude angle, and to perform power pre-adjustment and active buffering on the amphibious UAV to control the amphibious UAV to enter the sea surface smoothly. The third module is used to perform PID control based on the current pitch angle, roll angle and angular velocity of the amphibious UAV until it is fully in the sea. This generates a restoring torque and enables the amphibious UAV to move underwater with six degrees of freedom until it is fully in the sea.

Images