Cross-medium unmanned aerial vehicle and PID control method thereof

Abstract

The invention discloses a cross-medium unmanned aerial vehicle and a PID control method thereof, realizes adaptive closed-loop control of the cross-medium unmanned aerial vehicle, and effectively solves the problem of control failure caused by environment switching. Compared with a traditional method, fault tolerance can be completed without sacrificing the degree of freedom of flight, and task execution continuity is ensured; and meanwhile, by dynamically matching control parameters of underwater high-resistance and overwater low-resistance environments, the motor overload risk and mechanical loss are remarkably reduced, the service life of equipment in a corrosive environment is prolonged, and thus the reliability and adaptability of the cross-medium unmanned aerial vehicle in a complex task scene are integrally improved.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicles (UAVs), and more particularly to a cross-media UAV and its PID control method. Background Technology

[0002] AAVs (autonomous aerial vehicles) can perform three-dimensional missions across air and water environments, making them valuable for applications in marine exploration, emergency rescue, and military reconnaissance. However, AAVs must overcome the challenges of two-fluid media (air / water) with significant density differences and complex environmental interference (such as wind, waves, and ocean currents). This leads to frequent propeller water-bumping during entry and exit from the water, accelerating motor and blade wear and even causing mechanical failures. Furthermore, the high drag of the underwater environment can easily cause motor overload, and salt corrosion or foreign object entanglement can also lead to rotor failure, seriously threatening the stability and mission reliability of the vehicle.

[0003] The core problem with existing technologies is: Structural limitations: Traditional quadcopters cannot dynamically adjust the rotor angle, making it difficult to reconfigure the thrust distribution after a failure; Insufficient control strategies: Existing fault-tolerant methods rely on sacrificing degrees of freedom (such as yaw angle), which limits mission execution capabilities; Poor cross-medium adaptability: The impact of high underwater resistance and corrosive environment on motor life is not comprehensively considered, resulting in a high risk of failure. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies, such as structural limitations, insufficient control strategies, and poor cross-media adaptability.

[0005] In a first aspect, the present invention provides a cross-media unmanned aerial vehicle, comprising: The drive mechanism includes a servo motor, a motor, a rotor, and a motor mount. The motor is mounted on the motor mount. The output end of the servo motor is equipped with a pull rod, which is connected to the motor mount. The motor is connected to the rotor drive. The body is equipped with a cross-shaped support arm. The four ends of the support arm have a first mounting position, a second mounting position, a third mounting position, and a fourth mounting position, respectively. The first mounting position and the third mounting position are coaxially and centrally symmetrical, and the second mounting position and the fourth mounting position are coaxially and centrally symmetrical. The first mounting position, the second mounting position, the third mounting position, and the fourth mounting position are respectively equipped with a drive mechanism. The body is also equipped with a depth sensor, an inertial measurement unit, and a PID controller.

[0006] Optionally, a buoyancy component is provided at the top of the support arm, and a depth sensor, an inertial measurement unit, and a PID controller are installed inside the buoyancy component.

[0007] Optionally, a positioning module is provided on the top of the buoyancy component.

[0008] Optionally, a bracket is provided at the bottom of the support arm, and a power supply module and a camera module are provided on the bracket.

[0009] Secondly, the present invention provides a PID control method for cross-media unmanned aerial vehicles, comprising the following steps: The operating environment of cross-media UAVs is analyzed through depth sensors, including underwater and surface operations. The angular velocity and linear velocity of the cross-medium unmanned aerial vehicle are obtained by inertial measurement unit. A mathematical model of the cross-medium unmanned aerial vehicle is established based on the angular velocity and linear velocity. The operation mode of the cross-medium unmanned aerial vehicle is determined based on the mathematical model. The operation mode includes normal operation mode and fault operation mode. The PID controller outputs a corresponding control strategy based on the operating environment and operating mode, and adjusts the motion attitude of the cross-media UAV based on the control strategy.

[0010] Optionally, the PID controller outputs a control strategy based on preset PID parameters, wherein the PID parameters are dynamically adjusted based on the operating environment and operating mode.

[0011] Optionally, if the fault mode is complete failure of a single rotor, the PID controller generates a control strategy for complete failure of a single rotor based on the first control allocation matrix.

[0012] Optionally, if the fault mode is complete failure of both rotors, the PID controller generates a control strategy for the fault mode of complete failure of both rotors based on the second control allocation matrix.

[0013] Optionally, the degree of drive mechanism failure can be determined by introducing a rotor output attenuation coefficient. The degree of drive mechanism failure includes insufficient power and complete failure. If the attenuation coefficient is greater than 1, it is determined that the drive mechanism has insufficient power; when the attenuation coefficient is equal to 1, it is determined that the drive mechanism has completely failed.

[0014] Optionally, if the fault mode is insufficient power of a single rotor, the PID controller generates a control strategy based on the third control allocation matrix for the fault mode of complete failure of a single rotor.

[0015] The beneficial effects of this invention are as follows: The cross-medium UAV of this application achieves dynamic adjustment of the rotor angle through a tiltable drive mechanism, effectively solving the problem of traditional quadcopters' difficulty in reconstructing thrust distribution after a failure. The cross-shaped symmetrical support arm design ensures structural stability and thrust balance. Combined with a depth sensor, inertial measurement unit, and PID controller, it can accurately perceive the operating environment and motion state, and output adaptive control strategies, thereby avoiding the sacrifice of degrees of freedom and significantly improving the attitude control accuracy, fault tolerance, and overall operational reliability of the UAV in complex cross-medium environments. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 These are schematic diagrams of the cross-media UAV in some embodiments; Figure 2 yes Figure 1 Enlarged view of section A in the middle; Figure 3 These are system block diagrams from some embodiments; Figure 4 This is a simulation control response curve of cross-medium motion of a cross-medium UAV during normal operation (a attitude angle, b servo tilt angle). Figure 5 This is a simulation control response curve of cross-medium motion of a cross-medium UAV when the single rotor fails completely (a attitude angle, b servo tilt angle). Figure 6 This is a simulation control response curve of cross-medium motion of a cross-medium UAV when the dual rotors completely fail (a attitude angle, b servo tilt angle). Figure 7 These are experimental data diagrams of cross-medium motion of a cross-medium UAV during normal operation (a. attitude angle, b. servo tilt angle). Figure 8 This is a diagram of cross-medium motion experimental data of a cross-medium UAV when the single rotor completely fails (a attitude angle, b servo tilt angle). Figure 9 This is a diagram of cross-medium motion experimental data of a cross-medium UAV when the dual rotors completely fail (a. attitude angle, b. servo tilt angle).

[0018] Figure 10 These are experimental data of the cross-medium motion of a cross-medium UAV when the dual rotors completely fail (a, d spatial trajectories (zx plane), b, e attitude response curves).

[0019] Explanation of reference numerals in the attached figures: 1. Drive mechanism; 101. Servo motor; 102. Motor; 103. Rotor; 104. Motor mount; 105. Tie rod; 2. Airframe; 201. Support arm; 202. First mounting position; 203. Second mounting position; 204. Third mounting position; 205. Fourth mounting position; 206. Buoyancy component; 207. Positioning module; 208. Bracket; 209. Power supply module; 210. Camera module. Detailed Implementation

[0020] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.

[0021] This invention provides a cross-media unmanned aerial vehicle, comprising: The drive mechanism 1 includes a servo motor 101, a motor 102, a rotor 103, and a motor 102 mount. The motor 102 is mounted on the motor 102 mount. The output end of the servo motor 101 is provided with a pull rod 105, which is connected to the motor 102 mount. The motor 102 is connected to the rotor 103 in a transmission connection. The body 2 is provided with a cross-shaped support arm 201. The four ends of the support arm 201 have a first mounting position 202, a second mounting position 203, a third mounting position 204, and a fourth mounting position 205, respectively. The first mounting position 202 and the third mounting position 204 are coaxially and centrally symmetrical, and the second mounting position 203 and the fourth mounting position 205 are coaxially and centrally symmetrical. The first mounting position 202, the second mounting position 203, the third mounting position 204, and the fourth mounting position 205 are respectively provided with a drive mechanism 1. The body 2 is also provided with a depth sensor (not shown in the figure), an inertial measurement unit (not shown in the figure), and a PID controller (not shown in the figure).

[0022] Among them, the PID controller refers to a feedback controller widely used in industrial control, which adjusts the control output based on the proportional, integral, and derivative terms of the error signal. In this application, it is used to output a control strategy based on the operating environment and operating mode to adjust the motion attitude of the cross-medium UAV. The depth sensor is a device used to measure the current depth of the medium in which the cross-medium UAV is located (e.g., underwater depth). Its output data can be used to determine the operating environment of the UAV (above or below water) and provide environmental parameters for the control system. The depth sensor data is denoted as , indicating that at that time, the cross-medium UAV is either above the water surface or flying in the air; conversely, at that time, the cross-medium UAV is underwater or operating underwater. By utilizing different values, the cross-medium UAV can intelligently select between underwater and airborne motion modes. The inertial measurement unit (IMU) is a device integrating sensors such as accelerometers and gyroscopes. It is used to measure the angular velocity, linear velocity, and attitude information of the cross-medium UAV, providing basic data for establishing the mathematical model of the UAV and determining the operating mode.

[0023] In implementation, the drive mechanism 1 is the core component for realizing the movement of the UAV across media. The drive mechanism 1 may include a motor 102, a rotor 103, and a motor 102 mount. The motor 102 is directly fixed to the motor 102 mount and drives the rotor 103 to rotate via a transmission mechanism to generate thrust. The motor 102 mount is directly mounted to the support arm 201 via a fixed connector. In this configuration, the direction of thrust is fixed, and the magnitude of thrust is mainly adjusted by changing the rotor 103 speed. However, to achieve dynamic adjustment of the thrust direction, the drive mechanism 1 can further incorporate a servo motor 101 and a lever 105. Specifically, the servo motor 101 can be configured to connect a lever 105 via its output end, the other end of which is connected to the motor 102 mount. The motor 102 mount and the support arm 201 can be rotatably connected. Therefore, the servo motor 101, through the push-pull action of the lever 105, can tilt the motor 102 mount along with the motor 102 and the rotor 103, thereby changing the direction of the thrust generated by the rotor 103. The fuselage 2 is the carrier platform for the cross-medium UAV, and its structural design is crucial to the stability of the UAV. The fuselage 2 is equipped with a cross-shaped support arm 201, which provides good symmetry and stability. The four ends of the support arm 201 are respectively provided with a first mounting position 202, a second mounting position 203, a third mounting position 204, and a fourth mounting position 205. These mounting positions are designed to fix the drive mechanism 1. To ensure the balance and uniform thrust distribution of the UAV during movement, the first mounting position 202 and the third mounting position 204 are configured coaxially and centrally symmetrically, while the second mounting position 203 and the fourth mounting position 205 are also configured coaxially and centrally symmetrically. This means that the two opposite mounting positions are on the same axis and are centrally symmetrical with respect to the fuselage 2. For example, holes or connecting seats for mounting drive mechanisms 1 can be reserved at the four ends of the cross-shaped support arm 201. The position and orientation of these holes or connecting seats are precisely calculated to ensure that the four drive mechanisms 1 can be evenly distributed and generate balanced thrust. Each mounting position is equipped with the aforementioned drive mechanism 1, thus forming a cross-shaped quadcopter 103 layout. The symmetrical diagonal wheel track design achieves structural stability and also provides a physical basis for PID control.

[0024] To achieve intelligent control and environmental adaptability for cross-medium UAVs, the airframe 2 integrates various sensors and control units. Specifically, the airframe 2 may be equipped with a depth sensor for real-time monitoring of the UAV's depth. For example, when the UAV is operating underwater, the depth sensor can provide accurate water depth data, allowing the control system to determine the current environment. Furthermore, the airframe 2 also includes an inertial measurement unit (IMU), which acquires kinematic parameters such as the UAV's angular velocity and linear velocity. The IMU can be a combination of a three-axis accelerometer and a three-axis gyroscope, whose data is used to perceive the UAV's attitude and motion state in real time. Based on this sensor data, the airframe 2 is also equipped with a PID controller. The PID controller can be an embedded processor or microcontroller running a PID control algorithm. This controller receives data from the depth sensor and the IMU and, according to preset control logic, outputs commands to adjust the operating state of the drive mechanism 1, thereby achieving precise control of the UAV's motion attitude. For example, the PID controller can determine that the UAV is in an underwater environment based on the data from the depth sensor, and calculate the required thrust adjustment based on the attitude data from the inertial measurement unit. Then, it sends these adjustments to the servo motors 101 and motors 102 of each drive mechanism 1 to maintain or change the attitude of the UAV.

[0025] Specifically, the support arm 201 includes a central frame and four branch arms. The four branch arms are mounted around the sides of the central frame, forming a cross-shaped support arm 201 together with the central frame. In some cases, the branch arms and the central frame can also be integrally formed. Further, each branch arm consists of two horizontal plates, which are spaced apart and mounted on the central frame. A connecting rod and a crossbeam are provided between the two horizontal plates. The servo motor 101 is fixed under the crossbeam. The motor 102 base includes a fixed base and a rotating base. The fixed base is fixed to the connecting rod, and the rotating base is rotatably connected to the fixed base. Specifically, the fixed base has a rotating shaft that passes through the rotating base, allowing the rotating base to rotate on the fixed base. The motor 102 is mounted on the rotating base. The output end of the servo motor 101 has a rudder head. The pull rod 105 is a ball joint pull rod 105. Ball joint pull rods 105 are provided at both ends of the rudder head, and the ball joint pull rods 105 at both ends of the rudder head are respectively connected to both sides of the motor 102 base. The rudder head is driven by the servo motor 101, and the rudder head pulls the rotating seat to tilt on the fixed seat via the ball joint rod 105. The rotating seat causes the rotor 103 to tilt.

[0026] This application's cross-medium UAV achieves dynamic adjustment of the rotor angle 103 through a tiltable drive mechanism 1, effectively solving the problem of difficulty in reconstructing thrust distribution after a failure in traditional quadcopters 103. The cross-shaped symmetrical support arm 201 ensures structural stability and thrust balance. Combined with a depth sensor, inertial measurement unit, and PID controller, it can accurately perceive the operating environment and motion state, and output adaptive control strategies, thereby avoiding the sacrifice of degrees of freedom and significantly improving the attitude control accuracy, fault tolerance, and overall operational reliability of the UAV in complex cross-medium environments.

[0027] In some embodiments, a buoyancy member 206 is provided at the top of the support arm 201, and a depth sensor, an inertial measurement unit, and a PID controller are installed inside the buoyancy member 206.

[0028] The buoyancy component 206 is a part used to provide additional buoyancy. Its main function is to increase the buoyancy of the cross-medium UAV in water, thereby effectively preventing the UAV from sinking when entering or operating on the water surface, and improving its stability during the transition between water surface and underwater. Specifically, the buoyancy component 206 can adopt a hollow structure, filled with air or other lightweight gases, utilizing the density difference between gas and water to generate buoyancy. Alternatively, the buoyancy component 206 can also be made of low-density materials, such as lightweight foamed materials like polystyrene foam or polyurethane foam, or lightweight composite materials, using the low-density characteristics of the materials themselves to provide buoyancy. Furthermore, the buoyancy component 206 can be designed as an inflatable / deflatable airbag structure, dynamically adjusting the required buoyancy of the UAV by controlling the inflation amount of the airbag to adapt to different cross-medium operation requirements.

[0029] By installing a buoyancy component 206 at the top of the support arm 201, the buoyancy component 206 provides additional buoyancy support for the cross-medium UAV, significantly enhancing the stability of the UAV during the surface or water entry phases. This effectively avoids sinking or violent splashing due to insufficient buoyancy, thus ensuring the UAV can successfully complete cross-medium transitions. Simultaneously, the depth sensor, inertial measurement unit, and PID controller are installed inside the buoyancy component 206, utilizing its structure to physically isolate and protect these critical electronic modules. This design effectively prevents damage to the electronic modules from complex environmental factors such as water immersion, salt corrosion, and foreign object entanglement, ensuring reliable and stable operation in high-resistance, high-corrosion underwater environments. This not only improves the protection level and service life of the UAV's core electronic components but also greatly enhances the overall reliability and mission execution capability of the cross-medium UAV in complex mission environments.

[0030] Specifically, the support arm 201 includes a central structure and four branch arms. There are four partition plates between each pair of branch arms. Each partition plate has a support column, and a support platform is provided on the support column. The buoyancy component 206 is set on the support platform. The buoyancy component 206 is composed of a buoyancy shell filled with buoyancy material. The buoyancy shell adopts a combination design of a bottom polyhedron and a top streamlined shape. It contains a specific volume of buoyancy material. The optimized configuration of the center of buoyancy (B) being higher than the center of gravity (G) ensures the attitude stability during cross-medium switching.

[0031] In some embodiments, the top of the buoyancy member 206 is provided with a positioning module 207.

[0032] The positioning module 207 is a device used to acquire information such as the position, velocity, and attitude of a cross-media UAV in three-dimensional space. Specifically, the positioning module 207 can employ a Global Navigation Satellite System (GNSS) receiver, such as GPS, BeiDou, or GLONASS systems, to calculate the UAV's real-time position by receiving satellite signals.

[0033] The buoyancy component 206 has a positioning module 207 on its top, meaning the positioning module 207 is installed at the highest point or on the upper surface of the buoyancy component 206. This can be achieved by directly integrating the positioning module 207 onto the top surface of the buoyancy component 206, or by designing a dedicated bracket 208 or mounting base to securely fix it to the top of the buoyancy component 206. In some embodiments, a telescopic or foldable structure can also be used, allowing the positioning module 207 to adjust its height in different media to optimize signal reception.

[0034] By employing the aforementioned technical solution, placing the positioning module 207 atop the buoyancy component 206 significantly improves the navigation accuracy and mission reliability of cross-medium UAVs in complex environments. Specifically, when the UAV is in the air, the positioning module 207, positioned atop the buoyancy component 206, effectively reduces the obstruction of global navigation satellite signals by the airframe structure, thereby improving signal reception quality and positioning accuracy. When the UAV is underwater, the buoyancy component 206 is typically located on the upper part of the UAV. Placing the positioning module 207 at the top, as close to the water surface as possible, or exposing it first upon exiting the water, facilitates rapid acquisition of positioning signals and reduces signal attenuation and interference from water, especially beneficial for positioning systems reliant on radio waves. During cross-medium entry and exit from water, the positioning module 207 can switch from one medium environment to another more quickly, providing continuous and stable positioning data to assist the UAV in achieving a smooth transition.

[0035] In some embodiments, the support arm 201 has a bracket 208 at its bottom, and the bracket 208 has a power supply module 209 and a camera module 210.

[0036] Specifically, the bracket 208 is a structural component used to support, fix, or connect other parts. Its main function is to provide a stable mounting platform for the power supply module 209 and the camera module 210, and to provide protection for these modules by utilizing their position and structural characteristics. The bracket 208 can be made of lightweight, high-strength materials (such as carbon fiber composites, high-strength engineering plastics, or corrosion-resistant aluminum alloys) to withstand corrosion and impact in cross-medium environments.

[0037] The power supply module 209 is a unit that provides the necessary electrical energy to the various components of the UAV, ensuring a continuous power supply for the UAV's operation both on and underwater. The power supply module 209 may include a high-energy-density battery pack, equipped with a waterproof sealed housing and overcharge / over-discharge protection circuitry. To optimize energy efficiency and extend flight time, the power supply module 209 may also integrate a power management unit (PMU) responsible for battery charge / discharge management, voltage conversion, and current distribution. Furthermore, the power supply module 209 can be designed as a modular, replaceable battery pack for easy replacement and mission deployment.

[0038] The camera module 210 is a device for capturing image or video data, providing visual information for environmental perception, target recognition, navigation assistance, or task recording. The camera module 210 can employ a high-resolution, low-light CMOS sensor and be equipped with a wide-angle or zoom lens to adapt to different lighting and observation requirements. To ensure normal operation in underwater environments, the camera module 210 should possess good waterproof, fog-proof, and pressure-resistant properties. Furthermore, the camera module 210 can integrate an image stabilization system (e.g., optical image stabilization or electronic image stabilization) to obtain clear and stable images.

[0039] Through the above technical solution, a bracket 208 is set at the bottom of the support arm 201, and a power supply module 209 and a camera module 210 are installed thereon, effectively solving the problem of module damage in cross-medium environments. Specifically, the bracket 208 is set at the bottom of the support arm 201. Utilizing the structural stability of the support arm 201, the bracket 208 is placed away from direct environmental exposure, reducing the risk of water immersion and corrosion. The power supply module 209 is set on the bracket 208. Based on the fixed support of the bracket 208, a continuous and reliable power supply is ensured, avoiding power outages caused by environmental factors. The camera module 210 is set on the bracket 208. Combined with the installation method of the bracket 208, the monitoring perspective is ensured to be stable and the equipment is protected from physical damage, thereby improving the adaptability and functional integrity of the UAV in complex media.

[0040] This invention provides a PID control method for a cross-media unmanned aerial vehicle (UAV), comprising the following steps: The operating environment of cross-media UAVs is analyzed through depth sensors, including underwater and surface operations. The angular velocity and linear velocity of the cross-medium unmanned aerial vehicle are obtained by inertial measurement unit. A mathematical model of the cross-medium unmanned aerial vehicle is established based on the angular velocity and linear velocity. The operation mode of the cross-medium unmanned aerial vehicle is determined based on the mathematical model. The operation mode includes normal operation mode and fault operation mode. The PID controller outputs a corresponding control strategy based on the operating environment and operating mode, and adjusts the motion attitude of the cross-media UAV based on the control strategy.

[0041] Specifically, this method first uses a depth sensor to monitor the depth information of the UAV's location in real time, thereby accurately distinguishing between underwater and surface operating environments. Since the underwater environment has significantly high drag characteristics, while the surface environment is mainly affected by aerodynamics, environmental identification is the foundation for implementing differentiated control strategies. The depth sensor continuously outputs depth data; when the detected depth value exceeds a preset threshold, it is determined to be an underwater operating environment; otherwise, it is determined to be a surface operating environment, providing key environmental parameters for subsequent control decisions.

[0042] Furthermore, angular velocity and linear velocity data of the unmanned vehicle operating across media are collected by an inertial measurement unit (IMU), and a dynamic mathematical model for the unmanned vehicle operating across media is established based on these real-time motion parameters. This mathematical model comprehensively considers the influence of medium characteristics on kinematics, such as the difference between the fluid drag coefficient in an underwater environment and the aerodynamic parameters in an above-water environment. Based on the output of the mathematical model, the system can accurately determine the current operating mode, which includes normal operating mode and fault operating mode. Specifically, when the IMU detects abnormal fluctuations in angular velocity or linear velocity (such as a sudden drop in rotor speed or attitude angle deviation exceeding the tolerance range), the mathematical model identifies it as a fault operating mode and locates the fault type (such as motor overload or rotor entanglement).

[0043] Based on this, the PID controller integrates environmental information and operating modes to dynamically generate and output corresponding control strategies. These strategies adjust the thrust distribution and attitude control parameters of each rotor in real time, taking into account the current environmental state (underwater or above water) and operating mode (normal or fault). For example, in an underwater fault operating mode, the PID controller compensates for the loss of the failed rotor by increasing the thrust output of the healthy rotor and optimizing the thrust direction, while avoiding sacrificing yaw freedom. In a normal above-water operating mode, the controller adjusts the control gain based on aerodynamic characteristics to ensure attitude stability. Ultimately, commands based on the control strategy drive the actuators to adjust the motion attitude of the cross-medium UAV, achieving smooth transition and precise control.

[0044] Through the above technical solution, this application achieves adaptive closed-loop control for cross-medium UAVs, effectively solving the control failure problem caused by environmental switching. Compared with traditional methods, this solution can achieve fault tolerance without sacrificing flight degrees of freedom, ensuring the continuity of mission execution. At the same time, by dynamically matching control parameters between underwater high-resistance and surface low-resistance environments, it significantly reduces the risk of motor overload and mechanical wear, extends the service life of equipment in corrosive environments, and thus improves the overall reliability and adaptability of cross-medium UAVs in complex mission scenarios.

[0045] The steps to establish a mathematical model are as follows: Define the body coordinate system , Located at the center of mass of the drone, The axis is defined as the forward direction of the UAV (i.e., the direction in which the UAV's center of mass points to the first mounting position), pointing to the position of the drive mechanism on the first mounting position. Axis perpendicular to The axis points to the position of the drive mechanism on the second mounting position. The axes follow the right-hand rule for frames of reference. Inertial frames of reference, however, are defined as follows: According to the Newton-Euler equations, the mathematical model of a tilting quadcopter AAV is as follows:

[0046] Furthermore, to describe the motion of the cross-medium UAV, the position and orientation of the UAV relative to the inertial frame are respectively represented by... Linear velocity and angular velocity can be represented as vectors. express. These are the resultant force and torque acting on the cross-medium UAV, respectively. It refers to the quality of cross-media drones. This is the inertial moment matrix of a serial cross-medium UAV. The velocities and angular velocities in the two coordinate systems can be obtained through the matrix. and The transformations are performed separately. The linear velocity transformation matrix from the body coordinate system to the inertial coordinate system is as follows:

[0047] in

[0048] Furthermore, a motion model for the cross-medium UAV is established. During the cross-medium motion, the forces acting on the UAV can be expressed as:

[0049] in This represents the resultant force acting on the drone during its cross-medium motion. This indicates the force generated by the drone's rotor. The restoring force is composed of buoyancy and gravity. Indicates the added mass force. This represents the damping force of the fluid. It represents errors and disturbances, such as drag, buoyancy and other linearization errors, as well as random disturbances that are difficult to measure, such as wind and waves.

[0050] During the cross-medium motion, the torque acting on the UAV can be expressed as:

[0051] in This represents the resultant torque exerted by the UAV during its cross-medium motion. This indicates the torque generated by the drone's rotor. This represents the restoring torque, which is composed of buoyancy and gravity. Indicates the additional mass torque. This represents the damping torque of the fluid. This represents the torque generated by errors and disturbances, such as drag, buoyancy, and other linearization errors, as well as random disturbances that are difficult to measure.

[0052] Resilience of cross-media drones and torque It is expressed as follows:

[0053] in It is the volume of the drone submerged in water. It is the density of water. It is the buoyancy center of the water-immersed part of the tiltable quadcopter AAV.

[0054] When a drone moves, the fluid exerts a reaction force on it; this is a type of inertial hydrodynamic force (added mass force). This can be represented by the following added mass matrix:

[0055] in Represents all fluid dynamics parameters.

[0056] Additional mass force and torque as follows:

[0057] in It is the coupled additional mass force matrix:

[0058] Fluid damping force and torque as follows:

[0059] In some embodiments, the PID controller outputs a control strategy based on preset PID parameters, wherein the PID parameters are dynamically adjusted based on the operating environment and operating mode.

[0060] Specifically, a PID controller is a proportional-integral-derivative (PI-D) controller that generates a control output by calculating the proportional (P), integral (I), and derivative (D) terms to reduce system errors. Preset PID parameters refer to the initial or default P, I, and D gain values ​​set for the PID controller at system startup or under specific operating conditions. These preset parameters can be determined in various ways. For example, they can be precisely calibrated before the UAV is put into use through offline simulation, experimental testing, or expert experience to ensure good control performance under typical operating conditions; or, based on the UAV's design characteristics and expected mission scenarios, one or more sets of default parameters can be pre-stored in the controller firmware and loaded during system startup. The PID controller calculates the control quantity based on the current error (the difference between the target value and the actual value) and the preset parameters. This control quantity is the control strategy, used to drive actuators (such as servos and motors) to adjust the UAV's attitude and position.

[0061] Building upon this, this application further proposes that PID parameters be dynamically adjusted based on the operating environment and operational information. Dynamic adjustment means that the P, I, and D parameters of the PID controller are no longer fixed but are modified and optimized in real time according to changes in the system's real-time state and external conditions. The operating environment is obtained through depth sensor analysis, including underwater and surface operation. Different media (air / water) have vastly different physical properties such as density, resistance, and buoyancy, requiring different control responses. The operating mode is determined based on the angular and linear velocities acquired by the inertial measurement unit and a mathematical model, including normal operation and fault operation modes. In normal mode, efficiency and accuracy may be prioritized, while in fault mode, stability and safety are given priority. Dynamic adjustment of PID parameters can be achieved in various ways. For example, an adaptive control algorithm can be used to switch between pre-stored sets of different PID parameters based on the medium type (surface / underwater) detected by the depth sensor; or the PID parameters can be adjusted in real time based on the angular and linear velocities fed back by the inertial measurement unit to cope with different flight / navigation states.

[0062] By introducing a dynamic adjustment mechanism for PID parameters based on the aforementioned PID control method, the problem of insufficient adaptability of preset static parameters in complex and variable cross-medium environments is solved. Specifically, based on the operating environment (above / below water) analyzed by depth sensors and the operating information (normal / fault mode) acquired by the inertial measurement unit, the PID parameters can be optimized in real time. During medium transitions, such as entering water from the air or exiting from underwater, the system can rapidly adjust the control gain according to the drastic changes in medium density, effectively suppressing rotor water splashing, reducing motor and blade losses, and avoiding control lag or overshoot caused by fixed parameters. In different operating modes, such as normal navigation or single-rotor or dual-rotor failures, the dynamically adjusted PID parameters enable the controller to respond more accurately, optimizing fault tolerance performance while ensuring stability, and improving the mission reliability and survivability of the UAV in complex environments. This dynamic adjustment mechanism significantly improves the control accuracy and stability of cross-medium UAVs in variable environments, reduces the risk of motor overload and rotor failure, thereby extending the service life of the UAV and broadening its application range.

[0063] The fault tolerance issues of cross-media UAVs under random motor failures are categorized into failure modes. These failure modes are classified into four types: normal operation, complete single-rotor failure (a single motor in the drive mechanism fails and cannot drive the corresponding rotor), complete dual-rotor failure (motors in both mounting positions fail and cannot drive the corresponding rotor), and insufficient power of any rotor (the motor in a certain mounting position is insufficient and cannot drive the corresponding rotor at the predetermined speed).

[0064] Under normal operating conditions, a cross-medium UAV can achieve tilting flight via servo motors, or it can achieve stable control like a conventional quadcopter by using four rotors with different speeds. The cross-medium UAV provided by this invention controls its attitude and position via tilting servo motors. The traction force generated by its rotors can be expressed as: Where i represents different installation positions, in the inertial coordinate system, the traction force can be expressed as: .

[0065] The lift force in the body coordinate system of a quadcopter can be expressed as:

[0066] The rotor torque can be expressed as:

[0067] in It is the tilt angle of each servo motor; It is the distance from the center of each rotor of a quadcopter to its center of mass.

[0068] Under the condition of complete single-rotor failure, taking the complete failure of the rotor at the first mounting position as an example, if the rotor at the first mounting position is selected as the failed rotor, the cross-medium configuration will change to a tilted three-rotor configuration. Since the two rotors on the same side of the quadcopter rotate in the same direction, when the rotor at the first mounting position fails, the torque generated by the rotor at the third mounting position is insufficient to offset the torque generated by the rotors at the second and fourth mounting positions, causing the cross-medium to oscillate... The shaft rotates. Furthermore, since the rotor in the first mounting position no longer generates lift, this will cause the fuselage to tilt, potentially leading to a cross-medium tipping over and damage. However, it should be noted that all rotors in this invention can be deflected under servo drive. When the deflection direction is opposite to the rotation direction, the resulting force and torque will balance the force and torque causing the rotation. Although the cross-medium UAV will tilt towards the side of the faulty rotor due to the influence of the remaining three rotors, this cross-medium UAV can still achieve stable and reliable flight with a constant attitude. The forces acting on the cross-medium UAV are as follows:

[0069]

[0070] Under conditions of complete dual-rotor failure, the rotors at the first and third mounting positions are selected as the faulty rotors. Due to the quadcopter configuration, when the cross-medium UAV switches to using two rotors rotating in opposite directions, the rotation directions of the dual rotors will be the same. This will cause rotation. To counteract the rotation in the yaw direction, the servo system needs to tilt the rotors to generate a counter-yawing on both rotors, thereby counteracting the rotation of the fuselage. When only the rotors at the second and fourth mounting positions are functioning normally, a yawing force opposite to the spin direction needs to be generated to counteract the torque generated by the two rotors rotating in the same direction. This can be achieved by driving the tilt servo, enabling the cross-medium UAV to counteract the spin and maintain stability. At this time, the forces acting on the cross-medium UAV are as follows:

[0071]

[0072] In some embodiments, the degree of drive mechanism failure is determined by introducing a rotor output attenuation coefficient. The degree of drive mechanism failure includes insufficient power and complete failure. If the attenuation coefficient is greater than 1, it is determined that the drive mechanism has insufficient power; when the attenuation coefficient is equal to 1, it is determined that the drive mechanism has completely failed.

[0073] Under conditions of insufficient rotor power, assuming that the rotational speed of any number of rotors is limited due to silt blockage, a rotor output attenuation coefficient is introduced. .like Then determine the first The rotor power at the mounting position is insufficient; when When, it is determined to be the first The rotor at the mounting position is completely malfunctioning. At this point, the underpowered thrust model is corrected to... Substituting these into the updated force and moment matrices of the UAV, as well as the control allocation matrix, we obtain the new thrust matrix:

[0074] The moment matrix is:

[0075] In normal operation mode, the actuator control allocation matrix for the tiltable quadcopter mode can be represented as:

[0076] in,

[0077]

[0078] The control allocation matrix can be obtained by finding the pseudo-inverse as follows:

[0079] In some embodiments, if the failure mode is complete failure of a single rotor, the PID controller generates a control strategy for complete failure of a single rotor based on the first control allocation matrix.

[0080] Specifically, after one rotor fails, the fuselage will lose balance and tilt in the direction of rotor failure. In the instant of loss of control, under the action of the controller, it can stably maintain its balance. The aircraft is tilted at an angle to avoid instability and crash. The transformation matrix of the fuselage coordinate system in its stable state can be expressed as:

[0081] The allocation matrix of the remaining drive mechanisms of a cross-medium UAV can be represented as:

[0082] At this point, inverting the above equation yields the first control allocation matrix as follows:

[0083] Right now: .

[0084] In some embodiments, if the fault mode is complete failure of the dual rotors, the PID controller generates a control strategy for the fault mode of complete failure of the dual rotors based on the second control allocation matrix.

[0085] Specifically, after the failure of both rotors, the allocation matrix of the remaining drive mechanism of the cross-medium UAV can be expressed as:

[0086] At this point, inverting the matrix yields the second control allocation matrix as follows:

[0087] therefore

[0088] In some embodiments, if the fault mode is insufficient power of a single rotor, the PID controller generates a control strategy based on a third control allocation matrix for a fault mode of complete failure of a single rotor.

[0089] When any rotor power is insufficient, substitute the following based on the normal operating model: The third control allocation matrix is ​​obtained:

[0090] .

[0091] The following is a verification description simulating a real-world application scenario: I. Experiments under normal operating mode: The cross-media UAV adopts a symmetrical layout with cross-shaped support arms, and the rotor is along the positive direction of the body coordinate system ( Shafts: M2, M4; Axis (M1, M3) are distributed and equipped with depth sensors to monitor the drone's depth in real time. The system determines whether it is in aerial or underwater mode. Simultaneously, it collects attitude angles via an IMU (Inertial Measurement Unit) and uses a GPS module to ensure positioning data in aerial mode, switching to inertial navigation in underwater mode.

[0092] in To work together, This is the resultant torque.

[0093]

[0094] When a drone moves across a medium, the fluid exerts a reaction force on it; this is a type of inertial hydrodynamics (added mass force). This can be represented by the following added mass matrix:

[0095]

[0096] in, It is the coupled additional mass force matrix:

[0097] A position and attitude dynamics model and a motion model are established based on the Newton-Euler equations. During cross-medium motion, the forces acting on the UAV can be expressed as:

[0098] Simultaneously, multi-modal PID parameter configuration is performed. Generally, low-damping parameters can be used in the air mode to reduce energy loss, while high-damping parameters can be used in the underwater mode to suppress fluid resistance disturbances.

[0099] Thrust distribution and control in quadcopter mode.

[0100] The PID controller generates control commands based on the desired trajectory and dynamically adjusts the rotational speed of the quadcopter through the thrust distribution matrix. ) and tilt angle ( ): Under normal operating conditions, the attitude and position of the cross-medium UAV are controlled by tilt servos. The traction force generated by its rotor can be expressed as: In an inertial coordinate system, it can be represented as: .

[0101] The lift force in the body coordinate system of a quadcopter can be expressed as:

[0102] The rotor torque can be expressed as:

[0103] Cross-media trajectory tracking and error control.

[0104] The following is a hypothetical experimental method: During flight, assuming the cross-medium UAV will... It follows a sinusoidal trajectory within the plane. One phase of this trajectory occurs in the air, at which point... The other stage is underwater, at which point... A trajectory tracking simulation was performed on the in-flight flight of a cross-medium UAV. The simulation results show that the cross-medium UAV exhibits excellent tracking and control performance in the air. However, due to the initial expected path altitude of 3 meters and the involvement of landing, the servos on the second and fourth mounting positions exhibit a sudden forward tilting motion, reaching an angle of 18°, before the stabilization tilt mechanism and attitude angle are adjusted.

[0105] During underwater movement, assuming the cross-medium UAV will... The trajectory follows a sinusoidal path within the plane. Trajectory tracking simulations were performed on the underwater motion of the cross-medium UAV. Simulation results show that a large amount of maneuvering control is required to achieve stability at the start of the motion, leading to a significant initial error. Hydrodynamic factors introduce a time delay effect during path tracking. Furthermore, upon reaching the highest point, i.e., the minimum peak of the sinusoidal path, the servos at the second and fourth mounting positions perform rapid maneuvers to control speed and direction during underwater motion. Simulation results demonstrate that it exhibits good tracking and control performance during underwater motion.

[0106] Subsequently, cross-medium switching and water emergence verification were conducted. For air-to-water aircraft, the ability to take off from water after performing underwater missions is crucial, as it directly impacts the effective transmission of mission data after completion. Therefore, separate simulations are needed to verify the water takeoff capability of this cross-medium UAV and evaluate its cross-domain flight performance.

[0107] II. Fault-tolerant control experiment for complete single-rotor failure: The structural design and layout of the UAV are the same as those of the aforementioned cross-medium UAV, and the position and attitude dynamics model and motion model based on the Newton-Euler equations are also the same.

[0108] First, fault detection and mode switching are performed. Assuming any rotor in the cross-medium UAV fails completely due to a fault, this would directly lead to a force imbalance on the UAV, making it unable to maintain a safe flight attitude. The quadcopter UAV might spin uncontrollably or even tip over. To mitigate the adverse effects of complete rotor failure, a pre-set equilibrium point for single rotor failure is established, the rotor and servo status is assessed, and failure control is implemented based on this assessment. For clarity, it is assumed that the rotor in the first mounting position fails completely due to a fault. The PID controller triggers a fault alarm by monitoring the motor feedback signal (a sudden drop in speed to 0) and switches to a tri-rotor fault-tolerant mode (a mode that adjusts the flight attitude by changing the tilt angle and speed of the remaining three rotors).

[0109] Then, the remaining rotor tilt angle is dynamically adjusted. The remaining three rotors (i.e., the rotors in the second, third, and fourth mounting positions) are deflected by the servo motors. When the deflection direction is opposite to the rotation direction, the resulting force and torque will balance the force and torque causing the rotation. Although the cross-medium UAV will tilt towards the side of the faulty rotor due to the influence of the remaining three rotors, the cross-medium UAV can still achieve stable and reliable flight with a constant attitude. Thrust distribution is reconfigured to counteract the yaw moment:

[0110] Torque distribution balances the spin effect using the following formula:

[0111] Stability verification was then conducted in tri-rotor mode. When the rotor in the first mounting position completely failed after 20 seconds, the cross-medium UAV experienced fluctuations and deviations during trajectory tracking, causing the fuselage to tilt forward. However, the controller switch effectively managed this process. Ultimately, through servo movements and the cross-medium UAV's gravity, the fuselage maintained a pitch angle of approximately 20 degrees, achieving stable path tracking control. At the switching moment, the servos in the second and fourth mounting positions tilted approximately 30 degrees to maintain the stability of the cross-medium UAV during rotor failure.

[0112] When a single rotor fails during underwater movement, the pitch angle of the cross-medium UAV changes drastically by approximately 20 degrees. Even with the failure of one rotor, the cross-medium UAV still successfully maintains underwater trajectory tracking control.

[0113] Continue to complete cross-medium mission continuity testing. In traditional tilting amphibious aircraft, if the rotor or tilting mechanism fails during an underwater mission, the cross-medium UAV cannot complete its water-emergence maneuver and return after the mission. To address this issue, we simulated and verified a water-emergence process after rotor failure, such as... Figure 5 As shown, the initial position of the cross-medium UAV was at a water depth of 1 meter. Figure 5 This diagram illustrates the attitude and angle changes of the servo motor during takeoff after a rotor failure. Due to the imbalance caused by the rotor malfunction during a sudden maneuver, the fuselage tilts underwater. Upon reaching the surface, the servo motor needs to restore balance to the asymmetrical rotor configuration for stable takeoff. Figure 5 As shown in (a), the cross-medium UAV maintains a pitch angle of 20° throughout flight. The remaining rotor generates torque, requiring servo tilting for balance, while simultaneously generating counter-torque to reduce rotation. Therefore, Figure 5 (b) shows that the tilt angles of the two servos differ by approximately 10°.

[0114] Finally, real-world experimental verification was completed. A cross-medium UAV cross-domain maneuverability experiment was conducted under underwater conditions with single-rotor failure. First, the cross-medium UAV was in normal working order upon entering the water, capable of performing relevant tasks underwater. To verify the surface maneuverability when a single rotor suddenly fails before takeoff, the cross-medium UAV was immersed in approximately 1 meter of water, and one rotor was shut down to simulate single-rotor failure. Experiments showed that when one rotor failed, the cross-medium UAV exhibited significant tilting as it moved vertically upwards in the water. However, under the fault-tolerant control strategy, stable underwater emergence and flight were achieved even with one rotor failure.

[0115] like Figure 8As shown in the experimental attitude data, after one rotor fails (the rotor in the first mounting position fails), the loss of the diagonal rotor generates a pitching moment underwater, resulting in a significant tilt during vertical upward motion in the water. During underwater motion, the maximum tilt angle reaches 20°, and the attitude returns to a horizontal position upon reaching the surface for takeoff. Figure 8 As shown in (a), after surfacing and taking off, to overcome the unbalanced torque caused by the rotor failure at the first mounting position, the servos at the second and fourth mounting positions tilt in the same direction to maintain balance, keeping the aircraft at an angle of approximately 25°. The loss of one rotor generates a torque. Figure 8 As shown in (a), in order to counteract this torque, there will be a tilt angle difference between the servo at the second mounting position and the servo at the fourth mounting position, which is basically consistent with the simulation analysis results.

[0116] III. Fault-Tolerant Control for Complete Dual Rotor Failure The structural design and layout of the UAV are the same as those of the aforementioned cross-medium UAV, and the position and attitude dynamics model and motion model based on the Newton-Euler equations are also the same.

[0117] First, fault detection and dual-rotor mode switching are performed. When both diagonal rotors (such as the rotor on the first mounting position and the rotor on the third mounting position) fail simultaneously, the uneven mass distribution along the longitudinal axis will directly lead to an imbalance of forces acting on the cross-medium UAV, making it unable to maintain a safe flight attitude. Simultaneously, since the remaining two rotors rotate in the same direction, rotational torque will be generated around the axis of the cross-medium UAV, resulting in unstable flight. To avoid flight failure caused by the failure of both diagonal rotors, we preset an equilibrium point when both diagonal rotors fail and perform fault control based on this state. The flight controller triggers a dual-fault protocol, shuts down the failed motor, and switches to dual-rotor mode (the rotor on the second mounting position and the rotor on the fourth mounting position operate).

[0118] Subsequently, symmetrical tilting and reverse torque generation occur. Under dual-rotor failure conditions (assuming failure of the rotor in the first mounting position and the rotor in the third mounting position), due to the quadcopter configuration, the remaining two rotors will rotate in the same direction. This will cause spin. To counteract the rotation in the yaw direction, the servo system needs to tilt the rotors to generate a counter-yawing on both rotors, thereby counteracting the fuselage rotation. When only the rotors in the second and fourth mounting positions of the cross-medium UAV are functioning normally, a yawing force opposite to the spin direction needs to be generated to counteract the torque generated by the two rotors rotating in the same direction. This can be achieved through servo drive, enabling the cross-medium UAV to counteract spin and maintain stability. At this time, the forces acting on the cross-medium UAV are as follows:

[0119]

[0120] Symmetrical tilt and generation of opposing torque. Under the condition of dual-rotor failure (assuming M1 and M3 failure), due to the quadcopter configuration, the remaining two rotors will rotate in the same direction. This will cause spin. To counteract the rotation in the yaw direction, the servo system needs to tilt the rotors to generate opposing yaws on both rotors, thereby counteracting the fuselage rotation. When only M2 and M4 are working normally in the AAV, a yaw force opposite to the spin direction needs to be generated to counteract the torque generated by the two rotors rotating in the same direction. This can be achieved by servo drive, enabling the AAV to counteract spin and maintain stability. At this time, the forces acting on the tilted dual-rotor AAV are as follows:

[0121]

[0122] Then, the cross-medium mission process in dual-rotor mode is performed. For example... Figure 10 As shown, it can be observed that at 20 seconds, when the rotors on the first and third mounting positions suddenly and completely fail, the cross-medium UAV experienced slight fluctuations and deviations under path-following control. To overcome the rotation, the remaining two rotors tilted, generating a small tilt angle in opposite directions, ultimately achieving tracking control of the desired path.

[0123] During underwater operation, a diagonal dual-rotor malfunction occurred at 20 seconds, followed by a control strategy switch. At the time of the malfunction, the pitch angle change was significant, with the servos at the second and fourth mounting positions tilting to stabilize the sudden attitude change. Although some trajectory tracking was achieved underwater, the relative error was relatively large.

[0124] Similarly, traditional tilt-rotor amphibious aircraft cannot achieve stable flight after the failure of both diagonal rotors, let alone perform cross-domain maneuvers from underwater to air. To verify the cross-medium UAV capability provided by this invention for cross-domain maneuvers after the failure of both diagonal rotors, simulation verification was conducted. For example... Figure 6 The diagram illustrates the cross-domain movement process from 1 meter underwater to the air, as well as the changes in the attitude angle and rudder deflection angle of the cross-medium UAV. From Figure 6 The attitude data in (a) shows that there are certain fluctuations during the water emergence process, with large fluctuations in pitch and yaw angles. After the water emergence flight, the flight attitude tends to stabilize. Figure 6As shown in (b), since the remaining two rotors rotate in the same direction, a rotational torque is generated. To counteract this torque, the remaining two yaws deflect in opposite directions by an angle of approximately 4°, thereby generating opposing torques to maintain a stable attitude.

[0125] Finally, a real-world experiment was conducted to verify the system's capabilities. An experiment was performed on the cross-domain motion of a cross-medium UAV with both diagonal rotors failing. Initially, the UAV was in normal operation upon entering the water. To verify its waterborne motion capability in the event of diagonal rotor failure, the water depth was set to approximately 1 meter, and both diagonal rotors were shut down to simulate a failure scenario. When both diagonal rotors failed, the UAV's body exhibited some rotation as it moved vertically upwards in the water. Under a fault-tolerant control strategy, stable control could be achieved by using tilting rotors. The experimental results show that even with the failure of both diagonal rotors, the system can still stably complete waterborne exit maneuvers and flight.

[0126] like Figure 9 As shown in the experimental attitude data, after the failure of two diagonally opposite rotors in the water (the rotors at the first and third mounting positions), a rotational torque is generated when the remaining two rotors rotate in the same direction (the rotors at the second and fourth mounting positions) and move vertically upwards in the water. This torque can be counteracted by a fault-tolerant control strategy, causing the remaining rotors to tilt in the opposite direction. Figure 4 As shown in (a), after rising from the water and taking off, although the cross-medium UAV can achieve stable flight through tilting rotors, its attitude will fluctuate to some extent due to the influence of control parameters and the fore and aft arms. A torque will be generated due to the losses from the two diagonal rotors. Figure 4 As shown in (b), in order to counteract this torque, the servo motors in the second mounting position and the fourth mounting position will have opposite tilt angles, which is basically consistent with the simulation analysis results.

[0127] Furthermore, 30 underwater discharge experiments were conducted for each of the three scenarios described above. Experimental statistics show that, without rotor failure, the success rate of underwater discharge reaches 100%. When one rotor fails, the success rate is 70%, with the main cause of failure being thrust imbalance, leading to the aircraft tilting and capsizing during the discharge. In the case of two rotor failures, the success rate of water discharge reaches 87%. Compared to a single rotor failure, water discharge results in greater instantaneous attitude stability. Most water discharge experiments also demonstrated the possibility of continuing the mission after rotor loss.

[0128] IV. Fault-Tolerant Control for Insufficient Power in Arbitrary Rotors The structural design and layout of the UAV are the same as those of the aforementioned cross-medium UAV, and the position and attitude dynamics model and motion model based on the Newton-Euler equations are also the same.

[0129] First, the dynamic model is simplified by introducing a rotor output attenuation coefficient. The attenuation coefficient matrix is:

[0130] The thrust equation simplifies to:

[0131] The new thrust matrix and torque matrix are obtained as follows:

[0132]

[0133] In the normal thrust distribution matrix The attenuation compensation term is superimposed to reconstruct the control allocation matrix.

[0134] 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 cross-media unmanned aerial vehicle, characterized in that, The utility model relates to a kind of cross-media unmanned aerial vehicle, including: Driving mechanism, including steering gear, motor, rotor, motor seat, motor is installed on motor seat, the output end of steering gear is equipped with pull rod, pull rod is connected with motor seat, motor is transmission connection with rotor; Body is equipped with cross type support arm, four ends of support arm have first installation site, second installation site, third installation site, fourth installation site respectively, first installation site and third installation site are coaxial center symmetry, second installation site and fourth installation site are coaxial center symmetry, first installation site, second installation site, third installation site, fourth installation site are equipped with driving mechanism respectively, body is further equipped with depth sensor, inertial measurement unit and PID controller.

2. The cross-medium drone of claim 1, wherein, The top of support arm is equipped with buoyancy piece, depth sensor, inertial measurement unit and PID controller are installed inside buoyancy piece.

3. The cross-medium drone of claim 1, wherein, The top of buoyancy piece is equipped with positioning module.

4. The cross-medium drone of claim 1, wherein, Support arm bottom is equipped with support, support is equipped with power supply module and camera module.

5. A PID control method of a cross-medium unmanned aerial vehicle, characterized by, Including the following steps: The operating environment of cross-media unmanned aerial vehicle is analyzed by depth sensor, and the operating environment includes underwater operation and water operation; The angular velocity and linear velocity of cross-media unmanned aerial vehicle are obtained by inertial measurement unit, and the mathematical model of cross-media unmanned aerial vehicle is established based on angular velocity and linear velocity, and the operating mode of cross-media unmanned aerial vehicle is determined based on mathematical model, wherein the operating mode includes normal operating mode and fault operating mode; PID controller outputs corresponding control strategy based on operating environment and operating mode, and adjusts the motion posture of cross-media unmanned aerial vehicle based on control strategy.

6. The PID control method of a cross-media drone according to claim 5, wherein, PID controller outputs control strategy based on preset PID parameter, wherein PID parameter is dynamically adjusted based on operating environment and operating mode.

7. The PID control method of a cross-media drone according to claim 5, wherein, If the fault mode is single rotor complete failure, then the PID controller generates a control strategy for single rotor complete failure based on the first control allocation matrix.

8. The PID control method of a cross-media drone according to claim 5, wherein, If the fault mode is double rotor complete failure, then the PID controller generates a control strategy for the fault mode of double rotor complete failure based on the second control allocation matrix. 9.The PID control method of the cross-medium UAV of claim 5, wherein, The degree of failure of the driving mechanism is determined by introducing the rotor output attenuation coefficient, which includes power deficiency and complete failure. If the attenuation coefficient is greater than 1, it is determined that the driving mechanism is power deficient. 10.The PID control method of a cross-medium UAV according to claim 9, wherein, If the attenuation coefficient is equal to 1, it is determined that the driving mechanism is completely failed. If the fault mode is single rotor power deficiency, then the PID controller generates a control strategy for the fault mode of single rotor complete failure based on the third control allocation matrix.

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