A high-efficiency multi-modal flight control method, system and storage medium for a near-ground quadrotor unmanned aerial vehicle

Abstract

The present invention provides a multi-modal control method, system and storage medium for near-ground operation missions of a four-rotor unmanned aerial vehicle (UAV), which relates to the field of UAV control technology. The invention aims to solve the problems that the existing UAV control method using only a single-mode controller design is difficult to adapt to reliable flight control under ground turbulence at different altitudes, and that the existing anti-interference flight control can only achieve partial states under ground turbulence. The present invention proposes to use the additional lift generated by ground turbulence for high-efficiency control, and to distinguish different modes at different altitudes to design a multi-modal height-dependent variable parameter controller, which can achieve high-performance and high-energy-efficiency flight control at different altitudes near the ground. Not only does it reduce the flight length during the operation, it also reduces the rotor lift demand, achieving the purpose of cost-saving and efficiency-enhancing high-efficiency flight control. While ensuring the flight stability of the UAV under near-ground turbulence, it also reduces its energy loss, achieving the purpose of cost-saving and efficiency-enhancing, and has high engineering application value.

Description

Technical Field

[0001] The present invention relates to the field of unmanned aerial vehicle (UAV) control technology, and in particular to a high-energy-efficiency near-ground quadrotor UAV multimodal flight control method, system, and storage medium. Background Art

[0002] Multimodal flight control is a key manifestation of the continuous intersection and integration of advanced aircraft technology and modern control theory. Its development is primarily driven by structural or parameter changes within the platform itself or its environment, necessitating the adoption of multimodal switching control design strategies to improve system performance. It is widely used in aerospace, near-surface sea, and land, as well as other military and civilian fields. Quadcopter drones (UAVs) are economical, maneuverable, and portable flight platforms capable of vertical takeoff and landing (VTOL), and capable of low-altitude access. Their application in missions such as target tracking, cargo delivery, and air-ground coordination continues to advance. However, as mission complexity increases, the demand for flight control methods based on multimodal approaches to enhance control performance is growing. Examples include variable-mode flight control for intermittently lost targets during tracking, multimodal control for deformable arms to balance flight agility and operational stability, and variable-mode control for dual-use air-to-ground UAVs to improve energy efficiency.

[0003] With the advancement of sensor and flight control technologies, in addition to the aforementioned dual-use air-to-ground drones, quadcopters are increasingly being used in near-ground operations. These include ground sample collection for environmental monitoring in areas such as oceans, wetlands, and agriculture, genetic resource collection for wildlife conservation, and near-ground information collection and perception. In these scenarios, quadcopters are relatively close to the ground, and the downward airflow from their rotors is quickly blocked by the ground, creating a reactionary turbulence that severely compromises the quadcopter's flight stability. Existing methods typically employ high-altitude circumnavigation and rapid takeoff and landing to minimize the presence of complex near-ground airflow. However, this increases the drone's operating path length and flight time, and is extremely inefficient in dense near-ground operations.

[0004] Research on flight control for quadrotor drones operating near the ground is steadily developing. Key approaches include robust control that treats complex turbulence as a disturbance to the flight control system, adaptive control that treats turbulence forces as variable parameters, and feedback control that ignores turbulence and responds quickly to state changes. In fact, recent analyses and modeling of various ground turbulence-induced disturbance forces have revealed a strong nonlinear correlation between rotor thrust and altitude above the ground. As altitude decreases, the turbulence reaction forces near the ground increase and their rate of increase, resulting in a complex multimodal phenomenon: none at high altitude, minimal at low altitude, smaller near the ground, and more severe close to the ground. Existing single-mode controllers struggle to ensure high-performance, stable, and reliable flight for quadrotors at varying altitudes. Therefore, a complex multimodal flight control approach is urgently needed to achieve ground control for quadrotors near the ground.

[0005] Furthermore, reducing flight power consumption, improving energy efficiency, and increasing operating time are key operational indicators for various types of electric-powered drones, including quadcopters. When a drone flies close to the ground, ground turbulence not only interferes with flight stability, but also creates an upward thrust for the drone. Existing research primarily focuses on actively suppressing thrust, designing flight controllers for single states such as attitude control and altitude / yaw angles. It does not consider controller design for all states of a quadcopter, making it difficult to achieve near-ground flight control for a quadcopter, nor is it possible to utilize the upward thrust inherent in ground turbulence to achieve high-efficiency flight control with low current and low lift output. This presents a difficult issue that needs to be studied by the academic community in the future. Summary of the Invention

[0006] The technical problems to be solved by the present invention are:

[0007] The single-mode controller design under the existing common UAV control scheme is difficult to adapt to reliable flight control under ground disturbances at different heights, and can only achieve anti-interference flight control in some states under the existing ground disturbances.

[0008] The present invention is to solve the above technical problems using the following technical solutions:

[0009] The present invention provides a high-efficiency multi-mode flight control method for a near-ground quadrotor unmanned aerial vehicle, comprising the following steps:

[0010] Step 1: Obtain the position, altitude, and attitude information of the near-ground operation quadrotor drone, and construct the UAV near-ground operation space rectangular coordinate system based on the initial position and the operating range size under the target mission;

[0011] Step 2: Based on the UAV's dynamic characteristics and the air disturbance caused by the ground reaction turbulence on the UAV, a UAV dynamic model considering the ground turbulence lift is constructed:

[0012]

[0013] Where x, y, and z are the positions of the drone in the inertial coordinate system, θ, φ, and ψ of the quadrotor drone are the pitch angle, roll angle, and yaw angle, respectively; p, q, and r are the angular velocities of the x, y, and z axes in the body coordinate system, respectively; g is the acceleration of gravity; m represents the body mass; and J is the x 、J x 、J z is the moment of inertia along the corresponding axis, C p 、C q 、C r is the air resistance coefficient, c stands for cosine, which is the abbreviation of cos, and s stands for sine, which is the abbreviation of sin; Q(h) is the air disturbance torque, which is the lift change under the ground disturbance at the current height h, T g / T ∞ =[1-(R / 4h) 2 ] -1 =Q(h), where T g is the propeller lift in ground effect, T ∞ is the lift generated at the same propeller speed when the drone is far away from the ground, R is the propeller blade diameter, T f,∞ is the total thrust, which is the sum of the thrusts generated by the four rotors, T p,∞ 、T q,∞ 、T r,∞ They are the control torques for roll, pitch, and yaw, and the torques are used to control the attitude of the drone;

[0014] According to formula (3), the angular velocity multi-modal linear variable parameter tracking control system is established:

[0015]

[0016] Where σ is the system mode corresponding to different flight altitudes, B s 、B w are the flight altitude dependence matrices corresponding to the linearized tracking control system, where is the system matrix under different modes, B s is the input matrix linearized by the dynamic model, B w is the identity matrix, e s , t s 、w、z s are tracking error, control input, system disturbance, and state observation respectively; w σ,k(h) The corresponding weight functions under different modes with the change of height;

[0017] According to formula (2), the angle closed-loop control system is established where η = [φ,θ,ψ] T , A is the system matrix, also the rotation matrix;

[0018] Step 3: In the attitude tracking control process, the reference attitude is the artificially given heading angle ψ r , and the reference signal θ calculated by the position loop r 、φ r ;according to Calculate the reference signal of angular velocity; where ρ r =[p,q,r] T , K η =diag{k φ ,k θ ,k ψ};according to Calculate the propeller lift T and rolling moment, pitching moment, and yaw moment, where w σ,k (h) varies with mode and flight altitude, is the mode-dependent control gain, which is determined by the flight altitude-dependent multi-mode system matrix B s 、B w 、C s Determine, calculate the angular velocity according to formula (3), and then calculate the angle according to formula (2), and perform attitude tracking control according to the established angular velocity multi-modal linear variable parameter tracking control system and angle closed-loop control system;

[0019] Step 4: First, perform altitude control of the fully driven UAV. The controller adopts the form of non-singular terminal sliding mode control and defines the altitude tracking error as: e z =zz r ;

[0020] Define the sliding surface

[0021] Calculate s z The derivative of , under the sliding mode condition, is Solve

[0022] Select the reaching law as -K z sgn(s z ); where Kz is the control gain, sgn(s z ) is s z The symbolic function of

[0023] Combined with the UAV's dynamic model, the total lift is solved through the altitude controller:

[0024]

[0025]

[0026] Substitute the result of formula (6) into formula (1) to solve the altitude of the drone;

[0027] Using the same sliding mode state and reaching law calculation method as altitude control

[0028] make:

[0029]

[0030] Taking into account the underactuated dynamics of the horizontal state, (1), (7) and (8) are combined to construct the horizontal state sliding mode controller as shown in (9):

[0031]

[0032] According to the attitude angle result obtained by solving (9), the propeller lift of the UAV is solved using the process of step 3, and the attitude angle result is brought into the dynamic model considering the ground spoiler lift to solve the horizontal position of the UAV;

[0033] Step 5: Repeat steps 2, 3, and 4 until the drone flying close to the ground reaches the desired position and attitude.

[0034] Furthermore, the attitude information in step 1 includes: the current ground altitude -z, roll angle φ, pitch angle θ, yaw angle ψ and drone propeller height h = -z + c b , where c b Parameters related to the body structure.

[0035] Furthermore, the direction of the rectangular coordinate system of the UAV near-ground operation space in step 1 coincides with the UAV body coordinate system at the start of the operation and remains unchanged throughout the entire operation process.

[0036] The present invention provides a multimodal control system for near-ground operation tasks of a quad-rotor unmanned aerial vehicle. The system has a program module corresponding to the steps of the method described in any one of the above technical solutions, and executes the steps in the above-mentioned multimodal control method for near-ground operation tasks of a quad-rotor unmanned aerial vehicle during operation.

[0037] The present invention provides a computer-readable storage medium, which stores a computer program. The computer program is configured to implement the steps in the multimodal control method for near-ground operation tasks of a four-rotor unmanned aerial vehicle described in any one of the above-mentioned technical solutions when called by a processor.

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

[0039] In response to the situation where a quadcopter UAV encounters varying degrees of ground turbulence interference at different altitudes during near-ground missions, the present invention proposes a method for utilizing the additional lift generated by ground turbulence for high-efficiency control and for designing a multi-modal, height-dependent variable parameter controller by distinguishing different modes at different altitudes. This method can achieve high-performance, high-efficiency flight control at different altitudes near the ground. Specifically, the present invention has the following beneficial effects:

[0040] ① Compared with the traditional single-mode robustness and adaptive control method, the present invention utilizes the multi-mode controller design concept to specifically design a multi-mode variable parameter controller at different flight altitudes, and dispatches it in real time according to the ground disturbance conditions to ensure high-performance flight of the quadrotor UAV during near-ground operations.

[0041] ② Compared with the traditional high-altitude circling to reduce the time near the ground for near-ground operation missions, the present invention fully considers the reaction lift generated by ground turbulence, and can use ground effect lift to achieve flight control under different ground turbulence conditions. It not only reduces the flight length during the operation, but also reduces the rotor lift demand, achieving the goal of high-efficiency flight control with cost savings and efficiency increases.

[0042] In summary, the present invention takes a four-rotor UAV operating near the ground as the application object, performs multi-modal improvement and optimization on the basis of traditional single-mode flight control, combines the rational utilization of ground turbulence lift, and realizes high-efficiency flight control of the four-rotor UAV during near-ground operation. While ensuring the flight stability of the UAV under near-ground turbulence, it also reduces its energy loss, achieves the purpose of cost saving and efficiency improvement, and has high engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of a multi-modal control method for a quadrotor UAV near-ground operation mission in an embodiment of the present invention;

[0044] Figure 2 is a modal partition diagram under flight altitude change in an embodiment of the present invention;

[0045] Figure 3 This is a framework diagram of the attitude loop tracking control of a quadrotor drone under ground disturbance in an embodiment of the present invention;

[0046] Figure 4 This is a diagram of the position loop tracking control framework of a quadrotor drone under ground disturbance in an embodiment of the present invention;

[0047] Figure 5 This is a diagram showing the attitude tracking effect of a quadrotor drone under ground disturbance in an embodiment of the present invention;

[0048] Figure 6 This is a diagram showing the position tracking effect of a quadrotor drone under ground turbulence interference in an embodiment of the present invention; DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below with reference to the accompanying drawings. Obviously, the described embodiments or examples are only some of the embodiments or examples of the present invention, and not all of them. Based on the embodiments or examples of the present invention, all other embodiments or examples obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0051] like Figure 1 As shown, the present invention provides a multi-modal control method for a quadrotor UAV near-ground operation mission, comprising the following steps:

[0052] Step 1: Obtain the position, altitude, and attitude information of the near-ground operation quadrotor drone, and construct the drone's near-ground operation space rectangular coordinate system based on the initial position and the operating range size under the target mission.

[0053] At the beginning of the operation, the gyroscope, accelerometer, barometer and other sensors are used to obtain the initial position and attitude information of the near-ground operation quadrotor drone. The attitude information includes: the current ground height -z, roll angle φ, pitch angle θ, yaw angle ψ and drone propeller height h = -z + c b , where c b is the body structure related parameter, and the constant is 0.02. According to the initial position and the target mission operation requirements, the operating range of the UAV is determined, and the UAV body coordinate system is established. Near-Earth Operation Mission Space Rectangular Coordinate System Body coordinate system F b Using the conventional definition, that is, x b 、y b 、z b They point to the front, left, and bottom of the frame respectively. The origin is the geometric center of the quadcopter (also the center of gravity). The rectangular coordinate system of the drone's near-ground operating space Direction and drone body coordinate system at the start of the operation During near-ground operations, the UAV's body coordinate transformation caused by its linear and angular velocities is converted into the global coordinate position of the mission space coordinate system, facilitating the implementation of the mission.

[0054] Step 2: Based on the rectangular coordinate system of the working space established in step 1, further establish a trajectory tracking control system model containing multiple modes during the operation process, such as Figure 2 As shown in the figure, the trajectory tracking control system under the interference of ground spoilers is divided into different modes according to the nonlinearity. Each mode corresponds to a different flight altitude range, and the control system design under the corresponding mode is performed. According to the current height h∈[min h1,max h1], where min h1 and max h1 are the minimum and maximum altitudes corresponding to the current mode, the lift change under the current ground spoilers is determined as: T g / T ∞ =[1-(R / 4h) 2 ] -1 =Q(h), where T g is the propeller lift in ground effect, T ∞ is the lift generated by the drone at the same propeller speed when the drone is far from the ground, and R is the propeller blade diameter. Define the drone's three-axis position states x, y, and z, and the three-axis rotation states θ, φ, and ψ, and construct a drone dynamic model that considers ground turbulence lift:

[0055]

[0056] Where x, y, and z are the positions of the drone in the inertial coordinate system, θ, φ, and ψ of the quadrotor drone are the pitch angle, roll angle, and yaw angle, respectively; p, q, and r are the angular velocities of the x, y, and z axes in the body coordinate system, respectively; g is the acceleration of gravity; m represents the body mass; and J is the x 、J x 、J z is the moment of inertia along the corresponding axis, C p 、C q 、C r is the air resistance coefficient, the control input T f,∞ 、T p,∞ 、T q,∞ 、T r,∞ are the total lift of the propeller and the corresponding shaft torque without considering ground turbulence, c stands for cosine, which is the abbreviation of cos, and s stands for sine, which is the abbreviation of sin;

[0057] like Figure 3 As shown, according to formula (3), the angular velocity multi-modal linear variable parameter tracking control system is established:

[0058]

[0059] Where σ is the system mode corresponding to different flight altitudes, B s 、B ware the flight altitude dependence matrices corresponding to the linearized tracking control system, where is the system matrix under different modes, B s is the input matrix linearized by the dynamic model, B w is the identity matrix, e s , t s 、w、z s are tracking error, control input, system disturbance, and state observation respectively; w σ,k (h) The corresponding weight functions under different modes with the change of height.

[0060] According to formula (2), the angle closed-loop control system is established where η = [φ,θ,ψ] T , is the system matrix, also known as the rotation matrix.

[0061] The subsequent outer loop position tracking is designed to consider the height controller T of the ground spoiler lift f,∞ , and design a virtual horizontal position controller θ r 、φ r Control the height and level respectively, and their reference signals are x r 、y r 、z r express.

[0062] Step 3: If Figure 4 As shown in the figure, in the attitude tracking control process, the reference attitude is the artificially given heading angle ψ r , and the reference signal θ calculated by the position loop r 、φ r ;according to Calculate the reference signal of angular velocity; where ρ r =[p,q,r] T , K η =diag{k φ ,k θ ,k ψ};according to Calculate the propeller lift T and rolling moment, pitching moment, and yaw moment, where w σ,k (h) varies with mode and flight altitude, is the mode-dependent control gain, which is determined by the flight altitude-dependent multi-mode system matrix B s 、B w 、C sIt is determined that for a multi-modal system, each mode under different altitude conditions corresponds to a different set of system matrices, and the mode-dependent control gain will be determined according to the current mode; the angular velocity is solved according to formula (3), and then the angle is solved according to formula (2), and the attitude tracking control is performed according to the established angular velocity multi-modal linear variable parameter tracking control system and angle closed-loop control system.

[0063] For a multi-mode variable parameter system, there exists a positive definite symmetric matrix X i and matrix W i k The following matrix inequalities are satisfied to ensure the stability and anti-interference ability of the system.

[0064]

[0065] X i <μ i,j X j

[0066] Note that the controller can realize the real-time adjustment of the UAV attitude and has a certain anti-interference ability (its robust performance index is Real-time tracking of the position loop and the manually given reference attitude is achieved, thereby updating the attitude of the quadrotor drone flying close to the ground. Where γ0 represents the performance index of the system, reflecting the sensitivity of the system to disturbances; Indicates the maximum value of the parameter between different modes in the switching system; λ i represents the smallest positive constant used to ensure that the derivative of the Lyapunov function is sufficiently negative; ε A Represents the average dwell time.

[0067] Step 4: First, perform altitude control of the fully driven UAV. The controller adopts the form of non-singular terminal sliding mode control and defines the altitude tracking error as: e z =zz r ;

[0068] Define the sliding surface

[0069] Calculate s z The derivative of , under the sliding mode condition, is Solve

[0070] Select the reaching law as -K z sgn(s z ); where Kz is the control gain, sgn(s z ) is s z The symbolic function of

[0071] Combined with the UAV's dynamic model, the total lift is solved through the altitude controller:

[0072]

[0073] Substitute the result of formula (6) into formula (1) to solve the altitude of the drone;

[0074] Since Q(h) is greater than 1 at all ground proximity heights and ground proximity modes, the drone can more accurately adjust its altitude. The reference attitude angle (virtual control input) corresponding to the horizontal position adjustment is further calculated using the same sliding mode state and reaching law calculation method as for altitude control.

[0075] make:

[0076]

[0077] Taking into account the underactuated dynamics of the horizontal state, (1), (7) and (8) are combined to construct the horizontal state sliding mode controller as shown in (9):

[0078]

[0079] According to the attitude angle result obtained by solving (9), the propeller lift of the UAV is solved using the process of step 3, and the attitude angle result is brought into the dynamic model considering the ground spoiler lift to solve the horizontal position of the UAV.

[0080] This part is based on the control input solution of the non-singular terminal sliding mode control method, which can effectively ensure the stability of the position loop tracking control system (using the Lyapunov method V = 1 / 2s 2 (It can be proven that the convergence law can overcome parameter uncertainty in the control system due to its sign-function structure.) Based on the current reference trajectory and the aforementioned control law, the control input / attitude reference angle is continuously calculated, utilizing the thrust and torque generated by the UAV's propeller speed and the inner-loop tracking control algorithm (see step three for details; after the inner-loop multimodal tracking solution, this is also converted into the UAV's propeller speed). Because ground turbulence lift provides additional support torque during near-ground flight, highly energy-efficient flight control is achieved.

[0081] Step 5: Repeat steps 2, 3, and 4 until the drone flying close to the ground reaches the desired position and attitude.

[0082] The drone's onboard altitude sensor is used to measure the drone's current altitude in real time to determine the current mode of the flight control system. Further, sensors such as IMU / GPS measure the current position / speed, attitude angle / angular velocity in real time. According to the current reference control instructions, the onboard flight control board is used to solve the control input. The solved control input is used to control the drone's position and attitude to achieve state updates. This cycle is repeated, continuously measuring the drone's current position and attitude to determine the mode of the flight control system. The control input is continued to be determined until the drone flying near the ground reaches the predetermined position and attitude.

[0083] The multimodal control method (algorithm) for near-ground operation tasks of a quadrotor unmanned aerial vehicle proposed in this invention is the underlying technical core of the invention, and various products can be derived based on the algorithm.

[0084] Based on the method proposed in the present invention, a multimodal control system for near-ground operation tasks of a quadrotor unmanned aerial vehicle is developed using a programming language. The system has program modules corresponding to the steps of the above-mentioned technical solution, and executes the steps in the above-mentioned multimodal control method for near-ground operation tasks of a quadrotor unmanned aerial vehicle during operation.

[0085] The developed system (software) computer program is stored on a computer-readable storage medium. The computer program is configured to implement the steps of the above-mentioned multimodal control method for near-ground operation missions of a quadrotor drone when called by a processor. This materializes the present invention on a carrier, becoming a computer program product.

[0086] Various implementations of the systems and techniques described herein can be realized in digital electronic circuitry, integrated circuitry, dedicated ASICs (application specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include being implemented in one or more computer programs that are executable and / or interpreted on a programmable system comprising at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0087] The computer programs (also referred to as programs, software, software applications, or code) of the present invention include machine instructions for a programmable processor and can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, device, and / or apparatus (e.g., a magnetic disk, an optical disk, a memory, a programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0088] Example 1

[0089] To verify the effectiveness of the energy-efficient near-ground quadrotor drone multi-modal flight control method proposed in the present invention, this embodiment uses system simulation to conduct tests and verification:

[0090] (1) Verification of the attitude control capability of UAV near-ground operation. The reference value of attitude angle tracking is set as θ r =0.1,φ r =-0.2,ψ r =0.01sin0.1t+0.1(t<20), ψ r =0.2t(t>20). During the attitude tracking process, the altitude change of the UAV obeys h=-0.075sin(0.25t+0.4)+0.125, so that the UAV flight control system switches between three modes distinguished by altitude (0.05m~0.1m, 0.1m~0.15m, 0.15m~0.2m). The state feedback controller parameters of the angular velocity loop are set to λ1=0.1, λ2=0.2, λ3=0.1, μ i,j =1.3,γ0=1.485. The average dwell time corresponding to the three modes is ε A = 2.624s, and the robustness index of the controller is γ = 0.4456. The obtained attitude control curve is as follows Figure 5 As shown in the figure, compared with the conventional controller design method that does not consider the ground spoiler lift, the proposed multi-modal high-energy-efficiency control scheme can converge the state to the established index faster while using smaller control input.

[0091] (2) Verification of the UAV’s near-ground tracking control capability. In the near-ground tracking control task of the quadrotor UAV, a constant reference yaw angle ψ is given. r =0.1, reference attitude angle θ r and φ rIt is dynamically calculated by the horizontal position controller; the initial values ​​of the drone position and velocity are set to zero, and the reference trajectory is a constant value x r =y r =z r =-a(a∈[0.05,0.1,0.2,0.4,0.8,1.6]). The designed multi-modal high-efficiency near-ground flight controller parameters are, where the parameters are adjusted according to the flight altitude and mode of the UAV. The test results are as follows Figure 6 Shown a x =a y =a z =5,b x =b y =b z =3,K x =K y =K z = 1, representing multi-modal variable parameter control and traditional state feedback control, respectively. When the desired altitude decreases, traditional tracking control methods are unable to effectively control the UAV to reach the reference altitude. However, the proposed multi-modal, energy-efficient flight controller leverages ground spoiler lift to ensure near-ground position tracking performance, achieves the desired lift and torque at a lower rotational speed, and adjusts its control parameters in real time based on the current altitude and mode, making it suitable for near-ground UAV flight control missions.

[0092] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art of the present invention may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A multi-modal control method for a quadrotor UAV near-ground operation mission, characterized in that: The steps include: Step 1: Obtain the position, altitude, and attitude information of the near-ground operation quadrotor drone, and construct the UAV near-ground operation space rectangular coordinate system based on the initial position and the operating range size under the target mission; Step 2: Based on the UAV's dynamic characteristics and the air disturbance caused by the ground reaction turbulence on the UAV, a UAV dynamic model considering the ground turbulence lift is constructed: Where x, y, and z are the positions of the UAV in the inertial coordinate system, θ, φ, and ψ are the pitch angle, roll angle, and yaw angle of the quadrotor UAV, respectively; p, q, and r are the angular velocities of the x, y, and z axes in the body coordinate system, respectively; g is the acceleration of gravity; m represents the body mass; and J is the x 、J x 、J z is the moment of inertia along the corresponding axis, C p 、C q 、C r is the air resistance coefficient, c stands for cosine, which is the abbreviation of cos, and s stands for sine, which is the abbreviation of sin; Q(h) is the air disturbance torque, which is the lift change under the ground disturbance at the current height h, T g / T ∞ =[1-(R / 4h) 2 ] -1 =Q(h), where Tg is the propeller lift under ground effect, T ∞ is the lift generated at the same propeller speed when the drone is far away from the ground, R is the propeller blade diameter, T f,∞ is the total thrust, which is the sum of the thrusts generated by the four rotors, T p,∞ 、T q,∞ 、T r,∞ They are the control torques for roll, pitch, and yaw, and the torques are used to control the attitude of the drone; According to formula (3), the angular velocity multi-modal linear variable parameter tracking control system is established: Where σ is the system mode corresponding to different flight altitudes, B s 、B w are the flight altitude dependence matrices corresponding to the linearized tracking control system, where is the system matrix under different modes, B s is the input matrix linearized by the dynamic model, B w is the identity matrix, e s , t s 、w、z s are tracking error, control input, system disturbance, and state observation respectively; w σ,k (h) The corresponding weight functions under different modes with the change of height; According to formula (2), the angle closed-loop control system is established where η = [φ,θ,ψ] T , A is the system matrix, also the rotation matrix; Step 3: In the attitude tracking control process, the reference attitude is the artificially given heading angle ψ r , and the reference signal θ calculated by the position loop r 、φ r ;according to Calculate the reference signal of angular velocity; where ρ r =[p,q,r] T , K η =diag{k φ ,k θ ,k ψ };according to Calculate the propeller lift T and rolling moment, pitching moment, and yaw moment, where w σ,k (h) varies with mode and flight altitude, is the mode-dependent control gain, which is determined by the flight altitude-dependent multi-mode system matrix B s 、B w 、C s Determine, calculate the angular velocity according to formula (3), and then calculate the angle according to formula (2), and perform attitude tracking control according to the established angular velocity multi-modal linear variable parameter tracking control system and angle closed-loop control system; Step 4: First, perform altitude control of the fully driven UAV. The controller adopts the form of non-singular terminal sliding mode control and defines the altitude tracking error as: e z =zz r ; Define the sliding surface Calculate s z The derivative of , under the sliding mode condition, is Solve Select the reaching law as -K z sgn(s z ); where K z is the control gain, sgn(s z ) is s z The symbolic function of Combined with the UAV's dynamic model, the total lift is solved through the altitude controller: Substitute the result of formula (6) into formula (1) to solve the altitude of the drone; Using the same sliding mode state and reaching law calculation method as altitude control make: Taking into account the underactuated dynamics of the horizontal state, (1), (7) and (8) are combined to construct the horizontal state sliding mode controller as shown in (9): According to the attitude angle result obtained by solving (9), the propeller lift of the UAV is solved using the process of step 3, and the attitude angle result is brought into the dynamic model considering the ground spoiler lift to solve the horizontal position of the UAV; Step 5: Repeat steps 2, 3, and 4 until the drone flying close to the ground reaches the desired position and attitude.

2. The multimodal control method for near-ground operation tasks of a quadrotor UAV according to claim 1, characterized in that: The attitude information in step 1 includes: the current ground altitude -z, roll angle φ, pitch angle θ, yaw angle ψ and the drone propeller height h = -z + c b , where c b Parameters related to the body structure.

3. The multimodal control method for near-ground operation tasks of a quadrotor UAV according to claim 2, characterized in that: The direction of the rectangular coordinate system of the UAV near-ground operation space described in step 1 coincides with the UAV body coordinate system at the start of the operation and remains unchanged throughout the operation process.

4. A multi-modal control system for a quad-rotor UAV near-ground operation mission, characterized in that: The system has a program module corresponding to the steps of the method described in any one of claims 1 to 3 above, and executes the steps in the above-mentioned multi-modal control method for near-ground operation tasks of a quad-rotor unmanned aerial vehicle during operation.

5. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and the computer program is configured to implement the steps in the multimodal control method for near-ground operation tasks of a quadrotor unmanned aerial vehicle according to any one of claims 1 to 3 when called by a processor.

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