High-energy-efficiency near-earth four-rotor unmanned aerial vehicle multi-mode flight control method and system and storage medium

Abstract

The invention discloses a quadrotor unmanned aerial vehicle near-earth operation task multi-mode control method and system and a storage medium, relates to the technical field of unmanned aerial vehicle control, and aims to solve the problem that an existing unmanned aerial vehicle control method is difficult to adapt to reliable flight control under ground disturbances at different heights by adopting a single-mode controller design. And the problem that anti-interference flight control of partial states can only be realized under the existing ground disturbance is solved. According to the invention, high-energy-efficiency control is carried out by utilizing extra lift force generated by ground turbulent flow, and a multi-mode height-dependent variable parameter controller is designed by distinguishing different modes at different heights, so that high-performance and high-energy-efficiency flight control at different heights near the ground can be realized. The flight length in the operation process is reduced, the lift force requirement of the rotor wings is lowered, and the purpose of cost-saving, efficiency-improving and high-energy-efficiency flight control is achieved. The flight stability of the unmanned aerial vehicle under near-earth disturbance is guaranteed, meanwhile, the energy loss of the unmanned aerial vehicle is reduced, the purposes of saving cost and improving efficiency are achieved, and high engineering application value is achieved.

Description

Technical Field

[0001] The present invention relates to the field of unmanned aerial vehicle control technology, and in particular to a high-energy-efficiency near-ground quad-rotor unmanned aerial vehicle multi-modal flight control method, system and storage medium. Background Art

[0002] Multimodal flight control is an important manifestation of the continuous intersection and integration of advanced aircraft technology and modern control theory. Its causes mainly include changes in the structure / parameters of the platform itself or the environment in which it is located, which requires the adoption of a multimodal switching control design strategy to improve system performance. It is widely used in military and civilian fields such as aerospace, near-ground sea and land. Quadcopter drones are economical / maneuverable / portable flight platforms that can take off and land vertically and have strong low-altitude accessibility. Their applications in target tracking, material delivery, air-ground coordination and other tasks are constantly advancing. As the complexity of tasks increases, the demand for flight control based on multimodal methods to improve control performance of quadcopter drones continues to deepen, such as variable mode flight control of quadcopter drones that are lost / not lost during intermittent target tracking, multimodal control of quadcopter drones with deformable arms to balance flight agility and operational stability, and variable mode control of air-ground dual-purpose quadcopter drones to improve energy efficiency.

[0003] With the development of sensor technology and flight control technology, in addition to the above-mentioned dual-purpose air-to-ground drones, there are more and more near-ground operation scenarios for quad-rotor drones, such as ground sample collection for environmental monitoring of oceans / wetlands / agriculture and forestry, genetic resource collection for wildlife protection, near-ground information collection and perception, etc. In these operation scenarios, the quad-rotor drone is close to the ground, and the airflow discharged downward by the rotor will be quickly blocked by the ground, forming a reaction turbulence, which seriously damages the flight stability of the quad-rotor drone. Most existing methods use high-altitude circling, rapid takeoff and landing, etc. to minimize the existence time of complex near-ground airflow, but this will increase the length of the drone's operation path and the corresponding flight time, and the efficiency is extremely poor in dense near-ground operation scenarios.

[0004] The existing research on flight control of quadrotor UAV near ground operation is gradually developing. The main methods include a series of single-mode control methods such as treating complex spoilers as disturbances of the flight control system for robust control, treating spoiler forces as variable parameters for adaptive control, or ignoring spoilers / fast response feedback control after state changes. In fact, in recent years, in the analysis and modeling of various disturbance forces generated by ground spoilers, it was found that the rotor thrust has a strong nonlinear correlation with its height above the ground. As its height above the ground continues to decrease, the reaction force of near-ground spoilers continues to increase, and the growth rate continues to increase, making its ground spoiler reaction force present a complex multi-modal phenomenon of no at high altitude, slight at low altitude, small near the ground, and large at the ground. The existing single-mode controller is difficult to ensure the high performance, stable and reliable flight of quadrotor UAVs at different altitudes. Therefore, a complex multi-modal flight control method is urgently needed to realize the near-ground flight control of quadrotor UAVs.

[0005] In addition, reducing power consumption during flight operations, improving energy efficiency, and increasing operating time are key operating indicators for various types of electric-driven drones, such as quadcopters. When a drone flies close to the ground, the ground turbulence interferes with flight stability, and the rising airflow in it can also form an upward thrust on the drone. Existing research mainly considers the active suppression of thrust, and designs flight controllers for single states such as attitude control and altitude / yaw angle of quadcopters. It does not consider controller design for all states of quadcopters, making it difficult to achieve near-ground flight control of quadcopters, nor is it possible to use the rising thrust contained in ground turbulence to achieve high-efficiency flight control with low current and low output lift. This is also a difficult problem that the academic community needs to study 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 altitudes, and can only achieve anti-interference flight control problems in some states under the existing ground disturbances.

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

[0009] The present invention provides a high-efficiency multi-mode flight control method for a near-ground quad-rotor 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 near-ground operation space rectangular coordinate system of the drone according to the initial position and the size of the operation range under the target task;

[0011] Step 2: Based on the UAV 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 gravitational acceleration; m represents the body mass; and J is 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-mode 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 They 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 kinetic 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 Solve 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, solve the angular velocity according to formula (3), then solve 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 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 z The symbolic function of

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

[0024]

[0025]

[0026] Substitute the result of formula (6) into formula (1) to solve the height 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 by 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 predetermined 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 described in step 1 coincides with the coordinate system of the UAV body at the beginning of the operation and remains unchanged during 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 quad-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] Aiming at the situation that the quad-rotor UAV is subject to different degrees of ground turbulence interference at different altitudes during near-ground missions, the present invention proposes to use the additional lift generated by the 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-efficiency flight control at different altitudes near the ground. Specifically, the beneficial effects of the present invention are:

[0040] ① Compared with the traditional single-mode robustness and adaptive control method, the present invention utilizes the multi-mode controller design idea to specifically design a multi-mode variable parameter controller at different flight altitudes, and performs real-time scheduling 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 close to the ground operation mission plan, the present invention fully considers the reaction lift generated by the ground spoiler, and can use the ground effect lift to achieve flight control under different ground spoilers. It not only reduces the flight length during the operation, but also reduces the rotor lift demand, thereby achieving the purpose of high-efficiency flight control with cost savings and efficiency increases.

[0042] To sum up, the present invention takes a four-rotor UAV operating near the ground as the application object, performs multi-mode improvement and optimization on the basis of traditional single-mode flight control, combines the rational use of ground spoiler lift, and realizes high-efficiency flight control of the four-rotor UAV during near-ground operations. While ensuring the flight stability of the UAV under near-ground spoiler, it also reduces its energy loss, thereby achieving 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 near-ground operation task of a quad-rotor UAV in an embodiment of the present invention;

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

[0045] Figure 3 This is a framework diagram of the attitude loop tracking control of a quad-rotor drone under ground spoiler interference in an embodiment of the present invention;

[0046] Figure 4 It is a framework diagram of the position loop tracking control of a quad-rotor drone under ground spoiler interference in an embodiment of the present invention;

[0047] Figure 5 This is a diagram showing the attitude tracking effect of a quad-rotor drone under the interference of ground spoiler in an embodiment of the present invention;

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

[0049] In order to enable those skilled in the art to better understand the scheme of the present invention, exemplary implementations or embodiments of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described implementations or embodiments are only implementations or embodiments of a part of the present invention, not all of them. Based on the implementations or embodiments of the present invention, all other implementations or embodiments obtained by ordinary technicians in the field 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 near-ground operation task of a quad-rotor UAV, 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 size of the operation range under the target task.

[0053] At the beginning of the operation, the initial position and attitude information of the near-ground operation quadrotor drone is obtained using sensors such as gyroscopes, accelerometers, and barometers. 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, determine the operating range of the UAV and establish the UAV body coordinate system Near-Earth Operation Task Space Cartesian 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 (also the center of gravity) of the quadcopter. The rectangular coordinate system of the drone's near-ground operating space Direction and drone body coordinate system at the start of operation During the near-ground operation, the UAV's body coordinate transformation caused by its linear velocity and angular velocity is converted into the global coordinate position of the mission space coordinate system, which is convenient for implementing the operation task.

[0054] Step 2: Based on the rectangular coordinate system of the working space established in step 1, a trajectory tracking control system model containing multiple modes during the operation process is further established, such as Figure 2 As shown in the figure, according to the nonlinear degree of the trajectory tracking control system under the interference of ground spoilers, it is divided into different modes. Each mode corresponds to a different flight altitude range, and the control system design under the corresponding mode is performed. According to the current altitude h∈[min h1,max h1], where min h1 and max h1 are the minimum altitude and maximum altitude corresponding to the current mode, respectively, 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 at the same propeller speed when the drone is far away from the ground, and R is the propeller blade diameter. Define the three-axis position states x, y, z, and three-axis rotation states θ, φ, and ψ of the drone, and construct a drone dynamics model considering ground spoiler 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 gravitational acceleration; m represents the body mass; and J is 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,∞ They are the total lift of the propeller and the torque of the corresponding shaft without considering the ground disturbance, 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-mode linear variable parameter tracking control system is established:

[0058]

[0059] Where σ is the system mode corresponding to different flight altitudes, B s , B wThey 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 kinetic 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 as the height changes.

[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 the 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 Solve 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 set of different 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 the matrix W i k The following matrix inequality is 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 real-time adjustment of the drone’s attitude and has a certain anti-interference ability (its robust performance index is Realize real-time tracking of the position loop and the artificially given reference attitude, so as to update the attitude of the quadrotor UAV flying close to the ground. In the formula, γ0 represents the performance index of the system, reflecting the sensitivity of the system to disturbance; 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 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 z The symbolic function of

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

[0072]

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

[0074] Since Q(h) is greater than 1 at different ground proximity heights and ground proximity modes, the UAV is more accurate when performing altitude adjustment. The reference attitude angle (virtual control input) corresponding to the horizontal position adjustment is further solved, using the same sliding mode state and reaching law calculation method as the 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] Based on the attitude angle result obtained by solving (9), the propeller lift of the UAV is solved using the process of step three, 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 proved that the symbolic function structure of the approaching law can overcome the parameter uncertainty in the control system. According to the current reference trajectory and the above control law, the control input / attitude reference angle is continuously solved, and the thrust, torque and inner loop tracking control algorithm generated by the propeller speed of the UAV are respectively used to achieve it (see step 3 for details, which will also be converted into the propeller speed of the UAV after the inner loop multi-modal tracking solution). Since the ground spoiler lift can provide additional support torque during the near-ground flight, high-efficiency flight control can be achieved.

[0081] Step 5: Repeat steps 2, 3 and 4 until the UAV flying close to the ground reaches the predetermined 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 command, 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 status updates. This cycle is repeated, continuously measuring the drone's current position and attitude to determine the mode of the flight control system, and continuing to determine the control input until the drone flying close to the ground reaches the predetermined position and attitude.

[0083] The multimodal control method (algorithm) for near-ground operation tasks of a quad-rotor unmanned aerial vehicle proposed in the present invention is the underlying technical core of the present 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 quad-rotor UAV 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 quad-rotor UAV during operation.

[0085] The computer program of the developed system (software) is stored on a computer-readable storage medium, and the computer program is configured to implement the steps of the above-mentioned multi-modal control method for near-ground operation tasks of a quad-rotor drone when called by a processor. That is, the present invention is materialized on a carrier to become a computer program product.

[0086] Various implementations of the systems and techniques described herein can be realized in digital electronic circuit systems, integrated circuit systems, 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 can be executed and / or interpreted on a programmable system including 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 codes) of the present invention include machine instructions for programmable processors, and these computer programs 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 device (e.g., disk, optical disk, memory, 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 machine-readable signals. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0088] Example 1

[0089] In order to verify the effectiveness of the energy-efficient near-ground quad-rotor UAV multi-modal flight control method proposed in the present invention, this embodiment uses system simulation for testing and verification:

[0090] (1) Verification of the attitude control capability of the UAV in near-ground operations. 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, the robustness index of the controller is γ = 0.4456. The obtained attitude control curve is as follows Figure 5 As shown, 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 position control capability in near-ground operations. In the near-ground tracking control task of a 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 drone. 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, which are multi-modal variable parameter control and traditional state feedback control, respectively. When the desired altitude is reduced, the traditional tracking control method cannot effectively control the UAV to reach the reference altitude. The proposed multi-modal high-efficiency flight controller can use the ground spoiler lift to ensure the near-ground position tracking performance, use a lower speed to obtain the desired lift and torque, and adjust its own control parameters in real time according to the current altitude and mode, so as to be suitable for the near-ground UAV flight control mission.

[0092] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art 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 protection scope of the present invention.

Claims

1. A highly energy-efficient multi-modal flight control method for a near-ground quad-rotor UAV, 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 near-ground operation space rectangular coordinate system of the drone according to the initial position and the size of the operation range under the target task; Step 2: Based on the UAV 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 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 gravitational acceleration; m represents the body mass; and J 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-mode linear variable parameter tracking control system is established: Where σ is the system mode corresponding to different flight altitudes, B s , B w They 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 kinetic 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 Solve 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, solve the angular velocity according to formula (3), then solve 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 z The derivative of , under the sliding mode condition, is Solve Select the reaching law as -K z sgn(s z );K z is the control gain, sgn(s z ) is z The symbolic function of Combined with the UAV's dynamic model, the total lift is solved by the altitude controller: Substitute the result of formula (6) into formula (1) to solve the height 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 by 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 predetermined position and attitude.

2. The multi-modal control method for near-ground operation tasks of a quad-rotor UAV according to claim 1 is characterized in that: The attitude information in step 1 includes: 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.

3. The multi-modal control method for near-ground operation tasks of a quad-rotor UAV according to claim 2 is 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 beginning of the operation and remains unchanged during the entire operation process.

4. A multi-modal control system for near-ground operation tasks of a quad-rotor UAV, 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 quad-rotor unmanned aerial vehicle according to any one of claims 1 to 3 when called by a processor.

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