Multirotor airspeed calculation method, device and computer-readable storage medium

Abstract

The present invention discloses a multi-rotor airspeed solution method, device and computer-readable storage medium, wherein the method comprises: establishing an airspeed solution mathematical model; defining a function f(V) according to the airspeed solution mathematical model in each solution cycle, and combining the real-time measured θ inclination angle and a x Acceleration, using the Newton iterative algorithm to solve the root of the equation f(V) = 0 in real time, as the real-time airspeed V. The present invention implements an airspeed calculation solution based on dynamic principles, fully utilizing dynamic principles and combining the unique control method of multi-rotor. Without adding hardware sensors, known attitude measurements and acceleration measurements are used as algorithm inputs, and the software algorithm calculates airspeed data with the required accuracy. This simplifies the hardware structure, reduces the risk of electrical failure, and saves manufacturing, debugging, and maintenance costs.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicles, and in particular to a multi-rotor airspeed calculation method, device, and computer-readable storage medium. Background Art

[0002] Unlike traditional aircraft, multirotors currently rely on ground speed control rather than airspeed control. Therefore, multirotors typically do not have airspeed sensors installed. However, airworthiness safety requirements for large multirotors, as well as considerations of payload strength, often require airspeed measurement and airspeed envelope protection.

[0003] Existing solutions, based on the aforementioned requirements, can consider retrofitting large multi-rotor aircraft with traditional airspeed measurement devices based on the dynamic / static pressure principle. However, these traditional airspeed sensors have significant limitations when used on large multi-rotor aircraft: first, they are susceptible to interference from the turbulent airflow of multiple propellers, or require significant structural installation costs to protect against airflow interference; second, for multi-rotor aircraft, airspeed measurement does not directly affect the control laws, and the installation of an airspeed meter would increase manufacturing, commissioning, and maintenance costs.

[0004] Therefore, how to propose an airspeed calculation algorithm based on dynamic principles without adding hardware sensors has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In order to solve the above technical defects in the prior art, the present invention proposes a multi-rotor airspeed solution method, which includes:

[0006] Establish the mathematical model for airspeed calculation k1(θ)·V+k2(θ·V 2 +k3(θ)·V 3 =mg tanθ-ma x , where m is mass, g is acceleration due to gravity, θ is the inclination angle, and a x is the acceleration, V is the airspeed, k1(θ), k2(θ), k3(θ) are the known 1st, 2nd, and 3rd order drag coefficient functions respectively;

[0007] The function f(V) is defined according to the airspeed solution mathematical model for each solution cycle, where f(V) = k3(θ)·V 3 +k2(θ)·V 2 +k1(θ)·V-mg tanθ+ma x , the θ inclination angle and the a x The acceleration is a real-time measurement value, and the Newton iteration algorithm is used to solve the root of the equation f(V)=0 in real time as the real-time airspeed V.

[0008] Optionally, before establishing the airspeed calculation mathematical model, the method includes:

[0009] Establish the multi-rotor 6-DOF dynamic constraint equation in the aircraft's horizontal coordinate system O-XYZ:

[0010]

[0011] Among them, ∑F P is the total thrust generated by the propeller rotation, ∑F L is the lift generated by the movement of the fuselage shape in the airflow field, ∑F D is the total aerodynamic resistance of the whole machine, ∑M is the total torque of the whole machine, J is the moment of inertia of the whole machine, a is the linear acceleration of the center of mass, w is the angular velocity of the whole machine rigid body motion, and α is the angular acceleration of the whole machine rigid body motion.

[0012] Optionally, before establishing the airspeed calculation mathematical model, the method further includes:

[0013] Under the control law constraints of attitude stabilization, altitude holding, and position tracking, the following assumptions are made:

[0014] The three-axis posture changes slowly, and the three-axis angular velocity ω x ≈ω y ≈ω z ≈0, triaxial acceleration α x ≈α y ≈α z ≈0;

[0015] The vertical direction changes slowly, the vertical acceleration a z ≈0;

[0016] Slow change of the moment of inertia of the three axes

[0017] The propeller lift is much greater than the body lift, that is, ∑F Lx ≈0,∑F Ly ≈0,∑F Lz ≈0.

[0018] Optionally, before establishing the airspeed calculation mathematical model, the method further includes:

[0019] Based on the above assumptions, the 6-DOF dynamic constraint equations of the multirotor are simplified to obtain the 3-DOF dynamic equations for longitudinal and lateral linear motion:

[0020]

[0021] Optionally, before establishing the airspeed calculation mathematical model, the method further includes:

[0022] Establish the longitudinal motion dynamics constraint equation:

[0023]

[0024] Among them, F prop is the total thrust generated by the propeller rotation, F drag is the total aerodynamic resistance of the whole machine.

[0025] Optionally, before establishing the airspeed calculation mathematical model, the method further includes:

[0026] Establish the aerodynamic constraint equation for longitudinal motion wind resistance:

[0027] F drag =k1(θ)·V+k2(θ)·V 2 +k3(θ)·V 3 .

[0028] Optionally, establishing an airspeed calculation mathematical model includes:

[0029] The airspeed calculation mathematical model is established based on the longitudinal motion dynamic constraint equation and the longitudinal motion windage aerodynamic constraint equation:

[0030] k1(θ)·V+k2(θ)·V 2 +k3(θ)·V 3 =mg tanθ-ma x .

[0031] Optionally, the method further includes:

[0032] Under no-wind conditions, steady flow conditions, or turbulent gust conditions, airspeed calculation is performed according to the airspeed calculation mathematical model.

[0033] The present invention also proposes a multi-rotor airspeed solution device, which includes a memory, a processor, and a computer program stored in the memory and runnable on the processor. When the computer program is executed by the processor, the steps of the multi-rotor airspeed solution method as described in any one of the above items are implemented.

[0034] The present invention also proposes a computer-readable storage medium, which stores a multi-rotor airspeed solution program. When the multi-rotor airspeed solution program is executed by a processor, the steps of the multi-rotor airspeed solution method as described in any one of the above items are implemented.

[0035] The multi-rotor airspeed calculation method, device and computer readable storage medium of the present invention are implemented by establishing an airspeed calculation mathematical model k1(θ)·V+k2(θ·V 2 +k3(θ)·V 3 =mg tanθ-ma x, where m is mass, g is acceleration due to gravity, θ is the inclination angle, and a x is the acceleration, V is the airspeed, k1(θ), k2(θ), and k3(θ) are the preset 1st, 2nd, and 3rd order drag coefficient functions, respectively; the function f(V) is defined according to the airspeed solution mathematical model of each solution cycle, where f(V) = k3(θ)·V 3 +k2(θ)·V 2 +k1(θ)·V-mg tanθ+ma x , the θ inclination angle and the a x Acceleration is measured in real time, and the Newton iteration algorithm is used to solve the root of the equation f(V) = 0 in real time, which is used as the real-time airspeed V. A dynamics-based airspeed calculation scheme has been implemented, fully utilizing dynamics principles and combining them with the unique control methods of multirotors. Without adding hardware sensors, known attitude and acceleration measurements are used as algorithm inputs, and the software algorithm calculates airspeed data with the required accuracy. This simplifies the hardware structure, reduces the risk of electrical failure, and saves manufacturing, commissioning, and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0037] Figure 1 This is the first flow chart of the multi-rotor airspeed calculation method of the present invention;

[0038] Figure 2 Schematic diagram of the coordinate system of the multi-rotor airspeed calculation method of the present invention;

[0039] Figure 3 It is a schematic diagram of longitudinal motion force analysis under reference motion of the multi-rotor airspeed solution method of the present invention. DETAILED DESCRIPTION

[0040] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] In the subsequent description, suffixes such as "module," "component," or "unit" used to represent elements are only used to facilitate the description of the present invention and have no specific meaning. Therefore, "module," "component," or "unit" can be used interchangeably.

[0042] Figure 1 This is the first flow chart of the multi-rotor airspeed calculation method of the present invention. This embodiment proposes a multi-rotor airspeed calculation method, which includes:

[0043] S1. Establish the mathematical model for airspeed calculation k1(θ)·V+k2(θ·V 2 +k3(θ)·V3 αmg tanθ-ma x , where m is mass, g is acceleration due to gravity, θ is the inclination angle, and a x is the acceleration, V is the airspeed, k1(θ), k2(θ), and k3(θ) are the preset 1st, 2nd, and 3rd order drag coefficient functions respectively;

[0044] S2. Define a function f(V) based on the airspeed solution mathematical model for each solution cycle, where f(V) = k3(θ)·V 3 +k2(θ)·V 2 +k1(θ)·V-mg tanθ+ma x , the θ inclination angle and the a x The acceleration is a real-time measurement value, and the Newton iteration algorithm is used to solve the root of the equation f(V)=0 in real time as the real-time airspeed V.

[0045] Please refer to Figure 2 The coordinate system diagram shown in FIG. 1 is a diagram showing a coordinate system. In this embodiment, first, the following coordinate system definitions are determined: the ground coordinate system O E -X E Y E Z E ; Body coordinate system O B -X B Y B Z B The horizontal coordinate system of the fuselage (i.e., the custom coordinate system) is O-XYZ, where the origin O is set at the center of mass of the fuselage, OX is set in the symmetry plane of the fuselage, pointing horizontally to the front of the fuselage, OZ is vertically downward, and OY follows the right-hand rule and points horizontally to the right side of the fuselage.

[0046] In this embodiment, the following sign convention is then determined: ∑F P and F prop is the total thrust generated by the propeller rotation, ∑F L is the lift generated by the movement of the fuselage shape in the airflow field, ∑F D and F drag is the total aerodynamic resistance of the whole machine, ∑M is the total torque of the whole machine, which includes the active torque generated by the propeller rotation and the additional torque generated by other aerodynamic forces, m is the mass of the whole machine, J is the moment of inertia of the whole machine, v is the linear velocity of the center of mass, a is the linear acceleration of the center of mass, w is the angular velocity of the whole machine rigid body motion, α is the angular acceleration of the whole machine rigid body motion, g is the acceleration of gravity, V is the airspeed, V wind is the incoming wind speed, V gnd is the ground speed, V desis the target ground speed, θ is the horizontal inclination angle of the fuselage (i.e., the roll angle or pitch angle of the fuselage), optionally, for longitudinal motion, θ is the pitch angle, k1(θ), k2(θ), k3(θ) are the 1st, 2nd, and 3rd order drag coefficient functions dynamically related to the horizontal inclination angle, optionally, the inclination angle θ and the a x The acceleration is a real-time measurement value. Furthermore, in this embodiment, the above physical quantity subscripts x, y, and z are used to represent the three-axis projection or component of the horizontal coordinate system of the corresponding body. b ,y b ,z b (x e ,y e ,z e ) represents the three-axis projection or component in the corresponding body coordinate system (i.e., the ground coordinate system).

[0047] In this embodiment, the above-mentioned mathematical model for airspeed calculation is analyzed, wherein: mass m and gravitational acceleration g are known quantities; it is known from aerodynamic related knowledge that there is a definite functional relationship between the drag coefficients k1(θ), k2(θ), k3(θ) and the inclination angle θ, and this functional relationship can be calculated offline by aerodynamic simulation or experimental calibration methods. For a long time, at the beginning of the design of the aircraft, it has been necessary to obtain the functional relationship between the drag coefficients k1(θ), k2(θ), k3(θ) and the inclination angle θ through aerodynamic simulation tests, that is, the above functional relationship can be considered as a known function; the inclination angle θ can be measured in real time by the attitude measurement system of the flight control system, and the acceleration a x The accelerometer of the flight control system measures the accelerometer in real time, or performs attitude transformation on the accelerometer measurement results to calculate a x , that is, θ, a x is a measurable known quantity. Further, in this embodiment, considering that the above-mentioned airspeed solution model is a cubic equation about the airspeed V in each solution cycle, this embodiment defines the function f(V):

[0048] f(V)=k3(θ)·V 3 +k2(θ)·V 2 +k1(θ)·V-mg tanθ+ma x .

[0049] Furthermore, this embodiment uses the Newton iteration algorithm to solve the root of the equation f(V)=0 in real time as the current real-time airspeed V of the multirotor aircraft.

[0050] Optionally, in this embodiment, before establishing the airspeed calculation mathematical model, the steps include:

[0051] Establish the multi-rotor 6-DOF dynamic constraint equation in the aircraft's horizontal coordinate system O-XYZ:

[0052]

[0053] Among them, ∑F P is the total thrust generated by the propeller rotation, ∑F L is the lift generated by the movement of the fuselage shape in the airflow field, ∑F D is the total aerodynamic resistance of the whole machine, ∑M is the total torque of the whole machine, J is the moment of inertia of the whole machine, a is the linear acceleration of the center of mass, w is the angular velocity of the whole machine rigid body motion, and α is the angular acceleration of the whole machine rigid body motion.

[0054] Optionally, in this embodiment, before establishing the airspeed calculation mathematical model, the method further includes:

[0055] Considering the general flight mode of a multirotor aircraft, namely the steady straight-line level flight mode, and under the control law constraints of attitude augmentation, altitude hold, and position tracking, the following assumptions are made:

[0056] The three-axis posture changes slowly, and the three-axis angular velocity ω x ≈ω y ≈ω z ≈0, triaxial acceleration α x ≈α y ≈α z ≈0;

[0057] The vertical direction changes slowly, the vertical acceleration a z ≈0;

[0058] Slow change of the moment of inertia of the three axes

[0059] The propeller lift is much greater than the body lift, that is, ∑F Lx ≈0,∑F Ly ≈0,∑F Lz ≈0.

[0060] Optionally, in this embodiment, before establishing the airspeed calculation mathematical model, the method further includes:

[0061] Based on the above assumptions, the 6-DOF dynamic constraint equations of the multirotor are simplified to obtain the 3-DOF dynamic equations for longitudinal and lateral linear motion:

[0062]

[0063] In the three-degree-of-freedom dynamic equations for longitudinal and lateral linear motion described in this embodiment, the lateral and longitudinal dynamic models are decoupled. Only the modeling process for the longitudinal (i.e., XOZ) plane dynamic model is described, and the resulting conclusions are also applicable to lateral motion. It should be noted that this embodiment primarily focuses on longitudinal dynamic modeling, and where ambiguity is not present, the subscripts x, y, and z are omitted.

[0064] Optionally, in this embodiment, before establishing the airspeed calculation mathematical model, the method further includes:

[0065] Establish the longitudinal motion dynamics constraint equation:

[0066]

[0067] Please refer to Figure 3 The schematic diagram of longitudinal motion force analysis under the reference motion is shown, where F prop is the total thrust generated by the propeller rotation, F drag is the total aerodynamic resistance of the whole machine.

[0068] Optionally, in this embodiment, before establishing the airspeed calculation mathematical model, the method further includes:

[0069] Establish the aerodynamic constraint equation for longitudinal motion wind resistance:

[0070] F drag =k1(θ)·V+k2(θ)·V 2 +k3(θ)·V 3 .

[0071] Optionally, in this embodiment, establishing an airspeed calculation mathematical model includes:

[0072] The airspeed calculation mathematical model is established based on the longitudinal motion dynamic constraint equation and the longitudinal motion windage aerodynamic constraint equation:

[0073] k1(θ)·V+k2(θ)·V 2 +k3(θ)·V 3 =mg tanθ-ma x .

[0074] Optionally, in this embodiment, the method further includes:

[0075] Under no-wind conditions, steady flow conditions, or turbulent gust conditions, airspeed calculation is performed according to the airspeed calculation mathematical model.

[0076] In this embodiment, considering that the modeling and solution process of the above-mentioned airspeed solution model do not impose any requirements on the external airflow state, the airspeed solution algorithm proposed in this embodiment is applicable to ground-no-wind conditions, steady flow field conditions, and turbulent gust conditions.

[0077] The beneficial effect of this embodiment is that by establishing the mathematical model k1(θ)·V+k2(θ·V 2 +k3(θ)·V 3 =mg tanθ-ma x, where m is mass, g is acceleration due to gravity, θ is the inclination angle, and a x is the acceleration, V is the airspeed, k1(θ), k2(θ), and k3(θ) are the preset 1st, 2nd, and 3rd order drag coefficient functions, respectively; the function f(V) is defined according to the airspeed solution mathematical model of each solution cycle, where f(V) = k3(θ)·V 3 +k2(θ)·V 2 +k1(θ)·V-mg tanθ+ma x , the θ inclination angle and the a x Acceleration is measured in real time, and the Newton iteration algorithm is used to solve the root of the equation f(V) = 0 in real time, which is used as the real-time airspeed V. A dynamics-based airspeed calculation scheme has been implemented, fully utilizing dynamics principles and combining them with the unique control methods of multirotors. Without adding hardware sensors, known attitude and acceleration measurements are used as algorithm inputs, and the software algorithm calculates airspeed data with the required accuracy. This simplifies the hardware structure, reduces the risk of electrical failure, and saves manufacturing, commissioning, and maintenance costs.

[0078] Based on the above embodiments, the present invention also proposes a multi-rotor airspeed solution device, which includes a memory, a processor, and a computer program stored on the memory and runnable on the processor. When the computer program is executed by the processor, the steps of the multi-rotor airspeed solution method as described in any one of the above items are implemented.

[0079] It should be noted that the above-mentioned device embodiment and method embodiment belong to the same concept, and their specific implementation process is detailed in the method embodiment, and the technical features in the method embodiment are applicable to the device embodiment, which will not be repeated here.

[0080] Based on the above embodiments, the present invention also proposes a computer-readable storage medium, which stores a multi-rotor airspeed solution program. When the multi-rotor airspeed solution program is executed by a processor, the steps of the multi-rotor airspeed solution method described in any one of the above items are implemented.

[0081] It should be noted that the above-mentioned medium embodiment and method embodiment belong to the same concept, and their specific implementation process is detailed in the method embodiment, and the technical features in the method embodiment are applicable to the medium embodiment, which will not be repeated here.

[0082] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0083] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0084] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better embodiment. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0085] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A multi-rotor airspeed calculation method, characterized in that: The method comprises: Establishing a mathematical model for airspeed calculation ,in, For the quality of the whole machine, is the acceleration due to gravity, is the horizontal inclination angle of the fuselage, is the X-axis component of the horizontal coordinate system of the body corresponding to the centroid linear acceleration, is the airspeed, 、 、 They are the preset 1st, 2nd and 3rd order drag coefficient functions respectively; The mathematical model for airspeed solution is defined as a function of each solution cycle ,in, , and stated It is a real-time measurement value, and the Newton iteration algorithm is used to solve the equation in real time. The root of .

2. The multi-rotor airspeed calculation method according to claim 1, characterized in that: Before establishing the airspeed calculation mathematical model, the following steps are included: In the horizontal coordinate system of the body The following is the establishment of the multi-rotor 6-DOF dynamic constraint equation: ； in, is the total thrust generated by the propeller rotation, It is the lift generated by the movement of the fuselage shape in the airflow field. is the total aerodynamic resistance of the whole machine, is the total torque of the whole machine, is the moment of inertia of the whole machine, is the linear acceleration of the center of mass, is the linear velocity of the center of mass, is the angular velocity of the entire rigid body motion, is the angular acceleration of the rigid body motion of the whole machine, the above physical quantities are subscripted ， ， Indicates the three-axis components of the corresponding body horizontal coordinate system.

3. The multi-rotor airspeed calculation method according to claim 2, characterized in that: Before establishing the mathematical model for airspeed calculation, the method further includes: Under the control law constraints of attitude stabilization, altitude holding, and position tracking, the following assumptions are made: The three-axis attitude changes slowly, and the three-axis angular velocity , three-axis acceleration ; The vertical direction changes slowly, the vertical center of mass acceleration ; Slow change of the moment of inertia of the three axes ; The propeller lift is much greater than the body lift, that is, , , .

4. The multi-rotor airspeed calculation method according to claim 3, characterized in that: Before establishing the mathematical model for airspeed calculation, the method further includes: Based on the above assumptions, the 6-DOF dynamic constraint equations of the multirotor are simplified to obtain the 3-DOF dynamic equations for longitudinal and lateral linear motion: 。 5. The multi-rotor airspeed calculation method according to claim 4, characterized in that: Before establishing the mathematical model for airspeed calculation, the method further includes: Establish the longitudinal motion dynamics constraint equation: ； in, is the total thrust generated by the rotation of the propeller, is the total aerodynamic resistance of the whole machine.

6. The multi-rotor airspeed calculation method according to claim 5, characterized in that: Before establishing the mathematical model for airspeed calculation, the method further includes: Establish the aerodynamic constraint equation for longitudinal motion wind resistance: 。 7. The multi-rotor airspeed calculation method according to claim 6, characterized in that: The method of establishing an airspeed calculation mathematical model comprises: The airspeed calculation mathematical model is established based on the longitudinal motion dynamic constraint equation and the longitudinal motion windage aerodynamic constraint equation: 。 8. The multi-rotor airspeed calculation method according to claim 7, characterized in that: The method further comprises: Under no-wind conditions, steady flow conditions, or turbulent gust conditions, airspeed calculation is performed according to the airspeed calculation mathematical model.

9. A multi-rotor airspeed calculation device, characterized in that: The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, the steps of the multi-rotor airspeed calculation method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a multi-rotor airspeed solution program, which, when executed by a processor, implements the steps of the multi-rotor airspeed solution method according to any one of claims 1 to 8.

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