Coaxial dual-rotor aircraft dynamics modeling method considering aerodynamic characteristics of rotors

Abstract

The invention provides a dynamic modeling method for a coaxial dual-rotor aircraft considering aerodynamic characteristics of rotors. The dynamic modeling method comprises the following steps: deducing a tension coefficient and a resistance moment coefficient based on a blade element theorem; deriving a tension coefficient based on a slip flow theorem; the tension coefficient deduced based on the leaf element theorem and the tension coefficient deduced based on the slip flow theorem are combined, Cy alpha and Cx are obtained through calculation, the actual inflow ratio lambda is obtained through calculation, and theoretically calculated tension T and resistance moment Q are obtained through calculation according to the actual inflow ratio; obtaining the resultant tension and resultant moment of the upper and lower propeller discs; the aerodynamic resultant force, the lateral force and the backward force of the propeller disc are obtained through calculation; and completing the construction of a dynamic model according to the trajectory motion model, the blade tension and resistance moment calculation model and the direct-current brushless motor model. According to the technical scheme, in the initial stage of the design stage of the aircraft, the influence of the unsteady aerodynamic characteristics of the rotor wings on the guidance control system is analyzed in a six-degree-of-freedom simulation mode, and the technical problem that the aircraft is unstable due to some aerodynamic characteristics of the rotor wings is solved.

Description

Technical Field

[0001] The invention relates to the technical field of guidance and control of small rotorcraft, and in particular to a coaxial twin-rotor aircraft dynamics modeling method taking into account the aerodynamic characteristics of the rotor. Background Art

[0002] Small coaxial rotor aircraft are small and easy to carry. They can take off and land vertically in complex environments, approach targets, and transmit target information or identify targets autonomously through image sensors. They are particularly suitable for performing reconnaissance and surveillance tasks in dangerous areas such as high pollution and high radiation that cannot be monitored by satellites, reconnaissance aircraft and personnel. Especially in military missions, if small aircraft carry micro high-efficiency warheads, electronic jamming equipment, etc., they can carry out close-range attacks on enemy personnel, high-value equipment and other targets, causing fatal or non-fatal damage.

[0003] Small coaxial rotor aircraft still face many difficulties when it comes to attacking targets, such as analyzing the impact of the rotor's unsteady aerodynamic characteristics on the guidance and control system in attack mode. Such impacts cause large fluctuations in the rotor's aerodynamic force and torque, and may even cause the aircraft to become unstable. Summary of the invention

[0004] The present invention provides a coaxial twin-rotor aircraft dynamics modeling method taking into account the aerodynamic characteristics of the rotors. The method can analyze the influence of the unsteady aerodynamic characteristics of the rotors on the guidance and control system by means of six-degree-of-freedom simulation in the early stage of the design, thereby avoiding the technical problem of aircraft instability caused by some rotor aerodynamic characteristics.

[0005] The present invention provides a coaxial twin-rotor aircraft dynamics modeling method considering the aerodynamic characteristics of the rotor, and the coaxial twin-rotor aircraft dynamics modeling method considering the aerodynamic characteristics of the rotor includes: deriving a single blade pull coefficient and a drag torque coefficient based on the blade element theorem; deriving a pull coefficient based on the slipstream theorem; and calculating and obtaining a pull coefficient C by combining the pull coefficient derived based on the blade element theorem and the pull coefficient derived based on the slipstream theorem. T The linear relationship between the lift coefficient of the blade element and the blade element angle of attack C yα The high-order nonlinear equation is: On the six-axis force test bench, the total moment of the aircraft is set to 0, and the pull and drag moment are measured by adjusting the rotor speed, and the test pull coefficient C is obtained by fitting. T And the test resistance moment coefficient C M , the test tension coefficient C T Substitute the theoretically derived tension coefficient C into T The linear relationship between the lift coefficient of the blade element and the blade element angle of attack C yα The linear relationship between the lift coefficient of the blade element and the angle of attack of the blade element is calculated in the high-order nonlinear equation C yα ; Based on the linear relationship between the lift coefficient of the blade element and the angle of attack of the blade element Cyα , calculate and obtain the inflow ratio λ and the drag coefficient component of the laboratory state of each blade element Based on the measured drag moment coefficient C in the experiment M , the inflow ratio λ and the drag coefficient component of the laboratory state Calculate and obtain the blade element drag coefficient C x ; based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα and the blade element drag coefficient C x , use the Newton iteration method to calculate and obtain the actual inflow ratio λ, and calculate and obtain C of the propeller disk in any state according to the actual inflow ratio T and C M , and make corrections to obtain the corrected drag coefficient and the corrected drag moment coefficient Furthermore, obtain the theoretically calculated thrust T and drag moment Q; obtain the thrust interference coefficient and drag moment interference coefficient between the upper propeller disk and the lower propeller disk through a six-force test bench; further obtain the combined thrust and resultant moment of the upper and lower propeller disks. Calculate and obtain the aerodynamic resultant force, lateral force, and backward force of the propeller disk according to the thrust of the propeller disk in any state; based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα , the blade element drag coefficient C x , the corrected drag coefficient the corrected drag moment coefficient the thrust of the propeller disk, the drag moment, the aerodynamic resultant force of the propeller disk, the lateral force, the backward force, the thrust interference coefficient, and the drag moment interference coefficient, and complete the construction of the dynamic model of the small coaxial dual-rotor aircraft according to the trajectory motion model, the blade thrust and drag moment calculation model, and the DC brushless motor model.

[0006] Further, the single-blade thrust coefficient C derived based on the blade element theorem T and the drag moment coefficient C M are where is the drag coefficient component, σ is the blade solidity, C yα is the linear relationship between the blade element lift coefficient and the blade element angle of attack, θ(r) is the pitch angle, is the non-dimensional variable of the distance from the blade element to the blade root, μ is the advance ratio, χ s is the longitudinal cyclic pitch under the constructed coordinate system, λ is the inflow ratio, C x is the blade element drag coefficient.

[0007] Further, the thrust coefficient derived based on the slipstream theorem is where k is the tip loss coefficient, λ c is the rise ratio, V0 is the relative velocity in the axial flow direction at infinity, Ω is the rotor speed, and R is the propeller disk radius.

[0008] Furthermore, the tension coefficient C T and the high-order non-linear equation of the linear relationship C yα between the blade element lift coefficient and the blade element angle of attack is

[0009] Furthermore, the inflow ratio λ of each blade element in the laboratory state can be obtained according to calculation.

[0010] Furthermore, the blade element drag coefficient C x can be obtained according to calculation.

[0011] Furthermore, the corrected tension coefficient and the corrected drag moment coefficient can be obtained according to calculation, where is the integral initial value of the non-dimensionalized variable of the distance from the blade element to the blade root.

[0012] Furthermore, the tension interference coefficient D T and the drag moment interference coefficient D M can be obtained according to where T s is the tension generated when the upper and lower blade disks work simultaneously, T up is the tension of the upper blade disk without interference, T down is the tension of the lower blade disk without interference, Q s is the drag moment generated when the upper and lower blade disks work simultaneously, Q up is the drag moment of the upper blade disk without interference, Q down is the drag moment of the lower blade disk without interference.

[0013] Furthermore, the aerodynamic resultant force, lateral force and backward force of the blade disk can be obtained according to calculation, where R s is the aerodynamic resultant force of the blade disk, H s is the backward force, S s is the lateral force, χ s is the longitudinal cyclic pitch, η s is the lateral cyclic pitch.

[0014] Furthermore, the longitudinal trajectory motion model is where m is the mass of the aircraft, V is the flight speed of the aircraft, α is the angle of attack, G is the gravity, ρ is the air density, θ is the flight inclination angle, F f is the body drag, C f is the drag coefficient of each component, and S is the reference area of each component.

[0015] By applying the technical solution of the present invention, a method for dynamic modeling of a coaxial twin-rotor aircraft considering the aerodynamic characteristics of the rotor is provided. This method is aimed at the aerodynamic characteristics of small coaxial rotor aircraft. Through the rotor aerodynamic theory analysis, the blade element theorem and the slipstream constant force are used to solve the propeller pull and drag torque under any condition. A dynamic model with moderate complexity for six-degree-of-freedom mathematical simulation that considers the state of the propeller angle of attack and other states can be obtained and dynamic simulation can be carried out. This method can take into account both computational efficiency and computational accuracy. This method can be used for the overall design and performance evaluation of small coaxial twin-rotor aircraft and the design of guidance and control systems for small aircraft. This method takes into account the influence of the unsteady aerodynamic characteristics of the rotor on the guidance and control system, and can achieve stable flight of the aircraft. It is of great significance to achieve stable flight for the design of guidance and control systems for towing such aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A schematic diagram of a testing machine installed on a six-axis force test bench according to a specific embodiment of the present invention is shown;

[0018] Figure 2 A schematic diagram of a flight trajectory curve provided according to a specific embodiment of the present invention is shown;

[0019] Figure 3 A schematic diagram of a flight speed curve provided according to a specific embodiment of the present invention is shown;

[0020] Figure 4 A schematic diagram of the total thrust curves of the upper and lower rotors provided in a specific embodiment of the present invention is shown;

[0021] Figure 5 A schematic diagram of the combined torque curves of the upper and lower rotors provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0025] like Figures 1 to 5 As shown, according to a specific embodiment of the present invention, a coaxial twin-rotor aircraft dynamics modeling method considering the aerodynamic characteristics of the rotor is provided. The coaxial twin-rotor aircraft dynamics modeling method considering the aerodynamic characteristics of the rotor includes: deriving the pull coefficient and the drag torque coefficient of a single blade based on the blade element theorem; deriving the pull coefficient based on the slipstream theorem; and calculating and obtaining the pull coefficient C by combining the pull coefficient derived based on the blade element theorem and the pull coefficient derived based on the slipstream theorem. T The linear relationship between the lift coefficient of the blade element and the blade element angle of attack C yα The high-order nonlinear equation is: On the six-axis force test bench, the total moment of the aircraft is set to 0, and the pull and drag moment are measured by adjusting the rotor speed, and the test pull coefficient C is obtained by fitting.T and the experimental resistance moment coefficient C M , substitute the experimental tensile force coefficient C T into the theoretically derived tensile force coefficient C T and the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα in the higher-order nonlinear equation to calculate and obtain the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα ; Based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα , calculate and obtain the inflow ratio λ and the tensile force coefficient component in the laboratory state of each blade element Based on the experimentally measured resistance moment coefficient C M , the inflow ratio λ in the laboratory state and the tensile force coefficient component calculate and obtain the blade element drag coefficient C x ; Based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα and the blade element drag coefficient C x , use the Newton iteration method to calculate and obtain the actual inflow ratio λ, and calculate and obtain C of the propeller disk in any state according to the actual inflow ratio T and C M , and make corrections to obtain the corrected tensile force coefficient and the corrected resistance moment coefficient Furthermore, obtain the theoretically calculated tensile force T and resistance moment Q; obtain the tensile force interference coefficient and the resistance moment interference coefficient between the upper propeller disk and the lower propeller disk through a six-axis force test bench; furthermore, obtain the combined tensile force and the resultant moment of the upper and lower propeller disks; calculate and obtain the aerodynamic resultant force, the lateral force and the backward force of the propeller disk according to the tensile force of the propeller disk in any state; based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα , the blade element drag coefficient C x , the corrected tensile force coefficient the corrected resistance moment coefficient the propeller disk tensile force, the resistance moment, the aerodynamic resultant force of the propeller disk, the lateral force, the backward force, the tensile force interference coefficient and the resistance moment interference coefficient, and complete the construction of the dynamic model of the small coaxial dual-rotor aircraft according to the trajectory motion model, the propeller blade tensile force and resistance moment calculation model, and the DC brushless motor model.

[0026] By using this configuration, a dynamic modeling method for coaxial twin-rotor aircraft considering the aerodynamic characteristics of the rotor is provided. This method is aimed at the aerodynamic characteristics of small coaxial rotor aircraft. Through the rotor aerodynamic theory analysis, the blade element theorem and the slipstream constant force are used to solve the propeller pull and drag torque under any condition. A dynamic model with moderate complexity for six-degree-of-freedom mathematical simulation considering the state of the propeller angle of attack can be obtained and dynamic simulation can be carried out. It can take into account the calculation efficiency and ensure the calculation accuracy at the same time. This method can be used for the overall design and performance evaluation of small coaxial twin-rotor aircraft and the design of guidance and control systems for small aircraft. This method takes into account the influence of the unsteady aerodynamic characteristics of the rotor on the guidance and control system, and can achieve stable flight of the aircraft. It is of great significance to achieve stable flight for the design of guidance and control systems for towing such aircraft.

[0027] Specifically, the purpose of the present invention is to provide a dynamic modeling method for a small coaxial twin-rotor aircraft that takes into account the aerodynamic characteristics of the rotor. In the early stage of designing such aircraft, dynamic simulation is used to support the overall design of the aircraft and the design of the traction guidance control system. In the aircraft, the propeller disk pull force T and the drag moment Q are related to the blade pull coefficient C. T and the drag moment coefficient C M The relationship between

[0028]

[0029]

[0030] The definitions of variables in Formula 1 are shown in Table 1.

[0031] Table 1

[0032] Symbol Meaning Unit T Disk thrust N Q Disk resistance moment N·m <![CDATA[C T > Thrust coefficient Dimensionless <![CDATA[C M > Resistance moment coefficient Dimensionless ρ Air density <![CDATA[kg / m 3 > Ω Rotor speed rad / s R Disk radius (distance from blade tip to rotation center) m A Disk area <![CDATA[m 2 >

[0033] In order to realize the dynamic modeling of the coaxial twin-rotor aircraft taking into account the aerodynamic characteristics of the rotor, the technical solution of the present invention specifically includes the following steps.

[0034] Step 1: Derive the thrust coefficient and drag torque coefficient of a single blade based on the blade element theorem.

[0035] The pull coefficient C of a single blade derived based on the blade element theorem T and the drag moment coefficient C M for

[0036]

[0037] in, is the tension coefficient component, σ is the blade solidity, C yα is the linear relationship between the lift coefficient of the blade element and the angle of attack of the blade element, θ(r) is the pitch angle, is the dimensionless variable of the distance from the blade element to the blade root, μ is the advance ratio, χ s is the longitudinal periodic pitch variation under the structural shaft system, λ is the inflow ratio, C x is the blade element drag coefficient. The variables in the above formula are defined as shown in Table 2 below.

[0038] Table 2

[0039]

[0040] Step 2: Derivation of the tension coefficient based on the slip flow theorem.

[0041] The tension coefficient derived based on the slip flow theorem is

[0042] Where k is the blade tip loss coefficient, λ c is the rise ratio, V0 is the relative velocity in the axial flow direction at infinity, Ω is the rotor speed, and R is the radius of the blade disc.

[0043] The definitions of variables in the above formula are shown in Table 3.

[0044] Table 3

[0045] Symbol Meaning Unit λ Ascent ratio Dimensionless k Tip loss coefficient Dimensionless

[0046] Step 3: Combine the tension coefficient derived from the blade element theorem with the tension coefficient derived from the slipstream theorem to calculate the tension coefficient C T The linear relationship between the lift coefficient of the blade element and the blade element angle of attack C yα The high-order nonlinear equation is: On the six-axis force test bench, the total moment of the aircraft is set to 0, and the thrust and drag moment are measured by adjusting the rotor speed to obtain the initial thrust coefficient C T and the initial resistance moment coefficient C M , the initial tension coefficient C T Substitute the tension coefficient C T The linear relationship between the lift coefficient of the blade element and the blade element angle of attack C yα The linear relationship between the lift coefficient of the blade element and the angle of attack of the blade element is calculated in the high-order nonlinear equation of yα ; Based on the linear relationship between the lift coefficient of the blade element and the angle of attack of the blade element C yα , calculate the inflow ratio λ and tension coefficient components of each blade element in the laboratory state Based on the initial resistance moment coefficient C M , inflow ratio λ and tension coefficient components in laboratory conditions Calculate the blade resistance coefficient C x ; For the initial tension coefficient C T and the initial resistance moment coefficient C M Make a correction to obtain the corrected tension factor and the corrected drag moment coefficient

[0047] Specifically, by combining Equation 2 and Equation 3, Equation 4 can be obtained:

[0048]

[0049] In a laboratory environment, by fixing the aircraft on a six-axis force test bench, these two parameters are calculated. When the aircraft is fixed, λ c = 0, μ = 0. The above equation is simplified as follows.

[0050]

[0051] The solutions of Equation 5 are as follows:

[0052]

[0053] Substituting Equation 6 into Equation 3, the theoretically derived lift coefficient C T and the linear relationship C yα between the blade element lift coefficient and the blade element angle of attack of a higher-order non-linear equation, as shown in the following equation:

[0054]

[0055] On the six-axis force test bench, the total moment of the aircraft is set to 0, and by adjusting the rotor speed, the lift and drag moment are measured, and the experimental lift coefficient C T and the experimental drag moment coefficient C M are obtained by fitting. Substituting the experimental lift coefficient C T into Equation 7 to calculate the linear relationship C yα between the blade element lift coefficient and the blade element angle of attack. Substituting the linear relationship C yα between the blade element lift coefficient and the blade element angle of attack into Equation 6, the inflow ratio λ in the laboratory state of each blade element can be obtained. Substituting the linear relationship C yα between the blade element lift coefficient and the blade element angle of attack into the third formula of Equation 2, the lift coefficient component Substituting the experimentally measured drag moment coefficient C M , the inflow ratio λ in the laboratory state, and the lift coefficient component into the fourth formula of Equation 2 to establish the relationship between the initial drag moment coefficient C M and the blade element drag coefficient C x , and then the blade element drag coefficient C x is obtained.

[0056] Step 4, based on the linear relationship C yα between the blade element lift coefficient and the blade element angle of attack and the blade element drag coefficient C x, the Newton - Raphson method is used to calculate and obtain the actual inflow ratio λ, and based on the actual inflow ratio λ, the C of the propeller disk in any state is calculated T and C M , and corrections are made to obtain the corrected thrust coefficient and the corrected drag - moment coefficient Furthermore, the theoretically calculated thrust T and drag - moment Q are obtained.

[0057] Specifically, in the present invention, in the case of knowing the linear relationship between the blade - element lift coefficient and the blade - element angle of attack C yα and the blade - element drag coefficient C x , substituting the advance ratio μ and the climb ratio λ c into Equation Four, the Newton - Raphson method is used to solve the equation to obtain λ in the actual state, as shown in Equation Nine below. The initial value of λ is calculated according to λ c = 0, μ = 0, χ s = 0.

[0058]

[0059] After calculating and obtaining the actual inflow ratio λ, substituting the actual inflow ratio λ into the first - line formula of Equation Three can calculate and obtain dC T , substituting dC T into the first - line formula of Equation Two can calculate and obtain the thrust coefficient C of the propeller disk in any state T . After calculating and obtaining the actual inflow ratio λ, substituting the actual inflow ratio λ into the fourth - line formula of Equation Two can calculate and obtain dC M , substituting dC M into the second - line formula of Equation Two can calculate and obtain the drag - moment coefficient C of the propeller disk in any state M . For C T and C M of the propeller disk in any state, corrections are made to obtain the corrected thrust coefficient and the corrected drag - moment coefficient

[0060] During the calculation of the thrust coefficient, the propeller - disk area should be corrected. First, from the propeller - root installation location to the rotor center, it is not an airfoil and no thrust is generated. Second, at the tip of the propeller blade, the air flow can bypass the tip from the high - pressure area on the lower surface to the low - pressure area on the upper surface, and the pressure difference between the upper and lower surfaces suddenly decreases, resulting in a decrease in thrust. This method unifies the blade - element theorem and the slip - stream theorem by adjusting the integration interval. The lower limit of the integration is determined according to the actual situation of the propeller blade, and the upper limit is taken as 0.97 according to engineering experience. The tip - loss coefficient k = 1.

[0061] The corrected thrust coefficient and the corrected drag - moment coefficient can be obtained according to Calculated and obtained, where is the initial integral value of the non-dimensional variable of the distance from the blade element to the blade root.

[0062] After obtaining the corrected drag coefficient and the corrected torque coefficient Substitute the corrected drag coefficient and the corrected torque coefficient into Formula 1, and the theoretically calculated drag T and torque Q can be obtained.

[0063] Step 5: Obtain the drag interference coefficient and torque interference coefficient between the upper and lower blade disks through a six-axis force test bench; thereby obtaining the combined drag and combined torque of the upper and lower blade disks.

[0064] In the present invention, let the drag interference coefficient between the upper and lower blade disks be D T , and the torque interference coefficient be D M . (Under laboratory conditions) The drag and torque of the upper and lower blade disks without interference are T up , Q up , T down , Q down . The drag and torque generated when the upper and lower blade disks work simultaneously are T s and Q s .

[0065]

[0066] Among them, T s is the drag generated when the upper and lower blade disks work simultaneously, T up is the drag of the upper blade disk without interference, T down is the drag of the lower blade disk without interference, Q s is the torque generated when the upper and lower blade disks work simultaneously, Q up is the torque of the upper blade disk without interference, Q down is the torque of the lower blade disk without interference.

[0067] After obtaining the drag interference coefficient and torque interference coefficient between the upper and lower blade disks through a six-axis force test bench, substitute the drag interference coefficient and torque interference coefficient into Formula 10, and the combined drag T s and combined torque Q s generated when the upper and lower blade disks work simultaneously can be obtained.

[0068] Step 6: Calculate and obtain the aerodynamic resultant force, lateral force, and backward force of the blade disk according to the drag of the blade disk in any state.

[0069] Specifically, in the present invention, the lateral force and the backward force of the propeller disk are along the positive direction of the O b Z b axis and the negative direction of the O b X b axis of the airframe system, respectively. The aerodynamic resultant force of the propeller disk is the resultant force of the pulling force, the lateral force and the backward force, and is approximately perpendicular to the plane of the propeller tip motion trajectory. When solving the backward force and the lateral force, this method ignores the blowing and flapping of the propeller tip trajectory plane relative to the control plane caused by the obliquely blowing airflow during forward flight, and believes that the inclination of the propeller tip trajectory plane is completely caused by the control of the swashplate. Then, there are the following approximate relationships.

[0070]

[0071] In the above formula, the variable definitions are shown in Table 4 below.

[0072] Table 4

[0073] Symbol Meaning <![CDATA[T s > Disk thrust <![CDATA[R s > Aerodynamic resultant force <![CDATA[H s > Backward force <![CDATA[S s > Lateral force <![CDATA[χ s > Longitudinal cyclic pitch <![CDATA[η s > Lateral cyclic pitch

[0074] Step 7, based on the linear relationship between the blade element lift coefficient and the blade element angle of attack C yα 、the blade element drag coefficient C x 、the corrected pulling force coefficient the corrected drag moment coefficient the propeller disk pulling force, the drag moment, the aerodynamic resultant force of the propeller disk, the lateral force, the backward force, the pulling force interference coefficient and the drag moment interference coefficient, and complete the construction of the dynamic model of the small coaxial dual-rotor aircraft according to the trajectory motion model, the propeller blade pulling force and drag moment calculation model, and the DC brushless motor model.

[0075] In the present invention, the trajectory motion model is where m is the mass of the aircraft, V is the flight speed of the aircraft, α is the propeller disk angle of attack, G is the gravity of the aircraft, ρ is the air density, θ is the flight inclination angle, F f is the airframe drag, C f is the drag coefficient of each component, and S is the reference area of each component.

[0076] The propeller disk pulling force and drag moment calculation model is

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] T=CT ρA(ΩR) 2

[0083] M = C M ρA(ΩR) 2 R

[0084]

[0085]

[0086] The DC brushless motor model is where J r is the moment of inertia of the upper rotor motor rotor, the rotor and other rotating components, Ω is the rotational speed of the motor rotor, K T is the KT value of the motor, R M is the equivalent resistance of the spot trace, u is the voltage of the motor circuit, K v is the KV value of the motor, i0 is the no-load current of the motor, and M is the blade drag torque.

[0087] To further understand the present invention, the following combines Figures 1 to 5 to elaborate in detail on the dynamic modeling method of the coaxial dual-rotor aircraft considering the aerodynamic characteristics of the rotor provided by the present invention.

[0088] As Figures 1 to 5 shown, according to a specific embodiment of the present invention, a dynamic modeling method of a coaxial dual-rotor aircraft considering the aerodynamic characteristics of the rotor is provided, and the modeling process is described taking a single upper rotor disk as an example.

[0089] 1. Conduct force measurement on a six-axis force test bench in a laboratory environment

[0090] The six-axis force test data of the single upper rotor disk are shown in the following table.

[0091] Table 5

[0092] Serial number Speed (revolutions per minute) Thrust (kgf) Absolute value of resistance moment (N·m) 1 320.0531 0.08469 0.0475 2 516.0809 0.226983 0.11942 3 711.0938 0.453903 0.21557 4 903.6849 0.731344 0.33907 5 1098.125 1.105035 0.49846 6 1280.435 1.573568 0.70051 7 1461.768 2.24005 0.9263 8 1642.146 2.642013 1.16928 9 1814.802 3.139308 1.42924 10 1981.98 3.723155 1.69563

[0093] The air density is 1.29 kg / m3, and the radius of the rotor disk is 0.3658 m. According to the above rotational speed, thrust, and drag torque test data, the thrust coefficient and drag torque coefficient of the rotor disk are fitted as follows.

[0094] C T = 0.01187, C M = 0.0014828 (Equation XII)

[0095] Similarly, in the laboratory environment, the thrust coefficient, drag torque coefficient of the lower rotor disk, and the thrust interference coefficient D T between the upper and lower rotor disks can be measured, and the drag torque interference coefficient is D M In the embodiment, D TTake 0.7, D M Take 1.1.

[0096] 2. Calculate the single blade element C yα and C x

[0097] The propeller attribute data is shown in the following table.

[0098] Table 6

[0099]

[0100]

[0101] Substitute the formula into formula 7 and solve it together with formula 14 to get the leaf element C yα and C x .

[0102] C yα =12.5126,C x =0.1420

[0103] 3. Kinetic model

[0104] The trajectory motion model, blade thrust model and DC brushless motor model are combined to obtain the dynamic model of a small coaxial twin-rotor aircraft.

[0105] (1) Solve the inflow ratio equation and the calculation model of propeller disk tension and drag torque

[0106]

[0107] (2) Brushless DC motor model

[0108]

[0109] In the above formula, the definitions of variables and their values ​​in the embodiments are shown in the following table.

[0110] Table 7

[0111]

[0112] (3) Trajectory motion model

[0113]

[0114] In the above formula, the definitions of variables and their values ​​in the embodiments are shown in the following table.

[0115] Table 8

[0116]

[0117]

[0118] In summary, the present invention provides a method for dynamic modeling of a coaxial twin-rotor aircraft taking into account the aerodynamic characteristics of the rotor. This method is aimed at the aerodynamic characteristics of small coaxial rotor aircraft. Through the rotor aerodynamic theory analysis, the blade element theorem and the slipstream constant force are combined to solve the propeller pull and drag torque under any condition. A dynamic model with moderate complexity for six-degree-of-freedom mathematical simulation that takes into account the state of the propeller angle of attack and other states can be obtained and dynamic simulation can be carried out. This method can take into account both computational efficiency and computational accuracy. This method can be used for the overall design and performance evaluation of small coaxial twin-rotor aircraft and the design of guidance and control systems for small aircraft. This method takes into account the influence of the unsteady aerodynamic characteristics of the rotor on the guidance and control system, and can achieve stable flight of the aircraft. It is of great significance to achieve stable flight for the design of guidance and control systems for towing such aircraft.

[0119] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0120] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dynamic modeling method for a coaxial dual-rotor aircraft considering the aerodynamic characteristics of the rotors, characterized in that, The dynamic modeling method of a coaxial helicopter considering the aerodynamic characteristics of the rotors includes: Deriving the lift coefficient and drag moment coefficient of a single blade based on the blade element theory; Deriving the lift coefficient based on the slipstream theory; The tension coefficient derived based on the blade element theorem and the tension coefficient derived based on the slip flow theorem are combined to calculate the tension coefficient C T The linear relationship between the lift coefficient of the blade element and the blade element angle of attack C yα High-order nonlinear equations; On a six - component force test bench, set the total torque of the aircraft to 0. By adjusting the rotor speed, measure the thrust and drag torque, and obtain the experimental thrust coefficient C T and the experimental drag torque coefficient C M . Substitute the experimental thrust coefficient C T into the high - order non - linear equation of the theoretical - derived thrust coefficient C T and the linear relationship C yα between the blade - element lift coefficient and the blade - element angle of attack to calculate and obtain the linear relationship C yα between the blade - element lift coefficient and the blade - element angle of attack; Based on the linear relationship C yα between the blade - element lift coefficient and the blade - element angle of attack, calculate and obtain the inflow ratio λ and the thrust - coefficient component dC Ts in the laboratory state of each blade - element. Based on the experimentally measured drag - torque coefficient C M , the inflow ratio λ in the laboratory state, and the thrust - coefficient component dC Ts , calculate and obtain the blade - element drag coefficient C x . Based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα and the blade element drag coefficient C x , the actual inflow ratio λ is calculated by using the Newton iteration method, and C of the propeller disk in any state is calculated based on the actual inflow ratio T and C M , and corrections are made to obtain the corrected thrust coefficient and the corrected drag moment coefficient Furthermore, the theoretically calculated thrust T and drag moment Q are obtained; Obtaining the lift interference coefficient and drag moment interference coefficient between the upper and lower rotor disks through a six-component force test bench, and further obtaining the combined lift and combined moment of the upper and lower rotor disks; Calculating the aerodynamic resultant force, lateral force, and backward force of the rotor disk according to the lift of the rotor disk in any state; Based on the linear relationship C between the blade element lift coefficient and the blade element angle of attack yα and the blade element drag coefficient C x , the corrected thrust coefficient the corrected drag moment coefficient The blade disk thrust, drag moment, blade disk aerodynamic resultant force, lateral force, backward force, thrust interference coefficient and drag moment interference coefficient are used to complete the construction of the dynamic model of the small coaxial dual-rotor aircraft according to the trajectory motion model, the blade thrust and drag moment calculation model, and the DC brushless motor model.

2. The dynamic modeling method of a coaxial contra-rotating rotorcraft considering the aerodynamic characteristics of the rotor according to claim 1, characterized in that, The pulling force coefficient C T The linear relationship C between the blade element lift coefficient and the blade element angle of attack yα The high-order nonlinear equation is 3. The dynamic modeling method of a coaxial dual-rotor aircraft considering the aerodynamic characteristics of the rotors according to claim 2, characterized in that, The inflow ratio λ of the laboratory state of each blade element can be obtained according to Calculation and acquisition.

4. The dynamic modeling method of a coaxial contra-rotating rotorcraft considering the aerodynamic characteristics of the rotor according to claim 3, characterized in that The blade element drag coefficient C x can be obtained by calculating according to ​ 5. The dynamic modeling method of a coaxial contra-rotating rotorcraft considering the aerodynamic characteristics of the rotor according to any one of claims 1 to 3, characterized in that The corrected pulling force coefficient and the corrected resistance moment coefficient can be obtained according to wherein, is the integral initial value of the non-dimensionalized variable of the distance from the blade element to the blade root.

6. The dynamic modeling method of a coaxial dual-rotor aircraft considering the aerodynamic characteristics of the rotors according to claim 4, characterized in that, The pull interference coefficient D T and the drag moment interference coefficient D M can be determined according to where T s is the pull generated when the upper and lower rotor disks work simultaneously, T up is the pull of the upper rotor disk without interference, T down is the pull of the lower rotor disk without interference, Q s is the drag moment generated when the upper and lower rotor disks work simultaneously, Q up is the drag moment of the upper rotor disk without interference, Q down is the drag moment of the lower rotor disk without interference.

7. The dynamic modeling method of a coaxial contra-rotating rotorcraft considering the aerodynamic characteristics of the rotor according to claim 5, characterized in that The longitudinal trajectory motion model is where m is the mass of the aircraft, V is the flight speed of the aircraft, α is the pitch angle of the propeller disk, G is the gravity of the aircraft, ρ is the air density, θ is the flight inclination angle, F f is the body drag, C f is the drag coefficient of each component, and S is the reference area of each component.

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