Method for establishing super-low-dimensional aerodynamic servo-elastic model of flying wing layout aircraft for flutter control

Abstract

This invention discloses a method for establishing an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of flying-wing aircraft, belonging to the field of aircraft aeroelasticity and control technology. The method first establishes a five-degree-of-freedom mechanical model including fuselage heave, pitch, etc.; derives the structural dynamic equations of the system based on the Lagrangian equations; and establishes an unsteady aerodynamic model considering aerodynamic sweep effects based on Theodorsen's unsteady aerodynamic theory and mean induced flow theory. Finally, it integrates the second-order dynamic model of the control surface actuators to obtain a complete aerodynamic servo-elastic state-space equation. This invention achieves an efficient and accurate description of complex dynamic behavior of rigid-elastic coupling with extremely low degrees of freedom, significantly improving computational efficiency and providing a powerful tool for rapid analysis and parametric research of flutter characteristics in flying-wing aircraft, as well as the design and verification of active flutter suppression controllers.

Description

Technical Field

[0001] This invention relates to the fields of structural dynamics, aeroelasticity, and flight control technology, specifically to a method for establishing an ultra-low-dimensional aero-servoelastic model for a flying wing aircraft used for flutter control. Background Technology

[0002] Flying wing aircraft, due to their superior aerodynamic efficiency and stealth capabilities, have become an important development direction in the modern aviation field. However, because these aircraft eliminate the traditional tail, their structures are highly flexible. Their rigid body flight mechanical modes (such as heave and pitch) are prone to coupling with the low-order elastic modes of the wing (such as bending and torsion), inducing an aeroelastic instability phenomenon known as rigid-elastic coupled flutter. This can lead to catastrophic structural damage at speeds far below those of traditional bending-torsional flutter, seriously threatening flight safety.

[0003] Existing research methods for rigid-elastic coupled flutter can be mainly divided into two categories: one is high-fidelity coupled simulation based on computational fluid dynamics and computational structural dynamics. This method has high accuracy but the model is complex and the computational cost is huge, making it difficult to use for rapid analysis and control design iteration; the other is a complex modeling method based on analytical mechanics and multibody dynamics. Although it can reveal some mechanisms, the model often still has many degrees of freedom, which is not conducive to guiding structural parametric design and aeroelastic optimization in the early stages of aircraft design.

[0004] Therefore, there is an urgent need to develop an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of flying-wing aircraft that can accurately capture the physical nature of rigid-elastic coupling flutter in flying-wing aircraft, has extremely high computational efficiency, and is easy to design controllers. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of flying-wing aircraft. This model equates the complex continuum aircraft structure to a five-degree-of-freedom mechanical model, forming a complete state-space model that can be used for time-domain simulation and stability analysis. It can be used for parametric analysis and aeroelastic optimization of flying-wing aircraft structures, and lays the foundation for the design and verification of active flutter suppression controllers.

[0006] The technical solution of this invention is as follows:

[0007] A method for establishing an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of a flying-wing aircraft, the method comprising the following steps:

[0008] Step 1: Set the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control as a five-degree-of-freedom dynamic model, including five degrees of freedom: fuselage heave, fuselage pitch, wing bending, wing twisting, and control surface deflection, to describe the rigid-elastic coupled aeroelastic effect of the flying wing aircraft.

[0009] Step 2: Determine all structural parameters in the five-degree-of-freedom dynamic model, and convert the complex flying wing aircraft into an ultra-low-dimensional mechanical model based on the principles of mechanics.

[0010] Step 3: Establish the structural dynamic equations of the five-degree-of-freedom dynamic model using the Lagrangian equation method. Calculate the kinetic and potential energy of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control in the inertial frame. The kinetic energy includes the translational and rotational kinetic energy of the fuselage, the translational and rotational kinetic energy of the wing, and the translational and rotational kinetic energy of the control surfaces. The potential energy includes the bending and torsional elastic potential energy of the wing and the torsional elastic potential energy of the hinge.

[0011] Step 4: Based on Theodorsen's unsteady aerodynamic theory and mean induced flow theory, considering the unsteady effects of aerodynamic forces generated by the fuselage and wing, as well as the sweep effect of the wing, and assuming that there is no mutual influence between the aerodynamic forces and flow characteristics acting on the fuselage and wing, unsteady aerodynamic modeling is performed on the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control, and the unsteady aerodynamic forces and aerodynamic moments of the fuselage and wing are calculated respectively.

[0012] Step 5: Calculate the total virtual work done by aerodynamic forces and aerodynamic torques on the virtual displacement, which is used to calculate the generalized force corresponding to the generalized coordinates of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control; Combine the structural dynamics equations established in Step 3 and the set second-order dynamics model of the actuator, establish the aero-servo-elastic dynamics equations of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control.

[0013] Step 6: Based on the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control, and using its pitch rate and wing vibration acceleration as feedback signals, design a flutter suppression control law to drive the control surface to deflect. Flutter suppression is achieved by changing the aerodynamic distribution of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control.

[0014] Furthermore, the setting of the ultra-low-dimensional aerodynamic servo elastic model of the flying wing aircraft used for flutter control as a five-degree-of-freedom dynamic model specifically means: equating the fuselage with a rigid wing that can freely rotate around its center of gravity. Point by angle Rotation, and relative to the inertial frame of reference. When performing buoyancy motion, the aerodynamic center of the fuselage is located at its quarter chord point. Location; Rotating reference frame Attached to the fuselage, at the first angular velocity Rotate;

[0015] The wing attaches to point P on the fuselage, due to bending... Axis deflection And due to the torsional rotation angle The aerodynamic center of the wing is located at its quarter chord point. The torsional motion is caused by a rotating reference frame attached to the wing. Capture, the second rotating reference frame at the second angular velocity Rotate;

[0016] The control surfaces are attached to the trailing edge of the wing at an angle. Deflection, the deflection motion is caused by a rotating coordinate system attached to the control surface. Capture, the third rotating reference frame with a third angular velocity Rotate;

[0017] The bending stiffness and torsional stiffness of the wing are respectively and The torsional stiffness of the control surface is Free flow velocity along The flow direction is from left to right; among them, and These are the half-chord lengths of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe the center of gravity positions of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe point P on the fuselage and the point of application of the wing's rotation axis, respectively. To describe the center of gravity of the control surface The dimensionless quantity defined by the position. A dimensionless quantity defined to describe the point of application of the rotation axis of the control surface.

[0018] Furthermore, the statement that the complex flying wing aircraft is equivalent to an ultra-low-dimensional mechanical model based on mechanical principles specifically refers to: first, determining the length and position of the average aerodynamic chord of the fuselage and wing respectively, and then, based on the half-span of the fuselage and wing... and Equivalent lifting surfaces for the fuselage and wings are established respectively;

[0019] Secondly, the points of application of aerodynamic forces are determined at the 1 / 4 chord points of the mean aerodynamic chords of the fuselage and wing, respectively. and ;

[0020] Then, determine the control points at the 3 / 4 chord point of the mean aerodynamic chord of the fuselage and wing, respectively. and Then, based on the projections of the fuselage center of mass and the wing center of mass onto their respective mean aerodynamic chords, the positions of the centers of mass in the mechanical model are determined. and ;

[0021] Finally, using the position of the elastic shaft on the mean aerodynamic chord of the wing, the connection points between the elastic shaft and the fuselage are determined. and .

[0022] Furthermore, the kinetic energy of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control in the inertial frame... With potential energy They are respectively:

[0023] ;

[0024] in, and These are the bending stiffness and torsional stiffness of the wing, respectively. To control the torsional stiffness of the surface; and These are the half-chord lengths of the fuselage and wings, respectively; and These are dimensionless quantities defined to describe the center of gravity positions of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe point P on the fuselage and the point of application of the wing's rotation axis, respectively. To describe the center of gravity of the control surface The dimensionless quantity defined by the position. A dimensionless quantity defined to describe the point of application of the rotation axis of the control surface; , and These are the static imbalance parameters for the fuselage, wings, and control surfaces, respectively; defined. ; , and These are the masses of the wings, fuselage, and control surfaces, respectively. , and These are the moments of inertia of the fuselage, wings, and control surfaces, respectively. These represent the fuselage heave (z) and fuselage pitch (z). wing bending h, wing twist and control surface deflection The first derivative of the five generalized coordinates with respect to time; These represent the fuselage heave (z) and fuselage pitch (z). wing bending h, wing twist and control surface deflection The second derivatives of the five generalized coordinates with respect to time.

[0025] Furthermore, the unsteady aerodynamic forces of the fuselage and wings calculated in step four... and aerodynamic torque They are respectively:

[0026] ;

[0027] in, For the incoming flow density, For the free flow velocity, For dynamic pressure, For the sweep angle of the wing, and These are the average induced flow velocities of the wing and fuselage, respectively. , , , , and They are respectively dimensionless quantities The relevant variables and expressions are as follows:

[0028] .

[0029] Furthermore, the generalized forces corresponding to the generalized coordinates of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control are as follows:

[0030] ;

[0031] in, These are respectively fuselage heave and buoyancy (Z) and fuselage pitch. wing bending h and wing twist The four generalized coordinates correspond to the generalized forces of virtual displacement.

[0032] Furthermore, the second-order dynamic model of the actuator specifically refers to:

[0033] The actuator is used to reflect the relationship between the control surface deflection angle command and the actual control surface deflection angle, which can be described as a second-order system:

[0034]

[0035] in, This is the actual control surface deflection angle. This is a command to control the surface deflection angle. For the natural frequency, For the damping ratio, and These are the actual control surface deflection angles. First and second derivatives with respect to time.

[0036] The beneficial effects of this invention are as follows: It provides an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of flying-wing aircraft, overcoming the shortcomings of existing technologies. By equating the complex continuum aircraft structure to a five-degree-of-freedom mechanical model, it can efficiently describe the coupled dynamic characteristics of the rigid body flight mechanical modes and aeroelastic modes of the aircraft. This provides an efficient analysis and design tool for parametric aeroelastic analysis, flutter boundary prediction, and flutter suppression control law design of flying-wing aircraft, thereby guiding the structural dynamics design of the aircraft. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the ultra-low-dimensional aerodynamic servo-elastic model structure of a flying wing aircraft used for flutter control in the embodiment.

[0038] Figure 2 This is a schematic diagram of the equivalent method of the ultra-low-dimensional mechanical model of the flying wing aircraft used for flutter control in the embodiment;

[0039] Figure 3 This is a flowchart of the modeling and analysis process for an ultra-low-dimensional aerodynamic servo-elastic model of a flying wing aircraft used for flutter control in the embodiments.

[0040] Figure 4 This is a schematic diagram of the simulation results of a low-speed, ultra-low-dimensional aerodynamic servo-elastic model of a flying wing aircraft used for flutter control in the embodiment. Detailed Implementation

[0041] To clearly illustrate the technical features of this patent, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings.

[0042] The method for establishing an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of a flying wing aircraft provided in this application includes the following steps:

[0043] Step 1: Establish an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of a flying wing aircraft. The model is a five-degree-of-freedom dynamic model, including five degrees of freedom: fuselage heave, fuselage pitch, wing bending, wing twisting, and control surface deflection. It is used to describe the rigid-elastic coupled aeroelastic effect of the flying wing aircraft.

[0044] Step 2: Determine all structural parameters in the five-degree-of-freedom dynamic model, and convert the complex flying wing aircraft into an ultra-low-dimensional mechanical model based on the principles of mechanics.

[0045] Step 3: Establish the structural dynamic equations of the five-degree-of-freedom dynamic model using the Lagrangian equation method. Calculate the kinetic and potential energy of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control in the inertial frame. The kinetic energy includes the translational and rotational kinetic energy of the fuselage, the translational and rotational kinetic energy of the wing, and the translational and rotational kinetic energy of the control surfaces. The potential energy includes the bending and torsional elastic potential energy of the wing and the torsional elastic potential energy of the hinge.

[0046] Step 4: Based on Theodorsen's unsteady aerodynamic theory and mean induced flow theory, considering the unsteady effects of aerodynamic forces generated by the fuselage and wing, as well as the sweep effect of the wing, and assuming that there is no mutual influence between the aerodynamic forces and flow characteristics acting on the fuselage and wing, unsteady aerodynamic modeling is performed on the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control, and the unsteady aerodynamic forces and aerodynamic moments of the fuselage and wing are calculated respectively.

[0047] Step 5: Calculate the total virtual work done by aerodynamic forces and aerodynamic torques on the virtual displacement, which is used to calculate the generalized force corresponding to the generalized coordinates of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control; Combine the structural dynamics equations established in Step 3 and the set second-order dynamics model of the actuator, establish the aero-servo-elastic dynamics equations of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control.

[0048] Step 6: Based on the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control, and using its pitch rate and wing vibration acceleration as feedback signals, design a flutter suppression control law to drive the control surface to deflect. Flutter suppression is achieved by changing the aerodynamic distribution of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control.

[0049] The ultra-low-dimensional aerodynamic servo-elastic model of a flying wing aircraft used for flutter control includes five degrees of freedom: fuselage heave, fuselage pitch, wing bending, wing twisting, and control surface deflection.

[0050] Furthermore, the setting of the ultra-low-dimensional aerodynamic servo elastic model of the flying wing aircraft used for flutter control as a five-degree-of-freedom dynamic model specifically means: equating the fuselage with a rigid wing that can freely rotate around its center of gravity. Point by angle Rotation, and relative to the inertial frame of reference. When performing buoyancy motion, the aerodynamic center of the fuselage is located at its quarter chord point. Location; Rotating reference frame Attached to the fuselage, at the first angular velocity Rotate;

[0051] The wing attaches to point P on the fuselage, due to bending... Axis deflection And due to the torsional rotation angle The aerodynamic center of the wing is located at its quarter chord point. The torsional motion is caused by a rotating reference frame attached to the wing. Capture, the second rotating reference frame at the second angular velocity Rotate;

[0052] The control surfaces are attached to the trailing edge of the wing at an angle. Deflection, the deflection motion is caused by a rotating coordinate system attached to the control surface. Capture, the third rotating reference frame with a third angular velocity Rotate;

[0053] The bending stiffness and torsional stiffness of the wing are respectively and The torsional stiffness of the control surface is Free flow velocity along The flow direction is from left to right; among them, and These are the half-chord lengths of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe the center of gravity positions of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe point P on the fuselage and the point of application of the wing's rotation axis, respectively. To describe the center of gravity of the control surface The dimensionless quantity defined by the position. A dimensionless quantity defined to describe the point of application of the rotation axis of the control surface.

[0054] Furthermore, the statement that the complex flying wing aircraft is equivalent to an ultra-low-dimensional mechanical model based on mechanical principles specifically refers to: first, determining the length and position of the average aerodynamic chord of the fuselage and wing respectively, and then, based on the half-span of the fuselage and wing... and Equivalent lifting surfaces for the fuselage and wings are established respectively;

[0055] Secondly, the points of application of aerodynamic forces are determined at the 1 / 4 chord points of the mean aerodynamic chords of the fuselage and wing, respectively. and ;

[0056] Then, determine the control points at the 3 / 4 chord point of the mean aerodynamic chord of the fuselage and wing, respectively. and Then, based on the projections of the fuselage center of mass and the wing center of mass onto their respective mean aerodynamic chords, the positions of the centers of mass in the mechanical model are determined. and ;

[0057] Finally, using the position of the elastic shaft on the mean aerodynamic chord of the wing, the connection points between the elastic shaft and the fuselage are determined. and .

[0058] Furthermore, the kinetic energy of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control in the inertial frame... With potential energy They are respectively:

[0059] ;

[0060] in, and These are the bending stiffness and torsional stiffness of the wing, respectively. To control the torsional stiffness of the surface; and These are the half-chord lengths of the fuselage and wings, respectively; and These are dimensionless quantities defined to describe the center of gravity positions of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe point P on the fuselage and the point of application of the wing's rotation axis, respectively. To describe the center of gravity of the control surface The dimensionless quantity defined by the position. A dimensionless quantity defined to describe the point of application of the rotation axis of the control surface; , and These are the static imbalance parameters for the fuselage, wings, and control surfaces, respectively; defined. ; , and These are the masses of the wings, fuselage, and control surfaces, respectively. , and These are the moments of inertia of the fuselage, wings, and control surfaces, respectively. These represent the fuselage heave (z) and fuselage pitch (z). wing bending h, wing twist and control surface deflection The first derivative of the five generalized coordinates with respect to time; These represent the fuselage heave (z) and fuselage pitch (z). wing bending h, wing twist and control surface deflection The second derivatives of the five generalized coordinates with respect to time.

[0061] Furthermore, the structural dynamic equations of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control, established based on the Lagrangian equation method, are as follows:

[0062] ;

[0063] Furthermore, the aforementioned unsteady aerodynamic modeling of the ultra-low-dimensional aerodynamic servo-elastic model for flutter control of a flying wing aircraft is performed. Based on Theodorsen's unsteady aerodynamic theory and mean induced flow theory, the unsteady effects of aerodynamic forces generated by the fuselage and wing, as well as the wing's sweep effect, are considered. It is assumed that there is no mutual influence between the aerodynamic forces and flow characteristics acting on the fuselage and wing, resulting in the unsteady aerodynamic forces of the fuselage and wing. and aerodynamic torque They are respectively:

[0064] ;

[0065] in, For the incoming flow density, For the free flow velocity, For dynamic pressure, For the sweep angle of the wing, and These represent the average induced flow velocities of the wing and fuselage, respectively. , , , , and They are respectively dimensionless quantities The relevant variables and expressions are as follows:

[0066] .

[0067] Furthermore, the aforementioned unsteady aerodynamic modeling of the ultra-low-dimensional aerodynamic servoelastic model of the flying wing aircraft used for flutter control is performed, based on the average induced flow theory, and the average induced velocity of the wing and fuselage is... and These can be represented as linear combinations of N induced flow states:

[0068] ;

[0069] in, It is determined using the least squares method. The system of first-order ordinary differential equations satisfied by the N induced flow states is expressed as:

[0070] ;

[0071] in,

[0072] ;

[0073] .

[0074] Furthermore, the generalized forces corresponding to the generalized coordinates of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control, obtained based on the total virtual work done by aerodynamic forces and aerodynamic torques on virtual displacements, are as follows:

[0075] ;

[0076] in, These are respectively fuselage heave and buoyancy (Z) and fuselage pitch. wing bending h and wing twist The four generalized coordinates correspond to the generalized forces of virtual displacement.

[0077] Furthermore, the aforementioned second-order dynamic model of the actuator specifically refers to the actuator reflecting the relationship between the control surface deflection angle command and the actual control surface deflection angle, described using a second-order system.

[0078] ;

[0079] in, This is the actual control surface deflection angle. This is a command to control the surface deflection angle. For the natural frequency, For the damping ratio, and These are the actual control surface deflection angles. First and second derivatives with respect to time.

[0080] Furthermore, the aero-servo-elastic dynamics equations of the ultra-low-dimensional aero-servo-elastic model for flutter control of the flying wing aircraft, combined with the structural dynamics equations and the second-order dynamics model of the actuator, are expressed as follows:

[0081] ; where, state vector , .

[0082] ;

[0083] ;

[0084] ; ; .

[0085] Example 1: The ultra-low-dimensional aerodynamic servo-elastic model for flutter control of a flying wing aircraft provided in this example follows the following technical approach: Figure 3 As shown. A flying wing aircraft has a sweep angle of 22.5°, fuselage and wingspan of 1.2m and 2.8m respectively, wing and fuselage chord lengths of 0.293m and 0.69837m respectively, wing and fuselage masses of 1.53×2kg and 10.2kg respectively, control surface mass of 0.0665×2kg, and wing moment of inertia of 0.0622×2kg / m. 2 The moment of inertia of the fuselage is 0.602 kg·m. 2 The moment of inertia of the control surfaces is 3.024 × 10⁻⁶. -4 kg.m 2 The wing bending stiffness is 1.47 × 10⁻⁶. 3 Nm 2 The wing's torsional stiffness is 3.1 × 10⁻⁶. 3 Nm 2 The torsional stiffness of the control surface is 50 N·m. 2 We established an ultra-low-dimensional aerodynamic servoelastic model for flutter control of a flying wing aircraft.

[0086] Step 1: Establish an ultra-low-dimensional aero-servoelastic model for flutter control of a flying wing aircraft, used to describe the rigid-elastic coupled aero-elastic effects of the flying wing aircraft. Combined with... Figure 1 The model diagram shown is as follows. and They are 1.47×10 3 3.1×10 3 Nm 2 , 50 N·m 2 , and 0.69837 / 2 and 0.293 / 2m, respectively, are dimensionless quantities describing the positions of the center of gravity of the fuselage and wing. and The values ​​are -0.132 and 0.066, respectively, representing dimensionless quantities describing the point of action between the fuselage (P) and the wing's rotation axis. and The values ​​are 0.8277 and -0.3515, respectively, describing the centroid of the control surface. Dimensionless quantity of position and point of action of the axis of rotation and The values ​​are 0.696246 and 0.39249, respectively.

[0087] Step 2: Determine all structural parameters in the five-degree-of-freedom dynamic model, and based on mechanical principles, combine... Figure 2The diagram illustrates an equivalent method for the ultra-low-dimensional mechanical model of a flying wing aircraft, transforming the complex flying wing configuration into an ultra-low-dimensional mechanical model. First, the length and position of the mean aerodynamic chords of the fuselage and wing are determined separately. Then, based on the half-span of the fuselage and wing… and First, equivalent lifting surfaces are established for the fuselage and wing, respectively. Second, the points of application of aerodynamic forces are determined at the 1 / 4 chord points of the mean aerodynamic chords of the fuselage and wing. and Then, determine the control points at the 3 / 4 chord point of the mean aerodynamic chord of the fuselage and wing. and Then, based on the projections of the fuselage center of mass and the wing center of mass onto their respective mean aerodynamic chords, the position of the center of mass in the mechanical model can be determined. and Finally, by using the position of the flexible shaft on the mean aerodynamic chord of the wing, the connection point between the flexible shaft and the fuselage can be determined. and This lays the foundation for further establishing the aeroelastic dynamics equations of this model.

[0088] Step 3: Establish the structural dynamic equations of the five-degree-of-freedom dynamic model using the Lagrangian equation method. Calculate the kinetic and potential energy of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control in the inertial frame. Also calculate the static imbalance parameters of the fuselage, wing, and control surfaces. The values ​​are -0.9597, 0.4175, and 0.303756, respectively. The mass of the wings, fuselage, and control surfaces is 1.047746. , and The moments of inertia of the fuselage, wings, and control surfaces are 1.53×2kg, 10.2kg, and 0.0665×2kg, respectively. , and They are 0.602 kg.m 2 0.0622×2kg.m 2 and 3.024×10 -4 kg.m 2 .

[0089] Step 4: Based on Theodorsen's unsteady aerodynamic theory and mean induced flow theory, considering the unsteady effects of aerodynamic forces generated by the fuselage and wing, as well as the wing's sweep effect, and assuming no mutual influence between the aerodynamic forces and flow characteristics acting on the fuselage and wing, unsteady aerodynamic modeling is performed on the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control. The unsteady aerodynamic forces and aerodynamic moments of the fuselage and wing are calculated separately. Incoming flow density. It is 1.03 kg / m 3 wing sweep angle 22.5 / 180 rad. Based on the average induced flow theory, the average induced velocity of the wing and fuselage is... and These are represented as linear combinations of N induced flow states, where N is 2.

[0090] Step 5: Calculate the total virtual work done by aerodynamic forces and aerodynamic torques on the virtual displacement, used to calculate the generalized forces corresponding to the generalized coordinates of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control. Further, combining the structural dynamics equations from Step 3 with the established second-order actuator dynamics model, establish the aero-servo-elastic dynamics equations for the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control. With the velocity range set to 0~50 m / s, simulation analysis is performed on the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control, yielding the following results: Figure 4 The simulation results of the low-speed ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft shown are used for flutter control. The flutter frequency is about 2.157 Hz and the flutter velocity is about 32.5 m / s.

[0091] Step 6: Based on the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control, and using its pitch rate and wing vibration acceleration as feedback signals, design a flutter suppression control law to drive the control surface to deflect. Flutter suppression is achieved by changing the aerodynamic distribution of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control.

[0092] Matters not covered in this invention are common knowledge.

[0093] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for establishing an ultra-low-dimensional aerodynamic servo-elastic model for flutter control of a flying wing aircraft, characterized in that, The method includes the following steps: Step 1: Define the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control as a five-degree-of-freedom dynamic model, including five degrees of freedom: fuselage heave, fuselage pitch, wing flex, wing twist, and control surface deflection. This model describes the rigid-elastic coupled aeroelastic effect of the flying wing aircraft. Specifically, defining the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control as a five-degree-of-freedom dynamic model means: treating the fuselage as an equivalent rigid wing that can freely rotate around its center of gravity. Point by angle Rotation, and relative to the inertial frame of reference. When performing buoyancy motion, the aerodynamic center of the fuselage is located at its quarter chord point. Location; First rotating reference frame Attached to the fuselage, at the first angular velocity Rotate; The wing attaches to point P on the fuselage, due to bending... Axis deflection And due to the torsional rotation angle The aerodynamic center of the wing is located at its quarter chord point. The torsional motion is caused by a second rotating reference frame attached to the wing. Capture, the second rotating reference frame at the second angular velocity Rotate; The control surfaces are attached to the trailing edge of the wing at an angle. Deflection, the deflection motion is caused by a third rotating reference frame attached to the control surface. Capture, the third rotating reference frame with a third angular velocity Rotate; The bending stiffness and torsional stiffness of the wing are respectively and The torsional stiffness of the control surface is Free flow velocity along The flow direction is from left to right; among them, and These are the half-chord lengths of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe the center of gravity positions of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe point P on the fuselage and the point of application of the wing's rotation axis, respectively. To describe the center of gravity of the control surface The dimensionless quantity defined by the position. A dimensionless quantity defined to describe the point of application of the rotation axis of the control surface; Step 2: Determine all structural parameters in the five-degree-of-freedom dynamic model, and convert the complex flying wing aircraft into an ultra-low-dimensional mechanical model based on the principles of mechanics. Step 3: Establish the structural dynamic equations of the five-degree-of-freedom dynamic model using the Lagrangian equation method. Calculate the kinetic and potential energy of the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control in the inertial frame. The kinetic energy includes the translational and rotational kinetic energy of the fuselage, the translational and rotational kinetic energy of the wing, and the translational and rotational kinetic energy of the control surfaces. The potential energy includes the bending and torsional elastic potential energy of the wing and the torsional elastic potential energy of the hinge. Step 4: Based on Theodorsen's unsteady aerodynamic theory and mean induced flow theory, considering the unsteady effects of aerodynamic forces generated by the fuselage and wing, as well as the sweep effect of the wing, assuming that there is no mutual influence between the aerodynamic forces and flow characteristics acting on the fuselage and wing, unsteady aerodynamic modeling is performed on the ultra-low-dimensional aerodynamic servo-elastic model of the flying wing aircraft used for flutter control, and the unsteady aerodynamic forces and aerodynamic moments of the fuselage and wing are calculated respectively. Step 5: Calculate the total virtual work done by the unsteady aerodynamic forces and aerodynamic torques on the virtual displacement, which is used to calculate the generalized force corresponding to the generalized coordinates of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control; Combine the structural dynamics equations established in Step 3 and the set second-order dynamics model of the actuator, establish the aero-servo-elastic dynamics equations of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control. Step 6: Based on the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control, and using its pitch rate and wing vibration acceleration as feedback signals, design a flutter suppression control law to drive the control surface to deflect. Flutter suppression is achieved by changing the aerodynamic distribution of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control.

2. The method according to claim 1, characterized in that, The phrase "equivalent to an ultra-low-dimensional mechanical model based on the principles of mechanics" specifically refers to: First, determine the length and position of the mean aerodynamic chord for the fuselage and wing respectively, based on the half-span of the fuselage and wing. and Equivalent lifting surfaces for the fuselage and wings are established respectively; Secondly, the points of application of aerodynamic forces are determined at the 1 / 4 chord points of the mean aerodynamic chords of the fuselage and wing, respectively. and ; Then, determine the control points at the 3 / 4 chord point of the mean aerodynamic chord of the fuselage and wing, respectively. and Then, based on the projections of the fuselage center of mass and the wing center of mass onto their respective mean aerodynamic chords, the positions of the centers of mass in the mechanical model are determined. and ; Finally, using the position of the elastic shaft on the mean aerodynamic chord of the wing, the connection points between the elastic shaft and the fuselage are determined. and .

3. The method according to claim 2, characterized in that, The kinetic energy of the ultra-low-dimensional aerodynamic servo-elastic model of a flying wing aircraft used for flutter control in the inertial frame described above. With potential energy They are respectively: ； in, and These are the bending stiffness and torsional stiffness of the wing, respectively. To control the torsional stiffness of the surface; and These are the half-chord lengths of the fuselage and wings, respectively; and These are dimensionless quantities defined to describe the center of gravity positions of the fuselage and wings, respectively. and These are dimensionless quantities defined to describe point P on the fuselage and the point of application of the wing's rotation axis, respectively. To describe the center of gravity of the control surface The dimensionless quantity defined by the position. A dimensionless quantity defined to describe the point of application of the rotation axis of the control surface; , and These are the static imbalance parameters for the fuselage, wings, and control surfaces, respectively; defined. ; , and These are the masses of the wings, fuselage, and control surfaces, respectively. , and These are the moments of inertia of the fuselage, wings, and control surfaces, respectively. These represent the fuselage heave (z) and fuselage pitch (z). wing bending h, wing twist and control surface deflection The first derivative of the five generalized coordinates with respect to time; These represent the fuselage heave (z) and fuselage pitch (z). wing bending h, wing twist and control surface deflection The second derivatives of the five generalized coordinates with respect to time.

4. The method according to claim 3, characterized in that, The unsteady aerodynamic forces of the fuselage and wings calculated in step four are described above. and aerodynamic torque They are respectively: ； in, For the incoming flow density, For the free flow velocity, For dynamic pressure, For the sweep angle of the wing, and These are the average induced flow velocities of the wing and fuselage, respectively. , , , , and They are respectively dimensionless quantities The relevant variables and expressions are as follows: 。 5. The method according to claim 4, characterized in that, The generalized forces corresponding to the generalized coordinates of the ultra-low-dimensional aero-servo-elastic model of the flying wing aircraft used for flutter control are as follows: ； in, These are respectively fuselage heave and buoyancy (Z) and fuselage pitch. wing bending h and wing twist The four generalized coordinates correspond to the generalized forces of virtual displacement.

6. The method according to claim 1, characterized in that, The second-order dynamic model of the actuator specifically refers to: The actuator is used to reflect the relationship between the control surface deflection angle command and the actual control surface deflection angle, which can be described as a second-order system: ； in, This is the actual control surface deflection angle. This is a command to control the surface deflection angle. For the natural frequency, For the damping ratio, and These are the actual control surface deflection angles. First and second derivatives with respect to time.

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