A Dynamic Simulation Analysis Method for Flexible Rope Flying Vehicle System

Abstract

This invention discloses a dynamic simulation analysis method for a rigid-flexible coupled multibody system. Through modeling and calibrating the nonlinear characteristics of ropes, finite element modeling of rigid-flexible coupled dynamics, dynamic simulation analysis of rigid-flexible coupled dynamics, variable thrust flight tests, and simulation reproduction of test results, a rigid-flexible coupled dynamic simulation analysis of a multibody aircraft system based on flexible rope connections is completed. This invention accurately simulates the nonlinear material properties and stress characteristics of the ropes, establishes a high-precision finite element model of the rigid-flexible coupled dynamics of the flexible rope aircraft system, and edits a solver for the dynamic simulation analysis of the rope system based on explicit dynamics theory. It enables the iterative updating of aerodynamic loads in the time domain for the rigid-flexible coupled body, and realizes a time-domain simulation analysis path for the multibody aircraft system considering the deformation of the flexible ropes. This algorithm does not require equilibrium iteration, has a fast calculation speed, and also solves the convergence control problem.

Description

Technical Field

[0001] This invention relates to a dynamic simulation analysis method for rigid-flexible coupled multibody systems, and particularly to a dynamic simulation analysis method for rigid-flexible coupled multibody aircraft systems connected by ropes, as well as a stable and controllable tethering method. Background Technology

[0002] Due to its advantages in reconnaissance, surveillance, and emergency operations, flexible rope aircraft systems have gradually become a research hotspot in both military and civilian fields in recent years. To reduce the development cost of flexible rope aircraft systems, rope arrangement research needs to be conducted during the design phase. Rigid-flexible coupling modeling technology and fluid-structure interaction simulation analysis should be used to verify the flight stability and operability of the flexible rope aircraft system, thereby ensuring a high success rate in flight tests and reducing the number of flight tests.

[0003] The structure of a flexible rope-connected aircraft system is unique, consisting of an airbag, a pod, and the flexible rope that connects them. Therefore, dynamic modeling requires consideration of the coupling between rigid and flexible bodies, resulting in high complexity, especially for the flexible rope component. During flight, the aircraft system is affected not only by the static buoyancy of the airbag itself and the tension of the rope, but also by the thrust provided by the pod's engine and the aerodynamic forces that change with flight speed and attitude. Therefore, co-simulation involves interdisciplinary issues such as structural mechanics, control, and aerodynamics. Achieving real-time data exchange between these disciplines is also one of the simulation challenges.

[0004] Currently, commonly used simulation analysis methods fall into two categories: the first is co-simulation using multibody dynamics software Adams and Simulink, and the second is dynamic simulation using explicit dynamics software. The first method has two main problems: Adams cannot directly model large-deformation flexible objects like ropes; it only models the rope as multiple rigid body segments. This fails to analyze the flight configuration changes caused by rope extension and retraction, and it cannot reflect the flexibility of ropes, such as their tendency to bend and their tensile strength. The modeling and simulation accuracy is low. Furthermore, Adams dynamics analysis uses implicit dynamics algorithms, requiring the calculation of stiffness matrices and iterative calculations, which can easily lead to non-convergence. The second method has the problem that aerodynamic loads can only be set during the finite element preprocessing stage. After the model is submitted for calculation, the aerodynamic loads cannot be reloaded, but during actual flight, the aerodynamic loads change with the airbag's attitude and velocity. This method cannot couple structural deformation with aerodynamic loads, and it cannot achieve real-time iterative loading of aerodynamic forces. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the aforementioned technical problems, this invention provides a high-precision rigid-flexible coupling dynamic modeling and fluid-structure simulation analysis method for flexible rope aircraft systems suitable for engineering applications. It accurately simulates the nonlinear material properties and stress characteristics of ropes, develops a dynamic simulation analysis solver for rope systems based on explicit finite element theory, and simultaneously develops an aerodynamic interpolation program and a fluid-structure coupling iterative control console program. This enables continuous iterative updates of aerodynamic loads in the time domain for the rigid-flexible coupled body, completing flight dynamics simulation analysis of variable-configuration aircraft considering the release and elastic expansion of flexible ropes. It also provides the capability to design and analyze aircraft rope tethering schemes, solving the problems of flight stability and maneuverability verification under different tethering schemes.

[0007] (II) Technical Solution

[0008] To solve the aforementioned technical problems and achieve the invention's objective, the present invention is implemented through the following technical solution:

[0009] Step 1: Modeling and calibrating the nonlinear characteristics of the rope;

[0010] A rope for connecting multi-body aircraft was selected, and the initial length of the test rope was determined based on the connection length of the rope on the aircraft. Tensile tests were then conducted with both ends of the rope fixed. The rope was stretched from its initial length, and the tensile force under each corresponding tensile increment was recorded to obtain the nonlinear material parameters of the rope. These parameters were then used as input to the rope dynamics model.

[0011] Step 2: Finite element modeling of rigid-flexible coupling dynamics

[0012] Rigid body models were created for the airbag, pod, rope reel, and steering pulley in the aircraft system. A finite element model of the rope was created using dedicated rope elements, and these were assembled to form a rigid-flexible coupled dynamic model of the flexible rope aircraft system. To simulate rope slippage between the reel and pulley, a contact model was established between the rope and the reel and pulley. When assigning rope material properties, a material that only bears tension and not compression was selected, and the rope stiffness obtained from the rope tensile test was used as input. Static buoyancy was applied at the centroid of the airbag, initial aerodynamic forces and moments were applied at the aerodynamic center point, and thrust was applied at the pod engine.

[0013] Step 3: Rigid-Flexible Coupling Dynamics Simulation Analysis

[0014] 1) Dynamic simulation of rigid-flexible coupling at time Tn

[0015] A dynamic simulation and analysis solver for a rope system was developed based on explicit finite element technology. The time-domain motion simulation analysis was performed on the rigid-flexible coupled dynamic model established in the second step. The analysis results can obtain the coordinates, velocities, and rope tension of the centroid of the airbag and the center of mass of the pod at time Tn.

[0016] 2) The kinematic output is converted into airbag attitude angles.

[0017] Based on the coordinates of the airbag centroid O, the coordinates of the front vertex A and the right vertex B in the local coordinate system at time Tn, as output in step 3(1), the pitch angle θ and yaw angle of the airbag are calculated. And the roll angle γ, further yielding the transformation matrix from the geodetic coordinate system to the body coordinate system.

[0018] 3) Kinematic output results are converted into angle of attack and sideslip angle.

[0019] Based on the velocity of the airbag centroid O at time Tn output in step 3(1), and the coordinate transformation matrix obtained in step 3(2), the velocity vector is transformed from the geodetic coordinate system to the body coordinate system. According to the formulas for solving the angle of attack and the sideslip angle, the sideslip angle β and the angle of attack α are obtained.

[0020] 4) Obtain real-time aerodynamic forces through aerodynamic data interpolation processing.

[0021] Based on aerodynamic coefficient data obtained from wind tunnel tests or fluid dynamics calculations, an aerodynamic interpolation program was developed. Using the sideslip angle β and angle of attack α calculated in real-time at time Tn as interpolation variables, the aerodynamic coefficients at time Tn were obtained, and then the real-time aerodynamic forces at the corresponding angles of attack and sideslip angles were calculated.

[0022] 5) Perform rigid-flexible coupling dynamic simulation analysis at time Tn+1.

[0023] Develop a fluid-structure interaction control console program to reload the aerodynamic forces obtained in step 3(4) onto the rigid-flexible coupled dynamic finite element model established in step 2, and repeat steps 3(1) to 4) to achieve real-time coupling of structural deformation and aerodynamic load, and complete the time-domain simulation analysis of the aircraft system considering the deformation of the flexible body at time Tn+1.

[0024] Fourth step virtual flight test

[0025] Four different flight tests were designed: Test 1, takeoff dynamics analysis; Test 2, climb dynamics analysis; Test 3, level flight dynamics analysis; and Test 4, turn dynamics analysis.

[0026] Step 5: Simulation Reproduction of Experimental Results

[0027] Based on the tethering scheme of the experimental aircraft and the on-site flight conditions, including thrust and the time-domain extension and retraction of the rope reel, simulation input parameters are set. Through the rigid-flexible coupling dynamic simulation analysis in the third step, the motion trajectory and velocity curves of the airbag and the pod are obtained. The motion trajectory and velocity data of the airbag and the pod obtained by flight test telemetry are compared to determine the effectiveness of the dynamic simulation analysis method and implementation path of the flexible rope flight vehicle system.

[0028] (III) Beneficial Effects

[0029] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention accurately simulates the nonlinear material properties and stress characteristics of ropes through rigid-flexible coupling modeling technology and fluid-structure interaction simulation analysis. It develops a solver for the dynamic simulation analysis of rope systems based on explicit finite element theory, and simultaneously develops an aerodynamic interpolation program and a fluid-structure interaction iteration console program. This accurately simulates the nonlinear material properties and stress characteristics of ropes, establishes a high-precision rigid-flexible coupling dynamic finite element model of a flexible rope aircraft system, and realizes the continuous iterative updating of aerodynamic loads in the time domain for the rigid-flexible coupled body. It also realizes a time-domain simulation analysis path for multi-body aircraft systems considering the deformation of flexible ropes. This algorithm does not require equilibrium iteration, has a fast calculation speed, and solves the convergence control problem. It provides the capability for designing and analyzing aircraft rope tethering schemes, and solves the verification problems of flight stability and maneuverability under different tethering schemes. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 This is a flowchart of the dynamic simulation analysis method for the flexible rope flight system according to an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of the rigid-flexible coupling dynamics finite element model of the flexible rope flight system according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the rigid body algorithm according to an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the construction of the rope unit interpolation function according to an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the kinematic pair model between the front and rear moving winches and the front and rear steering pulleys and the pod in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the kinematic pair model between the left and right moving winch and the left and right steering pulleys and the pod in an embodiment of the present invention;

[0037] Figure 7 This is a flowchart of the aerodynamic force application process according to an embodiment of the present invention;

[0038] Figure 8 This is a schematic diagram of the airbag aerodynamic force application point according to an embodiment of the present invention;

[0039] Figure 9 This is a schematic diagram of a virtual takeoff test of an aircraft according to an embodiment of the present invention;

[0040] Figure 10 This is a schematic diagram of a virtual flight test of an aircraft according to an embodiment of the present invention;

[0041] Figure 11 This is a schematic diagram of a virtual flight climb test according to an embodiment of the present invention;

[0042] Figure 12 This is a schematic diagram of a virtual test of an aircraft turning according to an embodiment of the present invention; Detailed Implementation

[0043] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0044] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0045] See Figure 1 The specific steps of a dynamic simulation analysis method and implementation approach for a flexible rope flight system are as follows:

[0046] S1: Modeling and Calibration of Nonlinear Characteristics of Ropes

[0047] A rope for connecting multi-body aircraft was selected, and its initial length of 5m was determined based on the connection length on the aircraft. Tensile tests were then conducted with both ends of the rope fixed. The rope was stretched at increments of 2cm, 4cm, 6cm, 8cm, 10cm, 12cm, and 14cm from its initial length. The tensile force at each increment was recorded, and the rope stiffness was obtained using K = F / Δx. This yielded the nonlinear material parameters of the rope, which were then used as input to the rope dynamics model.

[0048] S2: Finite element modeling of rigid-flexible coupling dynamics

[0049] Figure 2 shows a schematic diagram of the rigid-flexible coupling dynamics finite element model of the flexible rope aircraft system. The airbags and pods in the aircraft system are considered rigid bodies, assigned weight and inertia properties. A rigid body is a series of elements with infinite stiffness; that is, a rigid body only undergoes translational or rotational motion and does not deform. The velocity, acceleration, etc., of any point on the rigid body can be linearly expressed through the velocity and acceleration of the center of gravity node of the rigid body.

[0050] See Figure 3 The solution for rigid body motion is performed in the global coordinate system. In the explicit iteration process, the weight, center of gravity, and moment of inertia of the rigid body are calculated first.

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] Among them, M CG Let X be the weight of the rigid body. CG Y CG Z CG Let X be the coordinates of the centroid. i Y i Z i Let I be the XYZ coordinates of point i. CG A is the moment of inertia; i Let I1, I2, and I3 be the transformation matrix of node i from the global coordinate system to the rigid body local coordinate system, and let I1, I2, and I3 be the moment of inertia components of XYZ.

[0057] The forces and moments acting on a rigid body are all applied at the central nodes of the rigid body, including:

[0058]

[0059]

[0060] The nodal accelerations and angular accelerations of the center of gravity of a rigid body can be solved using the kinematic equations of a rigid body.

[0061]

[0062]

[0063] The velocity v of node i i This can be expressed as:

[0064]

[0065] Among them, v CG u is the velocity of the rigid body. i Let r be the velocity vector of any node relative to the centroid node; i Let be the distance from node i to the centroid. For rigid body angular velocity;

[0066] The acceleration a of node i i This can be expressed as:

[0067]

[0068] Among them, a CG The nodal acceleration is the center of gravity of the rigid body. For rigid body angular acceleration;

[0069] Angular acceleration α of node i i This can be expressed as:

[0070] α i =A i A CG α CG

[0071] The rope is made of flexible fiber material, which can only withstand tensile loads and cannot withstand compression, torsion, bending, or other loads. Therefore, this invention develops a special one-dimensional unit to simulate the arresting cable. This unit can only withstand tension, but cannot withstand compression, bending moment, or torque.

[0072] See Figure 4 The arresting cable element contains two nodes N1 and N2, with a length of L and an area of ​​A. The distance from any point N on the arresting cable element to N1 is l, which, after normalization, can be set as s = l / L. The position q of the element in the global coordinate system... e This can be expressed as:

[0073]

[0074] The displacement of any point N on the element can be expressed as:

[0075] r(s,t)=N(s)q e

[0076] Where N(s) is the shape function of the arresting cable element:

[0077] N(s)=[N1I 2×2 N2I 2×2 ]

[0078] N1 = -(s-1)

[0079] N2 = s

[0080] Among them, I 2×2 It is a 2x2 identity matrix.

[0081] The deformation of the arresting cable element can be expressed as:

[0082]

[0083] in

[0084]

[0085] in, Take the first derivative of the shape function N(s) of the arresting cable element with respect to time.

[0086] Based on the material constitutive relation of the arresting cable element, the stress of the arresting cable element can be obtained:

[0087] σ=Eε

[0088] Where E is the rope stiffness.

[0089] The pod is modeled as a rigid body, as are the left and right moving winches, the front and rear moving winches, the left and right steering pulleys, and the front and rear steering pulleys. Since these components are mounted on the pod and can rotate freely, it is necessary to define motion constraint models between them and the pod, i.e., revolute pairs between rigid bodies, such as... Figure 5-6 As shown.

[0090] Static buoyancy is applied at the centroid of the airbag, aerodynamic force and aerodynamic torque are applied at the aerodynamic center point, and thrust is applied at the pod engine.

[0091] S3: Dynamic Simulation Analysis of Rigid-Flexible Coupling

[0092] During the flight of a flexible rope aircraft system, the aerodynamic forces it experiences are consistently one of the main factors affecting the aircraft's attitude. These aerodynamic forces are determined by the angle of attack, sideslip angle, and velocity of the airbag. Throughout the flight, the aircraft's speed and attitude constantly change. The aerodynamic forces applied to the aircraft further contribute to these changes in speed and attitude. This paper employs explicit finite element method technology to develop a coupled aerodynamic and structural dynamics solution program. The calculation flow is as follows: Figure 7 As shown:

[0093] Specifically, it includes:

[0094] S31: Dynamic Simulation of Rigid-Flexible Coupling at Time Tn

[0095] Based on explicit dynamics, a dynamic simulation analysis solver for the rope system was developed and edited. The dynamic simulation analysis was performed on the rigid-flexible coupled dynamic finite element model established in the second step. The analysis results can obtain the coordinates, velocities, and rope tension of the centroid of the airbag and the center of mass of the pod at time Tn.

[0096] S32: Kinematic output results are converted into airbag attitude angles.

[0097] See Figure 8 Schematic diagram of the aerodynamic application point of the airbag, based on the coordinates of the airbag centroid at time Tn output in S31 [x o y o z o ], coordinates of the front vertex A [x A y A z A ] and the coordinates of the right vertex B [x B y B z B Calculate the pitch angle θ and yaw angle using the following formulas. And roll angle γ.

[0098]

[0099] S33: Kinematic output results are converted into angle of attack and sideslip angle.

[0100] According to the output of S31 at time Tn, the velocity of the centroid O of the airbag is [v]. xO v yO v zO The coordinate transformation from the ground coordinate system to the projectile coordinate system is as follows:

[0101]

[0102] Find the velocity [v] in the projectile coordinate system. x v y v z ]=P*[v xO v yO v zO ]

[0103] Based on the definitions of angle of attack and sideslip angle, the sideslip angle β and angle of attack α are obtained as follows:

[0104]

[0105] S34: Aerodynamic data interpolation processing to obtain real-time aerodynamic forces

[0106] Based on aerodynamic coefficient data obtained from wind tunnel tests or fluid dynamics calculations, interpolation calculations are designed. The sideslip angle β and angle of attack α calculated in real time at time Tn are used as interpolation variables to obtain the aerodynamic coefficients at time Tn, including: Cx, Cy, Cz, Cmz, Cmy, Cmx, My2, Mx2. Where: Cx is the axial force coefficient, Cy is the normal force coefficient, Cz is the lateral force coefficient, Cmz is the pitching moment coefficient, Cmy is the yaw moment coefficient, Cmx is the roll moment coefficient, My2 is the yaw moment caused by roll, and Mx2 is the roll moment caused by yaw. This is the cross-damping moment coefficient;

[0107] After obtaining the aerodynamic coefficients, the aerodynamic data are calculated using the following formula:

[0108] (1) Axial force

[0109] X = -C x *q*S

[0110] in, Dynamic pressure, unit: Pa;

[0111] S represents the airbag reference area.

[0112] (2) Normal force, lateral force

[0113] Y = C y *q*S

[0114] Z = C z *q*S

[0115] Where Y is the normal force, Z is the lateral force, and C is the lateral force. y Cz is the normal force coefficient, and Cz is the lateral force coefficient.

[0116] (3) Pitch, yaw, and roll moments

[0117] M z(y,x) =C mz(y,x) *q*S*L

[0118] Where M z M y M x These are the pitching moment, yaw moment, and roll moment, respectively. mz C my C mx These are the pitch, yaw, and roll moment coefficients. The reference lengths for pitch moment and yaw and roll moment are different.

[0119] (4) Pitch damping moment, yaw damping moment, roll damping moment

[0120]

[0121]

[0122] in, The pitch (yaw, roll) damping moment coefficient;

[0123] ω z (ω x ω y ) represent pitch (yaw, roll) angular velocities, respectively.

[0124] (5) Cross-damping moment

[0125]

[0126]

[0127] Among them, M y2 M is the yaw moment caused by roll. x2 The rolling moment caused by yaw. This is the cross-damping moment coefficient.

[0128] S35: Perform rigid-flexible coupling dynamic simulation analysis at time Tn+1

[0129] The aerodynamic forces obtained in step S34 are reloaded onto the rigid-flexible coupled dynamic finite element model established in step S2, and steps S31-S34 are repeated to achieve real-time coupling of structural deformation and aerodynamic load, and to complete the time-domain simulation analysis of the aircraft system considering the deformation of the flexible body at time Tn+1.

[0130] S4: Virtual Flight Test

[0131] like Figure 9-12 Four flight tests with different engine thrusts were designed: Test 1, takeoff dynamics analysis; Test 2, climb dynamics analysis; Test 3, level flight dynamics analysis; Test 4, turn dynamics analysis.

[0132] Specifically:

[0133] Experiment 1, Takeoff Dynamics Analysis: The thrust of a single engine is above 40N during takeoff;

[0134] Experiment 2, Climb Dynamics Analysis: When changing from level flight to climb, the engine thrust is increased to 60N.

[0135] Experiment 3, Level Flight Dynamics Analysis: After the aircraft has taken off completely, it continues to climb under the thrust of the engine. After climbing to a certain altitude, the engine thrust decreases to 32N.

[0136] Experiment 4, Turning Dynamics Analysis: After takeoff and stabilization, the thrust of the left and right engines increases and decreases by 10N respectively.

[0137] S5: Simulation and reproduction of experimental results

[0138] The motion trajectories and velocity curves of the airbag and pod were obtained based on flight test telemetry data. Engine thrust data from S4 was used as the thrust curve input for the simulation model. Through rigid-flexible coupling dynamic simulation analysis in S3, the motion trajectories and velocity curves of the airbag and pod were obtained. The simulation results based on the thrust input from flight test one showed that the aircraft system took off smoothly and flew in a straight line; the simulation results based on the thrust input from flight test two showed that the aircraft system took off smoothly and then turned left after a period of flight. The comparison between the flight test and simulation analysis results verified the effectiveness of the dynamic simulation analysis method and implementation path for the flexible rope aircraft system.

[0139] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A dynamic simulation analysis method for a flexible rope flight vehicle system, characterized in that, Includes the following steps: S1: Perform nonlinear characteristic modeling and calibration of the rope; specifically: Select the ropes used for connecting multi-body aircraft and determine the initial length of the test ropes; conduct tensile tests, record the tensile force under the corresponding tensile increments, obtain the nonlinear material parameters of the ropes, and use these parameters as inputs to the rope dynamics model; S2: Perform rigid-flexible coupling dynamic finite element modeling; Rigid body models were established for the airbags, pods, rope reels, and steering pulleys in the aircraft system. A finite element model of the rope was established using dedicated rope elements. The ropes were then assembled to form a rigid-flexible coupled dynamic model of the flexible rope aircraft system. A contact model was established between the ropes, reels, and pulleys. When assigning rope material properties, a material that only bears tension and not compression was selected, and the rope stiffness obtained from the rope tensile test was used as input. S3: Perform dynamic simulation analysis of rigid-flexible coupling; A dynamic simulation analysis solver for rope system dynamics was developed based on explicit dynamics, and dynamic simulation analysis was performed on the rigid-flexible coupled dynamic finite element model established in step S2. S4: Conduct virtual flight tests; Virtual flight tests were conducted by designing flight tests with four different engine thrusts. S5: Simulate and reproduce the test results; based on the tethering scheme of the test aircraft and the on-site flight conditions, including thrust and the time-domain extension and retraction of the rope reel, set the simulation input parameters, and obtain the motion trajectory and velocity curve of the airbag and pod through the rigid-flexible coupling dynamic simulation analysis in step S3. Compare the motion trajectory and velocity data of the airbag and pod obtained by flight test telemetry to determine the effectiveness of the dynamic simulation analysis method of the flexible rope flight vehicle system.

2. The dynamic simulation analysis method for the flexible rope flight system according to claim 1, characterized in that, Step S2 further includes applying static buoyancy at the centroid of the airbag, applying initial aerodynamic force and aerodynamic torque at the aerodynamic center point, and applying thrust at the pod engine.

3. The dynamic simulation analysis method for the flexible rope flight system according to claim 2, characterized in that, Step S2 further includes calculating the velocity and acceleration of any point on the rigid body; specifically: The velocity v of node i i This can be expressed as: Among them, v CG u is the velocity of the rigid body. i Let r be the velocity vector of any node relative to the centroid node; i Let be the distance from node i to the centroid. For rigid body angular velocity; The acceleration a of node i i This can be expressed as: Among them, a CG For rigid body acceleration; This is the angular acceleration at the center of gravity; Angular acceleration α of node i i This can be expressed as: a i =A i A CG a CG Among them, A i Let a be the transformation matrix from the global coordinate system to the rigid body's local coordinate system for node i; CG Let α be the nodal acceleration at the center of gravity of the rigid body. CG The nodal angular acceleration of the center of gravity of a rigid body.

4. The dynamic simulation analysis method for the flexible rope flight system according to claim 3, characterized in that, Step S2 further includes constructing the rope element interpolation function, and further includes: The arresting cable unit contains two nodes N1 and N2, with a length of L and an area of ​​A. The distance from any point N to N1 on the arresting cable unit is l, which is normalized and set to s = l / L. Shape function of the arresting cable element: N(s)=[N1I 2×2 ,N2I 2×2 ] N1 = -(s-1) N2 = s Among them, I 2×2 It is a 2x2 identity matrix.

5. The dynamic simulation analysis method for the flexible rope flight system according to claim 1, characterized in that, Step S3 further includes: S31: Dynamic simulation of rigid-flexible coupling at time Tn; A dynamic simulation analysis solver for a rope system was developed based on explicit finite element technology. The time-domain motion simulation analysis was performed on the rigid-flexible coupled dynamic model established in step S2. The analysis results can obtain the coordinates, velocities, and tension of the rope at time Tn for the centroid of the airbag and the center of mass of the pod. S32: Kinematic output results are converted into airbag attitude angles; Based on the coordinates of the airbag centroid at time Tn, the coordinates of the front vertex and the right vertex of the local coordinate system output in step S31, the pitch angle, yaw angle and roll angle of the airbag are obtained, and the transformation matrix from the geodetic coordinate system to the body coordinate system is further obtained. S33: Kinematic output results are converted into angle of attack and sideslip angle; Based on the velocity of the airbag centroid at time Tn output in step S31 and the coordinate transformation matrix obtained in step S32, the velocity vector is transformed from the geodetic coordinate system to the body coordinate system. The sideslip angle and angle of attack are obtained according to the formulas for solving the angle of attack and sideslip angle. S34: Real-time aerodynamic forces are obtained through aerodynamic data interpolation; Based on the aerodynamic coefficient data obtained from wind tunnel tests or fluid dynamics calculations, an aerodynamic interpolation program is written; and the sideslip angle and angle of attack calculated in real time at time Tn are used as interpolation variables to obtain the aerodynamic coefficients at time Tn, and then the real-time aerodynamic forces at the corresponding angle of attack and sideslip angle are calculated. S35: Perform rigid-flexible coupling dynamic simulation analysis at time Tn+1; The aerodynamic forces obtained in step S34 are reloaded onto the rigid-flexible coupled dynamic finite element model established in step S2, and steps S31-S34 are repeated to achieve real-time coupling of structural deformation and aerodynamic load, and to complete the time-domain simulation analysis of the aircraft system considering the deformation of the flexible body at time Tn+1.

6. The dynamic simulation analysis method for the flexible rope flight system according to claim 5, characterized in that, The airbag attitude angle is calculated in step S32 as follows: Based on the coordinates of the airbag centroid O at time Tn output in S31 [x O y O z O ], coordinates of the front vertex A [x A y A z A ] and the coordinates of the right vertex B [x B y B z B Calculate the pitch angle θ and yaw angle using the following formulas. and roll angle γ; 7. The dynamic simulation analysis method for the flexible rope flight system according to claim 5, characterized in that, The angle of attack and sideslip angle are calculated in step S33 as follows: According to the output of S31 at time Tn, the velocity of the centroid O of the airbag is [v]. xO v yO v zO The coordinate transformation from the ground coordinate system to the projectile coordinate system is as follows: Find the velocity [v] in the projectile coordinate system. x v y v z ]=P*[v xO v yO v zO ] Based on the definitions of angle of attack and sideslip angle, the sideslip angle β and angle of attack α are obtained as follows:

8. The dynamic simulation analysis method for the flexible rope flight system according to claim 5, characterized in that, Step S34 aerodynamic calculation includes axial force, normal force, lateral force; pitching moment, yaw moment, roll moment, pitching damping moment, yaw damping moment, roll damping moment, and cross damping moment.

9. The dynamic simulation analysis method for the flexible rope flight system according to claim 8, characterized in that: The method for calculating the cross-damping moment is as follows: Among them, M y2 M is the yaw moment caused by roll. x2 The rolling moment caused by yaw. ω is the cross-damping moment coefficient; z ω y ω z These are pitch, yaw, and roll angular velocities, respectively. ρ is dynamic pressure; S is the airbag reference area.

10. The dynamic simulation analysis method for a flexible rope flight system according to claim 1, characterized in that, The virtual flight test in step S4 specifically includes test one, takeoff dynamics analysis; test two, climb dynamics analysis; test three, level flight dynamics analysis; and test four, turn dynamics analysis.

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