CN116933381A - Dynamic simulation analysis method for flexible rope aircraft system - Google Patents
Dynamic simulation analysis method for flexible rope aircraft system Download PDFInfo
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Abstract
The application discloses a dynamic simulation analysis method of a rigid-flexible coupling multi-body system; and the rigid-flexible coupling dynamics simulation analysis of the multi-body aircraft system based on flexible rope connection is completed through rope nonlinear characteristic modeling and calibration, rigid-flexible coupling dynamics finite element modeling, rigid-flexible coupling dynamics simulation analysis, variable thrust flight test and test result simulation reproduction. According to the application, the nonlinear material properties and the stress characteristics of the rope are accurately simulated, a rigid-flexible coupling dynamics finite element model of a high-precision flexible rope aircraft system is established, a rope system dynamics simulation analysis solver is edited based on an explicit dynamics theory, the continuous iterative updating of pneumatic loads of rigid-flexible coupling bodies in a time domain is realized, a time domain simulation analysis path of a multi-body aircraft system considering flexible rope deformation is realized, the algorithm does not need to carry out balance iteration, the calculation speed is high, and the convergence control problem is also solved.
Description
Technical Field
The application relates to a dynamic simulation analysis method for a rigid-flexible coupled multi-body system, in particular to a dynamic simulation analysis and a stable and controllable mooring method for a rigid-flexible coupled multi-body aircraft system connected through ropes.
Background
Due to the advantages of flexible control, quick response, long-term air residence and the like in the aspects of performing tasks such as investigation monitoring, emergency combat and the like, the flexible rope aircraft system has gradually become a research hotspot in the military and civil fields in recent years. In order to reduce the development cost of the flexible rope aircraft system, rope arrangement research needs to be carried out in a scheme stage, and the flight stability and operability of the flexible rope aircraft system are verified through rigid-flexible coupling modeling technology and fluid-solid coupling simulation analysis, so that the success rate of flight tests is ensured, and the number of flight tests is reduced.
The aircraft system connected by the flexible ropes is special in structure and consists of an airbag, a nacelle and the flexible ropes which play a role in connection, so that rigid body and flexible body coupling are required to be considered in dynamic modeling, the dynamic modeling complexity is high, and particularly the modeling difficulty of the flexible rope part is high; the flying process of the aircraft system is influenced by the static buoyancy and rope tension of the air bag, the thrust provided by the nacelle engine and the aerodynamic force changed along with the flying speed and the attitude, so that the joint simulation relates to the multi-disciplinary intersection problems of structural mechanics, control, aerodynamics and the like, and how to realize the real-time exchange of data of each disciplinary is also one of simulation difficulties.
The current common simulation analysis method adopts the multi-body dynamics software Adams and Simulink to jointly simulate, and adopts the explicit dynamics software to carry out dynamics simulation. The problem of the first method is that ADAMS software cannot directly model large-deformation flexible objects such as ropes, only the ropes are divided into a plurality of sections of rigid bodies for modeling, the flight configuration change caused by the retraction of the ropes cannot be analyzed, the characteristics of flexible ropes such as easy bending, drawability and incompressibility and the like cannot be reflected, and the modeling simulation precision is low; and the Adams dynamics analysis adopts an implicit dynamics algorithm, a rigidity matrix is required to be calculated, iterative calculation is carried out, and the calculation non-convergence condition is easy to generate. The second method has the problem that the pneumatic load can only be set in the finite element pretreatment stage, and the pneumatic load can not be reloaded after the model is submitted to calculation, but in the actual flight process, the pneumatic load changes along with the change of the posture and the speed of the air bag. The method cannot realize structural deformation and pneumatic load coupling and cannot realize aerodynamic real-time iterative loading.
Disclosure of Invention
(one) solving the technical problems
In order to solve the technical problems, the application provides a high-precision rigid-flexible coupling dynamics modeling and fluid-solid simulation analysis method suitable for a flexible rope aircraft system for engineering application, which is used for accurately simulating nonlinear material properties and stress characteristics of ropes, developing a dynamic simulation analysis solver of the rope system based on an explicit finite element theory, simultaneously developing a aerodynamic force interpolation program and a fluid-solid coupling iteration console program, realizing continuous iteration update of aerodynamic load of a rigid-flexible coupling body in a time domain, completing the flight dynamics simulation analysis of a variable-configuration aircraft by taking flexible rope retraction and elastic extension into consideration, providing design analysis capability of rope mooring schemes of the aircraft, and solving flight stability and operability verification problems under different mooring schemes.
(II) technical scheme
In order to solve the technical problems and achieve the aim of the application, the application is realized by the following technical scheme:
the first step: modeling and calibrating nonlinear characteristics of the rope;
selecting ropes for connecting the multi-body aircraft, determining the initial length of the test ropes according to the connection length of the ropes on the aircraft, and fixing the two ends of the ropes for tensile test. The rope is stretched on the basis of the initial length, the stretching force under the corresponding stretching increment is recorded respectively, the nonlinear material parameter of the rope is obtained, and the parameter is used as the input of a rope dynamic model.
And a second step of: finite element modeling of rigid-flexible coupling dynamics
The method comprises the steps of respectively building rigid body models of an air bag, a nacelle, a rope winder and a steering pulley in an aircraft system, building a vertical finite element model by adopting a special rope unit for ropes, assembling to form a rigid-flexible coupling dynamic model of the flexible rope aircraft system, and building a contact model between the ropes and the reel and between the ropes and between the pulleys for simulating the sliding of the ropes between the reel and the pulleys. When the rope material attribute is given, selecting a material which only bears the stress, and taking the rope rigidity obtained by a rope tensile test as an input. Static buoyancy is applied at the centroid of the air bag, aerodynamic force and aerodynamic moment at the initial moment are applied at the aerodynamic center point, and thrust is applied at the nacelle engine.
Third step rigid-flexible coupling dynamics simulation analysis
1) Rigid-flexible coupling dynamics simulation at Tn moment
And developing a rope system dynamics simulation analysis solver based on an explicit finite element technology, performing time domain motion simulation analysis on the rigid-flexible coupling dynamics model established in the second step, and obtaining coordinate values, speed and rope tension of an airbag centroid and a pod centroid at the moment Tn according to analysis results.
2) The kinematic output result is converted into an air bag attitude angle
Obtaining the pitch angle theta and yaw angle of the air bag according to the coordinate value of the air bag centroid position point O at the moment Tn output in the third step 1), the coordinate value of the front vertex A and the coordinate value of the right vertex B of the local coordinate systemAnd the roll angle gamma further obtains a transformation matrix from the geodetic coordinate system to the machine body coordinate system.
3) Conversion of kinematic output results into angle of attack and sideslip
And 3) obtaining a coordinate transformation matrix according to the velocity of the air bag centroid point O at the moment Tn output in the third step 1) and the third step 2), transferring a velocity vector from a geodetic coordinate system to a machine body coordinate system, and obtaining a sideslip angle beta and an attack angle alpha according to a solving formula of the attack angle and the sideslip angle.
4) Aerodynamic force data interpolation processing to obtain real-time aerodynamic force
And writing a aerodynamic force interpolation program according to aerodynamic force coefficient data obtained by wind tunnel test or hydrodynamic force calculation. And the sideslip angle beta and the attack angle alpha calculated in real time at the moment Tn are used as interpolation variables to obtain the pneumatic coefficient at the moment Tn, and then the real-time aerodynamic force under the corresponding attack angle and sideslip angle is calculated.
5) Simulation analysis of rigid-flexible coupling dynamics at Tn+1 moment
And (3) developing a fluid-solid coupling control console program, reloading the aerodynamic force obtained in the third step (4) on the rigid-flexible coupling dynamics finite element model established in the second step, and repeating the third steps (1) to 4), so as to realize real-time coupling of structural deformation and aerodynamic load and complete time domain simulation analysis of the aircraft system taking the flexible body deformation into consideration at the moment Tn+1.
Fourth step virtual flight test
Four different flight tests were designed: the method comprises the steps of firstly, analyzing takeoff dynamics; test two, climbing dynamics analysis, test three, flat fly dynamics analysis, test four and turning dynamics analysis.
Fifth step test result simulation reproduction
According to the mooring scheme of the test machine and the on-site flight state, including the time domain retraction amount of the thrust and the rope reel, setting simulation input parameters, obtaining the motion track and the speed curve of the air bag and the nacelle through rigid-flexible coupling dynamics simulation analysis in the third step, comparing the motion track and the speed data of the air bag and the nacelle obtained through remote measurement with the flight test, and judging the dynamics simulation analysis method of the flexible rope aircraft system and the effectiveness of the realization path.
(III) beneficial effects
Compared with the prior art, the application has the beneficial effects that: according to the application, the nonlinear material property and the stress property of the rope are accurately simulated through rigid-flexible coupling modeling technology and fluid-solid coupling simulation analysis, a dynamic simulation analysis solver of the rope system is developed based on an explicit finite element theory, a aerodynamic force interpolation program and a fluid-solid coupling iteration control console program are developed at the same time, the nonlinear material property and the stress property of the rope are accurately simulated, a rigid-flexible coupling dynamic finite element model of the high-precision flexible rope aircraft system is established, the continuous iterative update of pneumatic load of the rigid-flexible coupling body on a time domain is realized, the time domain simulation analysis path of the multi-body aircraft system considering the deformation of the flexible rope is realized, the algorithm does not need to carry out balance iteration, the calculation speed is high, the convergence control problem is also solved, the design analysis capability of the aircraft rope mooring scheme is provided, and the flight stability and operability verification problems under different mooring schemes are solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
FIG. 1 is a flow chart of a method of dynamic simulation analysis of a flexible rope aircraft system in accordance with an embodiment of the present application;
FIG. 2 is a schematic representation of a rigid-flexible coupled dynamics finite element model of a flexible rope aircraft system according to an embodiment of the application;
FIG. 3 is a schematic diagram of a rigid body algorithm of an embodiment of the present application;
fig. 4 is a schematic diagram of the construction of a rope unit interpolation function according to an embodiment of the application;
FIG. 5 is a schematic diagram of a kinematic pair between a forward and backward motion winch, a forward and backward diverting pulley and a nacelle according to an embodiment of the present application;
FIG. 6 is a schematic diagram of a side-to-side motion accessory model between a side-to-side motion winch, a side-to-side diverting pulley and a nacelle according to an embodiment of the present application;
FIG. 7 is a flow chart of a aerodynamic force application process according to an embodiment of the present application;
FIG. 8 is a schematic representation of the point of application of pneumatic force to an airbag in accordance with an embodiment of the present application;
FIG. 9 is a schematic view of an aircraft takeoff virtual test according to an embodiment of the present application;
FIG. 10 is a schematic illustration of a fly-flat virtual test of an aircraft in accordance with an embodiment of the present application;
FIG. 11 is a schematic illustration of an aircraft climb virtual test of an embodiment of the application;
FIG. 12 is a schematic illustration of an aircraft turn virtual test of an embodiment of the application;
Detailed Description
Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
Other advantages and effects of the present disclosure will become readily apparent to those skilled in the art from the following disclosure, which describes embodiments of the present disclosure by way of specific examples. It will be apparent that the described embodiments are merely some, but not all embodiments of the present disclosure. The disclosure may be embodied or practiced in other different specific embodiments, and details within the subject specification may be modified or changed from various points of view and applications without departing from the spirit of the disclosure. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by one of ordinary skill in the art without inventive effort, based on the embodiments in this disclosure are intended to be within the scope of this disclosure.
Referring to fig. 1, a dynamic simulation analysis method for a flexible rope aircraft system comprises the following specific steps:
s1: modeling and calibration of nonlinear characteristics of rope
Selecting ropes for connecting the multi-body aircraft, determining the initial length of the test rope by 5m according to the connecting length of the ropes on the aircraft, and fixing the two ends of the rope for tensile test. The stretching increment of the rope is respectively 2cm, 4cm, 6cm, 8cm, 10cm, 12cm and 14cm on the basis of the initial length, the stretching force under the corresponding stretching increment is recorded, the rigidity of the rope is obtained through K=F/deltax, the nonlinear material parameter of the rope is obtained, and the parameter is used as the input of a rope dynamics model.
S2, finite element modeling of rigid-flexible coupling dynamics
Referring to fig. 2, a schematic diagram of a rigid-flexible coupled dynamic finite element model of a flexible rope aircraft system is shown. The airbags and pods in the aircraft system are considered rigid bodies, imparting a weight inertia attribute. The rigid body is a series of units endowed with infinite rigidity, namely, the rigid body only moves in a translational or rotational mode and cannot deform. The speed, acceleration, etc. of any point on the rigid body can be expressed linearly by the speed, acceleration, etc. of the rigid body center of gravity node.
Referring to fig. 3, the solution of the rigid motion is performed under a global coordinate system. In an explicit iterative process, the weight, center of gravity, and moment of inertia of the rigid body are first calculated.
Wherein M is CG Is the weight of rigid body, X CG 、Y CG 、Z CG Is the barycentric coordinate, X i 、Y i 、Z i Is the XYZ coordinates of point I, I CG Is the moment of inertia; a is that i For the transformation matrix of the node I from the global coordinate system to the rigid body local coordinate system, I 1 、I 2 、I 3 The moment of inertia component of XYZ.
The force and moment born by the rigid body are applied to the center node of the rigid body, and the method comprises the following steps:
the node acceleration and the angular acceleration of the center of gravity of the rigid body can be solved through the rigid body kinematics equation.
Velocity v of node i i Can be expressed as:
wherein v is CG Is a rigid body velocity; u (u) i A velocity vector for any node relative to the center of gravity node; r is (r) i As the distance from node i to the center of gravity,is the angular velocity of the rigid body;
acceleration a of node i i Can be expressed as:
wherein a is CG Node acceleration being the center of gravity of the rigid body;is the rigid angular acceleration;
angular acceleration a of node i i Can be expressed as:
α i ＝A i A CG α CG
the rope is made of flexible fiber materials, can only bear load in the tensile direction, and cannot bear load such as compression, torsion and bending. Therefore, the application develops a special one-dimensional unit to simulate the arresting rope, and the unit can only bear tensile force, cannot bear compressive force and cannot bear bending moment and torque.
Referring to fig. 4, the stopper cable unit includes 2 nodes N 1 、N 2 The length of the material is L, and the area of the material is A; any point N to N on the arresting cable unit 1 Is L, s=l/L can be given by normalization. Position q of a cell in a global coordinate system e Can be expressed as:
the displacement of any point N on the cell can be expressed as:
r(s，t)＝N(s)q e
wherein N(s) is a shape function of the stopper cable unit:
N(s)＝[N 1 I 2×2 ，N 2 I 2×2 ]
N 1 ＝-(s-1)
N 2 ＝s
wherein I is 2×2 An identity matrix of 2 x 2.
The deformation of the stopper-cord unit may be expressed as:
wherein the method comprises the steps of
Wherein,,the form function N(s) of the arresting cable unit is obtained by conducting once over time.
According to the material constitutive relation of the arresting cable unit, the stress of the arresting cable unit can be obtained:
σ＝Eε
wherein E is rope stiffness.
The nacelle is modeled by a rigid body, and the left and right motion winch, the front and rear motion winch, the left and right diverting pulley and the front and rear diverting pulley are modeled by a rigid body, and since the left and right motion winch, the front and rear motion winch, the left and right diverting pulley and the front and rear diverting pulley are mounted on the nacelle and can rotate freely, it is necessary to define a motion constraint model between the left and right motion winch, the front and rear motion winch, the left and right diverting pulley and the front and rear diverting pulley and the nacelle, that is, a revolute pair between the rigid bodies, as shown in fig. 5 to 6.
Static buoyancy is applied at the centroid of the air bag, aerodynamic force and aerodynamic moment are applied at the aerodynamic center point, and thrust is applied at the nacelle engine.
S3: simulation analysis of rigid-flexible coupling dynamics
The aerodynamic forces borne by the flexible rope aircraft system during the flight are always one of the main factors affecting the attitude of the aircraft. Aerodynamic forces experienced by an aircraft are determined by the angle of attack, sideslip angle, and velocity of the airbag. In the whole flight process, the speed and the attitude of the airplane are continuously changed. After aerodynamic forces are applied to the aircraft, there are changes that further contribute to the speed, attitude of the aircraft. Using explicit finite element techniques, aerodynamic and structural dynamics coupling solvers were developed and the computational flow is shown in fig. 7:
the method specifically comprises the following steps:
s31: rigid-flexible coupling dynamics simulation at Tn moment
Based on the explicit dynamics development and editing rope system dynamics simulation analysis solver, dynamics simulation analysis is carried out on the rigid-flexible coupling dynamics finite element model established in the second step, and the analysis result can obtain coordinate values, speed and rope tension of the airbag centroid and the pod centroid at the moment Tn.
S32: the kinematic output result is converted into an air bag attitude angle
Referring to FIG. 8, an airbag aerodynamic force application point diagram is shown, according to the coordinates [ x ] of the airbag centroid position point 0 at the Tn time output in S31 o y o z o ]Front vertex A coordinate [ x A y A z A ]And right vertex B coordinate [ x B y B z B ]The pitch angle θ and yaw angle are obtained according to the following formulaAnd a roll angle γ.
S33: conversion of kinematic output results into angle of attack and sideslip
According to the output Tn time airbag centroid point O speed [ v ] in S31 xO v yO v zO ]The coordinate transformation is carried out, and the coordinate transformation matrix from the ground coordinate system to the projectile coordinate system is as follows:
obtaining velocity [ v ] in the projectile coordinate system x v y v z ]＝P*[v xO v yO v zO ]
According to the definition of the attack angle and the sideslip angle, the sideslip angle beta and the attack angle alpha are obtained as follows:
s34: aerodynamic force data interpolation processing to obtain real-time aerodynamic force
According to aerodynamic coefficient data obtained by wind tunnel test or hydrodynamic calculation, designing interpolation calculation, taking sideslip angle beta and attack angle alpha calculated in real time at Tn moment as interpolation variables to obtain aerodynamic coefficient at Tn moment, comprising: cx, cy, cz, cmz, cmy, cmx, my2, mx2,Wherein: cx is the axial force coefficient, cy is the normal force coefficient, cz is the lateral force coefficient, cmz is the pitch moment coefficient, cmy is the yaw moment coefficient, cmx is the roll moment coefficient, my2 is the yaw moment due to roll, mx2 is the roll moment due to yaw, and%>Is a cross damping moment coefficient;
after obtaining the aerodynamic coefficients, aerodynamic data is calculated by the following formula:
(1) Axial force
X＝-C x *q*S
Wherein,,dynamic pressure, unit: pa;
s is the reference area of the air bag.
(2) Normal and lateral forces
Y＝C y *q*S
Z＝C z *q*S
Wherein Y is normal force, Z is lateral force, C y As normal force coefficient, cz lateral force coefficient.
(3) Pitching, yawing and rolling moment
M z(y,x) ＝C mz(y,x) *q*S*L
Wherein M is z 、M y 、M x Respectively pitching moment, yawing moment and rolling moment, C mz 、C my 、C mx The pitch moment is different from the reference length of the yaw moment and the roll moment for the pitch moment, the yaw moment and the roll moment coefficients.
(4) Pitch damping moment, yaw damping moment, roll damping moment
Wherein,,damping moment coefficients for pitch (yaw, roll);
ω z (ω x ，ω y ) Pitch (yaw, roll) angular velocity, respectively.
(5) Cross damping moment
Wherein M is y2 For yaw moment caused by rolling, M x2 For the moment of roll caused by yaw,is a cross damping moment coefficient.
S35: simulation analysis of rigid-flexible coupling dynamics at Tn+1 moment
And (3) reloading aerodynamic force obtained in the step (S34) on the rigid-flexible coupling dynamics finite element model established in the step (S2), repeating the steps (S31-S34) to realize real-time coupling of structural deformation and aerodynamic load, and completing time domain simulation analysis of the aircraft system taking the flexible body deformation into consideration at the moment Tn+1.
S4: virtual flight test
As in fig. 9-12, four different engine thrust flight tests were designed: the method comprises the steps of firstly, analyzing takeoff dynamics; test two, climbing dynamics analysis, test three, flat fly dynamics analysis, test four and turning dynamics analysis.
The method comprises the following steps:
test one, takeoff dynamics analysis: the thrust of the single engine is more than 40N during take-off;
test two, climbing dynamics analysis: when the flat flying state is changed into the climbing state, the method is realized by increasing the thrust of the engine, and the thrust is increased to 60N;
test three, flat fly dynamics analysis: after the aircraft completely takes off, the aircraft continues to climb under the pushing of the engine, and when the aircraft climbs to a certain height, the engine thrust is reduced to 32N;
test four, cornering dynamics analysis: after the take-off is stable, the left and right engine thrust is respectively increased and decreased by 10N.
S5: simulation reproduction of test results
And obtaining the motion trail and the speed curve of the air bag and the nacelle according to the flight test telemetry data. And (3) inputting the engine thrust data of the S4 as a thrust curve of a simulation model, and obtaining a motion track and a speed curve of the air bag and the nacelle through rigid-flexible coupling dynamics simulation analysis of the S3. According to the simulation reproduction result of the thrust input of the flight test, the aircraft system stably takes off and flies in a straight line; and (3) according to simulation reproduction results of the two thrust inputs of the flight test, enabling the aircraft system to take off stably, and turning left after flying for a period of time. According to the flight test and simulation analysis comparison result, the dynamic simulation analysis method of the flexible rope aircraft system and the effectiveness of the realization path are verified.
The above examples are only illustrative of the preferred embodiments of the present application and are not intended to limit the scope of the present application, and various modifications and improvements made by those skilled in the art to the technical solution of the present application should fall within the scope of protection defined by the claims of the present application without departing from the spirit of the present application.
Claims (10)
1. The dynamic simulation analysis method for the flexible rope aircraft system is characterized by comprising the following steps of:
s1: modeling and calibrating nonlinear characteristics of the rope; the method comprises the following steps:
selecting ropes for connecting the multi-body aircraft, and determining the initial length of the test ropes; carrying out a tensile test, respectively recording the tensile force under the corresponding tensile increment to obtain nonlinear material parameters of the rope, and taking the parameters as the input of a rope dynamic model;
s2, performing finite element modeling of rigid-flexible coupling dynamics;
respectively building rigid body models of an air bag, a nacelle, a rope winder and a steering pulley in the aircraft system, modeling a vertical finite element model by adopting a special rope unit, assembling to form a rigid-flexible coupling dynamics model of the flexible rope aircraft system, and building a contact model between the rope and a reel and between the rope and the pulley; when the rope material attribute is given, selecting a material which only bears the stress and is not bearing the stress, and taking the rope rigidity obtained by a rope tensile test as input;
s3: performing rigid-flexible coupling dynamics simulation analysis;
based on the explicit dynamics development editing rope system dynamics simulation analysis solver, performing dynamics simulation analysis on the rigid-flexible coupling dynamics finite element model established in the step S2;
s4: performing a virtual flight test;
performing a virtual flight test by designing flight tests of four different engine thrust;
s5: performing simulation reproduction of test results; according to the mooring scheme of the test machine and the on-site flight state, including the time domain retraction amount of the thrust and the rope reel, setting simulation input parameters, obtaining the motion track and the speed curve of the air bag and the nacelle through the rigid-flexible coupling dynamics simulation analysis of the step S3, comparing the motion track and the speed curve with the motion track and the speed data of the air bag and the nacelle obtained through the remote measurement of the flight test, and judging the effectiveness of the dynamic simulation analysis method of the flexible rope aircraft system.
2. The method of dynamic simulation analysis of a flexible rope aircraft system according to claim 1, wherein step S2 further comprises applying static buoyancy at the centroid of the air bag, aerodynamic force and aerodynamic moment at the initial moment at the aerodynamic center point, and thrust at the nacelle engine.
3. The method according to claim 2, wherein the step S2 further comprises calculating the velocity and acceleration of any point on the rigid body; the method comprises the following steps:
velocity v of node i i Can be expressed as:
wherein v is CG Is a rigid body velocity; u (u) i A velocity vector for any node relative to the center of gravity node; r is (r) i As the distance from node i to the center of gravity,is the angular velocity of the rigid body;
acceleration a of node i i Can be expressed as:
wherein a is CG Is a rigid acceleration;is the angular acceleration of the center of gravity;
angular acceleration a of node i i Can be expressed as:
α i ＝A i A CG α CG
wherein A is i A transformation matrix from a global coordinate system to a rigid body local coordinate system for the node i; a, a CG Node acceleration, alpha, of rigid body center of gravity CG Rigid body center of gravityIs defined as the angular acceleration of the node.
4. A flexible rope aircraft system dynamics simulation analysis method according to claim 3, wherein said step S2 further comprises a rope unit interpolation function construction, further comprising:
the arresting cable unit comprises 2 nodes N 1 、N 2 The length of the material is L, and the area of the material is A; any point N to N on the arresting cable unit 1 The distance of (2) is L, and normalization processing is adopted, so that s=l/L;
shape function of the stopper cable unit:
N(s)＝[N 1 I 2×2 ,N 2 I 2×2 ]
N 1 ＝-(s-1)
N 2 ＝s
wherein I is 2×2 An identity matrix of 2 x 2.
5. The method of dynamic simulation analysis of a flexible rope aircraft system according to claim 1, wherein step S3 further comprises:
s31: simulating rigid-flexible coupling dynamics at the moment Tn;
developing a rope system dynamics simulation analysis solver based on an explicit finite element technology, performing time domain motion simulation analysis on the rigid-flexible coupling dynamics model established in the step S2, and obtaining coordinate values, speed and rope tension of an airbag centroid and a pod centroid at the moment Tn according to analysis results;
s32: converting the kinematic output result into an air bag attitude angle;
according to the coordinates of the centroid position point of the air bag, the coordinates of the front top point and the coordinates of the right top point of the local coordinate system at the Tn moment output in the step S31, the pitch angle, the yaw angle and the roll angle of the air bag are obtained, and a transformation matrix from the geodetic coordinate system to the machine body coordinate system is further obtained;
s33: the kinematic output result is converted into attack angle and sideslip angle;
obtaining a coordinate transformation matrix according to the Tn moment airbag centroid speed output in the step S31 and the step S32, transferring a speed vector from a geodetic coordinate system to a machine body coordinate system, and obtaining a sideslip angle and an attack angle according to a solving formula of the attack angle and the sideslip angle;
s34: the aerodynamic force data interpolation processing obtains real-time aerodynamic force;
according to aerodynamic coefficient data obtained by wind tunnel test or hydrodynamic calculation, writing a aerodynamic interpolation program; the sideslip angle and the attack angle calculated in real time at the moment Tn are used as interpolation variables, the pneumatic coefficient at the moment Tn is obtained, and then the real-time aerodynamic force under the corresponding attack angle and sideslip angle is calculated;
s35: carrying out Tn+1 moment rigid-flexible coupling dynamics simulation analysis;
and (3) reloading aerodynamic force obtained in the step (S34) on the rigid-flexible coupling dynamics finite element model established in the step (S2), repeating the steps (S31-S34) to realize real-time coupling of structural deformation and aerodynamic load, and completing time domain simulation analysis of the aircraft system taking the flexible body deformation into consideration at the moment Tn+1.
6. The method for dynamic simulation analysis of a flexible rope aircraft system according to claim 5, wherein the air bag attitude angle in step S32 is calculated as follows:
according to the coordinates [ x ] of the centroid position point O of the air bag at the moment Tn output in S31 O y O z O ]Front vertex A coordinate [ x A y A z A ]And right vertex B coordinate [ x B y B z B ]The pitch angle θ and yaw angle are obtained according to the following formulaAnd a roll angle γ;
7. the method according to claim 5, wherein the attack angle and sideslip angle are calculated in the following manner in step S33:
according to the output Tn time airbag centroid point O speed [ v ] in S31 xO v yO v zO ]The coordinate transformation is carried out, and the coordinate transformation matrix from the ground coordinate system to the projectile coordinate system is as follows:
obtaining velocity [ v ] in the projectile coordinate system x v y v z ]＝P*[v xO v yO v zO ]
According to the definition of the attack angle and the sideslip angle, the sideslip angle beta and the attack angle alpha are obtained as follows:
8. the method of dynamic simulation analysis of a flexible rope aircraft system according to claim 5, wherein the aerodynamic force calculation in step S34 includes axial force, normal force, lateral force; pitch moment, yaw moment, roll moment, pitch damping moment, yaw damping moment, roll damping moment, and cross damping moment.
9. The flexible rope aircraft system dynamics simulation analysis method according to claim 8, wherein: the method for calculating the cross damping moment comprises the following steps:
wherein M is y2 Yaw moment induced for rolling，M x2 For the moment of roll caused by yaw,is a cross damping moment coefficient; omega z 、ω y 、ω z Pitch, yaw, roll angular velocities, respectively; />Is dynamic pressure; s is the reference area of the air bag.
10. The method according to claim 1, wherein the virtual flight test in step S4 specifically includes a test one, takeoff dynamics analysis; test two, climbing dynamics analysis, test three, flat fly dynamics analysis, test four and turning dynamics analysis.
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