CN114611416B - LS-SVM modeling method for nonlinear unsteady aerodynamic characteristics of missile - Google Patents
LS-SVM modeling method for nonlinear unsteady aerodynamic characteristics of missile Download PDFInfo
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Abstract
The invention relates to a missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method, which decomposes the missile aerodynamic force into the sum of static aerodynamic force and aerodynamic force increment generated by dynamic motion, and adopts the LS-SVM modeling method to establish a dynamic aerodynamic force increment model, wherein a finite sampling point is used for approximately describing a motion process so as to reflect the influence of the motion process on the aerodynamic characteristic; solving a linear equation set of the LS-SVM by adopting a singular value decomposition method, and carrying out model training; and determining the penalty factor and the kernel width by adopting a training-checking method so as to improve the generalization performance of the LS-SVM model. The method aims to provide a missile large-attack-angle aerodynamic force modeling method based on machine learning.
Description
Technical Field
The invention belongs to the technical field of aerodynamics, and particularly relates to an LS-SVM (least squares-support vector machine) modeling method for nonlinear unsteady aerodynamic characteristics of a missile.
Background
The maneuverability of a large angle of attack is an important design index of modern tactical missiles. Particularly for air-launched missiles, the over-the-shoulder launching is realized by utilizing large attack angle maneuver, the combat response time can be greatly shortened, and the survival probability of the aerial carrier and the combat efficiency of the missiles are improved. No matter the missile is launched over the shoulder in the traditional way or launched over the shoulder in the novel way of self-overturning, the missile can experience a stall state with a large attack angle, and aerodynamic force presents high unsteady and strong nonlinear characteristics. At this time, the pneumatic derivative model based on the quasi-stationary assumption is not applicable, and a nonlinear unsteady pneumatic force model needs to be established.
The problem of missile nonlinear unsteady aerodynamic modeling is not reported in a published literature at present. In the prior art, the large-attack-angle unsteady aerodynamic modeling is only carried out on an airplane or a wing, and mainly comprises the following steps:
prior art 1: the method for modeling the large-attack-angle Unsteady aerodynamic force of an airplane based on a least square support vector machine proposed by Wang Qing et al (Wang Q, et al. uncertain aerodynamic modeling at high and of using the above mentioned supporting vector machines. Chinese Journal of Aeronautics, 2015, 28(3): 659-668). In the method, a finite sampling point is adopted to replace a time history and is used as an input vector of the LS-SVM, and a LS-SVM model is constructed by taking a full-scale pneumatic coefficient or a dynamic increment of the pneumatic coefficient as output; determining penalty factors using k-fold cross-checkingAnd width of nucleus. However, in this document, the linear system of equations in the LS-SVM is solved directly when the sample size is large (e.g., N)>5000) In time, the coefficient matrix a is numerically singular and the training algorithm cannot be performed.
Prior art 2: least square support vector machine-based wing unsteady dynamic process unsteady aerodynamic modeling method (Chen Shenlin, et al, Unstable unsteady aerodynamic modeling based on least square support vector machine with generation excitation, Chinese Journal ofAeroneautics, 2020, 33(10): 2499-2509). In the method, a finite sampling point is adopted to replace a time history and is used as an input vector of the LS-SVM, and a full-scale pneumatic coefficient is used as output to construct an LS-SVM model; determining penalty factors using leave-one-out cross-validationAnd width of nucleus. However, in the document, a Cholesky decomposition method is adopted to solve a linear equation set in the LS-SVM, and when the sample size is large, the problem that the value of the coefficient matrix a is singular and the training algorithm cannot be performed also exists.
Disclosure of Invention
In order to solve the problems, the invention provides a missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method, which decomposes the missile aerodynamic force into the sum of static aerodynamic force and aerodynamic force increment generated by dynamic motion, and adopts the LS-SVM modeling method to establish a dynamic aerodynamic force increment model, wherein a finite sampling point is used for approximately describing a motion process so as to reflect the influence of the motion process on the aerodynamic characteristic; solving a linear equation set of the LS-SVM by adopting a singular value decomposition method, and carrying out model training; and determining the penalty factor and the kernel width by adopting a training-checking method so as to improve the generalization performance of the LS-SVM model.
The technical scheme adopted by the invention is as follows: the LS-SVM modeling method for the nonlinear unsteady aerodynamic characteristics of the missile comprises the following steps:
s1: preparing data: calculating according to the missile aerodynamic force CFD to obtain a dynamic data table between a static aerodynamic force/aerodynamic moment coefficient, a large-amplitude pitching oscillation aerodynamic force/moment coefficient and a time course, and obtaining an input data file of pneumatic modeling after data processing; decomposing aerodynamic force into the sum of aerodynamic force increment generated by static aerodynamic force and dynamic motion by adopting a superposition principle to establish an LS-SVM model, and dividing an input data file of aerodynamic modeling into a training sample set, a checking sample set and a modeling sample set;
s2: model training: taking a training sample set as a model inputIn value, given an initial penalty factorAnd width of nucleusObtaining connection weight by singular value decompositionAnd biasb;
S3: checking: taking a check sample set as an input value, checking the output error of the established LS-SVM model, and using a penalty factor corresponding to the current minimum output errorAnd width of nucleusIf the value is the optimal value, if the global search is completed, the step S5 is executed, otherwise, the step S4 is executed;
s4: adjusting: adjusting penalty factorsAnd width of nucleusRepeatedly executing the steps S2 and S3;
s5: aerodynamic modeling: taking a modeling sample set as an input value of the LS-SVM model, and determining a penalty factorAnd width of nucleusTraining LS-SVM model, and obtaining final connection weight value by singular value decomposition methodAnd biasbPredicting the output of a modeled sample setAnd (6) outputting the value.
Preferably, in step S1, the specific method of data processing is:
s1.1: uniformly transforming the reference points of the aerodynamic moment coefficients to the center of mass of the missile;
s1.2: calculating the angle of attack at each moment in the dynamic data tableAngular rate of attackAnd pitch rate;
S1.3: calculating dimensionless timeNon-dimensional angle of attack rateAnd dimensionless pitch angle rate;
S1.4: and after the processing of the steps S1.1 to S1.3, intercepting one period of data to generate an input data file for pneumatic modeling.
Preferably, all input variables in the input data file for pneumatic modeling are normalized to the interval [ -1,1] with their maximum and minimum values to generate a training sample set, a check sample set, and a modeling sample set.
Preferably, in step S1, the specific method for dividing the input data file for pneumatic modeling into the training sample set, the verification sample set, and the modeling sample set includes: and selecting the pneumatic data of part of states as a verification sample set, taking the rest pneumatic data as a training sample set, and taking the modeling sample set as the sum of the training sample set and the verification sample set.
Preferably, the singular value decomposition method obtains the connection weightAnd biasbThe specific method comprises the following steps: respectively constructing matrixes by calculating kernel functions of input samples and known output samples according to the selected sample setAAndbconnection weightAnd biasbIs a linear system of equations:and (3) solving the least square solution of the linear equation system by adopting a singular value decomposition method.
Preferably, the input variables of the training sample set, the checking sample set and the modeling sample set are the angle of attack at the current moment and the angle of attack at the previous n momentsAnd corresponding angle of attack rateAnd pitch rate(ii) a And the output variables of the training sample set, the checking sample set and the modeling sample set are dynamic aerodynamic force increment.
Preferably, the time interval between n time angles of attack is chosen, and the dimensionless time interval between n time angles of attack is 1.35).
Preferably, dynamic aerodynamic force incrementWhereinCFor the pneumatic force and moment coefficients,,is static aerodynamic forceAnd (4) the coefficient.
Preferably, in step S3, the output errors are the root mean square error RMSE and the relative root mean square error RMSE (%).
The invention has the following beneficial effects:
1) because the configuration of the airplane and the guided missile is different, the aerodynamic characteristics are different in the unsteady motion; the method is suitable for modeling the nonlinear unsteady aerodynamic force of the guided missile, the prior art only aims at the maneuvering of an airplane with a large attack angle or the dynamic movement of wings, but not aims at the maneuvering scene of the guided missile with the large attack angle, and the method has engineering practical value for modeling the nonlinear unsteady aerodynamic force of the guided missile;
2) the least square solution of a linear equation set in the LS-SVM is calculated by adopting a singular value decomposition method, LS-SVM training is carried out, the robustness of a training algorithm is greatly improved, and the method is suitable for missile nonlinear unsteady aerodynamic modeling with a large sample scale (for example, N is more than 5000);
3) the method adopts a training-checking method to carry out modeling, determines penalty factors and kernel width, and greatly reduces the calculated amount, thereby avoiding the problem of overlarge calculated amount in the prior art when the wind tunnel test/CFD calculated state number is large;
4) the invention is directed to dynamic aerodynamic augmentationThe LS-SVM modeling is carried out, so that on one hand, the adverse effect of dynamic wind tunnel test/CFD calculation errors on static aerodynamic prediction results can be avoided, and on the other hand, the generalization performance of the aerodynamic model is improved to a certain extent; the pitch angle rate is used as one of input variables of the LS-SVM, so that the influence of pitch damping on the aerodynamic characteristics can be accurately reflected, and the prediction result is more accurate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a dynamic aerodynamic force increment LS-SVM model;
FIG. 2 is a flow chart of aerodynamic LS-SVM modeling;
FIG. 3 shows the data after being processed(center angle of attack 45 degrees, amplitude 45 degrees);
FIG. 4 shows the data after being processed(center angle of attack 90 degrees, amplitude 45 degrees);
FIG. 5 shows the data after being processed(center angle of attack 135 degrees, amplitude 45 degrees);
FIG. 6 shows the data after being processed(center angle of attack 90 degrees, amplitude 90 degrees);
FIG. 7 shows the result after data processing(center angle of attack 45 degrees, amplitude 45 degrees);
FIG. 8 shows the result after data processing(center angle of attack 90 degrees, amplitude 45 degrees);
FIG. 9 shows the result after data processing(center angle of attack 135 degrees, amplitude 45 degrees);
FIG. 10 shows the result after data processing(center angle of attack 90 degrees, amplitude 90 degrees);
FIG. 11 shows the result after data processing(center angle of attack 45 degrees, amplitude 45 degrees);
FIG. 12 shows the result after data processing(center angle of attack 90 degrees, amplitude 45 degrees);
FIG. 13 shows the data after being processed(center angle of attack 135 degrees, amplitude 45 degrees);
FIG. 14 shows the result after data processing(center angle of attack 90 degrees, amplitude 90 degrees);
FIG. 15 is a drawing showingThe verification result of the LS-SVM model (center attack angle 45 degrees, amplitude 45 degrees);
FIG. 16 is a drawing showingThe verification result of the LS-SVM model (center attack angle 90 degrees, amplitude 45 degrees);
FIG. 17 is a drawing showingThe verification result of the LS-SVM model (center attack angle 135 degrees, amplitude 45 degrees);
FIG. 18 is a drawing showingThe verification result of the LS-SVM model (center attack angle 90 degrees, amplitude 90 degrees);
FIG. 19 is a drawing showingThe verification result of the LS-SVM model (center attack angle 45 degrees, amplitude 45 degrees);
FIG. 20 is a drawing showingThe LS-SVM model of (center angle of attack 90 degrees, amplitude 45 degrees)
FIG. 21 is a drawing showingThe LS-SVM model of (center attack angle 135 degree, amplitude 45 degree)
FIG. 22 is a drawing showingThe LS-SVM model of (center angle of attack 90 degrees, amplitude 90 degrees)
FIG. 23 is a drawing showingThe verification result of the LS-SVM model (center attack angle 45 degrees, amplitude 45 degrees);
FIG. 24 is a drawing showingThe verification result of the LS-SVM model (center attack angle 90 degrees, amplitude 45 degrees);
FIG. 25 is a schematic view ofThe verification result of the LS-SVM model (center attack angle 135 degrees, amplitude 45 degrees);
FIG. 26 is a schematic view ofThe verification result of the LS-SVM model (center attack angle 90 degrees, amplitude 90 degrees);
FIG. 27 is a schematic view ofComparing the predicted result of the LS-SVM model of (1) with CFD data (center attack angle 45 degrees, amplitude 45 degrees);
FIG. 28 is a drawing showingComparing the predicted result of the LS-SVM model of (1) with CFD data (center attack angle is 90 degrees, amplitude is 45 degrees);
FIG. 29 is a schematic view ofComparing the predicted result of the LS-SVM model of (1) with the CFD data (center attack angle of 135 degrees, amplitude of 45 degrees);
FIG. 30 is a drawing showingComparing the predicted result of the LS-SVM model with CFD data (the central attack angle is 90 degrees, and the amplitude is 90 degrees);
FIG. 31 is a drawing showingComparing the predicted result of the LS-SVM model of (1) with CFD data (center attack angle 45 degrees, amplitude 45 degrees);
FIG. 32 is a schematic view ofComparing the predicted result of the LS-SVM model of (1) with CFD data (center attack angle is 90 degrees, amplitude is 45 degrees);
FIG. 33 is a drawing showingComparing the predicted result of the LS-SVM model of (1) with the CFD data (center attack angle of 135 degrees, amplitude of 45 degrees);
FIG. 34 is a schematic view ofComparing the predicted result of the LS-SVM model with CFD data (the central attack angle is 90 degrees, and the amplitude is 90 degrees);
FIG. 35 is a schematic view ofComparing the predicted result of the LS-SVM model of (1) with CFD data (center attack angle 45 degrees, amplitude 45 degrees);
FIG. 36 is a schematic view ofComparing the predicted result of the LS-SVM model with CFD data (the central attack angle is 90 degrees, and the amplitude is 45 degrees);
FIG. 37 is a schematic view ofComparing the predicted result of the LS-SVM model of (1) with the CFD data (center attack angle of 135 degrees, amplitude of 45 degrees);
FIG. 38 is a schematic view ofComparing the predicted result of the LS-SVM model with CFD data (the central attack angle is 90 degrees, and the amplitude is 90 degrees);
is axial force coefficient (unit: dimensionless),is the normal force coefficient (unit: dimensionless),is the pitching moment coefficient (unit: dimensionless), alpha is the angle of attack (unit: degree), CFD is the result calculated by using the computational fluid dynamics method numerical value, and mod represents the result modeled by the technology of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention develops a nonlinear unsteady aerodynamic modeling method based on a least square support vector machine (LS-SVM) aiming at the problem of modeling the large-attack-angle maneuvering aerodynamic of a missile.
(1) Unsteady aerodynamic LS-SVM model
In the attack angle plane, the missile aerodynamic force and moment are nonlinear functions of Mach number, attack angle, pitch angle rate and pitch rudder deflection angle. The method adopts a superposition principle to decompose the aerodynamic force into the sum of static aerodynamic force and aerodynamic force increment generated by dynamic motion, namely:
in the formula:Cfor the pneumatic force and moment coefficients,;Mis Mach number;is an angle of attack;is the pitch rudder deflection angle;for non-dimensional pitch angle rates,;lis a reference length (projectile length);Vis the incoming flow velocity.
In the formula (1), the reaction mixture is,the static aerodynamic coefficient is a nonlinear function of Mach number, attack angle and pitch rudder deflection angle;generated for dynamic motionThe aerodynamic increment (D, which is omitted for simplicity and convenience to indicate the increment), is a non-linear functional of the motion history, which is denoted here by brackets to distinguish it from the usual function, where the effect of pitch rudder deflection is negligible.
For large-amplitude oscillation wind tunnel test or CFD calculation, the Mach number is fixed and unchanged, and the pitch rudder deflection angleKeeping 0, the formula (1) can be simplified to
LS-SVM modeling in the invention aims at dynamic aerodynamic force incrementTo proceed with. Under the condition of not considering the bifurcation phenomenon, the 'memory' time of aerodynamic force to the motion process is limited, the motion process can be approximately replaced by a limited number of sampling points, and the invention adopts the attack angle at the current momentAngle of attack from the first n momentsTo approximate the angle of attack course, then:
dynamic aerodynamic force incrementThe LS-SVM model of (1) is shown in fig. 1. For a given predicted sample inputxThe output of LS-SVM prediction is
In the formula:xan input vector of the prediction sample of (a), see equation (5);yan output of the prediction samples of;an input vector (also called a support vector) which is a training sample, see equation (6); kernel functionThe Radial Basis Function (RBF) is used, see equation (7).
(2) LS-SVM training algorithm
At a given penalty factorAnd width of nucleusIn the case of (2), penalty factor in the present inventionGiven range of 3.0-7.0, core widthIs in the range of 0.05-0.17, and can be selected in the range of the interval, for the training sample setBuilding a system matrixAAndb:
in the formula
Training sample points for modeling problem of nonlinear unsteady aerodynamic force of missileNIn the thousands and even tens of thousands, an accurate solution cannot generally be solved. In the invention, a least square solution of the linear equation set (10) is solved by a singular value decomposition method.
For matrixASingular value decomposition:
least squares solution of the system of linear equations (10) to
WhereinA + To representAGeneral inverse of
If the linear system of equations has a solution, then the least squares solution is the solution to the linear system of equations.
(3) Penalty factor and kernel width determination
Penalty factor in LS-SVM modelingAnd width of nucleusThe fitting accuracy and generalization performance of the LS-SVM are determined. In order to make the LS-SVM have better generalization performance, the two parameters also need to be optimized. The invention adopts a simpler training-checking method, which comprises the following steps:
step 1: selecting partial state pneumatic data as a verification sample setAnd the rest pneumatic data are used as a training sample set;
Step 2: for a given parameterAndusing training sample setsPerforming LS-SVM training to obtain model parametersAnd(connection weight bias);
step 3: using a set of check samplesPerforming a check to check for root mean square error of the sample setAs a check error;
step4 adjusting parametersAnd(the search range is determined according to the empirical value, and the global search is performed in the search range), in the embodiment, the penalty factorGiven range of 3.0-7.0, core widthThe given range of (1) is 0.05-0.17, and the selection can be carried out in the range of the interval, and Step2 and Step3 are repeatedly executed until the verification error reaches the minimum value (within an allowable range).
FIG. 2 shows a flow chart of missile nonlinear unsteady aerodynamic LS-SVM modeling.
The invention is further explained by taking a nonlinear unsteady aerodynamic LS-SVM model established by using CFD (computational fluid dynamics) calculation data of certain missile layout as a specific example.
(1) Data preparation
The computational state of aerodynamic force CFD of a certain missile layout is listed in Table 1, and the computational data comprises: static aerodynamic force and moment coefficients and large amplitude pitch oscillation aerodynamic force and moment coefficient time histories.
TABLE 1 certain missile layout aerodynamic force CFD calculation state
The provided pneumatic data are processed as follows in sequence:
a. uniformly transforming the reference points of the aerodynamic moment coefficients to the center of mass of the missile;
c. calculating dimensionless timeNon-dimensional angle of attack rateAnd dimensionless pitch angle rate。
After the processing, one period of data is intercepted, and an input data file for pneumatic modeling is generated. The static and dynamic aerodynamic properties are shown in figures 3-14. As can be seen, the longitudinal aerodynamic force and moment coefficientsThe method has the advantages that the nonlinear and unsteady characteristics are obvious, and the regularity of the hysteresis loop along with the change of parameters such as an attack angle, frequency and the like is good.
(2) Input/output variable selection
In the modeling of longitudinal aerodynamic force LS-SVM, the input variable is taken as、、、To reflect the effect of the course of the angle of attack and the instantaneous pitch angle rate on the aerodynamics, wherein= 1.35; output variables are measured as dynamic aerodynamic incrementsWherein。
All input variables are regularized to the interval [ -1,1] with their maximum and minimum values:
in the formula:(ii) a Superscript "(n)" indicates regularization; the subscripts "max" and "min" represent the maximum and minimum values, respectively, of the corresponding quantities in all sample points.
(3) Penalty factor and kernel width determination
Determining the optimal penalty factor through training-checking by using the pneumatic data of the following states as the checking data and the pneumatic data of the other states as the training dataAnd width of nucleus:
Table 2 lists the LS-SVM training-verification results and errors, including the root mean square error RMSE and the relative root mean square error RMSERMSE (%) is defined by formula (18) and formula (19), respectively. The verification states are shown in FIGS. 15-18, 19-22, and 23-26, respectively、、Comparison of model prediction results with CFD data. As can be seen from the table and the figure, for the check state,andthe model prediction result is in good accordance with CFD data, and the LS-SVM model has good generalization performance;the model prediction results slightly deviate from the CFD data, mainly due to pitching oscillationThe CFD data of (1) has a large hysteresis loop, but the hysteresis loop size does not vary significantly with the oscillation frequency (see fig. 3-6), in other words, from static to low frequency dynamic motion,there is a "jumping" phenomenon, and the model has some difficulty describing this phenomenon.
TABLE 2 LS-SVM training-verification results and errors
(4) Aerodynamic modeling
All pneumatic data are used as modeling samples and determinedAndperforming LS-SVM training to obtain weightAnd biasb。
Table 3 lists the LS-SVM modeling error, and FIGS. 27-30, 31-34, and 35-38 show the results respectively、、Comparison of model prediction results with CFD data. As can be seen from the table and the figures,andthe model prediction result is well consistent with CFD data, and the modeling error is small;the model prediction result is slightly worse in conformity with the CFD data, and the modeling error is slightly larger because of the CFD dataThe hysteresis loop varying little with the oscillation frequency, and the model predicts the resultThe hysteresis loop changes obviously along with the oscillation frequency. In a general view, the established LS-SVM model can better describe the nonlinear and unsteady characteristics of the aerodynamic characteristics of the missile changing along with the attack angle.
TABLE 3 LS-SVM modeling error
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that suitable changes and modifications of the above embodiments are within the scope of the claimed invention as long as they are within the spirit and scope of the present invention.
Claims (9)
1. The LS-SVM modeling method for the nonlinear unsteady aerodynamic characteristics of the missile is characterized by comprising the following steps of:
s1: preparing data: a dynamic data table between static aerodynamic force/aerodynamic moment coefficients of the missile, large-amplitude pitching oscillation aerodynamic force/moment coefficients and time histories is obtained by wind tunnel tests or CFD calculation, and an input data file of pneumatic modeling is obtained after data processing; decomposing aerodynamic force into the sum of aerodynamic force increment generated by static aerodynamic force and dynamic motion by adopting a superposition principle to establish an LS-SVM model, and dividing an input data file of aerodynamic modeling into a training sample set, a checking sample set and a modeling sample set;
s2: model training: taking a training sample set as a model input value, and giving an initial penalty factorAnd width of nucleusObtaining connection weight value by singular value decomposition methodAnd biasb;
S3: checking: taking a check sample set as an input value, checking the output error of the established LS-SVM model, and using a penalty factor corresponding to the current minimum output errorAnd width of nucleusIf the value is the optimal value, if the global search is completed, the step S5 is executed, otherwise, the step S4 is executed;
s4: adjusting: adjusting penalty factorsAnd width of nucleusRepeatedly executing the steps S2 and S3;
s5: aerodynamic modeling: taking a modeling sample set as an input value of the LS-SVM model, and determining a penalty factorAnd width of nucleusTraining LS-SVM model, and obtaining final connection weight value by singular value decomposition methodAnd biasbAnd predicting the output value of the modeling sample set.
2. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 1, characterized in that: in step S1, the specific method of data processing is:
s1.1: uniformly transforming the reference points of the aerodynamic moment coefficients to the center of mass of the missile;
s1.2: calculating the angle of attack at each moment in the dynamic data tableAngular rate of attackAnd pitch rate;
S1.3: calculating dimensionless timeNon-dimensional angle of attack rateAnd dimensionless pitch angle rate;
S1.4: and after the processing of the steps S1.1 to S1.3, intercepting one period of data to generate an input data file for pneumatic modeling.
3. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 2, characterized in that: after all input variables in the input data file of the pneumatic modeling are regularized to an interval [ -1,1] by using the maximum value and the minimum value of the input variables, a training sample set, a check sample set and a modeling sample set are generated.
4. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 1, characterized in that: in step S1, the specific method for dividing the input data file for pneumatic modeling into the training sample set, the verification sample set, and the modeling sample set is as follows: and selecting the pneumatic data of part of states as a verification sample set, taking the rest pneumatic data as a training sample set, and taking the modeling sample set as the sum of the training sample set and the verification sample set.
5. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 1, characterized in that: singular value decomposition method for obtaining connection weightAnd biasbThe specific method comprises the following steps: respectively constructing matrixes by calculating kernel functions of input samples and known output samples according to the selected sample setAAndbconnection weight valueAnd biasbIs a linear system of equations:and (3) solving the least square solution of the linear equation system by adopting a singular value decomposition method.
6. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 1, characterized in that: the input variables of the training sample set, the checking sample set and the modeling sample set are attack angle at the current moment and attack angles at the previous n momentsAnd corresponding angle of attack rateAnd pitch rate(ii) a And the output variables of the training sample set, the checking sample set and the modeling sample set are dynamic aerodynamic force increment.
7. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 6, characterized in that: the dimensionless time interval between n time angles of attack is chosen to be 1.35.
8. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 7, characterized in that: dynamic aerodynamic force incrementWhereinCFor the pneumatic force and moment coefficients,,in order to be a static aerodynamic coefficient,in order to be the axial force coefficient,as a function of the normal force coefficient,is the pitch moment coefficient.
9. The missile nonlinear unsteady aerodynamic characteristic LS-SVM modeling method according to claim 1, characterized in that: in step S3, the output errors are the root mean square error RMSE and the relative root mean square error RMSE (%).
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