A feedforward control method for airfoil gust mitigation based on circulation control technology

Abstract

The present invention relates to the field of aircraft control technology, and in particular to an airfoil gust mitigation feedforward control method based on circulation control technology, comprising: modifying the trailing edge shape of a NACA0012 airfoil, and arranging jet holes at the trailing edge to form a circulation controlled airfoil; performing a fluid simulation experiment on the circulation controlled airfoil based on the gust speed, and constructing a model in which the airfoil lift coefficient is disturbed by the gust speed; performing a fluid simulation experiment on the circulation controlled airfoil based on the jet momentum coefficient, and constructing a model in which the airfoil lift coefficient is controlled by the jet momentum coefficient; based on the above model, obtaining a gust mitigation feedforward control model in which the input is the vertical gust speed and the output is the jet momentum coefficient; using the gust mitigation feedforward control model to control the jet at the trailing edge, and completing the gust mitigation control of the circulation controlled airfoil; the present invention can improve the ability of an aircraft to resist a gust disturbance environment.

Description

Technical Field

[0001] The present invention relates to the field of aircraft control technology, and in particular to an airfoil gust mitigation feedforward control method based on circulation control technology. Background Art

[0002] Jet control technology uses jet holes placed on the wing to modify flow characteristics, thereby controlling the flow by delaying / accelerating transitions, suppressing / enhancing turbulence, and preventing / promoting separation, thereby actively regulating the aircraft's lift and drag. Circulation control technology is one of the control methods of jet control technology. It involves blowing a jet tangentially onto a deflected flap or curved surface, guiding the airflow through a large deflection angle. The balance between centripetal force and pressure differential maintains the attached flow, creating a wall effect, thereby regulating the wing's circulation and changing lift.

[0003] Gusts are a typical atmospheric disturbance phenomenon, manifested as wind speeds that change dramatically in a short period of time. Gusts can generate additional unstable aerodynamic forces and moments, affecting handling quality and adversely affecting the comfort and safety of the aircraft. Under the action of sudden vertical gusts, the aircraft will experience instantaneous large accelerations, affecting handling quality and causing the common "bumping" phenomenon during flight. For passengers on civil aircraft, vertical gusts of moderate intensity or above, exceeding 6m / s, will significantly affect the riding experience, while gusts of more than 15m / s can even cause damage to the aircraft structure, endangering flight safety. In addition, gusts will cause additional aerodynamic loads on the wings, which will have a significant impact on the increase in the aircraft's structural weight, and gust loads will also accelerate wing structural fatigue. Therefore, in recent years, gust load mitigation technology has become a focus of research at home and abroad. Summary of the Invention

[0004] In view of the above problems, the present invention provides an airfoil gust mitigation feedforward control method based on circulation control technology, which solves the technical problem in the prior art that aircraft have poor resistance to gust disturbances.

[0005] The present invention provides an airfoil gust mitigation feedforward control method based on circulation control technology, comprising the following steps:

[0006] Step S1, modifying the trailing edge shape of the NACA0012 airfoil and arranging jet holes on the trailing edge to form a circulation control airfoil;

[0007] Step S2: determining a gust speed parameter of a circulation-controlled airfoil under gust disturbance, performing a fluid simulation experiment on the circulation-controlled airfoil based on the gust speed, obtaining first experimental values ​​of the gust speed parameter and the wing lift coefficient; and constructing a model of the airfoil lift coefficient under gust speed disturbance based on the first experimental values;

[0008] Step S3: determining the jet momentum coefficient of the circulation-controlled airfoil during flight, performing a fluid simulation experiment on the circulation-controlled airfoil based on the jet momentum coefficient to obtain second experimental values ​​of the jet momentum coefficient and the wing lift coefficient; and constructing a model in which the airfoil lift coefficient is controlled by the jet momentum coefficient based on the second experimental values;

[0009] Step S4: Based on the model in which the lift coefficient of the airfoil is disturbed by the vertical gust velocity and the model in which the lift coefficient of the airfoil is controlled by the jet momentum coefficient, a gust mitigation feedforward control model is obtained, whose input is the vertical gust velocity and whose output is the jet momentum coefficient;

[0010] Step S5: Using the gust mitigation feedforward control model to control the jet at the trailing edge, thereby completing the gust mitigation control of the circulation control airfoil.

[0011] Preferably, the step S1 specifically includes: for the NACA0012 airfoil, removing the original pointed trailing edge and replacing it with a semicircular trailing edge, and respectively providing jet grooves at the upper and lower positions of the semicircular trailing edge.

[0012] Preferably, the step S2 specifically includes:

[0013] Step S2-1: using the vertical gust velocity that satisfies the 3211 multi-step excitation signal as the gust velocity parameter, performing a simulation experiment using a computational fluid dynamics numerical calculation method to obtain data on the vertical gust velocity and lift coefficient changing over time;

[0014] Step S2-2: Based on the data of vertical gust velocity and lift coefficient changing with time, a model of the lift coefficient of the circulation-controlled airfoil being disturbed by vertical gust velocity is established by least square method and ARMA model identification method.

[0015] Preferably, in step S2-1, the 3211 multi-step excitation signal includes four signal segments arranged in chronological order with a duration ratio of 3:2:1:1, and the speed amplitude ratio of each signal segment is 1:-1:1:-1.

[0016] Preferably, the step S2-2 specifically includes:

[0017] The vertical gust speed u obtained g and the corresponding lift coefficient C of the circulation-controlled airfoil l As external variables and system variables respectively, the weight coefficient of the ARMA model of lift coefficient disturbed by gusts is solved by the least square method;

[0018] The ARMA model expression of the airfoil lift coefficient subject to vertical gust velocity disturbance is:

[0019]

[0020] Among them C l (k) represents the lift coefficient C l The value at time k, i, j is the weight coefficient index, is the weight coefficient of the gust disturbance ARMA model determined by the least squares method, u g (kj) represents the value of vertical gust speed at time kj, and are the orders of the lift coefficient term and the vertical gust velocity term in the gust disturbance ARMA model, respectively, which can be determined by obtaining the minimum root mean square error between the lift coefficient predicted by the model and the lift coefficient obtained by simulation.

[0021] Preferably, the step S3 specifically includes:

[0022] Step S3-1, introducing a jet whose blowing momentum coefficient varies with time and satisfies random white noise at the jet hole, performing a simulation experiment using a computational fluid dynamics numerical calculation method, and obtaining data on the lift coefficient and jet momentum coefficient of the circulation-controlled airfoil varying with time;

[0023] Step S3-2: Based on the data of the lift coefficient and the jet momentum coefficient of the circulation-controlled airfoil changing over time, a model for the influence of the lift coefficient of the circulation-controlled airfoil on the jet momentum coefficient is established by using the least squares method and the ARMA model identification method;

[0024] Step S3-3: Based on the model in which the lift coefficient of the circulation-controlled airfoil is controlled by the jet momentum coefficient, solve the feedback controller parameters to obtain the optimal feedback-controlled jet momentum coefficient of the lift coefficient of the circulation-controlled airfoil.

[0025] Preferably, the step S3-2 specifically includes:

[0026] The jet momentum coefficient C is obtained μ and the corresponding lift coefficient C of the circulation-controlled airfoil l As external variables and system variables respectively, the ARMA model of lift coefficient affected by jet momentum coefficient is solved by least square method;

[0027] The ARMA model expression of the lift coefficient affected by the jet momentum coefficient is:

[0028]

[0029] Among them, C μ (kj) represents the value of the jet momentum coefficient at time kj, A i , B j The weight coefficient of the ARMA model for the jet momentum coefficient determined by the least squares method.a With n b are the orders of the lift coefficient term and the jet momentum coefficient term in the jet control ARMA model, respectively, which can be determined by obtaining the minimum root mean square error between the lift coefficient predicted by the model and the lift coefficient obtained by simulation.

[0030] Preferably, the step S3-3 specifically includes:

[0031] Rewrite the lift coefficient circulation control model into a discrete state space form:

[0032]

[0033] in:

[0034]

[0035] B=[B0 0 0 … 0 1 0 0 … 0] T

[0036]

[0037] D=B0

[0038] The optimal control index function is defined as:

[0039]

[0040] Where J is the optimal control index, x is the state vector, Q is the semi-positive definite weight matrix, R is the weight coefficient, R>0, and t is the time;

[0041] The Riccati algebraic equation satisfied by the optimal state feedback gain is:

[0042] PA+A T P-PBR -1 B T P+Q=0

[0043] Among them, P is an auxiliary constant matrix to be solved, A T , B T are the transpose of A and B, R -1 is the reciprocal of R;

[0044] After solving P, the optimal feedback matrix K is obtained as:

[0045] K=R -1 B T P

[0046] Finally, the optimal feedback control jet momentum coefficient C is obtained μ for:

[0047] C μ=-Kx.

[0048] Preferably, the step S4 specifically includes:

[0049] Using the model of lift coefficient being disturbed by vertical gust velocity, the vertical gust velocity u of the incoming flow is input g , and the lift coefficient C caused by gusts is obtained l ;

[0050] C l As the lift coefficient C at time k-1 l (k-1) is substituted into the state vector x(k), and from the optimal control matrix K, the jet momentum coefficient of the optimal feedback control when the input is the vertical gust speed is obtained;

[0051] The final input is the vertical gust speed u g , the output is the jet momentum coefficient C μ , the controlled quantity is the lift coefficient C l Feedforward control model for gust mitigation of circulation controlled airfoil.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) This paper uses computational fluid dynamics numerical calculation methods and ARMA model identification methods to establish a model for the lift coefficient of a circulation-controlled airfoil affected by vertical gust velocity disturbances. This enables the system to accurately predict lift changes caused by gusts.

[0054] (2) By introducing the jet momentum coefficient and establishing a model of its influence on the lift coefficient, the present invention can effectively regulate the jet momentum to cope with the influence of vertical gusts.

[0055] (3) The present invention generates aerodynamic forces of equal magnitude and opposite direction through circulation control technology, thereby reducing the wing gust load, improving the flight performance of the aircraft in a gust disturbance environment, and effectively mitigating the impact of gusts. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0057] Figure 1 This is a flow chart of the airfoil gust mitigation feedforward control method based on circulation control technology provided by the present invention.

[0058] Figure 2 Schematic diagram of the circulation-controlled airfoil provided by the present invention.

[0059] Figure 3 Schematic diagram of vertical gust velocity variation over time for 3211 multi-step excitation gusts used for identification provided by the present invention.

[0060] Figure 4 Schematic diagram of the prediction effect of the airfoil lift coefficient gust disturbance model identified by the present invention on the lift coefficient change caused by "1-cos" type gusts.

[0061] Figure 5 This is a schematic diagram of the gust mitigation control effect provided by the present invention. DETAILED DESCRIPTION

[0062] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0063] In order to illustrate the effectiveness of the method proposed by the present invention, the above technical solution of the present invention is described in detail below through a specific embodiment. Figure 1 As shown, a feedforward control method for airfoil gust mitigation based on circulation control technology is disclosed. The specific implementation steps are as follows:

[0064] Step S1, modifying the trailing edge shape of the NACA0012 airfoil and arranging jet holes on the trailing edge to form a circulation control airfoil;

[0065] In this step, the trailing edge shape of the NACA0012 airfoil is modified. The specific modification method is as follows: the original sharp trailing edge is removed at 94.3% of the original airfoil chord length and replaced with a semicircular trailing edge with a radius r of 0.714% times the chord length, thus constructing the Coanda trailing edge commonly used in jet airfoils. At the same time, jet grooves are set on the upper and lower parts of the trailing edge, and the ratio of the height of the jet groove to the radius of the semicircular trailing edge is 1:20. The modified circulation control airfoil is as follows Figure 2 shown.

[0066] Step S2: determining a gust speed parameter of a circulation-controlled airfoil subjected to gust disturbance, performing a fluid simulation experiment on the circulation-controlled airfoil based on the gust speed, and obtaining first experimental values ​​of the gust speed parameter and the wing lift coefficient; and constructing a model of the airfoil lift coefficient subjected to vertical gust speed disturbance based on the first experimental value.

[0067] A fluid simulation experiment was carried out on the circulation-controlled airfoil using a computational fluid dynamics numerical calculation method. Gust disturbances were introduced using the moving boundary method. The vertical gust velocity was used as the gust velocity parameter. The data on the time-varying lift coefficient of the circulation-controlled airfoil was calculated when the time-varying characteristics of the vertical gust velocity satisfied the 3211 multi-step excitation signal.

[0068] The schematic diagram of the vertical gust velocity disturbance signal is as follows: Figure 3 As shown, the 3211 multi-step excitation signal includes four signal segments arranged in time sequence with a duration ratio of 3:2:1:1, and the speed amplitude ratio of each signal segment is 1:-1:1:-1.

[0069] The vertical gust speed u obtained g and the corresponding circulation-controlled airfoil lift coefficient C l The weighted coefficients of the time series variables are solved by the least squares method as external variables and system variables respectively, and the ARMA model identification method is used to establish a model of the lift coefficient of the circulation-controlled airfoil subjected to vertical gust velocity disturbance. The ARMA model expression of the airfoil lift coefficient subjected to gust disturbance is:

[0070]

[0071] Among them C l (k) represents the lift coefficient C l The value at time k, i, j is the weight coefficient index, is the weight coefficient of the gust disturbance ARMA model determined by the least squares method, u g (kj) represents the value of vertical gust speed at time kj, and are the orders of the lift coefficient term and the vertical gust velocity term in the gust disturbance ARMA model, respectively, which can be determined by obtaining the minimum root mean square error between the lift coefficient predicted by the model and the lift coefficient obtained by simulation.

[0072] In order to verify the accuracy of the identified gust disturbance model in predicting the gust response of the airfoil, a "1-cos" gust load was applied to the airfoil, and the CFD simulation results were compared with the model prediction results, as shown in Figure 2. Figure 4 As shown in Figure 2, it can be seen that the model obtained through ARMA model identification can accurately predict the change of lift coefficient caused by gust disturbance.

[0073] Step S3: determining the jet momentum coefficient of the circulation-controlled airfoil during flight, performing a fluid simulation experiment on the circulation-controlled airfoil based on the jet momentum coefficient, and obtaining second experimental values ​​of the jet momentum coefficient and the wing lift coefficient; and constructing a model in which the airfoil lift coefficient is controlled by the jet momentum coefficient based on the second experimental values.

[0074] In this step, a fluid simulation experiment is conducted on the circulation-controlled airfoil using a computational fluid dynamics numerical calculation method. Using the velocity inlet boundary condition, a jet with a time-varying characteristic of the blowing momentum coefficient that satisfies random white noise is introduced at the jet hole. The data on the lift coefficient and the jet momentum coefficient of the circulation-controlled airfoil are calculated as they vary with time. The expression for the momentum coefficient of the jet is:

[0075]

[0076] in, is the mass flow rate at the jet outlet; V jet is the jet velocity; ρ ∞ is the far-field incoming current density; V ∞ is the far-field incoming flow velocity; S represents the reference area. For a two-dimensional airfoil, it is the chord length c of the airfoil.

[0077] The jet momentum coefficient C is obtained μ and the corresponding circulation-controlled airfoil lift coefficient C l The weighted coefficients of the time series variables are solved by the least square method as external variables and system variables respectively. The ARMA model identification method is used to establish a model in which the lift coefficient of the circulation-controlled airfoil is controlled by the jet momentum coefficient.

[0078] The ARMA model expression of the airfoil lift coefficient affected by the jet momentum coefficient is:

[0079]

[0080] Among them, C μ (kj) represents the value of the jet momentum coefficient at time kj, A i , B j The weight coefficient of the ARMA model for the jet momentum coefficient determined by the least squares method. a With n b are the orders of the lift coefficient term and the jet momentum coefficient term in the jet control ARMA model, respectively, which can be determined by obtaining the minimum root mean square error between the lift coefficient predicted by the model and the lift coefficient obtained by simulation.

[0081] In the above formula, C l (k) and C μ (k) is rewritten as a state vector:

[0082] x(k)=[C l (k-1)…C l (kn a )C μ (k-1)…C μ (kn b +1)]

[0083] Then, based on the model in which the lift coefficient of the circulation controlled airfoil is controlled by the jet momentum coefficient, the feedback controller parameters are solved to obtain the optimal feedback controlled jet momentum coefficient of the lift coefficient of the circulation controlled airfoil.

[0084] The airfoil lift coefficient circulation control model obtained by step S3 can be rewritten into the form of discrete state space:

[0085]

[0086] in:

[0087]

[0088] B=[B0 0 0 … 0 1 0 0 … 0] T

[0089]

[0090] D=B0

[0091] The optimal control index function is defined as:

[0092]

[0093] Where J is the optimal control index, x is the state vector, Q is the semi-positive definite weight matrix, R is the weight coefficient, R>0, and t is time.

[0094] The Riccati algebraic equation satisfied by the optimal state feedback gain is:

[0095] PA+A T P-PBR -1 B T P+Q=0

[0096] Among them, P is an auxiliary constant matrix to be solved, A T , B T are the transpose of A and B, R -1 It is the reciprocal of R.

[0097] After solving P, the optimal feedback matrix K is obtained as:

[0098] K=R -1 B T P

[0099] Finally, the optimal feedback control jet momentum coefficient is obtained as:

[0100] C μ =-Kx

[0101] Step S4: Based on the model in which the lift coefficient of the airfoil is disturbed by the vertical gust velocity and the model in which the lift coefficient of the airfoil is controlled by the jet momentum coefficient, a gust mitigation feedforward control model is obtained, whose input is the vertical gust velocity and whose output is the jet momentum coefficient;

[0102] In this step, the present invention uses the model of the circulation control airfoil lift coefficient being disturbed by the vertical gust speed, by inputting the vertical gust speed u of the incoming flow g , we can get the lift coefficient change C caused by gusts l . l As the lift coefficient C at time l-1 l (l-1) is substituted into the state vector x(k), and the optimal control matrix K can be used to derive the jet momentum coefficient of the optimal feedback control when the input is the vertical gust speed, thereby achieving the vertical gust speed u g , the output is the jet momentum coefficient C μ , the controlled quantity is the airfoil lift coefficient C l Gust mitigation feedforward control of a circulation controlled airfoil.

[0103] Step S5: Using the gust mitigation feedforward control model to control the jet at the trailing edge, thereby completing the gust mitigation control of the circulation control airfoil.

[0104] Applying this method, load reduction is implemented in MATLAB simulation software for gust disturbances with vertical wind speed varying randomly with time. The effect is as follows: Figure 5 As shown in the figure, it can be seen that after the control is applied, the amplitude of the lift coefficient change caused by the gust is significantly reduced, which greatly improves the safety of the aircraft flying in a gust disturbance environment.

[0105] Although the specific embodiments of the present invention depict various actions or steps in a specific order, this should be understood as requiring such actions or steps to be performed in the specific order shown or in a sequential order, or requiring that all illustrated actions or steps should be performed to obtain the desired results. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although a number of specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of this disclosure. Certain features described in the context of separate embodiments can also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single implementation can also be implemented in multiple implementations individually or in any suitable sub-combination. The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered within the scope of protection of the present invention.

[0106] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

Claims

1. A feedforward control method for airfoil gust mitigation based on circulation control technology, characterized in that: The following steps are involved: Step S1, modifying the trailing edge shape of the NACA0012 airfoil and arranging jet holes on the trailing edge to form a circulation control airfoil; The step S1 specifically includes: For the NACA0012 airfoil, the original pointed trailing edge is removed and replaced with a semicircular trailing edge, and jet slots are respectively provided at the upper and lower positions of the semicircular trailing edge; Step S2: determining a gust speed parameter of a circulation-controlled airfoil under gust disturbance, performing a fluid simulation experiment on the circulation-controlled airfoil based on the gust speed, obtaining first experimental values ​​of the gust speed parameter and the wing lift coefficient; and constructing a model of the airfoil lift coefficient under gust speed disturbance based on the first experimental values; The step S2 specifically includes: Step S2-1: using the vertical gust velocity that satisfies the 3211 multi-step excitation signal as the gust velocity parameter, performing a simulation experiment using a computational fluid dynamics numerical calculation method to obtain data on the vertical gust velocity and lift coefficient changing over time; Step S2-2: Based on the data of vertical gust velocity and lift coefficient changing with time, a model of the lift coefficient of the circulation-controlled airfoil being disturbed by vertical gust velocity is established by using the least squares method and the ARMA model identification method; Step S3: determining the jet momentum coefficient of the circulation-controlled airfoil during flight, performing a fluid simulation experiment on the circulation-controlled airfoil based on the jet momentum coefficient to obtain second experimental values ​​of the jet momentum coefficient and the wing lift coefficient; and constructing a model in which the airfoil lift coefficient is controlled by the jet momentum coefficient based on the second experimental values; Step S4: Based on the model in which the lift coefficient of the airfoil is disturbed by the vertical gust velocity and the model in which the lift coefficient of the airfoil is controlled by the jet momentum coefficient, a gust mitigation feedforward control model is obtained, whose input is the vertical gust velocity and whose output is the jet momentum coefficient; Step S5: Using the gust mitigation feedforward control model to control the jet at the trailing edge, thereby completing the gust mitigation control of the circulation control airfoil.

2. The airfoil gust mitigation feedforward control method based on circulation control technology according to claim 1 is characterized in that: In step S2-1, the 3211 multi-step excitation signal includes four signal segments arranged in time sequence with a duration ratio of 3:2:1:1, and the speed amplitude ratio of each signal segment is 1:-1:1:-1.

3. The airfoil gust mitigation feedforward control method based on circulation control technology according to claim 2 is characterized in that: The step S2-2 specifically includes: The vertical gust speed obtained and the corresponding lift coefficient of the circulation-controlled airfoil The weight coefficients of the ARMA model of lift coefficient affected by gust disturbance are solved by the least square method using them as external variables and system variables respectively.

4. The airfoil gust mitigation feedforward control method based on circulation control technology according to claim 3 is characterized in that: The step S3 specifically includes: Step S3-1, introducing a jet whose blowing momentum coefficient varies with time and satisfies random white noise at the jet hole, performing a simulation experiment using a computational fluid dynamics numerical calculation method, and obtaining data on the lift coefficient and jet momentum coefficient of the circulation-controlled airfoil varying with time; Step S3-2: Based on the data of the lift coefficient and the jet momentum coefficient of the circulation-controlled airfoil changing over time, a model for the influence of the lift coefficient of the circulation-controlled airfoil on the jet momentum coefficient is established by using the least squares method and the ARMA model identification method; Step S3-3: Based on the model in which the lift coefficient of the circulation-controlled airfoil is controlled by the jet momentum coefficient, solve the feedback controller parameters to obtain the optimal feedback-controlled jet momentum coefficient of the lift coefficient of the circulation-controlled airfoil.

5. The airfoil gust mitigation feedforward control method based on circulation control technology according to claim 4 is characterized in that: The step S3-2 specifically includes: The jet momentum coefficient obtained and the corresponding lift coefficient of the circulation-controlled airfoil The ARMA model in which the lift coefficient is affected by the jet momentum coefficient is solved by the least squares method using the two variables as external variables and system variables respectively.

6. The airfoil gust mitigation feedforward control method based on circulation control technology according to claim 5, characterized in that: The step S4 specifically includes: Using the model in which the lift coefficient is disturbed by the vertical gust velocity, the vertical gust velocity of the incoming flow is input , and the lift coefficient due to gusts is obtained ; Will As Lift coefficient at time Substitute the state vector , by the optimal control matrix , the jet momentum coefficient of the optimal feedback control is obtained when the input is the vertical gust speed; The final input is the vertical gust speed , the output is the jet momentum coefficient , the controlled quantity is the lift coefficient Feedforward control model for gust mitigation of circulation controlled airfoil.

Images