A method for enhancing stability of an aircraft based on variable aerodynamic surfaces

Abstract

The present application belongs to the technical field of flight dynamics, and particularly relates to a kind of aircraft stability enhancement method based on variable aerodynamic surface.The present application includes: S1, obtaining the six-degree-of-freedom motion equation of the aircraft;S2, bringing the helicopter flight state parameters and control parameters into the six-degree-of-freedom motion equation to obtain the motion equation of the current flight state;S3, performing small perturbation linearization processing on the motion equation of the current flight state to obtain the aerodynamic derivative matrix A, performing characteristic analysis on A to obtain the stability characteristic value;S4, judging the stability characteristic value, if the stability characteristic value falls in level 2 or level 3, stability correction is needed;S5, determining the control quantity that needs to be adjusted, and adjusting the aerodynamic surface parameters by the servo;when the stability characteristic value falls in level 2, the control quantity that needs to be adjusted is determined as the deflection angle rate, and when the stability characteristic value falls in level 3, the control quantity that needs to be adjusted is determined as the deflection angle rate, the span length and the chord length.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flight mechanics, and particularly relates to a method for enhancing stability of an aircraft based on variable aerodynamic surfaces. BACKGROUND

[0002] The stability of an aircraft is a very important design requirement. With the increase of flight speed, the stability of the aircraft gradually deteriorates, frequent correction of the control is required, the control load of the pilot is increased, and the driving feeling is deteriorated. Different components of a conventional aircraft play different stability roles, and the main component for controlling the stability is a vertical tail. In the conventional design, the design and adjustment are also based on these components. However, these adjustment designs are all designed in a stable state, and are based on fixed aerodynamic surface characteristic parameters. The conventional stability design process is performed through a wind tunnel test. Through modeling of the aircraft and full-aircraft blowing calculation, an aerodynamic surface parameter (area and installation angle) that meets the stability requirement of the full speed stage as much as possible is selected. In the later period, the full-aircraft stability requirement is met as much as possible through test flight and flight control adjustment. However, this method cannot maximize the efficiency of the aerodynamic surface, and cannot achieve optimal stability in the full speed stage. SUMMARY

[0003] The method for enhancing the stability of the aircraft based on the variable aerodynamic surface learns from the previous research results, and develops a stability enhancement method based on multiple variable parameters of the aerodynamic surface on this basis. The method can enhance the stability in the longitudinal and lateral directions, and simultaneously performs optimization analysis and judgment based on multiple variable parameters of the aerodynamic surface, so that the stability enhancement efficiency and effect are greatly improved.

[0004] To achieve the above object, the technical scheme is adopted to realize the method.

[0005] A method for enhancing the stability of an aircraft based on variable aerodynamic surfaces, the method comprising:

[0006] S1, obtaining a six-degree-of-freedom motion equation of the aircraft;

[0007] S2, bringing the helicopter flight state parameters and control parameters into the six-degree-of-freedom motion equation to obtain a motion equation of the current flight state;

[0008] S3, performing small perturbation linearization processing on the motion equation of the current flight state to obtain an aerodynamic derivative matrix A, and performing characteristic analysis on A to obtain a stability characteristic value;

[0009] S4, judging the stability characteristic value. If the stability characteristic value falls in level 2 or level 3, stability correction is required;

[0010] S5, determining the control amount that needs to be adjusted, adjusting the aerodynamic surface parameters by the rudder; when the stability eigenvalue falls in level 2, determining the control amount that needs to be adjusted as the deflection angle rate, when the stability eigenvalue falls in level 3, determining the control amount that needs to be adjusted as the deflection angle rate, the span, and the chord.

[0011] Further, in S1, the six-degree-of-freedom motion equation contains the rotor, the tail rotor, the fuselage, the horizontal tail, the elevator, the vertical tail, the rudder, the flap, the aileron, the winglet, and the change parameters thereof, and the change parameters are at least the deflection angle rate, the span, and the chord.

[0012] Further, in S2, the motion equation of the current flight state is (DE-A)X=B(U+T);

[0013] wherein X is the state parameter of the helicopter, containing the pitch angle, the pitch angle rate, the roll angle, and the roll angle rate; U is the control parameter of the helicopter, being four control amounts: the total distance control amount, the longitudinal control amount, the lateral control amount, and the heading control amount; T is the control amount, containing the deflection angle rate, the span, and the chord of the horizontal tail containing the elevator, the vertical tail containing the rudder, the flap, the aileron, and the winglet; B is the control coefficient matrix, D is the parameter matrix of the helicopter, and E is the unit matrix.

[0014] Further, S5 includes:

[0015] S51, obtaining the flight state parameter of the helicopter, if the stability eigenvalue falls in the range of level 3, adjusting the deflection angle rate, the span, and the chord in the control amount at the same time, the new control amount is T+△T, and the motion equation of the adjusted flight state is obtained;

[0016] S52, judging the stability eigenvalue of the motion equation of the adjusted flight state, evaluating whether the attitude change value of the helicopter is less than or equal to the preset angle, if greater than the preset angle, setting the new control amount as T+△T / 2, obtaining the motion equation of the adjusted flight state;

[0017] S53, returning to S52 until the attitude change value of the helicopter is less than or equal to the preset angle;

[0018] S54, secondly evaluating whether the real part of the stability eigenvalue is unchanged or reduced;

[0019] if the real part of the stability eigenvalue is unchanged or reduced, adjusting the value △T as the aerodynamic surface adjustment coefficient, and inputting the rudder to control;

[0020] if the real part of the stability eigenvalue is increased, setting the new control amount as T-△T, obtaining the motion equation of the adjusted flight state, and returning to S52.

[0021] Further, S5 further includes:

[0022] If the stability eigenvalue falls in the range of level 2, the deflection angle rate is adjusted preferentially, and the new control amount is T+△T;

[0023] S52 to S54 are executed.

[0024] Further, in S51, the single adjustment value of the deflection angle rate is not more than 1 degree per second, and the single adjustment value of the chord length and the span length is not more than 0.1 m.

[0025] Further, in S52, the preset angle is 0.5 degrees.

[0026] Further, in S5,

[0027] When the control amount of the longitudinal aerodynamic surface is adjusted, the adjustment is performed in the following priority order: the tail plane, the elevator, and the V-shaped tail.

[0028] When the control amount of the lateral aerodynamic surface is adjusted, the adjustment is performed in the following priority order: the vertical tail, the rudder, the V-shaped tail, the flap, the aileron, and the winglet.

[0029] The aircraft stability enhancement method of the present application is realized based on variable aerodynamic surfaces, that is, the characteristics of the aerodynamic surfaces are adjusted by the control system to realize the enhancement of the aircraft stability. The flight control system adjusts the deflection angle rate, the chord length, and the span length of the aerodynamic surfaces (the tail plane including the elevator, the vertical tail including the rudder, the flap, the aileron, and the winglet) by controlling the rudder and other components to enhance the stability of the aircraft. The related parameters of the longitudinal aerodynamic surfaces (the tail plane including the elevator, the flap, and the aileron) are adjusted to improve the longitudinal force and moment, so that the attitude, the longitudinal stability, and the maneuverability of the whole machine can be adjusted; the related parameters of the lateral aerodynamic surfaces (the vertical tail including the rudder and the winglet) are adjusted to improve the lateral force and moment, so that the lateral stability and maneuverability can be improved. The main basis for determining the adjustment amount of the above components is the real-time solution of the stability of the aircraft, and the optimal deflection angle rate, area, size, or combination thereof is selected. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A working flow diagram of the aircraft stability enhancement method based on variable aerodynamic surfaces provided for the embodiment of the present application is shown.

[0031] Figure 2 A stability eigenvalue judgment basis diagram provided for the embodiment of the present application is shown.

[0032] Figure 3 A diagram showing that the flight control system acquires the main motion parameters of the aircraft provided for the embodiment of the present application is shown.

[0033] Figure 4The stability characteristic value change schematic diagram before and after the application is provided for the embodiments of the application. DETAILED DESCRIPTION

[0034] The technical solutions of the application are described in detail below with reference to the drawings.

[0035] The embodiments of the application provide a method for enhancing the stability of an aircraft based on a variable aerodynamic surface, and the method comprises the following steps:

[0036] S1, acquiring a six-degree-of-freedom motion equation of the aircraft;

[0037] S2, bringing the helicopter flight state parameters and control parameters into the six-degree-of-freedom motion equation to obtain a motion equation of the current flight state;

[0038] S3, performing small perturbation linearization processing on the motion equation of the current flight state to obtain an aerodynamic derivative matrix A, and performing characteristic analysis on A to obtain a stability characteristic value;

[0039] S4, judging the stability characteristic value, and if the stability characteristic value falls within grade 2 or grade 3, stability correction is needed;

[0040] S5, determining the control amount that needs to be adjusted, and adjusting the aerodynamic surface parameters by a steering engine; when the stability characteristic value falls within grade 2, the control amount that needs to be adjusted is determined as a deflection angle rate, and when the stability characteristic value falls within grade 3, the control amount that needs to be adjusted is determined as the deflection angle rate, the span length and the chord length.

[0041] In S1, the six-degree-of-freedom motion equation comprises the rotor, the tail rotor, the fuselage, the horizontal tail, the elevator, the vertical tail, the rudder, the flap, the aileron, the winglet and their change parameters, and the change parameters are at least the deflection angle rate, the span length and the chord length.

[0042] In S2, the motion equation of the current flight state is (DE-A)X=B(U+T).

[0043] Wherein X is the state parameter of the helicopter, including the pitch angle, the pitch angle rate, the roll angle and the roll angle rate; U is the control parameter of the helicopter, which is four control amounts: the total distance control amount, the longitudinal control amount, the lateral control amount and the heading control amount; T is the control amount, including the deflection angle rate, the span length and the chord length of the horizontal tail including the elevator, the vertical tail including the rudder, the flap, the aileron and the winglet; B is the control coefficient matrix, D is the parameter matrix of the helicopter, and E is the unit matrix.

[0044] S5 comprises:

[0045] S51, obtain the helicopter flight state parameter, if the stability eigenvalue falls in the range of level 3, simultaneously adjust the deflection angle rate, the span, the chord in the control quantity, the new control quantity is T+△T, obtain the motion equation of the adjusted flight state;

[0046] S52, judge the stability eigenvalue of the motion equation of the adjusted flight state, evaluate whether the attitude change value of the helicopter is less than or equal to the preset angle, if greater than the preset angle, set the new control quantity as T+△T / 2, obtain the motion equation of the adjusted flight state;

[0047] S53, return to S52 until the attitude change value of the helicopter is less than or equal to the preset angle;

[0048] S54, secondly evaluate whether the real part of the stability eigenvalue is unchanged or reduced;

[0049] If the real part of the stability eigenvalue is unchanged or reduced, the adjustment value△T is taken as the aerodynamic surface adjustment coefficient and input to the steering wheel for control;

[0050] If the real part of the stability eigenvalue is increased, set the new control quantity as T-△T, obtain the motion equation of the adjusted flight state, and return to S52.

[0051] S5 further comprises: if the stability eigenvalue falls in the range of level 2, preferentially adjust the deflection angle rate, and the new control quantity is T+△T;S52 to S54 are executed.

[0052] In S51, the single adjustment value of the deflection angle rate is not more than 1 degree per second, and the single adjustment value△T of the span and the chord is not more than 0.1 m.

[0053] In S52, the preset angle is 0.5 degrees.

[0054] In S5, when the control quantity adjustment is performed on the longitudinal aerodynamic surface, the adjustment is performed in the following priority order: the tail plane, the elevator, the V-shaped tail;When the control quantity adjustment is performed on the lateral aerodynamic surface, the adjustment is performed in the following priority order: the vertical tail, the rudder, the V-shaped tail, the flap, the aileron, and the winglet.

[0055] As shown in Figure 1 the detailed steps of the technical scheme embodiment of the application are as follows:

[0056] 1. The motion equation of the aircraft is a six-degree-of-freedom motion equation containing the rotor, the tail rotor, the fuselage, the tail plane, the elevator, the vertical tail, the rudder, the flap, the aileron, the winglet and their change parameters (deflection angle, span, installation angle), which contains the balance equation of force and moment, and the stability eigenvalue of the aircraft can be obtained by solving the linearized equation set.

[0057] 2. The flight control system acquires the helicopter flight state parameters and control parameters (including pitch angle, pitch angle rate, roll angle, roll angle rate, collective pitch control, longitudinal control, lateral control, heading control), and introduces the relevant parameters into the motion equation of the aircraft to form the motion equation of the current flight state in real time: (DE-A)X=B(U+T); wherein X is the state parameter of the helicopter, including pitch angle, pitch angle rate, roll angle, roll angle rate. U is the control parameter of the helicopter, which is four control quantities: collective pitch control, longitudinal control, lateral control, heading control. T is the control quantity, including the deflection angle rate of the tail with elevator, the tail with rudder, the flap, the aileron, and the winglet, the span, and the chord. B is the control coefficient matrix, D is the parameter matrix of the helicopter, and E is the unit matrix.

[0058] 3. The motion equation of the current flight state formed in real time is subjected to small perturbation linearization processing to obtain the aerodynamic derivative matrix A, and the stability characteristic values are obtained by performing characteristic analysis on A;

[0059] 4. The stability characteristic values are judged according to Figure 2 (the upper figure is the longitudinal and lateral, and the lower figure is the heading), if the stability characteristic values fall within the range of level 1, it is not within the scope of the method, and if the stability characteristic values fall within the range of level 2 or level 3, stability correction is required.

[0060] 5. The flight state parameters of the helicopter are acquired, if the stability characteristic values of the previous step fall within the range of level 3, the deflection angle rate, the span, and the chord in the control quantity are all adjusted, the new control quantity is T+△T, and the single adjustment value△T does not exceed 1 degree per second or 0.1 m, to obtain the adjusted flight state motion equation

[0061] 6. Repeat 3 and 4, first evaluate the state parameter (attitude) change value of the helicopter, which is less than or equal to 0.5 degrees; secondly, evaluate whether the real part of the stability characteristic value is unchanged or reduced, if it is satisfied, the adjustment value△T is taken as the aerodynamic surface adjustment coefficient, and the steering engine is controlled;

[0062] 7. If the real part of the stability characteristic value increases, set the new control quantity as T-△T, obtain the adjusted flight state motion equation, and repeat the judgment of 6.

[0063] 8. If the stability characteristic value obtained in 4 falls within the range of level 2, the deflection angle rate is adjusted first, the new control quantity is T+△T. The single adjustment value△T does not exceed 1 degree per second; repeat 6-7.

[0064] 9. The adjustment value△T obtained is implemented by each steering engine to adjust the aerodynamic surface parameters.

[0065] 8. For the new configuration of helicopter, there are multiple aerodynamic surfaces, and after comprehensive, there are dozens of adjustable parameters, and for different control axes, these aerodynamic surfaces can be divided into longitudinal and lateral categories. According to the priority of adjustment, the following is the order:

[0066] Longitudinal: tail, elevator, V-tail

[0067] Lateral: vertical tail, rudder, V-tail, flap, aileron, winglet

[0068] If there is more complex coupling in the V-tail, the adjustment of the parameters of the aerodynamic surfaces of the tail with the elevator and the vertical tail with the rudder is preferred in the implementation.

[0069] The process of the implementation of the method is shown in Figure 1 The flight control system obtains the main motion parameters of the aircraft Figure 3 ), analyzes them through the stability real-time solving module, judges whether the stability requirements are met (different aircraft standards are different), if met, enters other control links, which is not discussed in this method. If the stability requirements are not met, the aerodynamic surface adjustment parameter coefficients are generated and output to the rudder, and then the parameters of each aerodynamic surface are adjusted. This stage can adjust a single aerodynamic surface parameter or multiple aerodynamic surface parameters at the same time. The adjustment of the aerodynamic surface parameters affects the motion parameters of the aircraft, and then forms a closed-loop control. The stability real-time solving module is solved through the motion equation of the aircraft.

[0070] After using the method, the stability eigenvalues of the helicopter have changed significantly, as shown in Figure 4 The stability of the helicopter is significantly enhanced, from level 3 to level 1.

[0071] The aircraft stability enhancement method of the application, after the flight information of the aircraft is collected by the sensor, the adjustment parameter coefficients are solved and generated through the flight control system, and then the characteristics of the aerodynamic surface are adjusted through the adjustment of the rudder and other components, which comprehensively ensures the longitudinal and lateral stability, and uses multiple aerodynamic surfaces for adjustment, which increases the ways and effects of the aircraft stability enhancement.

[0072] The aircraft stability enhancement method of the present application is realized based on variable aerodynamic surfaces, that is, the aircraft stability is enhanced by adjusting the characteristics of the aerodynamic surfaces through the control system. The flight control system adjusts the deflection angle rate, the span, the chord length, etc. of the aerodynamic surfaces (including the elevator of the horizontal tail, the rudder of the vertical tail, the flap, the aileron, the winglet, etc.) through the control of the rudder, etc. to enhance the stability of the aircraft. The related parameters of the longitudinal aerodynamic surfaces (including the elevator of the horizontal tail, the flap, the aileron, etc.) are adjusted to improve the longitudinal force and moment, so as to adjust the attitude, the longitudinal stability and the maneuverability of the whole machine; the related parameters of the lateral and horizontal aerodynamic surfaces (including the rudder of the vertical tail, the winglet, etc.) are adjusted to improve the lateral and horizontal force and moment, so as to improve the lateral and horizontal stability and maneuverability, etc. The main basis for determining the adjustment amount of the above components is the real-time solution result of the stability of the aircraft, and the optimal deflection angle rate, area, size or combination thereof is selected.

[0073] The aircraft stability enhancement method of the present application comprehensively ensures the longitudinal and lateral stability by adjusting the characteristics of the aerodynamic surfaces through the adjustment of the rudder, etc. after the flight information of the aircraft is collected by the sensor, the adjustment parameter coefficient is solved and generated by the flight control system, and multiple aerodynamic surfaces are used for adjustment, so as to increase the approach and effect of the aircraft stability enhancement.

Claims

1. A method of flight vehicle stability augmentation based on a variable aerodynamic surface, characterized by, The method comprises: S1, obtaining a six-degree-of-freedom motion equation of the aircraft; S2, bringing the helicopter flight state parameters and control parameters into the six-degree-of-freedom motion equation to obtain a motion equation of the current flight state; S3, performing small perturbation linearization processing on the motion equation of the current flight state to obtain an aerodynamic derivative matrix A, and performing characteristic analysis on A to obtain a stability characteristic value; S4, judging the stability characteristic value, if the stability characteristic value falls within grade 2 or grade 3, stability correction is needed; S5, determining the control quantity to be adjusted, and adjusting the aerodynamic surface parameters by the steering engine; when the stability characteristic value falls within grade 2, the control quantity to be adjusted is determined as the deflection angle rate, and when the stability characteristic value falls within grade 3, the control quantity to be adjusted is determined as the deflection angle rate, the span length and the chord length.

2. A method of variable aerodynamic surface based aircraft stability augmentation according to claim 1, wherein, In S1, the six-degree-of-freedom motion equation comprises rotors, tail rotors, fuselages, horizontal tails, elevators, vertical tails, rudders, flaps, ailerons, winglet small wings and their change parameters, and the change parameters are at least the deflection angle rate, the span length and the chord length.

3. The method of claim 1, wherein, In S2, the motion equation of the current flight state is (DE-A)X=B(U+T); Wherein X is the state parameter of the helicopter, including the pitch angle, the pitch angle rate, the roll angle and the roll angle rate; U is the control parameter of the helicopter, which is four control quantities: total distance control quantity, longitudinal control quantity, lateral control quantity and heading control quantity; T is the control quantity, including the deflection angle rate, the span length and the chord length of the horizontal tail including the elevator, the vertical tail including the rudder, the flap, the aileron and the winglet small wing; B is the control coefficient matrix, D is the parameter matrix of the helicopter, and E is the unit matrix.

4. The method for enhancing stability of an aircraft based on a variable aerodynamic surface according to claim 1, wherein S5 It comprises: S51, obtaining the helicopter flight state parameters, if the stability characteristic value falls within the grade 3 range, the deflection angle rate, the span length and the chord length in the control quantity are adjusted at the same time, the new control quantity is T+△T, and the motion equation of the adjusted flight state is obtained; S52, performing stability characteristic value judgment on the motion equation of the adjusted flight state, evaluating whether the attitude change value of the helicopter is less than or equal to the preset angle, if greater than the preset angle, setting a new control quantity as T+△T / 2, obtaining the motion equation of the adjusted flight state; S53, returning to S52 until the attitude change value of the helicopter is less than or equal to the preset angle; S54, secondly evaluating whether the real part of the stability characteristic value is unchanged or reduced; If the real part of the stability characteristic value is unchanged or reduced, the adjustment value△T is taken as the aerodynamic surface adjustment coefficient and input to the steering engine for control; If the real part of the stability characteristic value is increased, a new control quantity is set as T-△T, the motion equation of the adjusted flight state is obtained, and S52 is returned.

5. A method of variable aerodynamic surface based vehicle stability augmentation according to claim 4, wherein, S5 further comprises: If the stability characteristic value falls within the grade 2 range, the deflection angle rate is preferentially adjusted, and the new control quantity is T+△T; S52 to S54 are executed.

6. A method of variable aerodynamic surface based aircraft stability augmentation according to claim 4, wherein, In S51, the single adjustment value of the deflection angle rate is not more than 1 degree per second, and the single adjustment value△T of the span length and the chord length is not more than 0.1 m.

7. The method of claim 4, wherein, In S52, the preset angle is 0.5 degrees.

8. The method of claim 1, wherein, In S5, When adjusting the control quantity of the longitudinal aerodynamic surface, the adjustment is performed in the following priority order: horizontal tail, elevator, V-tail; When adjusting the control quantity of the lateral aerodynamic surface, the adjustment is performed in the following priority order: vertical tail, rudder, V-tail, flap, aileron, winglet.

Images