Method for improving degree-of-freedom flutter speed of telescopic wing unmanned aerial vehicle with high aspect ratio

Abstract

The invention discloses a method for improving the flutter speed of the body degree of freedom of a high-aspect-ratio telescopic wing unmanned aerial vehicle, which is characterized in that the telescopic wing of the unmanned aerial vehicle is used for asymmetrically stretching to obtain the asymmetrical configuration of the wing, and the flutter speed of the body degree of freedom of the asymmetrically-configured high-aspect-ratio wing is inhibited so as to improve the flutter speed of the unmanned aerial vehicle. The asymmetric configuration of the unmanned aerial vehicle is realized by controlling the asymmetric expansion and contraction of the high-aspect-ratio telescopic wing, so that the flutter speed of the high-aspect-ratio unmanned aerial vehicle is improved.

Description

Technical Field

[0001] The invention relates to the technical field of aeroelastic design of aircraft, and in particular to a method for improving the flutter speed of the freedom degree of an unmanned aerial vehicle with a large aspect ratio and a retractable wing. Background Art

[0002] Flutter is a self-excited divergent vibration caused by the coupling of unsteady aerodynamic forces and the elastic structure of the aircraft. It can cause catastrophic damage to the aircraft structure and has a significant impact on the safety and aerodynamic performance of the aircraft. It has always been a dynamic aeroelastic problem of the aircraft that the aircraft model design department focuses on. The large aspect ratio telescopic wing structure has low stiffness and high flexibility, and the aeroelastic problem is more prominent. The first-order natural frequency of the elastic vibration of the wing structure is very easy to couple with the short-period mode of the aircraft rigid body pitch motion, resulting in the interaction between the rigid body motion such as sinking, pitching and aeroelastic motion, leading to aeroelastic divergence or rigid body motion divergence, and dynamic instability occurs at a flight speed lower than the design limit speed, causing structural damage and seriously endangering flight safety. This aeroelastic instability caused by the participation of rigid body motion is called body freedom flutter.

[0003] Existing active flutter suppression technologies mainly include aerodynamic energy method, piezoelectric actuator method and pole configuration method, etc. For active flutter suppression of body freedom, the control system usually controls the deflection of the operating surface to achieve the purpose of flutter suppression. However, these methods have limited improvement in flutter speed and cannot correct large aspect ratio aircraft from body freedom flutter. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the flutter speed of the freedom degree of a large aspect ratio telescopic wing drone. The present invention realizes the asymmetric configuration of the drone by controlling the asymmetric extension and retraction of the large aspect ratio telescopic wing, thereby improving the flutter speed of the large aspect ratio drone.

[0005] Technical solution: A method for improving the flutter speed of the body freedom degree of a large aspect ratio telescopic wing unmanned aerial vehicle, using the unmanned aerial vehicle telescopic wing to perform asymmetric extension and retraction to obtain an asymmetric configuration of the wing, suppressing the body freedom degree flutter of the asymmetric configuration of the large aspect ratio wing, so as to improve the flutter speed of the unmanned aerial vehicle.

[0006] The aforementioned method for increasing the degree of freedom flutter speed of a large aspect ratio telescopic wing drone comprises the following steps:

[0007] Step 1: Establish a full-wingspan dynamics model of a retractable-wing UAV, perform flutter analysis, and obtain the flutter velocity of the UAV in a full-wingspan state;

[0008] Step 2: discretize the telescopic control amount according to the telescopic stroke of the telescopic wing, determine all unmanned aircraft configurations at different telescopic states of the left and right wings after discrete telescopic extension, and select all asymmetric configurations;

[0009] Step 3: Perform aerodynamic trim analysis on all asymmetric configurations obtained in step 2 to determine the range of asymmetric configurations that can be trimmed using rudder surfaces;

[0010] Step 4: Establish dynamic models of the asymmetric configurations determined in step 3 respectively, perform flutter analysis to obtain the flutter speed and flutter type under each configuration, and then determine the asymmetric configuration that can be used to improve the flutter speed of the retractable wing UAV.

[0011] The aforementioned method for improving the flutter speed of the freedom degree of a large aspect ratio telescopic wing unmanned aerial vehicle also includes step 5: according to the asymmetric configuration determined in step 4, the initial symmetric configuration drives the motor to perform an asymmetric deformation in a manner of retracting the wing on one side to achieve the corresponding asymmetric configuration.

[0012] In the aforementioned method for improving the body freedom flutter speed of a large aspect ratio telescopic wing drone, in step 1, the flutter type of the full wingspan dynamics model is body freedom flutter.

[0013] In the aforementioned method for improving the flutter speed of the degree of freedom of a large aspect ratio telescopic wing unmanned aerial vehicle, in step 2, the discretization method of the telescopic control amount is: discretizing the telescopic stroke of 0.5m into five levels of control amount, each level is 0.1m.

[0014] In the aforementioned method for improving the flutter speed of the large aspect ratio telescopic wing UAV body, a total of 36 configurations are obtained after discretization, including 30 asymmetric configurations and 6 symmetric configurations.

[0015] In the aforementioned method for improving the flutter speed of the body freedom degrees of a large aspect ratio telescopic wing UAV, in step 4, the asymmetric configuration that can be used to improve the flutter speed of the telescopic wing UAV is a critical asymmetric configuration for changing the flutter form; the critical asymmetric configuration for changing the flutter form is a critical asymmetric configuration for changing the flutter form of the telescopic wing UAV from body freedom degree flutter to bending-torsion coupled flutter.

[0016] In the aforementioned method for improving the flutter speed of the high aspect ratio telescopic wing unmanned aerial vehicle body, in step 4, the critical asymmetric configuration of the flutter form change is obtained by flutter analysis using finite element software.

[0017] In the aforementioned method for improving the flutter speed of the large aspect ratio telescopic wing drone body, the asymmetric configuration is a configuration that utilizes the asymmetric telescopic mode of the telescopic wing to change the structural stiffness and mass distribution of the drone, thereby improving its flutter characteristics.

[0018] Beneficial effects: In order to solve the problems of poor flutter speed improvement effect in the existing body freedom flutter active suppression technology, the present invention utilizes the asymmetric configuration of the large aspect ratio telescopic wing to change the flutter form of the telescopic wing UAV from body freedom flutter to bending-torsion coupled flutter, thereby greatly and effectively improving its flutter speed while maintaining the aerodynamic performance of the wing with a large aspect ratio.

[0019] The present invention adopts asymmetric telescopic technology, which increases the elastic modal frequency of the wing structure after telescopic deformation, thereby changing the modal coupling situation and transforming the body freedom flutter into bending-torsion coupling flutter, greatly improving the flutter speed of the telescopic wing UAV.

[0020] The present invention adopts hierarchical discrete telescopic control, which makes the control of the telescopic variant of the UAV more accurate and simple. At the same time, all telescopic state structures can be determined to calculate their flutter speeds, and the symmetric configuration can be quickly and accurately transformed into an asymmetric configuration, thereby increasing the flutter speed of the telescopic wing UAV to a predetermined value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of a method for improving the flutter speed of a large aspect ratio telescopic wing drone body according to the present invention;

[0022] Figure 2 A three-dimensional diagram of a UAV for verifying the effect of the asymmetric state of the retractable wings on the flutter speed improvement in an embodiment of the present invention;

[0023] Figure 3 The telescopic-wing UAV is initially symmetrically configured as 1 in the first embodiment of the present invention;

[0024] Figure 4 1 is the flutter calculation result of the initial symmetrical configuration 1 of the telescopic wing UAV in the first embodiment of the present invention; wherein (a) is the Vf diagram, and (b) is the Vg diagram;

[0025] Figure 5 The asymmetric configuration 2 of the telescopic wing UAV in the first embodiment of the present invention;

[0026] Figure 6 1 is the flutter calculation result of the asymmetric configuration 2 of the telescopic wing UAV in the first embodiment of the present invention; wherein (a) is the Vf diagram, and (b) is the Vg diagram;

[0027] Figure 7 The asymmetric configuration 3 of the telescopic wing UAV in the first embodiment of the present invention;

[0028] Figure 8 1 is the flutter calculation result of the asymmetric configuration 3 of the telescopic wing UAV in the first embodiment of the present invention; wherein (a) is the Vf diagram, and (b) is the Vg diagram;

[0029] Fig. 9 The telescopic-wing UAV is initially symmetrically configured as the second embodiment of the present invention;

[0030] Fig.10 1 is the flutter calculation result of the initial symmetrical configuration 2 of the telescopic wing UAV in the second embodiment of the present invention; wherein (a) is the Vf diagram, and (b) is the Vg diagram;

[0031] Fig.11 The asymmetric configuration 4 of the telescopic wing UAV in the second embodiment of the present invention;

[0032] Fig.12 Calculation results of flutter of the asymmetric configuration 4 of the telescopic wing UAV in the second embodiment of the present invention; wherein (a) is the Vf diagram, and (b) is the Vg diagram. DETAILED DESCRIPTION

[0033] A method for improving the flutter speed of the body freedom of a large aspect ratio telescopic wing drone, using the telescopic wing to perform asymmetric extension and retraction to achieve an asymmetric configuration of the wing, suppressing the body freedom flutter of the large aspect ratio wing, and greatly improving the flutter speed of the drone. The technical solution in the embodiment of the present invention is to solve the above problem, see Figure 1 , the overall steps are as follows:

[0034] Step 1: Establish a full-wingspan dynamics model of a retractable-wing UAV, perform flutter analysis, obtain the flutter velocity of the UAV in a full-wingspan state, and determine that the flutter type is body-freedom flutter;

[0035] Step 2: discretize the telescopic control amount according to the telescopic stroke of the telescopic wing, and determine all unmanned aircraft configurations when the left and right wings are in different telescopic states after discrete telescopic extension. For example, the telescopic stroke of 0.5m is discretized into five levels of control amount, each level is 0.1m, and a total of 36 configurations can be obtained, including 30 asymmetric configurations and 6 symmetric configurations;

[0036] Step 3: Perform aerodynamic trim analysis on all asymmetric configurations obtained in step 2 to determine the range of asymmetric configurations that can be trimmed using rudder surfaces;

[0037] Step 4: Establish dynamic models of the available configurations determined in step 3 respectively, perform flutter analysis to obtain flutter speeds and flutter types under different configurations, and then determine an asymmetric configuration that can be used to improve the flutter speed of the telescopic wing UAV;

[0038] Step 5. Based on the result obtained in step 4, the initial symmetrical configuration drives the motor to perform an asymmetrical transformation in a manner of retracting the wing on one side, so as to achieve an asymmetrical configuration and thereby enhance the flutter speed of the telescopic wing UAV.

[0039] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0040] Embodiment 1

[0041] See also Figure 2 This embodiment provides a retractable wing drone 100, including a fuselage 110 and a retractable wing 120, wherein a left wing retractable section 121 and a right wing retractable section 122 are arranged on the outer wing section of the retractable wing 120. The retractable wing 120 has a wingspan of 2.4 m when fully extended and a wingspan of 1.4 m when fully retracted, and a length of 0.5 m for the left wing retractable section 121 and the right wing retractable section 122.

[0042] See also Figure 3 In this embodiment, the telescopic wing 120 has a wingspan of 2.4m when fully extended and 1.4m when fully retracted. The length of the left wing telescopic section 121 and the right wing telescopic section 122 is 0.5m. The control system can use the double-sided motors 123 and 124 to independently control the left and right telescopic sections 121 and 122. The telescopic stroke is set to 0.1m per level, with a total of five levels of instructions. Based on this setting, the telescopic wing drone 100 can achieve a total of 36 wing configurations through telescopic deformation, including six symmetrical left and right wing configurations and thirty asymmetric configurations.

[0043] In this embodiment, the telescopic wing drone 100 is used as follows: Figure 3 When the basic symmetrical configuration 1 shown is flying, the wingspan of the telescopic wing UAV 100 is 2.4 m and the aspect ratio is 18.4. Figure 4 As shown in the figure, the flutter speed of the retractable-wing UAV is 39m / s through flutter analysis, and the flutter form is body freedom flutter.

[0044] For the initial symmetric structure 1, the corresponding balancing asymmetric configurations are asymmetric configuration 2 and asymmetric configuration 3:

[0045] By controlling the left motor 123 to retract the left wing telescopic section 121 by 0.1m, the Figure 5 The wing asymmetric configuration 2 is shown. Figure 6 As shown, the flutter speed of the retractable-wing UAV in asymmetric configuration 2 is calculated to be 57.5 m / s, and the flutter form is still body freedom flutter.

[0046] By controlling the left motor 123 to retract the left wing telescopic section 121 by 0.2m, the Figure 7 The wing asymmetric configuration 3 is shown. Figure 8 As shown in the figure, the flutter speed of the retractable-wing UAV in asymmetric configuration 3 is calculated to be 105 m / s, and the flutter form is changed to classic bending-torsion coupled flutter.

[0047] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0048] The asymmetric configuration 1 of the wing is realized by using the asymmetric extension of the telescopic wing, which increases the critical speed of the degree of freedom flutter of the telescopic wing unmanned aircraft by 47%;

[0049] Asymmetric configuration 2 with a greater degree of asymmetry changes the flutter form of the telescopic wing UAV from body freedom flutter to bending-torsion coupling flutter, increasing the flutter speed by 169%.

[0050] Discrete hierarchical control can ensure that the UAV can achieve the target asymmetric state quickly and accurately.

[0051] For configurations with large aspect ratios, the effect of flutter suppression of asymmetric configurations achieved through unilateral indentation is very good.

[0052] Embodiment 2

[0053] The difference between the second embodiment and the first embodiment is that the initial symmetrical configuration for asymmetric telescopic extension is different, and the initial aspect ratio of the telescopic wing is also different. The aspect ratio of the wing in the second embodiment is 16.6.

[0054] In this embodiment, if Fig. 9 As shown, when the telescopic wing UAV 100 is flying in the initial symmetrical configuration 2, the wingspan of the telescopic wing UAV 100 is 2.2 m and the aspect ratio is 16.6. Fig.10 As shown in the figure, through flutter analysis, the flutter speed of the retractable-wing UAV is 58m / s, and the flutter form is body freedom flutter.

[0055] For the initial symmetrical configuration 1, the asymmetrical configurations that can be balanced include asymmetrical configuration 4, etc. By controlling the left motor 131 to slide the left wing telescopic section 121 inward by 0.3m, the asymmetrical configuration 4 of the wing is achieved. Fig.11 The flutter calculation results of asymmetric configuration 4 are shown in Fig.12 As shown, the calculated flutter speed of the retractable-wing UAV in asymmetric configuration 4 is 115 m / s, and the flutter form is body freedom flutter.

[0056] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0057] The asymmetric configuration 4 of the wing is achieved by using the asymmetric extension of the telescopic wing, which increases the critical speed of the telescopic wing UAV body degree of freedom flutter by 98%;

[0058] The asymmetric configuration achieved by asymmetric deformation changes the flutter form of the UAV from body freedom flutter to bending-torsion coupling flutter.

[0059] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0060] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for increasing the degree of freedom flutter speed of a large aspect ratio telescopic wing drone, characterized in that: The asymmetric configuration of the wing is obtained by asymmetric extension and retraction of the telescopic wing of the UAV, and the body degree of freedom flutter of the asymmetric high aspect ratio wing is suppressed to increase the flutter speed of the UAV.

2. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 1 is characterized in that: The following steps are involved: Step 1: Establish a full-wingspan dynamics model of a retractable-wing UAV, perform flutter analysis, and obtain the flutter velocity of the UAV in a full-wingspan state; Step 2: discretize the telescopic control amount according to the telescopic stroke of the telescopic wing, determine all unmanned aircraft configurations at different telescopic states of the left and right wings after discrete telescopic extension, and select all asymmetric configurations; Step 3: Perform aerodynamic trim analysis on all asymmetric configurations obtained in step 2 to determine the range of asymmetric configurations that can be trimmed using rudder surfaces; Step 4: Establish dynamic models of the asymmetric configurations determined in step 3 respectively, perform flutter analysis to obtain the flutter speed and flutter type under each configuration, and then determine the asymmetric configuration that can be used to improve the flutter speed of the retractable wing UAV.

3. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 2 is characterized in that: The method further comprises step 5: according to the asymmetric configuration determined in step 4, the motor is driven by the initial symmetric configuration to perform an asymmetric transformation in a manner of retracting the wing on one side, so as to realize the corresponding asymmetric configuration.

4. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 2, characterized in that: In step 1, the flutter type of the full-span dynamic model is body-freedom flutter.

5. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 2, characterized in that: In step 2, the discretization method of the telescopic control amount is: discretize the telescopic stroke 0.5m into five levels of control amount, each level is 0.1m.

6. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 5, characterized in that: After discretization, a total of 36 configurations were obtained, including 30 asymmetric configurations and 6 symmetric configurations.

7. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 2, characterized in that: In step 4, the asymmetric configuration that can be used to increase the flutter speed of the telescopic wing UAV is a critical asymmetric configuration for changing the flutter form; the critical asymmetric configuration for changing the flutter form is a critical asymmetric configuration for changing the flutter form of the telescopic wing UAV from body freedom flutter to bending-torsion coupled flutter.

8. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 7, characterized in that: In step 4, the critical asymmetric configuration of the flutter form change is obtained by flutter analysis using finite element software.

9. The method for improving the flutter speed of the high aspect ratio telescopic wing drone body according to claim 1, characterized in that: The asymmetric configuration is a configuration that utilizes the asymmetric extension and retraction of the retractable wings to change the structural stiffness and mass distribution of the drone, thereby improving its flutter characteristics.

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