A method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) in terms of its degrees of freedom.

Abstract

This invention discloses a method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) with a body degree of freedom. The method is characterized by using the UAV's telescopic wing to perform asymmetrical extension and retraction to obtain an asymmetrical wing configuration, thereby suppressing body degree of freedom flutter in the asymmetrical configuration of the high aspect ratio wing and thus improving the flutter velocity of the UAV. This invention achieves an asymmetrical configuration of the UAV by controlling the asymmetrical extension and retraction of the high aspect ratio telescopic wing, thereby increasing the flutter velocity of the high aspect ratio UAV.

Description

Technical Field

[0001] This invention relates to the field of aeroelastic design technology for aircraft, and in particular to a method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aircraft. Background Technology

[0002] Flutter is a self-excited divergent vibration caused by the coupling of unsteady aerodynamics and the elastic structure of an 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 key aeroelastic problem of aircraft design departments. High aspect ratio telescopic wings have low stiffness and high flexibility, making aeroelastic problems more prominent. The first natural frequency of the elastic vibration of its wing structure is very easy to couple with the short-period mode of the pitch motion of the aircraft rigid body. This leads to problems such as heave and pitch, where rigid body motion and aeroelastic motion interact, resulting in aeroelastic divergence or rigid body motion divergence. At flight speeds below the design limit, dynamic instability occurs, causing structural damage and seriously endangering flight safety. This aeroelastic instability phenomenon caused by rigid body motion is called volume degree-of-freedom flutter.

[0003] Existing active flutter suppression technologies mainly include aerodynamic energy methods, piezoelectric actuator methods, and pole placement methods, etc. For active flutter suppression of volume degrees of freedom, the control system usually controls the deflection of the operating surfaces to suppress flutter. However, these methods have limited effect on improving flutter velocity and cannot recover high aspect ratio aircraft from volume degrees of freedom flutter. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the flutter speed of a high-aspect-ratio telescopic wing unmanned aerial vehicle (UAV). This invention achieves an asymmetric configuration of the UAV by controlling the asymmetric extension and retraction of the high-aspect-ratio telescopic wing, thereby improving the flutter speed of the UAV.

[0005] Technical Solution. A method for improving the flutter velocity of a large aspect ratio telescopic wing UAV, which utilizes the asymmetric telescopic wing of the UAV to obtain an asymmetric wing configuration, suppresses the flutter velocity of the large aspect ratio wing with the asymmetric configuration, and thus improves the flutter velocity of the UAV.

[0006] The aforementioned method for increasing the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) includes the following steps:

[0007] Step 1: Establish a full-span dynamic model of the telescopic wing UAV, perform flutter analysis, and obtain the flutter velocity of the UAV in its full-span state;

[0008] Step 2: Discretize the telescopic control quantity according to the telescopic wing's telescopic stroke, determine all unmanned aircraft configurations under different telescopic states of the left and right wings after discrete telescopic extension, and filter out all asymmetric configurations from them;

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

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

[0011] The aforementioned method for increasing the flutter speed of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) airframe also includes step 5: based on the asymmetric configuration determined in step 4, the initial symmetric configuration drive motor performs an asymmetric variant by retracting one side of the wing to achieve the corresponding asymmetric configuration.

[0012] In the aforementioned method for improving the flutter velocity of the body degrees of freedom of a high aspect ratio telescopic wing UAV, in step 1, the flutter type of the full wingspan dynamic model is body degree of freedom flutter.

[0013] In the aforementioned method for improving the flutter velocity of the high aspect ratio telescopic wing unmanned aircraft, in step 2, the discretization method of the telescopic control quantity is as follows: the telescopic stroke of 0.5m is discretized into five levels of control quantity, each level being 0.1m.

[0014] In the aforementioned method for improving the flutter velocity of the degrees of freedom of a high aspect ratio telescopic wing unmanned aircraft, a total of 36 configurations were obtained after discretization, including 30 asymmetric configurations and 6 symmetric configurations.

[0015] In the aforementioned method for increasing the flutter velocity of a high aspect ratio telescopic wing UAV, in step 4, the asymmetric configuration that can be used to increase the flutter velocity 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 the critical asymmetric configuration for changing the flutter form of the telescopic wing UAV from body degree-of-freedom flutter to bending-torsional coupled flutter.

[0016] In the aforementioned method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) body, step 4 involves obtaining the critical asymmetric configuration for changing the flutter mode using finite element software for flutter analysis.

[0017] In the aforementioned method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) with varying degrees of freedom, the asymmetric configuration is a configuration that uses the asymmetric telescopic extension method of the telescopic wing to change the structural stiffness and mass distribution of the UAV, thereby improving its flutter characteristics.

[0018] Beneficial effects: In order to solve the problem of poor flutter speed improvement in existing active flutter suppression technology, this invention uses an asymmetric configuration of a high aspect ratio telescopic wing to change the flutter mode of the telescopic wing UAV from volume degree-of-freedom flutter to bending-torsional coupling flutter, thereby significantly and effectively improving its flutter speed, while maintaining the aerodynamic performance of the wing with a high aspect ratio.

[0019] This invention employs asymmetric telescoping technology, which increases the elastic modal frequency of the wing structure after telescoping deformation, thereby changing the modal coupling and transforming volume degree-of-freedom flutter into bending-torsional coupled flutter, significantly improving the flutter speed of the telescoping wing UAV.

[0020] This invention employs hierarchical discrete scaling control, which makes the scaling variant control of UAVs more precise and convenient. At the same time, it can determine the flutter speed of all scaling states and calculate the structure, and can quickly and accurately transform from a symmetrical configuration to an asymmetrical configuration, thereby increasing the flutter speed of the scaling wing UAV to a predetermined value. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) according to the present invention.

[0022] Figure 2 This is a 3D image of a UAV used in an embodiment of the present invention to verify the effect of the asymmetric state of the telescopic wing on the flutter speed improvement.

[0023] Figure 3 This is the initial symmetrical configuration 1 of the telescopic wing UAV in Embodiment 1 of the present invention;

[0024] Figure 4 The flutter calculation results are for the initial symmetrical configuration 1 of the telescopic wing UAV in Embodiment 1 of the present invention; where (a) is the Vf diagram and (b) is the Vg diagram.

[0025] Figure 5 This refers to the asymmetric configuration 2 of the telescopic wing UAV in Embodiment 1 of the present invention;

[0026] Figure 6 The flutter calculation results are for the asymmetric configuration 2 of the telescopic wing UAV in Embodiment 1 of the present invention; where (a) is the Vf diagram and (b) is the Vg diagram.

[0027] Figure 7 This refers to the asymmetric configuration 3 of the telescopic wing UAV in Embodiment 1 of the present invention;

[0028] Figure 8 The flutter calculation results are for the asymmetric configuration 3 of the telescopic wing UAV in Embodiment 1 of the present invention; where (a) is the Vf diagram and (b) is the Vg diagram.

[0029] Figure 9 This is the initial symmetrical configuration 2 of the telescopic wing UAV in Embodiment 2 of the present invention;

[0030] Figure 10 The flutter calculation results are for the initial symmetrical configuration 2 of the telescopic wing UAV in Embodiment 2 of the present invention; where (a) is the Vf diagram and (b) is the Vg diagram;

[0031] Figure 11 This refers to the asymmetric configuration 4 of the telescopic wing UAV in Embodiment 2 of the present invention;

[0032] Figure 12 The flutter calculation results are for the asymmetric configuration 4 of the telescopic wing UAV in Embodiment 2 of the present invention; where (a) is the Vf diagram and (b) is the Vg diagram. Detailed Implementation

[0033] A method for improving the flutter velocity of a high-aspect-ratio telescopic wing unmanned aerial vehicle (UAV) is proposed. This method utilizes asymmetric telescopic extension to achieve an asymmetric wing configuration, suppressing flutter in the high-aspect-ratio wing and significantly improving the flutter velocity of the UAV. The technical solution in this embodiment addresses the aforementioned problem; see [link to relevant documentation]. Figure 1 The overall steps are as follows:

[0034] Step 1: Establish a full-span dynamic model of the telescopic wing UAV, perform flutter analysis, obtain the flutter velocity of the UAV in the full-span state, and determine the flutter type as body degree-of-freedom flutter;

[0035] Step 2: Discretize the telescopic control quantity according to the telescopic wing's telescopic stroke, and determine all unmanned aircraft configurations for different telescopic states of the left and right wings after discretization. For example, a telescopic stroke of 0.5m is discretized into five levels of control quantity, each level being 0.1m, resulting in a total of 36 configurations, including 30 asymmetric configurations and 6 symmetric configurations.

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

[0037] Step 4: Establish dynamic models for the available configurations determined in Step 3, perform flutter analysis to obtain flutter velocities and flutter types under different configurations, and then determine the asymmetric configurations that can be used to improve the flutter velocity of telescopic wing UAVs.

[0038] Step 5: Based on the results obtained in Step 4, the initial symmetrical configuration drive motor performs an asymmetrical variant by retracting one wing, thereby achieving an asymmetrical configuration and improving the flutter speed of the telescopic wing UAV.

[0039] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0040] Example 1

[0041] See Figure 2 This embodiment provides a retractable wing unmanned aerial vehicle (UAV) 100, including a fuselage 110 and a retractable wing 120. A left retractable wing section 121 and a right retractable wing section 122 are provided on the outer wing section of the retractable wing 120. The retractable wing 120 has a wingspan of 2.4m when fully extended and 1.4m when fully retracted. The lengths of the left retractable wing section 121 and the right retractable wing section 122 are 0.5m each.

[0042] See 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 lengths of the left telescopic section 121 and the right telescopic section 122 are 0.5m each. The control system can independently control the left and right telescopic sections 121 and 122 using dual motors 123 and 124. The telescopic stroke is set to 0.1m per level, with a total of five levels of commands. Based on this configuration, the telescopic wing UAV 100 can achieve 36 different wing configurations through telescopic deformation, including six symmetrical configurations and thirty asymmetrical configurations.

[0043] In this embodiment, the retractable wing UAV 100 can, as... Figure 3 When flying in the basic symmetrical configuration 1 shown, the telescopic wing UAV 100 has a wingspan of 2.4m and an aspect ratio of 18.4. (As shown...) Figure 4 The flutter analysis showed that the flutter velocity of the telescopic wing UAV was 39 m / s, and the flutter mode was body degree-of-freedom flutter.

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

[0045] By controlling the left motor 123, the left wing telescopic section 121 is retracted by 0.1m, thus achieving... Figure 5 The wing asymmetric configuration 2 is shown. (As shown in the image) Figure 6 As shown, the flutter velocity of the telescopic wing UAV in asymmetric configuration 2 is calculated to be 57.5 m / s, and the flutter mode is still body degree of freedom flutter.

[0046] By controlling the left motor 123, the left wing telescopic section 121 is retracted by 0.2m, thus achieving... Figure 7 The wing configuration shown is asymmetric configuration 3. (See example...) Figure 8 As shown, the flutter velocity of the telescopic wing UAV in asymmetric configuration 3 is calculated to be 105 m / s, and the flutter mode is changed to classic bending-torsional coupling flutter.

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

[0048] By utilizing the asymmetric extension and retractable wing to achieve an asymmetric wing configuration, the critical velocity for flutter of the degrees of freedom of the telescopic wing unmanned aircraft was increased by 47%.

[0049] The asymmetric configuration 2, with a greater degree of asymmetry, changes the flutter mode of the telescopic wing UAV from volume degree-of-freedom flutter to bending-torsional coupled flutter, increasing the flutter speed by 169%.

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

[0051] For configurations with a large aspect ratio, the effect of suppressing flutter in asymmetric configurations by unilateral indentation is excellent.

[0052] Example 2

[0053] The difference between Example 2 and Example 1 is that the initial symmetrical configuration for asymmetric telescoping is different, and the initial aspect ratio of the telescoping wing is also different. In Example 2, the wing aspect ratio is 16.6.

[0054] In this embodiment, as Figure 9 As shown, when the telescopic wing UAV 100 flies in its initial symmetrical configuration 2, its wingspan is 2.2m and its aspect ratio is 16.6. Figure 10 As shown, the flutter velocity of the telescopic wing UAV under this state is 58 m / s, and the flutter mode is body degree-of-freedom flutter.

[0055] For the initial symmetrical configuration 1, balancing asymmetrical configurations include asymmetrical configuration 4, etc. By controlling the left motor 131 to slide the left wing extension section 121 inward by 0.3m, the asymmetrical wing configuration 4 is achieved. Figure 11 As shown. The flutter calculation results for asymmetric configuration 4 are obtained through flutter calculations, as shown below. Figure 12 As shown, the calculated flutter velocity of the telescopic wing UAV in asymmetric configuration 4 is 115 m / s, and the flutter mode is body degree-of-freedom flutter.

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

[0057] By utilizing the asymmetric extension and retraction of the telescopic wing to achieve the asymmetric wing configuration 4, the critical velocity for flutter of the telescopic wing unmanned aircraft's degrees of freedom was increased by 98%.

[0058] The asymmetric configuration achieved by asymmetric deformation changes the flutter mode of the UAV from volume-degree-of-freedom flutter to bending-torsional coupled 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 modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle (UAV) in terms of its degree of freedom, characterized in that, By utilizing the telescopic wings of a UAV to achieve asymmetrical extension and retraction, an asymmetrical wing configuration is obtained. This suppresses body flutter of the high aspect ratio wing in the asymmetrical configuration, thereby improving the flutter speed of the UAV. The steps include: Step 1: Establish a full-span dynamic model of the telescopic wing UAV, perform flutter analysis, and obtain the flutter velocity of the UAV in its full-span state; Step 2: Discretize the telescopic control quantity based on the telescopic wing's telescopic stroke, determine all unmanned aircraft configurations for different telescopic states of the left and right wings after discretization, and filter out all asymmetric configurations; The discretization method for the telescopic control quantity is: discretize the 0.5m telescopic stroke into five levels of control quantity, each level being 0.1m; Step 3: Perform static aerodynamic trim analysis on all asymmetric configurations obtained in Step 2 to determine the range of asymmetric configurations that can be trimmed using control surfaces; Step 4: Establish dynamic models for the asymmetric configurations determined in Step 3, perform flutter analysis to obtain the flutter velocity and flutter type for each configuration, and then determine the asymmetric configuration that can be used to improve the flutter velocity of the telescopic wing UAV. The asymmetric configuration that can be used to improve the flutter velocity of the telescopic wing UAV is the critical asymmetric configuration for changing the flutter form. The critical asymmetric configuration for changing the flutter form is the critical asymmetric configuration for changing the flutter form of the telescopic wing UAV from volume degree-of-freedom flutter to bending-torsional coupled flutter. The critical asymmetric configuration for changing the flutter form is obtained by flutter analysis using finite element software. Step 5: Based on the asymmetric configuration determined in Step 4, the initial symmetric configuration drive motor performs an asymmetric variant by retracting one wing to achieve the corresponding asymmetric configuration.

2. The method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle according to claim 1, characterized in that, In step 1, the flutter type of the full wingspan dynamic model is body-degree-of-freedom flutter.

3. The method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle according to claim 1, characterized in that, After discretization, a total of 36 configurations were obtained, including 30 asymmetric configurations and 6 symmetric configurations.

4. The method for improving the flutter velocity of a high aspect ratio telescopic wing unmanned aerial vehicle according to claim 1, characterized in that, The aforementioned asymmetric configuration is a configuration that uses the asymmetric extension and retraction of telescopic wings to change the structural stiffness and mass distribution of the UAV, thereby improving its flutter characteristics.

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