A flutter control method and control device for a high aspect ratio wing

Abstract

The present application discloses a large aspect ratio wing flutter control method and control device thereof, including: obtaining the initial flutter speed of the wing; installing a steel cable on the wing, and applying a preload force to the steel cable in flight through a servo mechanism to limit the wing torsion; obtaining the extended flutter speed of the wing after the steel cable applies the preload force; enabling the wingtip angular displacement sensor during the flight of the UAV, and the wingtip angular displacement sensor is used to monitor the wingtip torsion angle and torsion angular velocity in real time; when the flight speed of the UAV exceeds the extended flutter speed, using the servo mechanism for dynamic control. The method solves the problem of how to increase the flutter speed, so that the UAV can fly safely at a higher speed, thereby improving its flight performance.

Description

Technical Field

[0001] The present application relates to the technical field of unmanned aerial vehicles, and in particular to a large aspect ratio wing flutter control method and a control device thereof. Background Art

[0002] As a potential dynamic instability problem, wing flutter has always been one of the key factors affecting the performance and safety of drones. The flutter phenomenon mainly originates from the interaction between aerodynamic force and structural elastic force during high-speed flight, which causes the wing structure to vibrate periodically. This vibration may not only cause structural fatigue, but also amplify rapidly, eventually leading to structural damage. Therefore, effective control of flutter is an important prerequisite for ensuring the safe flight of drones.

[0003] High aspect ratio wing design is a common method for modern high-altitude, long-endurance UAVs to pursue efficient lift-to-drag ratio, increase flight distance and hovering time. However, due to the relatively low stiffness of the wing, it is easy to produce large deformation during flight, especially under high-speed flight conditions, the interaction between the elastic deformation of the wing and the aerodynamic force is more intense, increasing the risk of flutter. The flutter speed is the maximum flight speed that a UAV can reach without causing structural damage, which has become an important factor limiting the performance improvement of such UAVs.

[0004] Therefore, how to increase the flutter speed so that the UAV can fly safely at a higher speed and thus improve its flight performance becomes a problem to be solved. Summary of the invention

[0005] In an embodiment of the present application, a large aspect ratio wing flutter control method is provided to solve the problem of how to increase the flutter speed so that the UAV can fly safely at a higher speed, thereby improving its flight performance.

[0006] In a first aspect, an embodiment of the present application provides a method for controlling the flutter of a large aspect ratio wing, comprising: obtaining an initial flutter velocity of the wing; installing a steel cable on the wing, and applying a preload to the steel cable through a servo mechanism in flight to limit the torsion of the wing; obtaining an extended flutter velocity of the wing after the preload is applied to the steel cable; enabling a wingtip angular displacement sensor during the flight of the UAV, the wingtip angular displacement sensor being used to monitor the wingtip torsion angle and torsion angular velocity in real time; and using a servo mechanism for dynamic control when the flight speed of the UAV exceeds the extended flutter velocity.

[0007] In a possible implementation, the wingtip angle displacement sensor is enabled during the flight of the UAV, including: when the flight speed of the UAV is between the initial flutter speed and the extended flutter speed, the wingtip angle displacement sensor is enabled.

[0008] In a possible implementation, when the flight speed of the UAV is lower than the extended flutter speed, it is determined whether the wingtip angular displacement sensor is faulty based on the wingtip torsion angle and torsion angular velocity monitored by the wingtip angular displacement sensor.

[0009] In a possible implementation, if the wingtip angle displacement sensor fails, the flight speed of the UAV is limited so that it is always no higher than the extended flutter speed.

[0010] In one possible implementation, the method for determining whether the wingtip angular displacement sensor is faulty is as follows: when the flight speed of the UAV is lower than the extended flutter speed, if the wingtip angular displacement exceeds the maximum angular displacement of the wing generated by the UAV under static load, it is determined that the wingtip angular displacement sensor is faulty.

[0011] In one possible implementation, when the flight speed of the UAV exceeds the extended flutter speed, a servo mechanism is used for dynamic control, including: when the leading edge of the wingtip is upward, the lower servo motor pulls the steel cable to apply a first pulling force, and the first pulling force is obtained based on the torsion angle and the torsion angular velocity; when the leading edge of the wingtip is downward, the upper servo motor pulls the steel cable to apply a second pulling force, and the second pulling force is obtained based on the torsion angle and the torsion angular velocity.

[0012] In a possible implementation, the method further includes: when the wingtip angular displacement sensor detects that the wingtip vibration has a divergent trend, reducing the flight speed of the UAV.

[0013] In one possible implementation, it is determined that the wingtip angular displacement sensor detects that the wingtip vibration has a divergent trend if any of the following conditions are met: the first condition: the wingtip angular displacement reaches or exceeds a preset ratio of the maximum angular displacement of the wing generated by the UAV under static load; the second condition: the amplitude ratio of the first and last cycles of the wingtip angular displacement exceeds a preset ratio in a preset number of consecutive vibration cycles.

[0014] In the second aspect, an embodiment of the present application provides a control device for a large aspect ratio wing flutter control method, including a winglet, an earring bolt, a wingtip angular displacement sensor and a servo mechanism; two winglets are respectively arranged at the wingtips of the wings on both sides of the UAV, extending up and down along a horizontal reference plane perpendicular to the wing, for reducing drag and providing an installation structure for a trailing edge traction steel cable; two earring bolts are respectively arranged at the trailing edge of a single-side winglet, for connecting and pulling the steel cable; each wingtip is equipped with a wingtip angular displacement sensor for real-time monitoring of the wingtip torsion angle and torsion angular velocity; the servo mechanism includes an upper left servo mechanism, a lower left servo mechanism, an upper right servo mechanism and a lower right servo mechanism, which are symmetrically arranged on the rear fuselage of the UAV, and each servo mechanism includes a servo motor and a cable collection box, for pulling the steel cable pulled out from the earring bolt.

[0015] In one possible implementation, the steel cable pulled out from the earring bolt on the wingtip of the left wing is fixed in the cable box of the upper left servo mechanism, and the steel cable pulled out from the earring bolt under the wingtip of the left wing is fixed in the cable box of the lower left servo mechanism; the steel cable pulled out from the earring bolt on the wingtip of the right wing is fixed in the cable box of the upper right servo mechanism, and the steel cable pulled out from the earring bolt under the wingtip of the right wing is fixed in the cable box of the lower right servo mechanism.

[0016] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects:

[0017] The embodiment of the present application provides a flutter control method for a large aspect ratio wing. By installing a steel cable on the wing and applying a preload, the torsion of the wing during flight is effectively limited, and the structural rigidity and dynamic stability of the wing are significantly improved. By limiting the torsion of the wing, the torsional vibration frequency of the wing is increased, thereby achieving an increase in the extended flutter speed, which means that the drone can fly safely in a wider speed range without triggering the flutter phenomenon. By enabling the wingtip angular displacement sensor, the torsion angle and torsion angular velocity of the wingtip can be monitored in real time, providing key data support. Once an abnormal torsion situation is detected, measures can be taken immediately to adjust it. This real-time monitoring mechanism greatly enhances the safety and reliability of flight. When the flight speed of the drone exceeds the extended flutter speed, the servo mechanism is used for dynamic control to further adjust the wing state and maintain flight stability. This dynamic response capability not only improves the flight performance of the drone, but also enhances its adaptability and survivability under extreme conditions. It solves the problem of how to increase the flutter speed so that the drone can fly safely at a higher speed, thereby improving its flight performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 A flow chart of a high aspect ratio wing flutter control method provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of a binary wing segment model provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of the original wing velocity damping curve provided in an embodiment of the present application;

[0022] Figure 4 A schematic diagram of a wing velocity damping curve after adding preload force provided in an embodiment of the present application;

[0023] Figure 5 A layout diagram of a drone provided in an embodiment of the present application;

[0024] Figure 6 A layout diagram of a winglet provided in an embodiment of the present application;

[0025] Figure 7 A schematic diagram of the connection between a winglet and a steel cable provided in an embodiment of the present application;

[0026] Figure 8 A schematic diagram of the arrangement of a servo mechanism provided in an embodiment of the present application;

[0027] Fig. 9 A schematic diagram of the servo mechanism structure provided in an embodiment of the present application;

[0028] Fig.10 A schematic diagram of a high aspect ratio wing flutter control server provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] The following describes some of the techniques involved in the embodiments of the present application to facilitate understanding, and they should be considered as merely exemplary. Therefore, it should be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, some descriptions of well-known functions and structures are omitted in the following description.

[0031] The present application embodiment provides a method for controlling the flutter of a large aspect ratio wing, such as Figure 1 As shown, the method includes steps S101 to S105. Among them, Figure 1 This is only an execution sequence shown in the embodiment of the present application, and does not represent the only execution sequence of a large aspect ratio wing flutter control method. In the case where the extended result can be achieved, Figure 1 The steps shown may be performed in parallel or reversed.

[0032] S101: Acquire the initial flutter velocity of the wing.

[0033] S102: Install steel cables on the wings and apply pre-tightening force to the steel cables through servo mechanisms in flight to limit wing torsion.

[0034] S103: Obtaining the extended flutter velocity of the wing after the pre-tensioning force is applied to the steel cable.

[0035] Specifically, by limiting the torsion of the wing, the torsional vibration frequency is increased to obtain an extended flutter speed, which is greater than the initial flutter speed when the steel cable is not installed.

[0036] Specifically, based on the results of the stress analysis, 10% of the maximum stress that may be generated in the dangerous part of the wing root under specific flight conditions is calculated as the target stress value. The dangerous part of the wing root refers to the area where the wing is connected to the fuselage. Specific flight conditions refer to the environmental and load conditions faced by the aircraft when performing specific tasks or flight phases, including flight speed, altitude, attitude, meteorological conditions, and factors such as load and trim. The target stress value is set to the stress level that should be generated when the preload force acts on the wing, ensuring that the stress in the dangerous part of the wing root will not exceed this target stress value.

[0037] Furthermore, the initial flutter velocity of the UAV is calculated when the cable is not installed, which is recorded as . This is the basic flutter performance of the aircraft without any additional structural reinforcement or adjustment. In order to improve the flutter characteristics of the aircraft, steel cables are installed on the wings, and pre-tension is applied to the steel cables by servo mechanisms during flight. The main purpose of this measure is to limit the torsion of the wing. As the torsion of the wing is restricted, its torsional vibration frequency increases accordingly. The flutter of the wing is caused by the coupling of the torsional mode with other bending modes. Therefore, when the torsion is effectively restricted, the flutter speed of the aircraft will also increase accordingly. After the steel cables are installed and traction is applied to the wings, the flutter speed of the aircraft is recalculated, and the extended flutter speed obtained at this time is recorded as Due to the limitation of wing torsion, the extended flutter speed is Significantly greater than the initial flutter velocity when no cable is installed .

[0038] It should be noted that flutter is a complex aeroelastic instability phenomenon that poses a great threat to flight safety. The flutter speed refers to the critical speed at which the wings of a drone flutter during flight. When the flight speed exceeds the flutter speed, the flutter phenomenon of the wings will intensify, which may cause structural damage and affect flight safety. By increasing the flutter speed, the drone can fly safely at a higher speed, thereby improving its flight performance.

[0039] A method for proving that the extended flutter velocity is greater than the initial flutter velocity when the wire rope is not installed comprises the following steps.

[0040] 1. Set up a two-dimensional wing section model, which is supported at the rigid center by a torsion spring and a linear spring.

[0041] 2. Clarify the parameters of the wing section, which include mass, the distance between the center of gravity and the rigid center, and the distance between the aerodynamic center and the rigid center.

[0042] 3. Define the two degrees of freedom of the wing segment. The two degrees of freedom are the deflection of the rigid center of the wing segment and the rotation angle of the wing segment around the rigid center.

[0043] The present application uses the vibration of a two-element wing section in an airflow to illustrate that the flutter speed increases after the torsional frequency increases. Figure 2 Schematic diagram of a two-dimensional wing segment model provided in an embodiment of the present application. The model is a simplified representation of a wing segment. It is a two-dimensional model that ignores the three-dimensional effects other than the width of the wing segment. Support method: The wing segment is supported by two springs on the rigid center. One is a torsion spring and the other is a linear spring. The mass of the wing segment is , whose center of gravity is located at Point. Center of gravity Point and rigid center The distance between points is , and the positive direction is the direction behind the center of gravity, that is, the direction behind the airflow. The aerodynamic center is located at point, its rigid center The distance between points is , and the aerodynamic center is in front, that is, the positive direction along the airflow direction. The aerodynamic center is the main position where the wing section generates lift. The wing section has two degrees of freedom, namely the deflection h of the rigid center starting from the static equilibrium point and the rotation angle around the rigid center. . Deflection of the rigid center Indicates the displacement of the wing section in the vertical direction, with downward being the positive direction. It indicates the rotation angle of the wing segment around the rigid center, and the positive direction is when the wing is tilted upward.

[0044] 4. Establish the equation of motion based on the parameters of the wing section and the principle of moment balance, and consider the lift generated by the airflow.

[0045] Specifically, the equation of motion is expressed as: .in, is the mass of the wing section, is the deflection of the rigid center, is the rotation angle around the rigid center, is the deflection of the rigid center The second derivative with respect to time, i.e. the acceleration of the deflection, is the half chord length of the wing segment, Center of gravity Point and rigid center The distance between points, is the rotation angle around the rigid center The second derivative with respect to time is the acceleration of the angle of rotation. is the stiffness coefficient of the linear spring, which represents the restoring force generated by the linear spring under unit deflection. is the lift generated by the airflow, is the inherent moment of inertia of the wing segment about the rigid center, is the stiffness coefficient of the torsion spring, which indicates the restoring torque generated by the torsion spring under unit rotation angle. Pneumatic Center Point and rigid center The distance between points. , is the static moment of the wing segment about the rigid center, , is the moment of inertia of the wing section about the center of rigidity.

[0046] therefore, The formula can be expressed as: The lift generated by the airflow can be expressed as: .in, is the wing section plane area, For speed pressure, , is the air density, is the flight speed of the drone, is the lift coefficient The derivative of the rotation angle about the rigid center is the slope of the lift line. It can be obtained through CFD (fluid dynamics) calculations or wind tunnel tests.

[0047] therefore, The formula can be rewritten as: .Will The flutter equation is taken as

[0048] 5. Assume that the solution is in the form of an exponential function, which includes the initial amplitude of the deflection of the wing section's rigid center, the initial amplitude of the wing section's rotation angle about the rigid center, and time.

[0049] The solution is of the form: .in, is the deflection of the rigid center, is the rotation angle around the rigid center, for The initial amplitude of for The initial amplitude of is an exponential function, is a complex number that determines the variables h and How it changes over time, , and are all constants, real part Determines the rate and stability of change, the imaginary part Determines the periodic or oscillatory behavior of system changes, is an imaginary unit. When , the system motion is stable. When , the system is in a critical state. , the system is unstable. Determines the periodicity of system changes or the frequency of oscillation. The system in this application can be understood as the dynamic response of the drone under the action of external forces.

[0050] 6. Substituting the solution into the flutter equation, we get the quartic equation about the eigenvalue, which is used as the characteristic equation. The flutter equation is obtained through the equation of motion and lift.

[0051] Substituting the solution into the flutter equation Formula, we get: .

[0052] The quartic equation of the eigenvalue of the formula is: .in, , , , .

[0053] Will The quartic equation of the eigenvalue of the formula is taken as the characteristic equation.

[0054] 7. Determine the stability of the wing section based on the coefficients of the characteristic equation and the value of the discriminant.

[0055] Specifically, the stability of the wing segment is judged according to the coefficient of the characteristic equation and the value of the discriminant, including: when the discriminant is greater than 0, the wing segment has two different vibration frequencies, and the wing segment is in a stable state. When the discriminant is equal to 0, the two vibration frequencies of the wing segment coincide, and the wing segment is in a critical state of flutter. When the discriminant is less than 0, the wing segment will flutter.

[0056] Furthermore, the discriminant is When the wing section is in a stable state, that is, a stationary state, the speed pressure , then the coefficients of the characteristic equation satisfy And the discriminant This means that the characteristic equation has two different real roots. Since , in a stable state, it can be considered is a pure imaginary number, indicating that the wing segment has two different vibration frequencies. As the flight speed of the drone increases, if , the wing segment will continue to vibrate at two different vibration frequencies. However, as the flight speed of the drone further increases, the gap between the two frequencies will gradually decrease, indicating that the stability of the system is gradually decreasing. When the flight speed of the drone reaches a certain critical value, the discriminant , then the two roots of the characteristic equation will coincide, that is, the two vibration frequencies will be the same. , the characteristic equation will have at least one root with a positive real part, i.e. , which means that the amplitude of the system will continue to expand and the wing section will flutter. Therefore, according to the discriminant It is reasonable to be regarded as the critical condition of chatter because it marks the turning point where the system changes from a stable vibration state to an unstable chatter state.

[0057] 8. Substituting the lift line slope into the flutter equation, we obtain an expression for the flutter divergence velocity.

[0058] 9. The influence of torsional frequency on flutter divergence velocity is analyzed according to the expression of flutter divergence velocity. When the torsional frequency increases, the flutter divergence velocity also increases accordingly, proving that the extended flutter velocity is greater than the initial flutter velocity when the cable is not installed.

[0059] Specifically, the lift line slope can be expressed as: , substituting the lift line slope into the flutter equation In the formula, we get: .set up , eliminate , Substitute the typical wing section data and assume: , , , , ,get: . Divide both ends by , and remember ,get: . The characteristic equation is: According to the critical condition of flutter, we get: Solved , the expression of flutter divergence velocity is: Among them, the subscript Indicates divergence, is the flutter divergence speed. For a specific airfoil, when the torsional frequency When increasing, unchanged, so the flutter divergence speed Increase, so the vibration speed is extended Greater than the initial flutter velocity when no cable is installed .

[0060] Figure 3 This is a schematic diagram of the original wing velocity damping curve provided in an embodiment of the present application, and the flutter speed is 97.5 m / s. Figure 4 This is a schematic diagram of the wing velocity damping curve after the preload is increased according to the embodiment of the present application, and the flutter speed is 122m / s. Figure 3 and Figure 4 As shown, after adding winglets to the wingtips of a certain type of aircraft flexible wing according to this application and pre-tightening through servo mechanisms and steel cables, the bending frequency remains basically unchanged, the first-order torsion frequency increases by 38%, and the flutter speed increases from 97.5m / s to 122m / s. Figure 3 and Figure 4 In the figure, different curves represent different flutter modes. As the speed increases, there is always a curve that crosses the horizontal axis first, indicating that the corresponding flutter mode begins to occur at this speed.

[0061] S104: The wingtip angular displacement sensor is enabled during the flight of the UAV. The wingtip angular displacement sensor is used to monitor the wingtip torsion angle and torsion angular velocity in real time.

[0062] The wingtip angle displacement sensor is enabled during the flight of the UAV, including: when the flight speed of the UAV is between the initial flutter speed and the extended flutter speed, the wingtip angle displacement sensor is enabled.

[0063] Specifically, when the flight speed of the UAV is between the initial flutter speed and the extended flutter speed, the wingtip torsion angle and torsion angular velocity data monitored by the wingtip angular displacement sensor are not directly used to control the flight state of the UAV or adjust any control parameters. Its main function is to provide real-time monitoring information so that the flight control system can understand the flutter state of the wing in a timely manner. Once an abnormal torsion is detected, measures can be taken immediately to make adjustments.

[0064] S105: When the flight speed of the drone exceeds the extended flutter speed, a servo mechanism is used for dynamic control.

[0065] When the flight speed of the UAV exceeds the extended flutter speed, a servo mechanism is used for dynamic control, including the following steps. When the leading edge of the wing tip is upward, the lower servo motor pulls the steel cable to apply a first pulling force, and the first pulling force is obtained based on the torsion angle and the torsion angular velocity. When the leading edge of the wing tip is downward, the upper servo motor pulls the steel cable to apply a second pulling force, and the second pulling force is obtained based on the torsion angle and the torsion angular velocity. When the wing tip angular displacement sensor detects that the wing tip vibration has a divergent trend, the flight speed of the UAV is reduced.

[0066] Specifically, the vibration of the wing tip is continuously monitored by the wing tip angular displacement sensor. When the wing tip angular displacement sensor detects that the wing tip vibration has a divergent trend, the control parameters of the servo motor are adjusted. For the lower servo motor, its control parameters are increased to enhance the first pulling force. For the upper servo motor, its control coefficient is adjusted to weaken the force in the opposite direction of the second pulling force.

[0067] Specifically, the pursuit of further improving the flight speed of the drone, when flying at a speed exceeding the extended flutter speed, uses servo motors to implement more precise dynamic control. Specifically, the direction of the leading edge of the wing tip (upward is considered the positive direction) is used as a reference to determine the method and size of the pulling force.

[0068] When the wing tip twist angle When the angle is greater than 0°, that is, when the leading edge of the wing tip is upward, the lower servo motor pulls the steel cable to generate the first pulling force. , the magnitude of this force is related to the torsion angle and the torsional angular velocity is proportional to .in, and are control parameters, which are all positive coefficients, which means that with the increase of torsion angle and torsion angular velocity, the first pulling force will also increase, so that the wing tip has a downward tendency to lower its head, effectively consuming and weakening the vibration energy. When the angle is less than 0°, that is, when the leading edge of the wing tip is downward, the upper servo motor pulls the steel cable to generate a second pulling force. , and its calculation formula is .at this time, and are control parameters, all of which are negative coefficients, indicating that as the torsion angle increases in the negative direction and the torsion angular velocity increases, the second pulling force The absolute value of will also increase, but in the opposite direction, that is, an upward head-up trend is generated to balance and suppress vibration. In both cases, a constant load is continuously applied to the two cables to ensure the stability and response speed of the system. When the flight speed of the drone exceeds the extended flutter speed and the wingtip sensor detects a divergent trend in the wingtip vibration, the control of the servo motor will be further strengthened. The specific method is to increase the control parameter and and reduce the control parameter and to more effectively suppress the occurrence of vibration.

[0069] To determine whether the wingtip angular displacement sensor detects that the wingtip vibration has a divergent trend, any of the following conditions must be met: The first condition: the wingtip angular displacement reaches or exceeds the preset ratio of the maximum angular displacement of the wing generated by the drone under static load. Specifically, the preset ratio can be set to 50%, which means that if the wingtip angular displacement reaches or exceeds half of the maximum angular displacement of the wing under static load, the wingtip vibration is considered to have a divergent trend. The second condition: the amplitude ratio of the first and last cycles of the wingtip angular displacement exceeds the preset ratio in a preset number of consecutive vibration cycles. Specifically, the preset number can be set to 5. If the vibration amplitude of the wingtip is within 5 consecutive cycles, the amplitude of the starting cycle, i.e., the first cycle, is compared with the amplitude of the last cycle, i.e., the fifth cycle, the latter is twice or more of the former, that is, the preset ratio is twice, which is also considered to be a vibration with a divergent trend. Any one of these two conditions being met will serve as a criterion for starting dynamic control.

[0070] When the UAV's flight speed is lower than the extended flutter speed, the wingtip angular displacement sensor is judged to be faulty based on the wingtip torsion angle and torsion angular velocity monitored by the wingtip angular displacement sensor. If the wingtip angular displacement sensor fails, the flight speed of the UAV is limited so that it is always no higher than the extended flutter speed to ensure flight safety. The way to determine the wingtip angular displacement sensor failure is as follows: when the UAV's flight speed is lower than the extended flutter speed, if the wingtip angular displacement exceeds the maximum angular displacement of the wing generated by the UAV under static load, the wingtip angular displacement sensor is judged to be faulty.

[0071] Specifically, the wingtip angular displacement must be strictly controlled within the maximum angular displacement that the aircraft can produce under static load. This limitation is one of the important measures to ensure flight safety. Once the monitored wingtip angular displacement exceeds the maximum angular displacement of the wing produced by the drone under static load, it means that there may be a sensor failure. At this time, measures should be taken immediately, such as limiting the flight speed of the drone to keep it below the extended flutter speed to prevent potential flight safety accidents.

[0072] An embodiment of the present application provides a control device for a high aspect ratio wing flutter control method, including a winglet, an earring bolt, a wingtip angular displacement sensor, and a servo mechanism.

[0073] Figure 5 This is a layout diagram of the drone provided in the embodiment of the present application. Figure 5 As shown in the figure, two winglets are respectively arranged at the wing tips on both sides of the UAV, extending up and down along the vertical wing horizontal reference plane, used to reduce drag and provide a mounting structure for the trailing edge traction cable. The design of the winglet not only helps to reduce air resistance during flight and improve the flight efficiency of the UAV, but also provides a stable mounting structure for the trailing edge traction cable.

[0074] Figure 6A layout diagram of the winglets provided in an embodiment of the present application. Figure 7 Schematic diagram of the connection between the winglet and the steel cable provided in the embodiment of the present application. Figure 6 and Figure 7 As shown, two earring bolts are respectively arranged at the trailing edge of the winglet on one side to connect and pull the steel cable. Each wing tip is equipped with a wing tip angle displacement sensor to monitor the wing tip twist angle and twist angular velocity in real time.

[0075] Specifically, the trailing edge refers to the edge of the winglet near the tail of the aircraft. The eyebolt provides a reliable connection point for the cable, ensuring that the cable can be firmly fixed to the winglet. The eyebolt connects and pulls the cable through the tensioning clamp.

[0076] Figure 8 A schematic diagram of the arrangement of a servo mechanism provided in an embodiment of the present application. Fig. 9 Schematic diagram of the servo mechanism structure provided in the embodiment of the present application. Figure 8 and Fig. 9 As shown, the servo mechanism includes an upper left servo mechanism, a lower left servo mechanism, an upper right servo mechanism and a lower right servo mechanism, which are symmetrically arranged on the rear fuselage of the drone. Each servo mechanism includes a servo motor and a cable box for pulling the steel cable pulled out from the earring bolt.

[0077] The steel cable pulled out from the earring bolt on the left wing tip is fixed in the cable box of the upper left servo mechanism, and the steel cable pulled out from the earring bolt under the left wing tip is fixed in the cable box of the lower left servo mechanism. The steel cable pulled out from the earring bolt on the right wing tip is fixed in the cable box of the upper right servo mechanism, and the steel cable pulled out from the earring bolt under the right wing tip is fixed in the cable box of the lower right servo mechanism. The servo motor of each servo mechanism can drive its corresponding cable box to rotate to pull the corresponding steel cable.

[0078] Specifically, the four servo mechanisms are symmetrically distributed, ensuring the balance and stability of the drone during flight. The servo motor of each servo mechanism can independently drive the corresponding cable box to rotate. When the servo motor receives a control signal, it adjusts the speed and direction according to the signal's instructions, thereby pulling the corresponding steel cable and applying a preload to limit the torsion of the wing, increase the torsional vibration frequency, and obtain an extended flutter speed. By increasing the flutter speed, the drone can fly safely at a higher speed, thereby improving its flight performance.

[0079] Some modules in the apparatus described in the present application can be described in the general context of computer executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, classes, etc. that perform specific tasks or implement specific abstract data types. The present application can also be practiced in distributed computing environments, in which tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0080] The devices or modules described in the above application embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described in various modules according to their functions. When implementing the embodiments of the present application, the functions of each module can be implemented in the same or multiple software and / or hardware. Of course, the module that implements a certain function can also be implemented by combining multiple sub-modules or sub-units.

[0081] The methods, devices or modules described in this application can be implemented in the form of computer-readable program codes. The controller can be implemented in any appropriate manner. For example, the controller can take the form of a microprocessor or processor and a computer-readable medium storing computer-readable program codes (such as software or firmware) that can be executed by the (micro)processor, logic gates, switches, application-specific integrated circuits (English: Application Specific Integrated Circuit, referred to as: ASIC), programmable logic controllers and embedded microcontrollers. Examples of controllers include but are not limited to the following microcontrollers: ARC 625D, Atmel AT91SAM, Microchip PIC18F26K20 and Silicone Labs C8051F320. The memory controller can also be implemented as part of the control logic of the memory. Those skilled in the art also know that in addition to implementing the controller in the form of pure computer-readable program codes, the controller can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, this controller can be considered as a hardware component, and the devices included in it for implementing various functions can also be regarded as structures within the hardware component. Or even, the means for realizing various functions may be regarded as both a software module for realizing the method and a structure within a hardware component.

[0082] like Fig.10As shown, an embodiment of the present application also provides a large aspect ratio wing flutter control server, including a memory 1001 and a processor 1002; the memory 1001 is used to store computer executable instructions; the processor 1002 is used to execute computer executable instructions to implement a large aspect ratio wing flutter control method described above in the embodiment of the present application.

[0083] An embodiment of the present application also provides a computer-readable storage medium, which stores executable instructions. When a computer executes the executable instructions, the high aspect ratio wing flutter control method described above in the embodiment of the present application can be implemented.

[0084] It can be seen from the description of the above implementation methods that those skilled in the art can clearly understand that the present application can be implemented by means of software plus necessary hardware. Based on this understanding, the technical solution of the present application can be essentially or partly contributed to the prior art in the form of a software product, or it can be reflected in the implementation process of data migration. The computer software product can be stored in a storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a mobile terminal, a server, or a network device, etc.) to execute the method described in the embodiment of the present application.

[0085] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. All or part of this application can be used in many general or special computer system environments or configurations.

[0086] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A high aspect ratio wing flutter control method, characterized in that: include: Get the initial flutter velocity of the wing; Steel cables are installed on the wings, and pre-tension is applied to the cables by servo mechanisms in flight to limit the torsion of the wings; Obtain the extended flutter velocity of the wing after the pre-tensioning force is applied to the steel cable; The wingtip angular displacement sensor is activated during the flight of the UAV, and is used to monitor the wingtip torsion angle and torsion angular velocity in real time; When the flying speed of the drone exceeds the extended flutter speed, a servo mechanism is used for dynamic control.

2. The high aspect ratio wing flutter control method according to claim 1, characterized in that: The wingtip angle displacement sensor is activated during the flight of the UAV, including: When the flight speed of the UAV is between the initial flutter speed and the extended flutter speed, the wingtip angle displacement sensor starts to be enabled.

3. The high aspect ratio wing flutter control method according to claim 1, characterized in that: When the flight speed of the UAV is lower than the extended flutter speed, whether the wingtip angular displacement sensor is faulty is determined based on the wingtip torsion angle and torsion angular velocity monitored by the wingtip angular displacement sensor.

4. The high aspect ratio wing flutter control method according to claim 3, characterized in that: If the wingtip angle displacement sensor fails, the flight speed of the drone is limited so that it is always no higher than the extended flutter speed.

5. The high aspect ratio wing flutter control method according to claim 3, characterized in that: The method for determining whether the wingtip angular displacement sensor is faulty is as follows: when the flight speed of the UAV is lower than the extended flutter speed, if the wingtip angular displacement exceeds the maximum angular displacement of the wing generated by the UAV under static load, the wingtip angular displacement sensor is determined to be faulty.

6. The high aspect ratio wing flutter control method according to claim 1, characterized in that: When the flight speed of the UAV exceeds the extended flutter speed, a servo mechanism is used for dynamic control, including: When the leading edge of the wing tip is upward, the lower servo motor pulls the steel cable to apply a first pulling force, wherein the first pulling force is obtained based on the torsion angle and the torsion angular velocity; When the leading edge of the wing tip is downward, the upper servo motor pulls the steel cable to apply a second pulling force, wherein the second pulling force is obtained based on the twist angle and the twist angular velocity.

7. The high aspect ratio wing flutter control method according to claim 1, characterized in that: Also includes: When the wingtip angular displacement sensor detects that the wingtip vibration has a divergent trend, the flight speed of the UAV is reduced.

8. The high aspect ratio wing flutter control method according to claim 7, characterized in that: To determine whether the wingtip angular displacement sensor detects a divergent trend in wingtip vibration, any of the following conditions must be met: The first condition: the wing tip angular displacement reaches or exceeds the preset ratio of the maximum angular displacement of the wing produced by the UAV under static load; The second condition is that the amplitude ratio of the first and last cycles of the wingtip angular displacement in a preset number of consecutive vibration cycles exceeds a preset ratio.

9. The control device of the high aspect ratio wing flutter control method according to any one of claims 1 to 8, characterized in that: It includes winglets, earring bolts, wingtip angular displacement sensors and servo mechanisms; Two winglets are respectively arranged at the wing tips on both sides of the UAV, extending up and down along the vertical wing horizontal reference plane, used to reduce drag and provide a mounting structure for the trailing edge traction cable; Two earring bolts are respectively arranged at the trailing edge of the winglet on one side, and are used to connect and pull the steel cable; Each wing tip is equipped with a wing tip angle displacement sensor for real-time monitoring of the wing tip twist angle and twist angular velocity; The servo mechanisms include an upper left servo mechanism, a lower left servo mechanism, an upper right servo mechanism and a lower right servo mechanism, which are symmetrically arranged on the rear fuselage of the UAV. Each servo mechanism includes a servo motor and a cable collection box for pulling the steel cable pulled out from the earring bolt.

10. The control device of the high aspect ratio wing flutter control method according to claim 9, characterized in that: The steel cable pulled out from the earring bolt on the left wing tip is fixed in the cable box of the upper left servo mechanism, and the steel cable pulled out from the earring bolt under the left wing tip is fixed in the cable box of the lower left servo mechanism; The steel cable pulled out from the earring bolt on the wingtip of the right wing is fixed in the cable box of the upper right servo mechanism, and the steel cable pulled out from the earring bolt under the wingtip of the right wing is fixed in the cable box of the lower right servo mechanism.

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