A test and analysis method for the water landing performance of fixed-wing amphibious UAV

Abstract

The present invention relates to the technical field of unmanned aerial vehicles, and specifically to a method for testing and analyzing the landing performance of a fixed-wing amphibious unmanned aerial vehicle on the water, comprising: preparing a test platform and an unmanned aerial vehicle; conducting a water landing test of the unmanned aerial vehicle; conducting a finite element simulation analysis of the water landing test of the unmanned aerial vehicle; comparing and analyzing the "water pool water pressure-time" change curve obtained by the test and the "water pool water pressure-time" simulated change curve obtained by the finite element simulation; based on the matching test results and finite element simulation results, obtaining the variation law of the core parameters of the unmanned aerial vehicle and the variation law of the attitude image during landing. The present invention remotely controls the attitude of the fixed-wing amphibious unmanned aerial vehicle during water landing through a handle, and can observe the landing performance during planned and unplanned water landings, solving the disadvantage of no rolling attitude caused by the traditional horizontal throwing method; the present invention simulates the forced landing performance of amphibious aircraft on the water surface through the finite element method, which can reduce the test investment and reduce the research cost.

Description

Technical Field

[0001] The invention relates to the technical field of unmanned aerial vehicles, and in particular to a method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle. Background Art

[0002] In recent years, with the increasing application of drones, different types of drones have emerged one after another. Among them, water drones can quickly patrol the water surface and have the advantages of taking off and landing on water. The water landing performance of amphibious drones is closely related to flight performance and safety. How to measure its water landing performance parameters and obtain relevant data has become a key issue affecting the design of amphibious drones.

[0003] At present, the water landing performance test of amphibious UAVs is mainly carried out by the hanger throwing method, which has the following disadvantages: 1. It requires a longer guide rail for acceleration, which increases the test cost; 2. There is friction between the throwing hanger and the aircraft model, which affects the flight attitude and speed; 3. The hanger throwing is generally a parallel movement, which makes it difficult to achieve water landing of the aircraft with a rolling attitude.

[0004] Therefore, it is necessary to design a test and analysis method for the water landing performance of fixed-wing amphibious UAVs. Summary of the invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle comprises the following steps:

[0007] Step 1, prepare a test platform and a UAV; the test platform includes a pool, a camera device, and a water pressure detection device. The pool is filled with clean water. The camera device is used to capture a posture image of the UAV when it lands in the pool. The water pressure detection device is used to detect the change in water pressure in the pool when the UAV lands. The UAV is a fixed-wing amphibious UAV;

[0008] Step 2, conducting a UAV landing test on a water surface; turning on the camera device and the water pressure detection device, manipulating the UAV to fly toward the pool in a predetermined posture and landing on the water surface of the pool, recording the image captured by the camera device and the water pressure change data detected by the water pressure detection device, and drawing a "pool water pressure-time" change curve;

[0009] Step 3, perform finite element simulation analysis on the UAV water landing test to obtain the "pressure-time" simulation change curve of the bottom of the UAV, the "pitch angle-time" simulation change curve of the UAV, and the "pool water pressure-time" simulation change curve;

[0010] Step 4, comparing and analyzing the "water pool water pressure-time" change curve obtained by the test and the "water pool water pressure-time" simulated change curve obtained by finite element simulation, and adjusting the parameters of the finite element simulation so that the finite element simulation results are consistent with the test results;

[0011] Step 5, based on the consistent test results and finite element simulation results, the core parameter change rules of the pressure and pitch angle of the UAV when landing on the water surface and the change rules of the attitude image when landing are obtained under the multi-factor coupling of the initial angle of attack, landing speed, and pitch angle.

[0012] Furthermore, the camera device includes a first high-speed camera, a second high-speed camera, and a third high-speed camera. The first high-speed camera is used to capture the posture image of the drone from the side, the second high-speed camera is used to capture the posture image of the drone above the water surface from the front, and the third high-speed camera is used to capture the posture image of the drone below the water surface from the front.

[0013] Furthermore, the bottoms of the first high-speed camera, the second high-speed camera, and the third high-speed camera are all provided with triangular fixing frames, and are arranged on the outside of the pool through the triangular fixing frames.

[0014] Furthermore, the water pool is a transparent acrylic material pool.

[0015] Furthermore, the water pressure detection device includes a plurality of pressure sensors, and the plurality of pressure sensors are distributed at the water surface boundary of the pool.

[0016] Furthermore, in step 3, the following steps are specifically included:

[0017] Step 3.1, draw a three-dimensional model of the test platform and the UAV, use Hypermesh software to divide the meshes of the UAV, air domain, and water domain in the three-dimensional model, and export them as a k file;

[0018] Step 3.2, import the k file into ls-prepost software for pre-processing; add the fluid-structure coupling keyword based on the ALE method to measure the pressure change at the bottom of the drone, set the parameters of the finite element simulation, and export the updated k file;

[0019] Step 3.3, submit the updated k file to the ls-dyna solver for calculation to generate a d3plot file, import the d3plot file into the ls-prepost software for post-processing, and obtain the "pressure-time" simulation change curve of the bottom of the drone, the "pitch angle-time" simulation change curve of the drone, and the "pool water pressure-time" simulation change curve.

[0020] Furthermore, in step 3.2, the adding of the fluid-structure coupling keyword based on the ALE method to measure the pressure change at the bottom of the drone specifically includes:

[0021] In the ALE method, an independent reference coordinate system is introduced in addition to the Lagrangian and Euler coordinates. The material differential equation in the independent reference coordinate system is:

[0022] ;

[0023] Where: represents the material coordinates in the Lagrangian coordinate system, represents the material coordinates of the Euler coordinate system, represents the velocity difference between the material and the reference frame, Indicates time;

[0024] From the relationship between the material derivative with respect to time and the geometric configuration derivative with respect to time, the ALE governing equation is derived, which is expressed by the following equilibrium equations:

[0025] The mass conservation equation:

[0026] ;

[0027] Momentum conservation equation:

[0028] ;

[0029] Energy conservation equation:

[0030] ;

[0031] Where: For material pressure, is the fluid density, is the fluid velocity, is the stress gradient, is the physical quantity per unit mass, is the spatial coordinate of the Lagrangian coordinate system, is the velocity gradient of the material point, For energy, is the velocity difference between the space and the reference coordinate system;

[0032] Represents the stress tensor, and its expression is:

[0033] ;

[0034] Where: is the specific stress, is the dynamic viscosity coefficient of the fluid, is the velocity gradient of a point in space.

[0035] It can be seen from the above description of the present invention that, compared with the prior art, the fixed-wing amphibious unmanned aerial vehicle water landing performance test and analysis method of the present invention has the following beneficial effects:

[0036] 1. The UAV of the present invention has diversified landing postures on the water surface; the posture of the fixed-wing amphibious UAV during water landing can be remotely controlled by a handle, and the landing performance during planned and unplanned water landing can be observed, which solves the disadvantage of no rolling posture caused by the traditional horizontal throwing method;

[0037] 2. The present invention can observe the omnidirectional posture of the UAV when it lands on the water surface, so as to more accurately analyze the landing performance on the water surface, and adopt a transparent landing pool to capture images under the water surface;

[0038] 3. The present invention reduces the test cost; by simulating the forced landing performance of an amphibious aircraft on the water surface through the finite element method, the test investment can be reduced and the research cost can be reduced;

[0039] 4. The present invention combines the test results and the finite element simulation results to analyze the water landing performance of the UAV, so that the obtained UAV water landing performance parameters are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of the steps of a method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle in a preferred embodiment of the present invention;

[0041] Figure 2 It is a top view schematic diagram of a test platform and a UAV in a preferred embodiment of the present invention;

[0042] Figure 3 A schematic side view of a camera device in a preferred embodiment of the present invention;

[0043] Explanation of the numbers in the figure: drone 1, pool 2, first high-speed camera 3, second high-speed camera 4, third high-speed camera 5, tripod fixing frame 6, pressure sensor 7. DETAILED DESCRIPTION

[0044] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0046] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Reference Figures 1 to 3 As shown, a preferred embodiment of the present invention is a method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle, comprising the following steps:

[0048] Step 1, prepare a test platform and a UAV 1; the test platform includes a pool 2, a camera device, and a water pressure detection device. The pool 2 is filled with clean water. The camera device is used to capture a posture image of the UAV 1 when it lands in the pool 2. The water pressure detection device is used to detect the change in water pressure in the pool 2 when the UAV 1 lands. The UAV 1 is a fixed-wing amphibious UAV;

[0049] Step 2, conducting a water landing test of the UAV 1; turning on the camera device and the water pressure detection device, manipulating the UAV 1 to fly toward the pool 2 in a predetermined posture and landing on the water surface of the pool 2, recording the image captured by the camera device and the water pressure change data detected by the water pressure detection device, and drawing a "pool water pressure-time" change curve;

[0050] Step 3, perform finite element simulation analysis on the water landing test of the UAV 1, and obtain the "pressure-time" simulation change curve of the bottom of the UAV 1, the "pitch angle-time" simulation change curve of the UAV 1, and the "pool water pressure-time" simulation change curve;

[0051] Step 4, comparing and analyzing the "water pool water pressure-time" change curve obtained by the test and the "water pool water pressure-time" simulated change curve obtained by finite element simulation, and adjusting the parameters of the finite element simulation so that the finite element simulation results are consistent with the test results;

[0052] Step 5, based on the consistent test results and finite element simulation results, obtain the core parameter change rules of pressure and pitch angle of UAV 1 when landing on the water surface and the change rule of attitude image when landing under the multi-factor coupling of initial attack angle, landing speed and pitch angle of UAV 1.

[0053] The UAV 1 of the present invention has various postures for landing on the water surface; the posture of the fixed-wing amphibious UAV during landing on the water surface is remotely controlled by a handle, and the landing performance during planned and unplanned water landing can be observed, which solves the disadvantage of no rolling posture brought by the traditional horizontal throwing method; the present invention can observe the all-round posture of the UAV 1 during landing on the water surface, so as to more accurately analyze the water landing performance, and adopt a transparent landing pool 2 to take images under the water surface; the present invention reduces the test cost; the forced landing performance of an amphibious aircraft on the water surface is simulated by the finite element method, which can reduce the test investment and reduce the research cost; the present invention combines the test results and the finite element simulation results to analyze the water landing performance of the UAV 1, so that the acquired water landing performance parameters of the UAV 1 are more accurate.

[0054] As a preferred embodiment of the present invention, it may also have the following additional technical features:

[0055] In this embodiment, the camera device includes a first high-speed camera 3, a second high-speed camera 4, and a third high-speed camera 5. The first high-speed camera 3 is used to shoot the posture image of the drone 1 from the side, the second high-speed camera 4 is used to shoot the posture image of the drone 1 above the water surface from the front, and the third high-speed camera 5 is used to shoot the posture image of the drone 1 below the water surface from the front. The camera device uses the first high-speed camera 3, the second high-speed camera 4, and the third high-speed camera 5 to capture the image of the drone 1 when it lands on the water surface in all directions.

[0056] In this embodiment, a triangular fixing frame 6 is provided at the bottom of each of the first high-speed camera 3, the second high-speed camera 4, and the third high-speed camera 5, and the triangular fixing frame 6 is provided on the outside of the pool 2. The first high-speed camera 3, the second high-speed camera 4, and the third high-speed camera 5 are fixed by the triangular fixing frame 6.

[0057] In this embodiment, the water pool 2 is a transparent acrylic material water pool. The use of a transparent acrylic material water pool facilitates the shooting of images under the water surface.

[0058] In this embodiment, the water pressure detection device includes a plurality of pressure sensors 7, and the plurality of pressure sensors 7 are distributed at the water surface boundary of the pool 2. Since the drone 1 will stir up water waves on the water surface when landing, and the water waves propagate toward the water surface boundary of the pool 2, a plurality of pressure sensors 7 are arranged at the water surface boundary to detect water pressure changes.

[0059] In this embodiment, in step 3, the following steps are specifically included:

[0060] Step 3.1, draw a three-dimensional model of the test platform and the UAV 1, use Hypermesh software to divide the meshes of the UAV 1, air domain, and water domain in the three-dimensional model, and export them as a k file;

[0061] Step 3.2, import the k file into ls-prepost software for pre-processing; add the fluid-structure coupling keyword based on the ALE method to measure the pressure change at the bottom of the drone 1, set the parameters of the finite element simulation, and export the updated k file;

[0062] Step 3.3, submit the updated k file to the ls-dyna solver for calculation to generate a d3plot file, import the d3plot file into the ls-prepost software for post-processing, and obtain the "pressure-time" simulation change curve of the bottom of UAV 1, the "pitch angle-time" simulation change curve of UAV 1, and the "pool water pressure-time" simulation change curve.

[0063] In this embodiment, in step 3.2, adding a fluid-structure coupling keyword based on the ALE method to measure the pressure change at the bottom of the drone 1 specifically includes:

[0064] In the ALE method, an independent reference coordinate system is introduced in addition to the Lagrangian and Euler coordinates. The material differential equation in the independent reference coordinate system is:

[0065] ;

[0066] Where: represents the material coordinates in the Lagrangian coordinate system, represents the material coordinates of the Euler coordinate system, represents the velocity difference between the material and the reference frame, Indicates time;

[0067] From the relationship between the material derivative with respect to time and the geometric configuration derivative with respect to time, the ALE governing equation is derived, which is expressed by the following equilibrium equations:

[0068] The mass conservation equation:

[0069] ;

[0070] Momentum conservation equation:

[0071] ;

[0072] Energy conservation equation:

[0073] ;

[0074] Where: For material pressure, is the fluid density, is the fluid velocity, is the stress gradient, is the physical quantity per unit mass, is the spatial coordinate of the Lagrangian coordinate system, is the velocity gradient of the material point, For energy, is the velocity difference between the space and the reference coordinate system;

[0075] Represents the stress tensor, and its expression is:

[0076] ;

[0077] Where: is the specific stress, is the dynamic viscosity coefficient of the fluid, is the velocity gradient of a point in space.

[0078] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and improved concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. A method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle, characterized in that: The following steps are involved: Step 1, prepare a test platform and a UAV; the test platform includes a pool, a camera device, and a water pressure detection device. The pool is filled with clean water. The camera device is used to capture a posture image of the UAV when it lands in the pool. The water pressure detection device is used to detect the change in water pressure in the pool when the UAV lands. The UAV is a fixed-wing amphibious UAV; Step 2, conducting a UAV landing test on the water surface; turning on the camera device and the water pressure detection device, manipulating the UAV to fly toward the pool in a predetermined posture and landing on the water surface of the pool, recording the image captured by the camera device and the water pressure change data detected by the water pressure detection device, and drawing a "pool water pressure-time" change curve; Step 3: Conduct finite element simulation analysis on the UAV water landing test to obtain the "pressure-time" simulation change curve of the bottom of the UAV, the "pitch angle-time" simulation change curve of the UAV, and the "pool water pressure-time" simulation change curve; Step 4, comparing and analyzing the "water pool water pressure-time" variation curve obtained by the test and the "water pool water pressure-time" simulation variation curve obtained by finite element simulation, and adjusting the parameters of the finite element simulation so that the finite element simulation results are consistent with the test results; Step 5, based on the consistent test results and finite element simulation results, the core parameter change rules of the pressure and pitch angle of the UAV when landing on the water surface and the change rules of the attitude image when landing are obtained under the multi-factor coupling of the initial angle of attack, landing speed, and pitch angle.

2. The method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle according to claim 1 is characterized in that: The camera device includes a first high-speed camera, a second high-speed camera, and a third high-speed camera. The first high-speed camera is used to capture the posture image of the drone from the side, the second high-speed camera is used to capture the posture image of the drone above the water surface from the front, and the third high-speed camera is used to capture the posture image of the drone below the water surface from the front.

3. The method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle according to claim 2 is characterized in that: The bottoms of the first high-speed camera, the second high-speed camera and the third high-speed camera are all provided with a triangular fixing frame, and are arranged outside the pool through the triangular fixing frame.

4. The method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle according to claim 1 is characterized in that: The water pool is a transparent acrylic material pool.

5. The method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle according to claim 1 is characterized in that: The water pressure detection device includes a plurality of pressure sensors, and the plurality of pressure sensors are distributed at the water surface boundary of the pool.

6. The method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle according to claim 1 is characterized in that: In step 3, the following steps are specifically included: Step 3.1, draw a three-dimensional model of the test platform and the UAV, use Hypermesh software to divide the meshes of the UAV, air domain, and water domain in the three-dimensional model, and export them as a k file; Step 3.2, import the k file into ls-prepost software for pre-processing; add the fluid-structure coupling keyword based on the ALE method to measure the pressure change at the bottom of the drone, set the parameters of the finite element simulation, and export the updated k file; Step 3.3, submit the updated k file to the ls-dyna solver for calculation to generate a d3plot file, import the d3plot file into the ls-prepost software for post-processing, and obtain the "pressure-time" simulation change curve of the bottom of the drone, the "pitch angle-time" simulation change curve of the drone, and the "pool water pressure-time" simulation change curve.

7. The method for testing and analyzing the water landing performance of a fixed-wing amphibious unmanned aerial vehicle according to claim 6 is characterized in that: In step 3.2, the fluid-structure interaction keyword based on the ALE method is added to measure the pressure change at the bottom of the drone, specifically including: In the ALE method, an independent reference coordinate system is introduced in addition to the Lagrangian and Euler coordinates. The material differential equation in the independent reference coordinate system is: ； Where: represents the material coordinates in the Lagrangian coordinate system, represents the material coordinates of the Euler coordinate system, represents the velocity difference between the material and the reference frame, Indicates time; From the relationship between the material derivative with respect to time and the geometric configuration derivative with respect to time, the ALE governing equation is derived, which is expressed by the following equilibrium equations: The mass conservation equation: ； Momentum conservation equation: ； Energy conservation equation: ； Where: For material pressure, is the fluid density, is the fluid velocity, is the stress gradient, is the physical quantity per unit mass, is the spatial coordinate of the Lagrangian coordinate system, is the velocity gradient of the material point, For energy, is the velocity difference between the space and the reference coordinate system; Represents the stress tensor, and its expression is: ； Where: is the specific stress, is the dynamic viscosity coefficient of the fluid, is the velocity gradient of a point in space.

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