An automated design method for paraglider ropes

Abstract

The present invention discloses an automated design method for parachute ropes of a high-gliding wing parachute. The method calls two-dimensional airfoil aerodynamic characteristic calculation software, combines the parachute canopy aerodynamic characteristic calculation model, and obtains the aerodynamic characteristics of the canopy at different attack angles; takes the maximum glide ratio as the design target, and determines the parachute rope installation angle according to the relationship between the glide angle, the attack angle and the glide ratio; finally, obtains the parachute rope parameters of the wing parachute that meet the high glide capability according to the parachute rope installation angle. The present invention integrates the aerodynamic characteristic calculation, the high glide ratio flight attitude design and the parachute rope parameter automatic design, and can quickly obtain the parachute rope configuration scheme of the wing parachute with high glide capability, thereby improving the accuracy and efficiency of the parachute rope design, which is of great significance to the structural design of the high-gliding wing parachute.

Description

Technical Field

[0001] The invention relates to the technical field of parachute design, in particular to an automatic design method for parachute ropes of a high-altitude glider parachute. Background Art

[0002] Ram parafoils are widely used in the field of precision airdrops, and high gliding ability is an important goal of parafoil structural design. The gliding ability of a parafoil is mainly borne by the canopy. The higher the lift-to-drag ratio of the parafoil canopy, the better the gliding ability. The lift-to-drag ratio of a parafoil has the following characteristics: before stalling, the lift-to-drag ratio increases with the increase of the angle of attack, reaches a maximum value before stalling, and then decreases again. Therefore, at a certain angle of attack, the lift-to-drag ratio of the parafoil has a maximum value. Therefore, by determining the optimal angle of attack, the maximum gliding performance of the parafoil can be obtained. Since there is a geometric correspondence between the parafoil's flight angle of attack, the gliding angle, and the parachute rope installation angle, the reasonable selection of the parafoil rope installation angle, the configuration of the parafoil chordal parachute rope length and distribution are important keys to ensure that the parafoil has a good flight angle of attack and improve the parafoil's gliding ability.

[0003] Traditional parafoil rope parameters are mostly determined by manual drawing. After the canopy is designed and made, the flight attitude corresponding to the best lift-to-drag ratio is determined by experiment. The two-dimensional plane diagram of the parafoil is manually drawn according to the airfoil structure and the attitude of the parafoil. Then, the intersection of the parafoil ropes and the position of the parafoil rope nodes on the lower wing are determined by geometric relationship drawing, and the parafoil rope assembly drawing is drawn. Finally, the actual parafoil rope length is calculated according to the proportion through manual measurement. Since the entire design process requires professional designers to draw and measure manually based on the experiment, the measurement error is large, and the designed parafoil often cannot achieve the optimal gliding attitude, resulting in poor gliding performance of the parafoil. At the same time, this manual drawing method has a large workload and low design efficiency. Therefore, it is necessary to establish an efficient automated design method for parafoil ropes to realize the digital automated design of parafoil ropes for high gliding parafoils and improve the design efficiency and accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is to propose an automated design method for the parachute ropes of a high-altitude paraglider, thereby realizing the automated operation of the entire design process and greatly improving the design accuracy and efficiency of the high-altitude paraglider.

[0005] In order to solve the above technical problems, the present invention provides an automatic design method for parachute ropes of a high-speed glider parachute, comprising the following steps:

[0006] Step 1, take the leading edge cut position of the airfoil chord as the coordinate origin O, the chord as the OX axis, and the upward direction as the Y axis, establish the OXY rectangular coordinate system, describe the two-dimensional parafoil airfoil in coordinate form, and output the parafoil airfoil as a YX.Dat data file;

[0007] Step 2: Read the YX.Dat airfoil data file through programming, automatically call the aerodynamic characteristics analysis software, and obtain the aerodynamic characteristics C of the two-dimensional parafoil airfoil as the angle of attack α changes. L,2D (α),C D,2D (α);

[0008] Step 3: According to the aerodynamic characteristics calculation model of the three-dimensional parafoil canopy, the aerodynamic characteristics C of the canopy at different attack angles are obtained based on the aerodynamic characteristics programming of the two-dimensional airfoil. L,3D (α),C D,3D (α);

[0009] Step 4: Based on the calculation results of the aerodynamic characteristics of the parafoil at different angles of attack, with the maximum glide ratio as the goal, establish an optimal angle of attack calculation model, and program to obtain the optimal angle of attack α of the parafoil p And the stable glide angle θ at this angle of attack p ;

[0010] Step 5: According to the geometric relationship of the parafoil during stable gliding, the parachute rope installation angle is φ p =θ p -α p Sure;

[0011] Step 6: In the OXY coordinate system, according to the pressure center position O s (x os ,y os ) and the equivalent length of the parachute line L sh Determine the coordinates of the parachute line intersection point C(x c ,y c ), the formula is

[0012]

[0013] Step 7: According to the number of parachute rope groups n and the relative spacing t of the control ropes, the lower wing surface is equally divided along the chord direction, and the parachute rope node points (A) of the lower wing surface are obtained through geometric relationship programming. i )coordinate;

[0014] Step 8: Based on the parachute line intersection point C(x c ,y c ) and the lower wing line node A i (x i ,y i ) coordinates, programming to obtain the length of each group of parachute ropes

[0015] Preferably, in step 2, according to the law of the aerodynamic characteristics of the two-dimensional parafoil airfoil changing with the angle of attack C L,2D (α), calculate the lift line slope k of the two-dimensional airfoil through linear fitting programming 2D .

[0016] Preferably, in step 3, the aerodynamic characteristics at different attack angles α are obtained by the following formula:

[0017] Lift coefficient C L,3D = k(α-α 0 )cos 2 β+k 1 sin 2 (α-α 0 )cos(α-α 0 ), where α 0 is the zero lift angle of attack, β is the anhedral angle of the parafoil, k 1 is the correction coefficient, and the lift line slope k of the parafoil is determined according to the lift line slope of the two-dimensional airfoil and the canopy aspect ratio. Where λ is the aspect ratio and ε is the non-elliptical load factor;

[0018] Drag coefficient in and They represent the canopy friction resistance, air inlet resistance and induced drag coefficient respectively. Where σ is the non-ellipticity induced angle coefficient.

[0019] Preferably, in step 4, the optimal angle of attack α p Select the angle of attack corresponding to the maximum lift-to-drag ratio of the parafoil canopy, and the stable gliding angle is given by get.

[0020] Preferably, in step 7, according to the leading edge point A of the lower wing 1 (x 1 ,y 1 ), trailing edge point B(x b ,y b ) coordinates, programming gives the functional expression of the wing surface:

[0021] The lower wing surface is equally divided along the chord direction to determine the lower wing surface node distribution of each group of parachute ropes, and the node coordinates A of the parachute ropes are determined by geometric relationships. i (x i ,y i ), (i∈1~n), the calculation formula is:

[0022]

[0023] According to the values ​​of different parachute rope group numbers n and the relative spacing t of the control ropes, a variety of parachute rope configuration schemes and corresponding parachute rope parameters are obtained.

[0024] The beneficial effects of the present invention are as follows: the present invention automatically analyzes the aerodynamic characteristics of the parafoil, determines the optimal flight posture of the parafoil and then calculates the parachute rope parameters, thereby realizing the automated operation of the entire design process, avoiding the errors caused by manual mapping and measurement, and greatly improving the design accuracy and efficiency; calling the aerodynamic characteristic analysis software, and establishing the optimal angle of attack selection model according to the aerodynamic characteristic law of the parafoil, so that the flight posture with the optimal gliding performance can be determined without tedious and expensive experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0026] Figure 2 It is a schematic diagram of the wing parachute posture and parachute rope distribution of the present invention.

[0027] Figure 3 It is a schematic diagram of the aerodynamic characteristics of the two-dimensional airfoil of the present invention.

[0028] Figure 4 It is a schematic diagram of the aerodynamic characteristics of the three-dimensional parafoil canopy of the present invention. DETAILED DESCRIPTION

[0029] In this embodiment, the span b of the parafoil is 8 m, the chord length c is 4 m, and the aspect ratio λ is 2.

[0030] An automated design process for paraglider ropes Figure 1 As shown in the figure, the design program is implemented by MATLAB programming. By integrating the canopy aerodynamic characteristics calculation program, the optimal gliding performance parafoil attitude design program and the parafoil line parameter automatic design program, only the two-dimensional airfoil needs to be input to automatically calculate the parafoil line parameters that meet the high gliding performance requirements. The design program specifically includes the following steps:

[0031] Step 1. In this example, a typical parafoil airfoil is selected, such as Figure 2 As shown, with the leading edge cut position of the airfoil chord as the coordinate origin O, the chord as the OX axis, and the upward direction as the Y axis, an OXY coordinate system is established to obtain the coordinate representation of the airfoil (as shown in Table 1), and the parafoil airfoil is output as a YX.Dat data file.

[0032] Table 1 Parafoil airfoil coordinates

[0033]

[0034] Step 2. Read the YX.Dat airfoil data file through programming, automatically call the aerodynamic characteristics calculation software xfoil, and obtain the aerodynamic characteristics C of the parafoil airfoil as the angle of attack changes L,2D (α),C D,2D (α), such as Figure 3 shown.

[0035] At zero lift angle of attack α 0 = -2.2° to stall angle α l =14°, the lift coefficient and the angle of attack are approximately linear. The slope k of the lift line of the two-dimensional airfoil is calculated by linear fitting programming 2D =4.11.

[0036] Step 3. According to the lift coefficient C of the parafoil canopy L,3D The calculation model of (α):

[0037] C L,3D = k(α-α 0 )cos 2 β+k 1 sin 2 (α-α 0 )cos(α-α 0 )

[0038] The slope of the lift line is given by Calculated, k = 2.235, lift line slope correction coefficient k 1 =0.67. The anhedral angle is Calculation, in this embodiment, the equivalent length of the parachute rope is L sh =4.8m, and the programmed β is 47.6°.

[0039] The variation law of the lift coefficient of the parafoil canopy with the angle of attack C in this embodiment can be obtained by programming. L,3D (α), the result is as follows Figure 4 shown.

[0040] According to the parafoil aerodynamic drag coefficient C D,3D (α) Calculation model:

[0041]

[0042] According to engineering experience, the friction coefficient of the canopy is Inlet resistance coefficient The induced drag coefficient of the airfoil is based on For calculation, the non-elliptical induced angle coefficient is taken as σ=0.01.

[0043] The variation law of the drag coefficient of the parafoil canopy with the angle of attack C in this embodiment can be obtained by programming. D,3D (α), the result is as follows Figure 4 shown.

[0044] Step 4. Calculate the lift-to-drag ratio at different angles of attack based on the calculation results of the three-dimensional aerodynamic characteristics of the parafoil like Figure 4 As shown. With high glide ratio as the goal, program to determine the optimal angle of attack α corresponding to the maximum lift-drag ratio of the parafoil p =10.5°.

[0045] From the glide angle formula Programming θ p =19.42°.

[0046] Step 5. When the parafoil is gliding steadily, Figure 2 As shown, v k Indicates the relative flow velocity direction, the airflow angle of attack, the glide angle and the parachute rope installation angle have a geometric relationship: φ p =θ p -α p , through programming to get φ p =8.92°;

[0047] Step 6. According to the pressure center position And parachute line installation angle φ p Get the coordinates of the parachute line intersection point C(x c ,y c ).like Figure 2 As shown, the coordinates of point C can be obtained from O s X s Y s Determination of the position relationship of the parachute system body axis: s X s The angle between the chord line OX and the axis is the installation angle φ p , the parachute rope intersection C is at O s Y s On the axis, the distance between the intersection of the parachute rope and the pressure center is O s C is equal to the equivalent length of the parachute rope. Then the C coordinate (x c ,y c ) is calculated as:

[0048]

[0049]

[0050] Determine the center of pressure based on engineering experience The coordinates of the parachute rope intersection point C can be obtained by programming (0.253, -4.742).

[0051] Step 7. According to the leading edge point A of the lower wing 1 (x 1 ,y 1 ), trailing edge point B(x b ,y b ) coordinates, programming gives the functional expression of the wing surface:

[0052] Divide the lower wing surface equally along the chord direction to determine the lower wing surface node distribution of each group of parachute ropes, such as Figure 2 As shown, the node coordinates A of the parachute rope are determined by geometric relationship. i(x i ,y i ), (i∈1~n). The calculation formula is:

[0053]

[0054] According to the values ​​of different parachute rope group numbers n and control rope relative spacing t, a variety of parachute rope configuration schemes and corresponding parachute rope parameters can be obtained. In this example, the number of parachute rope groups n = 4 and the control rope relative spacing t = 1.6 are selected, and the coordinates of all parachute rope nodes on the lower wing surface are calculated by programming:

[0055] A 1 (0.320,-0.114),A 2 (1.120,-0.089),A 3 (1.919,-0.065),A 4 (2.719,-0.040)

[0056] Step 8. Based on the paracord intersection point C(x c ,y c ) and the lower wing line node A i (x i ,y i ), (i∈1~n) coordinates, by the formula The length of each group of parachute ropes distributed along the chord direction is programmed as follows:

[0057] L 1 =4.628m,L 2 =4.732m,L 3 =4.965m,L 4 =5.310m

[0058] The length of the control rope BC is 6.044m. The above steps are completely executed automatically through programming, and the results of each step are automatically output without manual intervention.

Claims

1. An automated design method for parachute ropes of a high-altitude hang glider, characterized in that: The steps include: Step 1, take the leading edge cut position of the airfoil chord as the coordinate origin O, the chord as the OX axis, and the upward direction as the Y axis, establish the OXY rectangular coordinate system, describe the two-dimensional parafoil airfoil in coordinate form, and output the parafoil airfoil as a YX.Dat data file; Step 2: Read the YX.Dat airfoil data file through programming, automatically call the aerodynamic characteristics analysis software, and obtain the aerodynamic characteristics C of the two-dimensional parafoil airfoil as the angle of attack α changes. L,2D (α),C D,2D (α); Step 3: According to the aerodynamic characteristics calculation model of the three-dimensional parafoil canopy, the aerodynamic characteristics C of the canopy at different attack angles are obtained based on the two-dimensional airfoil aerodynamic characteristics programming. L,3D (α),C D,3D (α); The aerodynamic characteristics at different attack angles α are obtained by the following formula: Lift coefficient C L,3D = k(α-α0)cos 2 β+k1sin 2 (α-α0)cos(α-α0), where α0 is the zero lift angle of attack, β is the anhedral angle of the parafoil, k1 is the correction coefficient, and the lift line slope k of the parafoil is determined according to the lift line slope of the two-dimensional airfoil and the canopy aspect ratio. Where λ is the aspect ratio and ε is the non-elliptical load factor; Drag coefficient in and They represent the canopy friction resistance, air inlet resistance and induced drag coefficient respectively. Where σ is the non-elliptical induced angle coefficient; Step 4: Based on the calculation results of the aerodynamic characteristics of the parafoil at different angles of attack, with the maximum glide ratio as the goal, establish an optimal angle of attack calculation model, and program to obtain the optimal angle of attack α of the parafoil p And the stable glide angle θ at this angle of attack p ; Optimal angle of attack α p Select the angle of attack corresponding to the maximum lift-to-drag ratio of the parafoil canopy, and the stable gliding angle is given by get; Step 5: According to the geometric relationship of the parafoil during stable gliding, the parachute rope installation angle is φ p =θ p -α p Sure; Step 6: In the OXY coordinate system, according to the pressure center position And the equivalent length of the parachute line L sh Determine the coordinates of the parachute line intersection point C(x c ,y c ), the formula is Step 7: According to the number of parachute rope groups n and the relative spacing t of the control ropes, the lower wing surface is equally divided along the chord direction, and the parachute rope node points (A) of the lower wing surface are obtained through geometric relationship programming. i ) coordinates; according to the leading edge point A1(x1,y1) and trailing edge point B(x b ,y b ) coordinates, programming gives the functional expression of the wing surface: Divide the lower wing surface equally along the chord direction to determine the lower wing surface node distribution of each group of parachute ropes, and determine the node coordinates A of the parachute ropes through geometric relationships i (x i ,y i ), (i∈1~n), the calculation formula is: According to the values ​​of different parachute rope group numbers n and the relative spacing t of the control ropes, a variety of parachute rope configuration schemes and corresponding parachute rope parameters are obtained; Step 8: Based on the parachute line intersection point C(x c ,y c ) and the lower wing line node A i (x i ,y i ) coordinates, programming to obtain the length of each group of parachute ropes 2. The automated design method for parachute lines of a high-altitude hang glider according to claim 1, characterized in that: In step 2, according to the law of aerodynamic characteristics of two-dimensional parafoil airfoil changing with angle of attack, C L,2D (α), calculate the lift line slope k of the two-dimensional airfoil through linear fitting programming 2D .

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