A parachute aerodynamic test method based on optoelectronic data fusion

Abstract

A parachute aerodynamic testing method using optoelectronic data fusion relates to the field of parachute testing. The optoelectronic data fusion parachute aerodynamic testing method obtains environmental data from a wind tunnel's stable section, establishes a real-time dynamic pressure correction mathematical model for the environmental data, and establishes a test space coordinate system. The angle of attack of the test parachute is calculated in real time within the test parachute's coordinate system. Input conditions for a PI control model are established based on different blockage ratios and wind speeds at the center of the test section, optimizing the proportional coefficient and integration time to achieve the optimal state. The actual lateral and longitudinal aerodynamic forces of the test parachute are converted based on optical interpretation of the test parachute's angle of attack and force analysis of the aerodynamic torque sensed by a force balance. The aerodynamic torque coefficient of the test parachute is calculated based on the nominal geometric characteristics of the test parachute and real-time dynamic pressure correction data. The optoelectronic data fusion parachute aerodynamic testing method, by fusing optoelectronic data with environmental parameters to conduct aerodynamic testing research, can optimize the accuracy of parachute aerodynamic characteristic test data.

Description

Technical Field

[0001] The present application relates to the field of parachute testing, and in particular to a parachute aerodynamic testing method using optoelectronic data fusion. Background Art

[0002] A parachute is a highly efficient aerodynamic deceleration device that provides drag, lift, and stability, and is widely used in aerospace. Parachutes are made of flexible, air-permeable fabric and undergo rapid structural deformation during deployment. Consequently, the physical phenomena involved, such as the flow characteristics around the canopy, the interaction between the payload and parachute system, and the pressure distribution of the parachute's dynamic loads, are highly complex. Understanding the parachute's operating mechanism is crucial for explaining aerodynamic phenomena such as canopy inflation "breathing" and base vibration. Practice has proven that theoretical research is unable to accurately calculate the parachute's operating mechanism. Wind tunnel testing, using instruments or measurement devices, can be used to measure parachute aerodynamic forces and flow fields, such as the six components of aerodynamic force, pressure distribution, and flow velocity around the canopy. From a theoretical perspective, parachute aerodynamic drag, one of its core technical indicators, is primarily composed of four components: friction drag, pressure differential drag, wave drag, and induced drag. While induced drag is nonexistent for a typical axisymmetric parachute, the parafoil's similar shape to a wing generates induced drag during descent, just as a wing does. The magnitude of the resistance generated by a parachute when moving in the air is related to factors such as movement speed, air density, object shape and geometric dimensions. Its aerodynamic parameters are mainly expressed by resistance characteristics.

[0003] At present, when various wind tunnel research and testing units or other universities in China carry out conventional parachute aerodynamic tests, they usually connect force sensors or various professional force balances to a single-pole device or a tensioning connection device, and then connect the parachute's connecting rope ring to the force balance or the load connector of the force sensor. The wind tunnel is used to establish dynamic pressure on the parachute canopy, and then the force sensor or professional force balance senses the parachute's aerodynamic force. The airflow air density parameter required for the dynamic pressure test and control process usually uses a quantitative value of 1.225kg / m 3, the dynamic pressure control mode generally adopts an open-loop motor steady speed control mode. In terms of data processing, the main work is to carry out tunnel wall interference correction, establish a rigid aerodynamic data conversion method, bracket interference correction and blockage factor correction, so that the parachute can obtain a purer aerodynamic force as much as possible. In fact, through the theoretical aerodynamic analysis of parachutes, it is found that due to the soft texture of parachutes and the large differences in parachute structures, the canopy flow field mostly presents a nonlinear aerodynamic coupling body, which will cause the wind tunnel airflow disturbance to change unsteadily, and the Reynolds number will also fluctuate with the fullness characteristics. Therefore, the conventional open-loop steady speed control method of wind tunnel dynamic pressure cannot eliminate the problem of large canopy flow velocity fluctuations due to the lack of a real-time correction dynamic pressure feedback link, resulting in a larger difference between the actual canopy dynamic pressure and the dynamic pressure felt by the pitot tube. In terms of data processing, in addition to the conventional data correction processing method mentioned above, since the wing parachute is a fully flexible structure and is only fixed by the parachute rope connection in the wind tunnel, the spatial position relationship of the wing parachute cannot be predetermined before the test. Moreover, during the wind test, the position of the wing parachute will change with the change of attitude or speed pressure. Accordingly, the position of the wing parachute moment reference point (the center of gravity of the wing parachute system and the 1 / 4 chord line of the longitudinal symmetry plane of the wing parachute, respectively) relative to the balance cannot be fixed like the rigid support of a rigid model. Affected by the flexible characteristics of the wing parachute, the parachute rope has a certain amount of lift after the wing surface is stressed, and the geometric relationship of the wing parachute connection state relative to the balance is non-steady. In addition, the angle sensor and the parachute rope have poor tracking performance. Under the influence of both, the data is inaccurate.

[0004] Therefore, a parachute aerodynamic test method is needed to improve the accuracy of aerodynamic tests and the repeatability of test data. Summary of the Invention

[0005] The purpose of this application is to provide a parachute aerodynamic test method using optoelectronic data fusion, which can optimize the accuracy of parachute aerodynamic characteristics test data to support parachute development and research.

[0006] This application is implemented as follows:

[0007] The present application provides a parachute aerodynamic test method using optoelectronic data fusion, comprising the following steps:

[0008] S1. Obtain atmospheric pressure, temperature and humidity data in the stable section of the wind tunnel;

[0009] S2. Based on the water vapor pressure distribution of the airflow in the stable section of the wind tunnel at saturation temperature, a mathematical model for real-time correction of dynamic pressure using multi-environmental parameter sensor data fusion technology is established;

[0010] S3. Establish a number of characteristic marking points representing the canopy shape on the canopy surface of the tested umbrella and calculate the spatial coordinates of the characteristic marking points;

[0011] S4. Establish the test space coordinate system: With the center of the bracket that fixes the parafoil in the wind tunnel test section as the coordinate system origin O, the direction downstream of the flow field as the positive direction of the X axis, and the vertically upward direction as the positive direction of the Y axis, establish a right-handed coordinate system O-XYZ. With the parafoil moment reference point as the wind axis system origin, determine different coordinates converted by aerodynamic forces: the balance coordinate system, the airflow coordinate axis system, the test parachute axis system, and the transition coordinate system. Calculate the test parachute's angle of attack in real time in the test parachute's coordinate system.

[0012] S5. Based on the actual frontal area of ​​the wind tunnel test parachute model and historical test data, the modal relationship between the rotational speed and wind speed under different blockage ratio conditions is developed. The input conditions of the PI control model are established based on different blockage ratios and the wind speed at the center of the test section. The proportional coefficient and integration time are optimized according to the transfer function principle of the PI controller to achieve the optimal state.

[0013] S7. Establish the dynamic pressure condition of the flow through the canopy of the test parachute according to step S2 and step S5. Then, based on the optical interpretation of the angle of attack of the test parachute and the force analysis of the aerodynamic torque sensed by the force measuring balance, convert the actual lateral aerodynamic force and longitudinal aerodynamic force of the test parachute. Calculate the aerodynamic torque coefficient of the test parachute based on the nominal geometric characteristics of the test parachute and the real-time dynamic pressure correction data.

[0014] In some optional embodiments, pressure sensors, temperature sensors, and humidity sensors are installed on the wall of the stable section of the wind tunnel to obtain atmospheric pressure, temperature, and humidity data of the stable section of the wind tunnel.

[0015] In some optional implementation schemes, when calculating the spatial coordinates of the feature marker points, the image point coordinates of the images synchronously taken by the cameras that meet the intersection conditions are interpreted respectively by the photogrammetric forward intersection method, and the spatial coordinates of the feature marker points are calculated according to the image point coordinates and the camera point coordinates according to the photogrammetric forward intersection method.

[0016] In some optional implementation schemes, when calculating the angle of attack of the test parachute in the coordinate system of the test parachute, the angle between the parachute ropes on the symmetry plane of the test parachute and the plane of the parachute rope fixing frame is calculated through the trigonometric function relationship using the spatial coordinate system data of the characteristic points according to the structural dimensions of the wing-shaped parachute, the balance and the parachute rope frame, and the geometric relationship between the parachute ropes and the chord length is used to calculate the angle of attack of the test parachute in real time.

[0017] In some optional implementation schemes, when establishing a dynamic pressure real-time correction mathematical model using multi-environmental parameter sensor data fusion technology, the dynamic pressure value of the wind tunnel test section is corrected in real time according to the following formula: Where: ρ 实 is the real-time density of airflow in the wind test section, kg / m 3 ; V A V is the wind speed on the left inner wall of the nozzle, m / s; B is the wind speed on the right inner wall of the nozzle, m / s; ΔP is the correction value of the dynamic pressure value of the test section.

[0018] In some optional embodiments, the real-time air density of the wind tunnel test section is 实 Calculated using the following formula:

[0019]

[0020] Where: ρ 实 is the real-time density of airflow in the wind tunnel test section, kg / m 3 ; P is the atmospheric pressure of the test section, kPa; T is the thermodynamic temperature of the test section, K; ψ is the relative humidity of the test section, %; P t is the partial pressure of water vapor in saturated air at the test section temperature t, Pa.

[0021] In some optional implementation schemes, the proportional coefficient and integral time are optimized to achieve the optimal state using the following formula based on the PI controller transfer function principle:

[0022]

[0023] Where: u(t) is the output signal of PI controller; K p is the proportional coefficient; e(t) is the PI controller input signal; T i is the integration time.

[0024] The beneficial effects of the present application are as follows: the parachute aerodynamic test method with optoelectronic data fusion provided in the present application establishes synchronous collection of optical data, velocity pressure and balance signals, and conducts refined aerodynamic test research based on data fusion technology through the fusion technology of optoelectronic data and environmental parameters, which can optimize the accuracy of parachute aerodynamic characteristics test data to support parachute development and research. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A schematic flow chart of a parachute aerodynamic testing method using optoelectronic data fusion provided in an embodiment of the present application;

[0027] Figure 2A schematic diagram of a coordinate system for measuring the angle of attack of an airfoil parachute in real time using the optical intersection measurement method and the plane of the parachute fixing frame on the symmetric plane of the airfoil parachute in the optoelectronic data fusion parachute aerodynamic testing method provided in an embodiment of the present application, utilizing the geometric relationship between the parachute lines and the airfoil chord length;

[0028] Figure 3 The PI control parameter is adjusted to K for the parachute aerodynamic test method of photoelectric data fusion provided in the embodiment of the present application. p =0.6 and T i =1.5 when adjusting the tracking curve of the output effect;

[0029] Figure 4 Schematic diagram of optical coordinate marker points used for longitudinal aerodynamic data conversion of parafoil;

[0030] Figure 5 Schematic diagram of optical coordinate marker points used for lateral aerodynamic data conversion of parafoil;

[0031] Figure 6 The parachute aerodynamic test method using optoelectronic data fusion provided in the embodiment of the present application obtains aerodynamic parameters of a parafoil axis system;

[0032] Figure 7 This is a schematic diagram of the trend of the lift and drag characteristics of the parafoil changing with the angle of attack in existing wind tunnel tests at home and abroad. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0034] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.

[0035] The features and performance of the parachute aerodynamic testing method using optoelectronic data fusion of the present application are further described in detail below in conjunction with the embodiments.

[0036] like Figure 1 As shown, the embodiment of the present application provides a parachute aerodynamic test method using optoelectronic data fusion, comprising the following steps:

[0037] S1. Install pressure sensors, temperature sensors, and humidity sensors on the walls of the stable section of the wind tunnel, install a high-definition high-speed camera to capture images of the canopy of the test parachute in the wind tunnel test section, install a pitot tube and corresponding differential pressure sensors on the walls on both sides of the wind tunnel test section, connect the trigger end of the time-controlled device to the aerodynamic force collector and the trigger signal end of the high-definition high-speed camera, and connect the differential pressure sensor to the speed and pressure controller; obtain environmental parameter data such as atmospheric pressure, temperature, and humidity of the stable section of the wind tunnel collected in real time by the pressure sensor, temperature sensor, and humidity sensor, and fix the canopy of the test parachute in the wind tunnel test section using a bracket;

[0038] S2. Based on the water vapor pressure distribution of the airflow in the stable section of the wind tunnel at saturation temperature, a mathematical model for real-time correction of dynamic pressure using multi-environmental parameter sensor data fusion technology is established;

[0039] During a wind tunnel test, the temperature inside the tunnel will rise by 3°C / h due to the prolonged friction between the airflow and the tunnel wall. Calculated based on 100 train trips, a six-hour working time will cause the temperature to rise by 18°C. Based on the distribution of water vapor pressure at saturated temperature, the air density and humidity in the test section will vary significantly, with statistics showing a humidity change of 20%. These environmental parameter changes result in a maximum difference of 15% in the corresponding dynamic pressure values ​​(relative to standard air conditions). Therefore, in order to obtain a more accurate approach to studying the correction of dynamic pressure under variable air density conditions, it is necessary to conduct technical research through theoretical calculations of specific environmental parameters.

[0040] The dynamic pressure value of the wind tunnel test section is corrected in real time according to the following formula: Where: ρ 实 is the real-time density of the airflow in the test section, kg / m 3 ; V A V is the wind speed on the left inner wall of the nozzle, m / s; B is the wind speed on the right inner wall of the nozzle, m / s; ΔP is the correction value of the dynamic pressure value of the test section.

[0041] The atmospheric pressure, temperature, and relative humidity of the test section are measured by the corresponding sensors installed in the wind tunnel. The partial pressure of water vapor in the saturated air at the test section temperature t is obtained by subtracting the temperature measured in the stable section and the data in Table 1. The real-time air density ρ of the test section is calculated using the following formula: 实 :

[0042]

[0043] Where: ρ 实 is the real-time density of the airflow in the test section, kg / m 3 ; P is the atmospheric pressure of the test section, kPa; T is the thermodynamic temperature of the test section, K; ψ is the relative humidity of the test section, %; P tis the partial pressure of water vapor in saturated air at the test section temperature t, Pa.

[0044] Table 1 Water vapor pressure data at saturation temperature (typical)

[0045]

[0046] The inner walls of sections A and B on both sides of the wind tunnel test section are the airflow boundaries. Considering that energy loss is mainly caused by friction between the airflow and the wind tunnel wall, the Bernoulli equation is applied to sections A and B to obtain the formula:

[0047]

[0048] Where: P B , P A are the static pressure values ​​of sections B and A on both sides of the wind tunnel test section, Pa; V B , V A are the wind speeds at sections B and A on both sides of the wind tunnel test section, m / s; ρ 实 is the real-time air density of the wind tunnel airflow, kg / m 3 ;K BA is the energy loss coefficient between section B and section A.

[0049] During the wind blowing test, the static pressure drop method is used to measure the static pressure drop of the inner wall of section A and the inner wall of section B on both sides of the wind tunnel test section and the real-time air density of the test section. The wind speed corresponding to the corrected dynamic pressure at the center point of the wind tunnel test section can be calculated in real time.

[0050] S3, such as Figure 4 and Figure 5 As shown, a number of characteristic marking points representing the canopy shape are established on the canopy surface of the test umbrella, and the spatial coordinates of the characteristic marking points are calculated; optionally, when calculating the spatial coordinates of the characteristic marking points, the image point coordinates of the images synchronously taken by the cameras that meet the intersection conditions are interpreted respectively by the photogrammetric forward intersection method, and the spatial coordinates of the characteristic marking points are calculated according to the image point coordinates and the camera station coordinates according to the photogrammetric forward intersection method.

[0051] S4. The atmospheric pressure, temperature, and humidity data signals collected by the pressure sensor, temperature sensor, and humidity sensor in the stable section of the wind tunnel are divided into two channels. One channel is connected to and input into the velocity pressure controller, and the other channel is connected to and input into the aerodynamic force collector. The time reference signal is unified, and the signal emitted by the time reference device is used as the test time zero point.

[0052] S5. Establish the test space coordinate system: take the center of the bracket of the fixed parafoil in the wind tunnel test section as the coordinate system origin O, the direction of the downstream field as the positive direction of the X axis, and the vertical upward direction as the positive direction of the Y axis to establish a right-handed coordinate system O-XYZ, and take the parafoil moment reference point as the wind axis origin to determine different coordinates converted by aerodynamic force: balance coordinate system, airflow coordinate axis system (wind axis system), test parafoil axis system and transition coordinate system. Use two cameras to synchronously shoot two digital images of the same scene from different angles, and construct a three-dimensional image based on the internal and external parameters and positional relationship of the two calibrated high-speed cameras. For the spatial geometric model of beam delivery, the three-dimensional coordinates of the parachute marking points in the scene are calculated, and then the angle of attack of the test parachute is further derived in real time in the coordinate system of the test parachute; wherein, the reference point of the wing parachute moment is the center of gravity of the parachute system, which changes with the change of the wing angle of attack; optionally, when calculating the angle of attack of the test parachute in the coordinate system of the test parachute, the angle between the parachute rope of the symmetry plane of the test parachute and the plane of the parachute rope fixing frame is calculated through the trigonometric function relationship through the spatial coordinate system data of the feature points, and the geometric relationship between the parachute rope and the chord length is used to calculate the angle of attack of the test parachute in real time.

[0053] The force balance is connected to the parachute rope fixing frame through the upper cover, and is connected to the angle adjustment mechanism on the bottom wall of the wind tunnel test section through the lower cover. When installing, ensure that the center of the balance coincides with the projection point of the parafoil theoretical torque reference point on the parachute rope fixing frame as much as possible. Figure 2 In the process, the optical "intersection measurement method" is used to measure the angle between the parachute rope on the symmetry plane of the airfoil parachute and the plane of the parachute rope fixing frame in real time, and the geometric relationship between the parachute rope and the airfoil chord length is used to calculate the airfoil parachute angle of attack in real time.

[0054] The coordinates of the reference point of the wing parachute moment, i.e. the origin of the wind axis system: O p X p Y p Z p is the balance coordinate system, OX q Y q Z q is the airflow coordinate axis system (wind axis system), O p X q Y q Z q is the body axis, OX b Y b Z b is the transition coordinate system.

[0055] Balance change a c When the angle between the wing-shaped parachute line and the balance plane is θ A becomes θ A ', but θ A '-θ A ≠a c In O p X bY b Z b In the coordinate system, according to the structural dimensions of the wing parachute, balance and parachute rope frame, the formula for the actual angle of attack of the wing parachute can be obtained:

[0056] According to the distance from the real-time torque reference point to points C and D in the optical test coordinate system and the structural geometric relationship, the coordinates (x, y, z) of point O can be obtained.

[0057] From the cosine theorem we get:

[0058]

[0059] From the law of sine we get:

[0060]

[0061] Therefore, we can get:

[0062]

[0063] O P x b y b z b The coordinate system rotates to O P x q y q z q Coordinate system, the coordinates of point O are:

[0064]

[0065] Subtract the calculated balance load from the bracket test result to get the result of deducting the interference of the single bracket. P x p y p z p Rotate to O P x q y q z q Axis system. The rotation transformation formula is as follows:

[0066] Y=Y P cosα C -X P sinα C ;

[0067] X=(X P cosα C +Y P sinα C )cosβ c -Z p sinβ c ;

[0068] M Z =M ZP cosβ c +(M yp sinα C -M xp cosβ c )sinβ c ;

[0069] Z=Z P cosβ c +(X P cosα C +Y P sinα C )sinβ c ;

[0070] M y =M yP cosα C +M xp sinα C ;

[0071] M x =(M xp cosα C -M yp sinα C )cosβ z +M zp sinβ c ;

[0072] Translate the load to the wind axis system with O(x0, y0, z0) as the moment reference point.

[0073] Y q1 =Y;

[0074] X q1 =X;

[0075] Z q1 =Z;

[0076] M zq1 =M Z -Y·x0-X·y0;

[0077] M yq1 =M y +Z·x0+X·z0;

[0078] M xq1 =M x +Y·z0-Z·y0;

[0079] According to the requirements of the parafoil test, the test results are given in the form of aerodynamic coefficients, and the calculation formula is as follows:

[0080]

[0081] In the above formula: α is the real-time attack angle of the parafoil; α c is the balance tilt angle; q is the real-time correction dynamic pressure of the data; s is the nominal area of ​​the tested parachute, b is the span, and c is the chord length; C Lw ,C Dw ,C mw ,C yw ,C nw ,C lw are the parachute lift coefficient, parachute drag coefficient, parachute pitch moment coefficient, parachute side force coefficient, parachute yaw moment coefficient, and parachute rolling torque coefficient after data fusion processing; X p , Y p , Z p , M xp , M yp , M zp are the drag, lift, lateral force, rolling torque, yaw moment, and pitch moment directly measured by the balance; X q1 , Y q1 , Z q1 , M xq1 , M yq1 , M zq1 They are respectively the resistance, lift, lateral force, rolling torque, yaw moment, and pitch moment of the wind axis system after the load is translated; X, Y, Z, M x , M y , M z The drag, lift, lateral force, rolling torque, yaw moment, and pitch moment of the wind axis after the original data of the balance are rotated and converted; β c Turn the balance; ∠O p AB; ∠O p BA;θ A θ is the angle between the leading edge of the parachute line and the plane of the balance before the balance is adjusted; A ' is the angle between the leading edge of the parachute line and the plane of the balance after the balance is adjusted; θ B is the angle between the trailing edge parachute line and the balance plane; X C , Y C , X D , Y D are the horizontal and vertical coordinates of points C and D in the parafoil body axis system respectively; AB, CD, AD, BC, OD, O p A, O P B etc. are corresponding known geometric lengths in plane ABCD.

[0082] S6. Based on the actual frontal area of ​​the wind tunnel test parachute model and historical test data, the modal relationship between the rotational speed and wind speed under different blockage ratio conditions is developed. The input conditions of the PI control model are established based on different blockage ratios and the wind speed at the center of the test section. The proportional coefficient and integration time are optimized according to the transfer function principle of the PI controller to achieve the optimal state.

[0083] During wind tunnel testing, whether it is a static force test or a dynamic parachute opening load test, different blockage ratios exist due to the limitations of the wind tunnel nozzle size. The blockage ratio is calculated as shown in the following formula.

[0084]

[0085] Where: S 模型 is the frontal area during the test, m 2 ;S 喷口 is the cross-sectional area of ​​the nozzle, m 2 .

[0086] Based on the actual frontal areas of wind tunnel test parachutes or models and historical test data, the blockage ratios currently experienced by wind tunnel test parachutes or models range from 3%, 5%, 10%, and 12%. When analyzing and resolving the modal relationship between rotational speed and wind speed under different blockage ratios, these commonly used blockage ratios and the wind speed (VC) at the center of the test section were used to establish the input conditions for the PI control model. Based on the transfer function principle of the PI controller, the proportional coefficient and integral time were optimized to achieve the optimal state.

[0087] The control parameters for low-speed wind tunnel airflow are: 1) fan motor speed; 2) wind speed (speed and pressure). The fan speed control system consists of a motor, power supply, speed measurement equipment, and a frequency converter. A variable frequency speed control system is used to control the main circuit control scheme for the AC asynchronous motor driving the fan blades. A rotary encoder mounted on the motor output shaft and a high-precision speed and pressure sensor installed in the wind tunnel test section provide feedback signals for motor speed and speed and pressure, respectively. The central control room host computer, through a programmable controller, implements fully digital dual-closed-loop control for stable speed and pressure.

[0088] The speed and pressure regulator uses a classic PI controller. PI control refers to the control deviation between the given value and the actual output value. The proportional and integral of the deviation are linearly combined to form the control quantity to control the controlled object. The control formula for optimizing the proportional coefficient and integral time to achieve the optimal state based on the transfer function principle of the PI controller is shown in the following formula:

[0089]

[0090] Where: u(t) is the output signal of PI controller; K p is the proportional coefficient; e(t) is the PI controller input signal; T iis the integration time; t is the time.

[0091] Among them, K p and T i It can be adjusted as needed to achieve the ideal control effect.

[0092] S7. Establish the dynamic pressure condition of the flow through the canopy of the test parachute according to step S2 and step S6. Then, based on the optical interpretation of the test parachute's angle of attack and the force analysis of the aerodynamic torque sensed by the force measuring balance, convert the actual lateral aerodynamic force and longitudinal aerodynamic force of the test parachute. Calculate the aerodynamic torque coefficient of the test parachute based on the nominal geometric characteristics of the test parachute and the real-time dynamic pressure correction data.

[0093] The optoelectronic data fusion parachute aerodynamic testing method provided in this application embodiment utilizes an innovative synchronous acquisition and control system for optical data, velocity, pressure, and balance signals. By integrating optoelectronic data with environmental parameters, a novel aerodynamic force conversion data processing method and a dual closed-loop dynamic pressure control method are proposed. This method further enhances the research on refined aerodynamic force testing based on data fusion technology. The results achieved are intended to further optimize the accuracy of parachute aerodynamic characteristic test data to support model development and related research.

[0094] The wing parachute described in this application is a wing-type parachute, that is, a tested parachute.

[0095] Example 1

[0096] Using the parachute aerodynamic testing method using optoelectronic data fusion provided in the aforementioned embodiments of this application, a steady-state dynamic pressure control system based on PI control technology and a real-time dynamic pressure correction technique based on multi-environmental parameter sensor data fusion were established. The method also included real-time fusion processing of aerodynamic and optoelectronic data. Wind speed and drag characteristic data were obtained for the stabilized parachute under both unsteady dynamic pressure and steady dynamic pressure conditions at wind speeds between 30m / s and 80m / s. The test data were summarized and analyzed, indicating a reduction in the fluctuation of the drag characteristic.

[0097] According to actual records, the corresponding data of wind speed and rotation speed under different wind tunnel blockage ratios are shown in Table 2.

[0098] Table 2 Corresponding data of wind speed and rotation speed under different blockage ratio conditions

[0099]

[0100] As can be seen from the table above, within the low wind speed range (0m / s to 30m / s), the wind speed ratio varies greatly, with an average of approximately 6. Within the common speed range (30m / s to 70m / s), the wind speed ratio is approximately 5.8 on average. Within the high wind speed range (70m / s to 100m / s), the wind speed ratio is approximately 5.7 on average. Input the above data into the PLC steady wind speed control module.

[0101] Adjusting PI control parameters (proportional coefficient, integral time) can effectively adjust the output effect of PI controller, thereby achieving the purpose of stable control. According to the transfer function principle of PI controller, increasing the proportional coefficient K p It can improve the system tracking speed, but if the proportional coefficient is too large, it will cause system oscillation; increase the integral time T i It can reduce the hysteresis of the integral and the overshoot, but when the integral time is too long, the system will slow down the error elimination. Therefore, first set the PI parameter to (K p =0.6, T i =1.5) to obtain the tracking curve as Figure 3 As shown:

[0102] Depend on Figure 3 The middle curve shows that the overall performance of the test parachute system has been greatly improved, without obvious overshoot and oscillation, and basically meets the requirements. Through subsequent continuous optimization, the control parameters of the PI controller are finally determined to be (K p =0.1, T i =2.9), write this parameter into the corresponding control module of PLC.

[0103] After setting the PI control parameters, we adjusted the wind tunnel control system's steady wind speed control function. We set a number of different wind speeds for a stabilized parachute test and examined the tracking performance to determine whether the parameters and accuracy met the required specifications. Finally, we obtained the tracking results for each wind speed condition, as shown in Table 3.

[0104] Table 3 Wind speed control accuracy debugging results

[0105] Serial number Set wind speed (m / s) Actual wind speed with unsteady dynamic pressure (m / s) Actual wind speed at steady dynamic pressure (m / s) 1 20 19.88～20.05 19.98～20.05 2 30 29.86～30.03 29.96～30.03 3 40 39.85～40.03 39.95～40.03 4 45 44.87～45.04 44.97～45.04 5 50 49.78～50.04 49.98～50.04 6 60 59.65～60.02 59.95～60.02 7 65 64.86～65.04 64.96～65.04 8 70 69.84～70.06 69.94～70.06 9 80 79.73～80.03 79.93～80.03

[0106] The angle between the parachute rope and the parachute rope fixing frame plane on the symmetrical surface of the airfoil is measured in real time by using the optical “intersection measurement method”. Figure 2 The geometric relationship coordinate points of the parachute rope and the chord length of the airfoil are marked, and the angle of attack of the parafoil is calculated in real time. In this process, it is assumed that the airfoil is kept in good condition, the chord length is unchanged, the parachute rope is stiff, and small deformation is not considered. Then, the aerodynamic parameters of the body axis system at two typical center of mass of the parafoil are processed using the photoelectric data processing formula. Figure 6 The typical characteristic coordinate point data are shown in Table 4.

[0107] Table 4 Coordinates of typical aerodynamic conversion characteristic points of single-layer parafoil

[0108]

[0109] Analysis of the above Figure 6 and Figure 7 As can be seen from the images and test data in Table 4, the lift characteristic curves of parafoils in wind tunnel tests both domestically and internationally show a consistent trend with angle of attack. They all increase approximately linearly and then slowly decrease as the angle of attack increases. At the same angle of attack, the single-layer parafoil has a greater lift coefficient and better lift characteristics. The pitching moment coefficients of both parafoils generally fluctuate around 0. The drag characteristic curves of the parafoils obtained in the wind tunnel tests of this application maintain a consistent trend, essentially achieving the optimization research effect.

[0110] To address the issue of inaccurate conversion of balance aerodynamic data due to the non-fixed moment reference point during parafoil wind tunnel testing, key research approaches were proposed, including optoelectronic time-scaling acquisition and real-time fusion processing of optoelectronic data. Using a single-layer parafoil as the test object, the team constructed a high-precision six-component balance test system, a high-definition camera system, a time-scaling system, and a real-time dynamic pressure correction system. The data obtained conformed to aerodynamic laws, providing data support for the optimized design of the aerodynamic characteristics of single-layer parafoils and an important reference for research on parafoil wind tunnel testing technology.

[0111] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A parachute aerodynamic test method using optoelectronic data fusion, characterized in that: The following steps are involved: S1. Obtain atmospheric pressure, temperature and humidity data in the stable section of the wind tunnel; S2. Based on the water vapor pressure distribution of the airflow in the stable section of the wind tunnel at saturation temperature, a mathematical model for real-time correction of dynamic pressure using multi-environmental parameter sensor data fusion technology is established; S3. Establish a number of characteristic marking points representing the canopy shape on the canopy surface of the tested umbrella and calculate the spatial coordinates of the characteristic marking points; S4. Establish the test space coordinate system: With the center of the bracket that fixes the parafoil in the wind tunnel test section as the coordinate system origin O, the direction downstream of the flow field as the positive direction of the X axis, and the vertically upward direction as the positive direction of the Y axis, establish a right-handed coordinate system O-XYZ. With the parafoil moment reference point as the wind axis system origin, determine different coordinates converted by aerodynamic forces: the balance coordinate system, the airflow coordinate axis system, the test parachute axis system, and the transition coordinate system. Calculate the test parachute's angle of attack in real time in the test parachute's coordinate system. S5. Based on the actual frontal area of ​​the wind tunnel test parachute model and historical test data, the modal relationship between the rotational speed and wind speed under different blockage ratio conditions is developed. The input conditions of the PI control model are established based on different blockage ratios and the wind speed at the center of the test section. The proportional coefficient and integration time are optimized according to the transfer function principle of the PI controller to achieve the optimal state. S6. Establish the dynamic pressure condition of the flow through the canopy of the test parachute according to step S2 and step S5. Then, based on the optical interpretation of the angle of attack of the test parachute and the force analysis of the aerodynamic torque sensed by the force measuring balance, convert the actual lateral aerodynamic force and longitudinal aerodynamic force of the test parachute. Calculate the aerodynamic torque coefficient of the test parachute based on the nominal geometric characteristics of the test parachute and the real-time dynamic pressure correction data.

2. The method for parachute aerodynamic testing based on optoelectronic data fusion according to claim 1, characterized in that: Pressure sensors, temperature sensors and humidity sensors are installed on the wall of the stable section of the wind tunnel to obtain atmospheric pressure, temperature and humidity data of the stable section of the wind tunnel.

3. The parachute aerodynamic test method based on optoelectronic data fusion according to claim 1, characterized in that: When calculating the spatial coordinates of the feature marker points, the image point coordinates of the images synchronously taken by the cameras that meet the intersection conditions are interpreted respectively by the photogrammetric forward intersection method, and the spatial coordinates of the feature marker points are calculated according to the image point coordinates and the camera station coordinates according to the photogrammetric forward intersection method.

4. The parachute aerodynamic test method based on optoelectronic data fusion according to claim 1, characterized in that: When calculating the angle of attack of the test parachute in the coordinate system of the test parachute, the angle between the parachute rope on the symmetry plane of the test parachute and the plane of the parachute rope fixing frame is calculated through the trigonometric function relationship using the structural dimensions of the airfoil parachute, the balance and the parachute rope frame through the spatial coordinate system data of the characteristic points, and the angle of attack of the test parachute is calculated in real time using the geometric relationship between the parachute rope and the chord length.

5. The method for parachute aerodynamic testing based on optoelectronic data fusion according to claim 1, characterized in that: When establishing a mathematical model for real-time correction of dynamic pressure using multi-environmental parameter sensor data fusion technology, the dynamic pressure value of the wind tunnel test section is corrected in real time according to the following formula: Where: ρ 实 is the real-time density of airflow in the wind tunnel test section, kg / m 3 ; V A is the wind speed on the left inner wall of the nozzle, m / s; V B is the wind speed on the right inner wall of the nozzle, m / s; ΔP is the correction value of the dynamic pressure value of the test section.

6. The method for parachute aerodynamic testing based on optoelectronic data fusion according to claim 5, characterized in that: The real-time density of airflow in the wind tunnel test section ρ 实 Calculated using the following formula: Where: ρ 实 is the real-time density of airflow in the wind tunnel test section, kg / m 3 ; P is the atmospheric pressure of the test section, kPa; T is the thermodynamic temperature of the test section, K; ψ is the relative humidity of the test section, %; P t is the partial pressure of water vapor in saturated air at the test section temperature t, Pa.

7. The method for parachute aerodynamic testing based on optoelectronic data fusion according to claim 1, characterized in that: According to the PI controller transfer function principle, the following formula is used to optimize the proportional coefficient and integral time to achieve the best state: Where: u(t) is the output signal of PI controller; K p is the proportional coefficient; e(t) is the PI controller input signal; T i is the integration time.

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