A method for measuring the level of a high-aspect-ratio flexible aircraft

Abstract

The application discloses a large-aspect-ratio flexible airplane horizontal measurement method, which sequentially measures positions of points of a fuselage, a wing and a tail in a gravity coordinate system (O XYZ1 ); then, based on a least square fitting method, differences between the points 1L, the points 1R, the points A and the points B in a gravity direction caused by large-aspect-ratio flexible deformation are isolated, and a scale parameter λ, a rotation parameter matrix R and a translation parameter T obtained through fitting calculation are used to construct an optimal fitting coordinate system (O XYZ2 ). All point coordinate (X1, Y1, Z1) of the airplane in the gravity coordinate system (O XYZ1 ) is sequentially converted into the fitting coordinate system (O XYZ2 ), and fitted point coordinate (X2, Y2, Z2) is obtained, so that the fitted result is more in line with the actual situation, and global deformation is identified. The application sets a weight fitting method in the airplane horizontal measurement process starting from isolating inherent deformation, reduces the overall fitting deviation, and makes the fitted result more in line with the actual situation, so that the horizontal measurement can be more accurate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft level measurement, and particularly relates to a large aspect ratio flexible aircraft level measurement method. BACKGROUND

[0002] Aircraft level measurement is an inspection of relative positions of various components of an aircraft, installation quality of components, and deformation of the components in use. With the rapid development of national advanced manufacturing industry, large equipment size and appearance measurement is faced with problems such as large measurement space, high relative precision requirement, and complex measured features. Laser tracker is one of the most effective means for large size measurement. For large rigid equipment, a multi-station measurement or a combination measurement of multiple measurement systems is often used. Common observation of public points by measurement instruments at different stations is performed, the respective measurement data is converted to the same coordinate system, and then full size fitting is performed according to the selection of key feature points, so as to effectively identify global deformation.

[0003] However, for flexible aircraft with small wings, such as solar energy and hydrogen energy, the whole machine has large relative deformation and unknown change amount, and there is local deformation near the key feature points which is not accurately identified in advance. When full machine measurement and analysis are performed, the traditional rigid body data processing method cannot effectively isolate the inherent deviation in global analysis, and the fitting error is transmitted to the final analysis result, which is easy to cause obvious incorrect analysis direction and conclusion which does not conform to the actual situation. SUMMARY

[0004] The application aims to provide a large aspect ratio flexible aircraft level measurement method, and aims to solve the above problems, reduce the deviation of flexible aircraft level measurement data analysis, and lay a foundation for analyzing the conclusion conforming to the actual situation.

[0005] The application is mainly realized by the following technical scheme:

[0006] A large aspect ratio flexible aircraft level measurement method comprises the following steps:

[0007] Step S1: in a theoretical coordinate system (O XYZ0 ), symmetrical key fitting points are selected in the lateral direction and the longitudinal direction of the aircraft respectively as lateral reference leveling points and longitudinal reference leveling points; the key fitting points are rigid points in the wing and landing gear connection area;

[0008] Step S2: a laser tracker is used to build a station, an original gravity coordinate system (O XYZ1 ) is established, and the Z-axis direction is consistent with the gravity direction; then, lateral leveling and longitudinal leveling are respectively performed based on the lateral reference leveling points and the longitudinal reference leveling points;

[0009] Step S3: the gravity coordinate system (OXYZ1 ) each point position; then, based on the least square fitting method, isolate the difference between point 1L, point 1R, point A, point B in the direction of gravity due to large aspect ratio flexible deformation, fitting calculation of the scale parameter λ, rotation parameter matrix R and translation parameter T, to construct the best fitting coordinate system (O XYZ2 ) :

[0010]

[0011] Wherein: (X1, Y1, Z1) is the coordinate in the gravity coordinate system (O XYZ1 ) ;

[0012] (X2, Y2, Z2) is the coordinate in the best fitting coordinate system (O XYZ2 ) ;

[0013] Step S31: first scale parameter λ solving;

[0014] According to the set of weights (P X , P Y , P Z ), using formula (2) to the theoretical coordinate system (O XYZ0 ) in the key fitting point coordinates of gravity center processing, the same reason for the corresponding point in the gravity coordinate system (O XYZ1 ) gravity center processing, converted to the respective gravity center as the origin of the gravity center coordinates, then, according to formula (3) to calculate the scale parameter λ:

[0015]

[0016] Wherein: (X0, Y0, Z0) is the coordinate in the theoretical coordinate system (O XYZ0 ) ;

[0017] The average value of each key fitting point coordinate in the theoretical coordinate system (O XYZ0 ) ;

[0018] The average value of each key fitting point coordinate in the gravity coordinate system (O XYZ1 ) ;

[0019] Step S32: solving the rotation parameter matrix R;

[0020] The rotation parameter matrix R is a three order orthogonal matrix, and |R| = 1, then R is expressed as formula (4) through the parameters containing a, b, c, respectively into the theoretical coordinate system (O XYZ0 ) and the gravity coordinate system (O XYZ1) in the key fitting point barycentric coordinates, and the equation formula (5) and formula (6) formed after the key fitting point barycentric coordinates are obtained, a, b and c can be calculated according to formula (7), and then R can be obtained from formula (4):

[0021]

[0022] Step S33: translation parameter T solving is performed;

[0023]

[0024] Wherein: (X T , Y T , Z T ) is the translation vector solved;

[0025] Step S4: the best fitting coordinate system (O XYZ2 ) is constructed, and the coordinates (X1, Y1, Z1) of all points of the aircraft in the gravity coordinate system (O XYZ1 ) are converted into the fitting coordinate system (O XYZ2 ) in turn, so that the fitting point coordinates (X2, Y2, Z2) are obtained, the fitting result is more in line with the actual situation, and global deformation is identified;

[0026]

[0027] In order to better realize the present application, further, in step S31, in order to reduce process iteration, when the aircraft is horizontally measured, λ=1.

[0028] In order to better realize the present application, further, in step S1, in the theoretical coordinate system (O XYZ0 ), two horizontal reference leveling points 1L and 1R close to the landing gear and symmetrical on the left / right wing are selected; in the theoretical coordinate system (O XYZ0 ), two longitudinal reference leveling points A and B on the fuselage and close to the frame beam of the wing leading edge are selected.

[0029] In order to better realize the present application, further, two horizontal reference leveling points are selected within 0.5m around the frame and beam; two longitudinal reference leveling points are selected within 0.5m around the frame beam on the fuselage and close to the wing leading edge.

[0030] To better realize the present application, further, in step S2, during lateral leveling, the left / right landing gear height is adjusted, the gravity direction coordinates of point 1L and point 1R are repeatedly observed, and the lateral horizontal adjustment target is that the height difference between point 1L and point 1R is ±Emm, E is a design allowable error. Specifically, the height difference between point 1L and point 1R is Hmm±Emm, H is 0 due to the symmetry of point 1L and point 1R, and E is an error allowed by a designer, which is generally 0.5.

[0031] To better realize the present application, further, in step S2, during longitudinal leveling, the front landing gear height is adjusted, the gravity direction coordinates of point A and point B are repeatedly observed, and the longitudinal horizontal adjustment target is that the height difference between point A and point B is Jmm±Emm, J represents a theoretical height difference between point A and point B, which is given by digital model measurement; and E is a design allowable error. Specifically, E is an error allowed by a designer, which is generally 0.5.

[0032] To better realize the present application, further, in step S2, before horizontal measurement, a state check is carried out by comparing a theoretical digital model state, so as to ensure that there is no factor affecting horizontal measurement and that there is no significant air flow near the aircraft.

[0033] To better realize the present application, further, in step S4, by comparing the differences between the points (X2, Y2, Z2) in the best fitting coordinate system (O XYZ2 ) and the points (X0, Y0, Z0) in the theoretical coordinate system (O XYZ0 ), the absolute deformation amount is obtained.

[0034] The beneficial effects of the present application are as follows:

[0035] (1) The present application establishes and systematically refines a complete set of methods for horizontal measurement of flexible large-aspect-ratio aircraft in combination with engineering practice. The traditional fitting method deviates from the actual situation due to the influence of flexible large deformation. To make up for the shortcomings of the prior art and reduce the analysis deviation of flexible aircraft measurement data, the present application proposes a weight fitting method in the process of aircraft horizontal measurement starting from isolating inherent deformation, the target is to reduce the overall fitting deviation, so that the result after fitting is more in line with the actual situation, and the horizontal measurement can be more accurate.

[0036] (2) A large number of tests are carried out on solar unmanned aircraft, hydrogen energy unmanned aircraft, unmanned glider, etc. by using the present application, and the processed results are in line with the actual situation through comparative analysis, which provides an important basis for precise control of large-aspect-ratio flexible unmanned aircraft. The present application considers the influence of deformation, and the thought can be popularized to the measurement of other large flexible objects and wide-area geographic survey, which is helpful for precise mapping. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A flow chart of a horizontal measurement method for a high aspect ratio flexible aircraft.

[0038] Figure 2 A point position diagram of key fitting feature points;

[0039] Figure 3 A Figure 2 A bottom view of key fitting feature points;

[0040] Figure 4 A schematic diagram of adjusting the height of the front and main landing gears respectively by using lifting pallets;

[0041] Figure 5 Point position information of key fitting feature points measured in the gravity coordinate system;

[0042] Figure 6 A fitting schematic diagram of each point in Example 1. DETAILED DESCRIPTION

[0043] Example 1:

[0044] A horizontal measurement method for a high aspect ratio flexible aircraft, as shown in Figure 1 , the specific steps are as follows:

[0045] a) Clearly define the purpose of horizontal measurement of high aspect ratio aircraft: focus on checking the symmetry of the aircraft, for flexible high aspect ratio configuration aircraft, the symmetry of the wing under symmetrical load needs to be measured and checked, in order to exclude the influence of deformation near the landing gear or support point position during the process of supporting the wing, the key fitting points are selected near the rigid points (such as near the frame and beam) of the wing and landing gear connection area, and the height difference of the key fitting points needs to be kept the same during measurement;

[0046] b) Selection and marking of key fitting feature points for horizontal adjustment of aircraft: since the main purpose of measurement is to predict the symmetry of the aircraft in the air, the focus of observation is the wing, in order to maximize the exclusion of the influence of tire displacement on the symmetry of the wing during the adjustment stage, two horizontal reference adjustment points are selected near the landing gear and in the rigid position (within 0.5m from the frame and beam) of the left / right wing symmetry, as shown in Figure 2 and Figure 3 , point 1L and point 1R in the theoretical coordinate system (O XYZ0 ).

[0047] c) Selection and marking of key fitting feature points for longitudinal adjustment of aircraft: in order to ensure safety when the aircraft is parked, the longitudinal position of the center of gravity of the whole aircraft needs to be adjusted as horizontal as possible, therefore, for longitudinal adjustment of flexible aircraft, the scheme is preferably to set two longitudinal reference adjustment points within 0.5m near the frame and beam near the leading edge of the wing on the fuselage, as shown inFigure 2 and Figure 3 As shown in FIG. 1, the point A and the point B in the theoretical coordinate system (O XYZ0 ).

[0048] d) Physical state confirmation: Before the horizontal measurement, the state is checked against the theoretical model state to ensure that there are no factors affecting the horizontal measurement. Measures such as closing doors and windows, air conditioners, and fans are taken to keep the air flow around the aircraft insignificant; if the aircraft is not in the same state as the theoretical model state, the measurement is invalid. Figure 4 As shown in FIG. 2, the height of the front landing gear and the main landing gear is adjusted using lifting trays and other tools.

[0049] e) Using a laser tracker to build a station, an original gravity coordinate system (O XYZ1 ) is established, so that the gravity direction coincides with the Z direction;

[0050] f) Transverse and longitudinal leveling: the height of the left / right landing gear is adjusted using a lifting tray, and the gravity direction coordinates of point 1L and point 1R are repeatedly observed. The transverse horizontal adjustment target is that the difference between point 1L'(Z) and point 1R'(Z) is 0 mm ± XX mm. The height of the front landing gear is adjusted using a lifting tray, and the gravity direction coordinates of point A and point B are repeatedly observed. The longitudinal horizontal adjustment target is that the difference between point A'(Z) and point B'(Z) is XX mm ± XX mm. Figure 5

[0051] g) The positions of each point on the fuselage, wings, and tail in the gravity coordinate system (O XYZ1 ) are measured in turn.

[0052] h) Based on the least squares fitting method, the difference between point 1L (or point 1R) and point A (or point B) in the gravity direction caused by the flexible deformation of the large aspect ratio is isolated, and the weights (P X P Y P Z ) are set in turn, as shown in Table 1. The best fitting (O XYZ2 ) is constructed using formula (1), and is defined as λ, which is a scale parameter, R, which is a rotation parameter matrix, and T, which is a translation parameter.

[0053]

[0054] i) When using the least squares iteration method for coordinate conversion, the scale parameter λ is first solved. According to the set weight, the key fitting point coordinates in the theoretical coordinate system (O XYZ0 ) are processed using formula (2) to obtain the barycentric coordinates, and the corresponding points in the gravity coordinate system (O XYZ1 ) are processed in the same way to obtain the barycentric coordinates with the barycenter as the origin. The scale parameter λ is calculated according to formula (3); to reduce the process iteration, when the aircraft is horizontally measured, λ can be approximately considered as 1.

[0055] ​

[0056] j) The rotation parameter matrix R is a third-order orthogonal matrix, and |R|=1. Then R can be expressed by parameters containing a, b, and c as formula (4). Substitute these into the theoretical coordinate system (O) XYZ0 ) and gravity coordinate system (O) XYZ1 The centroid coordinates of the key fitting points in the equations are obtained, and the equations (5) and (6) formed after the centroids of the key fitting points are obtained. a, b, and c can be calculated according to equation (7), and R can be obtained from equation (4).

[0057]

[0058]

[0059] The translation parameter T can be obtained from formula (8) k).

[0060]

[0061] l) Based on the scale parameter λ, rotation parameter matrix R, and translation parameter T, sequentially transform the gravity coordinate system (O). XYZ1 Transfer the coordinates of all points on the plane to the fitted coordinate system to obtain the fitted coordinates of all points (X2 Y2 Z2).

[0062]

[0063] Furthermore, the absolute deformation can be obtained by comparing the differences between (X2 Y2 Z2) and (X0 Y0 Z0) at each point.

[0064] As shown in Table 2, more information can be obtained to provide accurate location data for determining the center of gravity of an aircraft.

[0065] As shown in Tables 1 and 2, horizontal measurements and weighted fitting were performed on a hydrogen-powered drone to obtain the coordinate information of all points; Figure 6 As shown, based on the present invention, more than 130 horizontal measurement points on a certain UAV were measured. Compared with the deviation analysis using traditional methods, the root mean square error after statistical activity can be effectively reduced, reducing the deviation of flexible aircraft measurement data analysis and more in line with the actual situation. After practical verification, the method mentioned in the present invention is reliable and has practical value.

[0066] Table 1. Weights set for key feature point fitting.

[0067]

[0068] Table 2 Comparison of data records after point fitting.

[0069]

[0070]

[0071] The above description is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change of the above embodiment according to the technical essence of the present application falls within the protection scope of the present application.

Claims

1. A method for measuring the level of a high aspect ratio flexible aircraft, characterized in that, Includes the following steps: Step S1: In the theoretical coordinate system ( O XYZ0 Under these conditions, symmetrical key fitting points are selected in the lateral and longitudinal directions of the aircraft, respectively, as the lateral reference leveling points and longitudinal reference leveling points of the aircraft; the key fitting points are the points of rigidity in the connection area between the wing and the landing gear. Step S2: Establish the original gravity coordinate system using a laser tracker. O XYZ1 And its Z-axis direction coincides with the direction of gravity; Then, horizontal and vertical leveling are performed based on the horizontal and vertical reference leveling points, respectively. Step S3: Measure the gravity coordinate system sequentially ( O XYZ1 The positions of various points on the fuselage, wings, and tail are then determined. Next, based on the least squares fitting method, the differences in gravity direction between points 1L, 1R, A, and B caused by the flexible deformation with a large aspect ratio are isolated, and the scale parameters obtained from the fitting calculation are... λ Rotation parameter matrix R With translation parameters T To construct the best-fit coordinate system ( O XYZ2 ): ； Where: (X1, Y1, Z1) is the gravity coordinate system ( O XYZ1 The coordinates are (X2, Y2, Z2) under the best-fit coordinate system; (X2, Y2, Z2) is the best-fit coordinate system. O XYZ2 Coordinates under ) Step S31: First, determine the scale parameters. λ Solve this problem; Based on the set weight (P) X P Y P Z Formula (2) is used to define the theoretical coordinate system. O XYZ0 The coordinates of the key fitting points in the coordinate system are centroided, and similarly, the coordinates of the gravity coordinate system are centroided. O XYZ1 The corresponding points in the graph are centroided and converted into centroided coordinates with their respective centroids as the origin. Then, the scale parameters are calculated according to formula (3). λ : ； ； Where: (X0, Y0, Z0) is the theoretical coordinate system ( O XYZ0 Coordinates under ) For the theoretical coordinate system ( O XYZ0 The average value of the coordinates of each key fitting point in the dataset; For the gravity coordinate system ( O XYZ1 The average value of the coordinates of each key fitting point in the dataset; Step S32: Perform rotation parameter matrix R Solve for the rotation parameter matrix. R Let R be a third-order orthogonal matrix, and |R|=1, then R Through containing a , b , c The parameters are expressed as in formula (4), and are substituted into the theoretical coordinate system ( O XYZ0 ) and gravity coordinate system O XYZ1 The centroid coordinates of the key fitting points in the equations are obtained, and the equations (5) and (6) are formed after the key fitting points are centroided. The equations (7) can be calculated from the equation. a , b , c Therefore, it can be derived from formula (4) R : ； ； ； ； Step S33: Set translation parameters T Solve this problem; ； Among them: (X) T Y T Z T () represents the translation vector obtained by solving; Step S4: Construct the best-fit coordinate system ( O XYZ2 ), and sequentially transform the gravity coordinate system ( O XYZ1 Transfer the coordinates of all points on the aircraft (X1, Y1, Z1) to the fitted coordinate system. O XYZ2 Under these conditions, the fitted point coordinates (X2, Y2, Z2) are obtained, making the fitted results more consistent with the actual situation, so as to identify global deformation; ； In step S1, in the theoretical coordinate system ( O XYZ0 Under the given conditions, select two lateral reference leveling points, 1L and 1R, on the rigid surface symmetrically positioned near the landing gear on the left and right wings; in the theoretical coordinate system ( O XYZ0 Under these conditions, select two longitudinal reference leveling points A and B on the fuselage, near the leading edge of the wing.

2. The method for measuring the level of a high aspect ratio flexible aircraft according to claim 1, characterized in that, In step S31, to reduce process iterations, when performing level measurements on the aircraft, λ =1.

3. The method for measuring the level of a high aspect ratio flexible aircraft according to claim 1, characterized in that, Select two lateral reference leveling points within 0.5m around the frame and beam; select two longitudinal reference leveling points within 0.5m around the frame and beam on the fuselage, near the leading edge of the wing.

4. The method for measuring the level of a high aspect ratio flexible aircraft according to claim 1, characterized in that, In step S2, during lateral leveling, the height of the left / right landing gear is adjusted, and the gravity direction coordinates of points 1L and 1R are repeatedly observed. The target for lateral horizontal adjustment is: the height difference between points 1L and 1R is ±Emm, where E is the design allowable error.

5. The method for measuring the level of a high aspect ratio flexible aircraft according to claim 4, characterized in that, In step S2, during longitudinal leveling, the height of the nose landing gear is adjusted, and the gravity direction coordinates of points A and B are repeatedly observed. The longitudinal horizontal adjustment target is: the height difference between points A and B is Jmm ± Emm, where J represents the theoretical height difference between points A and B, given by digital model measurement; and E is the design allowable error.

6. A method for measuring the level of a high aspect ratio flexible aircraft according to any one of claims 1-5, characterized in that, In step S2, before the horizontal measurement, a status check is carried out against the theoretical numerical model to ensure that there are no factors that affect the horizontal measurement and that there is no significant airflow near the aircraft.

7. The method for measuring the level of a high aspect ratio flexible aircraft according to claim 1, characterized in that, In step S4, by comparing the best-fit coordinate system ( O XYZ2 Points (X2, Y2, Z2) in the coordinate system and the theoretical coordinate system ( O XYZ0 The absolute deformation is obtained by calculating the differences between points (X0, Y0, Z0) under the given conditions.

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