Method for digitally measuring deflection angular velocity of control surface and monitoring deformation of control surface

Abstract

The invention relates to a method for accurately measuring the angle of a control surface and monitoring the shape deformation of the control surface after the control surface of an airplane is controlled to rotate by using a flight control system, and belongs to the technical field of measurement. A method for digitally measuring the deflection angular velocity of a control surface and monitoring the deformation of the control surface comprises the following steps: constructing a reference measurement field, and adjusting the control surface to an initial zero position; arranging at least two groups of industrial measurement cameras, and setting a shooting interval; arranging a plurality of mark points, coding points and reference scales on the surface of the control surface; shooting an appearance image when the control surface is in a zero position; the control surface is controlled to rotate to a design theoretical limit angle; and fitting the shape surface of the control surface at the zero position and the shape surface of the control surface at a certain angle, comparing the angle values of the fitted shape surfaces in the two states to obtain the shape of the control surface and the average angular velocity of the deflection of the control surface, and fitting the mark points on the control surface with the shape of the control surface to obtain the shape of the control surface in each time period. The method has the advantages that the measurement method is standardized, and the measurement efficiency is improved.

Description

Technical Field

[0001] This invention relates to a method for accurately measuring the control surface angle and monitoring the deformation of the control surface shape after the control surface is rotated by the flight control system of an aircraft, and belongs to the field of measurement technology. Background Technology

[0002] Control surfaces are typically located on the wings and tail of an aircraft. By changing their position and angle, the lift, drag, and direction of the aircraft can be altered, thereby enabling maneuvers such as turning, climbing, and descending. Control surfaces are movable components that control the aircraft's attitude and direction, and are an important part of the aircraft's control system. The pilot controls actuators via the control stick and pedals. These actuators are connected to the control surfaces, and the extension or retraction (linear motion) of the mechanical stick drives the control surfaces to rotate around their axes. Due to unavoidable errors during manufacturing and assembly, the rotation angle and angular velocity of the control surfaces also have errors. The smaller the error in the rotation angular velocity, the higher the accuracy of aircraft control. Achieving precise control of the control surface angular velocity will effectively improve the aircraft's aerodynamic efficiency and handling performance. Therefore, it is necessary to accurately measure the rotation angular velocity of the control surfaces and optimize the mechanical structure to improve aircraft performance.

[0003] Traditional measurement methods cannot achieve accurate measurement of angular velocity. Existing measurement methods can only measure the angle of the control surface, and still have many technical problems.

[0004] One measurement method involves selecting a characteristic reference point on both the fuselage and the control surface, and measuring the change in distance between the two points when the control surface deflects. This essentially converts the measured angle into the length of a straight line. However, this method relies heavily on the manufacturing accuracy of the characteristic reference points. When the manufacturing accuracy of the characteristic reference points is poor, the measurement method will have a large error.

[0005] Another measurement method involves leveling the aircraft, fixing the angle measuring instrument to the control surface and zeroing it, then using the flight control system to deflect the control surface and recording the readings at each position to measure the control surface deflection angle. However, since it's often impossible to set a fixed point for the angle measuring instrument on the control surface, it's usually attached with tape. When the control surface rotates at high speeds, large angles, or is perpendicular to the ground, the angle measuring instrument inevitably experiences shaking and offset, leading to measurement errors. Furthermore, it's impossible to know if the control surface deforms during the deflection process. Summary of the Invention

[0006] The purpose of this invention is to provide a method for digitally measuring the angular velocity of a control surface and monitoring its deformation. By using an industrial photogrammetry system, the angular velocity of the control surface can be accurately measured, and the changes in the shape of the control surface before and after deflection can be monitored.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation, comprising the following steps.

[0008] (1) Construct a reference measurement field and adjust the rudder surface to the initial zero position;

[0009] (2) Deploy at least two sets of industrial measuring cameras and set the shooting interval t. n ;

[0010] (3) Arrange several marker points, coding points and reference scales on the surface of the rudder surface;

[0011] (4) Take a picture of the shape of the control surface when it is at zero position;

[0012] (5) Rotate the control surfaces to the design theoretical limit angle;

[0013] (6) Fit the shape of the rudder surface at zero position and the shape of the rudder surface at a certain angle, compare the angle values ​​of the fitted shape of the rudder surface in the two states, obtain the shape of the rudder surface and the average angular velocity of the rudder surface deflection, fit the mark point on the rudder surface with the shape of the rudder surface, and obtain the shape of the rudder surface in each time period.

[0014] Preferably, in step (6), the coordinates (x, y) of the marker point on the rudder surface during the rudder surface deflection process are... n y n , z n The coordinates of points at different deflection angles are fitted to form a plane: A n x+B n y+C n z+D n =0; By calculating the angles between different planes, the deflection angle θ of the control surface is obtained. n That is, to obtain the average angular velocity over different time periods.

[0015] Preferably, in step (6), the plane is formed by fitting using the linear least squares method.

[0016] Preferably, in step (6), fitting the point coordinates to a plane includes the following steps:

[0017] (1) Considering the shape of the control surface as a plane, its plane equation in three-dimensional space is:

[0018] z = ax + by + c

[0019] (2) Assume a set of data points (x i y i , z i ), i = 1, 2, ..., n; for each data point, the predicted value Δz on the fitting plane. i =axi +by i +c;

[0020] (3) Solve for the values ​​of a, b, and c:

[0021] Calculate residual e i residual e i It is the actual value z i With the predicted value Δz i The difference between

[0022] e i =z i -Δz=z i -(ax i +by i +c)

[0023] The residual sum of squares (SSE) is:

[0024]

[0025] Take the partial derivatives of the SSE function with respect to a, b, and c, and set them equal to zero:

[0026]

[0027] Preferably, in step (6), the average angular velocity over different time periods is calculated. The steps include: (1) Calculating the angle between the two planes.

[0028] Plane 1:

[0029] A1x+B1y+C1z+D1=0

[0030] Plane 2:

[0031] A²x + B²y + C²z + D² = 0

[0032] Then the normal vector of plane 1 is:

[0033]

[0034] Then the normal vector of plane 1 is:

[0035]

[0036] Calculate the dot product of two normal vectors:

[0037]

[0038] Calculate the magnitude of the two normal vectors:

[0039]

[0040] Calculate the cosine of the angle θ between the two planes:

[0041]

[0042] Calculate the included angle θ using the inverse cosine function:

[0043]

[0044] Calculate the average angular velocity over different time periods

[0045]

[0046] Preferably, there are no fewer than 50 marker points or coding points on the same measurement object.

[0047] Preferably, the angle between the measuring camera and the object being measured is 60° to 120°.

[0048] Preferably, the distance between the measuring camera and the object being measured is equal to the length and width of the object being measured.

[0049] Compared with the prior art, the present invention has the following advantages: it can effectively improve the measurement accuracy of the control surface deflection angle and the control surface shape, standardize the measurement method, improve the measurement efficiency, and can be universally applied to all similar control surface structures. Attached Figure Description

[0050] Figure 1 This is a schematic diagram illustrating the principle of direct measurement using dual cameras and dual images in an embodiment of the present invention.

[0051] The coordinate system O-xyz is the spatial coordinate system of the left camera, and its image plane coordinate system is the coordinate system O1-X1Y1. The effective focal length is f1.

[0052] Coordinate system Or-x r y r z r Let O be the right camera's spatial coordinate system, and let O be the image plane coordinate system. r Y r The effective focal length is f r Let the coordinate system of object point P in O-xyz be (X,Y,Z).

[0053] The coordinates of its corresponding image point p in the left image in the O-xyz region are (x, y, -f1).

[0054] The corresponding image point p in the right image r In O r -x r y r z r The coordinates in (x) r,y r ,-f r );

[0055] Figure 2 This describes the measurement workflow in an embodiment of the present invention;

[0056] Figure 3 This is the scheme for arranging marker points on the rudder surface in this embodiment of the invention;

[0057] Figure 4 This is the scheme for constructing a digital measurement field in the embodiments of the present invention;

[0058] Figure 5 This is a schematic diagram of the rudder surface deflection angle measurement in an embodiment of the present invention;

[0059] 1. Marker point; 2. Product control surface; 3. Measurement area; 4. Encoding point; 5. Initial zero position of control surface; 6. Upper deflection limit angle; 7. Lower deflection limit angle. Detailed Implementation

[0060] The following is in conjunction with the appendix Figure 1-5 The present invention is further described in detail as follows: An industrial photogrammetry system, such as the VSTARS system, Metronor system, DPA-Pro system or MPS system, is prepared, which mainly includes an industrial measuring camera, a reference ruler, a marker point 1, a coding point 4, etc.

[0061] Reference ruler: A scale that provides measurement values ​​for industrial photogrammetry systems. The base material is generally carbon fiber. Each ruler has evenly distributed markers and coded points that can be identified by the industrial photogrammetry system. The scaling ratio can be obtained through calculation, and its length measurement uncertainty is less than one-third of the uncertainty of the length measurement of the system being measured.

[0062] Marker Point 1: Markers used in industrial photogrammetry systems are generally directional reflective markers. They are characterized by a reflective brightness that is hundreds or even thousands of times higher than that of diffuse white markers, which can easily obtain the image of the target object itself by "hiding".

[0063] Coded point 4: This is an artificial marker point with its own digital encoding information. It can be automatically identified through image processing and other methods to achieve automatic matching of artificial markers in industrial photogrammetry systems; it can also serve as a common point between different images to achieve automatic stitching of photogrammetric images.

[0064] Using the tools described above, construct a reference measurement field; set up multiple sets of cameras (at least two sets are required) around the control surface being measured; and set a fixed shooting interval t. n Several marker points are arranged on the surface of the rudder; the rudder is manipulated to complete the deflection; thereby achieving accurate measurement of the rudder's rotational angular velocity and shape change.

[0065] Mathematically, this is expressed as the coordinates (x, y) of a marker point on the control surface during the control surface deflection process. n y n , z n The coordinates of points at different deflection angles are fitted to form a plane: A n x+B n y+C n z+D n =0; By calculating the angles between different planes, the deflection angle θ of the control surface is obtained. n That is, to obtain the average angular velocity over different time periods.

[0066] The mathematical expression of the technical solution is as follows.

[0067] Since the surface of the control surface can be approximated as a plane, the measured points can be fitted to form a plane using the linear least squares method. The mathematical principle of fitting point coordinates to a plane is as follows:

[0068] The shape of the control surface can be approximated as a plane.

[0069] The equation of a plane in three-dimensional space can usually be expressed as:

[0070] z = ax + by + c

[0071] Suppose a set of data points (x i y i , z i ), i = 1, 2, ..., n. For each data point, the predicted value Δz on the fitting plane. i =ax i +by i +c

[0072] residual e i It is the actual value z i With the predicted value Δz i The difference between them:

[0073] e i =z i -Δz=z i -(ax i +by i +c)

[0074] The residual sum of squares (SSE) is:

[0075]

[0076] Take the partial derivatives of the SSE function with respect to a, b, and c, and set them equal to zero:

[0077]

[0078] The three equations above form a system of linear equations, which can be written in matrix form:

[0079]

[0080] Solving this equation will give us the values ​​of a, b, and c.

[0081] The mathematical expression for calculating the angle between two planes is as follows:

[0082] If the equations of the two planes are respectively:

[0083] Plane 1:

[0084] A1x+B1y+C1z+D1=0

[0085] Plane 2:

[0086] A²x + B²y + C²z + D² = 0

[0087] Then the normal vector of plane 1 is:

[0088]

[0089] Then the normal vector of plane 1 is:

[0090]

[0091] Calculate the dot product of two normal vectors:

[0092]

[0093] Calculate the magnitude of the two normal vectors:

[0094]

[0095] Calculate the cosine of the angle θ between the two planes:

[0096]

[0097] Calculate the included angle θ using the inverse cosine function:

[0098]

[0099] Calculate the average angular velocity over different time periods

[0100]

[0101] like Figure 1-5 As shown, the specific implementation process of photogrammetry work is as follows: Figure 2 As shown;

[0102] (1) The aircraft enters the shooting area, adjusts the product control surface 2 to the initial zero position 5, and completes all preparations.

[0103] (2) Deploy industrial measuring cameras, set shooting intervals, and complete the calibration of multiple cameras. Adjust the angle between the measuring camera and the object being measured to ensure that it is optimally between 60° and 120°. Adjust the distance between the measuring camera and the object being measured, generally to be equal to the length and width of the object being measured;

[0104] (3) Marker point 1 is placed on the measured rudder surface, such as Figure 3 As shown, in Figure 3 The document provides a scheme for arranging marker point 1. Marker point 1 should be placed on a surface with good flatness and high rigidity. The density of marker point 1 should be determined according to the shape of the area being measured and the measurement requirements. Generally, the number of marker points (including coded point 4) on the same measurement object should not be less than 50. The arrangement scheme for areas requiring special attention should be differentiated to facilitate data analysis.

[0105] (4) Arrange coding point 4 and the reference scale, fix the relative positional relationship between coding point 4 and the reference scale, and construct a digital measurement field, such as... Figure 4 As shown, coding points 4 should be evenly distributed on the part of the product being measured, in a position that is not easily obstructed and can be photographed from multiple angles. Coding points 4 should be arranged in the X, Y, and Z directions within the measurement area 3. For example... Figure 5 As shown, taking the layout scheme in the Y direction as an example, it is also necessary to avoid arranging three or more coding points 4 on the same straight line, and prohibit the use of coding points with the same serial number in all measurement tasks of the same product in the same flight; the reference ruler should be placed in a position that is easy to be photographed, and the relative pose of the reference ruler and the product being measured should not change during the shooting process;

[0106] (5) Take a picture of the shape of the control surface when it is at zero position;

[0107] (6) Rotate the control surface to the design theoretical limit angle. For example, if the design requires the control surface deflection limit angle 6 to be 30° and the downward deflection limit angle 7 to be 45°, then rotate the control surface upward to the 30° position and then downward to the 45° position.

[0108] (7) During the rotation process, the camera automatically repeats the measurement work at regular intervals in the standard measurement field to obtain the spatial changes of the marker points on the rudder surface in each time period.

[0109] (8) Data processing: Fit the shape of the control surface at zero position to the shape of the control surface at a certain angle. Compare the angle values ​​of the fitted shape of the control surface in the two states to obtain the shape of the control surface and the average angular velocity of the control surface deflection. By fitting the marker points on the control surface to the shape of the control surface, the shape of the control surface at each time period can be obtained.

Claims

1. A method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation, characterized in that: Includes the following steps, (1) Construct a reference measurement field and adjust the rudder surface to the initial zero position; (2) Deploy at least two sets of industrial measuring cameras and set the shooting interval t. n ; (3) Arrange several marker points, coding points and reference scales on the surface of the rudder surface; (4) Take a picture of the shape of the control surface when it is at zero position; (5) Rotate the control surfaces to the design theoretical limit angle; (6) Fit the shape of the rudder surface at zero position and the shape of the rudder surface at a certain angle, compare the angle values ​​of the fitted shape of the rudder surface in the two states, obtain the shape of the rudder surface and the average angular velocity of the rudder surface deflection, fit the mark point on the rudder surface with the shape of the rudder surface, and obtain the shape of the rudder surface in each time period.

2. The method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation according to claim 1, characterized in that: In step (6), the coordinates (x, y) of the marker point on the control surface during the control surface deflection process are... n y n , z n The coordinates of points at different deflection angles are fitted to form a plane: A n x+B n y+C n z+D n =0; By calculating the angles between different planes, the deflection angle θ of the control surface is obtained. n That is, to obtain the average angular velocity over different time periods.

3. The method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation according to claim 1, characterized in that: In step (6), the plane is formed by fitting using the linear least squares method.

4. The method for digitally measuring the angular velocity of the control surface and monitoring its deformation according to claim 1 or 2, characterized in that: In step (6), fitting the point coordinates to a plane includes the following steps: (1) Considering the shape of the control surface as a plane, its plane equation in three-dimensional space is: z = ax + by + c (2) Assume a set of data points (x i y i , z i ), i = 1, 2, ..., n; For each data point, the predicted value Δz on the fitting plane i =ax i +by i +c; (3) Solve for the values ​​of a, b, and c: Calculate residual e i residual e i It is the actual value z i With the predicted value Δz i The difference between e i =z i -Δz=z i -(ax i +by i +c) The residual sum of squares (SSE) is: Take the partial derivatives of the SSE function with respect to a, b, and c, and set them equal to zero:

5. The method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation according to claim 1, characterized in that: In step (6), the average angular velocity over different time periods is calculated. Includes the following steps, (1) Calculate the angle between the two planes. Plane 1: A1x+B1y+C1z+D1=0 Plane 2: A²x + B²y + C²z + D² = 0 Then the normal vector of plane 1 is: Then the normal vector of plane 1 is: Calculate the dot product of two normal vectors: Calculate the magnitude of the two normal vectors: Calculate the cosine of the angle θ between the two planes: Calculate the included angle θ using the inverse cosine function: Calculate the average angular velocity over different time periods 6. The method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation according to claim 1, characterized in that: There shall be no fewer than 50 markers or coded points on the same measurement object.

7. The method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation according to claim 1, characterized in that: The angle between the camera and the object being measured is 60° to 120°.

8. The method for digitally measuring the deflection angular velocity of a control surface and monitoring its deformation according to claim 1, characterized in that: The distance between the measuring camera and the object being measured is equal to the length and width of the object being measured.

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