Monocular vision dual-rotor tip distance measurement system and method for flight testing

Abstract

The application provides a monocular vision double-rotor tip-path plane measurement system and method for flight test. In the method, a calibration plate is placed at a position of a plane perpendicular to the central point of the vertical direction of the upper and lower blade tips and the optical axis of the camera, and the calibration plate is moved so as to be located in the field of view of the camera. Then, the camera parameters are adjusted so that the calibration image meets the definition requirement. When the rotor rotates, the reflector sweeps the photoelectric sensor to generate a pulse signal of one per revolution. The trigger control box outputs the camera trigger signal to three cameras after the pulse signal is multiplied by four and processed. The cameras take pictures of the point light source markers of the upper and lower blades under the control of the trigger signal. The cameras transmit the pictures to the onboard notebook computer, and the onboard notebook computer processes and calculates the camera measurement data. After the camera measurement data is corrected, the tip-path plane is finally obtained. The application can realize real-time and reliable measurement and monitoring of the upper and lower rotor tip-path plane in the flight test process of the coaxial double-rotor helicopter, and improve the flight safety.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of helicopter rotor test and measurement, and particularly relates to a monocular vision dual-rotor tip distance measurement system and method for flight test. BACKGROUND

[0002] Due to the structural characteristics of coaxial and counter-rotating upper and lower rotors, the upper and lower rotor tips approach each other in the direction of the rear of the upper rotor and the front of the lower rotor of the coaxial dual-rotor helicopter. Especially in the differential pitch and high-speed flight states of the upper and lower rotors, there is a risk of tip collision. Therefore, it is necessary to measure and monitor the tip distance of the upper and lower rotors in real time. There are methods of machine vision, millimeter wave radar, electromagnetic near-field induction, etc. for measuring the tip distance of coaxial dual-rotor. Among them, the machine vision method has been widely used due to its intuitive and visible advantages. At present, the machine vision tip distance measurement methods in use are divided into two categories: binocular stereo vision and monocular vision, and their advantages and disadvantages are as follows:

[0003] (1) The binocular stereo vision measurement method simulates the principle of human left and right eye perception and recognition of objects, uses two cameras arranged adjacent to each other to perform stereo imaging and image processing on the upper and lower rotor tip parts to obtain the tip distance, and is a non-contact measurement method with high measurement accuracy. However, since the left and right images need to be associated and analyzed, the calculation and processing speed is slow, and the real-time performance is not strong.

[0004] (2) The current monocular vision measurement method requires the camera to be installed at a position not less than the length of the blade diameter from the hub and at the same height as the rotor disc plane. Therefore, it is only suitable for ground test of coaxial rotors and cannot be used for flight test, which cannot guarantee the safety of flight. SUMMARY

[0005] In order to solve the problems of low reliability and low safety of flight test in real-time measurement and monitoring of the tip distance of the upper and lower rotors in the related art, the application provides a monocular vision dual-rotor tip distance measurement system and method for flight test, which can realize real-time and reliable measurement and monitoring of the tip distance of the upper and lower rotors during flight test of the coaxial dual-rotor helicopter, and improve the safety of flight test. The technical solution is as follows:

[0006] In a first aspect, a monocular vision dual-rotor tip distance measurement method for flight test is provided, and the method comprises:

[0007] Step one, install a camera on each of the front, rear and tail of the coaxial helicopter, the field of view direction is directly opposite to the front, side and rear of the upper and lower rotor blades overlap position; install a photoelectric sensor on the upper end surface platform of the main reducer, the photosensitive cover is vertically upward, the corresponding reflector is pasted on the rotor automatic tilting device moving ring or the lower surface of the blade root, to ensure that the rotor rotates one circle and triggers the photoelectric sensor once; install a plurality of point light source markers in the cavities at the tip positions of the upper and lower blades, the light outlet cover of the point light source marker is flush with the lower surface of the blade, to ensure that the three cameras installed on the fuselage can take clear pictures; install a trigger control box and an onboard notebook computer in the equipment cabin, to trigger the camera for collection and process and display the transmitted image data;

[0008] Step two, place the calibration plate at the center point vertically above the upper and lower blade tips and on the plane perpendicular to the camera optical axis, move the calibration plate to make it located in the camera field of view; then adjust the camera parameters to make the calibration image meet the clarity requirement;

[0009] Step three, when the rotor rotates, the reflector sweeps across the photoelectric sensor, generating a pulse signal every circle; the trigger control box outputs the camera trigger signal to the three cameras after 4 times frequency multiplication and conditioning of the pulse signal; the cameras take pictures of the point light source markers of the upper and lower blades under the control of the trigger signal; the cameras transmit the pictures to the onboard notebook computer, which processes and calculates the camera measurement data; after correction of the camera measurement data, the tip clearance is finally obtained.

[0010] Optionally, in step three, the camera measurement data is the upper blade tip flapping amount and the lower blade tip flapping amount, and the relationship formula for determining the tip clearance based on the camera measurement data is: tip clearance = upper blade tip flapping amount - lower blade tip flapping amount + initial static blade spacing.

[0011] Optionally, in step three, the camera measurement data is corrected, and the tip clearance is determined based on the corrected camera measurement data, which specifically includes:

[0012] Step 1, obtain the external parameters, including the horizontal distance x from the camera installation point to the rotor shaft, the vertical distance y from the camera installation point to the lower blade, the horizontal distance a from the camera installation point to the upper and lower blade tips, and the vertical distance b from the camera installation point to the upper and lower blade tips;

[0013] Step 2, define the blade tip flapping range, i.e. the y-axis coordinate Ybt of the blade tip in the hub coordinate system;

[0014] Step 3, according to the rigid characteristics of the blade, define the blade tip flapping trajectory as an approximate circular arc, based on the constraint equation get X bt where r is the blade radius;

[0015] Step 4, translate and rotate (X bt , Y bt ) to camera coordinate system, get (X ct , Y ct ) by transformation formula;

[0016] Step 5, project (X ct , Y ct ) to camera calibration plane, get the spatial vector distance Y′ ct of the tip of the paddle in the y direction on the calibration plane in the camera coordinate system by projection formula;

[0017] Step 6, calculate the theoretical field of view , where Hc is the size of the optical target surface, and f is the focal length of the lens;

[0018] Step 7, determine the theoretical y-axis coordinate Y it of the tip of the paddle in the image coordinate system by the derivation formula;

[0019] Step 8, fit the coordinates Y it of the tip of the paddle in the image coordinate system and the coordinates Y bt of the tip of the paddle in the paddle hub coordinate system by the least squares fitting algorithm to obtain the fitting function: where a, b, and c are the coefficients obtained by fitting;

[0020] Step 9, align the data of the static paddle distance and the initial paddle tip image coordinates to obtain a new fitting function: where a', b', and c' are the coefficients of the new fitting function;

[0021] Step 10, substitute the y-axis coordinate Y it of the paddle tip marker point calculated by image processing into the new fitting function: to obtain the corrected vertical flap of the upper and lower paddle tips Y bt ;

[0022] Step 11, calculate the actual paddle distance = corrected upper paddle tip flap - corrected lower paddle tip flap + initial static paddle distance.

[0023] Optionally, the transformation formula in step 4 is: where, D is the static paddle distance, a is the horizontal distance from the camera mounting point to the upper and lower paddle tips, and b is the vertical distance from the camera mounting point to the upper and lower paddle tips.

[0024] Optionally, the projection formula in step 5 is:

[0025] Optionally, the derivation formula in step 7 is where Y pxsTotal number of image Y axis pixels.

[0026] Optionally, step 9 is specifically: first, initializing theoretical Y it , then detecting the current blade tip mark point record Y' it , calculating error pixel ΔY it =Y it -Y' it , substituting the fitting function to obtain new fitting parameters, that is, performing x-axis translation on the fitting function to greatly reduce the installation error.

[0027] Optionally, in step two, the camera focal length, aperture, exposure time are adjusted, and the camera focal length satisfies f represents the lens focal length, L is the distance from the camera to the point light source mark point, Hc is the longitudinal size of the camera optical target surface, and H view is the longitudinal size of the shooting field of view.

[0028] In a second aspect, a monocular vision dual-rotor blade tip distance measurement method for flight test is provided, and the method comprises the following steps:

[0029] The cameras arranged on the side front, side rear and tail of the coaxial dual-rotor helicopter are arranged to face the front, side and rear overlapping positions of the upper and lower rotor blades.

[0030] The photoelectric sensor installed on the upper end surface platform of the main speed reducer has a photosensitive cover vertically upward and is pasted on the reflecting sheet of the rotor automatic tilting device moving ring or the lower surface of the blade root.

[0031] The multiple point light source mark points installed in the cavities at the blade tip positions of the upper and lower blades have light emitting covers flush with the lower surfaces of the blades, so that the three cameras installed on the fuselage can be clearly shot.

[0032] The trigger control box and the airborne notebook computer installed in the equipment cabin are used for triggering and collecting the cameras and processing and displaying the transmitted image data.

[0033] The calibration plate is located at the position of the plane perpendicular to the optical axis of the camera and passing through the center point of the vertical direction of the upper and lower blade tips

[0034] The monocular vision dual-rotor blade tip distance measurement system and method for flight test provided by the application utilize three cameras and corresponding photoelectric sensors, trigger control boxes, point light source mark points, airborne notebook computers and the like to form a measurement system, respectively collect the point light source mark point images of the upper and lower blades at the front, side and rear overlapping moments, identify and process the images, finally calculate and correct the blade tip distance values, realize real-time and reliable measurement and monitoring of the upper and lower rotor blade tip distances in the flight test process of the coaxial dual-rotor helicopter, and improve the flight test safety. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic diagram of a monocular vision dual-rotor tip path measurement system for flight test;

[0036] Figure 2 It is a design drawing of point light source marking point blade internal installation;

[0037] Figure 3 It is an optical imaging schematic diagram;

[0038] Figure 4 It is a camera oblique calibration schematic diagram;

[0039] Figure 5 It is a data correction schematic diagram. DETAILED DESCRIPTION

[0040] The application will be further described in detail below through specific embodiments and drawings.

[0041] The coaxial dual-rotor is a new rotor configuration, and the tip path of the upper and lower rotors needs to be monitored in the flight test in the research and development stage. The multi-view vision tip path measurement method has the disadvantages of slow calculation processing speed and poor real-time performance, and the currently used monocular vision tip path method can only be used for ground test due to the requirements and limitations of the camera installation position, and cannot be used in flight.

[0042] The application provides a monocular vision dual-rotor tip path measurement system and method for flight test, which is suitable for measuring and monitoring the tip path of the upper and lower rotors under different total path and cyclical variable path states in the flight test of a coaxial dual-rotor helicopter, thereby ensuring flight safety and evaluating the aerodynamic performance and aerodynamic interference characteristics of the rotor system under different design states. It is a non-contact measurement method, has the advantages of fast processing speed, high measurement accuracy, and being suitable for different scenes of ground test and flight test.

[0043] Please refer to Figure 1 An embodiment of the application provides a monocular vision dual-rotor tip path measurement system for flight test, which comprises a camera, a photoelectric sensor, a trigger control box, a point light source marking point, an airborne notebook computer and the like.

[0044] The camera is selected from a high-data-transmission-rate industrial camera with a gigabit network interface, and the resolution is determined according to the size of the shooting field of view and the accuracy requirement; the camera frame rate p is greater than or equal to (Nr·K) / 60, Nr is the rotor speed (rpm), and k is the number of single-rotor blade; and the exposure time is determined according to the linear velocity of the blade movement, so that the imaging of the target object is clear and no trailing is generated.

[0045] The photoelectric sensor is selected as a TTL high-speed output type photoelectric sensor, and the trigger delay is less than or equal to 0.3 ms, which is used in cooperation with the reflective sheet pasted on the lower surface of the rotor automatic tilting device dynamic ring or the blade root, to ensure that one pulse signal is generated per rotation.

[0046] The trigger control box has two modes of internal triggering and external triggering: the external triggering mode is triggered by the rotor photoelectric sensor; and the internal triggering mode is triggered by an internal timer. The trigger control box can multiply (blade pieces) and delay the internal and external trigger signals and then output three groups of trigger signals, respectively, to three cameras. The trigger delay is adjustable, covering the time length of a single blade rotation; and the phase difference between the three groups of trigger signals can be adjusted according to the camera installation position.

[0047] The size and brightness of the point light source mark point are determined according to the imaging distance and the use environment, to ensure that the camera can clearly image; in order to not damage the aerodynamic shape of the blade, the point light source mark point is embedded into the blade, as shown in Figure 2 .

[0048] The onboard notebook computer is connected with the three cameras through three gigabit network interfaces, and is mainly used for image calibration, camera acquisition control, image processing and display, and the time t for processing and displaying three frames of images (1 frame of image / camera*3 cameras) is less than or equal to 1 / p, and p is the camera frame rate.

[0049] The method of the embodiment of the application utilizes a monocular vision double-rotor tip distance measurement system for flight test installed on a helicopter, collects images of the upper and lower blades of the coaxial double-rotor at the front, side and rear overlapping positions, obtains the flap values of the upper and lower rotor tips through image processing and calculation, and corrects the upper and lower rotor tip flap values to obtain the coaxial double-rotor tip distance value.

[0050] The specific measurement method is as follows:

[0051] 1. Equipment installation and connection

[0052] A camera is installed on each of the front side, rear side and tail of the coaxial dual-rotor helicopter, and the field of view direction is directly opposite the front, side and rear of the upper and lower rotor blade overlap positions. A photoelectric sensor is installed on the upper end surface platform of the main reducer, and the photosensitive cover is vertically upward, and the corresponding light reflecting sheet is pasted on the rotor automatic tilting device moving ring or the lower surface of the blade root, so as to ensure that the photoelectric sensor is triggered once in one rotation of the rotor. Eight point light source markers are installed in the cavities at the blade tip positions of the upper and lower blades, and the point light source marker light cover is flush with the lower surface of the blade, so as to ensure that the three cameras installed on the fuselage can take clear pictures. A trigger control box and an onboard notebook computer are installed in the equipment cabin, which are used for triggering and collecting the cameras and processing and displaying the transmitted image data. After the equipment is installed, the power line, network line and TTL trigger signal line are connected and tested.

[0053] 2. Camera parameter calibration

[0054] After the equipment is installed, camera parameter calibration is required before measurement. First, place the calibration board at the position of point C as shown in Figure 4 , which is perpendicular to the line CE, and move the calibration board so that it is in the field of view of the camera. Then adjust the camera parameters, mainly the camera focal length, aperture and exposure time, so that the calibration image has high clarity. Among them, the camera focal length satisfies: f = (L·Hc) / Hview, f represents the lens focal length, L is the distance from the camera to the point light source marker, Hc is the longitudinal dimension of the camera optical target surface, and Hview is the longitudinal dimension of the shooting field of view, as shown in Figure 3 .

[0055] 3. Camera measurement data correction

[0056] The error of the camera in measuring the distance between the upper and lower blade tips of the dual-rotor is mainly caused by the oblique view of the camera, and the data can be corrected by the following method:

[0057] Symbol definition: b: blade, bt: blade tip, c: camera, i: image.

[0058] Coordinate system definition: (X bt , Y bt ): blade hub coordinate system (the upper rotor rotation center as the origin, X axis as the upper blade, Y axis as the rotation axis, and the direction reference Figure 5 );

[0059] (X c , Y c ): camera coordinate system (the camera installation point as the origin, the lens direction as the X axis, and the direction reference Figure 5 );

[0060] (X i , Yi ): image coordinate system (with the upper left corner as the origin, the direction reference Figure 5 );

[0061] Constant definition: D: static blade spacing, r: blade radius, Ypxs: total number of image Y-axis pixels;

[0062] Blade tip coordinate definition: (X bt ,Y bt ): coordinates of the blade tip point in the hub coordinate system.

[0063] (X ct ,Y ct ): coordinates of the blade tip point in the camera coordinate system.

[0064] (X it ,Y it ): coordinates of the blade tip point in the image coordinate system.

[0065] (X' ct ,Y' ct ): coordinates of the blade tip point projected onto the camera calibration plane in the camera coordinate system.

[0066] Step 1, obtain the external parameters, including the horizontal distance x from the camera mounting point to the rotor shaft, the vertical distance y from the camera mounting point to the lower blade, the horizontal distance a from the camera mounting point to the upper and lower blade tips, and the vertical distance b from the camera mounting point to the upper and lower blade tips;

[0067] Step 2, define the blade tip flapping range, i.e. the y-axis coordinate Ybt of the blade tip in the hub coordinate system;

[0068] Step 3, based on the rigidity characteristics of the blade, define the blade tip flapping trajectory as an approximate circular arc, based on the constraint equation get X bt , where r is the blade radius;

[0069] Step 4, translate and rotate (X bt , Y bt ) to the camera coordinate system, and use the transformation formula to get (X ct , Y ct ); the transformation formula is:

[0070] Step 5, project (X ct , Y ct ) onto the camera calibration plane, and use the projection formula to get the spatial vector distance Y' ct of the blade tip in the y direction in the camera coordinate system on the calibration plane; the projection formula is:

[0071] Step 6, calculate the theoretical field of view wherein Hc is the optical target size, and f is the lens focal length;

[0072] Step 7, using the derived formula, determine the theoretical y-axis coordinate Y of the blade tip point in the image coordinate system it ;

[0073] The derived formula is wherein Y pxs is the total number of image Y-axis pixels.

[0074] Step 8, through the least square fitting algorithm, fit the coordinate Y of the blade tip point in the image coordinate system it and the coordinate Y of the blade tip point in the hub coordinate system bt to obtain the fitting function as follows: wherein a, b, c are the coefficients obtained by fitting;

[0075] Step 9, using the static blade spacing and the initial blade tip image coordinate to perform data alignment, to obtain a new fitting function as follows: wherein a', b', c' are the coefficients of the new fitting function.

[0076] Specifically, according to the static blade spacing and the initial blade tip image coordinate to perform further data alignment and fitting, the specific form is as follows: first, initialize the theoretical Y it , then detect the blade tip mark point record Y' it at this time, calculate the error pixel ΔY it =Y it -Y′ it , substitute the fitting function to obtain new fitting parameters, that is, perform x-axis translation on the fitting function, so as to greatly reduce the installation error.

[0077] Step 10, substitute the blade tip mark point y-axis coordinate Y it into the formula:

[0078] to obtain the corrected upper and lower blade tip vertical flapping amount Y bt ;

[0079] Step 11, calculate the actual blade spacing = corrected upper blade tip flapping amount - corrected lower blade tip flapping amount + initial static blade spacing.

[0080] An embodiment of the present application also provides a monocular vision double-rotor blade tip distance measuring system for flight test, comprising:

[0081] The cameras arranged on the front side, rear side and tail of the coaxial double-rotor helicopter are arranged to face the front, side and rear upper and lower rotor blade overlapping positions.

[0082] The photoelectric sensor is installed on the top surface of the main reducer, and the light cover is vertically upward and pasted on the reflective sheet of the rotor automatic tilting device or the lower surface of the blade root;

[0083] The multiple point light source markers are installed in the cavities of the upper and lower blade tips, and the light covers are flush with the lower surfaces of the blades;

[0084] The trigger control box and the onboard notebook computer are installed in the equipment cabin, used for triggering the camera to collect and process and display the transmitted image data;

[0085] The calibration plate is located at the position of the plane which passes through the center point of the upper and lower blade tips and is perpendicular to the optical axis of the camera.

[0086] The above only expresses the embodiments of the present application, the description is more specific and detailed, but cannot be understood as the limitation of the patent scope. It should be noted that for the ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which belongs to the protection scope of the present application. In addition, the parts not described in the present application are all the conventional technology.

Claims

1. A monocular vision tip-to-tip measurement method for flight testing of a dual rotor, characterized in that, The method comprises: Step one, a camera is installed on each of the front side, rear side and tail of the coaxial dual-rotor helicopter, the field of view direction is directly opposite the front, side and rear upper and lower rotor blade overlap positions; a photoelectric sensor is installed on the upper end surface platform of the main reducer, the photosensitive cover is vertically upward, the corresponding reflector is pasted on the rotor automatic tilting device dynamic ring or the lower surface of the blade root, ensuring that the rotor rotates one circle and triggers the photoelectric sensor once; a plurality of point light source markers are installed in the cavities at the upper and lower blade tip positions, the light outlet cover of the point light source marker is flush with the lower surface of the blade; a trigger control box and an onboard notebook computer are installed in the equipment cabin, used for triggering and collecting the cameras and processing and displaying the transmitted image data; Step two, the calibration plate is placed at the position of the center point vertically through the upper and lower blade tips and perpendicular to the camera optical axis, and the calibration plate is moved to be located in the field of view of the camera; then the camera parameters are adjusted, so that the calibration image meets the clarity requirement; Step three, when the rotor rotates, the reflector sweeps through the photoelectric sensor, generating a pulse signal of one circle per revolution; the trigger control box outputs the camera trigger signal to the three cameras after four times frequency multiplication and conditioning of the pulse signal; the cameras take pictures of the point light source markers of the upper and lower blades under the control of the trigger signal; the cameras transmit the pictures to the onboard notebook computer, and the onboard notebook computer processes and calculates the camera measurement data; after the camera measurement data is corrected, the final blade tip distance is obtained; In step three, the camera measurement data is the upper blade tip flapping amount and the lower blade tip flapping amount, and the relationship formula for determining the blade tip distance based on the camera measurement data is: blade tip distance=upper blade tip flapping amount-lower blade tip flapping amount+initial static blade spacing.

2. The method of claim 1, wherein, In step three, the camera measurement data is corrected, and the blade tip distance is determined based on the corrected camera measurement data, which specifically comprises: Step 1, obtaining external parameters, the external parameters including the horizontal distance x from the camera installation point to the rotor shaft, the vertical distance y from the camera installation point to the lower blade, the horizontal distance a from the camera installation point to the upper and lower blade tips, and the vertical distance b from the camera installation point to the upper and lower blade tips; Step 2, define the range of the blade tip flapping, that is, the y-axis coordinate Y of the blade tip in the hub coordinate system bt ; Step 3, define the blade tip flapping trajectory as a circular arc based on the blade rigidity characteristics X = r sin (θ - φ) bt where r is the blade radius, X bt is the x-axis coordinate of the blade tip in the hub coordinate system; Step 4, translate and rotate (X bt , Y bt ) to the camera coordinate system, and get (X ct , Y ct ) by using the transformation formula, X ct is the x-axis coordinate of the paddle tip in the camera coordinate system, and Y ct is the y-axis coordinate of the paddle tip in the camera coordinate system; Step 5, project (X ct , Y ct ) to the camera calibration plane, and get the spatial vector distance of the tip of the oar in the y direction of the calibration plane in the camera coordinate system using the projection formula ; Step 6, calculate the vertical dimension of the field of view taken where Hc is the optical target surface size, f is the lens focal length, and D is the static paddle spacing. Step 7, determine the theoretical y-axis coordinate Y of the tip point in the image coordinate system by using the derived formula it ; Step 8. Fit the coordinates Y of the tip point in the image coordinate system by least square method it and the coordinates Y of the tip point in the hub coordinate system bt to obtain the fitting function as follows: where a1, b1, c1 are the coefficients obtained by fitting. Step 9, data alignment is performed using the static blade pitch and the initial blade tip image coordinates to obtain a new fitting function: wherein are the coefficients of the new fitting function; Step 10, the y-axis coordinate Y of the tip marker point calculated by image processing it Substitute the new fitting function to get the y-axis coordinate of the corrected tip in the hub coordinate system, that is, the corrected vertical flapping amount of the upper and lower tips. Step 11, calculating the actual blade spacing=the y-axis coordinate of the corrected upper blade tip in the hub coordinate system-the y-axis coordinate of the corrected lower blade tip in the hub coordinate system+the initial static blade spacing.

3. The method of claim 2, wherein, The transformation formula in step 4 is: ， wherein .

4. The method of claim 3, wherein, The projection formula in step 5 is: 。 5. The method of claim 2, wherein, The formula derived in step 7 is where Y pxs is the total number of pixels in the Y axis of the image.

6. The method of claim 2, wherein, Step 9 is: first, initialize the theoretical Y it , then detect the current tip marker point record , calculate the error pixels , and substitute the fitting function to obtain new fitting parameters, that is, X-axis translation of the fitting function.

7. The method of claim 2, wherein, In step two, the camera focal length, aperture, and exposure time are adjusted, with the camera focal length being adjusted to satisfy , where f represents the lens focal length, L is the distance from the camera to the point light source marker point, Hc is the vertical dimension of the camera optical target surface, and H view is the vertical dimension of the field of view.

8. A monocular vision twin-rotor tip distance measuring system for flight testing, characterized by, The system is used for the method of any one of claims 1 to 7, and the system comprises: The cameras arranged on the front side, rear side and tail of the coaxial dual-rotor helicopter, the field of view direction being directly opposite the front, side and rear upper and lower rotor blade overlap positions; The photoelectric sensor installed on the upper end surface platform of the main reducer, the photosensitive cover being vertically upward, and the reflector being pasted on the rotor automatic tilting device dynamic ring or the lower surface of the blade root; The plurality of point light source markers installed in the cavities at the upper and lower blade tip positions, the light outlet cover being flush with the lower surface of the blade; The trigger control box and the onboard notebook computer installed in the equipment cabin, used for triggering and collecting the cameras and processing and displaying the transmitted image data; The calibration plate at the position of the center point vertically through the upper and lower blade tips and perpendicular to the camera optical axis.

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