Monocular vision dual-rotor blade tip distance measuring system and method for flight test

Abstract

The invention provides a monocular vision dual-rotor blade tip distance measuring system and method for flight test, and the method comprises the steps: placing a calibration plate at a plane position which passes through the central point of the vertical direction of the tips of upper and lower blades and is vertical to the optical axis of a camera, and moving the calibration plate to enable the calibration plate to be located in the view field of the camera; adjusting camera parameters to enable the calibration image to meet the definition requirement; when the rotor rotates, the light reflecting sheet sweeps the photoelectric sensor to generate a pulse signal of one pulse signal in each circle; the trigger control box outputs camera trigger signals to the three cameras after carrying out quadruplicated frequency and conditioning on the pulse signals; the camera photographs the point light source mark points of the upper paddle and the lower paddle under the control of the trigger signal; the camera transmits a picture to the airborne notebook computer, and the airborne notebook computer processes and calculates the picture to obtain camera measurement data; after camera measurement data are corrected, the blade tip distance is finally obtained; according to the invention, real-time and reliable measurement and monitoring of the upper and lower rotor tip distance in the flight test process of the coaxial dual-rotor helicopter can be realized, and the test flight safety is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of helicopter rotor test and measurement, and in particular, relates to a monocular vision dual-rotor blade tip pitch measurement system and method for flight testing. Background Art

[0002] Due to the structural characteristics of the coaxial and counter-rotating upper and lower rotors, the tips of the upper and lower rotors of a coaxial twin-rotor helicopter will be close to each other on the rearward side of the upper rotor and the forward side of the lower rotor. Especially when the upper and lower rotors are in differential pitch change and flying at high speeds, there is a risk of the tips of the blades colliding. Therefore, it is necessary to measure and monitor the pitch of the upper and lower rotors in real time. There are methods for measuring the tip pitch of coaxial twin rotors based on different principles, such as machine vision, millimeter-wave radar, and electromagnetic near-field induction. Among them, the machine vision method has been widely used due to its advantage of intuitive and visible measurement. At present, the machine vision tip pitch measurement methods in use are divided into two categories: binocular stereo vision and monocular vision. The advantages and disadvantages are as follows:

[0003] (1) The binocular stereo vision measurement method simulates the principle of human left and right eyes to perceive and recognize objects. It uses two cameras arranged adjacent to each other on the left and right to perform stereo imaging and image processing on the upper and lower rotor blade tips to obtain the blade tip distance. It is a non-contact measurement method with the advantage of high measurement accuracy. However, since it requires correlation analysis of the left and right images, it has the disadvantages of slow calculation and processing speed and poor real-time performance.

[0004] (2) The currently used monocular vision measurement method is only suitable for coaxial rotor ground tests, and cannot be used for flight tests, because the camera needs to be installed at a distance from the hub that is no less than the blade diameter and at the same height as the rotor disk plane. Therefore, it cannot guarantee flight safety. Summary of the invention

[0005] In order to solve the problem that the relevant technology has low reliability and low test flight safety when measuring and monitoring the upper and lower rotor tip pitches in real time, the present application provides a monocular vision dual-rotor blade tip pitch measurement system and method for flight test, which can realize real-time and reliable measurement and monitoring of the upper and lower rotor blade tip pitches during the flight test of a coaxial dual-rotor helicopter, thereby improving the test flight safety; the technical solution is as follows:

[0006] In a first aspect, a monocular vision dual-rotor blade tip pitch measurement method for flight testing is provided, the method comprising:

[0007] Step 1: Install a camera on the front, rear and tail of the side of the coaxial twin-rotor helicopter, with the field of view facing the overlapping position of the upper and lower rotor blades in the front, side and rear; install the photoelectric sensor on the upper end surface platform of the main reducer, with the photosensitive cover vertically facing upward, and the corresponding reflective sheet is pasted on the dynamic ring of the rotor automatic tilt device or the lower surface of the blade root to ensure that the photoelectric sensor is triggered once the rotor rotates one circle; install multiple point light source marking points in the cavity at the tip position of the upper and lower blades respectively, and the light output cover of the point light source marking point is flush with the lower surface of the blade to ensure that the three cameras installed on the fuselage can take clear pictures; install the trigger control box and the onboard laptop computer in the equipment cabin to trigger the camera for acquisition and process and display the transmitted image data;

[0008] Step 2: Place the calibration plate on a plane that passes through the center of the upper and lower blade tips in a vertical direction and is perpendicular to the camera optical axis, and move the calibration plate so that it is within the camera field of view; then adjust the camera parameters so that the calibration image meets the clarity requirements;

[0009] Step three, when the rotor rotates, the reflector sweeps across the photoelectric sensor, generating a pulse signal for each circle; the trigger control box quadruples the pulse signal and conditions it, then outputs a camera trigger signal to three cameras; the camera takes pictures of the point light source marking points on the upper and lower blades under the control of the trigger signal; the camera transmits the picture to the onboard laptop computer, which processes and calculates the picture to obtain the camera measurement data; after correcting the camera measurement data, the blade tip pitch 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 for determining the blade tip pitch based on the camera measurement data is: blade tip pitch = 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 blade tip pitch is determined based on the corrected camera measurement data, specifically including:

[0012] Step 1, obtain 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, that is, the y-axis coordinate Ybt of the blade tip in the hub coordinate system;

[0014] Step 3: Based on the rigidity characteristics of the blade, define the blade tip flapping trajectory as an arc. Based on the constraint equation Get X bt , where r is the blade radius;

[0015] Step 4: (X bt , Y bt ) is translated and rotated to the camera coordinate system, and the transformation formula is used to obtain (X ct , Y ct );

[0016] Step 5: (X ct , Y ct ) is projected onto the camera calibration plane, and the projection formula is used to obtain the space vector distance Y′ of the propeller tip in the y direction of the calibration plane in the camera coordinate system. ct ;

[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: Use the derived formula to determine the theoretical y-axis coordinate Y of the blade tip in the image coordinate system. it ;

[0019] Step 8: Use the least squares fitting algorithm to find the coordinate Y of the blade tip in the image coordinate system. it and the coordinate Y of the blade tip in the hub coordinate system bt Perform fitting and obtain the fitting function as follows: Where a, b, and c are the coefficients obtained by fitting;

[0020] Step 9: Use the static propeller pitch and the initial propeller tip image coordinates to align the data and obtain a new fitting function: Where a′, b′, c′ are the coefficients of the new fitting function;

[0021] Step 10: The y-axis coordinate Y of the blade tip mark point obtained by image processing it Substitute the new fitting function: Get the corrected vertical swing amount Y of the upper and lower blade tips bt ;

[0022] Step 11, calculate the actual propeller pitch = the corrected upper propeller tip flapping amount - the corrected lower propeller tip flapping amount + the initial static propeller pitch.

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

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

[0025] Optionally, the derived formula in step 7 is where Y pxsis the total number of pixels on the Y axis of the image.

[0026] Optionally, step 9 is specifically as follows: first initialize the theoretical Y it Then detect the blade tip mark at this time and record Y′ it , calculate the error pixel ΔY it =Y it -Y′ it , substitute into the fitting function and refit to obtain new fitting parameters, that is, translate the fitting function on the x-axis to greatly reduce the error caused by the installation.

[0027] Optionally, in step 2, adjust the camera focal length, aperture, and exposure time, and the camera focal length satisfies f is the focal length of the lens, L is the distance from the camera to the point light source mark, Hc is the longitudinal dimension of the camera optical target surface, H view It is the longitudinal size of the shooting field of view.

[0028] In a second aspect, a monocular vision dual-rotor blade tip pitch measurement method for flight testing is provided, the method comprising:

[0029] The cameras installed on the front, rear and tail of the coaxial twin-rotor helicopter have their field of view facing the overlapping position of the upper and lower rotor blades in the front, side and rear;

[0030] The photoelectric sensor is installed on the upper end surface platform of the main reducer, with its photosensitive cover facing vertically upward and pasted on the reflective sheet on the lower surface of the rotor automatic tilt device ring or the blade root;

[0031] Multiple point light source marking points are installed in the cavity at the tips of the upper and lower blades, and their light output covers are flush with the lower surface of the blades, ensuring that the three cameras installed on the fuselage can take clear pictures;

[0032] The trigger control box and onboard laptop computer installed in the equipment cabin are used to trigger the camera to collect data and process and display the transmitted image data;

[0033] The calibration plate is located on a plane that passes through the center of the upper and lower blade tips and is perpendicular to the camera optical axis.

[0034] The present invention provides a monocular vision twin-rotor blade tip pitch measurement system and method for flight test, which utilizes three cameras and corresponding photoelectric sensors, a trigger control box, point light source marking points, an onboard laptop computer, etc. to form a measurement system, respectively collect point light source marking point images of upper and lower blades at overlapping moments in front, side and rear, identify and process the images, and finally calculate and correct the blade tip pitch value, thereby realizing real-time and reliable measurement and monitoring of the upper and lower rotor blade tip pitches during the flight test of a coaxial twin-rotor helicopter, and improving the safety of the test flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of a monocular vision dual-rotor blade tip pitch measurement system used for flight testing;

[0036] Figure 2 Mark the point light source with the blade internal installation design;

[0037] Figure 3 This is the principle diagram of optical imaging;

[0038] Figure 4 This is a schematic diagram of camera squint calibration;

[0039] Figure 5 Correction schematic for data. DETAILED DESCRIPTION

[0040] The present application is further described in detail below through specific implementation methods and drawings.

[0041] Coaxial twin rotors are a new rotor configuration. During the flight test in the development phase, the blade tip pitch of the upper and lower rotors needs to be monitored. The multi-vision blade tip pitch measurement method has the disadvantages of slow calculation and processing speed and poor real-time performance. The currently used monocular vision blade tip pitch method can only be used for ground tests and cannot be used in flight due to the requirements and limitations of the camera installation position.

[0042] The present application proposes a monocular vision twin-rotor blade tip pitch measurement system and method for flight testing, which is suitable for measuring and monitoring the upper and lower rotor blade tip pitches under different total pitch and cyclic pitch change states in coaxial twin-rotor helicopter flight tests, 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 with fast processing speed and high measurement accuracy, and has the advantages of being suitable for different scenarios of ground tests and flight tests.

[0043] See also Figure 1 An embodiment of the present invention provides a monocular vision dual-rotor blade tip distance measurement system for flight testing, including a camera, a photoelectric sensor, a trigger control box, a point light source marker, an onboard laptop computer, etc.

[0044] The camera uses a high data transmission rate industrial camera with a gigabit network interface, and the resolution is determined according to the shooting field size and accuracy requirements; the camera frame rate p ≥ (Nr·K) / 60, Nr is the rotor speed (rpm), k is the number of single rotor blades; the exposure time is determined according to the linear velocity of the blade to ensure that the target object is clearly imaged without ghosting.

[0045] The photoelectric sensor uses a TTL high-speed output type photoelectric sensor with a trigger delay of ≤0.3ms. It is used in conjunction with a reflective sheet pasted on the rotor automatic tilt device dynamic ring or the lower surface of the blade root to ensure that a pulse signal is generated for each rotation.

[0046] The trigger control box has two modes: internal trigger and external trigger. The external trigger mode is triggered by the rotor photoelectric sensor; the internal trigger mode is triggered by the internal timer. The trigger control box can output three groups of trigger signals after multiplying the internal and external trigger signals (several times of the propeller blades) and delaying them, and send them to three cameras respectively. Among them, the trigger delay can be adjusted to cover the length of time a single propeller blade rotates one circle; the phase difference between the three groups of trigger signals output can be adjusted according to the camera installation position.

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

[0048] The onboard laptop is connected to three cameras through three Gigabit network ports. It is mainly used for image calibration, camera acquisition control, image processing and display, etc. The time t≤1 / p for processing and displaying three frames of images (1 frame image / camera*3 cameras) at the same time, where p is the camera frame rate.

[0049] The method of the embodiment of the present invention utilizes a monocular vision twin-rotor blade tip pitch measurement system installed in a flight test on a helicopter to collect images of the upper and lower blades of the coaxial twin-rotor at overlapping positions in the front, side, and rear; obtains the flapping values ​​of the upper and lower blade tips of the rotor through image processing and calculation; and performs data correction on the upper and lower blade tip flapping values ​​to obtain the coaxial twin-rotor blade tip pitch value.

[0050] The specific measurement method is as follows:

[0051] 1. Equipment installation and connection

[0052] A camera is installed on the front, rear and tail of the coaxial twin-rotor helicopter, with the field of view facing the overlapping position of the upper and lower rotor blades in the front, side and rear. The photoelectric sensor is installed on the upper end platform of the main reducer, with the photosensitive cover facing vertically upward. The corresponding reflective sheet is pasted on the rotor automatic tilt device dynamic ring or the lower surface of the blade root to ensure that the rotor rotates one circle and triggers the photoelectric sensor once. 8 point light source marking points are installed in the cavity at the tip position of the upper and lower blades, and the point light source marking point light cover is flush with the lower surface of the blade to ensure that the three cameras installed on the fuselage can take clear pictures. The trigger control box and the onboard laptop are installed in the equipment cabin to trigger the camera to collect and process and display the transmitted image data. After the equipment is installed, connect and test the power cord, network cable, and TTL trigger signal cable.

[0053] 2. Camera parameter calibration

[0054] After the equipment is installed, the camera parameters need to be calibrated before measurement. First, place the calibration plate as shown in the figure. Figure 4 The plane position passing through point C and perpendicular to the straight line CE is shown, and the calibration plate is moved so that it is within the camera field of view; then the camera parameters are adjusted, mainly the camera focal length, aperture, and exposure time, so that the calibration image has a higher definition. Among them, the camera focal length satisfies: f = (L·Hc) / Hview, f represents the focal length of the lens, 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 Hview is the longitudinal size of the shooting field of view, such as Figure 3 shown.

[0055] 3. Camera measurement data correction

[0056] The error of the camera measuring the upper and lower blade tip pitch of the twin rotor is mainly caused by the camera's squint. The data can be corrected by the following methods:

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

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

[0059] (X c ,Y c ): Camera coordinate system (with 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 and the direction reference Figure 5 );

[0061] Constant definition: D: static propeller pitch, r: radius of the propeller blade, Ypxs: total number of pixels on the Y axis of the image;

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

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

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

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

[0066] Step 1, obtain 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;

[0067] Step 2, define the blade tip flapping range, that is, 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 arc. Based on the constraint equation Get X bt , where r is the blade radius;

[0069] Step 4: (X bt , Y bt ) is translated and rotated to the camera coordinate system, and the transformation formula is used to obtain (X ct , Y ct ); the transformation formula is:

[0070] Step 5: (X ct , Y ct ) is projected onto the camera calibration plane, and the projection formula is used to obtain the space vector distance Y′ of the propeller tip in the y direction of the calibration plane in the camera coordinate system. ct ; The projection formula is:

[0071] 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;

[0072] Step 7: Use the derived formula to determine the theoretical y-axis coordinate Y of the blade tip in the image coordinate system. it ;

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

[0074] Step 8: Use the least squares fitting algorithm to find the coordinate Y of the blade tip in the image coordinate system. it and the coordinate Y of the blade tip in the hub coordinate system bt Perform fitting and obtain the fitting function as follows: Where a, b, and c are the coefficients obtained by fitting;

[0075] Step 9: Use the static propeller pitch and the initial propeller tip image coordinates to align the data and obtain a new fitting function: Where a′, b′, and c′ are the coefficients of the new fitting function.

[0076] Specifically, further data alignment and fitting are performed based on the static propeller pitch and the initial propeller tip image coordinates. The specific form is: first initialize the theoretical Y it Then check the blade tip mark point at this time and record Y' it , calculate the error pixel ΔY it =Y it -Y′ it , substitute into the fitting function and refit to obtain new fitting parameters, that is, translate the fitting function on the x-axis to greatly reduce the error caused by the installation.

[0077] Step 10: Set the y-axis coordinate of the propeller tip mark point to it Substituting into the formula:

[0078] Get the corrected vertical swing amount Y of the upper and lower blade tips bt ;

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

[0080] An embodiment of the present invention further provides a monocular vision dual-rotor blade tip pitch measurement system for flight testing, comprising:

[0081] The cameras installed on the front, rear and tail of the coaxial twin-rotor helicopter have their field of view facing the overlapping position of the upper and lower rotor blades in the front, side and rear;

[0082] The photoelectric sensor is installed on the upper end surface platform of the main reducer, with its photosensitive cover facing vertically upward and pasted on the reflective sheet on the lower surface of the rotor automatic tilt device ring or the blade root;

[0083] Multiple point light source marking points are installed in the cavity at the tip positions of the upper and lower blades, and their light output covers are flush with the lower surface of the blades;

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

[0085] The calibration plate is located on a plane that passes through the center points of the upper and lower propeller blades in the vertical direction and is perpendicular to the camera optical axis.

[0086] The above only expresses the implementation methods of the present application, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. In addition, the parts that are not detailed in this application are all conventional technologies.

Claims

1. A monocular vision dual-rotor blade tip pitch measurement method for flight testing, characterized in that: The method comprises: Step 1: Install a camera on the front, rear and tail of the side of the coaxial twin-rotor helicopter, with the field of view facing the overlapping position of the upper and lower rotor blades in the front, side and rear; install the photoelectric sensor on the upper end surface platform of the main reducer, with the photosensitive cover vertically facing upward, and the corresponding reflective sheet is pasted on the dynamic ring of the rotor automatic tilt device or the lower surface of the blade root to ensure that the photoelectric sensor is triggered once the rotor rotates one circle; install multiple point light source marking points in the cavity at the tip position of the upper and lower blades respectively, and the light output cover of the point light source marking point is flush with the lower surface of the blade; install the trigger control box and the onboard laptop computer in the equipment cabin to trigger the camera for acquisition and process and display the transmitted image data; Step 2: Place the calibration plate on a plane that passes through the center of the upper and lower blade tips in a vertical direction and is perpendicular to the camera optical axis, and move the calibration plate so that it is within the camera field of view; then adjust the camera parameters so that the calibration image meets the clarity requirements; Step three, when the rotor rotates, the reflector sweeps across the photoelectric sensor, generating a pulse signal for each circle; the trigger control box quadruples the pulse signal and conditions it, then outputs a camera trigger signal to three cameras; the camera takes pictures of the point light source marking points on the upper and lower blades under the control of the trigger signal; the camera transmits the picture to the onboard laptop computer, which processes and calculates the picture to obtain the camera measurement data; after correcting the camera measurement data, the blade tip pitch is finally obtained.

2. The method according to claim 1, characterized in that In step three, the camera measurement data is the upper blade tip flapping amount and the lower blade tip flapping amount. The relationship formula for determining the blade tip pitch based on the camera measurement data is: blade tip pitch = upper blade tip flapping amount - lower blade tip flapping amount + initial static blade pitch.

3. The method according to claim 1, characterized in that In step three, the camera measurement data is corrected, and the blade tip pitch is determined based on the corrected camera measurement data, specifically including: Step 1, obtain 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 blade tip flapping range, that is, the y-axis coordinate Ybt of the blade tip in the hub coordinate system; Step 3: Based on the rigidity characteristics of the blade, define the blade tip flapping trajectory as an arc. Based on the constraint equation Get X bt , where r is the blade radius; Step 4: (X bt , Y bt ) is translated and rotated to the camera coordinate system, and the transformation formula is used to obtain (X ct , Y ct ); Step 5: (X ct , Y ct ) is projected onto the camera calibration plane, and the projection formula is used to obtain the space vector distance Y′ of the propeller tip in the y direction of the calibration plane in the camera coordinate system. ct ; 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; Step 7: Use the derived formula to determine the theoretical y-axis coordinate Y of the blade tip in the image coordinate system. it ; Step 8: Use the least squares fitting algorithm to find the coordinate Y of the blade tip in the image coordinate system. it and the coordinate Y of the blade tip in the hub coordinate system bt Perform fitting and obtain the fitting function as follows: Where a, b, and c are the coefficients obtained by fitting; Step 9: Use the static propeller pitch and the initial propeller tip image coordinates to align the data and obtain a new fitting function: Where a′, b′, and C′ are the coefficients of the new fitting function; Step 10: The y-axis coordinate Y of the blade tip mark point obtained by image processing it Substitute the new fitting function: Get the corrected vertical swing amount Y of the upper and lower blade tips bt ; Step 11, calculate the actual propeller pitch = the corrected upper propeller tip flapping amount - the corrected lower propeller tip flapping amount + the initial static propeller pitch.

4. The method according to claim 3, characterized in that: The transformation formula in step 4 is: in, D is the static propeller spacing, a is the horizontal distance from the camera installation point to the upper and lower propeller tips, and b is the vertical distance from the camera installation point to the upper and lower propeller tips.

5. The method according to claim 3, characterized in that: The projection formula in step 5 is:

6. The method according to claim 3, characterized in that The formula derived in step 7 is where Y pxs is the total number of pixels on the Y axis of the image.

7. The method according to claim 3, characterized in that Step 9 is as follows: First, initialize the theory Y it Then detect the blade tip mark at this time and record Y′ it , calculate the error pixel ΔY it =Y it -Y′ it , substitute into the fitting function and refit to obtain new fitting parameters, that is, perform X-axis translation on the fitting function.

8. The method according to claim 1, characterized in that In step 2, adjust the camera focus, aperture, and exposure time. The camera focus meets f is the focal length of the lens, L is the distance from the camera to the point light source mark, Hc is the longitudinal dimension of the camera optical target surface, H view It is the longitudinal size of the shooting field of view.

9. A monocular vision dual-rotor blade tip pitch measurement system for flight testing, characterized in that: For use in the method described in any one of claims 1 to 8, the system comprises: The cameras installed on the front, rear and tail of the coaxial twin-rotor helicopter have their field of view facing the overlapping position of the upper and lower rotor blades in the front, side and rear; The photoelectric sensor is installed on the upper end surface platform of the main reducer, with its photosensitive cover facing vertically upward and pasted on the reflective sheet on the lower surface of the rotor automatic tilt device ring or the blade root; Multiple point light source marking points are installed in the cavity at the tips of the upper and lower blades, and their light output covers are flush with the lower surface of the blades; The trigger control box and onboard laptop computer installed in the equipment cabin are used to trigger the camera to collect data and process and display the transmitted image data; The calibration plate is located on a plane that passes through the center points of the upper and lower propeller blades in the vertical direction and is perpendicular to the camera optical axis.

Images