Rapid calculation method for pitch of blade tips of coaxial dual-rotor helicopter

Abstract

The invention belongs to the field of bending deformation calculation of cantilever beam structures in material mechanics, and particularly relates to a method for rapidly calculating the distance between blade tips of a coaxial dual-rotor helicopter. An upper rotor telemetering collector and a lower rotor telemetering collector are respectively mounted on upper and lower blades of the coaxial dual-rotor helicopter; strain gauges are respectively adhered to the upper and lower paddles; the upper rotor telemetering collector and the lower rotor telemetering collector are two sets of blade strain load collectors for synchronously collecting and are respectively used for collecting strain signals of an upper blade adhered with a strain gauge and a lower blade adhered with a strain gauge; and the photoelectric pulse sensor is arranged at a preset position at the top of the machine body and is vertically and upwards mounted.

Description

Technical Field

[0001] The invention belongs to the field of material mechanics cantilever beam structure bending deformation calculation, and in particular relates to a method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter. Background Art

[0002] In order to reduce the aerodynamic drag during high-speed forward flight, the coaxial high-speed helicopter designed based on the concept of forward blades usually reduces the hub spacing between the upper and lower rotors during design. The unique lift bias characteristics of the coaxial twin-rotor configuration further increase the risk of collision between the upper and lower rotor tips. Currently, there are three feasible solutions based on blade multi-profile strain response, machine vision recognition, and millimeter-wave radar ranging.

[0003] The tip deflection measurement based on the strain response of multiple blade sections is often more accurate in static calibration tests. However, during the high-speed rotation of the blade, the flapping strain of the root section is significantly coupled with the centrifugal force, which will significantly interfere with the measurement of the tip deflection. In addition, since the change in the upper and lower rotor tip spacing caused by the collective pitch and cyclic pitch control will not produce strain response, the tip spacing caused by the change in pitch angle cannot be reflected by strain, which further increases the measurement error of the tip spacing.

[0004] The biggest problem with the blade tip image recognition method based on machine vision technology is that it is extremely difficult to identify the blade tip mark features under complex and changing background exposure environments. Even when the camera is in a strong exposure environment for a long time (facing the sun), the measurement system will be completely unable to recognize the blade tip mark. This defect is insurmountable.

[0005] The blade tip spacing test solution based on millimeter wave radar requires the radar module to be encapsulated in the blade tip structure of the upper or lower rotor. The Doppler effect and multipath effect interference caused by the high-speed relative motion of the upper and lower rotors will have a great impact on the blade tip spacing measurement results, so the calculation error is often large, and there is anomaly interference that cannot be eliminated. Summary of the invention

[0006] Technical problem solved by the present invention: The technical solution of the present invention aims at the problems existing in the blade multi-profile strain response method in the background technology, and provides a high-precision method for fast calculation of the blade tip spacing of a coaxial twin-rotor. The method obtains a mapping matrix set of the full combination profile strain and blade tip deflection of no less than 3 profiles through static calibration. Further, a total pitch power calibration test is carried out to obtain the measurement results of the full profile combination strain and the blade tip spacing measurement results based on machine vision technology, and a subset with consistent changes in Δ total pitch / Δ blade tip deflection is found in the strain / blade tip deflection mapping matrix set. The profile combination corresponding to this subset is a profile combination with low centrifugal force coupling interference, and the strain values ​​of these profiles can be used as input for blade tip deflection calculation. Further, the control amount of the upper and lower rotors and the compensation coefficient of the blade tip flapping displacement are obtained by statically changing the pitch angle. Further, the real-time azimuth angle of the strain blades of the upper and lower rotors is obtained through the 0 azimuth pulse signal. Furthermore, the real-time pitch angle of the strain blade can be calculated through the real-time azimuth angle of the upper and lower rotor strain blades and the control collective pitch and cyclic pitch. Furthermore, high-precision blade tip spacing measurement can be achieved through matrix product of the selected strain profile combined response and mapping matrix plus real-time pitch angle control response compensation.

[0007] The technical solution of the present invention:

[0008] A method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter, wherein an upper rotor telemetry collector 1 and a lower rotor telemetry collector 2 are respectively installed on the upper and lower blades of the coaxial twin-rotor helicopter; and strain gauges 6 are respectively attached to the upper and lower blades; the upper rotor telemetry collector 1 and the lower rotor telemetry collector 2 are two sets of blade strain load collectors for synchronous collection, which are respectively used to collect strain signals of an upper blade 4 attached with a strain gauge and a lower blade 5 attached with a strain gauge; a photoelectric pulse sensor 3 is arranged at a preset position on the top of the fuselage, and the photoelectric pulse sensor 3 is installed vertically upward, and the method comprises:

[0009] S1, static calibration: select one blade from each of the upper and lower rotors to complete the flapping full-bridge strain gauge patch of the same n sections, perform static calibration on the upper and lower blades respectively, and obtain the flapping full-bridge strain ε of the n sections of the upper and lower blades respectively. u , ε d and the tip deflection of the upper and lower blades l u , l d , obtain the linear mapping matrix K of the combined strain matrix of the upper and lower blade sections and the blade tip deflection u , K d ;

[0010] S2, according to the dynamic measurement results of the blade tip image recognition method based on machine vision technology and the blade tip deflection measurement method based on the blade multi-profile strain response, select the linear mapping matrix K u , K dThe optimal set of coefficients in ;

[0011] S3, obtain the control compensation coefficient C d ;

[0012] S4, determining the coincidence azimuth angle of the strain collection points of the upper rotor telemetry collector 1 and the lower rotor telemetry collector 2;

[0013] S5, respectively calculating the strain displacement and control compensation displacement of the rotor strain blade tip at the coincident azimuth of the strain collection point;

[0014] S6, calculating the blade tip spacing of the coaxial twin-rotor helicopter at the coincident azimuth of the strain collection point according to the strain displacement of the rotor strain blade tip at the coincident azimuth of the strain collection point, the control compensation displacement, and the spacing between the upper and lower rotor discs.

[0015] Furthermore,

[0016] The upper blade 4 with the strain gauge attached and the lower blade 5 with the strain gauge attached are attached with the swinging full-bridge strain gauge 6 at the 1 / 4 chord position of the same section, and the number of sections is at least 3.

[0017] Furthermore, S1 is specifically:

[0018] Select one blade from each of the upper and lower rotors to complete the flapping full-bridge strain gauge patch of the same n sections, perform static calibration on the upper and lower blades respectively, and obtain the flapping full-bridge strain ε of the n sections of the upper and lower blades respectively. u , ε d and the tip deflection of the upper and lower blades l u , l d ;

[0019] The total number of combinations of 3 or more sections selected from n sections is Then, the upper and lower strain response matrices E of all combinations of 3 or more profiles are obtained. u and E d , by solving the linear equations of upper and lower blade strain and blade tip deflection and E d ×K d =L d , obtain the linear mapping matrix K of the combined strain matrix of the upper and lower blade sections and the blade tip deflection u , K d .

[0020] Furthermore, S2 is specifically:

[0021] The blade tip spacing measurement system 7 based on machine vision technology is installed at the 90° position of the fuselage to perform data verification of the blade tip deflection calculation results. The test state shall be no less than two, including at least 0°, maximum total spacing, and the maximum total spacing. The azimuth pulse signal obtained by the photoelectric pulse sensor 3 synchronously controls the blade tip spacing measurement system 7 based on machine vision technology and the upper rotor telemetry collector 1 and the lower rotor telemetry collector 2 to perform external triggering collection, and obtains image data and upper and lower rotor strain blade strain data in two test states respectively;

[0022] Through difference analysis, the total distance from 0° to the maximum total distance is obtained. When the upper and lower rotor blade tip deflection image method is measured, the strain is and The strain calculation rule calculates the strain difference of all sections in two states to obtain the relative strain change value E. u and E d , multiplied by the linear matrix K of the combined strain and deflection of the upper and lower rotor blade sections u , K d , get all the upper and lower rotor blades Tip deflection corresponding to the profile combination

[0023] Comparison of rotor strain blade tip deflection collection Each element in Measurement value with image method Find the cross-sectional combined strain corresponding to the element with the smallest error value And the one-dimensional linear matrix coefficient K corresponding to this combination ue , and then obtain the cross-sectional combined strain E corresponding to the lower rotor strain blade de And the one-dimensional linear matrix coefficient K corresponding to this combination de .

[0024] Furthermore, S3 is specifically:

[0025] By statically raising the lower blade pitch, the blade tip spacing measurement system 7 based on machine vision technology is used to obtain the trailing edge mark point at the first chord line position of the upper blade tip profile and the leading edge mark point at the second chord line position of the lower blade tip profile, respectively, and the pitch is raised from 0° to the maximum total pitch. Deflection change Δl under the state ut , Δl dt， The control compensation coefficient c is obtained by dividing the change in blade tip deflection by the change in total pitch. u 、c d .

[0026] Furthermore, S4 is specifically:

[0027] Rotate the blades in a static state so that the photoelectric pulse sensor 3 is in a triggered state, and calculate the current spatial positions of the upper and lower rotor strain blade tips through trigonometric geometry, so as to obtain the initial positions of the upper and lower rotor strain blades in the triggered state. and

[0028] The upper rotor telemetry collector 1 and the lower rotor telemetry collector 2 are set to the same sampling rate S fixed frequency acquisition. When the rotor speed is stable at N, the photoelectric pulse sensor 3 collects the phase of the sampling points between two consecutive pulse rising edges, and calculates the sampling points between the two pulse rising edges point by point to obtain the phase angle of each sampling point in one circle;

[0029] The specific method is: based on the rising edge of the continuous pulse signal collected by the photoelectric pulse sensor 3, the strain data of the upper and lower rotor strain blades are intercepted in the whole cycle, and the first sampling point after exceeding the first rising edge threshold represents the initial orientation of the upper and lower rotor strain blades. and The upper rotor strain blade is in the positive rotation direction, so the phase of the upper rotor strain blade increases by 6×N / S degrees point by point, and the lower rotor strain blade is in the reverse rotation direction, so the phase of the lower rotor strain blade decreases by 6×N / S degrees point by point, and so on, to obtain the azimuth angle corresponding to the i-th strain sampling point of the upper blade 4 and the lower blade 5 with the strain gauge attached in one circle of sampling points and

[0030]

[0031]

[0032] Finally, the overlapping positions of the upper and lower blades of the coaxial twin rotor are fixed at eight positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

[0033] Further, S5, the strain displacement of the rotor blade tip at the coincident azimuth of the strain collection point is calculated, specifically:

[0034] The combined strain response of the effective section when the upper and lower rotor strain blades are in the 8 overlapping positions in the 1-circle strain data and The effective section combined strain of the upper and lower rotor blades is multiplied by the one-dimensional linear matrix coefficient K of the upper and lower rotor blades respectively. ue , K de The strain displacements of the upper and lower rotor blades when they are in 8 overlapping positions are: and

[0035] Further, S5, the control compensation displacement of the rotor strain blade tip at the coincident azimuth of the strain collection point is calculated, specifically:

[0036] Based on the current state of the control amount, the rotor collective pitch θ 0U 、Upper rotor longitudinal cyclic pitch change A 1U 、Lateral cyclic pitch change of upper rotor B 1U 、Lower rotor total pitch θ 0L , Differential longitudinal periodic pitch A 1L , Differential lateral periodic pitch variation B 1L , Advance control angle The upper rotor strain blade is in eight positions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° n Pitch angle The lower rotor strain blade is in eight positions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° n Pitch angle Use the upper and lower rotor control compensation coefficients C respectively u , C d Multiply the pitch angle θ of the upper and lower rotor strain blades in eight overlapping phases u ,θ L Obtain the control compensation displacement at eight overlapping phases

[0037] Furthermore, S6 is specifically:

[0038] The strain displacement of the rotor blade tip at eight positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° Plus the control compensation displacement of the rotor blade tip Subtract the strain displacement of the blade tip from the lower rotor strain Then subtract the control compensation displacement of the lower rotor strain blade tip Adding the distance D between the upper and lower rotor discs, we can obtain the blade tip spacing of the coaxial twin-rotor helicopter at eight directions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

[0039] This method realizes the coupling interference of centrifugal force on the root strain of the blade through the combination of effective strain profiles, which greatly improves the measurement accuracy of the strain method; the effective strain profile combination is the combination with the lowest error. In actual tests, it is found that there are many other profile combination schemes that can also achieve centrifugal force coupling, and the error will not exceed 5mm. Therefore, other profile combination schemes can also be used as alternative schemes in flight tests. When the signal of the strain gauge of an individual profile is abnormal, it can be immediately switched to the alternative scheme to continue to monitor the blade tip spacing, which significantly increases the robustness and reliability of the system; compared with other methods such as the image method, the strain method has a higher technical maturity and a stronger ability to adapt to the flight environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of a hardware system involved in a method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter provided in an embodiment of the present invention;

[0041] Figure 2 A schematic diagram of the installation and measurement of the photoelectric pulse sensor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0043] The hardware system involved in the method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter provided in an embodiment of the present invention is as follows: Figure 1 As shown, it includes: an upper rotor telemetry collector 1, a lower rotor telemetry collector 2, a photoelectric pulse sensor 3, an upper blade 4 with a strain gauge 6 attached, and a lower blade 5 with a strain gauge 6 attached.

[0044] The upper rotor telemetry collector 1 and the lower rotor telemetry collector 2 are two sets of blade strain load collectors for synchronous collection, which are used to collect strain signals of the upper blade 4 and the lower blade 5 attached with strain gauges respectively. The installation position is selected at the upper and lower rotor hubs, and the closer to the rotation center, the better. The nonlinear error of the collector is not higher than 0.1%, and the clock error of the two sets of collectors does not exceed 100 microseconds.

[0045] The upper blade 4 and the lower blade 5 with the strain gauge attached are attached with a swinging full-bridge strain gauge 6 at the 1 / 4 chord position of the same section, and the minimum number of sections is not less than 3. In order to obtain better system robustness, the swinging full-bridge strain gauge 6 is usually attached to not less than 6 sections.

[0046] The typical resistance value of the strain gauge 6 is 350Ω, the two-grid parallel layout structure, the strain gauge temperature self-compensation material is a composite material, the sensitivity coefficient dispersion is ≤±1%, and the fatigue life is ≥10 7 .

[0047] The measurement range of the photoelectric pulse sensor 3 is not less than 2 meters, and the response time is not more than 300 microseconds. The photoelectric pulse sensor 3 is arranged at the 160° position on the top of the fuselage. The photoelectric pulse sensor 3 is installed vertically upward. Select any lower rotor blade and rotate the blade to the 160° position, that is, directly above the photoelectric pulse sensor 3. The laser emitted by the photoelectric pulse sensor 3 hits the lower surface of the lower blade. A 10 cm (length) × 2 cm (width) reflective paper is pasted in the span direction as the center of the laser reflection point on the lower surface of the lower blade. Figure 2 .

[0048] A fast calculation method for the blade tip spacing of a coaxial helicopter twin rotor is proposed. A blade is selected from each of the upper and lower rotors to complete the flapping full-bridge strain gauge patch of the same n sections. The upper and lower blades are statically calibrated respectively to obtain the flapping full-bridge strain ε of the n sections of the upper and lower blades. u , ε d and the tip deflection of the upper and lower blades l u , l d Based on the modal characteristics of blade flapping motion (blade tip deflection displacement is mainly caused by low-order flapping excitation), at least three sections are needed to accurately calculate the blade tip deflection. Therefore, all combinations of 3 or more sections selected from n sections total Then, the upper and lower strain response matrices E of all combinations of 3 or more profiles are obtained. u and E d , by solving the linear equation E of the upper and lower blade strain and blade tip deflection u ×K u =L u and E d ×K d =L d , we can obtain the linear mapping matrix K of the combined strain matrix of the upper and lower blades and the tip deflection u , K d ,in:

[0049]

[0050]

[0051]

[0052]

[0053] Furthermore, in order to eliminate the coupling interference of centrifugal force on the flapping strain of the profile near the root, the effective strain profile combination is selected as the input parameter of the blade tip deflection by conducting a coaxial twin-rotor ground test. A blade tip spacing measurement system 7 based on machine vision technology is installed at the 90° position of the fuselage to perform data verification of the blade tip deflection calculation results. The test conditions are no less than 2, including at least 0°, maximum total distance, and maximum total distance. The azimuth pulse signal obtained by the photoelectric pulse sensor 3 synchronously controls the blade tip spacing measurement system 7 based on machine vision technology and the upper rotor telemetry collector 1 and the lower rotor telemetry collector 2 to perform external triggering acquisition, and obtains image data and upper and lower rotor strain blade strain data under two test conditions respectively. Through difference analysis, the total pitch changes from 0° to the maximum total pitch When the upper and lower rotor blade tip deflection image method is measured, the strain is and The strain calculation law calculates the strain E of all cross sections in two states u and E d The difference is multiplied by the linear matrix K of the combined strain and deflection of the upper and lower rotor blade sections. u , K d , you can get the strain of the upper and lower rotor blades Tip deflection corresponding to the profile combination and Comparison of rotor strain blade tip deflection collection Each element in Measurement value with image method Find the cross-sectional combined strain E corresponding to the element with the smallest error value ue And the one-dimensional linear matrix coefficient K corresponding to this combination ue , that is, it is believed that the blade tip deflection value obtained by multiplying the strain set (one-dimensional matrix) of the combined section by the corresponding coefficient set (one-dimensional matrix) can eliminate the coupling interference of large centrifugal loads; similarly, the combined strain E of the effective section of the lower rotor strain blade can be obtained de And the one-dimensional linear matrix coefficient K corresponding to this combination de ;

[0054] Furthermore, the manipulation system changes the blade pitch angle, and the resulting change in the blade tip attitude is unrelated to the strain response, so the blade tip attitude change cannot be measured by strain, that is, the manipulation compensation displacement. Therefore, by statically raising the lower blade pitch, the blade tip spacing measurement system 7 based on machine vision technology is used to obtain the trailing edge mark point at the 0.95 chord line position of the upper blade tip profile and the leading edge mark point at the 0.05 chord line position of the lower blade tip profile, respectively, from 0° to the maximum total pitch. Deflection change under state The control compensation coefficient C can be obtained by dividing the change in blade tip deflection by the change in total pitch.u , C d ;

[0055] Furthermore, the blades are rotated in a static state so that the photoelectric pulse sensor 3 is in a triggered state, and the current spatial positions of the upper and lower rotor strain blade tips are calculated by trigonometric geometry, thereby obtaining the initial positions of the upper and lower rotor strain blades in the triggered state. and

[0056] Furthermore, the upper rotor telemetry collector 1 and the lower rotor telemetry collector 2 are set to the same sampling rate S fixed frequency acquisition. When the rotor speed is stable at N (rpm), it can be considered that the phase of the sampling points between the rising edges of two consecutive pulses collected by the photoelectric pulse sensor 3 is evenly distributed, and the sampling points between the rising edges of the two pulses are calculated point by point to obtain the phase information of each sampling point in 1 circle. The specific method is: based on the rising edge of the continuous pulse signal collected by the photoelectric pulse sensor 3, the strain data of the upper and lower rotor strain blades are intercepted for a whole cycle, and the first sampling point after exceeding the first rising edge threshold represents the initial orientation of the upper and lower rotor strain blades. and The upper rotor strain blade is in the positive rotation direction, so the phase of the upper rotor strain blade increases by 6×N / S(°) point by point, and the lower rotor strain blade is in the reverse rotation direction, so the phase of the lower rotor strain blade decreases by e×N / S(°) point by point. By analogy, the azimuth information corresponding to the i-th strain sampling point of the upper blade 4 and the lower blade 5 with the strain gauge attached in one circle of sampling points can be obtained. and

[0057]

[0058]

[0059] Furthermore, the coincidence positions of the upper and lower blades of the coaxial twin rotor are usually fixed at eight positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. The combined strain response of the effective profile when the upper and lower rotor strain blades are in the above eight coincidence positions is indexed in one circle of strain data. and The effective section combined strain of the upper and lower rotor blades is multiplied by the one-dimensional linear matrix coefficient K of the upper and lower rotor blades respectively. ue , K de It can be obtained that the strain displacements of the upper and lower rotor blades when they are in the above 8 coincident positions are and

[0060] Furthermore, based on the control amount of the current state, the rotor collective pitch θ0U 、Upper rotor longitudinal cyclic pitch change A 1U 、Lateral cyclic pitch change of upper rotor B 1U 、Lower rotor total pitch θ 0L , Differential longitudinal periodic pitch A 1L , Differential lateral periodic pitch variation B 1L , advance control angle Γ, upper rotor strain blade (positive rotation direction) in eight directions ω: 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315° n Pitch angle The lower rotor strain blade (counter-rotation direction) is in eight positions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° n Pitch angle Use the upper and lower rotor control compensation coefficients C respectively u , C d Multiply the pitch angle θ of the upper and lower rotor strain blades in 8 overlapping phases U ,θ L That is, the control compensation displacement at 8 overlapping phases is obtained

[0061] Furthermore, the strain displacement of the rotor blade tip at eight positions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° is used. Plus the control compensation displacement of the rotor blade tip Subtract the strain displacement of the blade tip from the lower rotor strain Then subtract the control compensation displacement of the lower rotor strain blade tip By adding the distance D between the upper and lower rotor discs, we can obtain the blade tip spacing of the coaxial twin-rotor helicopter at eight directions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

Claims

1. A method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter, characterized in that: An upper rotor telemetry collector (1) and a lower rotor telemetry collector (2) are respectively installed on the upper and lower blades of a coaxial twin-rotor helicopter; and strain gauges (6) are respectively attached to the upper and lower blades; the upper rotor telemetry collector (1) and the lower rotor telemetry collector (2) are two sets of blade strain load collectors for synchronous collection, and are respectively used to collect strain signals of an upper blade (4) attached with a strain gauge and a lower blade (5) attached with a strain gauge; The photoelectric pulse sensor (3) is arranged at a preset position on the top of the fuselage, and the photoelectric pulse sensor (3) is installed vertically upward. The method comprises: S1, static calibration: select one blade from each of the upper and lower rotors to complete the flapping full-bridge strain gauge patch of the same n sections, perform static calibration on the upper and lower blades respectively, and obtain the flapping full-bridge strain ε of the n sections of the upper and lower blades respectively. u , ε d and the tip deflection of the upper and lower blades l u , l d , obtain the linear mapping matrix K of the combined strain matrix of the upper and lower blade sections and the blade tip deflection u , K d ; S2, according to the dynamic measurement results of the blade tip image recognition method based on machine vision technology and the blade tip deflection measurement method based on the blade multi-profile strain response, select the linear mapping matrix K u , K d The optimal set of coefficients in ; S3, obtain the control compensation coefficient C h , C d ; S4, determining the coincidence azimuth angles of the strain collection points of the upper rotor telemetry collector (1) and the lower rotor telemetry collector (2); S5, respectively calculating the strain displacement and control compensation displacement of the rotor strain blade tip at the coincident azimuth of the strain collection point; S6, calculating the blade tip spacing of the coaxial twin-rotor helicopter at the coincident azimuth of the strain collection point according to the strain displacement of the rotor strain blade tip at the coincident azimuth of the strain collection point, the control compensation displacement, and the spacing between the upper and lower rotor discs.

2. A method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: The upper blade (4) for sticking the strain gauge and the lower blade (5) for sticking the strain gauge are stuck with a swinging full-bridge strain gauge (6) at the 1 / 4 chord position of the same section, and the number of sections is at least 3.

3. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S1 is specifically: Select one blade from each of the upper and lower rotors to complete the flapping full-bridge strain gauge patch of the same n sections, perform static calibration on the upper and lower blades respectively, and obtain the flapping full-bridge strain ε of the n sections of the upper and lower blades respectively. u , ε d and the tip deflection of the upper and lower blades l u , l d ; The total number of combinations of 3 or more sections selected from n sections is Then, the upper and lower strain response matrices E of all combinations of 3 or more profiles are obtained. u and E d , by solving the linear equation E of the upper and lower blade strain and blade tip deflection u ×K h =L u and E d ×K d =L d , obtain the linear mapping matrix K of the combined strain matrix of the upper and lower blade sections and the blade tip deflection u , K d .

4. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S2 is specifically: A blade tip spacing measurement system (7) based on machine vision technology is installed at the 90° position of the fuselage to perform data verification of the blade tip deflection calculation results. The test conditions are no less than two, including at least 0°, maximum total pitch θ max ; The azimuth pulse signal obtained by the photoelectric pulse sensor (3) is used to synchronously control the blade tip spacing measurement system (7) based on machine vision technology and the upper rotor telemetry collector (1) and the lower rotor telemetry collector (2) to perform external triggering collection, and respectively obtain image data and upper and lower rotor strain blade strain data under two test states; Through difference analysis, the total distance from 0° to the maximum total distance θ is obtained. max When the upper and lower rotor blade tip deflection image method is measured, the strain is and The strain calculation rule calculates the strain difference of all sections in two states to obtain the relative strain change value E. u and E d , multiplied by the linear matrix K of the combined strain and deflection of the upper and lower rotor blade sections u , K d , get all the upper and lower rotor blades Tip deflection corresponding to the profile combination and Comparison of rotor strain blade tip deflection collection Each element in Measurement value with image method Find the cross-sectional combined strain E corresponding to the element with the smallest error value ue And the one-dimensional linear matrix coefficient K corresponding to this combination us , and then obtain the cross-sectional combined strain E corresponding to the lower rotor strain blade ds And the one-dimensional linear matrix coefficient K corresponding to this combination ds .

5. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S3 is specifically: By statically raising the lower blade pitch, a blade tip spacing measurement system (7) based on machine vision technology is used to obtain the trailing edge mark point at the first chord line position of the upper blade tip profile and the leading edge mark point at the second chord line position of the lower blade tip profile, respectively, and the pitch is raised from 0° to the maximum total pitch θ max Deflection change Δl under the state ue , Δl ds The control compensation coefficient c is obtained by dividing the change in blade tip deflection by the change in total pitch. u 、c d .

6. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S4 is specifically: Rotate the blades in a static state so that the photoelectric pulse sensor 3 is in a triggered state, and calculate the current spatial positions of the upper and lower rotor strain blade tips through trigonometric geometry, so as to obtain the initial positions of the upper and lower rotor strain blades in the triggered state. and The upper rotor telemetry collector (1) and the lower rotor telemetry collector (2) are set to the same sampling rate S for fixed frequency acquisition. When the rotor speed is stabilized at N, the photoelectric pulse sensor (3) acquires the uniform distribution of the phases of the sampling points between two consecutive pulse rising edges, and calculates the sampling points between the two pulse rising edges point by point to obtain the phase angle of each sampling point in one circle. The specific method is: based on the rising edge of the continuous pulse signal collected by the photoelectric pulse sensor (3), the strain data of the upper and lower rotor strain blades are intercepted in a whole cycle, and the first sampling point after exceeding the first rising edge threshold represents the initial orientation of the upper and lower rotor strain blades. and The upper rotor strain blade is in the positive rotation direction, so the phase of the upper rotor strain blade increases by 6×N / S degrees point by point, and the lower rotor strain blade is in the reverse rotation direction, so the phase of the lower rotor strain blade decreases by 6×N / S degrees point by point, and so on, to obtain the azimuth angle corresponding to the i-th strain sampling point of the upper blade (4) and the lower blade (5) attached with the strain gauge in a circle of sampling points and Finally, the overlapping positions of the upper and lower blades of the coaxial twin rotor are fixed at eight positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

7. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S5, calculate the strain displacement of the rotor blade tip at the coincident azimuth of the strain collection point, specifically: The combined strain response of the effective section when the upper and lower rotor strain blades are in the eight overlapping positions in a circle of strain data and The effective section combined strain of the upper and lower rotor blades is multiplied by the one-dimensional linear matrix coefficient K of the upper and lower rotor blades respectively. us , K ds The strain displacements of the upper and lower rotor blades when they are in 8 overlapping positions are: and 8. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S5, calculate the control compensation displacement of the rotor strain blade tip at the coincident azimuth of the strain collection point, specifically: Based on the current state of the control amount, the rotor collective pitch θ 0U 、Upper rotor longitudinal cyclic pitch change A 1U 、Lateral cyclic pitch change of upper rotor B 1U 、Lower rotor collective pitch θ 0L , Differential longitudinal periodic pitch A 1L , Differential lateral periodic pitch variation B 1L , advance control angle г, the upper rotor strain blade is in eight positions of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°ω n The pitch angle θ at U =θ 0U +A 1U ×cos(ω n +Γ)-B 1U ×sin(ω n +Γ), the pitch angle θ of the lower rotor strain blade at eight azimuths ωn of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° L =θ 0L +A 1L ×cos(360-ω n +Γ)+B 1L ×sin(360-w n +Γ), using the upper and lower rotor control compensation coefficients C u , C d Multiply the pitch angle θ of the upper and lower rotor strain blades in eight overlapping phases U ,θ L Obtain the control compensation displacement at eight overlapping phases 9. The method for quickly calculating the blade tip spacing of a coaxial twin-rotor helicopter according to claim 1, characterized in that: S6 is specifically: The strain displacement of the rotor blade tip at eight positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° Plus the control compensation displacement of the rotor blade tip Subtract the strain displacement of the blade tip from the lower rotor strain Then subtract the control compensation displacement of the lower rotor strain blade tip Adding the distance D between the upper and lower rotor discs, we can obtain the blade tip spacing of the coaxial twin-rotor helicopter at eight directions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

Images