Double-rotor blade tip distance measuring system and method based on three-dimensional optical perception

Abstract

The invention belongs to the technical field of helicopter rotor tests, and relates to a double-rotor blade tip distance measuring system and method based on stereo optical perception, and the system comprises three photosensitive arrays and a data display and management platform. The three photosensitive arrays are arranged below the rotor wing, and when the rotor wing rotates over the photosensitive arrays, the photosensitive arrays generate photosensitive signals; and the photosensitive signal is used for calculating the blade tip distance and displaying the blade tip distance data on the data display and management platform.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter rotor test and relates to a dual-rotor blade tip pitch measurement system and method based on stereo optical perception. Background Art

[0002] A coaxial twin-rotor helicopter is a helicopter rotor configuration in which the upper and lower rotors rotate coaxially and in opposite directions. In order to reduce hub drag, the coaxial twin-rotor helicopter adopts a structural design in which the axial spacing between the upper and lower rotors is small; at the same time, due to the lift offset of the upper and lower rotors, the upper and lower rotor blades will be close to each other on the rearward side of the upper rotor and the forward side of the lower rotor, resulting in the risk of blade tip collision, which is one of the important risks in the development of helicopters with this configuration.

[0003] At present, the main methods for measuring the tip pitch of coaxial twin rotors in China include radio measurement, computer vision measurement, optical tracking sensor (Universal Tracking Device, UTD) measurement, etc. These methods have the following advantages and disadvantages:

[0004] (1) The radio measurement method uses a pair of radio transmitting and receiving devices installed inside the tip structures of the upper and lower rotor blades, respectively. The tip pitch is obtained by processing and analyzing the strength and phase of the radio wave signal transmitted by the transmitting device and received by the receiving device. It is a non-contact measurement method with the advantages of simple principle and machine-mountable advantages, but it has the disadvantage of requiring modification of the blade structure.

[0005] (2) The computer vision measurement method uses a camera to perform monocular imaging of the upper and lower rotor blade tips or uses multiple cameras to perform stereoscopic imaging of the upper and lower rotor blade tips, and then processes the image to obtain the blade tip distance. It is a non-contact measurement method. Among them, the monocular vision measurement method has the advantage of fast calculation and processing speed, but it has the disadvantage of being unable to be used for flight test due to the limitation of camera installation position; while the multi-eye vision measurement method has the advantage of being able to be used for flight test and having high measurement accuracy, but it has the disadvantages of slow calculation and processing speed and poor real-time performance;

[0006] (3) UTD uses optical principles for non-contact measurement. When the rotor blades rotate and pass through two photoelectric devices (1# and 2#) within a certain angle of view inside the UTD, the photoelectric surfaces of the 1# and 2# photoelectric devices can sense the change in optical intensity due to the blades blocking the light in the field of view. After the light intensity signal is photoelectrically converted and shaped, a series of pulse signals representing the motion trajectory of the blades can be obtained. These time-series pulse signals are collected, filtered and processed to obtain the distance between the upper and lower rotor tips. It has the advantages of easy installation and can be installed and used, but it has the disadvantage of being unable to measure the tip distance when the blades overlap. Summary of the invention

[0007] The purpose of the present invention is: to address the shortcomings of the above-mentioned method, and to propose a twin-rotor blade tip pitch measurement system and method based on stereoscopic optical perception. The system and method expand the two UTD photosensitive devices into multiple photosensitive devices to form a photosensitive array, and expand the measurement surface formed by two points to form a measurement stereo domain, completely covering the movement trajectory of the blade after entering the field of view, and realizing accurate measurement of the blade tip pitch at the moment of blade overlap. It has the advantages of fast calculation and processing speed and no need to modify the blade structure. It is suitable for measuring and monitoring the upper and lower rotor blade tip pitches under different total pitch and periodic pitch change states in ground and flight tests of coaxial twin-rotor helicopters, thereby ensuring the safety of the test and evaluating the aerodynamic performance and aerodynamic interference characteristics of the rotor system under different design states.

[0008] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0009] A dual-rotor blade tip pitch measurement system based on stereo optical perception, comprising: three photosensitive arrays and a data display and management platform;

[0010] The three photosensitive arrays are arranged below the rotor, and the photosensitive arrays generate photosensitive signals when the rotor passes over the photosensitive arrays;

[0011] The photosensitive signal is used to calculate the blade tip pitch and display the blade tip pitch data on the data display and management platform.

[0012] Furthermore, the dual rotor has a total of N intersection positions, where N is twice the number of upper or lower rotor blades; the three photosensitive arrays are respectively located directly below the three intersection positions, and the lines connecting the three intersection positions and the rotor rotation center are 90° to each other.

[0013] Furthermore, the vertical distance between the photosensitive array and the lower blade is greater than the blade radius and less than the blade diameter.

[0014] Furthermore, the photosensitive array points to 0.8R to 0.9R of the blade.

[0015] Further, the system further comprises: an azimuth angle sensor, the azimuth angle sensor being mounted on a fixed ring of the automatic tilt mechanism, and a reflective sheet being pasted on a movable ring of the automatic tilt mechanism or a lower surface of a blade root;

[0016] The reflected light signal collected by the azimuth sensor is multiplied by N times and used as the trigger signal of the photosensitive array.

[0017] Further, the photosensitive array includes: a plurality of groups of photosensitive devices for sensing the change in light intensity when the blades are swept, and generating a sequence of photosensitive signals including sweep time and height information;

[0018] The photoelectric conversion circuit converts the photosensitive signal into an analog electrical signal;

[0019] The signal conditioning circuit filters, amplifies, and shapes the analog electrical signal into a standard analog electrical signal;

[0020] The digital-to-analog conversion circuit converts the analog quantity of the standard electrical signal into a digital electrical signal;

[0021] The data processing circuit completes digital signal processing, including denoising and feature enhancement processing, dynamic tracking and resolution of blade tip motion in the optical sensing domain, etc.

[0022] The data transmission circuit transmits the processed and solved blade tip pitch data to the data display and management platform according to the specified communication protocol;

[0023] The speed signal conditioning circuit conditions and multiplies the rotor speed signal on the aircraft and provides it to the data processing circuit;

[0024] The power interface circuit and the power conversion circuit are connected to the external AC / DC power supply and converted into power that meets the requirements of each module and circuit.

[0025] A method for measuring the tip pitch of a dual-rotor blade based on stereoscopic optical perception, the method being implemented by the system, the method comprising the following steps:

[0026] Step 1: Sample the analog signal output by the photosensitive array and process the array data r[n] sampled N times as a group. [n] =s [n] +u [n] , where s [n] is the rectangular pulse sequence output by the photosensitive array, u [n] The mean is 0 and the variance is δ 2 Gaussian noise sequence;

[0027] Step 2: Decompose the array data r[n];

[0028] 1) Set a low-pass filter to decompose the sequence p[k], q according to the signal characteristics 1 [k], q 2 [k]

[0029] 2) First level decomposition:

[0030]

[0031]

[0032] Where N is the number of sampling points per revolution, T is the rotor rotation period, r[k] is the original array signal, c[n], d[n] and e[n] are the signals after the first layer of decomposition respectively;

[0033] 3) Second level decomposition:

[0034]

[0035] Among them, c[k] is the first-layer decomposition signal, cc[n], dc[n], and ec[n] are the second-layer decomposition signals respectively.

[0036] Step 3: De-noising the decomposed array data;

[0037] The sequences d[n], e[n], dc[n], and ec[n] are denoised using a hard threshold function (the threshold value is δ / 3) to obtain new sequences:

[0038] d′ [n] , e′ [n] , dc′ [n] ,ec′ [n]

[0039] Step 4: Reconstruct the array data after denoising;

[0040]

[0041]

[0042] in Photosensitive array reconstructed after denoising

[0043] Step 5: Establish a photosensitive device position array Dm*n according to the number and position distribution of photosensitive devices in the photosensitive array;

[0044] D N×M ={d i,j}, i=1,2,...N; j=1,2,...M

[0045] Where N and M are the number of rows and columns of the photosensitive array,

[0046] Step 6: Establish a photosensitive device timing array model Tn*m according to the rotor speed;

[0047] T N×M =VD N×M ={t i,j}, i=1,2,...N; j=1,2,...M

[0048] Step 7: Match the reconstructed data to the photosensitive device timing array model;

[0049]

[0050] Where P L×N×M To match the timing array formed, S M×Mis the reconstructed photosensitive array at the current moment, Δt is the matching time interval, and L is the number of matching times

[0051] Step 8: Separate the reconstructed data matched to the timing array model of the photosensitive device according to the rotation direction of the upper and lower rotors to obtain the timing array U formed by the upper blades. L×N×M and the timing array B formed by the lower blade L×N×M ;

[0052] Step 9: Calculate the blade tip pitch based on the separated upper and lower blade timing arrays.

[0053] Will U L×N×M and B L×N×M Input the blade tip pitch geometry calculation formula (determined by the photosensitive array position matrix Dm*n and the relative position of the photosensitive array and the blade) to calculate the blade tip pitch of the upper and lower rotors.

[0054] Furthermore, the method further includes: repeating steps one to nine to respectively obtain the blade tip pitches of three intersection positions where the three photosensitive arrays are located, and calculating the blade tip pitches of other intersection positions based on the blade tip pitches of the three intersection positions.

[0055] Beneficial effects of the present invention: The coaxial twin rotor is a new rotor configuration, and the blade tip pitches of the upper and lower rotors need to be monitored during ground and flight tests in the development stage. The radio blade tip pitch measurement method has the disadvantage that the blade structure needs to be modified, the monocular vision measurement method has the disadvantage that the camera installation position is limited and it cannot be used for flight test, the multi-vision blade tip pitch measurement method has the disadvantages of slow calculation and processing speed and weak real-time performance, and the UTD blade tip pitch measurement method has the disadvantage of being unable to measure the blade tip distance at the moment of blade overlap; the dual-rotor blade tip pitch measurement system and method based on stereoscopic optical perception adopted in the present invention utilizes three PTS sensors and corresponding azimuth sensors, data display and management platforms, etc. to form a measurement system, collects the light intensity changes of the upper and lower blades of the coaxial dual-rotor sweeping through the field of view of the PTS sensor before and after the overlap moment, and finally calculates the blade tip pitch value at the moment of blade overlap after photoelectric conversion and conditioning, signal processing and solution of the photosensitive signal, thereby realizing real-time and reliable measurement and monitoring of the upper and lower rotor blade tip pitches of the coaxial dual-rotor helicopter in ground and flight tests, and ensuring the safety of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic diagram of the principle of a dual-rotor blade tip pitch measurement system based on stereo optical perception;

[0057] Figure 2 This is a schematic diagram of the installation method of a single photosensitive array;

[0058] Figure 3 This is a schematic diagram of the installation positions of the three photosensitive arrays;

[0059] Figure 4 This is the principle diagram of blade tip pitch measurement at different overlapping positions. DETAILED DESCRIPTION

[0060] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] A dual-rotor blade tip pitch measurement system based on stereo optical perception mainly includes two parts: photoelectric tracking sensors (PTS) and data display and management platform. Among them, PTS is composed of photosensitive array, photoelectric conversion circuit, signal conditioning circuit, digital-to-analog conversion circuit, data processing circuit, data transmission circuit, speed signal conditioning circuit, power interface circuit and power conversion circuit, such as Figure 1 As shown:

[0062] Among them, the photosensitive array is composed of multiple groups of photosensitive devices, which sense the changes in light intensity swept by the blades and generate a photosensitive signal sequence including the sweeping time and height information.

[0063] The photoelectric conversion circuit converts the photosensitive signal into an analog electrical signal.

[0064] The signal conditioning circuit filters, amplifies, and shapes the analog electrical signal into a standard analog electrical signal.

[0065] The digital-to-analog conversion circuit converts the analog quantity of the standard electrical signal into a digital electrical signal.

[0066] The data processing circuit completes digital signal processing, including denoising and feature enhancement processing, dynamic tracking and resolution of blade tip motion within the optical perception domain, etc.

[0067] The data transmission circuit transmits the processed and solved blade tip pitch data to the data display and management platform according to the specified communication protocol.

[0068] The speed signal conditioning circuit conditions and multiplies the rotor speed signal on the aircraft (several times the blades) and then provides it to the data processing circuit.

[0069] The power interface circuit and the power conversion circuit are connected to the external AC / DC power supply and converted into power that meets the requirements of each module and circuit.

[0070] The data display and management platform realizes the display, storage, analysis and data management of blade tip pitch data.

[0071] The appearance of the photoelectric tracking sensor and data display and management platform is as follows Figure 2 , 3 shown.

[0072] A method for measuring a dual-rotor blade tip pitch measurement system based on stereoscopic optical perception. This method uses a dual-rotor blade tip pitch measurement system based on stereoscopic optical perception installed on a test bench or a helicopter to collect the light intensity changes of the upper and lower blades of the coaxial dual-rotor sweeping through the PTS sensor field of view before and after the overlap moment, and generate a corresponding photosensitive signal sequence; after photoelectric conversion, signal conditioning, and digital-to-analog conversion of the photosensitive signal, a digital electrical signal containing sweep time and height information is obtained; after processing and solving the digital electrical signal, the blade tip pitch of the coaxial dual-rotor at the overlap moment is obtained. The specific measurement method is as follows:

[0073] 1. Equipment installation and connection

[0074] A PTS sensor is installed below each of the three overlapping positions of the coaxial twin-rotor helicopter blades. The vertical distance from the PTS sensor to the lower blade is not less than the blade radius length. The photosensitive array points to the position of 0.8 to 0.9R of the blade, respectively. Figure 4 As shown in the figure; the azimuth sensor that provides the speed signal is installed in a position that is relatively still and less affected by external vibration and other environmental factors. The corresponding reflective sheet is attached to the rotor automatic tilt device dynamic ring or the lower surface of the blade root to ensure that the rotor rotates once and triggers the azimuth sensor once; the data display and management platform is placed in the helicopter equipment cabin to display, store, analyze and manage the blade tip pitch data transmitted by the PTS sensor. After the equipment is installed, connect and test the power cord, data communication cable, and speed signal input cable.

[0075] 2. Weak light signal conditioning, denoising and reconstruction

[0076] After the equipment is installed, the weak light domain signals sensed by the PTS sensor need to be conditioned, denoised and reconstructed during the measurement process. First, after signal conditioning such as filtering and signal conversion, amplification, filtering and shaping, a photosensitive array diagram of the blade position at the current time is formed; then, the minimum energy framework denoising algorithm in l2 space is used to remove the noise to achieve rectangular pulse signal denoising and enhancement; finally, by analyzing the different statistical characteristics of the decomposition coefficients of the original signal series and the noise series in the Parseval framework, the decomposition coefficients are corrected according to these characteristics and the signal is reconstructed to restore the original signal.

[0077] 3. Dynamic tracking of propeller tip motion within the optical sensing domain

[0078] The photosensitive devices in the photosensitive array sense the light changes caused by the passing of the blades in the light domain. Since the devices in the photosensitive array are arranged in a specific positional relationship, the rectangular pulses generated by the blades rotating at a fixed speed passing through different photosensitive devices have a specific time relationship. The photosensitive array image information based on the time series is captured and tracked, and a mathematical model of the blade tip motion trajectory is established to achieve the separation of the sensing signals of the upper and lower blades. The steps are as follows:

[0079] a) Establish a photosensitive device position array according to the position distribution in the photosensitive array:

[0080] D N×M ={d i,j}, i=1,2,...N; j=1,2,...M

[0081] Where N and M are the rows and columns of the photosensitive array.

[0082] b) Establish a photosensitive device timing array model based on the rotor speed:

[0083] T N×M =VD N×M ={t i,j}, i=1,2,...N; j=1,2,...M

[0084] c) Model matching is performed on the rectangular array formed by the blade after passing through the entire optical domain at a fixed time interval △t to achieve tracking of the rectangular pulse formed by the blade in the optical domain:

[0085]

[0086] Among them, S N×M It is the distribution matrix of the rectangular pulses sensed by the photosensitive array device at the current moment.

[0087] d) P L×N×M By performing matrix operations, we can obtain the timing matrix of the rectangular pulses sensed by each photosensitive device on the blade, and separate them according to the rotation direction as follows:

[0088]

[0089] e) Tip pitch calculation for three PTS sensor installation locations

[0090] Will U N×M×L , B N×M×L Input into the propeller pitch geometry calculation formula to get the propeller pitch when the current blades overlap.

[0091] f) Calculation of the tip pitch of the remaining five blade overlap positions

[0092] The blade heights measured by three PTS sensors can determine a propeller disc plane, of which the tip pitches at the three positions where the PTS sensors are installed can be measured directly, and the tip pitches at the other five overlapping positions can be indirectly estimated through the position of the propeller disc plane.

[0093] The above is only a specific embodiment of the present invention, and the present invention is described in detail. The unexplained part is a conventional technology. However, the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A dual-rotor blade tip pitch measurement system based on stereoscopic optical perception, characterized in that: The system includes: three photosensitive arrays and a data display and management platform; The three photosensitive arrays are arranged below the rotor, and the photosensitive arrays generate photosensitive signals when the rotor passes over the photosensitive arrays; The photosensitive signal is used to calculate the blade tip pitch and display the blade tip pitch data on the data display and management platform.

2. The system according to claim 1, characterized in that: The dual rotor has a total of N crossing positions, where N is twice the number of upper or lower rotor blades; the three photosensitive arrays are located directly below the three crossing positions, and the lines connecting the three crossing positions and the rotor rotation center are 90° to each other.

3. The system according to claim 2, characterized in that: The vertical distance between the photosensitive array and the lower blade is greater than the blade radius and less than the blade diameter.

4. The system according to claim 3, characterized in that: The photosensitive array points to the position 0.8R to 0.9R of the blade.

5. The system according to claim 4, characterized in that: The system further comprises: an azimuth angle sensor, the azimuth angle sensor being mounted on a fixed ring of the automatic tilt mechanism, and a reflective sheet being pasted on a movable ring of the automatic tilt mechanism or a lower surface of a blade root; The reflected light signal collected by the azimuth sensor is multiplied by N times and used as the trigger signal of the photosensitive array.

6. The system according to claim 5, characterized in that: The photosensitive array includes: multiple groups of photosensitive devices for sensing the change in light intensity when the blades are swept, and generating a photosensitive signal sequence including sweeping time and height information; The photoelectric conversion circuit converts the photosensitive signal into an analog electrical signal; The signal conditioning circuit filters, amplifies, and shapes the analog quantity of the electrical signal into a standard analog electrical signal; The digital-to-analog conversion circuit converts the analog quantity of the standard electrical signal into a digital electrical signal; The data processing circuit completes digital signal processing, including denoising and feature enhancement processing, dynamic tracking and resolution of blade tip motion in the optical sensing domain, etc. The data transmission circuit transmits the processed and solved blade tip pitch data to the data display and management platform according to the specified communication protocol; The speed signal conditioning circuit conditions and multiplies the rotor speed signal on the aircraft and provides it to the data processing circuit; The power interface circuit and the power conversion circuit are connected to the external AC / DC power supply and converted into power that meets the requirements of each module and circuit.

7. A method for measuring the tip pitch of a dual rotor based on stereoscopic optical perception, the method being implemented by the system according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: Step 1: Sample the analog signal output by the photosensitive array and process the array data r[n] sampled N times as a group. [n] =s [n] +u [n] , where s [n] is the rectangular pulse sequence output by the photosensitive array, u [n] The mean is 0 and the variance is δ 2 Gaussian noise sequence; Step 2: Decompose the array data r[n]; 1) Set a low-pass filter to decompose the sequence p[k], q according to the signal characteristics 1 [k], q 2 [k] 2) First level decomposition: Where N is the number of sampling points per circle, T is the rotor rotation period, r[k] is the original array signal, c[n], d[n] and e[n] are the signals after the first layer of decomposition respectively; 3) Second level decomposition: Among them, c[k] is the first-layer decomposition signal, cc[n], dc[n], and ec[n] are the second-layer decomposition signals respectively. Step 3: De-noising the decomposed array data; The sequences d[n], e[n], dc[n], and ec[n] are denoised using a hard threshold function (the threshold value is δ / 3) to obtain new sequences: d′ [n] 、e′ [n] 、dc′ [n] 、ec′ [n] Step 4: Reconstruct the array data after denoising; in Photosensitive array reconstructed after denoising Step 5: Establish a photosensitive device position array Dm*n according to the number and position distribution of photosensitive devices in the photosensitive array; D N×M ={d i,j },i=1,2,...N;j=1,2,...M Where N and M are the number of rows and columns of the photosensitive array, Step 6: Establish a photosensitive device timing array model Tn*m according to the rotor speed; Step 7: Match the reconstructed data to the photosensitive device timing array model; Where P L×N×M To match the timing array formed, S N×M is the reconstructed photosensitive array at the current moment, Δt is the matching time interval, and L is the number of matching times Step 8: Separate the reconstructed data matched to the timing array model of the photosensitive device according to the rotation direction of the upper and lower rotors to obtain the timing array U formed by the upper blades. L×N×M and the timing array B formed by the lower blade L×N×M ; Step 9: Calculate the blade tip pitch based on the separated upper and lower blade timing arrays. Will U L×N×M and R L×N×M Input the blade tip pitch geometry calculation formula (determined by the photosensitive array position matrix Dm*n and the relative position of the photosensitive array and the blade) to calculate the blade tip pitch of the upper and lower rotors.

8. The method according to claim 7, characterized in that: The method further includes: repeating steps one to nine to respectively obtain the blade tip pitches of three intersection positions where the three photosensitive arrays are located, and calculating the blade tip pitches of other intersection positions according to the blade tip pitches of the three intersection positions.

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