Telemetering system and method with TOP trigger signal and capable of realizing cascade synchronization

Abstract

The invention belongs to the technical field of helicopter rotor tests, and discloses a telemetering system and method with TOP trigger signals and capable of achieving cascade synchronization. The system comprises a wireless module, a Beidou signal switching module, an acquisition module, a circuit board, a battery, an upper computer, a sensor assembly, a non-rotating table body and an equipment shell. The rotor system is arranged on the non-rotating table body, and the equipment shell is mounted above a propeller hub of the rotor system; the circuit board is arranged at the opening of the equipment shell; the battery is connected below the circuit board; a wireless module, a Beidou signal switching module and an acquisition module are connected above the circuit board; the sensor assembly is mounted on the rotor system and is connected with the acquisition module through a cable; the Beidou signal switching module is used for receiving Beidou signals; and the wireless module is used for communicating with an upper computer.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter rotor testing, and in particular relates to a telemetry system and method with a TOP trigger signal capable of cascading synchronization. Background Art

[0002] During ground tests or flight tests of helicopter rotors, the dynamic characteristics of the rotors need to be analyzed, so the rotation signals on the blades and rotating shafts need to be collected and monitored. In the past, conventional rotor tests often used a preamplifier plus a slip ring. This method has complex system construction and large signal noise interference. In addition, with the new trend of developing electric-driven aircraft, the rotor size is smaller and the structure is more compact. Without the drive shaft of traditional conventional rotors, slip rings cannot be installed. As a result, in many electric-driven rotor tests, rotation signal data cannot be collected, including rotor blade flapping, vibration, torsional load, rotor shaft tension, torque and bending moment load, which cannot provide strong support for the design. Summary of the Invention

[0003] The purpose of the present invention is: in view of the particularity of the electric-driven rotor structure, it is impossible to install conventional collector ring equipment to collect rotational load signals and TOP signals. A telemetry system and method with cascaded synchronization of TOP trigger signals are proposed. The entire telemetry system weighs 600g and has dimensions of diameter D*height H=120mmX60mm. It can be conveniently and quickly installed on small and medium-sized electric-driven rotor hubs. While effectively collecting rotational load signals such as blades and rotor shafts, it can also collect speed TOP signals. Cascaded synchronous collection of multiple telemetry systems can be performed to ensure synchronous data analysis during multi-rotor tests. The collected signal data can be stored locally in the system, and real-time monitoring and storage of rotational signal data on a host computer can be achieved through wireless transmission. At the same time, the telemetry collection system supports offline collection and subsequent recovery, which facilitates data analysis.

[0004] Technical Solution

[0005] A telemetry system with cascade synchronization and TOP trigger signal, including: a wireless module, a Beidou signal adapter module, an acquisition module, a circuit board, a battery, a host computer, a sensor component, a non-rotating platform, and an equipment housing;

[0006] The rotor system is set on a non-rotating platform, and the device housing is installed above the rotor system's hub; the circuit board is installed in the opening of the device housing, and the battery is connected below the circuit board; the wireless module, Beidou signal transfer module, and acquisition module are connected above the circuit board;

[0007] The sensor assembly is installed on the rotor system and connected to the acquisition module through a cable; the Beidou signal adapter module is used to receive Beidou signals; and the wireless module is used to communicate with the host computer.

[0008] The sensor assembly includes: a load measurement assembly and a rotational speed measurement assembly;

[0009] The acquisition module acquires the flapping load of the rotating blade, the lead-lag load of the rotating blade, the tensile load of the rotating shaft, and the rotational speed pulse signal;

[0010] The host computer sets the acquisition period T = 0.1 s of the rotational speed pulse signal, and the number of high-level rotational speed pulses acquired within the T time is recorded as k;

[0011] If k < 2, then T is assigned the value of T + 0.05 s until k ≥ 2, and then the rotational speed is measured using the end-period rotational speed measurement method;

[0012] If k ≥ 2, then FFT analysis is performed on the flapping load of the rotating blade, the lead-lag load of the rotating blade, and the tensile load of the rotating shaft to obtain the first 5 main peak frequencies within 200 Hz of the three load signals. The first 5 main peak frequencies of the flapping load of the blade are H = [H1 H2 H3 H4 H5], the first 5 main peak frequencies of the lead-lag load of the blade are B = [B1 B2 B3 B4 B5], and the first 5 main peak frequencies of the tensile load of the rotor shaft are T = [T1 T2 T3 T4 T5], forming a matrix HBT of 15 elements = [H1 H2 H3 H4 H5 B1 B2 B3 B4 B5 T1 T2 T3 T4 T5];

[0013] Traverse the elements of the HBT matrix. If there are two frequencies X and Y that satisfy Y = S * X, X ∈ HBT, Y ∈ H and Y ∈ B and Y ∈ T, then the rotational speed R = X * 60.

[0014] Furthermore, the system also includes: a receiving antenna outdoors, a Beidou relay module, and a transmitting antenna indoors. In the wind tunnel test, the outdoor Beidou signal is introduced indoors to facilitate the telemetry equipment to receive the Beidou clock signal through the Beidou signal transfer module; the signals such as flapping, lead-lag, torsion, and rotational speed on the blades in the rotor system are connected to the acquisition module of the telemetry system through cables to acquire the load signals; a switch and a wireless AP: mainly receive the data signals transmitted by the telemetry system through the wireless module. The wireless transmission is in the WiFi mode, using the 2.4 GHz frequency band to achieve point-to-point wireless communication between the AP base station and the telemetry system terminal. The link layer uses the Ethernet protocol as the core to achieve addressing and verification of information transmission, realizing multi-system wireless networking with a communication distance of at least 100 meters. The wireless transmission stability: the number of lost data packets / data frames per hour ≤ 3. The wireless AP then transmits the data to the host computer through the switch and network cable for storage, processing, and analysis.

[0015] Furthermore, the device housing is a cylindrical housing with an open upper end; the device housing is installed on the hub through an intermediate adapter. The cylinder has better symmetry, and the connection design with the intermediate adapter is reasonable and has reliable anti-loosening measures. At the same time, it has anti-vibration and anti-shock designs to meet the vibration and shock requirements of the test bench usage environment.

[0016] Furthermore, the load measurement component is a Wheatstone full bridge pasted on the blade. Its schematic diagram is shown in Figure 4, where Vi+ and Vi- are the output voltages of the bridge circuit, and Eg+ and Eg- are the excitation voltages of the bridge circuit. 1) Input mode selection: The channel can select different input modes such as strain full bridge and voltage (thermocouple) through a program-controlled internal relay switch; 2) Range switching: The required gains for each gear are achieved through program-controlled gain switching, and an instrument amplifier with switchable gain is used to ensure each gain gear; 3) Low-pass filtering: The cut-off frequency of the low-pass filter can be set to meet the requirements of the 2k frequency response of the measurement signal and ensure the signal-to-noise ratio; 4) Single-ended to differential conversion: The single-ended signal is converted into a differential signal for 16-bit ADC acquisition; 5) Bridge voltage: Multiple gears of bridge voltage switching are achieved through DA switching.

[0017] Furthermore, the rotational speed measurement component includes: a photoelectric sensor and a reflective sticker;

[0018] The photoelectric sensor is installed on the side wall of the intermediate adapter;

[0019] The reflective sticker is pasted on the non-rotating body and is directly below the photoelectric sensor.

[0020] Furthermore, the center of mass of the whole composed of the intermediate adapter, the device housing, and all the devices carried by the device housing coincides with the rotation center of the rotor system; the circuit board and the devices carried on the circuit board are arranged symmetrically according to the rotation center of the rotor system; the wireless module, the Beidou signal transfer module, and the acquisition module are designed in a centrosymmetric arrangement; a trimming structure is designed on the circuit board to compensate for the mass eccentricity of the circuit board; the installation position and mass of the trimming structure are obtained through simulation; threaded holes are evenly arranged on the periphery of the circuit board, and mass blocks are installed on the threaded holes to eliminate the mass eccentricity caused by processing and installation errors.

[0021] The calculation process of the installation orientation and mass of the counterweight block is as follows:

[0022] Step a: Define the high-pulse trigger point of the rotational speed pulse signal as the zero-phase point, record the phase difference between the first-order fundamental frequency signal of a certain load of the blade and the zero-phase point as Φ1, and record its amplitude as A1. Then the initial vector point of the load is D1(A1, Φ1);

[0023] Step b: Try to install a mass block with a mass of m in any threaded hole. The phase of the mass block with a mass of m relative to the zero phase point is Φ. Calculate the phase angle Φ2 of the first-order fundamental frequency signal relative to the zero phase point again. The amplitude is recorded as A2 and recorded as D2(A2,Φ2).

[0024] Step c: D2-D1=D3(A3,Φ3), where D3 is the effect of the m counterweight on the dynamic balance in the Φ phase;

[0025] The amplitude of the impact is A3, the phase is Φ0=Φ-Φ3, the unit mass affects the load amplitude A3 / m, and the mass impact phase leads Φ0;

[0026] Step d: Trim the initial load D1 (A1, Φ1) according to D3. The dynamic balance requires loading a counterweight m'=A1*A3 / m at the phase Φ'=Φ1-Φ0.

[0027] The circuit and mounting structure design of all rotating parts adopts a centrally symmetrical arrangement in the design, and the circuit boards and components are arranged as symmetrically as possible along the axis;

[0028] The circuit layout can minimize mass eccentricity. Any remaining torque that cannot be balanced by circuit layout measures is balanced by structural design. Structural design uses simulation to simulate the mass eccentricity caused by the circuit layout. This eccentricity is balanced through structural design, ensuring that the center of mass coincides with the center of rotation after the design is completed.

[0029] Furthermore, the circuit board is a multi-layer circuit board, which consists of the following from top to bottom: top layer, power ground layer, power layer, signal layer, +15V power supply layer and bottom layer, and the power layer has a large area of copper cladding;

[0030] The circuit board design rationally partitions the power ground layer, power layer, and signal layer. A large copper layer is applied to the power layer. After numerous tests and comparisons, a design was found that minimizes ground impedance and circuit noise, effectively suppressing interference. Components are strategically arranged, shielding and isolating electromagnetic interference sources such as digital and CPU clock generators. Analog components are kept separate, and connectors and their pins are placed on one side of the printed board, away from high-speed components, effectively suppressing common-mode current radiation. Sensitive components are partitioned and kept away from electromagnetic interference sources.

[0031] The ground wires of the power supply voltage, digital circuit, and analog circuit are separated independently. And the most appropriate positions are found through experiments to short - circuit different ground wires. The information acquisition device effectively suppresses the electromagnetic interference radiated into space by the transient supply current in the line and the common - impedance coupling interference caused by the inductance of the supply line by reducing the characteristic impedance of the supply line and using filtering and decoupling capacitors. Incompatible signal lines are kept away from each other, and multiple - layer and mutually - perpendicular wiring methods are adopted to reduce the electric - field and magnetic - field coupling interference between signal lines. The routing positions of high - speed signal lines are reasonably designed, and the shortest - routing method and shielding measures are adopted to avoid interfering with other signal lines.

[0032] A telemetry method with TOP trigger signal and cascade synchronization, which is implemented based on the system, includes the following steps:

[0033] 1) Install the lightweight telemetry system and turn on the power;

[0034] 2) Set parameters according to the test requirements, including: range, filter, input mode, bridge mode, sampling frequency;

[0035] 3) When multiple lightweight telemetry systems need to synchronously collect data, check whether the Beidou communication is normal;

[0036] 4) If synchronous collection is not required or the Beidou signal cannot be received, directly use the internal clock of the lightweight telemetry system for signal collection;

[0037] Collect the flapping load of the rotating blade, the lead - lag load of the rotating blade, and the tensile load of the rotating shaft; collect the rotational - speed pulse signal; the process of calculating the rotational speed is as follows:

[0038] Step 1: Given that the collection period T of the rotational - speed pulse signal is 0.1 s, the number of high - level pulses of the rotational speed collected within T time is denoted as k;

[0039] Step 2: If k < 2, jump to Step 3; if k ≥ 2, then jump to Step 6;

[0040] Step 3: T = T + 0.05 s;

[0041] Step 4: Determine whether k is greater than or equal to 2. If so, jump to Step 5; otherwise, return to Step 3;

[0042] Step 5: There are k - 1 complete rotor rotations collected within T time, and there is an incomplete low - level pulse data at each end; these data are all saved in the matrix in the form of specific digital points. At this time, the total number of points between the last two high - level points at the end of the matrix is defined as n;

[0043] The total number of points from the start S of the entire T time domain to the first high level in the entire T time domain is denoted as n1; the total number of points from the first high level to the end E in the entire T time domain is denoted as n2; then within the entire T time domain, the rotor rotates a total of circles;

[0044] Obtain the rotor speed ;

[0045] Step 6: Perform FFT analysis on the flapping load of the rotating blade, the drag load of the rotating blade, and the tensile load of the rotating shaft to obtain the first 5 main peak frequencies within 200 Hz of the three load signals. The first 5 main peak frequencies of the flapping load of the blade are H = [H1 H2 H3 H4 H5], the first 5 main peak frequencies of the drag load of the blade are B = [B1 B2 B3 B4 B5], and the first 5 main peak frequencies of the tensile load of the rotor shaft are T = [T1 T2 T3 T4 T5], forming a matrix HBT of 15 elements = [H1 H2 H3 H4 H5 B1 B2 B3 B4 B5 T1 T2 T3 T4 T5];

[0046] Step 7: Traverse the elements of the HBT matrix. If there are two frequencies X and Y that satisfy Y = S * X, X ∈ HBT, Y ∈ H and Y ∈ B and Y ∈ T, then the rotational speed R = X * 60;

[0047] 5) All the sampled data of the rotational speed signal are transmitted to the host computer in real time for display processing, analysis, and network data distribution;

[0048] 6) After the test, send a stop command to stop sampling.

[0049] Furthermore, the process of collecting the rotational speed signal is as follows:

[0050] The rotational speed signal collected when the photoelectric sensor is triggered is a pulse signal with a high level of 10V, and the voltage value collected when not triggered is a low level of 0V.

[0051] The end-period rotational speed measurement method, the measurement period time is T time, the number of high-level pulses of the rotational speed collected within T time is k, k - 1 complete rotations of the rotor, and there is an incomplete low-level pulse data at both the beginning and the end; all these data are stored in the matrix in the form of specific digital points. At this time, the total number of points between the last two high levels in the matrix is defined as n;

[0052] The total number of points from the start S of the entire T time domain to the first high level in the entire T time domain is denoted as n1; the total number of points from the first high level to the end E in the entire T time domain is denoted as n2; then within the entire T time domain, the rotor rotates a total of circles;

[0053] Obtain the rotor speed .

[0054] The measurement period is T = 0.2 s. To achieve high-precision measurement of the rotational speed, if the number of high-level pulses of the rotational speed collected within 0.2 s is k = 2, that is, k - 1 = 2 - 1 = 1 complete rotation of the rotor, and there is an incomplete low-level pulse data at each end. These data are saved in the matrix as specific digital points. At this time, the total number of points between the last two high levels at the end of the matrix is defined as n;

[0055] It is the number of points between the first 10 V and the penultimate 10 V; the total number of points from the start S of 0.2 s to the first high level 10 V in the entire 0.2 s time domain is denoted as n1;

[0056] Such as in the matrix the number of points between the first 0 and the first 10 V; the total number of points from the last high level 10 V in the entire 0.2 s time domain to the end E is denoted as n2, such as in the matrix the number of points between the first 10 V and the first 0 V; then within 0.2 s, the rotor rotates a total of

[0057]

[0058] and the rotational speed of the rotor can be obtained

[0059] ;

[0060] If n = 200, n1 = 70, n2 = 30, then the rotational speed is 180 rpm, providing a new high-precision rotational speed measurement accuracy compared with the existing frequency measurement method and period method.

[0061] Furthermore, when it is necessary to collect data of multiple rotor systems simultaneously, connect multiple said telemetry systems to the same host computer, and all telemetry systems receive Beidou signals. A synchronization pulse is output every 1 s through the Beidou clock. Multiple sets of telemetry systems perform time synchronization after receiving the synchronization pulse to eliminate the running time error of the internal clock, thereby realizing time synchronization between different telemetry systems and realizing cascaded synchronous acquisition of multiple telemetry systems. For each output AD clock, the absolute time corresponding to this clock can be known. In this way, for each AD acquisition data, the corresponding Beidou time tag can be added to this data.

[0062] The technical effects of the present invention are:

[0063] A telemetry system and method with a TOP trigger signal that can be cascaded and synchronized are proposed. The entire telemetry system weighs 0.6 kg, and its size is diameter D * height H = 120 mm X 60 mm. It can be conveniently and quickly installed on the hubs of medium and small electric drive rotors. While effectively collecting rotational load signals such as blade and rotor shaft signals, it can also collect the rotational speed TOP signal, and can perform cascaded synchronous acquisition of multiple telemetry systems for easy data analysis. Brief Description of the Drawings

[0064] Figure 1 It is a schematic diagram of a telemetry system with a TOP trigger signal that can be cascaded and synchronized.

[0065] Figure 2 It is a schematic diagram of the internal structure of a telemetry system with a TOP trigger signal that can be cascaded and synchronized.

[0066] Figure 3 It is a schematic diagram of the installation position for adjusting the dynamic balance of the telemetry system.

[0067] Figure 4 It is a flowchart of the load signal acquisition of the telemetry system.

[0068] Figure 5 It is a schematic diagram of the multi-layer circuit board design.

[0069] Figure 6 It is a flowchart of the working signal transmission of the telemetry system.

[0070] Figure 7 It is an internal transmission diagram of the rotational speed signal.

[0071] Figure 8 It is a schematic diagram of the rotational speed measurement principle.

[0072] Figure 9 It is a schematic diagram of two unsynchronized systems.

[0073] Figure 10 It is a schematic diagram of two synchronized systems.

[0074] Figure 11 It is a schematic diagram of the rotational speed signal and the load signal.

[0075] Figure 12 It is a schematic diagram of the calculation process of the counterweight.

[0076] Figure 13 It is a schematic diagram of the rotational speed calculation process. Detailed Implementation Manner

[0077] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

[0078] In this application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation.

[0079] In addition, terms such as "installed", "set", "provided with", "connected", "connected to", "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0080] The following further describes the present invention in conjunction with the accompanying drawings and embodiments:

[0081] A telemetry system with a TOP trigger signal that can be cascaded and synchronized, as Figure 1 and Figure 2 shown, includes a collection module ①, a wireless module ②, and a Beidou signal transfer module ③, all placed on the top layer of the system. The circuit board ④ is placed in the middle layer of the system and adopts a multi-point fastening method to avoid the cantilever beam state. The battery assembly ⑤ is placed at the bottom layer of the system and consists of four lithium batteries with a total capacity of 40 wh, and can work continuously at full load for 4 h. The entire structure forms a compact stepped series structure, ensuring that the system is small in size and light in weight. The entire telemetry system selects a cylindrical structure and is installed on the upper surface of the hub of the rotor system through an intermediate adapter. The connection with the intermediate adapter is reasonably designed and has reliable anti-loosening measures. At the same time, it has anti-vibration and anti-shock designs to meet the requirements of the vibration and shock use environment of the test bench. In addition, it also includes a host computer ⑥ (including collection program software).

[0082] Dynamic balance design of the telemetry system

[0083] To ensure that the system quality center coincides with the rotation center after installation, the circuit and installation structure of all rotating components are designed in a centrally symmetric layout. The circuit board and components are arranged as symmetrically as possible around the axis;

[0084] The circuit layout can minimize the mass eccentricity as much as possible. The torque that cannot be balanced by the circuit layout measures is balanced by the structural design. The structural design fits the mass eccentricity caused by the circuit layout through simulation, and balances the mass eccentricity through the structural design, so as to ensure that the quality center coincides with the rotation center after the design is completed.

[0085] In addition to design guarantee measures such as symmetrically arranging components and symmetrically balancing structural design, there is also an installation position for adjusting the mass block of the rotational center of mass on the rotating part installation structure, such as Figure 3 shown. On the circumference with a diameter of φ114 on the outer circle of the system, there are 24 M3 threaded holes. Additional mass blocks can be installed on these threaded holes to balance the offset of the system quality center caused by factors such as machining errors.

[0086] The installation orientation and mass calculation process of the counterweight are as follows:

[0087] Step a: Define the high-pulse trigger point of the rotational speed pulse signal as the zero-phase point. Denote the phase difference between the first-order fundamental frequency signal of a certain load of the blade and the zero-phase point as Φ1, and its amplitude as A1. Then the initial load vector point is D1(A1, Φ1), as Figure 12 shown;

[0088] Step b: Try to install a mass block with a mass of m at any threaded hole. The phase of the mass block with a mass of m relative to the zero-phase point is Φ. Calculate the phase angle Φ2 of the first-order fundamental frequency signal relative to the zero-phase point again, and denote the amplitude as A2, denoted as D2(A2, Φ2);

[0089] Step c: D2 - D1 = D3(A3, Φ3), and D3 is the influence of the counterweight m at phase Φ on the dynamic balance;

[0090] The amplitude of the influence is A3, the phase is Φ0 = Φ - Φ3, the amplitude of the influence of the unit mass on the load is A3 / m, and the phase of the mass influence is advanced by Φ0;

[0091] Step d: Balance the initial load D1(A1, Φ1) according to D3. Then, to balance the dynamic balance, a counterweight m' = A1 * A3 / m needs to be loaded at the phase Φ' = Φ1 - Φ0.

[0092] Design of the load signal acquisition circuit for the telemetry system

[0093] Currently, the load signals on the rotor blades are all collected by attaching a Wheatstone full bridge. The principle is as Figure 4As shown, where Vi+ and Vi- are the output voltages of the bridge circuit, and Eg+ and Eg- are the excitation voltages of the bridge circuit.

[0094] 1) Input mode selection: The channel can select different input modes such as a full-bridge strain gauge and voltage (thermocouple) through a program-controlled internal relay switch.

[0095] 2) Range switching: The function of achieving various gain levels required is realized through program-controlled gain switching, and an instrumentation amplifier with switchable gain is used to ensure each gain level.

[0096] 3) Low-pass filtering: The cut-off frequency of the low-pass filter can be set to meet the requirements of the 2k frequency response of the measured signal and ensure the signal-to-noise ratio.

[0097] 4) Single-ended to differential conversion: Convert the single-ended signal into a differential signal for acquisition by a 16-bit ADC.

[0098] 5) Bridge voltage: Multiple levels of bridge voltage switching are achieved through DA switching.

[0099] Anti-interference design of the acquisition system of the telemetry system

[0100] As Figure 5 shown, a multi-layer circuit board is adopted. From top to bottom, the circuit board is successively: the top layer, the power ground layer, the power layer, the signal layer, the +15V power supply, and the bottom layer. In the circuit board design, the power ground layer, the power layer, and the signal layer are reasonably partitioned. The power layer is extensively copper-plated. Through multiple experimental comparisons, a reasonable design for suppressing interference with the minimum ground impedance and the minimum circuit noise is found. The components are reasonably arranged. Components such as the electromagnetic interference source digital and CPU clock generator are shielded and isolated and kept away from analog devices. Measures such as placing the connector and its pins on one side of the printed circuit board and away from high-speed devices are taken to effectively suppress the radiation of common-mode current. When designing the printed circuit board, the sensitive devices are partitioned and kept away from the electromagnetic interference source.

[0101] For all printed circuit boards, the ground wires of the power supply voltage, digital circuit, and analog circuit are independently separated, and the most appropriate positions are found through experiments to short-circuit different ground wires. The information acquisition device effectively suppresses the electromagnetic interference radiated into space by the transient supply current in the line and the common-impedance coupling interference caused by the inductance of the supply line by reducing the characteristic impedance of the supply line and using filtering and decoupling capacitors. Incompatible signal lines are kept away from each other, and a multi-layer and mutually perpendicular wiring method is adopted to reduce the electric field and magnetic field coupling interference between signal lines. The positions of high-speed signal lines are reasonably designed, and the shortest wiring method and shielding measures are adopted to avoid interfering with other signal lines.

[0102] Working signal transmission process of the telemetry system

[0103] As Figure 6As shown in the figure, the outdoor receiving antenna, Beidou relay module, and indoor transmitting antenna are mainly used in wind tunnel tests to introduce outdoor Beidou signals into the indoor, facilitating the telemetry system to receive Beidou clock signals through the Beidou signal transfer module.

[0104] Rotor system, acquisition module: The signals such as flapping, lag, torsion, and rotational speed on the blades in the rotor system are connected to the acquisition module of the telemetry system through cables to acquire load signals.

[0105] Switch, wireless AP: It mainly receives the data signals transmitted by the telemetry system through the wireless module. The wireless transmission is via the WiFi method, using the 2.4GHz frequency band to achieve point-to-point wireless communication between the AP base station and the telemetry system terminal. The link layer uses the Ethernet protocol as the core to achieve addressing and verification of information transmission, realizing multi-system wireless networking with a communication distance of at least 100 meters. The wireless transmission stability: The number of lost data packets / data frames per hour ≤ 3. The wireless AP then transmits the data to the host computer through the switch and network cable for storage, processing, and analysis.

[0106] The working steps of the telemetry system are as follows:

[0107] 1) After all systems are installed, turn on the power of all instruments, start the control software, read the information of all acquisition instruments, and give corresponding prompts, that is, how many acquisition instruments are working.

[0108] 2) According to the test requirements, set the parameters of the acquisition instrument, such as range, filter, input mode, bridge mode, sampling frequency, etc.

[0109] 3) When system synchronous acquisition work is required, check whether Beidou communication is normal to ensure synchronous accuracy.

[0110] 4) If synchronous acquisition is not required or Beidou signals cannot be received due to site weather reasons, the system can directly use the internal clocks of each system for acquisition without connecting to the Beidou clock, but synchronous accuracy is not guaranteed.

[0111] 5) Start sampling to check whether the system can work properly. If not, find the reason.

[0112] 6) All sampled data is transmitted to the relevant computers in real-time through wireless and wired Ethernet for display processing, analysis, and network data distribution.

[0113] 7) After the test, send a stop command, and the acquisition instrument will immediately stop sampling after receiving the stop command.

[0114] Design method for the acquisition of the rotational speed TOP signal trigger signal

[0115] Such as Figure 7As shown, a photoelectric sensor is connected to a telemetry acquisition module and rotated. A reflective sticker is attached to the non-rotating platform to collect the top speed signal. When triggered, the collected speed signal is a 10V high-level pulse signal. When not triggered, the collected voltage is a 0V low-level signal. The speed signal enters the speed circuit and the speed sensor inputs the speed channel. After the pulse signal is processed by the shaping circuit, it is input to the speed module in the FPGA (programmable logic device). After capturing the speed pulse frequency based on the clock frequency, the speed value is calculated, the key phase is measured, and the combined value is sent to the control card via the backplane data bus.

[0116] Automatic speed measurement method based on load spectrum: According to the high correlation between rotor load signal spectrum and rotor speed, such as Figure 11 As shown, the current real-time rotor speed can be obtained through spectrum analysis of the load signal. The speed response speed obtained by this path can reach the millisecond level and the accuracy can reach 0.01%. In addition, this method can solve the problem that the photoelectric sensor signal is susceptible to electromagnetic interference and is affected by external light sources in outdoor test and flight environments, resulting in incorrect speed measurement. In the rotor test, let the number of rotor blades be S. The flapping vibration signal frequency of the blade mainly includes the rotor speed fundamental frequency, the blade passing frequency (S*speed fundamental frequency), and the blade flapping vibration natural frequency. The load signal frequency on the rotor shaft mainly includes the rotor speed fundamental frequency, the second-order fundamental frequency, the third-order fundamental frequency...the blade passing frequency (S*speed fundamental frequency), and 50HZ public frequency interference, etc.

[0117] When the rotor speed is below 600rpm, the rotor load value is very small and the peak value of the load spectrum analysis is not obvious, so the speed measurement method is divided into two cases, such as Figure 13 As shown, the measurement process is as follows:

[0118] 1) When the rotor speed is below 600 rpm:

[0119] Step 1: Given a speed signal acquisition period T = 0.1s, the number of speed high-level pulses collected within T time is recorded as k;

[0120] Step 2: If k < 2, it means that there are no two high pulses within the time T, that is, the rotor has not made a complete circle. Then continue to sample at a period of T = T + 0.05s until K ≥ 2.

[0121] Step 3: Calculate the data collected during the time T, which contains k-1 complete rotor rotation circles, with an incomplete low-level pulse at the beginning and end. These data are stored in the matrix in the form of specific digital points. The total number of points between the last two high-level pulses in the matrix is defined as n.

[0122] The total number of points from the start S of the entire T time domain to the first high level in the entire T time domain is denoted as n1; the total number of points from the first high level to the end E in the entire T time domain is denoted as n2; then within the entire T time domain, the rotor rotates a total of circles;

[0123] Obtain the rotor speed ;

[0124] By the method of measuring speed through the end period, as Figure 8 shown, the measurement period time is T = 0.2 s. To achieve high-precision speed measurement, for example, the number of high-level pulses of the speed collected within 0.2 s is k = 2. That is, k - 1 = 2 - 1 = 1 complete rotation of the rotor, and there is an incomplete low-level pulse data at each end. These data are saved in the matrix as specific digital points. At this time, the total number of points between the last two high levels in the matrix is defined as n, which is the number of points between the first 10 V and the penultimate 10 V; the total number of points from the start S of 0.2 s to the first high level 10 V in the entire 0.2 s time domain is denoted as n1, such as the number of points between the first 0 and the first 10 V in the matrix ; the total number of points from the last high level 10 V to the end E in the entire time domain of 0.2 s is denoted as n2, such as the number of points between the first 10 V and the first 0 V in the matrix ; then within 0.2 s, the rotor rotates a total of

[0125] ,

[0126] and the rotor speed can be obtained

[0127] ;

[0128] If n = 200, n1 = 70, n2 = 30, then the speed is 180 rpm, providing a new high-precision speed measurement accuracy for low speeds compared to the existing frequency measurement method and period method.

[0129] When the rotor speed is greater than 600 rpm,

[0130] Step 4: Given the signal acquisition period T = 0.1 s, the number of high-level pulses of the rotational speed collected within time T is denoted as k. When K ≥ 2, perform FFT analysis on the flapping, lagging, and rotational shaft tension loads of the rotating blade. Analyze the first 5 main peak frequencies within 200 Hz of the three load signals. Let the first 5 main peak frequencies of the blade flapping be H = [H1 H2 H3 H4 H5], the first 5 main peak frequencies of the blade lagging be B = [B1 B2 B3 B4 B5], and the first 5 main peak frequencies of the rotor shaft tension be T = [T1 T2 T3 T4 T5]. Form a matrix HBT with 15 elements: HBT = [H1 H2 H3 H4 H5 B1 B2 B3 B4 B5 T1 T2 T3 T4 T5]

[0131] Step 5: Traverse the elements of the HBT matrix. If there exist two frequencies X and Y that satisfy Y = S * X, where X ∈ HBT, Y ∈ H, Y ∈ B, and Y ∈ T, then the rotational speed R = X * 60;

[0132] For example, when the number of rotor blades is 5 and T = 0.1 s, the number of high-level pulses of the rotational speed k = 3 within 0.1 s. Analyze the rotor loads. The first 5 main peak frequencies of the blade flapping are H = [3.5 16.7 2 42.4 78.3 106], the first 5 main peak frequencies of the blade lagging are B = [7.6 21.2 42.4 63.6 106], and the first 5 main peak frequencies of the rotor shaft tension are T = [21.2 50 100 106 200]. Then HBT = [3.5 16.7 2 42.4 78.3 106 7.6 21.2 42.4 63.6 106 21.2 50 100 106 200]. In HBT, there exists Y = 106 Hz = X * 5 = 21.2 * 5, and Y = 106 Hz belongs to the elements of H, B, and T. So at this time, the rotational speed R = X * 60 = 21.2 * 60 = 1272 rpm

[0133] Multi-system cascaded synchronous acquisition: In multi-rotor experiments, it is often necessary to use multiple telemetry systems simultaneously. Multiple telemetry systems can be used simultaneously and the time axes can be synchronized and aligned.

[0134] When each system can receive GPS well, each system can receive the second pulse signal of Beidou in real time. Through the Beidou clock, an accurate synchronous pulse is output every 1 s. The two telemetry acquisition systems perform time synchronization after receiving the synchronous pulse to eliminate the timekeeping error of the internal clock of the acquisition instrument, thereby achieving time synchronization between different systems and realizing multi-system cascaded synchronous acquisition; the synchronization accuracy is better than 1 us. For each output AD clock, the absolute time corresponding to this clock can be known. In this way, for each AD acquisition data, the corresponding Beidou time tag can be added to this data. As Figure 9As shown, the data acquisition time coordinate points of the telemetry system 1 and the system 2 at the same moment are 11:10:10 and 11:10:12 respectively, with a 2-second time asynchrony. Then, at a certain moment, they both receive the Beidou second pulse signal, and the time is parsed as 11:10:11. At this time, the time of the telemetry 1 is accurate, and the system time of the telemetry 2 is advanced. Therefore, the telemetry 2 updates the time data label with the Beidou second pulse signal. Since the sampling rate of the system is fixed and defined as f, the time interval between every two data points is 1 / f. Therefore, the data points collected by the telemetry 2 can be re-corresponded with the received Beidou time as the reference. After synchronization, as Figure 10 shown.

[0135] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A telemetry system with a TOP trigger signal that can be cascaded and synchronized, characterized in that: The telemetry system includes: a wireless module, a Beidou signal transfer module, a collection module, a circuit board, a battery, a host computer, a sensor assembly, a non-rotating platform, and an equipment housing; The rotor system is arranged on the non-rotating platform, and the equipment housing is installed above the hub of the rotor system; the circuit board is installed at the opening of the equipment housing, and the battery is connected below the circuit board; the wireless module, the Beidou signal transfer module, and the collection module are connected above the circuit board; The sensor assembly is installed on the rotor system and is connected to the collection module through a cable; the Beidou signal transfer module is used to receive Beidou signals; the wireless module is used to communicate with the host computer; The sensor assembly includes: a load measurement assembly and a rotational speed measurement assembly; The collection module collects the flapping load of the rotating blade, the lead-lag load of the rotating blade, the tensile load of the rotating shaft, and the rotational speed pulse signal; The host computer sets the collection period T of the rotational speed pulse signal to T = 0.1 s, and the number of high-level pulses of the rotational speed collected within the T time is recorded as k; If k < 2, then T is assigned as T + 0.05 s until k ≥ 2, and then the rotational speed is measured by the end-period rotational speed measurement method; If k ≥ 2, then FFT analysis is performed on the flapping load of the rotating blade, the lead-lag load of the rotating blade, and the tensile load of the rotating shaft to obtain the first 5 main peak frequencies within 200 Hz of the three load signals. The first 5 main peak frequencies of the flapping load of the blade are H = [H1 H2 H3 H4 H5], the first 5 main peak frequencies of the lead-lag load of the blade are B = [B1 B2 B3 B4 B5], and the first 5 main peak frequencies of the tensile load of the rotor shaft are T = [T1 T2 T3 T4 T5], forming a matrix HBT of 15 elements = [H1 H2 H3 H4 H5 B1 B2 B3 B4 B5 T1 T2 T3 T4 T5]; Traverse the elements of the HBT matrix. If there are two frequencies X, Y that satisfy Y = S * X, X ∈ HBT, Y ∈ H and Y ∈ B and Y ∈ T, then the rotational speed R = X * 60.

2. The telemetry system according to claim 1, characterized in that: The equipment housing is a cylindrical housing with an opening at the top; the equipment housing is installed on the hub through an intermediate adapter.

3. The telemetry system according to claim 1, characterized in that: The load measurement assembly is a Wheatstone full bridge pasted on the blade.

4. The telemetry system according to claim 1, characterized in that: The rotational speed measurement assembly includes: a photoelectric sensor and a reflective sticker; The photoelectric sensor is installed on the side wall of the intermediate adapter; The reflective sticker is pasted on the non-rotating platform and is directly below the photoelectric sensor.

5. The telemetry system according to claim 2, characterized in that: The center of mass of the whole composed of the intermediate adapter, the equipment housing, and all the devices carried by the equipment housing coincides with the rotation center of the rotor system; The circuit board and the devices carried on the circuit board are arranged symmetrically with respect to the rotation center of the rotor system; The wireless module, the Beidou signal transfer module, and the collection module are designed in a centrosymmetric arrangement; A trimming structure is designed on the circuit board to compensate for the mass eccentricity of the circuit board; the installation position and mass of the trimming structure are obtained through simulation; Threaded holes are evenly arranged on the peripheral edge of the circuit board, and mass blocks are installed on the threaded holes to eliminate the mass eccentricity caused by machining and installation errors; the calculation process of the installation orientation and mass of the counterweight block is as follows: Step a: Define the high-pulse trigger point of the rotational speed pulse signal as the zero-phase point. Denote the phase difference between the first-order fundamental frequency signal of a certain blade load and the zero-phase point as Φ1, and its amplitude as A1. Then the initial load vector point is D1(A1, Φ1). Step b: Try to install a mass block with mass m in any threaded hole. The phase of the mass block with mass m relative to the zero-phase point is Φ. Calculate the phase angle Φ2 of the first-order fundamental frequency signal relative to the zero-phase point again, and denote the amplitude as A2, denoted as D2(A2, Φ2). Step c: D2 - D1 = D3(A3, Φ3), where D3 is the influence of the mass m at phase Φ on the dynamic balance. The amplitude of the influence is A3, and the phase is Φ0 = Φ - Φ3. The amplitude of the load influenced by unit mass is A3 / m, and the phase of the mass influence is ahead by Φ0. Step d: Balance the initial load D1(A1, Φ1) according to D3. Then, for dynamic balance, a counterweight m' = A1 * A3 / m needs to be loaded at the phase Φ' = Φ1 - Φ0.

6. The telemetry system according to claim 1, wherein: The circuit board is a multi-layer circuit board, which from top to bottom are: top layer, power ground layer, power layer, signal layer, +15V power supply layer, and bottom layer. The power layer is covered with copper on a large area. The power supply voltages, digital circuit grounds, and analog circuit grounds in each layer of the circuit board are separated independently.

7. A telemetry method with a TOP trigger signal that can be cascaded and synchronized, the method being implemented based on the telemetry system described in any one of claims 1-6, characterized in that: It includes the following steps: 1) Install the telemetry system and turn on the power. 2) Set parameters according to the test requirements, including: range, filter, input mode, bridge mode, sampling frequency. 3) When multiple telemetry systems need to synchronously collect data, check whether the Beidou signal reception is normal. 4) If synchronous collection is not required or the Beidou signal cannot be received, directly use the internal clock of the telemetry system to collect signals; collect the flapping load of the rotating blade, the lead-lag load of the rotating blade, and the tensile load of the rotating shaft; collect the rotational speed pulse signal; the process of calculating the rotational speed is as follows: Step 1: Given the collection period T = 0.1s of the rotational speed pulse signal, denote the number of high-level pulses of the rotational speed collected within time T as k. Step 2: If k < 2, jump to Step 3; if k ≥ 2, then jump to Step 6. Step 3: T = T + 0.05s. Step 4: Determine whether k is greater than or equal to 2. If so, jump to Step 5, otherwise return to Step 3. Step 5: Within time T, k - 1 complete rotor rotations are collected, and there is an incomplete low-level pulse data at both the head and the tail; all these data are saved in the matrix in the form of specific digital points. At this time, the total number of points between the last two high levels at the end of the matrix is defined as n. The total number of points from the start S of the entire T time domain to the first high level of the entire T time domain is denoted as n1; the total number of points from the first high level to the end E of the entire T time domain is denoted as n2; then within the entire T time domain, the rotor rotates a total of revolutions; Obtain the rotor speed ; Step 6: Conduct FFT analysis on the flapping load of the rotating blade, the drag load of the rotating blade, and the tensile load of the rotating shaft to obtain the first 5 main peak frequencies within 200 Hz of the three load signals. The first 5 main peak frequencies of the flapping load of the blade are H = [H1 H2 H3 H4 H5], the first 5 main peak frequencies of the drag load of the blade are B = [B1 B2 B3 B4 B5], and the first 5 main peak frequencies of the tensile load of the rotor shaft are T = [T1 T2 T3 T4 T5], forming a matrix HBT with 15 elements: HBT = [H1 H2 H3 H4 H5 B1 B2 B3 B4 B5 T1 T2 T3 T4 T5]; Step 7: Traverse the elements of the HBT matrix. If there are two frequencies X and Y that satisfy Y = S * X, where X ∈ HBT, Y ∈ H, Y ∈ B, and Y ∈ T, then the rotational speed R = X * 60; 5) All signal sampling data is transmitted to the host computer in real time for display processing, analysis, and network data distribution; 6) After the test, send a stop command to stop sampling.

8. The method according to claim 7, wherein: The rotational speed pulse signal collected when the photoelectric sensor is triggered is a pulse signal with a high level of 10 V, and the rotational speed pulse signal collected when not triggered is a low level of 0 V.

9. The method according to claim 7, characterized in that: When it is necessary to collect data of multiple rotor systems simultaneously, connect multiple said telemetry systems to the same host computer, and all telemetry systems receive Beidou signals. A synchronization pulse is output every 1 s through the Beidou clock. Multiple sets of telemetry systems perform time synchronization after receiving the synchronization pulse to eliminate the running time error of the internal clock, thereby achieving time synchronization between different telemetry systems and realizing cascaded synchronous acquisition of multiple telemetry systems.

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