Pole tower inclination angle monitoring system based on photoelectric oscillator

Abstract

The invention discloses a tower inclination angle monitoring system based on a photoelectric oscillator, and relates to the technical field of tower inclination angle monitoring, which comprises the following steps of: mapping angle information to OEO oscillation frequency, and resolving an inclination parameter in real time by utilizing a field programmable gate array (FPGA) to complete online monitoring of the tower inclination angle. The feasibility and effectiveness of the system for monitoring the inclination angle of the tower in real time are verified through experiments.

Description

Technical Field

[0001] The present invention relates to the technical field of pole tower inclination angle monitoring, and more specifically, to a pole tower inclination angle monitoring system based on a photoelectric oscillator. Background Art

[0002] my country has a wide distribution of land area, diverse and complex geological conditions, different terrain and geology in the areas where the transmission lines pass, and complex climate and environment. The factors such as icing and dancing of the transmission line conductors will lead to the tilt of the transmission line towers and even the collapse of the towers, thus causing huge economic losses and seriously affecting the safe and stable operation of the power grid. Therefore, in order to prevent such accidents, the power industry currently uses manual inspections and traditional transmission line tower tilt status monitoring devices for monitoring. In this scenario, the existing traditional transmission line tower tilt status monitoring devices and active electrical signal sensors, and traditional electrical domain sensing technologies are difficult to take into account both economy and stability at the same time.

[0003] The above disclosed technical solutions have at least the following technical problems: Manual inspections are mostly based on experience and a single method, which consumes a lot of manpower and material resources. Due to the influence of terrain and topography, some tower tilts cannot be discovered in time, posing safety hazards. Existing active electrical signal sensors have problems such as complex wiring, heavy system maintenance workload, power supply required for monitoring equipment, strong electromagnetic interference affecting signal transmission, and long-term stability of equipment. Traditional electrical domain sensing technology performs poorly in terms of energy attenuation and phase noise.

[0004] In view of the above problems, the present invention proposes a solution. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a tower tilt angle monitoring system based on an optoelectronic oscillator, which solves the problems of low stability, economy and reliability of traditional transmission line tower tilt state monitoring devices by establishing a frequency-tilt angle mapping model.

[0006] To achieve the above object, the present invention provides the following technical solutions: A tower tilt angle monitoring system based on a photoelectric oscillator comprises two modules, namely a tilt angle sensing module and a signal processing module.

[0007] Tilt angle sensing module: responsible for the integrated design of the photoelectric oscillator and the tilt angle sensor to detect the tilt angle of the tower in real time, including the sensor and the photoelectric oscillator system; Signal processing module: used to receive data from the sensor module, map the angle information to the OEO oscillation frequency, calculate the tilt parameters in real time through the field programmable logic gate array, obtain accurate tilt angle information, and perform further alarm and recording functions.

[0008] In a preferred embodiment, the sensor comprises a dual-axis tilt sensor, which measures the tilt angle through the force exerted by gravity on the tower and the acceleration generated when the tower tilts.

[0009] In a preferred embodiment, the real-time detection of the inclination angle of the tower is specifically as follows: based on a dual-axis inclination sensor installed on the transmission line tower, the vertical inclination angle and the lateral inclination angle of the tower are measured, a mechanical model sensor that reflects the inclination condition of the transmission line tower is established, and a rough inclination angle of the tower is calculated based on a preset transmission line tower inclination formula.

[0010] In a preferred embodiment, the optoelectronic oscillator is specifically: based on the optoelectronic oscillator, the change of the transmission tower inclination angle is converted into the change of the OEO cavity length, and the real-time information of the inclination angle is obtained by monitoring the system output frequency.

[0011] In a preferred embodiment, the tilt angle sensing module includes an OEO system, and the linearly polarized broadband light emitted by the ASE light source passes through an isolator and enters a magneto-optical switch, and the light field switches in the X / Y directions respectively and enters a Sagnac loop, and the Sagnac loop is composed of a polarization controller and a polarization-maintaining optical fiber; the output light field is modulated by a phase modulator and enters an erbium-doped fiber amplifier for amplification, coupled to a dispersion-compensating optical fiber and converts the phase information into intensity information.

[0012] In a preferred embodiment, the signal processing module specifically performs frequency division and shaping processing on the microwave signal generated by the OEO system to convert it into a digital signal; uses FPGA to perform high-speed digital signal acquisition, calculates the signal frequency, and obtains real-time tilt angle information.

[0013] In a preferred embodiment, the microwave signal generated by the OEO system is subjected to frequency division and shaping processing, specifically: the intensity information is transmitted to the FRR, and the optical signal is converted into an electrical signal via a photodetector; the electrical signal is amplified in power by an electrical amplifier, and then divided into two paths by a power divider; one path is fed back to the PM to form an OEO oscillation loop, and when the gain of the entire resonant loop is greater than the loss, the OEO loop establishes oscillation; the other path is transmitted to the signal processing module to complete real-time signal processing; in the signal processing module, PS2 further divides the signal into two paths, one path enters the electrical spectrum analyzer to observe the microwave signal output by the OEO oscillation loop; the other path enters the mixer as a radio frequency signal; the signal output by the microwave source is used as the radio frequency signal of the mixer, and the signal output by the radio frequency source is used as the local oscillator signal of the mixer.

[0014] In a preferred embodiment, the high-speed digital signal acquisition and signal frequency calculation using FPGA are specifically as follows: when the input signals are multiplied, the mixer generates a sum frequency term and an intermediate frequency term, the sum frequency term is filtered out by a low-pass filter, and the intermediate frequency term is retained; based on the tunability of the system tilt angle, the frequency of the intermediate frequency term signal is further reduced by a frequency divider and enters a comparator; the threshold voltage of the comparator is set, and a high level is output when the input signal level is higher than the threshold voltage, and a low level is output when the input signal level is lower than the threshold voltage; the conversion from analog signal to digital signal is realized by the comparator; the frequency of the signal is calculated by the counter function of the FPGA, and the real-time processing of the OEO frequency offset signal is realized, thereby obtaining the tilt angle change information.

[0015] The technical effects and advantages of the tower tilt angle monitoring system based on the photoelectric oscillator of the present invention are as follows: The high-precision tilt angle monitoring system based on OEO of the present invention adopts photoelectric fusion technology to realize the dynamic online monitoring of the tilt angle of the transmission tower in the whole process and wireless data transmission. The present invention is based on the optical fiber sensing system, which has the characteristics of strong anti-electromagnetic interference ability, low power consumption operation and low cost; each device of the system has the advantage of being integrable, so that it has good reliability and scalability in future transmission tower monitoring, operation and maintenance, overhaul, emergency prevention and other aspects; fully exploit the advantages of photonic technology, use the thermal effect of optical fiber length, transfer the tilt angle information to the change of OEO oscillation frequency, and realize a 0.1° high-precision tilt angle monitoring system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of a tower tilt angle monitoring system based on a photoelectric oscillator according to the present invention; Figure 2 Schematic diagram of the high-precision tilt angle monitoring system for transmission towers based on OEO; Figure 3 Model of transmission line tower tilt; Figure 4 Schematic diagram of dual-axis installation; Figure 5 FPGA-based signal processing flow chart; Figure 6 LTC5552 mixer circuit diagram; Figure 7 The time domain waveform of the intermediate frequency signal output by the mixer; Figure 8 HMC394 frequency divider circuit diagram; Fig. 9 The time domain waveform of the 32-frequency division circuit output; Fig.10 ADCMP602 voltage comparator circuit diagram; Fig.11 Time domain waveform of the ADCMP602 voltage comparator output; Fig.12 ASE output spectrum; Fig.13 Global image of SI output spectrum at 25 °C; Fig.14 Detail of SI output spectrum slice at 25 °C; Fig.15 The OEO system outputs the 4.124 GHz microwave signal electrical spectrum; Fig.16 Detail of the spectrum of 4.124 GHz microwave signal; Fig.17 The electrical spectrum of microwave signals when the OEO resonant cavity is coupled with the FRR; Fig.18 Frequency stability measurement within 30 minutes; Fig.19 Tilt angle value after FPGA analysis; Fig. 20 The curve of oscillation frequency versus tilt angle analyzed by FPGA; Fig.21 Comparison curve of OEO system and set value. DETAILED DESCRIPTION

[0017] 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.

[0018] Embodiment 1, Figure 1The invention provides a tower inclination angle monitoring system based on a photoelectric oscillator, comprising an inclination angle sensing module and a signal processing module.

[0019] Tilt angle sensing module: responsible for the integrated design of the photoelectric oscillator and the tilt angle sensor to detect the tilt angle of the tower in real time, including the sensor and the photoelectric oscillator system; Signal processing module: used to receive data from the sensor module, map the angle information to the OEO oscillation frequency, calculate the tilt parameters in real time through the field programmable logic gate array, obtain accurate tilt angle information, and perform further alarm and recording functions.

[0020] In the tilt angle sensor module, the experiment built Figure 2 The transmission tower tilt angle monitoring system shown in the figure. The observation equipment used in the experiment is an optical spectrum analyzer (OSA, YOKOGAWA, AQ6370C) and an electrospectrometer (ESA, Agilent, N9010A). Fig.12 This is the spectrum of the ASE light source. It can be seen from the figure that the central wavelength of the wide-spectrum light output by ASE is 1550 nm, the 3-dB spectrum width is 7.36 nm, and it has good power flatness.

[0021] The tilt angle sensing module includes an optoelectronic optical communication system (OEO). The basic principle of this system is to convert optical signals into electrical signals, and then convert electrical signals back into optical signals. OEO is mainly composed of an optical fiber transmission system, an optoelectronic converter, and an electro-optical converter. Specifically, the linearly polarized broadband light emitted by the ASE light source enters the magneto-optical switch after passing through the isolator, and then the light field switches to the X / Y directions respectively and enters the Sagnac loop (SI). The SI consists of a polarization controller (PC) and a section of polarization maintaining fiber (PMF). Its output light field is modulated by a phase modulator (PM) and enters an erbium-doped fiber amplifier (EDFA) for amplification and is coupled to a section of dispersion compensating fiber (DCF).

[0022] The role of the DCF is to convert phase information into intensity information and then transmit it to the FRR. The FRR consists of a section of single-mode optical fiber and a 3dB optical coupler (OC2).

[0023] Photoelectric detector (PD) converts light signals into electrical signals.

[0024] The electrical signal is amplified by an electronic amplifier (EA1) and then divided into two paths by a power splitter (PS1).

[0025] One of the paths is fed back to the PM to form an OEO oscillation loop. When the gain of the entire resonant loop is greater than the loss, the OEO loop establishes oscillation. The other path is transmitted to the signal processing module to complete real-time signal processing. In the signal processing module, PS2 further divides the signal into two paths, one of which enters the electrical spectrum analyzer (ESA) to observe the microwave signal output by the OEO oscillation loop. The other path enters the mixer (Mixer, Mix) as a radio frequency (RF) signal. At the same time, the signal output by the microwave source is used as the local oscillator (LO) signal of the Mix.

[0026] The low-pass filter is used to filter out the sum frequency terms after mixing and retain the intermediate frequency signal.

[0027] After EA2 amplifies the microwave signal power, it is further processed by the frequency divider to reduce the frequency. The analog signal is then transmitted to the comparator to complete the conversion from analog signal to digital signal. The FPGA is used to collect signals and combine the edge detection function to complete the acquisition of the current signal frequency, thereby realizing the real-time processing of the tilt angle parameter.

[0028] Using FPGA for signal acquisition combined with edge detection has the following significant advantages: High speed and parallel processing: FPGA's parallel processing capability allows multiple data streams to be processed simultaneously, which makes the signal acquisition and processing process very fast. Compared with traditional processors, FPGA can achieve higher sampling rates and faster response times, which is especially important for real-time systems.

[0029] Accurate frequency measurement: Edge detection technology can accurately capture the rising and falling edges of the signal, providing high-precision frequency measurement. This accuracy is critical for monitoring subtle tilt angle changes and can improve the overall reliability and accuracy of the system.

[0030] Real-time processing capability: FPGA can process the collected data in real time, without transmitting the data to an external processing unit for analysis. This built-in processing capability reduces latency and enables the system to respond to changes in signals and make adjustments or sound alarms in a timely manner.

[0031] Flexibility and customizability: FPGA can be programmed to implement a variety of functions and algorithms, which means that the signal processing process can be customized according to specific needs to adapt to different application scenarios. This flexibility helps to achieve targeted optimization, such as filtering, data integration and complex calculations.

[0032] Stability and reliability: FPGA hardware implementation is usually more stable than software implementation and can maintain high reliability in complex and dynamic environments. This is especially important for application scenarios that require high stability, such as real-time monitoring systems.

[0033] In the tilt angle sensing module, the transmission line tower tilt online monitoring system is based on the dual-axis tilt sensor installed on the transmission line tower to measure the vertical tilt angle and lateral tilt angle of the tower, and establish a mechanical model that reflects the tilt condition of the transmission line tower. Among them, the basic parameters are as follows: O is the tower foundation, the top of the tower before tilt is P, the top of the tower after tilt is P', the tilt angle of the tower is θ, the vertical tilt angle of the tower is α, the lateral tilt angle of the tower is β, the tower height is h, and the mathematical model of the transmission line tower tilt is as follows: Figure 3 shown.

[0034] The dual-axis tilt sensor can measure the vertical tilt angle α and the lateral tilt angle β of the tower. Ignoring the influence of the tower material deformation, we get: (1) Since P'E⊥OP, and the sum of the interior angles of a triangle is 180°, we can get θ = 2γ. In △OP'P, according to the properties of an isosceles triangle: (2) Right now: (3) Using the properties of trigonometric functions, we can get: (4) From equations (2) and (3), we can get: (5) According to the properties of right triangles in △PDE, △PEF, △PEP': (6) According to the Pythagorean theorem |DE|2+|EF|2=|P'E|2, we can get: (7) From θ = 2γ we get: (8) Where: θ is the inclination angle of the tower; α is the vertical inclination angle of the tower; β is the lateral inclination angle of the tower.

[0035] From the formula for calculating the inclination of transmission line towers, we can see that there are two state parameters that need to be monitored: the vertical inclination angle α of the tower and the lateral inclination angle β of the tower. Therefore, a dual-axis inclination sensor needs to be installed on the tower to monitor the inclination of the tower.

[0036] In a dual-axis monitoring system, the principle is as follows Figure 4 As shown in the figure, a cantilever rod is fixed in the X and Y directions respectively, and a heavy weight is fixed with a metal wire at the bearing connection of the double rods to form a pendulum structure. The sensing optical fiber (Lx0, Ly0) is placed tightly between the cantilever rod and the metal wire. When the tower is tilted, the cantilever rod forms an angle with the vertical direction. Figure 4 It can be seen that: (9) By combining equations in equation 9, we can get: (10) Similarly, we can get: (11) Therefore, the angle information can be transferred to the length parameter. In the present invention, we use an optoelectronic oscillator to complete the tilt angle-length mapping.

[0037] The relationship between the fundamental frequency fb of OEO and the loop length L can be expressed as: (12) Where c is the speed of light in vacuum and n is the equivalent refractive index of the OEO loop.

[0038] The oscillation frequency fm of OEO is a high-order oscillation mode, and its value is N times of the fundamental frequency, so fm can be expressed as: (13) Assuming that the length of the OEO loop changes by ΔL, the corresponding fundamental frequency changes by Δfb. According to equation (13), we have: (14) The oscillation frequency change corresponding to the fundamental frequency change Δfb is recorded as Δfm, and the starting frequency after the loop length changes is recorded as fm*. Then according to formula (14), we have: (15) Combining equations (14) and (15), we can get the expression of Δfm: (16) From equation (16), we can see that when the OEO works in a high-order oscillation mode, the fundamental frequency change caused by the change in loop length will be amplified N times. This phenomenon is the cumulative amplification effect of the OEO. Combining equations (15) and (16) gives equation (17): (17) According to formula (17), the expression of ΔL can be obtained as: (18) Formula (18) is the relationship between the change in loop length and the change in oscillation frequency of a single-loop OEO. The tilt angle measurement system proposed in this paper includes the X direction and the Y direction, which together constitute a dual-loop OEO. Therefore, for the dual-loop OEO, Formula (18) can be rewritten as: (19) (20) Among them, Lx and Ly in the formula are the original loop lengths in the X and Y directions, Δfm_x and Δfm_ are the changes in oscillation frequency before and after the transmission tower is tilted in the two directions, fm_x* and fm_y* are the oscillation frequencies after tilting in the two directions, and ΔLx and ΔLy on the left side of the formula are the changes in loop length before and after the target displacement in the two directions.

[0039] There are several main benefits of deploying dual-axis tilt sensors on towers: Comprehensive monitoring: The dual-axis tilt sensor can simultaneously measure the tilt angle of the tower in two vertical directions, providing more comprehensive tilt information. Compared with a single-axis sensor, it can more accurately capture the tilt of the tower in different directions, helping to identify and analyze possible structural problems.

[0040] Improved accuracy: By measuring in two axes, the overall tilt of the tower can be determined more accurately, rather than relying on measurements in a single direction. This improves data accuracy and system reliability.

[0041] Enhanced stability: Dual-axis sensors can detect tilt changes in multiple directions, allowing early identification of potential stability issues. Timely detection of changes in tower tilt helps preventive measures and avoid structural failures.

[0042] Optimize maintenance and safety: Real-time dual-axis tilt data can help operators better understand the status of the tower and formulate a reasonable maintenance plan. For scenarios with high safety requirements, this detailed data helps reduce the risk of accidents.

[0043] Adapt to complex environments: In actual applications, poles and towers may be affected by various environmental factors, such as wind, earthquake, etc. Dual-axis sensors can more comprehensively reflect the comprehensive impact of these complex factors on poles and towers, and provide more accurate monitoring results.

[0044] From the above deduction, it can be known that the change of the transmission tower inclination angle can be converted into the change of the OEO cavity length, and the real-time information of the inclination angle can be obtained by monitoring the output frequency of the system.

[0045] In the data processing module, the RF source output signal is used as the local oscillator signal of the mixer, which is recorded as , the microwave signal output by the OEO system is used as the RF signal, denoted as , the two signals are expressed as: (twenty one) Where: Respectively represent the amplitude of the local oscillator signal and the RF signal, Represent the center frequencies of the local oscillator signal and the RF signal respectively.

[0046] The basic principle of a mixer is to use the characteristics of nonlinear elements (such as diodes or transistors) to achieve frequency mixing of two signals. Its output signal is expressed as: (twenty two) It can be seen from the above formula that the mixer generates sum frequency and intermediate frequency when the input signals are multiplied. The sum frequency is filtered out by a low-pass filter, and the intermediate frequency is retained. Considering the tunability of the system tilt angle, the frequency of the intermediate frequency signal is further reduced by a frequency divider, and then the signal enters the comparator. The threshold voltage of the comparator is set, and a high level is output when the input signal level is higher than the threshold voltage, and a low level is output when the input signal level is lower than the threshold voltage. Therefore, the conversion of analog signals to digital signals is realized by the comparator. Finally, the counter function of the FPGA is used to calculate the frequency of the signal, realize the real-time processing of the OEO frequency offset signal, and then obtain the tilt angle change information.

[0047] Step 1: The wide spectrum light output by ASE enters SI through the isolator to complete spectrum slicing. The isolator is used to ensure unidirectional transmission of the light field. The length of the PMF is 14.6 m, and the beat length at a wavelength of 1550 nm is less than 3 mm. The experimental temperature is 25 °C. The spectral characteristics of the SI output are shown in Fig.13 As shown in the figure, the ASE light source is divided into more than 50 channels, and the fluctuation of the channel envelope is Figure 4 Stay consistent. Fig.14 Detail of a spectral slice showing a sinusoidal broadband signal with a channel spacing (FSR) of 0.192 nm.

[0048] Step 2: The sinusoidal broadband signal output by SI enters PM (Thorlabs, LN53S-FC), with a modulation bandwidth of 10 GHz and a half-wave voltage of 3.5 V. EDFA is used to compensate for the optical power loss during phase modulation. The length of DCF (YOFC) is 9.524 km, and the group velocity dispersion is measured by a dispersion measurement system (EG&G, CD400L), with a value of -1263 ps / nm. The amplified optical signal passes through DCF and enters FRR, where FRR consists of an 80:20 coupler OC2 (= 0.2) and a single-mode fiber with a length of 732.6 m. PD (Multiplex, MTRX192L) realizes the conversion of optical and electrical signals, and its 3-dB response bandwidth is 10 GHz. EA (Conquer, DR10G7009) has a 3 dB bandwidth of 10 GHz, which is used to achieve positive gain in the electrical domain to ensure that the gain of the OEO resonant cavity is greater than the loss. When the FRR is disconnected, the microwave oscillation signal output by the OEO system is as follows: Fig.15 As shown. The electric spectrum shows that the center frequency of the oscillation signal is 4.124 GHz. When, the theoretical calculation of the OEO oscillation frequency is 4.124 GHz. From the experimental results, it can be seen that the theoretical value and the experimental value are consistent. Fig.16 A local enlarged image of the signal is given. Due to the 9.524 km resonant cavity, side modes with a frequency interval of 21 kHz appear near the center frequency. The side-mode suppression ratio (SMSR) at this time is about 19.3 dB. Because the mode interval is small, mode hopping is observed in the experiment.

[0049] Step 3: Next, the FRR is coupled to the OEO resonant cavity through OC2. The microwave signal spectrum when the MPF is cascaded is: Fig.17 In the figure, side modes with spacings of 21 kHz and 273 kHz can be observed simultaneously. The mode spacing of 21 kHz is determined by the length of the OEO resonant cavity, which is 9.524 km, and the side mode suppression ratio is about 53.6 dB. The mode spacing of 273 kHz is determined by the length of the single-mode fiber in the FRR, which is 732.6 m. By comparison Fig.16 It can be seen that the cascaded MPF can effectively improve the side mode suppression ratio, while avoiding the occurrence of mode hopping, ensuring the stability of the oscillation frequency during the subsequent tilt angle monitoring process.

[0050] Step 4: To measure the measurement resolution of the proposed tilt angle sensing system, the frequency deviation of the OEO oscillation signal was recorded using the “Maxhold” mode of the spectrometer at 25 °C. The frequency range was set to 500 kHz and the observation was continued for 30 minutes. Fig.18As shown, the maximum frequency drift was observed to be 26.7 kHz, corresponding to a tilt angle measurement resolution of 0.005° for the system.

[0051] In the signal processing module, the frequency is calculated through the FPGA-based frequency acquisition circuit and logic design. First, the microwave signal generated by the OEO system is divided and shaped to convert it into a digital signal. Then, the FPGA is used for high-speed digital signal acquisition, the signal frequency is calculated, and the real-time tilt angle information is obtained. The current signal processing flowchart is as follows Figure 5 shown.

[0052] Define the threshold of the tilt angle. When the angle exceeds the preset safety threshold, an alarm is triggered. The angle data and events are recorded in the storage system, such as database, log file, etc., for subsequent analysis and audit.

[0053] In the mixer circuit design, the LTC5552 mixer chip is used to mix the OEO oscillation signal with the microwave source, thereby reducing the frequency of the microwave signal. The input bandwidth of the LTC5552 chip is 3 GHz-20 GHz, and the intermediate frequency bandwidth is DC-6 GHz. The LTC5552 chip design circuit is as follows Figure 6 As shown in the figure. In the experiment, the 4.124 GHz microwave signal output by the OEO system is used as the RF signal of the mixer. The frequency of the microwave signal output by the RF source is set to 4.3 GHz, which is used as the LO signal of the mixer. After the sum frequency term is filtered out by the low-pass filter, the time domain waveform of the intermediate frequency signal is shown in the figure. Figure 7 As shown, the intermediate frequency signal frequency is 176 MHz.

[0054] In the frequency division circuit design, after the electric amplifier performs power compensation on the intermediate frequency signal, the intermediate frequency signal is further divided by 32 using the HMC394 frequency divider. The HMC394 chip can perform programmable frequency division on signals in the frequency band of 100 MHz to 2.2 GHz, with a maximum frequency division ratio of 32. In the current design, the frequency of the intermediate frequency signal will be greater than 100 MHz as the test tilt angle increases, so this chip can meet the current design needs. This part of the circuit is as follows Figure 8 In the experiment, the intermediate frequency signal (176 MHz) is input into the frequency division circuit, and the time domain waveform after frequency division is as follows: Fig. 9 As shown in the waveform diagram, we can see that the intermediate frequency signal has been divided to 5.5 MHz.

[0055] In the shaping circuit design, the high-precision comparator ADCMP602 is used as the core device. The chip input signal bandwidth is 200 MHz. The current analog signal level is compared with the threshold voltage to complete the conversion of analog signal to digital signal. This part of the circuit is as follows Fig.10As shown. The role of the shaping circuit is to prepare for the subsequent digital signal that meets the FPGA level specification. In the experiment, the threshold voltage of the comparator is set to 100 mV, and the output voltage signal is as follows Fig.11 By comparison Fig. 9 It can be seen that the frequency of the signal remains unchanged and the shaping circuit has converted the analog signal into a digital signal.

[0056] In the digital frequency processing and transmission module, after the comparator outputs the digital signal, the FPGA is used to analyze it. The FPGA system working clock is 200 MHz, and the sampling rate of the input pin is 5 ns / time. The frequency of the above-mentioned digital signal after shaping is 5.5 MHz. According to the Nyquist sampling theorem, the FPGA can realize high-precision acquisition and calculation of the current digital signal frequency. In the digital frequency processing process, the frequency calculation is completed by using the cycle counting method. The specific process is: set 50 ms as a measurement cycle, and count the rising edge time difference of two adjacent digital pulses at a sampling rate of 200 MHz in this cycle. After obtaining the statistical average value of the pulse repetition time in a measurement cycle, the frequency of the measured signal is calculated based on this value. Then the current tilt angle is obtained through the mapping relationship between frequency and tilt angle.

[0057] To verify the tilt angle monitoring accuracy of this system, a PMF with a length of 14.6 m was placed on the tilt angle slide and the tilt angle was set to 0°. Considering that the measurement accuracy refers to the deviation of the results of repeated measurements under certain conditions, the FPGA was used to continuously collect the OEO oscillation frequency for 1 second to obtain 20 sets of tilt angle data, such as Fig.18 The standard deviation of this group of data is 0.02°, which is taken as the measurement accuracy of the system.

[0058] To verify the tunability of the proposed OEO tilt angle monitoring, the tilt angle is set to change in the range of 0°~5° with a step of 0.1°. The change of OEO oscillation frequency at different tilt angles is recorded through the tilt angle analysis results on the FPGA side. The relationship between the frequency change of the microwave signal and the tilt angle is shown in Fig. 20 As shown in the figure. The green circular scattered points are the recorded experimental values, and the blue solid line is the linear fitting curve of the experimental data. From the fitting curve, it can be seen that the oscillation frequency has a good linear relationship with the change of the tilt angle. Then the comparison curve of the setting value of the high-precision tilt turntable of the system is obtained, as shown in the figure. Fig.21 In the figure, the horizontal axis is the tilt angle setting value, and the vertical axis is the experimental value of the tilt angle measurement of this system. It can be seen that the two sets of data have a good linear relationship.

[0059] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0060] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product.

[0061] Those of ordinary skill in the art will appreciate that the modules and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0062] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0063] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0064] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A tower tilt angle monitoring system based on an optoelectronic oscillator, characterized in that: It includes two modules, namely the tilt angle sensing module and the signal processing module; Tilt angle sensing module: responsible for the integrated design of the photoelectric oscillator and the tilt angle sensor to detect the tilt angle of the tower in real time, including the sensor and the photoelectric oscillator system; Signal processing module: used to receive data from the sensor module, map the angle information to the OEO oscillation frequency, calculate the tilt parameters in real time through the field programmable logic gate array, obtain accurate tilt angle information, and perform further alarm and recording functions.

2. The tower inclination angle monitoring system based on the optoelectronic oscillator according to claim 1 is characterized in that: The sensor comprises a dual-axis tilt sensor, which measures the tilt angle through the force exerted by gravity on the pole tower and the acceleration generated when the pole tower tilts.

3. The tower inclination angle monitoring system based on the optoelectronic oscillator according to claim 2 is characterized in that: The real-time detection of the inclination angle of the tower is specifically as follows: Based on the dual-axis inclination sensor installed on the transmission line tower, the vertical inclination angle and lateral inclination angle of the tower are measured, a mechanical model sensor that reflects the inclination condition of the transmission line tower is established, and the rough inclination angle of the tower is calculated based on the preset transmission line tower inclination formula.

4. The tower inclination angle monitoring system based on the optoelectronic oscillator according to claim 3 is characterized in that: The photoelectric oscillator is specifically: Based on the optoelectronic oscillator, the change of the transmission tower inclination angle is converted into the change of the OEO cavity length, and the real-time information of the inclination angle is obtained by monitoring the output frequency of the system.

5. The tower inclination angle monitoring system based on the optoelectronic oscillator according to claim 4 is characterized in that: The tilt angle sensing module includes an OEO system, in which the linearly polarized broad-spectrum light emitted by the ASE light source passes through an isolator and enters a magneto-optical switch, and the light field switches in two directions, X / Y, respectively, and enters a Sagnac loop, wherein the Sagnac loop is composed of a polarization controller and a polarization-maintaining optical fiber; the output light field is modulated by a phase modulator and enters an erbium-doped fiber amplifier for amplification, coupled to a dispersion-compensating optical fiber, and converts phase information into intensity information.

6. The tower inclination angle monitoring system based on the optoelectronic oscillator according to claim 5 is characterized in that: The signal processing module is specifically: Perform frequency division and shaping on the microwave signals generated by the OEO system and convert them into digital signals; FPGA is used for high-speed digital signal acquisition, signal frequency calculation, and real-time tilt angle information.

7. The tower inclination angle monitoring system based on the optoelectronic oscillator according to claim 6 is characterized in that: The frequency division and shaping processing of the microwave signal generated by the OEO system is specifically as follows: Transmitting the intensity information to the FRR, converting the optical signal into an electrical signal via a photodetector; The electrical signal is amplified by an electrical amplifier and then divided into two paths by a power divider; One of the paths is fed back to the PM to form an OEO oscillation loop. When the gain of the entire resonant loop is greater than the loss, the OEO loop starts to oscillate. The other channel is transmitted to the signal processing module to complete real-time signal processing; In the signal processing module, PS2 further divides the signal into two paths, one of which enters the spectrum analyzer to observe the microwave signal output by the OEO oscillation loop; the other enters the mixer as a radio frequency signal; The signal output by the microwave source is used as the radio frequency signal of the mixer, and the signal output by the radio frequency source is used as the local oscillator signal of the mixer.

8. The tower inclination angle monitoring system based on optoelectronic oscillator according to claim 7 is characterized in that: The method of using FPGA to collect high-speed digital signals and calculate signal frequency is specifically as follows: The mixer generates sum frequency terms and intermediate frequency terms when multiplying the input signals. The sum frequency terms are filtered out by a low-pass filter, and the intermediate frequency terms are retained. Based on the tunability of the system tilt angle, a frequency divider is used to further reduce the frequency of the intermediate frequency signal and enter the comparator; Set the comparator threshold voltage. When the input signal level is higher than the threshold voltage, the output is high level. When the input signal level is lower than the threshold voltage, the output is low level. The conversion of analog signal to digital signal is realized through comparator; The frequency of the signal is calculated using the counter function of the FPGA to achieve real-time processing of the OEO frequency offset signal and obtain the tilt angle change information.

9. The tower inclination angle monitoring system based on optoelectronic oscillator according to claim 8, characterized in that: The transmission line tower inclination formula is as follows: Among them, θ is the inclination angle of the tower, α is the vertical inclination angle of the tower, and β is the lateral inclination angle of the tower.

10. The tower inclination angle monitoring system based on optoelectronic oscillator according to claim 9, characterized in that: The mixer multiplies the input signal by the formula, specifically: Among them, the RF source output signal is used as the local oscillator signal of the mixer, which is recorded as , the microwave signal output by the OEO system is used as the RF signal, denoted as , Respectively represent the amplitude of the local oscillator signal and the RF signal, Represent the center frequencies of the local oscillator signal and the RF signal respectively.

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