CN117055023A - Vegetation penetrating type slope deformation monitoring radar system and monitoring method thereof - Google Patents
Vegetation penetrating type slope deformation monitoring radar system and monitoring method thereof Download PDFInfo
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- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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Abstract
The invention provides a vegetation penetrating type slope deformation monitoring radar system and a monitoring method thereof, which belong to the field of radar detection, and the system is smaller in size and better in portability compared with a conventional radar system, can realize vegetation penetrating detection and complete a slope landslide early warning function of slope topography in a covered area by designing an arc scanning deformation monitoring radar working in an L-band, sending signals to a monitoring area, receiving echo signals, preprocessing the echo signals, imaging according to the echo signals, selecting and updating PS points of imaging results, and then carrying out deformation inversion on an updated PS set.
Description
Technical Field
The invention relates to a vegetation penetration type slope deformation monitoring radar system and a monitoring method thereof, belonging to the field of radar detection.
Background
The geological features of China are complex, the types of climates are various, and the geological disasters have a large number of hidden dangers and are widely distributed. Among them, landslide and collapse have become one of the main disaster forms in recent years, especially in mountain areas, high levels and other areas, and the life and property safety of people is seriously threatened due to the complex geological structure and frequent occurrence of geologic disasters such as landslide. Therefore, landslide hazard monitoring and early warning are always one of important subjects for slope stability research.
The core of landslide hazard early warning is to obtain hidden danger body deformation information through slope safety monitoring and to predict landslide position, landslide surface area and landslide time. In recent years, after the manual monitoring means and the optical monitoring method, the electromagnetic spectrum is the same as that of the optics, but the microwave band monitoring radar with lower frequency and longer wavelength has gradually become a new direction and development trend applied to slope monitoring due to the principle advantages of full-day, all-weather, non-contact, large area, high precision and fixed point unattended operation.
The radar can obtain high-precision deformation monitoring results based on the technical principles of Synthetic Aperture Radar (SAR) high-resolution imaging and differential interferometry. At present, a plurality of research institutions at home and abroad have developed research on slope deformation monitoring radars, and a plurality of radar products with various systems such as linear scanning type, array type and the like are provided. The existing products can realize the surface deformation monitoring of the scenes such as bare mines, but the products are mostly based on Ku or X wave bands, and are limited by large attenuation of electromagnetic waves when the wave bands penetrate vegetation, so that displacement monitoring of the surfaces of hidden danger bodies under vegetation coverage can not be realized by well penetrating the vegetation. A circular arc ground based interferometric synthetic aperture radar is described, for example, in the CN 109917386a patent. The scheme provides the universal circular arc synthetic aperture radar which can realize the slope deformation monitoring function of non-vegetation scenes. However, the product is based on the X-band, besides poor vegetation penetrability, the system design is simpler, and if the scheme is used for designing an L-band system, the problems of oversized size, performance deterioration and the like can be caused. In addition, GAMMA-L of GAMMA company has better vegetation penetrability based on L wave band design, but radar is a linear scanning system, and measurement needs to be carried out on a sliding rail with the length of 12 meters, so that the requirement of outdoor portable installation and layout cannot be met.
Disclosure of Invention
In view of the above, the invention provides a vegetation penetrating type slope deformation monitoring radar system and a monitoring method thereof, which can meet the requirements of field portable installation and layout and have better vegetation penetrating type.
A vegetation penetration type slope deformation monitoring radar system comprising: the radar device comprises an antenna (1), a radar host (2), a turntable (3), a counterweight module (4), a first connecting rod and a second connecting rod;
the radar main machine is arranged on the turntable, the antenna is connected with the radar main machine through a first connecting rod, the first connecting rod is parallel to the turntable, the counterweight module is connected with the radar main machine through a second connecting rod, and the second connecting rod is connected on the opposite side of the antenna and parallel to the turntable;
an antenna for transmitting and receiving signals;
the radar host is used for supplying power to the antenna and the turntable, processing signals transmitted and received by the antenna and sending control instructions to the turntable and the antenna;
a turntable for controlling rotation of the radar system;
the counterweight module is used for counterweight the system and keeping the balance of the system;
the radar host works in an L wave band.
Further, the radar host calculates the system transmitting power according to the following radar equation for the signals transmitted by the antenna:
wherein P is t For the system transmit power, L s Is the system loss factor, k is the Boltzmann constant, T 0 Is the standard noise temperature, F n Is the noise coefficient, B is the system bandwidth, R is the acting distance, G is the antenna gain, lambda is the center frequency wavelength, T s For azimuth accumulation time, c is light velocity, θ sa For beam width synthesis, nE sigma 0 Is the equivalent backscattering coefficient.
The system loss factor additionally counts vegetation attenuation loss term L p The method comprises the following steps:
L s ＝L s1 + p
wherein, vegetation attenuation loss term L p Is set as a value L s1 Is a loss factor of a system device.
A vegetation penetration type slope deformation monitoring method comprises the following steps:
step one, setting a monitoring angle and a monitoring distance range of a radar host, generating a control instruction by the radar host according to the monitoring angle and the monitoring distance range, sending the control instruction to a turntable and an antenna, controlling a radar system to scan at a uniform speed by the turntable according to the instruction, and sending a radio frequency signal to a monitoring area by the antenna and receiving a echo signal by the antenna;
step two, the antenna sends the echo signals to the radar host, the radar host carries out data preprocessing on the echo signals, and then imaging is carried out according to the preprocessed echo signals;
step three, the radar host extracts a PS point set from the imaging result and updates the PS point set in real time;
performing deformation inversion on each point in the PS point set to obtain deformation information of each point; setting a deformation threshold, comparing the magnitude relation between deformation information of each point and the deformation threshold, if the deformation information is larger than the deformation threshold, sending out landslide early warning, and if the deformation information is not larger than the deformation threshold, not sending out landslide early warning;
the PS point set is a pixel point set with amplitude stability and phase stability meeting the required values in the imaging result.
Further, the PS point update includes the steps of:
firstly, extracting a PS point set from an imaging result according to an amplitude deviation threshold method, and setting a correlation coefficient threshold;
secondly, extracting one point which is not selected from the PS point set in the imaging result, calculating the deformation of the point in a time window, and filtering;
filtering all points in the point set adjacent to the point space extracted in the second step, calculating an average deformation amount, and calculating a correlation coefficient between the average deformation amount and the deformation amount of the points extracted in the second step;
fourth, comparing the correlation coefficient threshold value with the magnitude relation of the correlation coefficient, if the correlation coefficient is larger than the correlation coefficient threshold value, adding the point extracted in the second step into the PS point set and executing the second step; otherwise, repeating the second step to the fourth step until all the points which are not selected into the PS point set pass through at least one time.
Further, the deformation is calculated by:
wherein lambda is the wavelength corresponding to the center frequency, delta phi is the phase change value extracted from the imaging result, and d is the deformation of the target in the radar sight line direction.
The beneficial effects are that:
the radar system works in the L wave band, compared with the existing radar system which mostly works in the Ku or X wave band, the radar system is limited by large attenuation of wave band vegetation and cannot meet the requirement of vegetation penetration, the radar system works in the L wave band to better realize vegetation penetration and realize deformation monitoring of the earth surface under vegetation coverage, the radar system is simple in structure and small in occupied volume, and the system can be mounted on a turntable to meet corresponding measurement requirements, so that the situation that a slide rail with the length of 12 meters is required to be mounted like a GAMMA-L radar produced by a GAMMA company is avoided, and the portability of the radar system is better than that of similar products.
Secondly, the invention adds the loss factor when designing the radar equation, and calculates the system loss factor L s In addition to the conventional system loss items such as signal processing loss and cable loss, the vegetation attenuation loss item L needs to be additionally counted p I.e. L s Corrected to L s +L p Compared with other systems, the system has higher calculation accuracy and better imaging accuracy of the monitoring target for vegetation.
Thirdly, PS points are updated in the imaging process, and some points which are discarded before are added into the PS point set through secondary judgment, so that the problem that the number of PS points which are discarded is avoided, the radar detection on vegetation type terrains is overcome, the amplitude stability and the phase stability of each point in a scene affected by vegetation are poor, and the number of effective PS points is less.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of the structure of the present invention.
Fig. 3 is a schematic diagram of an antenna structure according to the present invention.
Fig. 4 is a flow chart of the signal processing according to the present invention.
Fig. 5 is a schematic diagram of a rotational imaging coordinate system according to an embodiment of the invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The invention provides a vegetation penetration type slope deformation detection radar system and a monitoring method thereof, which specifically comprise the following contents:
a vegetation penetration type slope deformation monitoring radar system, as shown in fig. 1, comprising: the radar device comprises an antenna (1), a radar host (2), a turntable (3), a counterweight module (4), a first connecting rod and a second connecting rod;
as shown in fig. 2, the radar host is mounted on the turntable, the antenna is connected with the radar host through a first connecting rod, the first connecting rod is parallel to the turntable, the counterweight module is connected with the radar host through a second connecting rod, and the second connecting rod is connected to the opposite side of the antenna;
an antenna for transmitting and receiving signals; comprising the following steps: the wide-beam transmitting antenna and the wide-beam receiving antenna are connected with the radio frequency unit to complete radio frequency signal transmission and echo signal reception, and the antenna is required to meet the requirements of ultra-wideband and wide-beam at the same time, so that the design difficulty is high. Such as the use of conventional microstrip antennas or feedhorns, can result in heavy antennas, high costs, and even difficulty in meeting performance requirements. In order to reduce the weight while meeting the ultra-wideband and wide-beam performance requirements, the scheme adopts an antenna form of a plurality of dipole arrays, and can meet the beam width and bandwidth requirements with simpler antenna configuration. In addition, in order to improve the reliability of the system, the antenna units and the like are designed in a light and small manner, a new antenna structure is adopted, the isolation of the system can be improved under the condition of not increasing the volume, the antenna structure shown in the attached figure 3 is adopted, the receiving and transmitting units of the antenna are separated, the heights of the two units in the horizontal direction are different, a gap is reserved in the middle, the left and right directions of the two units are not close to each other, the gap is reserved in the middle, the receiving and transmitting antennas are pulled apart by a certain distance in the horizontal dimension and the vertical dimension, and the isolation between the antennas can be increased under the condition of not remarkably increasing the size. Simultaneously, two units are fixed on the rotating shaft on the connecting rod through the chain, and the antenna rotating shaft structure can realize pitching adjustment of the receiving and transmitting antenna so as to adapt to the requirements of different monitoring scenes
The radar host is used for supplying power to the antenna and the turntable, processing signals transmitted and received by the antenna, sending control instructions to the turntable and the antenna, and working in an L wave band; the radar host mainly comprises a radio frequency unit, a signal processor and a power supply unit. The high-stability crystal oscillator arranged in the radio frequency unit provides reference clocks for the radio frequency unit and the signal processor; meanwhile, the radio frequency unit receives the DDS signal sent by the signal processor, completes signal up-conversion to generate an ultra-wideband, low-phase-noise and high-stability L-band radio frequency signal, and sends the signal to a transmitting antenna of the antenna module after power amplification; in addition, the radio frequency unit receives the radio frequency echo signal returned by the receiving antenna, generates a baseband signal after low noise amplification and quadrature down-conversion of the signal, and sends the baseband signal to the signal processor after power conditioning. Here, in order to obtain a high-phase noise transmission signal in an ultra-wideband range, the frequency conversion part does not adopt a conventional scheme of mixing a baseband with a local oscillator, but adopts a scheme of directly multiplying the DDS signal with high-phase noise to a required frequency band. The signal processor comprises a programmable main control chip, a data memory, an analog-to-digital converter and a direct digital frequency synthesizer, and has the main functions of realizing time sequence and working state control of all system sub-modules such as a radio frequency unit, a turntable and the like; and generating a broadband high-phase noise DDS signal, providing the signal to the radio frequency unit, receiving a baseband signal returned by the radio frequency unit, performing AD sampling, preprocessing the sampled signal, and transmitting the preprocessed signal to the external display control unit. The power supply unit can complete power-on and power-off control of the whole system under the control of the digital unit so as to meet the low power consumption requirement of long-term use in the field.
The system transmit power design section, here without derivation, gives a form of radar equation as follows:
wherein P is t For the system transmit power, L s Is the system loss factor, k is the Boltzmann constant, T 0 Is the standard noise temperature, F n Is the noise coefficient, B is the system bandwidth, R is the acting distance, G is the antenna gain, lambda is the center frequency wavelength, T s For azimuth accumulation time, c is light velocity, θ sa For beam width synthesis, NE sigma 0 Is the equivalent backscattering coefficient. To adapt to the vegetation penetration requirement, the system loss factor L is calculated s In addition to the conventional system loss items such as signal processing loss and cable loss, the vegetation attenuation loss item L needs to be additionally counted p I.e. L s Corrected to L s +L p In the present embodiment, meter L p =20 dB, this setting is the setting with the best imaging effect.
A turntable for controlling rotation of the radar system; the full system is driven to complete uniform speed sector or circumference scanning under the control of the signal processor, and the full system has the characteristic of high heavy rail precision. The turntable receives the control instruction of the signal processor, completes corresponding actions, and feeds back state information such as states and positions to the signal processor in real time.
And the counterweight module is used for counterweight the system and keeping the balance of the system.
In summary, the invention designs the arc scanning deformation monitoring radar working in the L-band, the radar system installs the antenna and the counterweight module on two sides of the radar host through the first connecting rod and the second connecting rod, the radar host is installed on the turntable, the system has small structural size, the scanning of the radar can be completed through the rotation of the turntable, the special sliding rail is not required to be installed, and the radar system is portable and easy to arrange. In the imaging and scanning aspects, the system works in an L wave band and has better vegetation penetration, an antenna of the system receives original echo data for preprocessing, then imaging, PS point selection and updating are carried out, and finally early warning judgment is carried out according to the deformation inversion result, so that the early warning function of the slope topography is completed.
The vegetation penetration type slope deformation monitoring method comprises the following steps of:
step one, setting a monitoring angle and a monitoring distance range of a radar host, generating a control instruction by the radar host according to the monitoring angle and the monitoring distance range, sending the control instruction to a turntable and an antenna, controlling a radar system to scan at a constant speed by the turntable according to the instruction, and sending a signal radio frequency signal to a monitoring area by the antenna and receiving an echo signal by the antenna;
firstly, selecting a region to be monitored according to a monitoring scene, setting a monitoring angle and a monitoring distance range, and secondly, controlling a system to perform uniform-speed continuous scanning to acquire original echo data (namely echo signals).
Step two, the antenna sends the echo signals to the radar host, the radar host carries out data preprocessing on the echo signals, and then imaging is carried out according to the preprocessed echo signals;
the signal preprocessing mainly carries out coherent accumulation on the original echo data to reduce the data volume, and the step is completed in a signal processor.
Imaging and calculating: in an arc scanning system, the operation amount can be greatly reduced by adopting the scheme of imaging in a polar coordinate system and converting an imaging result into a rectangular coordinate system. As shown in fig. 5, a coordinate system is established at the radar rotation scan plane. The system rotation center is taken as an origin, a scanning center angle is defined as 0 degrees, and the sampling rotation direction is a positive direction. The length L of the rotating shaft and the scanning angle range are phi. The initial scan point coordinates areTermination scan Point coordinates +.>The sampling trace is shown in the solid line portion of the circumference of fig. 5. The preprocessed data are equivalent to discrete sampling data with equal intervals on a sampling track, and coordinates of the discrete sampling data are defined as (L, mdelta theta), wherein delta theta is a sampling interval and is a fixed value; m is an integer and satisfies->
The imaging process is as follows:
2.1, carrying out pulse compression on the sampled data after signal preprocessing to obtain a signal expression of m sampling points, wherein the signal expression is as follows:
wherein, p () is the distance from the target to the sampling point, R is the distance from the target to the sampling point, lambda is the wavelength of the transmitted signal, K is the frequency modulation rate, and c is the speed of light.
2.2 in the scene (R 0 ,θ 0 ) The imaging result can be obtained by the following formula
Wherein,m is required to satisfy θ is the antenna beam width.
2.3 converting the imaging result to rectangular coordinates
Defining the angular bisector of the scanning area to be outwards in the Y-axis positive direction; the X axis is perpendicular to the Y axis, and the rotation direction is the positive direction of the X axis. Then A (R) 0 ,θ 0 ) The corresponding rectangular coordinates are (R 0 sin(θ 0 ),R 0 cos(θ 0 ))。
Step three, the radar host extracts a PS point set from the imaging result and updates the PS point set in real time;
performing deformation inversion on each point in the PS point set to obtain deformation information of each point; setting a deformation threshold, comparing the magnitude relation between deformation information of each point and the deformation threshold, if the deformation information is larger than the deformation threshold, sending out landslide early warning, and if the deformation information is not larger than the deformation threshold, not sending out landslide early warning; the PS point set is a pixel point set with amplitude stability and phase stability meeting the required values in the imaging result.
And updating the PS point on the basis of the imaging result. The amplitude stability and the phase stability of each point in the scene are poor under the influence of vegetation. The PS point set needs to be updated periodically.
3.1, extracting a PS point set from an imaging result according to an amplitude dispersion threshold method, and setting a correlation coefficient threshold;
and selecting a relatively stable point as a PS point by adopting a conventional method based on amplitude dispersion, correlation coefficient and the like, and adding the relatively stable point into the PS point set.
3.2, extracting one point which is not selected from the PS point set in the imaging result, calculating the deformation of the point in a time window, and filtering;
3.3, performing secondary judgment on the point set which is not selected as the PS point: extracting deformation of a non-PS point in a time window, filtering, calculating an average deformation after filtering of a point set adjacent to the point space, and calculating a correlation coefficient with the point deformation, wherein the specific implementation mode is as follows:
filtering all points in the point set which are spatially adjacent to the points in the second step, calculating the average deformation quantity of all points in the point set, and calculating the correlation coefficient of the average deformation quantity and the deformation quantity of the points extracted in the second step.
3.4, comparing the correlation coefficient threshold value with the magnitude relation of the correlation coefficient, if the correlation coefficient is larger than the correlation coefficient threshold value, adding the point in the second step into the PS point set, and executing the step 3.2; if the correlation coefficient is not greater than the correlation coefficient threshold, repeating steps 3.2 to 3.4 until all points not selected into the PS point set pass through steps 3.2 to 3.4 at least once.
When the correlation coefficient exceeds the threshold value, the point has larger fluctuation but similar deformation trend with the space adjacent point, and the point is added into the PS point set at the moment, so that the PS point updating is completed after all the points are judged for the second time.
The deformation inversion and early warning are to obtain deformation information of each pixel point through the steps of differential interference processing, atmospheric phase correction, deformation extraction and the like on the basis that continuous time sequence imaging results are obtained and PS points are selected. And then landslide early warning is carried out by judging whether the deformation rate and the acceleration exceed the threshold or not
The deformation is calculated by the following method:
wherein lambda is the wavelength corresponding to the center frequency, delta phi is the phase change value extracted from the imaging result, d is the deformation of the target in the radar sight direction, and the part is similar to the deformation monitoring radars of other systems and will not be described in detail.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (5)
1. A vegetation penetration type slope deformation monitoring radar system, comprising: the radar device comprises an antenna (1), a radar host (2), a turntable (3), a counterweight module (4), a first connecting rod and a second connecting rod;
the radar main machine is arranged on the turntable, the antenna is connected with the radar main machine through a first connecting rod, the first connecting rod is parallel to the turntable, the counterweight module is connected with the radar main machine through a second connecting rod, and the second connecting rod is connected on the opposite side of the antenna and parallel to the turntable;
an antenna for transmitting and receiving signals;
the radar host is used for supplying power to the antenna and the turntable, processing signals transmitted and received by the antenna and sending control instructions to the turntable and the antenna;
a turntable for controlling rotation of the radar system;
the counterweight module is used for counterweight the system and keeping the balance of the system;
the radar host works in an L wave band.
2. The system of claim 1, wherein the radar host calculates a system transmit power for a signal transmitted by the antenna according to the following radar equation:
wherein P is t For the system transmit power, L s Is the system loss factor, k is the Boltzmann constant, T 0 Is the standard noise temperature, F n Is the noise coefficient, B is the system bandwidth, R is the acting distance, G is the antenna gain, lambda is the center frequency wavelength, T s For azimuth accumulation time, c is light velocity, θ sa For beam width synthesis, NE sigma 0 Is equivalent backscattering coefficient;
the system loss factor additionally counts vegetation attenuation loss term L p The method comprises the following steps:
L s ＝L s1 + p
wherein, vegetation attenuation loss term L p Is set as a value L s1 Is a loss factor of a system device.
3. A vegetation penetration type slope deformation monitoring method based on the system of claim 1 or 2, comprising the steps of:
step one, setting a monitoring angle and a monitoring distance range of a radar host, generating a control instruction by the radar host according to the monitoring angle and the monitoring distance range, sending the control instruction to a turntable and an antenna, controlling a radar system to scan at a uniform speed by the turntable according to the instruction, and sending a radio frequency signal to a monitoring area by the antenna and receiving a echo signal by the antenna;
step two, the antenna sends the echo signals to the radar host, the radar host carries out data preprocessing on the echo signals, and then imaging is carried out according to the preprocessed echo signals;
step three, the radar host extracts a PS point set from the imaging result and updates the PS point set in real time;
performing deformation inversion on each point in the PS point set to obtain deformation information of each point; setting a deformation threshold, comparing the magnitude relation between deformation information of each point and the deformation threshold, if the deformation information is larger than the deformation threshold, sending out landslide early warning, and if the deformation information is not larger than the deformation threshold, not sending out landslide early warning;
the PS point set is a pixel point set with amplitude stability and phase stability meeting the required values in the imaging result.
4. The method of claim 3, wherein the PS point update comprises the steps of:
firstly, extracting a PS point set from an imaging result according to an amplitude deviation threshold method, and setting a correlation coefficient threshold;
secondly, extracting one point which is not selected from the PS point set in the imaging result, calculating the deformation of the point in a time window, and filtering;
filtering all points in the point set adjacent to the point space extracted in the second step, calculating average deformation of all points in the point set, and calculating correlation coefficients of the average deformation and the deformation of the points extracted in the second step;
fourth, comparing the correlation coefficient threshold value with the magnitude relation of the correlation coefficient, if the correlation coefficient is larger than the correlation coefficient threshold value, adding the point extracted in the second step into the PS point set and executing the second step; otherwise, repeating the second step to the fourth step until all the points which are not selected into the PS point set pass through at least one time.
5. The method of claim 4, wherein the deformation is calculated by:
wherein lambda is the wavelength corresponding to the center frequency, delta phi is the phase change value extracted from the imaging result, and d is the deformation of the target in the radar sight line direction.
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