364 results about "Direct wave" patented technology

The invention discloses a target positioning method and system based on a single reference station, and relates to the field of wireless positioning, and the method comprises the steps: generating vortex electromagnetic waves carrying orbital angular momentum based on a transmitting end of a reference station, and generating a time-varying phase modulation transmitting signal and a metasurface time-varying coding sequence through a programmable metasurface; a time-varying phase modulation emission signal forms a multipath superposition effect in a propagation environment, a receiving end obtains a mixed signal of a direct wave and a reflected wave, and the receiving end carries out OAM mode separation on the mixed signal of the direct wave and the reflected wave through a spiral phase plate and an annular array to obtain signal components in different modes; and based on the signal component and the metasurface time-varying coding sequence, reconstructing an equivalent virtual array response by adopting a compressed sensing algorithm. According to the invention, the orbital angular momentum modal separation technology and the metasurface dynamic coding technology are creatively fused, and high-precision real-time direction finding in a complex multi-path environment is realized under a single base station architecture.

The invention relates to the technical field of TDOA (time difference of arrival) positioning, and provides an ultrasonic three-dimensional positioning method based on beam enhancement and TDOA, which comprises the following steps: extracting initial space parameters based on beam scanning of an array receiving signal, carrying out iterative optimization on beam weight to adjust a direct wave component and suppress reflection interference, constructing a closed-loop optimization mechanism, and carrying out beam enhancement and TDOA positioning. Calculating an enhanced signal and an array element reliability measurement index through frequency domain segmentation and energy normalization; forming an optimization array based on the array element reliability measurement index, extracting a time delay parameter from the optimization array, constructing a distance measurement equation set, and calculating an initial estimation value of a target position by adopting a weighted optimization algorithm; and constructing a residual error model, constructing an optimized weight matrix by combining an array element reliability measurement index and a signal quality index, iteratively calculating a target coordinate until a convergence condition is met, and outputting a final three-dimensional coordinate. According to the method, the comprehensive performance of ultrasonic three-dimensional positioning in the aspects of anti-interference performance, stability and positioning precision in a complex environment is improved, and error source control is realized.

The invention relates to the technical field of power system fault positioning, in particular to a power distribution network fault accurate positioning method, device and system based on the traveling wave principle, and the method comprises the steps: deploying traveling wave detection equipment at two ends of a certain section of line of a power distribution network, and enabling the traveling wave detection equipment to be used for synchronously collecting potential fault traveling wave signals; analyzing based on the acquired potential fault traveling wave signal, and screening out a fault traveling wave; in the time union set of the local time windows at the two ends, marking the fault traveling wave with the maximum peak value in the single end as a direct wave, analyzing the waveform similarity between the direct wave and the fault traveling wave arriving after the direct wave, and screening out a reflected wave according to the peak value difference; and based on the arrival time of the direct waves and the reflected waves at the two ends, calculating the distance from the fault point to the two ends of the line through a positioning formula to position the fault point. The invention aims to improve the positioning precision of the fault point in the power distribution network by analyzing the distribution characteristics of the pseudo traveling wave signal.

The invention relates to the technical field of communication, and discloses a high-precision measurement method for radial velocity of a shallow sea underwater acoustic target based on ray sound field reconstruction. According to the method, a multipath channel joint resolving system is innovatively constructed for the problem that the target speed measurement precision is limited due to a shallow sea complex propagation environment. According to the system, a compound ray model of shallow sea multipath sound propagation is established, and a joint representation equation containing channel impulse response and target motion parameters is constructed by analyzing a time delay-Doppler coupling mechanism of three typical paths of direct waves, water surface reflected waves and water bottom reflected waves. Especially for the multipath interference effect in the shallow sea waveguide environment, the time-frequency domain separation criterion of each path signal is deduced, and a theoretical basis is laid for feature information extraction. The method provides a new technical means for underwater target tracking and positioning, underwater acoustic communication Doppler compensation and marine environment dynamic monitoring, and particularly has an important application prospect in the fields of underwater unmanned cluster collaboration and the like.

The invention provides an underwater positioning system combining sound ray propagation modeling and multipath interference suppression, which relates to the technical field of marine equipment and comprises a self-adaptive underwater sound sensing and environment cognition module, an environment self-adaptive sound ray propagation modeling module, a multipath suppression and direct wave extraction module and a multi-dimensional information fusion and self-adaptive positioning calculation module. The self-adaptive underwater sound sensing and environment cognition module is used for realizing multi-mode sensing and real-time environment feature recognition of underwater sound signals, and the environment self-adaptive sound ray propagation modeling module is used for constructing a dynamically updated sound wave propagation model and providing a propagation path and time constraint for positioning calculation; the multi-path suppression and direct wave extraction module is used for carrying out multi-path signal separation and extracting direct wave features with confidence marks, and the multi-dimensional information fusion and self-adaptive positioning calculation module is used for completing high-precision positioning calculation; according to the system, deep fusion of an environment model and signal processing can be realized, and the positioning precision and robustness of the underwater vehicle in a complex underwater sound environment are remarkably improved.

The invention relates to a near-surface defect positioning method based on a laser ultrasonic surface wave, which comprises the following steps of: extracting a defect tiny inverse signal and calculating reflection time delay by utilizing a high-frequency surface wave signal excited by laser through a wavenumber domain method to determine a defect position, and determining the burial depth of the defect through a reflection wave amplitude value of the defect; comprising the steps of S1, laser ultrasonic finite element simulation; s2, acquiring high-frequency laser ultrasonic signals; s3, direct wave and reflected wave extraction and time delay calculation; s4, determining defect space coordinates; and S5, determining the burial depth of the defect. The method makes full use of the advantages of high frequency and long propagation distance of surface waves, can effectively solve the problem of defect detection and positioning of the tested piece, can quickly detect the submillimeter defects, is high in positioning precision, and is suitable for positioning and detecting the submillimeter defects on the near surface of a structure.

The invention discloses a BIM (Building Information Modeling)-based large-span post-tensioned bonded prestressed beam construction method. The BIM-based large-span post-tensioned bonded prestressed beam construction method comprises the following steps: collecting a vibration signal of a working rib and a matt rib reference signal of a matt rib; inputting the dummy rib reference signal into an adaptive filtering algorithm to which phase preserving constraint is applied, and performing noise cancellation processing on the working rib vibration signal to generate a purified pressure wave signal; performing multi-scale decomposition on the purified signal, extracting propagation time delay of the direct wave based on coherence analysis among components, and generating a phase-time delay characteristic matrix; and based on pre-configured geometric parameters of the BIM three-dimensional model, a real-time stress distribution field is calculated through inversion according to the phase-time delay characteristic matrix, and the real-time stress distribution field is synchronously updated to the BIM three-dimensional model. According to the method, the phase distortion problem under noise interference is solved through a physical reference channel and phase preserving filtering, the accuracy of time delay extraction is improved through a multi-path separation technology, and high-precision and high-robustness real-time monitoring of the prestress is achieved.

An antenna apparatus includes a board, an integrated circuit chip including a transmitting antenna and a receiving antenna and mounted on the board, a waveguide having a first aperture provided on the board side and surrounding the transmitting antenna and the receiving antenna in aperture view, a second aperture provided on a rear side with respect to the first aperture in a radiation direction of the transmitting antenna, and a first inner wall surface connecting the first aperture and the second aperture, a radio wave lens fixed to the second aperture, and a first radio wave absorber disposed on the first aperture side in a space surrounded by the first inner wall surface. At least part of the first radio wave absorber is located inside a first path of a first direct wave, and the first radio wave absorber is located outside a second path of a second direct wave.

The invention discloses a bridge image crack identification method and system based on a deep neural network. The method comprises the following steps: acquiring a bridge B-Scan image through ground penetrating radar equipment; performing preprocessing such as normalization, direct wave weakening and automatic gain enhancement on the image; features are extracted on the basis of an improved OfficientDeet-D3 network, a MoHAttention module is introduced into a backbone network to enhance weak crack features, a BiFPN structure is optimized through deep separable convolution in the feature fusion process to improve the detection capacity of a small-scale crack target, and crack position frames, types and confidence information are output; the system comprises a data acquisition module, a preprocessing module, a neural network detection module and an output display module. According to the method, high-precision and high-robustness identification of the internal hidden crack can be realized, and the method is suitable for rapid detection and intelligent monitoring application in actual bridge inspection engineering.

The invention discloses a bionic joint humanoid robot navigation positioning method, device and equipment, and the method comprises the steps: monitoring a landing shock wave signal and reflection echo data of a robot, carrying out the time domain expansion of the shock wave signal to form a pulse characteristic spectrum, extracting multipath propagation components, and carrying out the time difference correlation to generate an environment response value. Screening a direct wave component by using an environmental response value, positioning a sound wave propagation trajectory, and detecting impedance mutation to construct an acoustic matrix. A strong reflection zone is identified through node analysis, a sound pressure gradient field is extracted to determine an obstacle boundary, and a landmark feature bit is determined in combination with an environmental response value. And adjusting a dynamic stride frequency interval based on a landmark feature bit, forming an adaptive detection sequence, and performing sparse processing to construct path configuration. The mechanical vibration component of the shock wave signal is used for piezoelectric conversion to generate recycled electric quantity, the recycled electric quantity is matched with path configuration power to determine a sensing period, intermittent sensing is executed to obtain detection data to construct a detection convergence field, and finally an accurate positioning window is determined and converted into position coordinates.

The invention provides an inter-satellite direct wave interference suppression method and system for synthetic aperture radar satellites. The method comprises the following steps: inputting SAR original echo data and system parameters thereof; calculating a pulse repetition frequency, a signal bandwidth and a frequency modulation rate; performing matched filtering and filtering on the original echo data to obtain an echo signal; and carrying out direct wave interference trapped wave processing and inverse matching filtering processing on the echo signal, and outputting original echo data after suppression processing. According to the method, signal self-correlation processing is adopted for detecting and suppressing the inter-satellite direct wave interference for the first time, the problem that an existing inter-satellite direct wave interference suppression processing method greatly depends on model applicability is solved, and important technical support is provided for subsequent large-scale SAR constellation earth imaging observation; direct wave interference is suppressed through a parameterization method, and the application effect of the SAR satellite in the fields of resource investigation, topographic mapping, disaster monitoring and the like is remarkably improved.

The invention discloses a deep rock mass fracture imaging method and system based on micro-seismic monitoring, and belongs to the technical field of geophysical exploration, and the method comprises the steps: collecting multi-channel micro-seismic event waveform data, obtaining a main seismic phase direct waveform and a scattering tail waveform through wave field separation, and carrying out the imaging of a deep rock mass fracture. Determining a three-dimensional space coordinate and an energy distribution form of the seismic source through joint inversion, carrying out clustering analysis, and constructing an initial three-dimensional space distribution form; each seismic source is regarded as an active excitation source, a scattering tail wave waveform is regarded as a reflection signal, scatterer three-dimensional point cloud data is generated through reverse time migration processing, analysis is carried out in combination with an initial three-dimensional space distribution form, and an enhanced fracture structure is formed; and finally, through topology analysis and orientation clustering, discrete scatterers are eliminated, and a fracture development map is generated. According to the method, a technical path of combining a main seismic phase direct wave inversion seismic source and a scattering tail wave inversion scatterer is adopted, high-precision and high-fidelity imaging of a deep rock mass movable fracture can be realized, and physical activity is revealed.

The invention relates to a shallow sea seabed node redirection method based on first arrival polarization characteristic constraint, a medium and equipment, and belongs to the technical field of geophysical exploration data processing. The method comprises the following steps that a common detection point gather is extracted from four-component seismic data collected in a simulated or field mode, first arrival time and a propagation azimuth angle are obtained, and a target function is constructed according to seismic record energy distribution, polarization characteristics and P and Z component correlation common constraint in a first arrival time window; solving orientation parameters; and performing orientation correction on seismic data acquired by the seabed nodes. Besides, the detector is redirected by comprehensively utilizing the energy, the polarization characteristic and the P and Z component correlation of the first-motion wave, so that the problems of application condition limitation and insufficient precision existing in a conventional method for redirecting by only utilizing the direct wave and multiplicity of solutions existing in a reflected wave energy method can be solved.

The invention discloses a QPS numerical ray tracing and multi-target optimization-based high-frequency sky-ground wave radar ionosphere electron concentration inversion method, which comprises the following steps of: firstly, carrying out FFT (Fast Fourier Transform) on radar echo data, constructing a radar echo distance-Doppler matrix, and according to the obtained radar echo distance-Doppler matrix, calculating the electron concentration of a high-frequency sky-ground wave radar ionosphere according to the obtained radar echo distance-Doppler matrix; determining an antenna direct wave group distance and a transmitting station-receiving station ground distance; then determining an optimal emission elevation angle by using randomly generated ionosphere parameters; and finally, taking the emission elevation angle data corresponding to the n groups of ionosphere parameters as an initial population, and carrying out iterative optimization on the initial population by utilizing a population optimization algorithm to obtain an optimal ionosphere parameter result, thereby realizing ionosphere electron concentration inversion. According to the scheme, the radar echo data and the randomly generated ionosphere parameters are combined, the amount of data needing to be calculated is remarkably reduced, accurate inversion of the ionosphere parameters is achieved through ray tracing and multi-target optimization, the structure is simpler, the method does not depend on a complex model or a large amount of experience data, and the method is suitable for large-scale popularization and application. The optimal ionosphere parameter can be approached more quickly and effectively, and the real-time performance and accuracy of ionosphere electron concentration inversion are improved.

The invention relates to the technical field of acoustic testing, in particular to a method for testing sensitivity of optical fiber curved surface array hydrophones, which comprises the following steps of: after determining coordinates of a sound source, each hydrophone of an optical fiber curved surface array and a standard hydrophone on a water test platform, transmitting a single-frequency pulse signal by the sound source; after the data acquisition system respectively acquires a signal received by the standard hydrophone and signals received by each hydrophone of the optical fiber curved surface array, the data analysis system generates an analog sound source signal, and direct waves received by the standard hydrophone and each hydrophone of the optical fiber curved surface array are quickly found by using a related algorithm; the optical fiber curved surface array hydrophone sensitivity testing method solves the problem of synchronization of different acquisition systems, is an effective supplement to an existing optical fiber curved surface array hydrophone sensitivity testing method, and has a wide application prospect.

The invention discloses a multi-transmitting and multi-receiving radar time synchronization method based on direct waves and differential GPS ranging, in an airborne distributed radar system formed by a plurality of radar units, two radar units at two ends of a baseline serve as signal transmitting sources, and all the radar units have signal receiving capability and are in a visual range. The two transmitting radars transmit linear frequency modulation waves with different carrier frequencies, and all the radars receive direct waves and echo signals reflected by a target. The direct waves contain time synchronization errors and baseline distance information between the corresponding transmitting and receiving radar platforms. Positioning information is obtained by means of a differential GPS module, baseline distance information in direct waves is eliminated, and the direct waves only containing time synchronization errors serve as reference signals. And then conjugate multiplication is carried out on the echo signal and the reference signal in the frequency domain, so that range-direction matched filtering and time synchronization error compensation can be carried out on the echo signal. All echo signals are processed one by one, and finally time synchronization of the distributed radar system is achieved.

The invention provides a while-drilling seismic acquisition method and device, and the method comprises the steps: 1, carrying out the while-drilling seismic excitation of a drill bit at a target interval, and obtaining an excited seismic source signal; 2, seismic signals generated after excitation are received through a node detector, and direct waves and reflected waves from an underground target interval are obtained; and step 3, intercepting the seismic signal while drilling, and combining and superposing the preprocessing to obtain an acquisition signal with a relatively high signal-to-noise ratio. According to the while-drilling earthquake acquisition method and device, while-drilling earthquake acquisition efficiency and data quality can be improved, and reliable original information is provided for further performing pre-drilling pressure prediction and stratum prediction by using the while-drilling earthquake.

The invention belongs to the technical field of earth exploration, and relates to an underground imaging method based on a reformed Marchenko method, which comprises the following steps: removing direct waves from seismic data, and carrying out seismic deconvolution to obtain preprocessed seismic data; selecting an underground imaging point, setting the underground imaging point as an underground focus point, and estimating a direct wave Green function from the underground focus point to a ground surface receiving point according to a background speed model; the direct wave Green function is reversed on a time axis to serve as an initial downlink focusing function, and an initial uplink focusing function is set to be zero; and performing iterative calculation according to the initial downlink focusing function and the initial uplink focusing function to obtain a downlink focusing function and an uplink focusing function after iteration, calculating a downlink green function and an uplink green function according to the uplink focusing function and the downlink focusing function, and imaging the underground imaging point. According to the method, iteration absolute convergence can be ensured by mediating convergence parameters, and finally an underground imaging result which is not influenced by multiple waves is obtained.

The invention discloses a symmetric path-based Lamb wave non-reference damage detection imaging method and system, and relates to the technical field of ultrasonic Lamb wave non-destructive detection and imaging, and the method comprises the steps: obtaining a preset symmetrically arranged sensor array, obtaining a response signal of a receiving sensor of each path based on a preset excitation signal, the response signals of the symmetrical paths are subjected to difference processing to obtain difference signals; calculating a wave packet of the difference signal by adopting Hilbert transform on the difference signal, extracting a scattered wave packet and a direct wave packet based on the wave packet of the difference signal, and respectively calculating the flight time of the scattered wave packet and the flight time of the direct wave packet; based on the flight time of the scattered wave packet and the flight time of the direct wave packet, calculating an elliptical orbit of the defect on each path, and based on the elliptical orbit of the defect on each path and by utilizing a spatial distribution function, obtaining defect pixel points in the imaging area; and the defect pixel points in the imaging area are subjected to weighted fusion to obtain a damage positioning imaging picture, so that the Lamb wave non-reference imaging of the damage is realized, and the detection efficiency is improved.

The invention discloses a low-slow small target detection and data fusion method based on 5G signals, and relates to a low-slow small target detection and data fusion method. The invention aims to solve the problems of low detection precision and difficulty in effective identification and tracking of the low-slow small target in the prior art. According to the invention, a 5G signal retroreflection detection system with separated transmitting end and receiving end is constructed, direct wave and multipath interference are eliminated by using 5G signal code division multiple access characteristics, and target position and speed information are obtained through two-dimensional matched filtering and two-dimensional sliding correlation processing; a 5G base station forward scattering detection system is established, and target detection is realized by analyzing target forward scattering signal characteristic parameters according to the Babinet principle; a specific data fusion algorithm is adopted to carry out fusion processing on heterogeneous data obtained by backward reflection and forward scattering, and accurate information such as target position, speed, attribute and the like is output. The invention belongs to the technical field of low-slow small target detection.

An SIP module integrated direct wave amplifier comprises a power supply control module, an X-band down-conversion module and an L-band down-conversion module, the power supply control module provides attenuation control signals and a low-ripple power supply for the X-band down-conversion module and the L-band down-conversion module, the X-band down-conversion module performs primary frequency conversion on externally received radio frequency signals, and the L-band down-conversion module performs secondary frequency conversion on the externally received radio frequency signals. The L-band down-conversion module performs secondary frequency conversion on the radio frequency signal subjected to primary frequency conversion by the X-band down-conversion module, the two down-conversion modules are arranged to realize structure modularization and standardization by adopting a SiP modularization mode, and each module is independent in function, so that the structure is simple, the cost is low, and the cost is low. Meanwhile, the serial-parallel conversion chip control circuit is adopted to control the numerical control attenuator to meet the requirements for high gain and large dynamic range of the direct wave amplifier, the architecture and the number of control circuits are simplified, and the circuit is easy to build, easy to use, convenient to integrate and high in selection flexibility.

The present application relates to a ring resonator comprising: a straight waveguide; and the runway type micro ring comprises an arc-shaped coupling section and a first straight arm connected with the arc-shaped coupling section, and the arc-shaped coupling section is coupled with the straight waveguide. Through the arrangement of the runway type micro-ring coupled with the straight waveguide, the perimeter of the annular waveguide can be increased while the communication performance index of the micro-ring is not affected, namely, the loop loss of the micro-ring is reduced, and the technical problem that the insertion loss is increased due to the increase of a transmission path due to the too large radius of the micro-ring in the related technology is solved.

The invention provides a satellite-borne bistatic SAR imaging system and method, and the method comprises the steps: employing a coding signal pulse sequence as a periodic transmission sequence for a transmission signal, and enabling any pulses to be in an orthogonal relation; the pulse repetition frequency is set based on the bistatic configuration, and the adopted pulse repetition frequency enables the inter-satellite direct wave and the bistatic SAR ground echo to be received at the same time, and the waveforms of radar emission signals corresponding to the inter-satellite direct wave and the bistatic SAR ground echo are different; on the basis of the setting of a coded signal pulse sequence and the setting of a pulse repetition frequency, inter-satellite direct waves and observation area bistatic SAR echoes which are aliasing together in time are obtained, and the inter-satellite direct waves and observation area bistatic SAR echo signals obtained at the same moment are orthogonal; based on the obtained inter-satellite direct wave and the observation area bistatic SAR echo which are mixed together in time, the inter-satellite direct wave and the observation area bistatic SAR echo are extracted respectively, and the spaceborne bistatic SAR imaging function under the suppression of the inter-satellite direct wave is achieved.

The invention discloses a step frequency continuous wave ground penetrating radar imaging device and a rapid imaging method, and belongs to the technical field of microwave ground penetrating imaging. The vector network analyzer is adopted, the radio frequency power amplifier is carried, the ultra-wideband directional antenna is combined, signals of a step frequency continuous wave system are adopted, the frequency range is 700 MHz to 3 GHz, the bandwidth is large, meanwhile, the large transmitting power can be achieved, and meanwhile the requirements for the detection depth and the detection resolution are met; according to the method, direct wave interference is eliminated by adopting a singular value decomposition algorithm, then the effective signal strength is improved based on an automatic gain algorithm, and finally clutter interference is eliminated by adopting a block matching algorithm, so that the signal-to-noise ratio is improved; according to the method, an F-K migration imaging algorithm is developed, processed data are converted to a frequency wavenumber domain through Fourier transform, wavenumber domain data are filled before fast inverse Fourier transform, and the transverse space sampling rate and the imaging speed are increased.

The invention provides a continuous wave sonar direct wave suppression method, device and equipment and a storage medium, and the method comprises the steps: intercepting a target segment signal from a received signal, the target segment signal being composed of continuous Nw sampling points in the received signal; an estimation channel corresponding to the target segment signal is solved through a basis tracking algorithm, a dictionary matrix of the basis tracking algorithm is an Nw * Nw Toeplitz matrix, the first column is the first to Nw sampling points of the transmitted signal, and the second to Nw elements of the first row are zero; if the current estimation channel meets a judgment condition, the current estimation channel is determined as a final channel, and the judgment condition includes that the maximum element value in the estimation channel is larger than a first threshold value; reconstructing a direct wave and a multipath signal thereof according to the transmitted signal and the final channel; and subtracting the direct wave and the multipath signal thereof from the received signal to obtain a suppression result. According to the invention, on the premise of ensuring that the target echo energy is not lost, the sidelobe interference of the direct wave is effectively eliminated.

The invention discloses a polyethylene pipe microwave defect detection system based on a multi-dimensional movement mechanism. The method comprises the steps that firstly, full-coverage scanning of a welding area is achieved through a clamp and a control device, and microwave reflection signals of a welding joint are collected and subjected to amplification, filtering and normalization processing; converting the frequency domain signal into a time domain B-scan image by using inverse fast Fourier transform (IFFT), and effectively inhibiting direct waves and high-frequency noise by using a wavelet transform threshold denoising method so as to enhance defect reflection characteristics; on the basis, the system can identify and position typical defects such as holes, slag inclusion, incomplete fusion and the like, and visual visualization of defect positions and forms is realized through the information display module. The system is compact in structure and high in detection precision, has the advantages of high automation degree, wide application range, simplicity and convenience in operation and the like, can realize rapid and accurate detection of weld defects of the polyethylene pipeline, and provides reliable technical guarantee for pipeline quality evaluation and safe operation.

The invention relates to the field of unmanned aerial vehicles, in particular to an unmanned aerial vehicle autonomous fixed-point landing control method based on an ultrasonic array algorithm, and the method comprises the steps: dividing the landing process of an unmanned aerial vehicle into a normal flight stage, a deceleration approaching stage and a near-ground landing stage, starting an ultrasonic beacon array in the approaching flight stage, and confirming the availability of a landing point; a horizontal azimuth angle, a yaw angle and a relative distance are calculated in real time in a deceleration approach stage to perform landing guidance, direct waves and multi-path reflection signals are analyzed in a near-earth landing stage, characteristic parameters such as time delay inequality and phase offset are extracted, an environment reflection space model is reversely constructed, then positioning correction is calculated, a pose fine adjustment instruction is generated, and the attitude fine adjustment instruction is subjected to attitude fine adjustment. And precise fixed-point landing of the unmanned aerial vehicle is realized. According to the method, high-precision positioning is kept under complex environment disturbance, and the stability, accuracy and efficiency of fixed-point landing of the unmanned aerial vehicle in a complex environment are improved by converting the multipath effect from an interference source to available positioning information.

The invention relates to the technical field of safety monitoring and health management in the service period of a diversion tunnel in water conservancy and hydropower engineering, in particular to a diversion tunnel inner surface acoustic echo point extraction method which comprises the following steps: (1) an omnidirectional sonar actively emits sound waves to irradiate the inner surface of the tunnel, and meanwhile, periodic sampling is performed to form a series of discrete echo data points; (2) filtering direct waves, multipath echoes and noise data points in the discrete echo data points, and reserving actual echo data points on the inner surface of the tunnel; (3) one frame of data in the actual echo data points is used as a processing unit, and the intensity value change rate R between the adjacent data points is calculated one by one; (4) distance information and intensity information represented by acoustic echo points on the inner surface of the diversion tunnel should be optimal values, the acoustic echo points should be distributed at positions with large reflection echo intensity values and dense reflection echo intensity values in a short-distance spherical wave propagation mode, and the distance and intensity information is considered as a whole; the next data point with the maximum intensity value change rate between the adjacent data points is taken as an acoustic echo point P of the current frame data; (5) acoustic echo point extraction is carried out on the discrete echo data points of the next frame according to the steps (3) and (4) until acoustic echo points of all data frames are extracted and stored; according to the method, the problem of multiple data points formed by echo periodic sampling can be effectively solved, tunnel inner surface acoustic echo points giving consideration to strength information and position information are extracted, and reliable data support is provided for reconstruction and disease detection and recognition of the diversion tunnel inner surface.

The invention relates to a diffracted guided wave-based metal cylinder crack detection method, which comprises the following steps of: axially arranging a sensor array on a metal cylinder in an array manner, and collecting signals of all sensing paths; the sensing path is a connecting line between each excitation sensor and each receiving sensor; preprocessing each received path signal, judging a direct wave and a diffracted wave, and constructing a damage index of each sensing path on the basis of the amplitude difference between the diffracted wave and the direct wave; according to the signal and the damage index of each sensing path, drawing a total damage path diagram in the whole detection range, counting intersection points of each damage path and calculating the damage index of the corresponding intersection point; an improved clustering algorithm is utilized to obtain effective damage intersection points and a weighted centroid, and a damage area of the metal cylinder is delimited based on the damage intersection points around the weighted centroid through a convex hull algorithm. Compared with the prior art, the method has the advantages that dependence on health reference data can be eliminated, the calculation complexity is effectively reduced, and the detection efficiency is improved.

The invention provides a 2D-MUSIC beam line damage positioning method and system, and relates to the technical field of material safety monitoring. By collecting reference guided wave signals at different temperatures, amplitude-phase changes of direct waves of all sensor channels are analyzed, and a temperature-induced amplitude-phase error matrix is constructed; the error matrix is introduced into a two-dimensional multiple signal classification (2D-MUSIC) algorithm, an ideal steering vector is corrected, and a spatial spectrum under an actual propagation model is reconstructed; a cost function is established in combination with noise subspace characteristics, and high-precision and high-robustness positioning of tiny damage is realized through iterative optimization and synchronous inversion of damage positions and channel error parameters. According to the method, the applicability and the positioning accuracy of the 2D-MUSIC algorithm in a variable-temperature environment are remarkably improved.