CN111273307A - High-precision chirped laser coherent fusion distance measurement method based on Kalman filtering algorithm - Google Patents
High-precision chirped laser coherent fusion distance measurement method based on Kalman filtering algorithm Download PDFInfo
- Publication number
- CN111273307A CN111273307A CN202010052444.5A CN202010052444A CN111273307A CN 111273307 A CN111273307 A CN 111273307A CN 202010052444 A CN202010052444 A CN 202010052444A CN 111273307 A CN111273307 A CN 111273307A
- Authority
- CN
- China
- Prior art keywords
- frequency
- ranging
- laser
- mode
- coherent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000001427 coherent effect Effects 0.000 title claims abstract description 50
- 230000004927 fusion Effects 0.000 title claims abstract description 25
- 238000001914 filtration Methods 0.000 title claims abstract description 21
- 238000000691 measurement method Methods 0.000 title abstract description 4
- 238000005259 measurement Methods 0.000 claims abstract description 62
- 238000012545 processing Methods 0.000 claims abstract description 14
- 238000001228 spectrum Methods 0.000 claims description 20
- 238000005070 sampling Methods 0.000 claims description 13
- 238000001514 detection method Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- 230000010355 oscillation Effects 0.000 claims description 7
- 230000003287 optical effect Effects 0.000 claims description 6
- 238000009825 accumulation Methods 0.000 claims description 5
- 230000001360 synchronised effect Effects 0.000 claims description 4
- 239000013307 optical fiber Substances 0.000 claims description 2
- 238000002156 mixing Methods 0.000 abstract description 2
- 239000011159 matrix material Substances 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 230000003595 spectral effect Effects 0.000 description 5
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 230000000737 periodic effect Effects 0.000 description 3
- 230000007123 defense Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000035559 beat frequency Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 238000007500 overflow downdraw method Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/491—Details of non-pulse systems
- G01S7/493—Extracting wanted echo signals
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/495—Counter-measures or counter-counter-measures using electronic or electro-optical means
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
- G06F17/18—Complex mathematical operations for evaluating statistical data, e.g. average values, frequency distributions, probability functions, regression analysis
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Radar, Positioning & Navigation (AREA)
- Data Mining & Analysis (AREA)
- Mathematical Optimization (AREA)
- Theoretical Computer Science (AREA)
- Mathematical Physics (AREA)
- Pure & Applied Mathematics (AREA)
- Computational Mathematics (AREA)
- Electromagnetism (AREA)
- Mathematical Analysis (AREA)
- Evolutionary Biology (AREA)
- Operations Research (AREA)
- Probability & Statistics with Applications (AREA)
- Bioinformatics & Computational Biology (AREA)
- Algebra (AREA)
- Bioinformatics & Cheminformatics (AREA)
- Databases & Information Systems (AREA)
- Software Systems (AREA)
- General Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Optical Radar Systems And Details Thereof (AREA)
Abstract
The invention discloses a chirp laser radar fusion distance measurement method based on a Kalman filtering algorithm. The frequency mixing signals are collected through the high-speed ADC, and the distance and radial speed information of the target is extracted in real time through the digital signal processing module. The system adopts linear frequency modulation laser with the bandwidth of 120MHz and the period of 90 mu s to carry out coherent ranging in a heterodyne ranging mode, and the accuracy of the coherent ranging reaches 1.373 m; a single-frequency laser of 200MHz is adopted to carry out coherent velocity measurement in a homodyne velocity measurement mode, and the coherent velocity measurement precision reaches 0.00946 m/s. According to the invention, on the premise of not increasing the power consumption of the system, the Kalman filtering algorithm is adopted to perform real-time data fusion on the target information to obtain continuous high-precision ranging information, so that the ranging precision of the system is improved by more than one order of magnitude, and the accuracy of laser coherent ranging is improved.
Description
Technical Field
The invention relates to a laser radar technology, in particular to a high-precision chirp laser coherent fusion ranging method based on a Kalman filtering algorithm, which can be applied to a coherent ranging laser radar system, greatly improves the precision and accuracy of coherent ranging, greatly weakens the noise influence of the coherent ranging system caused by laser modulation, solves the problem that the distance information of a long-distance moving target is difficult to extract, and effectively improves the dynamic range of distance detection.
Background
The large dynamic range coherent ranging speed measurement laser radar technology has important application value in the aspects of space target relative positioning and aircraft autonomous navigation. How to realize detection in a larger distance range, how to realize high-frequency detection, how to effectively improve the measurement accuracy of distance and speed is a blank of the current technology, and is also a difficult problem to be solved [3 ].
With the support of naval air force and missile defense organization, the first coherent CO2 lidar was demonstrated by lincoln laboratories in 1967, and improvements were subsequently made in laser power, broadband detectors, and transceiver telescope calibers. [1]Terrestrial broadband, high power, range-doppler radar, with a wavelength of 10.6um, called "fire pool" (firepot) radar, was studied for space defense in 1972. The laser radar uses CO2A laser and a four-quadrant HgCdTe detector, by which the target can be precisely tracked. In thatIn 1977 the lidar successfully achieved tracking of satellites and aircraft with corner reflectors with a tracking accuracy of 1 μ rad. In 1981, the fire pool laser radar is provided with a high power amplification system (LRPA) to form a large system, and the system needs to be cooled by water, the laser wavelength is 10.59 mu m, the aperture of a telescope is 1.2m, and the beam divergence is 10 mu rad [1, 2]]。
In a system for long-distance coherent distance and speed measurement by linear frequency modulation, strict requirements are put forward on the modulation of a transmitted laser signal in order to achieve higher distance and speed measurement precision. The linear frequency modulation system measures distance and speed, and the precision of measuring distance and speed has a very direct relation with the linearity of linear frequency modulation. The linearity is not good, which causes the signal spectrum of the coherent echo and local oscillator to be broadened, the signal-to-noise ratio to be poor, and it is difficult to obtain an accurate frequency value, and further difficult to accurately obtain the target distance and speed.
The Shanghai technical and physical research institute of Chinese academy of sciences in China has studied the homodyne and heterodyne detection of chirp amplitude modulation for many years. In 2010, Mengzhawa adopts a Mach-Zehnder amplitude modulator (M-Z interferometric modulator) to perform amplitude modulation on laser in a laboratory, adopts a DDS (Direct frequency synthesizer) to realize high-precision linear frequency modulation to drive the Mach-Zehnder amplitude modulator, obtains chirp amplitude modulation laser with broadband and high linearity, and further builds a heterodyne all-fiber experimental system. The experiment detects about 1km of optical fiber, the obtained distance resolution capability is superior to 0.15m (1 ns in time), and the minimum detection sensitivity can be superior to 0.1nW when the local oscillation power is 1 mW. [4]
In the chirped frequency modulation heterodyne ranging system, "slope interference" caused by chirp is generated, and the noise and signal coupling are difficult to be directly eliminated, which affects the ranging accuracy of the system and sometimes generates wrong data points with large errors, so that the ranging signal is difficult to be continuously and accurately extracted. And because of the limitation of the bandwidth of the frequency modulation, the current frequency modulation range is limited, the resolution can be improved only by changing the frequency modulation period or the echo sampling rate, and the precision of distance measurement cannot be improved.
Reference to the literature
[1]A.B.Gschwendtner,W.E.Keicher.Development of Coherent Laser Radarat Lincoln Laboratory[J].Lincoln Laboratory Journal,2000,12(2)
[2] Sunjiefeng, Yan people, Liudeban, et al. remote laser imaging radar progress [ J ] laser and optoelectronics progress, 2009,46(8):49-54.
[3] Wujun, flood and violence, Heshiping, et al, a large-range dynamic range high-repetition-frequency coherent ranging and speed measuring laser radar (I), system and performance [ J ], Infrared and millimeter wave academic newspaper, 2014,33(6), 680 and 690.
[4] Mengwanhua, surging, huihua, et al, research on key technologies of chirped amplitude modulated coherent detection lidar [ J ] optics report, 2010,30(8):2446.
Disclosure of Invention
The invention aims to provide a high-precision chirped laser coherent fusion ranging method based on a Kalman filtering algorithm on the basis of the prior coherent Doppler ranging laser radar technology, and solves the problems that the prior coherent ranging radar has low ranging precision, obvious noise interference, difficulty in continuously and accurately extracting ranging signals and small ranging dynamic range.
The radar fusion ranging scheme adopted by the invention is shown in figure 1:
firstly, the system enters a heterodyne ranging mode to obtain coherent ranging data, after the heterodyne ranging mode is finished, current initial distance data are input into a Kalman filter, the system is immediately switched to a homodyne speed measurement mode to obtain target speed data and transmit the target speed data to the Kalman filter, a continuous and stable high-precision fusion ranging result is obtained through Kalman data fusion, and after the homodyne speed measurement mode is finished, the system returns to the heterodyne ranging mode.
In the heterodyne ranging mode, the emitted laser light is chirp-modulated and linearly varied with time from an initial frequency f1 to f2 by τ. The emitted laser light simultaneously serves as a Reference signal (Reference), the elapsed time Δ t from the emission to the reception of the laser light, due to the chirp, exists a fixed frequency difference fR of the echo laser light (Received echo) with respect to the Reference signal over a period of time, which frequency difference can be obtained by mixing or coherent beat frequency. If the distance from the laser radar to the target is R, fR is as follows: (wherein, B ═ f 2-f 1 is modulation bandwidth, and the target distance R can be obtained through fR.)
fR＝(f2-f1)Δt/τ＝2BRcτ
In the homodyne velocity measurement mode, a laser with unmodulated single frequency is adopted to transmit a signal, only a Doppler velocity frequency shift signal can be obtained, the laser has a Doppler effect as a sound wave, the laser transmitted by a narrow linewidth laser with the wavelength of lambda irradiates a moving target with the velocity of v in the laser sight line direction to generate a Doppler frequency shift fd, the light velocity is c, and the target velocity can be reversely deduced by the Doppler frequency shift:
v＝λ·fd/2
the input of the Kalman filter is the initial distance of the target and the measured radial speed of the target. The purpose of kalman filtering in the measurement process is to give an estimate of the system state at the current time t, combine the current system state prediction based on the state at time t-1 with the measured parameters at time t, and the filter calculates its solution in a recursive manner.
The target state at the current time consists of distance and radial velocity:
state prediction based on the state at the previous time can be described by:
Xt＝A*Xt-1+Wt-1
the method is equivalent to the following steps:
wherein Wt-1Gaussian state noise vector and covariance matrix E expected as zeroxA is the state transition matrix, ΔtIs the measurement period.
In the present invention, we only consider target range estimation, so the observation matrix only contains range observations:
H＝[1 0]
the observation equation is as follows:
Zt＝H*Xt+nt
where n is a zero mean Gaussian and covariance matrix EzThe measurement noise of (2).
The kalman equation describes the prediction of the current state and the state estimation update as:
wherein K represents a kalman gain, wherein,
the prediction covariance matrix representing the error, and P represents the covariance matrix of the state estimation error. Measurement noise EzCovariance matrix and state error estimate ExThe covariance matrix of (a) has the following meaning: since the measured values are greatly affected by noise, we assign a larger value to EzThis means that we rely more on predictions of model-based filters than noise-based measurements. This means that we depend on the accuracy of the model, and therefore the covariance matrix Ex has smaller values.
The structure of the radar system related to the invention is shown in figure 2, an FPGA chip is used for controlling a DDS chip to generate a linear frequency modulation signal with high linearity and high periodic stability, the DDS chip drives an acousto-optic frequency shifter to realize the linear frequency modulation of high linearity and high periodic stability of emission laser and local oscillation laser, a narrow linewidth laser is used for generating modulated coherent laser of the linear frequency modulation, the coherent laser is divided into two parts according to a certain proportion by a beam splitter, wherein the large energy part is used for emission, and the small energy part is used as a local oscillation; the large energy part is transmitted by a circulator and a coaxial receiving and transmitting telescope, echo laser is received by the coaxial receiving and transmitting telescope, is changed into one path of echo optical signal by the circulator, finally enters a 90-degree optical bridge together with a local oscillator signal to form 4 paths of output optical signals, and balanced detectors of the path I and the path Q output and enter a high-speed ADC (analog to digital converter) to be converted into digital signals to form a path I signal and a path Q signal and enter a digital signal processing module inside the FPGA (field programmable gate array); a complex number is formed by the I path signal and the Q path signal, and a distance frequency shift and Doppler frequency shift superposed signal in an echo signal is extracted through digital signal processing and a spectrum subdivision algorithm. By carrying out differential processing on the superposed signals, the distance and radial velocity information of the target can be acquired in real time. In the chirped frequency modulation heterodyne ranging system, "slope interference" caused by chirp is generated, and the noise and signal coupling are difficult to be directly eliminated, which affects the ranging accuracy of the system and sometimes generates wrong data points with large errors, so that the ranging signal is difficult to be continuously and accurately extracted. And because of the limitation of the bandwidth of the frequency modulation, the current frequency modulation range is limited, the resolution can be improved only by changing the frequency modulation period or the echo sampling rate, and the precision of distance measurement cannot be improved. Because the coherent system does not need to modulate the frequency of the laser when homodyne speed measurement, only the Doppler frequency shift information caused by the target speed needs to be extracted, the noise interference is small, the measurement precision is not limited by the frequency modulation range, the measurement precision and the accuracy are high, and the extraction is convenient. The invention uses the speed information for distance measurement precision and accuracy correction on the premise of not increasing the complexity of the system so as to improve the precision and accuracy of coherent distance measurement. According to the invention, a Kalman filtering algorithm is adopted, the ranging information and the speed measurement information are fused, and the target distance is predicted in real time by using the target initial distance information and the target radial speed information, so that continuous high-precision ranging information is obtained. According to the method, the data are fused through the Kalman filtering algorithm, so that the precision of the laser coherent ranging is improved, the noise interference caused by a coherent ranging system is effectively avoided, and the accuracy of the laser coherent ranging is improved.
The system adopts two modes to realize the purpose of high-precision frequency modulation laser coherent ranging, and is divided into a heterodyne ranging mode and a homodyne speed measurement mode:
heterodyne ranging mode: generating chirp signals by a DDS (direct digital synthesizer), collecting echo signals and local oscillation coherent signals generated after the chirp signals pass through a coherent detection system to a digital signal processing module by a high-speed ADC (analog to digital converter), taking 8192 points of collected data as a sampling period, synchronizing the sampling period with an DDS frequency modulation period by using synchronous signals in the same period, carrying out fast real-time FFT (fast Fourier transform) during sampling, carrying out real-time accumulation on frequency spectrums obtained after each FFT (fast Fourier transform) processing, and obtaining a target distance and a target speed by a decoupling algorithm; after the heterodyne ranging mode is finished, the current initial distance data are input into a Kalman filter, the system is immediately switched to a homodyne speed measurement mode, target speed data are obtained in real time in the same mode without decoupling and are transmitted into the Kalman filter, high-precision target distance information can be predicted in real time through Kalman data fusion, accordingly continuous and stable high-precision fusion distance data are obtained, and after the homodyne speed measurement mode is finished, the system returns to the heterodyne ranging mode. The laser emission signal subjected to linear frequency modulation is adopted under the heterodyne ranging mode, a superposed signal of a distance frequency shift and a Doppler velocity frequency shift can be obtained in a frequency spectrum, and ranging and speed measurement can be simultaneously realized under the mode, but slope interference caused by linear frequency modulation can be generated under the mode, and the noise and signal coupling are difficult to directly eliminate, so that the ranging accuracy of a system can be influenced, wrong data points with large errors can be generated sometimes, and the ranging signal is difficult to continuously and accurately extract. In addition, in the mode, due to the limitation of the bandwidth of the frequency modulation band, the current frequency modulation range is limited, the resolution can be improved only by changing the frequency modulation period or the echo sampling rate, and the accuracy of distance measurement cannot be improved.
Homodyne velocity measurement mode: the laser emission signal with single frequency without modulation is adopted, only the signal of Doppler velocity frequency shift can be obtained, low-frequency noise caused by laser emission signal modulation can be avoided in the mode, only the Doppler frequency shift information caused by target velocity needs to be extracted when the coherent system measures the velocity, the frequency modulation of the laser is not needed, and the high-precision target velocity signal can be directly obtained. The system adopts a spectrum subdivision algorithm to extract a distance frequency shift and Doppler frequency shift superposed signal in an echo signal, adopts a pipeline continuous subdivision mode to acquire the frequency between a target peak and four adjacent points thereof, and obtains more reliable peak frequency points through algorithm comparison.
The specific working flow of the high-precision chirped laser coherent fusion distance measurement data processing method based on the Kalman filtering algorithm is as follows:
1. the digital signal processing module receives digital sequences from the I channel and the Q channel and forms the digital sequences into a complex sequence V, wherein the real part of the complex sequence V is data of the I channel at the same moment, and the imaginary part of the complex sequence V is data of the Q channel at the same moment.
2. The complex sequence is a sampling period according to 8192 points, the sampling period and the dds frequency modulation period are synchronized by adopting a synchronization signal with the same period, the purpose of doing so is to enable the signal phase of each spectrum accumulation to be consistent, thereby effective spectrum accumulation can be carried out, fast real-time FFT is carried out at the same time of sampling, the spectrum obtained after each FFT treatment is accumulated in real time, and the signal-to-noise ratio is effectively improved.
3. In the chirped frequency modulation heterodyne ranging mode, a frequency shift signal with the superposition of the target distance and the target speed is obtained, and the 'slope interference' caused by linear frequency modulation is generated at low frequency. And the echo energy of a distant target is weaker, and the amplitude of a signal spectrum peak is lower (lower than that of low-frequency noise). Searching the position of a signal spectrum peak by adopting a segmented threshold method and a spectrum subdivision algorithm, wherein the corresponding frequency is a signal superposed by a Doppler frequency signal and a distance difference frequency signal brought by the velocity, and obtaining the target distance and velocity by a decoupling algorithm;
4. when initial distance information is obtained in a ranging mode, the system is switched to a homodyne speed measurement mode, a frequency spectrum with only a single spectral peak except for zero frequency is obtained in the homodyne speed measurement mode, the mirror image frequency point amplitude of the spectral peak is very small, the position of the spectral peak is searched in real time in the frequency spectrum accumulation process, the spectral peak is considered as a signal when the amplitude of the spectral peak reaches a certain threshold value, the corresponding frequency is a Doppler frequency signal brought by the speed, target speed can be obtained through real-time resolving, a state equation and an observation equation of a target are established through a Kalman filtering algorithm, high-precision target distance information can be predicted in real time through the radial speed of the target at the time t-1 and initial distance data, and therefore continuous and stable high-precision ranging information is obtained.
Advantageous effects
Compared with a microwave radar, the laser radar adopted by the system has the advantages that the divergence angle is greatly reduced, and the accuracy of a measured target is greatly improved.
Through orthogonal detection, common mode noise is effectively inhibited, the signal-to-noise ratio of the system is improved, and extraction of measurement parameters is facilitated.
The target distance is predicted in real time through a Kalman filtering algorithm, so that the interference of system noise is effectively reduced, and continuous and reliable target distance information is obtained. The distance information and the speed information of the target are fused through a Kalman filtering algorithm, and the accuracy of distance measurement is effectively improved. And because the Kalman filtering algorithm only needs to store the target state information at the moment of t-1, the occupied system resources are less, the operation speed is high, and the large power consumption is not brought while the system is optimized.
Drawings
FIG. 1 is a diagram of a radar fusion ranging scheme, in which a system first enters a heterodyne ranging mode to obtain an initial target distance, and then the system switches to a homodyne speed measurement mode to perform real-time speed measurement; and fusing the initial distance of the target and the real-time speed measurement result by adopting a Kalman filtering algorithm to obtain high-precision distance information of the target, and returning the system to the heterodyne distance measurement mode after the homodyne speed measurement mode is finished.
Fig. 2 is a block diagram of a system of chirped laser coherent fusion range radar according to the present invention, which includes: an FPGA microprocessor; a DDS chip; an acousto-optic frequency shifter; a narrow linewidth laser; a fiber optic circulator; a coaxial transceiver telescope; a 90-degree optical bridge; a balance detector; high-speed ADC.
Fig. 3 is a schematic diagram of the high-precision chirped laser coherent fusion ranging operation according to the present invention, in which a chirped signal is generated by a DDS, an echo and a local oscillator coherent signal generated after passing through a coherent detection system are collected by a high-speed ADC to a digital signal processing module, and a target distance and a target speed are obtained through familiar signal processing; obtaining distance information of a target in a heterodyne ranging mode, and obtaining target speed information in a homodyne speed measurement mode; and continuous and stable high-precision fusion distance data are obtained in real time through Kalman data fusion.
Fig. 4 is a comparison diagram of the ranging result of the uniform motion target, wherein: fig. 1 is a simulation result diagram, and fig. 2 is an experimental measurement result diagram.
Detailed Description
The specific implementation of the laser radar coherent ranging and speed measuring fusion method based on the Kalman filtering algorithm comprises the following steps:
1) the system adopts two working modes of cyclic detection to realize high-precision chirped laser coherent fusion ranging, namely a heterodyne ranging mode and a homodyne speed measurement mode. The method comprises the steps that firstly, a system enters a heterodyne ranging mode to obtain an initial distance of a target, then the system is switched to a homodyne speed measurement mode to carry out real-time speed measurement, meanwhile, a Kalman filtering algorithm is adopted to fuse the initial distance of the target and a real-time speed measurement result to obtain high-precision distance information of the target, and after the homodyne speed measurement mode is finished, the system returns to the heterodyne ranging mode.
2) In the heterodyne ranging mode, an FPGA chip is adopted to control a DDS chip to generate continuous sawtooth wave signals with high linearity and high periodic stability, the frequency modulation period is 90 microseconds, the frequency modulation amplitude is 60 megahertz, and the frequency modulation center frequency is 200 megahertz. The DDS chip drives the acousto-optic frequency shifter to realize the linear frequency modulation of high linearity and high period stability of emission laser and local oscillation laser, the narrow linewidth laser generates the coherent laser of the modulated linear frequency modulation, the coherent laser is divided into two parts according to a certain proportion by the beam splitter, wherein the large energy part is used for emission, and the small energy part is used as the local oscillation.
3) The echo light and the local oscillator light form I, Q two paths of signals through a 90-degree optical bridge, a high-speed ADC (AD6645) is adopted to sample the I, Q signal, two paths of 12-bit-width digital sequences output by the high-speed ADC form a complex number V in a digital signal processing module, the real part of the complex number V is from I channel ADC data at the same moment, and the imaginary part of the complex number V is from Q channel ADC data at the same moment. The sampling period of continuously acquired complex data V is synchronous with the DDS frequency modulation period, and each time N is 8192 points to perform real-time FFT processing to obtain a signal frequency spectrum, the obtained signal frequency spectrums are accumulated in real time, peak value detection is performed by adopting a pipeline frequency spectrum subdivision mode, the frequency between a target peak and four adjacent points is acquired, and more reliable peak value frequency points are obtained through algorithm comparison;
4) because the laser emission signal subjected to linear frequency modulation is adopted in the ranging mode, a superposed signal of distance frequency shift and Doppler velocity frequency shift can be obtained in a frequency spectrum, ranging and speed measurement can be simultaneously realized in the mode, but in the mode, a system can generate slope interference caused by linear frequency modulation, the slope interference is difficult to eliminate, the measurement precision is difficult to improve, error points are easy to generate, and some errors are brought to the measurement of the target speed and the distance due to the rapid movement of a target in the mode.
5) And (2) predicting the distance and the speed of the target in real time by adopting a Kalman filtering algorithm, wherein the Kalman filtering aims to provide the estimation of the system state at the current moment t in the measurement process, the current system state prediction based on the moment t-1 state is combined with the actual measurement parameter at the time t, and the filter calculates the solution of the system state in a recursion mode. And then comparing the predicted result with the actual measurement result to obtain a continuous and stable measurement result.
6) And after the heterodyne ranging mode is finished, inputting the current ranging result into a Kalman filter, switching to a homodyne speed measurement mode, and controlling a DDS chip to generate a sinusoidal signal with single frequency by adopting an FPGA chip, wherein the frequency is 200 MHz.
7) Because the laser emission signal with single unmodulated frequency is adopted in the speed measurement mode, only the signal of Doppler velocity frequency shift is obtained, low-frequency noise caused by laser emission signal modulation is avoided in the mode, and high-precision target velocity data can be directly obtained. The speed data are transmitted to a Kalman filter in real time, high-precision target distance information can be predicted in real time through Kalman data fusion, accordingly continuous and stable high-precision fusion distance data are obtained, and after the homodyne speed measurement mode is finished, the system returns to the heterodyne distance measurement mode.
8) Through experimental verification, the Chirp laser coherent fusion distance measurement method based on the Kalman filtering algorithm can effectively improve the distance measurement precision of the system from 1.37m to within 0.1m, the precision is improved by at least one order of magnitude, and the accuracy of the system is greatly improved.
Claims (1)
1. A chirp laser radar fusion distance measuring method based on Kalman filtering algorithm is realized on a frequency modulation coherent laser distance measuring radar system, wherein the frequency modulation coherent laser distance measuring radar system comprises a Field Programmable Gate Array (FPGA), a digital frequency synthesizer (DDS), an acousto-optic frequency shifter (AOFS), a coaxial transceiver telescope, an optical fiber circulator, a narrow-line-width laser, a 90-degree optical bridge, a balance detector, a high-speed ADC (analog to digital converter), a digital signal processing module and a Kalman digital filter; the method is characterized by comprising the following steps:
the fusion ranging method of the frequency modulation laser coherent ranging radar system comprises a heterodyne ranging mode and a homodyne speed measurement mode, wherein:
heterodyne ranging mode: generating chirp signals by a DDS (direct digital synthesizer), collecting echo signals and local oscillation coherent signals generated after the chirp signals pass through a coherent detection system to a digital signal processing module by a high-speed ADC (analog to digital converter), taking 8192 points of collected data as a sampling period, synchronizing the sampling period with an DDS frequency modulation period by using synchronous signals in the same period, carrying out fast real-time FFT (fast Fourier transform) during sampling, carrying out real-time accumulation on frequency spectrums obtained after each FFT (fast Fourier transform) processing, and obtaining a target distance and a target speed by a decoupling algorithm;
after the heterodyne ranging mode is finished, inputting the current initial distance data into a Kalman filter, immediately switching the system to a homodyne speed measurement mode, acquiring target speed data in real time in the same mode without decoupling, transmitting the target speed data to the Kalman filter, and predicting high-precision target distance information in real time through Kalman data fusion so as to acquire continuous and stable high-precision fusion distance data; adopting a laser emission signal subjected to linear frequency modulation under an heterodyne ranging mode, obtaining a superposed signal of a distance frequency shift and a Doppler velocity frequency shift in a frequency spectrum, and simultaneously realizing ranging and velocity measurement under the mode;
homodyne velocity measurement mode: the laser emission signal with single frequency without modulation can only obtain the signal of Doppler velocity frequency shift, and the low-frequency noise caused by the modulation of the laser emission signal can be avoided in the mode, because the coherent system only needs to extract the Doppler frequency shift information caused by the target velocity when measuring the velocity, and does not need to modulate the frequency of the laser, the high-precision target velocity signal can be directly obtained; the system adopts a spectrum subdivision algorithm to extract a distance frequency shift and Doppler frequency shift superposed signal in an echo signal, adopts a pipeline continuous subdivision mode to acquire the frequency between a target peak and four adjacent points thereof, and obtains more reliable peak frequency points through algorithm comparison.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010052444.5A CN111273307A (en) | 2020-01-17 | 2020-01-17 | High-precision chirped laser coherent fusion distance measurement method based on Kalman filtering algorithm |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010052444.5A CN111273307A (en) | 2020-01-17 | 2020-01-17 | High-precision chirped laser coherent fusion distance measurement method based on Kalman filtering algorithm |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111273307A true CN111273307A (en) | 2020-06-12 |
Family
ID=70997263
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010052444.5A Pending CN111273307A (en) | 2020-01-17 | 2020-01-17 | High-precision chirped laser coherent fusion distance measurement method based on Kalman filtering algorithm |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111273307A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111751834A (en) * | 2020-06-30 | 2020-10-09 | 重庆大学 | High-speed high-precision dynamic ranging method based on optical frequency modulation interference and single-frequency interference |
| CN112347613A (en) * | 2020-10-19 | 2021-02-09 | 西安空间无线电技术研究所 | Method for quickly designing waveform bandwidth of microwave speed and distance measuring sensor |
| CN112557373A (en) * | 2019-09-26 | 2021-03-26 | 南京理工大学 | Zero-difference type broadband microwave spectrometer |
| CN112882036A (en) * | 2021-01-19 | 2021-06-01 | 中国人民解放军军事科学院国防科技创新研究院 | Sonar audio speed and distance measuring device and method |
| CN113671520A (en) * | 2021-08-11 | 2021-11-19 | 数量级(上海)信息技术有限公司 | Range finding filtering tracking method and system for quantum laser radar |
| CN113794991A (en) * | 2021-11-15 | 2021-12-14 | 西南交通大学 | Single-base-station wireless positioning system based on UWB and LoRa |
| CN113848557A (en) * | 2021-08-27 | 2021-12-28 | 南京理工大学 | Interference identification method for composite detection |
| CN114838803A (en) * | 2022-04-29 | 2022-08-02 | 北京杏林睿光科技有限公司 | Vibration measuring device and vibration measuring method |
| CN115356742A (en) * | 2022-08-08 | 2022-11-18 | 深圳市圳阳精密技术有限公司 | High-precision externally-adjusted FMCW laser ranging system and method based on phase splicing |
Citations (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5847817A (en) * | 1997-01-14 | 1998-12-08 | Mcdonnell Douglas Corporation | Method for extending range and sensitivity of a fiber optic micro-doppler ladar system and apparatus therefor |
| WO2002091017A2 (en) * | 2001-05-04 | 2002-11-14 | Lockheed Martin Corporation | System and method for measurement domain data association in passive coherent location applications |
| US6573982B1 (en) * | 1991-09-18 | 2003-06-03 | Raytheon Company | Method and arrangement for compensating for frequency jitter in a laser radar system by utilizing double-sideband chirped modulator/demodulator system |
| CN101236253A (en) * | 2008-03-07 | 2008-08-06 | 中国科学院上海光学精密机械研究所 | High precision speed-measuring distance-measuring radar system and method |
| CN102004255A (en) * | 2010-09-17 | 2011-04-06 | 中国科学院上海技术物理研究所 | Chirp amplitude laser infrared radar distance-Doppler zero-difference detection system |
| CN102608615A (en) * | 2012-03-08 | 2012-07-25 | 东华大学 | Laser radar speed/range measurement method based on chirp amplitude modulation and coherent detection |
| CN104035101A (en) * | 2014-06-12 | 2014-09-10 | 中国科学院上海技术物理研究所 | Intensity code based synthetic aperture laser radar system |
| JP2014185872A (en) * | 2013-03-22 | 2014-10-02 | Mitsubishi Electric Corp | Radar system |
| CN105204030A (en) * | 2015-09-22 | 2015-12-30 | 中国科学院上海技术物理研究所 | Data processing method for coherent homodyne speed measurement laser radar with optical orthogonal demodulation |
| US20160103214A1 (en) * | 2014-10-08 | 2016-04-14 | Src, Inc. | Use of Range-Rate Measurements in a Fusion Tracking System via Projections |
| CN105572690A (en) * | 2016-03-07 | 2016-05-11 | 中国科学技术大学 | Double-frequency coherent wind lidar based on single-frequency continuous light EOM modulation |
| US20160170023A1 (en) * | 2014-06-13 | 2016-06-16 | Thales | Relative speed measuring doppler lidar |
| CN107064969A (en) * | 2017-03-06 | 2017-08-18 | 哈尔滨工程大学 | A kind of GNSS receiver phase estimator and compensation method |
| CN107407732A (en) * | 2014-10-24 | 2017-11-28 | 波尔特公司 | For the position searching using RF through the polygon measurement of Partial synchronization or Trilateration methods and system |
-
2020
- 2020-01-17 CN CN202010052444.5A patent/CN111273307A/en active Pending
Patent Citations (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6573982B1 (en) * | 1991-09-18 | 2003-06-03 | Raytheon Company | Method and arrangement for compensating for frequency jitter in a laser radar system by utilizing double-sideband chirped modulator/demodulator system |
| US5847817A (en) * | 1997-01-14 | 1998-12-08 | Mcdonnell Douglas Corporation | Method for extending range and sensitivity of a fiber optic micro-doppler ladar system and apparatus therefor |
| WO2002091017A2 (en) * | 2001-05-04 | 2002-11-14 | Lockheed Martin Corporation | System and method for measurement domain data association in passive coherent location applications |
| CN101236253A (en) * | 2008-03-07 | 2008-08-06 | 中国科学院上海光学精密机械研究所 | High precision speed-measuring distance-measuring radar system and method |
| CN102004255A (en) * | 2010-09-17 | 2011-04-06 | 中国科学院上海技术物理研究所 | Chirp amplitude laser infrared radar distance-Doppler zero-difference detection system |
| CN102608615A (en) * | 2012-03-08 | 2012-07-25 | 东华大学 | Laser radar speed/range measurement method based on chirp amplitude modulation and coherent detection |
| JP2014185872A (en) * | 2013-03-22 | 2014-10-02 | Mitsubishi Electric Corp | Radar system |
| CN104035101A (en) * | 2014-06-12 | 2014-09-10 | 中国科学院上海技术物理研究所 | Intensity code based synthetic aperture laser radar system |
| US20160170023A1 (en) * | 2014-06-13 | 2016-06-16 | Thales | Relative speed measuring doppler lidar |
| US20160103214A1 (en) * | 2014-10-08 | 2016-04-14 | Src, Inc. | Use of Range-Rate Measurements in a Fusion Tracking System via Projections |
| CN107407732A (en) * | 2014-10-24 | 2017-11-28 | 波尔特公司 | For the position searching using RF through the polygon measurement of Partial synchronization or Trilateration methods and system |
| CN105204030A (en) * | 2015-09-22 | 2015-12-30 | 中国科学院上海技术物理研究所 | Data processing method for coherent homodyne speed measurement laser radar with optical orthogonal demodulation |
| CN105572690A (en) * | 2016-03-07 | 2016-05-11 | 中国科学技术大学 | Double-frequency coherent wind lidar based on single-frequency continuous light EOM modulation |
| CN107064969A (en) * | 2017-03-06 | 2017-08-18 | 哈尔滨工程大学 | A kind of GNSS receiver phase estimator and compensation method |
Non-Patent Citations (10)
| Title |
|---|
| SHAOHUI CHEN: "À Trous Wavelet Based Four-Dimensional Evapotranspiration Assimilation" * |
| SIYUE ZHU: "Material design and Property of High Viscosity Asphalt used in Pervious Asphalt Pavement" * |
| 于啸;洪光烈;凌元;舒嵘;: "啁啾调幅激光雷达对距离和速度的零差探测" * |
| 井李强;郑刚;孙彬;王欢;白浪;: "基于调频连续波干涉技术的运动目标距离测量" * |
| 余杨: "新型双频相干脉冲压缩测速测距激光雷达" * |
| 宋楠;李桂英;: "基于零差检测的LFMCW激光雷达系统研究" * |
| 张良: "双向比对技术弹丸空间位置高精度测量方法" * |
| 曾朝阳: "线性调频连续波激光雷达测量方法研究" * |
| 舒嵘;凌元;崔桂华;洪光烈;: "着陆导航激光多普勒雷达" * |
| 谭显裕: "激光雷达测距方程研究" * |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112557373A (en) * | 2019-09-26 | 2021-03-26 | 南京理工大学 | Zero-difference type broadband microwave spectrometer |
| CN111751834B (en) * | 2020-06-30 | 2024-02-20 | 重庆大学 | High-speed high-precision dynamic ranging method based on optical frequency modulation interference and single-frequency interference |
| CN111751834A (en) * | 2020-06-30 | 2020-10-09 | 重庆大学 | High-speed high-precision dynamic ranging method based on optical frequency modulation interference and single-frequency interference |
| CN112347613A (en) * | 2020-10-19 | 2021-02-09 | 西安空间无线电技术研究所 | Method for quickly designing waveform bandwidth of microwave speed and distance measuring sensor |
| CN112347613B (en) * | 2020-10-19 | 2024-05-14 | 西安空间无线电技术研究所 | Rapid design method for waveform bandwidth of microwave speed and distance measuring sensor |
| CN112882036A (en) * | 2021-01-19 | 2021-06-01 | 中国人民解放军军事科学院国防科技创新研究院 | Sonar audio speed and distance measuring device and method |
| CN113671520A (en) * | 2021-08-11 | 2021-11-19 | 数量级(上海)信息技术有限公司 | Range finding filtering tracking method and system for quantum laser radar |
| CN113848557A (en) * | 2021-08-27 | 2021-12-28 | 南京理工大学 | Interference identification method for composite detection |
| CN113848557B (en) * | 2021-08-27 | 2024-05-17 | 南京理工大学 | Interference identification method for composite detection |
| CN113794991B (en) * | 2021-11-15 | 2022-02-11 | 西南交通大学 | Single-base-station wireless positioning system based on UWB and LoRa |
| CN113794991A (en) * | 2021-11-15 | 2021-12-14 | 西南交通大学 | Single-base-station wireless positioning system based on UWB and LoRa |
| CN114838803A (en) * | 2022-04-29 | 2022-08-02 | 北京杏林睿光科技有限公司 | Vibration measuring device and vibration measuring method |
| CN114838803B (en) * | 2022-04-29 | 2023-11-10 | 北京杏林睿光科技有限公司 | Vibration measuring device and vibration measuring method |
| CN115356742A (en) * | 2022-08-08 | 2022-11-18 | 深圳市圳阳精密技术有限公司 | High-precision externally-adjusted FMCW laser ranging system and method based on phase splicing |
| CN115356742B (en) * | 2022-08-08 | 2023-09-29 | 深圳市圳阳精密技术有限公司 | High-precision external-adjustment FMCW laser ranging system and method based on phase splicing |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111273307A (en) | High-precision chirped laser coherent fusion distance measurement method based on Kalman filtering algorithm | |
| CN111337902B (en) | Multi-channel high-repetition-frequency large-dynamic-range distance and speed measuring laser radar method and device | |
| EP2930532B1 (en) | Simultaneous forward and inverse synthetic aperture imaging ladar | |
| US6559932B1 (en) | Synthetic aperture ladar system using incoherent laser pulses | |
| CN110376607B (en) | Synthetic aperture laser radar system | |
| US11327158B1 (en) | Techniques to compensate for mirror Doppler spreading in coherent LiDAR systems using matched filtering | |
| Buell et al. | Demonstration of synthetic aperture imaging ladar | |
| CN103076611B (en) | Method and device for measuring speed and distance by coherent detecting laser | |
| CN104597452A (en) | Symmetrical triangular linear frequency modulation continuous wave type laser radar target detecting method | |
| US20210382164A1 (en) | Multi-tone continuous wave detection and ranging | |
| Li et al. | Estimation of high-frequency vibration parameters for terahertz SAR imaging based on FrFT with combination of QML and RANSAC | |
| CN114152951A (en) | Frequency-adjustable continuous wave laser radar detection method and system | |
| JP2023545775A (en) | Ghost reduction technology in coherent LIDAR systems | |
| CN111190189B (en) | Multifunctional double frequency modulation coherent laser radar | |
| CN104111450A (en) | Method and system for detecting object micro Doppler characteristics by use of double pulses | |
| CN116699572A (en) | Method for compensating vibration error of coherent laser radar based on secondary compensation | |
| Wang et al. | Radon-fourier transform in fmcw radar | |
| Dawidowicz et al. | First polish SAR trials | |
| CN104297759A (en) | Hyperbolic wave forward difference self-scanning direct-view synthetic aperture laser imaging radar | |
| Huang et al. | Ground moving target imaging and motion parameter estimation using Radon-second-order WVD transform | |
| Li et al. | Estimation and correction of vibration-induced range cell migration for FMCW synthetic aperture ladar | |
| US20230131584A1 (en) | Multi-tone continuous wave detection and ranging | |
| Gao et al. | The laboratory demonstration and signal processing of the inverse synthetic aperture imaging ladar | |
| Wang et al. | Two-Stage Time-Varying Vibration Compensation for Coherent LiDAR Based on the Adaptive Differential Evolution Method | |
| Tan et al. | A Fast Algorithm for SAR Imaging of Ground Moving Target Based on TRP-DPT and NUFFT |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WD01 | Invention patent application deemed withdrawn after publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20200612 |