CN117388819A

CN117388819A - Laser radar timing correction method, device and equipment

Info

Publication number: CN117388819A
Application number: CN202311606936.4A
Authority: CN
Inventors: 蒋难得; 谷迁; 谢理; 胡攀攀
Original assignee: Wuhan Wanji Photoelectric Technology Co Ltd
Current assignee: Wuhan Wanji Photoelectric Technology Co Ltd
Priority date: 2023-11-27
Filing date: 2023-11-27
Publication date: 2024-01-12

Abstract

The method comprises the steps of carrying out feature extraction on echo signals based on a threshold value to obtain a plurality of geometric feature quantities used for determining the form of the echo signals, generating feature extraction results of the echo signals based on the geometric feature quantities, obtaining timing correction corresponding to the feature extraction results from preset feature correction data based on the feature extraction results, wherein the preset feature correction data is obtained by determining sample timing correction based on the sample feature extraction results and the sample echo signals, carrying out timing correction processing on the laser radar based on the timing correction, solving the problem of non-monotonous feature quantities and timing correction in the timing correction, reducing the dispersion of the feature quantities and the timing correction, improving the ranging accuracy, enabling the timing correction relation to solve the reusability of channels and the reusability of radars of the same model, and greatly improving the implementation efficiency of engineering.

Description

Laser radar timing correction method, device and equipment

Technical Field

The present disclosure relates to the field of radar ranging, and in particular, to a method, an apparatus, and a device for laser radar timing correction.

Background

Due to the characteristics of high resolution, good concealment, strong anti-interference capability and the like, the laser ranging technology has been widely applied to the military, production and life fields. The distance measurement is performed on the object to be measured based on the ToF (Time of Flight) principle, and the timing Time is required to be accurate for the distance measurement. The flight time is calculated by the timing unit, the timing accuracy is related to the reflectivity (material) of the measured object besides the resolution of the timing unit, and the timing time of the echo needs to be corrected and compensated, so that the real distance of the measured object can be accurately calculated by the timing values of different reflecting surfaces (materials).

In the prior art, the timing time of the echo is corrected and compensated by adopting a proper characteristic quantity (such as pulse width, peak value, multiple pulse width, slope and the like) and a proper correction method. But the selection of the characteristic quantity is required to be in a range, and the monotonous and small dispersion degree is realized; the correction method is required to be capable of adapting to the signal distribution rule well. For sipms, the response speed of the sipms to echo photons is high, the response characteristic is not a simple linear relation, but a poisson index relation, and the echo characteristic quantity of the sipms may not be monotonic characteristic for different optical path structures.

Therefore, in order to facilitate SiPM timing accuracy and improve target ranging accuracy, there is a need for a laser radar timing correction method that solves the problem of non-monotonic characteristic quantity and excessive dispersion of correction values corresponding to the characteristic quantity.

Disclosure of Invention

The application provides a laser radar timing correction method, device and equipment, wherein the relation between an echo signal and correction quantity is established in advance, when the radar is used, the timing correction quantity value is determined based on the relation to carry out deviation correction, and the problems of non-monotonous characteristic quantity and overlarge dispersion of correction values corresponding to the characteristic quantity in radar ranging are solved.

According to an aspect of the present application, a laser radar timing correction method is provided, the method includes:

acquiring an echo signal;

determining a front edge time and a back edge time based on a preset threshold value, performing feature extraction on the echo signals based on the preset threshold value, the front edge time and the back edge time to obtain a plurality of geometric feature quantities used for determining the form of the echo signals, and generating a feature extraction result of the echo signals based on the geometric feature quantities;

based on the feature extraction result, timing correction corresponding to the feature extraction result is obtained from preset feature correction data; the preset characteristic correction data is obtained by determining based on a sample characteristic extraction result and a sample timing correction of a sample echo signal, the sample characteristic extraction result is generated based on a sample geometric characteristic quantity for determining the form of the sample echo signal in the echo signal sample set, and the sample geometric characteristic quantity is obtained by extracting characteristics of the echo signal sample set based on a sample threshold value, sample leading time and sample trailing time;

And performing timing correction processing on the laser radar based on the timing correction amount.

In one possible implementation, the preset threshold includes a first threshold and a second threshold, the first threshold being greater than the second threshold,

the determining the leading edge time and the trailing edge time based on the preset threshold, and performing feature extraction on the echo signal based on the preset threshold, the leading edge time and the trailing edge time to obtain a plurality of geometric feature quantities for determining the form of the echo signal, and generating a feature extraction result of the echo signal based on the geometric feature quantities, including:

acquiring the time of an echo signal at the first threshold value, acquiring a first front edge time and a first back edge time, and acquiring the time of the echo signal at the second threshold value, and acquiring a second front edge time and a second back edge time, wherein the first front edge time is earlier than the first back edge time, and the second front edge time is earlier than the second back edge time;

performing feature extraction on the echo signals based on the first threshold value, the second threshold value, the first front edge time, the first back edge time, the second front edge time and the second back edge time to obtain a plurality of geometric feature quantities;

And combining the geometric feature quantities according to a preset combination relation to obtain a feature combination result, and taking the feature combination result as a feature extraction result of the echo signal.

In one possible implementation manner, the combining the geometric feature quantities according to a preset combination relationship to obtain a feature combination result, and taking the feature combination result as a feature extraction result of the echo signal includes:

combining the geometric feature quantities according to a preset combination relation to obtain a plurality of combination results;

and obtaining the characteristic combination result based on at least one of the plurality of combination results, and taking the characteristic combination result as a characteristic extraction result of the echo signal.

In one possible implementation manner, the obtaining, based on the feature extraction result, a timing correction corresponding to the feature extraction result from preset feature correction data includes:

and inquiring the preset characteristic correction data based on the characteristic extraction result to obtain the timing correction corresponding to the characteristic extraction result.

In one possible implementation, the sample threshold includes a first sample threshold and a second sample threshold, the first sample threshold being greater than the second sample threshold,

The method further comprises the steps of:

acquiring an echo signal sample set, wherein the echo signal sample set is an echo signal received by a laser radar under different distances after transmitting signals to different reflecting surfaces;

acquiring the time of each sample echo signal at the first sample threshold value, obtaining a first sample leading edge time and a first sample trailing edge time, and acquiring the time of each sample echo signal at the second threshold value, obtaining a second sample leading edge time and a second sample trailing edge time, wherein the first sample leading edge time is earlier than the first sample trailing edge time, and the second sample leading edge time is earlier than the second sample trailing edge time;

performing feature extraction on each sample echo signal based on the first sample threshold, the second sample threshold, the first sample leading edge time, the first sample trailing edge time, the second sample leading edge time and the second sample trailing edge time to obtain a plurality of sample geometric feature quantities for determining the morphology of each sample echo signal;

generating a sample feature extraction result of each sample echo signal according to a plurality of sample geometric feature quantities of the morphology of each sample echo signal;

And determining and obtaining the preset characteristic correction data according to the sample characteristic extraction result of each sample echo signal and the sample timing correction of each sample echo signal.

In one possible implementation manner, the generating the sample feature extraction result of each sample echo signal according to the plurality of sample geometric feature quantities of the morphology of each sample echo signal includes:

and combining a plurality of geometric feature quantities of each sample echo signal according to the preset combination relation to obtain a plurality of combination results, and obtaining a sample feature combination result of each sample echo signal based on at least one of the plurality of combination results as the feature of each sample echo signal.

In one possible implementation, the method further includes:

a sample timing correction for each echo signal sample is determined based on the speed of light, the distance of each sample echo signal, and the first sample lead time of each sample echo signal.

In one possible implementation manner, after the generating the sample feature extraction result of each sample echo signal according to the plurality of sample geometric feature quantities of the morphology of each sample echo signal, the method further includes:

Encoding the characteristics of each sample echo signal to obtain a sample characteristic code of each sample echo signal;

correspondingly, the determining, according to the sample feature extraction result of each sample echo signal and the sample timing correction of each sample echo signal, the preset feature correction data includes:

and determining and obtaining the preset characteristic correction data according to the sample characteristic code of each sample echo signal and the sample timing correction of each sample echo signal, wherein the sample characteristic code of each sample echo signal is used as an index of the sample timing correction of each sample echo signal in the preset characteristic correction data so as to inquire the timing correction according to the characteristic code.

based on the preset encoding mode of the characteristic correction amount data, encoding the characteristic extraction result to obtain the characteristic code of the echo signal;

and taking the characteristic code of the echo signal as an index, and inquiring the preset characteristic correction quantity data to acquire the timing correction quantity.

In one possible implementation manner, the performing timing correction processing on the laser radar based on the timing correction amount includes:

acquiring parameters of a laser pulse signal and system parameters of a laser radar;

determining and obtaining a target timing correction amount of the laser radar based on the parameters of the laser pulse signals, the system parameters of the laser radar and the timing correction amount according to the laser radar distance correction relation;

and performing timing correction processing on the laser radar based on the target timing correction amount of the laser radar.

In one possible implementation, the parameters of the laser pulse signal include a laser pulse signal transmission start time and an echo signal timing end time, the system parameters of the laser radar include a laser radar internal zero point and a laser radar external zero point,

the determining, according to the laser radar distance correction relationship, a target timing correction amount of the laser radar based on the parameter of the laser pulse signal, the system parameter of the laser radar and the timing correction amount includes:

and determining and obtaining the target timing correction of the laser radar based on the laser pulse signal emission starting point time, the echo signal timing end point time, the laser radar internal zero point, the laser radar external zero point and the timing correction according to the laser radar distance correction relation.

In another aspect, there is provided a lidar timing correction device, the device comprising:

the data acquisition module is used for acquiring echo signals;

the characteristic extraction module is used for determining a front edge time and a back edge time based on a preset threshold value, carrying out characteristic extraction on the echo signals based on the preset threshold value, the front edge time and the back edge time to obtain a plurality of geometric characteristic quantities used for determining the form of the echo signals, and generating a characteristic extraction result of the echo signals based on the geometric characteristic quantities;

the timing correction amount acquisition module is used for acquiring timing correction amount corresponding to the feature extraction result from preset feature correction amount data based on the feature extraction result; the preset characteristic correction data is obtained by determining based on a sample characteristic extraction result and a sample timing correction of a sample echo signal, the sample characteristic extraction result is generated based on a sample geometric characteristic quantity for determining the form of the sample echo signal in the echo signal sample set, and the sample geometric characteristic quantity is obtained by extracting characteristics of the echo signal sample set based on a sample threshold value, sample leading time and sample trailing time;

And the timing correction processing module is used for performing timing correction processing on the laser radar based on the timing correction.

In a possible implementation manner, the preset threshold includes a first threshold and a second threshold, where the first threshold is greater than the second threshold, and the feature extraction module is configured to:

In one possible implementation manner, the feature extraction module is configured to:

In one possible implementation manner, the timing correction amount acquisition module is configured to:

the timing correction amount acquisition module includes a characteristic correction amount data determination unit configured to:

In one possible implementation manner, the characteristic correction amount data determining unit is configured to:

In one possible implementation manner, the timing correction processing module is configured to:

the timing correction processing module is further used for:

In another aspect, there is provided an electronic device comprising a processor and a memory, the memory storing at least one instruction or at least one program, the at least one instruction or the at least one program being loaded and executed by the processor to implement the lidar timing correction method of any of the above aspects.

In another aspect, a computer readable storage medium having stored therein at least one instruction or at least one program loaded and executed by a processor to implement a lidar timing correction method according to any of the above aspects is provided.

In another aspect, a computer program product or computer program is provided, the computer program product or computer program comprising computer instructions stored in a computer readable storage medium. The processor of the electronic device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions to cause the electronic device to perform the lidar timing correction method of any of the aspects described above.

According to the method and the device, the echo signals are subjected to feature extraction based on the threshold value to obtain a plurality of geometric feature quantities used for determining the form of the echo signals, the feature extraction results of the echo signals are generated based on the geometric feature quantities, the timing correction corresponding to the feature extraction results is obtained from the preset feature correction data based on the feature extraction results, the preset feature correction data are obtained by determining the sample timing correction based on the sample feature extraction results and the sample echo signals, the timing correction processing is carried out on the laser radar based on the timing correction, the problem that the feature quantities and the timing correction are not monotonous in the timing correction is solved, the dispersion degree of the feature quantities and the timing correction is reduced, the ranging accuracy is improved, the multiplexing of channels and the multiplexing of radars of the same model can be solved by the timing correction relation, and the implementation efficiency of engineering is greatly improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic flow chart of a laser radar timing correction method according to an embodiment of the present application;

FIG. 2 is a schematic illustration of a non-monotonic echo provided by an embodiment of the present application;

FIG. 3 is a schematic diagram of timing correction provided in an embodiment of the present application for different optical path structure feature quantities;

FIG. 4 is a schematic diagram of a lidar transmit pulse and echo signal provided by an embodiment of the present application;

FIG. 5 is a schematic diagram of the difference in echo timing of different reflection surfaces at the same distance according to the embodiment of the present application;

FIG. 6 is a schematic diagram of echo signal characteristics provided by an embodiment of the present application;

FIG. 7 is a schematic diagram of feature correction data provided by an embodiment of the present application;

FIG. 8 is another schematic diagram of feature correction data provided by an embodiment of the present application;

FIG. 9 is a schematic diagram of a feature correction data discontinuity solution provided in an embodiment of the present application

Fig. 10 is a block diagram of a laser radar timing correction apparatus according to an embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present application based on the embodiments herein.

The embodiment of the application provides a laser radar timing correction method. SiPM (Silicon photomultiplier ) arrays are gradually becoming the mainstream choice for multi-line vehicle-mounted lidar due to its high gain, high sensitivity, low bias voltage, insensitivity to magnetic fields, compact structure, etc. with VCECL (Vertical Cavity Surface Emitting Laser ) arrays. The time-of-flight measurement ToF (Time of Flight) is to obtain the target distance by measuring the round-trip flight time of the laser pulse between the laser source and the target surface, and the distance measurement principle is simple and clear, and the pulse laser pulse width is narrow, the duration is short, the instantaneous power is high, and thus the detection distance is long. SiPM lidars range an object under test based on time-of-flight principles. The Time of flight is calculated by a timing unit, which may be an ADC (Analog-to-Digital Converter ) or a TDC (Time-to-Digital Converters, time-to-digital converter). The timing unit marks the laser pulse emission time as a timing starting point, extracts a certain time point in an echo formed by reflecting the emission pulse by the measured object as a timing end point, and the time between the timing starting point and the timing end point is light flight time. Referring to fig. 1, the laser radar timing correction method includes steps S101 to S107.

In step S101, an echo signal is acquired.

In one possible implementation, the echo signal is that after the laser pulse emitted by the radar encounters the target object in the propagation process, the target object reflects and scatters the laser pulse, and the laser pulse enters the radar to form an echo pulse signal, and the echo pulse signal is further processed to obtain target parameters such as distance, azimuth, speed, shape and the like.

In one possible implementation, for sipms, the response speed of the sipms to echo photons is fast, the response characteristic is not a simple linear relationship, but a poisson exponential relationship, and the echo characteristic quantity of the sipms may not be monotonic for different optical path structures. As shown in fig. 2, the pulse width is taken as a characteristic quantity, and in fig. 2, the echo trailing edge has multiple intersections, and the timing leading edge and the pulse width have the condition of one pulse width to multiple leading edges.

In one possible implementation manner, the SiPM has probability and certain randomness on photon excitation, which is expressed as front-back jitter on echo, and the front-back jitter of the echo signal can be caused by adding instability of a circuit, so that the dispersion of timing correction quantity corresponding to the feature quantity becomes larger due to superposition of the two components, and the accuracy of timing correction is reduced. As shown in fig. 3, the SiPM lidar timing correction may have a problem of non-monotonic characteristic quantity (one pulse width corresponds to AB two timing correction amounts) and a problem of large dispersion of the timing correction value corresponding to the characteristic quantity (the range CD of the timing correction value corresponding to the same pulse width is too large) for different optical path structures.

In one possible implementation manner, the time of flight is calculated by a timing unit (ADC or TDC), the timing unit marks the emission time of the laser pulse as a timing start point, extracts a certain time point in an echo formed by reflecting the emission pulse by the object to be measured and marks the time point as a timing end point, and the time between the timing start point and the timing end point is the optical time of flight. As shown in fig. 2, the a-point transmission time is denoted as a timing start point, and Pi is a point on the echo signal. In theory, any point on the echo signal can be used as a timing end point, and in actual use, a point with sharp characteristics is found to be used as the timing end point. Specifically, the threshold V1 is used for cutting off the echo signal, so that the front edge time B and the back edge time C, B or C can be used as timing end points, and BC is recorded as echo pulse width; the peak point D may also be taken as the timing end point.

In one possible implementation, as shown in fig. 4, at the same distance, the measured objects with different emissivity have different timing values reflected by SiPM detection. If the front edge time is counted, the timing value of the strong reflecting surface is smaller, and the timing value of the weak reflecting surface is larger. If the peak value is counted, the peak value point of the strong and weak reflection surfaces fluctuates in a certain range. In practice, the measured object distances are the same, and the theoretical timing times should be equal, so that correction and compensation are needed to be performed on the timing times of the echoes, so that the real distances of the measured objects can be accurately calculated by the timing values of different reflecting surfaces (materials). The threshold is selected in relation to the echo signal, the second threshold V2 is required to ensure that the noise floor of the echo signal is not cut, preferably at the falling edge intersection (low) as shown in fig. 3, and the first threshold V1 is generally selected at the falling edge intersection (high) as shown in fig. 3 to reduce the correction dispersion of the signal.

In the implementation mode, the echo signals are acquired, and the proper threshold value is selected, so that the characteristic extraction of the echo signals is conveniently carried out by setting the proper threshold value later.

In step S103, a front edge time and a back edge time are determined based on a preset threshold, and feature extraction is performed on the echo signal based on the preset threshold, the front edge time and the back edge time, so as to obtain a plurality of geometric feature quantities for determining the form of the echo signal, and a feature extraction result of the echo signal is generated based on the geometric feature quantities.

In one possible implementation, the leading edge time and the trailing edge time of the first threshold and the second threshold refer to four time values corresponding to the intersection points on the echo obtained by cutting the echo of the echo signal through two different voltage values in the processing process after the reflected photon is detected by the SiPM. Specifically, as shown in fig. 5, the first threshold is V1 in the figure, and the second threshold is V2 in the figure. Cutting echo signals by using V1 to obtain first front edge time T1 and first back edge time T2; the echo signal is cut by V2, and a second front edge time T3 and a second back edge time T4 are obtained.

In one possible implementation, the feature extraction is performed on the echo signal based on a first threshold V1, a second threshold V2, a first front edge time T1, a first back edge time T2, a second front edge time T3, and a second back edge time T4, and a plurality of geometric feature quantities for determining a morphology of the echo signal are calculated. Specifically, the plurality of geometric feature amounts may be:

The leading edge difference = T1-T3,

trailing edge difference = T4-T2,

second threshold pulse width=t4-T3,

triangular peak = (V1-V2)/(T4-T3)/(T1-T3) + (T4-T2) ],

the leading edge slope= (T1-T3)/(V1-V2),

trailing edge slope= (T4-T2)/(V1-V2),

when the second threshold is not cut, t1=t2=0, at this time, the leading edge difference=0, the trailing edge difference=0, and the triangular peak= (V1-V2) × (T4-T3)/2.

In this implementation manner, a calculation manner for calculating different geometric feature amounts may be established in advance, so as to obtain a plurality of geometric feature amounts for determining the form of the echo signal, and a feature extraction result of the echo signal is generated based on the geometric feature amounts, so as to ensure that the generated feature extraction result uniquely determines the echo form.

In a possible implementation manner, the combining the geometric feature quantities according to a preset combination relationship to obtain a feature combination result, and taking the feature combination result as a feature extraction result of the echo signal includes:

In one possible implementation, three of the plurality of geometric feature quantities are combined according to a preset combination relationship to obtain a geometric combination of uniquely determined echo morphology, and the geometric combination is represented by a, b and c. Specifically, a may be taken as a leading edge difference, c as a trailing edge difference, and b as a second threshold pulse width; taking a as a front edge difference, c as a rear edge difference and b as a triangular peak value; taking a as a front slope, taking c as a back slope, and taking b as a second threshold pulse width.

In one possible implementation, the combination of the geometric quantities that uniquely determine the echo morphology obtained by combining three of the geometric characteristic quantities according to the preset combination relationship may be other combinations than the three listed above, or other three combination quantities obtained by cross-combining the above combinations.

In this implementation manner, a combination manner of different geometric feature quantities may be established in advance, so as to obtain a plurality of combinations for determining the morphology of the echo signal, and a feature extraction result of the echo signal is generated based on at least one combination of the combinations, so that the feature extraction result is convenient to encode subsequently.

In step S105, based on the feature extraction result, a timing correction amount corresponding to the feature extraction result is obtained from preset feature correction amount data; the preset characteristic correction data is obtained by determining based on a sample characteristic extraction result and a sample timing correction of a sample echo signal, the sample characteristic extraction result is generated based on a sample geometric characteristic quantity for determining the form of the sample echo signal in the echo signal sample set, and the sample geometric characteristic quantity is obtained by extracting characteristics of the echo signal sample set based on a sample threshold value, sample leading edge time and sample trailing edge time.

In one possible implementation, an index is obtained based on the feature extraction result, and the preset feature correction amount data is queried to obtain a timing correction amount corresponding to the index.

In one possible implementation, different ways of indexing may be devised, pointing to timing corrections of the corresponding index.

In the implementation mode, the feature correction data is established in advance, the feature correction data is queried based on the feature extraction result, the timing correction corresponding to the feature extraction result is obtained, the feature extraction result corresponds to the timing correction one by one, and the problem that the feature quantity and the timing correction are not monotonous in the timing correction is solved.

The method further comprises the steps of:

In one possible implementation, the sample threshold includes a first sample threshold and a second sample threshold, the first sample threshold being greater than the second sample threshold, the first sample threshold being the same value as the first threshold, the second sample threshold being the same value as the second threshold.

In one possible implementation, feature extraction is performed on each sample echo signal based on a first sample threshold, a second sample threshold, a first sample lead time, a first sample trailing time, a second sample lead time, and a second sample trailing time, resulting in a plurality of sample geometric feature quantities for determining a morphology of each sample echo signal. Specifically, the feature extraction is performed in the same manner as in step S103, and the sample geometric feature amount is calculated in the same manner as in step S103.

In the implementation mode, echo signals received under different distances after signals are transmitted to different reflecting surfaces by the laser radar are utilized to obtain echo signal sample sets, characteristic correction quantity data are established based on the echo signal sample sets, characteristic extraction results of each echo signal sample in the graph are in one-to-one correspondence with timing correction quantities, timing correction is carried out on the laser radar based on the characteristic correction quantity data, and ranging accuracy is improved.

In one possible implementation, the first sample threshold, the second sample threshold, the first sample lead time, the second sample lead time, and the second sample lead time obtain a plurality of sample geometric feature amounts of each sample echo signal, combine the plurality of sample geometric feature amounts to obtain a plurality of combined results, and obtain a sample feature combination result of each sample echo signal based on at least one of the plurality of combined results. Specifically, the combination of the plurality of sample geometric feature amounts is the same as the combination of the plurality of geometric feature amounts in step 103.

In the implementation manner, the sample characteristic combination result of each sample echo signal is used as the characteristic of each sample echo signal, the characteristic is used for distinguishing different sample echo signals, the calculation amount of the echo signals for indexing the characteristic correction amount data is reduced, the ranging accuracy is improved, and the timing correction duration is reduced.

In one possible implementation, a sample timing correction for each echo signal sample is determined based on the speed of light, the distance of each sample echo signal, and the first sample lead time of each sample echo signal.

In one possible implementation, echo signals received at different distances after the laser radar transmits signals to different reflection surfaces are acquired, and an echo signal sample set is formed. Specifically, each echo signal sample corresponds to a timing correction amount delta T,

δT＝2L/C-T1

wherein L is the true distance value of the corresponding echo, C is the speed of light, and T1 is the first sample front time.

In this implementation, according to the relation between the speed of light, the distance of each sample echo signal and the first sample leading edge time of each sample echo signal and the sample timing correction amount of each echo signal sample, the sample timing correction amount of each echo signal sample is calculated, the sample timing correction amount is calculated by selecting a unified parameter, and the error of the sample timing correction amount is reduced.

In one possible implementation, the sample feature extraction result of each sample echo signal is encoded, so as to obtain a graph ID (Identity document, identity) of each sample echo signal. Specifically, the sample feature extraction results are represented by b, a and c, and each sample feature extraction result is converted into 16 system, and are combined into new numbers in a bit-by-bit sequence, such as b=0x1770, a=0x01f4, c=0x0384, and id=0x 177001f40384, wherein b, a and c can be converted by adopting a certain dimension, because the resolution of the ADC and the TDC has a precision problem when extracting the timing value, and b can be converted by b=b/32 because the precision of the TDC can only be 32 ps; when the pulse width variation width of the signal is large, the compression encoding range may be divided by the dimension.

In one possible implementation, it is preferable to use 1 byte each for b, a, c for the encoded representation.

In one possible implementation manner, the preset characteristic correction data is determined according to a sample characteristic extraction result of each sample echo signal and a sample timing correction amount of each sample echo signal. Specifically, the sample characteristic extraction result of each sample echo signal is encoded to obtain a graph ID of each sample echo signal, and the relationship between the graph ID and the sample timing correction amount is established.

In one possible implementation, as shown in fig. 7, a relationship between the map ID and the sample timing correction amount is established: converting each group ac and corresponding delta T into image pixels by taking b as an image index; for image b, the pixel values at rank ac are determined by multiple sets of non-zero ac- δT weights; for the image b, determining the position with the pixel value of 0 at the row-column ac by adopting a local neighborhood method and a full-image mean method; for image b, the pixel value of the whole image is 0, and then the neighborhood average value of the image b-1 and the image b+1 is adopted for determination.

In one possible implementation, for example, take a as the leading edge difference, take c as the trailing edge difference, take b as the second threshold pulse width, b=6000 ps, a=500 ps, c=800 ps, δt= -600ps. Then the graph id= (6000 > > 5) | (500 > > 5) | (800 > > 5) =0xb80F 19. Specifically, for the echo pattern of 0xB80F19, the timing correction amount is at the image index of 0xB8, row 0x0F, column 0x19, and the pixel value is (-600+8000)/32=231, with 8000 being the maximum timing correction compensation amount absolute value.

In one possible implementation, this may cause problems with resampling and discontinuity of the bac due to the limited number of echo signal samples acquired. Specifically, for a given b, the same graph ID (bac) of the acquired echo signal corresponds to a plurality of δts, i.e. repeated sampling, where a weighted determination may be employed. The weighting method may be a mean value or a weighted value of a preset weight. Specifically, as shown in fig. 8, for a given b, the acquired echo signal cannot cover the pixels at each row and column of the whole image, i.e. the problem of sampling discontinuity, the local neighborhood non-0 pixel values are averaged and δt (b, a=3, c=3) =average {237,235,234,230}.

In one possible implementation, as shown in fig. 8, at a=1, c=1, the local neighborhoods are all 0 due to the sampling discontinuity, then all non-zero pixel values of the entire image b are averaged for a given.

In one possible implementation, as shown in fig. 9, due to the sampling discontinuity, the whole sub-map pixel point of the image b is all 0, and then the neighborhood average at the corresponding row and column of the two maps is used to determine through the b-1 and b+1 images.

In this implementation, the preset characteristic correction data is determined according to the sample characteristic code of each sample echo signal and the sample timing correction of each sample echo signal. Compared with the method of the low threshold pulse width-timing correction under the monotone condition, the original timing correction is determined by the average value of the same low threshold pulse width timing correction, the interval of the real timing correction is compressed into 1 point, when the signal jitter is larger, the fluctuation range of the real timing correction is larger, and the distance calculated by the 1 average value point is larger in deviation, namely the dispersion is larger. By adopting the method, for the same low-threshold pulse width b, a plurality of different timing correction amounts are mapped to different pixel points through a and c, so that the dispersion of the timing correction amounts is compressed, and the corresponding relation between the graph ID and the timing correction amounts is determined. As many image sequences b as possible and pixel values in the images b as possible can be obtained by acquiring echo signals of sufficiently different distances from different reflection surfaces. The distance measurement accuracy can be improved.

In step S107, a time correction process is performed on the laser radar based on the time correction amount.

In one possible implementation manner, the feature extraction result is encoded based on a preset encoding manner of the feature correction amount data, so as to obtain a feature encoding chart ID of the echo signal, and a corresponding image b is found through the chart ID, and pixel values at corresponding rows and columns in the corresponding image are converted into the timing correction amount δt.

In this implementation, the preset characteristic correction data is determined according to the sample characteristic code of each sample echo signal and the sample timing correction of each sample echo signal. Compared with the method of low threshold pulse width-timing correction in the monotone case, the original timing correction is determined by the average value of the same low threshold pulse width timing correction, the interval of the real timing correction is compressed to 1 point, and when the signal jitter is larger, the real timing correction is real

In one possible implementation, the timing correction in the scheme refers to the correction of δt, and the timing deviation correction excluding the internal and external zero points, which belong to the system parameters of the lidar, may be determined by calibration.

In the implementation mode, according to the laser radar distance correction relation, parameters of laser pulse signals and system parameters of the laser radar in timing correction are acquired, and accurate timing correction of the radar can be obtained.

In one possible implementation manner, in the lidar range correction relationship, the timing time given by the timing unit needs to be converted according to the following relationship:

T _{true sense} ＝T _e -T _s -δT-T _I0 -T _E0

Wherein:

T _{true sense} Real timing time, through which accurate distance can be calculated;

T _s the starting time of laser pulse emission;

T _e a timing end point for laser pulse echo, such as T3 described above;

δT is the timing correction

T _I0 For internal zero of the corresponding channel, generally means from transmission to actual execution of transmissionInternal delay of operation, i.e. internal zero;

T _E0 an external time delay, i.e. an external zero, aligned with respect to each channel of the radar's global coordinate system.

In the implementation mode, the laser radar is corrected according to the distance correction relation of the laser radar, so that the ranging accuracy is improved.

In one possible implementation, for an on-board SiPM lidar, the multiple lines are typically present, and there is a deviation in the characteristics of the multiple channel signals that are similar in design. In particular, the graph ID-timing modifier relationship may be a collection of multiple wire bundles, common to multiple channels.

In one possible implementation, the graph ID-timing correction relationship set may be reusable for similar echo signal characteristics for the same model of vehicle SiPM radar. Namely, through engineering means, as long as a complete graph ID-timing correction relation is established, a correction relation can be unified by a plurality of wire harnesses of the same radar, and even a plurality of radars of the same product can share the correction relation.

In one possible implementation, the lidar timing correction method is not limited to SiPM radar, but is applicable to APD (Avalanche Photo Diode ) radar.

In one exemplary embodiment, the echo signals are feature extracted based on a threshold, a leading edge time and a trailing edge time, resulting in a plurality of geometric feature quantities for determining the morphology of the echo signals; carrying out unique characterization on the echo signal according to the geometric quantity, and carrying out graph ID coding; obtaining timing correction of a corresponding map ID from a preset characteristic correction map; the method comprises the steps that a preset characteristic correction map is obtained by determining based on a sample characteristic extraction result and a sample timing correction of a sample echo signal, the characteristic correction map is supplemented by adopting an image neighborhood mean method, the sample characteristic extraction result is generated based on sample geometric characteristic quantity used for determining the form of the sample echo signal in an echo signal sample set, and the sample geometric characteristic quantity is obtained by carrying out characteristic extraction on the echo signal sample set based on a sample threshold value, sample front time and sample back time; and performing timing correction processing on the laser radar based on the timing correction amount.

In the implementation mode, a graph ID coding mode is adopted, timing correction is mapped to pixels in an image row and column, and a graph ID-timing correction one-to-one relationship is established; the image neighborhood mean method is adopted to deduce and supplement the discontinuity of sampling, so that the integrity of the graph ID can be effectively improved; the graph ID-timing correction quantity corresponds to each other one by one, so that the problem that the characteristic quantity and the timing correction quantity are not monotonous in the timing correction can be solved; the relation of the graph ID and the timing correction can solve the reusability of channels and even the reusability of radars of the same model, and the implementation efficiency of engineering is greatly improved.

Fig. 10 shows a schematic structural diagram of a laser radar timing correction apparatus 1000 provided in an embodiment of the present application, where the apparatus has a function of implementing the laser radar timing correction method in the foregoing method embodiment, and the function may be implemented by hardware or may be implemented by executing corresponding software by hardware. As shown in fig. 10, the apparatus may include:

a data acquisition module 1001, configured to acquire an echo signal;

the feature extraction module 1002 is configured to determine a front edge time and a back edge time based on a preset threshold, perform feature extraction on the echo signal based on the preset threshold, the front edge time and the back edge time, obtain a plurality of geometric feature quantities for determining a morphology of the echo signal, and generate a feature extraction result of the echo signal based on the geometric feature quantities;

A timing correction amount acquisition module 1003, configured to acquire a timing correction amount corresponding to the feature extraction result from preset feature correction amount data based on the feature extraction result; the preset characteristic correction data is obtained by determining based on a sample characteristic extraction result and a sample timing correction of a sample echo signal, the sample characteristic extraction result is generated based on a sample geometric characteristic quantity for determining the form of the sample echo signal in the echo signal sample set, and the sample geometric characteristic quantity is obtained by extracting characteristics of the echo signal sample set based on a sample threshold value, sample leading time and sample trailing time;

and the timing correction processing module 1004 is used for performing timing correction processing on the laser radar based on the timing correction.

In a possible implementation manner, the preset threshold includes a first threshold and a second threshold, where the first threshold is greater than the second threshold, and the feature extraction module 1002 is configured to:

In one possible implementation manner, the feature extraction module 1002 is configured to:

In one possible implementation, the timing correction amount acquisition module 1003 is configured to:

The timing correction amount acquisition module 1003 includes a characteristic correction amount data determination unit configured to:

In one possible implementation, the timing correction processing module 1004 is configured to:

the timing correction processing module 1004 is further configured to:

It should be noted that, in the apparatus provided in the foregoing embodiment, when implementing the functions thereof, only the division of the foregoing functional modules is used as an example, in practical application, the foregoing functional allocation may be implemented by different functional modules, that is, the internal structure of the device is divided into different functional modules, so as to implement all or part of the functions described above. In addition, the embodiments of the apparatus and the method provided in the foregoing embodiments belong to the same concept, and specific implementation processes of the embodiments of the laser radar timing correction method are detailed in the embodiments and are not described herein again.

In an exemplary embodiment, there is further provided a laser radar, which is composed of a power driving unit, a transmitting unit, a receiving unit, a processing unit, a timing unit and a timing correction unit, wherein the timing unit extracts a timing leading edge and a timing trailing edge by using two thresholds, and the timing correction unit performs timing correction by using the method, and the timing unit may be an ADC or a TDC.

The embodiment of the application provides an electronic device, which comprises a processor and a memory, wherein at least one instruction or at least one section of program is stored in the memory, and the at least one instruction or the at least one section of program is loaded and executed by the processor to realize any laser radar timing correction method provided by the embodiment of the method.

The memory may be used to store software programs and modules that the processor executes to perform various functional applications and data processing by executing the software programs and modules stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, application programs required for functions, and the like; the storage data area may store data created according to the use of the device, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device. Accordingly, the memory may also include a memory controller to provide access to the memory by the processor.

Embodiments of the present application also provide a computer readable storage medium that may be disposed in an electronic device to store at least one instruction or at least one program for implementing a lidar timing correction method, where the at least one instruction or the at least one program is loaded and executed by the processor to implement any of the lidar timing correction methods provided by the method embodiments described above.

Alternatively, in the present embodiment, the storage medium may include, but is not limited to: a U-disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a removable hard disk, a magnetic disk, or an optical disk, or other various media capable of storing program codes.

It should be noted that: the foregoing sequence of the embodiments of the present application is only for describing, and does not represent the advantages and disadvantages of the embodiments. And the foregoing description has been directed to specific embodiments of this specification. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for the device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments in part.

It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program for instructing relevant hardware, where the program may be stored in a computer readable storage medium, and the storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.

The foregoing description of the preferred embodiments of the present application is not intended to limit the invention to the particular embodiments of the present application, but to limit the scope of the invention to the particular embodiments of the present application.

Claims

1. A method for laser radar timing correction, the method comprising:

acquiring an echo signal;

2. The lidar timing correction method of claim 1, wherein the predetermined threshold comprises a first threshold and a second threshold, the first threshold being greater than the second threshold,

3. The method for correcting laser radar timing according to claim 2, wherein,

the combining the geometric feature quantities according to a preset combination relation to obtain a feature combination result, and taking the feature combination result as a feature extraction result of the echo signal, including:

4. The method for correcting laser radar timing according to claim 1, wherein,

the step of obtaining the timing correction corresponding to the feature extraction result from preset feature correction data based on the feature extraction result includes:

5. The lidar timing correction method of claim 1 wherein the sample threshold comprises a first sample threshold and a second sample threshold, the first sample threshold being greater than the second sample threshold,

the method further comprises the steps of:

6. The method for laser radar timing correction according to claim 5, wherein,

the generating a sample feature extraction result of each sample echo signal according to the plurality of sample geometric feature quantities of the morphology of each sample echo signal comprises:

7. The lidar timing correction method of claim 5, further comprising:

8. The method for laser radar timing correction according to claim 5, wherein,

after generating the sample feature extraction result of each sample echo signal according to the plurality of sample geometric feature quantities of the morphology of each sample echo signal, the method further comprises:

9. The method for laser radar timing correction according to claim 8, wherein,

10. The method for correcting laser radar timing according to claim 1, wherein,

the timing correction processing for the laser radar based on the timing correction amount comprises the following steps:

11. The method of claim 10, wherein the parameters of the laser pulse signal include a start time of laser pulse signal emission and an end time of laser pulse signal timing, the system parameters of the laser radar include a laser radar internal zero point and a laser radar external zero point,

12. A lidar timing correction device, the device comprising:

the data acquisition module is used for acquiring echo signals;

13. An electronic device comprising a processor and a memory, wherein at least one instruction or at least one program is stored in the memory, the at least one instruction or the at least one program being loaded and executed by the processor to implement the lidar timing correction method of any of claims 1 to 11.

14. A computer readable storage medium having stored therein at least one instruction or at least one program, the at least one instruction or the at least one program being loaded and executed by a processor to implement the lidar timing correction method of any of claims 1 to 11.