CN117686995A - Laser radar echo time identification method and device and communication equipment - Google Patents
Laser radar echo time identification method and device and communication equipment Download PDFInfo
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Abstract
The application is applicable to the technical field of radar ranging, and provides a method and a device for identifying laser radar echo time and communication equipment, wherein the method comprises the following steps: performing waveform identification on the laser echo to obtain a waveform identification result, wherein the waveform identification result is used for indicating whether the laser echo is a saturated echo or not; and selecting a corresponding time discrimination strategy according to the waveform discrimination result to discriminate the echo time of the laser echo. By the method, the accuracy of the obtained echo time can be improved.
Description
Technical Field
The application belongs to the technical field of radar ranging, and particularly relates to a laser radar echo time identification method, a laser radar echo time identification device, communication equipment and a computer readable storage medium.
Background
Lidar is able to detect its own distance from a target by emitting a laser beam. The characteristics of the laser radar enable the laser radar to be applied to the fields of unmanned driving, intelligent networking and the like, and along with the rapid development of the fields, the requirements on the ranging distance and the ranging precision of the laser radar are higher and higher.
In order to meet the distance measurement requirement of a long distance to a moving object, a main stream laser radar still adopts a pulse type direct flight time (Direct Time of Flight, DTOF) measurement method, and the method is characterized by strong energy, high heavy frequency and short single distance measurement time, and the working principle is as follows: the distance information is obtained by calculating the time of flight conversion between the transmitted pulse and the received pulse. In order to achieve the distance measurement accuracy of the centimeter (cm) level, the method for identifying the echo time of the receiving and transmitting pulse is very important.
In the existing method, a front edge time identification method is generally adopted for identifying echo time: and comparing the laser echo with a preset voltage threshold through a comparator, and if the signal amplitude exceeds the preset voltage threshold, judging that the time corresponding to the signal amplitude is the arrival time of the echo.
However, the accuracy of the echo time identified by the method is still low, so a new method for identifying the echo time needs to be provided to solve the above technical problems.
Disclosure of Invention
The embodiment of the application provides a method, a device and communication equipment for identifying the echo time of a laser radar, which can solve the problem of lower accuracy of the existing method in determining the echo time.
In a first aspect, an embodiment of the present application provides a method for identifying a laser radar echo time, including:
performing waveform identification on the laser echo to obtain a waveform identification result, wherein the waveform identification result is used for indicating whether the laser echo is a saturated echo or not;
and selecting a corresponding time discrimination strategy according to the waveform discrimination result to discriminate the echo time of the laser echo.
Optionally, the selecting a corresponding time discrimination policy according to the waveform identification result to discriminate the echo time of the laser echo includes:
and determining the echo time according to the sampling point of the waveform front edge of the saturated echo under the condition that the waveform identification result indicates that the laser echo is the saturated echo.
Optionally, the determining the echo time according to the sampling point of the waveform front edge of the saturated echo includes:
selecting sampling points with the amplitude smaller than a preset calculation threshold value from the waveform front edge of the saturated echo, and selecting sampling points with the amplitude larger than the calculation threshold value;
performing polynomial fitting according to the selected sampling points to obtain a fitted polynomial;
and determining the echo moment according to the fitted polynomial and the calculation threshold.
Optionally, before the polynomial fitting is performed according to the selected sampling points, the method further includes:
constructing a polynomial before fitting according to the waveform front shape of the saturated echo;
and performing polynomial fitting according to the selected sampling points to obtain a fitted polynomial, wherein the polynomial fitting comprises the following steps:
and performing polynomial fitting on the polynomial before fitting according to the selected sampling points to obtain the polynomial after fitting.
Optionally, the selecting a corresponding time discrimination policy according to the waveform identification result to discriminate the echo time of the laser echo includes:
and determining the echo time according to a target sampling point of the unsaturated echo under the condition that the waveform identification result indicates that the laser echo is the unsaturated echo, wherein the target sampling point comprises a sampling point of a waveform front edge and a sampling point of a waveform rear edge of the unsaturated echo.
Optionally, the determining the echo time according to the target sampling point of the unsaturated echo includes:
determining centroid time of the unsaturated echo according to the target sampling point of the unsaturated echo;
and determining the echo moment according to the centroid moment.
Optionally, before the centroid time of the unsaturated echo is determined according to the target sampling point of the unsaturated echo, the method further includes:
determining a peak value of the unsaturated echo;
and determining a calculation window on the unsaturated echo by taking the point of the peak value as the center, and taking the sampling point in the calculation window as the target sampling point.
In a second aspect, an embodiment of the present application provides a laser radar echo time identifying device, including:
the waveform identification module is used for carrying out waveform identification on the laser echo to obtain a waveform identification result, and the waveform identification result is used for indicating whether the laser echo is a saturated echo or not;
and the echo time determining module is used for selecting a corresponding time discrimination strategy according to the waveform identification result to discriminate the echo time of the laser echo.
In a third aspect, embodiments of the present application provide a communication device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the method according to any one of the first aspects when executing the computer program.
In a fourth aspect, embodiments of the present application provide a computer-readable storage medium storing a computer program which, when executed by a processor, implements a method according to any one of the first aspects.
In a fifth aspect, embodiments of the present application provide a computer program product which, when run on a communication device, causes the communication device to perform the method of any one of the first aspects above.
Compared with the prior art, the embodiment of the application has the beneficial effects that:
in the embodiment of the application, whether the laser echo is a saturated echo is firstly identified, and then the echo time of the laser echo is identified by selecting a corresponding time identification strategy according to the obtained waveform identification result. Since the laser radar has a large dynamic range of reflected light energy when performing long-range ranging, the laser echo of the laser radar generally includes a saturated echo and an unsaturated echo. Meanwhile, because waveforms of the saturated echo and the unsaturated echo are different, the time discrimination strategies of echo time corresponding to the saturated echo and the unsaturated echo are different, so that the method and the device select the corresponding time discrimination strategy to discriminate the echo time of the laser echo according to the waveform discrimination result of whether the laser echo is the saturated echo or not, and the accuracy of the obtained echo time can be improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a schematic diagram of a walking error according to an embodiment of the present application;
FIG. 2 is a flow chart of a method for identifying a laser radar echo time according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a relative relationship between a sampling point and a calculation threshold according to an embodiment of the present application;
FIG. 4 is a schematic diagram of a relative relationship between a calculation window and a non-saturated echo according to an embodiment of the present disclosure;
FIG. 5 is a schematic diagram of a trailing edge of an echo time bias waveform according to another embodiment of the present application;
FIG. 6 is a schematic diagram of a reflective surface with saturated and unsaturated signals at the same location according to an embodiment of the present application;
FIG. 7 is a flow chart of a method for calculating time of flight according to another embodiment of the present application;
fig. 8 is a schematic flow chart of an FPGA master control chip according to an embodiment of the present disclosure;
fig. 9 is a schematic structural diagram of a laser radar echo time discrimination device according to an embodiment of the present application;
fig. 10 is a schematic structural diagram of a communication device according to an embodiment of the present application.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system configurations, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It should also be understood that the term "and/or" as used in this specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise.
When ranging is performed using a lidar, it is necessary to determine the echo time of the laser echo.
When the echo time (i.e., the echo arrival time) is identified by the leading edge time identification method, a fixed level is used for identification. However, since the signal amplitude is changed, there is a large walking error (here, the walking error is shown as Δt in fig. 1) in the timing result. That is, as the signal amplitude changes, such as when the waveform changes from saturated to unsaturated, there will be a large error in the resulting echo time, thereby affecting the final ranging accuracy.
In order to improve accuracy of determined echo time, the embodiment of the application provides a laser radar echo time identification method. In the identification method, whether the laser echo is a saturated echo is firstly identified, and then a corresponding time identification strategy is selected according to the identification result to identify the echo time. Since the dynamic range of reflected light energy of the long-range lidar is basically above 10≡5, the echo usually has two conditions of saturated echo and unsaturated echo. Since the echo time corresponding to the saturated echo and the echo time corresponding to the unsaturated echo are usually different, the echo time of the laser echo is identified by selecting a corresponding time identification strategy according to the waveform identification result of whether the laser echo is the saturated echo or not, and the accuracy of the determined echo time can be improved.
The following describes a method for identifying the echo time of the laser radar according to the embodiment of the present application with reference to the accompanying drawings.
Fig. 2 is a schematic flow chart of a method for identifying laser radar echo time according to an embodiment of the present application, which is described in detail below:
s21, carrying out waveform identification on the laser echo to obtain a waveform identification result, wherein the waveform identification result is used for indicating whether the laser echo is a saturated echo or not.
The laser echo refers to laser reflected by the laser radar after encountering an object. As can be seen by analysis, the dynamic range of reflected light energy of a long-range lidar is generally above 10≡5, and waveforms corresponding to the reflected light energy generally comprise both saturated and unsaturated conditions. However, since the echo times corresponding to the saturated echo and the unsaturated echo are usually different, it is necessary to determine whether the laser echo is the saturated echo before the echo time is recognized.
Optionally, in order to improve the accuracy of the obtained waveform identification result, S21 includes:
the laser echo is amplified by an amplifying circuit, the amplified laser echo is converted into a dispersion digital signal by an analog-to-digital sampling module (ADC sampling module), and then waveform identification is carried out by a field programmable gate array (Field Programmable Gate Array, FPGA) main control module of the laser radar.
Optionally, to avoid identifying noise, after obtaining the discrete digital signals, a digital filter is used to boost the overall signal-to-noise ratio of the discrete digital signals, the amplitude range of the background noise is counted, and the effective signal (i.e., the effective echo) is identified based on the amplitude range of the background noise. Where background noise refers to the total noise in the electroacoustic system, except for the useful signal.
Further, in order to reduce the probability of erroneous judgment when the signal amplitude approaches the upper limit of the background noise, a preset value is added to the amplitude range of the background noise as an effective signal recognition threshold V th_sig Greater than the threshold V th_sig The samples below this threshold are considered valid echoes and the samples below this threshold are considered noise and are not processed.
In this embodiment of the present application, it may be determined whether the laser echo is a saturated echo by identifying a waveform peak of the laser echo: the wave peak value V_peak_critical when critical saturation is obtained by the early test, if the peak value Vpeak of the laser echo is larger than the V_peak_critical, the current laser echo is judged to be the saturated echo, otherwise, the current laser echo is judged to be the unsaturated echo (or the unsaturated echo). Further, considering that there is a step in ADC sampling, the peak time is not guaranteed, so in order to avoid identifying the unsaturated echo as a saturated echo, the voltage Δvadc_sample is reserved, i.e. at the peak Vpeak of the laser echo>V_peak_critical-ΔV adc_sample When the current laser echo is determined to be a saturated echo, otherwise, the current laser echo is determined to be a non-saturated echo.
In addition to identifying whether the laser echo is a saturated echo by the waveform peak, it is also possible to determine whether the laser echo is a saturated echo or a non-saturated echo by calculating the slope of the laser echo and determining whether the laser echo is a saturated echo or a non-saturated echo based on the change in the slope. Of course, in actual situations, other methods may also be used to determine whether the laser echo is a saturated echo, which will not be described herein.
S22, selecting a corresponding time discrimination strategy according to the waveform recognition result to discriminate the echo time of the laser echo.
Here, the echo time refers to the time at which the laser echo returns. After the echo time is calculated, the laser flight time can be calculated according to the starting time of laser emission of the laser radar, and then the distance between the laser radar and the object can be calculated.
The moment discrimination strategy here is: a strategy for identifying the echo time of a laser echo. It should be noted that the time discrimination policy corresponding to the saturated echo is different from the time discrimination policy corresponding to the unsaturated echo.
In the embodiment of the application, whether the laser echo is a saturated echo is firstly identified, and then the echo time of the laser echo is identified by selecting a corresponding time identification strategy according to the obtained waveform identification result. Since the laser radar has a large dynamic range of reflected light energy when performing long-range ranging, the laser echo of the laser radar generally includes a saturated echo and an unsaturated echo. Meanwhile, because waveforms of the saturated echo and the unsaturated echo are different, the time discrimination strategies of echo time corresponding to the saturated echo and the unsaturated echo are different, so that the method and the device select the corresponding time discrimination strategy to discriminate the echo time of the laser echo according to the waveform discrimination result of whether the laser echo is the saturated echo or not, and the accuracy of the obtained echo time can be improved.
In some embodiments, when the laser echo is determined to be a saturation echo, the S22 includes:
and determining the echo time according to the sampling point of the waveform front edge of the saturated echo under the condition that the waveform identification result indicates that the laser echo is the saturated echo.
Specifically, in consideration of the fact that the rising edge slope of the waveform of the saturated echo is large, jitter is small, and after the signal is saturated, even if the saturation degree is different, the difference of the waveform front edge is small, most of energy is converted into signal pulse width broadening, at this time, the echo time is determined according to the sampling point of the waveform front edge, the deviation of the obtained echo time is small, and therefore the accuracy of the obtained echo time can be improved.
When the echo time of the laser echo is determined according to the sampling points of the waveform front edge of the laser echo, part or all of the sampling points of the waveform front edge can be selected for waveform fitting, and the echo time is calculated according to the fitting result.
In some embodiments, to improve accuracy of the fitted result, the determining the echo time according to the sampling point of the waveform front of the saturated echo includes:
a1, selecting sampling points with the amplitude smaller than a preset calculation threshold value from the waveform front edge of the saturated echo, and selecting sampling points with the amplitude larger than the calculation threshold value.
The number of sampling points smaller than the preset calculation threshold may be set to N1 (where N1 is a natural number greater than or equal to 1), the number of sampling points greater than the calculation threshold may be set to N2 (where N2 is a natural number greater than or equal to 1), and N1 may be equal to N2 or may not be equal to N2. Assuming the calculation threshold employs V th_cal Indicating n1=2 and n2=3, the selected sampling point may be as shown in fig. 3.
The preset calculation threshold is an amplitude value, which can be determined by the following ways: and selecting points with smaller time deviation corresponding to the same threshold under saturated echoes with different amplitudes, wherein the amplitude corresponding to the selected points is the calculated threshold. That is, the above-described calculation threshold is determined based on the threshold time at which the saturated echo jitter of different magnitudes is minimum. When the calculation threshold value is determined from the point where the jitter is smallest, it can be ensured that the dispersion of the time of flight calculated from the calculation threshold value is smallest, that is, it can be ensured that the probability of repeated measurement as the same distance is higher.
Of course, in practical situations, the above calculation threshold may be set by the user according to the actual requirement, which is not limited herein.
A2, performing polynomial fitting according to the selected sampling points to obtain a polynomial after fitting.
Specifically, a polynomial before fitting is firstly constructed, the independent variable of the polynomial before fitting is the moment of a sampling point, the dependent variable is the amplitude of the sampling point, and then parameters corresponding to the polynomial before fitting are calculated according to the moment and the amplitude corresponding to each sampling point, so that a polynomial after fitting is obtained.
A3, determining the echo time according to the fitted polynomial and the calculation threshold.
Specifically, the calculated threshold is used as the amplitude of the polynomial after fitting, and the moment corresponding to the amplitude is calculated, and the moment is the echo moment.
In the embodiment of the application, the selected sampling points comprise the sampling points with the amplitude smaller than the preset calculation threshold value and the sampling points with the amplitude larger than the calculation threshold value, so that the sampling points participating in the fitting polynomial can be ensured to be more comprehensive, the accuracy of the fitted polynomial can be improved, and the accuracy of echo time calculated according to the fitted polynomial can be ensured.
In some embodiments, to improve the accuracy of the polynomial before fitting of the construction, the construction may be performed in combination with the waveform front shape, that is, before the A2, further comprising:
and constructing a polynomial before fitting according to the waveform front shape of the saturated echo.
Correspondingly, the A2 includes:
and performing polynomial fitting on the polynomial before fitting according to the selected sampling points to obtain the polynomial after fitting.
In this embodiment, the order of the polynomial before fitting is configured according to the waveform front shape of the saturated echo, for example, when the waveform front shape is a straight line, the order of the configured polynomial before fitting may be set to be first order, and when the waveform front shape is a curve, the order of the polynomial before fitting may be set to be second order or multiple order. In some embodiments, the shape of the waveform front of the saturated echo may be determined from the waveform displayed by the oscilloscope.
In the embodiment of the application, since the orders of the polynomials are different, the shapes of the corresponding graphs are also different, so that the order of the polynomial before fitting is determined according to the shape of the waveform front edge, and the accuracy of the polynomial before fitting of the final structure can be improved.
In some embodiments, when the laser echo is determined to be a non-saturated echo, the S22 includes:
and determining the echo time according to a target sampling point of the unsaturated echo under the condition that the waveform identification result indicates that the laser echo is the unsaturated echo, wherein the target sampling point comprises a sampling point of a waveform front edge and a sampling point of a waveform rear edge of the unsaturated echo.
In the embodiment of the present application, considering that the laser echo of the unsaturated signal is similar to a gaussian waveform, that is, the waveform front edge of the laser echo is in a curve form, if the calculation threshold is determined by the sampling point of the waveform front edge to calculate the echo time, a large walking error exists. However, when the sampling points involved in calculating the echo time include the sampling points of the waveform leading edge and the sampling points of the waveform trailing edge of the unsaturated echo, the accuracy of the obtained echo time can be improved when the echo time is calculated by the method because the sampling points involved in calculation are more comprehensive.
In some embodiments, taking into account gaussian waveforms of different magnitudes, the centroid moments (i.e. the moments corresponding to the shape center positions) are substantially close, so that the echo moment can be determined according to the centroid moments, where the determining the echo moment according to the target sampling point of the unsaturated echo includes:
and B1, determining the centroid time of the unsaturated echo according to the target sampling point of the unsaturated echo.
And B2, determining the echo time according to the centroid time.
Specifically, the centroid time can be determined by calculating the mean value of the coordinate values of each target sampling point, namely, the echo time is determined.
For example, assume that the number of target sampling points is n, t i The sampling time v of the ith target sampling point i For the amplitude of the ith target sampling point, the echo time t center The method comprises the following steps:
it should be noted that if the sampling point of the laser echo passes the valid signal recognition threshold V th_sig And distinguishing, wherein the target sampling point is the sampling point of the effective waveform.
In some embodiments, in consideration of the fact that the higher the signal duty ratio is, the smaller the influence of noise is, in order to improve the accuracy of the determined echo time, a target sampling point may be selected near the peak, and before the B1, the method further includes:
c1, determining the peak value of the unsaturated echo.
Specifically, the peak value of the unsaturated echo may be determined by comparing the magnitudes of a plurality of sampling points.
And C2, determining a calculation window on the unsaturated echo by taking the point of the peak value as the center, and taking the sampling point in the calculation window as the target sampling point.
The size of the calculation window is related to the number of target sampling points, for example, when the number of required target sampling points is large, the calculation window centered on the peak point is set to be large, otherwise, the calculation window is set to be small. Wherein the relative relation between the calculation window and the unsaturated echo can be as shown in fig. 4.
In this embodiment of the present application, since the calculation window is determined with the point where the peak value is located as the center, and the target sampling point is the sampling point in the calculation window, the distance between the sampling point outside the calculation window and the point of the peak value is greater than the distance between the target sampling point and the point of the peak value. The closer to the peak, the higher the signal duty ratio is, the less affected by noise, so that the accuracy of the obtained echo time can be improved by calculating the echo time at the target sampling point determined by the method.
In some embodiments, considering that the laser echo is affected by circuit adjustment (such as amplifying circuit device and peripheral filtering condition, etc.) so that the waveform does not completely conform to the gaussian waveform, as shown in fig. 5, when the front edge of the waveform is steep and the back edge of the waveform is slow, the echo time of the waveform is biased towards the back edge of the waveform rather than the center time, so in order to further improve the accuracy of the centroid time of the obtained unsaturated echo, the calculated centroid time may be corrected according to the waveform peak value size.
Specifically, the received light intensity of the laser radar can be adjusted at the same position to collect the corresponding relation between the unsaturated echo peak value and the centroid time in the whole amplitude range, and the centroid time of different amplitudes is unified to the time t_center_min with the minimum amplitude, so that a compensation relation table of different peak values is established. Thus, after the echo time is calculated according to step B2, the calculated echo time is corrected in combination with the established compensation relation table.
In the embodiment of the present application, since centroid moments of different magnitudes are unified to t_center_min, mainly because the smaller the magnitude is, the less obvious the left-right edge asymmetry is, and the closer the obtained calculation result (i.e., centroid moment) is to the peak moment. Wherein the minimum amplitude is peak minimum (peak_min), which is V th_sig 。
After determining the echo time corresponding to the saturated echo or the unsaturated echo, the laser flight time can be calculated by combining the starting time of laser emission of the laser radar. In some embodiments, as shown in fig. 6, since there is a reflectivity difference between the reflective surfaces at the same location, a saturated signal and an unsaturated signal may occur, and since there is a difference between the echo timings determined according to the timing discrimination strategies corresponding to the saturated echo and the unsaturated echo, respectively, there is a difference between the echo positions calculated according to the echo timings having the difference, it is necessary to compensate for the difference calculated by the two timing discrimination strategies:
actual flight time = echo time-t_start (0) -t_zero delay.
When a saturated echo occurs, the echo time in the above formula is t_pos_time, where t_pos_time is the echo time corresponding to the saturated echo, and when an unsaturated echo occurs, the echo time in the above formula is the time corresponding to the unsaturated t_center, where the time corresponding to the unsaturated t_center is the echo time corresponding to the unsaturated echo.
Where t_start (0) is the start time of laser radar laser emission.
Wherein, t_zero delay is: the discharge pulse t_start (0) to the actual luminescence and the laser echo (saturated echo or unsaturated echo) are input to the ADC sampling module, wherein hardware delay exists, and the integral delay time is collectively called as t_zero delay and is used for representing the deviation value between the calculation result and the actual distance.
In order to more clearly describe the method for identifying the echo time of the lidar provided in the embodiment of the present application, the following description is made with reference to fig. 7 and 8.
Fig. 7 is a schematic flow chart of a method for calculating flight time according to an embodiment of the present application.
In fig. 7, an FPGA main control chip controls a Laser Diode (LD) to drive and emit Laser pulses, reflected Laser echoes are processed by a receiving and amplifying circuit, and then enter an ADC sampling chip to sample, convert the Laser echoes into discrete digital signals, and transmit the discrete digital signals back to the FPGA chip, the FPGA performs waveform recognition and internal processing calculation on the sampled signals to obtain echo moments, and outputs flight time data calculated according to the echo moments to a timing data output module.
Fig. 8 is a schematic flow chart of an FPGA main control chip according to an embodiment of the present application.
In FIG. 8, after ADC sampling data is input into FPGA, the whole signal to noise ratio is improved through digital filtering logic, the background noise amplitude range is counted, and a preset value is added on the basis as an effective signal recognition threshold V th_sig Greater than the threshold V th_sig Is considered to be a valid echo, less than the threshold V th_sig Is considered noise, and is not processed; in the effective signal sampling points, waveform peak values Vpak are identified according to the amplitude change trend of the front and rear points, whether the current laser echo is a saturated echo is judged according to the Vpak, and corresponding processing is carried out according to the judging result.
For saturated echo, extracting a sampling point fitting curve of the waveform front edge, and calculating a threshold V th_cal Is taken as the echo timing point, and the echoThe moment corresponding to the wave timing point is the echo moment.
And extracting full-range waveform sampling points for the unsaturated echo, and calculating centroid time according to the extracted sampling points to be used as echo time corresponding to the unsaturated echo.
And subtracting the laser light emitting START time (namely t_start (0)) and the zero point delay (namely t_zero point delay) of the respective time discrimination strategy after the echo time corresponding to the saturated echo or the unsaturated echo is calculated, so as to obtain the final laser flight time.
It should be understood that the sequence number of each step in the foregoing embodiment does not mean that the execution sequence of each process should be determined by the function and the internal logic of each process, and should not limit the implementation process of the embodiment of the present application in any way.
Corresponding to the method for identifying the echo time of the lidar described in the above embodiments, fig. 9 shows a block diagram of a device for identifying the echo time of the lidar according to the embodiment of the present application, and for convenience of explanation, only the portion related to the embodiment of the present application is shown.
Referring to fig. 9, the laser radar echo time discrimination device 9 includes: a waveform identification module 91 and an echo time determination module 92. Wherein:
the waveform identifying module 91 is configured to identify a waveform of the laser echo, and obtain a waveform identifying result, where the waveform identifying result is used to indicate whether the laser echo is a saturated echo.
And the echo time determining module 92 is configured to select a corresponding time discrimination strategy according to the waveform identification result to discriminate the echo time of the laser echo.
In the embodiment of the application, whether the laser echo is a saturated echo is firstly identified, and then the echo time of the laser echo is identified by selecting a corresponding time identification strategy according to the obtained waveform identification result. Since the laser radar has a large dynamic range of reflected light energy when performing long-range ranging, the laser echo of the laser radar generally includes a saturated echo and an unsaturated echo. Meanwhile, because waveforms of the saturated echo and the unsaturated echo are different, the time discrimination strategies of echo time corresponding to the saturated echo and the unsaturated echo are different, so that the method and the device select the corresponding time discrimination strategy to discriminate the echo time of the laser echo according to the waveform discrimination result of whether the laser echo is the saturated echo or not, and the accuracy of the obtained echo time can be improved.
In some embodiments, the echo time determination module 92 is specifically configured to:
and determining the echo time according to the sampling point of the waveform front edge of the saturated echo under the condition that the waveform identification result indicates that the laser echo is the saturated echo.
In some embodiments, the determining the echo time according to the sampling point of the waveform front of the saturated echo includes:
selecting sampling points with the amplitude smaller than a preset calculation threshold value from the waveform front edge of the saturated echo, and selecting sampling points with the amplitude larger than the calculation threshold value;
performing polynomial fitting according to the selected sampling points to obtain a fitted polynomial;
and determining the echo moment according to the fitted polynomial and the calculation threshold.
In some embodiments, before said fitting of the polynomial according to each of said sampling points selected, further comprises:
constructing a polynomial before fitting according to the waveform front shape of the saturated echo;
and performing polynomial fitting according to the selected sampling points to obtain a fitted polynomial, wherein the polynomial fitting comprises the following steps:
and performing polynomial fitting on the polynomial before fitting according to the selected sampling points to obtain the polynomial after fitting.
In some embodiments, the echo time determination module 92 is specifically configured to:
and determining the echo time according to a target sampling point of the unsaturated echo under the condition that the waveform identification result indicates that the laser echo is the unsaturated echo, wherein the target sampling point comprises a sampling point of a waveform front edge and a sampling point of a waveform rear edge of the unsaturated echo.
In some embodiments, the determining the echo time according to the target sampling point of the unsaturated echo includes:
determining centroid time of the unsaturated echo according to the target sampling point of the unsaturated echo;
and determining the echo moment according to the centroid moment.
In some embodiments, before the determining the centroid time of the unsaturated echo according to the target sampling point of the unsaturated echo, the method further includes:
determining a peak value of the unsaturated echo;
and determining a calculation window on the unsaturated echo by taking the point of the peak value as the center, and taking the sampling point in the calculation window as the target sampling point.
It should be noted that, because the content of information interaction and execution process between the above devices/units is based on the same concept as the method embodiment of the present application, specific functions and technical effects thereof may be referred to in the method embodiment section, and will not be described herein again.
Fig. 10 is a schematic structural diagram of a communication device according to an embodiment of the present application. As shown in fig. 10, the communication device 10 of this embodiment includes: at least one processor 100 (only one processor is shown in fig. 10), a memory 101, and a computer program 102 stored in the memory 101 and executable on the at least one processor 100, the processor 100 implementing the steps in any of the various method embodiments described above when executing the computer program 102.
The communication device 10 may be a computing device such as a desktop computer, a notebook computer, a palm computer, a cloud server, etc. The communication device may include, but is not limited to, a processor 100, a memory 101. It will be appreciated by those skilled in the art that fig. 10 is merely an example of communication device 10 and is not intended to limit communication device 10, and may include more or fewer components than shown, or may combine certain components, or may include different components, such as input-output devices, network access devices, etc.
The processor 100 may be a central processing unit (Central Processing Unit, CPU), and the processor 100 may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), field-programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory 101 may in some embodiments be an internal storage unit of the communication device 10, such as a hard disk or a memory of the communication device 10. The memory 101 may in other embodiments also be an external storage device of the communication device 10, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash Card (Flash Card) or the like, which are provided on the communication device 10. Further, the memory 101 may also include both internal storage units and external storage devices of the communication device 10. The memory 101 is used for storing an operating system, application programs, boot loader (BootLoader), data, other programs, etc., such as program codes of the computer program. The memory 101 may also be used to temporarily store data that has been output or is to be output.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-described division of the functional units and modules is illustrated, and in practical application, the above-described functional distribution may be performed by different functional units and modules according to needs, i.e. the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-described functions. The functional units and modules in the embodiment may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit, where the integrated units may be implemented in a form of hardware or a form of a software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working process of the units and modules in the above system may refer to the corresponding process in the foregoing method embodiment, which is not described herein again.
The embodiment of the application also provides a network device, which comprises: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, which when executed by the processor performs the steps of any of the various method embodiments described above.
Embodiments of the present application also provide a computer readable storage medium storing a computer program which, when executed by a processor, implements steps that may implement the various method embodiments described above.
The present embodiments provide a computer program product which, when run on a communication device, causes the communication device to perform steps that may be implemented in the various method embodiments described above.
The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the present application implements all or part of the flow of the method of the above embodiments, and may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, where the computer program, when executed by a processor, may implement the steps of each of the method embodiments described above. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable medium may include at least: any entity or device capable of carrying computer program code to a camera device/communication apparatus, recording medium, computer Memory, read-Only Memory (ROM), random access Memory (RAM, random Access Memory), electrical carrier signals, telecommunications signals, and software distribution media. Such as a U-disk, removable hard disk, magnetic or optical disk, etc. In some jurisdictions, computer readable media may not be electrical carrier signals and telecommunications signals in accordance with legislation and patent practice.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus/network device and method may be implemented in other manners. For example, the apparatus/network device embodiments described above are merely illustrative, e.g., the division of the modules or units is merely a logical functional division, and there may be additional divisions in actual implementation, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection via interfaces, devices or units, which may be in electrical, mechanical or other forms.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (10)
1. A method for identifying the echo time of a laser radar, comprising:
performing waveform identification on the laser echo to obtain a waveform identification result, wherein the waveform identification result is used for indicating whether the laser echo is a saturated echo or not;
and selecting a corresponding time discrimination strategy according to the waveform discrimination result to discriminate the echo time of the laser echo.
2. The method for discriminating an echo time of a laser radar according to claim 1, wherein selecting a corresponding time discrimination strategy based on the waveform recognition result, comprises:
and determining the echo time according to the sampling point of the waveform front edge of the saturated echo under the condition that the waveform identification result indicates that the laser echo is the saturated echo.
3. The method for discriminating an echo time of a lidar according to claim 2, wherein the determining the echo time from sampling points of a waveform front of the saturated echo includes:
selecting sampling points with the amplitude smaller than a preset calculation threshold value from the waveform front edge of the saturated echo, and selecting sampling points with the amplitude larger than the calculation threshold value;
performing polynomial fitting according to the selected sampling points to obtain a fitted polynomial;
and determining the echo moment according to the fitted polynomial and the calculation threshold.
4. A method of discriminating a laser radar echo time as in claim 3, further comprising, prior to said polynomial fitting based on each of said selected sample points:
constructing a polynomial before fitting according to the waveform front shape of the saturated echo;
and performing polynomial fitting according to the selected sampling points to obtain a fitted polynomial, wherein the polynomial fitting comprises the following steps:
and performing polynomial fitting on the polynomial before fitting according to the selected sampling points to obtain the polynomial after fitting.
5. The method for discriminating an echo time of a laser radar according to any one of claims 1 to 4 wherein the selecting a corresponding time discrimination strategy based on the waveform discrimination result discriminates the echo time of the laser echo, includes:
and determining the echo time according to a target sampling point of the unsaturated echo under the condition that the waveform identification result indicates that the laser echo is the unsaturated echo, wherein the target sampling point comprises a sampling point of a waveform front edge and a sampling point of a waveform rear edge of the unsaturated echo.
6. The method for discriminating an echo time of a lidar of claim 5 wherein said determining said echo time from a target sampling point of said unsaturated echo comprises:
determining centroid time of the unsaturated echo according to the target sampling point of the unsaturated echo;
and determining the echo moment according to the centroid moment.
7. The method for discriminating an echo time of a lidar of claim 6, further comprising, prior to said determining a centroid time of said unsaturated echo from a target sampling point of said unsaturated echo:
determining a peak value of the unsaturated echo;
and determining a calculation window on the unsaturated echo by taking the point of the peak value as the center, and taking the sampling point in the calculation window as the target sampling point.
8. A laser radar echo time discrimination apparatus, comprising:
the waveform identification module is used for carrying out waveform identification on the laser echo to obtain a waveform identification result, and the waveform identification result is used for indicating whether the laser echo is a saturated echo or not;
and the echo time determining module is used for selecting a corresponding time discrimination strategy according to the waveform identification result to discriminate the echo time of the laser echo.
9. A communication device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the method according to any of claims 1 to 7 when executing the computer program.
10. A computer readable storage medium storing a computer program, characterized in that the computer program when executed by a processor implements the method according to any one of claims 1 to 7.
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