CN113156396A - Method and device for optimizing influence of interference source on laser radar - Google Patents
Method and device for optimizing influence of interference source on laser radar Download PDFInfo
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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- G01S7/4804—Auxiliary means for detecting or identifying lidar signals or the like, e.g. laser illuminators
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Abstract
The invention discloses a method and a device for optimizing the influence of an interference source on a laser radar, wherein the laser radar sequentially transmits a first transmitting pulse and a second transmitting pulse towards a target direction according to a preset time interval and respectively collects echo signals returned by the two transmitting pulses; wherein the light intensity of the first transmitted pulse is less than that of the second transmitted pulse; when the distance between the interference source and the target is close, all echo signals of the second transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals of the first transmitting pulse to obtain effective target echoes; when the distance between the interference source and the target is far, all echo signals of the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals of the second transmitting pulse, so that effective target echoes are obtained. Through the double-pulse transmitting scheme, echoes of interference sources such as rain, snow, dust and the like can be filtered based on a multi-echo technology, and effective identification of targets is realized.
Description
Technical Field
The invention belongs to the technical field of laser radars, and particularly relates to a method and a device for optimizing influence of an interference source on a laser radar.
Background
The laser radar can be used for detecting three-dimensional space information of surrounding environment and completing reconstruction of a three-dimensional point cloud system, and has wide application in multiple fields and a plurality of specific application scenes. Meanwhile, the laser radar can be applied to various environments, and most of the laser radar is applied to outdoor environments particularly in the industrial field. The outdoor environment is comparatively abominable, receives the interference of interference sources such as sleet dust very easily to influence laser radar's normal detection.
At present, the technical means of removing the influence of rain, snow, dust and the like by the laser radar is to adopt a multi-echo technology, namely, echoes caused by interference sources such as rain, snow, dust and the like and target effective echoes are detected together, and screening and filtering are carried out through a system. Taking an interference source as an example of raindrops, as shown in fig. 1, when the raindrops are far away from a target, an interference echo and a target echo are separated on a time axis, and the interference echo can be effectively identified and filtered through a multi-echo algorithm, so that the target can be clearly and stably detected.
However, if the distance between the interference source and the target is too close and the interference source and the target are both close to the laser radar device, the transmission distance of the detection echo transmitted by the laser radar device in the space is not far, the light intensity is not attenuated too much, the divergence size of the light spot is not large, and at the moment, the echoes generated by the interference source and the target cannot be effectively separated. As shown in fig. 2, when the raindrops are close to the target, the interference echoes caused by the raindrops overlap with the target echoes, and at this time, the multi-echo algorithm cannot effectively identify and filter the interference echoes, so that the laser radar is affected by interference sources such as rain, snow, dust and the like in some special applications.
Disclosure of Invention
Aiming at the defects or the improvement requirements of the prior art, the invention provides a method and a device for optimizing the influence of an interference source on a laser radar, and aims to solve the technical problem that the influence of interference sources such as rain, snow, dust and the like on the laser radar cannot be effectively identified and filtered by a multi-echo technology in some special application scenes.
To achieve the above object, according to one aspect of the present invention, there is provided a method for optimizing an influence of an interference source on a lidar, comprising:
the laser radar transmits a first transmitting pulse and a second transmitting pulse in sequence towards a target direction according to a preset time interval, and echo signals returned by the two transmitting pulses are collected respectively; wherein the light intensity of the first transmitted pulse is less than that of the second transmitted pulse;
when the distance between the interference source and the target is close, all echo signals corresponding to the second transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the first transmitting pulse, so that effective target echoes are obtained finally;
and when the distance between the interference source and the target is longer, all echo signals corresponding to the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the second transmitting pulse, so that effective target echoes are finally obtained.
Preferably, the first transmit pulse and the second transmit pulse satisfy the following relationship:
wherein, P1Is the peak power, P, of the first transmit pulse2Is the peak power of the first transmit pulse.
Preferably, after obtaining the valid target echo, the method further comprises:
performing curve fitting on the target echo to obtain a fitting function of the target echo, and determining an initial time zero point of the corresponding transmission pulse by performing reverse time deduction on the fitting function;
and calculating the flight time of the corresponding transmitted pulse according to the starting time zero point, and further calculating the distance between the target and the laser radar according to the flight time.
Preferably, the curve fitting is performed on the target echo to obtain a fitting function of the target echo, and a starting time zero point of the corresponding transmission pulse is determined by performing reverse time deduction on the fitting function, specifically:
performing curve fitting based on a plurality of echo signal intensities above a signal threshold on a time axis to obtain a fitting function of the target echo;
and carrying out reverse time deduction on the fitting function to enable the intensity of the echo signal to approach a zero value, and further calculating the starting time zero point of the corresponding transmitting pulse.
Preferably, the calculating of the flight time of the corresponding transmission pulse according to the starting time zero point and the further calculating of the distance between the target and the laser radar according to the flight time specifically include:
calculating the zero point of the ending time of the corresponding transmission pulse according to the zero point of the starting time of the corresponding transmission pulse and the symmetry axis of the echo signal curve;
calculating the flight time of the corresponding transmission pulse according to the starting time zero point and the ending time zero point of the corresponding transmission pulse;
and calculating the distance between the target and the laser radar according to the flight time and the flight speed of the corresponding transmitted pulse.
Preferably, the source of interference is rain, snow, hail or dust.
According to another aspect of the present invention, there is provided an apparatus for optimizing the effect of an interference source on a lidar, comprising a lidar, a processor and a memory;
the laser radar is used for sequentially transmitting a first transmitting pulse and a second transmitting pulse towards a target direction according to a preset time interval and respectively collecting echo signals returned by the two transmitting pulses; wherein the light intensity of the first transmitted pulse is less than that of the second transmitted pulse;
the memory stores an instruction which can be executed by the processor, and the instruction is used for filtering all echo signals corresponding to the second transmitting pulse when the interference source is close to the target after being executed by the processor, and performing multi-echo screening and filtering processing on the echo signals corresponding to the first transmitting pulse; when the distance between the interference source and the target is long, all echo signals corresponding to the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the second transmitting pulse, so that effective target echoes are obtained finally.
Preferably, the laser radar includes a laser transmitter configured to transmit a first transmit pulse and a second transmit pulse sequentially toward a target direction at a preset time interval.
Preferably, the lidar further comprises a high-speed digital-to-analog converter for high-speed digital-to-analog sampling of the full waveform of the echo signals returned by the two transmit pulses.
Preferably, the lidar is a one-dimensional lidar, a two-dimensional lidar or a three-dimensional lidar.
Generally, compared with the prior art, the technical scheme of the invention has the following beneficial effects: in the method for optimizing the influence of the interference source on the laser radar, two pulses are adopted for each transmission, wherein the front pulse is a small light intensity pulse, and the rear pulse is a large light intensity pulse. In the actual test, if the distance between the interference source and the target is short, all the echo signals with large light intensity are filtered based on the echo signals with small light intensity; if the distance between the interference source and the target is long, all the echo signals with small light intensity are filtered based on the echo signals with large light intensity. By the double-pulse transmitting scheme, interference echoes of interference sources such as rain, snow, dust and the like can be filtered based on multi-echo identification and filtering technology no matter how far the distance between the interference source and the target is, so that the target can be effectively identified.
Drawings
FIG. 1 is a diagram of echo signals when an interference source is far away from a target in a single pulse transmission situation;
FIG. 2 is a diagram of an echo signal when an interference source is close to a target in a single pulse transmission case;
FIG. 3 is a flowchart of a method for optimizing the effect of an interference source on a lidar according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a transmission signal during a double pulse transmission according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of echo signals when the interference source and the target are close to each other in the case of double-pulse transmission according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating filtered target echo signals when the interference source and the target are closer to each other in the case of dual-pulse transmission according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of echo signals when the interference source and the target are far apart in the case of double-pulse transmission according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of filtered target echo signals when the interference source and the target are far apart from each other in the case of double-pulse transmission according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of discrete echo signal strength of high-speed sampling according to an embodiment of the present invention;
FIG. 10 is a flowchart of a method for calculating a distance using a target echo according to an embodiment of the present invention;
FIG. 11 is a flowchart illustrating a process for verifying the rationality of the zero point of the start time according to an embodiment of the present invention;
FIG. 12 is a schematic diagram of a piecewise fitting to echo signal strength according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom", "left", "right", "front", "rear", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of describing the present invention but do not require that the present invention must be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Example 1
At present, the application of the laser radar is to emit only one detection pulse in each direction, and in the transmission process of optical signals, especially in outdoor environment application, the optical signals are often affected by interference sources such as rain, snow, dust and the like, and other interference echoes are generated outside a target. For the situation, the full waveform can be rapidly sampled based on a high-speed digital-analog sampling technology, and the echo situation of the full waveform is reconstructed, namely a multi-echo technology. Therefore, generally, echoes of interference sources such as rain, snow, dust and the like can be screened and filtered based on a multi-echo technology, so that the target can be effectively identified. However, there are some special application scenarios, that is, when the distance between the interference source such as rain, snow, dust, etc. and the target is too close, the echo of the interference source and the echo of the target are not separated on the time axis, that is, there is an overlap of signals, as shown in fig. 2. At this time, the multi-echo technology based on the laser radar cannot effectively identify and filter environmental influences such as rain, snow, dust and the like, so that effective identification of environmental targets is influenced.
Based on the application scenario, the embodiment of the invention improves the transmitted pulse, provides a method for optimizing the influence of an interference source on a laser radar, and can solve the problems; the interference source may be rain, snow, hail or dust, which are relatively common in an outdoor environment. As shown in fig. 3, the method provided by the embodiment of the present invention mainly includes:
With reference to fig. 4, the present invention improves the transmitted pulse, changes the traditional single transmitted pulse into the double transmitted pulse, the laser radar transmits the first transmitted pulse with a larger light intensity first, and then transmits the second transmitted pulse with a smaller light intensity after the preset time interval τ. That is, the peak power of the first transmission pulse is lower than the peak power of the second transmission pulse, and the preferred configuration is as shown in equation (1).
Wherein, P1Is the peak power, P, of the first transmit pulse2Is the peak power of the first transmit pulse. The peak power values of the two transmit pulses defined in the formula (1) can be obtained based on power sampling, and if a certain power is saturated, the signal intensity is reduced to be less than half, so that the echo signals of the two transmit pulses can be effectively identified and distinguished. In practical use, optimal configuration can be performed according to the situation, and a proper peak power collocation is selected. Meanwhile, because the received photoelectric response curve is saturated backwards, the selection of the time interval tau is more flexible, and the pulse with smaller light intensity is not easy to cover the pulse with larger light intensity backwards.
After the double-pulse transmission, the echo signals returned by the two pulses need to be detected and received, and here, the full waveforms of the echo signals returned by the two transmitted pulses are respectively sampled by a high-speed digital-to-analog sampling technology, so that the echo signal diagram shown in fig. 5 or fig. 7 can be obtained. Due to the existence of the interference source, each emission pulse can obtain two echo curves, and the receiving time interval of the echo signals of the two emission pulses is also tau, namely, the echo signal of the first emission pulse with higher light intensity is received firstly, and the echo signal of the second emission pulse with lower light intensity is received after the time interval tau. Based on the above-mentioned configuration of the dual emission pulses, the aforementioned problem of interference sources such as rain, snow, dust, etc. can be optimized, and how to optimize will be described in detail in step 102 and step 103.
And 102, when the distance between the interference source and the target is short, all echo signals corresponding to the second transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the first transmitting pulse, so that effective target echoes are obtained finally.
When the distance between the interference source and the target is short and the distance between the interference source and the target is short, the transmission distance of the transmitted pulse in space is short, the divergence of the light spot of the transmitted pulse is small, the transmission loss is small, and the echo signals incident on the interference source and the target are strong, so that two echoes are strong. Wherein "closer" as described herein in terms of distance is a range of distances known to those skilled in the art, and if the target echo and the interference echo overlap when the pulse is transmitted, those skilled in the art generally consider the interference source and the target to be closer together; if the spot divergence is small when the transmit pulse is transmitted, then those skilled in the art will generally consider the interfering source and target to be closer to the lidar.
Based on the above theoretical analysis, at this time, when two transmit pulses with time interval τ are used as shown in fig. 4, the first transmit pulse returns two echoes with relatively low light intensity, and the second transmit pulse returns two echoes with relatively high light intensity as shown in fig. 5. As can be seen from fig. 5, the two echoes of the first transmit pulse can be clearly resolved and identified, while the two echoes of the second transmit pulse coincide and cannot be clearly resolved. At this time, based on full waveform sampling, the system can sample and reconstruct all echo signals, and because the interference echo corresponding to the second transmitting pulse is overlapped with the target echo, the interference echo and the target echo cannot be identified effectively, so that all echo signals need to be filtered; and the interference echo corresponding to the first transmit pulse can be screened and filtered based on the multiple echoes, so that an effective target echo can be obtained based on the first transmit pulse, as shown in fig. 6, and effective identification of a target is realized.
And 103, when the distance between the interference source and the target is long, all echo signals corresponding to the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on echo signals corresponding to the second transmitting pulse, so that effective target echoes are obtained finally.
When the distance between the interference source and the target is far and the distance between the interference source and the target is far away from the laser radar, the transmission distance of the transmitted pulse in the space is far, the light spot of the transmitted pulse is spread to a larger size, the loss of the transmitted pulse in the space is larger, and the whole echo signal incident on the interference source and the target is weaker. Where "farther" as described herein in terms of distance is a range of distances known to those skilled in the art, a person skilled in the art would typically consider the interfering source and target to be farther apart if the target echo and interfering echo do not overlap when the pulse is transmitted; if the spot of the transmitted pulse is already heavily spread, the source and target of the interference are generally considered by those skilled in the art to be further away from the lidar.
Based on the above theoretical analysis, when two transmit pulses with time interval τ are used as shown in fig. 4, the first transmit pulse returns two echoes with relatively low light intensity, and the second transmit pulse returns two echoes with relatively high light intensity, as shown in fig. 7. As can be seen from fig. 7, both echo signals of the first transmit pulse are weak, and are usually lower than the power sampling threshold of the sampling circuit, so the system automatically filters out; even if the power sampling threshold is higher than the power sampling threshold of the sampling circuit, after all the echoes are selected by the system through a full waveform sampling technology, weak echoes near the power threshold can be filtered out integrally. The power of the second transmit pulse is higher, so that a longer distance can be transmitted, and the corresponding interference echo and the target echo are clear and cannot be covered, so that the interference echo corresponding to the second transmit pulse can be screened and filtered based on multiple echoes, and thus an effective target echo can be obtained based on the second transmit pulse, as shown in fig. 8, and effective identification of a target is realized.
In the method provided by the embodiment of the invention, each emission adopts two pulses, wherein the front is a small light intensity pulse, and the rear is a large light intensity pulse. In the actual test, if the distance between the interference source and the target is short, all the echo signals with large light intensity are filtered based on the echo signals with small light intensity; if the distance between the interference source and the target is long, all the echo signals with small light intensity are filtered based on the echo signals with large light intensity. Through the double-pulse transmitting scheme, no matter how far the distance between the interference source and the target is, the interference echoes of the interference sources such as rain, snow, dust and the like can be filtered based on a multi-echo identification and filtering technology to obtain effective target echoes, so that the target can be effectively identified.
Example 2
The correct target echo has been screened out by the method in embodiment 1, and then the flight time of the corresponding transmit pulse can be calculated based on the target echo, so as to calculate the distance between the target and the laser radar device.
Assuming that fig. 9 shows the echo signal strength corresponding to the target echo retained after screening, in a theoretical situation, only the time of the starting point O needs to be sampled, and the pulse flight time can be determined, so as to calculate the distance between the target and the laser radar device. However, in practical situations, the detector has a large noise signal, and completely submerges the starting point O, so that the time of the starting point O cannot be obtained through effective sampling. In order to obtain an accurate starting time zero point and further accurately calculate the distance between the target and the laser radar, after obtaining the effective target echo, the following steps may be performed as shown in fig. 10:
In step 101, a high-speed digital-to-analog converter in the laser radar may perform time-axis sampling on the echo signal to obtain discrete signal voltage values, that is, a plurality of discrete echo signal intensities are obtained, and finally, the retained target echo also corresponds to the plurality of discrete echo signal intensities, as shown in fig. 9, it can be seen that the target echo is substantially parabolic. Based on the signal intensities of a plurality of discrete echoes corresponding to the target echo, the determination process of the starting time zero point is as follows:
firstly, curve fitting is carried out based on a plurality of echo signal intensities above a signal threshold on a time axis, and a fitting function of the target echo is obtained. Let the time axis of the starting point O be t0The time corresponding to the maximum value of the echo signal intensity is tpAccording to the shape of the parabolic distribution of the echo signal intensity, a preferred fitting function of the target echo is as follows:
wherein v (t) represents the echo signal intensity, which changes with time; the coefficient a represents the height of the peak of the echo signal curve, namely the height of the echo signal intensity; the coefficient c represents the transverse expansion width of the echo signal curve on the time axis. The formula (2) can better fit the variation of the echo signal intensity, different coefficients represent the height and the transverse expansion amplitude of the echo signal intensity, and the specific fitting process can be realized by means of the existing mathematical model, which is not described in detail herein. For the target echo obtained by high-speed sampling as shown in fig. 9, although the bottom noise still submerges the starting point on the time axis, the fitting function of the target echo can still be effectively reconstructed based on the sampling values above the signal threshold. It should be particularly noted here that the more sampling values of the echo signal intensity, the denser the sampling interval, the more accurate the reconstructed fitting function is, the more practical values can be fitted, and the more accurate the finally obtained starting time zero point is.
And then, performing reverse time deduction on the fitting function to enable the intensity of the echo signal to approach a zero value, and further calculating the starting time zero point of the corresponding transmitting pulse. Theoretically, the value of v (t) in the formula (2) is not equal to zero, which means that zero cannot be obtained by reverse calculation; therefore, the invention provides a method for calculating an approximate zero value, which is used for replacing an actual zero value, and further calculating to obtain a zero point of the starting time, as shown in formula (3).
V(t)≤ε (3)
The selection of the small amount epsilon is combined with the actual precision requirement to carry out corresponding calculation, and the basic rule is as follows: the smaller the value of the small amount epsilon is selected, the higher the time precision of the finally calculated starting time zero point is.
When the distance between the interference source and the target is close, obtaining effective target echo based on the first transmitted pulse, so that the starting time zero point of the first transmitted pulse is calculated, and the corresponding transmitted pulse refers to the first transmitted pulse; when the interference source is far away from the target, a valid target echo is obtained based on the second transmit pulse, and therefore the starting time zero of the second transmit pulse is calculated here, and the corresponding transmit pulse is the second transmit pulse.
And 202, calculating the flight time of the corresponding transmitted pulse according to the starting time zero point, and further calculating the distance between the target and the laser radar according to the flight time. The method comprises the following specific steps:
firstly, according to the starting time zero point of the corresponding transmission pulse and the symmetry axis of the echo signal curve, calculating the ending time zero point of the corresponding transmission pulse. With particular reference to fig. 9, the zero point t of the start time of the corresponding transmit pulse0And end time zero t1Theoretically, it is symmetrical, and the symmetry axis is the time tpCorresponding vertical lines (i.e., dashed straight lines in the figure); thus, the start time zero point t is calculated in step 2010Then, the end time zero point t of the corresponding transmission pulse can be determined by a symmetry method1. Besides, the starting time zero point t can be derived with reference to the reverse time in step 2010The method comprises the steps of carrying out forward time deduction on the fitting function to enable the intensity of the echo signal to approach zero value, and calculating the starting time zero point t of the corresponding transmission pulse1。
Then, according to said starting time zero point t of the corresponding transmitted pulse0And said end time zero point t1Calculating the flight time delta t of the corresponding transmission pulse: Δ t ═ t1-t0。
And finally, calculating the distance d between the target and the laser radar according to the flight time delta t and the flight speed v of the corresponding transmitted pulse: d ═ Δ t × v.
By the method provided by the embodiment of the invention, the distance between the target and the laser radar equipment can be accurately calculated by screening the retained target echoes.
Example 3
In addition to the above embodiment 2, to ensure the zero point t of the initial time of the extrapolation0After said step 201, i.e. after said determining of the starting time zero of the corresponding transmit pulse by reverse time derivation of said fitting function, the rationality of (d) for the starting time zero t may be further increased0The step of verifying. Referring to FIG. 11, for the start time zero point t0The verification method specifically comprises the following steps:
As shown in fig. 12, the time period corresponding to each segment is denoted as Δ t by dividing the portion above the threshold of the time axis signal into three segments as an example1、Δt2、Δt3Then all discrete echo signal intensities are equally divided into three groups, corresponding to three time segments respectively. Then respectively for Δ t1、Δt2、Δt3And performing curve fitting on a plurality of echo signal intensities corresponding to the time periods to obtain a corresponding piecewise fitting function in each time period. As can be seen in connection with FIG. 12, the time period Δ t1Corresponding to a piecewise fitting function of increasing echo signal intensity with time, time period deltat2The discrete echo signal intensity in the inner part corresponds to a piecewise fitting function of a parabolic shape with a time period delta t3A piecewise fitting function corresponding to a time-dependent decrease in echo signal intensity. The specific fitting process of each piecewise fitting function can be realized by means of the existing mathematical model, and details are not described herein.
And 302, respectively performing time deduction on each piecewise fitting function, and further calculating at least two piecewise starting time zeros corresponding to the transmission pulse. The deduction can be carried out according to the following principles:
and for the piecewise fitting function on the left side of the symmetry axis of the echo signal curve, performing reverse time deduction on the piecewise fitting function to enable the echo signal intensity to approach a zero value or take the zero value, and calculating a corresponding piecewise starting time zero point. For example, for time period Δ t in FIG. 121The corresponding piecewise fitting function can carry out reverse time deduction, so that the intensity of the echo signal directly takes a zero value to obtain a corresponding piecewise starting time zero point; for a time period Δ t2The corresponding piecewise fitting function may be similar to the formula (2), and the value of v (t) is not equal to zero, so that reverse time deduction can be performed to make the echo signal intensity approach zero, and obtain the corresponding piecewise starting time zero.
For the piecewise fitting function at the right side of the symmetry axis of the echo signal curve, forward time deduction is carried out on the piecewise fitting function to enable the echo signalAnd (4) the intensity approaches zero value or zero value is taken, and the corresponding segment starting time zero point is calculated. For example, for time period Δ t in FIG. 123The corresponding segment fitting function can carry out forward time deduction, so that the intensity of the echo signal directly takes a zero value to obtain a corresponding segment ending time zero point, and then the segment ending time zero point is symmetrical relative to a symmetrical axis to obtain a corresponding segment starting time zero point; for a time period Δ t2The corresponding segment fitting function may be similar to the formula (2), and the value of v (t) is not equal to zero, so that forward time deduction can be performed, the intensity of the echo signal approaches zero, a corresponding segment ending time zero point is obtained, and symmetry is performed with respect to a symmetry axis, and a corresponding segment starting time zero point is obtained.
Taking fig. 12 as an example, the segment fitting function corresponding to each time segment deduces and calculates a corresponding segment start time zero, and then three segment start time zeros are calculated in total. For convenience of description, the time period Δ t may be described1、Δt2、Δt3Respectively recording the zero points of the segment starting time calculated by the segment fitting function as t01、t02、t03。
Based on the starting time zero points of the segments obtained in the previous step, the starting time zero point t obtained in the step 201 can be adjusted0And (6) carrying out verification. The following two verification methods are provided:
(1) the first method comprises the following steps:
and comparing every two of the at least two segment starting time zeros, and judging whether the difference value between every two segment starting time zeros exceeds a preset deviation. And if the difference value between the two segment starting time zero points exceeds the preset deviation, the starting time zero point of the current deduction is considered to be unreasonable, and the next pulse emission is continued after abandoning treatment. And if the difference value between the starting time zero points of every two segments does not exceed the preset deviation, the starting time zero point of the current deduction is considered to be reasonable, and the flight time of the transmitted pulse is continuously calculated according to the starting time zero point. The preset deviation can be flexibly set according to actual requirements, and a smaller fixed value is usually selected.
Taking FIG. 12 as an example, the segment start time zero points t can be respectively set01、t02、t03And comparing every two segments, and judging whether the difference value between the starting time zero points of every two segments exceeds a preset deviation. If t is01And t02、t01And t03、t02And t03The difference between the two signals does not exceed the preset deviation, which indicates that the starting time zeros obtained by the different piecewise fitting functions are very similar, and the detection can be considered as normal detection, where the starting time zero t obtained in step 201 is0And is reasonable, and can be directly used for subsequent calculation. If t is01And t02If the difference between the two signals exceeds the preset deviation, it can be considered that the transmission pulse may be disturbed by imbalance in the transmission process during the detection, and the starting time zero point t obtained in step 2010Is unreasonable, the initial time zero point t obtained by the detection needs to be obtained0And (5) giving up processing.
Wherein, in the case that the difference between the starting time zero points of every two segments does not exceed the preset deviation, the starting time zero point t obtained in the step 201 can be further processed0And (6) correcting. For example, all segment start time zeros may be compared to the start time zeros t obtained in step 2010The average is taken as the starting time zero used in the final calculation.
(2) And the second method comprises the following steps:
and respectively comparing each segment starting time zero point with the starting time zero point deduced this time, and judging whether the difference value between each segment starting time zero point and the starting time zero point exceeds a preset deviation or not. If the difference value between the starting time zero point of any one of the segments and the starting time zero point exceeds the preset deviation, the starting time zero point of the current deduction is considered to be unreasonable, and the next pulse emission is continued after abandoning treatment. And if the difference value between the starting time zero point of each segment and the starting time zero point does not exceed the preset deviation, the starting time zero point of the current deduction is considered to be reasonable, and the flight time of the corresponding transmitted pulse is continuously calculated according to the starting time zero point.
Compared with the first method, the second method introduces the starting time zero point t calculated in step 201 during the comparison judgment0All the calculation results are compared with the starting time zero point t0Compared with the prior art, the comparison result is more visual, and the verification effect is more accurate.
Taking FIG. 12 as an example, the segment start time zero points t can be respectively set01、t02、t03And the starting time zero point t obtained in the step 2010Comparing the two to judge the starting time zero point and the starting time zero point t of each segment0Whether the difference between them exceeds a preset deviation. If t is01And t0、t02And t0、t03And t0The difference values between the two values do not exceed the preset deviation, which shows that the starting time zero points obtained by different piecewise fitting functions and the starting time zero point t directly obtained by the fitting function0Very close, the detection may be considered as normal detection, and the starting time zero point t obtained in step 201 is described0And is reasonable, and can be directly used for subsequent calculation. If t is01And t0If the difference between the two signals exceeds the preset deviation, it can be considered that the transmission pulse may be disturbed by imbalance in the transmission process during the detection, and the starting time zero point t obtained in step 2010Is unreasonable, the initial time zero point t obtained by the detection needs to be obtained0And (5) giving up processing.
Wherein, when the difference between the starting time zero point of each segment and the starting time zero point does not exceed the preset deviation, the starting time zero point t obtained in the step 201 can be further processed0And (6) correcting. For example, all segment start time zeros may be compared to the start time zeros t obtained in step 2010The average is taken as the starting time zero used in the final calculation.
By the method provided by the embodiment of the invention, the zero point of the initial time of the fitting function estimation can be effectively verified, the processing is abandoned when the verification result is unreasonable, and the method is continuously used for calculating the distance between the subsequent target and the laser radar when the verification result is reasonable, so that the abnormal detection can be effectively screened and filtered, and the accuracy of the final distance calculation result is ensured.
Example 4
On the basis of the foregoing embodiments 1 to 3, the embodiment of the present invention further provides an apparatus for optimizing the influence of the interference source on the lidar, which is capable of implementing the foregoing method, and mainly includes the lidar, a processor, and a memory. The processor and the memory may be disposed independently, or may be disposed integrally with the lidar, that is, disposed inside the lidar, which is not limited herein.
The laser radar is used for sequentially transmitting a first transmitting pulse and a second transmitting pulse towards a target direction according to a preset time interval tau and respectively collecting echo signals returned by the two transmitting pulses; wherein the light intensity of the first emission pulse is smaller than that of the second emission pulse, and the peak power of the first emission pulse is lower than that of the second emission pulse, and the preferred configuration is as shown in formula (1) in embodiment 1.
The laser radar may specifically be a one-dimensional laser radar, a two-dimensional laser radar, or a three-dimensional laser radar, which is not limited herein. The laser radar is internally provided with a laser transmitter and a high-speed digital-to-analog converter, and the laser transmitter is used for sequentially transmitting a first transmitting pulse and a second transmitting pulse towards a target direction according to a preset time interval tau so as to complete double-pulse transmission; the high-speed digital-to-analog converter is used for performing high-speed digital-to-analog sampling on the full waveform of the echo signals returned by the two transmitting pulses to obtain the echo signal pattern shown in fig. 5 or fig. 7.
The processor and the memory may be connected by a bus or other means.
The memory stores instructions executable by the processor. Specifically, the memory, as a non-volatile computer-readable storage medium for a method of optimizing the influence of the interference source on the lidar, may be used to store a non-volatile software program and a non-volatile computer-executable program, such as the method of steps 102 and 103 in embodiment 1, the method of steps 201 and 202 in embodiment 2, and the method of steps 301 and 303 in embodiment 3.
The processor executes the instructions stored in the memory to execute the methods of step 102 and step 103 in embodiment 1, that is, when the distance between the interference source and the target is short, all echo signals corresponding to the second transmit pulse are filtered, and multi-echo screening and filtering processing is performed on the echo signals corresponding to the first transmit pulse to finally obtain an effective target echo; when the distance between the interference source and the target is long, all echo signals corresponding to the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the second transmitting pulse, so that effective target echoes are obtained finally. The method of step 201-202 in embodiment 2 and the method of step 301-303 in embodiment 3 may also be performed, which are not described herein again.
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 non-volatile solid state storage device. In some embodiments, the memory optionally includes memory located remotely from the processor, and these remote memories may be connected to the processor through a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Those of ordinary skill in the art will appreciate that all or part of the steps of the various methods of the embodiments may be implemented by associated hardware as instructed by a program, which may be stored on a computer-readable storage medium, which may include: read Only Memory (ROM), Random Access Memory (RAM), magnetic or optical disks, and the like.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method of optimizing the effect of an interference source on a lidar comprising:
the laser radar transmits a first transmitting pulse and a second transmitting pulse in sequence towards a target direction according to a preset time interval, and echo signals returned by the two transmitting pulses are collected respectively; wherein the light intensity of the first transmitted pulse is less than that of the second transmitted pulse;
when the distance between the interference source and the target is close, all echo signals corresponding to the second transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the first transmitting pulse, so that effective target echoes are obtained finally;
and when the distance between the interference source and the target is longer, all echo signals corresponding to the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the second transmitting pulse, so that effective target echoes are finally obtained.
2. The method of optimizing the effect of interference sources on lidar of claim 1, wherein the first transmit pulse and the second transmit pulse satisfy the relationship:
wherein, P1Is the peak power, P, of the first transmit pulse2Is the peak power of the first transmit pulse.
3. The method of optimizing the effect of interference sources on lidar according to claim 1, wherein after obtaining a valid target echo, the method further comprises:
performing curve fitting on the target echo to obtain a fitting function of the target echo, and determining an initial time zero point of the corresponding transmission pulse by performing reverse time deduction on the fitting function;
and calculating the flight time of the corresponding transmitted pulse according to the starting time zero point, and further calculating the distance between the target and the laser radar according to the flight time.
4. The method according to claim 3, wherein the curve fitting is performed on the target echo to obtain a fitting function of the target echo, and the starting time zero of the corresponding transmission pulse is determined by performing reverse time deduction on the fitting function, specifically:
performing curve fitting based on a plurality of echo signal intensities above a signal threshold on a time axis to obtain a fitting function of the target echo;
and carrying out reverse time deduction on the fitting function to enable the intensity of the echo signal to approach a zero value, and further calculating the starting time zero point of the corresponding transmitting pulse.
5. The method according to claim 3, wherein the method for optimizing the influence of the interference source on the lidar comprises calculating a flight time of a corresponding transmitted pulse according to the starting time zero point, and further calculating a distance between the target and the lidar according to the flight time, specifically:
calculating the zero point of the ending time of the corresponding transmission pulse according to the zero point of the starting time of the corresponding transmission pulse and the symmetry axis of the echo signal curve;
calculating the flight time of the corresponding transmission pulse according to the starting time zero point and the ending time zero point of the corresponding transmission pulse;
and calculating the distance between the target and the laser radar according to the flight time and the flight speed of the corresponding transmitted pulse.
6. The method of optimizing the effect of an interference source on lidar according to any of claims 1-5, wherein the interference source is rain, snow, hail, or dust.
7. An apparatus for optimizing the effect of an interference source on a lidar, comprising a lidar, a processor, and a memory;
the laser radar is used for sequentially transmitting a first transmitting pulse and a second transmitting pulse towards a target direction according to a preset time interval and respectively collecting echo signals returned by the two transmitting pulses; wherein the light intensity of the first transmitted pulse is less than that of the second transmitted pulse;
the memory stores an instruction which can be executed by the processor, and the instruction is used for filtering all echo signals corresponding to the second transmitting pulse when the interference source is close to the target after being executed by the processor, and performing multi-echo screening and filtering processing on the echo signals corresponding to the first transmitting pulse; when the distance between the interference source and the target is long, all echo signals corresponding to the first transmitting pulse are filtered, and multi-echo screening and filtering processing is carried out on the echo signals corresponding to the second transmitting pulse, so that effective target echoes are obtained finally.
8. The apparatus for optimizing the effect of an interference source on a lidar of claim 7, wherein the lidar includes a laser transmitter configured to transmit the first transmit pulse and the second transmit pulse sequentially toward the target at predetermined time intervals.
9. The apparatus for optimizing the effect of an interference source on a lidar of claim 7, wherein the lidar further comprises a high-speed digital-to-analog converter for high-speed digital-to-analog sampling of a full waveform of echo signals returned by the two transmit pulses.
10. The apparatus for optimizing the effect of an interference source on a lidar of claim 7, wherein the lidar is a one-dimensional lidar, a two-dimensional lidar, or a three-dimensional lidar.
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