Method and system for detecting target in blind area of laser radar

Abstract

The invention discloses a method and a system for detecting a target in a blind area of a laser radar, which can quickly and accurately judge whether a target object is in the blind area of the laser radar by setting a blind area detection range, judging whether an echo signal is in the blind area detection range and judging the waveform of the echo signal in the blind area detection range. Therefore, a basis is provided for the distance measurement of the target object in the next step, and the accuracy and usefulness of the data obtained by the laser radar are ensured.

Description

Technical Field

[0001] The present invention relates to the field of laser radar ranging technology, and in particular to a method and system for detecting targets in a laser radar blind area. Background Art

[0002] Lidar is a radar system that emits laser beams to detect the position, speed and other characteristic quantities of a target. By emitting a detection signal (laser beam) to the target and then receiving the signal reflected from the target (target echo), the relevant information of the target can be obtained by analyzing the received signal, such as the target's distance, direction, height, speed, attitude, and even shape parameters, so as to detect, track and identify targets such as aircraft and missiles.

[0003] LiDAR has a blind spot within a certain close distance. The blind spot of LiDAR is mainly caused by two factors: one is the dead time, that is, the shortest time required for LiDAR to receive a laser pulse and then receive the next new laser pulse; the other is because of the need to eliminate the interference of stray light. Within a specific distance, LiDAR will ignore all received information within a certain close distance to ensure that the data obtained by LiDAR is accurate and useful.

[0004] Currently, no effective solution has been proposed to solve the problem that target objects in blind spots cannot be measured. Summary of the invention

[0005] In view of this, the present invention provides a method and system for detecting targets in a laser radar blind area, so as to solve the problems existing in the above-mentioned background technology.

[0006] A method for detecting a target in a laser radar blind area comprises the following steps:

[0007] S1, set the blind spot detection range;

[0008] S2, determine whether the echo signal is within the blind spot detection range, if yes, execute step S3; otherwise, use the time-of-flight method to determine the distance of the target object;

[0009] S3, determine the waveform of the echo signal. If the echo signal is an M-shaped wave, it means that the target object is in the blind spot of the laser radar, and an indication signal is issued; otherwise, repeat this step until the program termination condition is met. If the M-shaped wave is still not detected after the program termination condition is met, it means that the target object is not in the blind spot of the laser radar.

[0010] Preferably, in step S1, the blind spot detection range is determined according to the equipment performance of the laser radar.

[0011] Preferably, the blind spot detection range is 2.5m±0.45m.

[0012] Preferably, the detection starting point of the blind spot detection range is set at a position 150±30 points away from the initial sampling point of the laser emitter, and the detection ending point is set at a position 255±30 points away from the initial sampling point of the laser emitter, wherein the step time interval is 1ns per point, and the distance interval is 1.5cm per point.

[0013] Preferably, before executing step S2, the echo signal needs to be noise filtered.

[0014] Preferably, in step S3, the pulse width of the echo signal can be used instead of the waveform to determine whether the target object is in the blind spot of the laser radar. When the pulse width of the echo signal is greater than a preset threshold, it indicates that the target object is in the blind spot of the laser radar and an indication signal is issued.

[0015] Preferably, the specific steps of determining the echo signal waveform in step S3 are:

[0016] Determine whether the echo signal enters the rising edge. When it is detected that the current voltage is greater than the pulse edge detection threshold and the voltage at the previous moment is less than the pulse edge detection threshold, it means that the echo signal is on the rising edge. At the same time, start pulse width counting and perform falling edge detection. When the end point level of the falling edge is greater than the pulse edge detection threshold, the falling edge is flipped at its end point, forming an M wave.

[0017] Preferably, the program termination condition in step S3 is that the number of echoes is greater than the maximum set number of echoes or the number of detection points of the laser radar has been completed.

[0018] A target detection system in a laser radar blind area, comprising an analog-to-digital converter and a control module;

[0019] The analog-to-digital converter is used to collect echo signals;

[0020] The control module includes a filter and a blind spot detection and judgment unit. The filter is used to filter the noise in the echo signal and transmit the filtered echo signal to the blind spot detection and judgment unit; the blind spot detection and judgment unit is used to judge whether the echo signal is within the blind spot detection range. If the echo signal is within the blind spot detection range, the waveform of the echo signal is judged. If the echo signal is an M-shaped wave, it means that the target object is within the blind spot of the laser radar and an indication signal is issued; if the echo signal is not within the blind spot detection range, the time-of-flight method is used to determine the distance of the target object.

[0021] The beneficial effects of the present invention are:

[0022] The present invention sets a blind spot detection range, determines whether the echo signal is within the blind spot detection range, and determines the waveform of the echo signal within the blind spot detection range. It can quickly and accurately determine whether the target object is within the blind spot of the laser radar, and send an indication signal, thereby providing a basis for the next step of measuring the distance of the target object, thereby ensuring the accuracy and usefulness of the data acquired by the laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the data flow of the target detection system in the blind area of ​​the lidar.

[0025] Figure 2 This is a schematic diagram of blind spot detection range setting.

[0026] Figure 3 This is a schematic diagram of rising edge detection.

[0027] Figure 4 This is a schematic diagram of falling edge detection.

[0028] Figure 5 This is a schematic diagram of M wave signal voltage detection.

[0029] Figure 6 It is a flow chart of the target detection method in the blind area of ​​the laser radar. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0031] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0032] In the following description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings. Therefore, "module" and "component" can be used interchangeably.

[0033] In order to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings.

[0034] The present invention provides a method for detecting a target in a blind area of ​​a laser radar, which specifically comprises the following steps:

[0035] S1, set the blind spot detection range.

[0036] The blind spot detection range is determined according to the equipment performance of the laser radar, and the blind spot detection range can be 2.5m±0.45m, that is, the detection starting point of the blind spot detection range is set at a position 150±30 points away from the initial laser pulse sampling point emitted by the laser transmitter, and the detection end point is set at a position 255±30 points away from the initial laser pulse sampling point emitted by the laser transmitter. The "point" refers to the laser pulse sampling point, wherein the step time interval is 1ns per point (that is, the time interval between two adjacent laser pulse sampling points is 1ns), and the distance interval is 1.5cm per point (that is, the distance interval between two adjacent laser pulse sampling points is 1.5cm).

[0037] As a best embodiment, the detection starting point ( Figure 2 The Startx position in the figure is set at a position 150 points away from the initial laser pulse sampling point emitted by the laser transmitter, and the detection end point ( Figure 2 The Stopx position in the figure is set at a position 255 points away from the initial laser pulse sampling point emitted by the laser transmitter.

[0038] S2, determine whether the echo signal is within the blind spot detection range, if yes, execute step S3; otherwise, use the time of flight (TOF) method to measure the distance of the target object.

[0039] Before executing step S2, the echo signal needs to be noise filtered. After the noise is filtered out, the echo signal is then subjected to blind spot detection. If it is detected that the echo signal is within the blind spot detection range, step S3 is executed.

[0040] S3, determine the waveform of the echo signal. If the echo signal is an M-shaped wave, it means that the target object is in the blind spot of the laser radar, and an indication signal is issued; otherwise, repeat this step until the program termination condition is met. If the M-shaped wave is still not detected after the program termination condition is met, it means that the target object is not in the blind spot of the laser radar.

[0041] That is, first, determine whether the echo signal enters the rising edge. When it is detected that the current voltage is greater than the pulse edge detection threshold and the voltage at the previous moment is less than the pulse edge detection threshold (rising edge condition, such as Figure 3 When the pulse width is counted and the falling edge detection is performed, it indicates that the echo signal is on the rising edge. At the same time, the pulse width is counted and the falling edge detection is performed to detect whether the echo meets the falling edge condition (the current voltage is less than the pulse edge detection threshold and the voltage at the previous moment is greater than the pulse edge detection threshold, such as Figure 4 As shown), if the falling edge condition is met, it means that the echo signal is not an M wave but a rectangular wave. The pulse width can be obtained according to the falling edge position of the current pulse, and this step is repeated to determine whether the echo signals formed by the laser pulses subsequently emitted by the laser radar are all rectangular waves. If the number of detected echoes is greater than the maximum set number of echoes or the number of detection points of the laser radar has been completed, the program terminates (for example, the number of detection points of the laser radar is 10 laser pulses, and the maximum set number of echoes is 6. If the number of echoes that meet this condition is greater than 6 or the detection of 10 laser pulses has been completed, the program terminates), indicating that the target object is not in the blind area of ​​the laser radar, and the time of flight method is used to perform normal measurement of the distance to the target object;

[0042] If the echo does not meet the falling edge condition, the level at the end point of the falling edge is greater than the pulse edge detection threshold and the falling edge is reversed at its end point, forming an M wave, such as Figure 5 As shown, the M-wave state valid pulse mWave_vld is triggered, indicating that the target object is in the blind area of ​​the laser radar.

[0043] When the target object is located in the blind spot of the laser radar, the echo signal is superimposed on the leading light pulse, causing the falling edge to flip at a higher level to form an M wave. Therefore, the falling edge of the leading light cannot be effectively detected in this range, and the leading light pulse is widened. Therefore, when executing step S3, the pulse width of the echo signal can also be used instead of the waveform to determine whether the target object is in the blind spot of the laser radar, that is, when the pulse width of the echo signal is greater than the preset threshold value, it indicates that the target object is in the blind spot of the laser radar and an indication signal is issued.

[0044] If the M wave is detected, the valid state indication mWave_nextVld of the M wave rising edge is given, and the leading edge time of the next pulse after the blind area is set as the trailing edge time of the M wave detection.

[0045] The present invention also provides a target detection system in a laser radar blind area, comprising an analog-to-digital converter and a control module;

[0046] The analog-to-digital converter is used to collect echo signals;

[0047] The control module includes a filter and a blind spot detection and judgment unit. The filter is used to filter the noise in the echo signal and transmit the filtered echo signal to the blind spot detection and judgment unit; the blind spot detection and judgment unit is used to judge whether the echo signal is within the blind spot detection range. If the echo signal is within the blind spot detection range, the waveform of the echo signal is judged. If the echo signal is an M-shaped wave, it means that the target object is within the blind spot of the laser radar and an indication signal is issued; if the echo signal is not within the blind spot detection range, the time-of-flight method is used to determine the distance of the target object.

[0048] In this embodiment, the analog-to-digital converter is a high-speed ADC; the control module adopts an FPGA chip, and its filter is a Fir module.

[0049] It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for detecting a target in a laser radar blind area, characterized in that: The specific steps include: S1, set the blind spot detection range; S2, determine whether the echo signal is within the blind spot detection range, if yes, execute step S3; otherwise, use the time-of-flight method to determine the distance of the target object; S3, determine the waveform of the echo signal. If the echo signal is an M-shaped wave, it means that the target object is in the blind spot of the laser radar, and an indication signal is issued; otherwise, repeat this step until the program termination condition is met. If the M-shaped wave is still not detected after the program termination condition is met, it means that the target object is not in the blind spot of the laser radar.

2. The method for detecting targets in a laser radar blind area according to claim 1, characterized in that: In step S1, the blind spot detection range is determined according to the equipment performance of the laser radar.

3. The method for detecting targets in a laser radar blind area according to claim 2, characterized in that: The blind spot detection range is 2.5m±0.45m.

4. The method for detecting targets in a laser radar blind area according to claim 3, characterized in that: The detection starting point of the blind spot detection range is set at a position 150±30 points away from the initial sampling point of the laser emitter, and the detection ending point is set at a position 255±30 points away from the initial sampling point of the laser emitter, wherein the step time interval is 1ns per point, and the distance interval is 1.5cm per point.

5. The method for detecting targets in a laser radar blind area according to claim 1, characterized in that: Before executing step S2, the echo signal needs to be noise filtered.

6. The method for detecting targets in a laser radar blind area according to claim 1, characterized in that: In step S3, the pulse width of the echo signal can be used instead of the waveform to determine whether the target object is in the blind spot of the laser radar. When the pulse width of the echo signal is greater than the preset threshold, it means that the target object is in the blind spot of the laser radar and an indication signal is issued.

7. The method for detecting targets in a laser radar blind area according to claim 1, characterized in that: The specific steps of determining the echo signal waveform in step S3 are: Determine whether the echo signal enters the rising edge. When it is detected that the current voltage is greater than the pulse edge detection threshold and the voltage at the previous moment is less than the pulse edge detection threshold, it means that the echo signal is on the rising edge. At the same time, start pulse width counting and perform falling edge detection. When the end point level of the falling edge is greater than the pulse edge detection threshold, the falling edge is flipped at its end point, forming an M wave.

8. The method for detecting targets in a laser radar blind area according to claim 1, characterized in that: The program termination condition in step S3 is that the number of echoes is greater than the maximum set number of echoes or the number of detection points of the laser radar has been completed.

9. A target detection system in a laser radar blind area, characterized in that: including an analog-to-digital converter and a control module; The analog-to-digital converter is used to collect echo signals; The control module includes a filter and a blind spot detection and judgment unit. The filter is used to filter the noise in the echo signal and transmit the filtered echo signal to the blind spot detection and judgment unit; the blind spot detection and judgment unit is used to judge whether the echo signal is within the blind spot detection range. If the echo signal is within the blind spot detection range, the waveform of the echo signal is judged. If the echo signal is an M-shaped wave, it means that the target object is within the blind spot of the laser radar and an indication signal is issued; if the echo signal is not within the blind spot detection range, the time-of-flight method is used to determine the distance of the target object.

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