CN118294925A

CN118294925A - Laser radar and detection control method

Info

Publication number: CN118294925A
Application number: CN202310004367.XA
Authority: CN
Inventors: 陈杰; 向少卿
Original assignee: Hesai Technology Co Ltd
Current assignee: Hesai Technology Co Ltd
Priority date: 2023-01-03
Filing date: 2023-01-03
Publication date: 2024-07-05
Also published as: WO2024146549A2; WO2024146549A3

Abstract

The invention provides a laser radar, comprising: an emission unit including a plurality of lasers configured to emit probe beams; a receiving unit including a plurality of detectors configured to receive echoes of the detection beam on the obstacle and convert the echoes into an electrical signal, wherein each detector has a corresponding laser, thereby forming a plurality of detection channels; and a processing unit configured to calculate a distance and/or a reflectivity of the obstacle from the echoes, wherein the plurality of detection channels are divided into a plurality of groups for detection in turn within at least one detection time slice, wherein different groups employ different luminous powers and different time windows for detecting environmental information of different distances.

Description

Laser radar and detection control method

Technical Field

The present invention relates generally to the field of photoelectric detection, and more particularly, to a laser radar and a detection control method.

Background

The laser radar is a commonly used ranging sensor, has the advantages of long detection distance, high resolution, strong active interference resistance, small volume, light weight and the like, and is widely applied to the fields of intelligent robots, unmanned aerial vehicles and the like.

The most important resources of the lidar are hardware resources corresponding to each channel, and time and power consumption are the most important resources. How to fully and efficiently utilize these resources and apply limited resources to the required target detection, and to generate a high-quality point cloud is of great importance to the lidar. In other words, in the case of fixed hardware, the rational application of resources to the scanning of obstacles within the region of interest (ROI, region of Interest) is a problem to be solved.

The matters in the background section are only those known to the public and do not, of course, represent prior art in the field.

Disclosure of Invention

In view of at least one of the drawbacks of the prior art, the present invention provides a lidar comprising:

an emission unit including a plurality of lasers configured to emit probe beams;

a receiving unit including a plurality of detectors configured to receive echoes of the detection beam on the obstacle and convert the echoes into an electrical signal, wherein each detector has a corresponding laser, thereby forming a plurality of detection channels; and

A processing unit configured to calculate a distance and/or a reflectivity of the obstacle from the echoes,

Wherein in at least one detection time slice, the plurality of detection channels are divided into a plurality of groups for detection in turn, wherein different groups adopt different luminous powers and different time windows for detecting environmental information of different distances.

According to one aspect of the invention, the smaller the transmit power employed for a detection channel with a smaller detection distance.

According to one aspect of the invention, the plurality of detection channels are configured into three groups, wherein the detection distance corresponding to the second group of detection channels is greater than the detection distance of the first group of detection channels and less than the detection distance of the third group of detection channels; the transmit power of the second set of detection channels is greater than the transmit power of the first set of detection channels and less than the transmit power of the third set of detection channels.

According to one aspect of the invention, the lasers of the first set of detection channels comprise one-fourth to one-half of the plurality of lasers.

According to one aspect of the invention, the lasers of the first set of detection channels are uniformly distributed among the plurality of lasers, and the processing unit is configured to: after the first group of detection channels complete detection, assigning values to detection results of other detection channels covered by the obstacle according to the obstacle detected by the first group of detection channels.

According to one aspect of the invention, the second set of detection channels is not coincident with the first set of detection channels; or the second set of detection channels is selected in part from detection channels of the first set of detection channels in which no obstacle is scanned.

According to an aspect of the invention, the third set of detection channels is selected from detection channels of the plurality of detection channels other than the first and second sets of detection channels; or the third set of detection channels is selected in part from detection channels of the first and second sets of detection channels in which no obstacle is scanned.

According to one aspect of the invention, the third set of detection channels is configured to: the detection is performed sequentially from bottom to top in the vertical plane.

According to one aspect of the invention, the third set of detection channels is selected from detection channels within ±5° of each side of the horizontal line of the plurality of detection channels.

According to one aspect of the invention, when the remaining flight time in the detection time slice is insufficient to complete the detection of the third group of detection channels, selecting a part of detection channels from the third detection channels for detection, and assigning the detection result of the part of detection channels to detection channels which are different from the part of detection channels by a fixed value in the next detection time slice of the laser radar.

The invention also provides a detection control method of the laser radar, wherein the laser radar comprises a plurality of lasers and a plurality of corresponding detectors, so as to form a plurality of detection channels, and the control method comprises the following steps: in at least one of the detection time slices,

Controlling a first set of detection channels of the plurality of detection channels to emit detection beams and to receive echoes;

Controlling a second set of the plurality of probe channels to transmit probe beams and receive echoes,

Wherein the first set of detection channels and the second set of detection channels do not completely coincide and employ different luminous powers and different time windows for detecting environmental information at different distances.

According to one aspect of the invention, for the detection channels with smaller detection distances, the transmission power is smaller, wherein the detection distance corresponding to the detection channels of the second group is larger than the detection distance of the detection channels of the first group, and the transmission power of the detection channels of the second group is larger than the transmission power of the detection channels of the first group.

According to an aspect of the present invention, the detection control method further includes: in the at least one detection time slice,

Controlling a third set of the plurality of probe channels to transmit probe beams and receive echoes,

The third group of detection channels are not completely overlapped with the first group of detection channels and the second group of detection channels, the detection distance corresponding to the third group of detection channels is larger than that of the second group of detection channels, and the transmission power of the third group of detection channels is larger than that of the second group of detection channels.

According to an aspect of the present invention, the lasers of the first set of detection channels are uniformly distributed among the plurality of lasers, and the detection control method further includes: after the first group of detection channels complete detection, assigning values to detection results of other detection channels covered by the obstacle according to the obstacle detected by the first group of detection channels.

According to one aspect of the invention, the step of controlling the third set of detection channels to emit detection beams comprises: the detection is sequentially performed from the lower side to the upper side of the laser radar.

According to one aspect of the invention, the step of controlling the third set of detection channels to transmit detection beams and to receive echoes comprises: when the residual flight time in the detection time slice is insufficient to complete the detection of the third group of detection channels, selecting part of detection channels from the third detection channels for detection, and assigning the detection result of the part of detection channels to detection channels which are different from the part of detection channels by fixed values in the next detection time slice of the laser radar.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:

FIG. 1 shows the number of points of a lidar graded by distance;

FIG. 2 illustrates areas of varying degrees of attention in an autopilot scenario;

FIG. 3 shows the relationship between the number of channels required for detection and the distance of an obstacle for the same obstacle;

The relationship between the distance from the lidar and the vertical angle of the wire harness is shown in fig. 4 a;

FIG. 4b shows the relationship between lidar detection pitch angle and obstacle distance;

FIG. 5 illustrates a lidar according to an embodiment of the invention;

FIG. 6a shows a transmitting unit according to one embodiment of the invention;

Fig. 6b shows a transmitting unit according to another embodiment of the invention;

fig. 7 shows a receiving unit according to an embodiment of the invention;

FIG. 8 shows a schematic diagram of transmit power for three groups of probing channels according to one embodiment of the invention;

FIG. 9 shows a schematic diagram of a detection scheme according to one embodiment of the invention;

FIG. 10 shows the results of a simulation of an embodiment of the present invention; and

Fig. 11 shows a detection control method of a lidar according to an embodiment of the present invention.

Detailed Description

Hereinafter, only certain exemplary embodiments are briefly described. As will be recognized by those of skill in the pertinent art, the described embodiments may be modified in various different ways without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be fixedly connected, detachably connected, or integrally connected, and may be mechanically connected, electrically connected, or may communicate with each other, for example; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is less level than the second feature.

The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. In order to simplify the present disclosure, components and arrangements of specific examples are described below. They are, of course, merely examples and are not intended to limit the invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.

The embodiments of the present invention will be described below with reference to the accompanying drawings, and it should be understood that the embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.

In order to achieve resource optimisation of the lidar, using more channels and power for scanning in areas that are more important for achieving unmanned driving, such as obstacles within a distance of 200m and within 10m above the ground, the invention provides an improved lidar and detection control method for the lidar.

Fig. 1 shows the number of points of the lidar counted by distance, which groups the points in the complete point cloud by distance. As shown in fig. 1, the horizontal axis is distance and the vertical axis is number of points, as can be seen from fig. 1: most of the points in the point cloud are concentrated within 50m of the lidar. In addition, in an autopilot scenario, the closer to the center field of view of the lidar, the more the area of interest to the customer. As shown in fig. 2, region C, which is the maximum field of view FOV of the radar, is of greater customer interest as the fill color deepens, e.g., region a, which may correspond to a 50 ° field of view in the horizontal direction and 12 ° field of view in the vertical direction of the lidar, may be of greater customer interest than region B.

The ROI area should be stereoscopic and as the distance increases, the pitch angle range of the radar beam covered near the horizon of interest will become smaller, i.e. fewer lines need to be used to complete the scan of it. Specifically, as shown in fig. 3, that is, for the same obstacle, as the distance between the obstacle and the laser radar increases (the horizontal axis is the distance, and left to right), the vertical angle span/radar channel number required for scanning the obstacle in the longitudinal direction decreases (31→32→33, the vertical angle range decreases, and the number of channel coverage in the radar decreases). As shown in fig. 3, six channels of lidar are required to complete a scan of a person when the person is in the leftmost position; when in the middle position, four channels of laser radar are needed to complete the scanning of the person; when in the rightmost position, two passes of the lidar are required to complete the scan of the obstacle.

In an autopilot scenario, the road sign (obstacle of interest to the unmanned user) is typically 7m in center-to-ground height, and more loosely, i.e., in a typical unmanned scenario, the user is not concerned with objects beyond horizon, such as 10m in height, such as distant buildings, terrain, trees, etc.

The relationship between the distance from the lidar and the perpendicular angle of the lidar beam is shown in fig. 4 a. In fig. 4a, α (negative) and β (positive) are pitch angles of the lidar, and from distances d and h in fig. 4a, angles α and β can be calculated. Thus, as shown in fig. 4b, the horizontal axis is distance and the vertical axis is vertical field angle. Objects in the height range of 0-10m at different distances from the lidar, the pitch range of the corresponding lidar is as in fig. 4b with two curves. The upper curve may be referred to as the 10m line, the lower curve is the ground line, the real ROI area between the two lines, and the lidar should concentrate resources to measure targets in this range. Here divided into 10m lines 12 and ground lines 11. Wherein after the point cloud of the lidar is obtained, the ground line is easy to calculate, the boundary of the ground line is clear and the characteristics are obvious, all the point clouds are concentrated above (vertical direction) the point clouds are basically not located below (vertical direction), and even if the point below the ground line is occasionally located, such as under an overhead or specular reflection, the point clouds are easy to filter out.

As can be seen in connection with fig. 4a and 4b, the vertical beam of the lidar incident on the ground differs with the distance from the lidar. More precisely, as the obstacle is further from the lidar, the vertical angle of the lidar incident on the ground, x, is smaller, up to infinity, x≡0. As shown by the 0 ° corresponding line in fig. 4a, the pitch angle of the lidar representing the wire harness emitted in this direction is 0 °.

The inventors have based on the studies and experiments shown in fig. 1-4 above, therefore, proposed a solution of the present application, in which the resources of the lidar can be used more for detection and scanning of the region of interest during the actual scanning detection process. Specifically, taking a mechanical laser radar as an example, the mechanical laser radar rotates in a horizontal plane to cover a horizontal view field of 360 degrees, and the plurality of detection channels are divided into a plurality of groups for detection in turn in at least one detection time slice, wherein different groups correspond to different preset detection distances and different luminous powers. For example, during a scan of one location, the detection channels are divided into three groups, each group of detection channels being responsible for detecting obstacles at different distances, from near to far, pitch angle from negative (< 0 °) to positive (> 0 °), resolution from low to high, with sufficient redundancy to ensure coverage of an object region within 10m height above the ground. Preferably, the lidar performs the above strategy of packet rotation detection during all of its detection time slices.

Fig. 5 shows a lidar 10 according to an embodiment of the application, the solution of which is described in detail below with reference to fig. 5.

As shown in fig. 5, the lidar 10 includes a transmitting unit 11, a receiving unit 12, and a processing unit 13. The emitting unit 11 may include lasers arranged in a row, for example, as shown in fig. 6a, where the emitting units 11 according to an embodiment of the present invention are attached to a plane board, specifically, may be vertical cavity lasers (VERTICAL CAVITY Surface EMITTING LASER, VCSEL), and light emitted by the emitting units 11 exits perpendicular to the emitting end, and after being shaped by an emitting lens group (not shown), exits from the laser radar 10 to different directions to cover a vertical field of view of the radar. Wherein the emission unit 11 includes a plurality of lasers L1, L2, L3, …, LN, N is an integer of 1 or more, for example, 1, 16, 32, 40, 64, 128, or 256, each of which can be driven to emit the probe beam L. The echo L' after the diffuse reflection of the probe beam L on the obstacle is returned to the lidar 10 and received by the receiving unit 12 of the lidar 10. The plurality of lasers L1, L2, L3, …, LN shown in fig. 6a are distributed in a one-dimensional array, to which the invention is not limited.

In another embodiment of the present invention, the plurality of lasers may be distributed in a two-dimensional array, as shown in fig. 6b, where the plurality of lasers are divided into a plurality of columns (5 columns are schematically shown in the figure), and the number of lasers in each column may be the same or different. In the case of multiple lasers, each laser generally corresponds to a particular vertical field angle in a vertical plane, the multiple lasers collectively covering the vertical field of view range of the lidar.

Fig. 7 shows a receiving unit 12 according to AN embodiment of the invention, wherein the receiving unit 12 comprises a plurality of detectors A1, A2, A3, …, AN, N being AN integer greater than or equal to 1, for example 16, 32, 40, 64, 128 or 256. Each detector is configured to receive an echo L' of the detection light beam L on the obstacle and to convert it into an electrical signal. The detectors are typically in a one-to-one correspondence, such as a one-to-one correspondence, or a one-to-many, many-to-one, or many-to-many relationship. Each detector Ai receives echoes L' produced by the probe beam L emitted by the corresponding laser Li, forming a plurality of probe channels. As shown in fig. 6 and 7, the laser forms N detection channels with the detector. Those skilled in the art will readily appreciate that the plurality of detectors may also be distributed in a two-dimensional array, and will not be described in detail herein.

For a rotating mechanical laser radar, the number of N is generally greater than 1, each detection channel corresponds to a view angle in one direction in a vertical plane, and the N detection channels jointly cover a vertical view field range of the laser radar in the vertical plane, and an optical machine rotor of the laser radar drives the transmitting unit 11 and the receiving unit 12 to rotate in a horizontal plane, so that a horizontal view field range of 360 degrees is covered. Similarly, for a rotating mirror type radar, the rotating mirror may deflect the incident beam and deflect the return beam to the detector, enabling scanning over a horizontal field of view, covering a range of horizontal fields of view, e.g., 120 ° in size. For a galvanometer lidar, the number of N may be equal to 1. For example, the probe light beam L emitted by the emitting unit is reflected to the outside of the laser radar through the vibrating mirror, and the vibrating mirror swings back and forth, so that the probe light beam L can be reflected to different angles in a vertical plane, and the swinging range of the vibrating mirror corresponds to the vertical field of view range of the laser radar in the vertical plane. Rotation or oscillation of the lidar in the horizontal plane provides a horizontal field of view range for the lidar. In addition, the number of lasers and the number of detectors may not be equal, for example, a plurality of lasers corresponds to one detector, which is within the scope of the present invention.

The processing unit 13 is configured to calculate the distance and/or the reflectivity of the obstacle from said echo L'. Specifically, the processing unit 13 determines the flight time according to the emission time of the probe beam L and the reception time of the echo L', so that the distance and/or the reflectivity of the obstacle can be determined.

According to the invention, the plurality of detection channels are divided into a plurality of groups for detection in turn in at least one detection time slice, wherein different groups use different luminous powers and different time windows for detecting environmental information of different distances. In the present invention, a detection time slice refers to a time period corresponding to a resolution of the lidar covered in a plane (e.g., a horizontal plane). Taking a rotating 128-wire mechanical lidar as an example, the angular resolution is, for example, 0.2 °, and in the time period from 0 ° rotation to 0.2 °,128 lasers are sequentially emitted, completing the detection of one period, and then going into the next time period (i.e., detection time slice) of 0.2 ° to 0.4 °. It will be readily appreciated by those skilled in the art that in each detection time slice, some of the lasers may be controlled to emit as desired, for example, half or a quarter of the 128 lasers may be selected for emission and detection. In the invention, in one detection time slice, a plurality of detection channels are grouped for detection in turn, and different groups correspond to different preset detection distances and adopt different luminous powers.

Taking three groups as an example, reserving different time windows for each group of detection channels, corresponding to different detection distances, and adopting different luminous powers to respectively perform multi-round detection. The following is an example. When the first group of detection channels corresponds to obstacle detection within 0-50m, the time window of the group of detection channels can be set to 0-333ns (2 x 50/speed of light c); when the second set of detection channels corresponds to obstacle detection within 50-100m, the time window of the set of detection channels may be set to 333ns-667ns; when the third set of detection channels corresponds to obstacle detection within 100-200m, the time window of the set of detection channels may be set to 667ns-1333ns. According to another embodiment of the invention, the first set of detection channels may correspond to obstacle detection within 0-40 m; the first set of detection channels may correspond to obstacle detection within 40-80 m; the first set of detection channels may correspond to obstacle detection within 80-200 m. Although in the above embodiment, the detection distances corresponding to the detection channels of each group are not overlapped with each other, it will be understood by those skilled in the art that the detection distances of the detection channels of each group may also have a certain degree of overlap, for example, 10% overlap, and the detection windows may also be adjusted accordingly.

The time window of each set of channels is briefly described below, taking the first set of detection channels as an example, by which a first round of detection is performed for obstacle detection within 0-30m, the time window may be set to 0-200ns, i.e. the detectors in the first set of detection channels are turned on only in the period of 0-200ns, so that these detectors have the ability to convert echoes into electrical signals only in the period of 0-200 ns; or alternatively, the detectors remain on all the time, only the output signals of the detectors in the first set of detection channels during a period of 0-200ns are read, and the output signals during other periods are not used to calculate the obstacle distance. The same is true for other sets of detection channels.

According to a preferred embodiment of the present invention, the smaller the detection distance corresponding to the detection channel, the smaller the transmission power used; the larger the corresponding detection distance of the detection channel is, the larger the adopted transmitting power is. Still referring to the above three sets of detection channels as an example, as shown in fig. 8, the detection distance corresponding to the second set of detection channels is greater than the detection distance of the first set of detection channels and is smaller than the detection distance of the third set of detection channels, so that the transmission power of the second set of detection channels is greater than the transmission power of the first set of detection channels and is smaller than the transmission power of the third set of detection channels. In this way, saturation of the detector of the receiving unit can be avoided or reduced and the power of the lidar can be saved. Taking the receiving unit 12 shown in fig. 7 as AN example, each detector A1, A2, A3, …, AN may comprise AN array of a plurality of single photon avalanche diodes SPADs, so each receiving unit is a photo-detection unit consisting of AN array of SPADs. Each detector has a maximum counting rate, namely, the maximum counting rate capable of responding in unit time, and after the maximum counting rate is reached, when the incident light intensity is further increased and the photon number is further increased, the output of the detector cannot be further increased, so that the intensity of the incident light cannot be reflected, and the laser radar measurement accuracy is poor. Under the condition of the same transmitting power, the echo intensity generated by the short-distance obstacle is high, so that the intensity of the echo received by the detection channel with a small detection distance is also high, and the detector is easy to saturate. According to the preferred embodiment of the invention, the situation that the detector is saturated can be avoided or reduced as much as possible by adopting small transmitting power for the detection channel with small detection distance, so that the detection precision of the laser radar is improved. And for a detection channel with a large detection distance, high transmission power is adopted, so that the intensity of echo is improved as much as possible, the signal-to-noise ratio of echo signal detection is improved, and the detection precision of the laser radar is improved. In addition, since the laser does not need to be operated at the maximum transmission power all the time, the power consumption level of the laser radar can be significantly improved.

In the above embodiment, the single scanning of the laser radar in a certain detection time slice is divided into 3 sections according to the detection distance, different distance sections adopt different groups of detection channels to perform multi-round scanning, and each group adopts different wire harnesses/channels and also adopts different luminous power. As shown in fig. 8, 0-200m uses the first group, the second group and the third group together to realize scanning, and the third group > the second group > the first group in terms of transmitting power, that is, the farther the distance, the larger the power used.

It will be readily appreciated by those skilled in the art that, in addition to the three sets of detection channels described above, two sets of detection channels may be divided for two-wheel detection, or four or more sets of detection channels may be divided for four-wheel detection or more, all of which are within the scope of the present invention. For example, dividing the detection channels into two groups for two-round detection, wherein the first group of detection channels corresponds to obstacle detection within 0-100 m; the first set of detection channels corresponds to obstacle detection within 100-200 m. By reducing the number of packets, the complexity of control can be reduced.

The selection of the detection channels of each group is described below by taking three groups of detection channels as examples.

According to a preferred embodiment of the invention, the groups of detection channels are preset. For example, the lasers of the first set of detection channels comprise one-fourth to one-half of the plurality of lasers, uniformly distributed among the plurality of lasers of the emitting unit shown in fig. 6a, such as lasers L1, L3, L5 …; the lasers of the second set of detection channels uniformly select half of the lasers, such as lasers L2, L6, L10 …, from the detection channels outside the first set; the remaining detection channels, such as lasers L4, L8, L12 …, serve as a third set of detection channels.

According to another preferred embodiment of the present invention, each set of detection channels may be dynamically selected, for example, a first set of detection channels is first selected, a first round of "light-emitting-receiving" detection is performed using the first set of detection channels, and then a second set of detection channels is dynamically determined based on the detection result (e.g., whether an obstacle is present) of the first set of detection channels; then a second round of "light-emitting-receiving" detection is performed using the second set of detection channels, and then a third set of detection channels is dynamically determined based on the detection results of the second set of detection channels. As described in detail below.

The lasers of the first set of detection channels may for example comprise one-fourth to one-half of the plurality of lasers, preferably being evenly distributed among the plurality of lasers, e.g. odd numbered lasers 1,3, 5, 7, … of the N lasers and corresponding detectors are selected as the first set of detection channels for the first round of detection. The first set of detection channels allows for both optical crosstalk of the coaxial light path and covers as much as possible of the target within about 30m, while reducing the resolution by half, but is still sufficient for detecting obstacles at close distances. In addition, since the emission power of the first group of detection channels is low, the time window is short, and most of targets of the laser radar are distributed in the range of 50m (see fig. 1), the targets in the range can be acquired as much as possible in the detection process of the first group of detection channels.

Further in accordance with a preferred embodiment of the present invention, after the first set of detection channels completes detection, the detection results of the other detection channels covered by the obstacle are assigned based on the obstacle detected by the first set of detection channels. For example, the first group of detection channels selects the 1 st, 3 rd and 5 th channels to emit light, and when the detection channels 1,3 rd and 5 th channels detect an obstacle, the detection channels can be assigned to other channels in the range of angles scanned to the target due to the spatial continuity of the obstacle, for example, the detection results of the 2 nd channels can be assigned based on the detection results (obstacle distance) of the 1 st and 3 rd channels (for example, the average value of the detection distances of the 1 st and 3 rd channels is assigned to the 2 nd channel), and the detection results of the 4 th channels can be assigned based on the detection results (obstacle distance) of the 3 rd and 5 th channels (for example, the average value of the detection distances of the 3 rd and 5 th channels is assigned to the 4 th channel). In this way, the 2 nd and 4 th channels can be directly and automatically skipped in the subsequent packet detection process, and the measurement is not required to be repeated.

In addition, in an autopilot scenario, high-reflection plates are often encountered, especially for close range detection, which can easily cause saturation of the detector. Even if the detection is performed with a small light intensity, the ranging accuracy is still affected and a ghost image is generated. Thus, according to a preferred embodiment of the present invention, a first set of detection channels may be allocated twice more time resources, scanned in multiple passes, the first pass being illuminated with a small intensity, the orientation of the high-reflection plate being determined by the reception conditions, one of the passes then avoiding the high-reflection plate, and the other pass being dedicated to tracking the high-reflection plate. It is necessary to build a data table tracking the highly inverted target, consider the OFFSET of the light angle, and update it continuously with the horizontal scan of the radar.

In the first group of detection channels, the plurality of lasers can emit light for detection at the same time, or can perform polling light emission detection according to a certain time sequence.

According to one embodiment of the invention, the second set of detection channels is responsible for scanning for obstructions within 30-120m, with medium transmit power, and rescanning approximately 1/2 of the channels. The second set of detection channels may be non-coincident with the first set of detection channels, e.g. about 1/2 of the detection channels are selected for detection outside the first set of detection channels. Or the second set of detection channels may have a certain overlap with the first set of detection channels. For example, for those channels in the first set of detection channels where no obstacle is detected, it is only possible to indicate that no obstacle is present in the 30m range, and that an obstacle may still be present at a greater distance, so for those channels in the first set of detection channels where no obstacle is scanned, it is still possible to select them into the second set of detection channels for the second set of detection.

Thus, the second set of detection channels may not overlap with the first set of detection channels, especially in case an object has been scanned in the first set of detection channels, since it is not necessary to perform a further round of scanning for a vertical orientation in which the first set of detection channels has been scanned to the object; if no object is scanned in the first set of detection channels, the portion of the channels scanned by the second set of detection channels may overlap the first set of detection channels, such as being uniformly selected over the entire field of view, to avoid or reduce missing low-contrast objects.

According to a preferred embodiment of the present invention, the third set of detection channels is selected from the plurality of detection channels other than the first and second sets of detection channels; or the third set of detection channels is selected in part from detection channels of the first and second sets of detection channels in which no obstacle is scanned. According to one embodiment of the present invention, the third set of detection channels includes detection channels of the first set of detection channels and the second set of detection channels, in which no obstacle is scanned, and other channels than the first and second sets of detection channels, so as to ensure that all detection channels can be controlled to perform detection once in the current horizontal direction of the laser radar. It is also preferred that the remaining channels of the first and second passes are angularly ordered, preferably with the additional measurements starting at a negative angle, i.e. the passes starting from below to above in the vertical plane.

In addition, after the first and second detection, the small amount of point cloud left between the horizon and the 10m line must be complemented, and only this part of the area needs to reach a long distance. According to a preferred embodiment of the present invention, the third set of detection channels is selected from detection channels within ±5° of both sides of the horizontal line in the plurality of detection channels, i.e. detection channels within ±5° of both sides of the horizontal line are selected from detection channels in which no obstacle is scanned in the first and second sets of detection channels, and other channels than the first and second sets of detection channels.

According to the spatial distribution of the point cloud, a target angle range of at most 3 ° above the ground line outside the range of about 100m is the focus of interest of the lidar, which is the range to be preferably complemented by the third-round detection. The range of the complementary measurements can then be decided based on the results of the first and second detection scans, without re-detecting in the third detection if the first and second detection have scanned the detection path of the object, because an obstacle has been detected in the previous two scans.

In the specific implementation, the complement measurement range and the astronomical line tracking of the third-wheel detection can further improve the safety of the radar. It is generally sufficient that the third wheel detects densely covered areas ranging from 5 ° from the vicinity of the horizon to the top.

For targets above the horizon, the laser radar is undetectable and has no echo response even with maximum light intensity. The boundary of the continuous area exceeding the range capability of the laser radar is the boundary, no target can be detected within the range from the boundary to the upper limit of the pitch angle, and by adopting the characteristic, the boundary can be found, namely, in the point cloud, the line can be obtained by starting to mark at the position without any point. The laser radar can construct a data table to dynamically track the change of the astronomical line and reduce dotting density for angles above the astronomical line so as to save power consumption. According to one embodiment of the invention, the ground line may be determined first, followed by the skyline. For example, the point cloud image may be divided by an arctangent function, so that the contrast of the two sides is obtained, and the ground line is the highest contrast. After locking the ground line, a 10m line is obtained, since the 10m line is a line 10m above the ground line, which is taken as the astronomical line.

Since the total time of the first, second and third wheel detection needs to be limited by the time interval between the position of the lidar and the next position (angular resolution of the lidar), situations may arise in which the third wheel detection is insufficient to complement all remaining channels (insufficient time of flight). In this case, according to a preferred embodiment of the present invention, when the remaining time of flight in the detection time slice is insufficient to complete the detection of the third set of detection channels, a part of the detection channels is selected from the third detection channels to detect, and the detection result of the part of the detection channels is assigned to the detection channels of the laser radar in the next detection time slice, which are different from the part of the detection channels by fixed values, respectively. In particular, a parity interleaving strategy may be adopted such that adjacent two horizontal resolution data are offset complementary and cover all channels. That is, as shown in FIG. 9, for channels that are not complemented, the data obtained at the first detection orientation is shifted by one or n (n.ltoreq.5) vertical channels as data at the second detection orientation. Assuming that the 1 st, 3 rd, 5 th channels are used for detection at the first detection azimuth θi (within the first detection time slice), and that the 1 st, 3 rd, 5 th channels are not detected at the second detection azimuth θi+1 (within the second detection time slice), the 1 st, 3 rd, 5 th channels are not detected by the first-round detection and the second-round detection, and that the 1 st, 3 rd, 5 th channels cannot be detected due to the limitation of the flight time in the third-round detection, the data of the 1 st, 3 rd, 5 th detection channels obtained at the first detection azimuth θi can be used as the detection result of the 1 st, 3 rd, 5 th channels at the second detection azimuth θi+1, so that the position variation caused by the movement of the object is considered to some extent by the staggering even in the case of an obstacle, and the accuracy is maintained.

In the whole, according to the embodiment of the invention, a single scanning in a certain horizontal direction is divided into n more than or equal to 2 sections according to the distance, different distance sections adopt different groups of detection units for carrying out multi-round scanning, and each round of scanning adopts different wire harnesses/channels and also adopts different luminous power. The scanning order of the third scan is preferably from a negative angle, the number of scans of the last or several scans is smaller than the total line, but the area can be dynamically allocated, the time sequence can be dynamically configured, and the method is different from a radar with fixed time sequence. By the method, resource optimization is realized, namely more channels and power are used for scanning the most concerned area of the laser radar, such as an obstacle in the range of 200m from the ground to 10m above the ground, and the whole power consumption can be saved to a certain extent.

The inventor carries out simulation and emulation on the invention, utilizes sine waves to simulate undulating ground, can set maximum gradient and period, adopts 0.05 gradient specifically, and is the maximum value of urban roads. The highway is generally lower than 0.03, and the radar installation height is 1.8m. Two objects are arranged on the road, one object is 1m high and is positioned in 100 m; one 10m high, located at 200 m. The roadside is provided with a guideboard, 5-8m high and is positioned in 30 m.

From the simulation results shown in fig. 10, the first round of detection is mainly focused on near targets. The second detection round covers all targets within 100m with half resolution. The third detection cycle then covers all targets in the stereoscopic ROI range completely.

Fig. 11 illustrates a method 100 for controlling detection of a lidar comprising a plurality of lasers and a corresponding plurality of detectors to form a plurality of detection channels, such as the lidar illustrated in fig. 5-7, in accordance with an embodiment of the present invention. Described in detail below with reference to fig. 10.

As shown in fig. 10, the control method 10 includes: in at least one of the detection time slices,

In step S101, a first set of detection channels of the plurality of detection channels is controlled to emit detection beams and to receive echoes;

in step S102, a second set of detection channels of the plurality of detection channels is controlled to emit detection beams and to receive echoes,

Wherein the first and second groups of detection channels do not completely coincide and employ different luminous powers and different time windows for detecting environmental information at different distances

According to a preferred embodiment of the invention, the transmission power is smaller for the detection channels with smaller detection distances, wherein the detection distance corresponding to the second set of detection channels is larger than the detection distance of the first set of detection channels, and the transmission power of the second set of detection channels is larger than the transmission power of the first set of detection channels.

According to a preferred embodiment of the present invention, the detection control method further includes: in the at least one detection time slice,

According to a preferred embodiment of the invention, the lasers of the first set of detection channels comprise one-fourth to one-half of the plurality of lasers.

According to a preferred embodiment of the present invention, the lasers of the first set of detection channels are uniformly distributed among the plurality of lasers, and the detection control method further comprises: after the first group of detection channels complete detection, assigning values to detection results of other detection channels covered by the obstacle according to the obstacle detected by the first group of detection channels.

According to a preferred embodiment of the invention, the second set of detection channels is not coincident with the first set of detection channels; or the second set of detection channels is selected in part from detection channels of the first set of detection channels in which no obstacle is scanned.

According to a preferred embodiment of the present invention, the third set of detection channels is selected from the plurality of detection channels other than the first and second sets of detection channels; or the third set of detection channels is selected in part from detection channels of the first and second sets of detection channels in which no obstacle is scanned.

According to a preferred embodiment of the present invention, the step of controlling the third set of detection channels to emit detection beams comprises: the detection is sequentially performed from the lower side to the upper side of the laser radar.

According to a preferred embodiment of the present invention, the third set of detection channels is selected from detection channels within ±5° of both sides of the horizontal line in the plurality of detection channels.

According to a preferred embodiment of the present invention, the step of controlling the third set of detection channels to emit detection beams and to receive echoes comprises: when the residual flight time in the detection time slice is insufficient to complete the detection of the third group of detection channels, selecting part of detection channels from the third detection channels for detection, and assigning the detection result of the part of detection channels to detection channels which are different from the part of detection channels by fixed values in the next detection time slice of the laser radar.

Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A lidar, comprising:

2. The lidar of claim 1, wherein a smaller transmit power is used for a detection channel with a smaller detection distance.

3. The lidar of claim 2, wherein the plurality of detection channels is configured in three groups, wherein the second group of detection channels corresponds to a detection distance that is greater than the detection distance of the first group of detection channels and less than the detection distance of the third group of detection channels; the transmit power of the second set of detection channels is greater than the transmit power of the first set of detection channels and less than the transmit power of the third set of detection channels.

4. A lidar according to any of claims 1-3, wherein the lasers of the first set of detection channels comprise one-fourth to one-half of the plurality of lasers.

5. The lidar of claim 4, wherein the lasers of the first set of detection channels are evenly distributed among the plurality of lasers, the processing unit being configured to: after the first group of detection channels complete detection, assigning values to detection results of other detection channels covered by the obstacle according to the obstacle detected by the first group of detection channels.

6. The lidar of claim 3, wherein the second set of detection channels is not coincident with the first set of detection channels; or the second set of detection channels is selected in part from detection channels of the first set of detection channels in which no obstacle is scanned.

7. The lidar of claim 3, wherein the third set of detection channels is selected from detection channels of the plurality of detection channels other than the first set of detection channels and the second set of detection channels; or the third set of detection channels is selected in part from detection channels of the first and second sets of detection channels in which no obstacle is scanned.

8. The lidar of claim 7, wherein the third set of detection channels is configured to: the detection is performed sequentially from bottom to top in the vertical plane.

9. The lidar of claim 7, wherein the third set of detection channels is selected from detection channels within ±5° of each side of a horizontal line in the plurality of detection channels.

10. The lidar of claim 7, wherein when a remaining time of flight in the detection time slice is insufficient to complete detection of the third set of detection channels, a portion of the detection channels is selected from the third detection channels for detection, and detection results of the portion of the detection channels are assigned to detection channels in a next detection time slice of the lidar that are different from the portion of the detection channels by fixed values, respectively.

11. A detection control method of a laser radar including a plurality of lasers and a corresponding plurality of detectors, thereby forming a plurality of detection channels, the control method comprising: in at least one of the detection time slices,

12. The detection control method according to claim 11, wherein the smaller the detection distance is, the smaller the transmission power is used for the detection channels, wherein the detection distance corresponding to the second group of detection channels is larger than the detection distance of the first group of detection channels, and the transmission power of the second group of detection channels is larger than the transmission power of the first group of detection channels.

13. The detection control method according to claim 12, further comprising: in the at least one detection time slice,

14. The detection control method according to any one of claims 11 to 13, wherein the lasers of the first group of detection channels include one-fourth to one-half of the plurality of lasers.

15. The detection control method of claim 14, wherein the lasers of the first set of detection channels are uniformly distributed among the plurality of lasers, the detection control method further comprising: after the first group of detection channels complete detection, assigning values to detection results of other detection channels covered by the obstacle according to the obstacle detected by the first group of detection channels.

16. The detection control method according to claim 13, wherein the second group of detection channels is not coincident with the first group of detection channels; or the second set of detection channels is selected in part from detection channels of the first set of detection channels in which no obstacle is scanned.

17. The detection control method according to claim 13, wherein the third group of detection channels is selected from detection channels other than the first group of detection channels and the second group of detection channels among the plurality of detection channels; or the third set of detection channels is selected in part from detection channels of the first and second sets of detection channels in which no obstacle is scanned.

18. The detection control method of claim 17, wherein the step of controlling the third set of detection channels to emit detection beams comprises: the detection is sequentially performed from the lower side to the upper side of the laser radar.

19. The detection control method according to claim 17, wherein the third group of detection channels is selected from detection channels within ±5° of both sides of a horizontal line among the plurality of detection channels.

20. The detection control method according to claim 17, wherein the step of controlling the third group of detection channels to emit detection beams and to receive echoes includes: when the residual flight time in the detection time slice is insufficient to complete the detection of the third group of detection channels, selecting part of detection channels from the third detection channels for detection, and assigning the detection result of the part of detection channels to detection channels which are different from the part of detection channels by fixed values in the next detection time slice of the laser radar.