JP2010249569A - Obstacle detection method and laser distance measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an obstacle detection method which detects a person as an obstacle even if the person enters a groove in a railroad crossing, and also to provide a laser distance measuring instrument. <P>SOLUTION: The distance measuring instrument is provided with: a light projection part 1 for projecting laser light LT; a scanning part for performing scanning with the laser light LT; a light receiving part 2 for receiving reflected laser light LR made to return by being reflected by pedestrians present in the railroad crossing; a signal processing part 3 for creating and sending pedestrian measurement data D by a light reception signal Sr from the light receiving part 2; and a control part 6 for receiving the measurement data D and outputting a measurement result. The control part 6 makes processing for sorting pedestrian measurement data D obtained continuously with a plurality of thresholds for height, and processing for recognizing pedestrians, based on height data by the thresholds for height. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an obstacle detection method and a laser distance measuring device that are used to detect the presence or absence of obstacles (including moving objects such as pedestrians and intruders, and objects such as stones and fallen trees) in railroad crossings and sites. It is about.

Conventionally, as a method similar to the above-described obstacle detection method, for example, there is a crossing pedestrian detection method disclosed in Patent Document 1. This detection method scans a laser beam on a pedestrian crossing, and measures the flight time based on the projection timing of this laser beam and the reception timing of the reflected laser beam reflected back by a pedestrian present on the pedestrian crossing. This is a method for detecting a pedestrian.
In this method, pedestrians and vehicles are detected by extracting measurement data having a predetermined height (for example, a height of about 30 cm above the ground) from data measured by scanning with laser light.

Patent 3472815

  However, in the conventional detection method described above, for example, when used to detect an obstacle such as a pedestrian or a vehicle in a level crossing, it is more than a recess such as a groove formed in the level crossing or a road surface beside a breaker. When a person enters a lowland area, the measurement data is out of the sorting process based on the height threshold, and there is a possibility that a detection failure may occur, and this problem can be solved. It has been a conventional problem.

  The present invention has been made by paying attention to the above-described conventional problems. For example, when used for detecting an obstacle such as a pedestrian or a vehicle in a railroad crossing, a person has entered a recess or a lowland part. However, an object of the present invention is to provide an obstacle detection method and a laser distance measurement device that can detect an obstacle.

  The invention according to claim 1 of the present invention scans the laser light projected toward the measurement area, and reflects the laser light projection timing and the reflected laser light returned by the obstacle present in the measurement area. The obstacle detection method for detecting the obstacle by measuring the time of flight based on the light reception timing of the plurality of height thresholds with respect to the three-dimensional data of the obstacle acquired for each scanning of the laser beam The obstacle detection method is configured to recognize the obstacle based on a plurality of height data extracted by this process, and this obstacle detection method configuration solves the above-mentioned conventional problems As a means to do.

In the obstacle detection method according to claim 2 of the present invention, the plurality of height thresholds are set such that at least one threshold is included in a recess arbitrarily selected from the recesses existing in the measurement area. Or set according to the unevenness existing in the measurement area.
Furthermore, the obstacle detection method according to claim 3 of the present invention subdivides the ground of the measurement area into a plurality of small areas based on the ground shape data in the measurement area acquired in advance, and a plurality of height thresholds. Are set at the same height for each of the subdivided small areas.

  On the other hand, a laser distance measuring device according to claim 4 of the present invention is present in a light projecting unit that emits laser light, a scanning unit that scans laser light emitted from the light projecting unit in the measurement area, and the measurement area. A light receiving unit that receives the reflected laser beam reflected and returned by the obstacle through the scanning unit, a control unit that issues a laser beam projection command to the light projecting unit and controls scanning by the scanning unit; A signal processing unit for measuring the flight time based on the light projection timing of the laser beam given from the control unit and the light reception timing of the reflected laser beam given from the light receiving unit, and obtaining three-dimensional data of the obstacle, The control unit recognizes the obstacle based on the process of selecting the three-dimensional data of the obstacle acquired at each scanning of the laser beam with a plurality of height thresholds and the plurality of height data extracted by this process. Processing It was configured to perform has been characterized, and the structure of the laser distance measuring device as a means for solving the conventional problems described above.

In the laser distance measuring device according to claim 5 of the present invention, in the control unit, the plurality of height threshold values include at least one threshold value in a recess arbitrarily selected from the recesses existing in the measurement area. It is set so that it may be set according to the unevenness which exists in a measurement area.
Furthermore, in the laser distance measuring device according to claim 6 of the present invention, the control unit divides the ground of the measurement area into a large number of small areas based on the ground shape data in the measurement area acquired in advance. The plurality of height thresholds are set at the same height for each of the subdivided small areas.

In the present invention, a semiconductor laser, a solid-state laser, a gas laser, or the like can be used as a laser beam to be projected, and a laser beam having a sine wave shape whose signal waveform is pulsed or phase-modulated is used.
In the obstacle detection method according to claim 3 of the present invention and the laser distance measurement device according to claim 6, when the ground is subdivided into a number of small areas based on the ground shape data within the measurement range acquired in advance. The size of the small area is determined based on the application location and detection target of the present invention.

In the obstacle detection method and laser distance measuring device according to the present invention, for example, when used for detection of an obstacle such as a pedestrian or a vehicle in a railroad crossing, the three-dimensional data continuously obtained by scanning with laser light. Based on the above, pedestrians and vehicles in the crossing are detected.
Here, even if there are people in recesses such as grooves and steps formed in the railroad crossing and parts of the ground that are lower than the road surface beside the breaker, multiple height thresholds, for example, unevenness such as grooves and steps, etc. Since the sorting process based on the height threshold set for each part is performed on the three-dimensional data, a person who has entered the recess can be detected as an obstacle.

  At this time, the ground shape in the level crossing is acquired and stored in advance, and the road surface of the level crossing is subdivided into a number of small areas based on the ground shape data in the level crossing, and the same for each of the subdivided small areas. If you set each height threshold, the height threshold will be almost in line with the shape of the ground in the railroad crossing. Obstacles that are not large in size can be detected.

  In addition, when a train without a train approach signal is not coming, if the ground shape data in the railroad crossing is measured and updated as needed, branches can be introduced due to the growth of standing trees, or the road surface can be covered by snow. It will be possible to respond quickly to environmental changes such as raising.

Since the obstacle detection method according to claims 1 and 2 of the present invention and the laser distance measurement device according to claims 4 and 5 have the above-described configuration, for example, detection of obstacles such as pedestrians and vehicles in a crossing. Even if a person enters a recess such as a groove in a railroad crossing or a lowland part, the present invention has an excellent effect that it can be detected as an obstacle.
Moreover, since the obstacle detection method according to claim 3 of the present invention and the laser distance measuring device according to claim 6 have the above-described configuration, they are also used for detecting obstacles such as pedestrians and vehicles in the crossing. In the case, in addition to obtaining the same effect as the obstacle detection method according to claims 1 and 2 and the laser distance measuring device according to claims 4 and 5 of the present invention, It is possible to detect an intruder or an obstacle whose height is not large, such as a stone.

  In addition, by measuring and updating the ground shape data at the level crossing as needed, it is possible to quickly respond to changes in the environment such as the branches of grown trees entering the level crossing or the road surface inside the level crossing being raised due to snow. It is possible to provide a very excellent effect that it is possible to cope with the above.

It is a block diagram which shows the obstacle detection method and laser distance measuring device which concern on one Example of this invention. It is a perspective explanatory view (a)-(e) which shows the measuring point of the laser distance measuring device in Drawing 1. It is side surface explanatory drawing (a) and plane explanatory drawing (b) which show the measurement condition by the laser distance measuring apparatus in FIG. FIG. 6 is an explanatory diagram (a) to (c) of a selection processing procedure based on a height threshold in a control unit of the laser distance measuring device in FIG. 1. It is side explanatory drawing (a) and plane explanatory drawing (b) which show the measurement condition by the obstacle detection method based on the other Example of this invention. FIGS. 6A and 6B are explanatory diagrams of selection processing points based on a height threshold at the time of measurement in FIGS.

Hereinafter, an obstacle detection method and a laser distance measurement device according to the present invention will be described with reference to the drawings.
[Example 1]
1 to 4 show an embodiment of an obstacle detection method and a laser distance measurement device according to the present invention. In this embodiment, the obstacle detection method and the laser distance measurement device according to the present invention are included in a railroad crossing. An example will be described for use in detecting obstacles such as pedestrians and vehicles.

  As shown in FIG. 1, the laser distance measuring device receives a reflected light LR of a projected laser beam LT and measures a distance to a pedestrian or vehicle (an obstacle in a measurement area) in a crossing. A distance measuring device, a light projecting unit 1 for projecting a laser beam LT, a light receiving unit 2 for receiving a reflected light LR and transmitting a light reception signal Sr, and measurement data including a measurement distance of an object from the light reception signal Sr (Three-dimensional data) A signal processing unit 3 that generates and transmits D, a laser radar head 7 that houses the light projecting unit 1, the light receiving unit 2, and the signal processing unit 3, and the laser radar head 7. And a control unit 6 that receives the measurement data D and outputs the measurement result. As shown in FIG. 2, the laser radar head 7 that houses the light projecting unit 1, the light receiving unit 2, and the signal processing unit 3 is disposed at the upper end of a column 8 that is erected on the ground E.

  The light projecting unit 1 is a device that emits laser light L in the measurement area and projects the light. The light projecting unit 1 includes, for example, a laser diode 1a serving as a light source, a light projecting lens 1b that collimates the laser light L, and an LD driver 1c that operates the laser diode 1a. The LD driver 1c operates the laser diode 1a so as to emit the laser beam L based on the trigger signal St from the signal processing unit 3, and outputs a pulsed projection synchronization signal Ss simultaneously with the projection of the laser beam L. Call the processing unit 3. Note that the projection synchronization signal Ss may be substituted by the trigger signal St.

  In FIG. 1, a laser beam LT transmitted through a light projecting lens 1b is substantially horizontal and substantially vertical by an optical system of a scanning unit composed of a polygon mirror 11 that is rotationally driven and a plane mirror 12 that is rotationally driven. Scanned in the direction. The polygon mirror 11 has, for example, four sides of a hexahedron mirrored, and is configured to be rotated by a motor 11a with the center of two opposing surfaces (upper and lower surfaces) as rotation axes. The motor 11a is operated by a motor driver 11b. The flat mirror 12 is connected to a side surface of a rotating shaft that is rotated by a motor 12a, for example. The motor 12a is operated by a motor driver 12b. The motor drivers 11 b and 12 b are controlled by a control signal Sm from the signal processing unit 3 and transmit a light projection condition signal Sc such as a scan angle and a swing angle to the signal processing unit 3. Such an optical system is merely an example, and is not limited to the illustrated configuration.

  The light receiving unit 2 is a device that receives the reflected light LR of the laser light LT projected in the measurement area. Here, the light projecting unit 1 and the light receiving unit 2 are provided separately so that the light projecting axis and the light receiving axis are shifted from each other, but the light projecting unit 1 and the light receiving axis are aligned with each other. The light receiving unit 2 may be integrally formed. The light receiving unit 2 includes, for example, a light receiving lens 2a that collects the reflected light LR, a photoelectric conversion element such as a photodiode that receives the collected reflected light LR and converts it into a voltage, an amplifier, and the like. 2b. The reflected light LR transmitted through the light projection window W on the front surface of the laser radar head 7 is guided to the light receiving lens 2 a through the plane mirror 12 and the polygon mirror 11. Then, the light receiving unit main body 2 b that has received the reflected light LR transmits a light receiving signal Sr converted into a voltage value to the signal processing unit 3.

The signal processing unit 3 is a device that transmits measurement data D including data such as measurement distance, received light intensity, and light projection conditions. The signal processing unit 3 includes a main signal processing unit 31 and a time measurement unit 32.
The main signal processing unit 31 transmits a trigger signal St, transmits a control signal Sm for the motor drivers 11b and 12b, receives a light projection condition signal Sc such as a scan angle and a swing angle, and a signal (light reception intensity) from the time measurement unit 32. Processing such as reception of signal Sq and time-of-flight signal Sd) and transmission of measurement data D is performed.

On the other hand, the time measurement unit 32 starts measuring time by receiving the light projection synchronization signal Ss, and grasps the time when the light reception signal Sr is received. Therefore, the time measuring unit 32 can measure the flight time until the projected laser beam LT is reflected by the object and received.
Further, the time measuring unit 32 may have a discrimination function for selecting a light reception signal Sr having a desired light reception intensity from the light reception signal Sr, and a gate function for excluding those having a short flight time from the light reception signal Sr. . Such discrimination function and gate function can efficiently eliminate noise.

  Then, the time measuring unit 32 transmits the received light intensity signal Sq and the flight time signal Sd of the received light signal Sr that has passed through the discrimination function and the gate function to the main signal processing unit 31. The main signal processing unit 31 converts the time-of-flight signal Sd into distance data by a formula of (light speed) × (time-of-flight) / 2, and a light projection condition signal such as a received light intensity signal Sq, a scan angle, and a swing angle. Measurement data D is created together with Sc and the like, and the measurement data D is transmitted to the control unit 6.

The control unit 6 is a computer that performs image processing, failure diagnosis, and error correction. The control unit 6 receives measurement data D and outputs measurement results to an output device 9 such as a display, a printer, or an alarm device.
Further, the control unit 6 sets conditions such as the scan angle and scan speed of the polygon mirror 11, the swing angle and swing speed of the plane mirror 12, and the transmission timing of the trigger signal St of the laser light L, and these control conditions Sh Is transmitted to the signal processing unit 3. The control unit 6 is usually disposed at a site away from the laser radar head 7.

Furthermore, the control unit 6 sets a height threshold value for each part such as a groove, a step, or a lowland formed in the railroad crossing, a selection process based on a plurality of height threshold values for the measurement data D, A process for recognizing an obstacle as a pedestrian or vehicle M1, M2 is performed based on the height data selected by the height threshold (FIGS. 2D and 2E).
In the laser distance measuring apparatus having such a configuration, first, as shown in FIG. 3, the measurement data D is obtained by scanning the laser light LT projected from the light projecting unit 1 in the measurement area in the railroad crossing.

  At this time, a threshold A having a predetermined height (for example, a height of about 30 cm above the road surface E) is set on the road surface E in the railroad crossing by the control unit 6, and measurement data is obtained every time the laser beam LT is scanned one time. As shown in FIG. 4 (a), the pedestrians T2 to T6, which are obstacles in the railroad crossing, are extracted by performing a sorting process based on a threshold value A of height with respect to D and extracting measurement data D having a predetermined height or more. Is detected.

  In addition, shaking the laser beam LT once in the left-right direction such as the X direction in FIG. 2D is referred to as one scan, and the laser is moved in the front-rear direction such as the Y direction in FIG. 2D while repeating this scan. When scanning the measurement area with the light LT and scanning the entire measurement area is called one frame, the process of extracting the measurement data D above the threshold value A may be performed for each scan or for each frame. You may go.

Here, in the detection result Da extracted by the threshold value A corresponding to the road surface E in the level crossing, data of the pedestrian T2 having a high height among the two pedestrians T1 and T2 entering the groove E1 in the level crossing. Is included, but the data of the pedestrian T1 having a low height (the portion indicated by the broken line in FIG. 4A) is not included.
A threshold value B corresponding to the bottom surface of the groove E1 is set in the groove E1 by the controller 6, and a selection process based on the height threshold value B with respect to the measurement data D is performed each time the laser beam LT is scanned once in the groove E1. The pedestrian T1, which is an obstacle in the groove E1, is detected as shown in FIG. 4B by extracting the measurement data D having a predetermined height or more in the groove E1. Also in this case, the process of extracting the measurement data D that is equal to or greater than the threshold value B may be performed for each scan or for each frame.

  And the detection result Db in which the data of the pedestrian T1 having a low height entering the groove E1 is reflected, and the data of the pedestrian T2 having a high height and the pedestrians T3 to T6 in the road E are reflected. When the detection result Da is combined, as shown in FIG. 4C, the detection result Dc reflecting the data of all the pedestrians T1 to T6 is obtained. Therefore, the pedestrian T1 is formed in the groove E1 in the crossing. , T2 can enter these pedestrians T1 and T2 as obstacles.

In addition, although the case where the groove | channel E1 which is a recessed part is one was demonstrated here, it is not limited to this, One or more recessed parts to make it a measurement object from several recessed parts which exist in a measurement area are arbitrarily set. You may make it select. In addition, when a plurality of recesses are selected, it is desirable to set the threshold value so that each includes at least one threshold value.
[Example 2]
5 and 6 show another embodiment of the obstacle detection method according to the present invention. In this embodiment as well, the present invention is used for detecting obstacles such as pedestrians and vehicles in a crossing. Will be described as an example.

In the obstacle detection method in this embodiment, first, before the operation of the laser distance measuring device described above, for example, at the time of initial setting at the time of installation at a railroad crossing, the laser distance measuring device is operated to detect the road surface E in the railroad crossing. Measurement is performed, and the ground shape data including the level difference thus obtained is stored in the control unit 6.
Next, as shown in FIG. 5, the laser beam LT projected from the light projecting unit 2 is scanned into the railroad crossing to obtain measurement data D.

At this time, as shown in FIG. 6A, based on the ground shape data F in the railroad crossing including the steps F1 to F6 acquired in advance as described above, the road surface E is changed to steps F1 to F6 (a number of small areas). ) And a threshold C having the same height is set for each of the subdivided steps F1 to F6.
Accordingly, if the selection process is performed with the height threshold value C for the measurement data D every time the laser beam LT is scanned, as shown in FIG. 6B, detection results Dd of all pedestrians T1 to T6 are obtained. Therefore, even if there are many steps F1 to F6 in the railroad crossing, pedestrians T1 to T6 on the road surface E and steps F1 to F6 can be detected as obstacles. Note that the process of extracting the measurement data D equal to or greater than the threshold C may be performed for each scan or for each frame.

In this obstacle detection method, the height threshold C substantially follows the ground shape in the railroad crossing, that is, the steps F1 to F6. Obstacles having a large height dimension can be detected.
In addition, if a train without a train approach signal is not coming, the ground shape data F in the railroad crossing can be measured and updated at any time. It will be possible to respond quickly to changes in the environment such as raising the price.

  In the above-described embodiment, the case where the present invention is applied to level crossing monitoring has been described as an example. However, the present invention is not limited to this, and as another application example, for example, the present invention may be used for crosswalk monitoring. It may also be applied to monitoring the site.

DESCRIPTION OF SYMBOLS 1 Light projection part 2 Light reception part 3 Signal processing part 6 Control part 11 Polygon mirror (scanning part)
12 Flat mirror (scanning part)
31 Main signal processing unit 32 Time measurement unit A, B, C Height threshold Da to Dd Detection result E Road surface (ground)
E1 Groove (concave)
F Ground shape data F1-F6 Level difference LR Reflected laser beam LT Projected laser beam T1-T6 Pedestrian (obstacle)

Claims (6)

Scan the laser beam projected toward the measurement area, measure the flight time by the projection timing of this laser beam and the reception timing of the reflected laser beam reflected back by the obstacle present in the measurement area, An obstacle detection method for detecting the obstacle,
The three-dimensional data of the obstacle acquired every time the laser beam is scanned is subjected to a process of selecting with a plurality of height thresholds, and the obstacle is recognized based on the plurality of height data extracted by this process. An obstacle detection method characterized by:   The plurality of height threshold values are set so that at least one threshold value is included in a concave portion arbitrarily selected from the concave portions existing in the measurement area, or set in accordance with the unevenness existing in the measurement area. Item 5. An obstacle detection method according to Item 1.   Based on the ground shape data in the measurement area acquired in advance, the ground of the measurement area is subdivided into a number of small areas, and a plurality of height thresholds are set at the same height for each of the subdivided small areas. The obstacle detection method according to claim 1. A light emitting unit that emits laser light;
A scanning unit that scans the laser light emitted from the light projecting unit in a measurement area;
A light receiving unit that receives reflected laser light reflected by an obstacle existing in the measurement area and returned through the scanning unit;
A control unit that issues a laser beam projection command to the light projecting unit and controls scanning by the scanning unit;
A signal processing unit for measuring the flight time based on the light projection timing of the laser beam given from the control unit and the light reception timing of the reflected laser beam given from the light receiving unit, and acquiring the three-dimensional data of the obstacle;
In the control unit, a process of selecting the three-dimensional data of the obstacle acquired for each scan of the laser beam with a plurality of height thresholds, and an obstacle based on the plurality of height data extracted by this process A laser distance measuring device characterized by performing recognition processing.   In the control unit, the plurality of height threshold values are set so that at least one threshold value is included in a concave portion arbitrarily selected from the concave portions existing in the measurement area, or matched to the unevenness existing in the measurement area. The laser distance measuring device according to claim 4, which is set as follows.   In the control unit, the ground of the measurement area is subdivided into a number of small areas based on the ground shape data in the measurement area acquired in advance, and a plurality of height thresholds are set for each of the subdivided small areas. The laser distance measuring device according to claim 4, wherein the laser distance measuring devices are set at the same height.

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