JP2020187096A - Object detector of autonomous moving body - Google Patents

Abstract

To provide an object detector of an autonomous moving body, which can detect the size of an object by a single laser sensor.SOLUTION: An object detector of an autonomous moving body includes: a laser sensor 30 which detects a distance to an object in association with a direction of the object and which acquires intensity of laser reflection in association with the direction of the object; and a controller 40. The controller 40 detects the size of the object by comparing the intensity of the laser reflection by the laser sensor 30 with a threshold, and increases the threshold as the distance to the object by the laser sensor 30 becomes larger and decreases it as the distance becomes smaller.SELECTED DRAWING: Figure 2

Description

The present invention relates to an object detection device for an autonomous moving body.

In Patent Document 1 and the like, a device that transmits ultrasonic waves or electromagnetic waves and detects an object existing in the vicinity from information on the direction and distance obtained when the transmitted ultrasonic waves or electromagnetic waves are received is generally known. There is. For example, a laser range finder can measure the direction and distance of an object by the reflected wave from the laser object at a predetermined angle.

Japanese Unexamined Patent Publication No. 2008-158690

By the way, in a vehicle traveling by recognizing the surrounding environment with a sensor (image, infrared ray, laser, etc.), the sensor detects an object (wall, person, etc.) and changes the traveling route and traveling speed according to the object.

Here, as shown in FIG. 7, when a laser range finder is used as the sensor, when the laser beam is irradiated from the point light source when detecting an object from the distance information of the sensor, the laser beam is separated from the light source. The farther away it is, the more it spreads and spreads. When the objects O100 and O101 are detected by the laser, an error occurs at the measurement point near the boundary position of the objects O100 and O101 even if they are the same objects O100 and O101 due to the characteristics of the laser. In other words, even if the object is actually the same, the object recognized by calculation is larger than the actual object as the object is farther away due to the expansion of the measurement points. If it is left as it is, the size of the object will be greatly different depending on the distance, and it will not be possible to recognize the same objects O100 and O101. For example, the object to be tracked cannot be recognized and is mistakenly recognized as another object. As a countermeasure, it is necessary to separately install a camera or the like and make a judgment by image processing or the like. As described above, there is a demand for the laser sensor alone to accurately detect the size of an object.

An object of the present invention is to provide an object detection device for an autonomous moving body capable of detecting the size of an object with a single laser sensor.

The object detection device of the autonomous moving body for solving the above problems includes a laser sensor that detects the distance to the object in association with the direction of the object and acquires the laser reflection intensity in association with the direction of the object, and the laser. A threshold value that increases the threshold value in the comparison unit as the distance from the comparison unit that detects the size of the object by comparing the laser reflection intensity and the threshold value by the sensor and the object by the laser sensor increases, and decreases the threshold value as the distance increases. The gist is to have a coordinating unit.

According to this, considering that the laser beam emitted from the laser sensor spreads as the distance from the laser sensor increases, the laser sensor is used when detecting the size of an object by comparing the laser reflection intensity of the laser sensor with the threshold value. The size of the object can be detected by the laser sensor alone by increasing the threshold value in the comparison unit as the distance to the object increases and decreasing the threshold value as the distance to the object increases.

Further, in the object detection device of the autonomous moving body, the threshold value adjusting unit may change the threshold value according to the scanning angle of the laser beam of the laser sensor.
Further, in the object detection device of the autonomous moving body, the threshold value adjusting unit may lower the threshold value when another object is behind the object.

According to the present invention, the size of an object can be detected by a single laser sensor.

Schematic diagram showing an autonomous mobile body. Top view showing an autonomous mobile body. Top view showing an autonomous moving body and an object. The figure which shows an example of the laser reflection intensity with respect to the measurement point number. Top view showing a laser beam and an object by a laser range finder to illustrate another example. The figure which shows an example of the laser reflection intensity with respect to the measurement point number for demonstrating another example. Top view showing a laser beam and an object with a laser range finder to explain the problem.

Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the autonomous mobile body 10 moves based on, for example, map information and its own position. The self-position may be, for example, detected by GPS or may be estimated by detecting a surrounding object using a sensor and comparing it with map information.

The autonomous mobile body 10 includes a machine base 20. The machine base 20 includes a plurality of wheels 21 and a drive mechanism 22 for traveling. The drive mechanism 22 is controlled to track, for example, a registered object (person) 110 to be tracked. The machine base 20 is, for example, a transport carriage for transporting a load.

The autonomous mobile body 10 includes a laser sensor 30 and a controller 40. The laser sensor 30 and the controller 40 are mounted on the machine base 20. The laser sensor 30 and the controller 40 constitute an object detection device 15 for an autonomous moving body. The controller 40 constitutes a comparison unit and a threshold value adjustment unit.

A laser range finder (LRF) is used as the laser sensor 30, and the laser sensor 30 is a two-dimensional laser (2D laser) sensor. In the present embodiment, the laser sensor 30 is fixed to the front portion of the upper surface of the machine base 20, and has a field of view of 270 ° at a predetermined angle in the horizontal direction by scanning a thin laser beam in the horizontal direction. Specifically, as shown in FIG. 2, the laser sensor 30 has a detection region A of 135 ° to the left and right with respect to the front surface. The laser sensor 30 detects the distance to the object in association with the direction (angle) of the object. Specifically, the total detection angle of 270 degrees is divided into 1080, the measurement points are 1080, and the distances L1 to L1080 are detected in association with the angles θ1 to θ1080. For example, the measurement point number 1 detects the distance L1 corresponding to the angle θ1, and the measurement point number 2 detects the distance L2 corresponding to the angle θ2. Similarly, at the measurement point number 1079, the distance L1079 corresponding to the angle θ1079 is detected, and at the measurement point number 1080, the distance L1080 corresponding to the angle θ1080 is detected. The irradiation range of the laser (detection region A) has a fan shape. The boundary between the inside of the detection area A and the outside of the detection area A is an arc-shaped first boundary B1 centered on the laser sensor 30 due to the irradiation distance, and a th-order extending radially from the laser sensor 30 due to the irradiation angle. It has two boundaries B2.

At each measurement point number, the laser sensor 30 can detect the distance to the object in association with the direction of the object and acquire the laser reflection intensity in association with the direction of the object.
As shown in FIG. 1, the controller 40 includes a CPU 41 and a storage unit 42 including a RAM, a ROM, and the like. Various programs for controlling the machine base 20 are stored in the storage unit 42. The controller 40 may include dedicated hardware that executes at least a part of the various processes, for example, an integrated circuit for a specific application: ASIC. The controller 40 may be configured as one or more processors operating according to a computer program, one or more dedicated hardware circuits such as an ASIC, or a circuit including a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memory stores a program code or a command configured to cause the CPU to execute the process. Memory, or computer-readable medium, includes anything that can be accessed by a general purpose or dedicated computer.

As shown in FIG. 3, the controller 40 detects the objects O1, O2, O3, and O4 existing around the machine base 20 from the detection result of the laser sensor 30. The object O1 in FIG. 3 is a wall located on the left side of the passage 50 and extends along the passage 50. The object O2 in FIG. 3 is a short wall located on the right side of the passage 50, and one surface extends along the passage 50. The objects O3 and O4 in FIG. 3 are the same objects located in the passage 50, the object O4 is located near the laser sensor 30, and the object O3 is located far away.

In FIG. 3, the laser sensor (laser range finder) 30 acquires data. At this time, the laser range finder can acquire distance data of 1080 points. In FIG. 3, the measurement points of the distance by the laser sensor (laser range finder) 30 are indicated by P.

The controller 40 detects objects O1, O2, O3, and O4 by extracting feature points from the data of the laser sensor (laser range finder) 30.
Then, the autonomous mobile body 10 controls traveling to track an object, for example. Specifically, the vehicle travels while detecting the positions of the objects O1, O2, O3, O4 (angle and distance from the machine base 20) and the sizes of the objects O1, O2, O3, O4.

Next, the action will be described.
In the autonomous moving body 10, the controller 40 detects an object based on the detection result of the laser sensor 30 and travels.

The laser sensor 30 detects the distance to the object in association with the direction of the object, and acquires the laser reflection intensity in association with the direction of the object.
Here, as described with reference to FIG. 7, the laser beam at the edge of the boundary becomes blurry as it goes farther, and the measurement point becomes larger.

Therefore, the laser reflection intensity is used to make a correction that minimizes the error at the measurement point based on the positional relationship at the boundary position of the object.
In FIG. 4, the horizontal axis is the number of the measurement point, and the vertical axis is the laser reflection intensity Sr. FIG. 4 shows a situation in which the laser reflection intensity Sr is strong at the measurement points Nos. 434 to 551, and the laser reflection intensity Sr is weak when the measurement points deviate from the measurement points Nos. 434 to 551.

When the laser sensor 30 acquires the direction (angle θ) and distance to the object and the laser reflection intensity Sr, the controller 40 compares the laser reflection intensity Sr with the threshold Vth. A sequence of measurement point numbers in which the laser reflection intensity Sr is larger than the threshold value Vth is recognized as the size of the object. Specifically, in FIG. 4, the number of the measurement point numbers 453 to the measurement point number 540 is the size of the object. This makes it possible to grasp the size of the object.

As described above, the controller 40 as the comparison unit has a function of comparing the laser reflection intensity Sr by the laser sensor 30 with the threshold value Vth to detect the size of the object.
Further, the controller 40 as the threshold value adjusting unit has a function of increasing the threshold value Vth as the distance to the object by the laser sensor 30 increases and decreasing the threshold value Vth as the distance to the object increases. That is, as shown in FIG. 7, an error is larger in an object having a short distance from the laser range finder and an object having a long distance from the laser range finder, even if the object is the same. In consideration of this, it is possible to reduce the error by increasing the threshold value Vth as the distance to the object by the laser sensor 30 increases.

This makes it possible to minimize the error between the actual size of the object and the size of the object recognized by the calculation.
Further, if the error becomes small, it can be used for identifying a specific object, and it is possible to improve the recognition rate of the object without the need to add a sensor such as a camera separately.

The details will be described below.
As an operation of the controller 40, when the laser sensor (laser range finder) 30 acquires data, an object is detected from the data of the laser sensor (laser range finder) 30.

Here, the boundary position of the object is determined from the laser reflection intensity information. Specifically, the boundary position of the object is determined from the position information (distance and angle) of the object. At this time, the size of the object is corrected.

Specifically, the threshold value Vth shown in FIG. 4 is determined by the distance to the object, and an effective measurement point is extracted.
That is, regarding the relationship between the actual size of the object and the size of the object recognized by the calculation, the size of the object recognized by the calculation is brought closer to the size of the actual object by changing the threshold value Vth according to the distance. Can be done. In this way, by making corrections that minimize the error at the measurement point using the laser reflection intensity Sr from the positional relationship at the boundary position of the object, the error between the actual size of the object and the size of the object recognized by calculation is performed. Can be minimized. As a result, it is possible to correct the contour of the object using the laser reflection intensity.

Further, the controller 40 as the threshold value adjusting unit changes the threshold value Vth according to the scanning angle of the laser beam of the laser sensor 30. Specifically, the threshold value Vth is increased toward the front side shown in FIG. 2, and the threshold value Vth is decreased toward the side surface side away from the front surface. This is because, as a characteristic of the laser element, even if the light source is a point, the light beam extends in the horizontal direction on the front side and the light beam extends in the vertical direction on the side surface side. Therefore, the threshold value Vth is raised toward the front side and the threshold value is increased toward the side surface side. By lowering Vth, the contour of the object can be obtained correctly.

According to the above embodiment, the following effects can be obtained.
(1) As a configuration of the object detection device 15 of an autonomous moving body, a laser sensor that detects the distance to the object in association with the direction of the object and acquires the laser reflection intensity Sr in association with the direction (angle θ) of the object. 30 and a controller 40 as a comparison unit and a threshold value adjustment unit are provided. The controller 40 as a comparison unit detects the size of the object by comparing the laser reflection intensity Sr by the laser sensor 30 with the threshold value Vth. The controller 40 as the threshold value adjusting unit raises the threshold value Vth in the comparison unit as the distance to the object by the laser sensor 30 increases, and decreases the threshold value Vth as the distance to the object increases.

Therefore, considering that the laser beam emitted from the laser sensor 30 spreads as the distance from the laser sensor 30 increases, it is generally possible to measure the laser beam accurately when it is close, but it tends to blur when it is far, but the laser sensor alone tends to blur. The size of the object can be detected.

That is, the size of the object can be detected while considering the distance to the object and the spread of the laser beam so that the size of the object can be recognized more accurately. As a result, the object can be detected with high accuracy, and for example, the tracking target which is the same object can be recognized.

(2) The controller 40 as the threshold value adjusting unit changes the threshold value Vth according to the scanning angle of the laser beam of the laser sensor 30, that is, on the front side of the vehicle and the side surface of the vehicle. For example, the front is blurred to the left and right to raise the threshold, and the side is blurred to the top and bottom to lower the threshold. Therefore, the size of the object can be detected more accurately.

The embodiment is not limited to the above, and may be embodied as follows, for example.
○ As shown in FIG. 5, when the reflecting object O20 exists behind the objects O10 and O11, the threshold value of the boundary position of the objects O10 and O11 is changed from Vth1 to Vth2 as shown in FIG.

In FIG. 5, behind the objects O10 and O11, there is an object (reflecting object) O20 that reflects a laser, the object O10 and the object O11 are the same object, and the object O10 is a laser sensor (laser range finder) 30. It is located near and the object O11 is located far away. In this case, the sizes of the objects O10 and O11 recognized by the calculation are almost the same.

Specifically, when the object O20 is behind the objects O10 and O11 by scanning, the laser beam becomes unblurred when it is found that the object O20 is behind, so the threshold value is lowered from Vth1 to Vth2 as shown in FIG. .. Therefore, in the comparison when the threshold value Vth1 is used, the number of the numbers from the measurement point number 459 to the measurement point number 534 is the size of the object, whereas in the comparison when the threshold value Vth2 is used, the measurement point number 451 The number of numbers from to measurement point number 542 is the size of the object. As a result, the error between the actual size of the object and the size of the object recognized by the calculation can be reduced.

In this way, the controller 40 as the threshold value adjusting unit may lower the threshold value Vth when another object O20 is behind the objects O10 and O11.
○ The controller 40 as the threshold value adjusting unit raises the threshold value Vth toward the front side and lowers the threshold value Vth toward the side surface away from the front side in order to change the threshold value Vth according to the scanning angle of the laser beam of the laser sensor 30. The reverse may be performed depending on the characteristics of the laser sensor. That is, the threshold value Vth may be lowered toward the front side and increased toward the side surface side away from the front side.

○ The autonomous moving body 10 is not limited to the case of traveling to track an object, and the autonomous moving body 10 can be applied to a case where the controller 40 detects an object and travels based on the detection result of the laser sensor 30.

15 ... Autonomous moving object detection device, 30 ... Laser sensor, 40 ... Controller, O1, O2, O3, O4 ... Object, Sr ... Laser reflection intensity, Vth ... Threshold.

Claims (3)

A laser sensor that detects the distance to an object in association with the direction of the object and acquires the laser reflection intensity in association with the direction of the object.
A comparison unit that detects the size of an object by comparing the laser reflection intensity and the threshold value of the laser sensor,
A threshold adjustment unit that raises the threshold value in the comparison unit as the distance to the object by the laser sensor increases, and decreases the threshold value as the distance to the object increases.
An object detection device for an autonomous mobile body, which comprises. The object detection device for an autonomous moving body according to claim 1, wherein the threshold value adjusting unit changes the threshold value according to a scanning angle of a laser beam of the laser sensor. The object detection device for an autonomous moving body according to claim 1 or 2, wherein the threshold value adjusting unit lowers the threshold value when another object is behind the object.