Distance measurement system, distance measurement method, and distance measurement program

Abstract

To calculate an accurate distance between a mobile robot and a glass wall.SOLUTION: According to an aspect of the present disclosure, there is provided a distance measurement device including a light emitting unit that emits a predetermined number of pulsed light beams at a predetermined period provided in a mobile robot device, a light receiving unit that receives reflected light of the pulsed light emitted by the light emitting unit, an intensity detection unit that detects intensity of an electric signal based on the reflected light received by the light receiving unit, and an extraction unit that extracts an electric signal used for calculating a distance from the mobile robot device based on the intensity of the electric signal detected by the intensity detection unit. A distance calculating unit configured to calculate a distance from the mobile robot apparatus to the glass wall based on a time of flight of the pulsed light corresponding to the electric signal extracted by the extracting unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distance measurement system, a distance measurement method, and a distance measurement program. [Background technology]

[0002] A technology known as SLAM (Simultaneous Localization and Mapping) is used to autonomously navigate indoors with mobile robots that provide various services. SLAM uses a laser range finder (LRF) equipped on the mobile robot to measure the shape of the environment around the mobile robot, generate a map, and simultaneously estimate the mobile robot's own position on the map.

[0003] Known technologies relating to this type of mobile robot are disclosed in Patent Documents 1 and 2 below. The autonomous mobile body described in Patent Document 1 is equipped with a laser range finder that acquires environmental information indicating the position and shape of objects present in the area of ​​movement. The autonomous mobile body moves while estimating its own position based on the environmental information acquired by the laser range finder, using a movement map related to the area of ​​movement. The movement map includes information indicating the light reflectance attributes of objects, improving the accuracy of the autonomous mobile body's self-position estimation even when optically transparent materials such as glass are present within the area of ​​movement.

[0004] The autonomous mobile body described in Patent Document 2 controls its movement based on an environmental map containing position information of obstacles in the movement area of ​​the autonomous mobile body and information on whether the obstacles are obstacles that can be measured by a beam, and its own position that has already been detected on the movement trajectory. The autonomous mobile body described in Patent Document 2 estimates its own position relative to a glass wall by recording in the environmental map whether the wall is a glass wall or not. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-223757 [Patent Document 2] Patent No. 5826795 Summary of the Invention [Problem to be solved by the invention]

[0006] The following technologies can be considered to enable a mobile robot to recognize glass walls when moving autonomously, but there are issues involved. Patent document 1 describes recording the reflectance of various objects in advance in an environmental shape map carried by a mobile robot, and patent document 2 describes recording whether or not an object is a glass wall in an environmental map, but these have the disadvantage of being time-consuming to embed information about glass walls in the environmental map in advance.

[0007] Another technique for mobile robots to detect glass walls is to use a polarization camera to detect S-polarized light, taking advantage of the phenomenon in which light reflected on the surface of a glass wall is polarized. However, this has the disadvantage of being very expensive.

[0008] Furthermore, there is a method that takes advantage of the property of glass walls that prevents far-infrared light (wavelengths of 10 μm or more) from passing through (high reflectivity), but this method has the disadvantages of having low resolution far-infrared cameras, possibly interfering with the near-infrared light of LiDAR, potentially raising the temperature of the irradiated object because far-infrared light is emitted, and also being expensive.

[0009] Furthermore, there is a method for detecting light rays (visible light) reflected specularly from a glass wall, but the detection range (specular reflection range) is very narrow, at around -10° to 10°, which has the disadvantage of requiring the mobile robot to move around the same place repeatedly for long periods of time.

[0010] Furthermore, there is a method of detecting glass walls using ultrasonic sensors, but while ultrasonic sensors can recognize the presence of a glass wall, they have the disadvantage of lacking the precision to determine the extent of the glass wall.

[0011] Another possibility is to attach an RFID tag to an object such as a glass wall, and when a mobile robot detects the RFID tag, the opaque wall can be drawn on the map created by SLAM. However, this has the disadvantages of spoiling the aesthetics of the object by attaching the RFID tag to it, and of the short communication distance between the RFID tag and the RFID reader installed on the mobile robot.

[0012] The present disclosure has been made in consideration of the above circumstances, and aims to provide a distance measurement device, a map creation device, a mobile robot, a distance measurement method, and a distance measurement program that enable a mobile robot to calculate the accurate distance to a glass wall. [Means for solving the problem]

[0013] The present disclosure has been made to solve the above-mentioned problems, and one aspect of the present disclosure is a distance measurement system including: a light-emitting unit provided in a mobile robot device that emits a predetermined number of pulsed light every predetermined period; a light-receiving unit that receives reflected light of the pulsed light emitted by the light-emitting unit; an intensity detection unit that detects the intensity of an electrical signal (photocurrent) based on the reflected light received by the light-receiving unit; an extraction unit that extracts an electrical signal used to calculate a distance from the mobile robot device from the reflected light received by the light-receiving unit based on the intensity of the electrical signal detected by the intensity detection unit; and a distance calculation unit that calculates the distance from the mobile robot device to a glass wall based on the time of flight of the pulsed light corresponding to the electrical signal extracted by the extraction unit.

[0014] Another aspect of the present disclosure is a distance measurement method including the steps of: a mobile robot device emitting a predetermined number of pulsed lights at predetermined intervals and receiving reflected light of the emitted pulsed lights; an intensity detection unit detecting the intensity of an electrical signal based on the reflected light; an extraction unit extracting an electrical signal used to calculate a distance from the mobile robot device to the reflected light based on the intensity of the electrical signal detected by the intensity detection unit; and a distance calculation unit calculating the distance from the mobile robot device to a glass wall based on the time of flight of the pulsed lights corresponding to the electrical signal extracted by the extraction unit.

[0015] Another aspect of the present disclosure is a distance measurement program that causes a computer to execute the steps of causing a mobile robot device to emit a predetermined number of pulsed light at predetermined intervals and receiving reflected light of the emitted pulsed light, detecting the intensity of an electrical signal based on the reflected light, extracting an electrical signal from the reflected light based on the intensity of the electrical signal to be used to calculate the distance from the mobile robot device, and calculating the distance from the mobile robot device to a glass wall based on the time of flight of the pulsed light corresponding to the extracted electrical signal. [Effects of the Invention]

[0016] According to one aspect of the present invention, the mobile robot can calculate the accurate distance to the glass wall. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing an example of a robot control system 1 according to an embodiment. [Figure 2] 4 is a flowchart showing an example of an operation procedure of the robot control system 1 according to the embodiment. [Figure 3] FIG. 4 is a diagram illustrating an example of temporal change in electrical signal intensity in the embodiment. [Figure 4] FIG. 10 is a diagram showing another example of temporal changes in the intensity of an electrical signal according to the embodiment. [Figure 5] FIG. 10 is a diagram illustrating an example of a normal distribution of electrical signal intensity according to an embodiment. [Figure 6] FIG. 10 is a diagram showing an example of map information when pulsed light is transmitted through a glass wall in a comparative example. [Figure 7] FIG. 2 is a diagram illustrating an example of map information according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] A distance measurement device, a map creation device, a mobile robot, a distance measurement method, and a distance measurement program to which the present invention is applied will be described below with reference to the drawings.

[0019] (Configuration of robot control system 1) 1 is a block diagram showing an example of a robot control system 1 according to an embodiment. The robot control system 1 includes, for example, a mobile robot device 100 and a server system 200. The mobile robot device 100 and the server system 200 have communication interfaces (not shown) such as a network interface card (NIC) or a wireless communication module, enabling transmission and reception of various types of information via a communication network NW. The communication network NW may include, for example, a general-purpose network such as the Internet, and a private network such as local 5G or Wi-Fi (registered trademark).

[0020] The robot control system 1 is, for example, an information processing system in which a mobile robot device 100 moves autonomously and the movement of the mobile robot device 100 is controlled by a server system 200. The mobile robot device 100 is a robot device that provides various services, such as acquiring various types of information about the inside of a building by moving around the building and transmitting the acquired information to the server system 200, or performing a predetermined action when a predetermined condition is met while moving around the building.

[0021] The mobile robot device 100 includes, for example, a communication unit 102, a light emitting unit 104, a light receiving unit 106, an intensity detecting unit 108, a control unit 110, and a driving unit 112. The communication unit 102 communicates with the server system 200 via the communication network NW. The light-emitting unit 104 and the light-receiving unit 106 are LRFs, for example, ToF sensors such as LiDAR. The light-emitting unit 104 includes a light-emitting element that emits near-infrared light, for example. The light-emitting unit 104 emits a predetermined number of pulsed light pulses every predetermined period. The light-receiving unit 106 is, for example, a photodiode or a single-photon avalanche diode (SPAD) sensor. The light-receiving unit 106 receives reflected light of the pulsed light emitted by the light-emitting unit 104 and generates an electrical signal. The intensity detection unit 108 detects the intensity of the electrical signal based on the reflected light received by the light receiving unit 106 . The control unit 110 controls the movement of the mobile robot device 100 in accordance with the distance from the mobile robot device 100 to the glass wall calculated by the distance calculation unit 212 (described later) or map information. The driving unit 112 generates a driving force for moving the mobile robot device 100 under the control of the control unit 110 .

[0022] The communication unit 102 transmits to the server system 200 an electric signal of the reflected light detected by the light receiving unit 106 and electric signal intensity information indicating the intensity of the electric signal. The communication unit 102 also transmits to the server system 200 position information of the mobile robot device 100 estimated by a SLAM processing unit (not shown). The communication unit 102 receives distance information or map information from the server system 200. In response to this, the control unit 110 controls the movement of the mobile robot device 100 based on the position information of the mobile robot device 100 and the distance information or map information.

[0023] The server system 200 includes one or more server devices that communicate with the mobile robot device 100 and perform processing in response to requests received from the mobile robot device 100. The server system 200 includes, for example, a data transmission / reception server 202, a data storage server 204, a pulse analysis server 206, and a map drawing server 208.

[0024] The data transmission and reception server 202 receives electrical signal strength information indicating the strength of the electrical signal from the mobile robot device 100. The data transmission and reception server 202 also transmits distance information indicating the distance from the mobile robot device 100 to the glass wall based on the electrical signal strength information to the mobile robot device 100. The data transmission and reception server 202 transmits map information drawn by the map drawing server 208 to the mobile robot device 100.

[0025] The data storage server 204 stores the electrical signal intensity information received from the intensity detection unit 108 , the distance information calculated by the pulse analysis server 206 , and the map information created by the map drawing server 208 .

[0026] The pulse analysis server 206 includes, for example, an extraction unit 210 and a distance calculation unit 212. The extraction unit 210 extracts an electrical signal used to calculate the distance from the mobile robot device 100 to the reflected light received by the light receiving unit 106 based on the intensity of the electrical signal detected by the intensity detection unit 108. The distance calculation unit 212 calculates the distance from the mobile robot device 100 to the glass wall based on the time of flight of the pulsed light corresponding to the electrical signal extracted by the extraction unit 210.

[0027] The map drawing server 208 draws map information based on the distance information calculated by the distance calculation unit 212, which indicates the distance between the mobile robot device 100 and various walls such as glass walls, and the position information of the mobile robot device 100.

[0028] The robot control system 1 of the embodiment has been described as including the intensity detection unit 108 in the mobile robot device 100 and the extraction unit 210 and distance calculation unit 212 in the server system 200, but is not limited to this. The mobile robot device 100 may be provided with the intensity detection unit 108, extraction unit 210, and distance calculation unit 212, and the server system 200 may be provided with the intensity detection unit 108, extraction unit 210, and distance calculation unit 212.

[0029] (2D LiDAR of mobile robotic device 100) The light emitting unit 104 and the light receiving unit 106 in this embodiment are configured by a two-dimensional LiDAR. The following description will be given using the specifications of a two-dimensional LiDAR from a certain manufacturer as an example. The specifications of the two-dimensional LiDAR from a certain manufacturer are not significantly different from the specifications of two-dimensional LiDAR from other manufacturers and are general. Assuming that the frequency of one scan in a 2D LiDAR is around 40 Hz, one scan takes around 25 milliseconds. A 2D LiDAR emits 2161 pulses during one 25-millisecond scan, emitting 86,440 pulses per second (= 2161 × 40 Hz). This means that the time required to emit one pulse is equivalent to 11.6 μs, and the pulsed light travels 3,856 m during this time. However, taking the round trip into account, the maximum measurement range is 1,928 m (= 3,856 m / 2). If the actual measurement distance of a 2D LiDAR is around 50 m, the flight time corresponding to the maximum measurement range is 300 nanoseconds. If one process is defined as the period from pulse emission to pulse reception, a 2D LiDAR can be said to be a sequential measurement device, performing one process at 11.6 μs intervals. In other words, the first process and the following second process are completely separated in time and do not intermix. If the sampling frequency of reflected light in such a 2D LiDAR is around 43,000 Hz, then the 2D LiDAR has the ability to sample up to around 1,075 reflected light samples (= 43,000 Hz / 40 Hz) with the light receiving sensor during one scan (25 milliseconds).

[0030] (Operation of robot control system 1) FIG. 2 is a flowchart showing an example of an operation procedure of the robot control system 1 according to the embodiment. While the mobile robot device 100 is moving (step S100), the light emitter 104 emits a predetermined number of pulsed light for a predetermined period of time, and the light receiver 106 acquires a predetermined number of electrical signals (step S102). The intensity detector 108 transmits electrical signal intensity information to the server system 200. The electrical signal intensity information includes a predetermined number of electrical signals for a predetermined period of time and data indicating the electrical signal intensity. The data transmission / reception server 202 acquires the electrical signal intensity information from the intensity detector 108, and the data storage server 204 stores the electrical signal intensity information. The pulse analysis server 206 extracts an electrical signal from the electrical signal intensity information, which is used by the extractor 210 to calculate the distance from the mobile robot device 100, based on the electrical signal intensity.

[0031] Fig. 3 is a diagram showing an example of temporal changes in the intensity of an electric signal in an embodiment, which shows the changes in the intensity of an electric signal detected when the mobile robot device 100 emits pulsed light in the following order: a wall other than a glass wall, a glass wall, and another wall other than a glass wall. The electric signal strength of light reflected by a wall other than a glass wall is higher than the electric signal strength of light reflected by a glass wall. Using this, pulse analysis server 206 determines whether or not an electric signal whose intensity is lower than first threshold TH1 has been detected within a predetermined period of time (step S104). If pulse analysis server 206 determines that an electric signal whose intensity is lower than first threshold TH1 has not been detected within a predetermined period of time (step S104: NO), pulse analysis server 206 causes distance calculation unit 212 to calculate the distance between mobile robot device 100 and the wall other than a glass wall (step S106).

[0032] When the pulse analysis server 206 determines that an electrical signal whose intensity is lower than the first threshold TH1 has been detected during a predetermined period (step S104: YES), the extraction unit 210 extracts an electrical signal whose intensity exceeds the second threshold TH2 (step S108).

[0033] When comparing the reflectance of reflected light over a specified period when measuring the distance to a glass wall using pulsed light with the light-receiving rate of reflected light over a specified period when measuring a wall other than a glass wall using pulsed light, it is believed that the reflectance of the former is lower. For example, the near-infrared reflectance of plate glass among glass walls is 8%, and the near-infrared reflectance of double-glazed glass is 16%. In contrast, among interior building materials other than glass, the near-infrared reflectance of concrete is 30%, that of marble is 60%, that of light-colored artificial stone is 50%, that of light-colored tile is 70%, that of light-colored brick is 40%, that of light-colored wallpaper is 70%, that of white plaster walls is 85%, that of aluminum is 75%, that of chrome is 70%, that of paulownia wood is 65%, that of cypress wood is 65%, and that of light-colored curtains is 50%. Therefore, the near-infrared reflectance of materials other than glass walls is significantly higher than that of glass walls. Taking advantage of this, the first threshold TH1 is set lower than the strength of the electrical signal from walls other than glass walls. As a result, the pulse analysis server 206 can detect the presence of a glass wall by determining that an electric signal whose intensity is lower than the first threshold value TH1 has been detected for a predetermined period of time.

[0034] Fig. 4 is a diagram showing another example of the change in the electrical signal strength over time in the embodiment. Fig. 4 shows the change in the electrical signal strength over time during a predetermined period in which the electrical signal strength is determined to be lower than the first threshold value TH1. That is, the electrical signal strength shown in Fig. 4 represents the result of detecting reflected light reflected by a glass wall.

[0035] When a glass wall is present in the environment in which the mobile robot 100 is moving, the following cases (1) to (4) are possible: (1) pulsed light (near-infrared light) emitted from the mobile robot 100 passes through the glass wall, is reflected by an object on the other side, and passes through the glass wall again before returning to the mobile robot 100; (2) pulsed light passes through the glass wall, is reflected by an object on the other side, and does not return to the mobile robot 100; (3) pulsed light is reflected by the interface of the glass wall and returns to the mobile robot 100; or (4) pulsed light is reflected by the interface of the glass wall and does not return. In case (1), a low-intensity electrical signal P2 is detected, such as a signal below the third threshold TH3 in FIG. 4. In contrast, in case (3), a high-intensity electrical signal P1 exceeding the second threshold TH2 is detected.

[0036] The extraction unit 210 extracts an electric signal having an electric signal intensity exceeding the second threshold value TH2 in order to extract the reflected light, as in the case (3), in which the pulsed light is reflected at the interface of the glass wall and returns to the mobile robot device 100. The second threshold value TH2 is a value for determining that the electric signal corresponds to the reflected light reflected by the glass wall out of the pulsed light incident on the glass wall. Specifically, as shown in Fig. 5, when the mean and standard deviation of the normal distribution of electrical signals smaller than the first threshold TH1 are μ and σ, the second threshold TH2 is set to a range in which an electrical signal strength between μ + 2σ and μ + 3σ is preferable, an electrical signal strength between μ + 2.5σ and μ + 3σ is more preferable, and an electrical signal strength between μ + 2.5σ and μ + 4σ is most preferable. Since the electrical signal of the pulsed light reflected by the interface of the glass wall and returning to the mobile robot device 100 is extracted within the range equal to or greater than the second threshold TH2, the distance calculation unit 212 measures the distance by performing the following arithmetic processing on the electrical signals that fall within this range. For example, for all pulses having an electrical signal strength between μ+2.5σ and μ+4σ, the pulse analysis server 206 calculates the time difference between the emission time of the LiDAR light pulse and the detection time of the received light pulse of the reflected light for each pulse. Then, the time differences between the light emission pulse and the received light pulse are summed for all pulses, and further divided by the total number of pulses to obtain the average time difference δ t Next, calculate the average time difference δ t The average distance d from the glass wall to the mobile robot device 100 can be calculated by multiplying this by the speed of light and dividing the product of the average time difference and the speed of light by 2, which indicates the distance the pulse traveled back and forth.

[0037] In this way, distance calculation unit 212 calculates the distance from mobile robot device 100 to the glass wall based on the time of flight of the pulsed light corresponding to the electrical signal extracted by extraction unit 210 (step S110). The time of flight of the electrical signal is the period from the emission time of the light emitting pulse to the detection time of the received light pulse (reflected light).

[0038] The map drawing server 208 updates the map information based on the distance from the mobile robot 100 to the wall calculated by the distance calculation unit 212 (step S112).

[0039] The mobile robot device 100 determines whether or not the movement has ended (step S114). The mobile robot device 100 determines that the movement has ended, for example, when it has reached the end position of a preset route. If the movement has ended, the mobile robot device 100 ends the processing of this flowchart (step S114: YES). If the movement has not ended, the mobile robot device 100 returns to step S100 and continues moving (step S114: NO).

[0040] When comparing the reflected light in which pulsed light is reflected by the glass wall and detected by the light receiving unit 106 (the above-mentioned case (3)), and the reflected light in which pulsed light passes through the glass wall, reflects off an object on the other side of the glass wall, passes through the glass wall again, and is detected by the light receiving unit 106 (the above-mentioned case (1)), it can be inferred that the electric signal strength in case (3) is higher than that in case (1) because the reflected light in case (1) has a longer flight time and passes through the glass wall twice. Also, it can be inferred that the number of samples of reflected light received by the light receiving unit 106 in case (1) or (3) is much less than the number of pulses (1,075) in one LiDAR scan (25 milliseconds). However, the number of pulses can be distinguished between case (1) and case (3) by providing statistical values ​​of the electric signal strength in the pulse analysis server 206, as shown in FIG. 4. Therefore, the pulse analysis server 206 can calculate the average time of flight (ToF) of the multiple electrical signals in case (3) extracted by the extraction unit 210, thereby calculating the average distance from the mobile robot device 100 to the glass wall during a specified time period of one scan.

[0041] Furthermore, for example, if the maximum movement speed of the mobile robot device 100 during scanning is 1 m / s, the mobile robot device 100 moves 25 mm for each scan, and therefore the next scan will be performed at a position 25 mm shifted from the previous scan. In this way, the pulse analysis server 206 calculates the average distance to the glass wall while moving the position of the mobile robot device 100 by 25 mm for each scan, and can ultimately calculate the distance between the movement path of the mobile robot device 100 and the entire glass wall.

[0042] (Map information) FIG. 6 is a diagram showing an example of map information when pulsed light is transmitted through a glass wall in a comparative example. The mobile robot device of the comparative example calculates the distance from the mobile robot device 100 to the wall based on the light reflected from the glass wall and walls other than the glass wall, without using the first threshold value TH1 and the second threshold value TH2. In the comparative example, even if the pulsed light passes through the glass wall as in the case (1) above, or even if the pulsed light is reflected as in the case (3), the average value of the electric signal strength over a predetermined period becomes small, and therefore the presence of the glass wall cannot be detected even if it exists.

[0043] FIG. 7 is a diagram showing an example of map information according to the embodiment. The mobile robot device 100 according to the embodiment extracts an electrical signal used to calculate the distance from the mobile robot device 100 to the glass wall based on the intensity of the electrical signal reflected from the light, and calculates the distance from the mobile robot device 100 to the glass wall based on the time-of-flight of the pulsed light corresponding to the extracted electrical signal. Furthermore, when the extraction unit 210 determines that the intensity of the electrical signal is lower than the first threshold value TH1, the mobile robot device 100 extracts an electrical signal having an intensity higher than the second threshold value TH2 from the electrical signals. This allows the map drawing server 208 to calculate the distance from the mobile robot device 100 to the glass wall based on the time-of-flight of the pulsed light corresponding to the electrical signal having an intensity higher than the second threshold value TH2. As a result, the map drawing server 208 can draw a wall at the position corresponding to the glass wall, as shown in FIG. 7 .

[0044] (Variation) The robot control system 1 described above determines that the electrical signal strength is lower than the first threshold value TH1, but instead of this, or in addition thereto, a process such as a modified example may be performed. The mobile robot device 100 of this modified example counts the number of electrical signals over a predetermined period of time and generates electrical signal count information indicating the number of electrical signals. The light receiving unit 106 and the intensity detecting unit 108 continuously receive the electrical signals, record the number and intensity of the electrical signals within a certain period of time, and transmit the information to the server system 200. As shown in FIG. 3, the extracting unit 210 may determine that a glass wall exists if the number of electrical signals within a certain period of time falls below a predetermined value. As a result, when the number of electrical signals is smaller than a predetermined value, the extraction unit 210 can extract electrical signals having an intensity higher than the second threshold value TH2 from the electrical signals. The predetermined value for the number of electrical signals is set to a value corresponding to the ratio of the number of received reflected light to the number of pulses when near-infrared light is irradiated onto the glass wall for a predetermined period of time.

[0045] (Effects of Robot Control System 1) According to the robot control system 1 of the embodiment, a distance measurement system can be realized, which includes: a light-emitting unit 104 that emits a predetermined number of pulsed lights every predetermined period; a light-receiving unit 106 that receives reflected light of the pulsed lights emitted by the light-emitting unit 104; an intensity detection unit 108 that detects the intensity of an electrical signal based on the reflected light received by the light-receiving unit 106; an extraction unit 210 that extracts an electrical signal used to calculate the distance from the mobile robot device 100 to the reflected light received by the light-receiving unit 106 based on the intensity of the electrical signal detected by the intensity detection unit 108; and a distance calculation unit 212 that calculates the distance from the mobile robot device 100 to the glass wall based on the time-of-flight of the pulsed lights corresponding to the electrical signal extracted by the extraction unit 210. The robot control system 1 allows the mobile robot device 100 to accurately calculate the distance to the glass wall. Furthermore, the robot control system 1 can prevent the glass wall portion from being displayed incorrectly on a map created by SLAM, such as that shown in FIG. 6, thereby making it possible to obtain an accurate map created by SLAM. Furthermore, the robot control system 1 can accurately determine the distance to the glass wall, thereby preventing the mobile robot device 100 from colliding with the glass wall.

[0046] Furthermore, in the robot control system 1, when the extraction unit 210 determines that the intensity of the electric signal is lower than the first threshold TH1, it extracts from the electric signals an electric signal having an intensity higher than a second threshold TH2. As a result, the robot control system 1 can determine the presence of a glass wall by taking advantage of the fact that the intensity of reflected light from a glass wall is lower than the intensity of reflected light from walls other than the glass wall, and can extract an electrical signal detected from the reflected light from the glass wall whose intensity is higher than the second threshold value TH2, thereby calculating the distance from the glass wall to the mobile robot device 100.

[0047] In addition, in the robot control system 1, the first threshold value TH1 is a value for determining that the electrical signal is lower than the electrical signal corresponding to the reflected light reflected by something other than the glass wall, and the second threshold value TH2 is a value for determining that the electrical signal corresponds to the reflected light reflected by the glass wall out of the pulsed light incident on the glass wall. As a result, the robot control system 1 determines that the electrical signal corresponding to the reflected light reflected by the glass wall is lower than that corresponding to the light reflected by an object other than the glass wall, and detects the electrical signal corresponding to the reflected light reflected by the glass wall from the pulsed light incident on the glass wall, thereby calculating the distance from the glass wall to the mobile robot device 100.

[0048] 5, in the robot control system 1, when the mean value of the normal distribution of the electric signal strength detected over a predetermined period of time is μ and the standard deviation is σ, the second threshold TH2 is preferably between μ+2σ and μ+3σ, more preferably between μ+2.5σ and μ+3σ, and most preferably between μ+2.5σ and μ+4σ. By setting the second threshold TH2 corresponding to such electric signal strengths, the electric signal strength of the received light pulse reflected at the interface of the glass wall can be selectively extracted, and the average distance from the glass wall to the mobile robot device 100 can be calculated. As a result, the robot control system 1 can statistically set a second threshold value TH2 and calculate the distance from the glass wall to the mobile robot device 100 using an electrical signal detected from the light reflected by the glass wall.

[0049] Furthermore, according to the robot control system 1, when the number of electrical signals is smaller than a predetermined value, the extraction unit 210 extracts electrical signals having an intensity higher than a second threshold value TH2 from among the electrical signals. As a result, according to the robot control system 1, it is possible to determine whether a glass wall is present by utilizing the fact that the number of reflected lights reflected by the glass wall and detected by the light receiving unit 106 is smaller than the number of reflected lights reflected by walls other than the glass wall.

[0050] The functions of the intensity detection unit 108, extraction unit 210, distance calculation unit 212, and map drawing server 208 in the above-described embodiments may be implemented by a computer. In this case, a program for implementing these functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may be a program for implementing only a portion of the above-described functions, or may be a program that can realize the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0051] Each embodiment and variant has been described, but these are merely examples and are not intended to be limiting. For example, one aspect of the present invention may be realized by combining any of the embodiments or variants, or a part of each embodiment or a part of each variant, with one or more other embodiments or one or more other variants.

[0052] <Additional Notes> (1) One aspect of this embodiment is a map drawing system including: a light-emitting unit provided in a mobile robot device that emits a predetermined number of pulsed light at predetermined intervals; a light-receiving unit that receives reflected light of the pulsed light emitted by the light-emitting unit; an intensity detection unit that detects the intensity of an electrical signal based on the reflected light received by the light-receiving unit; an extraction unit that extracts an electrical signal used to calculate a distance from the mobile robot device to the reflected light received by the light-receiving unit based on the intensity of the electrical signal detected by the intensity detection unit; a distance calculation unit that calculates the distance from the mobile robot device to a glass wall based on the time of flight of the pulsed light corresponding to the electrical signal extracted by the extraction unit; and a map drawing unit that draws map information based on the distance calculated by the distance calculation unit.

[0053] (2) One aspect of this embodiment is a control system including: a light-emitting unit provided in a mobile robot device that emits a predetermined number of pulsed light at predetermined intervals; a light-receiving unit that receives reflected light of the pulsed light emitted by the light-emitting unit; an intensity detection unit that detects the intensity of an electrical signal based on the reflected light received by the light-receiving unit; an extraction unit that extracts an electrical signal used to calculate a distance from the mobile robot device from the reflected light received by the light-receiving unit based on the intensity of the electrical signal detected by the intensity detection unit; a distance calculation unit that calculates the distance from the mobile robot device to a glass wall based on the time of flight of the pulsed light corresponding to the electrical signal extracted by the extraction unit; and a control unit that controls movement of the mobile robot device based on the distance calculated by the distance calculation unit. [Explanation of symbols]

[0054] 1. Robot Control System 100 Mobile robot device 102 Communications Department 104 Light-emitting part 106 Light receiving part 108 Intensity detection unit 110 control section 112 Drive unit 200 Server System 202 Data transmission and reception server 204 Data Storage Server 206 Pulse Analysis Server 208 Map drawing server 210 Extraction part 212 Distance calculation unit

Claims

1. a light emitting unit provided in the mobile robot device for emitting a predetermined number of pulsed lights at predetermined intervals, and a light receiving unit for receiving reflected light of the pulsed lights emitted by the light emitting unit; an intensity detection unit that detects the intensity of an electrical signal based on the reflected light received by the light receiving unit; an extracting unit that extracts an electrical signal used to calculate a distance from the mobile robot device to the reflected light received by the light receiving unit based on the intensity of the electrical signal detected by the intensity detecting unit; a distance calculation unit that calculates a distance from the mobile robot device to a glass wall based on a time of flight of pulsed light corresponding to the electrical signal extracted by the extraction unit; A distance measurement system comprising:

2. The distance measurement system according to claim 1 , wherein the extracting unit extracts, from the electric signals, an electric signal having an intensity higher than a second threshold value when the extracting unit determines that the intensity of the electric signal is lower than a first threshold value.

3. the first threshold is a value for determining whether the electrical signal corresponding to the reflected light is lower than the electrical signal corresponding to the reflected light reflected by an object other than the glass wall, The second threshold value is a value for determining that the electrical signal corresponds to light reflected by the glass wall out of the pulsed light incident on the glass wall. The distance measurement system according to claim 2 .

4. the second threshold is set to an electrical signal strength within a range of μ+2σ to μ+4σ, where μ is a mean value and σ is a standard deviation of a normal distribution of electrical signal strengths lower than the first threshold; the distance calculation unit calculates the distance from the mobile robot device to the glass wall based on an electric signal having an electric signal strength within a range of μ+2σ to μ+4σ. The distance measurement system according to claim 2 .

5. The distance measurement system according to claim 1 , wherein the extracting unit extracts, from the electrical signals, electrical signals having an intensity higher than a second threshold value when the number of the electrical signals is smaller than a predetermined value.

6. a step in which the mobile robot device emits a predetermined number of pulsed light beams at predetermined intervals and receives reflected light of the emitted pulsed light beams; an intensity detection unit detecting the intensity of an electrical signal based on the reflected light; an extracting unit extracting an electrical signal used to calculate a distance from the mobile robot device to the reflected light based on the intensity of the electrical signal detected by the intensity detecting unit; a distance calculation unit calculating a distance from the mobile robot device to a glass wall based on a time of flight of pulsed light corresponding to the electrical signal extracted by the extraction unit; A distance measurement method including:

7. On the computer, a step of causing the mobile robot device to emit a predetermined number of pulsed light beams at predetermined intervals and receiving reflected light of the emitted pulsed light beams; detecting an intensity of an electrical signal based on the reflected light; extracting an electrical signal used to calculate a distance from the mobile robotic device to the reflected light based on the intensity of the electrical signal; calculating a distance from the mobile robot device to a glass wall based on a time of flight of pulsed light corresponding to the extracted electrical signal; A distance measurement program that executes the above.

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