Mobile robot and mobile system

Abstract

To provide a mobile robot capable of precisely estimating the position.SOLUTION: A disclosed mobile robot is a mobile robot that moves on a running surface 200 arranged with multiple wireless tags T. The mobile robot includes: a first tag reader 101 that is capable of reading the wireless tags within a first detection range; a second tag reader 102 that is capable of reading the wireless tags within a second detection range wider than the first detection range; and a position estimation unit 104 that estimates the own location based on the detection result by the first tag reader 101 and the detection result the second tag reader 102.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mobile robot. [Background technology]

[0002] Patent Document 1 discloses a position detection method using an RFID tag. In Patent Document 1, a reader mounted on a moving object reads the RFID tag. The reader then reads position information from the RFID tag. When the moving object moves, a speed detection unit detects the moving speed. A position calculation unit calculates the moving distance and moving direction of the moving object based on the moving speed, and calculates the moving object position based on the relative relationship with the position information of the RFID tag. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-249566 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve detection accuracy, tags need to be placed densely. However, placing tags densely means that a large number of tags need to be installed, which makes it difficult to reduce installation costs.

[0005] The present invention has been made in consideration of the above background, and has an object to provide a mobile robot capable of estimating its own position with high estimation accuracy. [Means for solving the problem]

[0006] The mobile robot according to the present disclosure is a mobile robot that moves on a running surface on which a plurality of wireless tags are provided, and includes a first tag reader capable of reading the wireless tags in a first detection range, a second tag reader capable of reading the wireless tags in a second detection range wider than the first detection range, and a position estimation unit that estimates its own position based on the detection results of the first tag reader and the detection results of the second tag reader. It is not possible to achieve both high estimation accuracy for self-position estimation and reduction in installation costs. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a mobile robot that can estimate its own position with high estimation accuracy while keeping installation costs down. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a mobile system using a mobile robot. [Diagram 2] FIG. 4 is a plan view illustrating a typical detection range of a tag reader. [Diagram 3] 4 is a flowchart showing the operation of the mobile robot. [Figure 4] FIG. 2 is a plan view showing a schematic diagram of a wireless tag provided on a traveling surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described below through embodiments of the invention, but the invention according to the claims is not limited to the following embodiments. In addition, not all of the configurations described in the embodiments are necessarily essential as means for solving the problems. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and repeated explanations are omitted as necessary.

[0010] The mobile robot according to this embodiment is a mobile robot that moves on a running surface on which a plurality of wireless tags are provided. The mobile robot is equipped with a first tag reader and a second tag reader. The first tag reader is capable of reading the wireless tags in a first detection range. The second tag reader is capable of reading the wireless tags in a second detection range that is wider than the first detection range. The mobile robot is equipped with a position estimation unit that estimates its own position based on the detection result by the first tag reader and the detection result by the second tag reader.

[0011] Fig. 1 is a block diagram showing an example of a configuration of a mobile robot 100 and a mobile system 1 according to the first embodiment. As shown in Fig. 1, the mobile system 1 includes at least the mobile robot 100 and a plurality of wireless tags T. Note that only the mobile robot 100 can be referred to as the mobile system 1.

[0012] The multiple wireless tags T are all RFID (Radio Frequency IDentifier) ​​tags such as NFC (Near Field Communication) tags, and are arranged in a matrix on the running surface 200 on which the mobile robot 100 runs. For example, identification information of the wireless tag T is recorded in each wireless tag T.

[0013] The wireless tag T stores unique identification information. In other words, the identification information includes an identifier that is different for each wireless tag T. The wireless tag T may be a passive tag that operates by wireless power supply from a tag reader. Of course, the wireless tag T may also be an active tag with a built-in battery.

[0014] The mobile robot 100 is configured to be able to move on a running surface 200 within a predetermined facility such as a hospital. The mobile robot 100 may be configured to be able to move autonomously, or may be configured to be able to move by user operation. The predetermined facility is not limited to a hospital, and may be a hotel, a shopping mall, or the like, as long as the mobile robot 100 can move there.

[0015] Mobile robot 100 includes first tag reader 101, second tag reader 102, memory unit 103, position estimation unit 104, control unit 106, drive unit 107, and sensor unit .

[0016] The first tag reader 101 is configured to be able to read information recorded in any of the multiple RF tags T that have approached within a predetermined distance range. Here, each RF tag T has identification information recorded therein. Therefore, the first tag reader 101 reads the identification information of any of the multiple RF tags T that have approached within a detection range.

[0017] The second tag reader 102 is configured to be able to read information recorded in any of the multiple RF tags T that have approached within a predetermined distance range. Here, each RF tag T has identification information recorded therein. Therefore, the second tag reader 102 reads the identification information of any of the multiple RF tags T that have approached within a detection range.

[0018] First tag reader 101 and second tag reader 102 are installed on the bottom surface of the housing of mobile robot 100 so as to face running surface 200. The detection range of first tag reader 101 is defined as a first detection range. The first detection range is defined according to a communication distance over which first tag reader 101 can transmit and receive radio signals with wireless tag T. The detection range of second tag reader 102 is defined as a second detection range. The second detection range is defined according to a communication distance over which second tag reader 102 can transmit and receive radio signals with wireless tag T.

[0019] The first tag reader 101 and the second tag reader 102 can read the identification information of the RF tag T in a contactless manner. The first tag reader 101 and the second tag reader 102 can read the information of the RF tag T from a location away from the RF tag T. The first tag reader 101 and the second tag reader 102 supply power to the RF tag T by wireless power supply. When power is supplied from the first tag reader or the second tag reader 102, the RF tag T transmits a radio signal including the identification information. The first tag reader or the second tag reader 102 modulates the identification information data with a carrier wave and transmits it as a radio signal. This allows the first tag reader or the second tag reader 102 to read the identification information of the RF tag T.

[0020] Second tag reader 102 has a second detection range that is wider than the first detection range of first tag reader 101. For example, second tag reader 102 and first tag reader 101 have different radio outputs or frequency bands. Specifically, second tag reader 102 has a higher radio output power than first tag reader 101. Increasing the radio output power increases the communication distance. Therefore, the second detection range of the second tag reader can be made wider than the first detection range of first tag reader 101.

[0021] Alternatively, the frequency band of the radio signal of first tag reader 101 can be a frequency band with a short communication distance, and the frequency band of the radio communication of the second tag reader can be a frequency band with a long communication distance. The frequency band of first tag reader 101 can be a frequency band such as HF (High Frequency) or LF (Low Frequency). The frequency band of second tag reader 102 can be a frequency band such as UHF (Ultra High Frequency) or a microwave. Of course, both the radio output and the frequency band of first tag reader 101 and second tag reader 102 may be different, or only one of them may be different.

[0022] The memory unit 103 stores the identification information and position information of each wireless tag T in association with each other. The position estimation unit 104 reads out, from the memory unit 103, position information associated with the identification information read from the wireless tag T by the first tag reader 101, and specifies the position information of the mobile robot 100. Note that, in addition to the identification information of the wireless tag T, the position information of the wireless tag T may be stored in each wireless tag T.

[0023] The memory unit 103 may also store map information such as facilities through which the mobile robot 100 moves. Specifically, the memory unit 103 stores the shape of the travel surface 200 corresponding to the building or facility as the map information. The map information may include information on the positions of the walls of the building and the width and length of the passage. Furthermore, the range in which the mobile robot 100 can move and the range in which it cannot enter may be set. In the map information, position coordinates indicating the position of each wireless tag T are associated with the identification information. The memory unit 103 stores the position coordinates of each wireless tag T on the map. Therefore, when the tag reader reads out the identification information of the wireless tag T, the position of the wireless tag T read by the mobile robot 100 can be identified.

[0024] The storage unit 103 is not limited to being provided in the mobile robot 100, but may be provided outside the mobile robot 100 and configured to be capable of communicating via a network.

[0025] The position estimation unit 104 estimates the self-position of the mobile robot 100 based on the detection results of the first tag reader 101 and the second tag reader 102. This allows the self-position (also called the robot position) of the mobile robot 100 on a map to be estimated. Specifically, the position on the map can be estimated from the identification information of the detected wireless tag T. In other words, the position estimation unit 104 estimates that the mobile robot 100 is in the vicinity of the wireless tag T within the detection range. The position estimation process in the position estimation unit 104 will be described later.

[0026] The control unit 106 performs overall control of the mobile robot 100. The control unit 106 performs movement control so that the mobile robot 100 moves based on the estimation result by the position estimation unit 104. For example, when a destination is given to the mobile robot 100 from outside, the control unit 106 refers to map information and searches for a route to the destination. Alternatively, the mobile robot 100 may be given a route to the destination from outside. The control unit 106 controls the drive unit 107 so that the mobile robot 100 moves along the route.

[0027] The driving unit 107 has a driving mechanism such as wheels and a motor for rotating the wheels. The driving unit 107 rotates the left and right wheels independently based on a control signal from the control unit 106. This allows the mobile robot 100 to move along a preset route. In other words, the mobile robot 100 moves so that the robot position estimated by the position estimation unit 104 moves along the route.

[0028] The sensor unit 108 has various sensors such as a distance measurement sensor. The distance measurement sensor is a LiDAR (Light Detection And Ranging) or a stereo camera, and detects the distance to a surrounding object. The sensor unit 108 may also have a motor encoder for detecting the rotation angle of a wheel, etc.

[0029] Note that the position estimation unit 104 may estimate the position based on the detection results of various sensors in the sensor unit 108, not limited to the detection results of the first tag reader 101 and the second tag reader 102. For example, when odometry is used, the position estimation unit 104 can estimate the position based on the detection results of the encoder of the wheel motor. Alternatively, when a distance measurement sensor is mounted on the mobile robot 100, the position estimation unit 104 estimates the position based on the detection results of the distance measurement sensor.

[0030] For example, the position estimation unit 104 may correct the self-position obtained by odometry based on the detection result of the tag reader. This makes it possible to appropriately correct the position error accumulated by odometry. If the self-position of the odometry is significantly deviated from the position coordinates of the wireless tag T from which the identification information has been read, the position estimation unit 104 corrects the robot position. This causes the robot position to be corrected to the periphery of the wireless tag T.

[0031] When the distance measuring sensor measures the distance to a nearby object, it can measure the shape of the wall, etc. Then, by matching the measured shape with map information, the position estimation unit 104 can estimate the self-position.

[0032] When the mobile robot 100 is an autonomous mobile robot, the control unit 106 can control the movement based on the surrounding result of the distance measurement sensor. For example, when an obstacle or a person is detected around the mobile robot 100 by the distance measurement sensor, the control unit 106 controls the movement so that the mobile robot 100 avoids the obstacle or the person.

[0033] The detection ranges of first tag reader 101 and second tag reader 102 will be described with reference to Fig. 2. Fig. 2 is a top view that illustrates the detection ranges of first tag reader 101 and second tag reader 102. Here, travel surface 200 on which wireless tags T are provided is illustrated as a horizontal XY plane. And, on travel surface 200, wireless tags T are arranged in an array along the XY directions.

[0034] Here, the description will be given assuming that the mobile robot moves along the X direction. The mobile robot 100 before movement is shown as mobile robot 100A, and the mobile robot 100 after movement is shown as mobile robot 100B.

[0035] Furthermore, the first detection range of first tag reader 101 of mobile robot 100A is shown as detection range RA1, and the second detection range of second tag reader 102 is shown as detection range RA2. Similarly, the first detection range of first tag reader 101 of mobile robot 100B is shown as detection range RB1, and the second detection range of second tag reader 102 is shown as detection range RB2.

[0036] The detection range RA1 and the detection range RB1 have the same area and shape. The detection range RA1 and the detection range RB1 are circular. For example, the radius of the detection range RA1 and the detection range RB1 matches the communication distance of the first tag reader 101. Furthermore, the center of the detection range RA1 matches the center of the mobile robot 100A. The center of the detection range RB1 matches the center of the mobile robot 100B.

[0037] The detection range RA2 and the detection range RB2 have the same area and shape. The detection range RA2 and the detection range RB2 are circular. For example, the radius of the detection range RA2 and the detection range RB2 matches the communication distance of the second tag reader 102. The center of the detection range RA2 matches the center of the mobile robot 100A. The center of the detection range RB2 matches the center of the mobile robot 100B.

[0038] The communicable distance of first tag reader 101 is defined as a first communicable distance, and the communicable distance of second tag reader 102 is defined as a second communicable distance. The first communicable distance is shorter than the second communicable distance.

[0039] Although the centers of the detection ranges RA1 and RA2 are shown as coinciding with the center of the mobile robot 100A, the center positions may be different. Although the centers of the detection ranges RB1 and RB2 are shown as coinciding with the center of the mobile robot 100B, the center positions may be different. Furthermore, although the detection ranges RA1 and RA2 are concentric circles, they do not have to be concentric circles.

[0040] Although the detection ranges RA1, RA2, RB1, and RB2 are each circular, they may be shapes other than circular. In other words, the detection ranges may have directionality. For example, the tag reader may have a detection range that is wider in the forward direction of the movement of the mobile robot 100.

[0041] Detection ranges RA2, RB2 of second tag reader 102 are larger than detection ranges RA1, RB1 of first tag reader 101. Specifically, detection range RA1 is included in detection range RA2, and detection range RB1 is included in detection range RB2. Detection range RA1 does not extend outside detection range RA2. Detection range RB1 does not extend outside detection range RB2.

[0042] The detection range RA2 includes four wireless tags TA1 to TA4. The detection range RA1 does not include the wireless tag T. The detection range RB2 includes two wireless tags TB1 and TB2. The detection range RB1 includes two wireless tags TB1 and TB2. In this way, the number of wireless tags T included in the second detection range of the second tag reader 102 is equal to or greater than the number of wireless tags T included in the first detection range of the first tag reader 101.

[0043] In mobile robot 100B, wireless tags TB1 and TB2 are included in detection range RA1 of first tag reader 101. Therefore, position estimation unit 104 estimates the position of mobile robot 100B based on the detection result of first tag reader 101. Position estimation unit 104 estimates that the position of mobile robot 100B is between wireless tags TB1 and TA2.

[0044] In this way, when RF tag T is included in detection range RA1 of first tag reader 101, position estimation unit 104 estimates the position based on the detection result of first tag reader 101. Since first tag reader 101 has a narrow detection range, position estimation unit 104 can estimate the position with high position accuracy. In other words, the estimated position will not deviate from the actual position beyond the communication distance of first tag reader 101. Therefore, the accuracy of the position estimated by position estimation unit 104 can be improved.

[0045] The estimated position of the mobile robot 100B is estimated to be a position not farther than the first communication distance from each of the two wireless tags TB1, TB2. The position estimation unit 104 may also estimate the distance to the wireless tags TB1, TB2 depending on the wireless strength with each of the wireless tags TB1, TB2. For example, when the wireless strength is high, the position estimation unit 104 estimates that the distance to the wireless tag T is short. When the wireless strength is low, the position estimation unit 104 estimates that the distance to the wireless tag T is short. This can further improve the estimation accuracy.

[0046] Furthermore, in mobile robot 100A, wireless tag T is not included in detection range RA1 of first tag reader 101. Therefore, position estimation unit 104 estimates the position of mobile robot 100A based on the detection result of second tag reader 102. Specifically, position estimation unit 104 estimates that the position of mobile robot 100A is between wireless tags TA1 to TA4.

[0047] The estimated position of the mobile robot 100A is estimated to be a position not farther than the second communication distance from each of the four wireless tags TA1 to TA4. The position estimation unit 104 may also estimate the distance to each of the wireless tags TA1 to TA4 depending on the wireless strength with each of the wireless tags TA1 to TA4. For example, when the wireless strength is high, the position estimation unit 104 estimates that the distance to the wireless tag T is short. When the wireless strength is low, the position estimation unit 104 estimates that the distance to the wireless tag T is short. This can further improve the estimation accuracy.

[0048] In this way, when the RF tag T is not included in the detection range RA1 of the first tag reader 101, the position estimation unit 104 estimates the position based on the detection result of the second tag reader 102. In other words, when the first tag reader 101 cannot read the identification information of the RF tag T, the position estimation unit 104 estimates the position based on the detection result of the second tag reader 102.

[0049] Since the second tag reader 102 has a wide detection range, the RFID tags T can be arranged at wider intervals. This reduces the number of RFID tags T that need to be installed, thereby reducing installation costs. In addition, by using the second tag reader 102 with a wide detection range, it is possible to prevent the occurrence of position loss. It is possible to achieve both self-location estimation with high estimation accuracy and reduced installation costs.

[0050] The method according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the position estimation method according to this embodiment. First, control unit 106 determines whether first tag reader 101 has been able to read the identification information (S101). In other words, control unit 106 determines whether first tag reader 101 has been able to detect one or more wireless tags T.

[0051] If the first tag reader 101 can read the identification information (YES in S101), the position estimation unit 104 estimates the position from the detection result of the first tag reader 101 (S102). Specifically, when the first tag reader 101 reads the identification information of the wireless tag T, the control unit 106 refers to map information to identify the position of the read wireless tag T. Then, the position estimation unit 104 can estimate that the mobile robot 100 is located within a circle within a first communication distance from the identified tag position. This allows the position estimation unit 104 to estimate the position with high estimation accuracy.

[0052] If the first tag reader 101 cannot read the identification information (NO in S101), the position estimation unit 104 estimates the position from the detection result of the second tag reader 102 (S103). In other words, if the first tag reader 101 cannot detect any wireless tag T, the position estimation unit 104 estimates the position from the detection result of the second tag reader 102. When the second tag reader 102 reads out the identification information of the wireless tag T, the control unit 106 refers to map information to identify the position of the wireless tag T. Then, the position estimation unit 104 can estimate that the mobile robot 100 is located within a circle within a second communication distance from the identified tag position. Therefore, even if the wireless tags T are sparsely placed, the mobile robot 100 can reliably estimate its own position.

[0053] By repeatedly performing the above-mentioned flow of the estimation process, the position estimation unit 104 can update the self-position of the mobile robot 100. For example, the position estimation unit 104 updates the self-position at regular intervals.

[0054] The mobile robot 100 may also be an autonomous mobile robot that moves autonomously. In this case, the position estimation unit 104 estimates its own position by referring to map information. That is, the position estimation unit 104 estimates its own position in the map information. The position estimation unit 104 can estimate a position on the map from the tag position of the detected wireless tag T. Since the robot can move based on its own position with high estimation accuracy, it can move autonomously appropriately.

[0055] The position estimation unit 104 may also estimate the self-position based on the measurement results of a distance measurement sensor that measures the distance to a surrounding object. That is, the position estimation unit 104 may estimate the self-position based on both the detection result of the tag reader and the measurement result of the distance measurement sensor. By using multiple sensing results, the estimation accuracy of the self-position can be improved.

[0056] (Example of placement of RFID tag T) Next, an example of the arrangement of the RFID tags T on the travel surface 200 will be described with reference to Fig. 4. Fig. 4 is a plan view that illustrates the arrangement of the RFID tags T on the travel surface 200. The travel surface 200 includes a high-precision region 201 and a low-precision region 202. In each of the high-precision region 201 and the low-precision region 202, a plurality of RFID tags T are arranged in an array.

[0057] In the high accuracy region 201, multiple RFID tags T are densely arranged, while in the low accuracy region 202, multiple RFID tags T are sparsely arranged. That is, in the high accuracy region 201, the RFID tags T are denser than in the low accuracy region 202. In the high accuracy region 201, the interval between adjacent RFID tags T is shorter, while in the low accuracy region 202, the interval between adjacent RFID tags T is longer.

[0058] In the high accuracy region 201, the RF tags T are arranged at a high density, so that the accuracy of estimating the position can be improved. For example, the RF tags T are arranged at intervals shorter than the first communication distance of the first tag reader 101. In this way, the first tag reader 101 can reliably detect the RF tags T. Therefore, the accuracy of estimating the position can be improved.

[0059] The high-precision area 201 is installed in a location within the facility where high positional accuracy is required. The location where high positional accuracy is required is, for example, the vicinity of the destination of the mobile robot 100, width On the other hand, a place where high positional accuracy is not required may be a low-density area. This allows the location to be estimated with appropriate accuracy. Also, in the low-accuracy area 202, an increase in the number of wireless tags T can be suppressed, and therefore installation costs can be suppressed.

[0060] The interval between the RF tags T in the high accuracy region 201 can be determined according to the first communication distance. For example, by setting the interval between the RF tags T in the high accuracy region 201 to be equal to or shorter than the first communication distance, the first tag reader 101 can reliably detect the RF tags T. This can improve the accuracy of position estimation. Also, the interval between the RF tags T in the low accuracy region 202 can be determined according to the second communication distance.

[0061] 4, the travel surface 200 is divided into two regions, the high-precision region 201 and the low-precision region 202, but it may be divided into three or more regions. The arrangement density of the wireless tags T may be changed for each region. Furthermore, a region in which the density gradually changes may be provided.

[0062] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention.

[0063] Furthermore, the present disclosure can realize a part or all of the control processing in the mobile system 1 by having a CPU (Central Processing Unit) execute a computer program. For example, the control unit 106, the position estimation unit 104, etc. can be implemented as a device capable of executing a program, such as a central processing unit (CPU) of a computer. Various functions can also be realized by a program.

[0064] The above-mentioned program includes a set of instructions (or software code) for making the computer perform one or more functions described in the embodiment when the program is loaded into the computer. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or the tangible storage medium includes a random-access memory (RAM), a read-only memory (ROM), a flash memory, a solid-state drive (SSD) or other memory technology, a CD-ROM, a digital versatile disc (DVD), a Blu-ray® disk or other optical disk storage, a magnetic cassette, a magnetic tape, a magnetic disk storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or a communication medium. By way of example and not limitation, the transitory computer-readable medium or the communication medium includes an electrical, optical, acoustic, or other form of propagating signal. [Explanation of symbols]

[0065] 1. Mobile System 100 Mobile Robot 101 First Tag Reader 102 Second Tag Reader 103 Storage section 104 Position estimation part 106 Control section 107 Drive unit 108 Sensor section 200 Running surface 201 High precision area 202 Low precision area T Radio tag

Claims

1. A mobile robot that moves on a running surface on which a plurality of wireless tags are provided in an array, a first tag reader capable of reading identification information of the wireless tag within a first detection range corresponding to a first communication distance; a second tag reader capable of reading identification information of the wireless tag within a second detection range corresponding to a second communication range that is wider than the first detection range and longer than the first communication range; a position estimating unit that estimates a self-position based on a detection result by the first tag reader and a detection result by the second tag reader; a storage unit that stores location information associated with the identification information of the wireless tag, determining whether the first tag reader has read the identification information of one or more wireless tags; When the first tag reader is able to read the identification information of one or more of the wireless tags, the first tag reader estimates a position in an area within a first communication distance from a position specified by position information corresponding to the identification information read by the first tag reader as the self-location; A mobile robot, when the first tag reader cannot read the identification information of the wireless tag, estimates its own position to be a position in an area within a second communication distance from a position identified by position information corresponding to the identification information read by the second tag reader.

2. A mobile robot as described in claim 1, wherein the first tag reader and the second tag reader are provided on the bottom surface of the housing of the mobile robot.

3. A plurality of wireless tags arranged in an array; A mobile system comprising the mobile robot according to claim 1 or 2, a high-density area in which the plurality of wireless tags are arranged at intervals shorter than the first communication distance; and low density areas spaced apart from the high density areas.

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