MOBILE ROBOT AND METHOD OF TRACKING MOBILE ROBOT

A mobile robot includes a mobile robot body, a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane, and a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit. The mobile robot travels along the travel locus detected by the detector.

BACKGROUND OF THE INVENTION

Technical Field

The present disclosure relates to a mobile robot configured to execute tracking control of a single or a plurality of mobile robots and a method of tracking a mobile robot.

Description of the Related Art

A technique for tracking control of a mobile robot includes a typically known method of detecting a target object to be tracked (such as a person or a mobile object) with use of a laser range scanner disposed at a front portion of the mobile robot and tracking the target object.

This method fails to enable distinction of the target object. In a case of tracking one of a plurality of persons, the person to be tracked may be lost and a person different from the tracking target may be tracked.

Assume another case of executing tracking control in accordance with the method described above with a plurality of mobile robots in a single-line formation. When a tracked robot turns around an obstacle or at a corner, tracking robots turn at the respective points. The mobile robot closer to the end of the line has a travel locus too close to the obstacle or the corner and thus highly possibly runs into the obstacle or the corner.

This problem can be solved by executing tracking control along an identical trajectory of causing the plurality of tracking mobile robots to travel along the locus of the tracked mobile robot at the forefront of the line (refer to Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-46926).

Such tracking control along the identical trajectory requires each of the mobile robots in the formation to accurately recognize the travel locus of the tracked mobile robot at the forefront of the formation and a current own position. The mobile robots accordingly need to move autonomously.

A technique of recognizing an own position of an autonomously mobile robot includes a typical method of comparing a preliminarily prepared map of landmarks with positions of the landmarks acquired by a laser range scanner.

FIG. 38is an outline view according to Patent Document 1, of tracking control along an identical trajectory. A tracked mobile robot20and a tracking mobile robot50each include a laser range scanner40and a communicator30. Assume that these robots20and50travel in a known environment of which an environmental map is prepared. The tracked mobile robot20moves autonomously. The mobile robot20recognizes an own position with use of the laser range scanner40and with reference to the environmental map, and teaches the tracking mobile robot50as needed with use of the communicator30a locus60of the recognized own position. The tracking mobile robot50tracks the taught locus60of the position of the tracked mobile robot20while sequentially recognizing an own position with use of the laser range scanner40.

This method requires a landmark like a wall in a travel environment for recognition of the own position of the tracking mobile robot50. The tracking mobile robot50fails to recognize the own position in a broad space including no wall or the like. In a case where each autonomously mobile robot loading cargo or a person reaches a destination (e.g. a boarding gate) in a large facility such as an air terminal and scattered autonomously mobile robots are then to be collected at one site, the mobile robots have difficulty in recognizing own positions because of the large facility. Tracking control along an identical trajectory cannot be executed in this case.

SUMMARY

The present disclosure has been achieved in view of such a conventional issue, and an object thereof is to provide a mobile robot configured to execute tracking control along an identical trajectory of a plurality of mobile robots even in an environment like a broad space including no wall or the like, where the mobile robots are inhibited from recognizing own positions, and provide a method of tracking the mobile robot.

One non-limiting and exemplary embodiment of the present disclosure provides a mobile robot comprising:

a mobile robot body;

a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane;

a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit;

a travel driving unit configured to drive to move the mobile robot body; and

a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector.

It should be noted that general or specific embodiments may be implemented as a system (or an apparatus), a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

Any one of the aspects of the present disclosure enables, in tracking travel of the plurality of mobile robots, the drawing unit in the mobile robot at the forefront of the line to draw the travel locus on the travel plane, enables the detector in the tracking mobile robot to detect the drawn travel locus, and enables the tracking mobile robot to travel along the detected travel locus. Accordingly, tracking control along an identical travel locus of a plurality of mobile robots is achieved even in an environment like a broad space including no wall or the like where the mobile robots are inhibited from recognizing own positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present disclosure will now be described below with reference to the accompanying drawings. Identical constituent elements will be denoted by identical reference signs. The drawings schematically depict their main constituent elements for easier understanding.

First Embodiment

A mobile robot according to the first embodiment of the present disclosure will initially be described with reference to the drawings.FIG. 1is a schematic explanatory view from the top of a mobile robot100according to the first embodiment of the present disclosure. The mobile robot100at least includes a mobile robot body1, a drawing unit6, a detector7, a travel driving unit15, and a controller14including a drive controller10.

The drawing unit6includes a marker6bconfigured to draw a travel locus5of the mobile robot100on a travel plane19of the mobile robot100.

The detector7detects the travel locus5drawn on the travel plane19by the drawing unit6.

The travel driving unit15is embodied by a driving device like a motor, and is configured to drive to positively and negatively rotate a pair of driving wheels2independently from each other. The travel driving unit15, the pair of driving wheels2, and a pair of trailing wheels3configure a travel driving device.

More specifically, the mobile robot body1of the mobile robot100further includes a distance sensor4and a travel plane determiner21.

The distance sensor4measures a distance to a position ahead of the mobile robot100, specifically, to an obstacle in a travel direction thereof.

The travel plane determiner21detects a material for the travel plane19to determine a type of the travel plane19.

The respective constituent elements will be described in detail below.

The distance sensor4is disposed at the front or the like of the mobile robot body1and is configured to measure a distance to an obstacle in the travel direction of the mobile robot100. The controller14receives measurement information. The controller14drive controls the travel driving unit15in accordance with the measurement information, to allow the mobile robot100to travel while avoiding the obstacle. The distance sensor4is exemplified by an infrared distance sensor.

The controller14is connected to the drawing unit6and the detector7, and independently controls drawing by the drawing unit6and detection by the detector7. The controller14includes a calculator9and the drive controller10.

The calculator9calculates the travel locus5to be tracked in accordance with movement trace information on the travel locus5detected by the detector7and acquired from the detector7.

The drive controller10executes tracking control by causing the travel driving unit15to drive control the pair of driving wheels2to achieve movement along the travel locus5calculated by the calculator9.

The drive controller10drive controls the travel driving unit15, the detector7, and the drawing unit6, independently from one another.

The mobile robot100can further include an operation unit16at least having a steering wheel and an operation panel used for steering a mobile robot101to a desired destination by a collector11boarding the mobile robot101. The travel driving unit15can alternatively be drive-controlled via the drive controller10of the controller14in accordance with an operation command inputted to the operation panel of the operation unit16by the collector11.

FIG. 2is a schematic sectional view from a side of the mobile robot100. The drawing unit6is provided at the mobile robot body1to be high enough to draw the travel locus5directly on the travel plane19. The detector7is provided at the mobile robot body1to be high enough to detect the travel locus5drawn on the travel plane19by the drawing unit6. The detector7is accordingly disposed ahead of the drawing unit6in the travel direction of the mobile robot100.

FIGS. 3A and 3Bare detailed views of the drawing unit6.FIG. 3Ais a plan view from the top of the mobile robot100, of the drawing unit6, whereasFIG. 3Bis a perspective view from the bottom of the mobile robot100, of the drawing unit6.

The drawing unit6includes an expandable portion6aconfigured to be axially expandable (e.g. vertically inFIG. 3B), the marker6bfixed at a distal end (e.g. the lower end inFIG. 3B) of the expandable portion6aand having a projecting end soaking paint, and a drawing unit driver6glike a motor configured to axially move the marker6bvia the expandable portion6aand drive-controlled by the drive controller10.

When the drawing unit6is activated, the drawing unit driver6glike a motor lowers the marker6bto extend the expandable portion6aaxially downward and the lower end of the marker6bcomes into direct contact with the travel plane19as a travel plane, so that the paint of the marker6bis directly applied to the travel plane19as the travel locus5. The travel locus5is exemplified by a belt-like straight line having a predetermined width of about several centimeters.

When the mobile robot100stops or the drawing unit6stops drawing, the drawing unit driver6glike a motor raises the marker6bto contract the expandable portion6aand prevent the marker6bfrom directly contacting the travel plane19.

Examples of the paint to be applied to the travel plane19include paint to be detected only by the detector7. More specific examples of the paint include paint that shines only when irradiated with black light or the like. Such specific examples of the paint include black light ink that has milky white color inapparent even when applied without irradiation with black light and apparently changes in color from milky white into red, green, or blue with irradiation with black light. Such paint applied to the travel plane19will conveniently be invisible to persons except for the mobile robot100. The above method includes drawing the travel locus5with use of paint, which can be replaced with colored powder, a tape, or the like.

The method of drawing the travel locus5can be selected after the travel plane determiner21detects the material for the travel plane19and determines the type of the travel plane19.

As shown inFIG. 3C, the travel plane determiner21includes a comparator21a, a material determiner21b, and a memory21c. The memory21cexemplarily stores a surface image of a hard tile and a surface image of a rug or a carpet, as well as information on paint to be applied to the hard tile and particles to be applied to the rug or the carpet and being substantially as large as lime. The comparator21areceives an image captured by a camera exemplifying an imaging device configuring the detector7. The comparator21acompares the received image with the image stored in the memory21c. According to an exemplary comparison method, the comparator21acompares the received image with the image stored in the memory21cin accordance with pattern matching. The material determiner21breceives a result of the comparison. The material determiner21bdetermines whether the received image relates to a hard tile, or a rug or a carpet, in accordance with the result of the comparison by the comparator21a, acquires information on the paint or the particles corresponding to the determined material in accordance with the information stored in the memory21c, and outputs, to the drawing unit6, the acquired information on the paint or the particles as information on the material to be used for drawing.

For example, in a case where the material determiner21bdetermines that the travel plane19is a hard tile or the like, the drawing unit6adopts the paint. In another case where material determiner21bdetermines that the travel plane19is a rug or a carpet, the drawing unit6draws the travel locus5by scattering the particles substantially as large as lime on the travel plane19, instead of applying paint that is hard to be removed from the rug or the carpet. Examples of the particles substantially as large as lime include particles having the maximum diameter more than 0 μm and equal to or less than 10 μm.

The information on the travel plane19stored in the memory21cis exemplified by the two types. The present embodiment is not limited to these types, but the memory21ccan alternatively store a preliminarily captured image of the travel plane19to be traveled by the mobile robot100and a drawing material to be applied to the travel plane19corresponding to the image, associating the image with the drawing material.

Examples of a device configured to scatter the particles substantially as large as lime include a particle discharge mechanism70as shown inFIG. 3D. The drawing unit6inFIGS. 3A and 3Bmay be referred as a first drawing unit, whereas the particle discharge mechanism70may be referred as a second drawing unit.

The particle discharge mechanism70includes a driving unit71, an encoder72, a particle storage tank73, and a discharge switching controller74. The driving unit71positively or negatively rotates a driving motor71bto positively or negatively rotate a drive shaft71aas a screw shaft so as to move the particle storage tank73screwed to the drive shaft71aforward or backward along the drive shaft71a. The particle storage tank73stores the particles and has a lower opening closed by a shutter73a. Under the control of the discharge switching controller74, the shutter73arotates positively or negatively about a rotary shaft of a motor73brotating positively or negatively, to open or close the lower opening of the particle storage tank73. When the drawing unit6starts drawing, the discharge switching controller74rotates the shutter73ato open the lower opening to allow the particles to drop from the particle storage tank73for drawing.

The travel driving unit15includes an encoder15ethat detects rotational speed of a motor15mto detect travel speed of the mobile robot100. The discharge switching controller74controls an opening degree of the shutter73asuch that particle density of the travel locus5on the travel plane19is not largely varied in accordance with the travel speed.

FIGS. 4A and 4Bare detailed views of the detector7.FIG. 4Ais a plan view from the top of the mobile robot100, of the detector7, whereasFIG. 4Bis a perspective view from the bottom of the mobile robot100, of the detector7.FIG. 4Cis a block diagram of the detector having an exemplary configuration, whereasFIG. 4Dis a block diagram of the detector having another exemplary configuration.FIG. 4Edepicts an image (a) captured by the camera and data (b) obtained by binarizing the image.

The detector7includes a plurality of paint detection sensors7aand a determiner7das exemplarily shown inFIG. 4C. The paint detection sensors7aeach include a light emitter7band a light receiver7c. The paint detection sensor7airradiates the travel plane19with light from the light emitter7b, causes the light receiver7cto receive light reflected at the travel plane19, and the determiner7ddetermines whether or not the travel plane19has the travel locus5in accordance with intensity of the light received by the light receiver7c. The light emitter7bis exemplified by an LED black light configured to emit black light. The light receiver7cis configured by a photo reflector and detects the black light emitted from the light emitter7b. The determiner7ddetermines that the travel plane19has the travel locus5in accordance with a result of the detection by the light receiver7c. The determiner7dcan determine that the travel plane19has the travel locus5in a case where the travel plane19and the travel locus5have a difference in color value equal to or more than a threshold and the travel locus5is linear. The plurality of paint detection sensors7ais exemplarily aligned in series to cross, for example, to be perpendicular to, the travel direction of the mobile robot100or an extending direction of the travel locus5. Provision of the plurality of the paint detection sensors7aenables calculation of a relative position of the mobile robot100to the travel locus5. The drive controller10in the mobile robot100executes tracking control in accordance with information on the relative position.

FIG. 4Fis a lower-side perspective view depicting an internal structure of the detector7inFIG. 4B, excluding a cover and the like. As shown inFIG. 4F, the paint detection sensors7aeach irradiate the travel plane19with light17efrom a photodiode17bfunctioning as the light emitter7band causes a photo reflector17cfunctioning as the light receiver7cto receive light17dreflected at the travel plane19, and the determiner7ddetermines whether or not the travel plane19has the travel locus5in accordance with reflectance of the light17dreceived by the photo reflector17c.FIG. 4Gexemplarily indicates a relationship between the reflectance and positions of the sensors7a. In a case where there are provided seven sensors7aas shown inFIG. 4F, the determiner7dcalculates a relative position of the travel locus to the mobile robot100in accordance with the position of the fourth sensor7ahaving the highest reflectance as indicated inFIG. 4G. Assume that the fourth sensor7ain the center in the width direction of the seven sensors7ain the travel direction of the mobile robot1has a relative position of zero. The determiner7dcalculates a degree of displacement, from the fourth sensor7a, of the sensor7ahaving detected the travel locus5. For example, when a sensor7adetecting the travel locus5is the fourth sensor7awith respect to the fourth sensor7ain the center, the determiner7ddetermines that the relative position is zero and the mobile robot100continuously travels straight. In a case where the third or second sensor7adetects the travel locus5, the determiner7ddetermines that the relative position is displaced by one or two to the left from the fourth sensor7a, and the travel driving unit15is controlled to turn the mobile robot100to the right. In another case where the fifth or sixth sensor7adetects the travel locus5, the determiner7ddetermines that the relative position is displaced by one or two to the right, and the travel driving unit15is controlled to turn the mobile robot100to the left.

The plurality of paint detection sensors in the detector7can be replaced with a wide-field imaging device. Examples of the imaging device include a camera7e. As shown inFIG. 4D, the detector7alternatively may include the camera7e, a binarizer7f, and a determiner7g. When the binarizer7fbinarizes an image captured by the camera7e, the travel plane19and the travel locus5can be distinguished from each other in color, as shown inFIG. 4E. For example, in a case where the paint or the particles used for drawing the travel locus5are lighter in color than the travel plane19, the determiner7gcan determine an area in the lighter color as the travel locus5. Specifically, assuming that the image (a) inFIG. 4Eis captured by the camera7e, the data (b) inFIG. 4Eis obtained by binarizing the image (a). In this case, the determiner7gcan determine the area of a white thick line at the center of the image as the travel locus5.

FIG. 5depicts a positional relationship among the distance sensor4, the drawing unit6, and the detector7provided at the mobile robot body1. The distance sensor4is configured to measure a distance to an obstacle in the travel direction of the mobile robot100, and is thus disposed at the front surface of the mobile robot body1. The drawing unit6and the detector7are disposed in series in the mobile robot body1in the travel direction of the mobile robot100. The detector7is disposed ahead of the drawing unit6in this case.

A first mobile robot100and a second mobile robot100accordingly have an identical travel locus. The mobile robots100can travel on a narrow passage as wide as the single mobile robot100. Assume that the drawing unit6and the detector7are disposed apart from each other by a distance Y. The distance Y will be referred to later.

A method of tracking the mobile robot100will be described next by exemplifying an air terminal requiring tracking along an identical locus of the mobile robots100. Specifically described is a collection system S100adopting tracking control of six mobile robots100. For convenience in the description, the six mobile robots100will be denoted by a first mobile robot101, a second mobile robot102, a third mobile robot103, a fourth mobile robot104, a fifth mobile robot105, and a sixth mobile robot106.

The collection system S100for the mobile robots100includes the first mobile robot101, the second mobile robot102, the third mobile robot103, the fourth mobile robot104, the fifth mobile robot105, and the sixth mobile robot106.

Briefly, in order to gather the two mobile robots100disposed in the vicinity of each of boarding gates A to C (in other words, locations T1to T3) shown inFIG. 6to be referred to later to form a mobile robot line and then collect the mobile robot line at a single collection site (in other words, a location T4), one of the mobile robots100disposed at the location T1as the boarding gate A most distant from the collection site T4is assumed to be at the forefront of the mobile robot line. The mobile robots100disposed at the locations T2and T3as the boarding gates B and C track a single travel locus drawn by the mobile robot100at the forefront, and all the mobile robots100in the mobile robot line are collected at the collection site T4.

FIG. 6is a view depicting a state where the six mobile robots101to106are disposed at the locations T1to T3in the collection system S100. The two mobile robots, namely, the first mobile robot101and the second mobile robot102are disposed next to each other at the location T1as the boarding gate A and are directed identically in the anteroposterior direction. The first mobile robot101is disposed ahead in the travel direction and the second mobile robot102is disposed behind in the travel direction of the first mobile robot101. Similarly, the two mobile robots, namely, the third mobile robot103and the fourth mobile robot104are disposed next to each other at the location T2as the boarding gate B and are directed identically in the anteroposterior direction. The third mobile robot103is disposed ahead in the travel direction and the fourth mobile robot104is disposed behind in the travel direction of the third mobile robot103. Similarly, the two mobile robots, namely, the fifth mobile robot105and the sixth mobile robot106are disposed next to each other at the location T3as the boarding gate C and are directed identically in the anteroposterior direction. The fifth mobile robot105is disposed ahead in the travel direction and the sixth mobile robot106is disposed behind in the travel direction of the fifth mobile robot105.

FIG. 7is a view of the collection site T4for the six mobile robots101to106in the collection system S100. The mobile robots101to106are collected sequentially at the collection site T4to form a single line such that the first mobile robot101is disposed at the forefront (e.g. the lower end inFIG. 7) in the travel direction.

FIG. 8is a view depicting a positional relationship of the mobile robots101to106disposed at the locations T1to T3as the boarding gates. A distance from the rear end of the mobile robot101,103, or105disposed ahead at the location to the front end of the mobile robot102,104, or106disposed behind will be referred to as an inter-robot distance, and the permissible maximum value of the inter-robot distance will be referred to as a maximum permissible inter-robot distance. Assume that a distance X is obtained by adding a distance D1from the drawing unit6included in each of the mobile robots101to106to the rear end of the mobile robot and a maximum permissible inter-robot distance D2.

Described next is a collection flow of the collection system S100for a plurality of mobile robots100executing tracking travel in a single line. A specific example thereof will be described after description of basic behavior.FIG. 9Ais a flowchart depicting the basic collection behavior.

Initially in step S40, the drive controller10determines whether or not the mobile robot100executing tracking travel in a single line of a plurality of mobile robots100is at the forefront of the line. This determination can be made by the collector11who manipulates the operation unit16to inform the drive controller10that this mobile robot100is at the forefront of the line. The drive controller10can alternatively determine that this mobile robot100is at the forefront of the line when the distance sensor4detects that there is no other mobile robot100ahead of this mobile robot100for a predetermined period. The drive controller10can still alternatively determine that this mobile robot100is at the forefront of the line in a case where the detector7detects no travel locus5even after this mobile robot100moves for a predetermined period or by a predetermined distance.

The flow proceeds to step S41if the drive controller10determines that this mobile robot100is at the forefront of the line. The flow proceeds to step S42if the drive controller10determines that this mobile robot100is not at the forefront of the line.

Subsequently, in step S41, since the mobile robot100is at the forefront of the line, the drive controller10controls to activate the drawing unit6in the mobile robot100at the forefront of the line so that the drawing unit6starts drawing the travel locus5on the travel plane19. The drive controller10controls the travel driving unit15while the drawing is executed. The mobile robot100at the forefront of the line having reached a predetermined position ends the basic collection behavior shown inFIG. 9A.

In step S42, the detector7in each of the mobile robots100tracking at the second and the subsequent positions in the line detects the travel locus5drawn on the travel plane19.

Subsequently, in step S43, the drive controller10in each of the mobile robots100tracking the detected travel locus5at the second and the subsequent positions in the line tracking, controls the travel driving unit15for tracking travel. The mobile robots100tracking at the second and the subsequent positions in the line then end the basic collection behavior shown inFIG. 9A.

Described next is the specific example of the collection flow of the collection system S100for the plurality of mobile robots100executing tracking travel in the single line.FIG. 9Bis a flowchart specifically exemplifying the specific collection behavior.FIG. 9Bexemplifies a case where the six mobile robots100eventually execute tracking travel in the single line.

Initially in step S1“activate the mobile robots at the boarding gate A”, the collector11expected to collect the mobile robots100moves to the location T1as the boarding gate A and activates the drawing unit6in the first mobile robot101and the detector7in the second mobile robot102disposed at the location T1as the boarding gate A to be ready for starting drawing and detection.

Subsequently, in step S2, the collector11boards the first mobile robot101and starts steering the first mobile robot101from the location T1as the boarding gate A toward the location T2as the boarding gate B. When the first mobile robot101starts travelling, under the control of the drive controller10, the drawing unit6in the first mobile robot101causes the marker6bto start drawing to leave the travel locus5on the travel plane19, and executes drawing after the detector7finds that there is no travel locus5. Such behavior corresponds to the drawing in step S41. The first mobile robot101subsequently executes only the drawing in step S41and needs to execute neither the detection in step S42nor the tracking in step S43.

In the second mobile robot102expected to track the first mobile robot101, the distance sensor4measures a distance to the first mobile robot101positioned thereahead and transmits the measured distance to the calculator9in the controller14. The distance sensor4is activated simultaneously when the mobile robot100is activated. The distance sensor4having been activated constantly measures a distance at a predetermined period interval or the like and transmits a result of the measurement to the calculator9. The drive controller10can thus determine that this mobile robot100is not at the forefront of the line. When the calculator9determines that the measured distance exceeds the distance X, the drive controller10receives information on the determination from the calculator9and controls the travel driving unit15such that the second mobile robot102continuously travels straight by the distance X from the current position (that is, the position at the determination) until the detector7detects the travel locus5.

The detector7in the second mobile robot102subsequently detects the travel locus5of the first mobile robot101and the calculator9calculates the travel locus5for tracking the first mobile robot101in accordance with a result of the detection. The drive controller10drive controls the travel driving unit15in accordance with the calculated travel locus5, so that the second mobile robot102tracks the travel locus5.

The detection and the tracking correspond to the detection in step S42and the tracking in step S43. When the second mobile robot102tracks the first mobile robot101, the distance sensor4in the second mobile robot102measures a distance to the preceding first mobile robot101and the controller14controls to execute tracking travel until the distance reaches a distance α. The distance α exceeds 0 cm and enables the distance sensor4in the second mobile robot102to detect the first mobile robot101positioned thereahead. The distance α can have a fixed numerical value or a certain numerical range.

In the following description, similarly to the second mobile robot102, the fourth mobile robot104tracking the third mobile robot103at the boarding gate B and the sixth mobile robot106tracking the fifth mobile robot105at the boarding gate C execute tracking travel to have the distance α from the preceding mobile robots103and105, respectively.

In step S2“steer the mobile robot to the boarding gate B” subsequent to step S1, as shown inFIG. 10, the collector11continuously steers the first mobile robot101to a common passage T10in the vicinity of the location T2as the boarding gate B. The collector11stops the first mobile robot101such that the mobile robots101and102align straight on the common passage T10in the vicinity of the location T2as the boarding gate B. The second mobile robot102travels to track the preceding first mobile robot101with the distance α therebetween along the travel locus5drawn by the first mobile robot101. The detection and the tracking correspond to the detection in step S42and the tracking in step S43.

The first mobile robot101executes only step S41in the basic behavior shown inFIG. 9A, whereas the second mobile robot102executes step S42and step S43other than step S41in the basic behavior shown inFIG. 9A.

In subsequent step S3“activate the mobile robots at the boarding gate B”, the collector11temporarily leaves the first mobile robot101and boards the third mobile robot103as shown inFIG. 11. The collector11then starts steering the third mobile robot103and manipulates the operation unit16to move the third and fourth mobile robots103and104at the location T2as the boarding gate B as in step S1and step S2and dispose on the common passage T10in the vicinity of the location T2as the boarding gate B such that the third and fourth mobile robots103and104are disposed behind the second mobile robot102and are directed identically and the first to fourth mobile robots101to104form a single line.

Specifically, the collector11steers the third mobile robot103to dispose the mobile robots103and104on the common passage T10in the vicinity of the location T2as the boarding gate B so that the detector7in each of the mobile robots103and104can detect the travel locus5drawn on the travel plane19by the drawing unit6in the first mobile robot101. The drive controller10subsequently activates the detector7in each of the mobile robots103and104. After the detector7is activated, the collector11boards the first mobile robot101again to restart steering the first mobile robot101on the common passage T10toward the location T3as the boarding gate C. The first mobile robot101thereafter executes only step S41in the basic behavior shown inFIG. 9A, whereas the second to fourth mobile robots102to104execute step S42and step S43other than step S41in the basic behavior shown inFIG. 9A.

The mobile robots103and104can be disposed not in accordance with manipulation of the operation unit16by the collector11but by means of a remote device configured to remotely steer the mobile robots103and104.

In subsequent step S4“steer the mobile robot to the boarding gate C”, as shown inFIG. 12, the collector11continuously steers the first mobile robot101to the common passage T10in the vicinity of the location T3as the boarding gate C. The collector11stops the first mobile robot101such that the mobile robots101to104align straight on the common passage T10in the vicinity of the location T3as the boarding gate C. The third and fourth mobile robots103and104travel to track the preceding second mobile robot102or the third mobile robot103with the distance α therebetween along the travel locus5drawn by the first mobile robot101. The detection and the tracking correspond to the detection in step S42and the tracking in step S43.

In this manner, the third and fourth mobile robots103and104execute step S42and step S43other than step S41in the basic behavior shown inFIG. 9A.

In subsequent step S5“activate the mobile robots at the boarding gate C”, the collector11temporarily leaves the first mobile robot101and boards the fifth mobile robot105as shown inFIG. 13. The collector11starts steering the fifth mobile robot105and manipulates the operation unit16to move the mobile robots105and106at the location T3as the boarding gate C as in step S1and step S2and dispose on the common passage T10in the vicinity of the location T3as the boarding gate C such that the mobile robots105and106are disposed behind the fourth mobile robot104and are directed identically and the first to sixth mobile robots101to106form a single line.

Specifically, the collector11steers the fifth mobile robot105to dispose the mobile robots105and106on the common passage T10in the vicinity of the location T3as the boarding gate C so that the detector7in each of the mobile robots105and106can detect the travel locus5drawn on the travel plane19by the drawing unit6in the first mobile robot101. The drive controller10activates the detector7in each of the mobile robots105and106. After the detector7is activated, the collector11boards the first mobile robot101again to restart steering the first mobile robot101toward the collection site T4. The first mobile robot101thereafter executes only step S41in the basic behavior shown inFIG. 9A, whereas the second to sixth mobile robots102to106execute step S42and step S43other than step S41in the basic behavior shown inFIG. 9A.

In subsequent step S6“steer the mobile robot to the collection site”, as shown inFIG. 14, the collector11continuously steers the first mobile robot101to the collection site T4. As shown inFIG. 15, the collector11stops the first mobile robot101such that the first to sixth mobile robots101to106align straight to be collected at the collection site T4. The third to sixth mobile robots103to106travel to track the preceding second mobile robot102, the third mobile robot103, the fourth mobile robot104, or the fifth mobile robot105with the distance α therebetween along the travel locus5drawn by the first mobile robot101. The detection and the tracking correspond to the detection in step S42and the tracking in step S43.

In subsequent step S7“store the mobile robots”, the collector11manipulates the operation unit16to move the first to sixth mobile robots101to106from the collection site T4to a storage site T11.

As exemplarily shown inFIG. 16, the collector11initially manipulates the operation unit16to cause the drive controller10to stop drawing by the drawing unit6in the first mobile robot101, and manipulates the operation unit16to move the first mobile robot101to the storage site T11. The second to sixth mobile robots102to106travel forward until the detector7in the second mobile robot102becomes unable to detect the travel locus5drawn by the drawing unit6in the first mobile robot101.

As shown inFIG. 17, the drive controller10subsequently stops detection by the detector7in the second mobile robot102, and the collector11manipulates the operation unit16to move the second mobile robot102to the storage site T11. The third to sixth mobile robots103to106travel forward until the detector7in the third mobile robot103becomes unable to detect the travel locus5drawn by the drawing unit6in the first mobile robot101. Such movement is repeated for each of the third to fifth mobile robots103to105.

As shown inFIG. 18, the drive controller10eventually stops detection by the detector7in the sixth mobile robot106, and the collector11manipulates the operation unit16to move the sixth mobile robot106to the storage site T11. The first mobile robot101is moved initially and

the remaining mobile robots are moved sequentially in the above example. The present embodiment is not limited in the order of moving the mobile robots, and any appropriate one of the second to sixth mobile robots102to106can be moved initially in place of the first mobile robot101.

As described above, in tracking travel of the plurality of mobile robots100, the drawing unit6in the mobile robot100at the forefront of the line draws the travel locus5on the travel plane19, the detector7in the tracking mobile robot100detects the drawn travel locus5, and the drive controller10controls the tracking mobile robots100to travel along the detected travel locus5. Accordingly, tracking control along the identical travel locus5of the plurality of mobile robots100is achieved even in a broad space such as an air terminal including no wall or the like where the mobile robots100cannot recognize own positions.

Second Embodiment

Described next with reference toFIG. 19is a collection system S200adopting tracking control of six mobile robots200according to the second embodiment of the present disclosure. For convenience in the description, the six mobile robots200will be denoted by a first mobile robot201, a second mobile robot202, a third mobile robot203, a fourth mobile robot204, a fifth mobile robot205, and a sixth mobile robot206.

Briefly, the collection system S200is achieved by the mobile robots200each including the constituent elements according to the first embodiment as well as an eraser8configured to erase the travel locus5drawn on the travel plane19.

FIG. 19is a schematic explanatory view from the top of the mobile robot200according to the second embodiment of the present disclosure. The mobile robot200includes the mobile robot body1, the drawing unit6, the detector7, the travel driving unit15, the controller14including the drive controller10, and the eraser8. The constituent elements identical with those included in the mobile robot100will be denoted by the identical reference signs and will not repeatedly be described in detail.

The eraser8is provided at the mobile robot body1and erases the travel locus5drawn on the travel plane19by the drawing unit6.

The controller14is connected to the drawing unit6, the detector7, and the eraser8, and independently controls drawing by the drawing unit6, detection by the detector7, and erasing by the eraser8.

FIG. 20is a schematic sectional view from a side of the mobile robot200. The drawing unit6and the detector7are configured and function similarly to those of the mobile robot100.

The drawing unit6adopts paint in a case where the travel plane19is a hard tile. Examples of the paint include paint that is completely volatilized to disappear by frictional heat. Such paint is specifically exemplified by friction erasable ink having the commercial name “METAMO COLOR” sold by PILOT CORPORATION.

FIGS. 21A and 21Bare detailed views of the eraser8.FIG. 21Ais a plan view from the top of the mobile robot200, of the eraser8, whereasFIG. 21Bis a perspective view from the bottom of the mobile robot200, of the eraser8.

The eraser8includes an expandable portion8aconfigured to be axially expandable (e.g. vertically inFIG. 21B), a resin portion8bfixed at a distal end (e.g. the lower end inFIG. 21B) of the expandable portion8aand having a projecting end, and an eraser driver8glike a motor configured to axially move the resin portion8bvia the expandable portion8aand drive-controlled by the drive controller10.

When the eraser8is activated, under control of the drive controller10, the eraser driver8glike a motor lowers the resin portion8bto extend the expandable portion8aaxially downward and thus, the lower end of the resin portion8bcomes into direct contact with the travel plane19. The resin portion8bis made of a material exemplified by elastomer and specifically exemplified by friction eraser sold by PILOT CORPORATION.

When the mobile robot200travels with the eraser8being activated and the lower end of the resin portion8bbeing in direct contact with the travel plane19, the travel plane19and the resin portion8bhave friction therebetween to generate heat that volatilizes the paint of the travel locus5drawn on the travel plane19to completely erase the travel locus5.

When the mobile robot200stops or the eraser8stops erasing, under control of the drive controller10, the eraser driver8glike a motor raises the resin portion8bto contract the expandable portion8aso as to prevent the resin portion8bfrom directly contacting the travel plane19.

The eraser8described above is configured correspondingly to the case where the travel locus5is drawn with paint.

In another case where the travel locus5is drawn with particles, the eraser8can be configured as follows. As another example, the eraser8alternatively includes a sucking device8hdisposed in series in the travel direction with the elements such as the eraser driver8gand configured to suck the particles applied onto the travel plane19. The sucking device8hsucks the particles to completely erase the travel locus5. The eraser8selects how to erase the travel locus5, specifically, which one to drive the sucking device8hor the eraser driver8g, in accordance with a result of determination by the travel plane determiner21.

As shown inFIG. 21C, the sucking device8hincludes a nozzle81, a dust box82, a first filter83, a dust collecting blade84, a motor85, and a second filter86. The motor85rotates the dust collecting blade84to cause the particles configuring the travel locus5to be sucked through the nozzle81into the dust box82. The first filter83catches most of the particles that are stored in the dust box82. The second filter86catches fine particles having passed through the first filter83.

FIG. 22depicts a positional relationship among the drawing unit6, the detector7, and the eraser8included in the mobile robot200. The drawing unit6, the detector7, and the eraser8are disposed in series in the travel direction. For example, the detector7, the drawing unit6, and the eraser8are disposed in the mentioned order from ahead to behind in the travel direction. Assume that the drawing unit6and the detector7are disposed apart from each other by a distance Y and the detector7and the eraser8are disposed apart from each other by a distance L.

FIG. 23is a view depicting a state where the six mobile robots, namely, the first to sixth mobile robots201to206are disposed at the locations T1to T3in the collection system S200. The two mobile robots, namely, the first mobile robot201and the second mobile robot202are disposed next to each other at the location T1as the boarding gate A and are directed identically in the anteroposterior direction. The first mobile robot201is disposed ahead in the travel direction and the second mobile robot202is disposed behind in the travel direction of the first mobile robot201. Similarly, the two mobile robots, namely, the third mobile robot203and the fourth mobile robot204are disposed next to each other at the location T2as the boarding gate B and are directed identically in the anteroposterior direction. The third mobile robot203is disposed ahead in the travel direction and the fourth mobile robot204is disposed behind in the travel direction of the third mobile robot203. Similarly, the two mobile robots, namely, the fifth mobile robot205and the sixth mobile robot206are disposed next to each other at the location T3as the boarding gate C and are directed identically in the anteroposterior direction. The fifth mobile robot205is disposed ahead in the travel direction and the sixth mobile robot206is disposed behind in the travel direction of the fifth mobile robot205.

FIG. 24is a view of the collection site T4for the six mobile robots, namely, the first to sixth mobile robots201to206in the collection system S200. The first to sixth mobile robots201to206are collected sequentially at the collection site T4to form a single line such that the first mobile robot201is disposed at the forefront in the travel direction.

FIG. 25is a view depicting a positional relationship of the first to sixth mobile robots201to206disposed at the locations T1to T3as the boarding gates. A distance from the rear end of the mobile robot201,203, or205disposed ahead at the location to the front end of the mobile robot202,204, or206disposed behind will be referred to as an inter-robot distance, and the permissible maximum value of the inter-robot distance will be referred to as a maximum permissible inter-robot distance D4. Assume that a distance X is obtained by adding the distance D3from the drawing unit6included in each of the mobile robots201to206to the rear end of the mobile robot and the maximum permissible inter-robot distance D4to each other.

Described next is a collection flow of the collection system S200for a plurality of mobile robots200executing tracking travel in a single line. A specific example thereof will be described after description of basic behavior.FIG. 26Ais a flowchart depicting the basic collection behavior.

Initially in step S50, when executing tracking travel in a single line of a plurality of mobile robots200, the drive controller10determines whether or not the mobile robot200is at the forefront of the line. This determination can be made by the collector11who manipulates the operation unit16to inform the drive controller10that this mobile robot200is at the forefront of the line. The drive controller10can alternatively determine that this mobile robot200is at the forefront of the line when the distance sensor4detects that there is no other mobile robot200ahead of this mobile robot200for a predetermined period. The drive controller10can still alternatively determine that this mobile robot200is at the forefront of the line in an exemplary case where the detector7detects no travel locus5even after this mobile robot200moves for a predetermined period or by a predetermined distance.

The flow proceeds to step S51if the drive controller10determines that this mobile robot200is at the forefront of the line. The flow proceeds to step S52if the drive controller10determines that this mobile robot200is not at the forefront of the line.

Subsequently, in step S51, the drive controller10controls to activate the drawing unit6and the detector7in the mobile robot200at the forefront of the line so that the drawing unit6starts drawing the travel locus5on the travel plane19and the detector7starts detection. That is, drawing is executed after the detector7finds that drawing is not executed. The drive controller10controls the travel driving unit15while the drawing and the detection are executed. The mobile robot200at the forefront of the line having reached a predetermined position ends the basic collection behavior shown inFIG. 26A.

In step S52, the detector7in each of the mobile robots200tracking at the second and the subsequent positions in the line detects the travel locus5drawn on the travel plane19.

Subsequently, in step S53, the drive controller10in each of the mobile robots200tracking the detected travel locus5at the second and the subsequent positions in the line controls the travel driving unit15for tracking travel.

Subsequently, in step S54, it is determined whether or not the mobile robot200is at the end of the line. In a case where the collector11collecting the mobile robots200manipulates the operation unit16to transmit, to the drive controller10, information that the mobile robot200is at the end of the line, in step S55, the eraser8in the mobile robot200at the end of the line erases the travel locus5and the drive controller10in the mobile robot200at the end of the line controls the travel driving unit15for tracking travel. The eraser8does not execute erasing without such information. The mobile robots200tracking at the second and the subsequent positions in the line then end the basic collection behavior shown inFIG. 26A.

Described next is the specific example of the collection flow of the collection system S200for the plurality of mobile robots200executing tracking travel in the single line.FIG. 265is a flowchart depicting the specific collection behavior.FIG. 26Bexemplifies a case where the six mobile robots200eventually execute tracking travel in the single line.

Initially in step S21“activate the mobile robots at the boarding gate A”, the collector11expected to collect the mobile robots200moves to the location T1as the boarding gate A, and activates the drawing unit6in the first mobile robot201and the detector7and the eraser8in the second mobile robot202disposed at the location T1as the boarding gate A to be ready for starting drawing and detection.

Subsequently, in step S22, the collector11boards the first mobile robot201and starts steering the first mobile robot201from the location T1as the boarding gate A toward the location T2as the boarding gate B. When the first mobile robot201starts travelling, under the control of the drive controller10, the drawing unit6in the first mobile robot201causes the marker6bto start drawing to leave the travel locus5on the travel plane19, and executes drawing after the detector7detects that there is no travel locus5. Such behavior corresponds to the drawing in step S51. The first mobile robot201subsequently executes only the drawing in step S51and needs to execute neither the detection in step S52nor the subsequent behavior.

In the second mobile robot202expected to track the first mobile robot201, the distance sensor4measures a distance to the first mobile robot201positioned thereahead and transmits the distance to the calculator9in the controller14. The drive controller10can thus determine that this mobile robot200is not at the forefront of the line. When the calculator9determines that the measured distance exceeds the distance X, the drive controller10receives information on the determination from the calculator9and controls the travel driving unit15such that the second mobile robot202continuously travels straight by the distance X from the current position until the detector7detects the travel locus5.

In order to achieve control of the travel driving unit15by the drive controller10for continuous straight travel by the distance X, the drive controller10has only to control the travel driving unit15such that the distance sensor4measures the distance to an identical obstacle shortened by the distance X in the travel direction. Alternatively, the travel driving unit15may include the encoder15econfigured to detect rotational speed of the motor15mand the drive controller10controls the travel driving unit15such that a distance obtained from the detected rotational speed is shortened by the distance X. The collection system S100according to the foregoing embodiment can similarly execute such control.

The detector7in the second mobile robot202subsequently detects the travel locus5of the first mobile robot201and the calculator9calculates the travel locus5for tracking the first mobile robot201in accordance with a result of the detection. The drive controller10drive controls the travel driving unit15in accordance with the calculated travel locus5, so that the second mobile robot202tracks the travel locus5. The detection and the tracking correspond to the detection in step S52and the tracking in step S53. The collector11manipulates the operation unit16to transmit, to the drive controller10, information that the second mobile robot202is at the end of the line during tracking. The eraser8in the second mobile robot202accordingly erases the detected travel locus5. Such behavior corresponds to the line end checking in step S54and the erasing in step S55. When the second mobile robot202tracks the first mobile robot201, the distance sensor4in the second mobile robot202measures a distance to the preceding first mobile robot201and the controller14controls to execute tracking travel such the distance is equal to the distance α. The distance α is similar to the distance α exemplified earlier.

In the following description, similarly to the second mobile robot202, the fourth mobile robot204tracking the third mobile robot203at the boarding gate B and the sixth mobile robot206tracking the fifth mobile robot205at the boarding gate C execute tracking travel to have the distance α from the preceding mobile robots203and205, respectively.

In step S22“steer the mobile robot to the boarding gate B” subsequent to step S21, as shown inFIG. 27, the collector11continuously steers the first mobile robot201to the common passage T10in the vicinity of the location T2as the boarding gate B. The collector11stops the first mobile robot201such that the mobile robots201and202align straight on the common passage T10in the vicinity of the location T2as the boarding gate B. The second mobile robot202travels to track the preceding first mobile robot201with the distance α therebetween on the travel locus5drawn by the first mobile robot201. The detection and the tracking correspond to the detection in step S52and the tracking in step S53. The travel locus5is completely erased by the activated eraser8in the second mobile robot202. The line end checking and the erasing correspond to the line end checking in step S54and the erasing in step S55.

The first mobile robot201executes only step S51in the basic behavior shown inFIG. 26A, whereas the second mobile robot202executes step S52and the subsequent steps other than step S51in the basic behavior shown inFIG. 26A.

In subsequent step S23“activate the mobile robots at the boarding gate B”, the collector11temporarily leaves the first mobile robot201and boards the third mobile robot203as shown inFIG. 28. The collector11manipulates the operation unit16to cause the drive controller10to stop erasing by the eraser8in the second mobile robot202. The collector11then starts steering the third mobile robot203and manipulates the operation unit16to move the third and fourth mobile robots203and204at the location T2as the boarding gate B as in step S21and step S22and dispose on the common passage T10in the vicinity of the location T2as the boarding gate B such that the third and fourth mobile robots203and204are disposed behind the second mobile robot202and are directed identically and the first to fourth mobile robots201to204form a single line.

Specifically, the collector11steers the third mobile robot203to dispose the mobile robots203and204on the common passage T10in the vicinity of the location T2as the boarding gate B so that the detector7in each of the mobile robots203and204can detect the travel locus5drawn on the travel plane19by the drawing unit6in the first mobile robot201. Then, the drive controller10activates the detector7in each of the mobile robots203and204. Thereafter, the collector11manipulates the operation unit16to cause the drive controller10in each of the disposed mobile robots to activate the drawing unit6and the detector7in the third mobile robot203and activate the detector7and the eraser8in the fourth mobile robot204. After these units are activated, the collector11boards the first mobile robot201again to restart steering the first mobile robot201on the common passage T10toward the location T3as the boarding gate C. The first mobile robot201thereafter executes only step S51in the basic behavior shown inFIG. 26A, whereas the second to fourth mobile robots202to204execute step S52and step S53other than step S51in the basic behavior shown inFIG. 26A. The fourth mobile robot204further executes step S54and step S55in the basic behavior shown inFIG. 26A.

After these units (namely, the drawing unit6, the detector7, and the eraser8) are activated, the collector11boards the first mobile robot201again to restart steering the first mobile robot201on the common passage T10toward the location T3as the boarding gate C. The third and fourth mobile robots203and204continuously travel straight by the distance X until the detectors7each detect the travel locus5, and the drive controller10in the third mobile robot203automatically stops drawing by the drawing unit6when the third mobile robot203travels by the distance Y after the detector7detects the travel locus5. In order to cause the drive controller10to automatically stop the drawing unit6after travel by the distance Y, the drive controller10has only to stop the drawing unit6after the drive controller10controls the travel driving unit15such that the distance sensor4measures the distance to an identical obstacle shortened by the distance Y in the travel direction. Alternatively, the travel driving unit15may include the encoder15econfigured to detect rotational speed of the motor15m, the drive controller10controls the travel driving unit15such that a travel distance of the mobile robot200obtained from the detected rotational speed is shortened by the distance Y, and the drive controller10then stops the drawing unit6.

In subsequent step S24“steer the mobile robot to the boarding gate C”, as shown inFIG. 29, the collector11continuously steers the first mobile robot201to the common passage T10in the vicinity of the location T3as the boarding gate C. The collector11stops the first mobile robot201such that the mobile robots201to204align straight on the common passage T10in the vicinity of the location T3as the boarding gate C. The third and fourth mobile robots203and204travel to track the preceding second mobile robot202or the third mobile robot203with the distance α therebetween along the travel locus5drawn by the first mobile robot201. The detection and the tracking correspond to the detection in step S52and the tracking in step S53.

In this manner, the third and fourth mobile robots203and204execute step S52and step S53other than step S51in the basic behavior shown inFIG. 26A.

The travel locus5is completely erased by the activated eraser8in the fourth mobile robot204. Such behavior corresponds to step S54and step S55in the basic behavior shown inFIG. 26A.

In subsequent step S25“activate the mobile robots at the boarding gate C”, the collector11temporarily leaves the first mobile robot201and boards the fifth mobile robot205as shown inFIG. 30. The collector11manipulates the operation unit16to cause the drive controller10to stop the eraser8in the fourth mobile robot204. The collector11starts steering the fifth mobile robot205and manipulates the operation unit16to move the mobile robots205and206at the location T3as the boarding gate C as in step S21and step S22and dispose on the common passage T10in the vicinity of the location T3as the boarding gate C such that the mobile robots205and206are disposed behind the fourth mobile robot204and are directed identically and the first to sixth mobile robots201to206form a single line.

Specifically, the collector11steers the fifth mobile robot205to dispose the mobile robots205and206on the common passage T10in the vicinity of the location T3as the boarding gate C so that the detector7in each of the mobile robots205and206can detect the travel locus5drawn on the travel plane19by the drawing unit6in the first mobile robot201, in other words, such that the mobile robots204to206align straight.

The collector11then activates the drawing unit6and the detector7in the fifth mobile robot205and activates the detector7and the eraser8in the sixth mobile robot206.

After these units (namely, the drawing unit6, the detector7, and the eraser8) are activated, the collector11boards the first mobile robot201again to restart steering the first mobile robot201toward the collection site T4. The mobile robots205and206continuously travel straight by the distance X until the detectors7each detect the travel locus5, and the drive controller10in the fifth mobile robot205automatically stops the drawing unit6when the fifth mobile robot205travels by the distance Y after the detector7detects the travel locus5.

The fifth and sixth mobile robots205and206subsequently execute step S52and step S53other than step S51in the basic behavior shown inFIG. 26A. The sixth mobile robot206further executes step S54and step S55in the basic behavior shown inFIG. 26A.

In subsequent step S26“steer the mobile robot to the collection site”, as shown inFIG. 31, the collector11continuously steers the first mobile robot201to the common passage T10in the vicinity of the collection site T4. As shown inFIG. 32, the collector11stops the first mobile robot201such that the first to sixth mobile robots201to206align straight to be collected at the collection site T4. The third to sixth mobile robots203to206travel to track the preceding second mobile robot202, the third mobile robot203, the fourth mobile robot204, or the fifth mobile robot205with the distance α therebetween along the travel locus5drawn by the first mobile robot201. The detection and the tracking correspond to the detection in step S52and the tracking in step S53.

In subsequent step S27“store the mobile robots”, the collector11manipulates the operation unit16to move the first to sixth mobile robots201to206from the collection site T4to a storage site T11.

As exemplarily shown inFIG. 33, the collector11initially manipulates the operation unit16to cause the drive controller10to stop drawing by the drawing unit6in the first mobile robot201, and manipulates the operation unit16to move the first mobile robot201to the storage site T11. The second to sixth mobile robots202to206travel forward until the detector7in the second mobile robot202becomes unable to detect the travel locus5drawn by the drawing unit6in the first mobile robot201.

As shown inFIG. 34, the drive controller10subsequently stops detection by the detector7in the second mobile robot202, and the collector11manipulates the operation unit16to move the second mobile robot202to the storage site T11. The third to sixth mobile robots203to206travel forward until the detector7in the third mobile robot203becomes unable to detect the travel locus5drawn by the drawing unit6in the first mobile robot201. Such movement is repeated for each of the third to fifth mobile robots203to205.

As shown inFIG. 35, when the sixth mobile robot206eventually travels forward and stops where no travel locus5is detected, the collector11causes the drive controller10to stop detection by the detector7and manipulates the operation unit16to move forward the sixth mobile robot206by the distance L.

The drive controller10then stops the eraser8, and the collector11manipulates to move the sixth mobile robot206to the collection site T4. The travel locus5is completely erased by the activated eraser8in the sixth mobile robot206.

The first mobile robot201is moved initially and the remaining mobile robots are moved sequentially in the above example. The present embodiment is not limited in the order of moving the first to fifth mobile robots201to205as long as the sixth mobile robot206including the activated eraser8moves last.

As described above, the mobile robots200can move while the eraser8is erasing the travel locus5drawn on the travel plane19. This configuration achieves tracking control of the plurality of mobile robots200along the identical travel locus5that is not left on the travel plane19.

Third Embodiment

Described next with reference toFIG. 36is a collection system S300adopting tracking control of six mobile robots300according to the third embodiment of the present disclosure. For convenience in the description, the six mobile robots300will be denoted by a first mobile robot301, a second mobile robot302, a third mobile robot303, a fourth mobile robot304, a fifth mobile robot305, and a sixth mobile robot306.

Briefly, the collection system S300is achieved by the mobile robots300each including the constituent elements according to the second embodiment and configured to automatically recognize the end of the line not by the collector11but by the mobile robots300.

FIG. 36is a schematic explanatory view from the top of the mobile robot300according to the third embodiment of the present disclosure. Similarly to the mobile robot200according to the second embodiment, the mobile robot300includes the mobile robot body1, the drawing unit6, the detector7, the travel driving unit15, the controller14including the drive controller10, the eraser8, as well as a rear tracking determiner12configured to determine whether or not there is any mobile robot200tracking from behind. The constituent elements identical with those included in the mobile robot100or200will be denoted by the identical reference signs and will not repeatedly be described in detail. Examples of the rear tracking determiner12, which will hereinafter be called the determiner12, include an image sensor and any other element configured to recognize any mobile robot300disposed behind the mobile robot300including the determiner12executing determination. The determiner12exemplarily configured by an image sensor compares image information acquired by the image sensor with information such as an outline or color of the mobile robot300, determines whether or not there is any mobile robot300, and transmits a result of the determination to the drive controller10in the controller14. In a case where the determiner12determines that there is no mobile robot300therebehind, the drive controller10in the controller14activates the eraser8. In another case where the determiner12determines that there is the mobile robot300therebehind, the controller14does not activate the eraser8.

In the collection flow according to the second embodiment, the collector11manipulates the operation unit16every time to activate and stop the eraser8in the mobile robot200at the end of the line. In contrast, the present third embodiment achieves automatically activating and stopping the eraser8in accordance with a result of determination by the controller14. A specific collection flow according to the present embodiment is similar to the collection flow according to the second embodiment. The following will thus mainly mention differences therebetween with reference to the collection flow shown inFIG. 37similar to the collection flow shown inFIG. 26B.

Initially in step S21A inFIG. 37“activate the mobile robots at the boarding gate A”, as inFIG. 26B, the collector11expected to collect the mobile robots300moves to the location T1as the boarding gate A and activates the drawing unit6in the mobile robot301and the detector7in the second mobile robot302disposed at the location T1as the boarding gate A to be ready for starting drawing and detection. The determiner12in the second mobile robot302constantly determines whether or not there is any additional mobile robot300behind the second mobile robot302in accordance with a locus drawn by the drawing unit6. If the determiner12in the second mobile robot302determines that there is no mobile robot300therebehind, the controller14activates the eraser8.

Subsequent step S22inFIG. 37is similar to step S22inFIG. 26A, and the collector11steers the mobile robot to the boarding gate B.

In subsequent step S23A inFIG. 37“activate the mobile robots at the boarding gate B”, the collector11temporarily leaves the first mobile robot301and boards the third mobile robot303. The collector11then manipulates the operation unit16to cause the drive controller10to move the third and fourth mobile robots303and304at the location T2as the boarding gate B as in step S21A and step S22and dispose on the common passage T10in the vicinity of the location T2as the boarding gate B such that the third and fourth mobile robots303and304are disposed behind the second mobile robot302and are directed identically. If the determiner12in the second mobile robot302determines that there is the additional mobile robot300behind the second mobile robot302, the drive controller10in the second mobile robot302stops the eraser8. The determiner12in the second mobile robot302constantly determines whether or not there is any additional mobile robot300behind the second mobile robot302. In a case where the third mobile robot303moves to be disposed behind the second mobile robot302, the determiner12determines that there is the additional mobile robot300behind the second mobile robot302. The determiner12transmits information on the determination to the drive controller10that stops the eraser8in the second mobile robot302.

Subsequent step S24inFIG. 37is similar to step S24inFIG. 26A, and the collector11steers the mobile robot to the boarding gate C.

In subsequent step S25A inFIG. 37“activate the mobile robots at the boarding gate C”, the collector11temporarily leaves the first mobile robot301and boards the fifth mobile robot305. The collector11manipulates the operation unit16to start steering the fifth mobile robot305and manipulates the operation unit16to move the mobile robots305and306at the location T3as the boarding gate C as in step S21A and step S22and dispose on the common passage T10in the vicinity of the location T3as the boarding gate C such that the mobile robots305and306are disposed behind the fourth mobile robot304and are directed identically and the first to sixth mobile robots301to306form a single line. The determiner12in the fourth mobile robot304determines that there is the additional mobile robot300behind the fourth mobile robot304, and the drive controller10stops the eraser8.

Subsequent step S26inFIG. 37is similar to step S26inFIG. 26A, and the collector11steers the mobile robot to the collection site.

In subsequent step S27A inFIG. 37“store the mobile robots”, when the drive controller10stops the detector7in the sixth mobile robot306at the end of the line, the collector11manipulates the operation unit16to move forward the sixth mobile robot306by the distance L and then manipulates the operation unit16to cause the drive controller10to stop the eraser8.

Assume that the determiner12is configured by an image sensor or the like to detect and determine whether or not there is any other mobile robot300therebehind and recognize whether or not the mobile robot300is at the end of the line. The collector11can specify the mobile robot306at the end of the line instead of detection with the image sensor or the like. In such a case, there can be provided an input unit configured to receive input of information by the collector11to cause the mobile robot306at the end of the line to recognize as being at the end of the line.

As described above, the controller14can activate the eraser8in a case where the determiner12thus provided determines that there is no mobile robot300therebehind. In another case where the determiner12determines that there is the mobile robot therebehind, the controller14can cause the drive controller10to stop the eraser8. This configuration achieves reduction in workload of the collector11as well as tracking control of the plurality of mobile robots300along the identical travel locus5that is not left on the travel plane19.

The present disclosure has been described by exemplifying the first to third embodiments and the modification examples. The present disclosure is obviously not limited to the first to third embodiments or the modification examples. The present disclosure is also applicable to the following modes.

Part or entirety of each of the controllers14like the drive controller10is specifically configured by a computer system including a microprocessor, a ROM, a RAM, a hard disk unit, a display unit, a keyboard, a mouse, and the like. The RAM or the hard disk unit stores a computer program. The controllers14each achieve the function when the microprocessor operates in accordance with the computer program. The computer program includes a plurality of command codes indicating commands to a computer for achievement of a predetermined function.

The constituent elements are each achieved by causing a program executor like a CPU to read and execute a software program stored in a recording medium such as a hard disk or a semiconductor memory.

Software achieving part or entirety of the elements in the controller14according to any one of the embodiments and the modification examples is a program relevant to a method of tracking a mobile robot according to the following aspects. Specifically, this program is a control program relevant to a method of tracking a mobile robot for causing a computer to execute the following control or the following determination.

This program can be downloaded from a server or the like to be executed, or can be read from a predetermined recording medium (e.g. an optical disk like a CD-ROM, a magnetic disk, or a semiconductor memory) preliminarily storing the program.

This program can be executed by a single or a plurality of computers. In other words, the program can be processed in a centralized or decentralized manner.

The embodiments of the present disclosure have been described in detail above with reference to the drawings, and various aspects of the present disclosure will be described below.

According to a first aspect of the present disclosure, there is provided a mobile robot comprising:

a mobile robot body;

a drawing unit provided at the mobile robot body and including a marker configured to draw a travel locus of the mobile robot on a travel plane;

a detector provided at the mobile robot body and configured to detect the travel locus drawn by the drawing unit;

a travel driving unit configured to drive to move the mobile robot body; and

a drive controller configured to drive control the travel driving unit such that the mobile robot body travels along the travel locus detected by the detector.

According to a second aspect of the present disclosure, there is provided the mobile robot according to the first aspect, wherein the drawing unit and the detector are disposed in series in the mobile robot body in a travel direction of the mobile robot and the drawing unit is positioned ahead of the detector.

According to a third aspect of the present disclosure, there is provided the mobile robot according to the first or second aspect, further comprising an eraser provided at the mobile robot body and configured to erase the travel locus drawn on the travel plane by the drawing unit.

According to a fourth aspect of the present disclosure, there is provided the mobile robot according to the third aspect, further comprising

a determiner provided at the mobile robot body and configured to determine whether or not the mobile robot is at an end of a line in accordance with information on whether or not there is any mobile robot behind the mobile robot body,

wherein when the determiner determines that the mobile robot is at the end of the line, the erasers erases the travel locus drawn on the travel plane by the drawing unit.

According to a fifth aspect of the present disclosure, there is provided the mobile robot according to any one of the first to fourth aspects,

assuming that the drawing unit including the marker is referred to as a first drawing unit,

the mobile robot further comprising:

a second drawing unit provided at the mobile robot body and including a particle discharge mechanism configured to scatter particles to draw the travel locus of the mobile robot on the travel plane; and

a travel plane determiner provided at the mobile robot body and configured to detect and determine a type of the travel plane,

wherein the first drawing unit or the second drawing unit is selectively driven in accordance with a result of determination by the travel plane determiner.

According to a sixth aspect of the present disclosure, there is provided a method of tracking a mobile robot when a plurality of mobile robots, each configured identically to the mobile robot according to anyone of the first to fifth aspects, executes tracking travel in a single line, the method comprising:

determining whether each of the mobile robots is at a forefront of the line;

in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and

in a second case where the mobile robot is not at the forefront of the line but is tracking, detecting the travel locus drawn on the travel plane by the detector in the tracking mobile robot; and tracking the detected travel locus by the tracking mobile robot to execute tracking travel.

According to a seventh aspect of the present disclosure, there is provided the method of tracking a mobile robot according to the sixth aspect, when a plurality of mobile robots, each configured identically to the mobile robot according to the fourth aspect, executes tracking travel in a single line, the method comprising:

determining whether each of the mobile robots is at a forefront of the line;

in a first case where the mobile robot is at the forefront of the line, moving the mobile robot at the forefront of the line while drawing the travel locus on the travel plane by the drawing unit; and

in a second case where the mobile robot is not at the forefront of the line but is tracking, tracking while detecting the travel locus by the detector in the tracking mobile robot; and determining by the determiner provided at the mobile robot body whether the mobile robot is at an end of the line, and when the determiner determines that the mobile robot is at the end of the line, executing tracking travel while erasing the travel locus by the eraser in the mobile robot at the end of the line.

Any of the various embodiments and the modification examples can be appropriately combined to achieve effects thereof. The present disclosure is applicable to appropriate combination among the embodiments, appropriate combination among the examples, appropriate combination among the embodiments and the examples, as well as appropriate combination of different features in the embodiments or the examples.

The mobile robot and the method of tracking the mobile robot according to any one of the aspects of the present disclosure are applicable to simultaneous collection of a plurality of mobile robots each loading cargo or a person in a large facility such an air terminal.