The present invention relates to an autonomous mobile device and a method of controlling an autonomous mobile device.
Autonomous mobile devices, such as robots and automated guided vehicles, need to, while moving, detect (i) an obstacle present ahead of the autonomous mobile devices or (ii) a difference in level of a floor surface so as to avoid crashing or falling. An infrared or ultrasonic proximity sensor had been widely used to detect such an obstacle or a difference in level of a floor surface.
However, although the infrared or ultrasonic proximity sensor can determine whether or not an obstacle is present ahead of the autonomous mobile devices, it is not possible to determine a specific location or a specific shape of the obstacle. Therefore, in a case where the infrared or ultrasonic proximity sensor is mounted on a robot, it is not possible to use the robot for a case where the robot needs move while avoiding an obstacle present forward in a moving direction by calculating in advance a distance to the obstacle. In view of this, a distance sensor such as a laser range finder (LRF) has been used instead of such a proximity sensor.
The autonomous mobile device 200 is configured such that, in a case where an obstacle is detected which is present in a wide area extending forward in a moving direction, a direction of a light path of a laser beam L10 is changed to a horizontal direction by changing inclination of the reflective plate 220 so that the reflective plate 220 is arranged horizontally (see (a) of
That is, according to the autonomous mobile device 200 of Patent Literature 1, it is possible to, with use of a single laser range finder 210, detect both (i) a distance to an obstacle present ahead of the autonomous mobile device 200 and (ii) a degree of a difference in level of a floor surface, by driving the reflective plate 220 so that the direction of the laser beam L10 is changed between the horizontal direction and the downward direction.
Japanese Patent Application Publication
Tokukai, No. 2011-96170 (Publication date: May 12, 2011)
The autonomous mobile device 200 of Patent Literature 1 is, however, problematic in that, since frequently switching the inclination of the reflective plate 220 imposes a heavy load on the driving section 221, the inclination of the reflective plate 220 is fixed in practical use and accordingly, only either an obstacle or a difference in level of a floor surface is detected. Moreover, since a space or a cost for mounting the driving section 221, used to drive the reflective plate 220, is required, there is a problem that it is not possible to provide a compact and inexpensive autonomous mobile device 200.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an autonomous mobile device which is compact and inexpensive and which is capable of almost simultaneously detecting (i) an obstacle present ahead of the autonomous mobile device and (ii) a difference in level of a floor surface.
An autonomous mobile device of the present invention is an autonomous mobile device which moves while detecting (i) an obstacle present ahead of the autonomous mobile device and (ii) a difference in level of a floor surface, including: a distance sensor which measures a distance to an object present in a scan area by scanning the scan area while emitting a laser beam in parallel to the floor surface; and mirrors each of which is provided in the scan area scanned by the distance sensor and each of which reflects part of the laser beam toward the floor surface.
The autonomous mobile device of the present invention is arranged such that the mirrors are provided on respective right and left sides of the distance sensor.
The autonomous mobile device of the present invention is arranged so as to include: an auxiliary mirror provided between (a) the mirrors and (b) the floor surface, the auxiliary mirror reflecting the laser beam toward forward part or backward part of the floor surface.
A method of controlling an autonomous mobile device of the present invention is a method of controlling an autonomous mobile device recited in any one of claims 1 through 3, the method including the steps of: (a) detecting a difference in level of a floor surface while a laser beam is being emitted to each of mirrors; and (b) urgently stopping the autonomous mobile device in a case where the difference in level of the floor surface is outside an allowable range.
The method of controlling an autonomous mobile device of the present invention is arranged such that the difference in level of the floor surface is not detected while the laser beam is being emitted to an edge of each of the mirrors.
According to the present invention, it is possible to provide an autonomous mobile device which is compact and inexpensive and which is capable of almost simultaneously detecting (i) an obstacle present ahead of the autonomous mobile device and (ii) a difference in level of a floor surface.
The following description will discuss an embodiment of the present invention with reference to the drawings.
A laser range finder 21 (LRF), serving as a scanning-type distance sensor, is provided at a middle of the distance detecting section 20. Mirrors 22a and 22b each of which reflects a laser beam emitted from the laser range finder 21 are provided on respective right and left sides of the distance detecting section 20. The laser range finder 21 and the mirrors 22a and 22b are fixed at respective given positions with use of attaching angles (not illustrated). A positional relationship between the laser range finder 21 and the mirrors 22a and 22b will be later described in detail.
The autonomous mobile device 1 further includes a controlling section 14 for controlling the motors 12a and 12b, the laser range finder 21, and the like. The controlling section 14 communicates with the motors 12a and 12b via a cable (not illustrated), radio transmission (not illustrated), or the like, and controls a rotation frequency of each of the motors 12a and 12b, which are provided on the respective right and left sides of the vehicle body 10, so that the autonomous mobile device 1 moves forward or backward or turns around. Furthermore, the controlling section 14 communicates with the laser range finder 21 via a cable (not illustrated), radio transmission (not illustrated), or the like, and reads a value outputted by the laser range finder 21 so as to (i) calculate a distance to an obstacle present ahead the autonomous mobile device 1 or (ii) calculate a height from a floor surface to the mirrors 22a and 22b and determine whether or not there is a difference in level of the floor surface.
According to the autonomous mobile device 1 of the present invention, a scan area scanned by the laser range finder 21, which is of a scanning type, is divided into three areas θ1, θ2, and θ3, and laser beams L1 through L3 emitted to the respective areas θ1, θ2, and θ3 are individually used to detect (i) an obstacle present ahead of the autonomous mobile device 1 or (ii) a difference in level of a floor surface (see
In the above configuration, each of the mirrors 22a and 22b has a reflective surface inclined downward at an angle of 45 degrees. The laser beam L1 emitted from the laser range finder 21 to the area θ1 is reflected by the reflective surface of the mirror 22a, and then emitted to the floor surface 100 ahead of the auxiliary wheel 13a. Similarly, the laser beam L3 emitted from the laser range finder 21 to the area θ3 is reflected by the reflective surface of the mirror 22b, and then emitted to the floor surface 100 ahead of the auxiliary wheel 13b. On the other hand, the laser beam L2 emitted from the laser range finder 21 to the area θ2 is emitted, in parallel with the floor surface 100, ahead of the autonomous mobile device 1 without being reflected by any of the mirrors 22a and 22b.
Meanwhile, the laser beam L2 emitted from the laser range finder 21 to the area θ2 is emitted forward in parallel with the floor surface without being reflected by any of the mirrors. It is therefore possible to detect an obstacle present ahead of the autonomous mobile device 1 and to urgently stop the autonomous mobile device 1 before the autonomous mobile device 1 crashes into the obstacle.
The controlling section 14 controls the motors 12a and 12b to drive the driving wheels 11a and 11b so that the autonomous mobile device 1 starts moving in a given direction (step S1). While the autonomous mobile device 1 is moving, the controlling section 14 determines whether or not the controlling section 14 has received a stop command (step S2). Note that the stop command is a command for intentionally causing movement of the autonomous mobile device 1 to be stopped. For example, the stop command may be incorporated in the autonomous mobile device 1 as a movement controlling program or alternatively inputted to the autonomous mobile device 1 by an external operating means. Upon receipt of the stop command, the controlling section 14 controls the motors 12a and 12b so that the autonomous mobile device 1 stops moving (step S3).
In the absence of the stop command, the controlling section 14 controls the autonomous mobile device 1 to continue moving in an autonomous movement mode. While the autonomous mobile device 1 is moving, the distance detecting section 20 detects an obstacle. In a case where the controlling section 14 determines that the obstacle is dangerous, the controlling section 14 controls the autonomous mobile device 1 to take an avoidance action.
In the autonomous movement mode, the controlling section 14 operates the laser range finder 21 so as to start a scan by emitting a laser beam (step S4). The controlling section 14 then determines which of the areas θ1 through θ3 the laser range finder 21 is scanning with use of the laser beam (steps S5 and S6). Note here that, as described with reference to
In a case where the controlling section 14 determines in the step S5 that the laser range finder 21 is scanning the area θ1 or θ3 with use of the laser beam, the controlling section 14 controls the laser range finder 21 to detect a difference in level of the floor surface 100 with use of the laser beams L1 and L3 reflected by the mirrors 22a and 22b, respectively, toward the floor surface 100 (step S7). The controlling section 14 then determines whether or not a degree of the difference in level of the floor surface 100 falls within an allowable range in which the movement of the autonomous mobile device 1 is not interrupted. In a case where the degree of the difference in level of the floor surface 100 thus detected falls within the allowable range, the controlling section 14 returns the process to the step S1, and controls the autonomous mobile device 1 to continue moving. In a case where the degree of the difference in level of the floor surface 100 is outside the allowable range, the controlling section 14 determines that the difference is dangerous, and controls the autonomous mobile device 1 to be urgently stopped (step S8).
On the other hand, in a case where the controlling section 14 determines in the step S6 that the laser range finder 21 is scanning the area θ2 with use of the laser beam, the controlling section 14 controls the laser range finder 21 to detect an obstacle present ahead of the autonomous mobile device 1 with use of the laser beam L2 emitted ahead of the autonomous mobile device 1 (step S9). The controlling section 14 then determines whether or not a distance to the obstacle falls within an allowable range. In a case where the distance thus detected to the obstacle falls within the allowable range in which the movement of the autonomous mobile device 1 is not interrupted, the controlling section 14 returns the process to the step S1, and controls the autonomous mobile device 1 to continue moving. In a case where the distance to the obstacle is outside the allowable range, the controlling section 14 determines that the distance is dangerous, and controls the autonomous mobile device 1 to be urgently stopped (step S10).
According to the method of controlling the autonomous mobile device 1 of the present invention, the laser range finder 21 carries out a scan with use of a laser beam. The laser range finder 21 detects (i) an obstacle present ahead of the autonomous mobile device 1 while emitting the laser beam forward and (ii) a difference in level of the floor surface 100 while emitting the laser beam to any one of the mirrors. It is therefore possible to provide an autonomous mobile device which is compact and inexpensive and which is capable of almost simultaneously detecting (i) an obstacle present ahead of the autonomous mobile device and (ii) a difference in level in a floor surface.
According to the configuration of the autonomous mobile device 2A illustrated in
According to the configuration of the autonomous mobile device 2B illustrated in
Note that the positions to which the respective laser beams are emitted can be adjusted by, instead of adjusting the inclination angles of the mirrors 22a and 22b, adjusting a distance dl from a laser range finder 21 to the mirrors 22a and 22b or alternatively adjusting both of the inclination angles of the mirrors 22a and 22b and the distance d1.
For example, in
As illustrated in
Therefore, according to the autonomous mobile device 3 of Embodiment 3, it is possible to detect a difference in level of the floor surface 100 while the autonomous mobile device 3 is moving both forward and backward, by (i) causing the laser beams L1 and L3 to be emitted toward the floor surface ahead of the auxiliary wheels 13a and 13b while the autonomous mobile device 3 is moving forward (arrow F) and (ii) causing the laser beams L1 and L3 to be emitted toward the floor surface behind the driving wheels 11a and 11b while the autonomous mobile device 3 is moving backward.
Note that the autonomous mobile device 3 can be arranged such that, by rotating the laser range finder 21 by 180 degree so as to carry out a scan by emitting a laser beam L2 backward, an obstacle present on a back side of the autonomous mobile device 3 is detected while the autonomous mobile device 3 is moving backward.
The present invention is not limited to the embodiments, but can be altered by a skilled person in the art within the scope of the claims. An embodiment derived from a proper combination of technical means each disclosed in a different embodiment is also encompassed in the technical scope of the present invention. Further, it is possible to form a new technical feature by combining the technical means disclosed in the respective embodiments.
The present invention is applicable to a business-use cleaning machine, an industrial transfer robot, and the like.
L1, L2, L3, L10 Laser beam
1, 2A, 2B, 3 Autonomous mobile device
10 Vehicle body
11a, 11b Driving wheel
13
a,
13
b Auxiliary wheel
14 Controlling section
20 Distance detecting section
21 Laser range finder
28 Auxiliary mirror
100 Floor surface
Number | Date | Country | Kind |
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2013-162118 | Aug 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2014/065543 | 6/12/2014 | WO | 00 |