Patent Publication Number: US-2016236347-A1

Title: Movable object controller and method for controlling movable object

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-028975, filed Feb. 17, 2015. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The embodiments disclosed herein relate to a movable object controller and a method for controlling a movable object. 
     2. Discussion of the Background 
     Japanese Unexamined Patent Application Publication No. 2010-67144 discloses a movable object system that uses a movable object to perform predetermined kind of work such as conveying a workpiece using a conveyor. 
     Specifically, the movable object system causes the movable object to move, successively determines whether an obstacle is in the forward course of movement of the movable object, and controls the speed of the movable object based on the determination. 
     In the movable object system, an image sensor successively picks up images of the forward course of movement of the movable object, and a movable object controller sets a plurality of detection regions in each of the images. The plurality of detection regions respectively correspond to predetermined distances (collision imaginary distances) from the front of the movable object. When an obstacle that has a possibility of collision is in any of the detection regions, the movable object controller decelerates or stops the movable object in accordance with the collision imaginary distance corresponding to the detection region. 
     SUMMARY 
     According to one aspect of the present disclosure, a movable object controller includes a speed controller and a region changer. The speed controller is configured to control a speed of a movable object based on whether an obstacle is in a monitor region. The region changer is configured to change a size of the monitor region based on the speed of the movable object. 
     According to another aspect of the present disclosure, a method for controlling a movable object includes controlling a speed of the movable object based on whether an obstacle is in a monitor region. A size of the monitor region is changed based on the speed of the movable object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1A  is a schematic perspective view of a self-movable carriage according to an embodiment; 
         FIG. 1B  is a schematic bottom view of the self-movable carriage according to the embodiment; 
         FIG. 2A  is a first schematic plan outlining a method for detecting an obstacle according to the embodiment; 
         FIG. 2B  is a second schematic plan outlining the method for detecting an obstacle according to the embodiment; 
         FIG. 2C  illustrates a first example of a monitor region according to the embodiment; 
         FIG. 2D  illustrates a second example of the monitor region according to the embodiment; 
         FIG. 2E  illustrates a third example of the monitor region according to the embodiment; 
         FIG. 3  is a block diagram of the self-movable carriage according to the embodiment; 
         FIG. 4  illustrates an example of monitor region information; 
         FIG. 5A  is a first illustration of size change of the monitor region and speed control. 
         FIG. 5B  is a second illustration of the size change of the monitor region and the speed control; 
         FIG. 5C  is a third illustration of the size change of the monitor region and the speed control; 
         FIG. 5D  is a fourth illustration of the size change of the monitor region and the speed control; and 
         FIG. 6  is a flowchart of a procedure for processing performed by a controller according to this embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     A movable object controller and a method for controlling a movable object according to embodiments will be described in detail below by referring to the accompanying drawings. It is noted that the following embodiments are provided for exemplary purposes only and are not intended for limiting purposes. 
     In the following embodiments, a self-movable type carriage (hereinafter referred to as “self-movable carriage”) for robot use is used a non-limiting example of the movable object. Other non-limiting examples of the movable object include AGVs (Automated Guided Vehicles). 
     First, a configuration of a self-movable carriage  1  according to an embodiment will be described by referring to  FIGS. 1A and 1B .  FIG. 1A  is a schematic perspective view of the self-movable carriage  1  according to this embodiment.  FIG. 1B  is a schematic bottom view of the self-movable carriage  1  according to this embodiment. 
     For ease of description,  FIGS. 1A and 1B  each illustrate a three-dimensional orthogonal coordinate system including a Z axis with its vertically upward direction being assumed the positive direction. This orthogonal coordinate system may also be illustrated in some other drawings referred to in the following description. 
     The self-movable carriage  1  according to this embodiment is a self-movable carriage for a robot used in handling work. As illustrated in  FIG. 1A , the self-movable carriage  1  includes a movable portion  2 , a motion mechanism  3 , and a platform  4 . The movable portion  2  accommodates a controller  20  (movable object controller), described later. 
     A robot  5  is mounted on the movable portion  2 . A non-limiting example of the robot  5  is a two-arm multi-articular robot as illustrated in  FIG. 1A . On the distal end of each of the two arms, an end effector is mounted. 
     The robot  5  performs a predetermined kind of handling work and takes articles to and from the platform  4  while controlling the positions and postures of the end effectors by making multi-articular motions. 
     The motion mechanism  3  moves the robot  5  to a predetermined destination together with the articles on the platform  4 . As illustrated in  FIG. 1B , the motion mechanism  3  includes a plurality of omni-directional wheels  3   a . By controlling which combination of the omni-directional wheels  3   a  to rotate, the self-movable carriage  1  is able to make omni-directional movements, such as in frontward and rearward directions, right and left directions, and in diagonal directions, and make rotational movements about any vertical axis. Examples of the omni-directional wheels  3   a  include, but are not limited to, Mecanum wheels and Omni wheels (registered trademark). 
     Next, a method for detecting an obstacle according to an embodiment will be outlined by referring to  FIGS. 2A and 2B .  FIGS. 2A and 2B  are respectively a first schematic plan and a second schematic plan outlining the method for detecting an obstacle according to this embodiment. 
     First, description will be made with regard to a method according to a comparative example, not illustrated, for detecting an obstacle. A known method for detecting an obstacle in moving movable objects such as the self-movable carriage  1  is to set a monitor region around the movable object for a laser scanner or a similar device to monitor, and to decelerate or stop the movable object in the monitor region when the laser scanner detects an obstacle in the monitor region. 
     This method, however, has only two options, namely, causing the movable object to travel at lower speed or to stop, regardless of whether the detected obstacle is at a substantial distance from the movable object in the monitor region. This situation is attributable to use of a fixed monitor region. 
     Thus, the method according to a comparative example for detecting an obstacle involves unnecessary low-speed travel or stopping of the movable object in the monitor region. This can make it difficult to shorten the tact time. 
     In view of this situation, this embodiment dynamically changes the monitor region in accordance with the environment surrounding the movable object. For example, in the embodiment illustrated in  FIG. 2A , the left picture is a monitor region MA set around the self-movable carriage  1 . When an obstacle OB is detected in the monitor region MA, the self-movable carriage  1  is decelerated and the size of the monitor region MA is reduced as represented by the right picture of  FIG. 2A . 
     In the embodiment illustrated in  FIG. 2A , when the obstacle OB is detected, the monitor region MA is reduced to a size not containing the obstacle OB. The reduction in size eliminates the need for decelerating the self-movable carriage  1  in the monitor region MA to a speed as low as the comparative example requires. That is, this embodiment enables the self-movable carriage  1  to travel at speeds that accord with the surrounding environment. This configuration contributes to the shortening of the tact time. 
     Also in this embodiment, when no obstacle OB is detected in the monitor region MA as represented by the left picture of  FIG. 2B , the size of the monitor region MA is increased as represented by the right picture of  FIG. 2B . 
     In the embodiment illustrated in  FIG. 2B , when no obstacle OB is detected, the increased size of the monitor region MA is maintained at least until the obstacle OB is detected. Maintaining the increased size allows the self-movable carriage  1  to be accelerated to a speed corresponding to the increased monitor region MA. That is, this embodiment enables the self-movable carriage  1  to travel at speeds that accord with the surrounding environment. This configuration contributes to the shortening of the tact time. 
     While in  FIGS. 2A and 2B  the size of the monitor region MA is changed, another possible embodiment is to dynamically change the shape of the monitor region MA. While in  FIGS. 2A and 2B  the monitor region MA has a rectangular shape, this should not be construed as limiting the shape of the monitor region MA. 
     As illustrated in  FIGS. 2A and 2B , dynamically changing the monitor region MA may involve precise and quick switch between reduction and increase of the size of the monitor region MA in the vicinity of the obstacle OB. In view of this situation, this embodiment provides a region that can be referred to as “dead zone” on the circumference of the monitor region MA, in addition to dynamically changing the monitor region MA in accordance with the surrounding environment. 
     This will be described in detail below by referring to  FIGS. 2C to 2E .  FIGS. 2C to 2E  illustrate first to third examples of the monitor region MA according to this embodiment. As illustrated in  FIG. 2C , in this embodiment, a first region A 1  and a second region A 2  are arranged in proximity order from the self-movable carriage  1 . The first region A 1  is a target region where speed control is performed, and the second region A 2  turns into a dead zone. 
     As used herein, the term “target region where speed control is performed” refers to a region where at least the self-movable carriage  1  is subjected to speed control, which includes stopping, deceleration, and acceleration. As illustrated in  FIG. 2C , in the first region A 1 , a stopping region A 1   a  and a deceleration region A 1   b  are arranged in proximity order from the self-movable carriage  1 . 
     The stopping region A 1   a  is a region where the speed control is control of stopping the self-movable carriage  1  when the obstacle OB is in the stopping region A 1   a . The deceleration region A 1   b  is a region where the speed control is control of decelerating the self-movable carriage  1  when the obstacle OB is in the deceleration region A 1   b  (or accelerating the self-movable carriage  1  when no obstacle OB exists). 
     As used herein, the term “turn into a dead zone” means that a region turns into a zone where the control of the self-movable carriage  1  is to maintain the speed of the self-movable carriage  1 . That is, the second region A 2  is a region where the speed of the self-movable carriage  1  is maintained when the obstacle OB is in the second region A 2 . The second region A 2  will be hereinafter occasionally referred to as “maintaining region A 2 ”. 
     By arranging the maintaining region A 2 , which turns into a dead zone, on the circumference of the monitor region MA, this embodiment eliminates or minimizes chattering-like fluctuation of the speed of the self-movable carriage  1  at the time of precise and quick switch between reduction and increase of the size of the monitor region MA. 
     Thus, in this embodiment, the monitor region MA has such a shape that the self-movable carriage  1  is at the center of the monitor region MA and surrounded by the stopping region A 1   a , the deceleration region A 1   b , and the maintaining region A 2  in this order. That is, this embodiment sets the omni-directional monitor region MA, leaving no blind spots, for the self-movable carriage  1 , which is capable of making omni-directional movements realized by the omni-directional wheels  3   a . This configuration ensures safety in the travel of the self-movable carriage  1  in accordance with the surrounding environment. This configuration also contributes to the shortening of the tact time. 
     The monitor region MA is formed using a laser scanner RS, which is equipped in the self-movable carriage  1 . 
     The laser scanner RS is provided in plural and thus capable of detecting obstacles in omni-directions of the self-movable carriage  1 , which is capable of making omni-directional movements. In this embodiment, three laser scanners RS 1  to RS 3  are provided as illustrated in  FIG. 2C . 
     Specifically, the laser scanner RS 1  forms, for example, a region indicated by the shaded portions of the monitor region MA illustrated in  FIG. 2D . The formation depends on the position at which this laser scanner is arranged and on the shape of the self-movable carriage  1 . 
     The laser scanner RS 2  forms, for example, a region indicated by the shaded portions of the monitor region MA illustrated in  FIG. 2E . The formation depends on the position at which this laser seamier is arranged and on the shape of the self-movable carriage  1 . The region formed by the laser scanner RS 2  and the region formed by the laser scanner RS 3  are a left-right symmetry, and therefore description of the region formed by the laser scanner RS 3  will not be elaborated. 
     Then, the regions formed by the laser scanners RS 1  to RS 3  are combined into the monitor region MA, which covers omni-directions of the self-movable carriage  1 . 
     In this embodiment, the laser scanners RS 1  to RS 3  are of binary output type. This is because being of binary output type enables binary determination of ON/OFF as to whether the obstacle OB exists, eliminating the need for more complicated and higher-load processing such as image analysis. Thus, being of binary output type facilitates detection of the obstacle OB. Moreover, generally, more binary output-type sensors comply with safety standards than sensors of other types do. 
     Next, a block configuration of the self-movable carriage  1  according to this embodiment will be described by referring to  FIG. 3 .  FIG. 3  is a block diagram of the self-movable carriage  1  according to this embodiment. It is noted that  FIG. 3  only shows those components necessary for description of the self-movable carriage  1 , omitting those components of general nature. 
     The following description by referring to  FIG. 3  will mainly focus on the internal configuration of the controller  20 , and may occasionally simplify or omit the components that have been already described. 
     As illustrated in  FIG. 3 , the controller  20  includes a control section  21 , an obstacle detector  22 , an indicator detector  23 , and a storage  24 . The control section  21  includes a monitor region setter  21   a , an obstacle determiner  21   b , a monitor region changer  21   c , and a guide  21   d . The guide  21   d  includes a speed controller  21   da  and a direction distance controller  21   db.    
     The storage  24  is a storage device such as a hard disc drive and a nonvolatile memory, and stores monitor region information  24   a.    
     It is noted that not all the components of the controller  20  illustrated in  FIG. 3  may necessarily be disposed in the controller  20 . A possible example is that the obstacle detector  22  holds the monitor region information  24   a , which is otherwise stored in the storage  24 . Another possible example is that the monitor region information  24   a  is stored in an upper-level device upper than the controller  20 , and obtained by the controller  20 , when necessary, from the upper-level device wirelessly or through any other manner of communication. While in  FIG. 3  the controller  20  is disposed inside the self-movable carriage  1 , the controller  20  may be disposed outside the self-movable carriage  1 . 
     A non-limiting example of the control section  21  is a Central Processing Unit (CPU) that is in charge of overall control of the controller  20 . The obstacle detector  22  is a detector that includes the laser scanners RS 1  to RS 3  and that forms the monitor region MA based on instructions from the monitor region setter  21   a  and the monitor region changer  21   c . The obstacle detector  22  scans the inside of the monitor region MA to determine whether the obstacle OB is in the monitor region MA. Then, the obstacle detector  22  outputs the determination in binary form to the obstacle determiner  21   b.    
     The indicator detector  23  is a detector that includes a sensor mounted on the self-movable carriage  1  and separate from the laser scanners RS 1  to RS 3 . The indicator detector  23  detects an indicator arranged in the travel region of the self-movable carriage  1  along the travel path of the self-movable carriage  1 . Then, the indicator detector  23  outputs a detection result to the direction distance controller  21   db . A non-limiting example of the indicator is a plate with a light reflecting material on the surface. The indicator is attached to a wall or any other surface along the travel path of the self-movable carriage  1 . 
     Thus, a sensor separate from the laser scanners RS 1  to RS 3 , which detect obstacles, is provided to detect the indicator. This configuration facilitates the control of obstacle detection and the control of indicator detection. 
     Based on the monitor region information  24   a , the monitor region setter  21   a  gives an instruction to the obstacle detector  22 . A non-limiting example of the instruction is an instruction for initial setting of the monitor region MA at the time of initial activation of the self-movable carriage  1 . 
     A non-limiting example of the monitor region information  24   a  will be described by referring to  FIG. 4 .  FIG. 4  illustrates an example of the monitor region information  24   a . In the monitor region information  24   a , one set of the monitor region MA is defined as a combination of the stopping region A 1   a , the deceleration region A 1   b  (A 1   a  and A 1   b  constitute the first region A 1 ), and the maintaining region A 2  (second region A 2 ). In the monitor region information  24   a , a plurality of sets of the monitor region MA are registered in advance. Each of the plurality of sets of the monitor region MA is different from other sets of the plurality of sets of the monitor region MA at least in size of the monitor region MA. 
     For example, as illustrated in  FIG. 4 , information on four sets, namely, monitor regions MA 1  to MA 4  is registered in the monitor region information  24   a . The monitor regions MA 1  to MA 4  are provided in advance in the following non-limiting size relationship: the monitor region MA 1 &lt;the monitor region MA 2 &lt;the monitor region MA 3 &lt;the monitor region MA 4 . 
     In the embodiment illustrated in  FIG. 4 , the deceleration region A 1   b  of each of the monitor regions MA 2  to MA 4  has approximately the same size as the size of the monitor region MA one level smaller. 
     Also as illustrated in  FIG. 4 , the monitor regions MA 1  to MA 4  in the monitor region information  24   a  are each correlated with information on speed control of the self-movable carriage  1 . Specifically, in the embodiment illustrated in  FIG. 4 , the monitor region MA 1  is correlated with “Speed of equal to or lower than 100 mm/s”. That is, when the self-movable carriage  1  travels with the monitor region MA 1  set, the speed of the self-movable carriage  1  is controlled at a “speed of equal to or lower than 100 mm/s”. 
     The monitor region MA 2  is correlated with “Speed of equal to or lower than 200 mm/s”. The monitor region MA 3  is correlated with “Speed of equal to or lower than 300 mm/s”. The monitor region MA 4  is correlated with “Speed of equal to or lower than 400 mm/s”. 
     Referring back to  FIG. 3 , the obstacle determiner  21   b  will be described. Based on the determination output from the obstacle detector  22 , the obstacle determiner  21   b  determines whether the obstacle OB is in the stopping region A 1   a , determines whether the obstacle OB is in the deceleration region A 1   b , and determines whether the obstacle OB is in the maintaining region A 2 . Then, the obstacle determiner  21   b  notifies its determination to the monitor region changer  21   c  and the speed controller  21   da.    
     Based on the determination from the obstacle determiner  21   b  and based on the monitor region information  24   a , the monitor region changer  21   c  instructs the obstacle detector  22  to change the size of the monitor region MA. Based on the determination from the obstacle determiner  21   b  and based on the monitor region information  24   a , the speed controller  21   da  controls the speed of the self-movable carriage  1 . 
     By referring to  FIGS. 5A to 5D , description will be made in detail with regard to size change of the monitor region MA and with regard to speed control based on the determination of the obstacle determiner  21   b .  FIGS. 5A to 5D  are first to fourth illustrations of size change of the monitor region MA and speed control. The following description by referring to  FIGS. 5A to 5D  is under the assumption that size change of the monitor region MA and speed control are performed based on the monitor region information  24   a  illustrated in  FIG. 4 . 
     First, as represented by the left picture of  FIG. 5A , the monitor region MA 1  is an initially set monitor region M, and the speed of the self-movable carriage  1  is controlled at a speed of equal to or less than 100 mm/s. In this control, when the obstacle determiner  21   b  determines that no obstacle OB is in the monitor region MA 1 , the speed controller  21   da  accelerates the self-movable carriage  1  to control its speed at equal to or less than 200 mm/s as represented by the right picture of  FIG. 5A . 
     When the self-movable carriage  1  is accelerated, the monitor region changer  21   c  instructs the obstacle detector  22  to enlarge the monitor region MA from the monitor region MA 1  to the monitor region MA 2 . The acceleration of the self-movable carriage  1  and the enlargement of the monitor region MA may be repeated, enlarging the monitor region MA 2  to the monitor region MA 3  or enlarging the monitor region MA 3  to the monitor region MA 4 , until the obstacle OB enters the monitor region MA. 
     Thus, when no obstacle OB is in the monitor region MA, the self-movable carriage  1  is accelerated and thus the monitor region MA is enlarged. This configuration contributes to the shortening of the tact time while keeping the self-movable carriage  1  moving at speeds that accord with the surrounding environment. 
     Next, as represented by the left picture of  FIG. 5B , the monitor region MA has been changed to the monitor region MA 2 , and the speed of the self-movable carriage  1  is controlled at a speed of equal to or less than 200 mm/s. In this control, when the obstacle determiner  21   b  determines that the obstacle OB is in the maintaining region A 2 , the speed controller  21   da  maintains the speed of the self-movable carriage  1  as represented by the right picture of  FIG. 5B . When the speed of the self-movable carriage  1  is maintained, the monitor region changer  21   c  maintains the monitor region MA at the monitor region MA 2 . 
     Thus, the speed of the self-movable carriage  1  and the size of the monitor region MA are maintained. This configuration eliminates or minimizes chattering-like fluctuation of the speed of the self-movable carriage  1 , that is, repeated acceleration and deceleration. This, in turn, ensures stable travel of the self-movable carriage  1 . 
     Next, as represented by the left picture of  FIG. 5C , in the state of the monitor region MA 2  being set, the speed of the self-movable carriage  1  is controlled at a speed of equal to or less than 200 mm/s. In this control, when the obstacle determiner  21   b  determines that the obstacle OB is in the deceleration region A 1   b , the speed controller  21   da  decelerates the self-movable carriage  1  to control its speed at equal to or less than 100 mm/s as represented by the right picture of  FIG. 5C . 
     When the self-movable carriage  1  is decelerated, the monitor region changer  21   c  instructs the obstacle detector  22  to diminish the monitor region MA from the monitor region MA 2  to the monitor region MA 1 . 
     Thus, when the obstacle OB is in the monitor region MA, the self-movable carriage  1  is decelerated and thus the monitor region MA is diminished. This configuration eliminates or minimizes unnecessary low-speed travel of the self-movable carriage  1  at least in the monitor region MA, enabling the self-movable carriage  1  to travel at substantial speed. This configuration, as a result, contributes to the shortening of the tact time while keeping the self-movable carriage  1  moving at speeds that accord with the surrounding environment. 
     Next, as represented by the left picture of  FIG. 5D , in the state of the monitor region MA 1  being set, the speed of the self-movable carriage  1  is controlled at a speed of equal to or less than 100 mm/s. In this control, when the obstacle determiner  21   b  determines that the obstacle OB is in the stopping region A 1   a , the speed controller  21   da  immediately stops the self-movable carriage  1  as represented by the right picture of  FIG. 5D . 
     As illustrated in  FIGS. 5A to 5D , the speed of the self-movable carriage  1  and the size of the monitor region MA are dynamically changed in accordance with where the obstacle OB is. This configuration ensures safety travel of the self-movable carriage  1  at optimal speeds that accord with the surrounding environment. That is, this configuration contributes to the shortening of the tact time while keeping the self-movable carriage  1  moving at speeds that accord with the surrounding environment. 
     Referring back to  FIG. 3 , the direction distance controller  21   db  will be described. Based on the indicator detected by the indicator detector  23 , the direction distance controller  21   db  controls the direction in which the self-movable carriage  1  should be guided and the distance over which the self-movable carriage  1  should be guided. 
     The guide  21   d  outputs an output signal to the motion mechanism  3  so as to guide the self-movable carriage  1 . The output signal includes a value for the speed control performed by the speed controller  21   da  and a value for the direction and distance control performed by the direction distance controller  21   db . In response to the output signal received from the guide  21   d , the motion mechanism  3  drives the driving devices (not illustrated) of the omni-directional wheels  3   a  to cause the self-movable carriage  1  to travel along the travel path specified by the indicator. 
     Next, a procedure for processing performed by the controller  20  according to this embodiment will be described by referring to  FIG. 6 .  FIG. 6  is a flowchart of a procedure for processing performed by the controller  20  according to this embodiment. It is noted that  FIG. 6  shows a procedure for processing performed during the time between initial activation of the self-movable carriage  1  and travel of the self-movable carriage  1  while detecting the indicator and the obstacle, and that the end of the processing is omitted. 
     As illustrated in  FIG. 6 , first, the monitor region setter  21   a  performs initial setting of the monitor region MA (step S 101 ). Then, the indicator detector  23  detects an indicator, and the guide  21   d  guides the self-movable carriage  1  based on the detected indicator. Thus, the self-movable carriage  1  travels (step S 102 ). 
     Then, during the travel of the self-movable carriage  1 , the obstacle detector  22  scans the monitor region MA at predetermined time intervals, for example (step S 103 ). 
     Then, based on the detection result detected by the obstacle detector  22 , the obstacle determiner  21   b  determines whether the obstacle OB is in the stopping region A 1   a  (step S 104 ). When a determination is made that the obstacle OB is in the stopping region A 1   a  (step S 104 , Yes), the speed controller  21   da  immediately stops the self-movable carriage  1  (step S 105 ), and the processing at and later than step S 103  is repeated. 
     When a determination is made that no obstacle OB is in the stopping region A 1   a  (step S 104 , No), the obstacle determiner  21   b  determines whether the obstacle OB is in the deceleration region A 1   b  (step S 106 ). 
     When a determination is made that the obstacle OB is in the deceleration region A 1   b  (step S 106 , Yes), the speed controller  21   da  decelerates the self-movable carriage  1  (step S 107 ) and the monitor region changer  21   c  reduces the size of the monitor region MA (step S 108 ). Then, the controller  20  repeats the processing at and later than step S 102 . 
     When a determination is made that no obstacle OB is in the deceleration region A 1   b  (step S 106 , No), the obstacle determiner  21   b  determines whether the obstacle OB is in the maintaining region A 2  (step S 109 ). 
     When a determination is made that the obstacle OB is in the maintaining region A 2  (step S 109 , Yes), the speed controller  21   da  maintains the speed of the self-movable carriage  1  (step S 110 ), and the monitor region changer  21   c  maintains the size of the monitor region MA (step S 111 ). Then, the controller  20  repeats the processing at and later than step S 102 . 
     When a determination is made that no obstacle OB is in the maintaining region A 2  (step S 109 , No), the speed controller  21   da  accelerates the self-movable carriage  1  (step S 112 ), and the monitor region changer  21   c  increases the size of the monitor region MA (step S 113 ). Then, the controller  20  repeats the processing at and later than step S 102 . 
     As has been described hereinbefore, the controller (movable object controller) according to this embodiment includes a speed controller and a monitor region changer (region changer). The speed controller controls the speed of the self-movable carriage (movable object) based on whether an obstacle is in the monitor region. The monitor region changer changes the size of the monitor region based on the speed of the self-movable carriage. 
     Thus, the controller according to this embodiment shortens the tact time while enabling the self-movable carriage to travel at speeds that accord with the surrounding environment. 
     While in the above-described embodiment the monitor region has been mainly described as a two-dimensional shape by referring to plan views of the self-movable carriage, the monitor region will not be limited to two-dimensional shape. Another possible embodiment is that the monitor region has a three-dimensional shape. 
     While in the above-described embodiment the monitor region information contains a plurality of sets of the monitor region different from each other at least in size of the monitor region, the plurality of sets of the monitor region may be different from each other in shape of the monitor region. 
     The monitor region will not be limited to the above-described shape surrounding the self-movable carriage. Another possible embodiment is that the self-movable carriage is capable of travelling only in the front and rear directions, and the monitor region has such a shape that covers only the front side and the rear side of the self-movable carriage. 
     While in the above-described embodiment the laser scanners have been described as being of binary output type, the laser scanners will not be limited to binary output type. 
     While in the above-described embodiment the self-movable carriage has been described as being for robot use, this should not be construed as limiting the use of the self-movable carriage. While in the above-described embodiment the robot-use self-movable carriage has been described as including a two-arm multi-articular robot to engage in handling work, the two-arm multi-articular robot should not be construed in a limiting sense. Other possible examples include a single-arm multi-articular robot and an orthogonal robot. 
     The movable object may not necessarily make only horizontal movements on a floor and other surfaces. Another possible embodiment is that the movable object is capable of making horizontal and vertical movements on a wall and a ceiling. 
     Obviously, numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present disclosure may be practiced otherwise than as specifically described herein.