Patent Publication Number: US-2013245823-A1

Title: Robot system, robot hand, and robot system operating method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Patent Application No. 2012-61506, which was filed on Mar. 19, 2012, Japanese Patent Application No. 2012-61507, which was filed on Mar. 19, 2012, and Japanese Patent Application No. 2012-61608, which was filed on Mar. 19, 2012, the disclosures of which are incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present disclosure relates to a robot system, a robot hand, and a robot system operating method. 
     DESCRIPTION OF THE RELATED ART 
     In the Japanese patent laid-open H09-277187, an arrangement for mounting a robot hand to an end portion of a robot arm provided to a robot is disclosed. 
     In the Japanese Patent laid-open H11-165291, a safety monitoring devices which monitor the safety of a single work area is also disclosed. 
     Further, in the Japanese Patent laid-open S63-216689; Japanese Patent laid-open 2009-148869; and Japanese Patent laid-open 2006-035346, robot systems configured to control a robot and an external mechanism provided to the robot exterior, are proposed. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the disclosure, there is provided a robot system, comprising a robot arm, a robot hand provided to the robot arm, and a plurality of finger members for holding a target object, installed to the robot hand. The robot hand comprises a hand main body portion which is connected to the robot arm and comprises an actuator, and a finger holding mechanism which replaceably holds at least a pair of the finger members is connected to the hand main body portion and is driven by the actuator. 
     According to another aspect of the disclosure, there is provided a robot system comprising a robot configured to perform work in one of a plurality of work areas, comprising a plurality of sensors configured to detect the presence of a person, respectively provided to the plurality of the work areas, and a control portion which stops the robot which exists in one work area when the sensor provided to the one work area detects the presence of a person, regardless of whether or not the sensor provided to another work area other than the one work area where the robot exists has detected the presence of a person. 
     According to another aspect of the disclosure, there is provided a robot system comprising a first robot comprising a first drive portion configured to achieve various postures for performing predetermined work, a second robot comprising a second drive portion configured to achieve various postures for performing predetermined work, a guide portion configured to, in coordination with the first drive portion and the second drive portion, moveably support the first robot and the second robot, and a control portion configured to control in coordination the first drive portion and the second drive portion so that an operation of the predetermined work of the first robot and the second robot is linked with a location movement of the first robot and the second robot along the guide portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system configuration diagram schematically showing the overall configuration of a robot system of first embodiment. 
         FIG. 2  is an explanatory view schematically showing the configuration of the robot. 
         FIG. 3  is an explanatory view for explaining the configuration of the hand. 
         FIGS. 4A and 4B  are explanatory views for explaining the configuration of the finger holding portion. 
         FIGS. 5A and 5B  are explanatory views for explaining the configuration of the finger holding portion. 
         FIGS. 6A and 6B  are perspective views showing the outer appearance of the finger storage box and pressing device. 
         FIG. 7  is an explanatory view for explaining the operation of installing the finger member to the finger holding mechanism. 
         FIG. 8  is an explanatory view for explaining the operation of removing the finger member from the finger holding mechanism. 
         FIG. 9  is an explanatory view for explaining the work procedure of the robot system. 
         FIG. 10  is an explanatory view for explaining the work procedure of the robot system. 
         FIG. 11  is an explanatory view for explaining the work procedure of the robot system. 
         FIG. 12  is an explanatory view for explaining the work procedure of the robot system. 
         FIG. 13  is an explanatory view for explaining the work procedure of the robot system. 
         FIG. 14  is an explanatory view showing the nut runner, end tool, and connecting member of a modification wherein an end tool of a nut runner is automatically replaceable. 
         FIG. 15  is an explanatory view schematically showing the configuration of the nut runner and end tool. 
         FIG. 16  is a diagram showing an overview of the robot system according to second embodiment. 
         FIG. 17  is a plan view showing the process layout of second embodiment. 
         FIG. 18  is a flowchart showing an outline of the safety monitoring operation of the robot system during work. 
         FIG. 19  is a flowchart showing an outline of the safety monitoring operation of the robot system during movement. 
         FIG. 20  is a diagram showing an overview of a robot system according to a modification in which a single robot is shared between two work areas. 
         FIG. 21  is a plan view showing a process layout of a modification in which a single robot is shared between two work areas. 
         FIG. 22  is a diagram showing an overview of a robot system according to a modification in which two robots are shared between three work areas. 
         FIG. 23  is a plan view showing a process layout of a modification in which two robots are shared between three work areas. 
         FIG. 24A  to  FIG. 24E  are schematic views showing the work steps that use a robot system according to a modification in which two robots are shared between three work areas. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments will now be described with reference to accompanying drawings. First embodiment will be described with reference to  FIG. 1  to  FIG. 15 . 
     As shown in  FIG. 1 , a robot system  1  of this embodiment is provided to a work area  100 . The work area  100  is an area for performing the work of assembling mechanical products, which includes a plurality of processes. The circumference of the work area  100  is enclosed by a fence  2 , restricting human entry. A door R 1  for the entry and exit of maintenance workers is provided in two locations in this work area  100 . Further, the work area  100  is divided into three areas: areas  100 A,  100 B, and  100 C. Work tables  101 A,  101 B, and  101 C are respectively provided to each of the areas  100 A to  100 C. Further, a door R 2  for transporting items in and out is provided to the area  100 A. Further, in the work area  100 , a plurality (plurality of types) of works W (target objects) such as parts or tools required by the work is respectively placed on the work tables  101 A to  101 C and in suitable locations. 
     The robot system  1  comprises two traveling carts  4 A and  4 B, two robots  10 A and  10 B, an overhead crane (in this example, a hoist)  20 , and a controller  30 . The traveling carts  4 A and  4 B travel across a traveling axis  3  provided across the three areas  100 A to  100 C. 
     According to this robot system  1 , in each of the areas  100 A to  100 C, a plurality of the works W is assembled. With this arrangement, an assembly process of units Ua, Ub, and Uc, which are semi-finished parts, is performed. That is, the units Ua, Ub, and Uc each constitute an aggregate of the plurality of works W. Subsequently, the units Ua, Ub, and Uc are further assembled to manufacture a unit Uabc (refer to  FIG. 11 , etc., described later) as a final assembly. According to this embodiment, this unit Uabc is the final work piece (details described later). 
     Each of the robots  10 A and  10 B is respectively provided onto the traveling carts  4 A and  4 B. 
     Further, a plurality of (pairs of) finger members  40  for grasping the work W is provided to the robot system  1 . The finger member  40  is installed to a hand  13  (refer to  FIG. 2  described later) of each of the robots  10 A and  10 B. For example, there are about  1  to  10  types of the works W that can be held by one type of the finger member  40  (the work W held by each of the finger members  40  has been determined). As a result, the finger member  40  needs to be selectively used to hold all of the works W. Of the plurality of pairs of finger members  40 , four specific pairs of the finger members  40  (finger members  40  having a high usage frequency, for example) are stored in finger storage boxes  50 A and  50 B. The finger storage boxes  50 A and  50 B are respectively provided on the traveling carts  4 A and  4 B in correspondence with each of the robots  10 A and  10 B. That is, each of the robots  10 A and  10 B and each of the finger storage boxes  50 A and  50 B are movable along the traveling axis  3 . With this arrangement, the robots  10 A and  10 B are capable of performing coordinated operations, such as holding and transporting in coordination the works W of a large weight and capacity, for example, when moved near each other. Note that, while not particularly shown, the finger members  40  that are only used in a specific area (the finger members  40  having a low usage frequency, etc.) are stored in a finger storage box  50  disposed in a location where the finger members  40  are used. 
     Further, work areas  102 A,  102 B, and  102 C are respectively provided to each of the areas  100 A to  100 B. A work table (not shown) and the like, for example, are provided to each of the work areas  102 A,  102 B, and  102 C. Further, a transporting cart  103  is arranged on a side opposite to the work area  102 A, with the traveling axis  3  therebetween. The transporting cart  103  is capable of carrying and moving the unit Uabc to the next process (not shown) via the door R 2 . 
     The hoist  20  is an overhead crane provided above the work area  100 . From the traveling rail (not shown) of the hoist  20  hangs a suspension hook  20 A. Then, the hoist  20  is capable of winding and unwinding the suspension hook  20 A via the control of the controller  30 . This hoist  20  suspends and supports the unit Uabc, etc., which is one example of a work of a large weight and capacity. For example, the robots  10 A and  10 B which operate in coordination and this hoist  20  hold and transport the unit Uabc. Specifically, the hoist  20  supports the vertical force (weight) applied by the unit Uabc. At this time, the robots  10 A and  10 B hold the unit Uabc so that it does not rotate. In this state, the unit Uabc is held and transported by being moved horizontally and fixed into a certain position/posture. 
     The controller  30  is made of a computer comprising a storage device, electronic computing device, and input device (each not shown). This controller  30  is communicably connected with the robots  10 A and  10 B, the hoist  20 , and the traveling carts  4 A and  4 B, controlling the operation thereof. Further, the aspects of the operation of the robots  10 A and  10 B, the hoist  20 , and the traveling carts  4 A and  4 B in the work are taught to the controller  30  via a suitable input device (a programming pendant, for example) in advance. 
     Note that, according to this example, the controller  30  controls the operation of the robots  10 A and  10 B, the hoist  20 , and the traveling carts  4 A and  4 B. Nevertheless, the present disclosure is not limited thereto. That is, for example, the computer that controls the operation of the robot  10 , the computer that controls the operation of the hoist  20 , and the computer that controls the operation of the traveling carts  4  may be configured separately. 
     As shown in  FIG. 2 , the robot  10  comprises a base  11  fixed on the traveling cart  4 , an arm  12  (robot arm) provided to this base  11 , and the hand  13  (robot hand) provided to the end of this arm  12 . 
     The arm  12  comprises a first structural member  121 , a second structural member  122 , a third structural member  123 , a fourth structural member  124 , a fifth structural member  125 , a sixth structural member  126 , and a flange portion  127 . Further, actuators Ac 1 , Ac 2 , Ac 3 , Ac 4 , Ac 5 , Ac 6 , and Ac 7  are respectively built into seven joint portions provided to the arm  12  (the first to sixth structural members  121  to  126  and the flange portion  127 ). The rotational position of each movable portion is inputted to the controller  30  as a signal from an encoder built into the actuator Ac. 
     The hand  13  comprises a hand main body  131  installed to the flange portion  127  provided to the end of the arm  12 , and a finger holding mechanism  132  installed to this hand main body  131 . An actuator (not shown) comprising a servo motor is built into the hand main body  131 . The rotational position of the movable portion is inputted to the controller  30  as a signal from an encoder built into the actuator. The finger holding mechanism  132  replaceably holds a pair of the finger members  40  of the plurality of pairs of the finger members  40  (details described later). 
     As shown in  FIG. 3 , a pair of pistons  133  and  133  is provided to the hand main body  131  in an opposing manner. The pair of pistons  133  and  133  is driven in directions mutually away from and toward each other (see the arrows in  FIG. 3 ) by the actuator built into the hand main body  131 . The finger holding mechanism  132  comprises a pair of finger holding portions  134  and  134  that are connected to this pair of pistons  133  and  133 . The pair of the finger holding portions  134  and  134  is configured bilaterally symmetrical. The pair of the finger holding portions  134  and  134  is capable of moving in directions mutually away from and toward each other, interlocked with the drive of the pair of pistons  133  and  133 , and replaceably holds the pair of the finger members  40  and  40 . 
     The following describes the detailed structure of the finger holding portion  134  using  FIG. 3 ,  FIGS. 4A and 4B , and  FIGS. 5A and 5B . Note that  FIGS. 4A and 4B  show states in which the finger holding portion  134  is not holding the finger member  40 . Of these,  FIG. 4A  corresponds to the state in which a link member  138  (described later) is in an engaged posture (described later).  FIG. 4B  corresponds to the state in which the link member  138  (described later) is in a released posture (described later). Note that  FIGS. 5A and 5B  show states in which the finger holding portion  134  is holding the finger member  40 . Of these,  FIG. 5A  corresponds to the state in which the link member  138  (described later) is in an engaged posture (described later).  FIG. 5B  corresponds to the state in which the link member  138  (described later) is in a released posture (described later). 
     As shown in  FIGS. 3 ,  4 A,  4 B,  5 A, and  5 B, each of the finger holding portions  134  is a link mechanism comprising a finger holding portion main body  150 , a receiving space  135 , four link members  136 ,  137 ,  138 , and  139 , two axises SH 1  and SH 2 , two connecting members  140  and  141 , and a compression spring  142  (elastic member). 
     The receiving space  135  is a space configured to receive (insert) the finger member  40 , and is provided to a side opposite to the other finger holding member  134  (the inner side). 
     The link member  136  (second link member) is provided rotatably around the axis SH 1  (second rotation axis). An end side of this link member  136  is a surface that is partially externally exposed. This surface  136   a  links to the operating surface. Hereinafter, this surface  136   a  is suitably called the operating surface  136   a.  The other end side of the link member  136  is connected with an end side of the link member  137  via the connecting member  140 . Further, the link member  136  is energized by the compression spring  142  housed in a concave portion  150   a  provided to the finger holding portion main body  150  to form the posture shown in  FIG. 4A  and  FIG. 5A  when the operating surface  136   a  is not pressed. That is, the compression spring  142  is energized so that the link member  136  forms the posture shown in  FIG. 4A  and  FIG. 5A  when the operating surface  136   a  is not pressed. Then, when the operating surface  136   a  is pressed when the posture is as shown in  FIG. 4A  and  FIG. 5A , the link member  136  rotates in one direction (a first direction; the direction of arrow A 1  shown in  FIG. 4A  and  FIG. 5A ) around the axis SH 1 , forming the posture shown in  FIG. 4B  and  FIG. 5B . Then, when the pressed state is released, the link member  136  rotates in the other direction (the direction of arrow A 2  shown in  FIG. 4B  and  FIG. 5B ) around the axis SH 1 , returning the posture to that shown in  FIG. 4A  and  FIG. 5A . 
     The other end side of the link member  137  connects with the link member  138  (first link member) via the connecting member  141 . That is, this link member  137  connects the link member  136  and the link member  138 . 
     The link member  138  comprises two protruding portions  138   a  and  138   b.  Further, the link member  138  is provided rotatably around the axis SH 2  (first rotation axis). Then, the link member  138  is configured so that it is capable of transitioning between the engaged posture (the posture shown in  FIG. 4A  and  FIG. 5A ) and the released posture (the posture shown in  FIG. 4B  and  FIG. 5B ) by rotating around the axis SH 2 . In the engaged posture, the link member  138  engages the finger member  40  inserted in the receiving space  135 . In the released posture, the link member  138  releases the engagement of the finger member  40 . That is, when the link member  138  is in an engaged posture, the protruding portion  138   a  protrudes inside the receiving space  135 . With this arrangement, the protruding portion  138   a  is capable of contacting a surface  40 Wb of the finger member  40  inserted into the receiving space  135 , on a side opposite to a surface  40 Wa that contacts the work W. Then, when the finger member  40  is inserted deep into the receiving space  135 , the protruding portion  138   a  engages with a concave portion  40   a  provided to the surface  40 Wb of the finger member  40 . With this arrangement, the finger member  40  is engaged at that position (the position shown in  FIG. 3  and  FIG. 5A ). Further, the link member  138  is partially externally exposed (the section indicated by reference numeral  138   c  in the figure). Note that the section indicated by this reference numeral  138   c  is hereinafter suitably called operating portion  138   c.    
     A concave portion  139   a  is provided to the link member  139 . The protruding portion  138   b  of the link member  138  is fit into this concave portion  139   a,  thereby connecting the link members  138  and  139 . Further, an end portion  139   b  of the link member  139  is externally exposed. Note that this end portion  139   b  is hereinafter suitably called the operating portion  139   b.    
     With the link members  136  to  139  thus connected, the link members  136  to  139  are interlocked. According to this embodiment, the link members  136  to  139  can be interlocked by pressing the operating surface  136   a  of the link member  136 , the operating portion  138   c  of the link member  138 , or the operating portion  139   b  of the link member  139 . 
     That is, the link member  136  is energized by the compression spring  142  as described above when the operating surface  136   a,  the operating portion  138   c,  and the operating portion  139   b  are not pressed. With this arrangement, the link members  136  to  139  form the postures shown in  FIG. 4A  and  FIG. 5A . That is, the link member  138  forms the engaged posture. 
     At such a time, when the operating surface  136   a,  the operating portion  138   c,  or the operating portion  139   b  is pressed, the link member  136  rotates in the direction of the arrow A 1 . Further, the link member  138  rotates in one direction (a second direction; the direction of arrow B 1  shown in  FIG. 4A  and  FIG. 5A ) around the axis SH 2 . Furthermore, the link member  139  is driven in one direction (the direction of arrow C 1  shown in  FIG. 4A  and  FIG. 5A ). Thus, the link members  136  to  139  are interlocked, causing the link members  136  to  139  to form the posture shown in  FIG. 4B  and  FIG. 5B . That is, the link member  138  is in the released posture. 
     Then, when the pressed state is released, the link member  136  rotates in the direction of the arrow A 2 . Further, the link member  138  rotates in the other direction (the direction of arrow B 2  shown in  FIG. 4B  and  FIG. 5B ) around the axis SH 2 . Furthermore, the link member  139  is driven in the other direction (the direction of arrow C 2  shown in  FIG. 4B  and  FIG. 5B ). Thus, the link members  136  to  139  are interlocked, causing the link members  136  to  139  to return to the posture shown in  FIG. 4A  and  FIG. 5A . That is, the link member  138  returns to the engaged posture. 
     As shown in  FIGS. 6A and 6B , the finger storage box  50  stores four specific pairs of the finger members  40 . A pressing device  60  is installed to this finger storage box  50 . The pressing device  60  comprises a pair of pressing members  61  comprising four protruding portions  61   a.  Each of the pressing members  61  is provided to an outer wall portion of the finger storage box  50  in correspondence with the four specific pairs of the finger members  40  stored in the finger storage box  50 . The pressing device  60  is communicably connected with the controller  30 . The operation of the pressing device  60  (vertical drive of the pair of the pressing members  61  described later, etc.) is controlled by the controller  30 . Note that the computer that controls the operation of the pressing device  60  may be provided separately from the controller  30 . 
     The pair of pressing members  61  and  61  is configured to be vertically driveable. When the pair is driven upward, the end portions of the pair of the protruding portions  61   a  provided to the pair of the pressing members  61  come in contact with and press against the operating surface  136   a  of the link member  136  of the pair of the finger holding portions  134  of the robot  10 . With this arrangement, the holding of the pair of the finger members  40  by the pair of the finger holding portions  134  is released. The pair of the finger members  40  released from the hold by the pair of the finger holding portions  134  drop due to gravitational force, and are stored in the finger storage box  50 . 
     That is, the pair of the finger members  40  corresponding to the shape, size, etc. of the work W serving as the holding target in the next work process is installed to the finger holding mechanism  132 . In this case, the robot  10  operates so that the receiving spaces  135  respectively provided to the pair of the finger holding portions  133  and  133  of the finger holding mechanism  132  are positioned above the pair of the finger members  40  and  40  stored in the finger storage box  50 . Subsequently, as shown in  FIG. 7 , the robot  10  lowers the hand  13  and inserts the finger member  40  into the receiving space  135 . At this time, when the finger member  40  is inserted a certain extent into the receiving space  135 , the protruding portion  138   a  of the link member  138  contacts an end portion (upper end portion in  FIG. 7 ) of the finger member  40 , and the end portion presses against the protruding portion  138   a.  With this arrangement, the link members  136  to  139  are interlocked, causing the link member  138  that forms an engaged posture to rotate in the direction of the arrow A 1  and in the direction of the arrow B 1 . Further, the link member  139  is driven in the direction of the arrow C 1 . Subsequently, when the finger member  40  is inserted deep into the receiving space  135 , the protruding portion  138   a  is inserted into the concave portion  40   a  of the finger member  40 . Then, the link member  138  rotates in the direction of the arrow A 2  and in the direction of the arrow B 2 . Further, the link member  139  is driven in the direction of the arrow C 2 . With the link members  136  to  139  thus interlocked, the protruding portion  138   a  engages with the concave portion  40   a,  and the finger member  40  is installed to the finger holding mechanism  132 . 
     On the other hand, when the finger member  40  is removed from the finger holding mechanism  132 , the robot  10  operates so that the operating surface  136   a  of the link member  136  is positioned above the pair of the protruding portions  61   a  of the pressing device  60 . The protruding portion  61   a  at this time is provided to a location corresponding to the location in which the pair of installed finger members  40  is stored. Then, as shown in  FIG. 8 , the pair of the pressing members  61  of the pressing device  60  is driven upward by the control of the controller  30 , causing the protruding portions  61   a  of the pressing members  61  to press against the operating surface  136   a.  With this arrangement, the link member  138 , which is in the engaged posture, rotates in the direction of the arrow A 1  and in the direction of the arrow B 1 . Further, the link member  139  is driven in the direction of the arrow C 1 . With the link members  136  to  139  thus interlocked, the engagement of the concave portion  40   a  of the finger member  40  by the protruding portion  138   a  of the link member  138  changes to a released state. As a result, the finger member  40  is removed from the finger holding mechanism  132 . The removed finger member  40  drops by gravitational force and is stored in its original position in the finger storage box  50 . 
     Accordingly, for example, when the process transitions to a process in which the work W is to be grasped, the robot  10  installs the finger members  40  corresponding to the shape, size, etc. of the work W to the finger holding mechanism  132  as described above, and grasps the work W. Then, when the process transitions to a process in which the work W that cannot be grasped by the finger members  40  installed in the current stage to the finger holding mechanism  132  is to be grasped, the robot  10  removes the finger members  40  as described above, installs other finger members  40  corresponding to the shape, size, etc. of the work W, and grasps the work W. 
     The following describes the work procedure of the robot system  1 , using  FIGS. 1 ,  9 ,  10 ,  11 ,  12 , and  13 . 
     First, as shown in  FIG. 1 , in each of the areas  100 A to  100 C, the robots  10 A and  10 B (or either one) grasp the work W on the work tables  101 A to  101 C as described above, and assemble the units Ua, Ub, and Uc. The work at this time is performed following a work procedure stored in advance in the controller  30 . Note that the assembly work of the units Ua, Ub, and Uc may be executed well consecutively or in parallel by the robots  10 A and  10 B. 
     Once the assembly work of the units Ua, Ub, and Uc is completed, the robots  10 A and  10 B respectively install the finger members  40  for holding the unit Uc to the finger holding mechanism  132  of the hand  13 . Then, the robots  10 A and  10 B, as shown in  FIG. 9 , hold and lift the unit Uc in coordination, moving the unit Uc directly above the traveling axis  3 . Subsequently, the traveling carts  4 A and  4 B operate, moving the unit Uc from the area  100 C to the area  100 B. Then, the assembly work of the unit Uc and the unit Ub is executed in the work area  102 B of the area  100 B, manufacturing a unit Ubc (refer to  FIG. 10  described later), which is a semi-finished part in which the units Uc and Ub are assembled. The unit Ubc, as shown in  FIG. 10 , is held in coordination by the robots  10 A and  10 B and provided to a predetermined location on the unit Ua in the work area  102 A of the area  100 A. Then, the work of assembling the unit Ubc to the unit Ua is executed, manufacturing the unit Uabc (refer to  FIG. 11  described later), which is the final work piece. 
     When the assembly work of the unit Uabc is completed, as shown in  FIG. 11 , the hoist  20  operates and the suspension hook  20 A of the hoist  20  is connected to the unit Uabc by the robots  10 A and  10 B. Then, the robots  10 A and  10 B respectively hold determined positions of the unit Uabc. Subsequently, the suspension hook  20 A is wound, lifting the unit Uabc. 
     Then, as shown in  FIG. 12 , with the operation of the traveling carts  4 A and  4 B, the lifted unit Uabc is moved to the transporting cart  103  side while changing the distance between the robots  10 A and  10 B. At this time, until the unit Uabc reaches the traveling axis  3 , the traveling carts  4 A and  4 B operate, gradually increasing the distance between the robots  10 A and  10 B. Then, after the unit Uabc passes the traveling axis  3 , as shown in  FIG. 13 , the traveling carts  4 A and  4 B operate, gradually decreasing the distance between the robots  10 A and  10 B. 
     With the robots  10 A and  10 B thus operating in coordination, the transporting and assembly work, etc., of the small-sized work W can be executed independently by each of the robots  10 A and  10 B. Further, when the units Uc and Ubc, which are aggregates of a plurality of the works W, are transported, transportation can be achieved using common robots, even if the weight is heavier, since each of the robots  10 A and  10 B work in coordination. Further, for the unit Uabc, which is even heavier in weight, each of the robots  10 A and  10 B and the traveling carts  4 A and  4 B work in coordination as the load in the direction of gravitational force is supported by the hoist  20 . With this arrangement, the unit Uabc can be horizontally moved while avoiding interference and the like of the arms  12  and  12  of the robots  10 A and  10 B. 
     As described above, in the robot system  1  of this embodiment, the finger holding mechanism  132  of the hand  13  of the robot  10  replaceably holds a pair of the finger members  40  of the plurality of pairs of the finger members  40 . With this arrangement, even in a case where work in which a plurality of the works W of different shapes, sizes, etc., is respectively held, the hand  13  (the actuator of the hand main body portion  131 ) may be commonly established, and the pair of the finger members  40  mounted to the finger holding mechanism  132  may be simply replaced in accordance with the shape, size, etc., of the work W. As a result, cost can be reduced compared to case where a plurality of hands is prepared and an ATC (auto tool changer) or the like is used to replace these hands in accordance with the shape, size, etc., of the work W, for example. Further, according to this embodiment, a storage space that stores the plurality of pairs of the finger members  40  just needs to be provided. As a result, it is possible to save space compared to a case where space for storing a plurality of hands is provided. As a result, as described above, it is possible to provide the finger storage box  50  that stores a plurality of the finger members  40  on the same traveling cart  4  as the robot  10 , and move the finger storage box  40  with the robot  10 . 
     Further, in particular, according to this embodiment, the finger holding mechanism  132  comprises a pair of the finger holding portions  133 . Then, each of the finger holding portions  133  of the pair serves as a link mechanism comprising the link members  136  to  139 . With this arrangement, the finger member  40  received by the receiving space  135  is engaged by the link member  138 , making it possible to hold the finger member  40 . Then, the link member  138  in the engaged posture is transitioned to a released posture, releasing the engagement of the finger member  40  by the link member  138  and releasing the hold of the finger member  40 . 
     Further, in particular, according to this embodiment, the link member  136  comprises the exposed operating surface  136   a,  rotating in the direction of the arrow A 1  when the operating surface  136   a  is pressed. With this arrangement, the operating surface  136   a  is pressed by the pressing member  61 , etc., rotating the link member  136  in the direction of the arrow A 1 . As a result, the link member  138  in the engaged posture can be transitioned to a released posture. Accordingly, the engagement of the finger member  40  by the link member  138  can be released, thereby releasing the hold of the finger member  40 . 
     Further, in particular, according to this embodiment, each of the finger holding portions  133  of the pair comprises the compression spring  142 . Each of the compression springs  142  energizes the link member  136  so that the link member  138  forms an engaged posture when the operating surface  136   a  is not pressed. With this arrangement, when the operating surface  136   a  is not pressed, the link member  138  can be changed to an engaged posture. As a result, the finger member  40  can be engaged by the link member  138 , making it possible to hold the finger member  40 . 
     Further, in particular, according to this embodiment, the link member  138  comprises the protruding portion  138   a,  and each of the plurality of finger members  40  comprises the concave portion  40   a  engaged by the protruding portion  138   a  of the surface  40 Wb. With the engagement of the concave portion  40   a  of the finger member  40  received in the receiving space  135  by the protruding portion  138   a  of the link member  138 , it is possible to reliably hold the finger member  40 . 
     Further, in particular, according to this embodiment, the present disclosure comprises the pressing device  60  comprising the pressing member  61  for pressing the operating surface  136   a.  The operating surface  136   a  is pressed by the pressing member  61  of the pressing device  60 , thereby rotating the link member  138  in the direction of the arrow B 1 . As a result, the link member  138  in the engaged posture can be transitioned to a released posture. Accordingly, the engagement of the finger member  40  by the link member  138  can be released, thereby releasing the hold of the finger member  40 . 
     Note that the first embodiment is not limited to the contents described above, and various modifications may be made without deviating from the spirit and scope of the disclosure. The following describes such modifications one by one. 
     (1-1) When the End Tool of the Nut Runner is Automatically Replaceable 
     That is, the nut runner (electric torque wrench) may be held by the finger member  40 , and the end tool installed to the end of the held nut runner (electric torque wrench) may be automatically replaceable. 
     As shown in  FIG. 14 , in this modification, a nut runner  200  is provided on the transporting cart  4  previously described, for example. The robot  10  holds a held portion  201  of the nut runner  200  using the pair of the finger members  40  installed to the finger holding mechanism  132  of the hand  13 . As a result, the robot  10  can hold the nut runner  200 . That is, the nut runner  200  also links to the target object. 
     One of a plurality of end tools  300  is replaceably installable to the end of the nut runner  200 . That is, for example, the end tool  300  is prepared in accordance with the type of fastening member MB, such as a screw, bolt, nut, etc., required for tightening together the works W during the assembly work. The plurality of the end tools  300  is inserted into an end tool tray  301  provided on the transporting cart  4  previously above, for example. Further, the fastening member MB is prepared in multiple types, and inserted into a supply tray  302  provided on the work table  101  previously above, for example. 
     Then, when the process transitions to a process where the tightening of the fastening member MB is performed, the robot  10  installs the finger member  40  corresponding to the shape, size, etc., of the grasped portion  201  of the nut runner  200  to the finger holding mechanism  132  as described above, and grasps the grasped portion  201 . With this arrangement, the robot  10  grasps the nut runner  200 , installs the end tool  300  corresponding to the type of the fastening member MB required at that time to the end of the grasped nut runner  200 , and attaches and tightens the fastening member MB. According to this modification, the replacement of the end tool  300  is not performed by human hands, but is automated. 
     As shown in  FIG. 15 , three springs  201 ,  202 , and  203  are provided to the nut runner  200 . The spring  201  comprises a function that executes a following action when the fastening member MB is tightened. The spring  202  comprises a function that alleviates the impact when tightening is completed. The spring  203  comprises a function for removing the end tool  300 . Further, the end tool  300  is installed to the end of the nut runner  200 . The end tool  300  comprises a bit  320 , a cylindrical sleeve  303 , and a cover portion  304  in communication with this sleeve  303 . A bit channel  350  is formed on the same axis line as the sleeve  303  and the cover portion  304 . The bit  320  is inserted into this bit channel  350 . An air-passable channel is formed around the entire circumference, between the bit  320  and the bit channel  350 . Further, an opening  399  is formed in the section of the cover portion  340  in which the end portion of the nut runner  200  is fitted. With the end tool  300  installed to the end of the nut runner  200 , one end side of an air hose  400  provided to the nut runner  200  is connected to the opening  399 . The other end side of the air hose  400  is connected to a suction air pump (not shown), and the air is suction from the bit channel  350  via the air hose  400 . With this arrangement, the fastening member MB can be suctioned to the end of the sleeve  303 . With such a configuration, even in a case where the end tool  300  is replaced with another, the air hose  400  does not need to be reconnected at that time. As a result, replacement of the end tool  300  can be automated. 
     According to this modification described above, the same advantages as those of the embodiment are achieved. 
     (1-2) Other 
     While the finger holding mechanism  132  is configured to replaceably hold a pair of the finger members  40  in the above, the present disclosure is not limited thereto. That is, the finger holding mechanism may be configured to replaceably hold three or more finger members. 
     While the robot  10  is configured using a robot having seven axes in the above, the present disclosure is not limited thereto, allowing configuration using a robot having six axes or less. 
     Further, while the robot  10  is configured using a single-arm robot having only the one arm  12  in the above, the present disclosure is not limited thereto. That is, the robot may be configured using a multiple-armed robot having two or more arms. 
     Further, while two robots  10  comprising the arm  12 , the hand  13 , etc., are provided to the robot system  1  in the above, the present disclosure is not limited thereto. That is, just one robot may be provided, or three or more robots may be provided. 
     Next, second embodiment will be described with reference to  FIG. 16  to  FIG. 21 . According to the robot system of second embodiment, two robots are shared in three work areas arranged side by side. According to the robot system of second embodiment, control that stops a robot is performed when the presence of a person is detected in a work area where a robot exists and work can be performed by the robot. On the other hand, control that stops a robot is not performed if the presence of a person is detected in a work area where a robot does not exist. 
     Configuration 
       FIG. 16  is a diagram showing an overview of a robot system  600  according to second embodiment.  FIG. 17  is a plan view showing the process layout of second embodiment. As shown in  FIG. 16  and  FIG. 17 , the robot system  600  comprises a first robot  610 , a second robot  620 , a tool storage space  615 , a sensor  630 , a sensor  640 , a sensor  650 , a moving portion  660 , and a control portion  670 . 
     In this embodiment, the first robot  610  and the second robot  620  are vertical articulated robots with six or seven degrees of freedom, respectively. The first robot  610  and the second robot  620  are installed to the moving portion  660 . The first robot  610  and the second robot  620  perform work on objects in part storage spaces E to G and on work tables X, X′, Y, Y′, Z, and Z′. 
     The control portion  670  comprises a single or plurality of controllers (computing devices). The control portion  670  controls the drive of the servo motors (not shown) of the first robot  610 , the second robot  620 , and the moving portion  660  based on an operation procedure stored in advance. Encoders that detect rotational positions are built into the servo motors of the first robot  610 , and the second robot  620 , and the moving portion  660 . A detection signal of each encoder is respectively inputted into the control portion  670 . 
     Further, the control portion  670  is connected with the sensors  630 ,  640 , and  650 . The signals of the sensors  630 ,  640 , and  650  are inputted to the control portion  670 . 
     As shown in  FIG. 17 , the robot system  600  is surrounded by a fence D and the part storage spaces E to G. A gate  601  is provided to the fence D. The gate  601  serves as an entrance into and an exit out from the fence D for the preparer when the operation of the robot system  600  has stopped. Note that the fence D may be configured in part or in whole using the walls, etc., of the building in which the robot system  600  is housed. The part storage spaces E to G are linearly disposed, and the moving portion  660  is arranged parallel thereto. 
     The first robot  610  and the second robot  620  are provided on a path  660 A of the moving portion  660 . The first robot  610  and the second robot  620  move on the path  660 A when driven by the servo motor (not shown) controlled by the control portion  670 . 
     A partition wall D 1  is provided between the part storage spaces E and F. A partition wall D 2  is provided between the part storage spaces F and G. The work area surrounded by the fence D and part storage spaces E to G forms a work area A (the dashed frame A in  FIG. 17 ), a work area B (the dashed frame B in  FIG. 17 ), and work area C (the dashed frame C in  FIG. 17 ) divided along the partition walls D 1  and D 2 . 
     According to this embodiment, the work areas A, B, and C each serve as a location (or an area) where the assembly work of machine units a, b, and c, each an assembled part made of a plurality of parts, is performed. 
     Further, the part storage space E, the work table X, and the work table X′ are disposed in the work area A. The part storage space F, the work table Y, and the work table Y′ are disposed in the work area B. The part storage space G, the work table Z, and the work table Z′ are disposed in the work area C. 
     Then, according to the robot system  600 , the first robot  610  and the second robot  620  are shared in the work areas A, B, and C. 
     That is, in the work areas A to C, at least one of the first robot  610  and the second robot  620  (hereinafter suitably and simply referred to as the “robots  610  and  620 ”) executes the assembly work on the parts respectively set up in the part storage spaces E to G. As a result, an assembled part (sub-assembly) is manufactured. 
     Further, according to the robot system  600 , the assembled product assembled in one of the work areas A to C is transported to another of the work areas A to C by the robots  610  and  620 , making it possible to manufacture a more complex assembled part by implementing further assembly work. 
     According to this second embodiment, the first robot  610  and the second robot  620  are mainly gathered in a single work area, either the work area A, B, or C, and work in coordination to assemble the manufacturing machine unit. Note that the first robot  610  and the second robot  620  may be distributed to different work areas to perform work independently. 
     Next, an example of the work procedure executed by the robot system  600  will be described. The robots  610  and  620  perform the assembly work of a unit a in the work area A. Subsequently, the robots  610  and  620  perform the assembly work of a unit b in the work area B, and the assembly work of a unit c in the work area C. The robots  610  and  620  transport the unit a from the work area A to the work area B and perform the assembly work of the unit a and the unit b in the work area B, thereby manufacturing a unit ab (not shown) as an assembled part. Next, the robots  610  and  620  transport the unit c from the work area C to the work area B and perform the assembly work of the unit ab and the unit c in the work area B, thereby manufacturing a unit abc (not shown) as an assembled part. According to this embodiment, the unit abc is the final work piece. 
     At this time, the first robot  610  and the second robot  620  receive a command from the control portion  670 , and perform work in work area A, B, or C. For example, to perform the assembly work of the unit b, the first robot  610  and the second robot  620  receive a command from the control portion  670  and get preferred parts from the part storage space F in coordination. Further, the first robot  610  and the second robot  620  temporarily store the parts on the work table Y. Furthermore, the first robot  610  and the second robot  620  carry the parts temporarily stored on the work table Y to the work table Y′, and perform the assembly work of the unit b on the work table Y′. 
     Next, the control based on the detection and detection result of the sensors  630 ,  640 , and  650  of this second embodiment will be described. The sensors  630 ,  640 , and  650  are motion sensors that respectively detect whether or not a preparer (person)  602  is present near the part storage space E, F, or G. The information detected by the sensors  630 ,  640 , and  650  is inputted to the control portion  670 . 
     According to this embodiment, the sensors  630 ,  640 , and  650  are transmissive area sensors. The sensors  630 ,  640 , and  650  detect that the preparer  602  is present if a light obstructing object exists in the effective sensor detection range. The sensor  630  senses the preparer  602  when the preparer  602  supplies parts to the part storage space E provided within the work area A. The sensor  640  senses the hand of the preparer  602  when the preparer  602  supplies parts to the part storage space F provided within the work area B. The sensor  650  senses the preparer  602  when the preparer  602  supplies parts to the part storage space G provided within the work area C. 
     The moving portion  660  moves the first robot  610  and the second robot  620  from one work area to another work area along the path  660 A as described above, based on an operation command from the control portion  670 . Note that the moving portion  660  may comprise two separate axes: a first axis where the first robot  610  is moved, and a second axis where the second robot  620  is moved. Or, the moving portion  660  may comprises a single shared axis shared by both the first robot  610  and the second robot  620 . When the moving portion  660  comprises a moving axis that is a single common axis, the first robot  610  and the second robot  620  are moved without changing relative positions. 
     Further, the movement by the moving portion  660  is performed when the work area is switched, for example. Or, the movement is performed when the first robot  610  and the second robot  620  perform work in coordination in a single work area and one of the robots is to retrieve parts or tools from another work area or a supply tool storage space  615 , etc. 
     The control portion  670  receives a selection input of the work area where work is to be performed from the operator. Then, the control portion  670  controls the first robot  610 , the second robot  620 , and the moving portion  660  so that the first robot  610  and the second robot  620  perform work in the received work area following a program created in advance. 
     Further, the control portion  670  monitors whether or not a sensor (the sensor  630 ,  640 , or  650 ) provided to a work area (hereinafter suitably “operation area”) where at least one of the first robot  610  and the second robot  620  exists detects the presence of the preparer  602 . For example, given that the work area A is the operation area, the control portion  670  monitors whether or not the sensor  630  detects the presence of the preparer  602 . Further, for example, given that the work area B is the operation area, the control portion  670  monitors whether or not the sensor  640  detects the presence of the preparer  602 . Further, for example, given that the work area C is the operation area, the control portion  670  monitors whether or not the sensor  650  detects the presence of the preparer  602 . Note that, according to this embodiment, the control portion  670  detects the area where the first robot  610  and the second robot  620  exist based on the position information from the encoder corresponding to the moving portion  660 . 
     Further, when the sensor provided to the operation area detects the presence of the preparer  602 , the control portion  670  stops the robot (at least one of the first robot  610  and the second robot  620 ) that exists in the operation area. Then, the control portion  670  issues an alarm signal. At that time, whether or not a sensor (sensor  630 ,  640 , or  650 ) provided to an area other than the operation area (hereinafter suitably “non-operation area”) has detected the presence of the preparer  602  does not matter. 
     Further, when a sensor provided to the operation area has not detected the presence of the preparer  602 , the control portion  670  does not execute stop control as described above on the robot (at least one of the first robot  610  and the second robot  620 ) that exists in the operation area. At that time as well, similar to the above, whether or not a sensor (the sensor  630 ,  640 , or  650 ) provided to a non-operation area has detected the presence of the preparer  602  does not matter. For example, given that the work area A is the operation area, the control portion  670  does not stop the robot that exists in the operation area A when the sensor  630  does not detect the presence of the preparer  602 . At that time, whether or not the sensor  640  provided to the work area B or the sensor  650  provided to the work area C has detected the presence of the preparer  602  does not matter. Further, for example, given that the work area B is the operation area, the control portion  670  does not stop the robot that exists in the operation area B when the sensor  640  has not detected the presence of the preparer  602 . At that time, whether or not the sensor  630  provided to the work area A or the sensor  650  provided to the work area C has detected the presence of the preparer  602  does not matter. Further, for example, given that the work area C is the operation area, the control portion  670  does not stop the robot that exists in the operation area C when the sensor  650  has not detected the presence of the preparer  602 . At that time, whether or not the sensor  630  provided to the work area A or the sensor  640  provided to the work area B detects the presence of the preparer  602  does not matter. 
     Further, when at least one of the first robot  610  and the second robot  620  has issued an alarm signal and stopped (hereinafter referred to as an “alarm/stop state”), the control portion  670  stops the issuance of the alarm signal and clears the stop state when an operator presses the Reset Alarm button (not shown). 
     Note that, before the moving portion  660  moves a robot (the first robot  610  and the second robot  620 ) from the work area where the robot exists to a predetermined work area, the control portion  670  monitors whether or not the sensor provided to the destination work area where the robot is to be moved has detected the presence of the preparer  602 . Then, when the sensor has detected the presence of the preparer  602 , the control portion  670  prohibits the robot from entering the destination work area, stopping the movement of the robot at a location prior to entry into the destination work area, etc. For example, before a robot is moved from the work area A to the work area B, the control portion  670  prohibits the robot from entering the work area B when the sensor  640  provided to the work area B has detected the presence of the preparer  602 . The control portion  170  stops the movement of the robot at the location of the work area A. 
     Further, when the sensor provided to the destination work area where the robot is prohibited entry no longer detects the presence of the preparer  602 , the control portion  670  permits the robot to enter the destination work area and the robot automatically recovers from the stop state. For example, when the sensor  640  provided to the work area B where robot entry is prohibited no longer detects the presence of the preparer  602 , the control portion  670  permits the robot to enter the work area B. As a result, the control portion  670  moves the robot from the work area A to the work area B. 
     Further, the control portion  670  may issue a warning in the destination work area where entry is prohibited. For example, the control portion  670  encourages the preparer  602  who appears to be present in the work area B where robot entry is prohibited to exit that area. That is, the control portion  670  issues in the work area B an alarm sound or an automatic announcement that calls for exit from the work area B. 
     Control Method  1   
       FIG. 18  is a flowchart showing an overview of the safety monitoring operation during work that is executed by the control portion  670  in order to achieve the above control details. 
     In step S 1 , first the control portion  670  determines whether or not the first robot  610  is in an alarm/stop state. If the first robot  610  is not in an alarm/stop state, the condition of step S 1  is not satisfied (step S 1 : No), and the flow proceeds to step S 3  described later. If the first robot  610  is in an alarm/stop state, the condition of step S 1  is satisfied (step S 1 : Yes), and the flow proceeds to step S 2 . 
     In step S 2 , the control portion  670  determines whether or not the Reset Alarm button has been pressed. If the Reset Alarm button has not been pressed, the condition of step S 2  is not satisfied (step S 2 : No), and the flow proceeds to step S 6  described later. If the Reset Alarm button has been pressed, the condition of step S 2  is satisfied (step S 2 : Yes), and the flow proceeds to step S 3 . 
     In step S 3 , the control portion  670  determines if the sensor provided to the work area where the first robot  610  exists has detected the presence of the preparer  602 . For example, if the first robot  610  exists in the work area A, the control portion  670  determines if the sensor  630  has detected the presence of the preparer  602 . If the sensor  630  has detected the presence of the preparer  602 , the condition of step S 3  is satisfied (step S 3 : Yes), and the flow proceeds to step S 4 . 
     In step S 4 , the control portion  670  sets the first robot  610  into an alarm/stop state. For example, if the sensor  630  provided to the work area A where the first robot  610  exists has detected the presence of the preparer  602 , the control portion  670  sets the first robot  610  into a stop state. Subsequently, the flow proceeds to step S 6  described later. 
     On the other hand, in the step S 3 , if the sensor  630  has not detected the presence of the preparer  602 , the condition of step S 3  is not satisfied (step S 3 : No), and the flow proceeds to step S 5 . In step S 5 , the control portion  670  maintains the operation state of the first robot  610  regardless of whether or not the sensor  640  and the sensor  650  have detected the presence of the preparer  602 . Specifically, if the first robot  610  is in an alarm/stop state, for example, the control portion  670  cancels the alarm/stop state. Further, if the first robot  610  is in an operation state, the control portion  670  continues the operation state. Once step S 5  ends, the flow proceeds to step S 6 . 
     In step S 6 , the control portion  670  determines whether or not the second robot  620  is in an alarm/stop state. If the second robot  620  is not in an alarm/stop state, the condition of step S 6  is not satisfied (step S 6 : No), and the flow proceeds to step S 8  described later. If the second robot  620  is in an alarm/stop state, the condition of step S 6  is satisfied (step S 6 : Yes), and the flow proceeds to step S 7 . 
     In step S 7 , the control portion  670  determines whether or not the Reset Alarm button has been pressed. If the Reset Alarm button has not been pressed, the condition of step S 7  is not satisfied (step S 7 : No), and the flow returns to the step S 1  and the same procedure is repeated. If the Reset Alarm button has been pressed, the condition of step S 7  is satisfied (step S 7 : Yes), and the flow proceeds to step S 8 . 
     In step S 8 , the control portion  670  determines if the sensor provided to the work area where the second robot  620  exists has detected the presence of the preparer  602 . For example, if the second robot  620  exists in the work area A, the control portion  670  determines if the sensor  630  has detected the presence of the preparer  602 . If the sensor  630  has detected the presence of the preparer  602 , the condition of step S 8  is satisfied (step S 8 : Yes), and the flow proceeds to step S 9 . 
     In step S 9 , the control portion  670  sets the second robot  620  into an alarm/stop state. For example, if the sensor  630  provided to the work area A where the second robot  620  exists has detected the presence of the preparer  602 , the control portion  670  sets the second robot  620  into a stop state. Subsequently, the flow returns to the step S 1  and the same procedure is repeated. 
     On the other hand, in the step S 8 , if the sensor  630  has not detected the presence of the preparer  602 , the condition of step S 8  is not satisfied (step S 8 : No), and the flow proceeds to step S 10 . In step S 10 , the control portion  670  maintains the operation state of the second robot  620  regardless of whether or not the sensor  640  and the sensor  650  have detected the presence of the preparer  602 . Specifically, if the second robot  620  is in an alarm/stop state, for example, the control portion  670  cancels the alarm/stop state. Further, if the second robot  620  is in an operation state, the control portion  670  continues the operation state. Once step S 10  ends, the flow returns to the step S 1  and the same procedure is repeated. 
     Control Method  2   
       FIG. 19  is a flowchart showing an overview of the safety monitor operation during movement that is executed by the control portion  670 . 
     In step S 21 , the control portion  670  monitors whether or not the first robot  610  is just about to move from one work area to another work area. If the first robot  610  is not just about to move from one work area to another work area, the condition of step S 21  is not satisfied (step S 21 : No) and the flow proceeds to step S 24  described later. If the first robot  610  is just about to move from one work area to another work area, the condition of step S 21  is satisfied (step S 21 : Yes) and the flow proceeds to step S 22 . 
     In step S 22 , the control portion  670  monitors whether or not the sensor provided to the destination work area has detected the presence of the preparer  602 . For example, when the first robot  610  is just about to move from the work area A to the work area B, the control portion  670  monitors whether or not the sensor  640  provided to the work area B has detected the presence of the preparer  602 . If the sensor  640  has not detected the presence of the preparer  602 , the condition of step S 22  is not satisfied (step S 22 : No), and the flow proceeds to step S 27  described later. If the sensor  640  has detected the presence of the preparer  602 , the condition of step S 22  is satisfied (step S 22 : Yes), and the flow proceeds to step S 23 . 
     In step S 23 , the control portion  670  prohibits entry of the first robot  610  into the destination work area. Further, the control portion  670  issues a warning in the destination work area of the first robot  610 . For example, the control portion  670  issues an alarm sound or an automatic announcement that calls for exit from the destination work area. Subsequently, the flow proceeds to step S 24 . 
     In step S 24 , the control portion  670  determines whether or not entry of the first robot  610  into the destination work area is prohibited. If entry of the first robot  610  into the destination work area is not prohibited, the condition is not satisfied (step S 24 : No), and the flow proceeds to step S 27  described later. If entry of the first robot  610  into the destination work area is prohibited, the condition is satisfied (step S 24 : Yes), and the flow proceeds to step S 25  described later. 
     In step S 25 , the control portion  670  monitors whether or not the sensor provided to the destination work area of the first robot  610  has detected the presence of the preparer  602 . If the sensor has detected the presence of the preparer  602 , the condition is satisfied (step S 25 : Yes), and the flow proceeds to step S 27  described later. If the sensor has not detected the presence of the preparer  602 , the condition is not satisfied (step S 25 : No), and the flow proceeds to step S 26 . 
     In step S 26 , the control portion  670  permits entry of the first robot  610  into the destination work area. Subsequently, the flow proceeds to step S 27 . 
     In step S 27 , the control portion  670  monitors whether or not the second robot  620  is about to move from one work area to another work area. If the second robot  620  is not just about to move from one work area to another work area, the condition of step S 27  is not satisfied (step S 27 : No) and the flow proceeds to step S 30  described later. If the second robot  620  is just about to move from one work area to another work area, the condition of step S 27  is satisfied (step S 27 : Yes) and the flow proceeds to step S 28 . 
     In step S 28 , the control portion  670  monitors whether or not the sensor provided to the destination work area has detected the presence of the preparer  602 . For example, when the second robot  620  is just about to move from the work area A to the work area B, the control portion  670  monitors whether or not the sensor  640  provided to the work area B has detected the presence of the preparer  602 . If the sensor  640  has not detected the presence of the preparer  602 , the condition of step S 28  is not satisfied (step S 28 : No), the flow returns to the step S 21 , and the same procedure is repeated. If the sensor  640  has detected the presence of the preparer  602 , the condition of step S 28  is satisfied (step S 28 : Yes), and the flow proceeds to step S 29 . 
     In step S 29 , the control portion  670  prohibits entry of the second robot  620  into the destination work area. Further, the control portion  670  issues a warning in the destination work area of the second robot  620 . For example, the control portion  670  issues an alarm sound or an automatic announcement that calls for exit from the destination work area. Subsequently, the flow proceeds to step S 30 . 
     In step S 30 , the control portion  670  determines whether or not entry of the second robot  620  into the destination work area is prohibited. If entry of the second robot  620  into the destination work area is not prohibited, the condition is not satisfied (step S 30 : No), the flow returns to the step S 21 , and the same procedure is repeated. If entry of the second robot  620  into the destination work area is prohibited, the condition is satisfied (step S 30 : Yes), and the flow proceeds to step S 31 . 
     In step S 31 , the control portion  670  monitors whether or not the sensor provided to the destination work area of the second robot  620  has detected the presence of the preparer  602 . If the sensor has detected the presence of the preparer  602 , the condition is satisfied (step S 31 : Yes), the flow returns to the step S 21 , and the same procedure is repeated. If the sensor has not detected the presence of the preparer  602 , the condition is not satisfied (step S 31 : No), and the flow proceeds to step S 32 . 
     In step S 32 , the control portion  670  permits entry of the second robot  620  into the destination work area. Subsequently, the flow returns to the step S 21  and the same procedure is repeated. 
     As described above, according to the robot system  600  of this embodiment, control that stops the robots  610  and  620  is not performed if the presence of the preparer  602  is detected in a work area where the robots  610  and  620  do not exist and where work cannot be performed by the robots  610  and  620 . As a result, the preparer  602  can execute the preparation process in another work area where robots do not exist while the robots  610  and  620  perform work in the work areas where the robots  610  and  620  do exist. That is, for example, the preparer  602  can safely enter the part storage spaces E to G of the work areas A to C other than that of the operation area, and set up the parts required for the assembly work of the work area. As a result, compared to a case where a plurality of types of assembled parts is manufactured in a single work area, the decrease in work efficiency caused by part preparation work can be alleviated. Further, if the presence of the preparer  602  is detected in a work area where the robots  610  and  620  exist and where work can be performed by the robots  610  and  620 , stop control of the robots  610  and  620  is performed. With this arrangement, the work performed by the robots  610  and  620  can be appropriately stopped according to circumstance. 
     (2-1) When One Robot is Shared between Two Work Areas 
     According to the robot system of this modification, similar to second embodiment, control that stops a robot is performed when the presence of a preparer  702  is detected in a work area where a robot exists and where work can be performed by the robot. On the other hand, control that stops a robot is not performed if the presence of the preparer  702  is detected in a work area where a robot does not exist. The components that are the same as those in the second embodiment will be denoted using the same reference numerals, and descriptions thereof will be suitably omitted or simplified. 
     Configuration 
       FIG. 20  is a diagram showing an overview of a robot system  700  according to this modification. As shown in  FIG. 20 , the robot system  700  comprises one robot  710 , a sensor  720 , a sensor  730 , and a control portion  740 . 
       FIG. 21  is a plan view showing the process layout of this modification. 
     As shown in  FIG. 21 , the robot system  700  includes a work area H (the dashed frame H in  FIG. 21 ) and a work area I (the dashed frame I in  FIG. 21 ). Further, the robot system  200  further includes a fence J that surrounds the work area H and the work area I. A robot mount M for mounting the robot  710  is disposed within the fence J. The robot system  700  is a robot system that shares the robot  710  between two work areas: the work area H and the work area I. For example, the work areas H and I are locations (or areas) where the assembly work of units h and i (not shown) of manufacturing machines configured using a plurality of units is respectively performed. A part storage space K and a work table N are disposed in the work area H. A part storage space L and a work table N′ are disposed in the work area I. 
     The robot  710  performs work in either the work area H or the work area I. The robot  710  receives a command from the control portion  740  and operates accordingly. According to this modification, the robot  710  is an articulated robot having six or seven axes, for example. For example, to perform the assembly work of the unit h, the robot  710  receives a command from the control portion  740  and gets preferred parts from the part storage space K. The robot  710  carries the parts to the work table N, and performs the assembly work of the unit h on the work table N. Further, to perform the assembly work of the unit i, the robot  710  receives a command from the control portion  740  and gets preferred parts from the part storage space L. The robot  710  carries the parts to the work table N′, and performs the assembly work of the unit i on the work table N′. 
     Here, a drive portion (hereinafter referred to as “drive portion  711 ”) of the robot  710  that is capable of rotating around the first axis closest to the robot mount M is capable of rotating all other axes (hereinafter referred to as “robot main components  712 ”) horizontally. Accordingly, the drive portion  711  moves the robot main components  712  between the work area H and the work area I. 
     Accordingly, the drive portion  711  of this modification is equivalent to the moving portion  660  of the second embodiment. Further, the robot main components  712  of this modification are equivalent to the first robot  610  and the second robot  620  of the second embodiment. Further, the sensors  720  and  730  are equivalent to the sensors  630 ,  640 , and  650  of the second embodiment. The sensor  720  senses the hand of the preparer (person)  702  when the preparer  702  supplies parts to the part storage space K provided within the work area H. Similarly, the sensor  730  senses the hand of the preparer  702  when the preparer  702  supplies parts to the part storage space L provided within the work area I. 
     The control portion  740  is equivalent to the control portion  660  of the second embodiment. That is, according to the control portion  740 , the controlled robots are simply reduced from two to one, and the number of work areas from three to two. Other than these points, the control portion  740  is functionally the same as the control portion  660 . 
     In the robot system  700  of the modification, the same advantages as those of the second embodiment are achieved. That is, according to the robot system  700 , control that stops the robot  710  is not performed if the presence of the preparer  702  is detected in a work area where the robot  710  does not exist and where work cannot be performed by the robot  710 . As a result, the preparer  702  can perform a preparation process in another work area where robots do not exist while the robot  710  performs work in the work area where the robot  710  exists. Further, stop control of the robot  710  is performed if the presence of the preparer  702  is detected in the work area where the robot  710  exists and where work can be performed by the robot  710 . With this arrangement, the work performed by the robot  710  can be appropriately stopped according to circumstance. 
     (2-2) When Two Robots are Shared between Three Work Areas 
     According to this modification, a robot system that shares two robots between three work areas arranged side by side is shown. The components that are the same as those in the second embodiment will be denoted using the same reference numerals, and descriptions thereof will be suitably omitted or simplified. 
     Configuration 
       FIG. 22  is a diagram showing an overview of a robot system  800  according to this modification.  FIG. 23  is a plan view showing the process layout of this modification. In  FIG. 22  and  FIG. 23 , the robot system  800  comprises the first robot  610 , the second robot  620 , the sensor  630 , the sensor  640 , the sensor  650 , a first drive portion  863 , a second drive portion  864 , and the control portion  670 . 
     In this modification, the first robot  610  and the second robot  620  are vertical articulated robots capable of posture changes with six or seven degrees of freedom, for example, by the first drive portion  863  and the second drive portion (described in detail later). Then, the first robot  610  and the second robot  620  are each installed to a rack rail  860 . 
     The control portion  670  controls the drive of servo motors described later of the first drive portion  863  and the second drive portion  864 , based on an operation procedure stored in advance. An encoder that detects a rotational position is built into each of the servo motors, and the detection signals of the encoders are respectively inputted into the control portion  670 . 
     The first robot  610  and the second robot  620  receive a command from the control portion  670 , and perform predetermined work in work area A, B, or C. Then, according to this modification, the first robot  610  comprises a servo motor and at least one of the first drive portions  863 , which comprises a pinion gear that is formed so that it engages with the rack of the rack rail  860  and rotates via the output of the servo motor. Further, the second robot  620  also comprises a servo motor and at least one of the second drive portions  864 , which comprises a pinion gear that is formed so that it engages with the rack of the rack rail  860  and rotates via the output of the servo motor. The first drive portion  863  and the second drive portion  864  are driven by a command from the control portion  670 , achieving an optimal suitable posture of the robots  610  and  620  required for each work previously described. 
     For example, to perform the assembly work of the unit b, the first robot  610  and the second robot  620  receive a command from the control portion  670  and get parts (target objects) from the part storage space F in coordination. The first robot  610  and the second robot  620  temporarily store the parts on the work table Y (first area). Furthermore, the first robot  610  and the second robot  620  transport the parts temporarily stored on the work table Y to the work table Y′ (second area), and perform the assembly work of the unit b on the work table Y′. The various postures required for this work are achieved by the drive of the first drive portion  863  and the second drive portion  864  based on commands from the control potion  670 . Note that the transport of the parts by the coordinated operation of the first robot  610  and the second robot  620  will be described later with reference to  FIG. 24A  to  FIG. 24E . 
     Further, the control portion  670  drives and controls the servo motors of the first drive portion  863  and the second drive portion  864 , causing the first robot  610  and the second robot  620  to move along the rack rail  860 . The control portion  670  instructs the servo motor of the first drive portion  863  so that the first robot  610  moves to the work area where work is to be performed. Similarly, the control portion  670  instructs the servo motor of the second drive portion  864  so that the second robot  620  moves to the work area where work is to be performed. 
     That is, the first drive portion  863  moves the first robot  610  along the rack rail  860  from a predetermined work area to another work area in coordination with the rack rail  860 . Further, the second drive portion  864  works moves the second robot  620  along the rack rail  860  from a predetermined work area to another work area in coordination with the rack rail  860 . The first drive portion  863  and the second drive portion  864  share the rack rail  860 . The rack rail  860  links to a guide portion that movably supports the first robot  610  and the second robot  620 . 
     Note that the rack rail  860  does not have to be shared between the first drive portion  863  and the second drive portion  864 , allowing a first rail and a second rail respectively corresponding to the first drive portion  863  and the second drive portion  864  to be separately provided. In such a case, the first rail and second rail may be disposed in a parallel or non-parallel manner. Further, in this modification, the first drive portion  863  and the second drive portion  864  share the one rack rail  860  as described above. Accordingly, the first robot  610  and the second robot  620  move on the same path. On the other hand, when the rack rail  860  includes the first rail and second rail and the first drive portion  863  and the second drive portion  864  use separate rails, the first robot  610  and the second robot  620  can move on different paths. That is, the first drive portion  863  moves the first robot  610  along the first rail, and the second drive portion  864  moves the second robot  620  along the second rail. 
     Further, the control portion  670  can control the servo motor of the first drive portion  863  and the servo motor of the second drive portion  864  so that the first robot  610  and the second robot  620  work in coordination following a program created in advance. That is, the control portion  670  controls the servo motor of the first drive portion  863  of the first robot  610  and the servo motor of the second drive portion  864  of the second robot  620 . With this arrangement, control is performed so that the work operation performed by the first robot  610  and the second robot  620  is linked with the positional movement of the first robot  610  and the second robot  620 . The control portion  670  moves the first robot  610  and the second robot  620  to the same work area, and controls the first robot  610  and the second robot  620  so that they work in coordination on the same work target. 
     According to this modification, mainly the first robot  610  and the second robot  620  are moved to one of the work areas A, B, and C. Then, the first robot  610  and the second robot  620  work in coordination on the same work target, assembling in coordination a unit of a manufacturing machine. Note that while two robots, the first robot  610  and the second robot  620 , are used according to this modification, three or more robots may be used. 
     Operation 
       FIG. 24A  to  FIG. 24E  show an example of the work steps executed by the robot system  800  according to this modification. The work steps are executed according to an operation step in which the first robot  610  and the second robot  620  performed the predetermined work operation, and a moving step in which the locations of the first robot  610  and the second robot  620  are moved. The following describes a process wherein the unit ab assembled and manufactured using the unit a and the unit b in the work area B is held in coordination by the first robot  610  and the second robot  620 , with reference to  FIG. 24A  to  FIG. 24E . Subsequently, the following describes a process wherein the first robot  610  and the second robot  620  transport a target object from the work table Y (first area) to the work table Y′ (second area) on the opposite side across the rack rail  860 . 
       FIG. 24A  is a schematic diagram showing a state (state a) in which the first robot  610  and the second robot  620  hold the object to be transported. The unit ab is provided on the work table Y as the object to be transported. The control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the first robot  610  and the second robot  620  hold the unit ab. At this time, the distance between the locations of the first robot  610  and the second robot  620  is a distance La. 
       FIG. 24B  is a schematic diagram showing a state (state b) in which the first robot  610  and the second robot  620  lift the unit ab. After the state a, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the first robot  610  and the second robot  620  lift the unit ab. At this time, the amount of drive via each of the drive portions  863  and  864  of the first robot  610  and the second robot  620  is set within an optimal range stored in advance in the control portion  670  for transporting heavy objects. The optimum range is set by a pre-test or simulation and stored in the control portion  670  based on a load that includes the weights of the first robot  610  and the second robot  620 , for example. 
     Further, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the locations of the first robot  610  and the second robot  620  are moved. As a result, the distance between the locations of the first robot  610  and the second robot  620  increases from the distance La to a distance Lb (distance La&lt;distance Lb). 
     As the first robot  610  and the second robot  620  lift the unit ab, the first drive portion  863  moves the first robot  610  along the rack rail  860 . Further, the second drive portion  864  moves the second robot  620  in the direction opposite the moving direction of the first robot  610  (the direction away from the location of the first robot  610 ) along the rack rail  860 . 
       FIG. 24C  is a schematic diagram showing a state (state c) in which the first robot  610  and the second robot  620  transport the unit ab. After the state b, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the first robot  610  and the second robot  620  transport the unit ab across the rack rail  860 . Further, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the locations of the first robot  610  and the second robot  620  are moved. As a result, the distance between the locations of the first robot  610  and the second robot  620  increases from the distance Lb to a distance Lc (distance La&lt;distance Lb&lt;distance Lc). 
     As the first robot  610  and the second robot  620  transport the unit ab, the first drive portion  863  moves the first robot  610  further along the rack rail  860 . Further, the second drive portion  864  moves the second robot  620  further in the direction opposite the moving direction of the first robot  610  (the direction away from the location of the first robot  610 ) along the rack rail  860 . 
       FIG. 24D  is a schematic diagram showing a state (state d) in which the first robot  610  and the second robot  620  transport the unit ab. After the state c, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the first robot  610  and the second robot  620  transport the unit ab across the rack rail  860  toward the work table Y′. Further, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the locations of the first robot  610  and the second robot  620  are moved. As a result, the distance between the locations of the first robot  610  and the second robot  620  decreases from the distance Lc to a distance Ld (distance Lc&gt;distance Ld). 
     As the first robot  610  and the second robot  620  transport the unit ab, the first drive portion  863  moves the first robot  610  further along the rack rail  860 . Further, the second drive portion  864  moves the second robot  620  further in the direction opposite the moving direction of the first robot  610  (the direction approaching the location of the first robot  610 ) along the rack rail  860 . 
       FIG. 24E  is a schematic diagram showing a state (state e) in which the first robot  610  and the second robot  620  provide the unit ab onto the work table Y′. After the state d, the control portion  670  controls the servo motors of the first drive portion  863  and the second drive portion  864  so that the first robot  610  and the second robot  620  provide the unit ab onto the work table Y′. Further, the control portion  670  controls the first drive portion  863  and the second drive portion  864  so that the locations of the first robot  610  and the second robot  620  are moved. As a result, the distance between the locations of the first robot  610  and the second robot  620  decreases from the distance Ld to a distance Le (distance Ld&gt;distance Le). 
     As the first robot  610  and the second robot  620  transport the unit ab, the first drive portion  863  moves the first robot  610  further along the rack rail  860 . Further, the second drive portion  864  moves the second robot  620  further in the direction opposite the moving direction of the first robot  610  (the direction approaching the location of the first robot  610 ) along the rack rail  860 . 
     According to the above example, the moving of the locations of the first robot  610  and the second robot  620  (moving step) is executed by moving both the locations of the first robot  610  and the second robot  620 . Nevertheless, the present disclosure is not limited to moving both. That is, it is sufficient to change (changing step) at least one of the locations of the first robot  610  and the second robot  620  in accordance with the execution of the transport (transporting step) of the unit ab from the state a to the state e. For example, the distance between the locations of the first robot  610  and the second robot  620  may be changed by changing the location of the second robot  620  and not the location of the first robot  610 . 
     Further, the first drive portion  863  and the second drive portion  864  are not necessarily limited to a configuration that includes a pinion and motor, as long as the first robot  610  and the second robot  620  are movable along the guide portion  860 . Furthermore, the guide portion  860  is not necessarily limited to the rack rail as long as the first robot  610  and the second robot  620  are movably supported. For example, in a case where the first drive portion  863  and the second drive portion  864  include a linear motor and the guide portion  860  includes a rail, the robots can be moved in a non-contact manner by magnetic levitation. 
     Conclusion 
     As described above, according to the robot system of this modification, the first drive portion  863  and the second drive portion  864  play the role of respectively moving the first robot  610  and the second robot  620  along the rack rail  860 , as well as the role of changing the postures of the first robot  610  and the second robot  620  in order to execute preferred work. That is, it is possible to perform work using a single robot or a plurality of robots in coordination, in accordance with work details. Accordingly, it is possible to prevent specifications from becoming excessive, such as in a case where a full-time mechanism is provided for simply moving robots. Further, the variation in work can be increased and the movable area during coordinated work can be enlarged. Furthermore, the transportable weight can be increased by making a plurality of robots hold the target object. 
     In particular, according to this modification, it is possible transport a large object to be transported (the unit ab in the above example) while applying the robots  610  and  620  of relatively small sizes. That is, normally a robot that is capable of transporting heavy weight by itself has increased dimensions, making small handling such as assembly difficult. Conversely, according to this modification, it is possible to use a small robot of a size capable of smoothly implementing the process of assembling relatively small parts to assemble a sub-assembly (the units a, b, and c). Then, by controlling in coordination the two small robots  610  and  620 , it is possible to further transport a large object to be transported that is the result of assembling a plurality of sub-assemblies. 
     Further, in particular, according to this modification, the drive of the drive portions  863  and  864  at the time of transport actively adjusts the distance between each of the robots  610  and  620 . With this arrangement, it is possible to transport the object to be transported with the postures of each of the robots  610  and  620  held within an optimal range for transporting a heavy object. With this arrangement, even if the weight is greater than the sum of the transportable weight of each robot based on standards, the object to be transported can be stably transported. Further, because the object to be transported is supported by each robot at respectively different locations, the decrease in the moment load of each robot serves as an advantage when transporting a heavy object to be transported, compared to a case of cantilevered support. 
     Note that while, according to the above, the present disclosure is applied to a case where each of the robot systems performs the assembly work of a machine product, the present disclosure is not limited thereto. That is, the present disclosure may be applied to a case where the robot system performs other work. 
     Further, other than that already stated above, techniques based on each of the above embodiments and modifications may be suitably used in combination well. 
     Although other examples are not individually described herein, various changes can be made to each of the above embodiments and modifications without departing from the spirit and scope of the present disclosure.