Abstract:
A robot system includes a crane unit, a crane moving mechanism, a robot, and a controller. The crane unit is to suspend a workpiece. The crane unit moves in a horizontal direction via the crane moving mechanism. The robot is to move the crane unit in the horizontal direction via the crane moving mechanism. The controller is configured to control the crane unit to move upwardly to suspend the workpiece after controlling the robot to bring the crane unit into an engaging state in which the crane unit engages with the workpiece located at a first position. The controller is configured to control the crane unit suspending the workpiece to move downwardly to place the workpiece at a second position after controlling the robot to move the crane unit toward the second position while the crane unit suspends the workpiece.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application of the U.S. patent application Ser. No. 12/870,850 filed Aug. 30, 2010, which claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2009-200796, filed Aug. 31, 2009. The contents of these applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a robot system and a method of manufacturing a workpiece. 
     2. Description of the Related Art 
     It is desirable to eliminate or save manpower in a manufacturing process or a transfer process by allowing a robot to carry out various works which have relied upon the manpower. 
     For example, in a manufacturing site for a machine product such as an industrial robot, in many cases, an integrated transfer line may not be provided due to the layout of a factory, and a transfer work is required for transferring a workpiece from a previous process to a next process. 
     In order to automate the work, for example, Japanese Patent Laid-Open Publication No. 2006-035397 suggests a robot that picks and transfers a workpiece or the like. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a robot system includes a crane unit, a crane moving mechanism, a robot, and a controller. The crane unit is to suspend a workpiece. The crane unit moves in a horizontal direction via the crane moving mechanism. The robot is to move the crane unit in the horizontal direction via the crane moving mechanism. The controller is configured to control the crane unit to move upwardly to suspend the workpiece after controlling the robot to bring the crane unit into an engaging state in which the crane unit engages with the workpiece located at a first position. The controller is configured to control the crane unit suspending the workpiece to move downwardly to place the workpiece at a second position after controlling the robot to move the crane unit toward the second position while the crane unit suspends the workpiece. 
     According to another aspect of the present invention, a robot system includes a robot and a controller. The controller is configured to control a motion of the robot and further configured to control a motion of the crane unit which is movable in a horizontal direction and a vertical direction. The controller is configured to control the crane unit to move upwardly to suspend the workpiece after controlling the robot to bring the crane unit into an engaging state in which the crane unit engages with the workpiece located at a first position. The controller is configured to control the crane unit suspending the workpiece to move downwardly to place the workpiece at a second position after controlling the robot to move the crane unit toward the second position while the crane unit suspends the workpiece. 
     According to further aspect of the present invention, in a method of manufacturing a workpiece, a robot is controlled to bring a crane unit into an engaging state in which the crane unit engages with the workpiece located at a first position. The crane unit is moved upwardly to suspend the workpiece. The crane unit is moved in a horizontal direction toward a second position while the crane unit suspends the workpiece. The crane unit is moved downwardly to place the workpiece at the second position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in further detail with reference to the accompanying drawings wherein: 
         FIG. 1  is a perspective view showing a system configuration according to a first embodiment; 
         FIG. 2  is a general arrangement plan schematically showing the system configuration; 
         FIG. 3  is a flowchart showing processing for executing an algorism; and 
         FIG. 4  is a perspective view showing a system configuration according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     A transfer system (Robot system)  100  according to this embodiment is part of a manufacturing line for machine products (workpieces W). The transfer system  100  transfers the workpieces W that have been processed in a previous process (first equipment, not shown) to a next process (second equipment, not shown). A workpiece W is illustrated as a box-like object, however, for example, the workpiece W may be actually a base member or an arm member for an industrial robot. The workpiece W may be any one of various types of machine products. 
     (General Configuration) 
     Referring to  FIGS. 1 and 2 , the transfer system  100  includes a robot (a manipulator unit)  101 , a hoist (a crane unit, supporting unit)  102 , a crane rail (a crane moving mechanism, moving unit)  103 , a carry-in belt (a first position)  104 , a first carry-out belt (a second position)  105 , a second carry-out belt (a second position)  106 , and a controller  107 . 
     The supporting unit  102  suspends and supports the workpiece W. The moving unit  103  allows the supporting unit  102  to move in a horizontal direction. In this embodiment, the hoist  102  serves as the supporting unit, and the crane rail  103  serves as the moving unit. 
     The controller  107  is a computer including a storage device, an electronic computer device, an input device, and a display device. The controller  107  is connected with actuators of the robot  101 , the hoist  102 , and the crane rail  103  through lines, so that the controller  107  communicates with the actuators. 
     The carry-in belt  104  includes a transfer conveyor. The workpieces W which have been processed in the previous process (not shown) are successively carried to the transfer system  100 . 
     The first carry-out belt  105  and the second carry-out belt  106  each include a transfer conveyor to transfer the workpieces W to the next process. 
     Any one of or all the carry-in belt  104 , the first carry-out belt  105 , and the second carry-out belt  106  may not have a transfer conveyor, and the workpieces W may be transferred from the previous process by using a transfer vehicle such as an automatic guided vehicle (AGV). In this case, the transfer vehicle may serve as the first position or the second position according to the first embodiment of the present invention. 
     (Crane Unit) 
     The hoist  102  and the crane rail  103  use an existing crane device in a production factory or the like. The crane rail  103  includes a pair of rail members  32  supported at a ceiling and extending in the horizontal direction in parallel to one another, and a rail member  31  bridged between the rail members  32 . 
     It is to be noted that “the horizontal direction” includes all directions orthogonal to the gravity direction. “The horizontal direction” is not a strictly mathematically defined horizontal direction, but may a horizontal direction including a direction component orthogonal to the gravity direction. 
     The rail member  31  is supported by the rail members  32  through a pair of carriers  33 . When the carriers  33  are driven, the rail member  31  moves in an extending direction of the rail members  32  (indicated by arrow A 1 ). The carriers  33  respectively have electric actuators (not shown). The controller  107  controls the motion of the carriers  33 . 
     The hoist  102  includes a hook  20 , a wire  21 , a winding device  22 , and a carrier  23 . 
     The carrier  23  is supported by the rail member  31 . When the carrier  23  is driven, the hoist  102  moves in an extending direction of the rail member  31  (indicated by arrow A 2 ). The carrier  23  has an electric actuator (not shown). The controller  107  controls the motion of the carrier  23 . 
     The wire  21  is wound and suspended by the winding device  22 . The hook  20  is suspended from a lowermost portion of the wire  21  through a pulley  20 A. 
     A coupling member (in this case, a wire)  20 B is coupled with the workpiece W in advance, and the hook  20  catches the coupling member  20 B. Thus, the hook  20  suspends the workpiece W and hence can support the workpiece W against the gravity. 
     The winding device  22  includes a servomotor. When the servomotor is driven, the winding device  22  winds or rewinds the wire  21  to drive the hook  20  in a vertical direction. 
     The servomotor of the winding device  22  and the controller  107  are connected with one another and communicate with one another. Rotation position information (a position signal) of the servomotor is input to an input terminal (a crane signal input section) of the controller  107 . The controller  107  transmits a driving signal to the servomotor. 
     (Manipulator Unit) 
     The robot  101  includes a pedestal  1  that is fixed to a floor by anchor bolts (not shown), and a rotary body  2  mounted on the pedestal  1  and being rotatable within a vertical plane. 
     The rotary body  2  has a pair of arms including a right arm (an arm)  3 R and a left arm (an arm)  3 L. 
     The right arm  3 R and the left arm  3 L have a configuration similar to one another except that the arms  3 R and  3 L are left-right symmetric. Each of the arms  3 R and  3 L is a seven-degree-of-freedom vertical articulated manipulator. Each of the arms  3 R and  3 L has movable portions. Each of the portions contains a servomotor. Driving of the servomotor is controlled in response to a signal from the controller  107 . 
     In particular, each of the right arm  3 R and the left arm  3 L includes a shoulder  4  that is rotatable along a horizontal plane (a plane parallel to the floor). An upper arm A-section  5  is swingably provided at the shoulder  4 . An upper arm B-section  6  is provided at a distal end of the upper arm A-section  5 . The upper arm B-section  6  provides a twisting motion around the upper arm A-section  5 . 
     In addition, a lower arm  7  is swingably provided at a distal end of the upper arm B-section  6 . A wrist A-section  8  is provided at a distal end of the lower arm  7 . A wrist B-section  9  is provided at a distal end of the wrist A-section  8 . 
     The wrist A-section  8  provides a twisting motion around the lower arm  7 . The wrist B-section  9  provides a rotating motion for a bending motion. 
     A flange  10  is provided at a distal end of the wrist B-section  9 . A hand unit  11  is attached to the flange  10 . When a servomotor for moving the flange  10  is driven, the hand unit  11  is rotated, and is stopped (positioned) at a position instructed by the controller  107 . 
     The hand unit  11  includes a pair of finger members that are advanced to and retracted from one another to grip an object. The advancing and retracting motion of the finger members is performed by a servomotor and controlled by the controller  107 . 
     The storage device in the controller  107  stores a work procedure in advance, and operates the robot  101 , the hoist  102 , and the crane rail  103  in accordance with the stored work procedure. 
     The controller  107  also stores a threshold T of a disturbance load (a torque) exerted on the servomotors in the robot  101 . If an external load higher than the threshold T is exerted on the servomotors, the controller  107  allows the servomotor to rotate in a direction in which the load is exerted (torque controller). 
     The transfer system according to this embodiment has the configuration as described above, and operates as follows. 
     Referring to  FIG. 3 , in step S 10 , if start of work is input from an input device of the controller  107 , the controller  107  reads a stored work procedure. 
     In step S 20 , the carriers  23  and  33  are operated, and the hook  20  is moved to a position above an end portion of the carry-in belt  104 . Also, the right arm  3 R and the left arm  3 L of the robot  101  are moved toward the carry-in belt  104 . 
     In step S 30 , the arms  3 R and  3 L are operated, so that each hand unit  11  grips the coupling member  20 B which has been fixed to the workpiece W and the hook  20  catches the workpiece W. 
     Steps S 10  to S 30  define means for causing the hoist  102  to support the workpiece W at a first position. 
     When the coupling member  20 B is caught, in step S 40 , the winding device  22  is operated, and the hook  20  is moved upward. Accordingly, the workpiece W is suspended by the wire  21 . 
     In step S 50 , the hand unit  11  of the right arm  3 R grips (holds) the hook  20 . In step S 60 , the hand unit  11  of the left arm  3 L grips (holds) a predetermined position of the workpiece W (a portion of the workpiece W deviated from the center of gravity). 
     If step S 60  is executed, in step S 70 , the carriers  23  and  33  and the robot  101  are operated, and the workpiece W is moved to a position above one of the first carry-out belt  105  and the second carry-out belt  106 . 
     In this embodiment, the workpieces W are moved alternately to the first carry-out belt  105  and the second carry-out belt  106  in that order. However, the transfer destination of the workpieces W may be determined whether the first carry-out belt  105  or the second carry-out belt  106  depending on a processing state of the next process or the type of the workpieces W. 
     In step S 80 , the winding device  22  is operated to rewind the wire  21  (extends the wire  21 ), and the supported workpiece W is moved downward. Thus, the workpiece W is placed on the first carry-out belt  105  or the second carry-out belt  106 . 
     When the workpiece W is placed, in step S 90 , the arms  3 R and  3 L release the coupling member  20 B from the hook  20 . The processing is repeated from step S 10 . 
     Steps S 50  to S 80  define means for causing the robot  101  to move the hoist  102  and to place the supported workpiece W at the second position. 
     With the transfer system according to this embodiment, when a workpiece W with a large weight is transferred from the carry-in belt  104  to the first carry-out belt  105  or the second carry-out belt  106 , the robot  101  allows the workpiece W to be caught by the hook  20  of the hoist  102  and to be suspended and supported. Thus, a workpiece W with a large weight can be reliably supported although a robot  101  with a small weight capacity is used. 
     The controller  107  controls the motions of the robot  101 , the winding device  22 , and the carriers  23  and  33 . Thus, the workpiece W that is supported along the rail member  31  and the rail members  32  can be moved in the horizontal direction. 
     The system can be constructed in corporation with the robot  101  merely by connecting the controller  107  with the servomotors and the electric actuators of the hoist  102  and the crane rail  103 , which already exist in a factory or the like. When the equipment is introduced, large equipment such as a crane need not be newly installed. The installation space can be saved. In addition, the cost for introducing the system can be saved. 
     The right arm  3 R holds the hook  20 , and then the left arm  3 L holds the workpiece W while the right arm  3 R holds the hook  20 . Thus, the workpiece W can be reliably held although the workpiece W is in a free (unstable) state in which the workpiece W is suspended by the wire  21 . 
     The right arm  3 R holds the hook  20  at the position corresponding to the center of gravity of the workpiece W, and the left arm  3 L holds the workpiece W at the position deviated from the center of gravity. Thus, the workpiece W can be transferred in a desirable posture while rotation of the wire  21  in a twisting direction is restricted. 
     Second Embodiment 
     A second embodiment will be described. Components not particularly described in this embodiment are similar to those according to the first embodiment. The same reference signs are applied to those components in the following description. 
     In this embodiment, a robot (a manipulator)  201  is a single-arm manipulator. 
     The robot  201  includes a pedestal  202 , a first member  203  rotatably coupled with the pedestal  202 , a second member  204  rotatably coupled with the first member  203 , and a third member  205  rotatably coupled with the second member  204 . 
     The respective rotary portions include servomotors. A controller  107  controls the motions of the servomotors. Similar to the first embodiment, the controller  107  also stores a threshold T of a disturbance load (a torque) exerted on the servomotors. If an external load higher than the threshold T is exerted on the servomotors, the controller  107  allows the servomotors to rotate in a direction in which the load is exerted (torque controller). 
     A hand unit  41  is coupled with a distal end of the third member  205 . An air cylinder  42  is attached to the hand unit  41 . The air cylinder  42  includes a rod member (not shown) that can protrude and be retracted. 
     The hand unit  41  is coupled with a pulley  20 A through a coupling member  20 B. The hand unit  41  is continuously suspended and supported by the hoist  102 . 
     In this embodiment, carriers  23  and  33  of the hoist  102  and a crane rail  103  do not include an actuator. The carriers  23  and  33  include driven wheels (not shown) that allow the carriers  23  and  33  to travel along the rail members  31  and  32 . 
     The transfer system according to this embodiment is thus configured. The controller  107  operates the robot  201  to move the hand unit  41  to a position above a carry-in belt  104 . At this time, the carrier  23  of the hoist  102 , and the carriers  33  of the crane rail  103  are moved to follow the motion of the robot  201 . 
     Then, when the winding device  22  is driven, the wire  21  is rewound, and the hand unit  41  is lowered to a position near the workpiece W. A rod member of an air cylinder  42  is inserted into a predetermined fitting hole of a workpiece W. The hand unit  41  holds the workpiece W. 
     When the workpiece W is held, the winding device  22  suspends and moves the hand unit  41  upward, and the workpiece W is suspended by the wire  21  through the hand unit  41 . 
     Then, the robot  201  is operated, and the hand unit  41  is moved to a position above a first carry-out belt  105  or a second carry-out belt  106 . At this time, the carrier  23  of the hoist  102 , and the carriers  33  of the crane rail  103  are moved to follow the motion of the robot  201 . 
     The winding device  22  is operated and the wire  21  is rewound. The supported workpiece W is moved downward and is placed on the first carry-out belt  105  or the second carry-out belt  106 . 
     When the workpiece W is placed, the air cylinder  42  is operated, the rod member is detached from the workpiece W, and the holding of the workpiece W with the hand unit  41  is released. 
     As described above, with the transfer system according to this embodiment, a workpiece W with a relatively large weight can be automatically transferred by using a manipulator with a simple structure as the robot  201 . In addition, since the hoist  102  continuously suspends the hand unit  41 , the hoist  102  can support the workpiece W merely by holding the workpiece W with the rod member or the like of the hand unit  41 . The motion for holding and releasing the workpiece W can be smoothly performed. Thus, working efficiency can be increased. 
     When the rod member is inserted into the fitting hole in the workpiece W, the hand unit  41  has to be positioned with high accuracy. However, the servomotors of the robot  201  may be rotated in a direction in which a load (an external force) is exerted. Thus, even if an error occurs in the positions or directions between the fitting hole and the rod member, the error is absorbed. The hand unit  41  can accurately hold the workpiece W. 
     The embodiments have been described. However, the transfer system according to the embodiments of the present invention is not limited to the embodiments, and may be appropriately modified within the scope of the present invention. 
     For example, in the above embodiments, each of the crane unit and the crane moving mechanism includes the rail members supported at the ceiling. The crane unit and the crane moving mechanism are not limited to the configurations described in the embodiments, and any configuration may be applied as long as the workpiece W is suspended and supported, and the supported workpiece W can be moved in the horizontal direction. 
     Also, similar to the first embodiment, a common hand unit may be attached to a manipulator having a pair of arms, and the hand unit may be continuously suspended and supported by a crane unit. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.