Patent Publication Number: US-2018043539-A1

Title: Robot, method of controlling the robot, and method of assembling workpiece, and method of conveying workpiece

Description:
TECHNICAL FIELD 
     The present disclosure relates to a robot, a method of controlling the robot, a method of assembling a workpiece, and a method of conveying the workpiece. 
     BACKGROUND ART 
     Conventionally, work assisting systems which assist works in a factory production line have been known (e.g., see Patent Document 1). 
     The work assisting systems include an industrial robot having a holding part which holds a component, a motion capture device which measures and transmits a manual work operation by a worker sequentially with time, a pressure sensor which detects and transmits a pressure applied to the worker&#39;s fingertip(s), a controller which controls the industrial robot based on data transmitted from the motion capture device and the pressure sensor. Thus, the controller controls the industrial robot with a similar work operation to the worker&#39;s manual work operation based on the data transmitted from the motion capture and the pressure sensor. Thereby, the component is movable to a component assembling position with substantial accuracy. 
     REFERENCE DOCUMENT OF CONVENTIONAL ART 
     Patent Document 
     [Patent Document 1] JP2011-156641A 
     DISCLOSURE 
     Problems to be Solved by the Disclosure 
     However, the work assisting system disclosed in Patent Document 1 has a problem that the worker needs to go to the place where the component is placed. 
     SUMMARY OF THE DISCLOSURE 
     According to one aspect of the present disclosure, a robot is provided, which includes a hand configured to hold a workpiece, a floating unit having a tip-end part and a base-end part and having a joint configured to operate within a given operating range, the hand being attached to the tip-end part, and the tip-end part being relatively movable with respect to the base-end part, a robot arm of which a tip-end part is attached to the base-end part of the floating unit and configured to move the hand and the floating unit, and a control device having a robot arm controller configured to control operation of the robot arm. The robot arm controller moves the hand and the floating unit so that the hand is located at a temporary target position. The temporary target position is a position from which the hand is movable to a target position by relatively moving the tip-end part of the floating unit with respect to the base-end part thereof, the tip-end part located at the temporary target position. 
     According to this configuration, since the hand can be located at the temporary target position near the target position by the robot alone, the burden on a worker can be reduced. 
     In addition, since the worker can operate the floating unit to move the hand from the temporary target position to the target position, the hand can be located at the target position even if the target position varies. 
     The floating unit may have a plurality of joints configured to operate within the given operating range, and the tip-end part may be relatively movable with respect to the base-end part with two or more degrees of freedom. 
     According to this configuration, the worker can manually move the hand located at the temporary target position in the direction of at least one degree-of-freedom to explore the target position, and the worker can manually move the hand in the direction of another degree-of-freedom so that the hand is located at the target position. Therefore, after the worker tunes finely the position of the hand which requires experience and sense of a worker, the hand can be located at the target position. 
     The robot may further include a fixing mechanism configured to regulate operation of the joint by being active and permit the operation of the joint by being inactive. The control device may have a fixing mechanism controller configured to control operation of the fixing mechanism. The fixing mechanism controller may activate the fixing mechanism when the robot arm controller moves the hand and the floating unit so that the hand is located at the temporary target position. 
     According to this configuration, the movement of the tip-end part of the floating unit can be prevented while the floating unit is moved by the robot arm. 
     The fixing mechanism may move the tip-end part of the floating unit by being active so that the floating unit takes a given posture, and maintain the given posture. 
     According to this configuration, an accurate positioning of the hand can be achieved. 
     The floating unit may include a limit position arrival detecting part configured to detect that the joint reaches a limit position of a given section within the given operating range. The fixing mechanism controller may deactivate the fixing mechanism after the robot arm controller moves the hand to the temporary target position, and in a state where the fixing mechanism is deactivated, when the limit position arrival detecting part detects that the joint reaches the limit position of the movable range, the robot arm controller may move the base-end part of the floating unit in a moving direction of the tip-end part of the floating unit by a given distance. 
     According to this configuration, the tip-end part of the floating unit can be moved outside the moving range of the tip-end part of the floating unit at the time of moving the hand so that the hand is located at the temporary target position. 
     The workpiece may be a component assembled to a product. The target position may be a position at which the component is located in a state where the component is assembled to the product. 
     According to this configuration, the robot can be applied to a production line of assembling products. 
     The joint of the floating unit may have a degree of freedom in the gravity direction. The floating unit may have a balancer configured to exert a force in the joint in a direction opposite from a force exerted in the joint by gravity. 
     According to this configuration, the hand and the workpiece held by the hand can easily be raised and lowered. 
     According to one aspect of the present disclosure, a method of controlling a robot is provided. The robot includes a hand configured to hold a workpiece, a floating unit having a tip-end part and a base-end part and having a joint configured to operate within a given operating range, the hand being attached to the tip-end part, and a tip-end part being relatively movable with respect to the base-end part, a robot arm of which a tip-end part is attached to the base-end part of the floating unit and configured to move the hand and the floating unit, and a control device having a robot arm controller configured to control operation of the robot arm. The robot arm controller moves the hand and the floating unit so that the hand is located at a temporary target position. The temporary target position is a position from which the hand is movable to a target position by relatively moving the tip-end part of the floating unit with respect to the base-end part thereof, the tip-end part located at the temporary target position. 
     According to this configuration, since the hand can be located at the temporary target position near the target position by the robot alone, the worker&#39;s burden can be reduced. 
     In addition, since the worker can operate the floating unit to move the hand from the temporary target position to the target position, the hand can be located at the target position even if the target position varies. 
     The floating unit may have a plurality of joints configured to operate within the given operating range, and the tip-end part may be relatively movable with respect to the base-end part with two or more degrees of freedom. 
     According to this configuration, the worker can manually move the hand located at the temporary target position in the direction of at least one degree-of-freedom to explore the target position, and the worker can manually move the hand in the direction of another degree-of-freedom so that the hand is located at the target position. Therefore, after the worker tunes finely the position of the hand which requires experience and sense of a worker, the hand can be located at the target position. 
     The robot may further include a fixing mechanism configured to regulate operation of the joint by being active and permit operation of the joint by being inactive. The control device may have a fixing mechanism controller configured to control operation of the fixing mechanism. The fixing mechanism controller may activate the fixing mechanism when the robot arm controller moves the hand and the floating unit so that the hand is located at the temporary target position. 
     According to this configuration, the movement of the tip-end part of the floating unit can be prevented while the floating unit is moved by the robot arm. 
     The fixing mechanism may move the tip-end part of the floating unit by being active so that the floating unit takes a given posture, and maintain the given posture. 
     According to this configuration, the accurate positioning of the hand can be achieved. 
     The floating unit may include a limit position arrival detecting part configured to detect that the joint reaches a limit position of a given section within the given operating range. The fixing mechanism controller may deactivate the fixing mechanism after the robot arm controller moves the hand to the temporary target position, and in a state where the fixing mechanism is deactivated, when the limit position arrival detecting part detects that the joint reaches the limit position of the movable range, the robot arm controller may move the base-end part of the floating unit in a moving direction of the tip-end part of the floating unit by a given distance. 
     According to this configuration, the tip-end part of the floating unit can be moved outside the moving range of the tip-end part of the floating unit at the time of moving the hand so as to locate at the temporary target position. 
     The workpiece may be a component assembled to a product. The target position may be a position at which the component is located in a state where the component is assembled to the product. 
     According to this configuration, the robot can be applied to the production line of assembling products. 
     The joint of the floating unit may have a degree of freedom in the gravity direction, and the floating unit may have a balancer configured to exert a force in the joint in a direction opposite from a force exerted in the joint by gravity. 
     According to this configuration, the hand and the workpiece held by the hand can easily be raised and lowered. 
     According to one aspect of the present disclosure, a method of assembling a workpiece to an assembling object by using a robot is provided. The robot includes a hand configured to hold a workpiece, a floating unit having a tip-end part and a base-end part and having a joint configured to operate within a given operating range, the hand being attached to the tip-end part, and the tip-end part being relatively movable with respect to the base-end part, a robot arm of which a tip-end part is attached to the base-end part of the floating unit and configured to move the hand and the floating unit, and a control device having a robot arm controller configured to control the robot arm. The robot arm controller moves the hand and the floating unit so that the hand is located at a temporary target position. By a worker relatively moving the tip-end part of the floating unit with respect to the base-end part, the workpiece held by the hand located at the temporary target position is moved to a destination of the workpiece and is assembled to the assembling object. 
     According to this configuration, since the hand can be located at the temporary target position near the target position by the robot alone, the worker&#39;s burden can be reduced. 
     In addition, since the worker can operate the floating unit to move the hand from the temporary target position to the target position, the hand can be located at the target position even if the target position varies. 
     According to one aspect of the present disclosure, a method of conveying a workpiece located at a given position by using a robot is provided. The robot includes a hand configured to hold a workpiece, a floating unit having a tip-end part and a base-end part and having a joint configured to operate within a given operating range, the hand being attached to the tip-end part, and the tip-end part being relatively movable with respect to the base-end part, a robot arm of which a tip-end part is attached to the base-end part of the floating unit and configured to move the hand and the floating unit, and a control device having a robot arm controller configured to control the robot arm. The robot arm controller moves the hand and the floating unit so that the hand is located at a temporary target position. A worker relatively moves the tip-end part of the floating unit with respect to the base-end part to move the hand located at the temporary target position to the given position, and causes the hand to hold the workpiece. The robot arm controller moves the hand and the floating unit to convey the workpiece held by the hand. 
     According to this configuration, since the hand can be located at the temporary target position near the target position by the robot alone, the worker&#39;s burden can be reduced. 
     In addition, since the worker can operate the floating unit to move the hand from the temporary target position to the target position, the hand can be located at the target position even if the target position varies. 
     Effects of the Disclosure 
     The present disclosure is capable of achieving an effect of reducing the worker&#39;s burden, and moving the hand to a target position even if the target position varies. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating one example of a structure of a robot according to Embodiment 1 of the present disclosure. 
         FIG. 2  is a perspective view illustrating one example of a structure of a floating unit of the robot of  FIG. 1 . 
         FIG. 3  is a view schematically illustrating one example of the structure of the floating unit of the robot of  FIG. 1 . 
         FIG. 4  is a view schematically illustrating one example of a structure of a fixing mechanism of the robot of  FIG. 1 . 
         FIG. 5  is a block diagram schematically illustrating one example of a structure of a control system of the robot of  FIG. 1 . 
         FIG. 6  is a flowchart illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 7A  is a view illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 7B  is a view illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 7C  is a view illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 7D  is a view illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 7E  is a view illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 8  is a perspective view illustrating one example of a structure of a floating unit of a robot according to Embodiment 2 of the present disclosure. 
         FIG. 9  is a view schematically illustrating one example of the structure of the floating unit of the robot of  FIG. 8 . 
         FIG. 10  is a block diagram schematically illustrating one example of a structure of a control system of the robot of  FIG. 8 . 
         FIG. 11  is a flowchart illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 12  is a view illustrating one example of operation of the robot of  FIG. 1 . 
         FIG. 13  is a flowchart illustrating one example of operation of a robot according to Embodiment 3 of the present disclosure. 
     
    
    
     MODES FOR CARRYING OUT THE DISCLOSURE 
     Aim of Present Disclosure 
     The present inventors have diligently examined an increase in efficiency of assembling a weighted component which is difficult for a worker to hold in a factory production line. 
     Conventionally, the work in which a weighted component placed in a component yard is carried to a position by the side of a product in a production line, and assembly of the weighted component to the product are performed, for example, according to the following procedure. 
     First, the worker moves a lifter into the component yard, and then ties the weighted component placed in the component yard with the lifter. The worker then operates the lifter to carry the weighted component from the component yard to the position by the side of the product in the production line. Next, the worker fits and assembles the component to the product. 
     Here, in the assembling of the component to the product in the production line, the worker may assemble the component to the product, after he/she grips and swings the component supported by the lifter to explore a fitting position of the component for a fine adjustment of the component position with respect to the product. Such a work is difficult for the conventional robot to perform because worker&#39;s experiences and senses influence the quality of work. 
     Thus, the present inventors have conceived of a robot, which includes a hand configured to hold a workpiece, a floating unit having a tip-end part and a base-end part. The hand is attached to the tip-end part. The floating unit includes a joint configured to operate within a given operating range and the tip-end part is capable of relatively moving with respect to the base-end part. The robot also includes a robot arm of which a tip-end part is attached to the base-end part of the floating unit, and is configured to move the hand and the floating unit, and a controlling device provided with a robot arm controller configured to control operation of the robot arm. The robot arm controller is configured to move the hand and the floating unit so that the hand is located at a temporary target position. The temporary target position is a position from which the tip-end part of the floating unit located at the temporary target position is relatively movable with respect to the base-end part in order to move the hand to a target position. 
     According to the present disclosure, since the hand can be located at the temporary target position near the target position by the robot alone, the worker&#39;s burden is reduced. 
     In addition, since the worker can operate the floating unit to move the hand from the temporary target position to the target position, the hand can be located at the target position even if the target position varies. 
     Hereinafter, embodiments of the present disclosure are described with reference to the accompanying drawings. Note that the present disclosure is not limited by the embodiments. Below, the same reference characters are assigned to the same or corresponding elements throughout the drawings to omit redundant description. 
     Embodiment 1 
       FIG. 1  is a view illustrating one example of a structure of a robot  100  according to Embodiment 1 of the present disclosure. 
     As illustrated in  FIG. 1 , the robot  100  is installed, for example, in a work place where a component C (workpiece) is assembled to a product T (e.g., a production line). That is, the component C is a member to be assembled to the product T (an assembling object). 
     In this production line, a pre-assemble storage area Pa of workpiece and an assembling area Pb are set (arranged) within an operating area of a hand  1  (described later) of the robot  100 . 
     The pre-assemble storage area Pa is a place where the component C to be assembled to the product T is kept temporarily. In the pre-assemble storage area Pa, the components C are precisely arranged at given positions by being held on a shelf (not illustrated), and the positions of the components C held on the shelf are stored beforehand in a controller  60  of a control device  6  (described later). 
     The assembling area Pb is a place where the component C is assembled to the product T. The product T is placed on the assembling area Pb. In a state where the component C is assembled to the product T placed on the assembling area Pb, a position at which the hand  1  and the component C held by the hand  1  are located constitutes a target position P 2  (see  FIG. 7E ). A temporary target position P 1  (see  FIG. 7B ) is set at a position from which the component C held by the hand  1  is movable to a target position P 2  which is a destination of the component C by relatively moving a tip-end part  2   a  (a hand attaching part  21  described later) of a floating unit  2  with respect to a base-end part  2   b  (a robot-arm attaching part  26  described later). That is, the temporary target position P 1  is set near the target position P 2  so that it is set at the position from which the hand  1  (and the component C held by the hand  1 ) is movable to the target position P 2  by relatively moving the tip-end part  2   a  of the floating unit  2  located at the temporary target position P 1  to the base-end part  2   b.    
     Entire Structure of Robot 
     As illustrated in  FIG. 1 , the robot  100  includes the hand  1  which holds the workpiece, the floating unit  2 , a robot body  3 , and the control device  6  (see  FIG. 5 ). 
     Hand 
     The hand  1  is configured to perform a holding operation in which it holds the component C, and a releasing operation in which it releases the held object. The hand  1  is attached to the tip-end part  2   a  of the floating unit  2 . 
     In this embodiment, the hand  1  is a device which adsorbs and holds the component C, and has an adsorption holding mechanism (not illustrated) which adsorbs and holds the component C and disables the adsorption holding of the component C by disabling the adsorption holding. The hand  1  includes handles  11  (see  FIG. 2 ) which the worker grips and moves the hand  1 , a first hand controller  12  (see  FIG. 5 ), and hand operating parts  13  (see  FIGS. 2 and 5 ). The first hand controller  12  controls the hand  1  so that it operates the hand  1  to perform the holding operation in which the hand  1  holds the component C and the releasing operation in which the hand  1  releases the component C. The hand operating parts  13  are configured to accept inputs of a holding instruction of the component C and a releasing instruction of the component C to the first hand controller  12 , respectively. 
     Robot Body 
     As illustrated in  FIG. 2 , the robot body  3  is, for example, an articulated industrial robot but it is not limited to this structure. The robot body  3  includes a robot base  31  and a robot arm  32 . 
     The robot base  31  is a pedestal which is placed on a placement surface such as a floor surface of the production line in a state where it is not fixed to the placement surface, and it supports the robot arm  32 , the floating unit  2 , and the hand  1 . 
     The robot arm  32  moves the floating unit  2  and the hand  1 . The robot arm  32  is provided with, for example, a plurality of joints so that a base-end part  32   a  is rotatably coupled to the robot base  31 . A tip-end part  32   b  of the robot arm  32  is attached to the base-end part  2   b  (the robot-arm attaching part  26  described later) of the floating unit  2 . The robot arm  32  includes a robot arm actuator (not illustrated) which drives a plurality of joint axes. 
     Floating Unit 
       FIG. 2  is a perspective view illustrating one example of a structure of the floating unit  2 .  FIG. 3  is a view schematically illustrating one example of the structure of the floating unit  2 . 
     As illustrated in  FIGS. 2 and 3 , the hand  1  is attached to the tip-end part of the floating unit  2 . The floating unit  2  has joints which operate within a given operating range, and the tip-end part thereof is configured to be relatively movable with respect to the base-end part. 
     In this embodiment, as illustrated in  FIG. 3 , the floating unit  2  has the plurality of joints which operate within the given operating range, and the tip-end part  2   a  thereof is relatively movable with two or more degrees of freedom with respect to the base-end part  2   b . The floating unit  2  includes, for example, the hand attaching part  21 , a first joint part  22 , a second joint part  23 , a third joint part  24 , a fourth joint part  25 , the robot-arm attaching part  26 , and first to fifth coupling pieces  41 ,  42 ,  43 ,  44  and  45  which sequentially couple these parts from the hand  1  to the robot arm  32  in a single-file manner. The floating unit  2  also includes a fixing mechanism  27 . 
     The hand attaching part  21  is a part to which the hand  1  is attached. 
     The first joint part  22  couples the first coupling piece  41  with the second coupling piece  42  rotatably about an axis extending in first directions D 1 . The first directions D 1  are, for example, vertical directions. The first coupling piece  41  is configured so as to be rotatable with respect to the second coupling piece  42  within a given operating range R 1 . That is, the first coupling piece  41  is coupled to the second coupling piece  42  via the first joint part  22  having a degree of freedom about the axis extending in the first directions D 1 . 
     The second joint part  23  couples the second coupling piece  42  to the third coupling piece  43  translatably in second directions D 2  which intersect the first directions D 1 . The second directions D 2  are directions which intersect, for example, perpendicularly with the first directions D 1  (i.e., horizontal directions). The second coupling piece  42  is configured so as to be translatable with respect to the third coupling piece  43  within a given operating range R 2 . That is, the second coupling piece  42  is coupled to the third coupling piece  43  via the second joint part  23  having a degree of freedom in the second directions D 2 . 
     The third joint part  24  couples the third coupling piece  43  to the fourth coupling piece  44  pivotably in the first directions D 1 . The third coupling piece  43  is configured so as to be pivotable with respect to the fourth coupling piece  44  within a given operating range R 3 . That is, the third coupling piece  43  is coupled to the fourth coupling piece  44  via the third joint part  24  having a degree of freedom in the first directions D 1  (parallel to the gravity direction). 
     In this embodiment, the third joint part  24  has a parallel link structure, and includes a pair of pivot links  24   a  extending parallel with each other, a tip-end side coupling part  24   b  which couples one ends of the pair of pivot links  24   a , and a base-end side coupling part  24   c  which couples the other ends of the pair of pivot links  24   a  and extends parallel with the tip-end side coupling part  24   b . One of the pair of pivot links  24   a  is coupled to the tip-end side coupling part  24   b , the other pivot link  24   a  is coupled to the tip-end side coupling part  24   b , one of the pair of pivot links  24   a  is coupled to the base-end side coupling part  24   c , and the other pivot link  24   a  is coupled to the base-end side coupling part  24   c , rotatably about axes extending in third directions D 3  (parallel to an outward direction perpendicular to the drawing surface of  FIG. 3 ; see  FIG. 2 ) which intersect both the first directions D 1  and the second directions D 2  and, thus, the axes constitute first to fourth joints  24   f ,  24   g ,  24   h  and  24   i , respectively. Therefore, when the tip-end part of the third joint part  24  is pivoted, the tip-end side coupling part  24   b  and the base-end side coupling part  24   c  are configured to be always pivotable while maintaining the distance therebetween and their postures. 
     The third coupling piece  43  is coupled to the tip-end side coupling part  24   b , and the fourth coupling piece  44  is coupled to the base-end side coupling part  24   c . Therefore, by pivoting the third joint part  24 , the hand  1  coupled to the tip-end part of the third joint part  24 , the hand attaching part  21 , the first coupling piece  41 , the first joint part  22 , the second coupling piece  42 , the second joint part  23 , and the third coupling piece  43  are relatively raised and lowered with respect to the fourth coupling piece  44  coupled to the base-end part of the third joint part  24 , the fourth joint part  25 , a fifth coupling piece  45 , and the robot-arm attaching part  26 . 
     The third joint part  24  is provided with a balancer mechanism  29 . The balancer mechanism  29  exerts on the third joint part  24  a force in a direction opposite from a force caused in the third joint part  24  by gravity. The balancer mechanism  29  generates, for example, a torque resisting a torque which is generated in the third joint part  24  by gravity acting on components etc. (e.g., the component C, the hand  1 , the hand attaching part  21 , the first coupling piece  41 , the first joint part  22 , the second coupling piece  42 , the second joint part  23 , and the third coupling piece  43 ) coupled to the tip-end part of the third joint part  24 . Therefore, the worker can easily raise and lower the component C relatively to the tip-end part  32   b  of the robot arm  32 . 
     The fourth joint part  25  couples the fourth coupling piece  44  to the fifth coupling piece  45  rotatably about an axis extending in the first directions D 1 . The fourth coupling piece  44  is configured to be rotatable with respect to the fifth coupling piece  45  within a given operating range R 4 . That is, the fourth coupling piece  44  is coupled to the fifth coupling piece  45  via the fourth joint part  25  having a degree of freedom about the axis extending in the first directions D 1 . 
     The robot-arm attaching part  26  is a part to which the tip-end part  32   b  of the robot arm  32  is attached. 
     Thus, since both the first joint part  22  and the fourth joint part  25  have a degree of freedom about the axis extending in the first directions D 1 , respectively, the floating unit  2  has degrees of freedom in the first directions D 1  and the second directions D 2 . Therefore, the tip-end part  2   a  of the floating unit  2  is relatively movable in the first directions D 1  and the second directions D 2  with respect to the base-end part  2   b.    
     Moreover, since the second joint part  23  has a degree of freedom in the second directions D 2 , it can relatively move the tip-end part  2   a  of the floating unit  2  more smoothly in the second directions D 2  with respect to the base-end part  2   b.    
     Furthermore, since the third joint part  24  has a degree of freedom in the first directions D 1  (parallel in the gravity direction), the tip-end part  2   a  of the floating unit  2  can be raised and lowered in the first directions D 1  relatively with respect to the base-end part  2   b.    
       FIG. 4  is a view schematically illustrating one example of a structure of the fixing mechanism  27 . 
     The fixing mechanism  27  is a mechanism which regulates operations of the joints of the floating unit  2  by being active, and permits the operations of the joints of the floating unit  2  by being inactive. That is, the fixing mechanism  27  regulates, by being active, the operations of the first to fourth joint parts  22 ,  23 ,  24  and  25  of the floating unit  2  to regulate the relative movement of the tip-end part  2   a  of the floating unit  2  with respect to the base-end part  2   b . The fixing mechanism  27  regulates, by being inactive, the operations of the first to fourth joint parts  22 ,  23 ,  24  and  25  of the floating unit  2  to permit the relative movement of the tip-end part  2   a  of the floating unit  2  with respect to the base-end part  2   b.    
     Moreover, the fixing mechanism  27  is a mechanism which relatively moves the tip-end part  2   a  of the floating unit  2  with respect to the base-end part thereof, by being active, so that the floating unit  2  takes and maintains a given posture. Therefore, in a state where the fixing mechanism  27  is activated, since a spatial relationship between the tip-end part  32   b  of the robot arm  32  and the hand  1  is fixed to a given spatial relationship, a robot arm controller  63  can identify the position of the hand  1 . The temporary target position P 1  is set to the position from which the hand is movable to the target position by disabling the fixing mechanism  27  of the floating unit  2  located at the temporary target position P 1  in the state where the fixing mechanism  27  is activated, and relatively moving the tip-end part  2   a  of the floating unit  2  with respect to the base-end part  2   b.    
     In this embodiment, the fixing mechanism  27  includes first to fourth fixing parts  71 - 74  (see  FIG. 4  for the first fixing part  71  and the fourth fixing part  74 ) corresponding to the first to fourth joint parts  22 ,  23 ,  24  and  25 . The first to fourth fixing parts  71 - 74  regulate, by being active, the operations of the corresponding joints after moving the joints to the given positions within the given operating range, and permit, by being inactive, the operations of the corresponding joint, respectively. 
     That is, the first coupling piece  41  is fixed at the given position within the given operating range R 1  with respect to the second coupling piece  42  by the first fixing part  71  becoming active. For example, as illustrated in  FIG. 4 , the first fixing part  71  has an arm  76  of which a base-end part is attached to the first coupling piece  41  and which extends in a direction perpendicular to the extending direction of the rotational axis of the first joint part  22 , and an arm pinching part  77  which is attached to the second coupling piece  42  and is configured to be openable and closable. Therefore, the arm  76  is pivoted by rotating the first joint part  22 . The arm pinching part  77  is configured to pinch the tip-end part of the arm  76  by closing in order to regulate the pivoting of the arm  76 . Thus, the first coupling piece  41  is regulated its operation with respect to the second coupling piece  42  after the first coupling piece  41  is located at the given position within the given operating range R 1 . 
     Moreover, the second coupling piece  42  is fixed, by the second fixing part  72  being active, at the given position within the given operating range R 2  with respect to the third coupling piece  43 . The second fixing part  72  is provided with an air cylinder mechanism  78  which relatively translates, by being active, a piston rod with respect to a cylinder. When the second coupling piece  42  is to be fixed to the third coupling piece  43 , the piston rod of the air cylinder mechanism  78  is moved to translate the second coupling piece  42  in one of the first directions D 1  with respect to the third coupling piece  43 , locate the second coupling piece  42  at one of limit positions of the operating range R 2 , and bias the second coupling piece  42  in a direction toward the one of the limit positions from the other limit position. Thereby, the second coupling piece  42  is regulated its operation with respect to the third coupling piece  43  after the second coupling piece  42  is located at the given position within the given operating range R 2 . 
     Furthermore, the third coupling piece  43  is regulated its operation with respect to the fourth coupling piece  44  after the third coupling piece  43  is located at the given position within the given operating range R 3 , by the third fixing part  73  being active. Since the structure of the third fixing part  73  is similar to the structure of the second fixing part  72 , detailed description thereof is omitted. 
     Moreover, the fourth coupling piece  44  is regulated its operation with respect to the fifth coupling piece  45 , at the given position within the given operating range R 4 , by the fourth fixing part  74  being active. Since the structure of the fourth fixing part  74  is similar to the structure of the first fixing part  71 , detailed description thereof is omitted. 
     Control Device 
       FIG. 5  is a block diagram schematically illustrating one example of a structure of a control system of the robot  100 . 
     As illustrated in  FIG. 5 , the control device  6  of the robot  100  includes the controller  60  and a memory part  61 , and, for example, is comprised of a micro controller, a CPU, an MPU, a logic circuit, a PLC, etc. The control device may be comprised of a single control device which performs a centralized control, or may be comprised of a plurality of control devices which perform a distributed control. 
     The memory part  61  includes a memory, such as a ROM and/or a RAM. The memory part  61  stores information for identifying the position of the component C placed in the pre-assemble storage area Pa, and information for identifying the temporary target position P 1 , and information for identifying the position of the hand  1  in a state where a spatial relationship between the tip end of the robot arm  32  and the hand  1  is fixed to a given spatial relationship by the fixing mechanism  27 . 
     The controller  60  includes a fixing mechanism controller  62 , the robot arm controller  63 , and a second hand controller  64 . The fixing mechanism controller  62 , the robot arm controller  63 , and the second hand controller  64  are functional blocks which are implemented by a computing unit executing a given control program stored in the memory part  61 . The robot arm controller  63  controls the robot arm  32 . The second hand controller  64  controls the operation of the hand  1  to operate the hand  1  so that the hand  1  performs the holding operation and the releasing operation. The second hand controller  64  may control the hand  1  via the first hand controller  12 . The fixing mechanism controller  62  controls the fixing mechanism  27 . 
     Example of Operation 
     Next, one example of operation of the robot  100  is described. 
       FIG. 6  is a flowchart illustrating the example of the operation of the robot  100 .  FIGS. 7A to 7E  are views illustrating one example of the operation of the robot  100 . 
     First, the fixing mechanism controller  62  enables the fixing mechanism  27  to regulate the relative movement of the tip-end part  2   a  of the floating unit  2  with respect to the base-end part  2   b , and fix the spatial relationship between the tip end of the robot arm  32  and the hand  1 , which are coupled via the floating unit  2 , to the given spatial relationship (Step S 10 ). 
     Next, as illustrated in  FIG. 7A , the robot arm controller  63  controls the robot arm  32  to move the hand  1  to the position at which the component C is placed in the pre-assemble storage area Pa based on the information for identifying the position of the component C placed in the pre-assemble storage area Pa stored in the memory part  61  (Step S 20 ). 
     Next, the second hand controller  64  controls the hand  1  to hold the component C by the hand  1  (Step S 30 ). 
     Next, as illustrated in  FIG. 7B , the robot arm controller  63  controls the robot arm  32  to move the hand  1  and the floating unit  2  based on the information for identifying the temporary target position P 1  stored in the memory part  61  so that the hand  1  is located at the temporary target position P 1  (Step S 40 ). As described above, the temporary target position P 1  is set as the position from which the hand  1  is movable to the target position P 2  by relatively moving the tip-end part  2   a  of the floating unit  2  located at the temporary target position P 1  with respect to the base-end part  2   b . However, the hand  1  may not be movable to the target position P 2  by relatively moving the tip-end part  2   a  of the floating unit  2  located at the temporary target position P 1  with respect to the base-end part  2   b , due to an error etc. in the position of the product T placed in the assembling area Pb. 
     Thus, since the component C can be conveyed by the robot  100  from the pre-assemble storage area Pa to the temporary target position P 1  which is set near the target position P 2 , the worker&#39;s burden is reduced and the work efficiency is increased. 
     Moreover, when the fixing mechanism  27  is activated at Step S 10 , and the robot arm controller  63  moves the hand  1  and the floating unit  2  so that the hand  1  is located at the temporary target position P 1 , since the fixing mechanism  27  is activated, and each operation of the plurality of joints of the floating unit  2  is regulated, the movement of the tip-end part  2   a  of the floating unit  2  is prevented while the floating unit  2  is moving. Moreover, since the spatial relationship between the tip end of the robot arm  32  and the hand  1 , which are coupled via the floating unit  2 , is fixed to the given spatial relationship, the hand  1  and the component C held by the hand  1  can accurately be located at the temporary target position P 1 . Furthermore, the robot  100  can be prevented from contacting, for example, the product T. 
     Next, the fixing mechanism controller  62  disables the fixing mechanism  27  (Step S 50 ). Thereby, the tip-end part  2   a  of the floating unit  2  is permitted to relatively move with respect to the base-end part  2   b , and it is possible for the worker to grip the handles  11  and manually move the component C held by the hand  1 . 
     Next, as illustrated in  FIGS. 7B and 7C , the worker grips the handles  11  and moves the hand  1  and the tip-end part  2   a  of the floating unit  2  to move the component C held by the hand  1  so that the target position P 2  is explored (Step S 60 ). In this embodiment, as illustrated in  FIG. 7B , it is performed by moving the component C in the second directions D 2  to align the component C with the position in the second directions D 2  with respect to the target position P 2 , subsequently, as illustrated in  FIG. 7C , moving the component C in the first directions D 1  to align the component C with the position in the first directions D 1  (height position) with respect to the target position P 2 , and, further, as further illustrated in  FIG. 7D , by the worker shaking the component C through the hand  1  near the target position P 2  while pressing the component C against the target position P 2 . Thus, the component C get into the target position P 2 , and the hand  1  and the component C held by the hand  1  can be located at the target position P 2 . Thus, since the floating unit  2  has the degree of freedom and the target position P 2  is explored by shaking the component C near the target position P 2  while pressing the component C against the target position P 2 , the assembling work of the component C can be performed quickly and the work efficiency is increased. Moreover, the hand can be located at the target position P 2  even if the target position P 2  varies. 
     Next, as illustrated in  FIG. 7E , the worker fits the component C into the product T, and moves the hand  1  and the component C held by the hand  1  to the target position P 2  (Step S 70 ). Note that, at Step S 60 , when the hand  1  and the component C held by the hand  1  have already been located at the target position P 2 , Step S 70  may be skipped. Thus, the component C can be assembled to the product T. 
     Then, when the component C is assembled to the product T, the worker operates the hand operating part  13  to input the releasing instruction of the component C, and the first hand controller  12  controls the hand  1  based on the releasing instruction to release the component C. 
     As described above, since the robot  100  of the present disclosure can independently move the hand  1  and the component C held by the hand  1  from the pre-assemble storage area Pa to the temporary target position P 1  set near the target position P 2 , the worker&#39;s burden is reduced. 
     In addition, since the worker operates the floating unit  2  to move the hand  1  from the temporary target position P 1  to the target position P 2 , the hand  1  can be located at the target position P 2  even if the target position P 2  varies. 
     Moreover, since the floating unit  2  of which the base-end part  32   a  is attached to the tip-end part  32   b  of the robot arm  32  has the plurality of joints, and the tip-end part is relatively movable with respect to the base-end part with two or more degrees of freedom, the worker can manually move the component C held by the hand  1  in the direction of at least one degree-of-freedom to explore the target position P 2  at which the component C is attached, the worker can manually move the hand  1  and the component C held by the hand  1  to the target position P 2  in the direction of another degree-of-freedom to assemble the component C to the product T. Therefore, the component C can be assembled to the product T after a worker tunes finely the position of the component C to the product T which requires experience and sense of a worker. Moreover, since a sensor which detects a worker&#39;s delicate assembling operation is not required, the structure of the system in which the worker cooperates with the robot is simplified, and it is advantageous to the manufacturing and the manufacturing cost is low. 
     Embodiment 2 
       FIG. 8  is a perspective view illustrating one example of a structure of a floating unit  202  of a robot  200  according to Embodiment 2 of the present disclosure. 
       FIG. 9  is a view schematically illustrating one example of the structure of the floating unit  202 . 
     The floating unit  202  has a limit position arrival detecting part  28  (see  FIG. 10 ). 
     The limit position arrival detecting part  28  detects that the joint of the floating unit  202  arrives at or reaches a limit position of a given section within the given operating range. 
     In this embodiment, the limit position arrival detecting part  28  includes, as illustrated in  FIG. 9 , first to fourth detecting parts  81 ,  82 ,  83  and  84  which correspond to the first to fourth joint parts  22   23 ,  24  and  25 , respectively. 
     The first detecting part  81  includes a pair of spring sensors  81   a  attached to the second coupling piece  42 , and a contactor  81   b  attached to the first coupling piece  41 . One of the pair of spring sensors  81   a  is configured to contact the contactor  81   b  when the first coupling piece  41  is located at one of the limit positions of the operating range R 1 , and the other spring sensor  81   a  is configured to contact the contactor  81   b  when the first coupling piece  41  is located at the other limit position of the operating range R 1 . When one of the spring sensors  81   a  contacts the contactor  81   b , the first detecting part  81  detects that the first joint part  22  reaches the limit position corresponding to the spring sensor  81   a  which detected the contact. 
     The second detecting part  82  includes a pair of spring sensors  82   a  attached to the third coupling piece  43 , and a pair of contactors  82   b  attached to the second coupling piece  42 . One of the pair of spring sensors  82   a  is configured to contact one of the pair of contactors  82   b  when the second coupling piece  42  is located at one of the limit positions of the operating range R 2 , and the other spring sensor  82   a  is configured to contact the other contactor  82   b  when the second coupling piece  42  is located at the other limit position of the operating range R 2 . When one of the spring sensors  82   a  contacts the contactor  82   b , the second detecting part  82  detects that the second joint part  23  reaches the limit position corresponding to the spring sensor  82   a  which detected the contact. 
     The third detecting part  83  includes a pair of spring sensors  83   a  attached to the fourth coupling piece  44 , and a contactor  83   b  attached to the third coupling piece  43 . One of the pair of spring sensors  83   a  is configured to contact the contactor  83   b  when the third coupling piece  43  is located at one of the limit positions of the operating range R 3 , and the other spring sensor  83   a  is configured to contact the contactor  83   b  when the third coupling piece  43  is located at the other limit position of the operating range R 3 . When one of the spring sensors  83   a  contacts the contactor  83   b , the third detecting part  83  detects that the third joint part  24  reaches the limit position corresponding to the spring sensor  83   a  which detected the contact. 
     The fourth detecting part  84  includes a pair of spring sensors  84   a  attached to the fifth coupling piece  45 , and a contactor  84   b  attached to the fourth coupling piece  44 . One of the pair of spring sensors  84   a  is configured to contact the contactor  84   b  when the fourth coupling piece  44  is located at one of the limit positions of the operating range R 4 , and the other spring sensor  84   a  is configured to contact the contactor  84   b  when the fourth coupling piece  44  is located at the other limit position of the operating range R 4 . When one of the spring sensors  84   a  contacts the contactor  84   b , the fourth detecting part  84  detects that the fourth joint part  25  reaches the limit position corresponding to the spring sensor  84   a  which detected the contact. 
     Note that, although the spring sensors are provided at the limit positions of the operating ranges R 1 -R 4 , respectively in this embodiment, the spring sensors may be provided inward of the limit positions of the operating ranges R 1 -R 4 , respectively. 
       FIG. 10  is a view schematically illustrating one example of a structure of a control system of the robot  200 . 
     As illustrated in  FIG. 10 , detection signals outputted from the limit position arrival detecting part  28  (the first to fourth detecting parts  81 ,  82 ,  83  and  84 ) are inputted into the controller  60 . 
     Example of Operation 
     Next, one example of operation of the robot  200  is described. 
       FIG. 11  is a flowchart illustrating the example of the operation of the robot  200 .  FIG. 12  is a view illustrating the example of the operation of the robot  200 . 
     Position Adjustment Operation of Floating Unit 
     At Step S 60  of Embodiment 1 (see  FIG. 6 ; in a state where the fixing mechanism  27  is deactivated after the component C is located at the temporary target position P 1 ), when the target position P 2  is not located within the moving range of a tip-end part  202   a  of the floating unit  202  located at the temporary target position P 1  due to an error etc. in the position of the product T placed in the assembling area Pb, the robot  200  adjusts the position of the floating unit  202  as follows. 
     First, at Step S 60  of Embodiment 1, when the worker moves the component C held by the hand  1 , the posture of the floating unit  202  changes so that the plurality of joints of the floating unit  202  operate. Here, the controller  60  determines whether the limit position arrival detecting part  28  detects that at least one of the plurality of joints of the floating unit  202  reaches the limit position of the given section within the given operating range (Step S 261 ). That is, the controller  60  determines whether the joint part corresponding to at least one of the first to fourth detecting parts  81 ,  82 ,  83  and  84  reaches the limit position. 
     If the controller  60  determines that none of the first to fourth joint parts  22 ,  23 ,  24  and  25  has reached the limit position (No at Step S 261 ), the controller  60  again determines whether at least one of the first to fourth joint parts  22 ,  23 ,  24  and  25  reaches the limit position. That is, the controller  60  waits until at least one of the first to fourth joint parts  22 ,  23 ,  24  and  25  arrives at the limit position. 
     On the other hand, if the controller  60  determines that at least one of the first to fourth joint parts  22 ,  23 ,  24  and  25  has reached the limit position (Yes at Step S 261 ), the robot arm controller  63  controls the robot arm  32  to move a base-end part  202   b  of the floating unit  202  (the robot-arm attaching part  26 ) in the moving directions of the hand  1  (the moving directions of the tip-end part  202   a  of the floating unit  202 ) by a given distance (Step S 262 ). 
     That is, if the first detecting part  81  detects that the first joint part  22  reaches the limit position, the robot arm controller  63  controls the robot arm  32  to move the base-end part  202   b  of the floating unit  202  in the moving directions of the hand  1  (the first directions D 1  and/or the third directions D 3 ) by a given distance. 
     Moreover, if the second detecting part  82  detects that the second joint part  23  reaches the limit position, the robot arm controller  63  controls the robot arm  32  to move the base-end part  202   b  of the floating unit  202  in the moving directions of the hand  1  (the second directions D 2 ) by a given distance. 
     Furthermore, if the third detecting part  83  detects that the third joint part  24  reaches the limit position, the robot arm controller  63  controls the robot arm  32  to move the base-end part  202   b  of the floating unit  202  in the moving directions of the hand  1  (the first directions D 1 ) by a given distance. 
     Here, since the handles  11  of the hand  1  are gripped by the worker, the tip-end part  202   a  of the floating unit  202  and the hand  1  are not interlocked with the operation of the base-end part  202   b  of the floating unit  202 , but the posture of the floating unit  202  changes. Thus, since the robot arm controller  63  moves the base-end part  202   b  of the floating unit  202  by the given distance to adjust the position of the floating unit  202 , the tip-end part  202   a  of the floating unit  202  can be moved outside the moving range of the tip-end part  202   a  of the floating unit  202  at the time of moving the hand  1  so that the component C is located at the temporary target position P 1 . Therefore, due to the error etc. in the position of the product T placed in the assembling area Pb, the component C can be moved to the target position P 2  even when the target position P 2  is not located within the moving range of the tip-end part  202   a  of the floating unit  202  located at the temporary target position P 1 . 
     Then, the controller  60  again determines whether the joint part corresponding to at least one of the first to fourth detecting parts  81 ,  82 ,  83  and  84  reaches the limit position (Step S 261 ). Thus, if the controller  60  again determines that the joint of the floating unit  2  has reached the limit position (Yes at Step S 261 ), the robot arm controller  63  controls the robot arm  32  to move the base-end part  202   b  of the floating unit  202  (the robot-arm attaching part  26 ) in the moving directions of the hand  1  (the moving directions of the tip-end part  202   a  of the floating unit  202 ) by the given distance. 
     Embodiment 3 
     Embodiment 1 is a mode in which the component C is assembled to the product T by using the robot  100 ; however, this embodiment is a mode in which the component C located at a given position is held and conveyed by the robot  100 . 
     In this embodiment, the target position is a position at which the component C placed in the pre-assemble storage area Pa is located. The temporary target position is set as a position where the hand  1  can hold the component C by relatively moving the tip-end part  2   a  of the floating unit  2  located at the temporary target position with respect to the base-end part  2   b  to move the hand  1  to the target position. 
     Example of Operation 
     Next, one example of operation of the robot  100  is described. 
       FIG. 13  is a flowchart illustrating one example of the operation of the robot  100  according to Embodiment 3. 
     First, the fixing mechanism controller  62  enables the fixing mechanism  27  to regulate the relative movement of the tip-end part  2   a  of the floating unit  2  with respect to the base-end part  2   b , and fix the spatial relationship between the tip-end part  32   b  of the robot arm  32  and the hand  1  which are coupled via the floating unit  2  to a given spatial relationship (Step S 310 ). 
     Next, the robot arm controller  63  controls the robot arm  32  to move the hand  1  to the temporary target position P 1  based on the information for identifying the position of the temporary target position P 1  stored in the memory part  61  (Step S 320 ). 
     Then, the fixing mechanism controller  62  deactivates the fixing mechanism  27  (Step S 330 ). Thereby, the relative movement of the tip-end part  2   a  of the floating unit  2  with respect to the base-end part  2   b  is permitted so that the worker is able to grip the handles  11  and manually move the hand  1 . 
     Next, the worker grips the handles  11  and moves the hand  1  to locate the hand  1  at the target position P 2  where the component C is located (Step S 340 ). Here, since the worker can visually confirm the position of the component C (the target position P 2 ) and move the hand  1  to the target position P 2 , the hand  1  can quickly be located at the position where the component C is located and the work efficiency is increased, even when the position of the component C varies. 
     Next, the worker operates the hand operating part  13  to input the holding instruction of the component C, and the first hand controller  12  controls the hand  1  based on the holding instruction to hold the component C (Step S 350 ). 
     Next, the fixing mechanism controller  62  enables the fixing mechanism  27  (Step S 360 ). 
     Next, the robot arm controller  63  controls the robot arm  32  to convey the component C (Step S 370 ). 
     Thus, by using the robot  100 , the hand  1  can quickly be moved to the position where the component C is located and the component C can be held by the hand  1  even when the component C placed in the pre-assemble storage area Pa varies. Thus, the efficiency of the conveyance work of the component C is increased. 
     For a person skilled in the art, many improvements and other embodiments of the present disclosure are apparent from the above description. Therefore, the above description is to be interpreted merely as illustration, and it is provided in order to teach a person skilled in the art the best mode which implements the present disclosure. Details of the structure and/or function may be substantially changed without departing from the spirit of the present disclosure. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
         C: Workpiece 
         T: Assembling Object 
         D 1 : First Directions 
         D 2 : Second Directions 
         D 3 : Third Directions 
         P 1 : Temporary Target Position 
         P 2 : Target Position 
         Pa: Pre-assemble Storage Area 
         Pb: Assembling Area 
         R 1 : Operating Range 
         R 2 : Operating Range 
         R 3 : Operating Range 
         R 4 : Operating Range 
           1 : Hand 
           2 : Floating Unit 
           2   a : Tip-end Part (of Floating Unit) 
           2   b : Base-end Part (of Floating Unit) 
           3 : Robot Body 
           6 : Control Device 
           11 : Handle 
           12 : First Hand Controller 
           13 : Hand Operating Part 
           21 : Hand Attaching Part 
           22 : First Joint Part 
           23 : Second Joint Part 
           24 : Third Joint Part 
           24   a : Pivot Link (of Third Joint Part) 
           24   b : Tip-end Side Coupling Part (of Third Joint Part) 
           24   c : Base-end Side Coupling Part (of Third Joint Part) 
           25 : Fourth Joint Part 
           26 : Robot-arm Attaching Part 
           27 : Fixing Mechanism 
           28 : Limit Position Arrival Detecting Part 
           29 : Balancer Mechanism 
           31 : Robot Base 
           32 : Robot Arm 
           32   a : Base-end Part (of Robot Arm) 
           32   b : Tip-end Part (of Robot Arm) 
           41 : First Coupling Piece 
           42 : Second Coupling Piece 
           43 : Third Coupling Piece 
           44 : Fourth Coupling Piece 
           45 : Fifth Coupling Piece 
           60 : Controller 
           61 : Memory Part 
           62 : Fixing Mechanism Controller 
           63 : Robot Arm Controller 
           64 : Second Hand Controller 
           71 : First Fixing Part 
           72 : Second Fixing Part 
           73 : Third Fixing Part 
           74 : Fourth Fixing Part 
           76 : Arm 
           77 : Arm Pinching Part 
           78 : Air Cylinder Mechanism 
           79 : Air Cylinder Mechanism 
           81 : First Detecting Part 
           81   a : Spring Sensor (of First Detecting Part) 
           81   b : Contactor (of First Detecting Part) 
           82 : Second Detecting Part 
           82   a : Spring Sensor (of Second Detecting Part) 
           82   b : Contactor (of Second Detecting Part) 
           83 : Third Detecting Part 
           83   a : Spring Sensor (of Third Detecting Part) 
           83   b : Contactor (of Third Detecting Part) 
           84 : Fourth Detecting Part 
           84   a : Spring Sensor (of Fourth Detecting Part) 
           84   b : Contactor (of Fourth Detecting Part) 
           100 : Robot