Patent Publication Number: US-2021178614-A1

Title: Shock absorbing device and robot having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to PCT/JP2019/033442 filed Aug. 27, 2019, and JP 2018-161628 filed Aug. 30, 2018, both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a shock absorbing device and a robot having the shock absorbing device. 
     BACKGROUND 
     Conventionally, shock absorbing devices reduce shock transmitted from a first object to a second object. As one example of such shock absorbing devices is a covering material which covers a manipulator. The covering material has a cushion layer, a contact sensor disposed on the outer side of the cushion layer, a proximity sensor disposed on the outer side of the contact sensor, and a coating layer disposed outermost. 
     Meanwhile, the covering material and other conventional shock absorbing devices generally include an outer shell containing the first object, such as an internal structure of the manipulator, a sensor which detects an external force applied by the second object to the outer shell or an external force applied by the second object to the first object via the outer shell, and a motion suppressing device which suppresses motion of the first object and the outer shell based on a value detected by the sensor. 
     However, such conventional shock absorbing devices have transmit some shock from the first object to the second object. Moreover, the external force applied by the second object to the outer shell, or the external force applied by the second object to the first object via the outer shell, may not be accurately detected by the sensor. Therefore, the motion suppressing device may not be able to suppress the motion of the first object and the outer shell as desired based on the value detected by the sensor. 
     SUMMARY 
     In order to solve the above-described problems, a shock absorbing device according to the present disclosure is configured to reduce shock transmitted from a first object to a second object. The shock absorbing device comprises an outer shell comprising of an elastic body, the outer shell configured to contain the first object; a sensor configured to detect one of a first external force applied by the second object to the outer shell, a second external force applied by the second object to the first object via the outer shell, and a physical quantity corresponding to one of the first and second external forces; and a motion suppressing device configured to suppress motion of the first object and the outer shell based on a value detected by the sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a worksite where a shock absorbing device and a robot having the shock absorbing device work cooperatively with a human body (human). 
         FIG. 2  is a schematic view illustrating a configuration of the shock absorbing device and the robot. 
         FIG. 3  is a block diagram illustrating components of the shock absorbing device and the robot. 
         FIG. 4(A)  is a perspective view illustrating a state where a first outer shell of the shock absorbing device as viewed from the outside. 
         FIG. 4(B)  is a perspective view illustrating a state where a first outer shell of the shock absorbing device as viewed from the inside. 
         FIG. 5(A)  is a schematic view of a snap-fit structure before fixing a pair of outer shell bodies of the shock absorbing device. 
         FIG. 5(B)  is a schematic view of a snap-fit structure after fixing a pair of outer shell bodies of the shock absorbing device. 
         FIG. 6(A)  is a front perspective view illustrating a state where the first outer shell of the shock absorbing device is attached to a wrist. 
         FIG. 6(B)  is a back perspective view illustrating a state where the first outer shell of the shock absorbing device is attached to a wrist. 
         FIG. 7(A)  is a view illustrating a positional relationship between the first outer shell of the shock absorbing device and a base-end part of a wrist structure of the robot. 
         FIG. 7(B)  is a view illustrating a positional relationship between the first outer shell of the shock absorbing device and a middle part of the wrist. 
         FIG. 7(C)  is a view illustrating a positional relationship between the first outer shell of the shock absorbing device and a tip-end part of the wrist. 
         FIG. 8  is a view illustrating a modification of a first outer shell back part of the first outer shell of the shock absorbing device. 
         FIG. 9(A)  is a perspective view illustrating a state before a second outer shell of the shock absorbing device is attached to a first link of the robot and a decorative label. 
         FIG. 9(B)  is a cross-sectional view illustrating a fixing part of the second outer shell of  FIG. 9(A)  and its peripheral part. 
         FIG. 10(A)  is a perspective view illustrating a state where the second outer shell of the shock absorbing device is attached to the first link of the robot. 
         FIG. 10(B)  is a cross-sectional view of the fixing part of  FIG. 10(A)  and its peripheral part. 
         FIG. 11  is a perspective view illustrating a state where a third outer shell of the shock absorbing device as seen from inside. 
         FIG. 12(A)  is a perspective view illustrating a state where the third outer shell of the shock absorbing device is attached to a second link of the robot as seen from a first surface side. 
         FIG. 12(B)  is a perspective view illustrating the state where the third outer shell of the shock absorbing device is attached to the second link of the robot as seen from a second surface side. 
         FIG. 12(C)  is a cross-sectional view illustrating the fixing part and its peripheral part. 
         FIG. 13(A)  is a schematic cross-sectional view illustrating an effect of the shock absorbing device before an external force is applied by a human body to the outer shell. 
         FIG. 13(B)  is a schematic cross-sectional view illustrating an effect of the shock absorbing device when the external force is applied by the human body. 
         FIG. 14  is a schematic view illustrating an experiment conducted by the present inventors in order to confirm the effect of the shock absorbing device. 
         FIG. 15  is a graph illustrating a result of the experiment conducted by the present inventors illustrated in  FIG. 14 . 
         FIG. 16(A)  is a view illustrating a positional relationship between a first outer shell of a conventional shock absorbing device and a base-end part of a wrist of an internal structure of a robot. 
         FIG. 16(B)  is a view illustrating the positional relationship between the first outer shell of the conventional shock absorbing device and a middle part of the wrist. 
         FIG. 16(C)  is a view illustrating the positional relationship between the first outer shell of the conventional shock absorbing device and a tip-end part of the wrist. 
         FIG. 17(A)  is a schematic cross-sectional view illustrating the conventional shock absorbing device before an external force is applied by the human body to an outer shell. 
         FIG. 17(B)  is a schematic cross-sectional view illustrating the conventional shock absorbing device when the external force is applied by the human body. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Hereinafter, a shock absorbing device and a robot having the shock absorbing device are described with reference to the accompanying drawings. Note that the present disclosure is not limited to these devices. Moreover, below, the same reference characters are given to the same or corresponding components throughout the drawings to omit redundant description. 
     (Robot  10 ) 
       FIG. 1  is a plan view illustrating a worksite where the shock absorbing device and the robot having the shock absorbing device according to an embodiment work cooperatively with a human body (human). As illustrated in  FIG. 1 , a robot  10  is an industrial robot which works cooperatively with human bodies P and P′ (a second object) at a worksite S. In detail, the robot  10  is installed between the human body P and the human body P′ within a limited space corresponding to a space for one person (e.g., 610 mm×620 mm). Then, the robot  10  can work cooperatively with the human bodies P and P′ on a plurality of workpieces W which are sequentially conveyed by a conveyor C. 
       FIG. 2  is a schematic view illustrating the entire configuration of the shock absorbing device and the robot having the shock absorbing device. As illustrated in  FIG. 2 , the robot  10  includes a pedestal  12  fixed to a carriage, a robot controlling device  18  accommodated in the pedestal  12  and illustrated by a broken line in  FIG. 1 , and a pair of robotic arms  20   a  and  20   b  supported by the pedestal  12 . Note that although an end effector which, for example, grips the workpiece W may be attached to a tip end of each of the robotic arms  20   a  and  20   b,  illustration and description thereof are omitted here. 
     (Pair of Robotic Arms  20   a  and  20   b ) 
     The pair of robotic arms  20   a  and  20   b  are horizontally articulated robotic arms which are movable with respect to the pedestal  12 . The pair of robotic arms  20   a  and  20   b  can operate independently from and in connection with each other. Note that since the robotic arm  20   b  has a similar configuration to the robotic arm  20   a,  only the robotic arm  20   a  is described here and similar description of the robotic arm  20   b  is suitably omitted. 
     The robotic arm  20   a  has joint parts J 1 -J 4  (joint axes). Then, the robotic arm  20   a  is provided with driving motors  30  corresponding to the joint parts J 1 -J 4  (see  FIG. 3 ). The robotic arm  20   a  has a first link  22 , a second link  24 , and a wrist  26 . 
     The first link  22  is coupled to a base shaft  14  fixed to an upper surface of the pedestal  12  by the rotary joint part J 1 , and thus, rotatable about a rotational axis L 1  defined passing through the axial center of the base shaft  14 . The second link  24  is coupled to a tip end of the first link  22  by the rotary joint part J 2 , and thus, rotatable about a rotational axis L 2  defined at the tip end of the first link  22 . 
     The wrist  26  has a mechanical interface  27  to which the end effector is attached, and is coupled to a tip end of the second link  24  via the linear-motion joint part J 3  and the rotary joint part J 4 . The wrist  26  is ascendable and descendible with respect to the second link  24  by the linear-motion joint J 3 . Moreover, the wrist  26  is rotatable about a vertical rotational axis L 3  with respect to the second link  24  by the rotary joint part J 4 . 
     The rotational axis L 1  of the first link  22  of the robotic arm  20   a  and the rotational axis L 1  of the first link  22  of the robotic arm  20   b  exist on the same straight line, and the first link  22  of the robotic arm  20   a  and the first link  22  of the robotic arm  20   b  are disposed with a height difference therebetween. 
     Although a concrete configuration of the robot controlling device  18  is not particularly limited, it may be implemented by a known processor (e.g., a CPU) operating in accordance with a program stored in a memory. 
     (Shock Absorbing Device  50 ) 
       FIG. 3  is a block diagram illustrating the entire configuration of the shock absorbing device and the robot having the shock absorbing device. As illustrated in  FIG. 3 , the robot  10  is further provided with a shock absorbing device  50  which reduces the shock transmitted from an internal structure (a first object) of the robot  10  to the human body P and the human body P′. The internal structure of the robot  10  includes a structure provided inside the robot  10  (e.g., the motors  30  provided inside the robotic arms  20   a  and  20   b,  an internal structure  22   a  of the first link, an internal structure  24   a  of the second link, and an internal structure  26   a  of the wrist (described later)). 
     The shock absorbing device  50  is provided with an outer shell  60  that contains and houses the internal structure (the first object) of the robot  10  and comprised of an elastic body with flexibility. The shock absorbing device  50  is further provided with a sensor  110  which detects an external force applied by the human bodies P and P′ (the second object) to the internal structure of the robot  10  via the outer shell  60 . Then, the shock absorbing device  50  is further provided with a motion suppressing device  120  which suppresses the motion of the robot  10  (e.g., the internal structure and the outer shell  60  of the robot  10 ) based on the value detected by the sensor  110 . 
     (Outer Shell  60 ) 
     The outer shell  60  constitutes an outer shell of the robot  10 . In detail, the outer shell  60  includes a first outer shell  70  constituting an outer shell of the wrist  26  of the robotic arm  20   a,  a second outer shell  80  constituting an outer shell of the first link  22  of the robotic arm  20   a,  and a third outer shell  90  constituting an outer shell of the second link  24  of the robotic arm  20   a.  That is, the outer shell  60  is configured as an outer shell of the internal structure of the robotic arm  20   a  (and the robotic arm  20   b ). 
     The outer shell  60  (i.e., each of the first outer shell  70 , the second outer shell  80 , and the third outer shell  90 ) has a wall that is thin, and a gap is formed between the outer shell  60  and the internal structure of the robot  10 . The thickness of the wall may be 5.0 mm or below. Alternatively, the thickness of the wall may be 1.0 mm or above and 2.0 mm or below. 
     Moreover, the elastic body which constitutes the outer shell  60  also has incompressibility. Note that the incompressibility as used herein refers to a property of the outer shell  60  that when it is applied with the external force by the human bodies P and P′ (the second object), its density (or a volume) does not change (or hardly changes) before and after an elastic deformation. 
     Moreover, the elastic body which constitutes the outer shell  60  is made of non-foamed resin. A primary component of the non-foamed resin is polyethylene. 
     The polyethylene may be LDPE (Low Density Polyethylene). Alternatively, the polyethylene may be HDPE (High Density Polyethylene), LLDPE (Linear Low Density Polyethylene), MPE (Metallocene Polyethylene, or polyethylene polymerized using metallocene catalyst), EVA (Ethylene-Vinyl Acetate), UHM WPE (Ultra High Molecular Weight Polyethylene), or any combination of these polyethylene, for example. 
     Moreover, an inner surface of the outer shell  60  opposing to the internal structure of the robot  10  is smooth. 
     Although the outer shell  60  further includes the first outer shell  70 , the second outer shell  80 , and the third outer shell  90  which constitute an outer shell of the robotic arm  20   b,  their configurations are the same as those of the outer shell of the robotic arm  20   a.  Therefore, below, only the outer shell of the first robotic arm  20   a  is described unless particularly needed, and similar description for the second robotic arm  20   b  is suitably omitted. 
     (First Outer Shell  70 ) 
       FIGS. 4(A) and 4(B)  are perspective views illustrating a state where the first outer shell of the shock absorbing device opens, where  FIG. 4(A)  is a view when seen from outside, and  FIG. 4(B)  is a view when seen from inside. As illustrated in  FIGS. 4(A) and 4(B) , the first outer shell  70  has a pair of first outer shell bodies  72   a  and  72   b,  and a first outer shell back part  76  coupling the back side of a base-end part of the first outer shell body  72   a  and the back side of a base-end part of the first outer shell body  72   b.    
     Each of the pair of first outer shell bodies  72   a  and  72   b  has two substantially bowl shapes connected vertically to each other, so that the pair of first outer shell bodies  72   a  and  72   b  can cooperatively contain the wrist internal structure  26   a  therein. 
     The first outer shell  70  can be attached to the wrist internal structure  26   a  in the following procedure, for example. 
     First, as illustrated in  FIG. 4(A) , the first outer shell  70  is opened so that the first outer shell bodies  72   a  and  72   b  are opened to be spread centering on the first outer shell back part  76 . 
     Next, an inner surface of the first outer shell back part  76  is slid from upward to be attached to the wrist internal structure  26   a.    
     Then, the first outer shell body  72   a  is inwardly bent at the connected part with the first outer shell back part  76 , and the first outer shell body  72   b  is inwardly bent at the connected part with the first outer shell back part  76 , so that an inner surface of the first outer shell body  72   a  and an inner surface of the first outer shell body  72   b  face to each other having the wrist internal structure  26   a  therebetween. 
     Finally, the first outer shell bodies  72   a  and  72   b  are fixed to each other by a snap-fit structure  73  (see  FIGS. 5(A) and 5(B) ) provided at end edges of the substantially bowl shapes of the first outer shell bodies  72   a  and  72   b  extending in the height direction on the opposite side of the second link  24 . 
       FIGS. 5(A) and 5(B)  are schematic views of the snap-fit structure which fixes the pair of first outer shell bodies of the shock absorbing device, where  FIG. 5(A)  is a view before the fixing, and  FIG. 5(B)  is a view after the fixing. As illustrated in  FIGS. 5(A) and 5(B) , the snap-fit structure  73  has a known structure in which a male part  73   a  provided to one of the first outer shell bodies  72   a  and  72   b,  and a female part  73   b  provided to the other one of them are engaged with each other using an elastic deformation of the male part  73   a.    
     Note that a plurality of snap-fit structures  73  may be provided having a gap therebetween in the height direction, to the end edges of the substantially bowl shapes of the first outer shell bodies  72   a  and  72   b  extending in the height direction on the opposite side of the second link  24 . Therefore, the first outer shell bodies  72   a  and  72   b  can be strongly fixed to each other. Moreover, the snap-fit structure  73  may be provided to the inner surfaces of the first outer shell bodies  72   a  and  72   b.  Accordingly, since the snap-fit structure  73  becomes invisible from outside when the first outer shell  70  is attached to the wrist internal structure  26   a,  an appearance can be improved and the snap-fit structure  73  can be prevented from being caught by other objects. 
       FIGS. 6(A) and 6(B)  are views illustrating a state where the first outer shell of the shock absorbing device is attached to the wrist, where  FIG. 6(A)  is a front perspective view, and  FIG. 6(B)  is a back perspective view. As illustrated in  FIGS. 6(A) and 6(B) , the first outer shell  70  has a curved part  101  protruding outwardly in a thickness direction (i.e., the opposite side from the wrist internal structure  26   a ). The curved part  101  is formed from the base-end part to the tip-end part of the first outer shell  70  by the end edges of the substantially bowl shapes of the first outer shell bodies  72   a  and  72   b,  which extend in the height direction on the opposite side of the second link  24 , being fixed to each other by the snap-fit structure  73 . 
     Note that a part of the wrist internal structure  26   a  may be exposed from the first outer shell  70 . As illustrated in  FIG. 6(B) , a vent  77  is provided on the first outer shell back part  76  so as to discharge heat generated by the wrist internal structure  26   a  to outside. 
       FIGS. 7(A) to 7(C)  are views illustrating a positional relationship between the first outer shell of the shock absorbing device and the internal structure of the robot, where  FIG. 7(A)  illustrates a base-end part of the wrist,  FIG. 7(B)  illustrates a middle part of the wrist, and  FIG. 7(C)  illustrates a tip-end part of the wrist. As illustrated in  FIGS. 7(A) to 7(C) , since the first outer shell  70  is formed to be thin, a gap is formed between the wrist internal structure  26   a  and the first outer shell  70 . Therefore, an internal space  79  is formed from the base-end part to the tip-end part of the wrist  26 . 
       FIG. 8  is a view illustrating a modification of the first outer shell back part of the shock absorbing device. As illustrated in  FIG. 8 , a part of the vent  77  may be notched so that a heat sink  78  is provided therein. Accordingly, the heat generated by the wrist internal structure  26   a  can further be discharged outside. 
     (Second Outer Shell  80 ) 
       FIGS. 9(A) and 9(B)  are views illustrating a state before the second outer shell of the shock absorbing device is attached to the first link of the robot, where  FIG. 9(A)  is a perspective view of the second outer shell, and the first link and a decorative panel, and  FIG. 9(B)  is a cross-sectional view illustrating a fixing part and its peripheral part of the second outer shell. 
     As illustrated in  FIG. 9(A) , the second outer shell  80  has a pair of second outer shell bodies  82   a  and  82   b.  The shapes of the pair of second outer shell bodies  82   a  and  82   b  are the same. The pair of second outer shell bodies  82   a  and  82   b  are attached to the first link internal structure  22   a  so as to cooperatively cover the entire area of the side surface, and edge parts of an upper surface and a bottom surface of the first link internal structure  22   a.    
     The pair of second outer shell bodies  82   a  and  82   b  are provided on their inner surfaces with a plurality of fixing parts  84 , which fix to the side surface of the first link internal structure  22   a.  As illustrated in  FIG. 9(B) , each fixing part  84  has a sponge foam  85  of which one principal surface is fixed to the inner surface of the second outer shell body  82   a  or  82   b,  and a hook-and-loop fastener  86  provided on the other principal surface of the sponge foam  85 . 
     The sponge foam  85  is made of, for example, a material with flexibility, which easily deforms when an external force is applied, and easily recovers the previous shape when the external force stops to be applied (e.g., a sponge as generally used in a kitchen). That is, the sponge foam  85  can elastically deform easily. 
     Note that the hook-and-loop fastener  86  may be attached to the principal surface of the sponge foam  85  by an adhesive etc. Although a decorative panel  23  is attached to an upper surface of the first link  22  of the first robotic arm  20   a,  the decorative panel  23  is not attached to that of the second robotic arm  20   b.    
     The second outer shell  80  can be attached to the first link internal structure  22   a  by, for example, the second outer shell body  82   a  and the second outer shell body  82   b  being horizontally flipped with respect to each other and contacted to the side surface of the first link internal structure  22   a,  so that the hook-and-loop fasteners  86  are fixed to hook-and-loop fasteners  87  provided at the corresponding positions in the first link internal structure  22   a.  Note that the hook-and-loop fasteners  86  of the second outer shell bodies  82   a  and  82   b  have one of a hook structure and a loop structure, and the hook-and-loop fasteners  87  of the first link internal structure  22   a  have the other one of the hook structure and the loop structure. 
       FIGS. 10(A) and 10(B)  are views illustrating a state where the second outer shell of the shock absorbing device is attached to the first link of the robot, where  FIG. 10(A)  is a perspective view, and  FIG. 10(B)  is a cross-sectional view of the fixing part and its peripheral part. 
     The second outer shell body  82   a  and the second outer shell body  82   b  are fixed to each other by fitting structures provided to their end surfaces. Note that the fitting structure may be a snap-fit structure similarly to the first outer shell  70 , or may be a known fitting structure provided with a pin and a corresponding pin receiver. 
     As illustrated in  FIG. 10(B) , the pair of second outer shell bodies  82   a  and  82   b  are fixed to the side surface of the first link internal structure  22   a  by the plurality of fixing parts  84 . In detail, the pair of second outer shell bodies  82   a  and  82   b  are pressed toward the first link internal structure  22   a,  and thus, the hook-and-loop fasteners  86  of the fixing parts  84  are fixed to the hook-and-loop fasteners  87  provided to the side surface of the first link internal structure  22   a.  Then, by the pressing being canceled, the sponge foams  85  elastically deform and maintain a state extending toward the side surface of the first link internal structure  22   a,  and thus, the pair of second outer shell bodies  82   a  and  82   b  are fixed to the side surface of the first link internal structure  22   a.    
     Note that as illustrated in  FIG. 10(A)  the second outer shell  80  has curved parts  102  protruding outwardly in its thickness direction (i.e., the opposite side from the first link internal structure  22   a ), similarly to the first outer shell  70 . End edges on both sides of the second outer shell bodies  82   a  and  82   b  extending in the height direction are fixed to each other so as to form the curved parts  102  entirely in the height direction on a base-end side and a tip-end side of the second outer shell  80   
     (Third Outer Shell  90 ) 
       FIG. 11  is a perspective view illustrating a state where the third outer shell of the shock absorbing device opens, when seen from inside. As illustrated in  FIG. 11 , the third outer shell  90  has a pair of third outer shell bodies  92   a  and  92   b.  Each of the pair of third outer shell bodies  92   a  and  92   b  has a third outer shell side part  93  which covers a side surface of the second link  24 , a third outer shell one surface part  94  which covers a part of a first surface of the second link  24 , a third outer shell other surface part  95  which covers a part of a second surface of the second link  24 . 
     In  FIG. 11 , the third outer shell side part  93  of each of the pair of third outer shell bodies  92   a  and  92   b  is curved so as to protrude outwardly when seen from above, and vertically extending edge parts of the respective third outer shell side parts  93  are coupled to each other so as to be inwardly bendable. The third outer shell side part  93  of each of the pair of third outer shell bodies  92   a  and  92   b  is provided on its inner surface with a plurality of fixing parts  96  configured similarly to the fixing parts  84  provided to the inner surface of the pair of second outer shell bodies  82   a  and  82   b.  That is, each fixing part  96  has a sponge foam  97  of which one principal surface is fixed to an inner surface of the third outer shell body  92   a  or  92   b,  and a hook-and-loop fastener  98  provided on the other principal surface of the sponge foam  97 . 
     In  FIG. 11 , the third outer shell one surface part  94  inwardly and horizontally extends from a lower-end edge of the third outer shell side part  93 . Note that the fixing part  96  similar to the one provided to the third outer shell side part  93  is provided to an inner surface of the third outer shell one surface part  94 . Moreover, the third outer shell other surface part  95  inwardly and horizontally extends from an upper-end edge of the third outer shell side part  93 . 
     The third outer shell  90  can be attached to the second link internal structure  24   a  by, for example, the third outer shell body  92   a  and the third outer shell body  92   b  being inwardly bent at the connected part, and contacted on the side surface of the second link internal structure  24   a,  so that the hook-and-loop fasteners  98  are fixed to hook-and-loop fasteners  99  provided at the corresponding positions in the second link internal structure  24   a.  Note that the hook-and-loop fasteners  98  of the third outer shell bodies  92   a  and  92   b  have one of the hook structure and the loop structure of the known hook-and-loop fastener, and the hook-and-loop fasteners  99  of the second link internal structure  24   a  have the other one of the hook structure and the loop structure. 
       FIGS. 12(A) to 12(C)  are views illustrating a state where the third outer shell of the shock absorbing device is attached to the second link of the robot, where  FIG. 12(A)  is a perspective view when seen from the first surface side,  FIG. 12(B)  is a perspective view when seen from the second surface side, and  FIG. 12(C)  is a cross-sectional view illustrating the fixing part and its peripheral part. 
     The third outer shell body  92   a  and the third outer shell body  92   b  are fixed to each other by a fitting structure provided to their end surfaces opposite from the end surfaces bendably connected to each other. Note that the fitting structure may be a snap-fit structure similarly to the first outer shell  70 , or may be a known fitting structure provided with a pin and a corresponding pin receiver. 
     As illustrated in  FIG. 12(C) , the pair of the third outer shell bodies  92   a  and  92   b  are fixed to the second link internal structure  24   a  by the plurality of fixing parts  96 . Note that since a mode of the fixing is similar to the fixing of the first link internal structure  22   a  to the second outer shell  80  as described above, description is not repeated. 
     Note that, as illustrated in  FIGS. 12(A) and 12(B) , the third outer shell  90  has a curved part  103  protruding outwardly in the thickness direction (i.e., the opposite side from the second link internal structure  24   a ), similarly to the first outer shell  70  and the second outer shell  80 . The end edges of the third outer shell bodies  92   a  and  92   b  extending in the height direction on the opposite side of the bendably connected part are fixed to each other so as to form the curved part  103  entirely in the height direction of the end edges. 
     (Sensor  110 ) 
     Returning to  FIG. 3 , the sensor  110  detects an amount of change in a rotational speed of the motors  30 , as an external force applied by the human bodies P and P′ to the internal structure of the robot  10  via the outer shell  60  (a first part) of the robotic arms  20   a  and  20   b.    
     (Motion Suppressing Device  120 ) 
     As illustrated in  FIG. 3 , the motion suppressing device  120  may be configured as a part of the robot controlling device  18 . Although a concrete configuration of the motion suppressing device  120  is not particularly limited, it may be implemented by a known processor (e.g., a CPU) operating in accordance with a program stored in a memory. 
     Note that the motion suppressing device  120  may suppress the operation (motion) of the robot  10  by suspending the operation of the robot  10 , for example. Alternatively, the operation of the robot  10  may be suppressed by reducing the speed or acceleration of the robot  10 , or may be suppressed by other modes. 
     (Effects) 
     Here, in order to describe the effects achieved by the shock absorbing device  50 , a conventional shock absorbing device  200  is described with reference to  FIGS. 16(A), 16(B), 16(C) , and  FIGS. 17(A) and 17(B) .  FIGS. 16  (A) to  16 (C) are views illustrating a positional relationship between a first outer shell of the conventional shock absorbing device and an internal structure of a robot, where  FIG. 16(A)  illustrates a base-end part of a wrist,  FIG. 16(B)  illustrates a middle part of the wrist, and  FIG. 16(C)  illustrates a tip-end part of the wrist.  FIGS. 17(A) and 17(B)  are schematic cross-sectional views illustrating the conventional shock absorbing device, where  FIG. 17(A)  is a view before an external force is applied by the human body to an outer shell, and  FIG. 17(B)  is a view when the external force is applied by the human body. 
     As illustrated in  FIGS. 17(A) and 17(B) , an outer shell  210  of the conventional shock absorbing device  200  (hereinafter, referred to as a “conventional outer shell  210 ”) has a thick wall. The thickness of the thick wall is, for example, 10 mm or above and 15 mm or below. Note that the conventional outer shell  210  is made of urethane foam as a primary component. As illustrated in  FIGS. 17(A) and 17(B) , when the conventional outer shell  210  is applied with the external force by the human body P etc., a part to which the external force is applied is compressed and its volume is reduced (or its density is increased). Accordingly, the conventional outer shell  210  functions to reduce the shock transmitted to the internal structure of the robot (here, an internal structure  26 ′ of the wrist). 
     However, this mode of reducing the shock has room for improvement in a degree of reducing the shock transmitted from the internal structure  26 ′ of the robot to the human body P. Moreover, an elasticity of the outer shell  210  pushing back the human body changes only linearly with respect to the change in the volume of the outer shell  210 . In other words, the elasticity of the outer shell  210  pushing back the human body P does not change largely, when the change in the volume of the outer shell  210  is comparatively small (that is, the external force applied by the human body P to the outer shell  210  is comparatively small). Therefore, a sensor may not detect the external force even when the external force is applied by the human body P to the outer shell  210 , and thus, a motion suppressing device which suppresses the motion of the robot based on the value detected by the sensor, may not operate as desired. As a result, the conventional shock absorbing device  200  may not control the operation of the robot as desired. 
     Moreover, since the conventional outer shell  210  is thick as described above, as illustrated in  FIGS. 17(A) and 17(B) , an inner surface thereof contacts or almost contacts with the internal structure of the robot. Therefore, when the external force is applied by the human body P, since the change in the volume of the outer shell  210  is obstructed by the internal structure of the robot, the shock absorbing function may not sufficiently be achieved. Moreover, a structure required to be inserted between the outer shell  210  and the internal structure of the robot (e.g., a harness), is difficult to be disposed. Furthermore, once the structure (e.g., the harness) is disposed, it easily contacts the outer shell  210  and the internal structure of the robot, thus easily being damaged. 
     On the other hand, the shock absorbing device  50  is provided with the outer shell  60  comprised of the elastic body with flexibility, and thus, the shock transmitted from the internal structure (the first object) of the robot  10  to the human body P (the second object) can be sufficiently reduced. 
       FIGS. 13(A) and 13(B)  are schematic cross-sectional views illustrating the effect of the shock absorbing device, where  FIG. 13(A)  is a view before the external force is applied by the human body to the outer shell, and  FIG. 13(B)  is a view when the external force is applied by the human body. As illustrated in  FIGS. 13(A) and 13(B) , a part of the outer shell  60  (here, the first outer shell  70 ) to which the external force is applied by the human body P is elastically deformed entirely in the thickness direction so as to deflect toward the internal space  79  (a gap). Therefore, the shock transmitted from the internal structure (here, the wrist internal structure  26   a,  the first object) of the robot  10  to the human body P (the second object) can be sufficiently reduced. 
     Moreover, the elasticity of the outer shell  60  pushing back the human body P promptly increases compared to the conventional outer shell  210 , when the external force applied by the human body P to the outer shell  60  is comparatively small. Therefore, the sensor  110  can more accurately detect the external force applied by the human body P to the outer shell  60  or the external force applied by the human body P to the internal structure of the robot  10  via the outer shell  60 . As a result, the motion suppressing device  120  can suppresses the motion of the internal structure of the robot  10  and the outer shell  60  as desired based on the value detected by the sensor. 
     Moreover, since the outer shell  60  is thin and the gap is formed between the internal structure of the robot  10  and the outer shell  60 , the outer shell  60  can elastically deform suitably without being obstructed by other structures, such as the internal structure of the robot  10  and the harness. Furthermore, the structure required to be inserted between the outer shell  60  and the internal structure of the robot  10  (e.g., the harness), can easily be disposed. Moreover, once the structure (e.g., the harness) is disposed as described above, it is unlikely to contact the outer shell  60  and the internal structure of the robot  10 , and thus, it can be prevented from being damaged. 
     Furthermore, by the thickness of the wall being 5.0 mm or below, the outer shell  60  can elastically deform suitably. Moreover, by the thickness of the wall being 1.0 mm or above and 2.0 mm or below, the outer shell  60  can elastically deform more suitably. 
     Then, since the elastic body constituting the outer shell  60  further has incompressibility, the outer shell  60  can elastically deform suitably, as illustrated in  FIGS. 13(A) and 13(B) . 
     Moreover, since the elastic body constituting the outer shell  60  is made of the non-foamed resin, the outer shell can easily be formed. For example, the outer shell  60  can easily be formed by an injection molding at low cost. Furthermore, the outer shell  60  can elastically deform suitably. 
     At least a part of the outer shell  60  has the curved parts ( 101 ,  102 , and  103 ) protruding outwardly in the thickness direction, and thus, the elasticity of the outer shell  60  pushing back the human body P, can be increased further quickly compared to the conventional outer shell  210 . Therefore, the sensor  110  can further accurately detect the external force applied by the human body P to the outer shell  60 , or the external force applied by the human body P to the internal structure of the robot  10  via the outer shell  60 . 
     Moreover, since the inner surface of the outer shell  60  opposing to the internal structure of the robot  10  is smooth (i.e., ribs etc. are not formed), the outer shell  60  can be formed easily. Moreover, since the rib etc. does not contact other structures, such as the internal structure of the robot  10  and the harness, the outer shell  60  can elastically deform suitably without being obstructed by the other objects. 
     Moreover, the sensor  110  detects the amount of change in the rotational speed of the motors  30 , as the external force applied by the human body P to the internal structures of the robotic arms  20   a  and  20   b  via the outer shell  60  (the first part) of the robotic arms  20   a  and  20   b.  Therefore, for example, unlikely to the conventional outer shell  210 , a contact sensor and a proximity sensor are unnecessary to be built in to detect the external force applied by the human body P. Thus, the outer shell  60  can be thin to suitably be deformed elastically. 
     (Modifications) 
     It is apparent for a person skilled in the art that many improvements and other embodiments of the present disclosure are possible from the above description. Therefore, the above description is to be interpreted only as illustration, and it is provided in order to teach a person skilled in the art the best mode for implementing the present disclosure. The details of the structures and/or the functions may be substantially changed, without departing from the spirit of the present disclosure. 
     Although in the above discussion the first link internal structure  22   a  and the second outer shell  80  are fixed to each other by the fixing parts  84  including the hook-and-loop fasteners, it is not limited to this. For example, the first link internal structure  22   a  and the second outer shell  80  may be fixed to each other using a threaded member. Accordingly, the first link internal structure  22   a  and the second outer shell  80  can easily be fixed to each other without a positional offset. Note that this structure is similarly applied to the attaching of the second link internal structure  24   a  to the third outer shell  90 . 
     Although the outer shell  60  is configured as the outer shell of the first robotic arm  20   a  and the second robotic arm  20   b,  it is not limited to this. For example, if the robot controlling device  18  can control the motion of the pedestal  12 , the outer shell  60  may be configured as an outer shell of the base shaft  14 , or an outer shell of the pedestal  12 . 
     Although the sensor  110  detects the amount of change in the rotational speed of the motors  30 , as the external force applied by the human bodies P and P′ (the second object) to the internal structure of the robot  10  via the outer shell  60 , it is not limited to this. For example, the sensor  110  may detect an amount of change in rotational positions of the motors  30  or an amount of change in current values flowing in the motors  30 , as the external force applied by the human bodies P and P′ (the second object) to the internal structure of the robot  10  via the outer shell  60 . 
     Although the sensor  110  detects the external force applied by the human bodies P and P′ (the second object) to the internal structure of the robot  10  via the outer shell  60 , and the motion suppressing device  120  suppresses the motion of the robot  10  based on the value detected by the sensor  110 , it is not limited to this. For example, the sensor  110  may detect the external force applied by the human bodies P and P′ to the outer shell  60 , or a physical quantity corresponding to one of the external forces described above (i.e., one of the external force applied by the human bodies P and P′ to the internal structure of the robot  10  via the outer shell  60 , and the external force applied by the human bodies P and P′ to the outer shell  60 ), and the motion suppressing device  120  may suppress the motion of the robot  10  based on the value detected by the sensor  110 . Note that the physical quantity corresponding to one of the external forces described above may be an amount of deflection of the outer shell  60 , or other physical quantities. 
     Although the elastic body constituting the outer shell  60  is made of the non-foamed resin and its primary component is polyethylene, it is not limited to this. The elastic body constituting the outer shell  60  may be made of non-foamed resin of which a primary component is polypropylene, polycarbonate, ethylene-vinyl acetate, olefin-based elastomer, styrene-based elastomer, polyamide (nylon), polystyrene, polyacetal, polyurethane, polyethylene terephthalate, vinyl chloride, or polylactic acid. Moreover, the elastic body constituting the outer shell  60  may be made of foamed resin. 
     Although each of the first robotic arm  20   a  and the second robotic arm  20   b  of the robot  10  has the four joint axes JT 1 -JT 4 , it is not limited to this. For example, each of the robotic arm  20   a  and the second robotic arm  20   b  may have one or more and three or less joint axes, or may have five or more joint axes. Then, the shock absorbing device  50  may be provided with the outer shell  60  which can suitably contain such a robotic arm, and other structures. 
     Although the robot  10  is configured as the horizontally articulated dual-arm robot having the first robotic arm  20   a  and the second robotic arm  20   b,  it is not limited to this. For example, the robot  10  may be configured as a horizontally articulated single-arm robot. Alternatively, the robot  10  may be a polar robot, a cylindrical robot, a cartesian coordinate robot, a vertically articulated robot, or other types of robot. Then, the shock absorbing device  50  may be provided with the outer shell  60  which can suitably contain such a robot, and other structures. 
     Although the robot  10  is the industrial robot which works cooperatively with the human bodies P and P′ (the second object) at the worksite S, it is not limited to this. For example, the robot  10  may be a so called “entertainment robot,” or may be other types of robot. 
     Although the second object is the human body P (P′) which works cooperatively with the robot  10  at the worksite S, it is not limited to this. For example, the second object may be a peripheral device which works cooperatively with the robot  10  at the worksite S, or may be other objects disposed at the worksite S. Moreover, when the robot  10  is disposed at a location different from the worksite S, the second object may be a human body or other objects existing at the location. 
     Although the shock absorbing device  50  is provided to the robot  10 , the first object is the internal structure of the robot  10 , and the outer shell  60  is the outer shell of the robot, it is not limited to this. For example, the shock absorbing device  50  (and the outer shell  60 ) may be provided to a robot (the first object) having a structure different from the robot  10 , to an electrical equipment (the first object) other than the robot, or to other first objects. 
     (Experimental Example) 
     Hereinafter, an experimental example conducted by the present inventors in order to confirm the effect of the present disclosure, is described.  FIG. 14  is a schematic view illustrating the experiment conducted by the present inventors in order to confirm the effect of the shock absorbing device.  FIG. 15  is a graph illustrating a result of the experiment. 
     As illustrated in  FIG. 14 , a sample  240  modeling the first outer shell  70  was manufactured as an example. In this example, the sample  240  was molded by injecting non-foamed resin containing LDPD (Low Density Polyethylene) as a primary component. Moreover, as illustrated in  FIG. 14 , a sample  240 ′ of the conventional first outer shell having a similar shape to the sample  240 , was manufactured as a comparative example. The sample  240 ′ of the comparative example was comprised of urethane foam of two-part liquid mixing type. 
     As illustrated in  FIG. 14 , each of the sample  240  of the example and the sample  240 ′ of the comparative example was placed on a surface plate  254 , and a center part thereof, which corresponds to the curved part  101  and is located at the highest, was pushed by a push-and-pull gauge  252  while its height being adjusted by a height gauge  250 . Accordingly, an elastic force accompanying a change in an amount of deflection (i.e., a force pushing back the push-and-pull gauge  252 ) was measured regarding each of the example and the comparative example. 
     The result of the experiment is illustrated in  FIG. 15 . Measurement values of the example are indicated by a solid line with markers of “Δ” for every deflection amount of 2 mm, and similarly, measurement values of the comparative example are indicated by a broken line with markers of “*”. 
     As illustrated in  FIG. 15 , in the comparative example, the measurement values show a linear shape, and the elastic force pushing back the push-and-pull gauge  252  hardly changes when the amount of deflection is comparatively small (i.e., when the external force applied to the sample  240 ′ of the comparative example is comparatively small). 
     On the other hand, in the example, the measurement values show a non-linear shape, and the elastic force pushing back the push-and-pull gauge  252  suddenly changes when the amount of deflection is comparatively small (i.e., when the external force applied to the sample  240  of the example is comparatively small, in detail, around a range at 0 mm or above and at 4 mm or below). That is, in this example, the elastic force pushing back the push-and-pull gauge  252  increases more quickly than that in the comparative example. As a result, the effects of the shock absorbing device according to the present disclosure are confirmed. 
     In accordance with the present disclosure, a shock absorbing device and a robot having the shock absorbing device may be capable of sufficiently reducing shock transmitted from a first object to a second object, and suppressing motion of the first object and an outer shell as desired based on a value detected by a sensor. The shock absorbing device may be configured to reduce shock transmitted from a first object to a second object, and includes an outer shell containing the first object and comprised of an elastic body having flexibility, a sensor configured to detect one of an external force applied by the second object to the outer shell, an external force applied by the second object to the first object via the outer shell, and a physical quantity corresponding to one of the external forces, and a motion suppressing device configured to suppress motion of the first object and the outer shell based on a value detected by the sensor. 
     According to this configuration, when the external force is applied to the outer shell by the second object, the outer shell is elastically deformed so as to deflect, and thus, the shock transmitted from the first object to the second object can be sufficiently reduced. When the external force applied by the second object to the outer shell is comparatively small, the elasticity of the outer shell pushing back the second object promptly increases compared to an outer shell of a conventional shock absorbing device. Therefore, the sensor can more accurately detect the external force applied by the second object to the outer shell or the external force applied by the second object to the first object via the outer shell. As a result, the motion suppressing device can suppress the motion of the first object and the outer shell as desired based on the value detected by the sensor. 
     The outer shell may have a wall, and a gap may be formed between the first object and the outer shell. According to this configuration, the outer shell can elastically deform suitably without being obstructed by other structures. For example, the outer shell may reduce the shock transmitted from the first object to the second object by a part of the outer shell to which the external force is applied by the second object being elastically deformed entirely in the thickness direction so as to deflect toward the gap. 
     The thickness of the wall may be 5.0 mm or below. According to this configuration, the outer shell can elastically deform suitably. The thickness of the wall may be 1.0 mm or above and 2.0 mm or below. According to this configuration, the outer shell can elastically deform more suitably. 
     The elastic body constituting the outer shell may further have incompressibility. According to this configuration, the outer shell can elastically deform suitably. The elastic body constituting the outer shell may be made of non-foamed resin. According to this configuration, the outer shell can easily be formed and elastically deform suitably. For example, a primary component of the non-foamed resin may be polyethylene. At least a part of the outer shell may have a curved part protruding outwardly in the thickness direction. According to this configuration, the elasticity of the outer shell pushing back the second object, can be increased further quickly compared to the outer shell of the conventional shock absorbing device. Therefore, the sensor can further accurately detect the external force applied by the second object to the outer shell, or the external force applied by the second object to the first object via the outer shell. 
     An inner surface of the outer shell opposing to the first object may be smooth. According to this configuration, the outer shell can easily be formed and can elastically deform suitably without being obstructed by the other objects. In order to solve the problem, a robot according to the present disclosure is provided, which includes any one of the shock absorbing devices described above, and the first object. The first object is an internal structure of the robot, and the outer shell is an outer shell of the robot. According to this configuration, when the external force is applied to the outer shell by the second object, the outer shell is elastically deformed so as to deflect, and thus, the shock transmitted from the internal structure of the robot (first object) to the second object can be sufficiently reduced. When the external force applied by the second object to the outer shell is comparatively small, the elasticity of the outer shell pushing back the second object promptly increases compared to an outer shell of a conventional shock absorbing device. Therefore, the sensor can more accurately detect the external force applied by the second object to the outer shell or the external force applied by the second object to the internal structure of the robot via the outer shell. As a result, the motion suppressing device can suppress the motion of the robot as desired based on the value detected by the sensor. 
     For example, the robot may further include a robotic arm having at least one joint axis, and a motor configured to drive the joint axis. The outer shell may include a first part configured to be an outer shell of the robotic arm. The sensor may detect, as an external force applied by the second object to the first object via the first part, one of an amount of change in a rotational position of the motor, an amount of change in a rotational speed of the motor, and an amount of change in a current value flowing in the motor. For example, the second object may be a human body, and the robot may be adapted to be an industrial robot configured to work cooperatively with the human body. 
     A shock absorbing device and a robot having the shock absorbing device can be provided, which are capable of sufficiently reducing shock transmitted from a first object to a second object, and suppressing motion of the first object and an outer shell as desired based on a value detected by a sensor. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           10  Robot 
           12  Pedestal 
           14  Base Shaft 
           18  Robot Controlling Device 
           20   a,    20   b  Robotic Arm 
           22  First Link 
           22   a  First Link Internal Structure 
           23  Decorative Panel 
           24  Second Link 
           24   a  Second Link Internal Structure 
           26  Wrist 
           26   a  Wrist Internal Structure 
           27  Mechanical Interface 
           30  Motor 
           50  Shock Absorbing Device 
           60  Outer Shell 
           70  First Outer Shell 
           72  First Outer Shell Body 
           73  Snap-Fit Structure 
           73   a  Male Part 
           73   b  Female Part 
           76  First Outer Shell Back Part 
           77  Vent 
           78  Heat Sink 
           79  Internal Space 
           80  Second Outer Shell 
           82  Second Outer Shell Body 
           84 ,  96  Fixing Part 
           85  Sponge Foam 
           86 ,  87 ,  98 ,  99  Hook-And-Loop Fastener 
           90  Third Outer Shell 
           92  Third Outer Shell Body 
           93  Third Outer Shell Side Part 
           94  Third Outer Shell One Surface Part 
           95  Third Outer Shell Other Surface Part 
           97  Sponge Foam 
           101 ,  102 ,  103  Curved Part 
           110  Sensor 
           120  Motion Suppressing Device 
           200  Conventional Shock Absorbing Device 
           210  Conventional Outer Shell 
           240  Sample 
           250  Height Gauge 
           252  Push-And-Pull Gauge 
           254  Surface Plate 
         J 1 -J 4  Joint Part 
         L 1 , L 2  Rotational Axis 
         C Conveyor 
         P Human Body 
         S Worksite 
         W Workpiece