Abstract:
A robot hand, which has an arbitrary object grasping function in the same manner as a human hand and a high precision and stable grasping function in the same manner as an industrial gripper and performs a pose similar to a human hand while having complete opposability without any increase in complexity or degree of freedom. The robot hand includes a base part, and a plurality of finger connection parts, and a plurality of finger modules connected to the plurality of finger connection parts. The finger connection parts connected to the base part are connected to adjacent finger connection parts by roll joints such that each pair the finger connection parts connected by the roll joints is driven together, and the finger connection parts adjacent to the finger connection parts connected to the base part are driven separately from the finger connection parts connected to the base part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 2010-0091492, filed on Sep. 17, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments relate to a robot hand enabling symmetrical grasping. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, utilization of robots continues to expand to a wider range of overall industries, and research and development of humanoid robots has been accelerated. 
         [0006]    In order to allow a humanoid robot to assist human housework, rapid grasping or manipulation of various objects used by the human is important. 
         [0007]    For this purpose, humanoid hands having high degree of freedom and size and function similar to those of humans have been developed. 
         [0008]    Most humanoid hands include 4˜5 fingers and have high degree of freedom, i.e., 8˜15 degrees of freedom. 
         [0009]    These humanoid hands are advantageous in that they enable the use of tools in a similar manner as humans. These humanoid hands also enable operation in environments designed for humans in a similar manner as humans. Moreover, these humanoid hands enable grasping and manipulating an arbitrary object in a similar manner as humans. 
         [0010]    On the other hand, industrial grippers are designed to precisely and stably grasp a specific object. 
         [0011]    Most industrial grippers include 2˜4 fingers, and the respective fingers are designed according to sizes and shapes of objects to be grasped. 
         [0012]    Further, these industrial grippers have 1˜4 degrees of freedom lower than those of the humanoid hands. 
         [0013]    Moreover, since all the fingers of the industrial grippers have the same shape and form complete symmetry (opposability), the industrial grippers achieve precise and stable grasping. 
         [0014]    However, when a new object needs to be grasped, a gripper needs to be replaced with a different one, and has difficulty in using a tool designed for humans. 
         [0015]    If humanoid hand mechanisms and grasping techniques are applied to an industrial robot, the industrial robot becomes capable of grasping and manipulating an arbitrary object located at an arbitrary position. 
         [0016]    Therefore, such an industrial robot may grasp various objects with one kind of hand without conventional gripper replacement, and use tools designed for humans, as needed. 
         [0017]    However, the humanoid hands have been developed so as to satisfy requirements of high degree of freedom, miniaturization and flexibility, and thus are difficult to keep up with positional accuracy, grasp stability and stiffness of the industrial grippers. 
         [0018]    Accordingly, introduction of a hand mechanism having advantages of both the humanoid hands and the industrial grippers is required. 
       SUMMARY 
       [0019]    Therefore, it is an aspect of an embodiment to provide a robot hand which has both an arbitrary object grasping function in the same manner as a human hand and a high precision and stable grasping function in the same manner as an industrial gripper. 
         [0020]    It is another aspect of an embodiment to provide a robot hand which performs a pose similar to a human hand while having complete opposability without any increase in complexity or degree of freedom. 
         [0021]    Additional aspects of embodiments will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of embodiments. 
         [0022]    In accordance with an aspect of an embodiment, a robot hand includes a base part, a plurality of finger connection parts provided on the base part such that some of the plurality of finger connection parts are connected to the base part, and a plurality of finger modules respectively connected to the plurality of finger connection parts so as to grasp an object, wherein, among the plurality of finger connection parts, finger connection parts connected to the base part are respectively connected to adjacent finger connection parts by roll joints such that each pair of the finger connection parts connected by the roll joints is driven together, and the finger connection parts adjacent to the finger connection parts connected to the base part are driven separately from the finger connection parts connected to the base part so that the plurality of finger modules performs symmetrical grasping. 
         [0023]    The finger connection parts connected to the base part may include a second finger connection part and a third finger connection part, the second finger connection part may be connected to a first finger connection part adjacent to the second finger connection part by the roll joints, and the third finger connection part may be connected to a fourth finger connection part adjacent to the third finger connection part by the roll joints. 
         [0024]    The roll joints connecting the second finger connection part and the first finger connection part and the roll joints connecting the third finger connection part and the fourth finger connection part may be formed so as to surround wires in a  FIG. 8  shape. 
         [0025]    In accordance with another aspect of an embodiment, a robot hand includes a base part, a plurality of finger connection parts provided on the base part such that some of the plurality of finger connection parts are connected to the base part, and a plurality of finger modules respectively connected to the plurality of finger connection parts so as to grasp an object, wherein, among the plurality of finger connection parts, finger connection parts connected to the base part are respectively connected to adjacent finger connection parts by roll joints such that each pair of the finger connection parts connected by the roll joints is driven together, the finger connection parts adjacent to the finger connection parts connected to the base part are driven separately from the finger connection parts connected to the base part so that the plurality of finger modules performs symmetrical grasping, and the plurality of finger connection parts connected by the roll joints is driven via connection of links. 
         [0026]    The finger connection parts connected to the base part may include a second finger connection part and a third finger connection part, the second finger connection part may be connected to a first finger connection part adjacent to the second finger connection part by the roll joints, and the third finger connection part may be connected to a fourth finger connection part adjacent to the third finger connection part by the roll joints. 
         [0027]    The roll joints connecting the second finger connection part and the first finger connection part and the roll joints connecting the third finger connection part and the fourth finger connection part may be formed so as to surround wires in a  FIG. 8  shape. 
         [0028]    In order to drive the second finger connection part and the first finger connection part connected by the roll joints and the third finger connection part and the fourth finger connection part connected by the roll joints, the second finger connection part and the first finger connection part may be connected by a first link and the third finger connection part and the fourth finger connection part may be connected by a second link. 
         [0029]    Motors and speed reducers may be installed in the second finger connection part and the third finger connection part so that the second finger connection part and the third finger connection part are rotated with respect to the base part by the motors and the speed reducers. When the second finger connection part is rotated, the first finger connection part connected to the second finger connection part by the roll joints may be rotated together with the second finger connection part, and when the third finger connection part is rotated, the fourth finger connection part connected to the third finger connection part by the roll joints may be rotated together with the third finger connection part. 
         [0030]    Motors and speed reducers may be installed in the first finger connection part and the fourth finger connection part so that the first link and the second link are rotated by the motors and the speed reducers, and via the rotation of the first link and the second link, the first finger connection part may be rotated about the second finger connection part and the fourth finger connection part may be rotated about the third finger connection part. 
         [0031]    In accordance with another aspect of an embodiment, a robot hand includes a base part, a plurality of finger connection parts provided on the base part such that some of the plurality of finger connection parts are connected to the base part, and a plurality of finger modules respectively connected to the plurality of finger connection parts so as to grasp an object, wherein among the plurality of finger connection parts, finger connection parts connected to the base part are respectively connected to adjacent finger connection parts by roll joints such that each pair of the finger connection parts connected by the roll joints is driven together, the finger connection parts adjacent to the finger connection parts connected to the base part are driven separately from the finger connection parts connected to the base part so that the plurality of finger modules performs symmetrical grasping, and the plurality of finger connection parts connected by the roll joints is driven via connection of pulleys and belts. 
         [0032]    The finger connection parts connected to the base part may include a second finger connection part and a third finger connection part, the second finger connection part may be connected to a first finger connection part adjacent to the second finger connection part by the roll joints, and the third finger connection part may be connected to a fourth finger connection part adjacent to the third finger connection part by the roll joints. 
         [0033]    The roll joints connecting the second finger connection part and the first finger connection part and the roll joints connecting the third finger connection part and the fourth finger connection part may be formed so as to surround wires in a  FIG. 8  shape. 
         [0034]    In order to drive the second finger connection part and the first finger connection part connected by the roll joints and the third finger connection part and the fourth finger connection part connected by the roll joints, motors may be respectively installed in the finger connection parts. A first small pulley may be fixed to the motor installed in the first finger connection part, a second small pulley may be fixed to the motor installed in the second finger connection part, a third small pulley may be fixed to the motor installed in the third finger connection part, a fourth small pulley may be fixed to the motor installed in the fourth finger connection part, and a first large pulley and a second large pulley may be fixed to the second finger connection part and the third finger connection part. 
         [0035]    A first belt may be configured to connect the first small pulley, the first large pulley and the third small pulley so as to transmit rotary force among the first small pulley, the first large pulley and the third small pulley, and a second belt may be configured to connect the second small pulley, the second large pulley and the fourth small pulley so as to transmit rotary force among the second small pulley, the second large pulley and the fourth small pulley. 
         [0036]    When the second small pulley is rotated by the motor installed in the second finger connection part, the second large pulley connected to the second small pulley by the second belt may be rotated, and when the second large pulley is rotated, the third finger connection part to which the second large pulley is fixed may be rotated. When the third small pulley is rotated by the motor installed in the third finger connection part, the first large pulley connected to the third small pulley by the first belt may be rotated, and when the first large pulley is rotated, the second finger connection part to which the first large pulley is fixed may be rotated. 
         [0037]    When the third finger connection part is rotated, the fourth finger connection part connected to the third finger connection part by the roll joints may be rotated together with the third finger connection part, and when the second finger connection part is rotated, the first finger connection part connected to the second finger connection part by the roll joints may be rotated together with the second finger connection part. 
         [0038]    When the first small pulley is rotated by the motor installed in the first finger connection part, the first finger connection part may be rotated about the second finger connection part, and when the fourth small pulley is rotated by the motor installed in the fourth finger connection part, the fourth finger connection part may be rotated about the third finger connection part. 
         [0039]    In accordance with a further aspect of an embodiment, a robot hand includes a base part, a plurality of finger connection parts provided on the base part such that some of the plurality of finger connection parts are connected to the base part, and a plurality of finger modules respectively connected to the plurality of finger connection parts so as to grasp an object, wherein among the plurality of finger connection parts, finger connection parts connected to the base part are respectively connected to adjacent finger connection parts by roll joints such that each pair of the finger connection parts connected by the roll joints is driven together, the finger connection parts adjacent to the finger connection parts connected to the base part are driven separately from the finger connection parts connected to the base part so that the plurality of finger modules performs symmetrical grasping, and the plurality of finger connection parts connected by the roll joints is driven via connection of gears. 
         [0040]    The finger connection parts connected to the base part may include a second finger connection part and a third finger connection part, the second finger connection part may be connected to a first finger connection part adjacent to the second finger connection part by the roll joints, and the third finger connection part may be connected to a fourth finger connection part adjacent to the third finger connection part by the roll joints. 
         [0041]    The roll joints connecting the second finger connection part and the first finger connection part and the roll joints connecting the third finger connection part and the fourth finger connection part may be formed so as to surround wires in a  FIG. 8  shape. 
         [0042]    The gears may include spur gears. 
         [0043]    In order to drive the second finger connection part and the first finger connection part connected by the roll joints and the third finger connection part and the fourth finger connection part connected by the roll joints, motors may be respectively installed in the finger connection parts. A first small gear may be fixed to the motor installed in the first finger connection part, a second small gear may be fixed to the motor installed in the second finger connection part, a third small gear may be fixed to the motor installed in the third finger connection part, a fourth small gear may be fixed to the motor installed in the fourth finger connection part, and a first large gear and a second large gear may be fixed to the second finger connection part and the third finger connection part. 
         [0044]    When the second small gear is rotated by the motor installed in the second finger connection part, the second large gear may be rotated by the rotation of the second small gear, and when the second large gear is rotated, the third finger connection part to which the second large gear is fixed may be rotated. When the third small gear is rotated by the motor installed in the third finger connection part, the first large gear may be rotated by the rotation of the third small gear, and when the first large gear is rotated, the second finger connection part to which the first large gear is fixed may be rotated. 
         [0045]    When the third finger connection part is rotated, the fourth finger connection part connected to the third finger connection part by the roll joints may be rotated together with the third finger connection part, and when the second finger connection part is rotated, the first finger connection part connected to the second finger connection part by the roll joints may be rotated together with the second finger connection part. 
         [0046]    When the first small gear is rotated by the motor installed in the first finger connection part, the first finger connection part may be rotated about the second finger connection part, and when the fourth small gear is rotated by the motor installed in the fourth finger connection part, the fourth finger connection part may be rotated about the third finger connection part. 
         [0047]    The gears may include internal gears. 
         [0048]    In order to drive the second finger connection part and the first finger connection part connected by the roll joints and the third finger connection part and the fourth finger connection part connected by the roll joints, motors may be respectively installed in the finger connection parts. A first small gear may be fixed to the motor installed in the first finger connection part, a second small gear may be fixed to the motor installed in the second finger connection part, a third small gear may be fixed to the motor installed in the third finger connection part, a fourth small gear may be fixed to the motor installed in the fourth finger connection part, and a first internal gear and a second internal gear may be fixed to the second finger connection part and the third finger connection part. 
         [0049]    When the second small gear is rotated by the motor installed in the second finger connection part, the second internal gear may be rotated by the rotation of the second small gear, and when the second internal gear is rotated, the third finger connection part to which the second large gear is fixed may be rotated. When the third small gear is rotated by the motor installed in the third finger connection part, the first internal gear may be rotated by the rotation of the third small gear, and when the first internal gear is rotated, the second finger connection part to which the first large gear is fixed may be rotated. 
         [0050]    When the third finger connection part is rotated, the fourth finger connection part connected to the third finger connection part by the roll joints may be rotated together with the third finger connection part, and when the second finger connection part is rotated, the first finger connection part connected to the second finger connection part by the roll joints may be rotated together with the second finger connection part. 
         [0051]    When the first small gear is rotated by the motor installed in the first finger connection part, the first finger connection part may be rotated about the second finger connection part, and when the fourth small gear is rotated by the motor installed in the fourth finger connection part, the fourth finger connection part may be rotated about the third finger connection part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0052]    These and/or other aspects of embodiments will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings of which: 
           [0053]      FIG. 1  is a perspective view illustrating a robot hand in accordance with an embodiment; 
           [0054]      FIG. 2  is a view schematically illustrating various symmetrical grasping strategies of the robot hand in accordance with an embodiment; 
           [0055]      FIG. 3  is a perspective view illustrating a robot hand in accordance with an embodiment in which a plurality of fingers connection parts is driven via connection of links; 
           [0056]      FIG. 4  is a view schematically illustrating the robot hand in accordance with an embodiment in which the plurality of fingers connection parts is driven via the connection of the links; 
           [0057]      FIG. 5  is a perspective view illustrating a robot hand in accordance with another embodiment in which a plurality of fingers is driven via connection of pulleys and belts; 
           [0058]      FIG. 6  is a view schematically illustrating the robot hand in accordance with an embodiment in which the plurality of fingers is driven via the connection of the pulleys and the belts; 
           [0059]      FIG. 7  is a perspective view illustrating a robot hand in accordance with another embodiment in which a plurality of fingers is driven via connection of spur gears; 
           [0060]      FIG. 8  is a view schematically illustrating the robot hand in accordance with an embodiment in which the plurality of fingers is driven via the connection of the spur gears; 
           [0061]      FIG. 9  is a perspective view illustrating a robot hand in accordance with another embodiment in which a plurality of fingers is driven via connection of internal gears; and 
           [0062]      FIG. 10  is a view schematically illustrating the robot hand in accordance with an embodiment in which the plurality of fingers is driven via the connection of the internal gears. 
       
    
    
     DETAILED DESCRIPTION 
       [0063]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
         [0064]      FIG. 1  is a perspective view illustrating a robot hand in accordance with an embodiment. 
         [0065]    As shown in  FIG. 1 , the robot hand  1  includes a base part  10 , a plurality of finger connection parts  20  provided on the base part  10  such that some of the plurality of finger connection parts  20  are connected to the base part  10 , and a plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20  so as to grasp an object. 
         [0066]    As shown in  FIG. 1 , the base part  10  corresponds to a human wrist, and the plurality of finger connection parts  20  and the plurality of finger modules  30  are provided on the base part  10 . 
         [0067]    The plurality of finger connection parts  20  provided on the base part  10  includes a first finger connection part  21 , a second finger connection part  23 , a third finger connection part  25  and a fourth finger connection part  27 . 
         [0068]    Although  FIG. 1  illustrates the plurality of finger connection parts  20  as including the four finger connection parts  21 ,  23 ,  25  and  27 , the number of the plurality of finger connection parts  20  is not limited thereto. 
         [0069]    As shown in  FIG. 1 , among the plurality of finger connection parts  20  provided on the base part  10 , the second finger connection part  23  and the third finger connection part  25  are directly connected to the base part  10 . 
         [0070]    The first finger connection part  21  adjacent to the second finger connection part  23  directly connected to the base part  10  is not directly connected to the base part  10 , but is connected to the second finger connection part  23  by roll joints. 
         [0071]    The fourth finger connection part  27  adjacent to the third finger connection part  25  directly connected to the base part  10  is not directly connected to the base part  10 , but is connected to the third finger connection part  25  by roll joints. 
         [0072]    The second finger connection part  23  and the first finger connection part  21  are connected by the roll joints and the third finger connection part  25  and the fourth finger connection part  27  are connected by the roll joints, thereby allowing rolling motions to be performed. 
         [0073]    The roll joints to perform rolling motions are formed so as to surround wires W in a  FIG. 8  shape, as shown in  FIG. 1 . 
         [0074]    The roll joints surrounding the wires W in the  FIG. 8  shape maintain closed states between the second finger connection part  23  and the first finger connection part  21  and between the third finger connection part  25  and the fourth finger connection part  27  without widening. 
         [0075]    Aside from surrounding the wires W in the  FIG. 8  shape, the roll joints may formed by gears (not shown) or through various other methods. 
         [0076]    Using the roll joints, the plurality of finger connection parts  20  may be formed in a simpler configuration and be more precisely driven. 
         [0077]    The first finger connection part  21  connected to the second finger connection part  23  by the roll joints is controlled so as to perform a rolling motion, and is thus driven together with driving of the second finger connection part  23  under the condition that the first finger connection part  21  is closely adhered to the second finger connection part  23  by the wires W. 
         [0078]    The fourth finger connection part  27  connected to the third finger connection part  25  by the roll joints is also controlled so as to perform a rolling motion, and is thus driven together with driving of the third finger connection part  25  under the condition that the fourth finger connection part  27  is closely adhered to the third finger connection part  25  by the wires W. 
         [0079]    Since the second finger connection part  23  and the first finger connection part  21  are connected by the roll joints and the third finger connection part  25  and the fourth finger connection part  27  are connected by the roll joints, the first finger connection part  21  is driven together with the second finger connection part  23  when the second finger connection part  23  is driven and the fourth finger connection part  27  is driven together with the third finger connection part  25  when the third finger connection part  25  is driven. Further, the first finger connection part  21  may be driven separately from the second finger connection part  23  and the fourth finger connection part  27  may be driven separately from the third finger connection part  25 . 
         [0080]    As shown in  FIG. 1 , the plurality of finger modules  30  is respectively connected to the plurality of finger connection parts  20  so as to grasp an object. 
         [0081]    The plurality of finger modules  30  includes a first finger module  31 , a second finger module  33 , a third finger module  35  and a fourth finger module  37 . 
         [0082]    Although  FIG. 1  illustrates the plurality of finger modules  30  as including the four finger modules  31 ,  33 ,  35  and  37 , the number of the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20  is varied according to the number of the plurality of finger connection parts  20 . 
         [0083]    Further, although  FIG. 1  illustrate the plurality of finger modules  30  as being respectively connected by two joints J so as to have  2  degrees of freedom, the structure of the plurality of finger modules  30  is not limited thereto and may be configured in various shapes so long as such shapes enable an object to be grasped. 
         [0084]    The plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20  is rotated symmetrically so as to grasp an arbitrary object, and, and grasps the object when the plurality of finger modules  30  is rotated and thus form symmetry. 
         [0085]    Hereinafter, various configurations to drive the plurality of finger connection parts  20  will be described. 
         [0086]    As shown in  FIGS. 3 and 4 , the plurality of finger connection parts  20  connected by the roll joints is driven via connection of links  40 . 
         [0087]    Motors (not shown) and speed reducers (not shown) are respectively installed in the plurality of finger connection parts  20  driven via the connection of the links  40 . 
         [0088]    In order to drive the second finger connection part  23  and the first finger connection part  21  connected by the roll joints and the third connection part  25  and the fourth finger connection part  27  connected by the roll joints, the second finger connection part  23  and the first finger connection part  21  are connected by a first link  41  provided on the lower portions of the second finger connection part  23  and the first finger connection part  21 , and the third finger connection part  25  and the fourth finger connection part  27  are connected by a second link  43  provided on the lower portions of the third finger connection part  25  and the fourth finger connection part  27 . 
         [0089]    Hereinafter, a process of performing symmetrical grasping using the plurality of finger connection parts  20  through the links  40  will be described in more detail. 
         [0090]    First, the second finger connection part  23  and the third finger connection part  25  of the plurality of finger connection parts  20  are rotated with respect to the base part  10  by the motors (not shown) and the speed reducers (not shown) respectively installed on the second finger connection part  23  and the third finger connection part  25 . 
         [0091]    When the second finger connection part  23  is rotated with respect to the base part  10 , the first finger connection part  21  connected to the second finger connection part  23  by the roll joints and controlled to perform the rolling motion is rotated together with the second finger connection part  23 . 
         [0092]    In the same manner, when the third finger connection part  25  is rotated with respect to the base part  10 , the first fourth connection part  27  connected to the third finger connection part  25  by the roll joints and controlled to perform the rolling motion is rotated together with the third finger connection part  25 . 
         [0093]    When the second finger connection part  23  and the third finger connection part  25  are rotated with respect to the base part  10  by the motors (not shown) and the speed reducers (not shown) respectively installed in the second finger connection part  23  and the third finger connection part  25 , the first finger connection part  21  and the fourth connection part  27  respectively connected to the second finger connection part  23  and the third finger connection part  25  by the roll joints are rotated together with the second finger connection part  23  and the third finger connection part  25 , and thus the plurality of finger connection parts  20  forms a symmetrical structure so as to grasp an object, as shown in  FIG. 2 . 
         [0094]    When the plurality of finger connection parts  20  forms the symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0095]    If the object is incapable of being grasped through the above symmetrical structure formed by the rotation of the second finger connection part  23  and the third finger connection part  25 , the first finger connection part  21  and the fourth finger connection part  27  need to be separately rotated to form another symmetrical structure so as to grasp the object. 
         [0096]    In order to form another symmetrical structure by separately rotating the first finger connection part  21  and the fourth finger connection part  27 , the first link  41  is rotated by the motor (not shown) and the speed reducer (not shown) installed in the first finger connection part  21 , and the second link  43  is rotated by the motor (not shown) and the speed reducer (not shown) installed in the fourth finger connection part  27 . 
         [0097]    When the first link  41  is rotated, the first finger connection part  21  is rotated about the second finger connection part  23 , and when the second link  43  is rotated, the fourth finger connection part  27  is rotated about the third finger connection part  25 . That is, the first finger connection part  21  and the fourth finger connection part  27  are separately rotated. 
         [0098]    When the first finger connection part  21  and the fourth finger connection part  27  are separately rotated and thus the plurality of finger connection parts  20  forms a new symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0099]    The above configuration in which the links  40  are connected is relatively simple, thereby allowing the robot hand  1  to have a simpler configuration. 
         [0100]    As shown in  FIGS. 5 and 6 , the plurality of finger connection parts  20  connected by the roll joints is driven via connection of pulleys  60  and belts  50 . 
         [0101]    Motors (not shown) are respectively installed in the plurality of finger connection parts  20  driven via the connection of the pulleys  60  and the belts  50 . 
         [0102]    In order to drive the second finger connection part  23  and the first finger connection part  21  connected by the roll joints and the third connection part  25  and the fourth finger connection part  27  connected by the roll joints, a first small pulley  61  is fixed to the motor (not shown) installed in the first finger connection part  21 , a second small pulley  62  is fixed to the motor (not shown) installed in the second finger connection part  23 , a third small pulley  63  is fixed to the motor (not shown) installed in the third finger connection part  25 , a fourth small pulley  64  is fixed to the motor (not shown) installed in the fourth finger connection part  27 , and a first large pulley  65  and a second large pulley  66  are fixed to the second finger connection part  23  and the third finger connection part  25 . 
         [0103]    Further, a first belt  51  is configured to connect the first small pulley  61 , the first large pulley  65 , and the third small pulley  63  so as to transmit rotary force, and a second belt  53  is configured to connect the second small pulley  62 , the second large pulley  66 , and the fourth small pulley  64  so as to transmit rotary force. 
         [0104]    Hereinafter, a process of performing symmetrical grasping using the plurality of finger connection parts  20  through the pulleys  60  and the belts  50  will be described in more detail. 
         [0105]    First, when the second small pulley  62  is rotated by the motor (not shown) installed in the second finger connection part  23 , rotary force of the second small pulley  62  is transmitted to the second large pulley  66  connected to the second small pulley  62  by the second belt  53  and the second large pulley  66  is rotated at a reduced rotational amount by the second belt  53 . 
         [0106]    When the second large pulley  66  is rotated at the reduced rotational amount, the third finger connection part  25  to which the second large pulley  66  is fixed is rotated at the reduced rotational amount. 
         [0107]    In the same manner, when the third small pulley  63  is rotated by the motor (not shown) installed in the third finger connection part  25 , rotary force of the third small pulley  63  is transmitted to the first large pulley  65  connected to the third small pulley  63  by the first belt  51  and the first large pulley  65  is rotated at a reduced rotational amount by the first belt  51 . 
         [0108]    When the first large pulley  65  is rotated at the reduced rotational amount, the second finger connection part  23  to which the first large pulley  65  is fixed is rotated at the reduced rotational amount. 
         [0109]    As described above, when the third finger connection part  25  is rotated, the fourth finger connection part  27  connected to the third finger connection part  25  by the roll joints is rotated together with the third finger connection part  25 , and when the second finger connection part  23  is rotated, the first finger connection part  21  connected to the second finger connection part  23  by the roll joints is rotated together with the second finger connection part  23 , and thus the plurality of finger connection parts  20  forms a symmetrical structure so as to grasp an object, as shown in  FIG. 2 . 
         [0110]    When the plurality of finger connection parts  20  forms the symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0111]    If the object is incapable of being grasped through the above symmetrical structure formed by the rotation of the second finger connection part  23  and the third finger connection part  25 , the first finger connection part  21  and the fourth finger connection part  27  need to be separately rotated to form another symmetrical structure so as to grasp the object. 
         [0112]    In order to form another symmetrical structure by separately rotating the first finger connection part  21  and the fourth finger connection part  27 , when the first small pulley  61  is rotated by the motor (not shown) installed in the first finger connection part  21 , the first finger connection part  21  is rotated about the second finger connection part  23  at a reduced rotational amount by the first belt  51 , and when the fourth small pulley  64  is rotated by the motor (not shown) installed in the fourth finger connection part  27 , the fourth finger connection part  27  is rotated about the third finger connection part  25  at a reduced rotational amount by the second belt  53 , thereby allowing the first finger connection part  21  and the fourth finger connection part  27  to be separately rotated. 
         [0113]    When the first finger connection part  21  and the fourth finger connection part  27  are separately rotated and thus the plurality of finger connection parts  20  forms a new symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0114]    The above configuration in which the pulleys  60  and the belts  50  are connected has a speed reducing function and does not require any separate speed reducer, and has little backlash and thus eliminates the need for any backlash reducing member. 
         [0115]    As shown in  FIGS. 7 and 8 , the plurality of finger connection parts  20  connected by the roll joints is driven via connection of spur gears  71 . 
         [0116]    Motors (not shown) are respectively installed in the plurality of finger connection parts  20  driven via the connection of the spur gears  71 . 
         [0117]    In order to drive the second finger connection part  23  and the first finger connection part  21  connected by the roll joints and the third connection part  25  and the fourth finger connection part  27  connected by the roll joints, a first small gear  71   a  is fixed to the motor (not shown) installed in the first finger connection part  21 , a second small gear  71   b  is fixed to the motor (not shown) installed in the second finger connection part  23 , a third small gear  71   c  is fixed to the motor (not shown) installed in the third finger connection part  25 , a fourth small gear  71   d  is fixed to the motor (not shown) installed in the fourth finger connection part  27 , and a first large gear  71 A and a second large gear  71 B are fixed to the second finger connection part  23  and the third finger connection part  25 . 
         [0118]    Hereinafter, a process of performing symmetrical grasping using the plurality of finger connection parts  20  through the spur gears  71  will be described in more detail. 
         [0119]    First, when the second small gear  71   b  is rotated by the motor (not shown) installed in the second finger connection part  23 , the second large gear  71 B engaged with the second small gear  71   b  is rotated at a reduced rotational amount by the rotation of the second small gear  71   b.    
         [0120]    When the second large gear  71 B is rotated at the reduced rotational amount, the third finger connection part  25  to which the second large gear  71 Bis fixed is rotated at the reduced rotational amount. 
         [0121]    In the same manner, when the third small gear  71   c  is rotated by the motor (not shown) installed in the third finger connection part  25 , the first large gear  71 A engaged with the third small gear  71   c  is rotated at a reduced rotational amount by the rotation of the third small gear  71   c.    
         [0122]    When the first large gear  71 A is rotated at the reduced rotational amount, the second finger connection part  23  to which the first large gear  71 A is fixed is rotated at the reduced rotational amount. 
         [0123]    As described above, when the third finger connection part  25  is rotated, the fourth finger connection part  27  connected to the third finger connection part  25  by the roll joints is rotated together with the third finger connection part  25 , and when the second finger connection part  23  is rotated, the first finger connection part  21  connected to the second finger connection part  23  by the roll joints is rotated together with the second finger connection part  23 , and thus the plurality of finger connection parts  20  forms a symmetrical structure so as to grasp an object, as shown in  FIG. 2 . 
         [0124]    When the plurality of finger connection parts  20  forms the symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0125]    If the object is incapable of being grasped through the above symmetrical structure formed by the rotation of the second finger connection part  23  and the third finger connection part  25 , the first finger connection part  21  and the fourth finger connection part  27  need to be separately rotated to form another symmetrical structure so as to grasp the object. 
         [0126]    In order to form another symmetrical structure by separately rotating the first finger connection part  21  and the fourth finger connection part  27 , when the first small gear  71   a  is rotated by the motor (not shown) installed in the first finger connection part  21 , the first finger connection part  21  is rotated about the second finger connection part  23  at a reduced rotational amount by the first large gear  71 A, and when the fourth small gear  71   d  is rotated by the motor (not shown) installed in the fourth finger connection part  27 , the fourth finger connection part  27  is rotated about the third finger connection part  25  at a reduced rotational amount by the second large gear  71 B, thereby allowing the first finger connection part  21  and the fourth finger connection part  27  to be separately rotated. 
         [0127]    When the first finger connection part  21  and the fourth finger connection part  27  are separately rotated and thus the plurality of finger connection parts  20  forms a new symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0128]    The above configuration in which the spur gears  71  are connected is relatively simple, thereby allowing the robot hand  1  to have a simpler configuration. 
         [0129]    As shown in  FIGS. 9 and 10 , the plurality of finger connection parts  20  connected by the roll joints is driven via connection of internal gears  73 . 
         [0130]    Motors (not shown) are respectively installed in the plurality of finger connection parts  20  driven via the connection of the internal gears  73 . 
         [0131]    In order to drive the second finger connection part  23  and the first finger connection part  21  connected by the roll joints and the third connection part  25  and the fourth finger connection part  27  connected by the roll joints, a first small gear  73   a  is fixed to the motor (not shown) installed in the first finger connection part  21 , a second small gear  73   b  is fixed to the motor (not shown) installed in the second finger connection part  23 , a third small gear  73   c  is fixed to the motor (not shown) installed in the third finger connection part  25 , a fourth small gear  73   d  is fixed to the motor (not shown) installed in the fourth finger connection part  27 , and a first internal gear  73 A and a second internal gear  73 B are fixed to the second finger connection part  23  and the third finger connection part  25 . 
         [0132]    Hereinafter, a process of performing symmetrical grasping using the plurality of finger connection parts  20  through the internal gears  73  will be described in more detail. 
         [0133]    First, when the second small gear  73   b  is rotated by the motor (not shown) installed in the second finger connection part  23 , the second internal gear  73 B engaged with the second small gear  73   b  is rotated at a reduced rotational amount by the rotation of the second small gear  73   b.    
         [0134]    When the second internal gear  73 B is rotated at the reduced rotational amount, the third finger connection part  25  to which the second internal gear  73 B is fixed is rotated at the reduced rotational amount. 
         [0135]    In the same manner, when the third small gear  73   c  is rotated by the motor (not shown) installed in the third finger connection part  25 , the first internal gear  73 A engaged with the third small gear  73   c  is rotated at a reduced rotational amount by the rotation of the third small gear  73   c.    
         [0136]    When the first internal gear  73 A is rotated at the reduced rotational amount, the second finger connection part  23  to which the first internal gear  73 A is fixed is rotated at the reduced rotational amount. 
         [0137]    As described above, when the third finger connection part  25  is rotated, the fourth finger connection part  27  connected to the third finger connection part  25  by the roll joints is rotated together with the third finger connection part  25 , and when the second finger connection part  23  is rotated, the first finger connection part  21  connected to the second finger connection part  23  by the roll joints is rotated together with the second finger connection part  23 , and thus the plurality of finger connection parts  20  forms a symmetrical structure so as to grasp an object, as shown in  FIG. 2 . 
         [0138]    When the plurality of finger connection parts  20  forms the symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0139]    If the object is incapable of being grasped through the above symmetrical structure formed by the rotation of the second finger connection part  23  and the third finger connection part  25 , the first finger connection part  21  and the fourth finger connection part  27  need to be separately rotated to form another symmetrical structure so as to grasp the object. 
         [0140]    In order to form another symmetrical structure by separately rotating the first finger connection part  21  and the fourth finger connection part  27 , when the first small gear  73   a  is rotated by the motor (not shown) installed in the first finger connection part  21 , the first finger connection part  21  is rotated about the second finger connection part  23  at a reduced rotational amount by the first internal gear  73 A, and when the fourth small pulley  73   d  is rotated by the motor (not shown) installed in the fourth finger connection part  27 , the fourth finger connection part  27  is rotated about the third finger connection part  25  at a reduced rotational amount by the second internal gear  71 B, thereby allowing the first finger connection part  21  and the fourth finger connection part  27  to be separately rotated. 
         [0141]    When the first finger connection part  21  and the fourth finger connection part  27  are separately rotated and thus the plurality of finger connection parts  20  forms a new symmetrical structure, the object is grasped by the plurality of finger modules  30  respectively connected to the plurality of finger connection parts  20 . 
         [0142]    The above configuration in which the internal gears  73  are connected is relatively simple, thereby allowing the robot hand  1  to have a simpler configuration. 
         [0143]    As is apparent from the above description, a robot hand in accordance with an embodiment has both an arbitrary object grasping function in the same manner as a human hand and a high precision and stable grasping function in the same manner as an industrial gripper through drive of a plurality finger connection parts using roll joints. 
         [0144]    Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.