Abstract:
This disclosure relates to a face robot which is operated similarly to the motion of a human head and a multi-joint manipulator which supports a robot&#39;s face, and more particularly, to a structure which may compensate an influence caused by the gravity and exerted on rotation parts rotating about its axes. A manipulator with a weight compensation mechanism of the disclosure is provided, the manipulator having rotation parts connected to a plurality of axes rotating about their axes, the manipulator including: a weight compensation mechanism that supports wires connected to the rotation parts receiving gravity in a rotation state by a spring and compensates an influence of gravity exerted on the rotation parts.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2011-0092421, filed on Sep. 14, 2011, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     This disclosure relates to a face robot which is operated similarly to the motion of a human head and a multi-joint manipulator which supports a robot&#39;s face, and more particularly, to a structure which may compensate an influence caused by the gravity and exerted on rotation parts rotating about its axes. 
     2. Description of the Related Art 
     In recent years, various kinds of robots have been developed so as to make the human&#39;s living environment more convenient or assist work in industrial fields. Especially, developed are many robot arms which are utilized in various industrial fields such as painting and welding. It is very important that the robot arms need to produce high torque, since such industrial multi-joint robot arms need to transfer and support a heavy load. 
     The multi-joint robot arm receives load torque due to the own weight thereof or the weight of the load, and the load torque directly affects the design of a driving unit such as a driving motor. In particular, the proportion of the torque element generated by the own weight of the robot arm in the load exerted on the driving motor is considerably high. 
     In the case where the capacity of the driving unit of the robot arm is determined in the related art, not only the torque generated by the load but also the gravity torque generated by the own weight of the robot arm need to be taken into consideration, which has a disadvantage in that the capacity of the power source for driving the robot arm inevitably increases. 
     Even in a robot face which is developed so as to move similarly to the motion of the human head, the proportion of the torque element generated by the own weight of the head is considerably high, which also causes a problem in that the capacity of a power source for driving a neck part needs to be increased. 
     In addition, simple ideas having a concept of theoretically compensating the gravity generated by the own weight of the robot arm or the like have been proposed, but any mechanism practically adopting the ideas cannot be developed yet. Furthermore, in the face robot, the structure of the neck joint is complex and the installation space thereof is not sufficiently ensured, which hinders the application example that employs the gravity compensation. 
     SUMMARY 
     This disclosure is directed to providing a manipulator which includes a weight compensation mechanism configured to reduce the capacity of an actuator necessary for a driving operation by compensating the gravity exerted on a rotation part of the manipulator corresponding to a neck part of a face robot using the elastic force of a spring and a face robot using the same. 
     Furthermore, this disclosure is directed to providing a manipulator which includes a weight compensation mechanism configured to be easily installed at a narrow space by compensating the gravity of the manipulator from the outside of a neck part using a wire for compensating the gravity of the manipulator corresponding to the neck part of the face robot with a narrow space and a face robot using the same. 
     In one general aspect, there is provided a manipulator with a weight compensation mechanism, the manipulator having rotation parts connected to a plurality of axes rotating about their axes, the manipulator including: a weight compensation mechanism that supports wires connected to the rotation parts receiving gravity in a rotation state by a spring and compensates an influence of gravity exerted on the rotation parts when the wires pressurize the spring or cancel the pressurized state thereof due to the rotation of respective rotation parts by the elastic restoring force of the spring. 
     Furthermore, according to the preferred embodiment of the disclosure, the axes of the manipulator may be divided into a first axis (yaw) matching the direction of gravity, a second axis (pitch), a third axis (pitch), and a fourth axis (roll). The manipulator may include a first rotation part that rotates about each of the first axis and the second axis and a second rotation part that rotates about each of the third axis and the fourth axis. A first wire of the weight compensation mechanism may be connected to the first rotation part and a second wire of the weight compensation mechanism may be connected to the second rotation part, thereby compensating the gravity generated when the first rotation part rotates about the second axis and the second rotation part rotates about the third axis and the fourth axis. 
     Furthermore, according to the preferred embodiment of the disclosure, the manipulator may include a first rotational bracket that is attached to the first axis fixed to a base plate and is rotatable about the first axis, a second rotational bracket that is rotatable about the third axis, and a connecting link that is connected to each of the first rotational bracket and the second rotational bracket through a first rotational joint and a second rotational joint so as to be relatively rotatable, and the second axis, the third axis, the first rotational joint, and the second rotational joint may constitute a parallelogram structure. 
     Furthermore, according to the preferred embodiment of the disclosure, the weight compensation mechanism may be divided into a first weight compensation part that compensates the gravity of the first rotation part and a second weight compensation part that compensates the weight of the second rotation part, the weight compensation mechanism may be installed at the bottom surface of the base plate provided with the manipulator, and the first wire and the second wire may extend in the direction of the first axis so as to be respectively connected to the first rotation part and the second rotation part. 
     Furthermore, according to the preferred embodiment of the disclosure, the first weight compensation part may include a guide bar that is fixed to the outside of the base plate at the first axis, a slider that moves along the guide bar, a sheave that is attached to the slider, a coil spring that provides an elastic restoring force of pushing the slider to the outside of the base plate, a tension controller to which one end of the first wire is fixed, and a first pulley that switches the direction of the first wire so that it extends in the direction of the first axis. The first wire of which one end is fixed to the tension controller may extend in the direction of the first axis through the sheave and the first pulley and may be fixed to the first rotation part. 
     Furthermore, according to the preferred embodiment of the disclosure, the first wire may pass through a hollow of the first axis and pass a second pulley attached to the first rotational bracket so that the other end of the first wire is fixed to a fixture attached to the first rotation part. 
     Furthermore, according to the preferred embodiment of the disclosure, the second weight compensation part may include a guide bar that is fixed to the outside of the base plate at the first axis, a slider that moves along the guide bar, a sheave that is attached to the slider, a coil spring that provides an elastic restoring force of pushing the slider to the outside of the base plate, a tension controller to which one end of the second wire is fixed, and a third pulley which switches the direction of the second wire so that it extends in the direction of the first axis. The second wire of which one end is fixed to the tension controller may be fixed to the second rotation part through the sheave and the first pulley, and pulleys supporting the second wire may be attached to the first rotational bracket, the connecting link, and the second rotational bracket. 
     Furthermore, according to the preferred embodiment of the disclosure, a second wire fixing part may be attached to the second rotation part, and the second wire fixing part may include a wire fixture that is rotatably attached to the second rotation part and a through hole that is formed in the lateral direction of the wire fixture so that the second wire passes therethrough and forms a slope in an entrance part to which the second wire is inserted. 
     Furthermore, according to the preferred embodiment of the disclosure, the second wire fixing part may include a fixing block that is attached and fixed to the front side of the second rotation part and supporting brackets that are fixed to both side surfaces of the fixing block and support the wire fixing part so as to be rotatable, and the other end of the second wire may pass through the second rotation part and the fixing block and be fixed to the inside of the through hole of the wire fixing part or the outer peripheral surface of the wire fixing part. 
     Furthermore, according to the preferred embodiment of the disclosure, a pulley assembly, which supports the second wire so that the second wire is positioned toward the second rotation part, may be attached to the second rotational bracket, and the pulley assembly may be rotatably attached to the second rotational bracket so as to be directed toward the second rotation part rotating about each of the third axis and the fourth axis. 
     Furthermore, according to the preferred embodiment of the disclosure, the pulley assembly may include a hollow shaft that is rotatably attached to the second rotational bracket, a rotation holder that is fixed to the upper end of the hollow shaft, and a pulley that is attached to the inside of the rotation holder, and the second wire may pass thorough the inside of the hollow shaft and extend toward the second rotation part through the pulley. 
     Furthermore, according to the preferred embodiment of the disclosure, a second wire guide may be attached to the rotation holder so that the second wire is guided toward the second rotation part. 
     Furthermore, according to the preferred embodiment of the disclosure, a fourth pulley which supports the second wire may be attached to the first rotational bracket, and pulleys which support the second wire so that the second wire extends toward the pulley assembly may be attached to the connecting link. 
     Furthermore, according to the preferred embodiment of the disclosure, in the manipulator, a first differential bevel gear may be attached between the first rotation part and a base so that the first rotation part rotates about the first axis and the second axis and a second differential bevel gear may be attached between the first rotation part and the second rotation part so that the second rotation part rotates about the third axis and the fourth axis. 
     Furthermore, according to the preferred embodiment of the disclosure, the first differential bevel gear may include a fixation gear that is fixed to the upper end of the first axis and two movement gears that are rotatably attached to the second axis, the first rotational bracket may be fixed to the upper end of the first axis, the second axis may be rotatably attached to the first rotational bracket, and the first rotation part may be rotatably attached to the second axis. 
     Furthermore, according to the preferred embodiment of the disclosure, two first actuators may be attached to the first rotation part, two first actuators may be connected to two movement gears so as to rotate the movement gears, and the first rotational bracket and the first rotation part may rotate about the first axis or the first rotation part may rotate about the second axis in accordance with the rotation directions of the movement gears. 
     Furthermore, according to the preferred embodiment of the disclosure, the second differential bevel gear may include a fixation gear which is fixed to the second rotation part and of which the center is fixed with the fourth axis and two movement gears that are rotatably attached to the third axis, the second rotational bracket may be rotatably fixed to the end of the fourth axis, the third axis may be rotatably attached to the second rotational bracket, and the second rotation part may be rotatably attached to the third axis. 
     Furthermore, according to the preferred embodiment of the disclosure, two second actuators may be attached to the first rotation part, two second actuators may be connected to two movement gears so as to rotate the movement gears, and the second rotation part may rotate about the third axis or the second rotation part may rotate about the fourth axis in accordance with the rotation directions of the movement gears. 
     Furthermore, according to the preferred embodiment of the disclosure, the tension controller may be a self-locking bolt to which one end of the first wire is fixed, and the self-locking bolt may be fastened to a nut fixed to the first weight compensation part. 
     Furthermore, according to the preferred embodiment of the disclosure, the tension controller may be a self-locking bolt to which one end of the second wire is fixed, and the self-locking bolt may be fastened to a nut fixed to the second weight compensation part. 
     Furthermore, in another aspect of the disclosure, there is provided a face robot including: a manipulator in which rotation parts connected to a plurality of axes rotate about their axes, and a weight compensation mechanism that supports wires connected to the rotation parts receiving gravity in a rotation state by a spring and compensates an influence of gravity exerted on the rotation parts when the wires pressurize the spring or cancel the pressurized state thereof due to the rotation of respective rotation parts by the elastic restoring force of the spring, wherein the axes of the manipulator are divided into a first axis (yaw) matching the direction of gravity, a second axis (pitch), a third axis (pitch), and a fourth axis (roll), wherein the manipulator includes a first rotation part that rotates about each of the first axis and the second axis and a second rotation part that rotates about each of the third axis and the fourth axis, wherein a first wire of the weight compensation mechanism is connected to the first rotation part and a second wire of the weight compensation mechanism is connected to the second rotation part, thereby compensating the gravity generated when the first rotation part rotates about the second axis and the second rotation part rotates about the third axis and the fourth axis, and wherein a robot&#39;s face is attached to the second rotation part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the disclosed exemplary embodiments will be more apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view showing a face robot according to the disclosure; 
         FIG. 2  is an operating conceptual diagram of a manipulator, which shows the operation of the face robot shown in  FIG. 1 ; 
         FIG. 3A  is a front view of the face robot shown in  FIG. 1 ; 
         FIG. 3B  is a side view of the face robot shown in  FIG. 1 ; 
         FIG. 4A  is a conceptual diagram showing the parallelogram connecting structure of a second axis, a third axis, a first rotational joint, and a second rotational joint of the manipulator; 
         FIG. 4B  is a front view of the manipulator shown in  FIG. 4A ; 
         FIG. 4C  is a cross-sectional view showing a state where a second rotation part of the manipulator shown in  FIG. 4A  rotates about a third axis; 
         FIG. 5  is a side view of the manipulator which is operated about the second axis; 
         FIG. 6  is a conceptual diagram showing the structure of a weight compensation mechanism; 
         FIG. 7A  is a perspective view showing a pulley assembly shown in  FIG. 6 ; 
         FIG. 7B  is an exploded perspective view of a pulley assembly shown in  FIG. 6 ; 
         FIG. 8A  is a perspective view showing a second wire fixing part which is attached to a second rotation part; 
         FIG. 8B  is an exploded perspective view of the second wire fixing part shown in  FIG. 8A ; 
         FIG. 8C  is a cross-sectional view of a second wire fixture shown in  FIG. 8B ; and 
         FIG. 9  is a conceptual diagram illustrating the operation of the second rotation part which rotates about the third axis. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments of a manipulator including a weight compensation mechanism and a face robot using the same according to the disclosure will be described in detail with reference to the accompanied drawings. 
     In the drawings,  FIG. 1  is a perspective view showing a face robot according to the disclosure,  FIG. 2  is an operating conceptual diagram of a manipulator, which shows the operation of the face robot shown in  FIG. 1 ,  FIG. 3A  is a front view of the face robot shown in  FIG. 1 , and  FIG. 3B  is a side view of the face robot shown in  FIG. 1 .  FIG. 4A  is a conceptual diagram showing the parallelogram connecting structure of a second axis, a third axis, a first rotational joint, and a second rotational joint of the manipulator,  FIG. 4B  is a front view of the manipulator shown in  FIG. 4A ,  FIG. 4C  is a cross-sectional view showing a state where a second rotation part of the manipulator shown in  FIG. 4A  rotates about a third axis, and  FIG. 5  is a side view of the manipulator which is operated about the second axis.  FIG. 6  is a conceptual diagram showing the structure of a weight compensation mechanism,  FIG. 7A  is a perspective view showing a pulley assembly shown in  FIG. 6 , and  FIG. 7B  is an exploded perspective view of a pulley assembly shown in  FIG. 6 .  FIG. 8A  is a perspective view showing a second wire fixing part which is attached to a second rotation part,  FIG. 8B  is an exploded perspective view of the second wire fixing part shown in  FIG. 8A ,  FIG. 8C  is a cross-sectional view of a second wire fixture shown in  FIG. 8B , and  FIG. 9  is a conceptual diagram illustrating the operation of the second rotation part which rotates about the third axis. 
     As shown in  FIGS. 1 to 3B , the face robot has a structure in which a manipulator  100  is attached to a top surface of a base  110  and a robot&#39;s face  101  is attached to the distal end of the manipulator  100 . In addition, a weight compensation mechanism  200  which compensates the weight of the manipulator  100  is attached to the base  110 . Here, the manipulator  100  is configured to be operated through the rotation about a first axis (yaw)  121 , a second axis (pitch)  122 , a third axis (pitch)  123 , and a fourth axis (roll)  124 . In addition, a first rotational bracket  151  is fixed to the first axis  121  so as to rotate about the first axis  121 , a second rotational bracket  152  is attached to the third axis  123  so as to rotate about the third axis  123 , and both ends of a connecting link  170  are respectively connected to the first rotational bracket  151  and the second rotational bracket  152  so as to be rotatable through rotational joints  171  and  172 . Here, the rotational joint which connects the first rotational bracket  151  and the connecting link  170  to each other is referred to as the ‘first rotational joint  171 ’, and the rotational joint which connects the second rotational bracket  152  and the connecting link  170  to each other is referred to as the ‘second rotational joint  172 ’. 
     In the manipulator  100  with such a structure, the second axis  122 , the third axis  123 , the first rotational joint  171 , and the second rotational joint  172  constitute the parallelogram structure (see  175  of  FIG. 6 ). 
     Hereinafter, the manipulator which includes the weight compensation mechanism with such a structure will be specifically described. 
     As shown in  FIGS. 1 and 2 , a base plate  111  is fixed to the top surface of the base  110  with a space therebetween, the manipulator  100  is attached to the top surface of the base plate  111 , and the robot&#39;s face  101  is attached to the free end of the manipulator  100 . Meanwhile, the manipulator  100  includes a first rotation part  141  which freely rotates about the first axis (yaw)  121  perpendicularly fixed to the center of the base plate  111  and the second axis (pitch)  122  perpendicularly positioned with respect to the first axis  121  and a second rotation part  142  which freely rotates about the third axis (pitch)  123  attached to the end of the first rotation part  141  so as to be parallel to the second axis (pitch)  122  and the fourth axis (roll)  124  perpendicularly attached with respect to the third axis  123 . In addition, the robot&#39;s face  101  is attached to the front side of the second rotation part  142 . In this way, the robot&#39;s face  101  which is attached to the second rotation part  142  has four degrees of freedom. 
     Hereinafter, the connecting relationship between the first rotation part  141  and the second rotation part  142  will be specifically described. 
     As shown in  FIGS. 4A to 4C , the first rotation part  141  is positioned on the top surface of the base plate  111 , a fixation gear  131 S of a first differential bevel gear  131  is fixed to the base plate  111 , the first axis  121  is fixed to the center of the fixation gear  131 S, and the first rotational bracket  151  is attached to the upper end of the first axis  121  so as to be rotatable. In addition, the second axis  122  is attached to the center of two movement gears  131 M of the first differential bevel gear  131  so as to be rotatable, and the lower end of the first rotation part  141  and the first rotational bracket  151  are respectively attached to the second axis  122  so as to be rotatable. 
     Meanwhile, the second rotation part  142  is attached to the upper end of the first rotation part  141 , and a second differential bevel gear  132  is attached so as to be rotatable about the third axis  123  and the fourth axis  124 , where a fixation gear  132 S of the second differential bevel gear  132  is fixed to the rear surface of the second rotation part  142  and the fourth axis  124  fixed to the center of the fixation gear  132 S is attached to the upper end of the first rotation part  141  so as to be rotatable. In addition, the third axis  123  is attached to the center of two movement gears  132 M of the second differential bevel gear  132  so as to be rotatable, and the upper end of the first rotation part  141  and the second rotational bracket  152  are respectively attached to the third axis  123  so as to be rotatable. 
     As shown in  FIG. 1 , two first actuators  161  are attached to the lower part of the first rotation part  141  so as to face each other, and are respectively connected to two movement gears  131 M of the first differential bevel gear  131  by timing belts, gears, or the like in a direct coupling manner. In addition, two second actuators  162  are attached to the upper part of the first rotation part  141  so as to face each other, and are respectively connected to two movement gears  132 M of the second differential bevel gear  132  by timing belts, gears, or the like in a direct coupling manner. 
     By controlling the operation directions, namely, the rotation directions of two first actuators  161  connected to the second axis  122 , the first rotation part  141  rotates about the first axis  121  and the second axis  122 . 
     Specifically, if two first actuators  161  are rotated in the opposite direction (while the rotation directions of the movement gears  131 M are equal to each other), the first rotation part  141  rotates about the first axis (yaw)  121 , and the first rotational bracket  151  also rotates about the first axis (yaw)  121 . 
     In contrast, if two first actuators  161  are rotated in the same direction (while the rotation directions of the movement gears  131 M are opposite to each other), the first rotation part  141  rotates about the second axis (pitch)  122 . 
     If the second rotation part  142  also rotates two second actuators  162  connected thereto in the same direction (while the rotation directions of the movement gears  132 M are opposite to each other), the second rotation part  142  rotates about the third axis (pitch)  123 . If two second actuators  162  are rotated in the opposite direction (while the rotation directions of the movement gears  132 M are equal to each other), the second rotation part  142  rotates about the fourth axis (roll)  124 . 
     Meanwhile, as shown in  FIGS. 4A and 5 , the first rotational bracket  151  is attached to the second axis  122  so as to be rotatable, and the second rotational bracket  152  is attached to the third axis  123  so as to be rotatable. In addition, both ends of the connecting link  170  are respectively connected to the first rotational bracket  151  and the second rotational bracket  152  by hinges, where one end of the connecting link  170  and the first rotational bracket  151  are connected to each other by the first rotational joint  171 , and the other end of the connecting link  170  and the second rotational bracket  152  are connected to each other by the second rotational joint  172 . Here, the second axis  122 , the first rotational joint  171 , the second rotational joint  172 , and the third axis  123  constitute the parallelogram structure  175 . In this manner, since the first rotational joint  171  and the second rotational joint  172  which connect the connecting link  170 , the first rotational bracket  151 , and the second rotational bracket  152  to each other constitute the parallelogram structure  175  together with the second axis  122  and the third axis  123 , the parallelogram structure may be maintained even if the first rotation part  141  rotates about the second axis  122 . Here, the first rotation part  141  and the connecting link  170  corresponding to two long edges of the parallelogram structure  175  move in parallel, and even when the second rotational bracket  152  corresponding to one short edge moves by the rotation of the first rotation part  141 , the second rotational bracket moves in parallel to the first rotational bracket  151 . 
     In the manipulator  100  with such a structure, the first rotation part  141  and the second rotation part  142  respectively rotating about the second axis  122  and the third axis  123  receive gravity depending on the position. In addition, herebelow, a mechanism for compensating the gravity exerted on the first rotation part  141  and the second rotation part  142  of the manipulator  100  will be described. 
     As shown in  FIG. 6 , the weight compensation mechanism  200  is divided into a first weight compensation part  210  which compensates the weight of the first rotation part  141  and a second weight compensation part  220  which compensates the weight of the second rotation part  142 . 
     The first weight compensation part  210  and the second weight compensation part  220  are attached to the bottom surface of the base plate  111 , a first wire  211  extending from the first weight compensation part  210  is attached to the first rotation part  141 , and a second wire  221  extending from the second weight compensation part  220  is attached to the second rotation part  142 . 
     Specifically, the inside of a case  212  of the first weight compensation part  210  is provided with a guide bar  216  which is positioned so as to extend to the outside of the base plate  111  about the first axis  121 , a slider  217  which moves along the guide bar  216 , a sheave  214  which is attached to the slider  217 , a coil spring  213  which is positioned along the guide bar  216  and provides an elastic force enabling the slider  217  to move to the outside of the base plate  111 , a tension controller  218  which is attached to the case  212  and to which one end of the first wire  211  is fixed, a first pulley  231  which is attached to the bottom surface of the base plate  111  and changes the direction of the first wire  211 , a second pulley  232  which is attached to the first rotational bracket  151  and changes the direction of the first wire  211 , and a fixture  219  which is attached to the first rotation part  141  and to which the other end of the first wire  211  is fixed. 
     One end of the first wire  211  is fixed to the tension controller  218 , the direction of the first wire  211  is switched so that the first wire  211  advances in the direction opposite to the entrance direction at the sheave  214 , the direction thereof is switched upward at the first pulley  231  so that the first wire  211  extends upward through the hollow formed in the first axis  121 , and the direction thereof is switched at the second pulley  232  so that the other end of the first wire  211  is fixed to the fixture  219  attached to the first rotation part  141 . 
     When looking into the operating relationship of the first weight compensation part  210  with such a structure, the first rotation part  141  rotates about the second axis (pitch)  122  by the first actuator  161 , but the first rotational bracket  151  does not rotate about the second axis  122 . Therefore, when the first rotation part  141  rotates about the second axis  122  to thereby widen a gap between the fixture  219  fixed to the first rotation part  141  and the second pulley  232  attached to the first rotational bracket  151 , that is, the first rotation part  141  is inclined forward or backward, the first wire  211  is tensioned while the first wire  211  is pulled toward the fixture  219 . At this time, since the slider  217  of the first weight compensation part  210  moves toward the spring fixing part  215  by the tension of the first wire  211 , the coil spring  213  is compressed. In this way, the elastic restoring force generated by the compression of the coil spring  213  compensates the torque (weight) generated as the first rotation part  141  rotates about the second axis  122 . 
     Meanwhile, the inside of a case  222  of the second weight compensation part  220  is provided with a coil spring  223 , a slider  227 , a sheave  224 , a guide bar  226 , and a third pulley  233  which has the same function as that of the first pulley  231  as in the above-described first weight compensation part  210 , and one end of the second wire  221  is fixed to a tension controller  228 . Furthermore, the second wire  221  advances in the direction opposite to the entrance direction at the sheave  224 , and the direction thereof is switched at the third pulley  233  so that the other end of the second wire  221  is fixed to the second wire fixing part  240  attached to the second rotation part  142 . In addition, the second wire  221  extending from the second weight compensation part  220  passes a fourth pulley  234  attached to the first rotational bracket  151 , a fifth pulley  235  attached to the portion of the first rotational joint  171 , a sixth pulley  236  attached to the portion of the second rotational joint  172 , a seventh pulley  237  attached to the second rotational bracket  152 , and a pulley assembly  250  attached to the second rotational bracket  152 , so that the other end of the second wire  221  is fixed to the second wire fixing part  240  attached to the second rotation part  142 . Here, as shown in  FIG. 4A , an auxiliary pulley  238  and the like which support the second wire  221  may be further attached depending on the type of the connecting link  170 , and the above-described pulleys may be changed in various forms in accordance with the switching directions of the wires. 
     Hereinafter, the pulley assembly  250  and the second wire fixing part  240  will be specifically described. 
     As shown in  FIGS. 7A and 7B , the pulley assembly  250  includes a fixing block  251  which is fixed to the upper end of the second rotational bracket  152 , a hollow shaft  252  which is rotatably attached to the perpendicular hollow of the fixing block  251  by a bearing  253 , a rotation holder  254  which is fixed to the upper end of the hollow shaft  252  and is opened upward, two pulleys  255  which are attached to the rotation holder  254 , and a second wire guide  256  which is attached to the rotation holder  254  and guides the advancing direction of the second wire  221  exiting between two pulleys  255  so that the second wire is directed toward the second wire fixing part  240 . In addition, the second wire  221  is positioned inside a groove formed along the circumferential surface of the pulley  255  while the circumferential surfaces of two pulleys  255  are in contact with each other, the pulley  255  rotates as the second wire  221  moves, and the rotation holder  254  rotates toward the second rotation part  142  as the second rotation part  142  rotates about each of the third axis  123  and the fourth axis  124 . 
     Meanwhile, the second wire  221 , of which the direction is switched by the seventh pulley  237 , passes through the hollow of the hollow shaft  252  and passes between two pulleys  255  of the pulley assembly  250 . In addition, after the direction of the second wire  221  is switched by the pulley  255 , the second wire  221  passes through the second rotation part  142  and is fixed to the second wire fixing part  240  which is attached to the front surface of the second rotation part  142 . 
     Furthermore, as shown in  FIGS. 8A to 8C , the second wire fixing part  240  includes a fixing block  241  which is fixed to the front side of the second rotation part  142 , supporting brackets  242  which are respectively fixed to both sides of the fixing block  241  fixed to the second rotation part  142 , and a wire fixture  243  which is positioned between the supporting brackets  242  and is rotatably attached to the supporting brackets  242  by bearings  244 . In addition, the fixing block  241  is provided with a through hole which enables the second wire  221  to enter toward the wire fixture  243 , and a through hole  245  is provided so that the wire fixture  243  or the second wire  221  passes therethrough, where a slope is formed in an entrance part  246  of the through hole  245  formed in the wire fixture  243 . The slope formed in the entrance part  246  is provided so as to prevent the second wire  221  from being bent perpendicularly when the wire fixture  243  rotates, so that the second wire  221  is maintained in a smoothly curved state by the slope of the entrance part  246  even when the wire fixture  243  rotates. In this way, since the second wire  221  is smoothly curved, it is possible to prevent the second wire  221  from being cut and prevent the wire fixture  243  from being broken in advance. Meanwhile, the end of the second wire  221  passes the inside of the through hole  245  of the wire fixture  243  or passes through the through hole  245  so as to be fixed to the outside thereof. 
     As shown in  FIG. 9 , the pulley assembly  250  and the second wire fixing part  240  support the second wire  221  so as to smoothly move when the second rotation part  142  rotates about the third axis (pitch) and the fourth axis (roll). 
     Herebelow, the weight compensation with respect to the second rotation part  142  will be described. 
     In the case where the position of the first rotation part  141  is fixed and the second rotation part  142  rotates about the third axis  123 , since the first rotation part  141  is fixed, the position of the second rotational bracket  152  included in the parallelogram structure  175  is also fixed and the position of the rotatable pulley assembly  250  fixed to the second rotational bracket  152  is also fixed. 
     Therefore, when the second rotation part  142  rotates about the third axis  123 , the second wire fixing part  240  rotates along the second rotation part  142  about the third axis  123  to thereby pull the second wire  221 , wherein when the second wire  221  moves toward the second wire fixing part  240 , the slider  227  of the second weight compensation part  220  moves toward the spring fixing part  225  due to the tension so as to compress the coil spring  223 . In this way, the elastic restoring force generated by the compression of the coil spring  223  compensates the torque (gravity) generated when the second rotation part  142  rotates about the third axis  123 . 
     Meanwhile, when the first rotation part  141  rotates about the second axis  122  while the rotation of the second rotation part  142  rotating about the third axis  123  is fixed, the second rotational bracket  152  rotates about the second axis  122  along the first rotation part  141 , and moves in parallel at the base plate  111  due to the parallelogram structure  175 . Therefore, when the first rotation part  141  rotates about the second axis  122  so that the robot&#39;s face  101  is inclined forward, the distance from the second wire fixing part  240  to the pulley assembly  250  is widened as the second rotational bracket  152  moves in parallel. Conversely, when the first rotation part  141  rotates about the second axis  122  so that the robot&#39;s face  101  is raised backward, the distance from the second wire fixing part  240  to the pulley assembly  250  is narrowed. In this case, the second wire  221  moves and the second weight compensation part  220  compensates the torque (gravity). At the same time, the torque (gravity) with the rotation of the first rotation part  141  is compensated by the first weight compensation part  210 . 
     Meanwhile, when the second rotation part  142  rotates about the third axis  123  while the rotation of the first rotation part  141  is fixed, the second wire fixing part  240  attached to the second rotation part  142  moves in the direction moving away from or close to the pulley assembly  250 . At this time, since the other end of the second wire  221  is fixed to the second wire fixing part  240 , the second wire  221  is tensioned. Due to the generated tension, the slider  227  of the second weight compensation part  220  moves, so that the coil spring  223  of the second weight compensation part  220  is expanded and contracted to compensate the torque (gravity) of the second rotation part  142 . Therefore, the second rotation part  142  does not rotate any more due to the effect of the gravity, and maintains the current posture in such a weightless state. 
     If the first rotation part  141  rotates about the second axis  122  at the same time when the second rotation part  142  rotates about the third axis  123 , as described above, the first weight compensation part  210  and the second weight compensation part  220  are respectively operated so as to compensate the torques (gravities) of the first rotation part  141  and the second rotation part  142 . However, as shown in  FIG. 5 , at the time when the first rotation part  141  rotates about the second axis  122 , when the rotation of the first rotation part  141  is compensated so that the second rotation part  142  is maintained perpendicularly while the second rotation part  142  rotates about the third axis  123 , specifically, when the second rotation part  142  turns forward and backward while being maintained perpendicularly even when the first rotation part  141  rotates, the distance between the second wire fixing part  240  and the pulley assembly  250  is uniform. In this case, since the second wire  221  does not move, the torque of the second weight compensation part  220  does not change, and the changed torque (gravity) is compensated only at the first weight compensation part  210 . 
     Hereinafter, the compensation with respect to the gravity generated when the second rotation part  142  rotates about the fourth axis  124  will be described. 
     The second rotation part  142  is rotatable about the fourth axis  124 . In this manner, when the second rotation part  142  rotates about the fourth axis  124 , the gap between the second wire fixing part  240  attached to the second rotation part  142  and the pulley assembly  250  attached to the second rotational bracket  152  is widened or narrowed. Therefore, the pulley assembly  250  is attached so as to be rotatable about the hollow shaft  252 , and hence the pulley assembly  250  rotates so as to be directed toward the position of the second wire fixing part  240 . Namely, the second wire  221  which extends from the second wire fixing part  240  through the pulley  255  of the pulley assembly  250  moves while being pulled toward the second wire fixing part  240  or vice versa as much as a variation in distance between the pulley assembly  250  and the second wire fixing part  240  when the second rotation part  142  rotates about the fourth axis  124 . This also compensates the torque (gravity) of the second rotation part  142  at the second weight compensation part  220 . 
     In this way, the weight compensation mechanism  200  compensates the influence caused by the gravity and exerted on the second axis  122 , the third axis  123 , and the fourth axis  124  except for the first axis  121  which is parallel to the direction of the gravity when the manipulator  100  is operated. Since the first axis  121  is parallel to the direction of the gravity, no variation occurs in the torque even when the first rotation part  141  and the second rotation part  142  rotate about the first axis  121 . 
     Meanwhile, the tension controllers  218  and  228  which are attached to the above-described weight compensation mechanism  200  are respectively equipped with functions of adjusting the tensions of the first wire  211  and the second wire  221  which are attached thereto. The function of adjusting the wire&#39;s tension may be change in various forms. As an example thereof, although not shown in the drawings, a bolt is perforated so as to form a through hole therein, a wire passes the through hole to be fixed thereto, and the fixed bolt is fastened to a nut which is fixed to a case. If the bolt of the tension controller with such a structure is rotated, the wire is wrapped around the bolt to thereby minutely adjust the tension of the wire. Preferably, a self-locking function is provided between the bolt and the nut. 
     As described above, in the manipulator with the weight compensation mechanism and the face robot using the same according to the disclosure, since the influence (torque) of gravity generated by the rotation of the rotation part constituting the manipulator may be compensated by the elastic restoring force of the spring, there is an advantage in that the power of the actuator rotating the rotation part may be reduced. In addition, since the rotation part may be driven by small power, there is an advantage in that the weight of the manipulator and the face robot may be reduced. Therefore, there is an advantage in that energy-saving effect may be obtained and manufacturing cost may be reduced. 
     Furthermore, in the manipulator with the weight compensation mechanism and the face robot using the same according to the disclosure, since the gravity is compensated at the outside of the manipulator by the connection with the rotation part through the wire so as to compensate the gravity, there is an advantage in that the gravity may be compensated without increasing the volume of the manipulator. Therefore, there is an advantage in that the weight compensation mechanism may be installed without increasing the thickness and the length of the narrow neck part compared to the robot&#39;s face. 
     While the exemplary embodiments have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of this disclosure as defined by the appended claims. 
     In addition, many modifications can be made to adapt a particular situation or material to the teachings of this disclosure without departing from the essential scope thereof. Therefore, it is intended that this disclosure not be limited to the particular exemplary embodiments disclosed as the best mode contemplated for carrying out this disclosure, but that this disclosure will include all embodiments falling within the scope of the appended claims.