Abstract:
A charging apparatus for a mobile robot enabling the mobile robot to move relatively freely even during charging using a wiring member, while preventing occurrence of an inconvenience such as damage to the wiring member, is provided. The charging apparatus includes a charging power source, a control board which controls the charging power source, and a wiring members for use in supplying electric power from the charging power source to a battery mounted on the mobile robot. The wiring member connected to the mobile robot to follow the movement of the robot. The charging apparatus further includes a detector which detects tension applied to the wiring member. When the wiring members is pulled, an appropriate measure to stop the mobile robot or disconnect the wiring member from the robot is taken in accordance with a signal from the tension detector.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an apparatus for charging a battery mounted on a mobile robot. 
         [0003]    2. Description of the Related Art 
         [0004]    There is conventionally known an apparatus for charging a mobile robot wherein a power-receiving connector is provided in place of the mobile robot and connected to a battery mounted on the robot, and a charging station including a charging power source and a power-feeding connector connected to the charging power source is installed within a range reachable by the mobile robot. With movement of the mobile robot, the power-receiving connector is connected to the power-feeding connector at the charging station for charging the battery by the charging power source (see, for example, Japanese Patent Application Laid-Open No. 2001-179663). 
         [0005]    According to this apparatus, when the battery level is lowered, the mobile robot is capable of autonomously moving to the place where the charging station is installed, and having the power-receiving connector connected to the power-feeding connector for automatic charging. 
         [0006]    In this conventional apparatus, however, the power-feeding connector is fixedly provided in the charging station. This means that the mobile robot has its movement restricted by the power-feeding connector via the power-receiving connector during charging, resulting in a considerably lowered degree of freedom in movement of the mobile robot. As such, the entertaining property of the mobile robot cannot be exerted effectively during charging, which would make the audience disappointed. 
         [0007]    If a wiring member having one end connected to a charging power source has its other end connected to the mobile robot to allow the wiring member to follow the movement of the robot, the mobile robot will be able to move in a relatively wide range during charging. The restricted length of the wiring member, however, may cause an inconvenience such as damage to the wiring member when the mobile robot makes a movement large enough to pull the wiring member. 
       SUMMARY OF THE INVENTION 
       [0008]    In view of the foregoing, an object of the present invention is to provide a charging apparatus for a mobile robot which allows the mobile robot to move relatively freely even during charging using a wiring member, and which also prevents occurrence of an inconvenience such as damage to the wiring member. 
         [0009]    To achieve the above object, the present invention provides a charging apparatus for charging a battery mounted on a mobile robot, which includes: a charging power source; a control board which controls the charging power source; a wiring member connected to the mobile robot to follow movement of the mobile robot and supplying electric power from the charging power source to the battery mounted on the mobile robot; and a tension detector which detects tension applied to the wiring member. 
         [0010]    According to the present invention, the battery is charged via the wiring member which follows the movement of the mobile robot. This allows the mobile robot to move relatively freely even during charging, and accordingly, the entertaining property of the mobile robot can effectively be exerted to entertain the audience. When the wiring member is pulled due to an excessive movement of the mobile robot, the tension detector detects the tension applied to the wiring member. 
         [0011]    The control board may be configured to transmit a motion restriction signal to the mobile robot in the event that the tension detector detects the tension applied to the wiring member, to instruct the mobile robot that its movement should be restricted. The signal may be a signal prohibiting the movement of the mobile robot in the direction away from the charging apparatus, a signal causing the mobile robot to move in the direction approaching the charging apparatus, or a signal causing the mobile robot to stop. This configuration can prevent the wiring member from being further pulled and, hence, avoid occurrence of an inconvenience such as damage to the wiring member. It is noted that a plurality of kinds of motion restriction signals may be transmitted to the mobile robot in a stepwise manner in accordance with the magnitude of the tension applied to the wiring member. 
         [0012]    Further, the control board may be configured to stop power supply from the charging power source in response to the tension detector detecting the tension applied to the wiring member. This allows the power supply to be stopped automatically in the event that the wiring member is pulled, without the need of manual intervention of an operator, which advantageously implements a failsafe mechanism. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a side view of the charging apparatus according to an embodiment of the present invention. 
           [0014]      FIG. 2(   a ) illustrates a tension detector of the charging apparatus of the embodiment. 
           [0015]      FIG. 2(   b ) illustrates the operation of a first microswitch in response to the tension applied to the wiring member. 
           [0016]      FIG. 2(   c ) illustrates the operation of a second microswitch in response to the tension applied to the wiring member. 
           [0017]      FIG. 3  is a flowchart illustrating charging control which is performed by a control board of the charging apparatus of the embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]      FIG. 1  shows a humanoid mobile robot  1  and a charging station  2  which is an apparatus for charging the mobile robot  1 . The mobile robot  1  has a control box  1   a  at the back, which houses a battery  1   b  therein. The mobile robot  1  also has a power-receiving connector  1   c  provided beneath the control box  1   a  and connected to the battery  1   b.    
         [0019]    The charging station  2  is provided with a charging power source  3 , a control board  4  which controls the charging power source  3 , and a wiring member  5  connected to the charging power source  3 . The charging station  2  is freely movable by means of wheels  2   a  attached to its bottom. Also attached to the bottom of the charging station  2  is a stopper  2   b , which can be raised and lowered freely. Lowering the stopper  2   b  can set the charging station  2  in a predetermined installation location. 
         [0020]    The wiring member  5  includes a cable  5   a  having one end connected to the charging power source  3 , and a power-feeding connector  5   b  attached to the other end of the cable  5   a . A connector mating/unmating device  6  is mounted on top of the charging station  2 . The connector mating/unmating device  6  is controlled by the control board  4  to mate and unmate the power-feeding connector  5   b  and the power-receiving connector  1   c . The mating/unmating device  6  has a connector holder  6   a  for holding the power-feeding connector  5   b , and an actuator  6   b  for moving the connector holder  6   a  forward and backward. 
         [0021]    The cable  5   a  is provided with a power-feeding line connected to the charging power source  3  as well as a signal line connected to the control board  4 . The power-feeding connector  5   b  and the power-receiving connector  1   c  each include not only a power-feeding terminal but also a signal terminal to allow two-way communication between the control board  4  and the mobile robot  1 . 
         [0022]    When the battery level of the battery  1   b  is lowered, the mobile robot  1  autonomously moves to the place where the charging station  2  is installed, and stops at a predetermined charging position where the power-receiving connector  1   c  is directly in front of the power-feeding connector  5   b . The connector mating/unmating device  6  is provided with a robot position sensor (not shown) which detects when the mobile robot  1  reaches the charging position, and a signal from the robot position sensor is input to the control board  4 . The control board  4 , in receipt of the signal from the robot position sensor, carries out charging control. 
         [0023]      FIG. 3  illustrates the charging control in detail. Firstly, it is determined whether the mobile robot  1  has reached the charging position based on a signal from the robot position sensor (S 1 ). If it is determined that the robot has reached the charging position, the process of connecting the wiring member  5  to the mobile robot  1  is performed (S 2 ). In this process, the actuator  6   b  of the connector mating/unmating device  6  is activated to move the connector holder  6   a  forward, to thereby connect the power-feeding connector  5   b  held by the connector holder  6   a  to the power-receiving connector  1   c . At this time, the power-feeding connector  5   b  is rotated via the connector holder  6   a  to lock the power-feeding connector  5   b  with the power-receiving connector  1   c . Upon completion of the connecting process, the connector holder  6   a  is moved backward (S 3 ). Next, a charging condition is transmitted from the mobile robot  1  to the control board  4  to start charging of the battery  1   b  by the charging power source  3  under that condition (S 4 ). 
         [0024]    When the connector holder  6   a  is moved backward, the connector holder  6   a  is disengaged from the power-feeding connector  5   b , causing the mobile robot  1  to be connected to the charging station  2  only via the wiring member  5 , as shown by a phantom line in  FIG. 1 . This allows the mobile robot  1  to move freely within the range where the wiring member  5  has slack and, thus, allows the mobile robot  1  to effectively exert its property of entertaining the audience. 
         [0025]    Next, it is determined whether a first microswitch  71 , which will be described later, is ON (S 5 ). If so, it is determined whether a charging stop signal has been input, which signal is to be output from the mobile robot  1  upon completion of charging of the battery  1   b  (S 6 ). If the charging stop signal is input, charging of the battery  1   b  with the charging power source  3  is stopped (S 7 ). At this time, the mobile robot  1  moves to return to the above-described charging position. When it is determined that the mobile robot  1  has returned to the charging position based on a signal from the robot position sensor (S 8 ), the process of disconnecting the wiring member  5  from the mobile robot  1  is performed (S 9 ). In this disconnecting process, the connector holder  6   a  is moved forward to hold the power-feeding connector  5   b  connected to the power-receiving connector  1   c , and then, the power-feeding connector  5   b  is turned in the unlocking direction via the connector holder  6   a  to release the lock. Thereafter, the connector holder  6   a  is moved backward to disconnect the power-feeding connector  5   b  from the power-receiving connector  1   c . This causes the mobile robot  1  to return to the completely free state shown by a solid line in  FIG. 1 . 
         [0026]    In the event that the mobile robot  1  moves too largely during charging due to a malfunction or the like, or if the wiring member  5  is shorter than a normal length, the wiring member  5  may be pulled during charging, in which case the wiring member  5  may be damaged or the charging station  2  may topple over. In view of the foregoing, according to the present embodiment, the charging station  2  is provided with a tension detector  7  which detects tension applied to the wiring member  5 . 
         [0027]    The tension detector  7 , as shown in  FIG. 2(   a ), has a pair of first and second microswitches  71  and  72 , which are arranged at an opening of a frame  2   c  provided at the charging station  2  through which the wiring member  5  is lead out. The first microswitch  71  cooperates with a collar  71   a  fixedly secured to the cable  5   a  of the wiring member  5 . When the cable  5   a  of the wiring member  5  is pulled by an excessive motion of the mobile robot  1  to cause the collar  71   a  to be pulled out forward from the cable lead-out opening  2   d  of the frame  2   c , as shown in  FIG. 2(   b ), the first microswitch  71  turns OFF. 
         [0028]    The second microswitch  72  cooperates with a collar-shaped stopper  72   a , which is fixedly secured to the cable  5   a  at the position behind the collar  71   a . When the collar  71   a  is pulled out and the cable  5   a  is further pulled out ahead of the frame  2   c , the stopper  72   a  abuts against a support plate  2   e  fixedly secured to the frame  2   c , as shown in  FIG. 2(   c ), to prevent the cable  5   a  from being pulled out any further. The second microswitch  72  turns ON when the stopper  72   a  abuts against the support plate  2   e . Accordingly, the tension detector  7  of the present embodiment is capable of detecting the pulled level of the wiring member  5  in a stepwise manner by means of the first microswitch  71  and the second microswitch  72 . 
         [0029]    Signals from the first and second microswitches  71  and  72  are input to the control board  4 . The control board  4  determines whether the first microswitch  71  is ON after initiation of charging, as described above (S 5 ), and when the first microswitch  71  turns OFF, it transmits a first motion restriction signal to the mobile robot  1  informing that the movement of the robot  1  should be restricted (S 10 ). In receipt of this signal, the mobile robot  1  ceases to further move to the direction away from the charging station  2 . It is noted that the first motion restriction signal may be a signal causing the mobile robot  1  to move in the direction approaching the charging station  2 . 
         [0030]    Next, it is determined whether the second microswitch  72  has turned ON (S 1 ). The process returns to step S 5  until the second microswitch  72  turns ON. When the mobile robot  1  moves toward the charging station  2 , the collar  71   a  is pulled backward through the lead-out opening  2   d  by means of a cable pull-in mechanism, not shown, so that the first microswitch  71  turns ON. In this case, the process proceeds to step S 6 , and the normal charging control as described above is carried out. 
         [0031]    On the other hand, if the wiring member  5  is continuously pulled due to the malfunction or the like even after the first motion restriction signal is transmitted to the mobile robot  1 , causing the second microswitch  72  to turn ON, the power supply from the charging power source  3  is stopped immediately, and a second motion restriction signal is transmitted to the mobile robot  1  to stop the mobile robot  1  immediately, and furthermore, an emergency alarm is issued from a buzzer or the like (S 12 ). This prevents the wiring member  5  from being damaged due to an excessive tensile force, and also prevents the charging station  2  from toppling over. Further, the power supply from the charging power source  3  is automatically stopped, without the need of intervention of the operator, which implements a failsafe mechanism. 
         [0032]    While the embodiment of the present invention has been described above with reference to the drawings, the present invention is not restricted thereto. For example, while the tension detector  7  is made up of the microswitches  71  and  72  in the above embodiment, a reel winding the wiring member  5  with a predetermined force may be provided, in which case the tension detector may be configured with a sensor which detects feed of the wiring member from the reel. Further, the tension detector may be configured with a force sensor such as a strain gauge attached to the wiring member  5 . Still further, the lock mechanism for locking the power-feeding connector  5   b  with the power-receiving connector  1   c  may be provided with a mechanical sensing unit which senses tension of the wiring member  5 , in which case when the tension of the wiring member  5  becomes more than a predetermined level, the movement of the sensing unit may release the lock to disconnect the power-feeding connector  5   b  from the power-receiving connector  1   c . In this case, the sensing unit serves as the tension detector.