Patent Publication Number: US-2022234197-A1

Title: Cable terminal end detection method and hand

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-011891, filed Jan. 28, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a cable terminal end detection method and a hand. 
     2. Related Art 
     For example, JP-A-2014-176917 (Patent Literature 1) describes a robot device that can detect the terminal end of the cable. The robot device described in Patent Literature 1 slides a gripping section to the terminal end side of the cable while gripping the cable with the gripping section and detects force generated by contact of the detecting section with a connector connected to the terminal end of the cable to thereby detect the terminal end of the cable. 
     However, in such a method, unless a member having a larger diameter than the cable such as the connector is disposed at the terminal end of the cable, the terminal end of the cable cannot be detected. 
     SUMMARY 
     A cable terminal end detection method according to an aspect is a cable terminal end detection method for detecting a terminal end of a linear cable including, when two axes crossing each other are represented as an X axis and a Z axis: a gripping step for gripping, using a hand including a first gripping section and a second gripping section disposed to be separated on the X axis and configured to open and close in a direction along the Z axis, the cable in two places separated in a longitudinal direction with the first gripping section and the second gripping section; a moving step for, in a state in which the cable is gripped by the hand, moving the cable to the first gripping section side in a direction along the X axis relatively to the hand; and a detecting step for detecting, with a tactile sensor disposed in the second gripping section to be in contact with the cable, that the cable has slipped out from the second gripping section and detecting that the terminal end of the cable is located between the first gripping section and the second gripping section. 
     A hand according to an aspect includes, when two axes orthogonal to each other are represented as an X axis and a Z axis: a first gripping section and a second gripping section configured to relatively move in a direction along the X axis and open and close in a direction along the Z axis; a tactile sensor disposed in the second gripping section; and an elastic body covering the tactile sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an overall configuration of a robot according to a preferred embodiment. 
         FIG. 2  is a perspective view showing a hand included in the robot shown in  FIG. 1 . 
         FIG. 3  is a sectional view showing a fingertip portion of the hand shown in  FIG. 2 . 
         FIG. 4  is a sectional view showing the fingertip portion of the hand shown in  FIG. 2 . 
         FIG. 5  is a flowchart showing a terminal end detection process for a cable. 
         FIG. 6  is a perspective view for explaining a terminal end detection method for a cable. 
         FIG. 7  is a perspective view for explaining the terminal end detection method for the cable. 
         FIG. 8  is a perspective view for explaining the terminal end detection method for the cable. 
         FIG. 9  is a graph showing force in an X-axis direction applied during terminal end detection work. 
         FIG. 10  is a graph showing force in a Z-axis direction applied during the terminal end detection work. 
         FIG. 11  is a graph showing force in a Y-axis direction applied during the terminal end detection work. 
         FIG. 12  is a perspective view for explaining a terminal end detection method for a cable. 
         FIG. 13  is a perspective view for explaining the terminal end detection method for the cable. 
         FIG. 14  is a perspective view for explaining the terminal end detection method for the cable. 
         FIG. 15  is a perspective view for explaining the terminal end detection method for the cable. 
         FIG. 16  is a perspective view for explaining the terminal end detection method for the cable. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A cable terminal end detection method and a hand according to the present disclosure are explained in detail below with reference to an embodiment shown in the accompanying drawings. 
       FIG. 1  is a perspective view showing an overall configuration of a robot according to a preferred embodiment.  FIG. 2  is a perspective view showing a hand included in the robot shown in  FIG. 1 .  FIGS. 3 and 4  are respectively sectional views showing a fingertip portion of the hand shown in  FIG. 2 .  FIG. 5  is a flowchart showing a terminal end detection process for a cable.  FIGS. 6 to 8  are respectively perspective views for explaining a terminal end detection method for a cable.  FIG. 9  is a graph showing force in an X-axis direction applied during terminal end detection work.  FIG. 10  is a graph showing force in a Z-axis direction applied during the terminal end detection work.  FIG. 11  is a graph showing force in a Y-axis direction applied during the terminal end detection work.  FIGS. 12 to 16  are respectively perspective views for explaining a terminal end detection method for a cable. 
     In the following explanation, for convenience of explanation, a X axis, a Y axis, and a Z axis, which are three axes orthogonal to one another, are illustrated in  FIGS. 2 to 4 ,  FIGS. 6 to 8 , and  FIGS. 12 to 16 , a direction along the X direction is referred to as “X-axis direction” as well, a direction along the Y axis is referred to as “Y-axis direction” as well, and a direction along the Z axis is referred to as “Z-axis direction” as well. An arrow direction distal end side of the axes is referred to as “plus side” as well and the opposite side of the arrow direction distal end side is referred to as “minus side” as well. 
     A robot  1  shown in  FIG. 1  includes a base  11 , a body  12  turnably coupled to the base  11 , a pair of multi-joint arms  13  and  14  coupled to the left and the right of the body  12 , a stereo camera  15  and a signal lamp  16  provided in the body  12 , a monitor  17  provided on the back side of the body  12 , hands  2 A and  2 B attached to the distal end portions of the multi-joint arms  13  and  14 , and a robot control device  18  that controls these sections. 
     The robot  1  having such a configuration performs predetermined work while checking the positions of a workpiece, a tool, and the like using the stereo camera  15 . In particular, in this embodiment, the robot  1  performs work for detecting the terminal end of a cable C. States of the robot  1 , for example, a driving state, a normal stop state, and an abnormal stop state can be easily checked using the signal lamp  16 . Since information concerning the robot  1  is displayed on the monitor  17 , the states of the robot  1  can be simply checked. The monitor  17  is, for example, a touch panel. It is possible to switch a display screen, give a command to the robot  1 , and change the given command by operating the touch panel. 
     The robot control device  18  receives a position command for the robot  1  from a not-shown host computer and controls driving of the sections to locate the body  12  and the multi-joint arms  13  and  14  in positions corresponding to the position command. The robot control device  18  is configured from, for example, a computer and includes a processor (CPU) that processes information, a memory communicably coupled to the processor, and an external interface. Various programs executable by the processor are stored in the memory. The processor reads and executes the various programs and the like stored in the memory. 
     The hands  2 A and  2 B are briefly explained. Since the hands  2 A and  2 B have the same configuration, in the following explanation, the hands  2 A and  2 B are collectively referred to as “hand  2 ”. 
     As shown in  FIG. 2 , the hand  2  includes a base  20  coupled to the distal end portions of the multi-joint arms  13  and  14  and a first gripping section  21  and a second gripping section  22  supported by the base  20 . The first gripping section  21  includes two finger sections  211  and  212  arranged in the Z-axis direction and capable of opening and closing in the Z-axis direction. Similarly, the second gripping section  22  includes two finger sections  221  and  222  arranged in the Z-axis direction and capable of opening and closing in the Z-axis direction. The first and second gripping sections  21  and  22  can relatively move in the X-axis direction and are capable of approaching and separating from each other. The opening and closing of the finger sections  211  and  212 , the opening and closing of the finger sections  221  and  222 , and the approach and the separation of the first and second gripping sections  21  and  22  are realized by a rack and pinion mechanism  23  including a pair of racks  231  and  232  and a pinion  233  and a motor  24  that rotates the pinion  233 . 
     As shown in  FIGS. 3 and 4 , a tactile sensor  251  is disposed on a surface  211   a  of the finger section  211  opposed to the finger section  212 . When the cable C is gripped by the finger sections  211  and  212 , the tactile sensor  251  receives reaction from the cable C. Similarly, a tactile sensor  252  is disposed on a surface  221   a  of the finger section  221  opposed to the finger section  222 . When the cable C is gripped by the finger sections  221  and  222 , the tactile sensor  252  receives reaction from the cable C. The tactile sensors  251  and  252  can respectively independently detect forces in the X-axis direction, the Y-axis direction, and the Z-axis direction. The tactile sensors  251  and  252  are not particularly limited if the tactile sensors  251  and  252  can exert functions thereof. 
     The tactile sensors  251  and  252  are respectively covered by elastic bodies  261  and  262  configured by an elastic material such as a rubber material. The elastic bodies  261  and  262  are deformed to follow a movement of the cable C, whereby force corresponding to the movement of the cable C is simply transmitted to the tactile sensors  251  and  252 . Therefore, as explained below, it is possible to more accurately detect the terminal end of the cable C. 
     A groove  271  with in the cable C engages is disposed in a position opposed to the tactile sensor  251  on a surface  212   a  of the finger section  212  opposed to the finger section  211 . As shown in  FIG. 4 , by causing the cable C to engage with the groove  271 , it is possible to more surely bring the cable C and the elastic body  261  into contact and transmit the reaction from the cable C to the tactile sensor  251 . It is also possible to effectively suppress unintended separation of the cable C from the first gripping section  21 . Similarly, a groove  272  in which the cable C engages is disposed in a position opposed to the tactile sensor  252  on a surface  222   a  of the finger section  222  opposed to the finger section  221 . As shown in  FIG. 4 , by causing the cable C to engage with the groove  272 , it is possible to more surely bring the cable C and the elastic body  262  into contact and transmit the reaction from the cable C to the tactile sensor  252 . It is also possible to effectively suppress unintended separation of the cable C from the second gripping section  22 . 
     Such a hand  2  has a configuration suitable for performing a terminal end detection method for the cable C explained below. Therefore, it is easier to carry out the terminal end detection method for the cable C. The configuration of the hand  2  is not particularly limited as long as the hand  2  includes the first and second gripping sections  21  and  22  and the tactile sensor  252  disposed in the second gripping section  22 . 
     The configuration of the robot  1  is briefly explained above. Subsequently, the terminal end detection method for the cable C performed using the robot  1  is explained in detail. The cable C is not particularly limited. However, a cable, on the outer circumferential surface of which unevenness is substantially absent and to the terminal end of which a terminal such as a connector is not connected, is preferable. That is, the cable C preferably has a shape that can be smoothly pulled out from the second gripping section  22  without being caught by the second gripping section  22  in a moving step S 2  explained below. The cable C having such a shape is suitable for the terminal end detection method in this embodiment. 
     As shown in  FIG. 5 , the terminal end detection method for the cable includes a gripping step S 1 , a moving step S 2 , a detecting step S 3 , a stopping step S 4 , a second gripping section moving step S 5 , a second gripping section gripping step S 6 , and a work step S 7 . The steps are explained below in order below. In  FIGS. 6 to 16  referred to below, for convenience of explanation, the hands  2 A and  2 B are simplified and illustrated. 
     Gripping Step S 1   
     First, the robot  1  grips the cable C with the hands  2 A and  2 B. The hand  2 A may grip the cable C in any way. On the other hand, as shown in  FIG. 6 , the hand  2 B separates the first gripping section  21  and the second gripping section  22  in the X-axis direction and grips to sandwich, with the first gripping section  21  and the second gripping section  22 , the cable C from the Z-axis direction in two places separated in the longitudinal direction of the cable C. In a state in which the cable C is gripped, as shown in  FIG. 4 , the cable C engages with the grooves  271  and  272  and comes into contact with the elastic bodies  261  and  262 . Therefore, the elastic bodies  261  and  262  are deformed to be crushed in the Z-axis direction. Force in the Z-axis direction acts on the tactile sensors  251  and  252 . 
     The hand  2 A strongly and firmly grips the cable C. On the other hand, the hand  2 B loosely grips the cable C with light force as long as the cable C does not separate from the first and second gripping sections  21  and  22  and the tactile sensors  251  and  252  can detect reaction from the cable C. Consequently, in the following moving step S 2 , it is possible to slide the cable C with respect to the hand  2 B with smaller force. Therefore, it is possible to further reduce tensile stress applied to the cable C and suppress disconnection of the cable C. 
     In the hand  2 B, it is preferable to secure a separation distance D between the first gripping section  21  and the second gripping section  22  sufficiently larger than width W of the second gripping section  22 . Consequently, later processes are smoothly performed. 
     Moving Step S 2   
     Subsequently, the robot  1  initializes the tactile sensors  251  and  252  and sets outputs to 0 (zero). Subsequently, as shown in  FIG. 7 , in a state in which the cable C is gripped by the hand  2 B, the robot  1  moves the cable C to an X-axis direction minus side, that is, the first gripping section  21  side relatively to the hand  2 B. Specifically, the robot  1  moves the hand  2 A to the X-axis direction minus side with the multi-joint arm  13  to pull the cable C to the X-axis direction minus side and moves the cable C to the X-axis direction minus side with respect to the hand  2 B. However, not only this, but the robot  1  may move the hand  2 B to an X-axis direction plus side with the multi-joint arm  14  to thereby move the cable C to the X-axis direction minus side with respect to the hand  2 B. This movement is continued until a later stopping step S 4 . 
     At this time, the cable C moves while rubbing against the first and second gripping sections  21  and  22 , that is, slides. Therefore, in this step, the elastic bodies  261  and  262  are deformed to be pulled to the X-axis direction minus side by the sliding of the cable C. Force Fx in the X-axis direction acts on the tactile sensors  251  and  252  according to the deformation. That is, in the moving step S 2 , since the elastic bodies  261  and  262  are deformed to be pulled in the X-axis direction while being deformed to be crushed in the Z-axis direction, force Fz in the Z-axis direction and the force Fx in the X-axis direction due to the deformation act on the tactile sensors  251  and  252 . Therefore, the force Fx in the X-axis direction and the force Fz in the Z-axis direction are output from the tactile sensors  251  and  252 . 
     Detecting Step S 3   
     When the moving step S 2  is continued, as shown in  FIG. 8 , the cable C slips out from the second gripping section  22  at certain timing. A terminal end Ce of the cable C is located between the first gripping section  21  and the second gripping section  22 . When the cable C slips out from the second gripping section  22 , since the forces Fz and Fx generated by the sliding with the cable C stop acting on the tactile sensor  252 , the forces Fx and Fx are not output from the tactile sensor  252 . Therefore, the robot  1  detects, based on a change in an output from the tactile sensor  252 , that the cable C has slipped out from the second gripping section  22 . 
     Examples of the forces Fx and Fz output from the tactile sensor  252  during the moving step S 2  are shown in  FIGS. 9 and 10 .  FIGS. 9 and 10  indicate that an output of the tactile sensor  252  is initialized at the number of steps “0”, the moving step S 2  is started at the number of steps “10”, and the cable C slips out from the second gripping section  22  at the number of steps “29”. In this way, the cable C slips out from the second gripping section  22 , whereby the output from the tactile sensor  252  clearly changes. Therefore, the robot  1  can easily detect that the cable C has slipped out from the second gripping section  22 . 
     On the other hand, in a state shown in  FIG. 8 , the cable C has not slipped out from the first gripping section  21 . Therefore, the forces Fx and Fz are continuously output from the tactile sensor  251 . Therefore, the forces Fz and Fx are not output only from the tactile sensor  252  of the tactile sensors  251  and  252 . Consequently, the robot  1  can detect that the cable C has slipped out from the second gripping section  22  and the terminal end Ce of the cable C is present between the first gripping section  21  and the second gripping section  22 . In this way, based on the forces Fz and Fx, it is possible to simply and surely detect that the cable C has slipped out from the second gripping section  22  and the terminal end Ce of the cable C is present between the first gripping section  21  and the second gripping section  22 . 
     During the moving step S 2 , force Fy in the Y-axis direction is output from the tactile sensors  251  and  252  other than the forces Fx and Fz. A state, specifically, a bending state of the cable C can be detected from the force Fy. For example, as the force Fy is stronger, it is possible to detect that the cable C bends in the direction of the force Fy. Therefore, the robot  1  can perform the moving step S 2  while grasping the state of the cable C. Consequently, the robot  1  can more smoothly perform the moving step S 2 . 
     An example of the force Fy output from the tactile sensor  252  during the moving step S 2  is shown in  FIG. 11 . Like  FIGS. 9 and 10 ,  FIG. 11  indicates that an output of the tactile sensor  252  is initialized at the number of steps “0”, the moving step S 2  is started at the number of steps “10”, and the cable C slips out from the second gripping section  22  at the number of steps “29”. It is also possible to detect, based on a change in the force Fy, that the cable C has slipped out from the second gripping section  22 . However, as it is seen from  FIG. 11 , the force Fy is smaller compared with the forces Fx and Fz. Therefore, the accuracy of the detection based on the force Fy is likely to be lower compared with the detection based on the forces Fx and Fz. 
     Stopping Step S 4   
     When detecting in the detecting step S 3  that the cable C slips out from the second gripping section  22  and the terminal end Ce of the cable C is present between the first gripping section  21  and the second gripping section  22 , the robot  1  quickly stops pulling the cable C to the X-axis direction minus side. Consequently, as shown in  FIG. 8 , a state in which the terminal end Ce is located between the first gripping section  21  and the second gripping section  22  is maintained. As explained above, the separation distance D between the first gripping section  21  and the second gripping section  22  is set sufficiently wider than the width W of the second gripping section  22 . Therefore, after the cable C slips out from the second gripping section  22 , by quickly stopping pulling the cable C to the X-axis direction minus side, it is possible to secure length L from the first gripping section  21  to the terminal end Ce of the cable C larger than the width W of the second gripping section  22 . Consequently, it is easy to perform later work. 
     Second Gripping Section Moving Step S 5   
     Subsequently, the second gripping section  22  is opened. As shown in  FIG. 12 , the first gripping section  21  and the second gripping section  22  are relatively moved along the X axis and the second gripping section  22  is located further on the X-axis direction minus side, that is, the first gripping section  21  side than the terminal end Ce of the cable C. In  FIG. 12 , because of the configuration of the hand  2 B, by moving the first gripping section  21  to the X-axis direction plus side and moving the second gripping section  22  to the X-axis direction minus side, the gripping section  22  is located further on the X-axis direction minus side than the terminal end Ce of the cable C. 
     Second Gripping Step Gripping Step S 6   
     Subsequently, as shown in  FIG. 13 , the cable C is gripped again by the second gripping section  22 , that is, a pair of finger sections  221  and  222 . Consequently, the cable C is gripped by the first gripping section  21  and the second gripping section  22  and the terminal end Ce of the cable C is projected from the second gripping section  22  to the X-axis direction plus side. Therefore, it is easy to approach the terminal end Ce and perform predetermined work on the terminal end Ce. 
     Work Step S 7   
     Subsequently, predetermined work is performed on the terminal end Ce. As explained above, since the terminal end Ce of the cable C is projected from the second gripping section  22 , it is easy to perform the predetermined work on the terminal end Ce. The predetermined work is not particularly limited. In this embodiment, first, work for removing a film of the cable C to expose a core material C 1  on the inside as shown in  FIG. 14 , inserting the terminal end Ce into a hole-shaped terminal T as shown in  FIG. 15 , and connecting the terminal end Ce and the terminal T with solder H as shown in  FIG. 16  is performed. 
     The terminal end detection method for the cable C using the robot  1  is explained above. As explained above, such a terminal end detection method is a cable terminal end detection method for detecting the terminal end of the linear cable C including, when two axes crossing each other are represented as an X axis and a Z axis, the gripping step S 1  for gripping, using the hand  2 B including the first gripping section  21  and the second gripping section  22  disposed to be separated on the X axis and configured to open and close in a direction along the Z axis, the cable C in two places separated in a longitudinal direction with the first gripping section  21  and the second gripping section  22 , the moving step S 2  for, in a state in which the cable C is gripped by the hand  2 B, moving the cable C to the first gripping section  21  side in a direction along the X axis relatively to the hand  2 B, and the detecting step S 3  for detecting, with the tactile sensor  252  disposed in the second gripping section  22  to be in contact with the cable C, that the cable C has slipped out from the second gripping section  22  and detecting that the terminal end Ce of the cable C is located between the first gripping section  21  and the second gripping section  22 . With such a method, it is possible to simply and easily detect the terminal end Ce of the cable C. Since the terminal end Ce can be detected while being gripped by the hand  2 B, it is possible to smoothly shift to work after that and work efficiency is improved. 
     As explained above, in the detecting step S 3 , it is detected based on the force Fx in the direction along the X axis applied to the tactile sensor  252  that the cable C has slipped out from the second gripping section  22 . Consequently, it is possible to simply and surely detect that the cable C has slipped out from the second gripping section  22 . 
     As explained above, in the detecting step S 3 , it is detected based on the force Fz in the direction along the Z axis applied to the tactile sensor  252  that the cable C has slipped out from the second gripping section  22 . Consequently, it is possible to simply and surely detect that the cable C has slipped out from the second gripping section  22 . 
     As explained above, when an axis crossing the X axis and the Z axis is represented as a Y axis, in the detecting step S 3 , a state of the cable C is detected based on the force Fy in a direction along the Y axis applied to the tactile sensor  252 . Consequently, it is possible to simply and surely detect the state of the cable C. 
     As explained above, the first gripping section  21  and the second gripping section  22  can relatively move in the direction along the X axis. The terminal end detection method includes, after the detecting step S 3 , the stopping step S 4  for stopping the relative movement of the hand  2 B and the cable C at the time when the terminal end Ce of the cable C is located between the first gripping section  21  and the second gripping section  22 , the second gripping section moving step S 5  for relatively moving the first gripping section  21  and the second gripping section  22  along the X axis and locating the second gripping section  22  further on the first gripping section  21  side than the terminal end Ce of the cable C, and a second gripping section gripping step S 6  for gripping the cable C with the second gripping section  22 . Consequently, the terminal end Ce of the cable C can be projected to the outer side of the hand  2 . Therefore, it is possible to smoothly perform work after that. 
     As explained above, the terminal end detection method includes, after the second gripping section gripping step S 6 , the work step S 7  for performing predetermined work on the terminal end Ce of the cable C. Consequently, the terminal end Ce of the cable C can be projected to the outer side of the hand  2 . Therefore, it is possible to easily perform this step. 
     As explained above, the hand  2 B includes, when two axes crossing each other are represented as an X axis and a Z axis, the first gripping section  21  and the second gripping section  22  configured to relatively move in a direction along the X axis and open and close in a direction along the Z axis, the tactile sensor  252  disposed in the second gripping section  22 , and the elastic body  262  covering the tactile sensor  252 . With such a configuration, the hand  2 B has a configuration suitable for the terminal end detection method explained above. 
     The cable terminal end detection method and the hand according to the present disclosure are explained above with reference to the embodiment shown in the figures. However, the present disclosure is not limited to this. The components of the sections can be replaced with any components having the same functions. Any other components may be added to the present disclosure. In the embodiment explained above, the X axis, the Y axis, and the Z axis are orthogonal to one another. However, the X axis, the Y axis, and the Z axis only have to cross and may not be orthogonal. 
     In the embodiment, the robot  1  pulls the cable C to the X-axis direction minus side with respect to the hand  2 B using the hand  2 A. However, a method of pulling the cable C is not particularly limited. For example, the cable C may be pulled using another robot or device. For example, the starting end of the cable C may be fixed to a fixing member different from the robot  1 . The cable C may be gripped by only the hand  2 B. By sliding the hand  2 B to the X-axis direction plus side, the cable C may be moved to the X-axis direction minus side with respect to the hand  2 B.