Abstract:
The present disclosure relates to a robot mechanism for nondestructive aging evaluation of a cable. The robot mechanism includes at least two inspection modules, and a coupler disposed between the at least two inspection modules and connected to each of the inspection modules to adjust a separation between the inspection modules. Each of the inspection modules approaches a cable and automatically inspects an aged state of the cable. The robot mechanism automatically measures an aged state of a cable in a nondestructive manner and establishes a database of cable aging, so that normal operation of the cable can be ensured through stable management of the cable by evaluating a replacement time and the aged state of the cable based on the database.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to development of machines in the field of mechatronics, such as a robot mechanism for nondestructive aging evaluation of a cable and, more particularly, to a robot mechanism that can automatically measure an aged state of a cable and establish a database based on the evaluation result to evaluate a replacement time. 
     2. Description of the Related Art 
     Conventionally, aging of a cable is directly detected by an operator using a portable cable aging tester which employs a personal digital assistant (PDA). However, since the portable cable aging tester is manually operated by the operator for direct measurement of the aged state of the cable, a significant measurement time is required and measured values vary depending on proficiency of the operator as the number of measurement points increases. 
     Further, when the cable undergoes changes in local shape and hardness due to exposure to the environment for long durations, the measured values can also vary depending on the measurement points for the same cable, such that repetitious measurement at several measurement points for a single cable is required for accurate aging evaluation of the cable. 
     Currently, these problems make it difficult to commercialize the portable cable aging tester which is a non-destructive aging tester for cables. 
     Thus, to solve such problems, it is necessary to achieve reduction in measurement time, enhancement of accuracy and efficiency in measurement, establishment of database through evaluation of many measurement points, and the like. 
     When establishing an evaluation database of cable aging by measuring a number of points on the cable within a short period of time at low cost, all of these procedures must be automatically performed. However, since studies have mainly focused on development of a nondestructive aging evaluation method, development of an automatic inspection method and an inspection method for various specimens is unsatisfactory in the art. 
     This invention aims at enhancement in measurement accuracy and repetitious characteristics, reduction in operation time, and improvement in operation efficiency of an aging tester by enabling automatic measurement of a variety of cables within a short period of time through application of the aging tester to a transfer robot mechanism. 
     [Reference Document] 
     Jong-seuk Kim, “A Study on Evaluation of Cable Aging through Instrumental Indentation Test,” Thesis for the Degree of Engineering Doctor, Chungnam University, 2004. 
     SUMMARY OF THE INVENTION 
     The present invention is conceived to solve the above problems of the related art, and an aspect of the invention is to provide a robot mechanism that is capable of automatically measuring an aged state of a cable in a nondestructive manner and establishing a database of cable aging, so that normal operation of the cable can be ensured through stable management of the cable by evaluating a replacement time and the aged state of the cable based on the database. 
     Another aspect of the invention is to provide a robot mechanism for nondestructive aging evaluation of a cable, which can automatically measure an aged state of a cable using a robot, instead of conventional manual measurement by a worker, thereby reducing the number of workers and operation time while improving stability in operation of the mechanism through establishment of a database for cable aging and lifetime expectation. 
     In accordance with an aspect of the invention, a robot mechanism for nondestructive aging evaluation of a cable includes at least two inspection modules, each approaching a cable and automatically inspecting an aged state of the cable, and a coupler disposed between the at least two inspection modules and connected to each of the inspection modules to adjust a separation between the inspection modules. 
     Each of the inspection modules may include a body assembled by a fastener, a transfer unit coupled to a lower portion of the body and moving along the cable, and a measurement unit disposed at a center of the lower portion of the body to perform measurement and inspection of a local aged state of the cable. 
     The transfer unit may include a pair of drive rollers provided to a lower surface of the body to move along an upper surface of the cable, a drive motor connected to the drive rollers to transmit power, and a detection sensor detecting a velocity of the drive rollers to control the drive rollers. Here, each of the drive rollers is provided with a plurality of O-rings, and the detection sensor includes a photo-interrupter for velocity detection and employs a one-turn step control method. 
     The measurement unit may include a drive motor secured to the lower portion of the body, a rotational shaft connected to an upper portion of the drive motor and driven by transmitted power, a drive gear connected to the rotational shaft to be associated with rotation of the rotational shaft, a driven gear engaging with the drive gear, a cylinder converting the rotation of the rotational shaft into up-down movement, a force sensor provided to a lower portion of the cylinder to measure or control a force generated by the cylinder, an indentation needle provided to a lower surface of the force sensor to contact the cable, and a cylinder guide member disposed at an upper portion of the cylinder to guide the cylinder during the up-down movement of the cylinder. Here, the cylinder guide member includes a body, a pair of through-holes formed in right and left sides of the body, respectively, a guide hole formed in a center of the body, and a pair of stoppers formed on left and right walls of the guide hole facing each other. 
     The cylinder may be formed at right and left sides thereof with insertion grooves corresponding to the stoppers. Further, the force sensor may be provided at the lower surface thereof with a cable securing member corresponding to the cylinder guide member and secured to the cable by a constant pressure. 
     The cable securing member may include a body, a pair of through-holes formed in right and left sides of the body, respectively, a recess formed in a center of the body, and a pair of contacts formed on a lower surface of the body and directly secured to an outer surface of the cable. The measurement unit may further include an elastic member between the cylinder guide member and the cable securing member, and an elastic member-guide member integrally formed with the cylinder guide member between the cylinder guide member and the cable securing member to guide the elastic member while allowing up-down movement of the cable securing member. 
     The coupler may be secured at a predetermined angle to one side of an upper portion of the body and be provided with a coupling guide member which allows adjustment of length thereof depending on a thickness of the cable. Here, the coupling guide member is mounted at 150 degrees relative to the cable. Odd numbers of the transfer units, the measurement units and the couplers adjusting the separation between the inspection modules are arranged at 120 degrees with respect to each other and are simultaneously driven. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention given in conjunction with the accompanying drawings, in which: 
         FIGS. 1 and 2  are a perspective view and a plan view showing a coupled relationship of a robot mechanism for nondestructive aging evaluation of a cable in accordance with an embodiment of the present invention; 
         FIGS. 3 and 4  are an assembled perspective view and an exploded perspective view of a transfer unit of the robot mechanism in accordance with the embodiment of the present invention; 
         FIGS. 5 and 6  are an exploded perspective view and an assembled perspective view of a measurement unit of the robot mechanism in accordance with the embodiment of the present invention; 
         FIG. 7  is a perspective view showing main components of the robot mechanism in accordance with the embodiment of the present invention; 
         FIG. 8  shows an operation state of one example of the robot mechanism in accordance with the embodiment of the present invention; and 
         FIG. 9  shows an operation state of another example of the robot mechanism in accordance with the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the invention will hereinafter be described in detail with reference to the accompanying drawings. 
     The invention relates to a robot mechanism designed for operation in extreme conditions, which is configured to evaluate aging of a cable due to long term use of the cable or due to various environments such as corrosive gas, ultraviolet radiation, high temperature, and the like. Referring to  FIGS. 1 and 2 , a robot mechanism for nondestructive aging evaluation of a cable in accordance with an embodiment of the invention includes inspection modules  1  and couplers  50 . 
     The robot mechanism includes at least two inspection modules  1 , and the coupler  50  is connected to each of the inspection modules  50  to adjust a separation between the inspection modules  1 . 
     Each of the couplers  50  includes a coupling guide member  51  that is secured at a predetermined angle to an upper portion of each of the inspection modules  1  and permits adjustment of length thereof depending on the thicknesses of cables C, C′ (see  FIGS. 8 and 9 ). 
     The coupling guide member  51  is mounted at an angle of 150 degrees on the upper portion of the inspection module  1  and comprises a pair of coupling guide members on right and left sides of the inspection module  1 , respectively. 
     Each of the inspection modules  1  includes a body  10 , a transfer unit  20 , and a measurement unit  30 . 
     The body  10  is divided into an upper case  60  and a lower case  70 , which are coupled to each other by a fastening member. 
     Referring to  FIGS. 3 and 4 , the transfer unit  20  includes a drive roller  23 , a drive motor  21 , and a velocity sensor  27 . 
     The drive roller  23  is provided to a lower surface of the lower case  70  of the body  10  and comprises a pair of rollers which are disposed at right and left sides of the lower surface thereof, respectively. 
     The drive roller  23  is provided with a plurality of O-rings  25  on an outer periphery thereof to allow the drive roller  23  to be accurately moved on the cables C, C′. 
     The drive motor  21  is connected to the drive roller  23  to transmit power thereto. 
     The drive motor  21  is composed of a DC motor and a gear. 
     The velocity sensor  27  is connected to the drive roller  23  and controls the velocity of the drive roller  23 , which is driven by the drive motor  21 . 
     The velocity sensor  27  is a photo-interrupter for velocity detection. In this embodiment, an appointed location control manner using a switch is adopted to provide a simple structure to the velocity sensor notwithstanding low continuity, instead of a continuous location control manner which allows the velocity sensor to be stopped at any location by simple movement in a forward and rearward direction. As a method of controlling the velocity of the drive roller, the velocity sensor  27  employs a one-turn step control method, thereby facilitating manufacture and realization of control logic. 
     Referring to  FIGS. 5 and 6 , the measurement unit  30  includes a drive motor  31 , a rotational shaft  31   a , a drive gear  32 , a driven gear  33 , a cylinder  35 , a force sensor  36 , and an indentation needle  39 . 
     The drive motor  31  is secured to the lower case  70  of the body  10 . 
     In this embodiment, the drive motor  31  is a DC servo motor. 
     The rotational shaft  31   a  is connected to an upper portion of the drive motor  31  and is driven by the power transmitted from the drive motor  31 . 
     The drive gear  32  is connected to the rotational shaft  31   a  and is associated with rotation of the rotational shaft  31   a.    
     The driven gear  33  engages with the drive gear  32 . 
     The cylinder  35  is provided to the lower surface of the driven gear  33  and converts rotation of a gear set  34  into up-down movement. 
     In this embodiment, the cylinder  35  has a spiral tap structure similar to a thread shape. 
     Referring to  FIG. 7(   a ), the cylinder  35  is formed with insertion grooves  35   a  that are formed to a predetermined depth on upper right and left sides of the cylinder  35 . 
     The force sensor  36  is provided to a lower portion of the cylinder  35  to measure or control a force generated by the cylinder  35 . 
     As for the force sensor  36 , a load cell or a thin film contact type sensor can be used. However, since the load cell is disadvantageous in view of size and weight and the thin film contact type sensor is disadvantageous in view of precision, it is desirable to use a piezoelectric force sensor which has a small size and low weight while ensuring high precision. 
     The indentation needle  39  is provided to a lower surface of the force sensor  36  to contact the cable C. 
     The cylinder  35  is provided at an upper portion thereof with a cylinder guide member  37  which guides the cylinder  35  to ensure a precise up-down movement of the cylinder  35 . 
     Further, the force sensor  36  is provided at the lower surface thereof with a cable securing member  41  which corresponds to the cylinder guide member  37  and is secured while applying a constant pressure to the cables C, C′. 
     Referring to  FIG. 7(   b ), the cylinder guide member  37  includes a body  37   a , first through-holes  37   b , a guide hole  37   c , and stoppers  37   d.    
     The first through-holes  37   b  comprise a pair of through-holes which are formed in right and left sides of the body  37   a , respectively. 
     The guide hole  37   c  is formed in the center of the body  37   a  and has a larger diameter than the first through-holes  37   b.    
     The stoppers  37   d  comprise a pair of stoppers which are respectively formed at right and left sides of an inner periphery of the guide hole  37   c  to face each other. 
     The stoppers  37   d  is fixedly inserted into the insertion holes  35   a  of the cylinder  35  to prevent the cylinder  35  from being rotated even when the driven gear  33  is driven by the drive gear  32 , so that the cylinder  35  can be accurately guided by the cylinder guide member  37 . 
     Referring to  FIG. 7(   c ), the cable securing member  41  includes a body  41   a , second through-holes  41   b , a recess  41   c , and contact portions  41   d.    
     The second through-holes  41   b  comprise a pair of through-holes which are formed in right and left sides of the body  41   a , respectively. 
     The second through-holes  41   b  are formed corresponding to the first through-holes  37   b  which are formed in the cylinder guide member  37 . 
     The recess  41   c  is formed in the center of the body  41   a.    
     The recess  41   c  has substantially the same diameter as that of the indentation needle  39  to guide the indentation needle  39  to precisely contact the cables C, C′ when the indentation needle  39  is brought into contact with the cables C, C′. 
     The contact portions  41   d  are formed on a lower surface of the body  41   a  and directly contact the cables C, C′ to be secured while applying a constant pressure to the cables C, C′. 
     On the other hand, the measurement unit  30  further includes elastic members  38  disposed between the cylinder guide member  37  and the cable securing member  41 , and elastic member-guide members  38   a  disposed between the first through-holes  37   b  of the cylinder guide member  37  and the second through-holes  41   b  of the cable securing member  41  to guide the elastic members  38 , respectively. 
     In this embodiment, at least two inspection modules  1  having the configuration as described above are arranged at an interval of 120 degrees and simultaneously operated. 
     One example of the robot mechanism according to the invention will be described with reference to  FIG. 8 . 
     In this example, the robot mechanism includes at least two inspection modules  1  arranged at an interval of 120 degrees. With the inspection modules  1  installed around a cable C, the coupling guide members  51  of the couplers  50  are slid corresponding to the size of the cable C. 
     After the coupling guide members  51  are slid, the drive motor  31  of each of the measurement units  30  secured to the lower portion of the body  10  receives measured valves. Here, as the rotational shaft  31   a  connected to the drive motor  31  and the drive gear  32  connected to the rotational shaft  31   a  are rotated in the “{circle around (1)}” direction, the driven gear  33  engaging with the drive gear  32  is rotated in the “{circle around (2)}” direction. 
     Then, the cylinder  35  performs up-down movement along the spiral tap formed therein, and the cable securing member  41  provided to the lower portion of the cylinder  35  is operated in the “{circle around (3)}” direction by rigidity of the elastic members disposed between the cylinder guide member  37  and the cable securing member  41  to force the contact portions  41   d  of the cable securing member  41  to be secured to an upper portion of an outer peripheral surface of the cable C. Further, the indentation needle  39  is lowered and press-fitted into the recess  41   c  of the cable securing member  41  to detect a degree of aging of the cable C. 
     Here, since the degree of aging can vary depending on the location of the cable C, the robot mechanism is designed to allow the transfer units  20  and the measurement units  30  of the at least two inspection modules  1  to be simultaneously operated for measurement of the degree of aging of the cable. 
     When measuring the degree of aging, a measurement signal is transmitted from the force sensor  36  to a computer through a controller and used to control an indentation testing mechanism. 
     When the measurement is finished, the couplers  50  of the inspection modules  1  are slid in the opposite direction to the initial direction in which the couplers  50  are moved for measurement of the aging degree. Then, the elastic members  38  are raised by the elastic member guide member  38   a  and the cable securing member  41  secured to the cable C is automatically raised and separated from the cable C, thereby completing the measurement. 
     Another example of the robot mechanism according to the invention will be described with reference to  FIG. 9 . 
     When evaluating a cable C′ having a different size from that of the cable C, the coupling guide member  51  of the coupler  50  in each of the inspection modules  1  is slid to correspond to the size of the cable C′. 
     The sequence after sliding of the coupling guide member  51  is the same as the above example. 
     As such, the robot mechanism according to this invention measures a force per unit area to evaluate the aged state of a cable. 
     Therefore, the measurement unit is designed to measure the force exerted on the indentation needle and the indentation depth corresponding to the force. 
     Further, since the degree of aging can vary depending on the location of the cable, the robot mechanism is configured to simultaneously measure a plurality of points on the cable and to automatically measure various portions of the cable. 
     Since the indentation distance must be measurable and the robot mechanism must be controlled at a predetermined velocity, the robot mechanism includes an encoder and a Proportional Integral Derivative (PID) controller. 
     The robot mechanism according to this invention allows all operations to be automatically performed to reduce the number of workers and operation time. Further, the cable securing member used for securing a cable unfolds a bent portion of the cable and minimizes measurement errors, which can occur due to a space (where an inner filing material is not present) in a cable jacket and due to an unsmooth surface of the cable, thereby providing the same measurement result even after repetitious testing. 
     Although some embodiments have been provided to illustrate the invention in conjunction with the drawings, it will be apparent to those skilled in the art that the embodiments are given by way of illustration only, and that various modifications, changes, and substitutions can be made without departing from the spirit and scope of the invention. The scope of the invention should be limited only by the accompanying claims and equivalents thereof.