Abstract:
A truck for examination of a vehicle body includes a moving module configured to move truck bases with a vehicle body fixed thereto, a sensor module configured to be moved by the moving module and to measure stop position distribution of the truck base that reaches a predetermined position, and a calibration module configured to adjust a position of the truck base based on the measured distribution. The examination truck may enhance reliability of measurement result of assembly precision in a system for measuring the assembly precision of the vehicle body in a vehicle body assembly line.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority to Korean Patent Application No. 10-2014-0166425, filed on Nov. 26, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a truck for examination of a vehicle body, and more particularly, to a calibration truck and a calibration method thereof, for calibrating a position of a truck with a vehicle body fixed thereto to enhance the reliability of measurement result of assembly precision in a system for measuring the assembly precision of the vehicle body in a vehicle body assembly line. 
     BACKGROUND 
     In an automobile assembly line, various components are coupled to a vehicle body B via a method such as welding, etc. as an automated process. In addition, a device for examining whether components are appropriately welded to a desired position as the result of assembly process is also automated. 
       FIG. 1  is a perspective view of a conventional truck structure. Referring to  FIG. 1 , the conventional truck structure is configured in such a way that a truck base  16  is placed on a truck rail  10  and moves along the truck base  16  by a moving magnet  12  installed on the truck rail  10 . 
     The truck base  16  moves up to a point in which a stopper  14  is installed, and examination is performed on a vehicle body B positioned on a fixed unit  91  on the truck base  16  stopped by the stopper  14 . 
     However, a measurement robot for the examination repeats measurements at a predetermined position, and thus when dispersion is concentrated on a stop position of the aforementioned truck base, dispersion also accumulates with regard to values measured by the measurement robot, and thus accurate examination result is not achieved. 
     SUMMARY 
     The present disclosure has been made to solve the above-mentioned problems occurring in the prior art while advantages achieved by the prior art are maintained intact. 
     An aspect of the present disclosure provides a truck structure and a calibration method thereof, for calibrating a position of a truck prior to examination to prevent examination result from being affected by a dispersion difference according to a difference in stop positions of the truck. 
     According to an exemplary embodiment of the present disclosure, a calibration truck includes a moving module configured to move a truck base with a vehicle body fixed thereto, a sensor module configured to be moved by the moving module and to measure stop position dispersion of the truck base that reaches a predetermined position, and a calibration module configured to adjust a position of the truck base based on the measured. 
     The moving module may include a moving magnet configured to be installed on a truck rail and to move the truck bases according to magnetism, and a stopper configured to determine a stop position of the truck. 
     The stopper may move between a position in which the stopper protrudes on a truck rail and a position in which the stopper goes into the truck rail. 
     The sensor module may include a light receiver formed on the truck base, and a sensor assembly configured to measure a position of the light receiver. 
     The sensor assembly may include a base at a fixed position, and a measuring sensor configured to move between a first position from the base toward the truck base and a second position spaced apart from the truck base and to measure the position of the light receiver at the first position. 
     The measuring sensor may be installed on a bracket installed in a motor cylinder fixed to the base and moved backward and forward according to an operation of the motor cylinder. 
     The calibration module may calibrate a position of a second truck base positioned on a first truck base with respect to the first truck base positioned on a truck rail. 
     The calibration truck may further include a pinion extending in parallel to a moving direction of any one of the first truck base and the second truck base, and a rack engaged with the pinion at the remaining one of the first truck base and the second truck base, wherein the position of the second truck base with respect to the first truck base may be calibrated via rotation of the rack. 
     The second truck base may be moved backward and forward in the same direction as a moving direction of the truck base by a linear guide installed on the first truck base. 
     According to another exemplary embodiment of the present disclosure, a method of calibrating a truck base using the calibration truck includes moving a truck base to a position in which the truck base is stopped by a stopper, measuring stop position dispersion of the stopped truck base, and calibrating and adjusting a position of the truck base using the measured dispersion. 
     The measuring may include moving a measuring sensor to a first position close to the truck base from a second position close to the base, detecting a position of a light receiver of the truck base at the first position, and moving the measuring sensor to the second position when the detecting is completed. 
     The method may further include calculating displacement between the measured position dispersion and a home position and determining whether calibration is performed by a calibration module, a calibration direction and a calibration amount. 
     The method may further include converting a direction of the calibration into a rotation direction of a motor for rotation of a rack, and converting the calibration amount into a rotation angle of the motor. 
     The method may further include examining assembly precision of a vehicle body mounted on a second truck base after calibration of the second truck base is completed in a direction determined in the converting and by as much as a predetermined distance. 
     The stopper may go below a surface of a truck rail and the truck base may move when the examining of the assembly precision is completed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings. 
         FIG. 1  is a perspective view of a conventional truck structure. 
         FIG. 2  is a perspective view illustrating a state in which a vehicle body is placed on a truck structure according to an embodiment of the present disclosure. 
         FIG. 3  is a perspective view illustrating a state in which a vehicle body is not placed on a truck structure according to an embodiment of the present disclosure. 
         FIG. 4  is an enlarged perspective view of a sensor module of a truck according to an embodiment of the present disclosure. 
         FIG. 5  is an enlarged perspective view of a calibration module of a truck according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments will now be described more fully with reference to the accompanying drawings. 
       FIG. 2  is a perspective view illustrating a state in which a vehicle body is placed on a truck structure according to an embodiment of the present disclosure.  FIG. 3  is a perspective view illustrating a state in which a vehicle body is not placed on a truck structure according to an embodiment of the present disclosure.  FIG. 4  is an enlarged perspective view of a sensor module of a truck according to an embodiment of the present disclosure.  FIG. 5  is an enlarged perspective view of a calibration module of a truck according to an embodiment of the present disclosure. 
     The calibration truck according to the present disclosure may be largely classified into three modules. 
     1. A moving module for moving truck first and second bases  20  and  30  to which a vehicle body B is fixed. 
     2. A sensor module for measuring stop position dispersion of the second truck base  30  that is moved by the moving module and reaches a predetermined position. 
     3. A calibration module for adjusting a position of the second truck base  30  based on the measured dispersion. 
     [Moving Module] 
     Referring to  FIG. 2 , the truck rail  10  corresponds to a moving path of the truck bases  20  and  30  on which the vehicle body B is mounted, and a series of equipments (not shown) for measuring the assembly precision of the vehicle body B are installed in parallel to each other on the moving path. 
     Moving magnets  12  are installed to be spaced apart from each other by a predetermined interval on the moving module. In this regard, the truck bases  20  and  30  are moved forward along the truck rail  10  according to change in magnetism of the moving magnets  12 . 
     A position where the truck bases  20  and  30  need to be stopped for examination of the vehicle body B is determined by a stopper  14  installed at the truck rail  10 , as illustrated in the drawings. 
     As illustrated in the drawings, the stopper  14  is operated with two positions of one position in which the stopper  14  protrudes above the truck rail  10  and another position in which the stopper  14  goes into the truck rail  10  when the stopper  14  retreats from the one position. When the stopper  14  protrudes, the truck base comes in contact with the stopper  14  and stops, and when the stopper  14  goes into the truck rail  10 , the truck base may be changed in a state in which the truck base is capable of being moved. 
     [Sensor Module] 
     The sensor module according to the present disclosure includes a light receiver  93  formed on the second truck base  30  and a sensor assembly  70  for measurement of a position of the light receiver  93  based on a fixed position separately from the truck base. 
     When the sensor assembly  70  performs measurement based on a position outside the truck base and the truck rail, dependently from the truck base and the truck rail, accurate measurement result is achieved. For example, the sensor assembly  70  may be installed on a base such as a robot at a stop position of the corresponding truck base. 
     The sensor assembly  70  includes a base  71  at a fixed position. In addition, the sensor assembly  70  further includes a measuring sensor  76  that moves between a first position from the base  71  toward the second truck base  30  and a second position spaced apart from the second truck base  30 . The measuring sensor  76  measures a position of the light receiver  93  at the first position toward the second truck base  30 . 
     For example, the measuring sensor  76  measures a distance to the light receiver  93  on the second truck base  30  from the measuring sensor  76  and compares the measured distance with a reference distance to determine whether the second truck base  30  is positioned at a home position and how far and which direction the second truck base  30  is spaced apart from the home position when the second truck base  30  is not positioned at the home position. 
     Needless to say, this measurement is performed on the assumption that displacement of the light receiver  93  on a plurality of second truck bases  30  moving on the truck rail  10  and displacement of the fixed unit  91  for mounting the vehicle body B are identical to each other. 
     As illustrated in the drawings, the light receiver  93  is installed on a front surface of the second truck base  30 , and thus the measuring sensor  76  needs to measure the position of the light receiver  93  in front of the second truck base  30 . However, a measurement position of the measuring sensor  76  is put on a moving path of the truck bases  20  and  30 , and thus interference occurs. 
     Thus, the measuring sensor  76  needs to be deviated from the moving path of the truck bases  20  and  30  except when the measuring sensor  76  performs measurement. 
     Accordingly, according to the present disclosure, the measuring sensor  76  may be installed in a motor cylinder  72  fixed to the base  71  so as to be moved backward and forward according to an operation of the motor cylinder  72 . For example, the measuring sensor  76  is installed on a bracket  74  that moves backward and forward by the motor cylinder  72  so as to be moved backward and forward. 
     [Calibration Module] 
     The calibration module of the calibration truck according to the present disclosure calibrates a position of the second truck base  30  positioned on the first truck base  20  with respect to the first truck base  20  positioned on the truck rail  10 . 
     To this end, according to the present disclosure, first, a pinion  41  extending in parallel to a moving direction of the truck base is installed at a lateral surface of the first truck base  20 . As illustrated in  FIG. 3 , opposite ends of the pinion  41  are fixed to the lateral surface of the first truck base  20  through a bracket. 
     Then a rack  43  engaged with the pinion  41  is installed at a lateral surface of the second truck base  30 . The rack  43  may be installed directly on an axis of a motor  45 , and opposite ends of the axis of the motor  45  may be supported by the bracket installed at the lateral surface of the second truck base  30  and the second truck base  30 , as illustrated in  FIG. 5 . 
     Needless to say, the support structure of the motor axis is not limited to this structure. Alternatively, the pinion  41  and the rack  43  may be installed at opposite sides, respectively. 
     In conclusion, by virtue of this structure, the position of the second truck base  30  with respect to the first truck base  20  may be calibrated via rotation of the rack  43 . 
     As illustrated in  FIG. 3 , two linear guides  47  are installed in parallel to each other on the first truck base  20  at opposite lateral surfaces in a longitudinal direction, and the second truck base  30  are placed on the linear guides  47 . 
     The second truck base  30  is capable of being moved backward and forward along the linear guides  47  installed on the first truck base  20 . 
     [Method of Calibrating Position of Truck Base] 
     The above configured calibration truck according to the present disclosure performs calibration using the following method. 
     First, the truck bases  20  and  30  are moved to a position in which the truck bases  20  and  30  come in contact with the stopper  14  protruding on the truck rail  10  and stop. 
     Then when the measuring sensor  76  is moved to a first position close to the second truck base  30  from a second position close to the base  71 , the measuring sensor  76  detects the position of the light receiver  93  of the second truck base  30  while being positioned at the first position, and then the measuring sensor  76  measures stop position dispersion of the truck bases  20  and  30  by moving the measuring sensor  76  back to the second position as an original position after the detection of the position of the light receiver  93  is completed. 
     The measured data is compared with a home position as a reference to calculate dispersion. The calculated data corresponds to displacement of a measured position with respect to the home position. Whether calibration is performed by the calibration module, a calibration direction and a calibration amount are determined and calculated based on the calculated data. 
     A calculated and determined calibration direction are converted into a rotation direction of the motor  45  for rotation of the rack  43  and the calibration amount is converted into a rotation angle of the motor  45 . When the motor  45  is rotated based on an operation command, the position of the second truck base  30  is calibrated. 
     When the calibration is completed, the assembly precision of the vehicle body B mounted on the second truck base  30  is examined. When the examination is completed, the stopper  14  goes below a surface of the truck rail  10  and the truck bases  20  and  30  are moved to a next stop position. 
     According to the present disclosure, a truck may be calibrated to a home position before a vehicle body is examined so as to prevent stop position dispersion of the truck from being reflected to a measured value of an examination robot, thereby achieving reliable examination result. 
     In addition, the detailed advantages of the present disclosure have been described above. 
     While the present disclosure has been particularly shown and described with reference to exemplary embodiments and drawings thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit of the present disclosure as defined by the following claims.