Abstract:
An assembly jig includes a jig frame, workpiece supports provided in the jig frame for supporting a workpiece, and actuators for moving the workpiece supports relative to the jig frame. Based on the results obtained by measuring the positions of reference points of the jig frame and the positions of the workpiece supports by means of a position measurement device, positional coordinates of the workpiece supports relative to a coordinate system fixed to the jig frame are calculated, and the actuators are operated so as to make the deviation of the calculated positional coordinates from the preset positional coordinates a predetermined value or less, thereby automatically correcting the misalignment of the workpiece supports relative to the jig frame. Thus, it is possible to easily and accurately correct the deteriorated precision of an assembly jig caused by the influence of aging and thermal expansion.

Description:
BACKGROUND OF THE INVENTION 
     The present application claims priority under 35 U.S.C. 119 of Japanese Patent Application No. 2002-9443 filed on Jan. 18, 2002, the entire contents thereof being hereby incorporated by reference. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     1. Field of the Invention 
     The present invention relates to a method for adjusting an assembly jig that includes a jig frame, a workpiece support provided in the jig frame for supporting a workpiece, and an actuator for moving the workpiece support relative to the jig frame. 
     2. Description of Background Art 
     In order to indicate the positions of rivet holes, bend lines, trim lines, etc. on a workpiece such as a skin panel of an aircraft, it is necessary for the workpiece to be positioned accurately and mounted rigidly on an assembly jig. The assembly jig is designed so that the workpiece is supported by a plurality of workpiece supports provided in a jig frame, but since the workpiece supports have a rigidity lower than the jig frame having a high rigidity, the positional relationship of the workpiece supports relative to the jig frame is slightly misaligned due to the influence of aging and changes in temperature. As a result, the positional relationship of the workpiece relative to the jig frame is also slightly misaligned. 
     The thus-caused misalignment is conventionally corrected by periodically measuring the positional relationship of the workpiece supports relative to the jig frame and placing a shim or a spacer on a part where the workpiece supports are fixed to the jig frame. 
     SUMMARY AND OBJECT OF THE INVENTION 
     When the positions of the workpiece supports relative to the jig frame are adjusted using a shim or a spacer, the operation is complicated, and not only does it require much time and labor, but there is also a limit to the precision of the adjustment, which is a problem. 
     The present invention has been carried out in view of such circumstances, and it is an object thereof to easily and accurately correct the deteriorated precision of an assembly jig caused by the influence of aging and thermal expansion. 
     In order to achieve the object of the invention, in accordance with the present invention, there is proposed a method for adjusting an assembly jig comprising a jig frame, a workpiece support provided in the jig frame for supporting a workpiece, and an actuator for moving the workpiece support relative to the jig frame, the method comprising: operating a position measurement device to determine the coordinates of fixed reference points of the jig frame; establishing preset coordinates of a measurement reference point of the workpiece support relative to the fixed reference points; operating the position measurement device to determine the measured coordinates of the measurement reference point relative to the fixed reference points; determining the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point; and operating the actuator, as needed, to adjust the position of the workpiece support so that the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point is no greater than a predetermined value. 
     With this method, the positional coordinates of the measurement reference point of the workpiece support relative to the coordinate system fixed to the jig frame are preset; the positions of the coordinate reference points of the jig frame and the position of the measurement reference point of the workpiece support are then measured by means of the position measurement device; the positional coordinates of the measurement reference point of the workpiece support relative to the coordinate system fixed to the jig frame are then calculated based on the measurement results obtained by the position measurement device; the deviation of the calculated positional coordinates from the preset positional coordinates of the workpiece support is calculated; and the actuator is operated so as to make the deviation the predetermined value or less. Therefore, even when the position of the workpiece support relative to the jig frame is misaligned due to aging or changes in temperature, the misalignment can be automatically corrected so as to make the positional coordinates of the measurement reference point of the workpiece support closer to the preset positional coordinates. As a result, it is unnecessary to carry out a complicated adjustment operation using a shim or a spacer each time the misalignment of the workpiece support occurs, and moreover the accuracy of the adjustment can be greatly enhanced in comparison with a manual operation. 
     The object of the invention is also realized by a method for adjusting an assembly jig comprising a jig frame, a plurality of workpiece supports provided in the jig frame for supporting a workpiece, and a separate actuator for moving each workpiece support relative to the jig frame, the method comprising: operating a position measurement device to determine the coordinates of fixed reference points of the jig frame; establishing preset coordinates of a measurement reference point of each workpiece support relative to the fixed reference points; operating the position measurement device to determine the measured coordinates of each measurement reference point relative to the fixed reference points; determining the deviation of the measured coordinates of each measurement reference point from the preset coordinates of the measurement reference point; and operating the actuator, as needed, to adjust the position of each workpiece support so that the deviation of the measured coordinates of each measurement reference point from the preset coordinates of the measurement reference point is no greater than a predetermined value. 
     The object of the invention is also realized by a system for positioning a workpiece, the system comprising: a jig frame; a workpiece support provided in the jig frame for supporting a workpiece; an actuator for moving the workpiece support relative to the jig frame; a position measurement device for determining (1) the coordinates of fixed reference points of the jig frame and (2) the measured coordinates of a measurement reference point of the workpiece support relative to the fixed reference points; means for establishing preset coordinates of the measurement reference point relative to the fixed reference points; means for determining the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point; and means for operating the actuator, as needed, to adjust the position of the workpiece support so that the deviation of the measured coordinates of the measurement reference point from the preset coordinates of the measurement reference point is no greater than a predetermined value. 
     In an embodiment of the invention, tooling balls are used to mark the coordinate reference points of the jig frame, and a tooling ball is used to mark the measurement reference point of the workpiece support. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a view of the entirety of an assembly jig and an adjustment system for the assembling jig; 
     FIG. 2 is a magnified view of a workpiece support as viewed in section 2 of FIG. 1; 
     FIG. 3 is a flowchart for disclosing the action of an initial adjustment of the assembly jig; and 
     FIG. 4 is a flowchart for disclosing the action of a regular adjustment of the assembly jig. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIGS. 1 and 2, an assembly jig J of this embodiment includes left and right support legs  10 , a rectangular jig frame  11  disposed rigidly between the support legs  10 , three workpiece supports  12   a  to  12   c  extending upward from a lower beam  11   a  of the jig frame  11 , and three workpiece supports  12   d  to  12   f  extending downward from an upper beam  11   b  of the jig frame  11 . Each of the workpiece supports  12   a  to  12   f  has a clamp  14  provided on the extremity thereof. The clamps  14  support a workpiece W, which is, for example, a skin panel of an aircraft. The base of each of the workpiece supports  12   a  to  12   f  is supported on the lower beam  11   a  or the upper beam  11   b  via an actuator  15 . The actuators  15  are electrically operated and can finely adjust the positions of the workpiece supports  12   a  to  12   f  relative to the lower or upper beam  11   a  or  11   b  in three directions that are orthogonal to each other. 
     Provided in the lower left, upper left, and lower right corners of the jig frame  11  of the assembly jig J are tooling balls  16 ,  17 ,  18 , each of which is used as a coordinate reference point. When adjusting the assembly jig J, a tooling ball  19  is mounted on the clamp  14  of each of the workpiece supports  12   a  to  12   f , the tooling ball  19  being used as a measurement reference point. 
     The adjustment system for the assembly jig J includes a position measurement device  21 , which is a laser device, and a personal computer  22  for controlling the operation of the actuators  15 , the personal computer  22  being connected to a 3-D CAD machine  23 . The 3-D CAD machine  23  stores the positional coordinates (X, Y, Z) of the tooling balls  19  at the extremities of the six workpiece supports  12   a  to  12   f  with regard to the three-dimensional orthogonal coordinate system fixed to the assembly jig J, that is, the three-dimensional orthogonal coordinate system where the lower left tooling ball  16  is its point of origin, its X axis extends in the direction toward the upper left tooling ball  17 , its Y axis extends in the direction toward the lower right tooling ball  18 , and its Z axis is orthogonal to both the X axis and the Y axis. These positional coordinates (X, Y, Z) can be calculated from the known shape of the workpiece W and the known relationship of the positions where the workpiece W is fixed to the jig frame  11  of the assembly jig J. 
     A procedure for carrying out an initial adjustment, when the assembly jig J is initially set up, is now explained by reference to the flowchart in FIG.  3 . 
     First, the positional coordinates (X, Y, Z) of the six tooling balls  19  relative to the three-dimensional orthogonal coordinate system fixed to the assembly jig J are set by the 3-D CAD machine  23  (step S 1 ), and data of these positional coordinates (X, Y, Z) are then converted into IGES (Initial Graphics Exchange Specification) format (step S 2 ). The IGES conversion involves data conversion between the positional coordinate data of the 3-D CAD machine  23  and the personal computer  22 . The assembly jig J is then provisionally assembled (step S 3 ). In this provisionally assembled state, since adjustment of the assembly jig J is not yet completed, the positions of the six tooling balls  19  relative to the three-dimensional orthogonal coordinate system fixed to the assembly jig J contain errors. 
     Subsequently, the data converted to IGES format obtained above (data relating to the positional coordinates (X, Y, Z) of the six tooling balls  19 ) are input into the personal computer  22  from the 3-D CAD machine  23  (step S 4 ), and the position measurement device  21  which is a laser device, then measures the positions of the three tooling balls  16 ,  17 ,  18  of the jig frame  11  and the positions of the six tooling balls  19  provided on the six workpiece supports  12   a  to  12   f  (step S 5 ). 
     The personal computer  22  next calculates the positional coordinates (X′, Y′, Z′) of the six tooling balls  19  relative to the three-dimensional orthogonal coordinate system using the positions of the three tooling balls  16 ,  17 ,  18  and the positions of the six tooling balls  19  (step S 6 ), and then calculates the deviations (X′-X, Y′-Y, Z′-Z) of the measured positional coordinates (X′, Y′, Z′) of the six tooling balls  19  from the preset positional coordinates (X, Y, Z) of the six tooling balls  19  (step S 7 ). Following this, the positions of the workpiece supports  12   a  to  12   f  (that is, the positions of the tooling balls  19 ) are adjusted so that the X-axis deviation X′-X, the Y-axis deviation Y′-Y, and the Z-axis deviation Z′-Z are all within predetermined values. In general, the initial adjustment requires a large amount of adjustment and therefore employs a shim or a spacer, but when the amount of adjustment is small, it can be carried out by operating the actuators  15 . 
     After the initial adjustment of the assembly jig J is completed as described above, regular adjustment of the assembly jig J is carried out by the procedure shown in FIG.  4 . 
     After a predetermined time for carrying out a periodic adjustment of the assembly jig J has passed (step S 11 ), the procedures of steps S 5  to S 7  in the flowchart shown in FIG. 3 are carried out. That is, the position measurement device  21  measures the positions of the three tooling balls  16 ,  17 ,  18  of the jig frame  11  and the positions of the six tooling balls  19  provided on the six workpiece supports  12   a  to  12   f  (step S 12 ); the positional coordinates (X′, Y′, Z′) of the six tooling balls  19  relative to the three-dimensional orthogonal coordinate system are calculated using the positions of the three tooling balls  16 ,  17 ,  18  and the positions of the six tooling balls  19  (step S 13 ); and the deviations (X′-X, Y′-Y, Z′-Z) of the measured positional coordinates (X′, Y′, Z′) of the six tooling balls  19  from the preset positional coordinates (X, Y, Z) of the six tooling balls  19  are calculated (step S 14 ). The positions of the workpiece supports  12   a  to  12   f  (that is, the positions of the tooling balls  19 ) are then adjusted by operating the actuators  15  so that the X-axis deviation X′-X, the Y-axis deviation Y′-Y, and the Z-axis deviation Z′-Z are all within the predetermined values (step S 15 ). 
     As described above, based on the results obtained by the position measurement device  21  for the positions of the three tooling balls  16 ,  17 ,  18  of the jig frame  11  and the positions of the six tooling balls  19  of the workpiece supports  12   a  to  12   f , the positional coordinates of the tooling balls  19  of the workpiece supports  12   a  to  12   f  relative to the three-dimensional orthogonal coordinate system fixed to the jig frame  11  are calculated, the actuators  15  are operated so that the deviations of the calculated positional coordinates (X′, Y′, Z′) of the six tooling balls  19  of the workpiece supports  12   a  to  12   f  from the preset positional coordinates (X, Y, Z) of the six tooling balls  19  are within the predetermined values, whereby the misalignment of the workpiece supports  12   a  to  12   f  relative to the jig frame  11  can be automatically corrected. 
     Furthermore, since manual adjustment is carried out only once in the initial adjustment of the assembly jig J, and the subsequent regular adjustment is automatically carried out, not only is it unnecessary to carry out a complicated adjustment operation using a shim or a spacer each time misalignment occurs in the workpiece supports  12   a  to  12   f , but also the precision of the adjustment can be greatly enhanced. 
     As described above, in accordance with the first aspect of the present invention, the positional coordinates of the measurement reference point of the workpiece support relative to the coordinate system fixed to the jig frame are preset; the positions of the coordinate reference points of the jig frame and the position of the measurement reference point of the workpiece support are then measured by means of the position measurement device; the positional coordinates of the measurement reference point of the workpiece support relative to the coordinate system fixed to the jig frame are then calculated based on the measurement results obtained by the position measurement device; the deviation of the calculated positional coordinates from the preset positional coordinates of the workpiece support is calculated; and the actuator is operated so as to make the deviation the predetermined value or less. Therefore, even when the position of the workpiece support relative to the jig frame is misaligned due to aging or changes in temperature, the misalignment can be automatically corrected so as to make the positional coordinates of the measurement reference point of the workpiece support closer to the preset positional coordinates. As a result, it is unnecessary to carry out a complicated adjustment operation using a shim or a spacer each time the misalignment of the workpiece support occurs, and moreover the accuracy of the adjustment can be greatly enhanced in comparison with a manual operation. 
     An embodiment of the present invention is explained in detail above, but the present invention can be modified in a variety of ways without departing from the spirit and scope of the present invention. 
     For example, the present invention is not limited to a skin panel of an aircraft and can be applied to any workpiece W, and the operation for the workpiece W mounted rigidly on the assembly jig J can be chosen freely. Furthermore, the position measurement device  21  is not limited to a laser device. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all modifications as would be obvious to one skilled in the art are intended to be include within the scope of the following claims.