Abstract:
According to an embodiment, a cartridge sensor shaft is allowed to butt against the vicinity of a positioning hole and is shifted toward the positioning hole. A coordinate offset error is then calculated based on a difference between the moving distance from the portion against which the cartridge sensor shaft butts to the portion at which the cartridge sensor shaft enters the positioning hole and the expected moving distance. The coordinate offset is adjusted by the calculated error. Further, in order to reduce measurement error, the cartridge sensor shaft is allowed to butt from both side of the positioning hole and shifted to detect the edges of the positioning hole, thereby calculating the coordinate offset error based on the two moving distances and two expected moving distances.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention:  
         [0002]     The present invention relates to a coordinate offset adjustment system and a coordinate offset adjustment method that adjust a coordinate offset, and more particularly to, a coordinate offset system and method that adjust an offset of the stop position of a picker mechanism in a collective magnetic tape drive.  
         [0003]     2. Description of the Related Art:  
         [0004]     Programs and data used in a computer are, in general, stored in a hard disk drive and transferred, as needed, from the hard disk drive to a main memory at execution time of the program. The hard disk drive is constantly at the risk of being damaged, and a given limitation is imposed on the capacity thereof. Therefore, a backup apparatus that can store a large volume of programs and data with high reliability is required, even if the backup device operates at a low speed. As the backup apparatus, a magneto-optical disk drive, a DVD drive, a tape drive, and the like are available. Among them, a magnetic tape drive is excellent in terms of reliability, storage capacity, and cost-performance, and a collective magnetic tape drive is used in order to back up a tremendous volume of data.  
         [0005]     A magazine is mounted on the collective magnetic tape drive. The magazine is proved with a plurality of cells arranged in a matrix form. Each cell houses a magnetic tape cartridge (hereinafter, referred to merely as “cartridge”). An accessor mechanism including a picker mechanism takes out a cartridge required in each occation from a cell that houses the cartridge and feeds the taken out cartridge to a tape drive. After completion of recording or reproduction operation in the tape drive, the accessor mechanism feeds the cartridge from the tape drive to the cell and inserts the cartridge into the cell.  
         [0006]     It is necessary that the picker mechanism that includes the cartridge is correctly stopped at the front of the target cell in order to complete the taking-out/insertion operation of the cartridge from/into the target cell normally. Therefore, a servo section that controls the stop position of the picker mechanism must grasp a cell coordinate and determine an offset of the stop position of the picker mechanism based on the cell coordinate.  
         [0007]      FIG. 1  is a perspective view showing a conventional detection system of a cell coordinate. Reference numeral  901  denotes a picker mechanism attached to an accessor mechanism that feeds a cartridge between a cell and a tape drive. Reference numeral  902  denotes an entrance of the magazine, which has a plurality of cell slots. The picker mechanism  901  includes a light emitting element  903  and a light receiving element  904 . The entrance  902  includes a Y-direction position detection hole  905  for each cell. The light emitted from the light emitting element  903  is received by the light receiving element  904  unless there is an obstacle in its path. In order to detect a Y-coordinate of each cell, the following operation is performed for each cell. The operation includes: shifting the picker mechanism  901  from bottom to top (in the direction in which Y-coordinate increases) in the vicinity of the Y-direction position detection hole  905 ; detecting the Y-coordinate of the picker mechanism  901  at the time when the light once intercepted in the peripheral portion of the Y-direction position detection hole  905  again enters the light receiving element  904  to allow the intensity of the light to be received by the light receiving element  904  to reach a predetermined threshold value; then shifting the picker mechanism  901  from top to bottom (in the direction in which Y-coordinate decreases) in the vicinity of the Y-direction position detection hole  905 ; detecting the Y-coordinate of the picker mechanism  901  at the time when the light once intercepted in the peripheral portion of the Y-direction position detection hole  905  again enters the light receiving element  904  to allow the intensity of the light to be received by the light receiving element  904  to reach a predetermined threshold value; and setting an average value of the detected two Y-coordinates as the Y-coordinate of the cell.  
         [0008]     However, there is the following problem with the above system.  
         [0009]     A long distance between the light emitting element  903  and light receiving element  904  makes it difficult to align the optical axes of the both elements such that the light emitted from the light emitting element  903  reaches the light receiving element  904 .  
         [0010]     Further, a cartridge  106  as shown in  FIG. 2  is to be inserted into a cell. In most cases, a white label  912  for bar code printing and the like is affixed to the cartridge  106 . Therefore, there is a possibility that a part of the light emitted from the light emitting element  903  illuminates the label  912 , and the light reflected by the label  912  enters the light receiving element  904 . As a result, the light receiving element  904  makes an error detection of the light in some cases. Further, error detections have occurred due to diffused reflection or ambient light.  
       SUMMARY OF THE INVENTION  
       [0011]     An object of the present invention is therefore to provide a coordinate offset adjustment system and a coordinate offset adjustment method capable of adjusting a coordinate offset without an occurrence of the error due to diffused reflection or ambient light.  
         [0012]     According to an aspect of the present invention, there is provided a coordinate offset adjustment system including: a reference point detection probe placement means for placing a reference point detection probe in a vicinity of a reference point; reference point detection probe shift means for shifting the reference point detection probe toward the reference point; a reference point detection means for, using the reference point detection probe, detecting the reference point while said reference point detection probe shift means shifts the reference point detection probe; and an offset adjustment means for adjusting a coordinate offset based on a moving distance between a position of the reference point detection probe at which said reference point detection probe placement means places the reference point detection probe and a position of the reference point detection probe at which said reference point detection means detects the reference point.  
         [0013]     In the above coordinate offset adjustment system, the position at which said reference point detection probe placement means places the reference point detection probe may be a position apart from an expectation reference point by a predetermined distance, the expectation reference point being a point that the reference point is supposed to be positioned, which is obtained based on the current offset, and said offset adjustment means may add a difference between the moving distance and a predetermined distance to the current offset to obtain a new offset.  
         [0014]     In the above coordinate offset adjustment system, said reference point detection probe placement means, said reference point detection probe shift means, and said reference point detection means may perform the placement, the shift, the detection at least two times in different directions, respectively, to obtain two or more moving distances, and said offset adjustment means may adjust the coordinate offset based on the two or more moving distances.  
         [0015]     In the above coordinate offset adjustment system, the reference point detection probe may be a mechanical probe, and the reference point may belong to a boundary having a mechanical step and may be detected based on a displacement of the mechanical probe in the boundary.  
         [0016]     In the above coordinate offset adjustment system, the mechanical probe may be a shaft.  
         [0017]     In the above coordinate offset adjustment system, the shaft may further have a function of detecting a cartridge that has been inserted into a cell.  
         [0018]     In the above coordinate offset adjustment system, the reference point detection probe may be an optical probe, the reference point may belong to a boundary having an optical difference, and the reference point detection probe may be an optical probe detecting the optical difference in the boundary to detect the reference point.  
         [0019]     According to the present invention, detecting the reference point using the reference point detection probe enables the coordinate offset to be adjusted based on the moving distance.  
         [0020]     According to the present invention, measurement error can be reduced.  
         [0021]     According to the present invention, errors due to diffused reflection or ambient light do not occur.  
         [0022]     According to the present invention, the need of dedicated probe for coordinate offset adjustment is eliminated, thereby to reduce cost, space, and the like.  
         [0023]     According to the present invention, a configuration that is not influenced by diffused reflection nor ambient light can be obtained. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a perspective view showing a mechanism including a cell coordinate detection system according to a conventional art;  
         [0025]      FIG. 2  is a perspective view showing a tape cartridge;  
         [0026]      FIG. 3  is a perspective view showing a collective tape drive according to an embodiment of the present invention;  
         [0027]      FIG. 4  is a perspective view showing a magazine according to the embodiment of the present invention;  
         [0028]      FIG. 5  is a perspective view showing a picker mechanism according to the embodiment of the present invention;  
         [0029]      FIG. 6  is a perspective view showing a vertical positioning hole included in the magazine and the peripheral portion thereof according to the embodiment of the present invention;  
         [0030]      FIG. 7  is a block diagram showing an electrical system for performing a coordinate offset adjustment method according to the embodiment of the present invention;  
         [0031]      FIG. 8  is a first flowchart for explaining the coordinate offset adjustment method according to the embodiment of the present invention;  
         [0032]      FIG. 9  is a second flowchart for explaining the coordinate offset adjustment method according to the embodiment of the present invention;  
         [0033]      FIG. 10  is a third flowchart for explaining the coordinate offset adjustment method according to the embodiment of the present invention;  
         [0034]      FIG. 11  is a fourth flowchart for explaining the coordinate offset adjustment method according to the embodiment of the present invention;  
         [0035]      FIG. 12  is a perspective view showing a state where a cartridge sensor shaft according to the embodiment of the present invention butts against a contact portion; and  
         [0036]      FIG. 13  is a view for explaining a calculation formula for calculating an offset value to be used in the coordinate offset adjustment method according to the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]     A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.  
         [0038]      FIG. 3  is a perspective view showing a collective magnetic tape drive according to an embodiment of the present invention. The collective magnetic tape-drive includes a tape drive  101 , two magazines  102  and an accessor mechanism  103 . Each of the magazines  102  includes a plurality of cells  105  arranged two dimensionally in X and Y directions. A cartridge  106  is housed in each of the cell  105 . The accessor mechanism  103  includes a picker mechanism  104 . The main body of the accessor mechanism  103  is movable in X-direction. The picker mechanism  104  is movable in Y-direction and can be rotated about Y-axis.  
         [0039]     In order to complete loading of the cartridge  106  that has been inserted into a certain cell into the tape drive  101 , the following operation is performed. That is, the position of the accessor mechanism  103  in X-direction is firstly shifted to the stop position corresponding to the position of the target cell in X-direction, the position of the picker mechanism  104  in Y-direction is then shifted to the stop position corresponding to the position of the target cell in Y-direction, the picker mechanism  104  is rotated to face the magazine  102  including the target cell, whereby the picker mechanism  104  faces the front of the target cell. After that, as described later, the cartridge  106  is taken out of the target cell and loaded into the picker mechanism  104 . Then the accessor mechanism  103  is shifted in X-direction, and the picker mechanism  104  is shifted in Y-direction and rotated to face the tape drive  101 . The cartridge  106  is then unloaded from the picker mechanism  104  and loaded into the tape drive  101 .  
         [0040]     When the cartridge  106  that has been loaded into the tape drive  101  is set back to the cell, the operation opposite to the above is performed.  
         [0041]     Referring to  FIG. 4 , the magazine  102  is divided into a first magazine  102 - 1  and second magazine  102 - 2 . The first magazine  102 - 1  includes a cell- 1  to cell- 12 . The second magazine  102 - 2  includes a cell- 13  to cell- 20 . Further, the first magazine  102 - 1  includes vertical (Y-direction) positioning holes  111 - 1  and  111 - 2 , and second magazine  102 - 2  includes vertical positioning holes  111 - 3  and  111 - 4 .  
         [0042]     Referring to  FIG. 5 , the picker mechanism  104  includes a cartridge sensor shaft  112  and a cartridge detection sensor  113 . The cartridge sensor shaft  112  and cartridge detection sensor  113  are mounted on a slide mechanism and can be shifted forward and backward in Z-axis direction in an integrated manner. Further, the cartridge sensor shaft  112  is extensible in Z-axis direction relative to the slide mechanism and is pushed or pulled in the extension direction by an elastic member such as a coil spring and the like. The cartridge detection sensor  113  detects whether the cartridge sensor shaft  112  is extending or retracting with respect to the slide mechanism.  
         [0043]     Therefore, whether the cartridge  106  has been inserted into a certain cell  105  or not is detected as follows: the picker mechanism  104  is shifted to the front of the target cell  105 ; the slide mechanism is forwarded in Z-axis direction; and the cartridge detection sensor  113  detects at this time whether the cartridge sensor shaft  112  butts against the cartridge  106  and retracts.  
         [0044]     In the present embodiment, the cartridge sensor shaft  112 , cartridge detection sensor  113 , and slide mechanism are used also for Y-coordinate offset adjustment, eliminating the need of dedicated parts for Y-coordinate offset adjustment to reduce cost.  
         [0045]      FIG. 6  is an enlarged view of the vertical positioning hole  111  and the peripheral portion thereof. The upper and lower parts of the vertical positioning hole  111  serve as an upper side contact portion  115  and lower side contact portion  116 , respectively. The line segment denoted by reference numeral  117  is the boundary between the vertical positioning hole  111  and upper side contact portion  115 , and the line segment denoted by reference numeral  118  is the boundary between the vertical positioning hole  111  and lower side contact portion  116 . An upper side reference point to be described later belongs to the boundary  117 , and a lower side reference point belongs to the boundary  118 .  
         [0046]     Next, a coordinate offset adjustment method according to the present embodiment will be described. As shown in  FIG. 7 , the coordinate offset adjustment method is performed using a ROM  301 , a CPU  302 , a rewritable nonvolatile memory  303 , an input/output interface (I/O)  304 , a servo section  305 , a cartridge detection sensor  113  and the like. The CPU  302  reads in and executes a program stored in the ROM  301  to perform each process of the coordinate offset adjustment method. The rewritable nonvolatile memory  303  stores stop positions in X- and Y-directions corresponding to each cell, and a stop position in X-direction, a center position in Y-direction, and a moving distance of the slide mechanism corresponding to each vertical positioning hole  111 . In the case of accessing a cell, the servo section  305  shifts the accessor mechanism  103  to the stop position in X-direction corresponding to a target cell and the peripheral portion thereof and shifts the picker mechanism  104  to the stop position in Y-direction corresponding to the target cell and the peripheral portion thereof In the case of adjusting a position offset, the servo section  305  shifts the accessor mechanism  103  to the stop position in X-direction corresponding to a target vertical positioning hole  111  and controls the picker mechanism  104  in the vicinity of the center position in Y-direction corresponding to the target vertical positioning hole  111 . The I/O  304  interfaces between the CPU  302  and servo section  305  and between the CPU  302  and cartridge detection sensor  113 .  
         [0047]     An offset is included in the center position in Y-direction corresponding to each vertical positioning hole  111 , and the offset is compensated by the coordinate offset adjustment method. An offset is also included in the stop position in Y-direction corresponding to each cell. The vertical positioning hole  111 - 1  has a first offset common among the cell- 1  to cell- 6  located in the vicinity thereof, the vertical positioning hole  111 - 2  has a second offset common among the cell- 7  to cell- 12  located in the vicinity thereof, the vertical positioning hole  111 - 3  has the second offset common among the cell- 13  to cell- 16  located in the vicinity thereof, and the vertical positioning hole  111 - 4  has the second offset common among the cell- 17  to cell- 20  located in the vicinity thereof.  
         [0048]     Referring to  FIG. 8 , firstly, the stop position X in X-direction and center position Y in Y-direction corresponding to a target vertical positioning hole  111  are read out from the rewritable nonvolatile memory  303  (step S  201 ). Next, the accessor mechanism  103  is shifted to the stop position X in X-direction read out in step S 201  (step S 202 ). Then, the picker mechanism  104  is shifted to the position obtained by adding a value A 1  to the center position Y in Y-direction read out in step  201  (step S 203 ). The value A 1  has been determined such that the cartridge sensor shaft  112  butts against the contact portion  115  without fail when the slide mechanism is forwarded under the condition that the difference between the offset currently retained and actual offset is not more than the allowable value. Next, the slide mechanism is forwarded to allow the cartridge sensor shaft  112  to butt against the contact portion  115  (step S 204 ). The positional relationship between the cartridge sensor shaft  112  and vertical positioning hole  111  at this stage is shown in  FIG. 12 . Next, a counter is initialized to 0 (step S 205 ). The picker mechanism  104  is then set back in Y-axis direction by one pulse (step S 206 ). The term “pulse” mentioned here is a pulse used in position servo and the like of the picker mechanism.  104  and is generated by a rotary encoder and the like. Next, the counter is incremented by 1 (step S 207 ). It is then determined whether the cartridge sensor shaft  112  still in contact with the contact potion  115  based on a detection signal from the cartridge detection sensor  113  (step S 208 ). When it has been determined that the cartridge sensor shaft  112  has been still in contact with the contact portion  115  (Yes in step S 208 ), the flow returns to step S 206 .  
         [0049]     Referring to  FIG. 9 , when the cartridge sensor shaft  112  is shifted away from the contact portion  115  and enters the vertical positioning hole  111  (No in step S 208 ), the counter value is assigned to a variable y 1 ′ (step S 209 ). Then the slider mechanism is set back to the initial position so that the cartridge sensor shaft  112  does not butt against the contact portions  115  and  116  even when the picker mechanism  104  is shifted (step S 210 ).  
         [0050]     Next, the picker mechanism  104  is shifted to the position obtained by subtracting a value A 2  from the center position Y in Y-direction read out in step S 201  (step S 211 ). The value A 2  has been determined such that the cartridge sensor shaft  112  butts against the contact portion  116  without fail when the slide mechanism is forwarded under the condition that the difference between the offset currently retained and actual offset is not more than the allowable value. Next, the slide mechanism is forwarded to allow the cartridge sensor shaft  112  to butt against the contact portion  115  (step S 212 ). The counter is then initialized to 0 (step S 213 ). The picker mechanism  104  is forwarded in Y-axis direction by one pulse (step S 214 ). The counter is then incremented by 1 (step S 215 ). It is then determined whether the cartridge sensor shaft  112  still in contact with the contact potion  116  based on a detection signal from the cartridge detection sensor  113  (step S 216 ). When it has been determined that the cartridge sensor shaft  112  has been still in contact with the contact portion  116  (Yes in step S 216 ), the flow returns to step S 214 .  
         [0051]     Referring to  FIG. 10 , when the cartridge sensor shaft  112  is shifted away from the contact portion  116  and enters the vertical positioning hole  111  (No in step S 216 ), the counter value is assigned to a variable y 2 ′ (step S 217 ). Then the slider mechanism is set back (step S 218 ) so that the cartridge sensor shaft  112  does not butt against the contact portions  115  and  116  even when the accessor mechanism  103  and picker mechanism  104  are shifted. Then the accessor mechanism  103  and picker mechanism  104  are set back to the initial positions (steps S 219 , S 220 ).  
         [0052]     An offset error AY is calculated by the following equation (step S 221 ).  
               Δ   ⁢           ⁢   Y     =         (       y   2   ′     -     y   2       )     -     (       y   1   ′     -     y   1       )       2             (   1   )             
 
         [0053]     An offset is then read out from the rewritable nonvolatile memory  303  (step S 222 ) and updated by adding the offset error ΔY that has been calculated in step S 221  to the offset that has been read out in step S 222  (step S 223 ). The offset that has been updated in step S 223  is then written into the rewritable nonvolatile memory  303  (step S 224 ).  
         [0054]     Next, a center position Yo in Y-direction before compensation is read out from the rewritable nonvolatile memory  303  (step S 225 ), and a new center position Y in Y-direction is then obtained by adding the offset that has been updated in step S 223  to the center position Yo in Y-direction before compensation that has been read out in step S 225  (step S 226 ). The center position Y in Y-direction that has been obtained in step S 226  is then written into the rewritable nonvolatile memory  303  (step S 227 ).  
         [0055]     In place of steps S 225  to  227 , the following operation may be performed. That is, the current center position Y in Y-direction is read out from the rewritable nonvolatile memory  303 , the offset error ΔY that has been calculated in step S 221  is added to the read out center position Y in Y-direction to update the center position Y in Y-direction, and the updated center position Y in Y-direction is written into the rewritable nonvolatile memory  303 . By this, it is possible to cope with the case where the center position Y in Y-direction has been changed by factors other than the offset that has been updated in step S 223 .  
         [0056]     Referring to  FIG. 11 , steps S 229  to S 231  are repeated for each cell having common offset value with respect to the vertical positioning hole  111  (step S 228 ).  
         [0057]     In step S 229 , a Y-direction stop position before compensation Yo, CELL  (i, j) related to the target cell is read out from the rewritable nonvolatile memory  303 . Next, a new Y-direction stop position Y CELL  (i, j) is obtained by adding the offset that has been updated in step S 223  to the Y-direction stop position before compensation Yo, CELL  (i, j) that has been read out in step S 229  (step S 230 ). The Y-direction stop position Y CELL  (i, j) that has been obtained in step S 230  is written into the rewritable nonvolatile memory  303 .  
         [0058]     In place of steps S 229  to S 231 , the following operation may be performed. That is, the current Y-direction stop position Y CELL  (i, j) is read out from the rewritable nonvolatile memory  303 , the offset error that has been calculated in step S 221  is added to the read out Y-direction stop position Y CELL  (i, j) to update the Y-direction stop position Y CELL  (i, j), and the updated Y-direction stop position Y CELL  (i,j) is written into the rewritable nonvolatile memory  303 . By this, it is possible to cope with the case where the Y-direction stop position Y CELL  (i, j) has been changed by factors other than the offset that has been updated in step S 223 .  
         [0059]     A description will next be given of the equation (1).  
         [0060]     Referring to  FIG. 13 , a Y-direction center position Y is set in the vicinity of the center of the vertical positioning hole  111 . The length from the boundary  117  to the Y-direction center position Y is assumed to be B 1 , and the length from the boundary  118  to the Y-direction center position Y is assumed to be B 2 . Further, lengths A 1  and A 2  are set as described above. With this condition, it cab be seen from  FIG. 13  that the distance y 1  that is obtained by repeating steps S 206  to S 208  unless there is offset error becomes 
 
 y   1   =A   1   −B   1  
 
 and the distance y 2  that is obtained by repeating steps S 214  to S 216  unless there is offset error becomes 
 
 y   2   =A   2   −B   2 . 
 
         [0061]     On the other hand, it can be seen from  FIG. 13  that the distance y 1 ′ that is obtained by repeating steps S 206  to S 208  when there is the offset error ΔY becomes 
 
 y   1′   =y   1   −ΔY,  
 
 and the distance Y 2 ′ that is obtained by repeating steps S 214  to S 216  when there is the offset error ΔY becomes 
 
 y   2′   =y   2   −ΔY  
 
         [0062]     Therefore, as to the offset ΔY, 
 
Δ Y=y   1   −y   1′  . . .   (2) or 
 
Δ Y=−t   2   +y   2′  . . .   (3) 
 
 is satisfied. Since y 1  and y 2  has been known, the offset error ΔY can be obtained by assigning y 1  and y 2  and measured y 1  and y 2  to the above equations. Although the offset error ΔY can be obtained using only one of the above two equations, the average of the results from the two equations can reduce further measurement error. It is the equation (1) that takes the average. Therefore, if there is an advantage greater than the advantage that reduces the measurement error, the offset error may be obtained by using only the equation (2) or the equation (3). 
 
         [0063]     In the above description, the cartridge sensor shaft is used. Alternatively, however, a plate or block may be used. Further, as long as the problem of the conventional art can be solved, optical distance measuring equipment (for example, equipment using a laser light) may be used in place of the cartridge sensor shaft. Further, two objects having different optical characteristics (for example, reflectance, and deflection characteristics) may be used in place of the vertical positioning hole  111  and contact portion and a difference between the two may be detected by an optical detection apparatus (for example, an apparatus having an integrated pair of light emitting section and light receiving section, or the apparatus obtained by adding a deflection glass). In the present invention, an object having a function of detecting a reference point belonging to the boundary  117  and  118 , such as the cartridge sensor shaft, plate, block, optical detection apparatus, and the like is defined as a reference point detection probe. Further, the distance measurement by a laser may be adopted.