Source: https://patents.justia.com/patent/7652841
Timestamp: 2019-10-22 16:07:29
Document Index: 550253688

Matched Legal Cases: ['art 12', 'art 14', 'art 12', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17', 'art 14', 'art 17', 'art 17', 'art 17', 'art 17', 'art 17']

US Patent for Servo controlling method, recording/reproducing apparatus, magnetic tape, and magnetic tape cartridge Patent (Patent # 7,652,841 issued January 26, 2010) - Justia Patents Search
Justia Patents Elongated Web Carrier (i.e., Tape)US Patent for Servo controlling method, recording/reproducing apparatus, magnetic tape, and magnetic tape cartridge Patent (Patent # 7,652,841)
Feb 5, 2008 - Hitachi Maxell, Ltd.
(b) of FIG. 1 is a schematic diagram illustrating a configuration of a track, which is an enlarged view of a portion encircled with a broken line in (a) of FIG. 1. A magnetic head 4 has a width dimension such that the magnetic head 4 is capable of scanning one data band 2 and two servo bands 3 simultaneously as shown in (b) of FIG. 1. The magnetic head 4 includes eight sets of first and second heads 4a and 4b, and two servo heads 4c capable of reproducing a servo signal recorded in the servo bands 3; each of the eight sets is composed of one first head 4a and one second head 4b that are capable of recording or reproducing digital data, and the eight sets are arranged in the width direction of the magnetic tape 1. When the magnetic tape 1 moves in a direction indicated by an arrow A shown in the drawing, the first head 4a functions as a data-recording head capable of recording digital data in the data band 2, while the second head 4b functions as a data-reproducing head capable of reproducing digital data recorded in the data band 2. When the magnetic tape 1 runs in a direction reverse to the arrow A direction in the drawing, the second head 4b functions as a data-recording head, and the first head 4a functions as a data-reproducing head. It should be noted that the numbers of the first head 4a, the second head 4b, and the servo head 4c are mere examples.
(c) of FIG. 1 is a schematic view illustrating a configuration of the servo band, which is an enlarged view of a portion encircled with a broken line in (b) of FIG. 1. By causing the magnetic head 4, in a current-carrying state, to scan the data band 2 shown in (a) of FIG. 1, digital data can be recorded in the data band 2 by the first head 4a (or the second head 4b) included in the magnetic head 4. Besides, digital data recorded in the data band 2 can be reproduced by the second head 4b (or the first head 4a) included in the magnetic head 4. Further, the servo head 4c included in the magnetic head 4 is capable of reproducing a servo signal recorded in the servo bands 3. With use of the servo signal reproduced, the position of the magnetic tape 1 or the magnetic head 4 in the tape width direction can be detected.
Next, the following describes an operation carried out when digital data are recorded in the magnetic tape 1. As shown in (b) of FIG. 1, when digital data are recorded in the magnetic tape 1, the magnetic tape 1 is enabled to run in the arrow A direction, and current is carried through the first head 4a, whereby the eight data tracks 5 are formed at the same time in one data band 2. When digital data are recorded throughout one data band 2 from a leading end to a terminating end thereof, the magnetic head 4 slightly shifts the position thereof in the width direction of the magnetic tape 1 as shown in FIG. 2, the magnetic tape 1 is running in a direction indicated by an arrow B, and digital data are recorded by the second head 4b from the terminating end to the leading end of the data band 2. In other words, digital data are recorded while the magnetic tape 1 is running forward and backward. By repeating such reciprocating motions several times, digital data can be recorded at a high density in one data band 2. After digital data are recorded in one data band 2 while the magnetic tape 1 is running forward and backward for a predetermined number of times, another data band 2 is subjected to the same control as described above, whereby digital data can be recorded.
As shown in (c) of FIG. 1, a servo track recorded in the servo band 3 is configured so that one servo frame is composed of a first sub-frame and a second sub-frame. Further, as shown in FIG. 3, the first sub-frame is composed of a first stripe group 3a and a second stripe group 3b. Still further, the second sub-frame is composed of a third stripe group 3c and a fourth stripe group 3d. The first stripe group 3a is composed of five stripes parallel with one another that are formed so as to tilt slightly with respect to the width direction of the servo band 3 (in the present embodiment, the azimuth angle is 6°±5°). The second stripe group 3b is composed of five stripes parallel with one another that are formed so as to tilt slightly with respect to the width direction of the servo band 3 (in the present embodiment, the azimuth angle is 6°±5°). It should be noted that the tilt directions of the first stripe group 3a and the second stripe group 3b are directions opposite to each other. The third stripe group 3c is composed of four stripes parallel with one another that tilt through the same angle in the same direction as the servo tracks of the first stripe group 3a. The fourth stripe group 3d is composed of four stripes parallel with one another that tilt through the same angle in the same direction as the stripes of the second stripe group 3b. In other words, the servo frame is composed of 18 stripes. All the stripe are magnetized in the same direction as indicated by arrows in an enlarged circle 3e. The enlarged circle 3e shows an enlarged view of a part of the stripes.
As described above with reference to (b) of FIG. 1 and FIG. 2, when digital data are recorded in the data band 2, the magnetic head 4 is moved in the tape width direction while the magnetic tape 1 is enabled to run. Therefore, with this, the scanning position of the servo head 4c on the servo band 3 moves in the tape width direction. As shown in FIG. 3, the stripes recorded in the servo band 3 are substantially in the symmetric chevron shape, the space between the first stripe group 3a and the second stripe group 3b varies in the tape width direction (so does the space between the third stripe group 3c and the fourth stripe group 3d). When the stripes thus recorded are read by the servo head 4c, the magnetic tape 1 is transported at a constant speed in a length direction, and therefore the time required for the servo head 4c to pass over the space between the first stripe group 3a and the second stripe group 3b varies with the scanning position of the servo head 4c in the tape width direction. For example, in (a) of FIG. 3, the time required for the servo head 4c to pass over the space between the first stripe group 3a and the second stripe group 3b when the servo head 4c scans along a centerline C is shorter than the time required for the servo head 4c to pass over the space between the first stripe group 3a and the second stripe group 3b when the servo head 4c scans along the reference line D.
According to the time required for the servo head 4c to pass over the space between the first stripe group 3a and the second stripe group 3b, a distance W between adjacent stripe groups in the tape length direction can be calculated. Then, with the distance W, a distance X between the adjacent stripe groups on the centerline C shown in FIG. 3, and a tilt Y of the stripes, it is possible to calculate positions Z of the servo head 3 and the servo track with respect to the servo band centerline C according to Formula 1 given as:
According to the positions Z with respect to the servo band centerline C calculated as described above, the positions of data tracks that the first head 4a and the second head 4b currently scan are determined.
However, if the edges of the magnetic tape 1 wave or the like, the servo head deviates from a target servo track. As a result, the time required for the passing over the space between the first stripe group 3a and the second stripe group 3b varies. Based on this variance value, an off-track value is calculated by the above-described head position calculating method, and the position of the magnetic head 4 is controlled so as to make the off-track value null, whereby the normal on-track state of the magnetic head 4 can be achieved.
FIG. 4A illustrates a configuration of stripes corresponding to the value “0”. FIG. 4B illustrates a configuration of stripes corresponding to the value “1”. In order to record the value “0” in the servo band 3, as shown in FIG. 4A, in recording the stripes of the first stripe group 3a and the second stripe group 3b, the interval (pitch P2) between the second and third stripes from the head of the stripe group in the tape running direction A, and the interval between the third and fourth stripes (the same interval as that of the pitch P2) are set wider as compared with the other intervals (pitch P1). In order to record the value “1” in the servo band 3, as shown in FIG. 4B, in recording the stripes of the first stripe group 3a and the second stripe group 3b, the interval (pitch P3) between the first and second stripes from the head of the stripe group in the tape running direction A, and the interval between the fourth and fifth stripes (the same interval as that of the pitch P3) are set wider as compared with the other intervals (pitch P4). By providing the regularity to the stripe intervals as shown in FIGS. 4A and 4B, the servo controlling operation can be executed, while various types of information composed of digital data can be contained in the servo track.
The recording signal processing part 12 controls current in a data head 15a according to digital data entered through the input terminal 11.
The reproduction signal processing part 14 is capable of converting data (analog signals) reproduced from the magnetic tape 21 by the data head 15a into digital data.
The head unit 15 corresponds to the magnetic head 4 shown in FIG. 1, and includes the data head 15a and the servo head 15b. The head unit 15 is arranged so as to be movable in the width direction of the magnetic tape 21. The data head 15a includes a data-recording head and a data-reproducing head that are equivalent to the first head 4a and the second head 4b shown in FIG. 1, respectively, but they are referred to collectively as “data head” in conjunction with FIG. 6. The data-recording head is subjected to current control by the recording signal processing part 12, so as to be capable of recording data in the magnetic tape 21. The data-reproducing head is capable of reproducing data recorded in the magnetic tape 21. In the head unit 15, eight of the data heads 15a are arranged in the width direction of the magnetic tape 1, as described above with reference to (b) of FIG. 1 Further, the servo head 15b is capable of reproducing a servo signal by scanning servo tracks recorded in the servo band 3. Two of the servo heads 15b are provided so as to simultaneously scan the two servo bands 3 arranged with data bands being interposed therebetween, as described above with reference to (b) of FIG. 1.
The control part 17 detects a current position of the head unit 15 according to the servo signal reproduced by the servo head 15b. Further, the control part 17 calculates an off-track value based on the current position information of the head unit 15 and tape variance information fed from the memory reader 19 (described later), and generates a control signal for controlling an operation of the actuator 18 based on the off-track value. The control signal thus generated is a signal with which the position of the head unit 15 can be controlled, and at least information about a motion direction of the head unit 15 and information about a motion value of the same.
In the magnetic tape 21, digital data are recorded by the data head 15a. In the present embodiment, since the magnetic tape 21 is in conformity with the LTO standards, a magnetic tape having a width of about 12.65 mm is used.
Next, the memory reader 19 communicates with the memory 22, and reads the LTM information stored in the memory 22 (Step S2). The LTM information read out of the memory 22 is entered in the control part 17. The control part 17 analyzes a motion of the magnetic tape 21 or distortion of a servo signal according to the LTM information. Further, the control part 17 reads a servo signal via the servo head 15b (Step S3). Next, the control part 17 analyzes the servo signal thus read out to detect a relative position of the magnetic tape 22 with respect to the magnetic head (Step S4). Based on the position information thus detected, the control part 17 calculates an off-track value (Step S5).
On the other hand, in the case where digital data recorded already in the magnetic tape 21 are reproduced, the processing operation of Steps S1 to S7 shown in FIG. 7A is executed, whereby the head unit 15 is moved to a position corresponding to a target track position on the magnetic tape 21. In this state, the reproduction signal processing part 14 converts a signal reproduced from the magnetic tape 21 by the data head 15a into digital data, and outputs the same via the output terminal 13. It should be noted that since the operation of the servo control upon reproduction is the same operation as the servo control upon recording, detailed descriptions of the same are omitted herein.
In the head servo tracking, a current position of the magnetic head is detected according to the servo signal, and an off-track value as a difference between a target track position and the current position of the magnetic head is calculated. The magnetic head is moved so as to make the off-track value null, whereby the magnetic head is enabled to follow the track. The off-track value is composed substantially of LTM attributed to the tape, LTM attributed to the drive, written-in errors such as distortions in the servo signal on the tape, and an off-track value attributed to electrical noises. As shown in (d) of FIG. 8, when the running motion of the magnetic tape 21 at a timing t1, the control part 17 predicts an off-track value resulting from LTM at a timing t3 according to LTM information read out of the memory 22, and calculates a motion value m1 of the head unit 15. As shown in (c) of FIG. 8, the control part 17 reads a servo signal with use of the servo head 15b in a period from t1 to t2. Next, in a period from t2 to t3, the control part 17 calculates an off-track value by calculating a position of the head unit 15 in the period from t1 to t2. Then, the control part 17 calculates a motion value m2 of the head unit 15 according to the calculated off-track value. Next, the control part 17 moves the head unit 15 at the timing t3 according to the calculated motion value (m1+m2).
20070076316 April 5, 2007 Kuse et al.
20080024905 January 31, 2008 Johnson et al.
8-30942 February 1996 JP
Patent number: 7652841
Patent Publication Number: 20080278844
Assignee: Hitachi Maxell, Ltd. (Ibaraki-shi, Osaka)
Inventors: Shinji Kawakami (Osaka), Toshio Kawakita (Osaka)
Application Number: 12/026,391
Current U.S. Class: Elongated Web Carrier (i.e., Tape) (360/77.12); Controlling The Head (360/75)
International Classification: G11B 5/584 (20060101); G11B 21/02 (20060101);