Data storage systems and magnetic tape recording media

Abstract

An apparatus according to one approach includes an array of skew detection transducers. The array of write transducers is spaced from the array of skew detection transducers along the intended direction of tape movement across the array of skew detection transducers. The array of read transducers is aligned with the array of write transducers in the intended direction of tape movement. The apparatus also includes a first actuator configured to operatively apply a force to the array of skew detection transducers to orient a longitudinal axis of the array of skew detection transducers substantially perpendicular to the actual direction of tape movement across the array of skew detection transducers. A magnetic recording medium according to one approach includes a magnetic recording tape including a longitudinal axis extending between distal ends of the magnetic recording tape, the magnetic recording tape including vertical stripes written into a servo skew pattern on the magnetic recording tape, the vertical stripes being oriented perpendicular to the longitudinal axis of the tape.

Description

[Technical Field]

[0001] The present invention relates to data storage systems, and more particularly, the present invention relates to tape-based data storage systems that have the ability to correct for the combined effects of tape distortion and tape dimensional stability. [Background technology]

[0002] In a magnetic storage system, a magnetic transducer reads and writes data from and to a magnetic recording medium. Data is written to a magnetic recording medium by moving a magnetic recording transducer to a location on the medium where the data is to be stored. The magnetic recording transducer then generates a magnetic field that encodes the data into the magnetic medium. Data is read from the medium by similarly positioning a magnetic read transducer and then sensing the magnetic field of the magnetic medium. Read and write operations may be independent or synchronized with the movement of the medium to ensure that data can be read from and written to the desired location on the medium.

[0003] An important ongoing goal in the data storage industry is to increase the density of data stored on media. In the case of tape storage systems, this goal has resulted in increasing the density of tracks and linear bits on recording tape and decreasing the thickness of the magnetic tape media. However, the development of smaller footprint, higher performance tape drive systems has created various challenges in the design of tape head assemblies for use in such systems.

[0004] In a tape drive system, the drive moves the magnetic tape at high speed over the surface of the tape head. Tape heads are typically designed to minimize the spacing between the head and the tape. Because spacing between the magnetic head and the magnetic tape is critical, the goal in these systems is to have the transducer's recording gap, the source of the recording magnetic flux, nearly touching the tape to provide a sharp write transition, and the read element nearly touching the tape to provide effective coupling of the magnetic field from the tape to the read element.

[0005] The amount of data stored on magnetic tape can be expanded by increasing the number of data tracks across the tape. More tracks are possible by reducing the reader and writer geometry, such as by using thin-film manufacturing techniques and magnetoresistive (MR) sensors. However, for various reasons, reader and writer geometries cannot be made arbitrarily small; therefore, a balance must be struck between factors such as tape distortion, lateral (e.g., perpendicular to the direction of tape movement) tape motion, transients, and lateral expansion and contraction of the tape, and the size of the reader / writer that provides acceptable written tracks and read signals.

[0006] As alluded to in the previous paragraph, one problem that limits areal density is misalignment caused by tape warping. As the tape advances over the surface of the tape head, an angular shift can occur in the relative angular relationship between the transducer array and the data tracks on the tape, which typically results in the transducers being misaligned from the data tracks on the tape. Misalignment caused by warping tends to be more pronounced on smaller tracks. Therefore, data may become unreadable from the tape, especially as tape capacity increases over time and tracks become smaller.

[0007] Another particular problem that limits areal density is misregistration caused by lateral expansion and contraction of the tape, commonly referred to as poor tape dimensional stability (TDS), or more properly, tape dimensional instability (TDI).

[0008] The lateral shrinkage and expansion of the tape is a well-known phenomenon that occurs due to many influences, including water absorption, thermal expansion and contraction, etc. The width of the tape can vary by up to about 0.1% due to TDS / TDI.

[0009] Various problems arise when tape dimensions change. There is an increased likelihood of overwriting shingled tracks during writing. Overwritten data is often irrecoverable. Similarly, if the tape width changes after the desired data has been written, the reader may no longer be positioned over the track being read, increasing read errors. The degree of misalignment is particularly great toward the outer edges of the reader array.

[0010] More permanent changes in the media's lateral dimensions can also occur, such as long-term media "creep" (also known in the art as "aging"), which tends to occur over time as the tape wraps around the hub of a tape cartridge. Long-term media creep is particularly problematic when addressing tape dimensional stability issues when the two ends of the tape exhibit creep in different ways. The inner wrap of tape located closest to the cartridge hub tends to expand laterally over time due to compressive stresses imposed by the wrap of tape wrapped around the hub. The wrap located toward the outer diameter of the tape spool experiences less compressive stress but higher tensile stresses, which tend to cause the tape to contract laterally (i.e., narrow over time). In response, the ends of the tape tend to exhibit lateral dimensional changes in opposite directions. Thus, creep causes the pitch of the shingled tracks to change to different degrees (non-uniformly) along the length of the tape over time.

[0011] Thus, while the width of the transducer array remains essentially fixed (in the absence of tilt or other mechanisms to adjust the spacing of the transducers presented to the tape), the spacing of the data tracks on the tape changes as the tape expands and contracts. Ideally, the reader track width would be the same as the width of the data track being read, providing the best signal. However, the sensor track width cannot be the same as the width of the data track because the sensor reads adjacent tracks during tape expansion or contraction, or due to lateral misalignment between the tape and the head, or both. Therefore, reader widths are currently designed to be significantly smaller than the width of the data track, and all readers within a particular head have the same track width. The reader track width is selected to accommodate worst-case conditions; that is, designers consider maximum expansion / contraction and lateral misalignment when determining the reader track width, so that each sensor is over a particular track at any given time.

[0012] Previous attempts at compensating for TDS problems involved statically tilting the magnetic head to adjust the transducer pitch presented to the tape to match the pitch of the current track. This tilt was adjusted as needed to provide a properly appearing transducer pitch. However, such attempts have proven prone to track placement errors caused by tape distortion during writing and reading. For example, in tape drives, it is well known that the tape will skew as it passes over the head in both directions of tape motion. If not compensated for, this distortion can cause track placement errors of one micron or more, an error that currently exceeds the pitch of a single track.

[0013] Another related issue with the tilt approach relates to read-while-write verification, which requires that the subsequent read transducer remain within range of the previously written track as the track is written. The read and write arrays are offset when the head is assembled to set the read transducer nominally aligned with the writer for the target static tilt angle. However, to ensure the reader remains within read-while-write range, small corrections to the tilt to accommodate changes in tape dimensions necessitate the use of a wider write pole than would otherwise be required. Furthermore, a wider writer creates write-head design issues, such as requiring more coil turns, and alone results in a reduction in the achievable tape areal capacity due to the space used by the last unshingled tracks written in each subdata band. This can result in a capacity reduction of as much as 20–30%.

[0014] A solution to the aforementioned problems is needed that will enable future increases in areal density. Summary of the Invention

[0015] The apparatus and methods presented herein address the difficulties encountered when attempting to increase storage density on magnetic tape media while maintaining high data rates per unit of tape speed.

[0016] An apparatus according to one aspect of the invention includes an array of skew detection transducers. The array of write transducers is spaced from the array of skew detection transducers along the intended direction of tape movement across the array of skew detection transducers. The array of read transducers is aligned with the array of write transducers in the intended direction of tape movement. The apparatus also includes a first actuator configured to operatively apply a force to the array of skew detection transducers to orient a longitudinal axis of the array of skew detection transducers substantially perpendicular to the actual direction of tape movement across the array of skew detection transducers.

[0017] Because the orientation of the array of skew-sensing transducers is parallel to the direction of lateral expansion or contraction of the tape, this orientation results in virtually no misalignment or deformation as a result of lateral expansion or contraction of the tape. Furthermore, this orientation makes the array of skew-sensing transducers insensitive to variations in pitch between the skew-sensing transducers.

[0018] In some approaches, the array of skew-detecting transducers is on a first module, and the arrays of read and write transducers are on at least one second module that is movable relative to the first module. A first actuator is configured to move the first module and the at least one second module together. The second actuator is configured to apply a force to the at least one second module in response to a determined state of lateral expansion of the tape to cause relative movement of the at least one second module with respect to the first module and adjust the tilt angle of the at least one second module. Such an approach allows compensation for both skew and TDS issues.

[0019] An apparatus according to another aspect of the present invention includes a first module including an array of skew-detecting transducers. The array of write transducers is spaced from the array of skew-detecting transducers along a direction of intended tape movement across the array of skew-detecting transducers. The array of read transducers is aligned with the array of write transducers in the direction of intended tape movement. The arrays of read and write transducers are on at least one second module. The at least one second module is movable relative to the first module. A first actuator is configured to move the first module and the at least one second module together. The second actuator is configured to apply a force to the at least one second module in response to a determined state of lateral expansion of the tape to cause relative movement of the at least one second module with respect to the first module and adjust the tilt angle of the at least one second module.

[0020] Such an embodiment allows compensation for both distortion and TDS issues.

[0021] An apparatus according to another aspect of the present invention includes a first module including an array of skew-detecting transducers. The array of write transducers is spaced from the array of skew-detecting transducers along the intended direction of tape movement across the array of skew-detecting transducers. The array of read transducers is aligned with the array of write transducers in the intended direction of tape movement. The arrays of read and write transducers are on at least one second module. The at least one second module is movable relative to the first module. A first actuator is configured to operatively apply a force to the array of skew-detecting transducers to maintain an orientation of the longitudinal axis of the array of skew-detecting transducers substantially perpendicular to the direction of tape movement. The longitudinal axes of the arrays of read and write transducers are not pivotable from that orientation relative to the longitudinal axis of the array of skew-detecting transducers. The first actuator is configured to move the first module and the at least one second module together.

[0022] Any of these techniques may be implemented in a magnetic data storage system, such as a tape drive system, which may include a magnetic head, a drive mechanism for passing a magnetic medium (e.g., recording tape) over the magnetic head, and a controller electrically coupled to the magnetic head.

[0023] A magnetic recording medium according to another aspect of the present invention includes a magnetic recording tape including a longitudinal axis extending between distal ends of the magnetic recording tape, the magnetic recording tape including longitudinal stripes written into servo-skew patterns of the magnetic recording tape, the longitudinal stripes being oriented perpendicular to the longitudinal axis of the magnetic recording tape.

[0024] In some techniques, the vertical stripes have no purpose other than to correct for distortion. In some techniques, the vertical stripes are positioned above and / or below a timing-based servo frame based on the chevrons of the servo pattern.

[0025] In addition to the advantages mentioned above, vertical stripes offer the additional advantage that the dedicated distortion detection transducer can be wider, since the angle between the vertical stripes and the longitudinal axis of the distortion detection transducer is 0 degrees. The use of wider transducers improves the signal to noise ratio (SNR), thereby improving detection.

[0026] Other aspects and techniques of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, illustrate by way of example the principles of the invention. [Brief explanation of the drawings]

[0027] [Figure 1A] 1 is a schematic diagram of a simplified tape drive system according to one approach. [Figure 1B] 1 is a schematic diagram of a tape cartridge according to one approach. [Figure 2A] FIG. 1 shows a side view of one approach to a flat-wrap, bidirectional, two-module magnetic tape head. [Figure 2B] 2B is a view of the tape bearing surface taken from line 2B of FIG. 2A. [Figure 2C] FIG. 2C is a detailed view taken from circle 2C of FIG. 2B. [Figure 2D] FIG. 10 is a detailed view of a partial tape bearing surface of a pair of modules. [Figure 3] FIG. 2 is a partial tape bearing surface view of a magnetic head having a write-read-write configuration. [Figure 4] FIG. 2 is a partial tape bearing surface view of a magnetic head having a read-write-read configuration. [Figure 5] A side view of one approach to a magnetic tape head that includes three modules, all of which typically lie along approximately parallel planes. [Figure 6] FIG. 1 is a side view of a magnetic tape head containing three modules in a tangential (tilted) configuration. [Figure 7] FIG. 1 is a side view of a magnetic tape head containing three modules in an overlapping configuration. [Figure 8A] Schematic diagram showing the principle of tape tenting. [Figure 8B] Schematic diagram showing the principle of tape tenting. [Figure 8C] Schematic diagram showing the principle of tape tenting. [Figure 9] FIG. 1 is a diagram illustrating files and indexes stored on magnetic tape according to one approach. [Figure 10] FIG. 1 illustrates a tape layout according to one embodiment of the present invention. [Figure 11] 1 illustrates a hybrid servo pattern written in a dedicated area of ​​a tape medium according to one embodiment of the present invention. [Figure 12] FIG. 2 shows a partial detailed view of a (TBS) pattern according to one embodiment of the present invention. [Figure 13] FIG. 13 shows a graph plotting sample versus amplitude for the TBS pattern of FIG. 12, according to one embodiment of the present invention. [Figure 14] FIG. 2 illustrates a block diagram of a servo pattern detector, according to one embodiment. [Figure 15A] FIG. 10 is a representative diagram showing the effect of tape skew on transducer location relative to transducer location. [Figure 15B] FIG. 10 is a representative diagram showing the effect of tape skew on transducer location relative to transducer location. [Figure 15C] FIG. 10 is a representative diagram showing the effect of tape skew on transducer location relative to transducer location. [Figure 15D] FIG. 10 is a representative diagram showing the effect of tape skew on transducer location relative to transducer location. [Figure 16A] FIG. 1 illustrates the effect of lateral expansion and contraction of a tape. [Figure 16B] FIG. 1 illustrates the effect of lateral expansion and contraction of a tape. [Figure 16C] FIG. 1 illustrates the effect of lateral expansion and contraction of a tape. [Figure 17] FIG. 10 illustrates the concept of using a distortion detection transducer to detect vertical stripes in a new servo distortion pattern for distortion tracking, according to one approach. [Figure 18] FIG. 1 shows an apparatus according to one approach. [Figure 19] FIG. 1 shows an apparatus according to one approach. [Figure 20] FIG. 19 shows the device of FIG. 18 with distortion correction applied. [Figure 21] FIG. 1 shows an apparatus according to one approach. [Figure 22] FIG. 22 shows the device of FIG. 21 with TDS compensation applied. [Figure 23] FIG. 22 shows the device of FIG. 21 with distortion correction and TDS compensation applied. [Figure 24] FIG. 1 shows an apparatus according to one approach. [Figure 25A] FIG. 2 is a conceptual diagram of a writer for writing inventive servo distortion patterns, according to one approach of the present invention. [Figure 25B] 25B shows a frame of an inventive servo distortion pattern written using the writer of FIG. 25A. [Figure 25C] FIG. 2 is a conceptual diagram of a writer for writing inventive servo distortion patterns, according to one approach of the present invention. [Figure 25D] FIG. 25D shows a frame of an inventive servo distortion pattern written using the writer of FIG. 25C. [Figure 25E] FIG. 2 is a conceptual diagram of a writer for writing inventive servo distortion patterns, according to one approach of the present invention. [Figure 25F] FIG. 25F shows a frame of an inventive servo distortion pattern written using the writer of FIG. 25E. [Figure 26] FIG. 10 illustrates an exemplary servo distortion pattern including vertical stripes for distortion detection according to one approach. [Figure 27] FIG. 10 illustrates an exemplary servo distortion pattern including vertical stripes for distortion detection according to one approach. [Figure 28] FIG. 1 illustrates an exemplary TBS pattern including vertical stripes for distortion detection according to one approach. [Figure 29] FIG. 1 illustrates an exemplary TBS pattern including vertical stripes for distortion detection according to one approach. [Figure 30] FIG. 1 illustrates an exemplary TBS pattern including vertical stripes for distortion detection according to one approach. [Figure 31] 1 is a flowchart of a method, according to one approach. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following description is made for the purpose of illustrating the general principles of the present invention and is not intended to limit the inventive concepts claimed herein. Moreover, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations.

[0029] In this specification, unless otherwise specifically defined, all terms are to be given their broadest possible interpretation, including the meaning implied by this specification and the meaning understood by a person skilled in the art and / or defined in dictionaries, treatises, etc.

[0030] It should also be noted that as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless specifically stated otherwise.

[0031] The following description discloses several preferred techniques for the magnetic storage system and its operation and / or components.

[0032] In one general aspect, an apparatus includes an array of skew-detecting transducers. The array of write transducers is spaced from the array of skew-detecting transducers along the intended direction of tape movement across the array of skew-detecting transducers. The array of read transducers is aligned with the array of write transducers in the intended direction of tape movement. The apparatus also includes a first actuator configured to operatively apply a force to the array of skew-detecting transducers to orient a longitudinal axis of the array of skew-detecting transducers substantially perpendicular to the actual direction of tape movement across the array of skew-detecting transducers.

[0033] In another general aspect, an apparatus includes a first module including an array of skew-detecting transducers. The array of write transducers is spaced from the array of skew-detecting transducers along a direction of intended tape movement across the array of skew-detecting transducers. The array of read transducers is aligned with the array of write transducers in the direction of intended tape movement. The arrays of read and write transducers are on at least one second module. The at least one second module is movable relative to the first module. A first actuator is configured to move the first module and the at least one second module together. The second actuator is configured to apply a force to the at least one second module in response to a determined state of lateral expansion of the tape to cause relative movement of the at least one second module with respect to the first module and adjust the tilt angle of the at least one second module.

[0034] In another general aspect, an apparatus includes a first module including an array of skew-detecting transducers. The array of write transducers is spaced from the array of skew-detecting transducers along the intended direction of tape movement across the array of skew-detecting transducers. The array of read transducers is aligned with the array of write transducers in the intended direction of tape movement. The arrays of read and write transducers are on at least one second module. The at least one second module is movable relative to the first module. A first actuator is configured to operatively apply a force to the array of skew-detecting transducers to maintain an orientation of the longitudinal axis of the array of skew-detecting transducers substantially perpendicular to the direction of tape movement. The longitudinal axis of the array of read and write transducers is not pivotable from that orientation relative to the longitudinal axis of the array of skew-detecting transducers. The first actuator is configured to move the first module and the at least one second module together.

[0035] In another general aspect, a magnetic recording medium includes a magnetic recording tape including a longitudinal axis extending between distal ends of the magnetic recording tape, the magnetic recording tape including longitudinal stripes written into a servo distortion pattern of the magnetic recording tape, the longitudinal stripes being oriented perpendicular to the longitudinal axis of the magnetic recording tape.

[0036] Figure 1A illustrates a simplified tape drive 100 of a tape-based data storage system that may be employed in connection with the present invention. It should be noted that while Figure 1A illustrates one particular implementation of a tape drive, the techniques described herein may be implemented in connection with any type of tape drive system.

[0037] As shown, a tape supply cartridge 120 and take-up reel 121 are provided to support tape 122. One or more of the reels may form part of a removable cartridge and are not necessarily part of tape drive 100. A tape drive such as that shown in FIG. 1A may further include a drive motor for driving tape supply cartridge 120 and take-up reel 121 to move tape 122 over any type of tape head 126. Such a head may include an array of readers, writers, or both.

[0038] Guide 125 guides tape 122 across tape head 126. Such tape head 126 is then coupled to controller 128 via cable 130. Controller 128 may be or include a processor and / or any logic for controlling any subsystem of drive 100. For example, controller 128 typically controls head functions such as servos, data writing, data reading, etc. Controller 128 may include at least one servo channel and at least one data channel, each of which includes data flow processing logic configured to process and / or store information written to and / or read from tape 122. Controller 128 may operate under any logic known in the art and disclosed herein and, therefore, in various ways, may be considered a processor with respect to any of the tape drive descriptions contained herein. Controller 128 may be coupled to any known type of memory 136 capable of storing instructions executable by controller 128. Additionally, controller 128 may be configured and / or programmable to perform or control some or all of the methods presented herein. Thus, controller 128 may be thought of as configured to perform various operations as programmed logic in one or more chips, modules, or blocks, or a combination thereof, software, firmware, or other instructions available to one or more processors, or a combination thereof, and the like.

[0039] Cable 130 may include read / write circuitry for transmitting data to be recorded on tape 122 to tape head 126 and for receiving data read from tape 122 by tape head 126. Actuator 132 controls the position of tape head 126 relative to tape 122.

[0040] An interface 134 may be provided for communication to send and receive data between tape drive 100 and a host (internal or external), as well as for controlling the operation of tape drive 100 and communicating the status of tape drive 100 to the host, all as will be understood by those skilled in the art.

[0041] FIG. 1B illustrates an exemplary tape cartridge 150 according to one approach. Such a tape cartridge 150 may be used with a system such as the system illustrated in FIG. 1A. As shown, the tape cartridge 150 includes a housing 152, a tape 122 within the housing 152, and a non-volatile memory 156 coupled to the housing 152. In some approaches, the non-volatile memory 156 may be incorporated within the housing 152, as shown in FIG. 1B. In other approaches, the non-volatile memory 156 may be attached to the inside or outside of the housing 152 without modifying the housing 152. For example, the non-volatile memory may be incorporated within an adhesive label 154. In one preferred approach, the non-volatile memory 156 may be a flash memory device, a read-only memory (ROM) device, or the like, and may be incorporated within or coupled to the inside or outside of the tape cartridge 150. The non-volatile memory is accessible by the tape drive and tape operating software (driver software), or by another device, or a combination thereof.

[0042] By way of example, FIG. 2A shows a side view of a flat-wrap, bidirectional, two-module magnetic tape head 200 that may be implemented in connection with the present invention. As shown, the head includes a pair of bases 202, each with a module 204, secured at a small angle α relative to one another. The bases may be "U-beams" adhesively bonded together. Each module 204 includes a substrate 204A and a closure 204B, along with a thin film portion, commonly referred to as a "gap," within which a reader and / or writer 206 is formed. During use, the tape 208 is moved over the modules 204 along a media (tape) support surface 209 to read and write data on the tape 208 using the reader and writer in the manner shown. The wrap angle θ at the edge of the tape 208 moving out onto the flat media support surface 209 is typically between about 0.1 degrees and about 3 degrees.

[0043] The substrate 204A is typically constructed of a wear-resistant material such as ceramic, and the closure 204B may be made of the same ceramic as the substrate 204A or a similar ceramic.

[0044] The readers and writers may be arranged in a piggyback or fused configuration. An exemplary piggyback configuration includes a (magnetically inductive) writer transducer above (or below) a (magnetically shielded) reader transducer (e.g., a magnetoresistive reader), with the writer pole and reader shield typically separated. An exemplary fused configuration includes one writer pole and one reader shield in the same physical layer (hence "fused"). The readers and writers may also be arranged in an interleaved configuration. Alternatively, each array of channels may be reader-only or writer-only. Either of these arrays may include one or more servo track readers to read servo data on the media.

[0045] Figure 2B shows the tape support surface 209 of one of the modules 204 taken from line 2B of Figure 2A. A representative tape 208 is shown in dashed lines. The module 204 is preferably long enough to support the tape as the head moves between the data bands.

[0046] In this example, the tape 208 includes 4 to 32 data bands, e.g., 16 data bands and 17 servo tracks 210 on a half-inch (1.27 cm) wide tape 208, as shown in FIG. 2B. The data bands are defined between the servo tracks 210. Each data band may include multiple data tracks (e.g., 1024 data tracks (not shown)). During read / write operations, the reader and / or writer 206 is positioned at a specific track location within one of the data bands. An outer reader (sometimes called a servo reader) reads the servo tracks 210. Servo signals are then used for track following, i.e., to keep the reader and / or writer 206 aligned with a specific set of tracks during read / write operations.

[0047] FIG. 2C shows multiple readers and / or writers 206 formed within gaps 218 on module 204 within circle 2C of FIG. 2B. As shown, reader and writer array 206 includes, for example, 16 writers 214, 16 readers 216, and 2 servo readers 212, although the number of these elements may vary. Exemplary approaches include 8, 16, 32, 40, and 64 active readers and / or writers 206 per array, with alternative interleaved designs including an odd number of readers or writers, such as 17, 25, 33, etc. An exemplary approach includes 32 readers per array and / or 32 writers per array, although the actual number of transducer elements may be even greater (e.g., 33, 34, etc.). Increasing the number of transducer elements allows tape movement to be slowed, thereby reducing tracking and mechanical difficulties due to speed, or allowing fewer "wraps" to be performed to write or read from the tape, or both. While the readers and writers may be arranged in a piggyback configuration as shown in FIG. 2C , the readers 216 and writers 214 may also be arranged in an interleaved configuration. Alternatively, each array of readers and / or writers 206 may be reader-only or writer-only, and each array may include one or more servo readers 212. As shown by considering FIGS. 2A and 2B-2C together, each module 204 may include complementary sets of readers and / or writers 206 for bidirectional reading and writing, read-while-write capabilities, backward compatibility, etc.

[0048] FIG. 2D shows a partial tape-bearing surface view of complementary modules of magnetic tape head 200 according to one approach. In this approach, each module includes multiple read / write (R / W) pairs and optional electrically insulating layer 236 formed on common substrate 204A in a piggyback configuration. Writer 214 and reader 216 are aligned parallel to the intended direction of tape media movement therethrough, forming R / W pairs exemplified by R / W pair 222. Note that the intended direction of tape movement is sometimes referred to herein as the tape movement direction, and these terms may be used interchangeably. Such tape movement direction may be inferred from the system design, for example, by examining guides, observing the actual tape movement direction relative to a reference point, etc. Furthermore, in a system operable for bidirectional reading and / or writing, both directions of tape movement are typically parallel, and therefore may be considered equivalent to each other.

[0049] There may be a plurality of R / W pairs 222, such as 8, 16, 32, etc. The R / W pairs 222 are shown aligned linearly, generally perpendicular to the direction of tape movement across them. However, the pairs may also be aligned diagonally, etc. Servo readers 212 are located outside the array of R / W pairs, and their function is well known.

[0050] Typically, the magnetic tape medium moves in either a forward or reverse direction, as indicated by arrow 220. The magnetic tape medium and head assembly 200 operate in a transducing relationship in a manner well known in the art. Head assembly 200 includes two thin-film modules 224 and 226 of generally identical construction.

[0051] Modules 224 and 226, coupled together with the space existing between their closures 204B (partially shown), form a single physical unit and provide play-while-write functionality by enabling the writer of the preceding module and the reader of the succeeding module aligned with the writer of the preceding module parallel to the direction of tape movement relative thereto. When modules 224, 226 of magnetic tape head 200 are constructed, layers are formed within gap 218 on a conductive substrate 204A (partially shown), such as AlTiC. The layers for R / W pair 222 generally include an insulating layer 236, a first shield 232, typically an iron alloy such as NiFe(-), cobalt zirconium tantalum (CZT), or Al-Fe-Si (Sendust), a sensor 234 for sensing data tracks on the magnetic media, a second shield 238, typically an iron-nickel alloy (e.g., approximately 80 / 20 at% NiFe, also known as Permalloy), first and second writer poles 228, 230, and a coil (not shown). The sensors may be of any known type, including sensors based on magnetoresistive (MR), GMR, AMR, tunneling magnetoresistance (TMR), and the like.

[0052] The first and second writer poles 228, 230 may be fabricated from a high magnetic moment material, such as approximately 45 / 55 NiFe. Note that these materials are provided merely as examples, and other materials may be used. Additional layers may be present, such as insulation between the shield and / or pole tip, and an insulating layer surrounding the sensor. Exemplary materials for insulation include alumina oxide and other oxides, insulating polymers, etc.

[0053] One approach to tape head 126 configuration includes multiple modules, preferably three or more. In a write-read-write (WRW) head, an outer module for writing flanks one or more inner modules for reading. Referring to FIG. 3, which illustrates a WRW configuration, outer modules 252, 256 each contain one or more arrays 260 of writers. Inner module 254 of FIG. 3 contains one or more arrays 258 of readers in a similar configuration. Variations of multi-module heads include RWR heads (FIG. 4), RRW heads, WWR heads, etc. In yet other variations, one or more of the modules may contain read / write pairs of transducers. Furthermore, there may be four or more modules. In yet other approaches, two outer modules may flank two or more inner modules, e.g., in a WRRW, RWWR, etc. arrangement. For simplicity, a WRW head will be primarily used herein to illustrate the approach of the present invention. Those skilled in the art, informed by the teachings herein, will understand how the permutations of the present invention apply to configurations other than the WRW configuration.

[0054] FIG. 5 illustrates a magnetic head 126 according to one approach of the present invention, including first, second, and third modules 302, 304, and 306, respectively, each including a tape-bearing surface 308, 310, and 312, respectively, which may be flat, contoured, or the like. While the term "tape-bearing surface" may appear to imply that the surface facing the tape 315 is in physical contact with the tape-bearing surface, this is not necessarily the case. Rather, only a portion of the tape may be in constant or intermittent contact with the tape-bearing surface, while another portion of the tape may rest (or "float") above the tape-bearing surface on a layer of air (sometimes referred to as air bearing). The first module 302 is referred to as the "leading" module because it is the first module encountered by the tape in a three-module design with the tape moving in the direction shown. The third module 306 is referred to as the "trailing" module. The trailing module is the last module encountered by the tape in a three-module design, following the middle module. The leading module 302 and the trailing module 306 are collectively referred to as the outer modules. Note also that the outer modules 302, 306 alternate as the leading module depending on the direction of tape 315 movement.

[0055] In one approach, the tape bearing surfaces 308, 310, 312 of the first, second, and third modules 302, 304, 306 lie on substantially parallel planes (which is intended to include parallel planes and near-parallel planes (e.g., planes between parallel and tangent, as in FIG. 6 )), with the tape bearing surface 310 of the second module 304 above the tape bearing surfaces 308, 312 of the first and third modules 302, 306. As explained below, doing so has the effect of creating a desired wrap angle α2 of the tape relative to the tape bearing surface 310 of the second module 304.

[0056] If the tape bearing surfaces 308, 310, and 312 were parallel or nearly parallel but along offset planes, intuitively, the tape would peel from the tape bearing surface 308 of the leading module 302. However, experimentation has shown that the vacuum created by the peeling edge 318 of the leading module 302 is sufficient to keep the tape adhered to the tape bearing surface 308 of the leading module 302. The trailing edge 320 of the leading module 302 (the end where the tape leaves the leading module 302) serves as an approximate reference point for defining the wrap angle α2 on the tape bearing surface 310 of the second module 304. The tape remains in close proximity to the tape bearing surface until it approaches the trailing edge 320 of the leading module 302. Therefore, the transducers 322 may be located near the trailing edges of the outer modules 302 and 306. These approaches are particularly suitable for write-read-write applications.

[0057] A benefit of this and other approaches described herein is that because the outer modules 302, 306 are fixed in a determined offset position relative to the second module 304, the inner wrap angle α2 is fixed when the modules 302, 304, 306 are bonded together or otherwise secured to the head. The inner wrap angle α2 is approximately tan -1 (δ / W), where δ is the height difference between the planes of the tape bearing surfaces 308, 310, and W is the width between the opposing ends of the tape bearing surfaces 308, 310. Exemplary inner wrap angles α2 are in the range of about 0.3° to about 1.1°, but can be any angle required by the design.

[0058] The inside wrap angle α2 on the side (leading edge) of the module 304 that receives the tape is advantageously larger than the inside wrap angle α3 on the trailing edge as the tape 315 rides onto the trailing module 306. This difference is beneficial because a smaller α3 typically tends to counter the steeper the resulting effective wrap angle has traditionally been.

[0059] Note that the tape bearing surfaces 308, 312 of the outer modules 302, 306 are positioned to achieve a negative wrap angle at the trailing edge 320 of the leading module 302. This is beneficial in that it helps reduce friction resulting from contact with the trailing edge 320, provided that the location of the crowbar region in the tape, which typically occurs at the head-off location, is properly considered. This negative wrap angle also reduces flutter and scraping against elements on the leading module 302. Furthermore, because the tape 315 floats above the tape bearing surface 312 in the trailing module 306, there is virtually no wear against elements as the tape moves in this direction. In particular, the tape 315 does not significantly ride on the tape bearing surface 312 of the third module 306 (though some contact may occur) due to air drag. This is acceptable because the leading module 302 is writing while the trailing module 306 is idle.

[0060] Write and read functions are performed by different modules at any one time. In one approach, the second module 304 includes multiple data readers and an optional servo reader 331, but no writers. The first and third modules 302, 306 include multiple writers 322 and no data readers, except that the outer modules 302, 306 may include optional servo readers. The servo readers may be used to position the heads during read and / or write operations. The servo readers on each module are typically located toward the ends of the array of readers or writers.

[0061] By having only the reader or side-by-side writer and servo reader in the gap between the substrate and the closure, the gap length can be significantly reduced. A standard head includes a piggybacked reader and writer, with a writer formed above each reader. A typical gap is 20 to 35 microns. However, irregularities on the tape can tend to droop into the gap and cause gap erosion. Therefore, the smaller the gap, the better. The smaller the gap enabled in this specification, the less likely it is to exhibit wear-related problems.

[0062] In some embodiments, the second module 304 includes a closure, while the first and third modules 302, 306 do not. If no closures are present, a hard coating is preferably added to the modules. One preferred coating is diamond-like carbon (DLC).

[0063] In the approach shown in FIG. 5 , the first, second, and third modules 302, 304, and 306 each include a closure 332, 334, and 336, respectively, which extend the tape-bearing surface of the associated module, thereby effectively positioning the read / write elements away from the edge of the tape-bearing surface. The closure 332 on the second module 304 can be a ceramic closure of the type typically found on tape heads. However, the closures 334 and 336 on the first and third modules 302 and 306 can be shorter than the closure 332 on the second module 304 when measured parallel to the direction of tape travel on each module. This allows the modules to be positioned closer together. One way to fabricate the shorter closures 334 and 336 is to overlap the standard ceramic closure of the second module 304 by an additional amount. Another method is to plate or deposit the thin-film closure on top of the elements during thin-film processing. For example, a thin film closure of a hard material such as sendust or an iron-nickel based alloy (eg, 45 / 55) can be formed over the module.

[0064] By using reduced thickness ceramic or thin film closures 334, 336 on the outer modules 302, 306, or no closures at all, the gap spacing between the writer and reader can be reduced to less than about 1 mm (e.g., about 0.75 mm), or 50% less than the spacing of commonly used linear tape open (LTO) tape heads. The spacing between the modules 302, 304, 306 can still be set to about 0.5 to 0.6 mm, which in some approaches is optimal for stabilizing tape movement above the second module 304.

[0065] Depending on the tape tension and stiffness, it may be desirable to tilt the tape-bearing surface of the outer module relative to the tape-bearing surface of the second module. Figure 6 illustrates an approach in which the modules 302, 304, and 306 are in a tangential or near-tangential (inclined) configuration. In particular, the tape-bearing surfaces of the outer modules 302 and 306 are approximately parallel to the tape at the desired wrap angle α2 of the second module 304. In other words, the planes of the tape-bearing surfaces 308 and 312 of the outer modules 302 and 306 are oriented approximately at the desired wrap angle α2 of the tape 315 relative to the second module 304. This approach also causes the tape to lift off the subsequent module 306, thereby reducing wear on the elements of the subsequent module 306. These approaches are particularly useful for write-read-write applications. Additional aspects of these approaches are similar to those previously described.

[0066] Typically, the wrap angle of the tape may be set approximately halfway between the approaches shown in FIGS.

[0067] FIG. 7 illustrates an approach in which modules 302, 304, and 306 are in an overlapping configuration. In particular, the tape support surfaces 308, 312 of the outer modules 302, 306 are slightly tilted relative to the tape 315 when set at the desired wrap angle α2 relative to the second module 304. In this approach, the tape does not lift off the subsequent modules, allowing the subsequent modules to be used for writing or reading. Thus, the leading module and the middle module can both perform read and / or write functions, while the subsequent module can read any previously written data. Therefore, these approaches are preferred for write-read-write, read-write-read, and write-write-read applications. In the latter approach, the closure should be wider than the tape canopy to ensure read functionality. A wider closure may require a wider gap separation. Therefore, a preferred approach has a write-read-write configuration, which allows for the use of a shortened closure and therefore a narrower gap separation.

[0068] Additional aspects of the approach shown in Figures 6 and 7 are similar to those previously described.

[0069] A 32-channel version of the multi-module head 126 may use a cable 350 with leads on the same or similar pitch as the current 16-channel piggyback LTO modules, or alternatively, the connections on the modules may be organ-keyboarded to reduce cable length by 50%. Unshielded cables for the upper and lower write pairs may be used for writers that may have an integrated servo reader.

[0070] The outer wrap angle α1 may be set in the drive by any type of guide known in the art, such as adjustable rollers, slides, or alternatively by outriggers integrated into the head. For example, a roller including an offset shaft may be used to set the wrap angle. The offset shaft creates an orbital arc of rotation, allowing for precise alignment of the wrap angle α1.

[0071] Conventional U-shaped spar assemblies may be used to assemble any of the aforementioned approaches. Thus, the mass of the resulting head may be maintained or reduced compared to previous generation heads. Alternatively, the module may be constructed as a single unit. Those skilled in the art with knowledge of this specification will understand that other known methods of manufacturing such heads may be suitable for use in constructing such heads. Furthermore, unless otherwise specified, processes and materials of the type known in the prior art may be suitable for use in the various approaches, consistent with the contents of this specification, as will be apparent to those skilled in the art upon reading this disclosure.

[0072] As the tape travels over the module, it is preferable for the tape to pass close enough to the magnetic transducers on the module so that reading and / or writing can be performed efficiently, e.g., with a low error rate. According to some approaches, tape tenting may be used to ensure that the tape passes close enough to the portion of the module that contains the magnetic transducer. To better understand this process, FIGS. 8A-8C illustrate the principle of tape tenting. FIG. 8A shows a module 800 including an upper tape support surface 802 that extends between opposing edges 804, 806. A stationary tape 808 is shown wrapped around the edges 804, 806. As shown in the figure, the bending stiffness of the tape 808 lifts the tape from the tape support surface 802. As shown in FIG. 8A, tension in the tape tends to flatten the tape's shape. When tape tension is minimal, the tape's curvature is greater than the parabolic curve shown in the figure.

[0073] FIG. 8B shows tape 808 in motion. The leading edge (i.e., the first edge the tape encounters as it moves) can act to strip air from the tape, thereby creating a subambient air pressure between tape 808 and tape support surface 802. In FIG. 8B, if the tape is moving from left to right, the leading edge is the left edge and the right edge is the trailing edge. As a result, atmospheric pressure above the tape forces the tape toward tape support surface 802, thereby creating tape tenting near each of the edges. The bending stiffness of the tape resists the effects of atmospheric pressure, thereby causing tape tenting near both the leading and trailing edges. Modeling predicts that the shapes of the two tents are very similar.

[0074] FIG. 8C shows how air pressure below ambient pressure forces tape 808 toward tape bearing surface 802 even when a subsequent guide 810 is positioned above the plane of the tape bearing surface.

[0075] Thus, tape tenting may be used to direct the path of the tape as it passes over the modules, preferably to ensure that the tape passes close enough to the portions of the modules containing the magnetic transducers so that reading and / or writing can be performed efficiently, e.g., with a low error rate.

[0076] Magnetic tapes may be stored in tape cartridges, which are then stored in storage slots or the like within a data storage library. Tape cartridges may be stored in the library so that they are physically accessible for retrieval. In addition to magnetic tapes and tape cartridges, data storage libraries may include data storage drives that store data on magnetic tapes, retrieve data from magnetic tapes, or both. Additionally, data libraries and their contained components may implement file systems that provide access to tapes and data stored on tapes.

[0077] A file system may be used to control how data is stored in and retrieved from memory. Thus, a file system may include the processes and data structures (e.g., how files are structured in memory) that an operating system uses to track files in memory. The Linear Tape File System (LTFS) is an exemplary form of file system that may be implemented in certain libraries to provide access to compatible tapes. It should be understood that the various techniques herein may be implemented using a wide range of file system formats, including, for example, IBM Spectrum Archive Library Edition (LTFS LE). However, to provide background and simply to assist the reader, some of the techniques below may be described with reference to LTFS, a type of file system format. This reference is made merely as an example and should not be considered a limitation on the invention defined in the claims.

[0078] A tape cartridge may be "loaded" by inserting the cartridge into a tape drive, and a tape cartridge may be "removed" by removing the tape cartridge from the tape drive. After being loaded into a tape drive, the tape in the cartridge may be "threaded" into the drive by physically pulling the tape (magnetic recording portion) from the tape cartridge and threading it over the magnetic head of the tape drive. Additionally, the tape may be attached to a take-up reel (e.g., see 121 in Figure 1A above) to move the tape over the magnetic head.

[0079] After a tape in a cartridge is threaded through a tape drive, it may be "mounted" by reading the metadata on the tape and placing the tape in a state where LTFS can use it as part of its file system. Furthermore, to "unmount" a tape, metadata is preferably first written to the tape (e.g., as an index), and then the tape may be removed from a state where LTFS can use it as part of its file system. Finally, to "unmount" a tape, the tape is removed from the take-up reel and physically placed back inside the tape cartridge. The cartridge may remain installed in the tape drive even after the tape is unloaded, for example, while awaiting another read or write request, or both. However, in other instances, the tape cartridge may be removed from the tape drive, for example, when the tape is unloaded as described above.

[0080] Magnetic tape is a sequential-access medium. Therefore, new data is written to the tape by appending it to the end of previously written data. Therefore, when data is recorded to a tape containing only one partition, metadata (e.g., allocation information) is sequentially appended to the end of the previously written data as the data is frequently updated and rewritten to the tape accordingly. As a result, when a tape is first mounted, the information at the end is read to access the most recent copy of the metadata corresponding to this tape. However, this read introduces a significant amount of delay into the process of mounting a particular tape.

[0081] To overcome this delay caused by single-partition tape media, the LTFS format includes a tape divided into two partitions: an index partition and a data partition. The index partition may be configured to store metadata, such as file allocation information (index), while the data partition may be configured to store the data itself.

[0082] 9, one approach illustrates a magnetic tape 900 including an index partition 902 and a data partition 904. As shown, data files and indexes are stored on the tape. As will be understood by those skilled in the art upon reading this description, the LTFS format allows index information to be recorded in the index partition 902 at the beginning of the tape 906.

[0083] When index information is updated, it is preferable to overwrite the previous version of the index information, thereby allowing the currently updated index information to be accessed in the index partition at the beginning of the tape. According to the specific example shown in FIG. 9, the latest version of the metadata, Index 3, is recorded in Index partition 902 at the beginning of the tape 906. Conversely, all three versions of the metadata, Index 1, Index 2, and Index 3, and the data, File A, File B, File C, and File D, are recorded in Data partition 904 of the tape. Although Index 1 and Index 2 are old (e.g., not updated) indexes, as previously described, because information is written to tape by appending information to the end of previously written data, these old indexes, Index 1 and Index 2, remain stored in Data partition 904 on the tape 906 without being overwritten.

[0084] The metadata contained in the index partition 902 and / or the data partition 904 may be updated in the same or different ways, depending on the desired approach. According to some approaches, for example, the metadata in the index partition and / or the data partition 902, 904 may be updated in response to a tape being unmounted so that the index can be quickly read from the index partition when the tape is remounted. Metadata is preferably also written to the data partition 904, so that a tape may be mounted with the metadata recorded in the data partition 904, for example, as a backup option.

[0085] According to one example, which is in no way intended to limit the invention, LTFS LE may be used to provide the ability to write an index to a data partition when explicitly instructed by the user to the system or at a time specified by a predefined period that may be set by the user, so as to mitigate data loss in the event of, for example, a sudden power outage.

[0086] Referring to FIG. 10 , an exemplary tape layout according to one embodiment is shown. As shown, a magnetic recording tape 1000 has a tape layout implementing five servo bands (servo band 0 through servo band 4) and four data bands (data band 0 through data band 3), as specified, for example, in the LTO and IBM® Enterprise formats. The height H of each timing-based servo (TBS) band is measured in a cross-track direction 1004, approximately perpendicular to the length L of the tape 1000. By way of example, the height H of each servo band may be approximately 186 microns in accordance with the LTO format. Furthermore, the pitch β between the servo bands shown in the figure may be approximately 2859 microns, also in accordance with the LTO format.

[0087] An exemplary tape head 1002 is also shown as including two modules and positioned over a portion of tape 1000, according to one approach. Read transducers, write transducers, or both, may be positioned in either module of tape head 1002 and may be used to read data from or write data to data bands, or both, according to any of the approaches described herein. Additionally, tape head 1002 may include a servo reader, which may be used to read servo patterns in the servo bands, according to any of the approaches described herein. It should also be noted that the dimensions of the various components included in FIG. 10 are provided by way of example only and are not intended to be limiting in any way.

[0088] Some tape drives may be configured to operate at low tape speeds, nanometer head positioning, or both. These tape drives use barium ferrite (BaFe) tape media, 4 or 8 data bands, and servo formats targeting 32 or 64 data channel operation to allow very low speed operation, support high-bandwidth actuator operation, and improve parameter estimation to minimize standard deviation of the position error signal (PES), thus enabling track density scaling for tape cartridge capacities of 100TB or more.

[0089] However, according to some approaches, magnetic tape may be further enhanced with features that provide additional functionality. Accordingly, HD servo patterns may be implemented along with standard TBS patterns. HD servo patterns may be used to improve track-following performance. Thus, a standard TBS servo pattern (e.g., as shown in FIG. 10) may be implemented in combination with one or more HD servo patterns. One implementation involves a servo pattern scheme in which the standard TBS patterns are retained and additional HD patterns are provided in dedicated, preferably currently unused, areas of the tape media. This type of pattern may be implemented, in some approaches, by increasing the number of data channels from 16 to 32 and reducing the width of the TBS pattern from 186 microns to 93 microns.

[0090] FIG. 11 shows a representation of a data band 1100 including a hybrid servo pattern 1110, which includes a TBS pattern 1102 written in a servo band of a tape medium 1108 and an HD pattern 1104 written in an HD band (e.g., a dedicated area). Furthermore, each HD pattern 1104 includes multiple HD tracks, each of which corresponds to a periodic waveform in a conventional manner. In some approaches, significant features of the TBS pattern 1102 are preserved, such as a servo frame structure including four servo bursts containing multiple servo stripes, with the servo stripes of adjacent servo bursts written at alternating azimuth angles. Other parameters of the conventional servo pattern, such as the height and other geometric dimensions of the servo pattern and the number of servo stripes per burst, may be varied as desired.

[0091] Detection of the periodic waveforms that form the HD pattern may be obtained by conventional HD servo detector circuits that implement complex algorithmic transforms (e.g., Discrete Fourier Transform (DFT), Fast Fourier Transform (FFT), etc.).

[0092] FIG. 12, with momentary reference to FIG. 5, illustrates a partial detailed view of a portion of a TBS pattern 1200 (e.g., a TBS frame of the TBS pattern shown in FIG. 10 or 11) according to an exemplary approach. As shown, multiple servo stripes 1202 together form a servo burst 1204, while corresponding pairs of servo bursts 1204 form a servo subframe. Thus, the illustrated TBS frame includes four servo bursts 1204 and two servo subframes. In this approach, the servo bursts 1204 included in the left servo subframe each include five servo stripes 1202, while the servo bursts 1204 included in the right servo subframe each include four servo stripes 1202. The servo stripes 1202 included in a particular servo burst 1204 are oriented to have the same azimuthal tilt, represented by angle α. Additionally, corresponding pairs of servo bursts 1204 have opposite azimuthal tilts, thereby forming a chevron pattern. The height H and thickness t of the servo stripes 1202 may vary depending on the servo writer used to write the TBS pattern. By way of example, and not intended to be limiting in any way, the height H may be approximately 186 μm, the angle α may be approximately 6°, and the thickness t may be approximately 2.1 μm. Furthermore, the spacing S between each of the servo stripes 1202 and / or the distance d between servo bursts 1204 having the same azimuthal tilt may vary depending on the desired approach. By way of example, and not intended to be limiting in any way, the spacing S may be approximately 5 μm and the distance d is approximately 100 μm. As previously mentioned, transitions such as the patterned transitions shown in FIG. 12 allow an estimate of the lateral position of the head to be determined by evaluating the relative timing of pulses generated by a servo reader reading servo stripe 1202 in servo burst 1204 as servo stripe 1202 passes over the servo reader.

[0093] Referring again to FIG. 11, the HD pattern 1104 may include periodic waveforms written on adjacent tracks. For example, two periodic waveforms characterized by two different spatial frequencies (a low frequency f1 and a high frequency f2), where f2>f1. However, a wider range of lateral head displacement is desirable. Therefore, to avoid ambiguity in determining the lateral displacement, different configurations of the HD pattern may be used.

[0094] FIG. 13 shows a graph 1300 plotting samples versus amplitude of the TBS pattern 1200 of FIG. 12 as detected as a servo read signal 1302 during read. A servo channel may decode a read signal received from a servo reader of a magnetic tape head reading the TBS pattern 1200. For example, as the servo stripe 1202 of the TBS pattern 1200 passes across the servo sensor, a double-pulse portion 1304 (comprising a positive peak and a negative peak) of the read signal 1302 is generated (e.g., for illustrative purposes, see the horizontal dashed line showing how the double-pulse portion of the read signal 1302 corresponds to the read position of the servo stripe). Thus, two or more of such double-pulse portions and their associated timing may be used in calculating a lateral position (y-position) estimate.

[0095] In one approach, the servo channel may provide a y position estimate to the track-following control system, for example, such a y position estimate may be calculated using Equation 1:

[0096]

number

[0097] As shown above, the lateral y-position estimate y in Equation 1 is a function of the distance d, the azimuthal tilt (angle α) of the servo stripes 1202, and the measured time B between pairs of corresponding servo stripes with the same azimuthal tilt (e.g., parallel stripes / / or \) from two different subframes. i , and the measured time A between corresponding pairs of servo stripes with opposite azimuthal tilts (e.g., stripes / \) from the same subframe. i may be incorporated.

[0098] For example, in the 5-5-4-4 pattern in Figure 13, for each servo subframe of TBS pattern 1200, A i Four measurements (i=0, 1, 2, 3) of B i Four measurements (i=0, 1, 2, 3) are performed. In some techniques, the distance d is sometimes called the "subframe length."

[0099] Conventional servo detectors, with appropriate modifications as necessary, may be used to process servo signals according to any of the techniques described herein. Figure 14 shows a block diagram of a servo detector 1400 configured for calculating a PES from a TBS pattern. A servo signal detector 1404 is used to detect a servo signal from a servo reader 1402. The output of the detector 1404 is then processed by a PES calculation unit 1410, which determines a PES estimate in a conventional manner, for example, based on timing information from the servo signal.

[0100] As previously mentioned, the amount of data stored on magnetic tape can be expanded by increasing the number of data tracks across the tape. More tracks are possible by reducing the geometry of the reader and writer, such as by using thin-film fabrication techniques and magnetoresistive (MR) sensors. However, for various reasons, reader and writer geometries cannot be made arbitrarily small. Factors such as tape distortion and the lateral expansion and contraction of the tape must be addressed to provide an acceptable read signal.

[0101] Regarding tape skew, by way of example, Figures 15A-15D illustrate the effect of tape skew on the position of the leader relative to the position of the leader. Figure 15A shows head 1500 relative to tape 1502, with the tape having a nominal width and oriented approximately parallel to the intended direction of tape travel 1501. As shown, leader 1504 is aligned with data tracks 1506 on tape 1502. However, Figure 15B illustrates the effect of skew. When tape 1502 is skewed, tape 1502 moves from an orientation approximately parallel to the intended direction of tape travel 1501 (e.g., as shown in Figure 15A) to an angle θ that is skewed relative to the intended direction of tape travel 1501. skew As shown, here, the leader 1504 is positioned along the boundary between the data tracks 1506. Depending on the degree and / or direction of the distortion, the degree of misalignment between the leader and its corresponding data track may vary. Furthermore, it should be noted that the exaggerated degree of distortion in the tape shown in FIG. 15B is presented merely as an example.

[0102] In various approaches, tape distortion may be compensated for by laterally moving the array of transducers and / or tilting the array of transducers relative to the longitudinal axis of the array, thereby selectively changing the position of the transducers within the array relative to the tape. Such tilting is preferably performed by rotating the array, although pivoting may also be employed in some approaches.

[0103] In one approach to compensating for tape distortion, the head may be moved perpendicular to the intended direction of tape travel to realign the transducer with the distorted data track. Smaller adjustments may be made so that the project reader span remains aligned with the track on the tape. Referring momentarily to Figure 15C, head 1500 is moved (e.g., shifted) perpendicular to the intended direction of tape travel 1501 to realign reader 1504 with the distorted data track 1506.

[0104] In another approach to compensating for tape distortion, the head may be tilted to position the longitudinal axis of the transducer array approximately perpendicular to the actual tape motion direction 1503 in order to realign the transducers with the distorted data tracks. Smaller adjustments may be made so that the reader projection field remains aligned with the tape tracks. Referring momentarily to Figure 15D, the head 1500 is moved (e.g., tilted) perpendicular to the actual tape motion direction 1503 in order to realign the reader 1504 with the distorted data tracks 1506.

[0105] This process of shifting and / or tilting the head to realign the transducers with the distorted data track is effective when only one module (one row of elements) is used. However, magnetic tape systems typically contain two or more modules, each containing one row of transducers, and the additional row of transducers allows for read verification during the write process. One difficulty in implementing this method with heads containing multiple arrays, such as those shown in Figures 2, 2C, and 3-7, is that while one array of transducers may be properly aligned with the track, other arrays of transducers may not. Conventional products containing two or more modules employ a bonding process to secure the modules relative to one another. Currently, this bonding process creates a single movable subassembly that is typically attached to a track-following actuator, typically driven by a voice coil system. In other words, if the lateral orientation of two or more modules that are fixed relative to one another is changed, the other rows of elements also move, making it impossible to keep all elements on track.

[0106] Figures 16A-16C illustrate the effect of TDS (i.e., lateral expansion and contraction of the tape) on the position of the leader relative to the tape. Figure 16A shows the head 1600 relative to the tape 1602, which has a nominal width. As shown, the leaders 1604 are aligned with the data tracks 1606 on the tape 1602. Figure 16B illustrates the effect of lateral contraction of the tape. As shown, the outermost leaders 1608 are positioned along the outer edges of the outer data tracks. Figure 16C illustrates the effect of lateral expansion of the tape. As shown, the outermost leaders 1608 are positioned along the inner edges of the outer data tracks. Because all of the leaders 1604 have the same width, the read signal level from each reader will generally be the same.

[0107] Various embodiments of the present invention, described below, enable compensation for both skew and TDS variations. In one embodiment, the device includes a head assembly incorporating a skew detector portion and an actuation mechanism that allows adjustment for tape skew following, track following, and TDS compensation. In some approaches, the actuation mechanism includes multiple actuators, e.g., one actuator for skew following and a second actuator for track following and TDS compensation. This new device solves the aforementioned problems by enabling more accurate track placement regardless of tape skew or TDS, thus enabling higher track densities and increased cartridge capacity. In some approaches, a new servo skew pattern is used in conjunction with the skew detector portion. In other approaches, the skew detector portion functions using a conventional TBS pattern.

[0108] 17A-17C illustrate the concept of detecting vertical stripes in a novel servo distortion pattern using a distortion-detecting transducer for distortion tracking with reference to system 1700. Optionally, this system 1700 may be implemented with features from any other approach shown herein, such as features described with reference to other figures, such as FIG. 1A. However, such system 1700 and other systems presented herein may be used in a variety of applications and / or permutations that may or may not be specifically described in the exemplary approach shown herein. Furthermore, system 1700 presented herein may be used in any desired environment. Accordingly, FIGS. 17A-17C (and other figures) may be considered to include any possible permutations.

[0109] As shown, skew detection transducers 1702 are positioned over the servo skew pattern on the magnetic recording tape 1703. These skew detection transducers 1702 may be positioned adjacent to the same data band on the tape, but can also be spaced apart across multiple data bands for enhanced skew detection. An array of two skew detection transducers 1702 is shown. Additionally, some approaches may include more than two skew detection transducers 1702, such as one skew detection transducer 1702 per servo band, one skew detection transducer 1702 for placement on every other servo band, or any configuration.

[0110] Each servo skew pattern includes vertical stripes 1704 along the servo skew pattern, where vertical in FIGS. 17A-17C refers to a perpendicular to the longitudinal axis of the tape 1703 extending between the distal ends of the tape. The vertical stripes 1704 are preferably disposed along the entire length of the tape 1703, but may be present on one or more portions of the tape 1703. The vertical orientation of the vertical stripes ensures that the vertical stripes are virtually immune to head expansion and differences in transducer pitch between heads, in addition to the effects of lateral expansion or contraction of the tape. Therefore, the distance between the skew-detecting transducers 1702 is not critical (due to the timing-based servo placement).

[0111] The width of the distortion detection transducer 1702 is preferably wider than the width of the TBS servo transducers in the device. The TBS servo transducers are typically as narrow as possible to improve accuracy when reading the diagonal stripes of the chevron pattern. Vertical stripes offer the advantage that the dedicated distortion detection transducer can be wider because the angle between the vertical stripe and the longitudinal axis of the distortion detection transducer is 0 degrees. The use of wider transducers improves the signal-to-noise ratio (SNR), thereby improving detection. However, in various approaches, the distortion detection transducer may have a width similar to that of the TBS servo transducer.

[0112] In FIG. 17A, the tape is not skewed and the longitudinal axis of the array of skew-detecting transducers 1702 is oriented perpendicular to the direction of actual tape movement 1706 across it.

[0113] In Figure 17B, the longitudinal axis of the tape is skewed by a σt range of more than or less than 90° from the longitudinal axis of the array of skew detection transducers 1702. The skew detector portion of system 1700 detects the skew based on the readout signals from the skew detection transducers 1702. In this case, assuming the tape 1703 is moving from right to left, the lower skew detection transducer 1702 detects the lower fringe 1704 before the upper skew detection transducer 1702 detects the upper fringe. Using known techniques, correction factors such as the angle of skew can be calculated from the delay between detections and any other relevant factors such as tape speed.

[0114] 17C, the calculated correction factor is then used to orient the longitudinal axis of the array of skew-detecting transducers 1702 substantially perpendicular (σt≈90°) to the direction of actual tape movement across the array of skew-detecting transducers. While the array of skew-detecting transducers 1702 may pivot about any desired axis of rotation 1710, a preferred axis of rotation 1710 is one positioned to minimize associated translation along the longitudinal axis 1814 of the array of skew-detecting transducers 1702.

[0115] FIG. 18 illustrates an apparatus 1800 according to one approach. Optionally, this apparatus 1800 may be implemented with features from any other approach shown herein, such as features described with reference to other figures, such as FIG. 1A . However, such apparatus 1800 and other apparatuses presented herein may be used in a variety of applications and / or permutations that may or may not be specifically described in the exemplary approaches shown herein. Furthermore, the apparatus 1800 presented herein may be used in any desired environment. Thus, FIG. 18 (and other figures) may be considered to include any possible permutations.

[0116] The apparatus 1800 includes an array of skew-detecting transducers 1702, such as the array described above with reference to Figures 17A-17C. Referring to Figures 17A-18, the array of skew-detecting transducers 1702 may, in use, have a longitudinal axis nominally oriented at a predefined angle relative to the intended direction of tape movement across the array of skew-detecting transducers 1702. The predefined angle preferably results in the longitudinal axis being maintained substantially perpendicular to the actual direction of tape movement across the longitudinal axis, as shown in Figures 17A-17C. Because the orientation of the array of skew-detecting transducers is parallel to the direction of lateral expansion or contraction of the tape, this orientation results in virtually no misalignment or deformation as a result of lateral expansion or contraction of the tape. Furthermore, this orientation makes the array of skew-detecting transducers insensitive to variations in pitch between skew-detecting transducers.

[0117] 18, the distortion detection converter 1702 resides in a module 1802 that is separate from the data converter module 1804. However, the distortion detection converter 1702 may reside in the same module as the data converter.

[0118] The number of skew detection transducers 1702 on module 1802 can be as few as two and as many as more than the number of servo bands on the tape for which device 1800 is designed. For example, if there are two skew detection transducers 1702, the skew detection transducers 1702 may be positioned to flank a single data band. However, it is more preferable for the skew detection transducers 1702 to be distributed farther apart than one data band so that the effects of tape skew presented to the skew detection transducers 1702 are more noticeable.

[0119] In a particularly preferred approach, three or more skew detection transducers 1702 are present in module 1802. In one approach, the number of skew detection transducers 1702 is equal to the number of servo bands on the tape for which device 1800 is designed. In a preferred approach, the number of skew detection transducers 1702 is sufficient to ensure that at least two of the skew detection transducers 1702 are located on the outermost servo bands, regardless of the data band in which the data transducers are located. FIG. 19 illustrates such an approach, in which elements common to the systems of FIGS. 17-18 share common numbers. As shown in FIG. 19, tape 1703 includes five servo bands 1902, each containing a servo track readable by a skew detection transducer 1702. Module 1802 includes eight skew detection transducers 1702. As shown by the shaded module 1802, the module 1802 is indexed across the tape to position the data transducers (not shown) over the data bands so that the skew detection transducer 1702 is always positioned over at least the outermost servo band 1902; in the example shown, the skew detection transducer 1702 is positioned over every servo band 1902 after each translation of the module 1802.

[0120] The data transducers may include read transducers, write transducers, or both, in any combination. As shown in FIG. 18 , the data transducers are on three modules 1804. In other approaches, data transducers may be present in one, two, four, etc. modules 1804. As background, assume that each outer data transducer module 1804 includes an array of write transducers 1806, and that the array of read transducers 1808 of the central data converter module 1804 is aligned with the array of write transducers 1806 in the intended direction of tape movement 1810 therebetween. Thus, the data transducers 1806, 1808 are spaced apart from the array of skew-detecting transducers along the intended direction of tape movement 1810. Note that the array of skew-detecting transducers 1702 may be positioned on any side of the array of data transducers. Furthermore, there may be more than one array of skew-detecting transducers 1702, for example, for each use when the tape moves in opposite directions. In the approach shown, the array of skew-detecting transducers 1702 is, in use, oriented nominally substantially perpendicular to the intended direction of tape movement across the array of skew-detecting transducers 1702 .

[0121] The first actuator 1812 is configured to operatively apply a force to the array of skew-detecting transducers 1702 to orient the longitudinal axis 1814 of the array of skew-detecting transducers 1702 substantially perpendicular to the direction of actual tape movement across the array of skew-detecting transducers 1702, thereby compensating for tape skew. The array of skew-detecting transducers 1702 may pivot about any desired axis of rotation 1710, but a preferred axis of rotation 1710 is one that is aligned with the longitudinal axis 1814 of the array of skew-detecting transducers 1702.

[0122] FIG. 20 illustrates an approach in which the longitudinal axes of the read and write transducer arrays 1806, 1808 shown in FIG. 18 are not pivotable relative to the longitudinal axis of the array of skew-detecting transducers 1702. For example, the modules 1802, 1804 may be glued together. Thus, a first actuator 1812 is configured to move the first module and at least one second module together. Note that the first actuator may include a mechanism for track following, or a track-following actuator may be present to adjust the lateral position of the data array, based on, for example, a TBS servo pattern configured to enable such alignment. As shown in FIG. 20, upon detection of tape skew, the first actuator rotates the array to follow the tape skew.

[0123] In a preferred approach, one or more, and preferably all, of the data converter modules 1804 are movable relative to the module 1802 containing the skew-detecting transducer 1702. Referring to FIG. 21, which shares common element numbers with FIG. 18, a first actuator 1812 is configured to move the modules 1802, 1804 together for skew tracking. A second actuator 2102 is configured to apply a force to one or more of the data converter modules 1804 to cause relative movement of the data converter modules 1804 with respect to the module 1802 in response to a determined state of lateral tape expansion, thereby adjusting the tilt angle of the data converter modules 1804 relative to the longitudinal axis of the array of skew-detecting transducers. The second actuator 2102 may position the data converter modules 1804 for track following using a TBS servo pattern.

[0124] Figure 21 shows an exemplary relative orientation of the components shown when the tape is not distorted and when the tape is neither expanded nor contracted. Figure 22 shows an exemplary relative orientation of the components shown in Figure 21 when the tape is not distorted but when the tape is contracted. Figure 23 shows an exemplary relative orientation of the components shown in Figure 21 when the tape is distorted and when the tape is expanded.

[0125] It is noted that the state of lateral expansion of the tape generally refers to the state of expansion or contraction of the tape. For example, the state of lateral expansion may be measured, for example, by a servo track following system using conventional techniques. Such measurements may be referenced to some nominal state, such as the state of the tape when the track being read was written, a state specified in a standard, or the like. Other types of alignment, such as track following, may be provided by either actuator. For example, a second actuator may be configured to provide track following to module 1804.

[0126] It is also noted that the actuators 1812, 2102 described herein may be of conventional design. For example, one or both actuators may include a piezoelectric actuator, a worm screw actuator, or the like. Additionally, either of the actuators 1812, 2102 may provide two or more types of actuation (e.g., skew following, lateral positioning for track following, or tilt for TDS correction, or a combination thereof). The separation of actuation functions provides a significant improvement over currently known solutions, particularly the integration of skew compensation and TDS compensation.

[0127] The array of distortion detection transducers 1702 may pivot about any desired axis of rotation 1710, although a preferred axis of rotation 1710 is along the longitudinal axis 1814 of the array of distortion detection transducers 1702. Similarly, the data converter module 1804 may pivot about any desired axis of rotation 2104, although a preferred axis of rotation 2104 is one that is centrally located relative to the data converter.

[0128] In a preferred approach, as shown in Figures 21-22, the longitudinal axes of the read and write transducer arrays 1806, 1808 are nominally tilted at greater than 0° from the longitudinal axis of the array of distortion detection transducers 1702. However, in another approach, as shown in Figures 18 and 20, the longitudinal axes of the read and write transducer arrays 1806, 1808 are parallel to the longitudinal axis of the array of distortion detection transducers 1702.

[0129] 1A, which may be used in combination with any or all of the features of FIGS. 18 and 21-22, a controller 128 is preferably coupled to the skew detection transducer 1702 and the actuators 1812, 2102 (the actuators shown collectively as 132 in FIG. 1A). In one approach, the controller 128 is configured to control the first actuator 1812 to compensate for tape skew and the second actuator 2102 to compensate for TDS, if present, based on a read signal from the skew detection transducer.

[0130] The controller may be configured to control operation of the read and write transducer arrays for track following based on read signals from the servo readers in a conventional manner. Thus, conventional servo readers may flank the write transducer array and / or the read transducer array to read conventional servo tracks (e.g., TBS servo tracks and / or HD servo tracks).

[0131] FIG. 24 illustrates an apparatus 2400 according to one approach. Optionally, this apparatus 2400 may be implemented with features from any other approach shown herein, such as features described with reference to other figures, such as FIG. 1A . However, such apparatus 2400 and other apparatuses presented herein may be used in a variety of applications and / or permutations that may or may not be specifically described in the exemplary approaches shown herein. Furthermore, the apparatus 2400 presented herein may be used in any desired environment. Thus, FIG. 24 (and other figures) may be considered to include any possible permutations.

[0132] The apparatus 2400 includes an array of skew detection transducers 1702, such as the array described above with reference to FIGS. 17A-17C, but the skew detection transducers 1702 are present in one or more of the data modules. Thus, there is no separate module for skew detection. Referring to FIG. 24, the array of skew detection transducers 1702 may be aligned along the longitudinal axis of the module 1804 and / or the data transducers 2402. The number of skew detection transducers 1702 is preferably such that at least two of the skew detection transducers 1702 are positioned on the outermost servo band, regardless of the data band in which the data transducers are positioned, for example, in a manner similar to that of FIG. 19.

[0133] Referring again to Figure 18, the distortion detection converter 1702 resides in a module 1802 that is separate from the data converter module 1804. However, the distortion detection converter 1702 resides in the same module as the data converter.

[0134] The number of skew detection transducers 1702 on module 1802 can be as few as two and as many as more than the number of servo bands on the tape for which device 1800 is designed. For example, if there are two skew detection transducers 1702, the skew detection transducers 1702 may be positioned to flank a single data band. However, it is more preferable for the skew detection transducers 1702 to be distributed farther apart than one data band so that the effects of tape skew presented to the skew detection transducers 1702 are more noticeable.

[0135] When the distortion detection transducer 1702 is used to read the vertical stripes 1704 (FIG. 17A), the controller may be configured to calculate a distortion correction value based on a readout signal from the distortion detection transducer reading the vertical stripes.

[0136] The vertical stripes may be present in any desired configuration on the magnetic recording tape, for example, within any desired servo track, and within any number of vertical stripes (e.g., two, three, four, or more vertical stripes) of frames. In some approaches, vertical stripes are present within a TBS pattern, for example, between each frame of a chevron pattern (or equivalently, an N-pattern, a W-pattern, etc.), between a selected number of frames of a chevron pattern (e.g., between groups of three frames, groups of five frames, etc.), etc.

[0137] In a preferred approach, vertical stripes for distortion detection are located above and / or below the TBS pattern.

[0138] Figure 25A shows a writer 2500 for writing an inventive servo distortion pattern according to one embodiment of the present invention. Figure 25B shows a frame of an inventive servo distortion pattern 2502 written using writer 2500. As shown, vertical stripes 1704 are present on top of a TBS servo pattern 2503 that includes chevrons 2504. In this case, a distortion detection transducer can be aligned with the track of vertical stripes 1704, while a TBS servo transducer, e.g., in a data module, can be aligned with chevrons 2504 for track following.

[0139] Figure 25C shows another example of a writer 2550 for writing an inventive servo skew pattern, according to one embodiment of the present invention. Figure 25D shows a frame of an inventive servo skew pattern 2552, according to one embodiment of the present invention. As shown, vertical stripes 1704 are present on top of a timing-based servo pattern 2553 that includes chevrons 2504. In this case, the skew detection transducer can be aligned with the track of the vertical stripes 1704, while a TBS servo transducer, e.g., of a data module, can be aligned with the chevrons 2504 for track following.

[0140] FIG. 25E illustrates another example of a writer 2570 for writing an inventive servo skew pattern, according to one embodiment of the present invention. In this case, the writing portion that writes the vertical stripes is independently addressable from the portion that writes the TBS pattern. FIG. 25F illustrates a frame of an inventive servo skew pattern 2572, according to one embodiment of the present invention. As shown, the vertical stripes 1704 reside above a timing-based servo pattern 2573 that includes chevrons 2504. In this case, the skew detection transducer can be aligned with the track of the vertical stripes 1704, while the TBS servo transducer, e.g., of a data module, can be aligned with the chevrons 2504 for track following.

[0141] In other embodiments, the vertical stripes 1704 are shorter to minimize the space on the tape required for the vertical stripes 1704. The layout of the vertical stripes can have any desired configuration, such as, for example, any of the arrangements shown in Figures 25B, 25D, and 25F. Figure 26 shows an example approach that is a variation of the pattern 2502 of Figure 25F. In the servo skew pattern 2602 of Figure 26, the vertical stripes 1704 are shorter to minimize the space on the tape required for the vertical stripes 1704. To ensure that the skew detection transducers are always over the shorter vertical stripes 1704, the skew module may include sets of skew detection transducers, with the pitch between the skew detection transducers in each set being shorter than the length of the vertical stripes 1704.

[0142] FIG. 27 shows yet another variation 2702 in which the diagonal stripes making up the chevron pattern are angled for reading by the TBS servo transducer of a tilted data module.

[0143] In a further approach, the vertical stripes may be present within a known servo pattern that includes vertical stripes, thereby qualifying such a pattern as a servo distortion pattern. Accordingly, various aspects of the present invention may function successfully with existing tape media. As shown in FIG. 28, the vertical stripes 1704 are present within a timing-based servo pattern 2802 that includes chevrons 2504 and vertical stripes 1704. FIG. 29 illustrates another example 2902 that includes sets of five and four vertical stripes 1704 and chevrons 2504. FIG. 30 illustrates another example 3002 that includes a single set of vertical stripes 1704 along with frames of five and four chevrons 2504. The output of the distortion-detecting transducer corresponding to the vertical stripes can be used for distortion correction.

[0144] Note that in various approaches, other embedded information may be present in the servo distortion pattern, such as linear position (LPOS) dithering. Additionally, in one approach, the device is configured to use information about vertical stripes only for distortion correction.

[0145] In yet another approach, the controller is configured to calculate skew correction values ​​based on read signals from skew detection transducers reading the chevrons of the timing-based servo pattern. The servo pattern may or may not include vertical stripes. In such an approach, a calculation may be performed to essentially identify a position corresponding to the midpoint (or other calculable point) between associated stripes of the upper and lower chevron patterns. Conceptually, an imaginary line may be generated between these two positions. This imaginary line may be perpendicular to the actual tape movement direction across this line, and a first actuator is used to align the longitudinal axis of the array of skew detection transducers with this imaginary line.

[0146] In a further approach, two or more arrays of skew detection transducers may be present in a non-tilt module, and more precisely, signals from the skew detection transducers are used to determine the tape skew and to tilt the array of data transducers to correct for the tape skew.

[0147] Thus, various embodiments of the present invention have been described that can compensate for changes in TDS in addition to overcoming the effects of tape distortion relative to the magnetic head by introducing improved methods of generating fine movements (e.g., micro-motion) to control the orientation of a module relative to the tape and / or one or more other modules within the magnetic head.

[0148] In use, a device according to any of the techniques described herein performs the functions presumed by the foregoing description.

[0149] Referring now to Figure 31, there is shown a flowchart of a method 3100, according to one approach. Method 3100 may be performed in accordance with the present invention in a variety of ways, particularly in any of the environments shown in Figures 1A-30. Of course, as one skilled in the art will understand upon reading this description, method 3100 may include more or fewer operations than those specifically illustrated in Figure 31.

[0150] Each of the steps of method 3100 may be performed by any suitable component of an operating environment using known techniques and / or techniques that will be readily apparent to one of ordinary skill in the art upon reading this disclosure. For example, in various approaches, method 3100 may be performed, in part or in whole, by any of the apparatuses described herein or other devices including one or more processors. A processor (e.g., a processing circuit, chip, or module, or a combination thereof) implemented in hardware and / or software and preferably including at least one hardware component may be utilized within any device to perform one or more steps of method 3100. Examples of processors include, but are not limited to, a central processing unit (CPU), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like, combinations thereof, or any other suitable computing device known in the art.

[0151] As shown in FIG. 31 , method 3100 includes operation 3102, in which a read signal from a dedicated skew detection transducer is processed to determine the skew of the tape relative to the skew detection transducer. In operation 3104, a skew correction signal is created based on the read signal from the dedicated skew detection transducer, and in operation 3106, is provided to an actuator that is effective to provide skew correction. Optional operation 3108 determines the expansion and / or contraction state relative to the TDS of the tape using known techniques, such as by reading TBS data from two different servo bands and calculating the degree of expansion or contraction. For example, using chevron-based TBS data, if the tape is perfect, the two servo signals should be virtually identical at a particular lateral position. If the tape has contracted or expanded, the servo signals will be different, and this difference can be used to determine the degree of contraction or expansion using known techniques. In operations 3110 and 3112, based on the determined expansion and / or contraction state associated with the TDS of the tape, a TDS correction signal is generated and provided to an actuator, preferably a second actuator, that is effective to provide TDS correction to one or more modules containing data transducers. Method 3100 may be performed during read and write operations. Additionally, other conventional processes, such as track following, read-while-write, etc., may be performed.

[0152] The present invention may be a system, method, or computer program product, or any combination thereof, at any possible level of technical detail of integration. The computer program product may include a computer-readable storage medium containing computer-readable program instructions for causing a processor to perform aspects of the present invention.

[0153] A computer-readable storage medium may be a tangible device that can hold and store instructions for use by an instruction execution device, such as, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. A non-exhaustive list of more specific examples of computer-readable storage media includes portable floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital versatile disk (DVD), memory sticks, floppy disks, mechanically encoded devices such as punch cards or ridge structures in grooves on which instructions are recorded, and any suitable combination thereof. As used herein, computer-readable storage media should not be construed as being ephemeral signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., light pulses passing through fiber optic cable), or electrical signals transmitted over wires.

[0154] The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to each computing / processing device or to an external computer or storage device over a network (e.g., the Internet, a local area network, a wide area network, or a wireless network, or a combination thereof) that may include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, or edge servers, or a combination thereof. A network adapter card or network interface within each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage on a computer-readable storage medium within each computing / processing device.

[0155] Computer-readable program instructions for carrying out the operations of the present invention may be source or object code written in any combination of one or more programming languages, including assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuits, or object-oriented programming languages ​​such as Smalltalk®, C++, and procedural programming languages ​​such as the "C" programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer as a standalone software package, partially on the user's computer and on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be to an external computer (e.g., via the Internet using an Internet Service Provider). In some embodiments, to carry out aspects of the present invention, electronic circuitry including, for example, programmable logic circuits, field programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), may execute computer-readable program instructions to customize the electronic circuitry by utilizing state information of the computer-readable program instructions.

[0156] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0157] These computer-readable program instructions may be provided to a processor of a computer or other programmable data processing apparatus to create a machine, such that the instructions, executed by the processor of the computer or other programmable data processing apparatus, create means for performing the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams. These computer-readable program instructions may be stored on a computer-readable storage medium and capable of directing a computer, programmable data processing apparatus, or other device, or combination thereof, to function in a particular manner, such that the computer-readable storage medium on which the instructions are stored comprises an article of manufacture containing instructions for performing aspects of the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams.

[0158] Computer-readable program instructions may be loaded into a computer, other programmable data processing apparatus, or other device such that the instructions, which execute on the computer, other programmable apparatus, or other device, perform the functions / acts specified in one or more blocks of the flowcharts and / or block diagrams, thereby causing a series of operable steps to be performed on the computer, other programmable apparatus, or other device to produce a computer-implemented process.

[0159] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of instructions, comprising one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions shown in the blocks may occur out of the order shown in the figures. For example, two blocks shown in succession may actually be executed concurrently as a single step, or may be executed substantially concurrently in a manner that partially or completely overlaps in time, or may even be executed in the reverse order, depending on the functionality involved.

[0160] It is also noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks included in the block diagrams and / or flowchart illustrations, can be implemented by special-purpose hardware-based systems that perform the specified functions or operations or execute a combination of special-purpose hardware and computer instructions.

[0161] Furthermore, systems according to various embodiments may include a processor and logic integrated into and / or executable by the processor, the logic configured to perform one or more of the processing steps enumerated herein. The processor may be any configuration as described herein, such as a discrete processor or processing circuit, including many components, such as processing hardware, memory, and I / O interfaces. By integrated, we mean that the logic is embedded in the processor as hardware logic, such as an application-specific integrated circuit (ASIC), FPGA, etc. By executable by the processor, we mean that the logic is hardware logic accessible by the processor, software logic (such as firmware, part of an operating system, part of an application program, etc.), or some combination of hardware and software logic, configured to cause the processor to perform some function when executed by the processor. The software logic may be stored in any memory type known in the art, local and / or remote memory. Any processor known in the art may be used, such as a software processor module or a hardware processor, or both, such as an ASIC, an FPGA, a central processing unit (CPU), an integrated circuit (IC), a graphics processing unit (GPU), etc.

[0162] It will be apparent from the description provided above that multiple combinations may be made and the various features of the systems and / or methods described above may be combined in any manner.

[0163] It will further be appreciated that embodiments of the present invention may be provided in the form of a service that is deployed for customers.

[0164] The inventive concepts disclosed herein are presented by way of example in multiple exemplary contexts, embodiments, or implementations, or combinations thereof, to illustrate their myriad features. Generally, it should be understood that the disclosed concepts should be considered modular and may be implemented in any combination, permutation, or integration thereof. Additionally, any modifications, variations, or equivalents of the features, functions, and concepts disclosed herein, as would be understood by a person skilled in the art upon reading this description, should also be considered within the scope of the present disclosure.

[0165] While various embodiments have been described above, it should be understood that these embodiments are presented by way of example only, and not limitation. Thus, the breadth and scope of embodiments of the present invention should not be limited by any of the above-described example embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. an array of distortion detection transducers; an array of write transducers spaced apart from said array of skew-detecting transducers along the intended direction of tape movement across said array of skew-detecting transducers; an array of read transducers aligned with the array of write transducers in the intended direction of tape movement; a first actuator configured to operatively apply a force to the array of skew-sensing transducers to orient a longitudinal axis of the array of skew-sensing transducers substantially perpendicular to a direction of actual tape movement across the array of skew-sensing transducers; a controller configured to calculate a skew correction value based on a read signal from the skew detection transducer, and to control the first actuator with the skew correction signal to compensate for tape skew; the skew detection transducers detect skew, which is tilt with respect to the direction of tape movement, without being affected by misalignment caused by lateral expansion and contraction of the tape, and the array of skew detection transducers, the array of write transducers, and the array of read transducers are on a first module; Device.

2. 2. The apparatus of claim 1, wherein a longitudinal axis of the array of read and write transducers is not pivotable from its orientation relative to the longitudinal axis of the array of distortion-sensing transducers, and the first actuator is configured to move the first module and at least one second module together.

3. 10. The apparatus of claim 1, wherein the array of distortion-sensing transducers is on a first module and the array of read and write transducers is on at least one second module.

4. the at least one second module is movable relative to the first module, and the first actuator is configured to move the first module and the at least one second module together; 4. The apparatus of claim 3, further comprising: a second actuator configured to apply a force to the at least one second module to cause relative movement of the at least one second module with respect to the first module in response to the determined state of lateral expansion of the tape and to adjust a tilt angle of the at least one second module.

5. 2. The apparatus of claim 1, wherein the longitudinal axes of the array of read and write transducers are nominally tilted greater than 0 degrees from the longitudinal axis of the array of distortion-sensing transducers.

6. 2. The apparatus of claim 1, further comprising a controller configured to control the first actuator based on a read signal from the skew detection transducer to compensate for tape skew.

7. a servo reader flanking the array of write transducers; a servo reader flanking the array of read transducers; and a controller configured to control operation of the array of read and write transducers for track following based on a read signal from the servo reader.

8. a magnetic head including the array of claim 6; a drive mechanism for passing a magnetic tape over the magnetic head; and the controller.

9. 7. The apparatus of claim 6, wherein the controller is configured to calculate a skew correction value based on the read signal from the skew detection transducer reading the vertical stripes of a timing-based servo pattern including chevrons and vertical stripes.

10. 7. The apparatus of claim 6, wherein the controller is configured to calculate a skew correction value based on the read signal from the skew detection transducer reading chevrons of a timing-based servo pattern.

11. a first module including an array of distortion-sensing transducers; an array of write transducers spaced apart from said array of skew-detecting transducers along the intended direction of tape movement across said array of skew-detecting transducers; an array of read transducers aligned with the array of write transducers in the intended direction of tape movement, the array of read transducers and write transducers being on at least one second module, the at least one second module being movable relative to the first module; a first actuator configured to move the first module and the at least one second module together; a second actuator configured to, in response to the determined state of lateral expansion of the tape, apply a force to the at least one second module to cause relative movement of the at least one second module with respect to the first module and adjust a tilt angle of the at least one second module; a first actuator configured to operatively apply a force to the first module to orient a longitudinal axis of the array of skew-sensing transducers substantially perpendicular to a direction of actual tape movement across the array of skew-sensing transducers; The skew detection transducer detects skew, which is tilt relative to the direction of tape movement, without being affected by misalignment caused by lateral expansion and contraction of the tape.

12. 12. The apparatus of claim 11, wherein the longitudinal axes of the array of read and write transducers are nominally tilted greater than 0 degrees from the longitudinal axis of the array of distortion-sensing transducers.

13. 12. The apparatus of claim 11, further comprising a controller configured to control the first actuator based on a read signal from the skew detection transducer to compensate for tape skew.

14. 14. The apparatus of claim 13, wherein the controller is configured to calculate a skew correction value based on the read signal from the skew detection transducer reading the vertical stripes of a timing-based servo pattern including chevrons and vertical stripes.

15. 14. The apparatus of claim 13, wherein the controller is configured to calculate a skew correction value based on the read signal from the skew detection transducer reading chevrons of a timing-based servo pattern.

16. a first module including an array of distortion-sensing transducers; an array of write transducers spaced apart from said array of skew-detecting transducers along the intended direction of tape movement across said array of skew-detecting transducers; an array of read transducers aligned with the array of write transducers in the intended direction of tape movement, the array of read transducers and the array of write transducers being on at least one second module; and a first actuator configured to operatively apply a force to the array of skew-sensing transducers to maintain an orientation of a longitudinal axis of the array of skew-sensing transducers substantially perpendicular to a direction of tape movement; a controller configured to calculate a skew correction value based on a read signal from the skew detection transducer, and to control the first actuator with the skew correction signal to compensate for tape skew; a longitudinal axis of the array of read and write transducers is not pivotable from its orientation relative to the longitudinal axis of the array of distortion-sensing transducers, and the first actuator is configured to move the first module and the at least one second module together; the skew detection transducer detects skew, which is tilt with respect to the direction of tape movement, without being affected by misalignment caused by lateral expansion and contraction of the tape; Device.

17. 17. The apparatus of claim 16, wherein a longitudinal axis of the array of read and write transducers is parallel to the longitudinal axis of the array of distortion-sensing transducers.

18. 18. The apparatus of claim 17, further comprising a controller configured to control the first actuator based on a read signal from the skew detection transducer to compensate for tape skew.

19. a servo reader flanking the array of write transducers; a servo reader flanking the array of read transducers; 20. The apparatus of claim 17, further comprising: a controller configured to control operation of the array of read and write transducers for track following based on a read signal from the servo reader.

20. 20. The apparatus of claim 19, wherein the controller is configured to calculate a skew correction value based on the read signal from the skew detection transducer reading the vertical stripes of a timing-based servo pattern including chevrons and vertical stripes.

21. 20. The apparatus of claim 19, wherein the controller is configured to calculate a skew correction value based on the read signal from the skew detection transducer reading chevrons of a timing-based servo pattern.

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