200.

The tape 204 comprises a first servo track 210A and a second servo track 210B. The first servo track 210A and the second servo track 210B are spaced apart allowing the tape head 200 to monitor and control the average position of the data heads 208A-208G relative to the data tracks 212A-212G on the tape 204. It is to be understood that while two servo tracks have been shown, the disclosure is not limited to two servo tracks. Rather, the number of servo tracks can be more or less than two, depending on the requirements of the embodiment.

The tape 204 further comprises a plurality of data tracks 212A-212G disposed between the first servo track 210A and the second servo track 210B. It is to be understood that while seven data tracks have been shown, the disclosure is not limited to the seven data tracks. Rather, the number of data tracks can be more or less than seven, depending on the requirements of the embodiment. In the embodiment of FIG. 2, the first servo element pair 206A reads its lateral position information (e.g., alignment) over the first servo track 210A. The second servo element pair 206B is aligned with the second servo track 210B. The combined information allows the servo actuator of the tape drive 200 to align the data heads 208A-208G such that the center data head (e.g., 208D) is centered on tape 204. The plurality of data heads 208A-208G is thus individually aligned with the plurality of data tracks 212A-212N for best case positioning. In this embodiment the first servo element pair 206A, the second servo element pair 206B, the first servo track 210A, the second servo track 210B, the plurality of data heads 208A-208G, and the plurality of data tracks 212A-212G are able to read and/or write the data accurately because all are aligned perpendicular to the direction of travel of the tape 204.

FIGS. 3A-3B illustrate methods 300, 350 for correcting dynamic lateral tape motion (LTM) in a tape drive, according to embodiments disclosed herein. The methods 300, 350 may be utilized with the tape drive 100 of FIGS. 1A-1C, such as being executed by the controller 140. The methods 300 and 350 may be used in combination with one another.

Method 300 begins at operation 302, where, prior to performing write and read operations, a reel rotation per minute (RPM) disturbance profile identification is performed, where one or more disturbances are detected along a length of a tape (i.e., from a beginning of the tape (BOT) to an end of the tape (EOT)). A position of the tape head and the tape are also decoded from the pre-written servo pattern. Position error signals (PESs) are calculated based on the difference between the position of tape head and the target position. The disturbance information is further identified based on prior or known information, such as reel radius and tape speed. The reel RPM disturbance profile identification may be performed at a factory or in the field, and may be performed numerous times while the tape moves at different speeds. The disturbance information may be stored in a table and are identified in the table by their corresponding longitudinal position (LPOS) along the length of the tape.

At operation 304, a filter is applied to one or more disturbances' frequency to acquire additional information of the disturbances, including frequency and magnitude of the disturbances. The frequency and magnitude of the disturbances are used to calculate new specific servo control parameters, such as a peak filter array. The filter array and the corresponding LPOS of the disturbances are stored in a table. The table may be stored in memory, such as the memory 428 shown in FIG. 4. The servo control parameters may also include tape speed, and tape head tilt, for example. The servo parameters are calculated in a factory setting in one embodiment, but may be calculated or updated in the field as needed.

At operation 306, the LPOS, frequency, and magnitude of the disturbances are acquired to calculate or generate an updated disturbance profile identification. Operation 306 may further include changing position signals of the LPOS from a time domain to a frequency domain. The updated disturbance profile identification may be further used to generate a peak filter array that can be stored in a look-up table, such as with the calculated servo parameters, and the table may be stored in memory. The applied filter that is used to create disturbance profile is based on known parameters of the tape drive, such as the speed and radius of the reels, the rotation frequency, harmonics, the tape length, and the tape thickness. The applied filter that is used to create disturbance profile may be a band pass filter, a low pass filter, or a high pass filter, for example.

FIG. 4 illustrates a process flow of a system on a chip (SoC), an integrated circuit (IC), or a field-programmable gate array (FPGA) utilized in the operations 304-308 of the method 300 of FIG. 3A, according to one embodiment. For simplicity, the SoC, IC, or FGPA will be referred to herein as circuit 400 or processor 400. The circuit 400 is used to implement aspects of the method 300. The circuit 400 is configured to use a filter 420 to acquire additional information of a disturbance that can be used to generate peak detection 422, from which a disturbance profile of the detected disturbance points 424 is created, leading to the generation of servo controller parameters 426, which enables the tape drive's servo control system to be tailored to the dynamic disturbances, and to store the controller parameters in the memory 428 for storage of updated disturbance profile identification.

At operation 308 of method 300, the updated disturbance profile identification is used to create a peak filter array, which is a factory setting lookup table, and is based on the disturbance profile. At operation 310, the peak filter array is used to calibrate and generate instructions for the controllers of the PZT actuator 608 (shown in FIG. 6A) and/or VCM actuator(s) 654, 656 (shown in FIG. 6A) in order to move the tape head to adjust a disturbance compensation to match a frequency and an amplitude of a disturbance during write and read operations. In one embodiment, the PZT controller 600 (shown in FIGS. 6A-6B) comprises 3 peak filters 630a, 632a, 634 to help adjust the frequency, and the VCM controller 650 (shown in FIGS. 6A-6B) comprises 2 peak filters 630b, 632b to help adjust the frequency. While 2 and 3 peak filters are shown, the controllers may comprise any number of peak filters.

FIG. 5 illustrates an exemplary table 500 comprising the peak filter array generated in the method 300 of FIG. 3A, according to one embodiment. As shown, the table 500 comprises the LPOS of each disturbance point, along with one or more servo parameters and disturbance information. The servo parameters are simply represented as (A_x-N_x), where x is a numeral identifying the peak filter parameters (i.e., 1-5 in the present example), and A-N represents the number of servo parameters.

FIG. 6A illustrates a block diagram of a servo control loop 601 of a tape head, according to one embodiment. The servo loop 601 may be utilized with the tape drive 100 of FIGS. 1A-1C, and/or with the tape head module assembly 200 of FIG. 2.

The servo loop 601 comprises a stepping motor controller 602, a PZT controller 600, a PZT estimator 604, a LTM controller 650, which may be a VCM controller 650, a tilt controller 652, and an actuator and amplifier system 640. The actuator and amplifier system 640 comprises a stepping motor 606, a PZT actuator 608, and two VCM actuators 654, 656, where when both VCM actuators 654, 656 move upward, the tape head moves upward accordingly; when both VCM actuators 654, 656 move downward, the head moves downward. If the left VCM actuator 654 moves downward while the right VCM actuator 656 moves upwards (with a greater force or displacement), the tape head tilts toward the left side; conversely, the tape head tilts toward the right side when the right VCM actuator 656 moves downward while the left VCM actuator 654 moves upwards.

Target commands (cmd) for each band are sent the stepping motor controller 602, which then instructs the stepping motor 606 to move or re-position to target a data band. PES are input into the PZT controller 600 and the LTM controller 650. The PZT controller 606 then provides the calculated control effort to the PZT actuator 608 and the PZT estimator 604, which estimates the tape head displacement by the PZT actuator 608, and provides the estimates to the LTM controller 650.

Similarly, the LTM controller 650 and the tilt controller 652 are configured to instruct the VCM actuators 654 and 656 to move or re-position as desired based on the PES input and the estimates the displacement provided from the PZT estimator 604. The VCM actuators 654, 656 then move based on a calculated control effort, move in a cross-track direction, or tilt as needed to compensate for any LTM. The instructions provided to the stepping motor 606, the PZT actuator 608, and the VCM actuators 654, 656 are then output to correctly position the various actuators as instructed by the controllers 602, 600, 650, 652.

FIG. 6B illustrates the PZT controller 600 and the VCM controller 650 used in the output of the method 300 of FIG. 3A, according to one embodiment. The PZT controller 600 and the VCM controller 650 may be part of the servo head controller 601 of FIG. 6A. The PZT controller 600 is configured to control the PZT actuator 608 of FIG. 6A (and/or the PZT actuator 127 of FIG. 1B), and the VCM controller 650 is configured to control the VCM actuators 654, 656 of FIG. 6A (and/or the VCM actuator 125 of FIG. 1B). The PZT controller 600 comprises a first peak filter 630a, a second peak filter 632a, a third peak filter 634, an integrator 636, and a notch 638. The VCM controller 650 comprises a first peak filter 630b, a second peak filter 632b, an integrator 656, a notch 658, and a lead 660. The LPOS of the disturbance points and the peak filter array are input to the first, second, and third peak filters 630a, 632a, 634 to serve as a lookup value from which one or more output values or servo control parameters are determined in order to instruct the PZT actuator controlled by the PZT controller 600 and the VCM actuator controlled by the VCM controller 650 to individually move the tape head to adjust a disturbance compensation to match a frequency and an amplitude of a disturbance during a read or a write operation.

FIGS. 7A-7D illustrate graphs 700, 725, 750, 775 showing how the peak filter array is used to adjust the frequency and/or amplitude of the disturbances targeting the disturbance points at a frequency domain using the method 300 of FIG. 3A, according to one embodiment. In the graphs 700, 725, 750, 767, the y-axis is magnitude (mag) in dB and the x-axis is frequency in Hz.

FIG. 7A illustrates a graph 700 showing the sensitivity of tape head control. FIG. 7B illustrates a graph 725 showing the peak filter array being applied to the initial or base frequency of the graph 700. FIG. 7C illustrates a graph 750 showing how the amplitude of the disturbance point is adjustable using the peak filter array of the graph 725. The arrow shown illustrates how the amplitude is adjustable along the y-axis. FIG. 7D illustrates a graph 775 showing how the frequency of the disturbance point is adjustable using the peak filter array of the graph 725. The arrow shown illustrates how the frequency is adjustable along the x-axis. By applying the peak filter array, both the amplitude and frequency of disturbance points can be adjusted as needed to minimize the impact of the disturbance caused.

Method 350 of FIG. 3B begins at operation 302, where, prior to performing write and read operations, a reel rotation per minute (RPM) disturbance profile identification is performed, where one or more disturbance points are detected in the frequency domain along a length of a tape (i.e., from a beginning of the tape (BOT) to an end of the tape (EOT)). A position of the tape head and the tape are also decoded from the pre-written servo pattern. Position error signals (PESs) are calculated based on the difference between the position of tape head and the target position. The disturbance profile identification is used to generate a peak filter array that is stored in a table, such as the table 500 of FIG. 5, in memory 428. As stated above, methods 300 and 350 could be used in combination, and operation 302 may be the same in each method 300, 350.

At operation 354, the tape is partitioned longitudinally into a plurality of zones based on the size of the peak filter array created in operation 308 of FIG. 3A and on the calculated servo parameters, like shown in FIG. 8. One peak of the peak filter array corresponds to one zone. FIG. 8 illustrates a tape 800 being partitioned into a plurality of zones 812a-812j, according to one embodiment. The zones 812a-812j may have different sizes, like shown in