# US 9,520,149 B1 · Direct current magnetoresistive jog offset compensation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,149 B1 - Document ID: US9520149B1 - Status: Granted - Kind: B1 - Application number: 15/170,859 - Filed: 2016-06-01 - Granted: 2016-12-13 - Earliest claimed: 2016-06-01 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Mingzhong Ding; Xiong Liu; Xiang Lu; Qiang Bi; Kian Keong Ooi - Web page: https://patentgrep.com/patent/US9520149B1 ## CPC - G11B 5/59627: {Aligning for runout, eccentricity or offset compensation (G11B5/5534, G11B5/59677, G11B5/59688 take precedence)} - G11B 5/59694: {System adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract Systems and methods for compensating for magnetoresistive (MR) jog offset direct current (DC) drift in a disc drive are described. In one embodiment, a method may include determining an occurrence of NOS, for example, by monitoring disc slip, to determine when the method should proceed. An MR jog offset DC drift amount is determined for each head of the disc drive. One of several approaches may be employed for determining the MR jog offset DC drift amount. By determining an MR jog offset DC drift amount for each head, a compensation profile is determined for the drive. The determined compensation profile may then be used during operation of the disc drive to compensate for the DC drift. One of several approaches may be employed for compensating based on the compensation profile. ## Claims ### Claim 1 A storage device comprising: a data storage medium comprising at least one disc; at least one magnetoresistive (MR) read/write head associated with the at least one disc; a non-operating shock (NOS) detector to determine an occurrence of NOS based at least in part on slip of the at least one disc; an MR jog offset direct current (DC) drift detector to determine an MR jog offset DC drift amount based at least in part on a variable read performed over at least one revolution of the at least one disc using the at least one MR read/write head when the NOS detector has determined the occurrence of NOS; and an MR jog offset compensator to compensate for the determined MR jog offset DC drift amount using the determined DC MR jog offset for the at least one MR read/write head. ### Claim 2 (depends on 1) The storage device of claim 1, comprising: a plurality of discs comprising the data storage medium; a plurality of MR read/write heads comprising the at least one MR read/write head, each of the plurality of MR read/write heads associated with a respective one of the plurality of discs, the MR jog offset DC drift detector to determine a plurality of MR jog offset DC drift amounts based on a corresponding plurality of variable reads, each of the plurality of variable reads using a respective one of the plurality of MR read/write heads, each of the determined plurality of MR jog offset DC drift amounts corresponding to the respective one of the plurality of MR read/write heads; and a correction profile determiner to determine a correction profile based at least in part on the determined plurality of MR jog offset DC drift amounts, the correction profile comprising a plurality of DC MR jog offsets corresponding to the plurality of MR read/write heads, the MR jog offset compensator to compensate for the determined plurality of MR jog offset DC drift amounts using the determined correction profile. ### Claim 3 (depends on 1) The storage device of claim 1, the MR jog offset compensator to compensate for the determined MR jog offset DC drift amount using write seek feedforward compensation. ### Claim 4 (depends on 1) The storage device of claim 1, the MR jog offset compensator to compensate for the determined MR jog offset DC drift amount by migrating data using shingled magnetic recording (SMR) band rewrite operation (BRO). ### Claim 5 (depends on 1) The storage device of claim 1, the variable read comprising a read from the group consisting of: a spiral read, a zig-zag read, and a sinusoidal read. ### Claim 6 (depends on 1) The storage device of claim 1, the variable read comprising a plurality of reads performed with different track offsets of the at least one MR read/write head. ### Claim 7 (depends on 1) The storage device of claim 1, the MR jog offset direct current (DC) drift detector to determine the MR jog offset DC drift amount based at least in part on a measurement from the group consisting of: a bit error rate (BER) measurement and a variable gain adjustment measurement. ### Claim 8 An apparatus comprising: an MR jog offset direct current (DC) drift detector to determine an MR jog offset DC drift amount based at least in part on a variable read performed over at least one revolution of at least one disc of a data storage medium using at least one MR read/write head based at least in part on an occurrence of non-operating shock; and a correction profile determiner to determine a DC MR jog offset for the at least one MR read/write head based at least in part on the determined MR jog offset DC drift amount. ### Claim 9 (depends on 8) The apparatus of claim 8, further comprising: an MR jog offset compensator to compensate for the determined MR jog offset DC drift amount using write seek feedforward compensation or by migrating data using shingled magnetic recording (SMR) band rewrite operation (BRO) based at least in part on the determined DC MR jog offset. ### Claim 10 (depends on 8) The apparatus of claim 8, the variable read comprising a read from the group consisting of: a spiral read, a zig-zag read, and a sinusoidal read. ### Claim 11 (depends on 8) The apparatus of claim 8, the variable read comprising a plurality of reads performed with different track offsets of the at least one MR read/write head. ### Claim 12 (depends on 8) The apparatus of claim 8, the MR jog offset direct current (DC) drift detector to determine the MR jog offset DC drift amount based at least in part on a measurement from the group consisting of: a bit error rate (BER) measurement and a variable gain adjustment measurement. ### Claim 13 A method comprising: determining an occurrence of non-operating shock (NOS) in a disc drive by monitoring disc slip; determining magneto-resistive (MR) jog offset direct current (DC) drift amount associated with the occurrence of NOS; determining a correction profile based at least in part on the MR jog offset DC drift amount; and compensating for MR jog offset DC drift using the correction profile. ### Claim 14 (depends on 13) The method of claim 13, compensating for the MR jog offset DC drift comprising: performing write seek feedforward compensation or migrating data using a shingled magnetic recording (SMR) band rewrite operation (BRO). ### Claim 15 (depends on 13) The method of claim 13, determining the MR jog offset DC drift amount comprising: writing data to a test track on a surface of a disc of the disc drive; and determining a change between a new center of the written data and a previous center of data written to the test track. ### Claim 16 (depends on 15) The method of claim 15, determining the change comprising: performing a spiral read of the test track over one revolution of the disc to obtain sector-wise bit error rate (BER) or variable gain adjustment (VGA) values; and determining a highest BER value of the sector-wise BER measurement values or a lowest VGA value of the sector-wise VGA values to identify the MR jog offset DC drift amount. ### Claim 17 (depends on 16) The method of claim 16, determining the correction profile comprising: obtaining MR jog offset DC correction values by repeating the spiral read and identification of the MR jog offset DC drift amount on a plurality of test tracks across the surface of the disc for each individual head. ### Claim 18 (depends on 15) The method of claim 15, determining the change comprising: performing a zig-zag read of the test track over one revolution of the disc to obtain a plurality of sector-wise bit error rate (BER) or variable gain adjustment (VGA) values for each sector; averaging the plurality of sector-wise BER or VGA values for each sector; and determining a highest BER value of the averaged sector-wise BER values or a lowest VGA value of the averaged VGA values to identify the MR jog offset DC drift amount. ### Claim 19 (depends on 15) The method of claim 15, determining the change comprising: performing a sinusoidal read of the test track over one revolution of the disc to obtain a plurality of sector-wise bit error rate (BER) or variable gain adjustment (VGA) values for each sector; averaging the plurality of sector-wise BER or VGA values for each sector; and determining a highest BER value of the averaged sector-wise BER values or a lowest VGA value of the averaged VGA values to identify the MR jog offset DC drift amount. ### Claim 20 (depends on 15) The method of claim 15, determining the change comprising: performing a plurality of reads of the test track at different offsets to measure a corresponding plurality of bit error rate (BER) or variable gain adjustment (VGA) values, each of the plurality of reads having a different reader offset; and determining a highest BER value of the plurality of BER values or a lowest VGA value of the plurality of VGA values to identify the MR jog offset DC drift amount value and direction.