# US 2013/0152695 A1 · Methods and devices for extracting off-track motion using microactuators > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0152695 A1 - Document ID: US20130152695A1 - Status: Published application - Kind: A1 - Application number: 13/326,575 - Filed: 2011-12-15 - Published: 2013-06-20 - Earliest claimed: 2011-12-15 - Assignees: Seagate Technology LLC - Inventors: Narayanan Ramakrishnan; Stefan Alexander Weissner - Web page: https://patentgrep.com/patent/US20130152695A1 ## CPC - G11B 5/5552: {using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means} - G11B 5/483: {Piezoelectric devices between head and arm, e.g. for fine adjustment} - 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 In certain embodiments, an apparatus includes a first piezoelectric (PZT) element poled in the same direction as a second PZT element. The first and second PZT elements are configured to be driven while simultaneously sensing motion. The apparatus further includes a circuit configured to add outputs of the first and second PZT elements, extract the sensed motion, and detect off-track motion from the extracted sensed motion. ## Claims ### Claim 1 An apparatus comprising: a first piezoelectric (PZT) element poled in the same direction as a second PZT element, the first and second PZT elements configured to be driven while simultaneously sensing motion; a circuit configured to add outputs of the first and second PZT elements, extract the sensed motion, and detect off-track motion from the extracted sensed motion. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein a sensing signal is responsive to the sensing motion of the first and second PZT elements, and wherein the first and second PZT elements are responsive to a drive signal. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the circuit further comprises: a filter configured to filter the drive and sensing signals of the first and second PZT elements into separate frequencies to allow the sensing signal to be isolated from the drive signal. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the filter is configured to filter the drive signal into a low frequency band and a high frequency band. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the first and second PZT elements are located near a distal end of a suspension in a hard disk drive. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the first and second PZT elements are located between a first distal end of the suspension and an opposite, second distal end of the suspension. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the first and second PZT elements are driven asymmetrically. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the first PZT element is configured to sense motion while the second PZT element is configured to be driven, during track-follow operations. ### Claim 9 (depends on 1) The apparatus of claim 1, further comprising: a second set of PZT elements configured to be driven while the first set of PZT elements sense motion. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the first and second PZT elements are located on a first suspension on a first side of a disk in a hard disk drive, and wherein the second set of PZT elements is located on a second suspension on a second side of the disk. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the circuit is configured to subtract signals from the first and second PZT elements from each other in a differential mode to reduce common-mode noise. ### Claim 12 A method comprising: sensing a sensing signal responsive to a motion of a first PZT element while simultaneously driving a second PZT element responsive to a driving signal; combining the sensing signal and the driving signal to create a composite signal; extracting sensed motion from the composite signal; and detecting off-track motion from the extracted sensed motion. ### Claim 13 (depends on 12) The method of claim 12, wherein the sensing step further comprises: sensing a sensing signal responsive to a motion of a first set of PZT elements while simultaneously driving a second set of PZT elements responsive to a driving signal. ### Claim 14 (depends on 13) The method of claim 13, wherein the first set of PZT elements is located on a first suspension on a first side of a disk in a hard disk drive, and wherein the second set of PZT elements is located on a second suspension on a second side of the disk. ### Claim 15 (depends on 12) The method of claim 12, further comprising: filtering a driving signal of the plurality of PZT elements and a sensing signal of the plurality of PZT elements into separate frequencies to allow the sensing signal to be isolated from the driving signal. ### Claim 16 (depends on 15) The method of claim 15, wherein the filtering includes filtering the driving signal into a low frequency band and a high frequency band. ### Claim 17 An apparatus comprising: a first and second microactuator configured to be driven while simultaneously sensing motion, the first microactuator configured to output a first sensing signal responsive to a first microactuator deformation, the second microactuator configured to output a second sensing signal responsive to a second microactuator deformation; and a controller configured to combine the first and second sensing signals to generate a composite signal to detect off-track motion. ### Claim 18 (depends on 17) The apparatus of claim 17, wherein the first and second microactuators are driven asymmetrically. ### Claim 19 (depends on 18) The apparatus of claim 18, further comprising: a third microactuator element configured to output a third sensing signal responsive to a third microactuator deformation, wherein the third sensing signal is subtracted from the first and second sensing signals.