Source: http://www.google.com/patents/US6064540?dq=7,346,545
Timestamp: 2014-03-13 16:34:07
Document Index: 756762218

Matched Legal Cases: ['art 54', 'art 56', 'art 58', 'art 54', 'art 56', 'art 58']

Patent US6064540 - Active control for stabilizing a servo-controlled actuator system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn active control mechanism and method for stabilizing a servo-controlled actuator system such as an actuator system in a data recording disk drive by compensating the vibrational modes of the actuator's arm assembly. The control mechanism has a sensing arrangement which can include one or more individual...http://www.google.com/patents/US6064540?utm_source=gb-gplus-sharePatent US6064540 - Active control for stabilizing a servo-controlled actuator systemAdvanced Patent SearchPublication numberUS6064540 APublication typeGrantApplication numberUS 09/050,858Publication dateMay 16, 2000Filing dateMar 30, 1998Priority dateMar 30, 1998Fee statusPaidPublication number050858, 09050858, US 6064540 A, US 6064540A, US-A-6064540, US6064540 A, US6064540AInventorsFu-Ying Huang, Wayne Isami Imaino, Francis C. LeeOriginal AssigneeInternational Business Machines CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (5), Non-Patent Citations (2), Referenced by (31), Classifications (20), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetActive control for stabilizing a servo-controlled actuator systemUS 6064540 AAbstract An active control mechanism and method for stabilizing a servo-controlled actuator system such as an actuator system in a data recording disk drive by compensating the vibrational modes of the actuator's arm assembly. The control mechanism has a sensing arrangement which can include one or more individual sensors attached to the actuator at locations where they generate signals in phase with the vibrational modes, and especially with all the major vibrational modes, of the arm assembly. A control mechanism derives from the signals an adjustment signal consisting of three corrective terms--a stiffening correction, an active damping correction and an inertia reduction correction--and the adjustment signal is used in the feedback control loop to stabilize the actuator system.
What is claimed is: 1. An active control mechanism for stabilizing an actuator system having an arm assembly, a controlled element mounted on said arm assembly and generating a position signal indicating a displacement of said controlled element, an actuator for moving said controlled element by moving said arm assembly, said arm assembly experiencing vibrational modes, said active control mechanism comprising:a) a sensing means attached to said actuator for generating signals correlated to said vibrational modes; b) a control means connected to said sensing means for deriving from said signals an adjustment signal comprising:1) a stiffening correction; 2) an active damping correction; 3) an inertia reduction correction; and c) a combining element connected to said control means, to said controlled element and to said actuator for combining said adjustment signal and said position signal to produce a feedback signal for driving said actuator. 2. The active control mechanism of claim 1, wherein said control means generates said signals in phase with said vibrational modes.
DESCRIPTION OF THE FIGURES FIG. 1 is an isometric view of an actuator system with an arm assembly according to the invention.
DETAILED DESCRIPTION FIG. 1 illustrates a preferred embodiment of a servo-controlled actuator system 10 for a hard disk drive. Actuator system 10 has an arm assembly 12 equipped with a controlled element 14, in this case a read/write head. Arm assembly 12 has a main arm 16 and a secondary arm 18 joined with main arm 16 by a joint 20. Entire assembly 12 is mounted on a hub 30. Head 14 is positioned above a disk 22 with concentric data tracks 24 and accesses various tracks 24 during operation by pivoting or rotating around hub 30. This general construction of arm assembly 12 is well-known in the art of hard disk drives.
To properly compensate these modes, as well as any other modes of arm assembly 12 requiring active compensation, sensors 32, 34 are positioned such that their signals are correlated to the modes of arm assembly 12. As is true of any mechanical system, when arm assembly 12 vibrates, the vibration can be decomposed into several vibrational modes which have their own unique vibration shapes called "mode shapes". The mode shape φ.sub.i of the i-th mode can be expressed as:
&#966;.sub.i =&#966;.sub.i (x,y,z),
which is a function of location (x,y,z). The net in-plane sway deformation Δ.sub.in-plane of coil 26 is then described by: ##EQU1## where F is the force applied on coil 26. Thus, the strain, ε.sub.i, experienced by sensor 32 due to the i-th vibrational mode is also a function of the mode shape φ.sub.i and is represented by:
&#949;.sub.i =&#949;.sub.i (&#966;.sub.i ).
When the sign of the sway deformation Δ.sub.in-plane is the same as the sign of strain ε.sub.i at the location of sensor 32, then the signal generated by sensor 32 is in phase with the i-th vibrational mode. Sensor 32 is placed at a location where such in-phase correlation exists between its signal and the i-th vibrational mode. Since two sensors 32, 34 are used in this particular embodiment, ε.sub.i is replaced by the sum of the strains multiplied by weighting factors on both sensor locations.
The table in FIG. 5 shows the phase relationship between output signal of sensor 32 and major modes i, j, and k with respect to sway deformation Δ.sub.in-plane. At location A the signal of sensor 32 is in phase with modes i, j, and k. At location B the signal of sensor 32 is out of phase with modes i and j, and at location C it is out of phase with mode k. Hence, the proper final location for permanently mounting sensor 32 is A.
The details of how the three correction terms are computed are explained in reference to the generalized diagram of FIG. 6. The computation applies to sensors 32, 34 as well as any number of sensors n. Hence, the diagram shows sensors 32 and 34 replaced by a number n of sensors 66, each delivering a partial signal a.sub.i S.sub.i such that the total signal 52 or S is: ##EQU2## where the a.sub.i 's are constants or weighting factors. In this embodiment sensors 66 are strain sensors and consequently partial signals S.sub.i are in effect strain signals ε.sub.i weighted by weighting factors a.sub.i.
Total strain signal S is delivered to stiffening part 54, active damping part 56 and inertia reduction part 58 alike. Stiffening part 54 is a multiplier or linear element which multiplies strain signal S by a negative constant -k to produce the stiffening correction. Active damping part 56 has a differentiator which differentiates stain signal S to yield strain rate DS/dt (S') and a linear element which multiplies S' by a negative constant -D to generate the active damping correction. Finally, inertia reduction part 58 has two differentiators and a linear element to differentiate strain signal S twice and multiply the resulting strain acceleration signal D.sup.2 S/dt.sup.2 (S") by a positive constant I. The linear elements and differentiators are well-known in the art and the way in which they have to be used to generate each of the three correction terms is apparent to a person of average skill in the art.
FIELD OF THE INVENTION This invention relates to an apparatus for and a method of active control for stabilizing multiple vibrational modes of an actuator system.
BACKGROUND OF THE INVENTION Servo-controlled actuator systems experience serious problems due to mechanical actuator resonances. These vibrational modes include the natural modes of the actuator and those of any intervening mechanical components. With increasing mechanical complexity, the vibrational modes of any given actuator system become difficult to predict. The problem is further compounded as the operating frequency of the actuator system is increased. The vibrational modes limit the control loop gain of the servo system, reduce bandwidth of the servo system, or both. This causes the controlled element, such as a transducer head, to experience excessive settling time after positioning, poor response to disturbances, poor tracking ability, or any combination of these.
Although Kobayashi's technique has been demonstrated, it can not be efficiently implemented without the use of notch filters. Furthermore, designing the feedback controller requires the designer to model the very complicated transfer function H.sub.d (s) of the servo-controlled system. This is computationally challenging and requires a considerable amount of processing time. In addition, because the poles and zeros of the compensator used in the feedback controller can not be predetermined, it is not possible to guarantee the existence of a stable compensator.
OBJECTS AND ADVANTAGES OF THE INVENTION Accordingly, it is a primary object of the present invention to provide an active control mechanism for stabilizing a servo-controlled actuator system and overcome the disadvantages of the prior art. Specifically, the control mechanism of the invention is designed to circumvent the limitations of the gain filtering approach and provide effective feedback over the actuator's entire range of operation by actively compensating for multiple vibrational modes, thus permitting higher bandwidth operation.
SUMMARY OF THE INVENTION These objects and advantages are attained by an active control mechanism for stabilizing a servo-controlled actuator system having an arm assembly, a controlled element mounted on the arm assembly, an actuator for moving the controlled element by moving the arm assembly and a position sensor, e.g., the controlled element itself, for generating a position signal indicating a displacement of the controlled element. The arm assembly experiences vibrational modes during operation which are compensated by the active control mechanism.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4093885 *Apr 16, 1976Jun 6, 1978Ampex CorporationTransducer assembly vibration sensorUS4922159 *May 9, 1988May 1, 1990Harris CorporationLinear precision actuator with accelerometer feedbackUS5426545 *Jan 31, 1994Jun 20, 1995Sidman; Michael D.Active disturbance compensation system for disk drivesUS5459383 *Jun 14, 1994Oct 17, 1995Quantum CorporationRobust active damping control systemEP0594522A1 *Sep 21, 1993Apr 27, 1994International Business Machines CorporationDisk drive servo system* Cited by examinerNon-Patent CitationsReference1 *Kobayashi, M. et al., MR 46 Carriage acceleration feedback multi sensing controller for sector servo systems, Interntl. Conf. on Micromechanics for Info. and Precision Equip., Tokyo, pp. 475 480, Jul. 20 23, 1997.2Kobayashi, M. et al., MR-46 Carriage acceleration feedback multi-sensing controller for sector servo systems, Interntl. Conf. on Micromechanics for Info. and Precision Equip., Tokyo, pp. 475-480, Jul. 20-23, 1997.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS6414813 *Jan 26, 2001Jul 2, 2002Seagate Technology LlcRotational acceleration correction in a disc driveUS6490121 *Oct 27, 2000Dec 3, 2002Seagate Technology LlcAccelerated servo control calculations method and apparatus for a disc driveUS6496323 *Jan 18, 1999Dec 17, 2002Matsushita Electric Industrial Co., LtdInformation recording/reproducing apparatus and methodUS6580579 *Jul 21, 2000Jun 17, 2003Seagate Technology LlcDisturbance rejection for disc drives using adaptive accelerometer feedforward servoUS6594106 *Oct 29, 1999Jul 15, 2003International Business Machines CorporationAdaptive servo estimator and compensator for coil and carriage deformation in voice coil motor driven hard disk driveUS6606213 *Jun 11, 1999Aug 12, 2003Seagate Technology LlcActuator resonance screening in disc drivesUS6614613 *Mar 16, 2000Sep 2, 2003International Business Machines CorporationPhase technique for active damping in a servo-controlled actuatorUS6621653 *Jun 9, 2000Sep 16, 2003Hitachi Global Storage Technologies Netherlands B.V.Secondary actuator system for mode compensationUS6667844 *Sep 23, 1999Dec 23, 2003Seagate Technology LlcActive vibration suppression of glide head suspension armUS6771454 *Sep 4, 2001Aug 3, 2004Seagate Technology LlcSuspension sense capability for windage controlUS6778348Aug 25, 2000Aug 17, 2004Ic Mechanics, Inc.Accelerometer-assisted servo writing for disk drivesUS6791786Dec 11, 2000Sep 14, 2004Seagate Technology LlcActive damping of two-stage actuator system in a disc driveUS6861854Oct 11, 2002Mar 1, 2005Maxtor CorporationPeizoelectric microactuator and sensor failure detection in disk drivesUS6888694Jun 4, 2002May 3, 2005Agency For Science, Technology And ResearchActive control system and method for reducing disk fluttering induced track misregistrationsUS6934117Jan 5, 2004Aug 23, 2005Hitachi Global Storage Technologies Netherlands B.V.Technique to compensate for resonances and disturbances on primary actuator through use of a secondary actuatorUS6977790May 3, 2002Dec 20, 2005Maxtor CorporationDesign scheme to increase the gain of strain based sensors in hard disk drive actuatorsUS7141951 *Feb 9, 2006Nov 28, 2006Hitachi Global Storage Technologies Netherlands B.V.Data storage apparatus with compensation for vibration and control method thereofUS7145307 *Feb 3, 2006Dec 5, 2006Hitachi Global Storage Technologies Netherlands B.V.Data storage apparatus and control method thereof with compensationUS7215504Oct 19, 2005May 8, 2007Western Digital Technologies, Inc.Disk drive using an optical sensor to detect a position of an actuator armUS7345841Feb 7, 2006Mar 18, 2008Hitachi Global Storage Technologies Netherlands B.V.Disk drive using a disturbance sensor for disturbance frequency-identification and suppressionUS7365932Dec 30, 2005Apr 29, 2008Western Digital Technologies, Inc.Disk drive comprising an optical sensor for vibration mode compensationUS7477691 *Jan 22, 1999Jan 13, 2009Snell & Wilcox LimitedVideo signal compressionUS7480116Jan 20, 2006Jan 20, 2009Western Digital Technologies, Inc.Disk drive employing coarse position feedback from mechanical position sensor to improve format efficiencyUS7495857Dec 30, 2005Feb 24, 2009Western Digital Technologies, Inc.Servo writing a disk drive by writing spiral tracks using a mechanical position sensorUS7515377 *Nov 5, 2007Apr 7, 2009Fujitsu LimitedStorage apparatus and control method for detecting vibration produced during seekingUS7619844Dec 30, 2005Nov 17, 2009Western Digital Technologies, Inc.Disk drive comprising a mechanical position sensor to prevent a runaway conditionUS7701661Nov 24, 2008Apr 20, 2010Western Digital Technologies, Inc.Disk drive employing coarse position feedback from mechanical position sensor to improve format efficiencyUS7760461Nov 24, 2008Jul 20, 2010Western Digital Technologies, Inc.Disk drive employing coarse position feedback from mechanical position sensor to improve format efficiencyUS7813083Jan 17, 2007Oct 12, 2010Maxtor CorporationDisk drive load arm structure having a strain sensor and method of its fabricationCN101025927BFeb 7, 2007Jun 23, 2010日立环球储存科技荷兰有限公司Disk drive using a disturbance sensor for disturbance frequency-identification and suppressionEP1493942A1 *Jun 24, 2004Jan 5, 2005Giat IndustriesActive vibration damping device for a weapon by tuning of the transmission* Cited by examinerClassifications U.S. Classification360/75, 318/610, 360/77.3, G9B/21.18, 318/615, 318/561, G9B/21.13International ClassificationG11B33/08, G05D3/12, G11B5/596, G11B21/08, G11B21/10, G11B5/55Cooperative ClassificationG11B5/59605, G11B21/081, G11B33/08, G11B5/5582, G11B21/10European ClassificationG11B21/10, G11B21/08ALegal EventsDateCodeEventDescriptionOct 25, 2012ASAssignmentFree format text: CHANGE OF NAME;ASSIGNOR:HGST, NETHERLANDS B.V.;REEL/FRAME:029341/0777Effective date: 20120723Owner name: HGST, NETHERLANDS B.V., NETHERLANDSFree format text: CHANGE OF NAME;ASSIGNOR:HITACHI GLOBAL STORAGE TECHNOLOGIES NETHERLANDS B.V.;REEL/FRAME:029341/0777Owner name: HGST NETHERLANDS B.V., NETHERLANDSSep 23, 2011FPAYFee paymentYear of fee payment: 12Sep 27, 2007FPAYFee paymentYear of fee payment: 8Sep 25, 2003FPAYFee paymentYear of fee payment: 4Feb 4, 2003ASAssignmentOwner name: HITACHI GLOBAL STORAGE TECHNOLOGIES NETHERLANDS B.Free format text: CHANGE OF NAME;ASSIGNOR:MARIANA HDD B.V.;REEL/FRAME:013746/0146Effective date: 20021231Jan 8, 2003ASAssignmentOwner name: MARIANA HDD B.V., NETHERLANDSFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INTERNATIONAL BUSINESS MACHINES CORPORATION;REEL/FRAME:013663/0348Effective date: 20021231Owner name: MARIANA HDD B.V. JOHAN HUIZINGALAAN 765AMSTERDAM,Mar 30, 1998ASAssignmentOwner name: INTERNATIONAL BUSINESS MACHINES CORPORATION, NEW YFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HUANG, FU-YING;LEE, FRANCIS C.;IMAINO, WAYNE I.;REEL/FRAME:009078/0877Effective date: 19980327RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google