GB2231976A - Position control - Google Patents

Position control Download PDF

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Publication number
GB2231976A
GB2231976A GB9009167A GB9009167A GB2231976A GB 2231976 A GB2231976 A GB 2231976A GB 9009167 A GB9009167 A GB 9009167A GB 9009167 A GB9009167 A GB 9009167A GB 2231976 A GB2231976 A GB 2231976A
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GB
United Kingdom
Prior art keywords
signal
head
disk drive
diodes
gain
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9009167A
Other versions
GB9009167D0 (en
Inventor
Takayuki Hoshino
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP24881689A external-priority patent/JPH0349081A/en
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Publication of GB9009167D0 publication Critical patent/GB9009167D0/en
Publication of GB2231976A publication Critical patent/GB2231976A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B21/00—Head arrangements not specific to the method of recording or reproducing
    • G11B21/02—Driving or moving of heads
    • G11B21/08—Track changing or selecting during transducing operation
    • G11B21/081—Access to indexed tracks or parts of continuous track
    • G11B21/083—Access to indexed tracks or parts of continuous track on discs
    • G11B21/085—Access to indexed tracks or parts of continuous track on discs with track following of accessed part
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/54—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head into or out of its operative position or across tracks
    • G11B5/55—Track change, selection or acquisition by displacement of the head
    • G11B5/5521—Track change, selection or acquisition by displacement of the head across disk tracks
    • G11B5/5552—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means
    • G11B5/5556—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means with track following after a "seek"
    • G11B5/556—Track change, selection or acquisition by displacement of the head across disk tracks using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means with track following after a "seek" control circuits therefor

Landscapes

  • Moving Of The Head To Find And Align With The Track (AREA)

Description

1 OF 'I'llE INVENTION DISK DRIVE BACKGROUND OF THE INVENTION Field of the
Invention lhe piesent invenlion relales to a disk drive which positions a head, onto a desired position on a disk to read/write data Descript ion of Rel ated Art As a method of pos it i on! ngr zt head onto a desired track of a disk to read/wri te data, it is well known to control a traveling, velocity of the head from its existing, position to the vicinity of the desired track, then to switch this X' e 1 () e i ty con tro 1 tion of and the con Irol to a posi ti on contrul by a closed-loop cii,Cuit. Such a method is intended to modify deviapositioning, caused by vibration from outside, shock like given to the head as a result of the velocity Llic f inal posi tioninir control of the con tro 1, by swi t c h in g 1 head from its velocity control to the position control.
1 is a block diagram showing, construction of a positioning control circuit in a magnetic disk drive disclosed in Japanese llatent Application Laid-Open No. 6310068(1 (1988), for example. In the figure, reference n(, 1 i c head. wh 1 ch wi. j tes/reads da ta ntimeral 1 designales 1 mall to/from a desired track of a iiial,,,iietic disk in a position A C I Use to a writ in g/ read i ng, SUrf ace of the magnetic disk. An actuator 2 holds the magnetic head 1 and actuates it in the radial direction of the magnetic disk. A demodulation circuit 11 demodtilates data on displacement between the posi- not ic head I and the posi ti on of the des! red tion of the mag track into an analogue positional signal, and outputs this IMSitional signal to a control signal generating circuit 12 and a switching point detecting circult 14, respectively. In response to the positional signal being outputted from the demodulation circuit IJ, the switching point detecting circuit 14 detects the position control to the position control position of setting, and output 15. The timer 15 operates to switch the velocity that is, the initiation a switching signal to a timer for a predetermined period s i nce it receives the swi tchi ng sil. rnzil, and during that period, a switch 16 is closed. While the switch 16 is closed, a gain at the control signal generating circuit 12 is increased. The control signal generating circuit 12 r applies the gain to the- positional signal and outputs a con tro 1 s i gna I f or con tro 1 1 i nj..r) ) the position of the magnetic head 1 to a power amp I i f i er. 13. The power amplifier 13 amplified this control signal outpulted thereto and outputs this to said actuator 2.
The operation of such a mtl,,,netic disk drive will be described below. Fig. 2 is a graph showing a velocity pro- file of the velocity control on the magnetic head, in which a vertical line shows velocity and a horizontal axis shows tilne. According to the velocity profile in a trapezoidal waveform as shown in Fig. 2, the actuator 2 is accelerated or decelei.aled b. a constant electric current to move the magnetic head 1 to seek the desired track. When the magnetic head 1 reaches a predetermined area in the vicinity of the desi red track, the vel oci ty control is swi tched to the position control. The demodulation circuit 11 demodulates data on displacement between the position of the desired track and mai,,.n(-,lic head 1 into an analogue positional signal and outputs this to the switching point detecting circuit 1.4. 1 n demodulation eircilit 11, e i]c II i ing th response Lu the pos it i onal s i gnal output ted from the the swi tching point detecting 14 detec Ls a seLting ini tiation posi tion for swi tchvelocity control to the position control, and outputs a switching signal to the timer 15. The timer 15 operates for a predetermined period since it receives the swi tching signal, and duri ng that period, the swi tch 16 is closed. Whi le the swi tch 16 is closed, a gain at the con'nal generating circui t 12 is increased.
trol sig The control signal generating circuit 12 applies the gain to the, positional signal so as to generate a control signal for controlling the position (if the magnetic head 1, and the power amplifier 13 amplifies this control signal and 3 out p ii ts Lh i s to the act uator 2 In response to the amPlified control signal, vibration of the actuator 2 is reduced - the set ting and. ends, then the magnetic head 1 is positioned onto the desii-ed track. After operating for the predetermined Period, the timer 15 stops, and the switch 16 is opened and the gain at the control signal generating circuit 12 is reduced to prevenL, abnormal oscillation in the positioning control circuit.
As for the conventional positioning control circuit in the disk drive, it takes slightly longer time for the setting, since when the head reaches the predetermined area in the vicinity of the desired track, the timer operates until the end of the setting in respOTIse to a switching signal outputted from the switching point detecting circuit as a result of detecting the setting, initiation position, then the switch is switched so that even when the head reaches closer to the desired track, Lhe gain is still increased as at the setting, initiation until the timer is up. In addition, the gain is increased by switching the switch 16, disturbance occurs as a transient phenomenon as a result of switching, there exists a problem that the head is positioned onto the desired track with less accuracy after the setting is completed.
S JMMARY OF 'I'llF, INVENTION 1 The f ore g o 1 ng, prob I em is so I v ed in a cc ord an c e wi th the present invention, and a primary object of the present invention is to provide a disk drive in which setting will end in a short time, and posi tioning of the head onto a desired posi tion of a disk can be done wi th high accuracy af ter the selting is completed, by increasing/decreasing a posilional signal for specifying the position of the head on the disk according to the indgnitude of the amplitude of this positional signal to output this as a,,nal nonlinear sig dets i red pos i t i on t ro 1 1 ed The 1,,.ain of a after a head reaches the vicinity of the on the disk and where an actuator is conaccording to the position of the head. above and furlher objects and features of the invention will more fully be apparent from the following detalled description with accompanying, drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram showing, construction of a conventional positioning control circuit in a magnetic disk dr i VC; Fig. 2 is a velocity profile of an actuator in a velocity control; Fig. 3 is a block diagram showing construction of a po s i t i on 1 rily, con t rn 1 c. j reu i 1 i n a magne t 1 c d 1 sk dr i ve i n accordance with an embodiment of the present invention; 1 F i g _,. 4 is a circui t diagram showing cons true lion of one embodimen 1 of a non I in ear operati ona l amp l if i er; Fig..5 is a 1,,,i.al)li showing input-output characteris ties of the nonlinear operational amplifier shown in Fig. 4; Figy. 6 is a circuit diagram showing construction of another embodiment of tile nonlineal. operational amplifier; and Fig. 7 is a graph showing. input-output characteristics:. of the nonlinear operational amplifier shown in Fig. 6.
drive N 1) W i n DESCRIPTION, OF THE PREFERMI) EM130DIMENTS will be described below construction of a disk accordance wi th the present invention wi th reference to the accompanying drawings.
Fill. 3 is at block dial.?,i,zAm showing construction of a 1)ositioningr control circult in a magnetic disk drive in accordance wi th the present invention. In the f igure, reference numeral 1 designates a magnetic head which writes/reads datta on a desired Irack of the magnetic disk, in a posi tion close to a i.ect)i.ciiiii,,./1-eacling surface of a nial-, rietic disk. An actuator 2 holds the magnetic hrad 1 and actnates it in the radial direction of the magnetic disk. A demodulation circuit 11 demodulates data on displacement between the position of of a desired the magnetic head 1 and the position track into an analogue 1)ositional signal, and 6 outputs this to a noril incar operational amp] if i er 21 Th i S nonlinear operational amplifier 21 determines a gain cor respo rid i rill, 1 (.) t h e mag, n i t ud e o f t lie amp 1 11 tide 0 1 t fie aria 1 ogue pos i t i onal s i irnal oiltpii t ted thereto, and accord! rig to the determi ned n, amp] i i i cc., the posi t ional signal and outputs th i s t o a co ri t r o 1 s S gri a 1 genera t 1 ng c i rcil 1 t 12.
Th e ef) n t i.o 1 s i gna 1 g enera t i ng, c i i-cu i t 12 genera t es a control signal for controlling the position of the magnetic head 1, i n response to the posi t i onal signal passed through the nonlinear operational amplifier 21, and outputs this to a power amplifier 13. The power amplifier. 13 amplifies this conti-t)l signal outputted thereto, and outputs this to said actuator 2.
Now will be described bcluw the operation of the magnetic disk drive described above. According to a velocity prnf i 1 e i n a ti.al)czoici.il waveform shown in Fig. 2, the actuator 2 is accelerated or decelerated by a constant electric current to muve the inagnetic head 1 to seek the desired t r 'I c, 1,1 - When the magnetic head 1 is moved to a predetermined area in the vicinity of the desired track, the velocity c(introl is switched to the position control. The demodulation circuit 11 demodulates positional displacement data obtained by cornparing posilional data of the desired track with positional data of a track on which the magnetic head 1 is existing, into an analogile poisitional signal and outputs 7 L h is to the non 1 i ne a r o p era t i on a I ampl if i er 2 1. The non linear operational amplifier 21 determines a gain of the positional signal according to the magnitude of the ampli tude of the posi Lional signal outputted from the demodula tion circui t 11 Specif ical ly, the posi tional signal is ampl if ied by a comparatively larger gain where the magnetic head is in a posi tion far from the desired track, and so is by a comparatively smaller gain where the magnetic head is in a position closer to the desired track, and is outputted to the control signal generating circui t. 12.
r circui t 12 generates a The control signal generating control signal for control I ing the posi tion of the magnetic head 1 in response to a nonlinear positional signal passed through the non] inear operational ampl if ier 21, and the power ampl if ier 13 ampl i f ics this control signal and outputs this to the actuator 2. In response to the amplified control signal, vibration t)f the actuator 2 is surely reduced and the setting is ended in a short time, then, the magnetic head I is positioned onto the desired track.
Fig. 4 is a circuit diagram showing construction of one embodiment of the non] inear operational ampl if ier 21, and Fig. 5 is a graph showing input-output characteris tics of the nonl incar operational ampl if ier 21 shown in Fig. 4. TWO pairs of resistors 111, RI and diodes D, D, each resistor R1 and diode I) being connected in series, tire connected in 8 1 paral 1 cl to an i npul resis tor 112 of one input terminal of a differential amplifier 21a, where each two diodes D, D are ari,anly,,ed to point the opposi te direction each other. addi Lion, another two pairs of resistors 112, R2 and I n diodes " and diode D being connected in D, D, each resisLor R series, are connected in parallel to the input resistor R3, where each two diodes D, D are arranged to point the opposite directi(_)n each other. The threshold voltage for operating the diode 1) connected to the resistor DI is III and and that for the diode 1) connected to the resistor D2 is E2. One end of the input icsistor IM on the resistors 111, R2 side is cnnnected to an input terminal of a positional signal (Yin) inputted from the demodulation circuit 11, and the other end of the input resistor R3 on the diodes D side is connected to the one input terminal of-the differential amplifier 21a. The other input terminal of the differential amplifier 21a is carthed. An output terminal of the differential amplifier 21a is connected to an output terminal ^nal (Vout) to the control for outputting a positional sig signal g-enerating circuit 12. A resistor 114 is connected between the inpuL terminal in(] oxiLput terminal of the differential amplifier 21a.
As the input-output characteristics shown in Fig. 5, the gain of such nonlinear operational amplifier 21 is set to be 114/113 when the amplitude of the positional signal 9 1 (V in) input ted f rom t lie demodu I at ion c i reu l t 11 l s sma l 1 er than an absolute value of El, to be R4/ (parallel resistance between R1 and R3) when the amplitude is larger than the absolute value of E1 and smaller than an absolute value of E2, and to be R4/(parallel resistance among R1, R2, and R3) amplitude is larger than the absolute value of E2.
when the In putted control response to the nonlinear positional signal outfrom the nonlinear operational amplifier 21, the signal generating circuit 12 generates a control signal for controlling the position of the magnetic head 1, and the power- amplifier 13 amplifies this control signal so as to output thi s to the actuator 2. As a result, the position control of the actuaLor 2 is surely executed ac- rnitude of the amplitude of the positional cording to the maj, signal, and the setting is ended in a short time, then, the magnetic head 1 is positioned onto the desired track.
Fig. 6 is a circuit diagram showing construction of another embodiment of the nonlinear operational amplifier 21. Two pairs of diodes Dl, D2 and resistors R1, R2, each diode DI or D2 and resistor Rl or R2 being connected in series, are connected in parallel to an input resistor R3 of one input terminal of the differential amplifier 21a, where each diode Dl or D2 jr, arranged to point the opposite direction each other. Between each pair of the diode DI and resistor Ill and the diode D2 and resistor R2, are connected 1 () 1 i npu t t c rmi n a 1 An ontput termina pull-up resistors 115 and R6, respectively. One end of the both pull-up resistors 115 and 116 is connected to a reference voltage Yee or -Vec, respectively. One end of the input resistor R3 at the- resistors Ill, 112 side is connected to an inpot terminal of x positional signal (Vin) inputted from the demodulation circuit 11, and the other end of the input resistor R3 at the diodes D1, D2 side is connected to one inpiit terminal of the differential amplifier 2la. The other of the differential amplifier 21a is earthed.
1 of the differential amplifier 21a is connected to an output terminal for outputting a positional signal (Youl) to the control signal generating circuit 12. Between the input terminal and output terminal of the differential amplifier 21a, is connected a resistor R4.
Fig. 7 is a graph showing input-output characteri sties of the aforementioned nonlinear operational amplifier 21, wherein reference characters Vs show a switching point of t 1) e 1.r a! n.
When E expresses respcc t j ve f orward vo 1 tag, e drop of the diodes DI and D2, Vin expresses voltage of the positional sil,,,nil (Vin) inpul ted f rom the demodulation circui t 11, in the case of Vin >[(E + Vec) 112/1161 + E, a gain of [he nonlinear operational amplifier 21 is R4/(parallel res is tanc, c be tw c c n R 3 and 112). And in the case of Vin <E(E + Y cc) 111 /115 1 - E, a gai n is to be IM/ (1) a r a 11 e I 11 1 resistance between R3 and IM. And in the case of E - (E + V cc) RI/1151 - E < V in < 1 (E + Vcc) R2/R61 + e, the gain is to be R4/113.
In this nonlinear operational amplifier 21, each of the pull-up resistor 11,5, 116 is connected between the resistor R1 and diode D] and the resistor 112 and diode D2, respectively, then, ea(.-fi vol tage + Vs, -Vs as the gain swi tching points can optionally be set, and optimizes the setting after swi tctiing to tbe posi ti on contro l.
In the embodiment shown in Figs. 4 and 5, two switching points are set to switch the grain in three steps, and in the embodiment shown in Figs. 6 and 7, one switching point is set to switch the gain in two steps, however, the number of the switching point is not limited to those mentioned above. It is also suitable for continilnusly changing the gain applying. a curvilinear function.
Furthermore, thoxigh the magnetic disk drive has been described as the embodiment. the present invention may be applicable for every drive which writes/reads data on a recording disk by moving a head.
As this invention may be embodied in several forms without departing from the spirit of essential characteristies thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the de- 12 1 scription preceding them, and all changes that fall within the meets anti bounds of the claims, nr equivalence of such meets and bounds thereof are Iherefore intended to be embraced by, the claims.
13 1

Claims (6)

  1. What is claimed is:
    A disk drive comprising: an actuator which holds a head for writing/reading data and moves said head to a desired position on a disk, and a position control circuit which controls the position of said actuliLor in order to locate said head on said des i red pos i t i on, said position control circuit including, means fni- detecting the position of said head on the disk and generates a positional signal according to the detected position of said head, mearis for generating:t nonlinear signal 1)), increasing/decreasing a gain of said positional signal, and means for generatingr a signal to control the position of said actuator in responsive to said nonlinear signal.
  2. 2. A disk drive as set forth in Claim 1, wherein said means for generating , the nonlinear signal includes a circuit with 2n pairs of resistors and diodes, each resister and diode being connected in series, connected in parallel to an inptil renislor. for a terminal of an amplifier, whose each two diodes are arranged to point the reverse direction each other, having threshold voltalye different for. each two diodes whereby the gain (if said pnsitional signal is in- 14 1 T creased/decreased in (n+l) steps according to said threshold voltage to generate said nonlinear signal.
  3. 3. A disk drive as set forth in Claim 1, wherein said nonI i near si 1,), xial is generated by con tinuously increasing/decreasi nlr, the gain of said posi tional signal.
  4. 4. A disk drive as set forth in Claim 1, wherein said means f or generating the non] i near signal includes a circui t with two pairs of resistors and diodes, each resistor and diode being connected in series having a pull-up resistor connected therebetween, connected in parallel to an input resistor for a terminal of an amplifier, said diodes being arranged to point the reverse direction each other.
  5. 5. A disk drive substantially as herein described with reference to either of Figures 4 and 6 of the accompanying drawings.
    0
  6. 6. A disk drive substantially as herein described with reference to Figure 3 with or without reference to Figures 4 and 5 or 6 and 7 of the accompanying drawings.
    Pub'ished 1990 at The Patent Office. State House. 66 71 High Holborn, London WC1R4TP. Further copies maybe obtained from The PateritOfficeSales Branch. St Ma-y Cray- Orpington. Kent BR5 3RD. Printed by Multiplex techmques ltd. St Mary Cray, Kent, Con. V87
GB9009167A 1989-04-24 1990-04-24 Position control Withdrawn GB2231976A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP10414789 1989-04-24
JP24881689A JPH0349081A (en) 1989-04-24 1989-09-25 Magnetic disk device

Publications (2)

Publication Number Publication Date
GB9009167D0 GB9009167D0 (en) 1990-06-20
GB2231976A true GB2231976A (en) 1990-11-28

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Application Number Title Priority Date Filing Date
GB9009167A Withdrawn GB2231976A (en) 1989-04-24 1990-04-24 Position control

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GB (1) GB2231976A (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0836188A1 (en) * 1996-10-10 1998-04-15 Koninklijke Philips Electronics N.V. Method of defining a dynamic system controller and the controller per se

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959820A (en) * 1974-09-16 1976-05-25 Honeywell Information Systems, Inc. System for increasing the number of data tracks in a magnetic recording system
US4190859A (en) * 1977-03-08 1980-02-26 Victor Company Of Japan, Ltd. Tracking control apparatus for use in apparatus for reproducing video signals from a rotary recording medium
GB2063527A (en) * 1979-11-17 1981-06-03 Universal Pioneer Corp Tracking servo system of recording-disc information reading and reproducing apparatus
US4326226A (en) * 1980-05-08 1982-04-20 Storage Technology Corporation Constant bandwidth automatic gain control
EP0097208A1 (en) * 1982-06-18 1984-01-04 International Business Machines Corporation Head positioning system with automatic gain control
US4677507A (en) * 1986-05-30 1987-06-30 Magnetic Peripherals Inc. Digital velocity control for a disk drive servo system
EP0247829A1 (en) * 1986-05-26 1987-12-02 Pioneer Electronic Corporation Method and apparatus for correcting loop gain of a fine adjustment servo loop
EP0260138A2 (en) * 1986-09-10 1988-03-16 Fujitsu Limited Servo control system
EP0314111A2 (en) * 1987-10-30 1989-05-03 Mitsubishi Denki Kabushiki Kaisha Storage apparatus including head drive control

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2739024A1 (en) * 1977-08-26 1979-03-01 Siemens Ag Control circuit for electronic measurement characteristic - has comparators to which different reference voltages are applied, with switches applying second reference voltages
JPS6195367A (en) * 1984-10-17 1986-05-14 Toshiba Corp Image forming device
JPS63269324A (en) * 1987-04-28 1988-11-07 Mitsubishi Electric Corp Optical disk driving device

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3959820A (en) * 1974-09-16 1976-05-25 Honeywell Information Systems, Inc. System for increasing the number of data tracks in a magnetic recording system
US4190859A (en) * 1977-03-08 1980-02-26 Victor Company Of Japan, Ltd. Tracking control apparatus for use in apparatus for reproducing video signals from a rotary recording medium
GB2063527A (en) * 1979-11-17 1981-06-03 Universal Pioneer Corp Tracking servo system of recording-disc information reading and reproducing apparatus
US4326226A (en) * 1980-05-08 1982-04-20 Storage Technology Corporation Constant bandwidth automatic gain control
EP0097208A1 (en) * 1982-06-18 1984-01-04 International Business Machines Corporation Head positioning system with automatic gain control
EP0247829A1 (en) * 1986-05-26 1987-12-02 Pioneer Electronic Corporation Method and apparatus for correcting loop gain of a fine adjustment servo loop
US4677507A (en) * 1986-05-30 1987-06-30 Magnetic Peripherals Inc. Digital velocity control for a disk drive servo system
EP0260138A2 (en) * 1986-09-10 1988-03-16 Fujitsu Limited Servo control system
EP0314111A2 (en) * 1987-10-30 1989-05-03 Mitsubishi Denki Kabushiki Kaisha Storage apparatus including head drive control

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Publication number Publication date
GB9009167D0 (en) 1990-06-20
DE4013009A1 (en) 1990-10-25

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