CA2091592A1 - Disk recording/reporduction device and a method of operation thereof - Google Patents
Disk recording/reporduction device and a method of operation thereofInfo
- Publication number
- CA2091592A1 CA2091592A1 CA 2091592 CA2091592A CA2091592A1 CA 2091592 A1 CA2091592 A1 CA 2091592A1 CA 2091592 CA2091592 CA 2091592 CA 2091592 A CA2091592 A CA 2091592A CA 2091592 A1 CA2091592 A1 CA 2091592A1
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- head
- recording
- disk
- velocity
- moving
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Abstract
ABSTRACT OF THE DISCLOSURE
The behavior of a linear motor with respect to disturbance vibration is reduced by detecting the moving speed of an optical head 1 (or a linear motor 2 moving the optical head 1) with a velocity sensor 11, amplifying the output thereof with an amplifier 13, and applying a negative feedback (velocity feedback) to the linear motor 2 via a driver 6. Because the gain of the tracking servo loop including the linear motor 2 is reduced by this velocity feedback, this gain reduction is compensated for by a phase lag compensating circuit 12 to improve anti-vibration performance.
The behavior of a linear motor with respect to disturbance vibration is reduced by detecting the moving speed of an optical head 1 (or a linear motor 2 moving the optical head 1) with a velocity sensor 11, amplifying the output thereof with an amplifier 13, and applying a negative feedback (velocity feedback) to the linear motor 2 via a driver 6. Because the gain of the tracking servo loop including the linear motor 2 is reduced by this velocity feedback, this gain reduction is compensated for by a phase lag compensating circuit 12 to improve anti-vibration performance.
Description
2 ~ 2 TITLE OF THE INVENTION
A Disk Recording/Reproduction Device and a Method ofOperation Thereof BACKGROUND OF THE INVENTION
S Field of the Invention The present invention relates to a disk recording/reproduction device which records information on a disk such as an optical disk and a magnetic disk and which reproduces recorded information, and a method of operating such a disk recording/reproduction device. ;
Description of the Background Art In a conventional disk recording/reproduction device, a structure is widely used where the head for recording and reproducing information is positioned by being moved to an arbitrary radial position of the disk using a linear motor or a swing arm. ~;
Fig. 12 is a block diagram schematically showing an example of structure of a conventional optical disk recording/reproduction device. A disk 7 is rotatably driven by a spindle motor 9. A plurality of tracks 8 are provided concentrically or spirally in disk 7. An optical head 1 directs an optical beam 3 to an arbitrary track 8 to carry out recording and reproduction of information.
Optical head 1 is fixed on a linear motor 2. Linear motor 2 includes a bearing portion 10 of a rolling or sliding - , : , : : ' . : : : ' ., : : : . . :
.. . . .
2 ~ 9 2 structure in contact with the bottom floor inside th0 main body of the device. Optical he~d 1 is driven radial of disk 7 by linear motor 2. -Optical head 1 is provided with a tracking error detecting unit 4 by its optical system. Tracking error detecting unit 4 detects the relative position deviation amount of the actual irradiated position with respect to the reference irradiated position b~ optical beam 3 in track 8 to provide a tracking error signal TES
representing the position deviation amount.
Tracking error signal TES is provided to a driver 6 via a phase compensating unit 5. Phase compensating unit 5 carries out a predetermined phase compensation for ;
tracking error signal TES. Driver 6 provides a driving ~--si~nal to linear motor 2 to cancel the tracking error .:~.
according to the phase compensated signal from phase ;
compensating unit 5. Linear motor 2 is driven according `~-to a driving signal provided from driver 6. As a result, :
optical head is driven radial of disk 7, whereby optical beam 3 is properly positioned on track 8.
Fig. 13 is a block diagram of a structure of a tracking servo loop which is a control loop for carrying out the position control of head 1. The tracking servo loop includes the elements of tracking error detecting unit 4, phase compensating unit 5, driver 6, and linear --2-- .
. .: , . . . : .. . ,, . :~.
2 t~
motor 2. The tracking servo loop is a control system of following a position Xo of optica] head 1 with a displacement Xi of track 8 as a desired value. If the product of all the gains of each element in the tracking servo loop is G(s), a followed error Xe is represented by the following equation (l):
Xe = {1 / (l + G(s))} Xi ... (l) The behavior of optical head 1 and the position relationship between optical beam 3 and track 8 will be described hereinafter when disturbance vibration is applied to the tracking servo loop of the above-described optical disk recording/reproduction device.
Fig. 14 is a kinematic model diagram of optical head l and its vicinity shown in Fig. 12. Assuming that the displacement of disturbance vibration is Y, the displacement of optical head 1 (or linear motor 2 driving ~ ;
optical head 1) is X, the mass of the movable portion of linear motor 2 including optical head 1 is M, and the equivalent spring constant and coefficient of viscosity generated in bearing lO of linear motor 2 are K and D, respectively, the following equation of (2) is obtained by an equation of motion according to Laplace transformation:
Ms X + Ds (X - Y) + K (X - Y) = 0 ... (2) where s represents Laplace operator.
By transforming equation (2), the ratio of ~ O ~ ~ ~j 9 2 displacement X of optical head 1 to displacement Y of disturbance vibration (X/Y) is obtained by the following equation (3):
(X/Y) = (Ds + K) / (Ms + Ds + K) = 1 - {(Ms2) / (Ms2 ~ Ds + K)}
= l - {K / (Ms + Ds ~ K)} {(Ms )} / K}
{Il)o2 / ( 52 + 2~o~1)0S + ~lo ) ~ ( S / ~I)o ) = 1 - Go(s) (S2 / ~o2) ... (3) ~O(s) in the above equation (3) is a normalized form .
of the transfer function of linear motor 2 representing the spring and mass system, and is well known as represented by the following equation (4). :
Go(s) = K / (Ms + Ds + K) = ~o2 / (S2 + 2~o~0 S + ~2~ ~-- (4) lS ~0 is the resonance angular frequency of linear motor 2 and ~0 is the damping value of linear motor 2, and are expressed by the following equations of (5) and (6), respectively.
~0 = (K / M)s ................................................ (5) ~o = D / {2 (MK) } ................................................. (6) Referring to Fig. 14, it is appreciated -that there is no influence of disturbance vibration to the tracking s~rvo loop of the optical disk recording/reproduction device if displacement X of optical head 1 is equal to displacement Y of disturbance vibration when disturbance ~4-:. -: . - - :
~ '3~ 2 vibration is e~erted. In other words, the difference between displacement Y and displacement X, (Y-X) is the component of the disturbance signal mixed into the tracking servo loop.
The ratio of the mixed disturbance vibration component (Y-X) to the exerted disturbance vibration is defined in the following equation (7) as a dis~urbance transmission rate B(s). This defined disturbance transmission rate B(s) is used in the following description.
B(s) = (Y - X) / Y = 1 - (X / Y) (7) Referring to equations (3) and (7), disturbance transmission rate B(s) is represented by the following equation (8).
B(s) = Go(s) ~ (s / ~0) -- (8) Therefore, it can be considered that disturbance transmission rate B(s) represents the deviation amount of optical head 1 with respect to track 8 generated by disturbance vibration. ~ :
The characteristics of transfer function Go(s) and disturbance transmission rate B(s) are graphed in Fig. 15.
~ig. 15 shows the characteristics of transfer function Go(s) of the spring-mass system and the characteristics of disturbance transmission rate B(s), where the gain is plotted along the ordinate and the angular frequency : ~ . ,. : .. , . . : :
plotted along the abscissa. The transfer function Go~s) is indicated by the solid line and the disturbance transmission rate B(s) is indicated by the broken line.
It can be appreciated from Fig. 15 that the characteristic of the transfer func-tion Go(s) is a second order low pass filter type with the resonance angular frequency ~0 as the breakpoint frequency. The characteris~ics of disturbance transmission rate B(s) is a second order high pass filter -type where the characteristics of transfer function Go(s) is rotated counter clockwise about resonance angular frequency ~0.
Consider the case where there is deviation in the position between optical head 1 and track 8 due to disturbance vibration introduced into the tracking servo loop, resulting in a offset of optical head 1. Viewing `~
the position of optical head 1 and the position of track 8 in a relative manner, it can be seen that the position of .
track 8 is deviated due to the disturbance vibration. In other words, the position of track 8 which is the followed desired value of the tracking servo loop is disturbed by disturbance vibration.
In view o~ the foregoing, a tracking servo loop is represented by a block diagram in Fig. 16. Referring to Fig. 16, displacement Y of disturbance vibration is multiplied by disturbance transmission rate B(s), which :f, ' ~ ' . - ., - - ~ :
. 3 ~ 2 yields the introduced amount of disturb~nce signal into the tracking servo loop. This B(s) Y is added to followed error Xe so as to disturb displacement Xi of track 8 which is the followed desired value.
In accordance with Fig. 16, followed error Xe is represented by the following equation (9).
Xe = {1 / (1 + G(s))~ Xi + {B(s) / (1 + G(s))} Y ~ --- (9) The second ter~. of the right hand side of equation (9) represents the increment of followed error Xe caused by disturbance vibration. In order to transform displacement Y of disturbance vibration into an acceleration dimension expression generally used from the displacement dimension, a Laplace operator 52 indicating a repeated differentiation is added to the numerator and denominator of the second term in equation (9) to obtain the following equation (10).
Xe = ~1 / (1 + G(s))} Xi + {3(s) / (1 + G(s)) s2}
Ys .,. (10) By extracting the transfer function to followed error Xe from disturbance vibration acceleration yS2 in the second term of the right hand side of equation (10), and defining that transfer function as disturbance suppression characteristics D(s), the following equation (11) is obtained.
2 ~ 9 ~ ~
D(s) = {B(s) / (1 ~ G(s)) s2} ... (11) The disturbance suppression characteristics D(s) of the above equation (11) represents the charactexistics suppressing the disturbance vibration in optical head l.
Followed error Xe ganerated by disturbance vibration acceleration Ys becomes lower as the value of disturbance suppression characteristics D(s) is smaller. This means that it is greatly immune to disturbance vibration. A
smaller disturbance suppression characteristics D(s) results in a tracking servo loop superior to anti-vibration performance.
It can be appreciated from the above equation (11) that ~he value of servo gain G(s~ is increased or the value of disturbance transmission rate B(s) reduced to lower disturbance suppression characteristics D(s) in order to improve anti-vibration performance.
A possible consideration to increase the servo gain G(s) to lower disturbance suppression characteristics D(s) is to enlarge the servo band. However, this method has a disadvantage of possibility of deviation in the servo by a defect in disk 7, or posing severe requirements to the characteristic strain of the machine system such as linear motor 2, and is not applicable in this case.
Another method is to raise the servo gain of the low frequency region where disturbance vibration is easily -8~
: . , - . , ~ .
- ~ , - ~ . .
; ~ . , .: ,.
~91~92 generatzd by means of phase lag compensation which is a kind of integral compensation. This is based on the fact that the frequency components o~ clisturbance vibration are easily generated normally in the range below several ten H~. This method will be describecl hereafter.
Fig. 17 shows an example of a galn curve of a servo gain G(s) of the tracking servo loop using the linear motor. In Fig. 17, the gain is plotted along the ordinate, and the angular frequency is plotted along the abscissa. By obtaining disturbance suppression characteristics D(s) according to equation (11) while taking into consideration the gain curve of Fig. 17 and ~he disturbance transmission rate B(s) characteristics o Fig. 15, the characteristics gain curve shown in Fig. 18 -is established.
Fig. 19 is a graph showing the frequency characteristics of a phase lag compensation L~(s) where a predetermined angular frequency ~v at the low frequency region is the upper limit angular frequency. In the graph of Fig. 19, the gain is plotted along the ordinate and the angular frequency plotted along the abscissa. By adding the element of phase lag compensation L~(s) haviny the frequency characteristics of Fig. 19 into the tracking servo loop having the gain curve of Fig. 17, the gain curve of that tracking servo loop is as shown in Fig. 20.
_g_ '~-20~1~92 It is appreciated from Fig. 20 that the servo gain of an angular frequency below the upper limit angular frequency ~v is higher than the gain shown in Fig. 17 due to phase lag compensation L~(s). The addition of such a phase lag compensation Ll(s) results in the gain curve of disturbance suppression characteristics D(s) as shown in Fig. 21. Because the servo gain in the low frequency -~
region rises as shown in Fig. 20 due to addition of phase lag compensation Ll(s), it is appreciated from Fig. 21 that the gain of disturbance suppression characteristics D(s) in the low frequency region below the upper limit frequency ~y is reduced. As a result, disturbance suppression characteristics D(s) is reduced in the lower ;~
frequency region where disturbance vibration is easily generated to allow improvement in anti-vibration performance.
However, if the upper limit angular frequency ~v phase lag compensation Ll(s) is further set higher to .
further improve the anti-vibration performance at the lower frequency resion taking advantage of the effect of such phase lag compensation, the phase margin in cut off angular frequency ~c Of the servo gain will be reduced, resulting in a problem of an unstable tracking servo loop.
A possible consideration to further improve anti- - -vibra~ion performance at the low frequency region is to .. . .. .. .
- : , 2 ~ 9 2 simply apply at least two stages of phase lag compensation to increase the servo gain at low frequency regions. In this case, the characteristics of the original linear motor will be a second order integral system in regions greater than resonance angular frequency ~0, resulting in an integral system of not less than the total of fourth order. Fig. 22 is a graph showing the vector locus of the servo gain when two stages of phase lag compensation are added. Referring to Fig. 22, the vector locus of the servo gain makes one rotation about point (-1, jO) clockwise. This will produce the problem that the tracking servo loop is not stable due to Nyquist stability criterion.
Thus, there is a limit in the method of reducing ~ `
disturbance suppression characteristics D(s) by simply applying phase lag compensation to increase the servo gain in low frequency regions.
A method of increasing disturbance suppression -characteristics D(s) can be considered by reducing disturbance transmission rate B(s) to improve anti-vibration performance. The method of reducing disturbance transmission rate B(s) of the mechanical behavior of linear motor 2 with respect to disturbance vibration will be described hereinafter.
If pre-load towards bearing unit 10 of linear motor 2 : - :: ,. . . i, ~, :, ", : .. .. :. . ; . . . . .
.: . .. ,, .. . : ~ . ~ -. - . ~ . . . . , , . -2~5~2 is increased to raise the equivalent spring ability, resonance angular frequency ~0 takes a higher value. As described in Fig. 15, the characteristics of disturbance transmission rate Bts) takes a high pass fllter type that decreases where the angular frequency is below the resonance angular frequency ~0. Therefore, if the resonance angular frequency ~0 is set to a resonance angular frequency ~0' higher than a predetermined resonance angular frequency ~0, disturbance transmission rate B(s) in the low frequency region is reduced as shown in Fig. 23.
Fig. 23 is a graph showing the change in disturbance transmission rate B(s) according to the change in resonance angular frequency ~0. In Fig. 23, the gain is plotted along the ordinate and the angular frequency is plotted along the abscissa, wherein disturbance -;~
transmission rate B(s) by the original resonance angular frequency ~0 and by the higher resonance angular frequency ~0' are indicated by a solid line and a chain dotted line, respectively.
It is appreciated from Fig. 23 that a higher ~ .
resonance angular frequency causes the characteristics of disturbance transmission rate B(s) to be shifted towards the high frequency side, whereby disturbance transmission rate B(s) in the low frequency region is reduced.
However, such a rise of the resonance angular .. . . ~ . .
2~592 frequency to ~0' causes the servo gain G(s) of an angular re~uency below resonance angular frequency ~0' to become lower than the original servo gain G(s), as shown in Fig.
24. Fig. 24 is a graph showing the change in servo gain S according to the change of resonance angular frequency.
In Fig. 24, the gain is plotted along the ordinate and the angular frequency plotted along the abscissa. The gain curve according to the original resonance angular frequency ~0 and that by the higher resonance angular .
frequency ~0' are shown by a solid line and a chain dotted line, respec~ively.
It can be appreciated from Fig. 24 that the gain curve by the higher resonance angular frequency ~0' has the servo gain G(s) reduced in the angular frequency below resonance angular frequency ~0' in comparison to the original gain curve because the servo gain G(s) below the `
resonance angular frequencies ~0 and ~0' is constant. ;' Therefore, disturbance suppression characteristics D(s) determined by disturbance transmission rate B(s) and servo gain G(s) is not improved by the above-described method. Also, increase in the pre-load to bearing unit lO
for carrying out the above-described method will promote abrasion of bearing unit 10, resulting in the problem of ~-reducing the mechanical lifetime of the device.
Thus, it was difficult to improve disturbance :: ~: . : .:
2~ .3~
suppression characteristics D~s) i-rom the conventional improving methods of anti-vibration performance. There were many problems regarding improvement of anti-vibration performance of a disk recording/reproduction device.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the anti-vibration performance of a disk recording/reproduction device.
Another object of the present invention is to improve lQ the anti-vibration per~ormance of a disk recording/reproduction device without degrading stability of the servo loop and lifetime of the mechanical system.
A disk recording/reproduction device according to the present inven~ion is a disk recording/reproduction device for recording and reproducing information to and from a disk having tracks that can record information, and includes a head, a moving velocity detecting circuit, a tracking error detecting circuit, a phase compensating ~ -unit including a phase lag compensating circuit, and a head driving circuit. The head is provided in a movable manner to record/reproduce information at an arbitrary radial position of the disk. The moving velocity detecting circuit detects the moving velocity of the head.
The tracking error detecting circuit detects error of the recording/reproduction position of the head with respect ~:, `.: ~ . . . , ' ~ .: .:
: ~ . ., ~ . . : .. . .
2g~5~2 to a track posi~ion of the disk, whereby ~he detected result is provided as a tracking error signal. The phase compensating unit applies phase compensation to a tracking error signal. The head driving circuit moves the head to cancel error of the recording/reproduction position of the head with respect to the track position according to the phase lag compensated result of the phase lag compensating circuit while applying damping to the head accordLng to the detected result of the moving velocity detecting circuit.
Because damping is applied to the operation of the :. .
head according to the detected result of the moving -velocity detecting circuit, the disturbance transmission rate in the head is reduced. Also, although the servo `~
gain regarding the control of the head is reduced by the ~-addition of this damping, the phase lag compensating circuit of the compensating unit compensates for phase lag of the tracking error signal, so that the lowered servo gain is raised.
Therefore, the disturbance transmission rate is reduced, and reduction of the servo gain caused by reduction of the disturbance transmission rate will be compensated for. Thus, the anti-vibration performance of the device can be improved without degrading stability of the servo loop and lifetime of the mechanical system 2~ 0 ~ 1 r~ ~ 2 because the disturbance transmission rate can be reduced without decreasing the servo gain.
A disk recording/reproduction device according to another aspect of the present invention is a disk S recording/reproduction device for recording and reproducing information to and from a disk having tracks that can record information, and includes a head, a first control circuit, and a second control circuit.
The head is provided in a movable manner to record/reproduce information at an arbitrary radial position of the disk. The first control circuit applies `~
damping to the operation of the head according to the moving velocity of the head. The second control circuit controls the position of the head to follow the position of the track and compensates for the transfer ~ `
characteristics of the head to compensate for the servo gain that is reduced by damping.
Because damping is applied to the operation of the head according to the moving velocity of the head by the first control circuit, the disturbance transmission rate of the head is reduced. Also, although the sexvo gain is reduced regarding the operation of the head due to load of this damping, the second control circuit compensates for the mechanical characteristics of the head to compensate -for reduction in the servo gain, whereby the servo gain is -2~31~2 raised.
Therefore, the disturbance transmission rate isreduced, and reduction of the servo gain is compensated for according to decrease of the disturbance transmission rate Thus, the anti-vibration performance of the device can be improved without degrading the stability of the servo loop and the lifetime of the mechanical system because the disturbance transmission rate is reduced without decreasing the servo gain.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram schematically showing a structure of an optical disk xecording/reproduction device according to an embodiment of the present invention.
Fig. 2 is a side view of an example of a velocity sensor.
Fig. 3 is a block diagram schematically showing another example of a velocity sensor.
Fig. 4 schematically shows an example of a position sensor used in the velocity sensor of Fig. 3.
Fig. 5 is a block diagram of the periphery of a - - -. .. , ;:; . ::. . ~ .
20~ l5~2 velocity feedback loop.
Fig. 6 is a graph showing the characteristlcs of the transfer function of a linear motor when velocity feedback is applied.
Fig. 7 is a graph showing characteristics of the disturbance transmission rate of a linear motor where , velocity feedback is applied.
Fig. 8 is a graph showing the characteristics of the transfer function of a linear motor where velocity feedbacX and phase lag compensation are combined.
Fig. 9 is a graph showing the disturbance suppression characteristics where velocity feedback and phase lag compensation are combined. ~`
Fig. 10 is a graph showing the vector locus of servo gain where velocity feedback and two stages of phase lag compensation are combined.
Fig. 11 is a graph showing the disturbance suppression characteristics where velocity feedback and ;~
two stages of phase lag compensation are combined.
Fig. 12 is a block diagram schematically showing a structure of a conventional optical disk recording/reproduction device.
Fig. 13 is a block diagram of a tracking servo loop.
Fig. 14 is a kinematic model diagram of an optical head and its vicinity.
: . ..
2 ~ 2 Fig. li is a g:raph showing the transfer function characteristics of a spring-mass system and disturbance - transmission rate characteristics.
Fig. 16 is a block diagram of a tracking servo loop -taking into consideration disturbance vibration.
Fig. 17 is a graph showing a gain curve of a tracking servo loop.
Fig. 18 is a gxaph showing disturbance suppression characteristics.
Fig. 19 is a graph showing fxequency characteristics of phase lag compensation.
Fig. 20 is a graph showing a gain curve of a tracking servo loop where phase lag compensation is applied.
Fig. 21 is a graph showing disturbance suppression characteristics where phase lag compensation is applied.
Fig. 22 is a graph representing a vector locus of a servo gain where two stages of phase lag compensation are applied.
Fig. 23 is a graph showing change in disturbance transmission rate according to change in resonance angular frequency.
Fig. 24 is a graph showing change in servo gain according to change in resonance angular frequency.
DESCRIPTION OF THE PREFERRED EM~ODIMENTS
Fig. l is a block diagram schematically showing a 2~ 592 structure of an optical disk recording/reproduction device according to an em~odiment of the present invention. The components in Fig. 1 similar to those shown in Fig. 12 have the same reference numbers denoted and their description will not be repeated. The structure of Fig. 1 differs from the structure of Fig. 12 in that a velocity sensor 11 for detec~ing velocity of an optical head 1 (or a linear motor 2 moving optical head 1) is provided, a velocity feedback loop is formed where the output of velocity sensor 11 is fed back negatively from driver 6 to linear motor 2 via an amplifier 13 and a substrator 22, and a phase lag compensating circuit 12 is included in phase compensating circuit 5.
Velocity sensor 11 is of the types shown in Figs. 2-4. Fig. 2 is a side view of an example of a velocity sensor 11. Velocity sensor 11 has either of a magnet 14 or a coil 15 fixed to optical head 1 (or linear motor 2) and the other fixed to the main body side of the optical disk recording/reproduction device. In velocity sensor 11 of such a structure, electromotive force is generated in coil 15 due to the relative motion of magnet 14 and coil 15. This electxomotive force has a constant relationship with respect to the velocity of relative motion.
Therefore, the electromotive force generated in coil 15 by this relative motion is provided as a velocity detection ' , , , . ' , . ~ ' ' . :
~ O ~ ~ tj 9 2 signal.
Fig. 3 is a block diagram schematicall~ showing another example of a velocity sensor 11. This velocity sensor 11 includes a position sensor 16 for detecting the position (displacement) of optica:l head 1 (or linear motor 2), and a differentiator 17 for d:ifferentiating the output of position sensor 16. Velocity sensor 11 has the position of optical head 1 detected by position sensor 16, whereby the detected position information is differentiated by differentiator 17. The output of differentiator 17 represents the velocity of optical head 1. !
A specific example of position sensor 16 of Fig. 3 is shown in Fig. 4. Referring to Fig. 4, a light emitting diode 18 is provided in optical head 1 (or linear motor 2). A PSD (Position Sensitive Device) 19 which is a~ -~
photodiode for detecting the position of optical head 1 is provided along the moving direction of optical head 1 in the main body of the device. Light emitting diode 18 is provided at a position to direct the emitted light towards the detecting face of PSD 19. Therefore, the position of incident light 20 into PSD 19 varies according to the position of optical head 1. PSD 19 has output terminals A
and B respectively provided at the either ends in the longitudinal direction. Photoelectric current flows from the irradiated position by incident light 20 towards output terminals A and B. The photoelectric current from output terminals A and B vary accordin~ to the resistance between the irradiated position of incident light 20 and 5 the respective output terminals A and B. This resistance increases according to the distance betw~en the irradiated position and the output terminal. By obtaining the ; difference of the photoelectric current outputs, the irradiated position by incident light 20 can be defined to identify the position of optical head 1.
The photoelectric current provided from output terminals A and s are provided to a differential amplifier 21. Differential amplifier 21 differential-amplifies these photoelectric current outputs to provide the same to differentiator 17 shown in Fig. 3 as the information representing the position of optical head 1.
The change of disturbance transmission rate B~s) will be described hereinafter where a velocity feedbacX loop as shown in Fig. 1 is formed. Fig. 5 is a block diagram of the periphery of the velocity feedback loop. A driving input U which is a signal supplied to driver 6 from phase compensating unit 5 is converted into a displacement X0 of optical head 1 (or linear motor 2) via a gain KD of driver 6, a thrust constant K~ of linear motor 2, and mechanical characteristics of linear motor 2 1/~Ms +Ds~K).
, ~, . . ~ , . , : .
~3~
Displacement XO is negatively fed back to driver 6 via a sensitivity ~y-S of velocity sensor 11 and a gain A of amplifier 13. M in the mechanical characteristics of the linaar motor is the mass (including mass of optical head l) of the movable portion of linear motor 2, D is the equivalent coeficient of viscosity generated in bearing unit 10 of linear motor 2, and K is the equivalent spring constant generated in bearing unit lO of linear motor 2.
The transfer function (XO/U) from driving input U to displacement XO in such a velocity feedback loop is expressed by the following equation (12).
(XO / U) = (KF KD) / {MS + (D + A KV KF KD) S
+ K}
= (KF ' KD / K) [K / {MS2 + (D + A KV
KF KD) S + K}]
= (KF KD / K) GO/ (S) .. (12) Go~(s) of the above equation ~12) is a normalized form of the lin~ar motor transfer function after the velocity feedback loop foxmation, and is expressed by the following equation (13).
&Ot(S) = K / {MS + (D + ~ KV K~ KD) S + K}
2 / (SZ + 2~o' ~o 5 + ~-)o ) ... (13) ~ 0 is the resonance angulax frequency of linear motor 2, and ~0~ is the damping value after velocity feedback . ' 2~9~g2 loop formation, and are represented by the following equations of (14) and (15), respectively.
= (K/M) ... (14) ~0' = (D + A ~ KV KF KD) ~ {2 (~IK) } ... (15) The damping value where a velocity feedback loop is not formed, i.e. ~0 of equation (6) is determined by the equivalent coefficient of viscosity D of bearing unit 10 of linear motor 2, spring constant K and mass M of the movable portion of linear motor 2. The damping value is generally in the range of 0.1-0.3, and approximately 0.5 at maximum.
However, the damping value of ~0' where a velocity feedback loop is formed is affected by the product of gain KD Of driver 6, thrust KF of linear motor 2, sensitivity Kv of velocity sensor 11, and gain A of amplifier 13 amplifying the output thereof according to the above equation of (15). Therefore, if thrust constant KF~ gain KD and sensitivity KV are determined, the damping value ~0'~
can be changed by varying gain A. Furthermore, because ~
the equivalent coefficient of viscosity D of the bearing ~ -portion in the numerator of equation (15) is a small value that is generated by rolling resistance and the like, (A-KV-K~-KD>>D) can be set by the value of gain A. In this case, ~0' is represented by the following equation ~16):
~0~ = (A Kv K~ KD) / {2 (~K) '5} . . . ( 16) -24~
-~ . , -. ~: . . . -.. . . . . .
2 ~ r ~1 r~
When the value of gain A is set so that ~o'>l, a breakpoint of characteristics appears in the characteristics of the normalized transfer function Go'(s) of linear motor 2 that is represented by equation (13).
5 Fig. 6 is a graph showing the characteristics of transfer function Go'(s) of linear motor 2 where a velocity feedback is applied. When the value of A is set so that ~o'>l, as described above, transfer function Go~(s) shows a breakpoint at angular frequency ~A lower than ~0 and at angular frequency ~B higher than ~0 with the resonance angular frequency ~0 as the center. Thus, the gain in the region between angular frequencies ~A and ~B iS reduced from the original gain.
The characteristics of disturbance transmission rate B'(s) takes a high pass filter type where the ~
characteristics of transfer function Go~(s) ls rotated ~ -counter clockwise about resonance angular frequency ~0, resulting in the characteristics shown in Fig. 7. Fig. 7 is a graph representing the characteristics of disturbance transmission rate B'(s) of the linear motor where velocity ~ -feedback is applied. As a result of the gain in the region between angular frequencies ~A and ~B reduced as shown in Fig. 6, the characteristics of disturbance transmission rate B'(s) is accordingly reduced in the region between angular frequencies ~A and ~B as shown in e~
Fig . 7 . Therefore, the angular frequency components in the region between angular frequencies ~A and ~B in disturbance vibration will not easily be introduced into the tracking servo loop.
A control similar to such a velocity feedback is carried out in a conventional disk recording/reproduction device. An example is described in "Development of CD-ROM
Drive System" Sanyo Technical View Vol. 19, No. 1, pp. 35-45, February 1987. However, there is no description of the object and meaning of a velocity feedback in this document. There are also disclosures in Japanese Patent ~aying-Open No. 61-227692, Japanese Patent Laying-Open No.
2-263367 and Japanese Patent Laying-Open No. 3-118481.
However, the control of velocity feedback described in these applications are all provided for the purpose of improving stability of control of the servo system. There `~
is no study nor description of employing the control for ;~
improving anti-vibration performance. It is not possible to improve anti-vibration performance with only the described velocity feedback due to reasons set forth in the following. ~ `
As already described with reference to the above equation of (11), disturbance suppression characteristics D(s) is determined by servo gain G(s) and disturbance transmission rate B(s). Therefore, the following problems - . : ~ . - ~` , . . .;
2 ~ 9 ~
will be generated by just applying velocity feedback.
When transfer function Go/(s) of linear motor 2 which - becomes the ba~is of servo gain G(s) is reduced in the region between angular frequencies ~A and ~B as shown in S Fig. 6, servo gain G(s) is also reduced in the same region of angular ~requency due to the ~elocity feedback.
Regardless of how much disturbance transmission rate B'(s) is reduced in the same region of angular fre~uency to lower the introducing amount of disturbance vibration, disturbance suppression characteristics D'(s) determlned by servo gain G'(s) and disturbance transmission rate B'(s) where a velocity feedback is applied will show no change with respect to the disturbance suppression -characteristics D(s) of Fig. 18 where velocity feedback is not applied. There is no change, whether good or bad, in the characteristics.
The invention of the present application is `~-characterized by including a phase lag compensating ~ -circuit 12 in the tracking servo loop for raising the gain of an angular frequency region below angular frequency ~B :
to a resonance angular frequency ~0, for example, in `
addition to the above-described velocity feedback loop.
Figs. 8(a) - (c) are graphs showing the characteristics of the transfer function of linear motor 2 where a velocity feedback and phase lag compensation are combined. Figs.
-~7-~ ;.. .... .. .
: , ~ - :.- .
2~9~ 5~2 8(a) - 8(c) show the charactexistics of phase lag compensation L2(s), of transfer unction G~'(s) of linear motor 2 where velocity feedback is applied, and of transfer funstion L2(s) ~ Go'(s) of linear motor 2 where velocity feedback and phase lag compensation are applied~
respectively. By introducing into the tracking servo loop a phase lag compensation Lz(s) having the characteristics so as to raise the gain in the angular frequency region below angular frequency ~3 to resonance angular frequency ~0 as shown in Fig. 8(a), transfer function Go'(s) of linear motor 2 where velocity feedback is applied has the gain in the region below angular frequency ~B compensated for as shown in Fig. 8(c). Accordingly, reduction of servo gain G'(s) is also compensated for.
lS Because there is no change in disturbance transmission rate B'(s) even when a phase lag compensating -circuit 12 is introduced into the tracking servo loop, disturbance suppression characteristics D'(s) has the `
characteristics in the low frequency region improved in comparison with that of Fig. 18, as shown in Fig. 9.
Fig. 9 is a graph showing the characteristics of disturbance suppression characteristics D'(s) where velocity feedback and phase lag compensation are combined.
It can be appreciated from Fig. 9 that the disturbance suppression characteristics D'(s) in the low frequency 2 ~ 9 ~
region of below angular fre~uency ~B is reduced by vixtue of reduction of disturbance transmission rate B'(s) by velocity feedback and compensation of servo gain G'(s) by phase lag compensation L2(s).
Thus, according to the present invention, the disturbance suppression characteristics is reduced to improve anti-vibration performance by reducing the disturbance transmission rate by a velocity feedback and compensating for only the servo gain reduced by that velocity feedback by phase lag compensation.
The inclination of the gain will not exceed -40 (dB/dec) even in the case where a phase lag compensation ~-~
L2(s) is applied as described above. Because the --characteristics of the tracking servo loop shows only a maximum of a second order lag characteristics, the phase lag compensation Ll(s) described with reference to Fig. l9 ~`
can further be applied to the tracking servo loop to further improve anti-vibration performance. Fig. 10 i5 a . ~;
graph representing the vector locus of servo gain G(s) where a velocity feedback and phase lag compensation of two stages are combined. In the case where a velocity feedback and a phase lag compensation L~(s) is combined and then further combined with a phase lag compensation Ll(s), the characteristics of the tracking servo loop is limited , to a third order lag characteristics. In such a case, the .. ... , . ., ... .... . , ,, ~
:.. , . .. - . .. ,, .. .,, , ..... ~....... .
: - . .. - .
-,~
2 0 ~
vector locus of the servo gain does not make one rotation clockwise about point (-l, jO) as shown in Fig. 10.
Therefore, the tracking servo loop is stable by Nyquist stability criterion.
Fig. ll is a graph representing the disturbance suppression characteristics D"(s) where a velocity feedback and two stages of phase lag compensation are combined. As described above, there is no change in disturbance ~ransmission rate B'(s) even if a phase lag compensation Ll(s) is further added, and only servo gain G'(s) in the region between angular frequencies ~u and ~v show an increase. Therefore disturbance suppression characteristics D"(s) is further reduced in the region between angular frequencies ~u and ~, whereby the anti-vibration performance of the device is further improved.
Although an optical disk recording/reproduction device of a structure where optical head 1 is linearly -~
moved to be positioned radial OI disk 7 by linear motor 2 in the present embodiment, the invention is not limited to this, and can be applied to a magnetic disk device of a structure where the head carrying out recording/reproduction of information is positioned by being moved along the circumferential track radial of the disk by a rotary arm.
In this case, a control as in the present embodiment ~ .. . .
J15~
can be carried out by providing a velocity sensor such as to detect the rotation velocity (angular velocity) o the rotary arm.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and i5 not to be taken by way o limitation, the spirit and scope of .
the present invention being limited only by the terms of -the appended claims. ::~
' ;
.,, , , . , , , ~
. ' : ` ~ ' ' ' .' '.
A Disk Recording/Reproduction Device and a Method ofOperation Thereof BACKGROUND OF THE INVENTION
S Field of the Invention The present invention relates to a disk recording/reproduction device which records information on a disk such as an optical disk and a magnetic disk and which reproduces recorded information, and a method of operating such a disk recording/reproduction device. ;
Description of the Background Art In a conventional disk recording/reproduction device, a structure is widely used where the head for recording and reproducing information is positioned by being moved to an arbitrary radial position of the disk using a linear motor or a swing arm. ~;
Fig. 12 is a block diagram schematically showing an example of structure of a conventional optical disk recording/reproduction device. A disk 7 is rotatably driven by a spindle motor 9. A plurality of tracks 8 are provided concentrically or spirally in disk 7. An optical head 1 directs an optical beam 3 to an arbitrary track 8 to carry out recording and reproduction of information.
Optical head 1 is fixed on a linear motor 2. Linear motor 2 includes a bearing portion 10 of a rolling or sliding - , : , : : ' . : : : ' ., : : : . . :
.. . . .
2 ~ 9 2 structure in contact with the bottom floor inside th0 main body of the device. Optical he~d 1 is driven radial of disk 7 by linear motor 2. -Optical head 1 is provided with a tracking error detecting unit 4 by its optical system. Tracking error detecting unit 4 detects the relative position deviation amount of the actual irradiated position with respect to the reference irradiated position b~ optical beam 3 in track 8 to provide a tracking error signal TES
representing the position deviation amount.
Tracking error signal TES is provided to a driver 6 via a phase compensating unit 5. Phase compensating unit 5 carries out a predetermined phase compensation for ;
tracking error signal TES. Driver 6 provides a driving ~--si~nal to linear motor 2 to cancel the tracking error .:~.
according to the phase compensated signal from phase ;
compensating unit 5. Linear motor 2 is driven according `~-to a driving signal provided from driver 6. As a result, :
optical head is driven radial of disk 7, whereby optical beam 3 is properly positioned on track 8.
Fig. 13 is a block diagram of a structure of a tracking servo loop which is a control loop for carrying out the position control of head 1. The tracking servo loop includes the elements of tracking error detecting unit 4, phase compensating unit 5, driver 6, and linear --2-- .
. .: , . . . : .. . ,, . :~.
2 t~
motor 2. The tracking servo loop is a control system of following a position Xo of optica] head 1 with a displacement Xi of track 8 as a desired value. If the product of all the gains of each element in the tracking servo loop is G(s), a followed error Xe is represented by the following equation (l):
Xe = {1 / (l + G(s))} Xi ... (l) The behavior of optical head 1 and the position relationship between optical beam 3 and track 8 will be described hereinafter when disturbance vibration is applied to the tracking servo loop of the above-described optical disk recording/reproduction device.
Fig. 14 is a kinematic model diagram of optical head l and its vicinity shown in Fig. 12. Assuming that the displacement of disturbance vibration is Y, the displacement of optical head 1 (or linear motor 2 driving ~ ;
optical head 1) is X, the mass of the movable portion of linear motor 2 including optical head 1 is M, and the equivalent spring constant and coefficient of viscosity generated in bearing lO of linear motor 2 are K and D, respectively, the following equation of (2) is obtained by an equation of motion according to Laplace transformation:
Ms X + Ds (X - Y) + K (X - Y) = 0 ... (2) where s represents Laplace operator.
By transforming equation (2), the ratio of ~ O ~ ~ ~j 9 2 displacement X of optical head 1 to displacement Y of disturbance vibration (X/Y) is obtained by the following equation (3):
(X/Y) = (Ds + K) / (Ms + Ds + K) = 1 - {(Ms2) / (Ms2 ~ Ds + K)}
= l - {K / (Ms + Ds ~ K)} {(Ms )} / K}
{Il)o2 / ( 52 + 2~o~1)0S + ~lo ) ~ ( S / ~I)o ) = 1 - Go(s) (S2 / ~o2) ... (3) ~O(s) in the above equation (3) is a normalized form .
of the transfer function of linear motor 2 representing the spring and mass system, and is well known as represented by the following equation (4). :
Go(s) = K / (Ms + Ds + K) = ~o2 / (S2 + 2~o~0 S + ~2~ ~-- (4) lS ~0 is the resonance angular frequency of linear motor 2 and ~0 is the damping value of linear motor 2, and are expressed by the following equations of (5) and (6), respectively.
~0 = (K / M)s ................................................ (5) ~o = D / {2 (MK) } ................................................. (6) Referring to Fig. 14, it is appreciated -that there is no influence of disturbance vibration to the tracking s~rvo loop of the optical disk recording/reproduction device if displacement X of optical head 1 is equal to displacement Y of disturbance vibration when disturbance ~4-:. -: . - - :
~ '3~ 2 vibration is e~erted. In other words, the difference between displacement Y and displacement X, (Y-X) is the component of the disturbance signal mixed into the tracking servo loop.
The ratio of the mixed disturbance vibration component (Y-X) to the exerted disturbance vibration is defined in the following equation (7) as a dis~urbance transmission rate B(s). This defined disturbance transmission rate B(s) is used in the following description.
B(s) = (Y - X) / Y = 1 - (X / Y) (7) Referring to equations (3) and (7), disturbance transmission rate B(s) is represented by the following equation (8).
B(s) = Go(s) ~ (s / ~0) -- (8) Therefore, it can be considered that disturbance transmission rate B(s) represents the deviation amount of optical head 1 with respect to track 8 generated by disturbance vibration. ~ :
The characteristics of transfer function Go(s) and disturbance transmission rate B(s) are graphed in Fig. 15.
~ig. 15 shows the characteristics of transfer function Go(s) of the spring-mass system and the characteristics of disturbance transmission rate B(s), where the gain is plotted along the ordinate and the angular frequency : ~ . ,. : .. , . . : :
plotted along the abscissa. The transfer function Go~s) is indicated by the solid line and the disturbance transmission rate B(s) is indicated by the broken line.
It can be appreciated from Fig. 15 that the characteristic of the transfer func-tion Go(s) is a second order low pass filter type with the resonance angular frequency ~0 as the breakpoint frequency. The characteris~ics of disturbance transmission rate B(s) is a second order high pass filter -type where the characteristics of transfer function Go(s) is rotated counter clockwise about resonance angular frequency ~0.
Consider the case where there is deviation in the position between optical head 1 and track 8 due to disturbance vibration introduced into the tracking servo loop, resulting in a offset of optical head 1. Viewing `~
the position of optical head 1 and the position of track 8 in a relative manner, it can be seen that the position of .
track 8 is deviated due to the disturbance vibration. In other words, the position of track 8 which is the followed desired value of the tracking servo loop is disturbed by disturbance vibration.
In view o~ the foregoing, a tracking servo loop is represented by a block diagram in Fig. 16. Referring to Fig. 16, displacement Y of disturbance vibration is multiplied by disturbance transmission rate B(s), which :f, ' ~ ' . - ., - - ~ :
. 3 ~ 2 yields the introduced amount of disturb~nce signal into the tracking servo loop. This B(s) Y is added to followed error Xe so as to disturb displacement Xi of track 8 which is the followed desired value.
In accordance with Fig. 16, followed error Xe is represented by the following equation (9).
Xe = {1 / (1 + G(s))~ Xi + {B(s) / (1 + G(s))} Y ~ --- (9) The second ter~. of the right hand side of equation (9) represents the increment of followed error Xe caused by disturbance vibration. In order to transform displacement Y of disturbance vibration into an acceleration dimension expression generally used from the displacement dimension, a Laplace operator 52 indicating a repeated differentiation is added to the numerator and denominator of the second term in equation (9) to obtain the following equation (10).
Xe = ~1 / (1 + G(s))} Xi + {3(s) / (1 + G(s)) s2}
Ys .,. (10) By extracting the transfer function to followed error Xe from disturbance vibration acceleration yS2 in the second term of the right hand side of equation (10), and defining that transfer function as disturbance suppression characteristics D(s), the following equation (11) is obtained.
2 ~ 9 ~ ~
D(s) = {B(s) / (1 ~ G(s)) s2} ... (11) The disturbance suppression characteristics D(s) of the above equation (11) represents the charactexistics suppressing the disturbance vibration in optical head l.
Followed error Xe ganerated by disturbance vibration acceleration Ys becomes lower as the value of disturbance suppression characteristics D(s) is smaller. This means that it is greatly immune to disturbance vibration. A
smaller disturbance suppression characteristics D(s) results in a tracking servo loop superior to anti-vibration performance.
It can be appreciated from the above equation (11) that ~he value of servo gain G(s~ is increased or the value of disturbance transmission rate B(s) reduced to lower disturbance suppression characteristics D(s) in order to improve anti-vibration performance.
A possible consideration to increase the servo gain G(s) to lower disturbance suppression characteristics D(s) is to enlarge the servo band. However, this method has a disadvantage of possibility of deviation in the servo by a defect in disk 7, or posing severe requirements to the characteristic strain of the machine system such as linear motor 2, and is not applicable in this case.
Another method is to raise the servo gain of the low frequency region where disturbance vibration is easily -8~
: . , - . , ~ .
- ~ , - ~ . .
; ~ . , .: ,.
~91~92 generatzd by means of phase lag compensation which is a kind of integral compensation. This is based on the fact that the frequency components o~ clisturbance vibration are easily generated normally in the range below several ten H~. This method will be describecl hereafter.
Fig. 17 shows an example of a galn curve of a servo gain G(s) of the tracking servo loop using the linear motor. In Fig. 17, the gain is plotted along the ordinate, and the angular frequency is plotted along the abscissa. By obtaining disturbance suppression characteristics D(s) according to equation (11) while taking into consideration the gain curve of Fig. 17 and ~he disturbance transmission rate B(s) characteristics o Fig. 15, the characteristics gain curve shown in Fig. 18 -is established.
Fig. 19 is a graph showing the frequency characteristics of a phase lag compensation L~(s) where a predetermined angular frequency ~v at the low frequency region is the upper limit angular frequency. In the graph of Fig. 19, the gain is plotted along the ordinate and the angular frequency plotted along the abscissa. By adding the element of phase lag compensation L~(s) haviny the frequency characteristics of Fig. 19 into the tracking servo loop having the gain curve of Fig. 17, the gain curve of that tracking servo loop is as shown in Fig. 20.
_g_ '~-20~1~92 It is appreciated from Fig. 20 that the servo gain of an angular frequency below the upper limit angular frequency ~v is higher than the gain shown in Fig. 17 due to phase lag compensation L~(s). The addition of such a phase lag compensation Ll(s) results in the gain curve of disturbance suppression characteristics D(s) as shown in Fig. 21. Because the servo gain in the low frequency -~
region rises as shown in Fig. 20 due to addition of phase lag compensation Ll(s), it is appreciated from Fig. 21 that the gain of disturbance suppression characteristics D(s) in the low frequency region below the upper limit frequency ~y is reduced. As a result, disturbance suppression characteristics D(s) is reduced in the lower ;~
frequency region where disturbance vibration is easily generated to allow improvement in anti-vibration performance.
However, if the upper limit angular frequency ~v phase lag compensation Ll(s) is further set higher to .
further improve the anti-vibration performance at the lower frequency resion taking advantage of the effect of such phase lag compensation, the phase margin in cut off angular frequency ~c Of the servo gain will be reduced, resulting in a problem of an unstable tracking servo loop.
A possible consideration to further improve anti- - -vibra~ion performance at the low frequency region is to .. . .. .. .
- : , 2 ~ 9 2 simply apply at least two stages of phase lag compensation to increase the servo gain at low frequency regions. In this case, the characteristics of the original linear motor will be a second order integral system in regions greater than resonance angular frequency ~0, resulting in an integral system of not less than the total of fourth order. Fig. 22 is a graph showing the vector locus of the servo gain when two stages of phase lag compensation are added. Referring to Fig. 22, the vector locus of the servo gain makes one rotation about point (-1, jO) clockwise. This will produce the problem that the tracking servo loop is not stable due to Nyquist stability criterion.
Thus, there is a limit in the method of reducing ~ `
disturbance suppression characteristics D(s) by simply applying phase lag compensation to increase the servo gain in low frequency regions.
A method of increasing disturbance suppression -characteristics D(s) can be considered by reducing disturbance transmission rate B(s) to improve anti-vibration performance. The method of reducing disturbance transmission rate B(s) of the mechanical behavior of linear motor 2 with respect to disturbance vibration will be described hereinafter.
If pre-load towards bearing unit 10 of linear motor 2 : - :: ,. . . i, ~, :, ", : .. .. :. . ; . . . . .
.: . .. ,, .. . : ~ . ~ -. - . ~ . . . . , , . -2~5~2 is increased to raise the equivalent spring ability, resonance angular frequency ~0 takes a higher value. As described in Fig. 15, the characteristics of disturbance transmission rate Bts) takes a high pass fllter type that decreases where the angular frequency is below the resonance angular frequency ~0. Therefore, if the resonance angular frequency ~0 is set to a resonance angular frequency ~0' higher than a predetermined resonance angular frequency ~0, disturbance transmission rate B(s) in the low frequency region is reduced as shown in Fig. 23.
Fig. 23 is a graph showing the change in disturbance transmission rate B(s) according to the change in resonance angular frequency ~0. In Fig. 23, the gain is plotted along the ordinate and the angular frequency is plotted along the abscissa, wherein disturbance -;~
transmission rate B(s) by the original resonance angular frequency ~0 and by the higher resonance angular frequency ~0' are indicated by a solid line and a chain dotted line, respectively.
It is appreciated from Fig. 23 that a higher ~ .
resonance angular frequency causes the characteristics of disturbance transmission rate B(s) to be shifted towards the high frequency side, whereby disturbance transmission rate B(s) in the low frequency region is reduced.
However, such a rise of the resonance angular .. . . ~ . .
2~592 frequency to ~0' causes the servo gain G(s) of an angular re~uency below resonance angular frequency ~0' to become lower than the original servo gain G(s), as shown in Fig.
24. Fig. 24 is a graph showing the change in servo gain S according to the change of resonance angular frequency.
In Fig. 24, the gain is plotted along the ordinate and the angular frequency plotted along the abscissa. The gain curve according to the original resonance angular frequency ~0 and that by the higher resonance angular .
frequency ~0' are shown by a solid line and a chain dotted line, respec~ively.
It can be appreciated from Fig. 24 that the gain curve by the higher resonance angular frequency ~0' has the servo gain G(s) reduced in the angular frequency below resonance angular frequency ~0' in comparison to the original gain curve because the servo gain G(s) below the `
resonance angular frequencies ~0 and ~0' is constant. ;' Therefore, disturbance suppression characteristics D(s) determined by disturbance transmission rate B(s) and servo gain G(s) is not improved by the above-described method. Also, increase in the pre-load to bearing unit lO
for carrying out the above-described method will promote abrasion of bearing unit 10, resulting in the problem of ~-reducing the mechanical lifetime of the device.
Thus, it was difficult to improve disturbance :: ~: . : .:
2~ .3~
suppression characteristics D~s) i-rom the conventional improving methods of anti-vibration performance. There were many problems regarding improvement of anti-vibration performance of a disk recording/reproduction device.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the anti-vibration performance of a disk recording/reproduction device.
Another object of the present invention is to improve lQ the anti-vibration per~ormance of a disk recording/reproduction device without degrading stability of the servo loop and lifetime of the mechanical system.
A disk recording/reproduction device according to the present inven~ion is a disk recording/reproduction device for recording and reproducing information to and from a disk having tracks that can record information, and includes a head, a moving velocity detecting circuit, a tracking error detecting circuit, a phase compensating ~ -unit including a phase lag compensating circuit, and a head driving circuit. The head is provided in a movable manner to record/reproduce information at an arbitrary radial position of the disk. The moving velocity detecting circuit detects the moving velocity of the head.
The tracking error detecting circuit detects error of the recording/reproduction position of the head with respect ~:, `.: ~ . . . , ' ~ .: .:
: ~ . ., ~ . . : .. . .
2g~5~2 to a track posi~ion of the disk, whereby ~he detected result is provided as a tracking error signal. The phase compensating unit applies phase compensation to a tracking error signal. The head driving circuit moves the head to cancel error of the recording/reproduction position of the head with respect to the track position according to the phase lag compensated result of the phase lag compensating circuit while applying damping to the head accordLng to the detected result of the moving velocity detecting circuit.
Because damping is applied to the operation of the :. .
head according to the detected result of the moving -velocity detecting circuit, the disturbance transmission rate in the head is reduced. Also, although the servo `~
gain regarding the control of the head is reduced by the ~-addition of this damping, the phase lag compensating circuit of the compensating unit compensates for phase lag of the tracking error signal, so that the lowered servo gain is raised.
Therefore, the disturbance transmission rate is reduced, and reduction of the servo gain caused by reduction of the disturbance transmission rate will be compensated for. Thus, the anti-vibration performance of the device can be improved without degrading stability of the servo loop and lifetime of the mechanical system 2~ 0 ~ 1 r~ ~ 2 because the disturbance transmission rate can be reduced without decreasing the servo gain.
A disk recording/reproduction device according to another aspect of the present invention is a disk S recording/reproduction device for recording and reproducing information to and from a disk having tracks that can record information, and includes a head, a first control circuit, and a second control circuit.
The head is provided in a movable manner to record/reproduce information at an arbitrary radial position of the disk. The first control circuit applies `~
damping to the operation of the head according to the moving velocity of the head. The second control circuit controls the position of the head to follow the position of the track and compensates for the transfer ~ `
characteristics of the head to compensate for the servo gain that is reduced by damping.
Because damping is applied to the operation of the head according to the moving velocity of the head by the first control circuit, the disturbance transmission rate of the head is reduced. Also, although the sexvo gain is reduced regarding the operation of the head due to load of this damping, the second control circuit compensates for the mechanical characteristics of the head to compensate -for reduction in the servo gain, whereby the servo gain is -2~31~2 raised.
Therefore, the disturbance transmission rate isreduced, and reduction of the servo gain is compensated for according to decrease of the disturbance transmission rate Thus, the anti-vibration performance of the device can be improved without degrading the stability of the servo loop and the lifetime of the mechanical system because the disturbance transmission rate is reduced without decreasing the servo gain.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram schematically showing a structure of an optical disk xecording/reproduction device according to an embodiment of the present invention.
Fig. 2 is a side view of an example of a velocity sensor.
Fig. 3 is a block diagram schematically showing another example of a velocity sensor.
Fig. 4 schematically shows an example of a position sensor used in the velocity sensor of Fig. 3.
Fig. 5 is a block diagram of the periphery of a - - -. .. , ;:; . ::. . ~ .
20~ l5~2 velocity feedback loop.
Fig. 6 is a graph showing the characteristlcs of the transfer function of a linear motor when velocity feedback is applied.
Fig. 7 is a graph showing characteristics of the disturbance transmission rate of a linear motor where , velocity feedback is applied.
Fig. 8 is a graph showing the characteristics of the transfer function of a linear motor where velocity feedbacX and phase lag compensation are combined.
Fig. 9 is a graph showing the disturbance suppression characteristics where velocity feedback and phase lag compensation are combined. ~`
Fig. 10 is a graph showing the vector locus of servo gain where velocity feedback and two stages of phase lag compensation are combined.
Fig. 11 is a graph showing the disturbance suppression characteristics where velocity feedback and ;~
two stages of phase lag compensation are combined.
Fig. 12 is a block diagram schematically showing a structure of a conventional optical disk recording/reproduction device.
Fig. 13 is a block diagram of a tracking servo loop.
Fig. 14 is a kinematic model diagram of an optical head and its vicinity.
: . ..
2 ~ 2 Fig. li is a g:raph showing the transfer function characteristics of a spring-mass system and disturbance - transmission rate characteristics.
Fig. 16 is a block diagram of a tracking servo loop -taking into consideration disturbance vibration.
Fig. 17 is a graph showing a gain curve of a tracking servo loop.
Fig. 18 is a gxaph showing disturbance suppression characteristics.
Fig. 19 is a graph showing fxequency characteristics of phase lag compensation.
Fig. 20 is a graph showing a gain curve of a tracking servo loop where phase lag compensation is applied.
Fig. 21 is a graph showing disturbance suppression characteristics where phase lag compensation is applied.
Fig. 22 is a graph representing a vector locus of a servo gain where two stages of phase lag compensation are applied.
Fig. 23 is a graph showing change in disturbance transmission rate according to change in resonance angular frequency.
Fig. 24 is a graph showing change in servo gain according to change in resonance angular frequency.
DESCRIPTION OF THE PREFERRED EM~ODIMENTS
Fig. l is a block diagram schematically showing a 2~ 592 structure of an optical disk recording/reproduction device according to an em~odiment of the present invention. The components in Fig. 1 similar to those shown in Fig. 12 have the same reference numbers denoted and their description will not be repeated. The structure of Fig. 1 differs from the structure of Fig. 12 in that a velocity sensor 11 for detec~ing velocity of an optical head 1 (or a linear motor 2 moving optical head 1) is provided, a velocity feedback loop is formed where the output of velocity sensor 11 is fed back negatively from driver 6 to linear motor 2 via an amplifier 13 and a substrator 22, and a phase lag compensating circuit 12 is included in phase compensating circuit 5.
Velocity sensor 11 is of the types shown in Figs. 2-4. Fig. 2 is a side view of an example of a velocity sensor 11. Velocity sensor 11 has either of a magnet 14 or a coil 15 fixed to optical head 1 (or linear motor 2) and the other fixed to the main body side of the optical disk recording/reproduction device. In velocity sensor 11 of such a structure, electromotive force is generated in coil 15 due to the relative motion of magnet 14 and coil 15. This electxomotive force has a constant relationship with respect to the velocity of relative motion.
Therefore, the electromotive force generated in coil 15 by this relative motion is provided as a velocity detection ' , , , . ' , . ~ ' ' . :
~ O ~ ~ tj 9 2 signal.
Fig. 3 is a block diagram schematicall~ showing another example of a velocity sensor 11. This velocity sensor 11 includes a position sensor 16 for detecting the position (displacement) of optica:l head 1 (or linear motor 2), and a differentiator 17 for d:ifferentiating the output of position sensor 16. Velocity sensor 11 has the position of optical head 1 detected by position sensor 16, whereby the detected position information is differentiated by differentiator 17. The output of differentiator 17 represents the velocity of optical head 1. !
A specific example of position sensor 16 of Fig. 3 is shown in Fig. 4. Referring to Fig. 4, a light emitting diode 18 is provided in optical head 1 (or linear motor 2). A PSD (Position Sensitive Device) 19 which is a~ -~
photodiode for detecting the position of optical head 1 is provided along the moving direction of optical head 1 in the main body of the device. Light emitting diode 18 is provided at a position to direct the emitted light towards the detecting face of PSD 19. Therefore, the position of incident light 20 into PSD 19 varies according to the position of optical head 1. PSD 19 has output terminals A
and B respectively provided at the either ends in the longitudinal direction. Photoelectric current flows from the irradiated position by incident light 20 towards output terminals A and B. The photoelectric current from output terminals A and B vary accordin~ to the resistance between the irradiated position of incident light 20 and 5 the respective output terminals A and B. This resistance increases according to the distance betw~en the irradiated position and the output terminal. By obtaining the ; difference of the photoelectric current outputs, the irradiated position by incident light 20 can be defined to identify the position of optical head 1.
The photoelectric current provided from output terminals A and s are provided to a differential amplifier 21. Differential amplifier 21 differential-amplifies these photoelectric current outputs to provide the same to differentiator 17 shown in Fig. 3 as the information representing the position of optical head 1.
The change of disturbance transmission rate B~s) will be described hereinafter where a velocity feedbacX loop as shown in Fig. 1 is formed. Fig. 5 is a block diagram of the periphery of the velocity feedback loop. A driving input U which is a signal supplied to driver 6 from phase compensating unit 5 is converted into a displacement X0 of optical head 1 (or linear motor 2) via a gain KD of driver 6, a thrust constant K~ of linear motor 2, and mechanical characteristics of linear motor 2 1/~Ms +Ds~K).
, ~, . . ~ , . , : .
~3~
Displacement XO is negatively fed back to driver 6 via a sensitivity ~y-S of velocity sensor 11 and a gain A of amplifier 13. M in the mechanical characteristics of the linaar motor is the mass (including mass of optical head l) of the movable portion of linear motor 2, D is the equivalent coeficient of viscosity generated in bearing unit 10 of linear motor 2, and K is the equivalent spring constant generated in bearing unit lO of linear motor 2.
The transfer function (XO/U) from driving input U to displacement XO in such a velocity feedback loop is expressed by the following equation (12).
(XO / U) = (KF KD) / {MS + (D + A KV KF KD) S
+ K}
= (KF ' KD / K) [K / {MS2 + (D + A KV
KF KD) S + K}]
= (KF KD / K) GO/ (S) .. (12) Go~(s) of the above equation ~12) is a normalized form of the lin~ar motor transfer function after the velocity feedback loop foxmation, and is expressed by the following equation (13).
&Ot(S) = K / {MS + (D + ~ KV K~ KD) S + K}
2 / (SZ + 2~o' ~o 5 + ~-)o ) ... (13) ~ 0 is the resonance angulax frequency of linear motor 2, and ~0~ is the damping value after velocity feedback . ' 2~9~g2 loop formation, and are represented by the following equations of (14) and (15), respectively.
= (K/M) ... (14) ~0' = (D + A ~ KV KF KD) ~ {2 (~IK) } ... (15) The damping value where a velocity feedback loop is not formed, i.e. ~0 of equation (6) is determined by the equivalent coefficient of viscosity D of bearing unit 10 of linear motor 2, spring constant K and mass M of the movable portion of linear motor 2. The damping value is generally in the range of 0.1-0.3, and approximately 0.5 at maximum.
However, the damping value of ~0' where a velocity feedback loop is formed is affected by the product of gain KD Of driver 6, thrust KF of linear motor 2, sensitivity Kv of velocity sensor 11, and gain A of amplifier 13 amplifying the output thereof according to the above equation of (15). Therefore, if thrust constant KF~ gain KD and sensitivity KV are determined, the damping value ~0'~
can be changed by varying gain A. Furthermore, because ~
the equivalent coefficient of viscosity D of the bearing ~ -portion in the numerator of equation (15) is a small value that is generated by rolling resistance and the like, (A-KV-K~-KD>>D) can be set by the value of gain A. In this case, ~0' is represented by the following equation ~16):
~0~ = (A Kv K~ KD) / {2 (~K) '5} . . . ( 16) -24~
-~ . , -. ~: . . . -.. . . . . .
2 ~ r ~1 r~
When the value of gain A is set so that ~o'>l, a breakpoint of characteristics appears in the characteristics of the normalized transfer function Go'(s) of linear motor 2 that is represented by equation (13).
5 Fig. 6 is a graph showing the characteristics of transfer function Go'(s) of linear motor 2 where a velocity feedback is applied. When the value of A is set so that ~o'>l, as described above, transfer function Go~(s) shows a breakpoint at angular frequency ~A lower than ~0 and at angular frequency ~B higher than ~0 with the resonance angular frequency ~0 as the center. Thus, the gain in the region between angular frequencies ~A and ~B iS reduced from the original gain.
The characteristics of disturbance transmission rate B'(s) takes a high pass filter type where the ~
characteristics of transfer function Go~(s) ls rotated ~ -counter clockwise about resonance angular frequency ~0, resulting in the characteristics shown in Fig. 7. Fig. 7 is a graph representing the characteristics of disturbance transmission rate B'(s) of the linear motor where velocity ~ -feedback is applied. As a result of the gain in the region between angular frequencies ~A and ~B reduced as shown in Fig. 6, the characteristics of disturbance transmission rate B'(s) is accordingly reduced in the region between angular frequencies ~A and ~B as shown in e~
Fig . 7 . Therefore, the angular frequency components in the region between angular frequencies ~A and ~B in disturbance vibration will not easily be introduced into the tracking servo loop.
A control similar to such a velocity feedback is carried out in a conventional disk recording/reproduction device. An example is described in "Development of CD-ROM
Drive System" Sanyo Technical View Vol. 19, No. 1, pp. 35-45, February 1987. However, there is no description of the object and meaning of a velocity feedback in this document. There are also disclosures in Japanese Patent ~aying-Open No. 61-227692, Japanese Patent Laying-Open No.
2-263367 and Japanese Patent Laying-Open No. 3-118481.
However, the control of velocity feedback described in these applications are all provided for the purpose of improving stability of control of the servo system. There `~
is no study nor description of employing the control for ;~
improving anti-vibration performance. It is not possible to improve anti-vibration performance with only the described velocity feedback due to reasons set forth in the following. ~ `
As already described with reference to the above equation of (11), disturbance suppression characteristics D(s) is determined by servo gain G(s) and disturbance transmission rate B(s). Therefore, the following problems - . : ~ . - ~` , . . .;
2 ~ 9 ~
will be generated by just applying velocity feedback.
When transfer function Go/(s) of linear motor 2 which - becomes the ba~is of servo gain G(s) is reduced in the region between angular frequencies ~A and ~B as shown in S Fig. 6, servo gain G(s) is also reduced in the same region of angular ~requency due to the ~elocity feedback.
Regardless of how much disturbance transmission rate B'(s) is reduced in the same region of angular fre~uency to lower the introducing amount of disturbance vibration, disturbance suppression characteristics D'(s) determlned by servo gain G'(s) and disturbance transmission rate B'(s) where a velocity feedback is applied will show no change with respect to the disturbance suppression -characteristics D(s) of Fig. 18 where velocity feedback is not applied. There is no change, whether good or bad, in the characteristics.
The invention of the present application is `~-characterized by including a phase lag compensating ~ -circuit 12 in the tracking servo loop for raising the gain of an angular frequency region below angular frequency ~B :
to a resonance angular frequency ~0, for example, in `
addition to the above-described velocity feedback loop.
Figs. 8(a) - (c) are graphs showing the characteristics of the transfer function of linear motor 2 where a velocity feedback and phase lag compensation are combined. Figs.
-~7-~ ;.. .... .. .
: , ~ - :.- .
2~9~ 5~2 8(a) - 8(c) show the charactexistics of phase lag compensation L2(s), of transfer unction G~'(s) of linear motor 2 where velocity feedback is applied, and of transfer funstion L2(s) ~ Go'(s) of linear motor 2 where velocity feedback and phase lag compensation are applied~
respectively. By introducing into the tracking servo loop a phase lag compensation Lz(s) having the characteristics so as to raise the gain in the angular frequency region below angular frequency ~3 to resonance angular frequency ~0 as shown in Fig. 8(a), transfer function Go'(s) of linear motor 2 where velocity feedback is applied has the gain in the region below angular frequency ~B compensated for as shown in Fig. 8(c). Accordingly, reduction of servo gain G'(s) is also compensated for.
lS Because there is no change in disturbance transmission rate B'(s) even when a phase lag compensating -circuit 12 is introduced into the tracking servo loop, disturbance suppression characteristics D'(s) has the `
characteristics in the low frequency region improved in comparison with that of Fig. 18, as shown in Fig. 9.
Fig. 9 is a graph showing the characteristics of disturbance suppression characteristics D'(s) where velocity feedback and phase lag compensation are combined.
It can be appreciated from Fig. 9 that the disturbance suppression characteristics D'(s) in the low frequency 2 ~ 9 ~
region of below angular fre~uency ~B is reduced by vixtue of reduction of disturbance transmission rate B'(s) by velocity feedback and compensation of servo gain G'(s) by phase lag compensation L2(s).
Thus, according to the present invention, the disturbance suppression characteristics is reduced to improve anti-vibration performance by reducing the disturbance transmission rate by a velocity feedback and compensating for only the servo gain reduced by that velocity feedback by phase lag compensation.
The inclination of the gain will not exceed -40 (dB/dec) even in the case where a phase lag compensation ~-~
L2(s) is applied as described above. Because the --characteristics of the tracking servo loop shows only a maximum of a second order lag characteristics, the phase lag compensation Ll(s) described with reference to Fig. l9 ~`
can further be applied to the tracking servo loop to further improve anti-vibration performance. Fig. 10 i5 a . ~;
graph representing the vector locus of servo gain G(s) where a velocity feedback and phase lag compensation of two stages are combined. In the case where a velocity feedback and a phase lag compensation L~(s) is combined and then further combined with a phase lag compensation Ll(s), the characteristics of the tracking servo loop is limited , to a third order lag characteristics. In such a case, the .. ... , . ., ... .... . , ,, ~
:.. , . .. - . .. ,, .. .,, , ..... ~....... .
: - . .. - .
-,~
2 0 ~
vector locus of the servo gain does not make one rotation clockwise about point (-l, jO) as shown in Fig. 10.
Therefore, the tracking servo loop is stable by Nyquist stability criterion.
Fig. ll is a graph representing the disturbance suppression characteristics D"(s) where a velocity feedback and two stages of phase lag compensation are combined. As described above, there is no change in disturbance ~ransmission rate B'(s) even if a phase lag compensation Ll(s) is further added, and only servo gain G'(s) in the region between angular frequencies ~u and ~v show an increase. Therefore disturbance suppression characteristics D"(s) is further reduced in the region between angular frequencies ~u and ~, whereby the anti-vibration performance of the device is further improved.
Although an optical disk recording/reproduction device of a structure where optical head 1 is linearly -~
moved to be positioned radial OI disk 7 by linear motor 2 in the present embodiment, the invention is not limited to this, and can be applied to a magnetic disk device of a structure where the head carrying out recording/reproduction of information is positioned by being moved along the circumferential track radial of the disk by a rotary arm.
In this case, a control as in the present embodiment ~ .. . .
J15~
can be carried out by providing a velocity sensor such as to detect the rotation velocity (angular velocity) o the rotary arm.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and i5 not to be taken by way o limitation, the spirit and scope of .
the present invention being limited only by the terms of -the appended claims. ::~
' ;
.,, , , . , , , ~
. ' : ` ~ ' ' ' .' '.
Claims (6)
1. A disk recording/reproduction apparatus for recording and reproducing information to and from a disk having a track in which information can be recorded, said disk recording/reproduction device comprising:
a head provided in a movable manner for recording and reproducing information in an arbitrary radial position of said disk, moving velocity detecting means for detecting the moving velocity of said head, tracking error detecting means for detecting error of the recording/reproduction position of said head with respect to a track position on said disk to provide the detected result as a tracking error signal, phase compensating means for applying a phase compensation to said tracking error signal, said phase compensating means including phase lag compensating means of at least one stage for applying a phase lag compensation to said tacking error signal, and head driving means for moving said head to cancel error of the recording/reproduction position of said head with respect to said track position according to the phase lag compensated result of said phase compensating means while applying damping to said head according to the detected result of said moving velocity detecting means.
a head provided in a movable manner for recording and reproducing information in an arbitrary radial position of said disk, moving velocity detecting means for detecting the moving velocity of said head, tracking error detecting means for detecting error of the recording/reproduction position of said head with respect to a track position on said disk to provide the detected result as a tracking error signal, phase compensating means for applying a phase compensation to said tracking error signal, said phase compensating means including phase lag compensating means of at least one stage for applying a phase lag compensation to said tacking error signal, and head driving means for moving said head to cancel error of the recording/reproduction position of said head with respect to said track position according to the phase lag compensated result of said phase compensating means while applying damping to said head according to the detected result of said moving velocity detecting means.
2. The disk recording/reproduction device according to claim 1, wherein said moving velocity detecting means comprises a magnet provided in one of said head and the main body of said disk recording/reproduction device, and a velocity detecting coil provided in the other of said head and said main body of said disk recording/reproduction device for providing as velocity information electromotive force generated by the relative motion between said velocity detecting coil and said magnet.
3. The disk recording/reproduction device according to claim 1, wherein said moving velocity detecting means comprises position detecting means for detecting the position of said head on its moving path, and differentiating means for time-differentiating the detected result of said position detecting means to provide the differentiated result as velocity information.
4. The disk recording/reproduction device according to claim 3, wherein said position detecting means comprises light emitting means provided in said head for emitting light in a direction crossing the moving direction of said head, light receiving means having a light receiving region along the moving direction of said head for receiving light of said light emitting means for providing current according to said light receiving position in the moving direction of said head in said light receiving region, and position signal output means responsive to current provided from said light receiving means for providing a signal representing the position of said head.
5. A method of operating a disk recording/reproduction device including a head for recording and reproducing information at an arbitrary radial position of a disk having a track in which information can be recorded, and head driving means for moving said head, comprising the steps of:
detecting the moving velocity of said head, detecting error of the recording/reproduction position of said head with respect to a track position on said disk, applying phase compensation including phase lag compensation to the detected error, and moving said head by said head driving means to cancel error in the recording/reproduction position of said head with respect to said track position according to the phase compensated result of the detected error and to apply damping to said head according to the detected result of said moving velocity detecting step.
detecting the moving velocity of said head, detecting error of the recording/reproduction position of said head with respect to a track position on said disk, applying phase compensation including phase lag compensation to the detected error, and moving said head by said head driving means to cancel error in the recording/reproduction position of said head with respect to said track position according to the phase compensated result of the detected error and to apply damping to said head according to the detected result of said moving velocity detecting step.
6. A disk recording/reproduction device for recording and reproducing information to and from a disk having a track in which information can be recorded, said disk recording/reproduction device comprising:
a head provided in a movable manner for recording and reproducing information at an arbitrary radial position of said disk, first control means for applying damping to the operation of said head according to the moving velocity of said head, and second control means for controlling the position of said head to follow said track position and for compensating for transfer characteristics of said head to compensate for the servo gain reduced by said damping.
a head provided in a movable manner for recording and reproducing information at an arbitrary radial position of said disk, first control means for applying damping to the operation of said head according to the moving velocity of said head, and second control means for controlling the position of said head to follow said track position and for compensating for transfer characteristics of said head to compensate for the servo gain reduced by said damping.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24468892A JPH0696539A (en) | 1992-09-14 | 1992-09-14 | Disk recording and reproduction apparatus |
| JP4-244688 | 1992-09-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2091592A1 true CA2091592A1 (en) | 1994-03-15 |
Family
ID=17122466
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2091592 Abandoned CA2091592A1 (en) | 1992-09-14 | 1993-03-12 | Disk recording/reporduction device and a method of operation thereof |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0696539A (en) |
| CA (1) | CA2091592A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5298269B2 (en) * | 2007-12-25 | 2013-09-25 | セミコンダクター・コンポーネンツ・インダストリーズ・リミテッド・ライアビリティ・カンパニー | Vibration compensation control circuit |
-
1992
- 1992-09-14 JP JP24468892A patent/JPH0696539A/en active Pending
-
1993
- 1993-03-12 CA CA 2091592 patent/CA2091592A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0696539A (en) | 1994-04-08 |
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