JPH09320061A - Speed control device for head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a stable speed control by preventing the influence of slide friction and performing feedforward control accurately. SOLUTION: The head speed control device has a DSP 10 for controlling, for example, a seek operation based on the output of a tracking error signal detection circuit 8. The DSP 10 has a target speed/target acceleration table 13 for generating a target speed and a target acceleration based on the current position of the head, an acceleration-to-current transducing part 16 for generating feedforward current by transducing the target acceleration into current, and an adder 17 for adding the feedforward current to the difference between the target speed obtained by a subtractor 14 and an actual speed. The head speed control device performs the feedforward/feedback control of a traveling speed, by supplying the output of the DSP 10 to the drive means of a carriage 5 via a linear motor drive circuit 41. And, the ratio of the feedforward current for the target acceleration differs between the acceleration and the deceleration of the head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for a head in a disk device such as a magneto-optical disk device, and particularly to speed control by setting a speed target value and an acceleration target value according to the current position of the head. The present invention relates to a speed control device.

[0002]

2. Description of the Related Art In a disk device such as a magneto-optical disk device, when performing a seek operation for moving the head to a target track, the head is moved while controlling the moving speed by a speed control device. As such a speed control device, one that sets a speed target value and an acceleration target value according to the current position of the head to perform speed control is used.

FIG. 5 shows an example of the structure of a speed control circuit in a conventional head controller.

The speed control circuit comprises a subtracter 51, a phase compensator 52, a linear motor (VCM) 53, and a speed detector 54. Speed target value SV1 of the linear motor 53 that drives the head in the direction traversing the track of the disk
Is input to the subtractor 51. The subtractor 51 obtains a target speed error signal SV2 which is a difference between the input speed target value SV1 and the actual speed signal SV3 detected by the speed detector 54 and input. The target speed error signal SV2 is input to the phase compensator 52 for improving the frequency characteristic of speed control, and the speed error signal phase-compensated by the phase compensator 52 is converted into a driving current by a driving circuit (not shown). And input to the linear motor 53.

The speed change caused by driving the linear motor 53 is again obtained as an actual speed signal SV3 via the speed detector 54, and this actual speed signal SV3 is input to the subtractor 51. In this way, feedback control is performed in which the drive speed of the linear motor 53 is controlled so as to follow the speed target value SV1. However, this configuration has a problem that the followability (immediate response) is poor because the feedback control system corrects the velocity error after it is generated.

FIG. 6 shows an example of the structure of the speed control circuit in the magneto-optical disk device.

The configuration of FIG. 6 is such that an adder 55 is newly added between the phase compensator 52 and the linear motor 53 in the speed control circuit of FIG. 5 to add a feedforward current IF. Since the seek profile (speed profile during seek operation) is predetermined and the current required for the linear motor 53 to move at that speed can be predicted to some extent, in this configuration, the current amount is fed back from the beginning. I try to inject it into the loop.

In this way, the feedforward /
The speed control system is combined with feedback, and the feedback system only needs to correct the error after the speed is controlled to some extent by the feedforward current, so that the load on the feedback system is reduced and the followability is improved as a result. That is, in the feedforward / feedback combined speed control circuit of FIG. 6, most of the drive current of the linear motor 53 is generated by the feedforward current IF.

The feedforward current IF is a value obtained by dividing the acceleration (target acceleration) determined by the velocity profile by the sensitivity of the linear motor 53. The feedforward current IF determined in this way is used as the target speed error S
By adding to V2, it becomes possible to move the linear motor 53 almost according to the target speed profile.

FIG. 7 shows an example of the speed profile and the feedforward current waveform of the linear motor during a normal seek operation in the speed control circuit of FIG. As shown in FIG. 7A, the velocity profile is configured to draw a trapezoidal velocity profile including an acceleration region, a constant velocity region, and a deceleration region. Therefore, the feedforward current IF is determined by the value obtained by dividing the acceleration of the velocity profile by the sensitivity of the linear motor, so the acceleration during acceleration is Aa [m / s / s] and the acceleration during deceleration is Ad [m / s / s]. s] and the sensitivity of the linear motor is k [m / s / s / A], the value of the feedforward current IF is Aa / k [A] during acceleration and Ad / k [A] during deceleration.

In recent years, with the spread of optical disc devices, further cost reduction is demanded.

Various approaches can be considered to realize cost reduction in the optical disk device, but as one method of cost reduction, there is a method in which the support of the linear motor for driving the head is constituted by a sliding bearing. That is, instead of supporting the carriage with respect to the guide shaft via a bearing, by using a sliding bearing that slidably supports the carriage, it is possible to omit the mechanical parts including the bearing. It is a thing. An example of this is disclosed in Japanese Patent Application Laid-Open No. 8-7310.

[0013]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the linear motor in which the carriage is slidably supported as in the configuration of Japanese Patent Publication No. 0, the force that always decelerates the carriage acts due to the sliding friction existing in the supporting portion.
Therefore, in order to generate the same acceleration, a larger driving force and a larger driving current are required during acceleration than during deceleration, and the driving sensitivity of the linear motor is apparently different during acceleration and during deceleration.

Even if a current corresponding to the target acceleration is fed forward to the above sliding support type linear motor with the above-mentioned conventional speed control circuit, the actual acceleration generated by the feed forward current is not always required. The target acceleration does not follow, and an error occurs in the feedforward. As described above, when the feedforward control system does not operate normally, the feedback function is not so strong, and as a result, the error in the speed control becomes large and the seek control may become unstable.

In this case, since a long-distance seek operation requires a long moving time, there is a possibility that the final velocity error can be reduced by the action of the feedback control system even if there is an error in the feedforward. Especially in seek operation over a short distance, the movement often ends before the feedback control system starts the operation of suppressing the speed error, and the error of the feedforward operation directly leads to the deterioration of the stability of the speed control operation. I will end up.

The present invention has been made in view of these circumstances. Even if a head is constructed by using a sliding bearing for cost reduction, it is not affected by sliding friction and is accurate. Feedforward control can be performed,
It is an object of the present invention to provide a head speed control device capable of realizing stable speed control.

[0017]

A head speed control device according to the present invention has a head for recording / reproducing information on / from a disk-shaped recording medium, and a radius of the recording medium by a guide shaft and a bearing. A carriage that is movably supported in any direction, a target speed generation means that generates a target movement speed of the head based on the current position of the head, and a target acceleration generation means that generates a target acceleration according to the target movement speed. A speed detecting means for detecting a current moving speed of the head, a speed error detecting means for obtaining a difference between an output of the target speed generating means and an output of the speed detecting means, and a feedforward current for the target acceleration. A feedforward current setting means to be obtained, and an addition for adding the output of the speed error detection means and the output of the feedforward current setting means. And means, and a driving means for driving in the radial direction of the recording medium the head by an output of said adding means, be one that controls the speed of the head,
When the feedforward current is set by the feedforward current setting means, the ratio of the feedforward current to the target acceleration is made different during acceleration and deceleration of the head.

By making the ratio of the feedforward current to the target acceleration different during acceleration and deceleration, a feedforward current capable of accurately generating the target acceleration with respect to the sensitivity of the driving means during acceleration and deceleration can be obtained. This can be set, and the feed-forward error will be small, and speed control will be stable.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a head access control device using an optical head according to an embodiment of the present invention. In this embodiment, a configuration example in which a head speed control device is mounted on an optical disk device will be shown. Here, parts that are not directly related to the description of the present embodiment, such as a reproduction signal processing circuit, a host computer interface circuit, or a focus control circuit, are omitted.

The optical disk apparatus is equipped with a spindle motor 2 for mounting an optical disk 1 provided with an information track for recording information, and rotationally driving the optical disk 1, and for recording and reproducing information on the optical disk 1. The objective lens 3 for irradiating the information beam of the optical disc 1 with the light beam 4 and the objective lens 3 are driven in the optical axis direction (vertical direction in the figure, focusing direction) as constituent elements of the optical head for performing the operation. A focus actuator 6 as a focus moving means, a carriage 5 having the objective lens 3, the focus actuator 6 and the like mounted thereon and movable in the radial direction of the optical disc 1 by a linear motor, and an optical device including a laser diode or a photodetector serving as a light source. The system 7 is provided.

Further, in the present embodiment, a preamplifier 42 for amplifying the output of the photodetector which is composed of at least two photodetectors, and a detection signal (tracking error signal: T which indicates a track deviation from the output of the preamplifier 42).
Tracking error signal detection circuit (T)
ES detection circuit) 8, a binarization circuit 9 that binarizes the output of the tracking error signal detection circuit 8, a digital signal processor (hereinafter referred to as DSP) 10 that controls seek operation and tracking operation, and a preamplifier. 42
Address detection circuit 43 for detecting the track address where the light beam 4 is located from the output of
A controller 44 for instructing the number of tracks and the direction thereof during the seek operation based on the output of the linear motor drive circuit 41, and a linear motor drive circuit 41 for supplying a drive current to the linear motor for driving the carriage 5 based on the output signal of the DSP 10. ,
A tracking / seek control system is configured with the above.

The carriage 5 is driven by the drive current supplied from the tracking actuator driver 10,
The light beam 4 can be moved together with the objective lens 3 and the focus actuator 6 so that the light beam 4 can irradiate all the information tracks in a direction that traverses the information tracks on the optical disc 1 (the horizontal direction in the drawing, the tracking direction). The periphery of the carriage 5 and the focus actuator 6 can be configured as shown in FIG. 2, for example.

As shown in FIG. 2, the focus actuator 6 includes a holder 2 for fixing the objective lens 3.
1. Leaf springs 22a and 22b that support the objective lens 3 so as to be movable in the focusing direction and substantially fixed in the tracking direction, and focus coils 23a and 23b for driving the objective lens 3. The carriage 5 has the focus actuator 6 mounted on the upper portion thereof, and is provided with a linear motor (VCM) formed on both sides by using tracking coils 24a and 24b as carriage driving means for driving the carriage.

As shown in FIG. 3, the carriage 5 and the focus actuator 6 are provided with guide shafts 31a and 31a.
b, assembled with magnetic circuits 32a and 32b,
The carriage 5 is slidably supported along the guide shafts 31a and 31b. By using the optical head having such a structure, the focus actuator 6 can be driven in the focusing direction by energizing the focus coils 23a and 23b, and the carriage 5 can be driven in the tracking direction by energizing the tracking coils 24a and 24b. You can Since the light beam 4 is also driven in the tracking direction by driving the carriage 5, it is possible to configure a fine-coarse integrated drive type tracking actuator. When the focus actuator 6 is assembled, the cover 33 covers the leaf springs 22a and 22b as shown in FIG.

The DSP 10 has a speed detecting function for measuring the pulse width of the binarized signal of the tracking error signal output from the binarizing circuit 9 to detect the speed, and counting the binarized signal to track count ( Track count function to count the number of moving tracks), target speed / acceleration generation function to generate speed profile (target speed) and acceleration profile (target acceleration) according to the track count value, convert target acceleration to current and feed forward It has functions such as a feedforward current generation function for obtaining a signal corresponding to a current and a speed control function for performing speed feedback control based on a target speed and a speed detection value.

Next, the operation of the head access control apparatus according to this embodiment will be described. The reflected light of the light beam 4 from the optical disc 1 is input to a photodetector divided into at least two, and the output of this photodetector is amplified by each preamplifier 42, and then the tracking error signal detection circuit 8 causes a tracking error signal. TES is obtained. The tracking error signal TES is a signal that changes to a substantially sinusoidal waveform with respect to the displacement, which becomes a zero level when the position of the light beam 4 is at the center of the track and substantially in the center between the tracks.

The tracking error signal TES is input to the DSP 10 via the binarizing circuit 9. The number of moving tracks is counted by counting the binarized signal in the track count unit 11 based on the binarized signal of the tracking error signal, and the speed detector 1
At 2, the velocity of the light beam 4 is detected by measuring the pulse width of the binarized signal.

The output of the preamplifier 42 is processed by the address detection circuit 43 to detect the track address where the light beam 4 is currently located. The controller 44 obtains the difference between the current track address and the track address to be accessed next, and instructs the DSP 10 on the number of tracks to perform the seek operation and the direction thereof. In response to this, DS
P10 drives the carriage 5 by performing speed control using both acceleration (current) feedforward / speed feedback while generating a speed profile and an acceleration profile according to the specified number of tracks by itself, and targets the light beam 4. Move to the truck.

Generation of the velocity profile in the actual DSP 10 is performed by setting the target velocity / the velocity developed in the memory in the DSP 10.
The target acceleration table 13 is used. That is, several speed profiles are prepared for the number of moving tracks, and an appropriate speed profile table is selected according to the number of tracks instructed by the controller 44. One table is set to support a certain number of tracks, and a different number of tracks is supported by adjusting the period of the constant speed portion of the speed profile shown in FIG. 4 (a). Done. When the velocity profile is determined, the acceleration required to realize the velocity profile (how the velocity changes) is also determined from the slope of the velocity profile, so the acceleration profile is stored together with the velocity profile in the memory in the DSP 10, A speed / target acceleration table 13 is formed.

When the seek operation is actually started and the speed control is started, the target speed VT and the target acceleration AT at that time are read from the target speed / target acceleration table 13. The target speed VT is obtained by the subtracter 14 from the difference between the target speed VT and the actual speed VD detected by the speed detector 12, and the difference signal of the output of the subtractor 14 is input to the phase compensation filter 15 composed of a digital filter. To be done.

On the other hand, the target acceleration AT is converted into a current value by converting the acceleration value into a current value in the acceleration-to-current conversion section 16, and becomes a signal corresponding to the feedforward current IF, and together with the output of the phase compensation filter 15, an adder 17 Is input to and added. The output of the adder 17 is branched into two, one of which is sent to the one input end of the polarity switch 19 as it is, and the other of which is sent to the other input end of the polarity switch 19 via the polarity inverting circuit 18. The polarity switch 19
Controller 4 outside the DSP 10 according to the seek direction
It operates by the instruction signal from 4 and outputs a signal of either polarity. The output of the polarity switch 19 is converted into an analog signal by the D / A converter 20, is input to the linear motor drive circuit 41, and is power-amplified.

Then, by supplying the drive current output from the linear motor drive circuit 41 to the tracking coils 24a and 24b, the linear motor (VCM) for driving the carriage 5 is driven, and the linear motor (VCM) is driven along the speed profile for the seek operation. The seek control using both feedforward and feedback is performed to move the light beam 4 to the target track at a constant speed.

Here, the conversion of the target acceleration into the feedforward current is performed as follows. If speed control is performed along the speed profile shown in FIG. 4A, the acceleration profile is the time derivative thereof,
It becomes as shown in FIG. In this case, the acceleration ATa during acceleration is equal to the acceleration ATd during deceleration, and ATa = ATd = AT
It has become. Since the feedforward current IF is a current necessary to generate the acceleration, it may be set to a value obtained by dividing the target acceleration AT by the driving sensitivity k of the linear motor. However, as described above, since the sliding support type linear motor has different driving sensitivities during acceleration and deceleration due to the sliding friction, the sliding support type linear motor as in the present embodiment is used. In the optical head access control device used, it is necessary to divide by the drive sensitivity in consideration of the change due to the friction to obtain the feedforward current IF.

For example, the linear motor sensitivity during acceleration is k
a [m / s / s / A], linear motor sensitivity during deceleration is kd [m / s / s]
/ A], the feedforward current IF when the target acceleration is AT [m / s / s] is IFa = AT during acceleration.
/ Ka [A], and IFd = AT / kd [A] during deceleration. Since a force that always decelerates acts on the carriage 5 due to sliding friction, ka <kd, so even if the acceleration is the same during acceleration and deceleration, the feedforward current IF
Becomes larger during acceleration, as shown in (c) of FIG.
It becomes relatively small during deceleration. It should be noted that whether acceleration or deceleration should be determined by the sign of the target acceleration.

As described above, according to this embodiment,
The feedforward current is determined by separately considering the sensitivity of the linear motor that is affected by sliding friction during acceleration and deceleration, and the result is obtained by changing the ratio of the feedforward current to the target acceleration during acceleration and deceleration. The feedforward current that can correctly generate the target acceleration can be set. As a result, the feedforward error becomes extremely small, so that a speed error is less likely to occur, and stable speed control operation and seek operation can be performed.

In this embodiment, the DSP is used for the arithmetic processing.
However, it is also possible to configure some or all of the functions by hardware so as to be performed by an electric circuit. However, it is often advantageous in terms of circuit scale and cost to perform arithmetic processing by DSP,
More desirable. Also, the phase compensation filter can be deleted if not necessary. This is because the drive current-speed relationship of the linear motor is generally a first-order lag system, so that the feedback system becomes stable without performing phase lead compensation unlike the position control system.

Further, the conversion from the target acceleration to the feedforward current was obtained by assuming different linear motor sensitivities during acceleration and deceleration, but it is also necessary to add an offset current according to the speed. Is also possible. For example, it is possible to feed forward a drive current that cancels the sliding friction in the constant speed portion.

The present invention can be applied to the linear motor as long as it is of a sliding support type, and even if the linear motor has a structure in which a precise actuator for tracking is further mounted, The present invention can be applied even to a structure in which a linear motor is driven to precisely position the light beam directly.
Particularly, in the latter configuration in which the presence of sliding friction is directly related to the driving of the light beam, the effect of the present invention is large.

In this embodiment, the long-distance seek operation (long seek) having the constant velocity area in the speed profile has been described, but in the case of the short-distance seek operation (short seek) having no constant velocity area. However, the idea is the same, and the present invention can be applied.

[Additional Notes] (1) A carriage having a head for recording / reproducing information on / from a disk-shaped recording medium, and a carriage supported by a guide shaft and a bearing so as to be movable in the radial direction of the recording medium. A target speed generating means for generating a target moving speed of the head based on the current position of the head, a target acceleration generating means for generating a target acceleration according to the target moving speed, and a current moving speed of the head. Speed detecting means for detecting, speed error detecting means for calculating a difference between the output of the target speed generating means and output of the speed detecting means, feedforward current setting means for calculating a feedforward current for the target acceleration, and the speed The addition means for adding the output of the error detection means and the output of the feedforward current setting means, and the output of the addition means A head speed control device for driving the head in the radial direction of the recording medium, the head speed control device controlling the speed of the head, wherein the head is set when the feedforward current is set by the feedforward current setting means. A speed control device for a head, wherein the ratio of the feedforward current to the target acceleration is made different during acceleration and deceleration.

According to Appendix 1, in the speed control system that feeds forward the current according to the target acceleration, the ratio of the feed forward current to the target acceleration is made different during acceleration and deceleration, so that during acceleration and deceleration. A feedforward current capable of accurately generating a target acceleration can be set for each, and a feedforward error becomes extremely small, so that a velocity error is less likely to occur, and stable velocity control operation and seek operation can be performed.

(2) The head speed control device as set forth in appendix 1, wherein the carriage is slidably supported by the guide shaft by the bearing.

According to appendix 2, stable speed control is possible even when a linear motor in which the carriage is slidably supported is used, and stable speed control can be realized even with a low-cost linear motor.

(3) The head has an optical element and a holder for holding the optical element, and supports the head so as to be movable in a direction substantially perpendicular to the recording surface of the recording medium. 3. The head speed control device according to appendix 2, wherein the holder is fixed to one end of the holder supporting means, and the other end of the holder supporting means is fixed to the carriage.

In the case of a structure in which the position of the objective lens is fixed on the carriage in the track direction and the position of the light beam is directly controlled by driving the linear motor (fine-coarse integrated type), the frictional force due to the sliding of the carriage is directly reflected. Although it acts as a disturbance on the control of the beam position, even in such a case, according to Supplementary Note 3, since feedforward is accurately performed, speed control can be stably performed.

(4) The head speed control device according to appendix 1, wherein the feedforward current setting means sets the ratio of the feedforward current to the target acceleration to a large value during acceleration and a small value during deceleration.

In Supplementary Note 4, by increasing the ratio of the feedforward current to the target acceleration during acceleration and decreasing it during deceleration, sliding friction can be effectively compensated.

[0048]

As described above, according to the present invention, even if the head is constructed by using the sliding bearing for cost reduction, it is not affected by the sliding friction and the feedforward is accurate. There is an effect that control can be performed and stable speed control can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a head access control device using an optical head according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration example of a carriage of an optical head and a periphery of a focus actuator.

FIG. 3 is a perspective view showing an example of a configuration around an optical head in which the carriage and the focusing actuator of FIG. 2 are assembled together with a magnetic circuit.

FIG. 4 is an operation explanatory diagram showing a velocity profile, an acceleration profile, and a feedforward current waveform of the access control device according to the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration example of a speed control circuit in a conventional head control device.

FIG. 6 is a block diagram showing a configuration example of a speed control circuit in a conventional magneto-optical disk device.

7 is an operation explanatory diagram showing an example of a speed profile and a feedforward current waveform of a linear motor during a normal seek operation in the speed control circuit of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk 3 ... Objective lens 4 ... Light beam 5 ... Carriage 8 ... Tracking error signal detection circuit 10 ... Digital signal processor (DSP) 11 ... Track count section 12 ... Speed detection section 13 ... Target speed / target acceleration table 14 ... Subtraction Unit 17 ... Adder 19 ... Polarity switch 41 ... Linear motor drive circuit 44 ... Controller

Claims (3)

[Claims] 1. A carriage that mounts a head for recording / reproducing information on / from a disk-shaped recording medium, and is supported by a guide shaft and a bearing so as to be movable in the radial direction of the recording medium; Target speed generating means for generating a target moving speed of the head based on the current position, target acceleration generating means for generating a target acceleration according to the target moving speed, and speed detection for detecting the current moving speed of the head. Means, a speed error detecting means for obtaining a difference between an output of the target speed generating means and an output of the speed detecting means, a feedforward current setting means for obtaining a feedforward current with respect to the target acceleration, and a speed error detecting means of the speed error detecting means. An addition means for adding an output and an output of the feedforward current setting means, and an output of the addition means for controlling the head. A head speed control device for controlling the speed of the head, the driving means driving the recording medium in a radial direction, wherein the head acceleration is performed when the feedforward current is set by the feedforward current setting means. A speed control device for a head, characterized in that a ratio of a feedforward current to a target acceleration is made different depending on time and deceleration. 2. The head speed control device according to claim 1, wherein the carriage is slidably supported by the guide shaft by the bearing. 3. The holder, which comprises an optical element and a holder for holding the optical element, and which supports the head so as to be movable in a direction substantially perpendicular to a recording surface of the recording medium. 3. The head speed control device according to claim 2, wherein the holder is fixed to one end of a supporting means, and the other end of the holder supporting means is fixed to the carriage.