Abstract:
A disk device includes a head part, an actuator part for moving the head part to an objective position, and a control part for controlling the actuator part, wherein the control part makes the actuator part shift to a reverse direction of the movement direction of the head part before a settling action of the head part starts being implemented.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to information recording and/or playback devices and methods of positioning of magnetic heads of the devices, and more particularly, to an information recording and/or playback device and a method of positioning of a magnetic head of the device, in which the magnetic head is positioned by dual-stage actuators.  
           [0003]    2. Description of the Related Art  
           [0004]    There is great demand to improve the speed and accuracy of positioning a magnetic head of a magnetic disk device. Because of this, a magnetic disk device which has a dual-stage servo system comprising a slight movement actuator and a rough movement actuator is proposed.  
           [0005]    For instance, a magnetic disk device having such the dual-stage servo system comprising a slight movement actuator and a rough movement actuator is described in Japanese Laid-Open Patent Application No. 11-031368.  
           [0006]    A magnetic disk device having a dual-stage servo actuator will be described.  
           [0007]    [0007]FIG. 1A is a plan view of the magnetic disk device having the dual-stage actuator. FIG. 1B is a vertical sectional-view taken on line A-A in FIG. 1A. FIG. 2 is a block diagram of the magnetic disk device having the dual-stage actuator.  
           [0008]    The magnetic disk device  1  includes a disk enclosure  11  and a circuit board assembly  12 .  
           [0009]    The disk enclosure  11  has a case  21  and a cover  22 . A magnetic disk  31 , a spindle motor  32 , a magnetic head  33 , a suspension  34  and an arm  35 , a slight movement actuator  36 , and a rough movement actuator  37  are built in a space between the case  21  and the cover  22  of the disk enclosure  11 .  
           [0010]    The magnetic disk  31  is clamped to the spindle motor  32 . The magnetic disk  31  rotates as the spindle motor  32  rotates. The spindle motor  32  is connected to the circuit board assembly  12  and rotates based on a driving signal provided by the circuit board assembly  12 .  
           [0011]    A magnetic head  33  is fixed on a head end part of the suspension  34 . The magnetic head  33  faces the magnetic disk  31 . The suspension  34  is provided on a head end part of the arm  35 . The suspension  34  is capable of circular movement driven and in a disk radius direction (an arrow A direction). The suspension  34  and arm  35  are connected to each other by the slight movement actuator  36 . The slight movement actuator  36 , for example, is comprised of a shear type piezo actuator and makes the suspension  34  move circularly and in the arrow A direction. The other end part of the arm  35  is connected with the rough movement actuator  37 . The rough movement actuator  37 , for example, is comprised of a voice coil motor (VCM) and makes the arm  35  move circularly and in the arrow B direction.  
           [0012]    The magnetic head  33  is connected to a flexible print wire board  38  by a print wire in the suspension  34  and the arm  35  or a lead line wired along the arms  34  and  35 . A head IC  39  is mounted on the flexible print wire board  38 . The head IC  39  is connected to the magnetic head  33 . The head IC  39  amplifies a recording signal which is supplied to the magnetic head  33  and a playback signal which is played back by the magnetic head  33 . In addition, the flexible print wire board  38  is connected with the slight movement actuator  36  and the rough movement actuator  37 .  
           [0013]    The head IC  39  is extended to a bottom surface side of the case  21  by the flexible print wire board  38 , and connected to the circuit board assembly  12 . The flexible print wire board  38  is connected to the spindle motor  32 , the slight movement actuator  36 , and the rough movement actuator  37 . The flexible print wire board  38  is extended from an inside part of the case  21  to an outside part of a bottom surface of the case  21 , that is, piercing the bottom surface.  
           [0014]    The circuit board assembly  12  is provided at an outside part of the bottom surface of the case  21 . Furthermore, the circuit board assembly  12  is connected to the flexible print wire board  38 . The circuit board assembly  12  has a structure in which a hard disk controller (HDC)  41 , a random access memory (RAM)  42 , a read only memory (ROM)  43 , a digital signal processor (DSP)  44 , a micro processor unit (MPU)  47 , a read channel (RDC)  45 , and a servo controller (SVC)  46  are mounted on the print wire board  38 .  
           [0015]    The HDC  41  is connected to a high ranked controller  51 , and thereby the HDC  41  controls a communication with the high ranked controller  51 . The RAM  42  is used as a buffer memory in which data communicated with the high ranked controller  51  are stored temporarily. The RDC  45  modulates the recording signal recorded in the magnetic disk  31  and demodulates the playback signal played back from the magnetic disk  31 , by the magnetic head  33 .  
           [0016]    The SVC  46  is connected to the spindle motor  32 , the slight movement actuator  36 , the rough movement actuator  37 , and the DSP  44 . The SVC  46  drives the spindle motor  32 , as a relative speed of the magnetic head  33  and the magnetic disk  31  becomes a designated value based on the playback signal which is played back by the magnetic head  33 . In addition, the SVC  46  controls the slight movement actuator  36  and the rough movement actuator  37  based on instructions from the MPU  44 . And thereby, the magnetic head  33  follows a track formed in the magnetic disk  31 .  
           [0017]    The MPU  44  controls the HDC  41 , the RDC  45 , and the SVC  46  by firm ware stored permanently in the ROM  43 , and thereby the MPU  44  controls an action of the whole of the device.  
           [0018]    It is required for the slight movement actuator  36  of the above-mentioned dual-stage servo actuator of the magnetic disk device to have a high speed ability. Because of this, a shear type piezo actuator is used as the slight movement actuator  36 .  
           [0019]    [0019]FIG. 3 is a plan view of the dual-stage actuator in which the shear type piezo actuator is used as the slight movement actuator  36  and the VCM is used as the rough movement actuator  37 . The piezo actuator has a movable area of “a”(a plus direction of “a” to a minus direction of “a”) where “a” is defined as a distance of 0.5 μm from a center position of the movable area. The rough movement actuator  37  has a movable area of “b” (a plus direction of “b” to a minus direction of “b”) where “b” is defined as a distance of 12 mm from a center position of the movable area.  
           [0020]    [0020]FIG. 4 is a view showing a frequency response of the piezo actuator namely the slight movement actuator  36 . FIG. 5 is a view showing a frequency response of the VCM namely the rough movement actuator  37 .  
           [0021]    The piezo actuator has a main resonance frequency of 9 kHz, as shown in FIG. 4. On the other hand, the VCM has a main resonance frequency of 5 kHz, as shown in FIG. 5. Therefore, the piezo actuator can act with a higher speed than the VCM.  
           [0022]    [0022]FIG. 6 is a block diagram of a track following control system of the dual-stage actuator.  
           [0023]    At the time of track following, a tracking error signal is necessary. The tracking error signal represents a difference between an information of an objective position of the head and an information of a present position of the head. The tracking error signal is supplied to a controller  62  for controlling the slight movement actuator  36  and a controller  63  for controlling the rough movement actuator  37 .  
           [0024]    The controller  62  controls the slight movement actuator  36  based on the tracking error signal. The controller  63  controls the rough movement actuator  37  based on the tracking error signal.  
           [0025]    The magnetic head  33  is moved a total amount by the slight movement actuator  36  and the rough movement actuator  37 . A position of the magnetic head  33  is fed back as information providing a present head position. With the above-mentioned operation, the magnetic head  33  is positioned at the objective position.  
           [0026]    [0026]FIG. 7 is a block diagram of a track seek control system of the dual-stage actuator.  
           [0027]    As shown in FIG. 7, in this system, a control by the slight movement actuator  36  and a control by the rough movement actuator  37  are implemented separately at the time of a track seek. When a seek action in which the magnetic head moves a long distance is implemented, the rough movement actuator  37  makes the magnetic head move. Initially the slight movement actuator  36  is not under feed-back control but is fixed in a designated position. The slight movement actuator  36  starts moving in a latter settling action of the seek action. After a distance between the magnetic head and the objective track becomes so short that the distance is within the movable area of the slight movement actuator  36 , the settling action is switched so as to use the slight movement actuator  36 .  
           [0028]    [0028]FIG. 8 is a view showing a wave form of a time response regarding the slight movement actuator, the rough movement actuator, and a head position, according to a conventional art. In FIG. 8, a position of the magnetic head  33  is expressed with a solid line, a driving position of the slight movement actuator  36  is expressed with a dashed line, and a driving position of the rough movement actuator  37  is expressed with an dash-dot line.  
           [0029]    When a center of a movable area of the slight movement actuator  36  reaches an objective position  0  of the magnetic head  33  at a time of t 0 , it is possible to make the objective position  0 , that is, move the magnetic head  33  to position  0 , by using the slight movement actuator  36 . Therefore, the action of the magnetic head  33  is changed from the seek action to the settling action. Since the slight movement actuator  36  is held at the center position of the movable area, the magnetic head  33  is positioned at a distance “a” from the objective position  0  in a minus direction.  
           [0030]    Once the settling action starts, the slight movement actuator  36  is driven. When the slight movement actuator  36  is shifted by “a” from the objective position  0  to a plus direction as shown by the dashed line in FIG. 8, the magnetic head  33  is shifted to the objective position  0  in a short period of time. At this time, the rough movement actuator  37  is shifted to the objective position  0  as shown by the one point doted line in FIG. 8. The slight movement actuator  36  is shifted as the rough movement actuator  37  is shifted to make the magnetic head  33  stay at the objective position  0 .  
           [0031]    Accordingly, the magnetic head  33  can be set in an allowable deviation area where the objective position  0  is a center of the area, as shown by the solid line in FIG. 8. After the settling action is implemented, the track following action is implemented. For example, information recording and/or information playback action is implemented.  
           [0032]    The seek action of the magnetic disk device  1  in which the dual-stage actuator servo system consisting of the slight movement actuator  36  and the rough movement actuator  37  is applied, for example, as described in “Masahito Kobayashi, Takashi Yamaguchi, Roberto Horowitz, “Track-Seeking Controller Design for Dual-Stage Actuator in Magnetic Disk Drives”, Proceedings of the American Control Conference, Chicago, Ill., June 2000”.  
           [0033]    A seek action over a short distance is mainly described in the above-mentioned reference. According to the reference, a response to an action in a range exceeding the movable area of the slight movement actuator  36  is improved by a switching means. The switching means allows a control loop of the slight movement actuator  36  and the rough movement actuator  37  to avoid mutual interference and switches respective objective paths at the time of a full operation of the slight movement actuator  36  and the rough movement actuator  37 .  
           [0034]    If the limitation of the movable area of the slight movement actuator  36  in the settling action of the magnetic disk device having a conventional dual-stage actuator is eased, it may be possible to switch the settling action at an earlier time than tO shown in FIG. 8. As a result of this, the seek action can be implemented in a shorter period of time. Although a response at the time of settling action is improved under the limitation of the movable area of the slight movement actuator  36 , the limitation of the movable area itself is not eased, in a method in the above-mentioned reference.  
           [0035]    In order to ease the movable area limitation of the slight movement actuator in the settling action of the magnetic disk device having a conventional dual-stage actuator, it is necessary to solve a difficult problem. That is, it is necessary to expand a range of a driving voltage, or reduce a rigidity of the actuator by making sacrifices to a resonance property of the slight movement actuator  36 .  
         SUMMARY OF THE INVENTION  
         [0036]    Accordingly, it is a general object of the present invention to provide a novel and useful information recording and/or playback device method in which positioning of a magnetic head of the information recording and/or playback device is implemented in a short period of time, where one or more of the problems described above are eliminated.  
           [0037]    Another and more specific object of the present invention is to provide a disk device including a head part, an actuator part for moving the head part to an objective position, and a control part for controlling the actuator part, wherein the control part makes the actuator part shift to a reverse direction of the movement direction of the head part before a settling action of the head part starts being implemented.  
           [0038]    According to the above invention, from a starting time of a seek action to the settling action, the head such as a magnetic head is shifted to a reverse direction of a current direction of a movement of the head. Therefore, it is possible to start implementing the settling action at an earlier timing than the conventional art, and thereby the head can be set at the objective position in a short period of time. Hence, the seek action is implemented quickly.  
           [0039]    In the above-mentioned device, the actuator part may comprise a slight movement actuator for a slight movement of the head part and a rough movement actuator for a rough movement of the head part. In addition, an objective position of the slight movement actuator may be shifted to a movement direction of the head part and an objective position of the rough movement actuator may be shifted to a reverse direction of the movement direction of the head part before a settling action of the head part starts being implemented.  
           [0040]    According to the above invention, the settling action, by which the magnetic head is set at the objective position, is implemented before the magnetic head reaches the actual objective position. And thereby, the seek action is implemented quickly.  
           [0041]    Other objects, features, and advantages of the present invention will be more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0042]    [0042]FIG. 1A is a plan view of a magnetic disk device having a dual-stage servo actuator.  
         [0043]    [0043]FIG. 1B is a vertical sectional-view taken on line A-A in FIG. 1A.  
         [0044]    [0044]FIG. 2 is a view showing a block structure of a magnetic disk device having a dual-stage servo actuator.  
         [0045]    [0045]FIG. 3 is a plan view of a dual-stage actuator in which a shear type piezo actuator is used as a slight movement actuator and a voice coil motor as a rough movement actuator.  
         [0046]    [0046]FIG. 4 is a view showing a frequency response of the piezo actuator.  
         [0047]    [0047]FIG. 5 is a view showing a frequency response of the voice coil actuator.  
         [0048]    [0048]FIG. 6 is a block diagram of a track following control system of the dual-stage actuator.  
         [0049]    [0049]FIG. 7 is a block diagram of a track seek control system of the dual-stage actuator.  
         [0050]    [0050]FIG. 8 is a view showing a wave form of a time response regarding a slight movement actuator, a rough movement actuator, and a head position, according to the conventional art.  
         [0051]    [0051]FIG. 9 is a flow chart of an action of a first embodiment of the present invention.  
         [0052]    [0052]FIG. 10 is a view showing a wave form of a time response regarding a slight movement actuator, a rough movement actuator, and a head position, according to the first embodiment of the present invention.  
         [0053]    [0053]FIG. 11 is a flow chart of an action of a second embodiment of the present invention.  
         [0054]    [0054]FIG. 12 is a view showing a wave form of a time response regarding a slight movement actuator, a rough movement actuator, and a head position, according to the second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0055]    A description will now be given, with reference to FIGS.  9 - 12 , of embodiments of the present invention.  
         [0056]    The magnetic disk device shown in FIGS. 1 and 2 is used in a first embodiment. In the first embodiment, from a starting time of a seek action to a time of a settling action, the slight movement actuator  36  is offset to a reverse direction of a seek direction in a movable area. In addition, the objective position of the slight movement actuator  36  is offset to the seek direction, and the objective position of the rough movement actuator  37  is offset to the reverse direction of the seek direction in a movable area except for a necessary margin for controlling.  
         [0057]    In the magnetic disk device of this embodiment, a firm ware implemented in the DSP  44  is different from one in the conventional disk device shown in FIGS. 1 and 2. Accordingly, a structure of the magnetic disk device in this embodiment is the substantially the same as the structure of the magnetic disk device shown in FIGS. 1 and 2, and explanation thereof will be omitted.  
         [0058]    [0058]FIG. 9 is a flow chart of an action of the first embodiment.  
         [0059]    In this embodiment, a seek action is implemented as in the following steps.  
         [0060]    In a step S 1 - 1 , the DSP  44  receives a seek order from the MPU  47 . In a step S 1 - 2 , the DSP  44  stops a feed-back control of the slight movement actuator  36  and starts a feed-back-control of the rough movement actuator  37  along an objective path calculated on a basis of a seek distance.  
         [0061]    In a step S 1 - 3 , the DSP  44  calculates a seek time based on the seek distance. The MPU  44  also calculates a changing rate of an amount of an offset in order to complete the offset of the slight movement actuator  36  within the seek time.  
         [0062]    The amount of the offset of the slight movement actuator  36  is increased and a calculation of an objective path of the rough movement actuator  37  and a feed-back-control to the objective path are implemented in a step S 1 - 4 , until a distance between a position of the magnetic head and an objective track is determined to become 2×“a” or less in a step S 1 - 5 .  
         [0063]    If the distance between the positions of the magnetic head and the objective track is determined to be 2×“a” or less in the step S 1 - 5 , a seek mode where the steps S 1 - 2  through S 1 - 5  are implemented is completed and a setting control mode starts in a step S 1 - 6 .  
         [0064]    In the step S 1 - 6 , a feed-back-control to respective objective tracks of the slight movement actuator  36  and the rough movement actuator  37  is started. When the position of the magnetic head is within an allowable deviation area, the DSP  44  transmits a completion of the seek action to the MPU  47  in a step S 1 - 7 , and a track following mode is implemented.  
         [0065]    [0065]FIG. 10 is a view showing a wave form of a time response regarding a slight movement actuator, a rough movement actuator, and a head position, according to the first embodiment of the present invention. In FIG. 10, a position of the magnetic head  33  is expressed with a solid line, a driving position of the slight movement actuator  36  is expressed with a dashed line, and a driving position of the rough movement actuator  37  is expressed with a dash dot line.  
         [0066]    When an end part of a plus “a” side of a movable area (minus “a” to plus “a”) of the slight movement actuator  36  reaches an objective position  0  of the magnetic head  33  at a time of t 10 , it is possible for the magnetic head  33  to reach the objective position  0  by using the slight movement actuator  36 . Hence, the action of the magnetic disk device is changed from the seek action to the settling action. Since the slight movement actuator  36  is shifted a distance of “a” to a reverse direction of a movement direction of the magnetic head  33  in this embodiment, the settling action starts at the time of t 10  earlier than tO shown in FIG. 8.  
         [0067]    Because of the shift of the slight movement actuator  36 , it is possible to move the rough actuator  37  more quickly than with a conventional device. That is, it is possible to start the settling action at an earlier time than with a conventional device.  
         [0068]    The magnetic head  33  is positioned at a place having a distance of 2×“a” from the objective position  0  to a minus direction.  
         [0069]    During the settling action, the slight movement actuator  36  is driven to make the magnetic head  33  become positioned at the objective position. The slight movement actuator  36  is shifted by “a” from the objective position  0  to a plus direction as shown by the dashed line in FIG. 10. Then, the rough movement actuator  37  is shifted to the objective position  0  as shown by the one point doted line in FIG. 10. The magnetic head  33  is shifted to the objective position  0  because of the shift of the rough movement actuator  37 . Since the magnetic head  33  is shifted as the rough movement actuator  37  is shifted, the slight movement actuator  36  makes the magnetic head  33  shift to follow the above mentioned shift of the magnetic head  33 .  
         [0070]    According to this embodiment, as shown by the solid line in FIG. 10, the magnetic head  33  is settled within the allowable deviation area where the objective position  0  is the center thereof. After the settling action is implemented, the track following mode is implemented. For instance, an action of information recording and/or playing back is implemented. Since the settling action can be implemented at an earlier time than with the conventional art according to this embodiment, it is possible to set the magnetic head  33  at the objective position  0  in a short period of time. As a result of this, it is possible to start implementing the action of information recording and/or playing back quickly.  
         [0071]    In this embodiment, at the time of the seek action and the settling action, the rough movement actuator  37  is controlled to make the rough movement actuator  37  shift to the objective position  0 . If the objective positions of both the slight movement actuator  36  and the rough movement actuator  37  are allowed to be shifted from an actual objective position  0  during the times of the seek action and the settling action, it is possible to implement the settling action more quickly.  
         [0072]    Next, a second embodiment will be described. In the second embodiment of the present invention, the objective position of the slight movement actuator  36  is shifted to a position having a distance of “a”-“c” from the actual objective position  0  to a plus direction, and the objective position of the rough movement actuator  37  is shifted to a position having a distance of “a”-“c” from the actual objective position  0  to a minus direction, where “c” is defined as a designated and overshooting distance. A structure of the magnetic disk device in this embodiment is substantially the same as the structure of the magnetic disk device shown in FIGS. 1 and 2, and explanation thereof will be omitted. Only an action of the MPU  44  in this embodiment will be described.  
         [0073]    [0073]FIG. 11 is a flow chart of an action of a second embodiment.  
         [0074]    In a step S 2 - 1 , the MPU  44  receives a seek order from the high ranked controller  51 . In a step S 2 - 2 , the MPU  44  stops a feed-back-control of the slight movement actuator  36  and starts a feed-back-control of the rough movement actuator  37  along an objective path calculated on a basis of a seek distance.  
         [0075]    In a step S 2 - 3 , the MPU  44  calculates a seek time on a basis of the seek distance. The MPU  44  also calculates a changing rate of an amount of an offset in order to complete the offset of the slight movement actuator  36  within the seek time.  
         [0076]    In a step S 2 - 4  the amount of the offset of the slight movement actuator  36  is increased and a control for following the paths of the rough movement actuator  37  are implemented until a distance between a position of the magnetic head  33  and the objective track is determined to become “a”+2×(“a”-“c”) or less in a step S 2 - 5 .  
         [0077]    If the distance between the positions of the magnetic head  33  and the objective track is determined to be “a”+2×(“a”-“c”) or less in the step S 2 - 5 , a seek mode where the steps S 2 - 2  through S 2 - 5  are implemented is completed and a settling control mode starts in a step S 2 - 6 .  
         [0078]    In the step S 2 - 6 , a feed-back-control to respective objective tracks of the slight movement actuator  36  and the rough movement actuator  37  starts, where the objective position of the slight movement actuator  36  has a distance of “a”-“c” from the objective position  0 . The objective position of the rough movement actuator  37  has a distance of r+(“a”-“c”) from the objective position  0 , where “r” represents a center of the track. That is, the feed-back-control starts in a state where the objective position of the slight movement actuator  36  is shifted to a position having a distance of “a”-“c” from the actual objective position  0  to a plus direction, and the objective position of the rough movement actuator  37  is shifted to a position having a distance of “a”-“c” from the actual objective position  0  to a minus direction.  
         [0079]    The feed-back-control is implemented until the position of the magnetic head  33  is determined to be within an allowable deviation area around objective position  0  in a step of S 2 - 7 .  
         [0080]    When the position of the magnetic head  33  is determined to be within an allowable deviation area in a step of S 2 - 7 , the DSP  44  transmits a completion of the seek action to the MPU  47  in a step S 2 - 8 .  
         [0081]    In this embodiment, the objective position of the slight movement actuator  36  is shifted to a position having a distance of “a”-“c” from the actual objective position  0  to a plus direction, and the objective position of the rough movement actuator  37  is shifted to a position having a distance of “a”-“c” from the actual objective position  0  to a minus direction. Therefore, in a step of S 2 - 9 , the objective position of the slight movement actuator  36  is brought close to “ 0 ” and the objective position of the rough movement actuator  37  is brought close to “r” after a seek action is completed.  
         [0082]    [0082]FIG. 12 is a view showing a wave form of a time response regarding a slight movement actuator, a rough movement actuator, and a head position, according to the second embodiment of the present invention. In FIG. 12, a position of the magnetic head  33  is expressed with a solid line, a driving position of the slight movement actuator  36  is expressed with a dashed line, and a driving position of the rough movement actuator  37  is expressed with an dash dot line.  
         [0083]    When an end part of a plus direction of “a” of a movable area (a plus direction of “a” to a minus direction of “a”) of the slight movement actuator  36  reaches an objective position  0  of the magnetic head  33  at a time of t 20 , it is possible to make the objective position  0  by the slight movement actuator  36 . Hence, the action of the magnetic disk device is changed from the seek action to the settling action. Since the slight movement actuator  36  is shifted by “a” to a reverse direction of a movement direction of the magnetic head  33 , namely a minus direction from the objective position  0  in this embodiment, the settling action starts at the time of t 20  earlier than t 0  shown in FIG. 8. At this time, since the rough movement actuator  37  is positioned at a place having a distance of “a”-“c” from the objective position  0  to a minus direction and the magnetic head  33  is positioned at a place having a distance of “a”+2×(“a”-“c”) from the objective position  0  to a minus direction, it is possible to implement the settling action at an earlier time than the first embodiment. Furthermore, it is possible to set the magnetic head  33  at the objective position  0  in a short period of time by implementing the settling action with the slight movement actuator  36  and the rough movement actuator  37 .  
         [0084]    According to this embodiment, as shown by the solid line in FIG. 12, the magnetic head  33  is settled within the allowable deviation area where the objective position  0  is the center thereof. After the settling action is implemented, the track following mode is implemented. For instance, an action of information recording and/or playing back is implemented. At this time, the objective position of the rough movement actuator  37  is changed from a position having a distance of (“a”+2 ×(“a”-“c”)) from the objective position  0 , to the objective position  0 . According to this embodiment, since the settling action is implemented with the slight movement actuator  36  and the rough movement actuator  37 , it is possible to implement the settling action at an earlier time than the first embodiment. Therefore, it is possible to set the magnetic head  33  at the objective position  0  with high speed. Hence, it is possible to start implementing the action of information recording and/or playing back quickly.  
         [0085]    In this embodiment, since the limitation of the moveable area of settling action of the slight movement actuator  36  is eased, it is possible to change the settling action at an earlier time than the conventional art. As a result of this, an elapsed time for seek can be reduced. Alternatively, a necessary movable area of the slight movement actuator  36  can be reduced to be a half or less area of the movable area for the slight movement actuator  36  in the conventional art. Hence, it is possible to simplify an electric circuit resulting from a reduction of a necessary driving voltage, or increase a resonance frequency based on an implement action of rigidity of the slight movement actuator  36  or reduce a resonance gain.  
         [0086]    Although the magnetic disk devices as devices for information recording and/or playing back are described in this specification, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. For instance, the present invention can be applied to an optical disk device such as an magnetic optical disk device.  
         [0087]    This patent application is based on Japanese priority patent application No. 2001-248218 filed on Aug. 17, 2001, the entire contents of which are hereby incorporated by reference.