Magnetic disk device and control method thereof

Abstract

To provide a highly reliable magnetic disk device capable of making respective magnetic heads accurately follow respective target positions, and to provide its control method.SOLUTION: The magnetic disk device includes a plurality of first actuators for displacing each magnetic head along a radial direction of the magnetic disk between an inner periphery and an outer periphery of the magnetic disk, a plurality of second actuators for displacing each magnetic head independently of each other in a direction along the radial direction of the magnetic disk, a plurality of third actuators for simultaneously displacing each magnetic head by the same amount in directions opposite to each other along the radial direction of the magnetic disk, and a controller. The controller controls driving of the first actuators, driving of the second actuators, and driving of the third actuators to cause the magnetic heads to seek target positions on the recording surfaces of the magnetic disks and follow target tracks at the target positions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a magnetic disk device including a magnetic disk and a magnetic head, and a control method thereof. [Background technology]

[0002] A magnetic disk device has a circular magnetic disk with a pair of recording surfaces on the front and back, and multiple magnetic heads that write and read data to each recording surface of the magnetic disk.When each magnetic head writes or reads data, it drives a motor (voice coil motor) to cause each magnetic head to seek to its respective target position (write position or read position) on each recording surface of the magnetic disk, and then causes it to follow (this is called track following or tracking) its respective target track at each target position.

[0003] To compensate for the tracking accuracy of this motor drive, some magnetic disk drives are equipped with multiple micro-actuators that independently and minutely displace each magnetic head in the radial direction of the magnetic disk. These magnetic disk drives are capable of so-called two-surface simultaneous positioning control, in which each magnetic head is controlled to seek to a target position on each recording surface of the magnetic disk and follow a target track at each target position. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 11,189,310 Summary of the Invention [Problem to be solved by the invention]

[0005] The amount of displacement of each magnetic head caused by the drive of each microactuator is small, so when controlling simultaneous positioning of two surfaces, it is difficult to accurately track each magnetic head to its respective target track, for example, when there is a large difference between the target position of one magnetic head and the target position of the other magnetic head.

[0006] An object of the embodiment is to provide a highly reliable magnetic disk drive that can accurately track each magnetic head to its respective target position, and a control method thereof. [Means for solving the problem]

[0007] The magnetic disk device of the embodiment comprises at least one circular magnetic disk having a pair of recording surfaces on the front and back sides; a plurality of magnetic heads for writing and reading data to each of the recording surfaces of the magnetic disk; a plurality of first actuators for displacing each of the magnetic heads along the radial direction of the magnetic disk between the inner and outer circumferences of the magnetic disk; a plurality of second actuators for displacing each of the magnetic heads independently of one another in directions along the radial direction of the magnetic disk; a plurality of third actuators for simultaneously displacing each of the magnetic heads by the same amount in opposite directions along the radial direction of the magnetic disk; and a controller for controlling the driving of each of the first actuators, each of the second actuators, and each of the third actuators, thereby causing each of the magnetic heads to seek to a respective target position on each of the recording surfaces of the magnetic disk and to follow a respective target track at each target position. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the overall configuration of each embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of one recording surface of a magnetic disk in each embodiment. [Figure 3] FIG. 3 is a diagram showing the configuration of each magnetic disk, each magnetic head, and each microactuator in each embodiment, together with their peripheral parts. [Figure 4] FIG. 4 is a diagram showing minute displacements of the magnetic heads caused by the second actuators of the embodiments. [Figure 5] FIG. 5 is a diagram showing minute displacements of the holding members caused by the third actuators in the embodiments. [Figure 6] FIG. 6 is a block diagram showing a seek and tracking control section of a controller in the first embodiment. [Figure 7] Figure 7 is a diagram showing the amount of displacement of one magnetic head by the first actuator, the amount of displacement of one magnetic head by the second actuator, and the amount of displacement of one magnetic head by the third actuator when the target positions of each magnetic head are DC offset from each other in each embodiment. [Figure 8] Figure 8 is a diagram showing the displacement amount of the other magnetic head by the first actuator, the displacement amount of the other magnetic head by the second actuator, and the displacement amount of the other magnetic head by the third actuator when the target positions of each magnetic head are DC offset from each other in each embodiment. [Figure 9] Figure 9 is a diagram showing the amount of displacement of one magnetic head by the first actuator, the amount of displacement of one magnetic head by the second actuator, and the amount of displacement of one magnetic head by driving the third actuator when the target positions of each magnetic head are AC offset from each other in each embodiment. [Figure 10] Figure 10 is a diagram showing the displacement amount of the other magnetic head by the first actuator, the displacement amount of the other magnetic head by the second actuator, and the displacement amount of the other magnetic head by the third actuator when the target positions of each magnetic head are AC offset from each other in each embodiment. [Figure 11] FIG. 11 is a block diagram showing a seek and tracking control section of a controller in the second embodiment. [Figure 12] FIG. 12 is a block diagram showing a seek and tracking control section of a controller in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [1] The first embodiment will be described with reference to the drawings. As shown in FIG. 1, the magnetic disk device 1 includes a magnetic disk 2 which is a recording medium, a spindle motor 3 which rotates the magnetic disk 2, and a magnetic head 10 which writes and reads data to and from the magnetic disk 2.

[0010] 2, the magnetic disk 2 has a circular shape and is coaxially fitted to the rotation shaft of the spindle motor 3, and includes a large number of tracks Tr arranged circumferentially and concentrically. Each track Tr includes a servo sector consisting of a servo pattern SB in which position data is recorded and a data area DT in which write data is stored.

[0011] 3, the magnetic disk 2 includes a pair of recording surfaces 2a and 2b on the front and back sides. A plurality of magnetic disks 2 are arranged coaxially on a spindle motor 3 at predetermined intervals. Each magnetic head 10 is arranged facing the recording surfaces 2a and 2b of the magnetic disks 2.

[0012] Each magnetic head 10 includes a slider 11, which includes a data write element and a data read element. When the magnetic disk 2 rotates, the slider 11 receives wind pressure from the rotation and floats up, causing the magnetic head 10 to float in a direction away from the magnetic disk 2.

[0013] Each magnetic head 10 is rotatably held by a plurality of actuators (first actuators) 20. As shown in Fig. 3, each actuator 20 includes a common rotating shaft 21. Each actuator 20 includes, as a holding member for holding the magnetic head 10, an arm 22 attached to the rotating shaft 21 and suspension members 24a, 24b attached to the tip of the arm 22.

[0014] The arms 22 of each actuator 20 are arranged spaced apart from each other, sandwiching one magnetic disk 2 between them. Each suspension member 24a is located on the side corresponding to the recording surface 2a of each magnetic disk 2, and each suspension member 24b is located on the side corresponding to the recording surface 2b of each magnetic disk 2.

[0015] A magnetic head 10 is attached to the tip of each suspension member 24a, and each magnetic head 10 faces the recording surface 2a of each magnetic disk 2. A magnetic head 10 is attached to the tip of each suspension member 24b, and each magnetic head 10 faces the recording surface 2b of each magnetic disk 2.

[0016] Furthermore, each actuator 20 commonly includes a voice coil motor 23 that rotates the rotating shaft 21, and the rotation of the rotating shaft 21, arm 22, and suspension members 24a, 24b based on the drive of this voice coil motor 23 displaces each magnetic head 10 along the radial direction of each magnetic disk 2 between a first position P1 shown by a dashed line on the inner side of each magnetic disk 2 and a second position P2 shown by a solid line on the outer side.

[0017] The voice coil motor 23 includes a coil 23c, a magnet, and a yoke, and when a drive current flows through the coil 23c, the arm 22 and the suspension members 24a and 24b of each actuator 20 are rotated.

[0018] A microactuator (second actuator) 25a for compensating for the tracking accuracy caused by driving the voice coil motor 23 is provided at the tip of the suspension member 24a on the side facing the recording surface 2a of the upper (first) magnetic disk 2. A microactuator (second actuator) 25b for compensating for the tracking accuracy caused by driving the voice coil motor 23 is provided at the tip of the suspension member 24b on the side facing the recording surface 2b of the same upper (first) magnetic disk 2.

[0019] The microactuator 25a includes a pair of piezoelectric elements A1 and A2, and by driving the piezoelectric elements A1 and A2, the magnetic head 10 of the suspension member 24a is slightly displaced (moved) in a direction along the radial direction of the magnetic disk 2 as shown in Figure 4, independently of the movement of the magnetic head 10 of the suspension member 24b.

[0020] The microactuator 25b includes a pair of piezoelectric elements A1 and A2, and by driving the piezoelectric elements A1 and A2, the magnetic head 10 of the suspension member 24b is slightly displaced (moved) in a direction along the radial direction of the magnetic disk 2 as shown in Figure 4, independently of the movement of the magnetic head 10 of the suspension member 24a.

[0021] Similarly, microactuator 25a is provided at the tip of suspension member 24a facing recording surface 2a of magnetic disk 2 in the middle (second) tier, and microactuator 25b is provided at the tip of suspension member 24b facing recording surface 2b of magnetic disk 2. Microactuator 25a is provided at the tip of suspension member 24a facing recording surface 2a of magnetic disk 2 in the lower (third) tier, and microactuator 25b is provided at the tip of suspension member 24b facing recording surface 2b of magnetic disk 2.

[0022] Meanwhile, a microactuator (third actuator) 26a for compensating for the tracking accuracy achieved by driving the voice coil motor 23 is provided at the base end (arm 22 side) of the suspension member 24a on the side facing the recording surface 2a of the upper (first) magnetic disk 2. A microactuator (third actuator) 26b for compensating for the tracking accuracy achieved by driving the voice coil motor 23 is provided at the base end (arm 22 side) of the suspension member 24b on the side facing the recording surface 2b of the same upper (first) magnetic disk 2.

[0023] The microactuator 26a includes a pair of piezoelectric elements B1 and B2, and by driving the piezoelectric elements B1 and B2, the suspension member 24a holding the magnetic head 10 is slightly displaced (moved) in a direction along the radial direction of the magnetic disk 2 as shown in Figure 5, independently of the movement of the suspension member 24b.

[0024] The microactuator 26b includes a pair of piezoelectric elements B1 and B2, and by driving the piezoelectric elements B1 and B2, the suspension member 24b holding the magnetic head 10 is slightly displaced (moved) in a direction along the radial direction of the magnetic disk 2 as shown in Figure 5, independently of the movement of the suspension member 24a.

[0025] However, the microactuators 26a and 26b are driven and controlled by a controller 30, which will be described later, to simultaneously slightly displace the suspension members 24a and 24b by the same amount in opposite directions.

[0026] A stopper ST and a ramp mechanism RL are disposed near each actuator 20. The stopper ST limits the movement position of the magnetic head 10 on the inner periphery of the magnetic disk 12. The ramp mechanism RL retracts the magnetic head 10 from above the magnetic disk 2 when the spindle motor 3 is stopped.

[0027] As shown in FIG. 1, the magnetic disk device 1 also includes a controller 30, which serves as the center of control, a head amplifier 41 that drives each magnetic head 10, a signal processing circuit 42 provided between the connection between the head amplifier 41 and the controller 30, a motor driver 43 that drives the spindle motor 3 and the voice coil motor 23 in response to commands from the controller 30, an MA (microactuator) driver 44 that drives each microactuator 25a, 25b and each microactuator 26a, 26b in response to commands from the controller 30, a DRAM 45 that is a memory storing programs and the like required for controlling the controller 30, a flash ROM 46 that is a memory storing various data required for controlling the controller 30, and a hard disk controller (HDC) 44 provided between the connection between the controller 30, the hard disk controller (HDC), and an external host device 50.

[0028] The head amplifier 41 amplifies write data signals sent from the signal processing circuit 42 to each magnetic head 10, and also amplifies data signals read by each magnetic head 10. The signal processing circuit 42 appropriately processes write data signals sent from the controller 30 to each magnetic head 10 and supplies them to the head amplifier 41, and also appropriately processes read data signals amplified by the head amplifier 41 and supplies them to the controller 30.

[0029] The controller 30 controls the driving of each actuator 20, the driving of each microactuator 25a, 25b, and the driving of each microactuator 26a, 26b, thereby causing each magnetic head 10 to seek and track to target positions Pta, Ptb, respectively, on each recording surface 2a, 2b of each magnetic disk 2. The controller 30 includes seek and tracking control sections 31, 32, 33 as the main functions related to this seeking and tracking.

[0030] The seek and tracking control section 31 controls the seek and tracking of the pair of magnetic heads 10 for the first-stage magnetic disk 2. The seek and tracking control section 32 controls the seek and tracking of the pair of magnetic heads 10 for the second-stage magnetic disk 2. The seek and tracking control section 33 controls the seek and tracking of the pair of magnetic heads 10 for the third-stage magnetic disk 2. Since the configurations of these seek and tracking control sections 31, 32, and 33 are the same, the configuration of the seek and tracking control section 31 is shown in Figure 6 as a representative example.

[0031] The seek / tracking control section 31 includes demodulation sections (demodulation means) 61, 62, difference detection sections (first difference detection means) 63, 64, average value detection section (average value detection means) 71, first actuator control section (first actuator control means) 72, second actuator control section (second actuator control means) 73, 74, difference detection section (second difference detection means) 75, and third actuator control section (third actuator control means) 76.

[0032] The demodulation section 61 demodulates the position data of the servo pattern SB contained in the read data of the magnetic head 10 on the recording surface 2a of the magnetic disk 2, thereby capturing the position Poa of the magnetic head 10 as the tracking position Poax relative to the target position Pta during seek and tracking of the magnetic head 10.

[0033] The demodulation section 62 demodulates the position data of the servo pattern SB contained in the read data of the magnetic head 10 on the recording surface 2b of the magnetic disk 2, thereby capturing the position Pob of the magnetic head 10 as a tracking position Pobx relative to the target position Ptb during seek and tracking of the magnetic head 10.

[0034] The difference detection section 63 detects the error ΔPa of the following position Poax of the magnetic head 10 relative to the target position Pta during seek and tracking of the magnetic head 10 on the recording surface 2 a of the magnetic disk 2 .

[0035] The difference detection section 64 detects an error ΔPb of the following position Pobx of the magnetic head 10 relative to a target position Ptb during seek and tracking of the magnetic head 10 on the recording surface 2 b of the magnetic disk 2 .

[0036] The average value detection section 71 detects the average value of the detection results (errors) ΔPb1 and ΔPb2 of the difference detection sections 63 and 64.

[0037] The first actuator control section 72 controls the displacement amount Pv of each magnetic head 10 caused by driving the voice coil motor 23 of the actuator 20 in accordance with the detection result (average value) of the average value detection section 71.

[0038] The second actuator control section 73 controls the displacement amount Pa of the magnetic head 10 on the recording surface 2a side by driving the microactuator 25a in accordance with the detection result (error) ΔPa of the difference detection section 63.

[0039] The second actuator control section 74 controls the displacement amount Pb of the magnetic head 10 on the recording surface 2b side by driving the microactuator 25b in accordance with the detection result (error) ΔPb of the difference detection section 64.

[0040] The difference detection section 75 detects the difference between the detection result (error) ΔPa of the difference detection section 63 and the detection result (error) ΔPb of the difference detection section 64.

[0041] The third actuator control section 76 simultaneously operates the suspension members (holding members) 24a, 24b by driving the microactuators 26a, 26b to displace +Pc, -Pc in opposite directions by equal amounts according to the detection result (the difference between ΔPa and ΔPb) from the difference detection section 75. Simultaneous displacement of the suspension members (holding members) 24a, 24b by equal amounts in opposite directions is called antiphase driving.

[0042] The displacement amount Pv operated by the first actuator control section 72, the displacement amount Pa operated by the second actuator control section 73, and the displacement amount +Pc operated by the third actuator control section 76 are added together, and this sum becomes the position Poa of one of the magnetic heads 10 on the recording surface 2a side.

[0043] The displacement amount Pv operated by the first actuator control section 72, the displacement amount Pb operated by the second actuator control section 74, and the displacement amount -Pc operated by the third actuator control section 76 are added together, and this becomes the position Pob of the other magnetic head 10 on the recording surface 2b side.

[0044] Figure 7 shows the temporal changes in the displacement amounts Pv, Pa, +Pc for one magnetic head 10 when the target positions Pta, Ptb of each magnetic head 10 are DC offset from each other, and Figure 8 shows the temporal changes in the displacement amounts Pv, Pa, +Pc for the other magnetic head 10.

[0045] Figure 9 shows the temporal changes in the displacement amounts Pv, Pa, +Pc for one magnetic head 10 when the target positions Pta, Ptb of each magnetic head 10 are AC offset from each other, and Figure 10 shows the temporal changes in the displacement amounts Pv, Pa, +Pc for the other magnetic head 10.

[0046] As described above, by detecting the average value of the error ΔPa in the tracking position of one magnetic head 10 relative to its target position Pta and the average value of the error ΔPa in the tracking position of the other magnetic head 10 relative to its target position Ptb, and manipulating the displacement amount Pv of each magnetic head 10 by driving the voice coil motor 23 of the actuator 20 according to the average value, it is possible to perform control, known as two-surface simultaneous positioning control, in which each magnetic head 10 seeks and tracks to its respective target positions Pta, Ptb on the recording surfaces 2a, 2b of the magnetic disk 2.

[0047] In addition, the displacement amount Pa of one magnetic head 10 driven by the microactuator 25a is controlled in accordance with the error ΔPa in the tracking position of one magnetic head 10 relative to its target position Pta, and the displacement amount Pb of the other magnetic head 10 driven by the microactuator 25b is controlled in accordance with the error ΔPb in the tracking position of the other magnetic head 10 relative to its target position Ptb, thereby improving the tracking accuracy of the voice coil motor 23 during two-surface simultaneous positioning control, thereby improving the reliability of two-surface simultaneous positioning control.

[0048] Then, the error ΔPa of the tracking position Poax of the magnetic head 10 relative to the target position Pta on the recording surface 2a of the magnetic disk 2 is detected, and the error ΔPb of the tracking position Pobx of the magnetic head 10 relative to the target position Ptb on the recording surface 2b of the magnetic disk 2 is detected, and the suspension members 24a, 24b are simultaneously displaced in opposite directions by the same amount according to the difference between the detected errors ΔPa, ΔPb by driving each microactuator 26a, 26b.Therefore, even if the difference (offset) between the target position Pta of one magnetic head 10 and the target position Ptb of the other magnetic head 10 is large as shown in Figures 7 to 10, the displacement amounts Pa, Pb by driving each microactuator 25a, 25b, which are the second actuators, do not become unnecessarily large.

[0049] That is, it is possible to reduce the displacements Pa and Pb caused by driving the microactuators 25a and 25b even when there is a large difference between the target position Pta of one magnetic head 10 and the target position Ptb of the other magnetic head 10. Because it is possible to reduce the displacements Pa and Pb caused by driving the microactuators 25a and 25b, it is possible to accurately track each magnetic head 10 to its respective target position Pta or Ptb.

[0050] Even if there is a large difference between the error ΔPa in the tracking position of one magnetic head 10 relative to the target position Pta of that magnetic head 10 and the error ΔPb in the tracking position of the other magnetic head 10 relative to the target position Ptb of that magnetic head, or even if there is an eccentric positional misalignment between the one magnetic head 10 and the other magnetic head 10, as described above, the displacement amounts Pa and Pb caused by driving the second actuators, i.e., the microactuators 25a and 25b, do not become unnecessarily large.

[0051] In other words, even if there is a large difference between the error ΔPa in the tracking position of one magnetic head 10 relative to its target position Pta and the error ΔPb in the tracking position of the other magnetic head 10 relative to its target position Ptb, or even if there is an eccentric positional misalignment between the one magnetic head 10 and the other magnetic head 10, the displacements Pa and Pb caused by the driving of each microactuator 25a, 25b can be reduced. Because the displacements Pa and Pb caused by the driving of each microactuator 25a, 25b can be reduced, each magnetic head 10 can be accurately tracked to its respective target positions Pta and Ptb.

[0052] [2] Second embodiment In the second embodiment, the configuration of the seek / tracking control sections 31, 32, and 33 of the controller 30 is slightly different from that in the first embodiment.

[0053] That is, as shown in FIG. 11, the difference detection section 75 detects the difference between the operation amount of the second actuator control section 73 for the displacement amount Pa of one magnetic head 10 due to the driving of the actuator 25a and the operation amount of the second actuator control section 73 for the displacement amount Pb of the other magnetic head 10 due to the driving of the actuator 25b. The other configurations are the same as those in the first embodiment.

[0054] In the second embodiment, even if there is a large difference between the target position Pta of one magnetic head 10 and the target position Ptb of the other magnetic head 10, or even if there is a large difference between the error ΔPa in the tracking position of one magnetic head 10 relative to the target position Pta of that magnetic head 10 and the error ΔPb in the tracking position of that magnetic head 10 relative to the target position Ptb of the other magnetic head, or even if there is an eccentric positional deviation between the one magnetic head 10 and the other magnetic head 10, the displacements Pa and Pb caused by driving the microactuators 25a and 25b can be reduced. This allows each magnetic head 10 to accurately track its respective target position Pta or Ptb.

[0055] [3] Third embodiment In the third embodiment, the configuration of the seek / tracking control sections 31, 32, and 33 of the controller 30 is slightly different from that in the first embodiment.

[0056] That is, as shown in FIG. 12, the average value detection section 71 calculates the average value of the operation amount of the second actuator control section 73 for the displacement amount Pa of one magnetic head 10 due to the driving of the actuator 25a and the operation amount of the second actuator control section 74 for the displacement amount Pb of the other magnetic head 10 due to the driving of the actuator 25b, and calculates the average value of the detection result (error) ΔPb1 of the difference detection section 63 and the detection result (error) ΔPb2 of the difference detection section 64, and detects the sum of both calculated average values. The other configurations are the same as those in the first embodiment.

[0057] In the third embodiment, even if there is a large difference between the target position Pta of one magnetic head 10 and the target position Ptb of the other magnetic head 10, or even if there is a large difference between the error ΔPa in the tracking position of one magnetic head 10 relative to the target position Pta of that magnetic head 10 and the error ΔPb in the tracking position of that magnetic head 10 relative to the target position Ptb of the other magnetic head, or even if there is an eccentric positional deviation between the one magnetic head 10 and the other magnetic head 10, the displacements Pa and Pb caused by driving the microactuators 25a and 25b can be reduced. This allows each magnetic head 10 to accurately track its respective target position Pta or Ptb.

[0058] [4] Variation The above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0059] 1...magnetic disk drive, 2...magnetic disk, 10...magnetic head, 11...slider, 20...actuator (first actuator), 21...rotating shaft, 22...arm, 23...voice coil motor, 24...suspension member, 25a, 25b...microactuators (second actuators), 26a, 26b...microactuators (third actuators), 30...controller, 31, 32, 33...seek / tracking control section, 61, 62...demodulation section (demodulation means), 63, 64...difference detection section (first difference detection means), 71...average value detection section (average value detection means), 72...first actuator control section (first actuator control means), 73, 74...second actuator control section (second actuator control means), 75...difference detection section (second difference detection means), 76...third actuator control section (third actuator control means).

Claims

1. At least one circular magnetic disk including a pair of recording surfaces on one side and the other, a plurality of magnetic heads for writing and reading data to and from the respective recording surfaces of the magnetic disk; a plurality of first actuators for displacing the magnetic heads along the radial direction of the magnetic disk between the inner and outer peripheries of the magnetic disk; a plurality of second actuators that displace the magnetic heads independently of one another in a radial direction of the magnetic disk; a plurality of third actuators for simultaneously displacing the magnetic heads by the same amount in mutually opposite directions along the radial direction of the magnetic disk; a controller that controls the driving of each of the first actuators, the second actuators, and the third actuators, thereby causing each of the magnetic heads to seek to a respective target position on each of the recording surfaces of the magnetic disk and follow a respective target track at each target position; A magnetic disk device comprising:

2. Each of the first actuators includes a holding member for holding each of the magnetic heads, and also includes a voice coil motor for rotating these holding members, and the rotation of each of the holding members based on the driving of this voice coil motor displaces each of the magnetic heads along the radial direction of the magnetic disk between the inner and outer peripheries of the magnetic disk, each of the second actuators includes a pair of piezoelectric elements, and by driving the pair of piezoelectric elements, the magnetic heads are minutely displaced independently of each other in a direction along the radial direction of the magnetic disks; each of the third actuators includes a pair of piezoelectric elements, and by driving the pair of piezoelectric elements, the holding members holding the magnetic heads are simultaneously and minutely displaced by the same amount in opposite directions along the radial direction of the magnetic disks; 2. The magnetic disk drive according to claim 1.

3. The controller a plurality of first difference detection means for detecting errors in the follow-up positions of the magnetic heads relative to the respective target positions during the seek and tracking operations; an average value detection means for detecting an average value of the detection results of the first difference detection means; a first actuator control means for controlling the displacement amount of each of the magnetic heads by driving each of the first actuators in accordance with the detection result of the average value detection means; a plurality of second actuator control means for controlling the displacement amount of each of the magnetic heads by driving each of the second actuators in accordance with the detection results of each of the first difference detection means; a second difference detection means for detecting a difference between the detection results of the first difference detection means; a third actuator control means for controlling the amounts of displacement of the holding members in opposite directions caused by the driving of the third actuators in accordance with the detection result of the second difference detection means; Including, 2. The magnetic disk drive according to claim 1.

4. The controller a plurality of first difference detection means for detecting errors in the follow-up positions of the magnetic heads relative to the respective target positions during the seek and tracking operations; an average value detection means for detecting an average value of the detection results of the first difference detection means; a first actuator control means for controlling the displacement amount of each of the magnetic heads by driving each of the first actuators in accordance with the detection result of the average value detection means; a plurality of second actuator control means for controlling the displacement amount of each of the magnetic heads by driving each of the second actuators in accordance with the detection results of each of the first difference detection means; second difference detection means for detecting a difference between the operation amounts of the second actuator control means; a third actuator control means for controlling the amounts of displacement of the holding members in opposite directions caused by the driving of the third actuators in accordance with the detection result of the second difference detection means; Including, 2. The magnetic disk drive according to claim 1.

5. The controller a plurality of first difference detection means for detecting errors in the follow-up positions of the magnetic heads relative to the respective target positions during the seek and tracking operations; a plurality of second actuator control means for controlling the displacement amount of each of the magnetic heads by driving each of the second actuators in accordance with the detection results of each of the first difference detection means; an average value detection means for calculating an average value of the operation amounts of the second actuator control means in response to the displacement amounts of the magnetic heads, and for calculating an average value of the detection results of the first difference detection means, and for detecting a sum of the two average values ​​thus calculated; a first actuator control means for controlling the rotation of each of the first actuators by driving the motor and the amount of displacement of each of the magnetic heads associated with the rotation of each of the first actuators in accordance with the detection result of the average value detection means; a second difference detection means for detecting a difference between the detection results of the first difference detection means; a third actuator control means for controlling the amounts of displacement of the holding members in opposite directions caused by the driving of the third actuators in accordance with the detection result of the second difference detection means; Including, 2. The magnetic disk drive according to claim 1.

6. At least one circular magnetic disk including a pair of recording surfaces on one side and the other, a plurality of magnetic heads for writing and reading data to and from the respective recording surfaces of the magnetic disk; a plurality of first actuators for displacing the magnetic heads along the radial direction of the magnetic disk between the inner and outer peripheries of the magnetic disk; a plurality of second actuators that displace the magnetic heads independently of one another in a radial direction of the magnetic disk; a plurality of third actuators that simultaneously displace the second actuators by the same amount in mutually opposite directions along the radial direction of the magnetic disk; A method for controlling a magnetic disk drive comprising: controlling the driving of each of the first actuators, the second actuators, and the third actuators, thereby causing each of the magnetic heads to seek to a respective target position on each of the recording surfaces of the magnetic disk and follow a respective target track at each target position; A method for controlling a magnetic disk device.

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