Magnetic disk drive and its control method

Abstract

The present invention provides a magnetic disk drive and a control method therefor that can suppress fluctuations in the amount of levitation of the magnetic head. [Solution] The drive of the first actuator is controlled to seek the magnetic head to a target position on the magnetic disk, and the drive of the second actuator is controlled to fine-tune the position of the magnetic head at the target position on the magnetic disk. The drive voltage to the second actuator is changed in steps by predetermined voltage clipping values. A high-frequency signal is superimposed on the drive voltage to the second actuator output from the second control section to detect fluctuations in the amount of levitation of the magnetic head, and the above voltage clipping values ​​are set based on the detection results.

Description

Technical Field

[0006] , ,

[0001] Embodiments relate to a magnetic disk drive including a magnetic disk and a magnetic head, and a control method therefor.

Background Art

[0002] A magnetic disk drive including a magnetic disk and a magnetic head includes an actuator that seeks (moves) the magnetic head in the radial direction of the magnetic disk, and when writing and reading data to and from the magnetic disk, seeks the magnetic head from the immediately preceding stop position to a target position (write position or read position) on the magnetic disk.

[0003] The actuator includes a voice coil motor for driving, and also includes a micro actuator that finely displaces the magnetic head in the radial direction of the magnetic disk to compensate for the accuracy of seeking by driving the voice coil motor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the drive voltage to the micro actuator changes suddenly, a large fluctuation occurs in the flying height (referred to as spacing) of the magnetic head with respect to the magnetic disk. Also, when high-frequency noise due to disturbance or the like is superimposed on the drive voltage to the micro actuator, unnecessary fluctuations occur in the flying height of the magnetic head. Such fluctuations in the flying height of the magnetic head vary for each magnetic disk drive and for each magnetic head.

[0006] An object of the embodiments is to provide a magnetic disk drive and a control method therefor that can suppress fluctuations in the flying height of the magnetic head. [Means for solving the problem]

[0007] The magnetic disk device of the embodiment includes: a magnetic disk; a magnetic head for writing and reading data to and from the magnetic disk; a first actuator for seeking the magnetic head in the radial direction of the magnetic disk; a second actuator for causing the magnetic head to undergo minute displacement in the radial direction of the magnetic disk; detection means for detecting the amount of levitation of the magnetic head relative to the magnetic disk; and a controller for controlling the driving of the first actuator and the driving of the second actuator. The controller includes: a first control section that outputs and controls a drive voltage to the first actuator to seek the magnetic head to a target position on the magnetic disk; a second control section that outputs and controls a drive voltage to the second actuator to fine-tune the position of the magnetic head at the target position on the magnetic disk; a voltage clipping section that gradually changes the drive voltage to the actuator by predetermined voltage clipping values; and an adjustment section that measures fluctuations in the amount of levitation detected by the detection means while superimposing a high-frequency signal on the drive voltage to the second actuator, and adjusts the voltage clipping value of the voltage clipping section based on the measurement result. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows the overall configuration of one embodiment. [Figure 2] Figure 2 is a cross-sectional view showing the main part of the magnetic head in the same embodiment. [Figure 3] Figure 3 is a block diagram of the main components of the controller in the same embodiment. [Figure 4] Figure 4 is a flowchart showing the control of the voltage clipping section in the same embodiment. [Figure 5] Figure 5 shows the change in the drive voltage Vm input to the voltage clipping section and the change in the drive voltage Vm output from the voltage clipping section in the same embodiment. [Figure 6] FIG. 6 is a flowchart showing the control of the protection section in this embodiment. [Figure 7] FIG. 7 is a flowchart showing the control of the adjustment section in this embodiment. [Figure 8] FIG. 8 is a diagram showing the variation in the flying height of the magnetic head when a high-frequency signal is superimposed on the drive voltage Vm in this embodiment. [Figure 9] FIG. 9 is a diagram showing the relationship between the frequency of the high-frequency signal and the flying height of the magnetic head when the voltage clip value Vmc in this embodiment is set to the test value Vmc2 and a high-frequency signal is superimposed on the drive voltage Vm. [Figure 10] FIG. 10 is a diagram showing the relationship between the frequency of the high-frequency signal and the flying height of the magnetic head when the voltage clip value Vmc in this embodiment is set to the test value Vmc1 (<Vmc2) and a high-frequency signal is superimposed on the drive voltage Vm. [Figure 11] FIG. 11 is a diagram of an approximate curve showing the flying height of the magnetic head when the voltage clip value Vmc in this embodiment is at the test values Vmc1 and Vmc2. [Figure 12] FIG. 12 is a diagram of an approximate curve showing the flying height of the magnetic head when the voltage amplitude value of the high-frequency signal N2 in this embodiment is at the test values Vh1 and Vh2. BEST MODE FOR CARRYING OUT THE INVENTION

[0009] An embodiment will be described with reference to the drawings. As shown in FIG. 1, the magnetic disk device 1 includes a magnetic disk 2 as a recording medium, a spindle motor 3 that rotationally drives the magnetic disk 2, and a magnetic head 10 that writes (records) and reads data to / from the magnetic disk 2. An actuator (first actuator) 20 that seeks the magnetic head 10 in the radial direction of the magnetic disk 2 is disposed near the magnetic disk 2.

[0010] The actuator 20, also referred to as an actuator block or head stack assembly (HSA), includes a rotating shaft 21, an arm 22 whose middle portion is held by the rotating shaft 21, a voice coil motor (VCM) 23 positioned at the base end of the arm 22, and a suspension member 24 provided at the tip of the arm 22 to hold the magnetic head 10.

[0011] When a drive voltage is supplied to the voice coil motor 23, it rotates the actuator 20 between the first position P1 (shown by the dashed line in the figure) and the second position P2 (shown by the solid line in the figure). As the actuator 20 rotates, the magnetic head 10 seeks (moves) in the radial direction of the magnetic disk 2.

[0012] A stopper ST and a ramp mechanism RL are positioned near the actuator 20. The stopper ST restricts the movement position of the magnetic head 10 to the inner circumference side of the magnetic disk 2. The ramp mechanism RL retracts the magnetic head 10 from the magnetic disk 2 when the spindle motor 3 is stopped.

[0013] Furthermore, the actuator 20 is equipped with a microactuator (MA; second actuator) 25 on the suspension member 24 to compensate for the seek accuracy of the voice coil motor 23. The microactuator 25 includes a pair of piezoelectric elements arranged along the radial direction of the magnetic disk 2, and the driving of both piezoelectric elements causes a minute displacement of the magnetic head 10 in the radial direction of the magnetic disk 2.

[0014] The magnetic disk device 1 includes a controller 30 which serves as the control center, a DRAM 51 which stores programs and other data necessary for controlling the controller 30, a flash ROM 52 which stores various data necessary for controlling the controller 30, an operation unit 53, and a hard disk controller (HDC) 50 provided between the controller 30 and the external host device 60.

[0015] As shown in FIG. 2, the magnetic head 10 includes a slider 11 at its tip, and a head element 12 on the lower surface side of the slider 11 (the side facing the magnetic disk 2). A plurality of servos with track information and positioning information written at equal intervals are arranged on the circumference of the magnetic disk 2, and the spaces between these servos are used as data areas. When the magnetic disk 2 rotates, the slider 11 is lifted by the air pressure generated by the rotation, and the magnetic head 10 is lifted away from the magnetic disk 2.

[0016] The head element 12 includes a write element 13 for writing magnetic data to the magnetic disk 2, a read element 14 for reading magnetic data from the magnetic disk 2, an electric heater for generating heat (simply referred to as a heater) 15, and a spacing sensor (detection means; also referred to as an HDI sensor) 16 for detecting the lift amount H (also referred to as spacing) of the magnetic head 10 with respect to the surface 2a of the magnetic disk 2. The write element 13 and the read element 14 are provided on the lower surface of the head element 12 in an exposed state.

[0017] When the magnetic disk 2 rotates, due to the action of the slider 11, the magnetic head 10 is lifted away from the surface 2a of the magnetic disk 2. In order to achieve high-density recording on the magnetic disk 2, it is necessary to reduce the lift amount H of the magnetic head 10 and bring the magnetic head 10 as close as possible to the surface 2a of the magnetic disk 2.

[0018] The controller 30 controls the supply of power to the electric heater 15 of the head element 12 while detecting the lift amount H of the magnetic head 10 with the spacing sensor 16. As a result, the electric heater 15 generates heat, and the head element 12 thermally expands toward the magnetic disk 2 due to this heat generation. Due to this thermal expansion, the write element 13 and the read element 14 protrude toward the magnetic disk 2 side and approach the surface 2a of the magnetic disk 2. The spacing sensor 16 is a resistance element whose electrical resistance value changes according to the ambient temperature, and detects the change in the electrical resistance value caused by the temperature change of the head element 12 as the lift amount H.

[0019] Furthermore, as shown in Figure 3, the controller 30 includes a demodulation section 31 that demodulates the position Po of the magnetic head 10 on the magnetic disk 2 from the read data of the magnetic head 10, a difference detection section 32 that detects the difference ΔP between the position Po demodulated by the demodulation section 31 and the target position Pt of the seek of the magnetic head 10, and a VCM control section (first control section) 33 and an MA control section (second control section) 34 to which the difference ΔP detected by the difference detection section 32 is input.

[0020] The VCM control section 33 outputs and controls the drive voltage to the voice coil motor 23 of the actuator 20 in order to cause the magnetic head 10 to seek to a target position Pt on the magnetic disk 2.

[0021] The MA control section 34 outputs and controls a drive voltage Vm to the microactuator 25 in order to fine-tune the position of the magnetic head 10 to the target position on the magnetic disk 2.

[0022] Furthermore, the controller 30 includes an overlay section 35, a voltage clipping section 36, an overlay section 37, a voltage limiting section 38, a frequency filter 39, a protection section 40, and an adjustment section 41.

[0023] The superposition section 35 superimposes the high-frequency signal (first high-frequency signal) N1 output by the adjustment section 41 onto the drive voltage Vm output from the MA control section 34 to the micro actuator 25. This superposition of the high-frequency signal N1 is also called excitation.

[0024] The voltage clipping section 36 gradually changes the drive voltage Vm output from the MA control section 34 to the microactuator 25 by a predetermined voltage clipping value Vmc. The control of the voltage clipping section 36 is shown in the flowchart of Figure 4, and the changes in the drive voltage Vm input to the voltage clipping section 36 and the changes in the drive voltage Vm output from the voltage clipping section 36 are shown in Figure 5.

[0025] In other words, the voltage clipping section 36 determines whether the drive voltage Vm output from the MA control section 34 is greater than the previous value Vml (S1). If the drive voltage Vm is greater than the previous value Vml (YES in S1), the voltage clipping section 36 determines whether the difference between the drive voltage Vm and the previous value Vml, "Vm-Vml", is greater than the voltage clipping value Vmc (S2).

[0026] If the difference "Vm-Vml" is greater than the voltage clipping value Vmc (YES in S2), the voltage clipping section 36 outputs a drive voltage Vm which is the sum of the previous value Vml and the voltage clipping value Vmc (S3). If the difference "Vm-Vml" is equal to or less than the voltage clipping value Vmc (NO in S2), the voltage clipping section 36 outputs the drive voltage Vm output from the MA control section 34 as is (S4).

[0027] If the drive voltage Vm is the same as or less than the previous value Vml (NO in S1), the voltage clipping section 36 determines whether the difference between the previous value Vml and the drive voltage Vm, "Vml-Vm", is greater than the voltage clipping value Vmc (S5).

[0028] If the difference "Vml-Vm" is greater than the voltage clip value Vmc (YES in S5), the voltage clip section 36 outputs a drive voltage Vm that is the value obtained by subtracting the voltage clip value Vmc from the previous value Vml (S6). If the difference "Vml-Vm" is equal to or less than the voltage clip value Vmc (NO in S5), the voltage clip section 36 outputs the drive voltage Vm output from the MA control section 34 as is (S4).

[0029] By employing this voltage clipping section 36, even if the drive voltage Vm output from the MA control section 34 to the micro actuator 25 changes abruptly, fluctuations in the levitation amount H of the magnetic head 10 can be prevented.

[0030] The drive voltage Vm output from the voltage clipping section 36 is supplied to the voltage limiting section 38 via the superposition section 37. The voltage limiting section 38 limits the drive voltage Vm to a specified value or less so that an excessive voltage is not applied to the microactuator 25. The drive voltage Vm that has passed through this voltage limiting section 38 is supplied to the microactuator 25.

[0031] The drive of this microactuator 25 is added to the drive of the voice coil motor 23 by the VCM control section 33, thereby determining the position Po of the magnetic head 10 on the magnetic disk 2. This position Po of the magnetic head 10 is fed back to the difference detection section 32 via the demodulation section 31.

[0032] The superposition section 37 superimposes the high-frequency signal (second high-frequency signal) N2 output by the adjustment section 41 onto the drive voltage Vm output from the voltage clipping section 36. This superposition of the high-frequency signal N2 is also called excitation.

[0033] The adjustment section 41, when a test mode is set by the operation of the operator's control unit 53 during the manufacturing process of the magnetic disk device 1, causes the MA control section 34 to output a predetermined drive voltage Vm, superimposes a sinusoidal high-frequency signal N1 having a predetermined voltage amplitude value onto the drive voltage Vm via the superposition section 35, measures the fluctuation of the levitation amount H detected by the spacing sensor 16, and sets the voltage clip value Vmc of the voltage clip section 36 based on the measurement result.

[0034] The adjustment section 41 includes the following means (1) to (4) as its primary function for setting the voltage clip value Vmc: (1) A first setting means that, when setting the above test mode, sequentially sets the voltage clip value Vmc of the voltage clip section 36 to a plurality of test values ​​(for example, two test values ​​Vmc1, Vmc2).

[0035] (2) A first detection means that, for each test value set by the first setting means described above, superimposes the high-frequency signal N1 on the drive voltage Vm output from the MA control section 34 and sequentially detects the maximum value of the levitation amount H (where the fluctuation range ΔH is large) Hmax detected by the spacing sensor 16 while changing the frequency of the high-frequency signal N1.

[0036] (3) A first generation means that generates an approximation curve (first approximation curve) that represents the relationship between each test value set by the first setting means and each maximum value Hmax detected by the first detection means.

[0037] (4) A second setting means that determines a voltage clip value Vmcx corresponding to the allowable value Hx of variation of the levitation amount H of the magnetic head 10 from the approximation curve generated by the first generation means, and sets (confirms) the determined voltage clip value Vmcx as the voltage clip value Vmc of the voltage clip section 36 in the magnetic disk device 1 after manufacturing.

[0038] The frequency filter 39 extracts the drive voltage Vm that has passed through the voltage limiting section 38, specifically the drive voltage Vm in the frequency range that includes the frequency of the high-frequency signal N1 when the maximum value Hmax of the levitation amount H is detected in the adjustment section 41.

[0039] The protection section 40 stops the operation of the light and microactuator 25 of the magnetic head 10 if the drive voltage Vm extracted by the frequency filter 39 exceeds a threshold Vms (fail-safe function).

[0040] Specifically, as shown in the flowchart in Figure 6, the protection section 40 determines whether the drive voltage Vm extracted by the frequency filter 39 exceeds the threshold Vms (S11). If the drive voltage Vm does not exceed the threshold Vms (NO in S11), the protection section 40 performs normal processing without protection (S12). However, if the drive voltage Vm exceeds the threshold Vms (YES in S11), the protection section 40, as a fail-safe measure for safety protection, stops writing data by the write element 13 of the magnetic head 10 (S13), stops controlling the levitation amount of the magnetic head 10 due to the heat generated by the electric heater 15 (S14), and further stops the output of the drive voltage Vm of the MA control section 34 in order to stop driving the microactuator 25 (S15). After executing this fail-safe measure, the protection section 40 returns to the determination in S11.

[0041] Furthermore, when setting the above test mode, the adjustment section 41 includes the following means (5) to (9) as the main functions relating to the frequency filter 39 and the protection section 40.

[0042] (5) A third setting means that, after the setting process of the second setting means described above, sets the frequency range of the high-frequency signal (first high-frequency signal) N1 that generates the maximum value Hmax of the levitation amount H as the frequency range to be extracted by the frequency filter 39.

[0043] (6) A fourth setting means that, after the setting process of the third setting means described above, outputs a sinusoidal high-frequency signal (second high-frequency signal) N2 from the adjustment section 41 and sequentially sets the voltage amplitude value of the high-frequency signal N2 to a plurality of test values ​​(for example, two test values ​​Vh1, Vh2).

[0044] (7) A second detection means that, for each test value set by the fourth setting means described above, superimposes the high-frequency signal N2 onto the drive voltage Vm output from the voltage clipping section 36 and detects the maximum value Hmax of the levitation amount H detected by the spacing sensor 16 while changing the frequency of the high-frequency signal N2.

[0045] (8) A second generation means that generates an approximation curve (second approximation curve) that represents the relationship between each test value set by the third setting means and each maximum value Hmax detected by the second detection means.

[0046] (9) A fifth setting means that determines the value Vmx of the drive voltage Vm corresponding to the allowable value Hx of fluctuation of the levitation amount H of the magnetic head 10 from the approximation curve generated by the second generation means, and sets (confirms) the determined value Vmx as the threshold Vms of the protection section in the magnetic disk device 1 after manufacturing.

[0047] The control performed by adjustment section 41 will be explained with reference to the flowchart in Figure 7. In the manufacturing process of the magnetic disk drive 1, an operator sets a test mode for the adjustment section 41 by operating the control unit 53.

[0048] When setting the test mode (YES in S21), the adjustment section 41 first sets the voltage clip value Vmc of the voltage clip section 36 to the test value (initial value for testing) Vmc2, and then superimposes a sinusoidal high-frequency signal N1 having a predetermined voltage amplitude value onto the drive voltage Vm output from the MA control section 34 (S22). As shown in Figure 8, the superposition of this high-frequency signal N1 causes a fluctuation in the levitation amount H of the magnetic head 10.

[0049] Then, the adjustment section 41 detects the maximum value of the levitation amount H (with a large fluctuation range ΔH) Hmax2 detected by the spacing sensor 16 while changing the frequency of the superimposed high-frequency signal N1 over a wide range as shown in Figure 9 (S23). In the example in Figure 9, the levitation amount H fluctuates greatly when the high-frequency signal N1 is in the frequency range of approximately 54,000 Hz to 60,000 Hz, and the maximum value of the levitation amount H, Hmax2, is located at approximately 55,000 Hz.

[0050] Next, the adjustment section 41 sets the voltage clip value Vmc of the voltage clip section 36 to a test value Vmc1, which is, for example, 60% of the test value Vmc2, and superimposes a sinusoidal high-frequency signal N1 having a predetermined voltage amplitude value on the drive voltage Vm output from the MA control section 34, as described above (S24). The superposition of this high-frequency signal N1 causes a fluctuation in the levitation amount H of the magnetic head 10, as shown in Figure 8.

[0051] Then, the adjustment section 41 detects the maximum value of the levitation amount H (with a large fluctuation range ΔH) Hmax1 detected by the spacing sensor 16 while changing the frequency of the superimposed high-frequency signal N1 over a wide range as shown in Figure 10 (S25). In the example in Figure 10, the levitation amount H fluctuates greatly when the high-frequency signal N1 is in the frequency range of approximately 54,000 Hz to 60,000 Hz, and the maximum value of the levitation amount H, Hmax1, is located at approximately 55,000 Hz.

[0052] After detecting the maximum values ​​Hmax2 and Hmax1, the adjustment section 41 generates the approximation curve shown in Figure 11, which represents the relationship between the set test values ​​Vmc2 and Vmc1 and the detected maximum values ​​Hmax2 and Hmax1 (S26).

[0053] Then, the adjustment section 41 determines the voltage clip value Vmcx corresponding to the allowable value Hx of variation in the levitation amount H of the magnetic head 10 from the approximation curve generated in S26, and sets (confirms) the determined voltage clip value Vmcx as the voltage clip value Vmc of the voltage clip section 36 in the magnetic disk device 1 after manufacturing (S27).

[0054] In other words, in magnetic disk drives 1 and magnetic heads 10 where the fluctuation range ΔH of the levitation amount H tends to be large, the voltage clipping value Vmc is reduced, while conversely, in magnetic disk drives 1 and magnetic heads 10 where the fluctuation range ΔH of the levitation amount H is not so large, the voltage clipping value Vmc is not suppressed more than necessary.

[0055] Thereafter, this voltage clip value Vmc is held in the voltage clip section 36 as information specific to the magnetic disk device 1 and the magnetic head 10.

[0056] In this way, by setting the voltage clip value Vmc of the voltage clip section 36 after confirming the variation in the floating height H due to the superposition of high-frequency noise or the like, even if high-frequency noise is superimposed on the drive voltage Vm output from the MA control section 34, unnecessary variation in the floating height H of the magnetic head 10 caused thereby can be suppressed.

[0057] After setting the voltage clip value Vmc in S27 above, the adjustment section 41 sets the frequency range of the high-frequency signal N1 at which the above maximum values Hmax2 and Hmax1 occur as the frequency range to be extracted by the frequency filter 39 (S28). Thereafter, this frequency range is held in the frequency filter 39 as information specific to the magnetic disk device 1 and the magnetic head 10. By setting this frequency range, the drive voltage Vm in the frequency range that leads to a large variation in the floating height H can be accurately extracted by the frequency filter 39.

[0058] Subsequently, the adjustment section 41 first superimposes a sine-wave high-frequency signal N2 with a voltage amplitude value set to the test value Vh2 on the drive voltage Vm output from the voltage clip section 36 (S29).

[0059] Then, the adjustment section 41 detects the maximum value Hmax2 of the floating height H detected by the spacing sensor 16 while changing the frequency of the superimposed high-frequency signal N2 in the same manner as in FIG. 9 (S30). [[ID=1"]]

[0060] Subsequently, the adjustment section 41 superimposes a sine-wave high-frequency signal N2 with a voltage amplitude value set to the test value Vh1 (<Vh2) on the drive voltage Vm output from the voltage clip section 36 (S31).

[0061] Then, the adjustment section 41 detects the maximum value Hmax1 of the levitation amount H detected by the spacing sensor 16 while changing the frequency of the superimposed high-frequency signal N2 in the same manner as in Figure 10 (S32).

[0062] After detecting the maximum values ​​Hmax2 and Hmax1, the adjustment section 41 generates the approximation curve shown in Figure 12, which represents the relationship between the set test values ​​Vh2 and Vh1 and the detected maximum values ​​Hmax2 and Hmax1 (S33).

[0063] Then, the adjustment section 41 determines the value Vmx of the drive voltage Vm corresponding to the allowable value Hx of variation in the levitation amount H of the magnetic head 10 from the approximation curve generated in S33, and sets (confirms) the determined value Vmx of the drive voltage Vm as the threshold Vms of the protection section 40 in the magnetic disk device 1 after manufacturing (S34). Thereafter, this threshold Vms is stored in the protection section 40 as information specific to the magnetic disk device 1 and the magnetic head 10.

[0064] In this way, by checking for fluctuations in the drive voltage Vm due to superposition of high-frequency noise and setting the threshold Vms of the protection section, it is possible to avoid issues such as abnormal lighting of the magnetic head 10 or abnormal driving of the micro actuator 25 due to the effects of high-frequency noise.

[0065] In the above embodiment, two test values ​​Vmc2 and Vmc1 were set as test values ​​for the clipping voltage value Vmc, and two test values ​​Vh2 and Vh1 were set as test values ​​for the high-frequency signal N2. However, there is no limit to the number of these test values, and they can be set as appropriate.

[0066] Furthermore, the above embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0067] 1...Magnetic disk drive, 2...Magnetic disk, 10...Magnetic head, 11...Slider, 12...Head element, 13...Write element, 14...Read element, 15...Electric heater, 16...Spacing sensor, 20...Actuator (first actuator), 21...Rotating shaft, 22...Arm, 23...Voice coil motor, 24...Suspension member, 25...Microactuator (second actuator), 30...Controller.

Claims

1. Magnetic disks and A magnetic head for writing and reading data to the magnetic disk, A first actuator that seeks the magnetic head in the radial direction of the magnetic disk, A second actuator that causes the magnetic head to undergo a minute displacement in the radial direction of the magnetic disk, A detection means for detecting the amount of levitation of the magnetic head relative to the magnetic disk, A controller that controls the driving of the first actuator and the driving of the second actuator, Equipped with, The aforementioned controller, A first control section outputs and controls a drive voltage to the first actuator in order to cause the magnetic head to seek to a target position on the magnetic disk, A second control section outputs and controls a drive voltage to the second actuator in order to fine-tune the position of the magnetic head to the target position on the magnetic disk, A voltage clipping section that changes the drive voltage to the second actuator output from the second control section in steps by predetermined voltage clipping values, An adjustment section that superimposes a high-frequency signal on the drive voltage to the second actuator output from the second control section, detects fluctuations in the amount of levitation detected by the detection means, and sets the voltage clip value of the voltage clip section based on the detection result, A magnetic disk drive equipped with the following features.

2. The aforementioned adjustment section is, When setting the test mode, the voltage clipping value of the voltage clipping section is sequentially set to multiple test values. For each of the above test value settings, a first high-frequency signal is superimposed on the drive voltage to the second actuator output from the second control section, and the maximum value of the levitation amount detected by the detection means is detected while changing the frequency of the first high-frequency signal. A first approximation curve is generated for each of the detected maximum values. The voltage clip value corresponding to the allowable value of the fluctuation in the amount of rise is determined from the first approximation curve generated above, and the determined voltage clip value is set as the voltage clip value of the voltage clip section. The magnetic disk device according to claim 1.

3. A frequency filter extracts drive voltages in a predetermined frequency range from the drive voltages output from the voltage clipping section to the second actuator, A protection section that stops the operation of the light of the magnetic head and the second actuator when the drive voltage extracted by the frequency filter exceeds a threshold, Further including, The magnetic disk device according to claim 2.

4. The aforementioned adjustment section is, The frequency range of the first high-frequency signal in which the maximum amount of the float occurs is set as the frequency range to be extracted by the frequency filter. The adjustment section outputs a second high-frequency signal, and sequentially sets the voltage amplitude value of the second high-frequency signal to multiple test values. For each of the above test value settings, the second high-frequency signal is superimposed on the drive voltage to the second actuator output from the voltage clipping section, and the maximum value of the levitation amount detected by the detection means is detected while changing the frequency of the second high-frequency signal. An approximate curve is generated for each of the detected maximum values. The value of the drive voltage to the second actuator corresponding to the allowable value of the fluctuation in the amount of levitation is determined from the approximation curve of each detection result, and the determined value is set as the threshold of the protection section. The magnetic disk device according to claim 3.

5. The first actuator includes a voice coil motor, and the voice coil motor drives the magnetic head to seek in the radial direction of the magnetic disk. The second actuator includes a piezoelectric element, and by driving the piezoelectric element, the magnetic head is subjected to a minute displacement in the radial direction of the magnetic disk. The magnetic disk device according to claim 1.

6. Magnetic disks and A magnetic head for writing and reading data to the magnetic disk, A first actuator that seeks the magnetic head in the radial direction of the magnetic disk, A second actuator that causes the magnetic head to undergo a minute displacement in the radial direction of the magnetic disk, A detection means for detecting the amount of levitation of the magnetic head relative to the magnetic disk, A first control section outputs and controls a drive voltage to the first actuator in order to cause the magnetic head to seek to a target position on the magnetic disk, A second control section outputs and controls a drive voltage to the second actuator in order to fine-tune the position of the magnetic head to the target position on the magnetic disk, A voltage clipping section that changes the drive voltage to the second actuator output from the second control section in steps by predetermined voltage clipping values, A control method for a magnetic disk device comprising: The system detects fluctuations in the amount of levitation detected by the detection means while superimposing a high-frequency signal on the drive voltage to the second actuator output from the second control section, and sets the voltage clip value of the voltage clip section based on the detection result. A method for controlling a magnetic disk drive.

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