Magnetic disk device and control method

Abstract

Embodiments provide a magnetic disk drive and control method capable of preventing degradation of microactuator components. When adjusting the position of a magnetic head using a microactuator, the magnetic disk drive control unit applies a third voltage value based on the second voltage value to the microactuator when the absolute value of the first voltage value applied to the microactuator is corrected based on hysteresis and the absolute value of the second voltage value applied to the microactuator is positive. Furthermore, the control unit operates at least one of the voice coil motor and / or the microactuator other than the microactuator applying the third voltage value to adjust for any shortfall in adjustment by the microactuator.

Description

[0001] This application claims priority from Japanese Patent Application No. 2021-137245 (filing date: August 25, 2021), the entire contents of which are incorporated herein by reference. Technical Field

[0002] The embodiments relate to a magnetic disk device and a control method. Background Art

[0003] Magnetic disk devices equipped with so-called microactuators are known. Such magnetic disk devices can finely adjust the position of a magnetic head relative to a magnetic disk by operating the microactuators, thereby improving positioning accuracy. Summary of the Invention

[0004] Microactuators have hysteresis. Since the displacement of a microactuator when a voltage is applied depends on past voltage history, the hysteresis exhibits different characteristics, such as nonlinear responsiveness when the voltage of the microactuator is increased and nonlinear responsiveness when the voltage is decreased. In such cases where hysteresis is present, it is sometimes necessary to correct the voltage value applied to the microactuator by taking the hysteresis into account. However, there are cases where, when the hysteresis correction process is performed, a voltage with a larger absolute value is applied to the microactuator than when there is no hysteresis. Applying a voltage with a large absolute value to a microactuator can cause degradation of the components that constitute the microactuator.

[0005] An object of the embodiment is to provide a magnetic disk device and a control method capable of preventing degradation of elements of a microactuator.

[0006] A magnetic disk device according to one embodiment includes: a magnetic disk; a magnetic head; a voice coil motor that moves the magnetic head to a predetermined position on the magnetic disk; a plurality of microactuators that adjust the position of the magnetic head; and a control unit that controls the operation of the voice coil motor and the plurality of microactuators. When the position of the magnetic head is adjusted by a first microactuator, which is one of the plurality of microactuators, the control unit applies a third voltage value based on the second voltage value to the first microactuator if the difference between the absolute value of a first voltage value applied to the first microactuator corrected based on hysteresis and the absolute value of a second voltage value applied to the first microactuator not corrected based on hysteresis is positive, and operates at least one of the voice coil motor and / or a second microactuator other than the first microactuator to adjust the position of the magnetic head to compensate for any shortfall in the adjustment by the first microactuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1This is a block diagram showing an example of the configuration of a magnetic disk device according to an embodiment.

[0008] Figure 2 This is a diagram showing an example of a control structure of a magnetic disk device having a plurality of actuators according to this embodiment.

[0009] Figure 3 This is a diagram showing an example of hysteresis according to this embodiment.

[0010] Figure 4 This is a diagram showing an example of hysteresis according to this embodiment.

[0011] Figure 5 This embodiment involves the amplification of Figure 4 Part of the diagram.

[0012] Figure 6 1 is a diagram showing an example of a time waveform of the absolute value of the MA voltage value according to this embodiment.

[0013] Figure 7 1 is a diagram showing an example of a time-axis waveform when a sinusoidal wave voltage is applied to the microactuator according to this embodiment.

[0014] Figure 8 This embodiment involves Figure 7 This is a graph showing the MA displacement when a sinusoidal voltage is applied.

[0015] Figure 9 This embodiment involves Figure 7 This is a diagram of voltage distribution that compares the probability of occurrence of the absolute value of the voltage when a sinusoidal voltage is applied.

[0016] Figure 10 This is a flowchart showing an example of a process of adjusting the displacement executed by the MA voltage / displacement distribution unit according to this embodiment.

[0017] Description of labels

[0018] 1 Magnetic disk device, 11 Magnetic disk, 12 Spindle motor, 13 Arm, 14 Load beam, 15 Magnetic head, 20 System on chip, 21 CPU, C positioning controller, PM microactuator, PV voice coil motor DETAILED DESCRIPTION

[0019] The following describes the embodiments with reference to the accompanying drawings. Furthermore, the disclosure is merely an example, and the invention is not limited by the contents described in the following embodiments. Any modifications that can be easily conceived by a person skilled in the art are naturally included within the scope of the disclosure. To make the description clearer, the drawings sometimes schematically illustrate the dimensions and shapes of various parts with respect to the actual implementation scheme. Sometimes, corresponding elements in multiple drawings are given the same reference numerals, and detailed descriptions are omitted.

[0020] Figure 1 This is a block diagram showing an example of the configuration of the magnetic disk device 1 .

[0021] The magnetic disk device 1 includes a head-disk assembly (HDA) 10 , a head amplifier integrated circuit (hereinafter referred to as a head amplifier IC) 16 , and a system on chip (SOC) 20 .

[0022] The HDA 10 includes a magnetic disk 11, a spindle motor (SPM) 12, an arm 13, and a voice coil motor (VCM) PV. The magnetic disk 11 is rotated by the spindle motor 12. A load beam 14 is mounted at the front end of the arm 13, and a magnetic head 15 is mounted at the front end of the load beam 14. The arm 13 is driven by the voice coil motor PV to move and control the magnetic head 15 to a specified position on the magnetic disk 11. Furthermore, a microactuator PM, which is a pair of piezoelectric elements (e.g., Pb(Zr, Ti)O3), is arranged near the mounting portion of the load beam 14 at the front end of the arm 13. By applying voltage to the pair of piezoelectric elements PM, the left and right piezoelectric elements expand and contract in opposite phases, causing the magnetic head 15 at the front end of the load beam 14 to displace in the radial direction (cross-track direction) on the magnetic disk 11. This adjusts the position of the magnetic head 15 in the radial direction of the magnetic disk 11. In this way, the magnetic disk device 1 includes a voice coil motor PV and a microactuator PM as a plurality of actuators for positioning the magnetic head 15. Furthermore, the microactuator PM may be disposed on the magnetic head 15. Furthermore, a configuration may be employed in which, for each magnetic head 15, the arm 13, the load beam 14, and the magnetic head 15 include a plurality of microactuators PM.

[0023] The magnetic head 15 has a structure in which a read head element and a write head element are separately mounted on a single slider. The read head element reads data recorded on the magnetic disk 11 , and the write head element writes data to the magnetic disk 11 .

[0024] The head amplifier IC 16 includes a read amplifier and a write driver. The read amplifier amplifies the read signal read by the read head element and transmits it to the read / write (R / W) channel 22. On the other hand, the write driver transmits a write current corresponding to the write data output from the R / W channel 22 to the write head element.

[0025] The SOC 20 includes a microprocessor (CPU) 21, a R / W channel 22, a disk controller 23, and a positioning controller C. The CPU 21 is the main controller of the drive and performs servo control of the positioning of the magnetic head 15 via the positioning controller C. It also performs data read / write control via the head amplifier IC 16. The R / W channel 22 includes a read channel that performs signal processing for reading data and a write channel that performs signal processing for writing data. The disk controller 23 performs interface control for controlling data transmission between a host system (not shown) and the R / W channel 22. The positioning controller C can be implemented as either hardware or software (firmware).

[0026] The memory 24 includes a volatile memory and a nonvolatile memory. For example, the memory 24 includes a buffer memory formed of a DRAM and a flash memory. The nonvolatile memory of the memory 24 stores programs and the like required for the processing of the CPU 21.

[0027] Figure 2 FIG. 1 is a diagram showing an example of a control structure of a magnetic disk device 1 having a plurality of actuators. Figure 2 In the embodiment, the magnetic disk device 1 has a voice coil motor PV and microactuators PM1 to PMn as a plurality of actuators. In addition, a positioning controller C is provided for controlling each of these plurality of actuators. More specifically, the positioning controller C is a voice coil motor controller CV for controlling the voice coil motor PV and an MA controller CM1 to CMn for controlling the microactuators PM1 to PMn. In addition, an MA voltage / displacement distribution unit 20a is provided as a control unit. The MA voltage / displacement distribution unit 20a performs a process of compensating for the displacement by using other actuators while suppressing the voltage applied to the microactuator PM. In addition, the already described Figure 1 The case of the magnetic disk drive in FIG is an example of a case where a voice coil motor PV and a microactuator PM are provided as multiple actuators. Thus, when the magnetic disk drive 1 includes a voice coil motor PV and a microactuator PM as multiple actuators, it may include a voice coil motor PV and multiple microactuators PM1 to PMn.

[0028] The MA voltage / displacement distribution unit 20a also includes hysteresis storage units 20H1 to 20Hn that store the hysteresis of each of the microactuators PM1 to PMn. This allows the MA voltage / displacement distribution unit 20a to store the hysteresis of each of the microactuators PM1 to PMn. This allows the MA voltage / displacement distribution unit 20a to appropriately distribute the displacement, as described below. The MA voltage / displacement distribution unit 20a is implemented by hardware or firmware within the chip 20, as already described.

[0029] exist Figure 2In the example, an input signal from a host system (not shown) passes through terminal T1 and is then input in parallel to the voice coil motor controller CV and MA controllers CM1-CMn. Furthermore, signals are input from each of the MA controllers CM1-CMn to the MA voltage / displacement distributor 20a. If the MA voltage / displacement distributor 20a determines, based on the signals input from the MA controllers CM1-CMn, that a microactuator is suppressing voltage for hysteresis correction, it distributes current and / or voltage to operate the voice coil motor PV and / or other microactuators to compensate for the displacement shortfall caused by the voltage suppression. A signal representing the distributed current is input to the voice coil motor PV via terminal T2, and / or a signal representing the distributed voltage is input from microactuator PM1 to microactuators PMn. Thus, while the voltage applied to microactuator PM for hysteresis correction is suppressed, the magnetic disk drive 1 can compensate for the displacement shortfall of that actuator using other actuators. Furthermore, signals output from the voice coil motor controller CV and the MA controllers CM1 to CMn are fed back to the terminal T1 , thereby correcting positioning errors.

[0030] Here, the hysteresis of the microactuator PM will be described.

[0031] As described above, the microactuator PM has hysteresis. Therefore, in order to improve the positioning accuracy of the microactuator PM, a process is performed to correct the hysteresis using a hysteresis model or an approximation.

[0032] Figure 3 is a graph showing an example of hysteresis. Figure 3 In FIG, the horizontal axis represents the voltage applied to the microactuator PM (hereinafter also referred to as MA voltage), and the vertical axis represents the displacement of the microactuator PM (hereinafter also referred to as MA displacement).

[0033] In having Figure 3 Consider a microactuator PM with hysteresis 104 shown, where the MA displacement 101 is changed to 102. The relationship between the MA voltage and the MA displacement is linear, as shown by 103, when there is no hysteresis, but nonlinear, as shown by 104, when there is hysteresis. Hereinafter, the MA voltage after hysteresis correction is referred to as a first MA voltage value (first voltage value), and the MA voltage without hysteresis is referred to as a second MA voltage (second voltage value).

[0034] When an MA shift of 105 is desired, the second MA voltage value becomes 106, but the first MA voltage value becomes 107, and the absolute value of the MA voltage value decreases. On the other hand, when an MA shift of 108 is desired, the second MA voltage value becomes 109, but the first MA voltage value becomes 110, and the absolute value of the MA voltage value increases.

[0035] Microactuators PM degrade when a voltage with a large absolute value is applied through their components. Therefore, as already described, it is preferable to avoid applying voltages with large absolute values as much as possible. The magnetic disk drive 1 of this embodiment corrects hysteresis by setting a third MA voltage value (the third voltage value) within a range smaller than the absolute value of the second MA voltage value when the absolute value of the MA voltage becomes larger than when there is no hysteresis. The magnetic disk drive 1 then adjusts the displacement shortfall caused by the application of the third MA voltage value by activating at least one of the other actuators, specifically the voice coil motor PV and / or the microactuator other than the microactuator applying the third MA voltage value. Furthermore, the magnetic disk drive 1 preferably allocates a voltage corresponding to the displacement shortfall to the actuator that has a voltage margin to compensate for the displacement shortfall. Furthermore, the magnetic disk drive 1 may also be configured to activate microactuators other than the microactuator applying the third MA voltage value prior to the voice coil motor PV. Hereinafter, the microactuator applying the third MA voltage value may also be referred to as the first MA.

[0036] Figure 4 is a diagram showing an example of hysteresis of the microactuator PM. Figure 5 It is magnified Figure 4 In addition, in Figure 4 、 Figure 5 In the figure, the horizontal axis is the MA voltage and the vertical axis is the MA displacement.

[0037] like Figure 4 and Figure 5 As shown, if it is desired to obtain an MA displacement 203 in the range of MA displacement 201 to MA displacement 202, where the absolute value of the second MA voltage value is greater than the absolute value of the first MA voltage value, using only the first MA, the required first MA voltage value 204 is greater than the absolute value 206 of the second MA voltage value 205 corresponding to the MA displacement 203. Therefore, the MA voltage / displacement distributor 20a applies a voltage value (third voltage value) less than the absolute value (second voltage value) 206 of the MA voltage to the first MA (here, voltage value 206 is applied) and distributes the difference between the MA displacement 203 obtained using only the first MA and the MA displacement 207 obtained when the absolute value 206 of the MA voltage is applied to the first MA to the other actuators. Here, the MA displacement 201 is the displacement at which the absolute value 208 of the first MA voltage and the absolute value of the second MA voltage 209 are equal.

[0038] Further, use Figure 6 Provide explanation. Figure 6 FIG is a diagram showing an example of a time waveform of the absolute value of the MA voltage value. Figure 6 In the figure, the horizontal axis is time and the vertical axis is the MA voltage value.

[0039] like Figure 6 As shown, the absolute value 403 of the first MA voltage value absolute value 401 and the second MA voltage value absolute value 402, whichever is smaller, is selected. The effect of reducing the MA voltage value is represented by areas 404 and 405 of the portion where the absolute value 403 is smaller than the absolute value 401 of the first MA voltage value in this embodiment.

[0040] Figure 7 : is a diagram showing an example of a time axis waveform when a sinusoidal voltage is applied to the microactuator PM. Figure 7 In the figure, the horizontal axis is time and the vertical axis is voltage.

[0041] This embodiment shows a method for selecting a voltage relative to time by selecting between a case without hysteresis correction and a case with hysteresis correction. This selection is determined by the CPU 21 based on whether the difference between the absolute value of a first voltage value applied to the microactuator PM, corrected based on hysteresis, and the absolute value of a second voltage value applied to the microactuator PM, which is not corrected based on hysteresis, is positive when the microactuator PM is adjusting its position.

[0042] Figure 8 Is to say Figure 7 The MA displacement when a sine wave voltage is applied is shown in the figure. Figure 8 In the figure, the horizontal axis is time and the vertical axis is displacement.

[0043] like Figure 8 As shown, it is shown that the total displacement obtained by adding the target MA displacement and the MA displacement of the allocation destination substantially matches the required displacement.

[0044] Figure 9 Is to express Figure 7 This is a graph of voltage distribution that compares the probability of occurrence of the absolute value of voltage when a sine wave voltage is applied. Figure 9 In the equation, the horizontal axis is voltage and the vertical axis is probability. Figure 9 The original is the case where no hysteresis-based correction is performed.

[0045] like Figure 9 As shown in FIG. 1 , it is shown that according to the process of this embodiment, the generation frequency of the MA voltage having a larger absolute value is suppressed.

[0046] Figure 10 FIG. 1 is a flowchart showing an example of a process for adjusting displacement performed by the MA voltage / displacement distribution unit 20a. Figure 10 As shown, when the position is adjusted by the microactuator PM, the MA voltage / displacement distribution unit 20a determines whether the difference between the absolute value of the first voltage value applied to the microactuator PM corrected based on the hysteresis and the absolute value of the second voltage value applied to the microactuator PM not corrected based on the hysteresis is positive (ST101).

[0047] If the MA voltage / displacement distribution unit 20a determines that the displacement is positive (ST101: YES), it applies a third voltage value derived from the second voltage value to the microactuator and operates at least one of the voice coil motor PV and / or the microactuator other than the microactuator applying the third voltage value to adjust for any shortfall in adjustment by the microactuator (ST102). The third voltage value is smaller than the second voltage value. If the MA voltage / displacement distribution unit 20a determines that the displacement is not positive (ST102: NO), no displacement adjustment is performed.

[0048] In the magnetic disk drive configured as described above, when the difference between the absolute values of the first and second voltage values is positive, a third voltage value is applied to the microactuator PM, and at least one of the voice coil motor PV and / or the microactuator to which the third voltage value is applied is operated to adjust for any shortfall in displacement achieved by the microactuator PM. Consequently, the magnetic disk drive 1 can avoid the application of a high voltage to the microactuator PM, thereby preventing degradation of the components of the microactuator PM.

[0049] Furthermore, in the above embodiment, when the difference between the absolute values of the first and second MA voltage values is determined to be positive, a third voltage value smaller than the absolute value of the second MA voltage value is applied as the first MA voltage, thereby distributing the shortfall in displacement to other actuators. However, the method of applying the voltage to the first MA is not limited to this. Alternatively, the method of applying the voltage to the first MA may be to predefine a domain for the second MA voltage value and use this domain to determine an arbitrary function between the second MA voltage value and a voltage value smaller than the second MA voltage value to determine the third MA voltage value.

[0050] In addition, several embodiments of the present invention have been described above, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways and can be omitted, replaced, or modified without departing from the scope of the invention. These embodiments and their variations are included within the scope and spirit of the invention and are included within the scope of the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: disk; magnetic head; a voice coil motor, which moves the magnetic head to a predetermined position on the magnetic disk; a plurality of microactuators for one of the magnetic heads, which adjust the position of the magnetic head; and a control unit that controls the operation of the voice coil motor and the plurality of microactuators, When the position of the magnetic head is adjusted by a first microactuator that is one of the plurality of microactuators, the control unit applies a third voltage value obtained based on the second voltage value to the first microactuator when a difference between an absolute value of a first voltage value applied to the first microactuator corrected based on a hysteresis and an absolute value of a second voltage value applied to the first microactuator not corrected based on the hysteresis is positive, and operates at least one of the voice coil motor and / or a second microactuator other than the first microactuator to adjust an amount shortfall in adjustment by the first microactuator. The third voltage value is lower than the second voltage value.

2. The magnetic disk device according to claim 1, The control unit converts the adjustment shortfall into an input to the voice coil motor, and applies the converted input to the voice coil motor.

3. The magnetic disk device according to claim 1, The control unit operates the second microactuator and the voice coil motor, the second microactuator and the voice coil motor having a margin for applied voltage.

4. The magnetic disk device according to claim 1, The control unit adjusts the insufficient amount of adjustment by preferentially operating the second microactuator out of the second microactuator and the voice coil motor.

5. A magnetic disk device comprising: disk; magnetic head; a voice coil motor, which moves the magnetic head to a predetermined position on the magnetic disk; a microactuator for adjusting the position of the magnetic head; and a control unit that controls the operations of the voice coil motor and the microactuator, When the position of the magnetic head is adjusted by the microactuator, the control unit applies a third voltage value obtained based on the second voltage value to the microactuator when a difference between an absolute value of a first voltage value applied to the microactuator and an absolute value of a second voltage value applied to the microactuator without being corrected based on the hysteresis is positive, and operates the voice coil motor to adjust for a shortfall in adjustment by the microactuator. The third voltage value is lower than the second voltage value.

6. A control method for a control unit of a magnetic disk device, The magnetic disk device comprises: disk; magnetic head; a voice coil motor, which moves the magnetic head to a predetermined position on the magnetic disk; a plurality of microactuators for one of the magnetic heads, which adjust the position of the magnetic head; and The control unit controls the operation of the voice coil motor and the plurality of microactuators. The control method includes: When the position of the magnetic head is adjusted by a first microactuator that is one of the plurality of microactuators, it is determined whether a difference between an absolute value of a first voltage value in which the voltage value applied to the first microactuator is corrected based on hysteresis and an absolute value of a second voltage value in which the voltage value applied to the first microactuator is not corrected based on the hysteresis is positive; If the difference is determined to be positive, a third voltage value obtained based on the second voltage value is applied to the first microactuator, and at least one of the voice coil motor and / or a second microactuator other than the first microactuator is operated to adjust for a shortfall in adjustment by the first microactuator. The third voltage value is lower than the second voltage value.

Images