Disk device manufacturing method and program

Abstract

To upgrade the precision in positioning a head in a disk unit.SOLUTION: According to the present embodiment, a head position error spectrum and frequency characteristic are measured by individually applying a test signal in units of a 1 / N cycle to a manipulation quantity of a VCM and a manipulation quantity of an MA in a condition preceding addition of an MA additional filter, a multi-rate sensitivity characteristic is calculated based on the frequency characteristic, and a frequency that should be corrected using the MA additional filter is identified based on the head position error spectrum and multi-rate sensitivity characteristic. In a state where each of plural candidates of the MA additional filter is added, a frequency characteristic is measured by applying the test signal in units of the 1 / N cycle to the manipulation quantity of the VCM and the manipulation quantity of the MA in relation to each frequency, a multi-rate sensitivity characteristic is calculated based on the frequency characteristic, and a candidate making a peak of the multi-rate sensitivity characteristic equal to or smaller than a threshold and minimizing the head position error is determined as the MA additional filter to be used.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a method for manufacturing a disk device and a program. [Background technology]

[0002] Generally, disk drives, such as hard disk drives, are equipped with a controller (software) that positions a head, such as a magnetic head, at a target position on the disk, which is the recording medium, i.e., at the track to be accessed. The head then reads and writes data at the position on the disk.

[0003] In recent years, research and development has been progressing on so-called two-stage actuators for disk drives, which use a voice coil motor (VCM) to move an arm with a head at its tip, and a microactuator (MA) at the tip of the arm to move the head minutely. In this case, the controller is divided into a VCM controller and an MA controller.

[0004] Furthermore, with regard to disk devices with dual-stage actuators, research and development is also underway into multi-rate control that controls the VCM and MA at N times (N: an integer of 2 or greater) the observation period of the position error signal (PES). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 7,576,940 [Patent Document 2] US Patent Application Publication No. 2022 / 0115038 [Patent Document 3] U.S. Patent No. 9,361,919 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the prior art, the accuracy of head positioning is insufficient in magnetic disk devices that perform multi-rate control using a two-stage actuator, and there is room for improvement.

[0007] Therefore, an object of this embodiment is to provide a method and program for manufacturing a disk device that can improve the accuracy of head positioning in a disk device that performs multi-rate control with a two-stage actuator. [Means for solving the problem]

[0008] A method for manufacturing a disk device of this embodiment is a method for manufacturing a disk device comprising: a disk for storing data; a head for reading / writing data from / to the disk; a first actuator for moving the entire arm having the head disposed at its tip; a second actuator provided at the tip of the arm for moving the head; a first controller for controlling the first actuator in accordance with a target position of the head at a multi-rate that is 1 / N cycle of a head position observation cycle (N: an integer of 2 or more); a second controller for controlling the second actuator in accordance with the target position of the head at the 1 / N cycle; and a first additional filter added between the first controller and the first actuator and outputting output data to the first actuator in accordance with input data from the first controller, wherein a calculation unit is configured to calculate a value of the first additional filter added to the first additional filter. and a step by the calculation unit, in a state where each of the plurality of candidates for the first additional filter has been added, measuring the frequency characteristics by applying a test signal to the operation amount of the first actuator and the operation amount of the second actuator at the 1 / N period, respectively, to measure the head position error spectrum and frequency characteristics, calculating a multi-rate sensitivity characteristic based on the frequency characteristic, and specifying a frequency to be corrected by the first additional filter based on the head position error spectrum and the multi-rate sensitivity characteristic. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a feedback control system of a conventional magnetic disk drive with a dual-stage actuator. [Figure 2]FIG. 2 is an explanatory diagram of a prior art method for measuring the sensitivity characteristics of a magnetic disk drive with a dual-stage actuator. [Figure 3] FIG. 3 is a diagram illustrating a schematic configuration of a magnetic disk device according to an embodiment. [Figure 4A] FIG. 4A is an explanatory diagram of a method for measuring the sensitivity characteristics of a magnetic disk drive according to an embodiment. [Figure 4B] FIG. 4B is an explanatory diagram of a method for measuring the sensitivity characteristics of a magnetic disk device according to an embodiment. [Figure 5] FIG. 5 is a block diagram of a feedback control system of the magnetic disk device according to the embodiment. [Figure 6] FIG. 6 is a diagram showing four types of patterns of candidates for the MA additional filter in the embodiment. [Figure 7] FIG. 7 is a flowchart showing a process for generating an MA additional filter when the maximum gain value of the multi-rate sensitivity characteristic is equal to or less than a threshold value in the embodiment. [Figure 8] FIG. 8 is a flowchart showing a process for generating an MA additional filter when the maximum gain value of the multi-rate sensitivity characteristic is greater than the threshold value in the embodiment. [Figure 9] FIG. 9 is a diagram showing the head position error spectrum before and after the design of the MA additional filter in the embodiment. [Figure 10] FIG. 10 is a diagram showing the single-rate sensitivity characteristics before and after designing the MA added filter in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of a method for manufacturing a disk device and a program according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments. To facilitate understanding of the embodiments, the prior art will first be described again.

[0011] (Prior Art) Fig. 1 is a block diagram of a feedback control system (software) of a conventional magnetic disk drive with a dual-stage actuator, and Fig. 2 is an explanatory diagram of a method for measuring the sensitivity characteristics of a conventional magnetic disk drive with a dual-stage actuator.

[0012] As shown in Figure 1, the VCM control object Pv and the MA control object Pm are arranged in parallel, with a VCM controller Cv provided for the VCM control object Pv and an MA controller Cm provided for the MA control object Pm. Symbols Mv and Mm represent the parts that implement double multi-rate control. Feedback control according to the target position T of the head is then performed by the VCM controller Cv and the MA controller Cm. An additional filter may also be added in parallel to the MA controller Cm.

[0013] Next, we will explain the sensitivity characteristic measurement method for a magnetic disk drive with a dual-stage actuator, with reference to Figure 2. A PES signal test signal ST containing multiple frequencies, such as a sweep signal, white noise, or M-sequence signal, is applied to the head position error while the head position error is observed. The time-series data for the PES signal test signal ST and the head position error are each converted to the frequency domain using a Fourier transform, and the transfer characteristics are calculated from the absolute value and phase angle of the ratio of complex values. The transfer characteristics are recorded as a PES signal log SL.

[0014] In conventional controller design, a numerical model of the controlled object is used to design the controller and simulate the sensitivity characteristics, but calibration is required to modify the numerical model based on the actually measured sensitivity characteristics. However, even after calibration, modeling errors can cause discrepancies between the predicted sensitivity characteristics and the actually measured values. Therefore, the accuracy of head positioning is insufficient, and there is room for improvement.

[0015] Therefore, the following describes a technique that can improve the accuracy of head positioning in a disk device that performs multi-rate control with a two-stage actuator.

[0016] (Embodiment) 3 is a diagram showing a schematic configuration of a magnetic disk device 100 according to an embodiment. The magnetic disk device 100 includes a disk 1 for storing data, a head 2 for reading and writing data from and to the disk 1, and an arm 3 on which a microactuator 16 and the head 2 are mounted.

[0017] The disk 1 is rotated by a spindle motor (not shown). The disk 1 has a number of concentric tracks 5 formed on its surface. Each track 5 includes a servo sector 6. Each servo sector 6 includes a servo area 7 and a data area 8. Each track 5 includes a predetermined number of servo areas 7 arranged at predetermined intervals in the circumferential direction. Servo information (position information) used by a head positioning control system to detect the position of the head 2 during normal read / write operations is recorded in the servo areas 7. Between the servo areas 7 are data areas 8, in which user data is recorded.

[0018] The head 2 has a structure in which a read head and a write head are separately mounted on a slider, for example. The read head reads servo information and user data recorded on the disk 1. During head positioning control, the read head reads servo information at regular intervals according to the rotational speed of the disk 1. The write head writes user data onto the disk 1.

[0019] The VCM 4 (first actuator) moves the entire arm 3, which has the head 2 disposed at its tip, in the radial direction of the disk 1. The microactuator 16 (second actuator) moves the head 2 minutely.

[0020] Furthermore, the magnetic disk device 100 includes a read / write channel (a signal processing circuit 9 and a position detection circuit 10), a controller 13, a VCM driving circuit 14, an MA driving circuit 15, and a vibration sensor 17.

[0021] A signal processing circuit 9 processes read signals and write signals corresponding to servo information and user data read by a read head included in the head 2. A position detection circuit 10 extracts servo information from the read signals and generates a position detection signal for detecting the position of the head 2.

[0022] The controller 13 includes a CPU (Central Processing Unit) 11, which is the main element of the head positioning control system, and a ROM 12 that stores the CPU's program (e.g., firmware) and various control parameters. The CPU 11 implements the feedback control system and feedforward control system that make up the head positioning control system. The CPU 11 calculates control values ​​(including manipulated variables) and controls the drive currents supplied to the VCM 4 and microactuator 16 via the VCM drive circuit 14 and MA drive circuit 15, respectively, to perform head positioning operations.

[0023] The vibration sensor 17 detects (observes) the acceleration of a disturbance (external vibration or external vibrating force) equivalent to vibration or impact applied to the magnetic disk device 100, and outputs the detection signal (analog signal) to the A / D conversion circuit 18. The A / D conversion circuit 18 converts the detection signal (acceleration signal) of the vibration sensor 17 into a digital value and outputs it to the CPU 11. The vibration sensor 17 is, for example, a shock sensor or an RV sensor.

[0024] The controller 13 also functions as a first controller that controls the VCM 4 in accordance with the target position of the head 2 at a multi-rate that is 1 / N (N: an integer equal to or greater than 2) of the head position observation period.

[0025] The controller 13 also functions as a second controller that controls the microactuator 16 in accordance with the target position of the head 2 at 1 / N cycles.

[0026] A method for creating the MA additional filter Ca (FIG. 5) (second additional filter) will be described below. The entity that performs the calculations may be referred to as a "calculation unit." The calculation unit is realized by, for example, the CPU 11, but may also be realized by other calculation means.

[0027] To give an overview of how the MA additional filter Ca is created, first, before the MA additional filter Ca is added, the calculation unit individually applies test signals at a 1 / N period to the operation amount of the VCM4 and the operation amount of the microactuator 16 to measure the head position error spectrum and frequency characteristics, calculates the multi-rate sensitivity characteristics based on the frequency characteristics, and executes the steps of identifying the frequency to be corrected by the MA additional filter Ca based on the head position error spectrum and multi-rate sensitivity characteristics.

[0028] Next, with each of the multiple MA-added filter candidates Ca added, the calculation unit measures the frequency characteristics by individually applying test signals at 1 / N cycles to the manipulated variable of the VCM 4 and the manipulated variable of the microactuator 16 for the identified frequency, calculates the multi-rate sensitivity characteristics based on the frequency characteristics, and executes the steps of determining the candidate MA-added filter Ca to be used that has a peak equal to or less than a threshold value and minimizes the head position error.

[0029] 4A and 4B are explanatory diagrams of a method for measuring the sensitivity characteristics of the magnetic disk device 100 according to the embodiment. Hereinafter, the VCM 4 may be referred to as "VCM" and the microactuator 16 may be referred to as "MA."

[0030] As shown in Figures 4A and 4B, multirate test signals are individually added to the double multirate VCM and MA control variables, and the time series of the multirate control variables is logged (recorded as VCM multilog ML). The VCM multirate test signal time series is Tv, the MA multirate test signal time series is Tm, the VCM multirate control variable with the test signal added is Iv, and the MA multirate control variable is Im. The frequency characteristics Kv and Km are defined as in the following equation (1). Kv = FFT(Iv) / FFT(Tv) Km = FFT(Im) / FFT(Tm) Equation (1)

[0031] Here, FFT represents the Fast Fourier Transform of a time series. FFT(Iv), FFT(Tv), FFT(Im), and FFT(Tm) are vectors whose elements are complex numbers calculated by the Fast Fourier Transform. FFT(Iv) / FFT(Tv) and FFT(Im) / FFT(Tm) represent element-by-element division of vectors.

[0032] After measuring the frequency characteristics Kv and Km, the predicted value of the feedback system sensitivity measurement is obtained by post-processing the numerical data. Here, if the VCM controller characteristic is Cv, the VCM controlled object characteristic is Pv, the MA controller characteristic is Cm, and the MA controlled object characteristic is Pm, the measurable frequency characteristic represents the transfer characteristic of the following equation (2). Kv=(1+Cm*Pm) / (1+Cv*Pv+Cm*Pm) Km=(1+Cv*Pv) / (1+Cv*Pv+Cm*Pm) (Formula 2)

[0033] By post-calculating (transforming) this characteristic using Matlab (a numerical calculation platform), the following (Equation 3) can be obtained. Cv*Pv=(Kv-1) / (1-Kv-Km) Cm*Pm=(Km-1) / (1-Kv-Km) (Equation 3)

[0034] Moreover, the multi-rate open loop characteristics are expressed as the following (Equation 4). Om=Cv*Pv+Cm*Pm (Formula 4)

[0035] Furthermore, the single-rate open-loop characteristics are expressed by the following (Equation 5), taking into account the folding back at the Nyquist frequency (half the sampling frequency). Os=Om+conj(flipud(Om)) (Equation 5)

[0036] Here, conj represents a complex conjugate operation, and flipud represents a folding operation. Finally, the following (Equation 6) is obtained as the sensitivity characteristic. Multi-rate sensitivity: 1 / (1+Om) Single-rate sensitivity: 1 / (1+Os) (Equation 6)

[0037] 5 is a block diagram of a feedback control system of a magnetic disk device 100 according to an embodiment. In FIG. 5, an MA additional filter Ca is added to FIG. 1. The MA additional filter Ca is added between an MA controller Cm (second controller) and an MA controlled object Pm (second actuator), and outputs output data to the MA controlled object Pm in response to input data from the MA controller Cm.

[0038] Based on the above multirate sensitivity measurement results, the MA added filter Ca is designed in the following order.

[0039] First, the VCM characteristic Cv*Pv, MA characteristic Cm*Pm, multi-rate sensitivity characteristic Km, and single-rate sensitivity characteristic Sm are measured, and for Km, the maximum gain value Xm=max(abs(Km)) and the frequency Fm at that time are calculated. Note that "abs" means absolute value.

[0040] If Xm is equal to or smaller than a predetermined threshold, the process proceeds to the process in FIG. 7, and if Xm is greater than the threshold, the process proceeds to the process in FIG.

[0041] FIG. 7 is a flowchart showing the generation process of an MA additional filter when the maximum gain value Xm of the multi-rate sensitivity characteristic is equal to or less than the threshold value (that is, when there is no problem with the current multi-rate sensitivity characteristic Km) in this embodiment.

[0042] First, in step S11, the calculation unit measures the gain value Sp of the frequency spectrum of the head position error time series data, and calculates the frequency value Fp at which the maximum gain value can be reached, and the frequency spectrum cumulative value Rp.

[0043] Next, in step S12, the calculation unit calculates the disturbance characteristic Gp=Sp / Sm from the single rate sensitivity characteristic Sm and the gain value Sp of the frequency spectrum.

[0044] Next, in step S13, the calculation unit calculates additional filters Ca1, Ca2, ... each of which has a feature point at the frequency Fp and is provided with multiple types of fixed strength (here, three types: "strong," "standard," and "weak") for the four types of MA additional filter candidate patterns (gain increase, gain decrease, phase increase, and phase decrease) shown in FIG. 6.

[0045] Next, in step S14, the calculation unit calculates the multi-rate sensitivity characteristic Km', maximum gain value Xm', and single-rate sensitivity characteristic Sm' after adding Ca using the VCM characteristic Cv*Pv, MA characteristic Cm*Pm, and additional filter candidates Ca1, Ca2, . . .

[0046] Next, in step S15, the calculation unit calculates the predicted gain value Sp'=Gp*Sm' of the frequency spectrum from the disturbance characteristic Gp and the single rate sensitivity characteristic Sm', and obtains the frequency spectrum cumulative value Rp'.

[0047] Next, in step S16, the calculation unit selects an additional filter Ca such that the maximum gain value Xm' is equal to or less than a predetermined threshold and the frequency spectrum cumulative value Rp' is minimized, and then the design is completed.

[0048] FIG. 8 is a flowchart showing the generation process of an MA additional filter when the maximum gain value of the multi-rate sensitivity characteristic is greater than the threshold value (that is, when there is a problem with the current multi-rate sensitivity characteristic Km) in this embodiment.

[0049] First, in step S21, the calculation unit measures the gain value Sp of the frequency spectrum of the head position error time series data.

[0050] Next, in step S22, the calculation unit calculates the disturbance characteristic Gp=Sp / Sm from the single rate sensitivity characteristic Sm and the gain value Sp of the frequency spectrum.

[0051] Next, in step S23, the calculation unit calculates additional filters Ca1, Ca2, ... each of which has a characteristic point at the frequency Fm and has multiple types of constant strength for the four types of additional filter candidate patterns (gain increase, gain decrease, phase increase, phase decrease) shown in FIG. 6.

[0052] Next, in step S24, the calculation unit calculates the multi-rate sensitivity characteristic Km', maximum gain value Xm', and single-rate sensitivity characteristic Sm' after adding Ca using the VCM characteristic Cv*Pv, MA characteristic Cm*Pm, and additional filter candidates Ca1, Ca2, . . .

[0053] Next, in step S25, the calculation unit calculates the predicted gain value Sp'=Gp*Sm' of the frequency spectrum from the disturbance characteristic Gp and the single rate sensitivity characteristic Sm', and obtains the frequency spectrum cumulative value Rp'.

[0054] Next, in step S26, the calculation unit determines whether there is an additional filter Ca such that the maximum gain value Xm' is equal to or less than a predetermined threshold and the frequency spectrum cumulative value Rp' is minimum. If the answer is Yes, the process proceeds to step S27; if the answer is No, the process proceeds to step S28.

[0055] In step S27, the calculation unit selects the corresponding additional filter Ca and ends the design.

[0056] In step S28, since the maximum gain value Xm' is not below the predetermined threshold value for all the MA-added filter candidates, the calculation unit records this as an error in the nonvolatile memory inside the drive or in the drive management information on the disk 1.

[0057] Next, a description will be given of the effects of adding the MA additional filter Ca. Fig. 9 is a diagram showing the head position error spectrum before and after the design of the MA additional filter in this embodiment.

[0058] For a specific frequency, adding the MA additional filter Ca reduces the gain of the head position error spectrum (Fig. 9(a)), and it can also be seen that the cumulative head position error spectrum improves the positioning accuracy (Fig. 9(b)).

[0059] 10 is a diagram showing the single-rate sensitivity characteristics before and after designing the MA additional filter in the embodiment. It can be seen that for a specific frequency, adding the MA additional filter Ca reduces the gain of the single-rate sensitivity, improving the positioning accuracy.

[0060] Thus, according to this embodiment, in a magnetic disk device 100 that performs multi-rate control using a two-stage actuator, the MA additional filter Ca created as described above is added between the MA controller Cm and the MA control object Pm, thereby improving the accuracy of head positioning.

[0061] Although the above embodiment has been described with reference to an MA additional filter, a VCM additional filter can also be created in a similar manner.

[0062] Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the invention described in the claims and their equivalents.

[0063] For example, in the processing of FIGS. 7 and 8, the case without an additional filter may also be included in the calculations for comparison.

[0064] Moreover, both the MA additional filter and the VCM additional filter may be created and used simultaneously. [Explanation of symbols]

[0065] 1 disk, 2 head, 3 arm, 4 VCM, 9 signal processing circuit, 10 position detection circuit, 11 CPU, 12 ROM, 13 controller, 14 VCM drive circuit, 15 MA drive circuit, 17 vibration sensor, 18 A / D conversion circuit

Claims

1. a disk for storing data; a head for reading / writing data from / to the disk; a first actuator that moves the entire arm having the head disposed at the tip thereof; a second actuator provided at the tip of the arm for moving the head; a first controller that controls the first actuator in accordance with a target position of the head at a multi-rate that is 1 / Nth of a head position observation period (N: an integer of 2 or more); a second controller that controls the second actuator in accordance with a target position of the head at the 1 / N period; a first additional filter that is added between the first controller and the first actuator and that outputs output data to the first actuator in response to input data from the first controller, a calculation unit measuring a head position error spectrum and a frequency characteristic by individually adding a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator in a state before the first additional filter is added, calculating a multi-rate sensitivity characteristic based on the frequency characteristic, and specifying a frequency to be corrected by the first additional filter based on the head position error spectrum and the multi-rate sensitivity characteristic; and a step of: the calculation unit, with each of the plurality of first additional filter candidates added, individually adding a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator for the frequency, measuring frequency characteristics; calculating a multi-rate sensitivity characteristic based on the frequency characteristics; and determining, as the first additional filter to be used, the candidate with a peak of the multi-rate sensitivity characteristic below a threshold and with which a head position error is minimized.

2. a disk for storing data; a head for reading / writing data from / to the disk; a first actuator that moves the entire arm having the head disposed at the tip thereof; a second actuator provided at the tip of the arm for moving the head; a first controller that controls the first actuator in accordance with a target position of the head at a multi-rate that is 1 / Nth of a head position observation period (N: an integer of 2 or more); a second controller that controls the second actuator in accordance with a target position of the head at the 1 / N period; a second additional filter that is added between the second controller and the second actuator and outputs output data to the second actuator in response to input data from the second controller, a calculation unit measuring a head position error spectrum and a frequency characteristic by individually adding a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator in a state before the second additional filter is added, calculating a multi-rate sensitivity characteristic based on the frequency characteristic, and specifying a frequency to be corrected by the second additional filter based on the head position error spectrum and the multi-rate sensitivity characteristic; and a step of: the calculation unit, with each of the plurality of second additional filter candidates added, individually adding a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator for the frequency, measuring frequency characteristics; calculating a multi-rate sensitivity characteristic based on the frequency characteristics; and determining, as the second additional filter to be used, the candidate with a peak of the multi-rate sensitivity characteristic below a threshold and with which a head position error is minimized.

3. a disk for storing data; a head for reading / writing data from / to the disk; a first actuator that moves the entire arm having the head disposed at the tip thereof; a second actuator provided at the tip of the arm for moving the head; a first controller that controls the first actuator in accordance with a target position of the head at a multi-rate that is 1 / Nth of a head position observation period (N: an integer of 2 or more); a second controller that controls the second actuator in accordance with a target position of the head at the 1 / N period; a first additional filter that is added between the first controller and the first actuator and that outputs output data to the first actuator in response to input data from the first controller, means for measuring a head position error spectrum and a frequency characteristic by individually applying a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator in a state before the first additional filter is added, calculating a multi-rate sensitivity characteristic based on the frequency characteristic, and specifying a frequency to be corrected by the first additional filter based on the head position error spectrum and the multi-rate sensitivity characteristic; a program for causing the program to function as a means for determining, with each of a plurality of candidates for the first additional filter added, a means for measuring frequency characteristics by individually adding a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator for the frequency, calculating a multi-rate sensitivity characteristic based on the frequency characteristics, and determining, as the first additional filter to be used, the candidate for which the peak of the multi-rate sensitivity characteristic is equal to or less than a threshold and which minimizes the head position error.

4. a disk for storing data; a head for reading / writing data from / to the disk; a first actuator that moves the entire arm having the head disposed at the tip thereof; a second actuator provided at the tip of the arm for moving the head; a first controller that controls the first actuator in accordance with a target position of the head at a multi-rate that is 1 / Nth of a head position observation period (N: an integer of 2 or more); a second controller that controls the second actuator in accordance with a target position of the head at the 1 / N period; a second additional filter that is added between the second controller and the second actuator and that outputs output data to the second actuator in response to input data from the second controller, means for measuring a head position error spectrum and a frequency characteristic by individually applying a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator in a state before the second additional filter is added, calculating a multi-rate sensitivity characteristic based on the frequency characteristic, and specifying a frequency to be corrected by the second additional filter based on the head position error spectrum and the multi-rate sensitivity characteristic; a program for causing the program to function as a means for determining, with each of a plurality of candidates for the second additional filter added, a means for measuring frequency characteristics by individually adding a test signal at the 1 / N period to the operation amount of the first actuator and the operation amount of the second actuator for the frequency, calculating a multi-rate sensitivity characteristic based on the frequency characteristics, and determining, as the second additional filter to be used, the candidate for which the peak of the multi-rate sensitivity characteristic is equal to or less than a threshold value and which minimizes the head position error.

Images