disc device

Abstract

Provided is a disc device that can achieve an external vibration suppression function that is compatible with the performance of an actuator, changes in the direction of external vibrations, and the like, in a disc device that has a two-stage actuator. The disc device detects vibrations from the outside, and generates a first actuator correction amount that is based on the vibrations and a coefficient. In addition, the disc device calculates a first operation amount that is based on the operation amount of the actuator (3) and the first actuator correction amount, and calculates a second actuator operation amount that is based on the operation amount of the micro actuator (16). The disc device calculates a current position that is based on the first operation amount and the second actuator operation amount. The disc device updates the coefficient of a filter in accordance with a position error and a vibration value that is based on the vibrations and a learning filter (36).

Description

[0001] This application claims priority to Japanese Patent Application No. 2022-049161 (Filing Date: March 24, 2022). This application incorporates the entire contents of the base application by reference thereto. TECHNICAL FIELD

[0002] Embodiments of the present application relate to a disk device. BACKGROUND

[0003] Generally, in a disk storage device (hereinafter referred to as "disk device") typified by a hard disk device, a head positioning control system for positioning a head such as a magnetic head on a target position, i.e., a track to be accessed, on a disk medium as a recording medium is incorporated. The head performs a read / write operation of data on the positioned target position on the disk medium.

[0004] Sometimes, by generating a feedforward input for correcting a head position error from an observed external vibration with an adaptive FIR filter, an external vibration suppression function that is adapted to the performance of an actuator, a variation in the direction of an external vibration, and the like can be realized in a head positioning control system incorporated in a disk device.

[0005] In recent years, a two-stage actuator in which a micro actuator (MA) is provided at the front end of an arm in addition to a VCM to drive a head slightly has been realized in a disk device. In addition, a controller is also divided into a VCM and an MA. Thus, in a disk device provided with a two-stage actuator, it is also desirable to realize an external vibration suppression function that is adapted to the performance of an actuator, a variation in the direction of an external vibration, and the like. SUMMARY

[0006] One embodiment is to provide a disk device in which an external vibration suppression function that is adapted to the performance of an actuator, a variation in the direction of an external vibration, and the like can be realized in a disk device provided with a two-stage actuator.

[0007] According to one embodiment, the disk device includes a vibration detection section that detects a vibration from the outside, an FIR filter section that generates a filter value based on the vibration detected by the vibration detection section and a coefficient of a filter, a first operation amount calculation section that calculates a first operation amount obtained by adding a first actuator operation amount calculated based on a position error of a current position from a target position and a first actuator correction amount based on the filter value, a position detection section that calculates a current position based on the first operation amount and a second actuator operation amount calculated based on the position error, and a coefficient update section that updates the coefficient of the filter based on the position error and a vibration value based on the vibration and a vibration value of a learning filter based on a characteristic Pv / (1+ a characteristic Cv of a controller of the first actuator * a characteristic Pv of the first actuator + a characteristic Cm of a controller of the second actuator * a characteristic Pm of the second actuator). BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a diagram showing one example of a configuration of a disk device according to the first embodiment.

[0009] Figure 2 is a diagram showing a configuration of a head positioning control system according to the first embodiment.

[0010] Figure 3 is a flowchart showing steps of a position adjustment process of a two-stage actuator according to the first embodiment.

[0011] Figure 4A is a graph showing a curve representing a change in a position error of a comparative example.

[0012] Figure 4B is a graph showing a curve representing a change in a position error in a case where an adaptive filter according to the first embodiment is applied.

[0013] Figure 5 is a diagram showing a configuration of a head positioning control system according to the second embodiment.

[0014] Figure 6A is a graph showing a gain transfer characteristic of an FIR filter.

[0015] Figure 6B is a graph showing a phase transfer characteristic of an FIR filter.

[0016] REFERENCE NUMERALS

[0017] 1 disk; 2 head; 3 actuator; 4 VCM; 9 signal processing circuit; 10 position detection circuit; 11 CPU; 12 ROM; 13 microcontroller; 14 VCM drive circuit; 15 MA drive circuit; 17 vibration sensor; 18 A / D conversion circuit. DETAILED DESCRIPTION

[0018] Hereinafter, a disk device according to the embodiments will be described in detail with reference to the drawings. Note that the present application is not limited by these embodiments.

[0019] (First Embodiment)

[0020] Figure 1 is a block diagram showing main parts of the disk device according to the present embodiment.

[0021] (Configuration of the disk device)

[0022] As shown in Figure 1 , the disk device according to the first embodiment has a disk 1 as a recording medium, a head 2 that performs a read / write operation of data, and an actuator 3 (first actuator).

[0023] The disk 1 is rotated by a spindle motor. The disk 1 is provided on a surface thereof with a large number of concentric tracks 5. Each track 5 contains a servo sector 6. The servo sector 6 contains a servo area 7 and a data area 8. Each track 5 contains a predetermined number of servo areas 7 arranged at predetermined intervals in a circumferential direction. In the servo area 7, servo information (position information) used for detecting the position of the head 2 in a head positioning control system at the time of a normal read / write operation is recorded. In addition, between the servo areas 7 are the data areas 8 in which user data is recorded.

[0024] Generally, the head 2 is constructed so that a read head and a write head are separately mounted on a slider. The read head reads out the servo information and the user data recorded on the disk 1. At the time of head positioning control, the read head reads out the servo information at certain intervals in accordance with the rotation speed of the disk 1. The write head writes the user data on the disk 1.

[0025] The actuator 3 carries the head 2 and moves the head 2 in a radial direction of the disk 1 by a driving force of a voice coil motor (VCM) 4. The VCM 4 is a narrow sense control object in the head positioning control system and is a main element of the actuator mechanism. In addition, a micro actuator 16 is provided at a front end of an arm of the actuator 3. The micro actuator 16 moves the head 2 slightly.

[0026] Further, the disk device has a read / write channel (signal processing circuit 9 and position detection circuit 10), a microcontroller 13, a VCM drive circuit 14, a MA drive circuit 15, and a vibration sensor 17.

[0027] The signal processing circuit 9 processes the read signals and write signals corresponding to the servo information or user data read from the read head contained in the head 2. Additionally, the 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.

[0028] The microcontroller 13 has a microprocessor (CPU) 11, which is a key component of the head positioning control system, and a ROM 12 that stores its program (firmware) and various control parameters. The CPU 11 implements the feedback control system and the feedforward control system that constitute the head positioning control system, as described later. The CPU 11 calculates control values ​​(including operational quantities described later) and controls the drive current supplied to the VCM4 and the micro actuator 16 via the VCM drive circuit 14 and the MA drive circuit 15 to execute the head positioning action.

[0029] Vibration sensor 17 detects (observes) the acceleration of an interference (external vibration or excitation force) equivalent to the vibration or impact applied to the disk assembly, and outputs the detected signal (analog signal) to A / D conversion circuit 18. A / D conversion circuit 18 converts the detected signal (acceleration signal) from vibration sensor 17 into a digital value and outputs it to CPU 11. Vibration sensor 17 is, for example, an impact sensor or an RV sensor. Vibration sensor 17 is an example of a vibration detection unit.

[0030] As described above, the disk device according to this embodiment has a two-stage actuator, which can realize an external vibration suppression function that adapts to the performance of the actuator and the change in the direction of external vibration.

[0031] (Head positioning control system)

[0032] Next, refer to Figure 2 The configuration and operation of the head positioning control system installed in the disc device according to the first embodiment will be described.

[0033] The head positioning system is a system that uses vibration values ​​detected by vibration sensor 17 to perform head position calculations. The head positioning system includes an FIR filter 31, a VCM controller 32, a VCM control object 33, an MA controller 34, an MA control object 35, a learning filter 36, and an FIR coefficient adjustment mechanism 37.

[0034] The system is realized by the CPU 11. The CPU 11 acquires the current position of the head 2 from the position detection circuit 10 in synchronization with the rotation angle of the disk 1. In addition, the CPU 11 constitutes a sample value control system that calculates the control value to be input to the control objects (the VCM control object and the MA control object) at certain time intervals (servo period). The VCM 4 and the micro-actuator 16 in the disk device of the present embodiment are driven by multi-rate control that drives at 1 / N (N is an integer of 2 or more) of the head position observation period. The timing of A / D conversion of the analog value of the detection result of the vibration sensor 17 is the same as the head position observation period, but since it is different from the servo information on the disk, the restriction of the conversion timing is small, and thus observation is also performed at a multi-rate at times.

[0035] In addition, the drive current value supplied to the VCM 4 is set with a limit value in advance by the VCM drive circuit 14. In addition, the drive current value supplied to the micro-actuator 16 is set with a limit value in advance by the MA drive circuit 156.

[0036] When the vibration is detected by the vibration sensor 17, the FIR filter 31 generates a filter value that is a correction value of the operation amount of the VCM 4 on the basis of the vibration value (acceleration) detected by the vibration sensor 17 and the FIR filter coefficient. The FIR filter 31 is one example of the FIR filter section.

[0037] Here, when the acceleration observed at the sample period is set as a0, a1, a2,... (the larger the suffix, the earlier the value), and the FIR filter coefficient is set as f0, f1, f2,..., the output value of the FIR filter 31 becomes the following formula (1).

[0038] FIR filter output: f0*a0 + f1*a1 + f2*a2 +... (1)

[0039] Further, the VCM controller 32 outputs a signal indicating an operation amount of the VCM based on a position error of the current position from the target position (1st actuator operation amount). Here, the current position refers to position information read by the head from the disc regardless of the 1st actuator / 2nd actuator. Further, the target position refers to a position where the head is accessing / wants to access on the disc regardless of the 1st actuator / 2nd actuator. Also, the CPU 11 inputs a signal obtained by adding the signal indicating the operation amount and the output value of the FIR filter 31 (1st actuator correction amount) to the VCM control object 33, so that the VCM control object 33 outputs the head position of the actuator 3 based on the signal obtained by the addition. Thus, the CPU 11 is an example of a 1st operation amount calculation section. Further, the operation amount of the VCM refers to, for example, an index value of how much the VCM should be moved, and the VCM driver IC determines / operates the current flowing in the coil of the VCM based on the index value.

[0040] The MA controller 34 outputs a signal indicating an operation amount based on the position error (2nd actuator operation amount). Also, the CPU 11 inputs the signal indicating the operation amount to the MA control object 35, so that the MA control object 35 outputs the head position of the micro actuator 16 based on the signal. Thus, the CPU 11 is an example of a 2nd head position calculation section. The CPU 11 detects the current position based on the output value of the VCM control object 33 (head position) and the output value of the MA control object 35 (head position). Thus, the CPU 11 detects the current position based on the 1st operation amount and the 2nd actuator operation amount. That is, the CPU 11 is an example of a position detection section. Further, the CPU 11 calculates the position error as a difference value between the target position and the current position. Further, the position error is input to the FIR coefficient adjustment mechanism 37, the VCM controller 32, and the MA controller 34.

[0041] The FIR coefficient adjustment mechanism 37 updates the coefficients of the filter based on the position error and the vibration value based on the vibration and the learning filter 36. Specifically, the FIR coefficient adjustment mechanism 37 updates the FIR filter coefficients indicated by the above formula (1) with each sample by the following formula (2). b0, b1, b2,... of formula (2) are accelerations after passing through the learning filter 36. G of formula (2) is a learning gain. Further, < - of formula (2) indicates variable assignment. The FIR coefficient adjustment mechanism 37 is an example of a coefficient update section.

[0042]

[0043] The learning filter 36 is a linear digital IIR filter with the following transfer characteristics as expressed in equation (3) when the characteristics of the VCM controller are set to Cv, the characteristics of the VCM controlled object are set to Pv, the characteristics of the MA controller are set to Cm, and the characteristics of the MA controlled object are set to Pm.

[0044] Learning filter: Pv / (1+Cv*Pv+Cm*Pm)…(3)

[0045] For the acceleration calculation method performed by learning filter 36, when the coefficients of the numerator of the learning filter transfer function are set to n0, n1, n2, ..., and the coefficients of the denominator are set to 1, d1, d2, ..., it becomes the following equation (4).

[0046] Learning filter output: b0

[0047] <-n0*a0+n1*a1+n2*a2…-d1*b1-d2*b2…(4)

[0048] Next, use Figure 3 The flowchart shown illustrates the steps of the position adjustment process for the two-stage actuator. The CPU 11 obtains the head position error (step S1) based on the target position and the detected position detected by the position detection circuit 10.

[0049] Additionally, CPU 11 acquires the external vibration detected by vibration sensor 17 (step S2). MA controller 34 calculates the operation amount of micro-actuator 16 based on position error (step S3). VCM controller 32 calculates the operation amount of actuator 3 based on position error (step S4). FIR filter 31 generates a filter value based on the external vibration and coefficients obtained from vibration sensor 17 (step S5). CPU 11 adds the filter value of FIR filter 31 to the operation amount of VCM controller 32 (step S6). CPU 11 outputs the MA operation amount (head position of micro-actuator 16) based on the operation amount of micro-actuator 16 (step S7). CPU 11 outputs the VCM operation amount (head position of actuator 3) based on the filter value of FIR filter 31 and the operation amount of VCM controller 32 (step S8).

[0050] The learning filter 36 performs a linear digital IIR filter operation represented by equation (3) based on the external vibration detected by the vibration sensor 17 (step S9). The FIR coefficient adjustment mechanism 37 updates the coefficients of the FIR filter 31 based on the position error and the signal output from the learning filter 36 (step S10).

[0051] Here, as mentioned above, we will examine the case without using an adaptive filter as a comparative example. Without an adaptive filter, the operation is determined without considering past position errors; therefore, the position error may not decrease. Here, in Figure 4A The graph shows the change in position error of the comparative example. The vertical axis represents the head position error, and the horizontal axis represents time. Figure 4A As shown, the position error does not converge even after time has elapsed.

[0052] Here, in Figure 4B The graph shows the change in position error when an adaptive filter is applied. The vertical axis represents the head position error, and the horizontal axis represents time. Figure 4B As shown, the position error converges after a predetermined time.

[0053] The disk device according to the first embodiment detects vibrations from the outside and generates a first actuator correction amount based on the vibration and coefficients. Furthermore, the disk device calculates a first operating amount based on the operating amount of actuator 3 and the first actuator correction amount, and calculates a second actuator operating amount based on the operating amount of micro-actuator 16. The disk device calculates the current position based on the first operating amount and the second actuator operating amount. The disk device updates the coefficients of the filter based on the position error and the vibration value based on the vibration and the learning filter 36.

[0054] In this way, disk 1 updates the coefficients of the filter based on the position error and the vibration value based on the vibration and learning filter 36, thereby reducing the position error and adjusting the head position. Therefore, even in a disk device with two-stage actuators, it is possible to achieve external vibration suppression function that adapts to the performance of the actuator, changes in the direction of external vibration, etc.

[0055] In the first embodiment, an example with predetermined transfer characteristics of the learning filter was described. However, in the second embodiment, a test signal is applied to the feedback control system of the two-stage actuator, and the head position error time series is measured to determine the parameters (identify).

[0056] exist Figure 5 The diagram shows the configuration of the head positioning control system for disk 1 according to the second embodiment. The head positioning control system according to the second embodiment focuses on generating a learning filter. The head positioning control system according to the second embodiment includes a VCM controller 32, a VCM control object 33, an MA controller 34, an MA control object 35, a head position error log 39, and a learning filter generation unit 38. Furthermore, descriptions of parts common to the first embodiment are omitted.

[0057] The VCM controller 32 outputs a signal representing an operation amount based on the position error (1st actuator operation amount). Also, the CPU 11 inputs a signal obtained by adding a signal representing the operation amount and a test signal (1st operation amount) to the VCM control target 33. Here, the test signal refers to a signal such as a scan signal, a white signal, an M-sequence, and the like.

[0058] The MA controller 34 outputs a signal representing an operation amount based on the position error (2nd actuator operation amount). Also, the CPU 11 inputs a signal representing the operation amount to the MA control target 35. The CPU 11 calculates a difference value (position error) between the current position of the two-stage actuator as a whole and the target position, obtained by adding the output value of the VCM control target 33 (head position) and the output value of the MA control target 35 (head position). Also, the CPU 11 stores the position error in the head position error log 39. The learning filter generation section 38 determines parameters based on the test signal and the head position error log 39, and thereby calculates the transfer characteristic of the learning filter 36, by a known technique. The learning filter generation section 38 inputs the calculated transfer characteristic to the learning filter 36. The learning filter generation section 38 is realized by, for example, the CPU 11 or the like.

[0059] Figure 6A A gain transfer characteristic of the FIR filter 27 calculated in the head positioning control system according to the 2nd embodiment is shown. Figure 6B A phase transfer characteristic thereof is shown. Reference numerals 41, 51 represent actual vibration transfer characteristics (G). Reference numerals 42, 52 represent characteristics of the FIR filter in the conventional system.

[0060] As shown in Figs. 5 and 6, the reference numeral 51 approximates to the reference numeral 41, and the reference numeral 52 approximates to the reference numeral 42. Figure 6A Figure 6B As shown in Figs. 5 and 6, the reference numeral 51 approximates to the reference numeral 41, and the reference numeral 52 approximates to the reference numeral 42.

[0061] The disc 1 according to the 2nd embodiment calculates the head position of the actuator 3 based on the test signal and the operation amount of the actuator 3, and generates the transfer characteristic of the learning filter 36 based on the difference value between the head position of the two-stage actuator as a whole and the target position.

[0062] Thus, the disc 1 can generate the transfer characteristic of the learning filter used in the position adjustment of the two-stage actuator using the test signal.

[0063] ​The above describes several embodiments of the present application, but these embodiments are presented as examples and are not intended to limit the scope of the application. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the application. These embodiments and / or variations thereof are included in the scope, spirit of the application, and are included in the scope of the application as recited in the claims and equivalents thereof.

Claims

1. A disk device comprising: a vibration detecting section that detects a vibration from outside; a FIR filter section that generates a filter value based on the vibration detected by the vibration detecting section and a coefficient of a filter; a first operation amount calculating section that calculates a first operation amount obtained by adding a first actuator operation amount calculated based on a position error of a current position from a target position and a first actuator correction amount based on the filter value; a position detecting section that calculates the current position based on the first operation amount and a second actuator operation amount calculated based on the position error; and a coefficient updating section that updates the coefficient of the filter based on the position error and a vibration value based on the vibration and a vibration value of a learning filter, the learning filter being a filter based on a characteristic Pv / (l + a characteristic Cv of a controller of a first actuator * a characteristic Pv of the first actuator + a characteristic Cm of a controller of a second actuator * a characteristic Pm of the second actuator).

2. The disk device according to claim 1, further comprising a learning filter generating section that generates the learning filter, wherein the first operation amount calculating section calculates the first operation amount based on a test signal and the first actuator operation amount in a case where the test signal is input instead of the first actuator correction amount, the position detecting section detects the current position based on the first operation amount and the second actuator operation amount, and the learning filter generating section generates the learning filter based on a difference value between the current position and the target position and the test signal.

3. The disk device according to claim 1, wherein the vibration detecting section detects the vibration at every certain sampling time. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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