阅读说明：本技术 磁盘装置以及头的寻道控制方法 (Magnetic disk device and seek control method of head ) 是由 原武生 于 2019-07-15 设计创作，主要内容包括：实施方式提供一种能够提高访问性能的磁盘装置以及头的寻道控制方法。本实施方式涉及的磁盘装置具备：盘；头,其对所述盘写入数据,从所述盘读取数据；致动器,其包括使所述头在所述盘上移动的音圈马达；以及控制器,其根据在所述盘上的寻道中的所述头的加速时能够施加于所述音圈马达的最大的第1电流值,增大在所述寻道中的所述头的减速时向所述音圈马达施加的第2电流值。(Embodiments provide a magnetic disk device capable of improving access performance and a seek control method of a head. The magnetic disk device according to the present embodiment includes: a disc; a head that writes data to the disk and reads data from the disk; an actuator comprising a voice coil motor that moves the head over the disk; and a controller that increases a 2 nd current value applied to the voice coil motor at the time of deceleration of the head in a seek according to a maximum 1 st current value that can be applied to the voice coil motor at the time of acceleration of the head in the seek on the disk.)

1. A magnetic disk device is provided with:

a disc;

a head that writes data to the disk and reads data from the disk;

an actuator comprising a voice coil motor that moves the head over the disk; and

a controller that increases a 2 nd current value applied to the voice coil motor at the time of deceleration of the head in a seek according to a maximum 1 st current value that can be applied to the voice coil motor at the time of acceleration of the head in the seek on the disk.

2. The magnetic disk apparatus according to claim 1,

the controller calculates the 1 st current value by accelerating the head in saturation during the acceleration.

3. The magnetic disk apparatus according to claim 1,

the controller changes a1 st change of the speed of the head with respect to the radial position of the disk, which is a reference at the time of the deceleration, in accordance with the 1 st current value.

4. The magnetic disk device according to claim 3,

the controller calculates a 2 nd change in the velocity of the head with respect to the radial position at the time of deceleration, which is larger than the 1 st change, based on the 1 st current value at the time of acceleration,

based on the 2 nd change, a 3 rd change in the velocity of the head with respect to the radial position at the time of the deceleration is calculated, the 3 rd change having a 2 nd inclination of the 2 nd change at the 1 st position that is the same as a1 st inclination of the 1 st change at the 1 st position at which the deceleration of the head is switched to the settling of the head.

5. The magnetic disk device according to claim 3,

the controller calculates a 2 nd change in the velocity of the head with respect to the radial position at the time of deceleration, which is larger than the 1 st change, based on the 1 st current value at the time of acceleration,

detecting a1 st speed of the 1 st change, a 2 nd position of the 2 nd change corresponding to a 2 nd acceleration, and a 2 nd speed of the 2 nd change corresponding to the 2 nd acceleration at a1 st position at which deceleration of the head is switched to rest of the head, the 2 nd acceleration being the same as the 1 st acceleration corresponding to the 1 st acceleration,

correcting the 2 nd change based on a1 st difference of the 1 st and 2 nd positions and a 2 nd difference of the 1 st and 2 nd velocities.

6. The magnetic disk apparatus according to claim 4 or 5,

the controller calculates the 2 nd change by multiplying the 1 st change by a square root of a1 st ratio of the 1 st current value to a 3 rd current value, the 3 rd current value being a current value applied to the voice coil motor smaller than the 1 st current value at the time of the acceleration.

7. The magnetic disk apparatus according to claim 6,

the 3 rd current value is a current value to be applied to the voice coil motor as a reference at the time of the acceleration.

8. The magnetic disk apparatus according to claim 1,

the 1 st current value is a maximum current value of the head at which the head is not saturated at the time of the acceleration.

9. A magnetic disk device is provided with:

a disc;

a head that writes data to the disk and reads data from the disk;

an actuator comprising a voice coil motor that moves the head over the disk; and

a controller that controls the head based on a 2 nd change in a velocity of the head with respect to a radial position at the time of deceleration, the 2 nd change having a 2 nd inclination at the 1 st position that is the same as a1 st inclination of the velocity of the head with respect to a1 st change in the radial position of the disk, which becomes a reference at the time of the deceleration of the head at a1 st position at which the deceleration of the head is switched to the settling of the head in a seek on the disk.

10. A seek control method of a head applied to a magnetic disk apparatus having a disk, a head that writes data to the disk and reads data from the disk, and an actuator including a voice coil motor that moves the head over the disk, the seek control method comprising:

increasing a 2 nd current value applied to the voice coil motor at the time of deceleration of the head in a seek according to a maximum 1 st current value applicable to the voice coil motor at the time of acceleration of the head in the seek on the disk.

Technical Field

Embodiments of the present invention relate to a magnetic disk device and a seek control method of a head.

Background

The magnetic disk apparatus changes a current or voltage applied to a Voice Coil Motor (VCM) when accelerating the head during a seek of the head. The magnetic disk apparatus can apply a larger current to the VCM when decelerating the head during the seek of the head than when accelerating the head by a counter electromotive force or the like.

Disclosure of Invention

Embodiments of the present invention provide a magnetic disk device and a seek control method of a head capable of improving access performance.

The magnetic disk device according to the present embodiment includes: a disc; a head that writes data to the disk and reads data from the disk; an actuator comprising a voice coil motor that moves the head over the disk; and a controller that increases a 2 nd current value applied to the voice coil motor at the time of deceleration of the head in a seek according to a maximum 1 st current value that can be applied to the voice coil motor at the time of acceleration of the head in the seek on the disk.

The magnetic disk device according to the present embodiment includes: a disc; a head that writes data to the disk and reads data from the disk; an actuator comprising a voice coil motor that moves the head over the disk; and a controller that controls the head based on a 2 nd change in a speed of the head with respect to a radial position at the time of deceleration, the 2 nd change having a 2 nd inclination at a1 st position that is the same as a1 st inclination of the speed of the head with respect to a1 st change in the radial position of the disk, which becomes a reference at the time of the deceleration of the head at a1 st position at which the deceleration of the head is switched to the settling of the head in a seek on the disk.

A seek control method of a head according to an embodiment is a seek control method applied to a magnetic disk device including a disk, a head that writes data to the disk and reads data from the disk, and an actuator including a voice coil motor that moves the head over the disk, the seek control method including: increasing a 2 nd current value applied to the voice coil motor at the time of deceleration of the head in a seek according to a maximum 1 st current value applicable to the voice coil motor at the time of acceleration of the head in the seek on the disk.

Drawings

Fig. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device according to an embodiment.

Fig. 2 is a plan view schematically showing an example of the position of the head with respect to the disk.

Fig. 3 is a diagram showing an example of a target speed curve according to the embodiment.

Fig. 4 is an enlarged view showing an example of a switching position of the settling mode (settling mode) of the target speed profile shown in fig. 3.

Fig. 5 is a diagram showing an example of a change in the head acceleration with respect to the radial position corresponding to the target velocity curve shown in fig. 4.

Fig. 6 is a diagram showing an example of a current flowing in the VCM when the seek operation of the head according to the embodiment is performed.

Fig. 7 is a diagram showing an example of the head speed when the seek operation shown in fig. 6 is performed.

Fig. 8 is a diagram showing an example of the head position when the seek operation shown in fig. 6 is performed.

Fig. 9 is a block diagram showing an example of a control system of a seek process of a head according to an embodiment.

Fig. 10 is a flowchart showing an example of each sampling process at the time of acceleration according to the embodiment.

Fig. 11 is a flowchart showing an example of a process of updating the mode switching condition according to the embodiment.

Detailed Description

Hereinafter, embodiments will be described with reference to the drawings. The drawings are exemplary and do not limit the scope of the invention.

(embodiment mode)

Fig. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device 1 according to the embodiment.

The magnetic disk device 1 includes a housing HS, a Head Disk Assembly (HDA)10, a driver IC20, a head amplifier integrated circuit (hereinafter referred to as a head amplifier IC or a preamplifier) 30, a volatile memory 70, a buffer memory (buffer memory) 80, a nonvolatile memory 90, and a system controller 130 as a single-chip integrated circuit. The magnetic disk device 1 is connected to a host system (hereinafter, simply referred to as a host) 100. A cross-section of HDA10 is schematically shown in fig. 1.

The HDA10 includes a magnetic disk (hereinafter referred to as a disk) DK, a spindle motor (hereinafter referred to as an SPM)13 that rotates the disk DK about a spindle 12, an arm AM on which a head HD is mounted, and a voice coil motor (hereinafter referred to as a VCM) 14. SPM13 and VCM14 are fixed to housing HS. The disk DK is attached to the spindle 12 and rotated by being driven by the SPM 13. The head HD is opposed to the disk DK. The arm AM and the VCM14 constitute an actuator AC. The actuator AC positions the head HD attached to the front end of the arm AM at a predetermined position of the disk DK by rotating about the rotation axis. The disk DK and the head HD may be provided in two or more numbers. For example, at least two or more discs DK and heads HD are provided, respectively.

Fig. 2 is a plan view schematically showing an example of the position of the head HD with respect to the disk DK. In the radial direction of the disk DK, the direction toward the spindle 12 is referred to as an inner direction (inner side), and the opposite direction to the inner direction is referred to as an outer direction (outer side). A direction perpendicular to the radial direction of the disc DK is referred to as a circumferential direction. Fig. 2 shows the rotation direction of the disk DK in the circumferential direction. The direction of rotation may be opposite to that shown in fig. 2.

The disc DK has a user data area UA available to a user and a system area SA in which information (hereinafter, also referred to as system information) necessary for system management is written, allocated to an area where data can be written. Hereinafter, the predetermined position in the radial direction of the disc DK may be referred to as a radial position, and the predetermined position in the circumferential direction of the disc DK may be referred to as a circumferential position. The radial position corresponds to a track, for example, and the circumferential position corresponds to a sector, for example. The radial position and the circumferential position may be simply referred to as positions.

The head HD mainly includes a slider, and has a write head WH and a read head RH actually mounted on the slider so as to face the disk DK. The write head WH writes data to the disc DK. The reading head RH reads data recorded on a track of the disc DK. As shown in fig. 2, the head HD is made to glide in the horizontal plane of the disk DK by, for example, rotationally driving the actuator AC around the bearing BR at the time of seek. Hereinafter, the position (e.g., radial position) of the head HD on the disk DK may be simply referred to as a head position.

The driver IC20 controls the driving of the SPM13 and the VCM14 under the control of the system controller 130 (specifically, an MPU50 described later). The driver IC20 includes the SPM control unit 21 and the VCM control unit 22. The SPM control section 21 controls the rotation of the SPM 13. The VCM control unit 22 controls the current supplied to control the driving of the VCM 14. Further, a part of the configuration of the driver IC20 (for example, the SPM control unit 21 and the VCM control unit 22) may be provided in the system controller 130.

The head amplifier IC (preamplifier) 30 amplifies a read signal read from the disk DK and outputs the amplified signal to a system controller 130 (specifically, a read/write (R/W) channel 40 described later). In addition, the head amplifier IC30 outputs a write current corresponding to the signal output from the R/W channel 40 to the head HD. The head amplifier IC30 includes a write signal control section 31 and a read signal detection section 32. The write signal control unit 31 controls the write current to be output to the head HD in accordance with control of a system controller 130 (specifically, an MPU60 described later). The read signal detection section 32 detects a signal written by the write head and/or a signal read by the read head. Further, a part of the configuration of the head amplifier IC30 (for example, the write signal control section 31 and the read signal detection section 32) may be provided in the system controller 130.

The volatile memory 70 is a semiconductor memory in which data stored when power supply is cut off is lost. The volatile memory 70 stores data and the like necessary for processing of each unit of the magnetic disk device 1. The volatile memory 70 is, for example, a dram (Dynamic Random Access memory) or an sdram (synchronous Dynamic Random Access memory).

The buffer memory 80 is a semiconductor memory that temporarily records data and the like transmitted and received between the magnetic disk device 1 and the host 100. The buffer memory 80 may be integrated with the volatile memory 70. The buffer Memory 80 is, for example, a DRAM (dynamic Random Access Memory), an SDRAM (synchronous dynamic Random Access Memory), a FeRAM (Ferroelectric Random Access Memory), an mram (magnetic Random Access Memory), or the like.

The nonvolatile memory 90 is a semiconductor memory that records stored data even when power supply is cut off. The nonvolatile Memory 90 is, for example, a Flash ROM (Flash Read Only Memory) of NOR type or NAND type.

The System controller (controller) 130 is implemented, for example, using a large scale integrated circuit (LSI) called a System-on-a-chip (soc) in which a plurality of elements are integrated on a single chip. The system controller 130 includes a read/write (R/W) channel 40, a Hard Disk Controller (HDC)50, and a Microprocessor (MPU) 60. The system controller 130 is electrically connected to the driver IC20, the head amplifier IC30, the volatile memory 70, the buffer memory 80, the nonvolatile memory 90, and the host system 100. Further, the system controller 130 may also have an SPM control section 21, a VCM control section 22, a write signal control section 31, and a read signal detection section 32. In addition, the system controller 130 may also include a driver IC20 and a head amplifier IC 30.

The R/W channel 40 executes signal processing of read data transferred from the disk DK to the host 100 and write data transferred from the host 100 in accordance with an instruction from an MPU60 described later. The R/W channel 40 has a circuit or function of measuring the signal quality of read data. The R/W channel 40 is electrically connected to, for example, a head amplifier IC30, HDC60, and MPU 60.

The HDC50 controls data transfer between the host 100 and the R/W channel 40 in accordance with an instruction from an MPU60 described later. The HDC50 is electrically connected to the R/W channel 40, MPU60, volatile memory 70, buffer memory 80, and nonvolatile memory 90, for example.

The MPU60 is a main controller that controls each unit of the magnetic disk apparatus 1 in accordance with instructions from the host 100 and the like. The MPU60 controls the actuator AC via the driver IC20, and executes servo control of positioning of the head HD. The MPU60 controls the write operation for writing data to the disk DK, and selects a storage destination of the write data. Further, the MPU60 controls the reading operation of reading data from the disk DK, and also controls the processing of reading data. The MPU60 is connected to each unit of the magnetic disk device 1. The MPU60 is electrically connected to, for example, the driver IC20, the R/W channel 40, and the HDC 50.

The MPU60 includes a seek control unit 61, a limit current calculation unit 62, and a speed control unit 63. The MPU60 executes the processing of these units, for example, the seek control unit 61, the limit current calculation unit 62, and the speed control unit 63 on firmware. The MPU60 may also include these components as a circuit. A part of the structure of the MPU60 may be provided in the HDC 50. For example, the seek control unit 61, the limit current calculation unit 62, and the speed control unit 63 may be provided in the HDC 50. The MPU60 may also include the structure and/or function of the HDC 50.

The seek control section 61 controls the seek of the head HD from a predetermined radial position (hereinafter, also referred to as a start position) of the disc DK to a target radial position (hereinafter, referred to as a target position or a target radial position) of the disc DK in accordance with an instruction from the host 100 or the like. The seek control unit 61 controls the speed of the head HD (hereinafter, also referred to as a head speed) during a seek period from the start position to the target position (hereinafter, simply referred to as a seek period). The seek control unit 61 controls the head speed from the start position during the seek, completes the control of the head speed in the vicinity of the target position, and switches from the control of the head speed to the control of the head rest (settling). For example, during the seek, the seek control unit 61 accelerates the speed of the head HD in a predetermined radial direction section (hereinafter, also referred to as an acceleration section) or a predetermined period (hereinafter, also referred to as an acceleration period), moves the head HD at a constant speed in a predetermined section (hereinafter, also referred to as a constant speed section) or period (hereinafter, also referred to as a constant speed period) next to the acceleration section, decelerates the head HD in a predetermined section (hereinafter, also referred to as a deceleration section) or period (hereinafter, also referred to as a deceleration period) next to the constant speed section, and positions the head HD at the target position by settling in a predetermined section (hereinafter, also referred to as a settling section) or period (hereinafter, also referred to as a settling period) next to the deceleration section. In other words, the seek control section 61 switches the control mode of the head speed during the seek. The seek control unit 61 switches between an acceleration mode for accelerating the head HD, a constant speed mode for moving the head HD at a constant speed, a deceleration mode for decelerating the head HD, and a settling mode for settling the head HD during a seek. In addition, a state in which the acceleration mode is being executed may be referred to as acceleration, a state in which the constant speed mode is being executed may be referred to as constant speed, a state in which the deceleration mode is being executed may be referred to as deceleration, and a state in which the settling mode is being executed may be referred to as settling. The seek control unit 61 may accelerate the head HD during the acceleration interval or the acceleration period during the seek period, decelerate the head HD during a deceleration interval following the acceleration interval or an acceleration period following the acceleration period, and settle the head HD at the target position during a settling interval following the acceleration interval or a settling period following the acceleration period.

The limit current calculation unit (limit voltage calculation unit) 62 calculates a current value (voltage value) to be applied to VCM 14. Hereinafter, the "current value or voltage value applied to VCM 14" may be simply referred to as "current value or voltage value". The limit current calculation unit (limit voltage calculation unit) 62 detects a current value (hereinafter referred to as a saturation current value) or a voltage value (hereinafter referred to as a saturation voltage value) when the saturation of the head HD is accelerated, and calculates (or estimates) a current value of a limit where the current or the voltage is not saturated (hereinafter referred to as a limit current value) or a voltage value of a limit where the current or the voltage is not saturated (hereinafter referred to as a limit voltage value) based on the saturation current value or the saturation voltage value. The limit current value (or limit voltage value) is a value that is smaller than the saturation current value (or saturation voltage value) and is close to the saturation current value (saturation voltage value). During acceleration, the limit current calculation unit 62 saturatively accelerates the head HD in a predetermined section (hereinafter, also referred to as a saturated acceleration section) or a predetermined period (hereinafter, also referred to as a saturated acceleration period), detects (or estimates) a saturated current value, and calculates the limit current value based on the saturated current value. Limit current calculation unit 62 can estimate the resistance value of VCM14 (hereinafter, also referred to as VCM resistance value or VCM resistance estimated value) based on the head speed when the saturation current value and the saturation current value are applied to VCM 14. The limit current calculation unit 62 can estimate the coil temperature of the VCM14 (hereinafter, also simply referred to as coil temperature) based on the VCM resistance value. Limit current calculating unit 62 may detect a current value or a voltage value.

The velocity control section 63 controls the head velocity via the VCM 14. In other words, the velocity control section 63 controls the head velocity by the current value (or voltage value) applied to the VCM 14. The speed control unit 63 may control the head speed by controlling the current value (or voltage value) applied to the VCM14 in accordance with the VCM resistance value and/or the coil temperature. The speed control unit 63 controls the head speed according to the set speed condition of the head HD, for example, a change in the target head speed with respect to the remaining distance to the target radial position (hereinafter referred to as a target speed profile). Hereinafter, the "target head speed" may be referred to as a "target speed". The speed control unit 63 controls the head speed according to a target speed profile (hereinafter, also referred to as a nominal speed profile) set based on a design nominal value, for example, a current value (hereinafter, referred to as a nominal current value) or a voltage value (hereinafter, referred to as a nominal voltage) set in the design, an environment temperature (hereinafter, referred to as a nominal environment temperature) set in the design, a coil temperature (hereinafter, referred to as a nominal coil temperature) set in the design, and the like.

The speed control unit 63 changes the speed condition during deceleration and controls the head speed according to the speed condition changed during deceleration. The speed control unit 63 increases the head speed at the time of deceleration and/or the current value (or the voltage value) at the time of deceleration, based on the limit current value (or the limit voltage value) calculated at the time of acceleration, as compared with the head speed at the time of deceleration and/or the current value (or the voltage value) at the time of deceleration set based on a design nominal value at the time of deceleration, for example, a nominal current value (or a nominal voltage) at the time of deceleration, a nominal ambient temperature at the time of deceleration, a nominal coil temperature at the time of deceleration, and the like. In other words, the speed control unit 63 increases the head speed at the time of deceleration and/or the current value (or the voltage value) at the time of deceleration based on the saturation current value (or the saturation voltage value) detected at the time of acceleration, as compared with the head speed at the time of deceleration and/or the current value (or the voltage value) at the time of deceleration set according to the design nominal value at the time of deceleration. Based on the limit current value (or the limit voltage value), the speed control unit 63 changes the target speed profile (hereinafter referred to as the target deceleration profile) set based on the design nominal value at the time of deceleration and serving as the reference at the time of deceleration to the target deceleration profile (hereinafter referred to as the limit deceleration profile) when the limit current value is applied to the CM 14. When the limit deceleration curve is changed from the target deceleration curve, the speed control unit 63 corrects the limit deceleration curve so that the state when the deceleration mode in the limit deceleration curve is switched to the settling mode matches the state before the change. For example, when the limit deceleration curve is changed from the target deceleration curve, the speed control unit 63 corrects the limit deceleration curve so that the radial position at which the deceleration pattern in the limit deceleration curve is switched to the settling pattern (hereinafter referred to as a settling pattern switching position) coincides with the settling pattern switching position in the target deceleration curve, and so that the acceleration of the head HD of the limit deceleration curve at the settling pattern switching position (hereinafter sometimes also referred to as a head acceleration) coincides with the head acceleration of the target deceleration curve at the settling pattern switching position, and controls the head speed according to the corrected limit deceleration curve. Hereinafter, the "head acceleration of the target deceleration curve at the settling mode switching position" may be referred to as a "settling mode switching acceleration". The position of the rest mode switching position corresponds to the boundary between the deceleration section and the rest section, and corresponds to the end of the deceleration section or the deceleration period. Further, based on the saturation current value, the speed control unit 63 may change the target deceleration curve set based on the design nominal value at the time of deceleration to the target deceleration curve in the case where the saturation current value is applied to the VCM14 (hereinafter, also referred to as the saturation deceleration curve), correct the limit deceleration curve so that the settling mode switching state coincides with the limit deceleration curve, and control the head speed according to the corrected saturation deceleration curve.

For example, the speed control unit 63 calculates a limit deceleration curve by multiplying the target deceleration curve by a coefficient x calculated based on a margin of a current value (or a voltage value) applied to the VCM14 at the time of acceleration (hereinafter, simply referred to as a current margin or a voltage margin) calculated from the limit current value. For example, the speed control unit 63 calculates a coefficient x (√ (limit current value/nominal current value)) corresponding to the square root of the ratio between the limit current value and the reference nominal current value based on the current margin, and multiplies the target deceleration curve by the coefficient x to calculate a limit deceleration curve. The nominal current value is, for example, smaller than the limit current value. The speed control unit 63 may calculate a coefficient x (limit voltage value/nominal voltage value at the time of acceleration) corresponding to the square root of the ratio between the limit voltage value and the nominal voltage value at the time of acceleration from the voltage margin, and multiply the target deceleration curve by the coefficient x to calculate a limit deceleration curve. The nominal voltage value is, for example, smaller than the limit voltage value. Since the target deceleration curve represents the change in the target speed with respect to the remaining distance, when this is multiplied by a coefficient x, the change in the remaining distance at each time and the change in the target speed at each time are x times, and therefore the acceleration, that is, the change in speed at each time is approximately x ^2 times. The speed control unit 63 detects a head speed (hereinafter referred to as a corresponding speed) and a head position (hereinafter referred to as a corresponding position) in a limit deceleration curve corresponding to the settling mode switching acceleration (the inclination of the target deceleration curve at the settling mode switching position), and calculates a target deceleration curve (hereinafter referred to as a corrected deceleration curve) obtained by correcting the limit deceleration curve based on a difference between the head speed (hereinafter also referred to as the settling mode switching speed) and the corresponding speed (hereinafter referred to as a speed correction value) corresponding to the settling mode switching position in the target deceleration curve and a difference between the settling mode switching position and the corresponding position (hereinafter referred to as a position correction value). The speed control unit 63 controls the head speed according to the corrected deceleration profile during deceleration.

For example, the speed control unit 63 calculates a corrected deceleration curve by the following equation (1).

Vref＿cr＝f(p+(p2－p1))×x+(v2－v1)···(1)

Here, Vref _ cr is a corrected deceleration curve, x is a coefficient for multiplying to the target deceleration curve to calculate the limit deceleration curve, f (p) is the target deceleration curve, p1 is the settling mode switching position, p2 is the inclination f '(p 2) × x of the limit deceleration curve that is the same as the inclination (settling mode switching acceleration) f' (p1) of the target deceleration curve at p1, that is, the corresponding position corresponding to f '(p 2) × ═ f' (p1), v1 is the value of the target deceleration curve f (p1) in the case of p ═ p1, that is, the settling mode switching speed, and v2 is the value of the limit deceleration curve f (p2) × x in the case of p ═ p2, that is the corresponding speed. Further, f' (p) is a derivative function of f (p). In other words, f' (p) corresponds to the first differential of f (p).

Fig. 3 is a diagram showing an example of a target speed curve according to the embodiment. In fig. 3, the horizontal axis represents the radial position, and the vertical axis represents the head speed. On the horizontal axis of fig. 3, the direction from the origin (0) to the positive arrow direction increases and the direction to the positive value decreases, and the direction from the origin (0) to the negative arrow direction decreases and the direction to the negative value increases. On the horizontal axis of fig. 3, the origin (0) corresponds to the target position in the seek. On the vertical axis of fig. 3, the direction from the origin (0) to the positive arrow direction increases and the direction from the origin to the negative arrow direction decreases. Fig. 3 shows a target deceleration curve L1, a limit deceleration curve L2, and a corrected deceleration curve L3.

In the example shown in fig. 3, the speed controller 63 multiplies the target deceleration profile L1 by a coefficient x to calculate a limit deceleration profile L2, and corrects the limit deceleration profile L2 to a corrected deceleration profile L3. The speed control unit 63 controls the speed of the head HD in accordance with the radial position in accordance with the corrected deceleration curve L3 during deceleration.

Fig. 4 is an enlarged view showing an example of the settling mode switching position D1 of the target speed curve shown in fig. 3, and fig. 5 is a view showing an example of a change in the head acceleration with respect to the radial position corresponding to the target speed curve shown in fig. 4. Changes in head acceleration with respect to radial position AL1, AL2, and AL3 are shown in fig. 5. The change AL1 in head acceleration shown in fig. 5 corresponds to the target deceleration curve L1 shown in fig. 4, the change AL2 in head acceleration shown in fig. 5 corresponds to the limit deceleration curve L2 shown in fig. 4, and the change AL3 in head acceleration shown in fig. 5 corresponds to the corrected deceleration curve L3 shown in fig. 4.

In fig. 4 and 5, the horizontal axis represents the radial position. On the horizontal axes of fig. 4 and 5, the direction from the origin (0) to the positive arrow direction increases and the direction from the origin to the negative arrow direction decreases. On the horizontal axes of fig. 4 and 5, the origin (0) corresponds to the target position in the seek. On the horizontal axes of fig. 4 and 5, the radial position D1 corresponds to the above-described settling mode switching position p1, and the radial position D2 corresponds to a corresponding position corresponding to the inclination (acceleration) of the limit deceleration curve that is the same as the inclination (settling mode switching acceleration) of the target deceleration curve L1 at the above-described settling mode switching position p 1. In addition, on the horizontal axis of fig. 4, the radial position D3 is a predetermined radial position that is farther from the target position than the radial positions D1 and D2.

In fig. 4, the vertical axis represents the head speed. On the vertical axis of fig. 4, the direction from the origin (0) to the positive arrow direction increases and the direction from the origin to the negative arrow direction decreases. The vertical axis of fig. 4 shows a head speed (a settling mode switching speed) VEL1 of the target deceleration curve L1 corresponding to the radial position (a settling mode switching position) D1, a head speed (a corresponding speed) VEL2 of the limit deceleration curve L2 corresponding to the radial position (a corresponding position) D2, a head speed VEL3 of the target deceleration curve L1 corresponding to the radial position D3, and a head speed VEL4 of the corrected deceleration curve L3 corresponding to the radial position D3.

In fig. 5, the vertical axis represents the head acceleration. The values on the vertical axis of fig. 5 correspond to 1 differentiation of the values on the vertical axis of fig. 4. On the vertical axis of fig. 5, the direction from the origin (0) to the positive arrow direction increases and the direction from the origin to the negative arrow direction decreases. The vertical axis of fig. 5 shows a head acceleration (a settling mode switching acceleration) ACC1 of a change AL1 in head acceleration corresponding to a radial position (a settling mode switching position) D1, a head acceleration ACC2 of a change AL2 in head acceleration corresponding to a radial position D2, and a head acceleration ACC3 of a change AL3 in head acceleration corresponding to a radial position D1. In fig. 5, the head acceleration (the stoning mode switching acceleration) ACC1 coincides with the head acceleration ACC 3.

For example, the speed control unit 63 calculates a coefficient x corresponding to the square root of the ratio of the nominal current value to the limit current value at the time of acceleration based on the current margin at the time of acceleration calculated from the limit current value, and multiplies the target deceleration curve L1 by the coefficient x to calculate a limit deceleration curve L2 as shown in fig. 4. The speed controller 63 detects the corresponding speed VEL2 of the limit deceleration curve L2 corresponding to the head acceleration ACC2 of the head acceleration change AL2, which is the same as the stay-mode switching acceleration ACC1 of the stay-mode switching position D1 in the target deceleration curve L1, and the corresponding position D2 corresponding to the head acceleration ACC 2. Speed control unit 63 corrects limit deceleration profile L2 to corrected deceleration profile L3 based on position correction value DD corresponding to the difference between the settling mode switching position D1 and corresponding position D2 and speed correction value DVL corresponding to the difference between settling mode switching speed VEL1 and head speed VEL 2. In other words, speed controller 63 calculates corrected deceleration curve L3 by moving limit speed curve L2 based on position correction value DD and speed correction value DVL such that corresponding speed VEL2 at corresponding position D2 of limit speed curve L2 matches with settling mode switching speed VEL1 at settling mode switching position D1 of target deceleration curve L1. At this time, the head acceleration ACC3 of the change AL3 in head acceleration corresponding to the stay mode switching position D1 coincides with the stay mode switching acceleration ACC1 corresponding to the stay mode switching position D1. For example, the corrected deceleration curve L3 is expressed by the above equation (1) as follows.

L3＝f(p+(D2－D1))×x+(VEL2－VEL1)···(2)

The speed control unit 63 controls the head speed in accordance with the corrected deceleration curve L3 during deceleration.

In the example shown in fig. 4, the head speed VEL4 at the radial position D3 of the corrected deceleration curve L3 is greater than the head speed VEL3 at the radial position D3 of the target deceleration curve L1. As described above, the corrected deceleration curve L3 and the target deceleration curve L1 match at the resettable mode switching position D1. By controlling the head speed in accordance with the corrected deceleration curve L3 as shown in fig. 4, the current value applied to VCM14 can be maximized, and the settling can be stabilized while increasing the head speed at the time of deceleration. For example, when the head speed is controlled in accordance with the target deceleration curve L1, the speed control unit 63 can apply a current value of about 7 to the VCM14 up to the nominal current value at the time of deceleration, but when the head speed is controlled in accordance with the corrected deceleration curve L3, a current value of about 9 to the nominal current value at the time of deceleration can be applied to the VCM 14.

Fig. 6 is a diagram showing an example of currents flowing through each VCM when the seek operation according to the present embodiment is performed. Fig. 7 is a diagram showing an example of the head velocity flowing through each VCM when the seek operation according to the present embodiment is performed. Fig. 8 is a diagram showing an example of the head position flowing through the VCM during the seek operation according to the present embodiment. In fig. 6 to 8, the horizontal axis represents time. On the horizontal axis of fig. 6 to 8, time elapses as the arrow moves toward the front end. In fig. 6, the vertical axis represents a current applied to VCM14 during a seek of head 15 (hereinafter, also referred to as a seek current). On the vertical axis of fig. 6, the seek current increases in the direction of a positive value as it goes from the origin (0) to the positive arrow direction, and decreases in the direction of a negative value as it goes from the origin (0) to the negative arrow direction. Fig. 6 shows a change CCL of the seek current when deceleration control is performed based on the corrected deceleration curve, for example, the corrected deceleration curve L3 of fig. 3 and 4, and a change TCL of the seek current when deceleration control is performed based on the target deceleration curve, for example, the target deceleration curve L1 of fig. 3 and 4. In fig. 7, the vertical axis represents the head speed during a seek of the head 15. On the vertical axis of fig. 7, the head speed increases in the positive direction as going from the origin (0) to the positive arrow direction, and decreases in the negative direction as going from the origin (0) to the negative arrow direction. Fig. 7 shows a change CVL of the head speed when deceleration control is performed based on the corrected deceleration curve, for example, the corrected deceleration curve L3 of fig. 3 and 4, and a change TVL of the head speed when deceleration control is performed based on the target deceleration curve, for example, the target deceleration curve L1 of fig. 3 and 4. In fig. 8, the vertical axis represents the head position during a seek of the head 15. On the vertical axis of fig. 8, the head position increases in the positive direction as going from the origin (0) to the positive arrow direction, and decreases in the negative direction as going from the origin (0) to the negative arrow direction. Fig. 8 shows a change CPL of the head position when deceleration control is performed based on the corrected deceleration curve, for example, the corrected deceleration curve L3 of fig. 3 and 4, and a change TVL of the head position when deceleration control is performed based on the target deceleration curve, for example, the target deceleration curve L1 of fig. 3 and 4. On the vertical axis of fig. 8, the origin (0) corresponds to the target position.

As shown in fig. 6, the seek current at the time of deceleration of the change CCL of the seek current is larger than the seek current at the time of deceleration corresponding to the arrow tip side of the horizontal axis in the change TCL of the seek current. In other words, by performing the deceleration control based on the corrected deceleration curve, the seek current at the time of deceleration increases as compared with the case where the deceleration control is performed based on the target deceleration curve.

As shown in fig. 7, by performing the deceleration control based on the corrected deceleration profile, the change in the head speed at the time of deceleration of the change in the head speed CVL is more rapid than the seek current at the time of deceleration of the change in the head speed TVL, as compared with the case of performing the deceleration control based on the target deceleration profile. In other words, by performing the deceleration control based on the corrected deceleration curve, the change in the head speed is abrupt as compared with the case where the deceleration control is performed based on the target deceleration curve.

As shown in fig. 8, the head position at the time of deceleration of the change in head position CPL reaches the target position more quickly than the seek current at the time of deceleration of the change in head position TPL. In other words, by performing the deceleration control based on the corrected deceleration curve, the seek time is shortened as compared with the case where the deceleration control is performed based on the target deceleration curve.

Fig. 9 is a block diagram showing an example of a control system SY for the seek processing of the head HD according to the present embodiment.

The magnetic disk apparatus 1 has a seek control system SY that performs a seek process of the head HD. The seek control system SY includes a target speed generator S1, a position Feedback (FB) controller S2, a speed Feedback (FB) controller S3, a mode switcher S4, an acceleration controller S5, a VCMS6, a state estimator S7, a limit current estimator S8, and calculators C1, C2, and C3.

The target speed generator S1 generates a target speed of the head HD. The position feedback controller S2 performs feedback control associated with the position (e.g., radius position) of the head HD. The velocity feedback controller S3 performs feedback control associated with the velocity of the head HD. The mode switch S4 switches the seek mode of the head HD, for example, an acceleration mode for accelerating the head HD, a constant speed mode for moving the head HD at a constant speed, a deceleration mode for decelerating the head HD, a settling mode for settling, and the like. The acceleration controller S5 controls the acceleration of the head HD. VCM S6 corresponds to VCM14 described above. The state estimator S7 is a state observer with plant models and/or internal state variables. The state estimator S7 estimates the position (e.g., radial position) of the next head HD. Limit current estimating unit S8 estimates (or calculates) a limit current value based on the saturation limit current and the like.

In the seek control system SY, the target position and the estimated speed are input to the arithmetic unit C1. The arithmetic unit C1 inputs outputs based on the target position and the estimated speed to the target speed generator S1, the position feedback controller S2, and the mode switch S4. The target speed generator S1 inputs an output (target speed) based on the target position, the estimated speed, and the output (limit current value) from the limit current estimating unit to the arithmetic unit C2. The arithmetic unit C2 inputs an output based on the output from the target speed generator S1 and the estimated position to the speed feedback controller S3 and the mode switch S4. The position feedback controller S2 inputs an output based on the target position to the mode switcher S4. The speed feedback controller S3 inputs an output based on the output from the operator C2 to the mode switch S4. In addition, in the seek control system SY, an elapsed time from the start of the seek of the head HD (hereinafter, simply referred to as an elapsed time) is input to the mode switch S4 and the acceleration controller S5. The accelerator controller S5 inputs an output based on the elapsed time and the output from the limit current estimating section S8 to the mode switch S4. The mode switch S4 performs mode switching, for example, switching of an acceleration mode, a constant speed mode, a deceleration mode, and a settling mode, based on the target position, the elapsed time, the output from the target speed generator S1, the output from the position feedback controller S2, the output from the speed feedback controller S3, and the output from the acceleration controller S5, and inputs a control signal for executing the switched mode to the VCM S6, the state estimator S7, and the limit current estimator S8. The VCM S6 is driven based on a control signal from the mode switch S4 to move the head HD to the observation position, and an output (observation position) based on the driving amount is input to the arithmetic unit C3. The operator C3 inputs to the state estimator S7 outputs based on the output (observed position) from the VCM S6 and the output (estimated position) from the state estimator S7. The state estimator S7 calculates an estimated acceleration, an estimated velocity, and an estimated position based on the control signal from the mode switch S4 and the output from the operator C3, inputs the estimated position to the operator C2, the operator C3, and the position feedback controller S2, inputs the estimated velocity to the operator C1, and inputs the estimated acceleration to the limit current estimator S8. The limit current estimating unit S8 estimates a limit current value based on the control signal from the mode switch S4 and the estimated acceleration from the state estimator S7, and inputs the limit current value to the target speed generator S1 and the acceleration controller S5.

Fig. 10 is a flowchart showing an example of each sampling process at the time of acceleration according to the present embodiment.

The MPU60 calculates the head position (B1001), estimates the head velocity and the head acceleration (B1002), and detects the saturated acceleration section (B1003). The MPU60 determines a current instruction value to be applied to the VCM14 to perform saturation acceleration (B1004), and applies the determined current instruction value to the VCM14 (B1005). The MPU60 estimates the next sampling state (B1006), updates the mode switching condition, for example, the settling mode switching condition (B1007), determines whether or not to execute the mode switching (B1008), and ends the processing.

Fig. 11 is a flowchart showing an example of the process of updating the mode switching condition according to the present embodiment. Fig. 11 corresponds to the process of updating the mode switching condition in B1007 in fig. 10.

The MPU60 updates the equivalent current force constant and the VCM resistance estimation value (B1101), and determines whether or not the equivalent current force constant and the VCM resistance estimation value have changed from the previous sampling (B1102). If it is determined that there is no change (B1102: no), the MPU60 ends the process. If it is determined that the change has occurred (B1102: yes), the MPU60 calculates a coefficient x (B1103). The MPU60 calculates a corresponding position p2(B1104) that satisfies f '(p 2) × ═ f' (p 1). The MPU60 calculates a limit deceleration curve by multiplying the target deceleration curve Vref by a coefficient x, for example, and detects the settling mode switching position p1 and the settling mode switching speed v1 corresponding to the settling mode switching position p 1. The MPU60 calculates the corresponding speed v2 ═ f (p2) based on the corresponding position p 2. The MPU60 corrects the target deceleration curve Vref to a corrected deceleration curve based on the coefficient x, the settling mode switching position p1, the settling mode switching speed v1, the corresponding position p2, and the corresponding speed v2 (B1105), updates the settling mode switching condition based on the corrected deceleration curve (B1106), and ends the process.

According to the present embodiment, the magnetic disk apparatus 1 accelerates the head HD in saturation during acceleration, detects the saturation current value, and calculates the limit current value based on the saturation current value. The magnetic disk apparatus 1 calculates a target deceleration curve based on a design nominal value at the time of deceleration, and multiplies the target deceleration curve by a coefficient x calculated based on a current margin at the time of acceleration calculated from a limit current value to calculate a limit deceleration curve. When the limit deceleration curve is changed from the target deceleration curve, the magnetic disk device 1 detects the corresponding position and the corresponding speed of the limit deceleration curve corresponding to the settling switching acceleration, and corrects the limit deceleration curve into a corrected deceleration curve based on the position correction value and the speed correction value. By decelerating the head speed according to the corrected deceleration curve during deceleration and performing the settling, the magnetic disk apparatus 1 can increase the current value applied to the VCM14 during deceleration, and can stabilize the settling while increasing the head speed during deceleration. Therefore, the magnetic disk apparatus 1 can shorten the seek time. Therefore, the magnetic disk apparatus 1 can improve the access performance.

Although several embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. 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 invention. These embodiments and modifications thereof are included in the scope and spirit of the invention, and are included in the invention described in the claims and the equivalent scope thereof.