Disk device

Abstract

To provide a disk device that reduces power consumption.SOLUTION: According to an embodiment, in a disk device, if there is a rotational latency, a controller increases an absolute value of a motor current in a first segment during a first period, changes the absolute value of the motor current in a second segment later than the first segment at a first average rate of change, decreases the absolute value of the motor current in a third segment later than the second segment at a second average rate of change, and decreases the absolute value of the motor current in a fourth segment later than the third segment at a third average rate of change. If there is no rotational latency, the controller increases the absolute value of the motor current in a fifth segment in a second period, changes the absolute value of the motor current in a sixth segment later than the fifth segment at a fourth average rate of change, and decreases the absolute value of the motor current in a seventh segment later than the sixth segment at a fifth average rate of change. The second period is a period in which the head is accelerated or decelerated. The fifth average rate of change is steeper than the fourth average rate of change.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present embodiment relates to a disk device. [Background technology]

[0002] A disk device having a motor realizes a predetermined control operation by supplying driving power to the motor, and it is desirable to reduce the power consumption of the disk device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,038,096 [Patent Document 2] U.S. Patent No. 9,275,667 [Patent Document 3] U.S. Patent No. 7,110,214 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment is to provide a disk device capable of reducing power consumption. [Means for solving the problem]

[0005] According to one embodiment, a disk device is provided that includes a head, a disk, a motor, and a controller. The disk has a recording surface. The motor seeks the head along the recording surface. When there is a rotational latency, the controller increases the absolute value of the motor current in a first section of the first period, changes the absolute value of the motor current at a first average rate of change in a second section after the first section of the first period, decreases the absolute value of the motor current at a second average rate of change in a third section after the second section of the first period, and decreases the absolute value of the motor current at a third average rate of change in a fourth section after the third section of the first period. The rotational latency is a time from when the head reaches a target track on the disk to when it reaches a target sector. The first period is a period during which the head is accelerated or decelerated. The second average rate of change is steeper than the first average rate of change. The third average rate of change is steeper than the second average rate of change. When there is no rotational latency, the controller increases the absolute value of the motor current in a fifth section of the second period, changes the absolute value of the motor current at a fourth average rate of change in a sixth section after the fifth section of the second period, and decreases the absolute value of the motor current at a fifth average rate of change in a seventh section after the sixth section of the second period. The second period is a period in which the head is accelerated or decelerated. The fifth average rate of change is steeper than the fourth average rate of change. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing the configuration of a disk device according to an embodiment. [Diagram 2] 4A to 4C are diagrams showing a seek operation in the embodiment. [Diagram 3] 4A and 4B are diagrams showing definitions of a seek period and each section thereof according to an embodiment. [Figure 4] FIG. 2 is a diagram showing an equivalent circuit of a VCM in the embodiment. [Diagram 5] FIG. 4 is a diagram showing a VCM current waveform when there is no rotational latency in the embodiment. [Figure 6] FIG. 4 is a diagram showing a VCM current waveform when there is a rotational latency in the embodiment. [Figure 7]FIG. 4 is a diagram showing a VCM current waveform when there is a rotational latency in the embodiment. [Figure 8] FIG. 11 is a diagram showing a VCM current waveform when there is a rotational latency time in the first modified example of the embodiment. [Figure 9] FIG. 13 is a diagram showing a VCM current waveform when there is a rotational latency time in a second modified example of the embodiment. [Figure 10] FIG. 13 is a diagram showing the functional configuration of a JIT seek control unit in a third modified example of the embodiment. [Figure 11] FIG. 13 is a diagram showing the functional configuration of a servo control unit in a third modified example of the embodiment. [Figure 12] FIG. 13 is a diagram showing the functional configuration of a JIT seek control unit in a fourth modified example of the embodiment. [Figure 13] FIG. 13 is a diagram showing the configuration of a servo control unit in a fourth modified example of the embodiment. [Figure 14] FIG. 13 is a diagram showing the functional configuration of a JIT seek control unit in a fifth modified example of the embodiment. [Figure 15] FIG. 13 is a diagram showing the configuration of a servo control unit in a fifth modified example of the embodiment. [Figure 16] FIG. 13 is a diagram showing the functional configuration of a JIT seek control unit in a sixth modified example of the embodiment. [Figure 17] FIG. 13 is a diagram showing the configuration of a servo control unit in a sixth modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, a disk device according to an embodiment will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiment.

[0008] (Embodiment) The disk device according to the embodiment has a motor, and realizes a predetermined control operation by supplying driving power to the motor, but is devised to reduce the power consumption of the disk device.

[0009] 1, the disk device 1 includes a head disk assembly (HDA) 10, a motor driver 20, a head amplifier 30, a controller 3, a volatile memory 70, a buffer memory 80, and a non-volatile memory 90. Fig. 1 is a diagram showing the configuration of the disk device 1. The controller 3 includes a read / write channel (RWC) 40, a microprocessor unit (MPU) 50, and a hard disk controller (HDC) 60.

[0010] The HDA 10 has a case 10a, a head H, an arm AM, a disk DK, a spindle motor 12, a voice coil motor (VCM) 13, bearings 14, and a housing HS. A lower case HSa and an upper case HSb (not shown) are fitted into the housing HS. The head H, the arm AM, the disk DK, the spindle motor 12, the voice coil motor (VCM) 13, and the bearings 14 are housed within the housing HS.

[0011] The disc DK has a recording surface S on the front and back sides, on which data is recorded. The disc DK is rotated by a spindle motor 12. The disc device 1 is provided with a plurality of discs DK. For simplification, FIG. 1 illustrates a configuration in which one disc DK is provided. Furthermore, a physical address, which is position information indicating a physical position on the recording surface S, is set for all recording surfaces S used in the disc device 1. The spindle motor 12 is driven by a current (or voltage) supplied from a motor driver 20.

[0012] A head H is provided for each recording surface S of the disk DK. The head H has a write head WH and a read head RH. The write head WH is used to write data to the disk DK. The read head RH is used to read data from the disk DK.

[0013] The arms AM support the heads H and are provided for each head H. The VCM 13 is driven by a current (or voltage) supplied from a motor driver 20. The arms AM and VCM 13 constitute an actuator. Driven by the VCM 13, the actuator seeks and moves the arm AM in a circumferential direction around the bearing 14, and controls the positioning of the head H on the recording surface S of the disk DK. The arm AM may further be provided with a microactuator MA that can be driven independently of the VCM 13 via a suspension 15 (see FIG. 2).

[0014] The motor driver 20 controls each moving part of the HDA 10 under the control of the controller 3. The motor driver 20 includes an SPM control unit 201, a VCM control unit 202, and an MA control unit 203.

[0015] The SPM control unit 201 supplies a current (or a voltage) to the spindle motor 12, and drives the spindle motor 12 at a predetermined rotation speed.

[0016] The VCM control unit 202 supplies a current (or voltage) to the VCM 13, drives the actuator, and controls the positioning of the head H along the radial direction of the disk DK.

[0017] The MA control unit 203 supplies a current (or voltage) to the microactuator MA, drives the microactuator MA, and finely adjusts the position of the head H along the radial direction of the disk DK.

[0018] The head amplifier 30 supplies a write signal (current) corresponding to the write data input from the RWC 40 to the head H. In addition, the head amplifier 14 amplifies the read signal (read data read from the disk DK by the head H) output from the head H and supplies it to the RWC 40.

[0019] The RWC 40 is a signal processing circuit. The RWC 40 encodes (code modulates) the write data input from the HDC 60 and outputs the encoded data to the head amplifier 30. The RWC 40 also decodes (code demodulates) the read data from the read signal transmitted from the head amplifier 30 and outputs the read data to the HDC 60.

[0020] The MPU 50 performs overall control of the disk device 1 in accordance with firmware stored in the non-volatile memory 90 or the disk DK. The firmware includes initial firmware that is executed first when the disk device 1 is started up, and control firmware used for normal operation of the disk device 1.

[0021] The controller 3 including the RWC 16, the HDC 60, and the MPU 50 may be configured as a one-chip integrated circuit (system-on-chip). The package of the controller 3 may be disposed on a printed circuit board outside the case of the HDA 10.

[0022] The HDC 60 controls data transmission and reception between the host system 2 and the HDC 60 via the I / F bus. The HDC 60 includes a host interface (host I / F) circuit (not shown). The HDC 60 receives commands from the host system 2, processes the commands, and performs servo control including seek control and tracking control according to the results of the command processing.

[0023] The HDC 60 includes a command processing unit 61 and a servo control unit 64 .

[0024] When the command processing unit 61 receives a write command including a logical address and write data from the host system 2, it processes the write command. The command processing unit 61 converts the logical address included in the write command into a physical address. The command processing unit 61 finds a target track and a target sector according to the logical address. The command processing unit 61 supplies command information including the target track and the target sector to the servo control unit 64. The command processing unit 61 supplies the write data to the head H via the RWC 40 and the head amplifier 30. When the head H completes writing the write data to the target sector, the command processing unit 61 returns a write completion notification to the host system 2.

[0025] When the command processing unit 61 receives a read command including a logical address from the host system 2, it processes the read command. The command processing unit 61 converts the logical address included in the read command into a physical address. The command processing unit 61 finds a target track and a target sector according to the logical address. The command processing unit 61 supplies command information including the target track and the target sector to the servo control unit 64. When the read data is read from the target sector by the head H, the command processing unit 61 returns the read data to the host system 2.

[0026] The command processing unit 61 includes a command queue control unit 611 and a reordering control unit 612 .

[0027] The command queue control unit 611 generates a command queue on the volatile memory 70 or the buffer memory 80. The command queue control unit 611 enqueues a command received from the host system 2 into the command queue. The command queue control unit 611 dequeues the top command in the command queue.

[0028] The reordering control unit 612 performs reordering when a predetermined condition is triggered. For example, the reordering control unit 612 rearranges the commands in the command queue so that commands with closer physical addresses are queued in ascending order.

[0029] The servo control unit 64 includes a seek control unit 62 and a tracking control unit 63 .

[0030] The seek control unit 62 acquires command information including a target track and a target sector from the command processing unit 61. The seek control unit 62 performs seek control to move the head H to the target track according to the command information. For example, the seek control unit 64 acquires servo information from the head H via the head amplifier 30 and the RWC 40, and obtains the current position of the head H according to the servo information. The seek control unit 64 determines the trajectory of the head H to the target track according to the current position of the head H. The seek control unit 64 determines a current instruction value according to the trajectory of the head H and supplies it to the VCM control unit 202 via the MPU 50. The VCM control unit 202 supplies a current (or voltage) to the VCM 13 according to the current instruction value to drive the actuator. This causes the head H to be positioned and controlled along the radial direction of the disk DK.

[0031] The seek control unit 62 can perform fastest seek control or JIT (Just In Time) seek control as the seek control.

[0032] The fastest seek control is a control in which there is no rotational latency. In the fastest seek control, the head H is controlled to move as fast as possible to the target sector of the target track. The fastest seek control can be realized in the shortest time possible from the start of the seek until the head H reaches the target sector of the target track.

[0033] JIT seek control is control when there is a rotational latency. In JIT seek control, the head H is controlled to move to the target sector of the target track by utilizing the rotational latency. In JIT seek control, there is a rotational latency of the disk DK from the start of the seek until the head H reaches the target track and then the target sector.

[0034] The seek control unit 62 includes a fastest seek control unit 621 and a JIT seek control unit 622 .

[0035] The fastest seek control unit 621 performs fastest seek control in response to the command information. The fastest seek control unit 621 controls the input current to the VCM 13 to move the head H from the current position to the position of the target sector of the target track at high speed.

[0036] For example, the motion acceleration data may be stored in advance in the non-volatile memory 90. The motion acceleration data is time-series data of the motion acceleration of the head H that can move at the fastest speed based on the relationship between the movement distance and movement time of the head H during seek control. When a command is received, the fastest seek control unit 621 refers to the motion acceleration data and determines the motion acceleration from the current position of the head H to the position of the target sector of the target track. The fastest seek control unit 621 determines a current instruction value according to the motion acceleration and supplies it to the VCM 13. As a result, the fastest seek control unit 621 executes the fastest seek control.

[0037] Alternatively, the parameters may be stored in advance in the non-volatile memory 90, and the formula for the motion acceleration may be set in the firmware. The formula for the motion acceleration may be a function expression indicating the motion acceleration of the head H that can move at the fastest speed based on the relationship between the movement distance and movement time of the head H during seek control for the parameters. When a command is received, the fastest seek control unit 621 obtains the parameters and applies them to the formula for the motion acceleration to calculate the motion acceleration of the head H. The fastest seek control unit 621 determines a current instruction value according to the motion acceleration and supplies it to the VCM 13. As a result, the fastest seek control unit 621 executes the fastest seek control.

[0038] The seek control unit 62 may receive the command information, estimate the time required to move the head H to the target track at the fastest seek, and determine whether or not a rotational delay of the disk DK will occur based on the estimation result. If a rotational delay will occur, the seek control unit 62 may determine to perform JIT seek control by the JIT seek control unit 622.

[0039] The JIT seek control unit 622 performs JIT seek control in response to the command information. The JIT seek control unit 622 controls the input current to the VCM 13, and moves the head H from the current position to the position of the target sector of the target track by utilizing the rotational latency.

[0040] For example, the motion acceleration data may be stored in the non-volatile memory 90 in advance. The motion acceleration data is time series data of the motion acceleration of the head H that can be moved by utilizing the rotational latency based on the relationship between the movement distance and movement time of the head H during seek control. When the JIT seek control unit 622 receives a command, it refers to the motion acceleration data and determines the motion acceleration from the current position of the head H to the position of the target track so as to utilize the rotational latency. The JIT seek control unit 622 may determine the motion acceleration so that the time from when the head H arrives at the target track until the processing of the target sector is started is greater than 0 and less than a certain threshold value. The JIT seek control unit 622 determines a current instruction value according to the motion acceleration and supplies it to the VCM 13. In this way, the JIT seek control unit 622 executes the JIT seek control.

[0041] Alternatively, the parameters may be stored in the non-volatile memory 90 in advance, and the formula for the motion acceleration may be set in the firmware. The formula for the motion acceleration may be a function expression indicating the motion acceleration of the head H that can be moved by utilizing the rotational latency time based on the relationship between the movement distance and movement time of the head H during seek control for the parameters. When the JIT seek control unit 622 receives a command, it obtains the parameters and applies them to the formula for the motion acceleration to calculate the motion acceleration of the head H. The JIT seek control unit 622 determines a current instruction value according to the motion acceleration and supplies it to the VCM 13. In this way, the JIT seek control unit 622 executes the JIT seek control.

[0042] Alternatively, the current command value data may be stored in advance in the non-volatile memory 90. The current command value data is time-series data of current command values ​​corresponding to the operating acceleration of the head H that can be moved by utilizing the rotational latency based on the relationship between the operating acceleration of the head H during seek control and the current command value. When a command is received, the JIT seek control unit 622 refers to the current command value data, determines a current command value from the current position of the head H to the position of the target track so as to utilize the rotational latency, and supplies the determined value to the VCM 13. In this way, the JIT seek control unit 622 executes JIT seek control.

[0043] Alternatively, the parameters may be stored in advance in the non-volatile memory 90, and the formula for the current command value may be set in the firmware. The formula for the current command value may be a function expression indicating a current command value corresponding to the operating acceleration of the head H that can be moved by utilizing the rotational latency time based on the relationship between the moving distance and moving time of the head H during seek control, for the parameters. When a command is received, the JIT seek control unit 622 obtains the parameters and applies them to the formula for the current command value to calculate the current command value for the head H and supplies it to the VCM 13. In this way, the JIT seek control unit 622 executes the JIT seek control.

[0044] The tracking control unit 63 controls the microactuator MA to cause the head H to perform tracking on the target track.

[0045] The volatile memory 70 is used for temporarily storing data and the like by the controller 3. The volatile memory 70 is, for example, a DRAM (Dynamic RAM) or an SRAM (Static RAM).

[0046] The buffer memory 80 has a write buffer and a read buffer. The write buffer temporarily stores data that is written to the disk DK by a command (e.g., a write command) that instructs writing of write data to the disk DK. The read buffer temporarily stores data that is read from the disk DK by a command (e.g., a read command) that instructs reading of read data from the disk DK.

[0047] The non-volatile memory 90 stores data in a non-volatile manner. The non-volatile memory 90 is, for example, a flash memory. The non-volatile memory 90 may store motion acceleration data, current indication value data, and parameters.

[0048] In the disk device 1, a seek operation is performed as shown in Fig. 2. Fig. 2 is a diagram showing a seek operation.

[0049] The SPM 12 is driven by a motor driver 20 to rotate the disk DK in a circumferential direction DR1. The VCM 13 is driven by a motor driver 20 to rotate the arm AM around a bearing 14 and move the head H supported at the tip of the arm AM in a radial direction DR2. This achieves a seek operation.

[0050] A plurality of tracks TR (for example, tracks TR1 to TR3) are concentrically defined on the disk DK. Each track TR includes a plurality of data sectors. Data can be written to each data sector. In FIG. 2, a plurality of data sectors SC1 and SC2 included in the track TR2 are illustrated as an example.

[0051] The seek control unit 64 may determine whether to perform JIT seek control or maximum speed seek control based on the relationship between the target sector of the disk DK and the current position of the head H.

[0052] For example, if the target track is track TR2, the target sector is data sector SC2, and the current position of head H is a circumferential position between data sectors SC1 and SC2 on track TR1, a rotational latency is expected to occur when seeking from the current track TR1 to the target track TR2. Therefore, the seek control unit 64 may determine to perform JIT seek control that adjusts the seek end time within the rotational latency until just before the target sector.

[0053] Here, the period during which a seek operation is performed is called a seek period, and each section within the seek period is defined in relation to the current waveform of the VCM 13 as shown in Fig. 3. Fig. 3 is a diagram showing the seek period and the definition of each section thereof.

[0054] Chart 6201 shows the current i VCM The chart 6202 shows the differential di of the current of VCM13. VCM The waveform of the current i VCM The direction of the current |i in the seek operation is positive when it accelerates the head H, and negative when it decelerates the head H. VCM Chart 6204 shows the absolute value of the differential of the current of VCM13 |di VCM The waveform of / dt| is shown.

[0055] In each of the charts 6201 to 6204, the horizontal axis indicates time. In the chart 6201, the vertical axis indicates the current i VCM In chart 6202, the vertical axis represents the differential di of the VCM13 current. VCM In the chart 6203, the vertical axis represents the absolute value of the current |i VCM In the chart 6204, the vertical axis represents the absolute value of the differential of the current of VCM13, |di VCMIndicates the magnitude of / dt|.

[0056] In the chart 6201, REF11 and REF12 indicate limit currents. A characteristic CV11 indicates the current i of the VCM13 during the seek period of the JIT seek control. VCM The characteristic CV11 falls within the range defined by the limit currents REF11 and REF12.

[0057] In the chart 6202, the characteristic CV12 is a time series characteristic of the differential value with respect to the characteristic CV11. In the chart 6203, the characteristic CV21 is a time series characteristic of the absolute value |i VCM In the chart 6204, the characteristic CV22 is a time series characteristic of the differential value |di VCM / dt| is a time series property.

[0058] The seek period Ts is the period from the start to the end of a seek operation, and includes an acceleration section Ta, a constant velocity section Tc, and a deceleration section Td.

[0059] In the acceleration section Ta, the controller 3 supplies a positive current i VCM In the constant velocity section Tc, the controller 3 supplies a current i of approximately zero to the VCM 13. VCM In the deceleration section Td, the controller 3 supplies a negative current i VCM is supplied to reduce the radial movement speed of the head H.

[0060] The acceleration section Ta includes a rising section A1, a flat section A2, and a falling section A3. In the rising section A1, the controller 3 controls the current i VCM In the flat section A2, the controller 3 controls the current i VCM In the falling section A3, the controller 3 changes the waveform of the current i of the VCM13 to be approximately flat along the limit current REF11. VCMThe waveform falls from the positive side.

[0061] The constant speed section Tc includes a flat section C1. In the flat section C1, the controller 3 controls the current i VCM Change the waveform to flat.

[0062] The deceleration section Td includes a rising section D1, a flat section D2, and a falling section D3. In the rising section D1, the controller 3 controls the current i VCM In the flat section D2, the controller 3 controls the current i VCM In the falling section D3, the controller 3 changes the waveform of the current i of the VCM13 to be approximately flat along the limit current REF12. VCM The waveform falls from the negative side.

[0063] The limit currents REF11 and REF12 are currents serving as electrical limits determined from the circuit characteristics of VCM13 based on the fact that VCM13 has an equivalent circuit as shown in Fig. 4. Fig. 4 is a diagram showing an equivalent circuit of VCM13.

[0064] The VCM13 outputs the set voltage V set is applied, and the motor driver 20 outputs a current i VCM The circuit 131 receives a set voltage V set The circuit 131 is an equivalent circuit seen from the perspective of a resistor R others and a circuit 1311. The circuit 1311 corresponds to the coil portion of the VCM 13. A resistor R others corresponds to the wiring connected to the coil portion of the VCM 13.

[0065] The circuit 1311 corresponds to an equivalent circuit from the viewpoint of the voltage supplied to the VCM 13. The circuit 1311 includes an inductance L VCM , resistance R VCM , current source I BEMF Includes the series connection of inductance L VCM corresponds to the inductance component of the coil part of the VCM 13. Resistance R VCMcorresponds to the resistance component of the coil part in the VCM 13. Current source I BEMF is the back electromotive force V of the coil in VCM13 BEMF Corresponding to the back electromotive force V BEMF A current according to the

[0066] Since the VCM 13 has the equivalent circuit shown in FIG. 4, the current i VCM can be expressed by the following Equation 1.

number

[0067] In Formula 1, R C is the combined resistance of the circuit 131. VCM is the inductance of the circuit 1311. V set is the set voltage. V BEMF is the back electromotive voltage and can be expressed by the following equation 2.

number

[0068] In Equation 2, v is the radial movement speed of the head H. f is the current force constant. The current i VCM The relationship between and the acceleration a of the head H can be expressed by the following formula 3.

number

[0069] In Equation 3, m is the equivalent mass of the head H.

[0070] In adjusting the current level in the acceleration section Ta, by changing the set voltage Vset in Equation 1 and adjusting the time of the constant velocity section Tc, it is possible to perform seek control for a longer time than the reference seek (for example, the fastest seek).

[0071] In the chart 6201 shown in FIG. 3, the current i VCM occurs according to Equation 1. During the time t2 to t3 (falling section A3), the current i VCM is discharged according to the time constant of the circuit 131 and approaches 0. During the period from time t3 to t4 (flat section C1), the current i VCM is maintained at approximately 0. During the time t4 to t6 (the rising section D1 and the flat section D2), the current i VCM occurs according to a formula corresponding to the reverse polarity of Formula 1. During the time t6 to t7 (falling section D3), the current i VCM is discharge-controlled according to the time constant of the circuit 131 and approaches zero.

[0072] The flat section A2 is also defined as follows. In the acceleration section Ta, the absolute value of the current |i VCM Starting from time t1 when | is at its maximum, the VCM13 current i VCM Before time t4 when the polarity of VCM13 is reversed, the absolute value of the differential of the current |di VCM This is the section whose end point is time t2, when / dt| is at its maximum.

[0073] The flat section D2 is also defined as follows. In the deceleration section Td, the absolute value of the current of the VCM 13 |i VCM Starting from time t5 when | is at its maximum, the VCM13 current i VCM Before time t7 when VCM13 becomes 0, the absolute value of the differential of the current |di VCM This section ends at time t6, when / dt| is at its maximum.

[0074] The supply voltage VCM13 is sup can be expressed by the following Equation 4.

number

[0075] As shown in Equations 1 and 4, the supply voltage V sup is the set voltage Vset Back voltage V BEMF In response, the VCM13 current i VCM is the back electromotive force V BEMF The limit currents REF11 and REF12 shown in Fig. 3 are electrical limits determined by the characteristics of the equivalent circuit of VCM13 (see Fig. 4).

[0076] For example, when there is no rotational latency, the fastest seek control is performed, and the current waveform of the VCM 13 at that time is as shown in Fig. 5. Fig. 5 is a diagram showing the VCM current waveform when there is no rotational latency.

[0077] Chart 6205 shows the current i of VCM13 VCM The chart 6206 shows the differential di of the current of VCM13. VCM A chart 6207 shows a waveform CV33 of the power consumption P of VCM13.

[0078] In each of the charts 6205 to 6207, the horizontal axis indicates time. In the chart 6205, the vertical axis indicates the current i VCM In Chart 6206, the vertical axis represents the differential di of the VCM13 current. VCM In the chart 6207, the vertical axis represents the magnitude of power consumption P of the VCM 13.

[0079] In the fastest seek control, the seek period Ts is from time t10 to t16, and processing TGT for the target sector is possible from time t16 when the seek period Ts ends, as shown in Fig. 5. In this case, there is no rotational latency.

[0080] In the fastest seek control, the constant velocity section Tc may be omitted. The period from time t10 to t13 is the acceleration section Ta, and the period from time t13 to t16 is the deceleration section Td.

[0081] As shown in the waveform CV31, in the acceleration section Ta, saturation acceleration control is performed, and the maximum input current i VCMcan be input to the VCM 13, but it is within the limit current REF31. In the deceleration section Td, in order to suppress the settling of the head H, the current i VCM is not the maximum current that can be input, but is a current that is somewhat restricted i VCM is input to VCM13.

[0082] In the acceleration section Ta, the period from time t10 to t11 is a rising section A1, the period from time t11 to t12 is a flat section A2, and the period from time t12 to t13 is a falling section A3.

[0083] In the rising section A1, the controller 3 controls the current i VCM The controller 3 controls the current i of the VCM 13 according to the formula 1. VCM may be varied.

[0084] In the flat section A2, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF31. VCM is changed at an average rate of change AR1. The average rate of change AR1 is the derivative di VCM The average rate of change AR1 is a value indicating a change along the limit current REF31, and can be a negative value. The controller 3 previously calculates the back electromotive voltage V BEMF In the flat section A2, the controller 3 may replace the current command value with the estimated value of the limit current REF31.

[0085] In the falling section A3, the controller 3 controls the current i VCM The waveform of falls from the positive side to zero at an average rate of change AR2. The average rate of change AR2 is the derivative di VCM / dt over the time of the falling section A3. The average rate of change AR2 is a value that indicates a steeper change than the average rate of change AR1, and is a negative value.

[0086] In the deceleration section Td, the period from time t13 to t14 is a rising section D1, the period from time t14 to t15 is a flat section D2, and the period from time t15 to t16 is a falling section D3.

[0087] In the rising section D1, the controller 3 controls the current i VCM The controller 3 controls the VCM 13 current i VCM may be varied.

[0088] In the flat section D2, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF32. VCM is changed at an average rate of change DR1. The average rate of change DR1 is the derivative di VCM The average rate of change DR1 is a value indicating a change along the limit current REF32 and can be a positive value. BEMF In the flat section D2, the controller 3 may replace the current command value with a value obtained by adding a predetermined value to the estimated value of the limit current REF32.

[0089] In the falling section D3, the controller 3 controls the current i VCM The waveform of falls from the negative side to zero at an average rate of change DR2. The average rate of change DR2 is the derivative di VCM / dt over the time of the falling section D3. The average rate of change DR2 is a positive value that indicates a steeper change than the average rate of change DR1.

[0090] As shown in the waveform CV33, in the acceleration section Ta, the current i VCM As the absolute value of increases, the power consumption P increases, and the current i VCM When the power consumption P reaches the limit current REF31 near t11, Rci VCM 2 Then, the current i VCMThe power consumption decreases as the absolute value of decreases. In the deceleration section Td, the current i VCM As the absolute value of increases, the power consumption increases, and the current i VCM When the power consumption P reaches the limit current REF32 near t14, Rci VCM 2 Then, the current i VCM As the absolute value of decreases, the power consumption decreases.

[0091] When there is a rotational latency ΔW, the first JIT seek control may be performed, and the current waveform of the VCM 13 in the first JIT seek control will be as shown by the dashed line in Fig. 6. Fig. 6 is a diagram showing the VCM current waveform when there is a rotational latency ΔW.

[0092] The first JIT seek control is a control in which a constant speed section Tc is added to the fastest seek control (see FIG. 5).

[0093] In the first JIT seek control, the chart 6208 shows the current i VCM The chart 6209 shows the differential di of the current of VCM13. VCM A chart 6210 shows a waveform CV43 of the power consumption P of the VCM13.

[0094] In each of the charts 6208 to 6210, the horizontal axis indicates time. In the chart 6208, the vertical axis indicates the current i VCM In Chart 6209, the vertical axis represents the differential di of the VCM13 current. VCM In the chart 6210, the vertical axis represents the magnitude of power consumption P of the VCM 13.

[0095] 6, in the first JIT seek control, the seek period Ts is from time t20 to t27, and there is a rotational latency time ΔW from time t27 when the seek period Ts ends to time t28. From time t28, processing TGT for the target sector becomes possible.

[0096] As shown in the waveform CV41, in the acceleration section Ta of the head H from the start of the seek control, the saturation acceleration control is suppressed, and the current i VCM can be input to the VCM 13, but is within the limit current REF41. In the deceleration section Td, the current i VCM The current i is further suppressed than the maximum current that can be input. VCM is input to VCM13.

[0097] In the acceleration section Ta, in the flat section A2, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM 13 along the limit current REF41. VCM is changed at an average rate of change AR11. The average rate of change AR11 is the derivative di VCM / dt can be obtained by averaging over the time of the flat section A2. The average rate of change AR11 becomes a value that indicates a change roughly along the limit current REF41, and can be a negative value.

[0098] In the deceleration section Td, in the flat section D2, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM 13 along the limit current REF42. VCM is changed at an average rate of change DR11. The average rate of change DR11 is the derivative di VCM / dt can be obtained by averaging over the time of the flat section D2. The average rate of change DR11 becomes a value that indicates a change roughly along the limit current REF42, and can be a positive value.

[0099] As shown in the waveform CV43, in the acceleration section Ta, the current i VCM As the absolute value of increases, the power consumption P increases, and the current i VCM Just after time t21 when the power consumption P reaches its peak, Rci VCM 2 Then, the current i VCM The power consumption P decreases as the absolute value of decreases. In the deceleration section Td, the current i VCM As the absolute value of increases, the power consumption P increases, and the current i VCMJust after time t14 when the power consumption P reaches its peak, Rci VCM 2 Then, the current i VCM As the absolute value of decreases, the power consumption P decreases.

[0100] In the first JIT seek control, the end time t27 is determined according to the rotational latency ΔW, and the length of the constant velocity section Tc is adjusted accordingly. In the first JIT seek control, there is a time margin for control, and there is a room to further suppress the saturation acceleration control.

[0101] Therefore, when there is a rotational latency time ΔW, the second JIT seek control may be performed. In the second JIT seek control, the current i VCM In the second JIT seek control, power consumption is reduced compared to the first JIT seek control.

[0102] The current waveform of the VCM 13 in the second JIT seek control is as shown by the solid line in FIG.

[0103] In the second JIT seek control, the chart 6208 shows the current i VCM The chart 6209 shows the differential di of the current of VCM13. VCM A chart 6210 shows a waveform CV53 of the power consumption P of the VCM13.

[0104] As shown in the waveform CV51, from the start of seek control to the acceleration section Ta of the head H, the current i changes flatly on the positive side. VCM can be input to the VCM 13. In the deceleration section Td, the current i VCM can be input to the VCM 13.

[0105] In the acceleration section Ta, in the flat section A2, the controller 3 controls the current i VCM The controller 3 changes the current iVCM is changed at the average rate of change AR21. The average rate of change AR21 is the derivative di VCM The average rate of change AR21 is generally close to zero, and may be substantially zero. The controller 3 controls the current i VCM current threshold i thp The current threshold i thp From time 20, the current i VCM It may be a value that is reached at time t21 when the value of

[0106] In the deceleration section Td, in the flat section D2, the controller 3 controls the current i VCM The controller 3 changes the current i VCM is changed at an average rate of change DR11. The average rate of change DR21 is the derivative di VCM The average rate of change DR21 is generally close to zero, and may be substantially zero. The controller 3 controls the current i VCM current threshold i thn The current threshold i thn From time 24, the current i VCM It may be a value that is reached at time t25 when the value of

[0107] As shown in the waveform CV53, in the acceleration section Ta, the current i VCM As the absolute value of increases, the power consumption P increases, and the current i VCM In the flat section A2, the power consumption P changes flatly, and then the current i VCM The power consumption P decreases as the absolute value of decreases. In the deceleration section Td, the current i VCM As the absolute value of increases, the power consumption P increases, and the current i VCM In the flat section D2 where the power consumption P changes flatly, the current i VCM As the absolute value of decreases, the power consumption P decreases.

[0108] Comparing the fastest seek control with the second JIT seek control, the differential d|i VCM The magnitude of | / dt is different.

[0109] The differential d|i of the absolute value of the current in the flat sections A2 and D2 shown in the waveform CV32 in FIG. VCM In comparison with the magnitude of | / dt, the differential d|i VCM The magnitude of | / dt is closer to zero.

[0110] The VCM13 current during the fastest seek when there is no rotational latency is i VCM_NoRotWait The current of the VCM 13 in the second JIT seek control performed when there is a rotational latency is i VCM_RotWait Then, the following formula 5 holds.

number

[0111] In Equation 5, the left side is the current i VCM_NoRotWait The left side is a negative value or zero. The right side is the current i VCM_RotWait The right-hand side of the equation is a negative value or zero.

[0112] Here, the power consumption P of the circuit 131 shown in FIG.

number

[0113] In Equation 6, Rc is the combined resistance of the circuit 131. As shown in Equation 6, the current i VCM has a square effect on the power consumption P. Therefore, as shown in the waveform CV51, the current i VCMThe average rate of change of the current i is made closer to zero than the waveform CV31 (see Figure 5) and the change is flattened (for example, made constant). VCM By suppressing the absolute value of, it is possible to reduce power consumption.

[0114] Assume that the times of corresponding sections A1, A2, A3, D1, D2, and D3 are equal in Figure 5 and Figure 6. Comparing the waveform CV33 shown in Figure 5 with the waveform CV53 shown in Figure 6, the integrated value of power consumption P of the waveform CV53 is lower than the integrated value of power consumption P of the waveform CV33 in the flat section A2. The integrated value of power consumption P of the waveform CV53 is lower than the integrated value of power consumption P of the waveform CV33 in the flat section D2.

[0115] That is, the second JIT seek control consumes less power than the fastest seek control.

[0116] For example, a 2.5% reduction in power consumption is expected in a seek distance that is 15% of the data area width on the disk DK.

[0117] In addition, the differential d|i of the absolute value of the current in the flat sections A2 and D2 shown in the waveform CV42 shown in FIG. VCM Compared to the magnitude of | / dt, the differential d|i VCM The magnitude of | / dt is closer to zero.

[0118] As shown in Equation 6, the current i VCM has a square effect on the power consumption P. Therefore, as shown in the waveform CV51, the current i VCM The average rate of change of the current i is made closer to zero than that of the waveform CV41, and the change is flattened (for example, made constant). VCM By suppressing the absolute value of, it is possible to reduce power consumption.

[0119] 6, in the flat section A2, the integrated value of power consumption P of the waveform CV53 is lower than the integrated value of power consumption P of the waveform CV43. In the flat section D2, the integrated value of power consumption P of the waveform CV53 is lower than the integrated value of power consumption P of the waveform CV43.

[0120] That is, the second JIT seek control consumes less power than the first JIT seek control.

[0121] The second JIT seek control is different from the first JIT seek control in that the current i VCM A function is added to make the average rate of change of the value closer to zero and flatten (for example, make it constant). This function is called the AFC (AccFlat const) function.

[0122] As described above, the limit currents REF41 and REF42 are electrical limits determined by the characteristics of the equivalent circuit of the VCM 13 (see FIG. 4). VCM If the average rate of change of approaches zero and the change is flattened (e.g., made constant), the current i VCM may exceed the limit currents REF41 and REF42. In this case, even if the AFC function is enabled, the current i VCM In response to the indicated value of REF41, REF42, a current exceeding the limit currents REF41 and REF42 cannot flow electrically in the VCM 13, and this may cause a breakdown in the control of the controller 3. It is difficult for the controller 3 to enable the AFC function without causing a breakdown in control.

[0123] Therefore, when there is a rotational latency time ΔW, the third JIT seek control may be performed. In the third JIT seek control, the current i VCMThe third JIT seek control adjusts the current i so that it falls within the limit currents REF41 and REF42 while flattening (for example, making constant) the indicated value of the current i. In the third JIT seek control, the flat section A2 and / or the flat section D2 are divided into a first flat section that does not exceed the limit currents REF41 and REF42 when the AFC function is enabled, and a second flat section that exceeds the limit currents REF41 and REF42. VCM The instruction value of REF41, REF42 is changed so as to match the limit currents REF41, REF42. As a result, in the third JIT seek control, the AFC function can be enabled within the limit currents REF41, REF42, and low power consumption can be achieved while maintaining access performance.

[0124] The current waveform of the VCM 13 in the third JIT seek control is as shown by the solid line in Fig. 7. Fig. 7 is a diagram showing the VCM current waveform when there is a rotational latency time ΔW. Fig. 7 illustrates, as the third JIT seek control, a control in which the AFC function is enabled in the acceleration section Ta and is not enabled in the deceleration section Td.

[0125] In the third JIT seek control, the chart 6211 shows the current i VCM The chart 6212 shows the differential di of the current of VCM13. VCM / dt waveform CV62 is shown.

[0126] As shown in the waveform CV61, in the acceleration section Ta, the current i VCM changes almost flatly on the positive side, and the current i VCM changes along the limit current REF51. In the deceleration section Td, the current i VCM increases to the negative side until the limit current REF52 is reached, and the current i VCM varies along the limit current REF52.

[0127] The controller 3 divides the flat section A2 (see FIG. 6) into a flat section A21 in which the limit current REF41 is not exceeded on the positive side and a flat section A22 in which the limit current REF41 is exceeded on the positive side when the AFC function is enabled, and in the flat section A22, VCMChange the indicated value to match the limit current REF41.

[0128] In the acceleration section Ta, the period from time t40 to t41 is the rising section A1, the period from time t41 to t42 is the flat section A21, the period from time t42 to t43 is the flat section A22, and the period from time t43 to t44 is the falling section A3.

[0129] In the rising section A1, the controller 3 controls the current i VCM The controller 3 controls the current i of the VCM 13 according to the formula 1. VCM may be varied.

[0130] In the flat section A21, the controller 3 controls the current i VCM The controller 3 changes the current i VCM is changed at the average rate of change AR31. The average rate of change AR31 is the derivative di VCM The average rate of change AR31 is generally close to zero, and may be substantially zero. The controller 3 controls the current i VCM current threshold i thp The current threshold i thp From time 40, the current i VCM It may be a value that is reached at time t41 when the time t2 is changed.

[0131] In the flat section A22, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF51. VCM is changed at the average rate of change AR32. The average rate of change AR32 is the derivative di VCM The average rate of change AR32 is a value indicating a steeper change than the average rate of change AR31, and can be a negative value. The controller 3 previously calculates the back electromotive voltage V BEMFIn the flat section A22, the controller 3 may replace the current command value with the estimated value of the limit current REF51.

[0132] In the falling section A3, the controller 3 controls the current i VCM The waveform of falls from the positive side to zero at an average rate of change AR33. The average rate of change AR33 is the derivative di VCM / dt over the time of the falling section A3. The average rate of change AR33 is a value that indicates a steeper change than the average rate of change AR32, and is a negative value.

[0133] In the deceleration section Td, the period from time t45 to t46 is a rising section D1, the period from time t46 to t47 is a flat section D2, and the period from time t47 to t48 is a falling section D3.

[0134] In the rising section D1, the controller 3 controls the current i VCM The controller 3 controls the VCM 13 current i VCM may be varied.

[0135] In the flat section D2, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF52. VCM is changed at an average rate of change DR31. The average rate of change DR31 is the differential di VCM The average rate of change DR31 is a value indicating a change along the limit current REF52, and can be a positive value. The controller 3 previously calculates the back electromotive voltage V BEMF In the flat section D2, the controller 3 may replace the current command value with a value obtained by adding a predetermined value to the estimated value of the limit current REF52.

[0136] In the falling section D3, the controller 3 controls the current i VCMThe waveform of falls from the negative side to zero at an average rate of change DR32. The average rate of change DR32 is the derivative di VCM / dt over the time of the falling section D3. The average rate of change DR32 is a positive value that indicates a steeper change than the average rate of change DR31.

[0137] In addition, in Fig. 7, for comparison, the current waveform of the VCM 13 in the first JIT seek control is shown by a dashed line. In the first JIT seek control, the chart 6211 shows the current i VCM 6 shows a waveform CV71 of VCM13. Waveform CV71 is similar to waveform CV41 (see FIG. 6). Chart 6212 shows the differential di VCM 6 shows waveform CV72 of / dt, which is similar to waveform CV42 (see FIG. 6).

[0138] The differential d|i of the absolute value of the current in the flat sections A21 and A22 shown in the waveform CV62 shown in FIG. VCM Compared to the magnitude of | / dt, the differential d|i VCM The magnitude of | / dt is closer to zero.

[0139] In response to this, in the third JIT seek control, the absolute value of the current |i VCM | can be suppressed, and power consumption can be reduced.

[0140] As described above, in this embodiment, in the disk device 1, the controller 3 predicts the limit current and makes the current command value of the VCM 13 follow the predicted limit current. VCM The controller 3 adjusts the current i so that it falls within the limit currents REF41 and REF42 while flattening (for example, making it constant) the indicated value of the current i in the case where the AFC function is enabled. The controller 3 divides the flat section A2 into a flat section A21 that does not exceed the limit currents REF41 and REF42 and a flat section A22 that does exceed the limit currents, and adjusts the current i in the flat section A22. VCMThe instruction value of REF41 is changed so as to match the limit currents REF41 and REF42. This enables the AFC function in the disk device 1 within the limit currents REF41 and REF42, thereby enabling low power consumption while maintaining access performance.

[0141] (First Modification of the Embodiment) In the third JIT seek control, the AFC function may be enabled in the deceleration section Td rather than in the acceleration section Ta, as shown by the solid line in Fig. 8. Fig. 8 is a diagram showing a VCM current waveform when there is a rotational latency time ΔW in the first modified example of the embodiment.

[0142] In the third JIT seek control, the chart 6213 shows the current i VCM The chart 6214 shows the differential di of the current of VCM13. VCM / dt waveform CV82 is shown.

[0143] As shown in the waveform CV81, in the acceleration section Ta, the current i VCM increases to the positive side until the limit current REF51 is reached, and the current i VCM changes along the limit current REF61. In the deceleration section Td, the current i VCM changes almost flatly on the negative side, and the current i VCM varies along the limit current REF62.

[0144] In the acceleration section Ta, the period from time t50 to t51 is a rising section A1, the period from time t51 to t52 is a flat section A2, and the period from time t52 to t53 is a falling section A3.

[0145] In the rising section A1, the controller 3 controls the current i VCM The controller 3 controls the current i of the VCM 13 according to the formula 1. VCM may be varied.

[0146] In the flat section A2, the controller 3 controls the current i VCMThe controller 3 changes the current i of the VCM13 along the limit current REF61. VCM is changed at an average rate of change AR41. The average rate of change AR41 is the derivative di VCM The average rate of change AR41 is a value indicating a change along the limit current REF61, and can be a negative value. The controller 3 previously calculates the back electromotive voltage V BEMF In the flat section A2, the controller 3 may replace the current command value with the estimated value of the limit current REF31.

[0147] In the falling section A3, the controller 3 controls the current i VCM The waveform of falls from the positive side to zero at an average rate of change AR42. The average rate of change AR42 is the derivative di VCM / dt can be obtained by averaging it over the time of the falling section A3. The average rate of change AR42 is a value that indicates a steeper change than the average rate of change AR41, and is a negative value.

[0148] The controller 3 divides the flat section D2 (see FIG. 6) into a flat section D21 in which the sum of the limit current REF62 and a predetermined value does not exceed the negative side, and a flat section D22 in which the sum exceeds the negative side, when the AFC function is enabled. VCM Change the indication value to match the limit current REF62.

[0149] In the deceleration section Td, the period from time t54 to t55 is the rising section D1, the period from time t55 to t56 is the flat section D21, the period from time t56 to t57 is the flat section D21, and the period from time t57 to t58 is the falling section D3.

[0150] In the rising section D1, the controller 3 controls the current i VCM The controller 3 controls the VCM 13 current i VCM may be varied.

[0151] In the flat section D21, the controller 3 controls the current i VCM The controller 3 changes the current i VCM is changed at an average rate of change DR41. The average rate of change DR41 is the differential di VCM The average rate of change DR41 is generally close to zero, and may be substantially zero. The controller 3 controls the current i VCM current threshold i thp The current threshold i thp From time 55, the current i VCM It may be a value that is reached at time t55 when the time t is changed.

[0152] In the flat section D22, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF62. VCM is changed at an average rate of change DR42. The average rate of change DR42 is the differential di VCM The average rate of change DR42 is a value indicating a steeper change than the average rate of change DR41, and can be a positive value. BEMF In the flat section D22, the controller 3 may replace the current command value with a value obtained by adding a predetermined value to the estimated value of the limit current REF62.

[0153] In the falling section D3, the controller 3 controls the current i VCM The waveform of falls from the negative side to zero at an average rate of change DR43. The average rate of change DR43 is the derivative di VCM / dt over the time of the falling section D3. The average rate of change DR43 is a positive value that indicates a steeper change than the average rate of change DR42.

[0154] In addition, in Fig. 8, for comparison, the current waveform of the VCM 13 in the first JIT seek control is shown by a dashed line. In the first JIT seek control, the chart 6213 shows the current i VCM The waveform CV91 is similar to the waveform CV41 (see FIG. 6). The chart 6214 shows the differential di of the current of VCM13. VCM 6 shows the waveform CV92 of / dt, which is similar to the waveform CV42 (see FIG. 6).

[0155] The differential d|i of the absolute value of the current in the flat sections D21 and D22 shown in the waveform CV92 shown in FIG. VCM Compared to the magnitude of | / dt, the differential d|i VCM The magnitude of | / dt is closer to zero.

[0156] In response to this, in the third JIT seek control, the absolute value of the current |i VCM | can be suppressed, and power consumption can be reduced.

[0157] In this way, the controller 3 divides the flat section D2 into a flat section D21 in which the sum of the limit current REF42 and a predetermined value does not exceed the negative side, and a flat section D22 in which the sum exceeds the negative side, when the AFC function is enabled. VCM The instruction value of REF61 is changed so as to match the limit current REF62. This enables the AFC function in the disk device 1 within the limit currents REF61 and REF62, thereby enabling low power consumption while maintaining access performance.

[0158] (Second Modification of the Embodiment) In the third JIT seek control, the AFC function may be enabled in both the acceleration section Ta and the deceleration section Td, as shown by the solid line in Fig. 9. Fig. 9 is a diagram showing a VCM current waveform when there is a rotational latency time ΔW in the second modified example of the embodiment.

[0159] In the third JIT seek control, the chart 6215 shows the current i VCM The chart 6216 shows the differential di of the current of VCM13. VCM / dt waveform CV102 is shown.

[0160] As shown in the waveform CV101, in the acceleration section Ta, the current i VCM changes almost flatly on the positive side, and the current i VCM changes along the limit current REF71. In the deceleration section Td, the current i VCM changes almost flatly on the negative side, and the current i VCM varies along the limit current REF72.

[0161] The controller 3 divides the flat section A2 (see FIG. 6) into a flat section A21 in which the limit current REF71 is not exceeded on the positive side and a flat section A22 in which the limit current REF71 is exceeded on the positive side when the AFC function is enabled, and in the flat section A22, VCM Change the indication value to match the limit current REF71.

[0162] In the acceleration section Ta, the period from time t60 to t61 is the rising section A1, the period from time t61 to t62 is the flat section A21, the period from time t62 to t63 is the flat section A22, and the period from time t63 to t64 is the falling section A3.

[0163] In the rising section A1, the controller 3 controls the current i VCM The controller 3 controls the current i of the VCM 13 according to the formula 1. VCM may be varied.

[0164] In the flat section A21, the controller 3 controls the current i VCM The controller 3 changes the current i VCM is changed at the average rate of change AR51. The average rate of change AR51 is the derivative di VCMThe average rate of change AR51 is generally close to zero, and may be substantially zero. The controller 3 controls the current i VCM current threshold i thp The current threshold i thp From time 40, the current i VCM It may be a value that is reached at time t41 when the time t2 is changed.

[0165] In the flat section A22, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF71. VCM is changed at the average rate of change AR52. The average rate of change AR52 is the derivative di VCM The average rate of change AR52 is a value indicating a steeper change than the average rate of change AR51, and can be a negative value. The controller 3 previously calculates the back electromotive voltage V BEMF In the flat section A22, the controller 3 may replace the current command value with the estimated value of the limit current REF71.

[0166] In the falling section A3, the controller 3 controls the current i VCM The waveform of falls from the positive side to zero at an average rate of change AR53. The average rate of change AR53 is the derivative di VCM / dt can be obtained by averaging it over the time of the falling section A3. The average rate of change AR53 is a value that indicates a steeper change than the average rate of change AR52, and is a negative value.

[0167] In the deceleration section Td, the period from time t65 to t66 is a rising section D1, the period from time t66 to t67 is a flat section D21, the period from time t67 to t68 is a flat section D22, and the period from time t68 to t69 is a falling section D3.

[0168] The controller 3 divides the flat section D2 (see FIG. 6) into a flat section D21 in which the sum of the limit current REF72 and a predetermined value does not exceed the negative side, and a flat section D22 in which the sum exceeds the negative side, when the AFC function is enabled. VCM Change the indication value to match the limit current REF72.

[0169] In the rising section D1, the controller 3 controls the current i VCM The controller 3 controls the VCM 13 current i VCM may be varied.

[0170] In the flat section D21, the controller 3 controls the current i VCM The controller 3 changes the current i VCM is changed at an average rate of change DR51. The average rate of change DR51 is the differential di VCM The average rate of change DR51 is generally close to zero, and may be substantially zero. The controller 3 controls the current i VCM current threshold i thp The current threshold i thp From time 65, the current i VCM It may be a value that is reached at time t66 when the value of

[0171] In the flat section D22, the controller 3 controls the current i VCM The controller 3 changes the current i of the VCM13 along the limit current REF72. VCM is changed at an average rate of change DR52. The average rate of change DR52 is the differential di VCM The average rate of change DR52 is a value indicating a steeper change than the average rate of change DR51, and can be a positive value. The controller 3 previously calculates the back electromotive voltage V BEMFIn the flat section D22, the controller 3 may replace the current command value with a value obtained by adding a predetermined value to the estimated value of the limit current REF72.

[0172] In the falling section D3, the controller 3 controls the current i VCM The waveform of falls from the negative side to zero at an average rate of change DR53. The average rate of change DR53 is the derivative di VCM / dt over the time of the falling section D3. The average rate of change DR53 is a positive value that indicates a steeper change than the average rate of change DR52.

[0173] 9, for comparison, the current waveform of the VCM 13 in the first JIT seek control is shown by a dashed line. In the first JIT seek control, the chart 6215 shows the current i VCM 6 shows a waveform CV111 of VCM13. Waveform CV111 is similar to waveform CV41 (see FIG. 6). Chart 6216 shows the differential di VCM 6 shows waveform CV112 of / dt, which is similar to waveform CV42 (see FIG. 6).

[0174] The differential d|i of the absolute value of the current in the flat sections A21, A22, D21, and D22 shown in the waveform CV112 shown in FIG. VCM Compared to the magnitude of | / dt, the differential d|i VCM The magnitude of | / dt is closer to zero.

[0175] In response to this, in the third JIT seek control, the absolute value of the current |i VCM | can be suppressed, and power consumption can be reduced.

[0176] In this way, the controller 3 divides the flat section A2 (see FIG. 6) into a flat section A21 in which the limit current REF71 is not exceeded on the positive side and a flat section A22 in which the limit current REF71 is exceeded on the positive side when the AFC function is enabled, and the current i VCM The controller 3 changes the indication value of the current i so that it follows the limit current REF71. The controller 3 divides the flat section D2 (see FIG. 6) into a flat section D21 that does not exceed a value obtained by adding a predetermined value to the limit current REF72 when the AFC function is enabled, and a flat section D22 that exceeds the value on the negative side. VCM The instruction value of REF71 is changed so as to match the limit current REF72. This enables the AFC function in the disk device 1 within the limit currents REF71 and REF72, thereby enabling low power consumption while maintaining access performance.

[0177] (Third Modification of the Embodiment) The third JIT seek control may be implemented in the JIT seek control unit 622 (see FIG. 1) as shown in FIG 10. FIG 10 is a diagram showing the functional configuration of the JIT seek control unit 622.

[0178] The JIT seek control unit 622 sets a target acceleration, and sets a current command value for the VCM 13 in consideration of the target acceleration and a BEMF (Back ElectroMotive Force) coefficient.

[0179] BEMF coefficient k BEMF When taking into consideration the above, the current i of the VCM13 in the rising section A1 and the flat section A2 shown in FIG. VCM can be expressed by the following Equation 1'.

number

[0180] In formula 1', V BEMF_set is the back electromotive voltage and can be expressed by the following equation 2'.

number

[0181] As shown in Equation 1' and Equation 2', the BEMF coefficient k BEMF is the current i of VCM13 VCM The counter electromotive force V BEMF is a coefficient that changes the degree of influence.

[0182] 10 has, as components for performing the third JIT seek control, a current threshold setting unit 6221, a conversion unit 6222, a target acceleration setting unit 6223, and a control instruction value determination unit 6224. The control instruction value determination unit 6224 has a BEMF coefficient setting unit 6225, a control instruction value calculation unit 6226, and a current instruction value update unit 6227.

[0183] The current threshold setting unit 6221 determines the absolute value |i VCM Current threshold I for limiting | th Set.

[0184] For example, the current threshold setting unit 6221 determines the current i VCM The current threshold i thp The current threshold setting unit 6221 may set the current i VCM The current threshold i thn may be set.

[0185] The conversion unit 6222 converts the current threshold I th , the acceleration threshold a th Convert to.

[0186] For example, the conversion unit 6222 converts the current threshold I thp The acceleration threshold value a of the flat section A2 is calculated by the following formula 7. thp Convert to.

number

[0187] The conversion unit 6222 converts the current threshold I thn The acceleration threshold value a of the flat section D2 is calculated by the following formula 8. thn Convert to.

number

[0188] The target acceleration setting unit 6223 sets the current threshold I th Acceleration threshold a according to th For example, the target acceleration setting unit 6223 receives a current threshold i thp Acceleration threshold a according to thp may be subjected to a current threshold i thn Acceleration threshold a according to thn The target acceleration setting unit 6223 may receive the acceleration threshold a th Target acceleration a according to tgt The target acceleration setting unit 6223 sets the target acceleration a tgt is supplied to the control instruction value calculation unit 6226.

[0189] The BEMF coefficient setting unit 6225 sets the BEMF coefficient k BEMF The BEMF coefficient setting unit 6225 sets the BEMF coefficient k BEMF is supplied to the control instruction value calculation unit 6226.

[0190] The control instruction value calculation unit 6226 uses a controller that takes into account the BEMF. tgt , target speed V tgt At the same time, the target acceleration a tgt is received from the target acceleration setting unit 6223, and the BEMF coefficient k BEMF The control instruction value calculation unit 6226 receives the target position P tgt , target speed V tgt , target acceleration a tgt , BEMF coefficient k BEMF The current command value of VCM13 is calculated using the above.

[0191] For example, the control instruction value calculation unit 6226 calculates the following current instruction value. In the rising section A1, the current instruction value rises to the positive side according to Equation 1′, and in the flat section A2, the current instruction value is approximately equal to the current threshold value i thp In the falling section A3, it falls from the positive side according to the time constant of the circuit 131. In the flat section C1, it is maintained at approximately zero. In the rising section D1, it rises to the negative side according to the formula with the polarity reversed from Formula 1′, and in the flat section D2, it falls to approximately the current threshold i thp and falls from the negative side in accordance with the time constant of the circuit 131 in the falling interval D3 (see FIG. 6).

[0192] The current command value update unit 6227 estimates a limit current taking the back electromotive voltage into consideration in advance. The current command value update unit 6227 may estimate a time series characteristic of the limit current (for example, the limit current REF71 shown in FIG. 9). Upon receiving a current command value from the control command value calculation unit 6226, the current command value update unit 6227 updates the current command value by adjusting the current command value so that it falls within the limit current. The current command value update unit 6227 may identify a portion of the current command value that exceeds the limit current, and replace the current command value of the exceeding portion with the limit current (or a value corresponding to the limit current).

[0193] For example, the current command value update unit 6227 may compare the current command value with the limit current, and divide the flat section A2 into a flat section A21 that does not exceed the limit current REF71 on the positive side, and a flat section A22 that exceeds the limit current REF71 on the positive side (see FIG. 9). The current command value update unit 6227 may replace the portion of the flat section A22 in the current command value with the limit current REF71. In response to this, the current command value update unit 6227 may finely correct the portion following the falling section A3.

[0194] The current command value update unit 6227 may compare the current command value with the limit current, and divide the flat section D2 into a flat section D21 that does not exceed a value obtained by adding a predetermined value to the limit current REF72 on the negative side, and a flat section D22 that exceeds the value on the negative side (see FIG. 9). The current command value update unit 6227 may replace the portion of the flat section A22 in the current command value with a value obtained by adding a predetermined value to the limit current REF72. In response to this, the current command value update unit 6227 may finely correct the portion following the falling section A3.

[0195] The current instruction value update unit 6227 outputs the updated current instruction value.

[0196] The third JIT seek control may be implemented in the servo control unit 64 (see FIG. 1) as shown in Fig. 11. Fig. 11 is a diagram showing the functional configuration of the servo control unit 64 in the third modified example of the embodiment.

[0197] The servo control unit 64 has a state estimation unit 645, subtractors 646 to 648, and an adder 649, in addition to the JIT seek control unit 622. The JIT seek control unit 622 has the same configuration as in FIG.

[0198] The control instruction value determination unit 6224 determines the target acceleration a tgt , target speed V tgt , target position P tgt Based on the above, the current indication value i VCM_tgt The control instruction value determination unit 6224 determines the target acceleration a tgt Applying this to equation 3, the current indication value i VCM_tgt The control instruction value determiner 6224 may determine the current instruction value i VCM_tgt to the VCM current application unit 2021 of the VCM control unit 202. The VCM current application unit 2021 supplies a current instruction value i VCM_tgt According to the VCM13 plant P VCM A current flows to the plant P. VCM corresponds to the transfer function of VCM13.

[0199] The control instruction value determination unit 6224 determines the target acceleration a tgt , target speed V tgt, target position P tgt Based on the above, the voltage indication value V MA_tgt The control instruction value determination unit 6224 determines the voltage instruction value V MA_tgt to the MA voltage application unit 2031 of the MA control unit 203. The MA voltage application unit 2031 supplies a voltage instruction value V MA_tgt According to the above, the plant P of the microactuator MA MA Voltage is applied to the plant P MA corresponds to the transfer function of the microactuator MA.

[0200] The state estimation unit 645 receives the current instruction value i VCM_tgt By using the observer, the current indication value I tgt_d The estimated position of the head MH based on p esti and the estimated speed v esti Request.

[0201] The adder 649 outputs the plant P VCM Signal from and plant P MA The position P of the head H is calculated by adding the signal from this to the signal from the subtractor 648 .

[0202] The subtractor 648 subtracts the estimated position P from the position P of the head H. esti Subtract the estimated error P err is calculated and fed back to the state estimation unit 645.

[0203] The state estimation unit 645 estimates the estimation error p err The head MH state estimate (estimated position p esti , estimated speed v esti ) is corrected.

[0204] The subtractor 646 subtracts the target velocity v tgt From the estimated speed v esti and subtract the speed error v e is calculated and supplied to the control instruction value determining unit 6224.

[0205] The subtractor 647 calculates the target position P tgt Estimated position P estiSubtract the position error P e is calculated and supplied to the control instruction value determining unit 6224.

[0206] For example, the control instruction value determination unit 6224 enables the AFC function in the flat sections A2 and D2 (see FIG. 6).

[0207] In the control instruction value determination unit 6224, the current threshold setting unit 6221 determines the seek distance d seek , rotation waiting time t RotWait , supply voltage V sup , the environmental temperature, and the VCM temperature, or a combination thereof, is used to refer to the firmware or the table in the non-volatile memory 90. As a result, the current threshold setting unit 6221 determines the current threshold i thp , current threshold value for deceleration section Td i thn Set.

[0208] The conversion unit 6226 calculates the current threshold value i for the acceleration section Ta by using Equations 7 and 8. thp , current threshold value for deceleration section Td i thn are the acceleration threshold a for the acceleration section Ta, thp , the acceleration threshold a for the deceleration section Td thn Convert to.

[0209] The target acceleration setting unit 6223 sets the obtained acceleration threshold value a for the acceleration section Ta. thp , the acceleration threshold a for the deceleration section Td thn The target acceleration is a tgt The target acceleration setting unit 6223 sets the target acceleration a tgt is supplied to the control instruction value calculation unit 6226.

[0210] In response to this, the control instruction value calculation unit 6226 calculates a current instruction value (see FIG. 6) that changes flatly in the flat sections A2 and D2.

[0211] The BEMF coefficient setting unit 6225 sets the BEMF coefficient k BEMF The BEMF coefficient setting unit 6225 sets the BEMF coefficient kBEMF is supplied to the control instruction value calculation unit 6226.

[0212] In response to this, the control instruction value calculation unit 6226 calculates the BEMF coefficient k BEMF Based on this, the current indication value is calculated while taking into account the degree of influence of the back electromotive force.

[0213] Here, the BEMF coefficient setting unit 6225 sets the BEMF coefficient k BEMF For example, the BEMF coefficient setting unit 6225 may change the average rate of change of the current command value by changing the BEMF coefficient k BEMF is set in the range of 0 to 1. This results in the calculated back electromotive force V BEMF_set The absolute value of can be reduced, and the calculated back electromotive force V can be calculated as in Equation 1' in the circuit equation. BEMF_set By using this, the average rate of change of the current indication value can be reduced.

[0214] The control instruction value calculation unit 6226 supplies the current instruction value to the current instruction value update unit 6227 .

[0215] The current instruction value update unit 6227 updates the assumed limit current i VCM_AFC_limit Request.

[0216] For example, the current instruction value update unit 6227 updates the power supply voltage limit value V AFC , current force constant K f_AFC , combined resistance R including VCM13 C_AFC Using the radial velocity v of the head H, the estimated limit current i is calculated using the following formula 9. VCM_AFC_limit Calculate.

number

[0217] Power supply voltage limit V AFC may be the lowest value (worst case value) in the design of the disk device 1, or may be a value measured during operation of the disk device 1.f_AFC may be the lowest value (worst case value) in the design of the disk device 1, or may be a value measured during operation of the disk device 1. C_AFC may be the maximum value (worst value) in the design of the disk device 1, or may be a value measured during operation of the disk device 1. The radial velocity v of the head H is a differential value of the position p or an estimated velocity v estimated by a state estimation unit. esti may also be used.

[0218] The combined resistance Rc is, for example, the set voltage Vset (see FIG. 4) and the current constant K f , the radial velocity of the head H v, the current of the VCM13 i VCM With k known, it can be estimated using the following Equation 10:

number

[0219] In addition, during seek operation including the saturated acceleration section, the combined resistance R including VCM13 C_AFC If the seek operation does not include the saturated acceleration section, the combined resistance R estimated during the seek operation including the saturated acceleration section can be estimated. C Alternatively, a combined resistance Rc obtained by estimating the heat dissipation from the coil of the VCM 13 over time and the heat generation from the coil of the VCM 13 due to a seek operation not including the saturation acceleration section may be used.

[0220] The current instruction value update unit 6227 updates the absolute value of the current instruction value and the assumed limit current i VCM_AFC_limit The current command value update unit 6227 compares the absolute value of the current command value with the assumed limit current i VCM_AFC_limit If the absolute value of (or the value obtained by subtracting a specified value from) is exceeded, the current indication value is set to the assumed limit current i VCM_AFC_limit The process of updating to is performed.

[0221] As a result, the current instruction value update unit 6227 divides the flat section A2 (see FIG. 6) into a flat section A21 that does not exceed the limit current REF71 on the positive side and a flat section A22 that exceeds the limit current REF71 on the positive side when the AFC function is enabled, and updates the current i VCM The indicated value is changed to match the limit current REF71 (see Figure 9).

[0222] Equivalently, the current instruction value update unit 6227 divides the flat section D2 (see FIG. 6) into a flat section D21 that does not exceed a value obtained by adding a predetermined value to the limit current REF72 when the AFC function is enabled, and a flat section D22 that exceeds the value on the negative side. VCM Change the indicated value to match the limit current REF72 (see Figure 9).

[0223] The current instruction value update unit 6227 updates the current instruction value i VCM_tgt to the VCM current application unit 2021.

[0224] 10 and 11 show an example of the operation when the controller 3 performs the seek control shown in FIG. 9. However, when the controller 3 performs the seek control shown in FIG. 7, the current threshold i thn Alternatively, when the controller 3 performs the seek control shown in FIG. thp The operations related to are omitted.

[0225] Even with this configuration, in the disk device 1, the AFC function can be enabled within the limit currents REF71 and REF72, and power consumption can be reduced while maintaining access performance.

[0226] (Fourth Modification of the Embodiment) The third JIT seek control may be implemented in a JIT seek control unit 622a as shown in Fig. 12. Fig. 12 is a diagram showing the functional configuration of a JIT seek control unit 622a in a fourth modified example of the embodiment.

[0227] The JIT seek control unit 622a determines an acceleration threshold value corresponding to the current threshold value, limits the target acceleration according to the acceleration threshold value, and sets a current instruction value for the VCM 13.

[0228] The JIT seek control unit 622a has a target acceleration limiting unit 6223a and a control instruction value determination unit 6224a instead of the target acceleration setting unit 6223 and the control instruction value determination unit 6224 (see FIG. 10). The BEMF coefficient setting unit 6225 is omitted from the control instruction value determination unit 6224a.

[0229] The target acceleration limiting unit 6223a limits the target acceleration a tgt and the acceleration threshold a th is received from the conversion unit 6222, and the acceleration threshold a th Using this, the target acceleration a tgt For example, the target acceleration limiting unit 6223a performs clipping processing on the acceleration threshold a th The part corresponding to the flat section A2 in thp and clipped at the acceleration threshold a th The part corresponding to the flat section D2 in thn The target acceleration limiting unit 6223a clips the target acceleration a tgt to the control instruction value determining unit 6224a.

[0230] In the control instruction value determination unit 6224a, the control instruction value calculation unit 6226 calculates the BEMF coefficient k BEMF Without using the target acceleration a tgt , target speed V tgt , target position P tgt Based on these, the current command value of VCM13 is calculated.

[0231] For example, the control instruction value calculation unit 6226 calculates the following current instruction value. In the rising section A1, the current instruction value rises to the positive side according to the formulas 1 and 2, and in the flat section A2, the current instruction value is approximately equal to the current threshold value i thpIn the falling section A3, it falls from the positive side according to the time constant of the circuit 131. In the flat section C1, it is maintained at approximately zero. In the rising section D1, it rises to the negative side according to the formulas 1 and 2, and in the flat section D2, it falls to approximately the current threshold i thp and falls from the negative side in accordance with the time constant of the circuit 131 in the falling interval D3 (see FIG. 6).

[0232] Other points are the same as those in the third modified example of the embodiment.

[0233] The third JIT seek control may be implemented in a servo control unit 64a as shown in Fig. 13. Fig. 13 is a diagram showing the functional configuration of a servo control unit 64a in a fourth modified example of the embodiment.

[0234] The servo control unit 64a has a JIT seek control unit 622a instead of the JIT seek control unit 622 (see FIG. 11). The JIT seek control unit 622a has a configuration similar to that in FIG.

[0235] In addition, the target acceleration a clipped by the target acceleration limiting unit 6223a tgt may not be smooth in the acceleration dimension. For example, it may change discontinuously in the dimension of the first derivative of the acceleration. This may cause mechanical vibration of the head H. In this case, as shown by the dotted lines in Figs. 12 and 13, the JIT seek control unit 622a may further include a smoothing filter 6228a.

[0236] The smoothing filter 6228a smooths the target acceleration a tgt The smoothing filter 6228a performs a smoothing process on the target acceleration a tgt to the control instruction value determining unit 6224a.

[0237] This results in a target acceleration a tgt can be made smooth in the acceleration dimension, for example, it can be made continuous in the dimension of the first derivative of acceleration, and the target acceleration a tgtIn response to this, the current instruction value set by the control instruction value determining unit 6224a can be made to change smoothly. This makes it possible to suppress mechanical vibrations of the head H.

[0238] The current instruction value update unit 6227 updates the absolute value of the current instruction value and the assumed limit current i VCM_AFC_limit The absolute value of the current indication is compared with the absolute value of the assumed limit current i VCM_AFC_limit If the absolute value of (or the value obtained by subtracting a specified value from) is exceeded, the current indication value is set to the assumed limit current i VCM_AFC_limit The point of performing the process of updating the information to the new information is the same as in the third modified example of the embodiment.

[0239] 12 and 13, the operation when the controller 3 performs the seek control shown in FIG. 9 is illustrated. When the controller 3 performs the seek control shown in FIG. 7, the current threshold i thn Alternatively, when the controller 3 performs the seek control shown in FIG. thp The operations related to are omitted.

[0240] Even with this configuration, in the disk device 1, the AFC function can be enabled within the limit currents REF71 and REF72, and power consumption can be reduced while maintaining access performance.

[0241] (Fifth Modification of the Embodiment) The third JIT seek control may be implemented in a JIT seek control unit 622b as shown in Fig. 14. Fig. 14 is a diagram showing the functional configuration of a JIT seek control unit 622b in a fifth modified example of the embodiment.

[0242] The JIT seek control unit 622b limits the current command value in accordance with a current threshold value, and sets the current command value for the VCM 13.

[0243] The JIT seek control unit 622b omits the conversion unit 6222 and the target acceleration limiting unit 6223a (see FIG. 12), and has a control instruction value determining unit 6224b instead of the control instruction value determining unit 6224a (see FIG. 10). The control instruction value determining unit 6224b further has a current instruction value limiting unit 6229b.

[0244] The current instruction value limiting unit 6229b receives the current instruction value from the control instruction value calculation unit 6226 and calculates the current threshold i th from the current threshold setting unit 6221, and the current threshold i th For example, the current command value limiting unit 6229b clips the portion of the current command value corresponding to the flat section A2 by using a current threshold i thp The part of the current indication value corresponding to the flat section D2 is clipped at the current threshold i thn The current command value limiting section 6229b supplies the current command value after the clipping process to the current command value updating section 6227.

[0245] Other points are the same as those in the fourth modified example of the embodiment.

[0246] The third JIT seek control may be implemented in a servo control unit 64b as shown in Fig. 15. Fig. 15 is a diagram showing the functional configuration of a servo control unit 64b in a fifth modified example of the embodiment.

[0247] The servo control unit 64a has a JIT seek control unit 622b instead of the JIT seek control unit 622a (see FIG. 13). The JIT seek control unit 622b has a configuration similar to that of FIG.

[0248] Note that the current command value clipped by the current command value limiting unit 6229b may not be smooth in the current dimension. For example, it may change discontinuously in the dimension of the first derivative of the current. This may cause mechanical vibration of the head H. In this case, as shown by the dotted lines in Figs. 14 and 15, the control command value determining unit 6224b may further include a smoothing filter 6228b.

[0249] The smoothing filter 6228b performs a smoothing process on the current command value clipped by the current command value limiting unit 6229b. The smoothing filter 6228b supplies the current command value after the smoothing process to the current command value updating unit 6227.

[0250] This makes it possible to smooth the current command value in the current dimension, for example, to make it continuous in the dimension of the first derivative of the current, thereby making it possible to suppress mechanical vibration of the head H.

[0251] The current instruction value update unit 6227 updates the absolute value of the current instruction value and the assumed limit current i VCM_AFC_limit The absolute value of the current indication is compared with the absolute value of the assumed limit current i VCM_AFC_limit If the absolute value of i exceeds the assumed limit current i (or the value obtained by subtracting a specified value from it), the current indication value is set to the assumed limit current i VCM_AFC_limit The point of performing the process of updating the information to the new information is the same as in the fourth modified example of the embodiment.

[0252] 14 and 15 show an example of the operation when the controller 3 performs the seek control shown in FIG. 9. However, when the controller 3 performs the seek control shown in FIG. 7, the current threshold i thn Alternatively, when the controller 3 performs the seek control shown in FIG. thp The operations related to are omitted.

[0253] Even with this configuration, in the disk device 1, the AFC function can be enabled within the limit currents REF71 and REF72, and power consumption can be reduced while maintaining access performance.

[0254] (Sixth Modification of the Embodiment) The third JIT seek control may be implemented in a JIT seek control unit 622c as shown in Fig. 16. Fig. 16 is a diagram showing the functional configuration of a JIT seek control unit 622c in a sixth modified example of the embodiment.

[0255] The JIT seek control unit 622c sets a target acceleration, and sets a current command value for the VCM 13 taking into account the target acceleration without taking into account the BEMF.

[0256] When BEMF is not taken into consideration, the current i of VCM13 in the rising section A1 and the flat section A2 shown in Figure 3 VCM can be expressed by the following formula 1".

number

[0257] The JIT seek control unit 622c has a control instruction value determination unit 6224c instead of the control instruction value determination unit 6224 (see FIG. 10). The control instruction value determination unit 6224c does not include the BEMF coefficient setting unit 6225.

[0258] The control instruction value calculation unit 6226c uses a controller that does not take into account the BEMF. tgt , target speed V tgt At the same time, the target acceleration a tgt The control instruction value calculation unit 6226c receives the target position P tgt , target speed V tgt , target acceleration a tgt The current command value of VCM13 is calculated using the above.

[0259] For example, the control instruction value calculation unit 6226c calculates the following current instruction value. In the rising section A1, the current instruction value rises to the positive side according to Equation 1'', and in the flat section A2, the current instruction value is approximately equal to the current threshold value i thp In the falling section A3, it falls from the positive side according to the time constant of the circuit 131. In the flat section C1, it is maintained at approximately zero. In the rising section D1, it rises to the negative side according to a formula with the polarity reversed from Formula 1'', and in the flat section D2, it falls to approximately the current threshold i thp and falls from the negative side in accordance with the time constant of the circuit 131 in the falling interval D3 (see FIG. 6).

[0260] The third JIT seek control may be implemented in a servo control unit 64c as shown in Fig. 17. Fig. 17 is a diagram showing the functional configuration of a servo control unit 64c in a sixth modified example of the embodiment.

[0261] The servo control unit 64c has a JIT seek control unit 622c instead of the JIT seek control unit 622 (see FIG. 10). The JIT seek control unit 622c has a configuration similar to that in FIG.

[0262] The current instruction value update unit 6227 updates the absolute value of the current instruction value and the assumed limit current i VCM_AFC_limit The absolute value of the current indication is compared with the absolute value of the assumed limit current i VCM_AFC_limit If the absolute value of i exceeds the assumed limit current i (or the value obtained by subtracting a specified value from it), the current indication value is set to the assumed limit current i VCM_AFC_limit The point of performing the process of updating the information to the new information is the same as in the third modified example of the embodiment.

[0263] 16 and 17, the operation when the controller 3 performs the seek control shown in FIG. 9 is illustrated. When the controller 3 performs the seek control shown in FIG. thn Alternatively, when the controller 3 performs the seek control shown in FIG. thp The operations related to are omitted.

[0264] Even with this configuration, in the disk device 1, the AFC function can be enabled within the limit currents REF71 and REF72, and power consumption can be reduced while maintaining access performance.

[0265] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0266] 1 disk device, 3 controller, 13 VCM, H head.

Claims

1. Head and a disk having a recording surface; a motor for seeking the head along the recording surface; A controller for controlling the motor; Equipped with The controller: when there is no rotational latency between when the head reaches a target track on the disk and when it reaches a target sector, an absolute value of a motor current is increased in a first section of a first period in which the head is accelerated or decelerated, an absolute value of the motor current is changed at a first average rate of change in a second section after the first section of the first period, and an absolute value of the motor current is decreased at a second average rate of change that is steeper than the first average rate of change in a third section after the second section of the first period, When the rotational latency time exists, the absolute value of the motor current is increased in a fourth section in the second period in which the head is accelerated or decelerated, the absolute value of the motor current is changed at a third average rate of change in a fifth section after the fourth section in the second period, the absolute value of the motor current is decreased at a fourth average rate of change that is steeper than the third average rate of change in a sixth section after the fifth section in the second period, and the absolute value of the motor current is decreased at a fifth average rate of change that is steeper than the fourth average rate of change in a seventh section after the sixth section in the second period. Disk device.

2. The controller estimates a limit current taking into consideration a back electromotive voltage, and when the rotation waiting time exists, reduces an absolute value of the motor current in the sixth section at the fourth average change rate according to a change in the absolute value of the limit current.

2. The disk device according to claim 1.

3. The controller estimates a limit current taking into consideration a back electromotive voltage, generates a current command value for the second period when the rotation waiting time exists, corrects the current command value for the sixth section that exceeds the limit current by replacing it with the limit current, and drives the motor with the corrected current command value.

3. The disk device according to claim 2.

4. The controller changes the absolute value of the motor current at the third average rate of change, which is closer to zero than the average rate of change of the absolute value of the limit current, in the fifth section.

3. The disk device according to claim 2.

5. Power supply voltage is V, back electromotive force is V ＢＥＭＦ , the circuit resistance of the motor is R, the controller calculates the limit current i ＶＣＭ＿ｌｉｍｉｔ of i ＶＣＭ＿ｌｉｍｉｔ =(V-V ＢＥＭＦ ) / R Estimate by 3. The disk device according to claim 2.

6. The controller uses the measured power supply voltage or the power supply voltage designed for the worst case conditions as the power supply voltage V.

6. The disk device according to claim 5.

7. Power supply voltage is V, back electromotive force is V ＢＥＭＦ , the motor current in the sixth section is i ＶＣＭ When the motor circuit resistance R is set as follows, the controller R=(V-V ＢＥＭＦ ) / i ＶＣＭ Using R estimated by 6. The disk device according to claim 5.

8. The controller detects the back electromotive force V ＢＥＭＦ When the measured back electromotive force or the radial velocity of the head is v and the current force constant is Kf, V ＢＥＭＦ =vKf V is estimated by ＢＥＭＦ Using 6. The disk device according to claim 5.

9. The controller uses, as the radial velocity v of the head, a differential of a position demodulated by servo information read from the disk by the head, or a velocity estimated from the demodulated position and a current indication value.

6. The disk device according to claim 5.

10. The controller controls the motor current i ＶＣＭ As the current sigma, a measured current, a current estimated by multiplying the second derivative of the position demodulated by the servo information read from the disk by the head by an acceleration-current conversion coefficient, or a current estimated by multiplying the acceleration estimated from the demodulated position and current indication value by the acceleration-current conversion coefficient is used.

8. The disk device according to claim 7.

11. The controller uses, as the circuit resistance R of the motor, a corrected R taking into consideration continuous heat dissipation between the time when the estimated R is measured and the time when the motor is used, and heat generation due to the operation of the motor.

9. The disk device according to claim 8.

Images