Magnetic disk device and control method thereof

Abstract

The embodiment relates to a magnetic disk device including a magnetic disk and a magnetic head and a control method thereof. A speed of the head during seeking is detected. When the seek is accelerated, the counter electromotive voltage induced in the coil of the voice coil motor is estimated on the basis of the detected speed and the position of the seek. Furthermore, when the seek is accelerated, an inductance voltage generated in an inductance component of a coil of the voice coil motor is obtained from the drive current of the voice coil motor, and the resistance of the coil of the voice coil motor is estimated on the basis of the obtained inductance voltage, the drive voltage of the voice coil motor, the drive current of the voice coil motor, and the estimated counter electromotive force voltage.

Description

[0001] This application claims priority to Japanese Patent Application No. 2024-096646 (Filing Date: June 14, 2024). This application incorporates the entire contents of the base application by reference thereto. TECHNICAL FIELD

[0002] Embodiments relate to a magnetic disk device having a magnetic disk and a magnetic head, and a control method thereof. BACKGROUND

[0003] A magnetic disk device having a magnetic disk and a magnetic head includes an actuator that holds the magnetic head so as to be able to track in a radial direction of the magnetic disk, and makes the magnetic head track (move) in the radial direction of the magnetic disk from a previously nearest (previous) stop position to a target position (write position or read position) on the magnetic disk at the time of writing data to and reading data from the magnetic disk.

[0004] In order to improve (high performance) the access performance of tracking, it is important to maximize the potential of a voice coil motor (VCM) that the VCM has. As one of the measures to maximize the potential of the VCM, there is a saturation acceleration function. The saturation acceleration function is a function of increasing the drive current of the VCM (referred to as an acceleration drive current) until saturation at the time of acceleration of tracking to maximize the acceleration of tracking.

[0005] However, at the time of deceleration of tracking, since the magnetic head must be reliably stopped at the target position, it is not possible to increase the drive current of the VCM (referred to as a deceleration drive current) to saturation. In order to increase the deceleration of tracking as much as possible in a range in which the deceleration drive current is not saturated, it is necessary to grasp the resistance value of the VCM, which is a fluctuation factor of the limit value of the deceleration drive current, so that the deceleration drive current is not saturated. SUMMARY

[0006] A magnetic disk device according to an embodiment includes a magnetic disk, a magnetic head that writes and reads data to and from the magnetic disk, a voice coil motor that includes a magnet and a coil to trace the magnetic head in a radial direction of the magnetic disk, and a controller that controls rotation of the magnetic disk and tracing of the magnetic head. The controller includes a tracing control unit that controls a drive current of the voice coil motor to trace the magnetic head from a stop position to a target position on the magnetic disk at an acceleration and a deceleration, a speed detection unit that detects a speed of the magnetic head during the tracing, a counter electromotive voltage estimation unit that estimates a counter electromotive voltage induced in the coil of the voice coil motor based on the speed detected by the speed detection unit and a position of the tracing at the acceleration, and a coil resistance estimation unit that calculates an inductance voltage generated in an inductance component of the coil of the voice coil motor from the drive current of the voice coil motor at the acceleration, and estimates a resistance of the coil of the voice coil motor based on the calculated inductance voltage, a drive voltage of the voice coil motor, the drive current of the voice coil motor, and the counter electromotive voltage estimated by the counter electromotive voltage estimation unit.

[0007] A main cause of variation in the limit value of the deceleration drive current is the coil resistance of the voice coil motor. By calculating the coil resistance, the deceleration drive current can be changed according to the varied limit value of the deceleration drive current, and the optimum deceleration drive current is always supplied to the voice coil motor, so that the access performance of the tracing can be improved.

[0008] According to the embodiment, a magnetic disk device that can calculate the coil resistance of the voice coil motor and a control method thereof can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 FIG. 1 is a diagram showing the overall configuration of an embodiment.

[0010] Figure 2 FIG. 2 is a diagram showing the main part of the configuration of a magnetic disk in an embodiment.

[0011] Figure 3 FIG. 3 is a diagram showing an equivalent circuit of a coil of a voice coil motor in an embodiment.

[0012] Figure 4 FIG. 4 is a diagram showing the variation of a drive current of the voice coil motor in an embodiment, with the distance of the tracing as a parameter.

[0013] Figure 5 FIG. 5 is a diagram showing the variation of an acceleration drive current of the voice coil motor in an embodiment, with the coil temperature of the voice coil motor as a parameter.

[0014] Figure 6It uses the coil temperature of the voice coil motor as a parameter. Figure 3 The graph shows the change in inductance voltage generated in the inductor component.

[0015] Figure 7 It is Figure 5 The acceleration is represented by a portion of the change in the driving current, magnified on its time axis.

[0016] Figure 8 It is Figure 6 A portion of the change in the inductor voltage is represented by a graph that magnifies its time axis.

[0017] Figure 9 It means Figure 7 acceleration using drive current and Figure 8 A graph showing the relationship between voltage and voltage.

[0018] Figure 10 This indicates the acceleration drive current in one embodiment and Figure 3 A diagram showing the format of the inductor voltage transformation table.

[0019] Figure 11 This is a flowchart illustrating the control of one implementation method.

[0020] Figure 12 This is a graph showing the limit value of the drive current for speed reduction of the voice coil motor in one embodiment.

[0021] Figure 13 This is a diagram illustrating the increase in the drive current for deceleration of the voice coil motor during short-distance seek in one embodiment compared to the conventional method.

[0022] Explanation of reference numerals in the attached figures

[0023] 1…Disk drive, 2…Disk, 10…Head, 23…Voice coil motor, 30…Controller, 30a…Position capture unit, 30b…Seek control unit, 30c…Settling determination unit, 30d…Speed ​​detection unit, 30e…Back EMF voltage estimation unit, 30f…Coil resistance estimation unit, 30g…Deceleration current adjustment unit, 43a…Current detector, 43b…Voltage detector. Detailed Implementation

[0024] [1] One embodiment will be described with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the disk drive 1 includes a disk 2 as a recording medium, a spindle motor 3 that drives the disk 2 to rotate, and a read / write head 10 for writing (writing) and reading (reading) data to the disk 2. An actuator 20 supporting the read / write head 10 is disposed near the disk 2.

[0026] The actuator 20 supports the magnetic head 10 so as to be traceable in the radial direction of the magnetic disk 2. This actuator 20 is also called an actuator block or a head stack assembly (HAS), and includes a rotary shaft 21, an arm 22 which holds a middle portion of the rotary shaft 21, a voice coil motor (VCM) 23 which is disposed at a base end portion of the arm 22, a suspension member 24 which is disposed at a front end portion of the arm 23 and holds the magnetic head 10, and the like.

[0027] The voice coil motor 23 includes a magnet 23m, a coil 23c, and a yoke 23y in which the magnet 23m is installed, and drives the magnetic head 10 in the radial direction of the magnetic disk 2 by flowing a drive current I VCM through the coil 23c, thereby rotating the actuator 20 between a first position shown by a dashed line and a second position shown by a solid line. With the rotation of the actuator 20, the magnetic head 10 is traceable (movable) in the radial direction of the magnetic disk 2 along a trajectory shown by X.

[0028] A stopper ST and a ramp mechanism RL are disposed in the vicinity of the actuator 20. The stopper ST limits the moving position of the magnetic head 16 on the inner peripheral side of the magnetic disk 2. The ramp mechanism RL retreats the magnetic head 16 from the magnetic disk 2 when the spindle motor 3 is stopped.

[0029] The disk device 1 includes a controller 30 which becomes the center of control, a head amplifier 41 which drives the magnetic head 10, a signal processing circuit 42 which is disposed between the head amplifier 41 and the connection of the controller 30, a motor driver 43 which is disposed between the voice coil motor 23 and the connection of the controller 30, a DRAM 44 which is a memory which stores a program and the like necessary for the control of the controller 30, a flash ROM 45 which is a memory which stores various data necessary for the control of the controller 30, a hard disk controller (HDC) 46 which is disposed between the controller 30 and the connection of an external host device 50, and the like.

[0030] The head amplifier 41 amplifies a data signal for writing from the signal processing circuit 42 to the magnetic head 10, and amplifies a data signal read by the magnetic head 10. The signal processing circuit 42 appropriately processes a data signal for writing from the controller 30 to the magnetic head 10 and supplies it to the head amplifier 41, and appropriately processes a read data signal amplified by the head amplifier 41 and supplies it to the controller 30.

[0031] The motor driver 43 controls the drive current of the spindle motor 3 and the drive current I VCM of the voice coil motor 23 according to an instruction from the controller 30. In addition, the motor driver 43 includes a current sensor 43s which detects the drive current I VCM(including the acceleration driving current I VCM_A and the deceleration driving current I VCD_D ) and a voltage detector 43b that detects the value of the driving voltage V VCM of the voice coil motor 23. A conversion table 45a used in processing of a deceleration current adjustment section 30g of the controller 30 described later is stored in the above-described flash ROM 45. The content of the conversion table 45a is described later.

[0032] As shown in Figure 2 , the magnetic disk 2 has a circular shape that is fitted coaxially to the rotation shaft of the spindle motor 3, and includes a plurality of tracks Tr that are arranged in the circumferential direction and concentrically. Each track Tr includes a servo sector that is composed of a servo pattern SB in which position data is recorded and a data area DT in which write data is stored.

[0033] The controller 30, as a main function, includes a position capture section (position capture unit) 30a, a seek control section (seek control unit) 30b, a stability determination section (determination unit) 30c, a speed detection section (speed detection unit) 30d, a counter electromotive voltage estimation section (counter electromotive voltage estimation unit) 30e, a coil resistance estimation section (coil resistance estimation unit) 30f, and a deceleration current adjustment section (deceleration current adjustment unit) 30g.

[0034] [Position Capture Section 30a]

[0035] The position capture section 30a captures the position Pos of the magnetic head 10 on the magnetic disk 2 based on the position data of the servo pattern SB included in the read data of the magnetic head 10.

[0036] [Seek Control Section 30b]

[0037] The seek control section 30b causes the magnetic head 10 to seek from a stop position on the magnetic disk 2 to a target position Pt by controlling the driving of the voice coil motor 23. Specifically, the seek control section 30b causes the magnetic head 10 to seek from the stop position on the magnetic disk 2 to the target position Pt while including acceleration and deceleration in order by controlling the driving current I VCM of the voice coil motor 23 of the actuator 20 based on the captured position Pos of the position capture section 30a.

[0038] [Stability Determination Section 30c]

[0039] The stability determination section 30c performs so-called stability (setting) determination that the magnetic head 10 has reached the target position Pt in a case where a certain period Cs elapses in a state where the captured position Pos of the position capture section 30a converges to a prescribed range that sandwiches the target position Pt when the magnetic head 10 seeks.

[0040] [Speed ​​Detection Department 30d]

[0041] When the magnetic head 10 accelerates during its seek, the speed detection unit 30d detects the speed (moving speed) v of the magnetic head 10 by calculating the historical record of the capture position Pos (the position history record of the magnetic head 10) based on the position capture unit 30a. hd Specifically, the speed detection unit 30d performs a differential operation on the capture position Pos of the position capture unit 30a, and detects the absolute value of the operation result as the seek speed v. hd .

[0042] [Back EMF Voltage Estimation Section 30e]

[0043] During the acceleration of the magnetic head 10 during track seeking, the back electromotive force voltage detection unit 30e detects the speed v based on the speed detection unit 30d. hd And by calculating the seek position of the magnetic head 10 (the capture position Pos of the position capture unit 30a), the back electromotive force voltage V induced in the coil of the voice coil motor 23 is estimated. BEMF Specifically, the back electromotive force voltage detection unit 30e detects the velocity v by the velocity detection unit 30d. hd And the BL constant k corresponding to the capture position Pos of the position capture unit 30a BL The product of these values ​​is used to estimate the back electromotive force voltage V induced in the coil of the voice coil motor 23. BEMF BL constant k BL It is a coefficient determined by the product of the magnetic flux density of the magnetic field applied from the magnet 23m of the voice coil motor 23 to the coil 23c and the effective length of the winding of the coil 23c present in the magnetic field.

[0044] V BEMF =v hd ×k BL

[0045] [Coil resistance estimation section 30f]

[0046] The coil resistance estimation unit 30f is based on the acceleration drive current I detected by the current detector 43a during the acceleration of the magnetic head 10 during its seek operation. VCM_A To determine the inductance voltage V generated in the inductance component L of the coil 23c of the voice coil motor 23. L Based on the calculated inductor voltage V L The driving voltage V of the voice coil motor 23 is detected by voltage detector 43b. VCM The back electromotive force voltage V estimated by the back electromotive force voltage estimation unit 30e BEMF and the acceleration drive current I detected by current detector 43a VCM_A, to estimate the resistance (resistance value) R of the coil 23c of the voice coil motor 23. The resistance R is referred to as a coil resistance R.

[0047] R = (|V VCM | - |V L | - |V BEMF |) / |I VCM_A |

[0048] [deceleration current adjustment section 30g]

[0049] The deceleration current adjustment section 30g adjusts the deceleration drive current I VCM_D of the voice coil motor 23 at the deceleration of the seek, by an operation based on the following equation of the coil resistance R estimated by the coil resistance estimation section 30f DecMax . The adjusted deceleration drive current is referred to as I DecMaxM .

[0050] I DecMaxM = I DecMax x (1 / R)

[0051] <Explanation related to estimation of coil resistance>

[0052] Figure 3 An equivalent circuit of the coil 23c of the voice coil motor 23 is shown in FIG. 6.

[0053] The coil 23c of the voice coil motor 23 has three elements of an inductance component L, a resistance component (= resistance value) R as a coil resistance, and a counter electromotive voltage Ec. V VCM is a drive voltage applied to the coil 23c. V L is a voltage generated in the inductance component L in conjunction with the application of the drive voltage V VCM . This voltage is referred to as an inductance voltage. V R is a voltage generated in the resistance R in conjunction with the application of the drive voltage V VCM . This voltage is referred to as a resistance voltage. V BEMF is a counter electromotive voltage induced in the coil 23c in conjunction with the operation of the magnet 23m at the seek of the magnetic head 10.

[0054] The coil resistance R varies in accordance with the temperature T of the coil 23c. Hereinafter, the temperature T is referred to as a coil temperature T. The counter electromotive voltage V BEMF varies in accordance with the seek speed of the magnetic head 10 and the magnetic flux density of the magnetic field applied from the magnet 23m of the voice coil motor 23 to the coil 23c. The magnetic flux density can vary in accordance with the change in the positional relationship of the magnetic head 10 and the magnet 23m in conjunction with the seek. Further, with respect to the magnetic flux density, for the sake of simplification of the explanation, it is treated as a constant value.

[0055] The drive voltage VVCM , the inductance voltage V L , the coil resistance R, and the counter electromotive voltage V R , and the relationship of the voltage V BEMF , the sampling time (t) is set to t, and the drive current flowing in the coil 23c is set to I VCM , is represented by the following equation (1).

[0056] V VCM = V L + V R + V BEMF = L(dI VCM / dt) + RI VCM + V BEMF … (1)

[0057] The "L(dI VCM / dt)" of the above equation (1) indicates that the response of the inductance voltage V VCM when the drive voltage V L is applied to the coil 23c is transient.

[0058] After the above equation (1) is arranged with respect to the drive current I VCM , it becomes the following equation (2).

[0059] I VCM = (V VCM - V L - V BEMF ) / R … (2)

[0060] This drive current I VCM is a current determined in accordance with the physical elements of the inductance component L, the resistance component R, and the counter electromotive voltage V BEMF , and thus is a saturation current (I VCM = I Lim ) flowing when the drive voltage V VCM is applied.

[0061] According to the above equation (2), it is apparent that the limit value I VCM of the drive current I Lim depends on the coil resistance R.

[0062] In the disk device, the coil temperature T can always vary in accordance with the frequency of the seek operation (i.e., the frequency of the commands received from the host device 50 per unit time) and / or the temperature condition of the disk device 1. As described above, since the coil resistance R varies in accordance with the coil temperature T, the limit value I VCM of the drive current I Lim can also always vary.

[0063] Figure 4 The diagram shows the drive current I controlled by the seek control unit 30b. VCM The change. By accelerating with drive current I. VCM_A The rise of the magnetic head 10 initiates its seek and accelerates (during the acceleration rise). Furthermore, at a predetermined timing, the acceleration is achieved using a drive current I. VCM_A Descending, deceleration using drive current I VCM_D The speed increases. As a result, actuator 20 decelerates (during acceleration / deceleration switching). Afterwards, the deceleration is driven by the drive current I. VCM_D During descent (during deceleration), after stabilization determination, the seek of the magnetic head 10 ends.

[0064] As mentioned earlier, to improve seek performance (high performance), it is important to maximize the potential of the voice coil motor 23. One measure to maximize the potential of the voice coil motor 23 is a saturation acceleration function. The saturation acceleration function is achieved by increasing the acceleration drive current I during seek acceleration. VCM_A Increase until saturation, that is, make it become I. VCM_A =I Lim－A This is controlled in a way that maximizes the acceleration function of seeking.

[0065] On the other hand, during deceleration during seek, in order to reliably stop the magnetic head 10 at the target position, the target position and the current position are compared at predetermined intervals, so that the difference between the target position and the current position becomes zero, thereby reducing the deceleration drive current I. VCM_D Increase or decrease. Therefore, during deceleration, the deceleration cannot be achieved using the drive current I. VCM_D Increase to saturation. To maximize the seek deceleration, it is necessary to control the deceleration drive current I. VCM_D The limit value I Lim_D And in deceleration, the drive current I VCM_D Control is performed within the unsaturated range. That is, it is necessary to satisfy I. VCM _D Lim_D The condition for deceleration using drive current I VCM_D Adjustments are needed. Limit value I Lim_D Since it depends on the coil resistance R, by calculating this coil resistance R, it is possible to achieve a deceleration drive current I that does not exceed the required value. VCM_D The limit value I VCM_D The pathfinding control.

[0066] like Figure 4 As shown, in the case of long seek distances (long-distance seek), the acceleration drive current I is used. VCM_A Saturation to become the maximum value I AccMax The timing is the inductor voltage V L ​The transient response converges and the inductor voltage V L The timing becomes 0V. Therefore, "L(dI)" in equation (1) above can be omitted. VCM The coil resistance (= resistance value) R is calculated as shown in equation (3). In addition, the seek can be considered in both the inner and outer circumferential directions of disk 12. In various cases, the polarity of the applied voltage is different, so the absolute value is introduced when transforming according to equation (1).

[0067] R = (|V VCM |-|V BEMF |) / |I AccMax |…(3)

[0068] However, just like Figure 4 As shown, in the case of short seek distance (short-distance seek), the acceleration drive current I... VCM_A Reaching the maximum value I, which is the saturation point AccMax Previously, the seek mode switched to deceleration. In this case, due to the inductor voltage V... L The transient response has not yet converged, that is, the inductor voltage V L Since it is not 0V, the coil resistance R cannot be calculated using the above formula (3).

[0069] Therefore, considering the acceleration during the seeker's upward acceleration, the driving current I is used for acceleration. VCM_A Before reaching saturation, the coil resistance R is estimated.

[0070] To estimate the acceleration drive current I VCM_A To determine the coil resistance R before reaching saturation, it is necessary to understand the inductor voltage V during the non-convergent transient response. L (Not 0V).

[0071] According to equation (1) above, the acceleration driving current I VCM_A Inductor voltage V before reaching saturation point L It is V L =L(dI) VCM / dt). That is, by adjusting the acceleration drive current I detected by the current detector 43a. VCM_A By differentiation, the acceleration driving current I can be determined. VCM_A Inductor voltage V before reaching saturation point L .

[0072] Furthermore, there are concerns about the acceleration of the seeker during the acceleration process using the drive current I. VCM_A Perform differentiation. That is, for the acceleration during the rise of the seek acceleration, use the drive current I. VCM_A, since the change per unit time is large, if it is assumed that the current detector 43a is an A / D converter with a limited dynamic range such as mounted on the motor driver 43, in order to capture the sharp change of the acceleration drive current I VCM_A , the gray scale (level, precision, Japanese: 諧調) is insufficient, and it is easy to generate detection errors (also called measurement errors). Moreover, this detection error may be further enhanced by differential processing. As a means to reduce the detection error, it is also possible to consider averaging the detection results of multiple samplings, but as Figure 5 shown, during the acceleration rise of the seek, the change of the acceleration drive current I VCM_A is not linear, so it is difficult to accurately obtain the average value by arithmetic mean with a relatively small computational load.

[0073] As a countermeasure, the correspondence information between the acceleration drive current I VCM_A detected by the current detector 43a and the inductance voltage V L is pre-held. Subsequently, by referring to this correspondence information based on the detection result of the current detector 43a, it is possible to eliminate the noise increase and averaging error caused by differential processing, and to estimate the inductance voltage V VCM_A before the acceleration drive current I L reaches the saturation point.

[0074] Figure 5 Taking the multiple coil temperatures T from 20°C to 80°C (which can be equivalently called multiple coil resistances R) as parameters, the change of the acceleration drive current I VCM flowing when a certain drive voltage V VCM_A is applied to the voice coil motor 23 over time is shown. In the general control of the voice coil motor 2, the function of applying a pulsed voltage to the voice coil motor 23 using PWM (Pulse Width Modulation) control or the like and changing the pulse width of the applied voltage to adjust the voltage level is utilized. The situation where a DC voltage of a certain level is continuously applied without changing such a pulse width is expressed as "applying a certain drive voltage V VCM to the voice coil motor 23".

[0075] Figure 6 is the result of calculating the inductance voltage V L =L(dI VCM / dt) when the acceleration drive current I Figure 5 flows. Since the actuator 20 installed as the coil 23c of the voice coil motor 23 uses a non-magnetic raw material, the change in the inductance component L caused by temperature change is negligibly small.​​​​

[0076] exist Figure 6 The inductor voltage V is within the time range of t = 0 to 50 (Sa). L It is in a transient response state. At a timing of t = 50 (Sa), the acceleration is achieved using a drive current I. VCM_A Reaching the maximum value I, which is the saturation point AccMax After t = 50 (Sa), acceleration is achieved using a driving current I. VCM_A Subject to back electromotive force voltage V BEMF The impact gradually decreased.

[0077] Figure 7 Will Figure 5 Acceleration using drive current I VCM_A Part of the change is represented by expanding its time axis. That is, it can be seen that: since the coil resistance R increases with the increase of the coil temperature T, the higher the coil temperature T, the faster the driving current I is. VCM_A The smaller.

[0078] According to the above V L =L(dI) VCM From the content represented by / dt), we can see that the acceleration is driven by the current I. VCM_A The greater the change per unit time, the greater the inductor voltage V. L The larger the value, the better.

[0079] Figure 8 Will Figure 6 Inductor voltage V L Part of the change is represented by magnifying its time axis. That is, it can be seen that as the coil resistance R increases, the accelerating drive current I... VCM_A The current flowing through the inductor decreases, and consequently, the inductor voltage V... L It gets smaller.

[0080] Figure 9 It indicates Figure 7 Acceleration drive current I under predetermined timing VCM_A and Figure 8 The inductor voltage V under this timing L The relationship is as described above. A certain driving voltage V is applied to the voice coil motor 23. VCM It is a prerequisite, therefore, Figure 9 The acceleration of the horizontal axis is achieved by the drive current I. VCM_A The change is caused by the change in coil temperature T (that is, the change in coil resistance R). Furthermore, according to... Figure 9 It can be seen that the acceleration is driven by the current I. VCM_A With inductor voltage V L The relationship is linear. If a certain driving voltage V is applied to the voice coil motor 23...VCM then by using this linearity, even if the inductance voltage V L is in a state of transient response, it is possible to estimate the inductance voltage V L without using the calculation of V VCM = L(dI VCM_A / dt) but according to the acceleration drive current I L .

[0081] <Operation at the time of manufacturing the disk device 1>

[0082] In the manufacturing process of the disk device 1, an operator performs the seek of the magnetic head 10 while executing the seek at at least two or more environmental temperatures, and records the drive current I VCM (acceleration drive current I VCM_A ) at an arbitrary plurality of time points t at the time of acceleration of the seek in succession. Also, the operator applies the inductance component L of the voice coil motor 23 and the above recorded each acceleration drive current I VCM_A to the operation of the above V L = L(dI VCM / dt) as a theoretical formula, to respectively find the inductance voltage V L corresponding to each acceleration drive current I VCM_A . The inductance component L used in this operation can be a value common to all of the disk devices 1 manufactured, or can be a value unique to each disk device 1. Also, these inductance components L can be design values, or can be measured values.

[0083] Also, the operator generates a conversion table 45a in which the above recorded each acceleration drive current I VCM_A and each inductance voltage V L corresponding to each of these acceleration drive currents I VCM_A are stored in correspondence, and stores this in the above flash ROM 45.

[0084] In the conversion table 45a, data I1, I2,... In are sequentially stored as values of each acceleration drive current I VCM_A , and data V1, V2,... Vn are sequentially stored as values of each inductance voltage V L corresponding to each of the data I1, I2,... In, respectively.

[0085] <Control by the controller 30>

[0086] The control performed by the controller 30 in the use stage after the disk device 1 is manufactured will be described with reference to the flowchart of Fig. 6. Figure 11

[0087] ​When the head 10 needs to seek (Sl), the controller 30 starts the seek (S2) of the head 10 from the stop position on the disk 2 to the target position Pt. Along with the start of the seek, the controller 30 detects the speed (moving speed) of the head 10 based on the history of the captured position Pos of the position capture section 30a (S3). Also, the controller 30 estimates the counter electromotive voltage V BL (S4) in the coil of the voice coil motor 23 by the product of the detected speed and the above BL constant k BEMF .

[0088] Also, the controller 30 obtains the inductance voltage V VCM_A by referring to the conversion table 45a based on the acceleration drive current I L detected by the current detector 43a, and estimates the resistance R of the coil 23c of the voice coil motor 23 by the operation of the following equation based on the obtained inductance voltage V L , the drive voltage V VCM of the voice coil motor 23 detected by the voltage detector 43b, the above estimated counter electromotive voltage V BEMF , and the acceleration drive current I VCM_A detected by the current detector 43a (S5).

[0089] R = (|V VCM | - |V L | - |V BEMF |) / |I VCM_A |

[0090] In the reference to the conversion table 45a, if the acceleration drive current I VCM_A detected by the current detector 43a is I1, the controller 30 reads out the inductance voltage V L = V1 corresponding to this I1 from the conversion table 45a. If the acceleration drive current I VCM_A detected by the current detector 43a is I2, the controller 30 reads out the inductance voltage V L = V2 corresponding to this I2 from the conversion table 45a. If the acceleration drive current I VCM_A detected by the current detector 43a is I3, the controller 30 reads out the inductance voltage V L = V3 corresponding to this I3 from the conversion table 45a.

[0091] In the case where the acceleration drive current I VCM_A detected by the current detector 43a is "I1 + ix" existing between I1 and I2 with respect to each other, the controller 30 reads out the inductance voltage V L = V1 corresponding to I1 and the inductance voltage V L=V2, and the voltage V at the two inductors read is calculated. L The inductance voltage V between each other L = "V1 + vx". Similarly, the acceleration drive current I detected by current detector 43a VCM_A In the case of "I2+ix" existing between I2 and I3, read the inductor voltage V corresponding to I2 from transformation table 45a. L =V2 and the inductor voltage V corresponding to I3 L =V3, calculate the voltage V between the two inductors read out. L The inductance voltage V between each other L = "V2+vx".

[0092] After estimating the coil resistance R, the controller 30 adjusts the deceleration drive current I based on the estimated result. VCM_D (S6)

[0093] Figure 12 This shows the deceleration drive current I when the ambient temperature (coil temperature T) is at room temperature. VCM_D It also shows three extreme values ​​I when the ambient temperature (coil temperature T) is at high temperature, normal temperature, and low temperature. Lim_D Assuming the disk device design is conducted at room temperature, Figure 12 The deceleration drive current I in VCM_D This is the standard current used in the design. For example... Figure 12 As shown, I VCM_D Designed so that even at its maximum value I DecMax The value should not exceed the limit value I at room temperature. Lim_D Limit value I Lim_D It can be theoretically calculated using the following formula. Furthermore, the inductor voltage V... L This differs from the value estimated during acceleration.

[0094] I Lim_D =(|V VCM |-|V L |-|V BEMF |) / R

[0095] From the above equation, we can see that the limit value I... Lim_D Clearly, it is inversely proportional to the coil resistance R, i.e., the coil temperature T. During the design, to ensure the driving current I for deceleration... VCM_D The maximum value I DecMax It will not become the limit value I at room temperature. Lim_D The above describes how the deceleration drive current I is adjusted based on the coil resistance R. VCM_D The maximum value I DecMax The variation can be followed by a limit value I that may change depending on the coil temperature T.Lim_D To set I DecMax The deceleration drive current I will be adjusted according to the coil resistance R. VCM_D The maximum value I DecMax Called I DecMaxM .

[0096] I DecMaxM =I DecMax ×(1 / R)

[0097] As described above, by estimating the coil resistance R, thus... Figure 13 As shown, even with a short seek distance, the deceleration drive current I can be used. VCM_D The maximum value I DecMax At its limit value I Lim_D Set it as large as possible within the range. That is, compared with the past (dashed line), it can significantly reduce the maximum value I. DecMax With limit value I Lim_D The difference in current margin I Mgn Therefore, it is possible to reduce the drive current I for deceleration. VCM_D Within the unsaturated range, maximize the seek deceleration. That is, improve access performance when the seek decelerates (high performance enhancement).

[0098] The controller 30 performs seek deceleration (S7) and moves towards stability determination (S8). In stability determination, when the capture position Pos of the position capture unit 30a converges to a predetermined range that sandwiches the target position Pt for a certain period (stabilization period), the controller 30 determines that the read / write head 10 has reached the target position Pt. The controller 30 captures this determination result as the end determination of seek (S9 "Yes") and ends seek.

[0099] [2] Variation Example

[0100] In the above embodiment, the acceleration drive current I detected by the current detector 43a is referenced. VCM_A The inductor voltage V can be obtained from transformation table 45a. L However, it is also possible to accelerate the vehicle by using the driving current I detected by the current detector 43a. VCM_A Applied to the above V L =L(dI) VCM / dt) of I VCM To perform differentiation, we can find the inductor voltage V. L In this case, it is not necessary to generate transformation table 45a in the manufacturing process of disk device 1.

[0101] The above-described embodiments are presented by way of example only, and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, substitutions, and changes can be made thereto without departing from the scope and spirit of the invention. These embodiments and / or modifications thereof contain within their scope and / or spirit the invention, and are included in the scope of the invention described in the claims and the equivalents thereof.

Claims

1. A disk device, comprising: a disk; a head that writes and reads data with respect to the disk; a voice coil motor that includes a magnet and a coil, and that causes the head to seek in a radial direction of the disk; and a controller that controls rotation of the disk and seeking of the head, the controller including: a seek control unit that causes the head to seek from a stop position on the disk to a target position in a manner including acceleration and deceleration by controlling a drive current of the voice coil motor; a velocity detection unit that detects a velocity of the head during the seeking; a back electromotive voltage estimation unit that estimates a back electromotive voltage induced in the coil of the voice coil motor based on the velocity detected by the velocity detection unit and a position of the seeking at the time of acceleration of the seeking; and a coil resistance estimation unit that estimates a resistance of the coil of the voice coil motor based on an inductive voltage generated in an inductive component of the coil of the voice coil motor according to the drive current of the voice coil motor, a drive voltage of the voice coil motor, the drive current of the voice coil motor, and the back electromotive voltage estimated by the back electromotive voltage estimation unit at the time of acceleration of the seeking.

2. The disk device according to claim 1, the controller further including a deceleration current adjustment unit that adjusts a deceleration drive current of the voice coil motor at the time of deceleration of the seeking based on the resistance estimated by the coil resistance estimation unit.

3. The disk device according to claim 1, the disk device further comprising:

4. The disk device according to claim 3, the controller further including a position detection unit that detects a position of the head on the disk based on a read signal of the head.

5. The disk device according to claim 4, the position detection unit including: a position detection signal generation unit that generates a position detection signal based on the read signal of the head; and a position detection signal processing unit that detects the position of the head on the disk based on the position detection signal generated by the position detection signal generation unit.

6. The disk device according to claim 3, the controller further including a position detection unit that detects a position of the head on the disk based on a read signal of the head.

7. The disk device according to claim 1, the controller further including a position capture unit that captures the position of the head on the disk based on a read signal of the head.

8. The disk device according to claim 7, the velocity detection unit detecting the velocity of the head during the seeking by differentiating the captured position of the position capture unit.

9. The disk device according to claim 7, the back electromotive voltage estimation unit estimating the back electromotive voltage by the product of the velocity detected by the velocity detection unit and a BL constant corresponding to the captured position of the position capture unit.

10. A control method of a disk device, the disk device comprising: a disk; a head that writes and reads data with respect to the disk; a voice coil motor that includes a magnet and a coil, and that causes the head to seek in a radial direction of the disk; and a controller that controls rotation of the disk and seeking of the head, in the control method, the head is caused to seek from a stop position on the disk to a target position in a manner including acceleration and deceleration by controlling a drive current of the voice coil motor, a velocity of the head during the seeking is detected, ​ ​ ​ ​ ​ a current detection unit that detects an acceleration drive current I as a drive current of the voice coil motor at acceleration of the seek VCM_A ; and a voltage detection unit that detects a driving voltage V of the voice coil motor VCM , The coil resistance estimation unit estimates a resistance component R of the coil of the voice coil motor on the basis of the following equation at the time of acceleration of the seek VCM_A The inductance voltage V generated in the inductance component L of the voice coil motor is found L The inductance voltage V generated in the inductance component L of the voice coil motor is found L The resistance component R of the coil of the voice coil motor is estimated by an operation of the following equation on the basis of the found inductance voltage V VCM , the drive voltage V detected by the voltage detection unit BEMF , the counter electromotive voltage V estimated by the counter electromotive voltage estimation unit VCM_A , and the acceleration drive current I detected by the current detection unit R = (|V VCM |-|V L |-|V BEMF |) / |I VCM_A |。 ​ The disk device also includes multiple acceleration drive currents I during the acceleration of the seek operation. VCM_A And according to these accelerations, the driving current I VCM_A Each of the generated multiple inductor voltages V L A transformation table was established and saved with corresponding relationships. The coil resistance estimation unit refers to the conversion table to find the inductance voltage V VCM_A The inductance voltage V L . ​ each of the drive currents I for acceleration stored in the conversion table VCM_A is the drive current I for acceleration recorded successively in the acceleration of the multiple seek performed at at least 2 or more environmental temperatures VCM_A , The inductance voltage V of each of the voice coil motors stored in the conversion table L is calculated by applying an operation to the inductance component L of the voice coil motor and the recorded drive current I for acceleration of each of the voice coil motors VCM_A is calculated by applying an operation to the inductance component L of the voice coil motor and the recorded drive current I for acceleration of each of the voice coil motors V L = L(dI VCM_A / dt). ​ Each of the inductance voltages V L is calculated by applying each of the recorded acceleration drive currents I VCM_A to an operation of the following equation, V L = L(dI VCM_A / dt). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ at the acceleration of the seek, estimating a counter electromotive voltage induced in the coil of the voice coil motor based on the detected speed and a position of the seek, at the acceleration of the seek, calculating an inductance voltage generated in an inductance component of the coil of the voice coil motor from a drive current of the voice coil motor, and estimating a resistance of the coil of the voice coil motor based on the calculated inductance voltage, a drive voltage of the voice coil motor, the drive current of the voice coil motor, and the counter electromotive voltage estimated by the counter electromotive voltage estimating unit.

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