Magnetic disk device and control method thereof

Abstract

To provide a magnetic disk device capable of obtaining coil resistance of a voice coil motor, and a control method thereof.SOLUTION: The speed of a magnetic head during a seek is detected. During seek acceleration, a back-EMF voltage is estimated to be induced in a coil of a voice coil motor based on the detected speed and the position of the seek. Then, during seek acceleration, the inductance voltage that is induced in the inductance component of the 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 based on the obtained inductance voltage, the drive voltage of the voice coil motor, the drive current of the voice coil motor, and the estimated back-EMF voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a magnetic disk device including a magnetic disk and a magnetic head, and a control method thereof. [Background technology]

[0002] A magnetic disk device equipped with a magnetic disk and a magnetic head includes an actuator that holds the magnetic head so that it can seek in the radial direction of the magnetic disk, and when writing or reading data to the magnetic disk, the magnetic head seeks (moves) in the radial direction of the magnetic disk from its previous stopping position to a target position (write position or read position) on the magnetic disk.

[0003] To improve seek access performance (high performance), it is important to maximize the potential of the voice coil motor (VCM). One way to maximize the potential of a voice coil motor is through the saturation acceleration function. The saturation acceleration function maximizes seek acceleration by increasing the voice coil motor's drive current (called the acceleration drive current) until it reaches saturation during seek acceleration.

[0004] However, during deceleration of a seek, the drive current of the voice coil motor (called the deceleration drive current) cannot be increased to the point of saturation because the magnetic head must be stopped reliably at the target position. In order to increase the seek deceleration as much as possible without saturating the deceleration drive current, it is necessary to understand the resistance value of the voice coil motor, which is a factor that varies the limit value of the deceleration drive current, so that the deceleration drive current does not saturate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 10,008,227 [Patent Document 2] U.S. Patent No. 9,947,352 [Patent Document 3] U.S. Patent No. 6,781,787 Summary of the Invention [Problem to be solved by the invention]

[0006] The main factor in fluctuations in the limit value of the deceleration drive current is the coil resistance of the voice coil motor. By determining this coil resistance, the deceleration drive current can be varied in accordance with the fluctuating limit value of the deceleration drive current, and the optimum deceleration drive current can be supplied to the voice coil motor at all times, thereby improving seek access performance.

[0007] An object of the embodiment is to provide a magnetic disk drive capable of determining the coil resistance of a voice coil motor and a control method thereof. [Means for solving the problem]

[0008] The magnetic disk device of the embodiment comprises: a magnetic disk; a magnetic head that writes and reads data to the magnetic disk; a voice coil motor that includes a magnet and a coil and causes the magnetic head to seek in the radial direction of the magnetic disk; and a controller that controls the rotation of the magnetic disk and the seeking of the magnetic head. The controller includes: a seek control means for controlling the drive current of the voice coil motor to cause the magnetic head to seek, including accelerating and decelerating, from a stop position on the magnetic disk to a target position; a speed detection means for detecting the speed of the magnetic head during the seek; a back electromotive force estimation means for estimating a back electromotive force induced in the coil of the voice coil motor based on the speed and the seek position detected by the speed detection means during the seek acceleration; and a coil resistance estimation means for determining 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 during the seek acceleration, and estimating the resistance of the coil of the voice coil motor based on the determined inductance voltage, the drive voltage of the voice coil motor, the drive current of the voice coil motor, and the back electromotive force estimated by the back electromotive force estimation means. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of a main part of a magnetic disk according to an embodiment. [Figure 3] FIG. 3 is a diagram showing an equivalent circuit of a coil of a voice coil motor according to an embodiment. [Figure 4] FIG. 4 is a diagram showing changes in the drive current of a voice coil motor with the seek distance as a parameter in one embodiment. [Figure 5] FIG. 5 is a diagram showing a change in the acceleration drive current of the voice coil motor in one embodiment, with the coil temperature of the voice coil motor as a parameter. [Figure 6]FIG. 6 is a diagram showing the change in inductance voltage occurring in the inductance component of FIG. 3, with the coil temperature of the voice coil motor as a parameter. [Figure 7] FIG. 7 is a diagram showing a part of the change in the acceleration drive current in FIG. 5 with the time axis enlarged. [Figure 8] FIG. 8 is a diagram showing a part of the change in inductance voltage in FIG. 6 with the time axis enlarged. [Figure 9] 9 is a diagram showing the relationship between the acceleration drive current in FIG. 7 and the voltage in FIG. 8. [Figure 10] 10 is a diagram showing the format of a conversion table between the acceleration drive current and the inductance voltage of FIG. 3 in one embodiment. [Figure 11] FIG. 11 is a flowchart showing the control of one embodiment. [Figure 12] FIG. 12 is a diagram showing limit values ​​of a deceleration drive current of a voice coil motor in one embodiment. [Figure 13] FIG. 13 is a diagram showing how the deceleration drive current of the voice coil motor during short distance seek in one embodiment increases compared to the conventional method. DETAILED DESCRIPTION OF THE INVENTION

[0010] [1] One embodiment will be described with reference to the drawings. 1, a magnetic disk device 1 includes a magnetic disk 2 which is a recording medium, a spindle motor 3 which rotates the magnetic disk 2, and a magnetic head 10 which writes and reads data to and from the magnetic disk 2. An actuator 20 which supports the magnetic head 10 is disposed near the magnetic disk 2.

[0011] The actuator 20 supports the magnetic head 10 so that it can seek in the radial direction of the magnetic disk 2. The actuator 20 is also called an actuator block or a head stack assembly (HSA), and includes a rotating shaft 21, an arm 22 whose midsection is held by the rotating shaft 21, a voice coil motor (VCM) 23 disposed at the base end of the arm 22, and a suspension member 24 provided at the tip of the arm 23 and holding the magnetic head 10.

[0012] The voice coil motor 23 includes a magnet 23m, a coil 23c, and a yoke 23y to which the magnet 23m is attached. A driving current I VCM The flow of current causes the actuator 20 to rotate between a first position indicated by the dashed line in the figure and a second position indicated by the solid line in the figure. As the actuator 20 rotates, the magnetic head 10 seeks (moves) in the radial direction of the magnetic disk 2 along a locus indicated by X in the figure.

[0013] A stopper ST and a ramp mechanism RL are disposed near the actuator 20. The stopper ST limits the movement position of the magnetic head 16 on the inner periphery side of the magnetic disk 12. The ramp mechanism RL retracts the magnetic head 16 from above the magnetic disk 2 when the spindle motor 3 is stopped.

[0014] The magnetic disk device 1 includes a controller 30 which is the center of control, a head amplifier 41 which drives the magnetic head 10, a signal processing circuit 42 which is provided between the connection between this head amplifier 41 and the controller 30, a motor driver 43 which is provided between the connection between the voice coil motor 23 and the controller 30, a DRAM 44 which is a memory which stores programs etc. necessary for controlling the controller 30, a flash ROM 45 which is a memory which stores various data necessary for controlling the controller 30, and a hard disk controller (HDC) 46 which is provided between the connection between the controller 30, the hard disk controller (HDC), and an external host device 50.

[0015] The head amplifier 41 amplifies a write data signal sent from the signal processing circuit 42 to the magnetic head 10, and also amplifies a data signal read by the magnetic head 10. The signal processing circuit 42 appropriately processes a write data signal sent from the controller 30 to the magnetic head 10 and supplies it to the head amplifier 41, and also appropriately processes a read data signal amplified by the head amplifier 41 and supplies it to the controller 30.

[0016] The motor driver 43 supplies the drive current I to the spindle motor 3 and the drive current I to the voice coil motor 23. VCM In response to an instruction from the controller 30, the motor driver 43 controls the driving current I VCM (Acceleration drive current I VCM_A and deceleration drive current I VCD_D and a current detector 43a for detecting the value of the drive voltage V of the voice coil motor 23. VCM The flash ROM 45 stores a conversion table 45a used in the processing of a deceleration current adjustment section 30g (to be described later) of the controller 30. The contents of the conversion table 45a will be described later.

[0017] 2, the magnetic disk 2 has a circular shape and is coaxially fitted to the rotation shaft of the spindle motor 3, and includes a large number of tracks Tr arranged circumferentially and concentrically. Each track Tr includes a servo sector consisting of a servo pattern SB in which position data is recorded and a data area DT in which write data is stored.

[0018] The controller 30 includes, as its main functions, a position acquisition section (position acquisition means) 30a, a seek control section (seek control means) 30b, a settling determination section (determination means) 30c, a speed detection section (speed detection means) 30d, a back electromotive force estimation section (back electromotive force estimation means) 30e, a coil resistance estimation section (coil resistance estimation means) 30f, and a deceleration current adjustment section (deceleration current adjustment means) 30g.

[0019] [Location Acquisition Section 30a] The position capture section 30 a 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 .

[0020] [Seek Control Section 30b] The seek control section 30b controls the driving of the voice coil motor 23 to move the magnetic head 10 from the stop position on the magnetic disk 2 to the target position Pt. Specifically, the seek control section 30b controls the drive current I of the voice coil motor 23 of the actuator 20 based on the capture position Pos of the position capture section 30a. VCM By controlling the above, the magnetic head 10 is caused to seek from a stop position on the magnetic disk 2 to a target position Pt, with acceleration and deceleration being sequentially included.

[0021] [Settling Determination Section 30c] When the magnetic head 10 seeks, the settling determination section 30c performs a so-called settling determination, which determines that the magnetic head 10 has reached the target position Pt when a certain period Cs has elapsed while the capture position Pos of the position capture section 30a is within a specified range that includes the target position Pt.

[0022] [Speed ​​Detection Section 30d] When the magnetic head 10 is accelerating in a seek, the speed detection section 30d detects the speed (movement speed) v of the magnetic head 10 by calculation based on the history of the captured position Pos of the position capture section 30a (the position history of the magnetic head 10). hd Specifically, the speed detection section 30d differentiates the position Pos captured by the position capture section 30a, and calculates the absolute value of the result of the differentiation as the seek speed v. hd Detect as.

[0023] [Back EMF Estimation Section 30e] The back electromotive force detection section 30e detects the velocity v detected by the velocity detection section 30d when the magnetic head 10 is accelerating during seek.hd and the back electromotive force V induced in the coil of the voice coil motor 23 by calculation based on the seek position of the magnetic head 10 (the capture position Pos of the position capture section 30a). BEMF Specifically, the back electromotive force detection section 30e estimates the speed v detected by the speed detection section 30d. hd and a BL constant k depending on the capture position Pos of the position capture section 30a. BL The back electromotive force V induced in the coil of the voice coil motor 23 is BEMF Estimate the BL constant k BL is a coefficient determined by the product of the magnetic flux density of the magnetic field applied to the coil 23c from the magnet 23m of the voice coil motor 23 and the effective length of the winding of the coil 23c present in that magnetic field. V BEMF =v hd ×k BL

[0024] [Coil Resistance Estimation Section 30f] The coil resistance estimation section 30f estimates the inductance voltage V generated in the inductance component L of the coil 23c of the voice coil motor 23 during the acceleration of the magnetic head 10 during seek. L The acceleration drive current I detected by the current detector 43a VCM_A The inductance voltage V L , the driving voltage V of the voice coil motor 23 detected by the voltage detector 43b VCM , the back electromotive force V estimated in the back electromotive force estimation section 30e BEMF、 and the acceleration drive current I detected by the current detector 43a. VCM_A The resistance (resistance value) R of the coil 23c of the voice coil motor 23 is estimated by the calculation of the following equation based on the above. The resistance R is referred to as coil resistance R. R=(|V VCM |-|V L |-|V BEMF |) / |I VCM_A |

[0025] [Deceleration current adjustment section 30g] The deceleration current adjustment section 30g calculates the deceleration drive current I of the voice coil motor 23 during deceleration of the seek by the following formula based on the coil resistance R estimated by the coil resistance estimation section 30f: VCM_D The maximum value of I DecMax After adjustment, the deceleration drive current is adjusted to I DecMaxM It is called. I DecMaxM =I DecMax ×(1 / R)

[0026] <Explanation about coil resistance estimation> An equivalent circuit of the coil 23c of the voice coil motor 23 is shown in FIG. The coil 23c of the voice coil motor 23 has three elements: an inductance component L, a resistance component (=resistance value) R which is the coil resistance, and a back electromotive force Ec. VCM is the drive voltage applied to the coil 23c. L is the driving voltage V VCM This voltage is called the inductance voltage. V R is the driving voltage V VCM is the voltage generated across resistor R when V is applied. BEMF is the back electromotive force induced in the coil 23c in accordance with the movement of the magnet 23m when the magnetic head 10 seeks.

[0027] The coil resistance R varies depending on the temperature T of the coil 23c. Hereinafter, the temperature T will be referred to as the coil temperature T. The back electromotive force V BEMF fluctuates depending on the seek speed of the magnetic head 10 and the magnetic flux density of the magnetic field applied to the coil 23c from the magnet 23m of the voice coil motor 23. This magnetic flux density can fluctuate depending on changes in the positional relationship between the magnetic head 10 and the magnet 23m that accompany the seek. For simplicity of explanation, the magnetic flux density is treated as a constant value.

[0028] Drive voltage V VCM , inductance voltage V L , voltage V across coil resistance R R , and the back electromotive force V BEMFThe relationship is such that the sampling time is t and the driving current flowing through the coil 23c is I VCM is expressed by the following equation (1). V VCM =V L +V R +V BEMF =L(dI VCM / dt)+RI VCM +V BEMF …(1)

[0029] "L(dI VCM / dt)” is the driving voltage V VCM When the inductance voltage V L This indicates that the response is transient.

[0030] The above equation (1) is expressed as the drive current I VCM When this is rearranged, the following equation (2) is obtained. I VCM =(V VCM -V L -V BEMF ) / R…(2)

[0031] This drive current I VCM is the inductance component L, the resistance component R, and the back electromotive force V BEMF Since the current is determined by the physical elements of the drive voltage V VCM is the saturation current that flows when VCM =I Lim ).

[0032] From the above equation (2), the drive current I VCM The limit value of I Lim It is clear that depends on the coil resistance R. In a magnetic disk drive, the coil temperature T can constantly change depending on the frequency of seek operations (i.e., the frequency per unit time of commands received from the host device 50) and the temperature status of the magnetic disk drive 1. As described above, the coil resistance R varies depending on the coil temperature T, so the drive current I VCM The limit value of I Lim can also constantly change.

[0033] Drive current I controlled by the seek control section 30b VCM The change in the acceleration drive current I VCM_A The magnetic head 10 starts seeking and accelerates due to the rising edge of the acceleration drive current I VCM_A falls and the deceleration drive current I VCM_D As a result, the actuator 20 decelerates (acceleration / deceleration switching period). After that, the deceleration drive current I VCM_D falls (deceleration fall period), and the seek of the magnetic head 10 is completed after the settling determination.

[0034] As mentioned above, in order to improve the access performance of the seek (to increase the performance), it is important to maximize the potential of the voice coil motor 23. One of the measures to maximize the potential of the voice coil motor 23 is the saturation acceleration function. The saturation acceleration function increases the acceleration drive current I VCM_A Increase until saturation, i.e., I VCM_A =I Lim-A This function maximizes the seek acceleration by controlling the speed so that

[0035] On the other hand, during deceleration of the seek, in order to stop the magnetic head 10 at the target position reliably, the target position and the current position are compared at predetermined time intervals, and the deceleration drive current I is adjusted so that the difference between the target position and the current position becomes zero. VCM_D Therefore, during deceleration, the deceleration drive current I VCM_D In order to increase the deceleration rate of the seek as much as possible, the deceleration drive current I VCM_D The limit value of I Lim_D and calculate the deceleration drive current I VCM_D It is necessary to control it within a range where I VCM_D Lim_D The deceleration drive current I VCM_D It is necessary to adjust the limit value I Lim_D ​depends on the coil resistance R, so by calculating this coil resistance R, the deceleration drive current I VCM_D The limit value of I VCM_D This allows for seek control that does not exceed the

[0036] As shown in Figure 4, when the seek distance is long (long distance seek), the acceleration drive current I VCM_A is saturated and reaches the maximum value I AccMax The timing at which this occurs is when the inductance voltage V L The transient response of converges and the inductance voltage V L This is the timing when "L(dI VCM / dt)" can be omitted, and the coil resistance (= resistance value) R can be found using the following equation (3). In addition, there are two possible seek directions, one in the inner circumferential direction and the other in the outer circumferential direction of the magnetic disk 12, and since the polarity of the applied voltage differs in each case, an absolute value is introduced when transforming equation (1). R=(|V VCM |-|V BEMF |) / |I AccMax |…(3)

[0037] However, as shown in the same Figure 4, when the seek distance is short (short distance seek), the acceleration drive current I VCM_A is the saturation point, I AccMax In this case, the seek switches to deceleration before the inductance voltage V L The transient response of the inductance voltage V L is not 0V, the coil resistance R cannot be calculated from the above equation (3).

[0038] Therefore, during the rise of the seek acceleration, the acceleration drive current I VCM_A Consider estimating the coil resistance R before it reaches its saturation point. Acceleration drive current I VCM_A In order to estimate the coil resistance R before it reaches the saturation point, the inductance voltage V before the transient response has converged is L (It is not 0V)

[0039] Acceleration drive current I VCM_A The inductance voltage V before reaching the saturation point L is calculated from the above equation (1) as V L =L(dI VCM That is, the acceleration drive current I detected by the current detector 43a is VCM_A By differentiating the acceleration drive current I VCM_A The inductance voltage V before reaching the saturation point L can be obtained.

[0040] In addition, the acceleration drive current I VCM_A There is a concern about differentiating the acceleration drive current I during the rise of the seek acceleration. VCM_A Since the change per unit time is large, if the current detector 43a is assumed to be an A / D converter with a limited dynamic range, such as that mounted on the motor driver 43, the acceleration drive current I VCM_A The gradation is insufficient to capture the sudden change in the current, and detection errors (also called measurement errors) are likely to occur. Moreover, there is a possibility that the detection errors will be further accentuated by the differentiation process. One way to reduce the detection errors is to average the detection results of multiple samples. However, as shown in Figure 5, during the rise of the seek acceleration, the acceleration drive current I VCM_A Since the change in is not linear, it is difficult to accurately calculate the average value using the arithmetic mean, which has a relatively small calculation load.

[0041] As a countermeasure, the acceleration drive current I detected by the current detector 43a VCM_A and inductance voltage V L The correspondence relationship information is stored in advance, and thereafter, by referring to the correspondence relationship information based on the detection result of the current detector 43a, the acceleration driving current I is calculated while eliminating noise increase due to differentiation processing and averaging error. VCM_A The inductance voltage V before reaching the saturation point L It is possible to estimate the following.

[0042] Figure 5 shows the relationship between the constant driving voltage VVCM The acceleration drive current I flows when the VCM_A The time change of the coil temperature T (which can be expressed as multiple coil resistances R) from 20°C to 80°C is shown as a parameter. In general control of the voice coil motor 23, a pulsed voltage is applied to the voice coil motor 23 using PWM (Pulse Width Modulation) control or the like, and the voltage level is adjusted by changing the pulse width of the applied voltage. However, the continuous application of a constant level of DC voltage without changing the pulse width is called a "constant drive voltage V". VCM is applied to the voice coil motor 23.

[0043] Figure 6 shows the acceleration drive current I VCM_A When the inductance voltage V L Above V L =L(dI VCM / dt) Since a non-magnetic material is used for the actuator 20 to which the coil 23c of the voice coil motor 23 is attached, the fluctuation of the inductance component L due to temperature change is assumed to be negligibly small.

[0044] In the time range of t = 0 to 50 (Sa) in Fig. 6, the inductance voltage V L is in a transient response state. At t=50(Sa), the acceleration drive current I VCM_A is the saturation point, I AccMax After t=50(Sa), the acceleration drive current I VCM_A is the back electromotive force V BEMF It gradually decreases due to the influence of

[0045] Figure 7 shows the acceleration drive current I VCM_A The time axis is expanded to show a part of the change in the accelerating drive current I. In other words, as the coil temperature T rises, the coil resistance R increases, and therefore the accelerating drive current I VCM_A It can be seen that becomes smaller.

[0046] Inductance voltage V L is the above V L =L(dI VCM / dt), the acceleration drive current I VCM_A The larger the change per time, the larger the value.

[0047] Figure 8 shows the inductance voltage V L The time axis is expanded to show a part of the change in the accelerating drive current I VCM_A The current flowing through the inductor decreases, and the inductor voltage V L It can be seen that becomes smaller.

[0048] FIG. 9 shows the acceleration drive current I VCM_A and the inductance voltage V at the same timing in Fig. 8 L As shown above, the constant driving voltage V VCM is applied to the voice coil motor 23, the acceleration drive current I VCM_A The change in is caused by the change in the coil temperature T (i.e., the change in the coil resistance R). Also, as can be seen from Figure 9, the acceleration drive current I VCM_A and inductance voltage V L There is a linear relationship between the driving voltage V VCM is applied to the voice coil motor 23, this linearity can be utilized to L Even if the transient response state is L =L(dI VCM / dt), the inductance voltage V L The acceleration drive current I VCM_A It is possible to estimate from

[0049] <Manufacturing operations of the magnetic disk device 1> In the manufacturing process of the magnetic disk device 1, an operator performs a seek of the magnetic head 10 at at least two or more environmental temperatures, and measures the drive current I at any multiple times t during the acceleration of the seek.VCM (Acceleration drive current I VCM_A ) are recorded one by one. Then, the worker records the inductance component L of the voice coil motor 23 and the acceleration drive current I VCM_A The theoretical formula is V L =L(dI VCM / dt), the driving current for each acceleration I VCM_A The corresponding inductance voltage V L The inductance component L used in this calculation may be a common value for all magnetic disk devices 1 manufactured, or may be a value specific to each magnetic disk device 1. Furthermore, the value of the inductance component L may be a design value or a measured value.

[0050] Then, the operator measures each of the acceleration drive currents I VCM_A and the driving current for these accelerations I VCM_A Each inductance voltage V is calculated as above. L A conversion table 45a is generated in which the above-mentioned correspondences are stored, and the conversion table 45a is stored in the flash ROM 45.

[0051] The conversion table 45a contains the acceleration drive current I VCM_A The data I1, I2, ... In are stored sequentially as values ​​of the inductance voltages V L The data V1, V2, . . . Vn are stored sequentially as values.

[0052] <Control of the controller 30> The control executed by the controller 30 when the magnetic disk device 1 is in use after manufacture will be described with reference to the flowchart of FIG.

[0053] When a seek of the magnetic head 10 is required (S1), the controller 30 starts a seek to move the magnetic head 10 from a stop position on the magnetic disk 2 to a target position Pt (S2). With the start of this seek, the controller 30 detects the speed (movement speed) of the magnetic head 10 based on the history of the capture position Pos in the position capture section 30a (S3). The controller 30 then compares the detected speed with the BL constant k BL The back electromotive force V induced in the coil of the voice coil motor 23 is BEMF is estimated (S4).

[0054] The controller 30 then calculates the inductance voltage V L The acceleration drive current I detected by the current detector 43a VCM_A The inductance voltage V L , the driving voltage V of the voice coil motor 23 detected by the voltage detector 43b VCM , the back electromotive force V estimated above BEMF、 and the acceleration drive current I detected by the current detector 43a. VCM_A The resistance R of the coil 23c of the voice coil motor 23 is estimated by the calculation of the following equation based on the above (S5). R=(|V VCM |-|V L |-|V BEMF |) / |I VCM_A |

[0055] When referring to the conversion table 45a, the controller 30 converts the acceleration driving current I detected by the current detector 43a into VCM_A If I1, the inductance voltage V corresponding to I1 L =V1 is read from the conversion table 45a. The acceleration drive current I detected by the current detector 43a VCM_A is I2, the controller 30 calculates the inductance voltage V corresponding to I2. L =V2 is read out from the conversion table 45a. The acceleration drive current I detected by the current detector 43a VCM_A is I3, the controller 30 calculates the inductance voltage V corresponding to I3. L=V3 is read from the conversion table 45a.

[0056] The acceleration drive current I detected by the current detector 43a VCM_A In the case of "I1+ix" existing between I1 and I2, the inductance voltage V corresponding to I1 is L = Inductance voltage V corresponding to V1 and I2 L =V2 is read from the conversion table 45a, and the two read inductance voltages V L The inductance voltage V between L Similarly, the acceleration drive current I detected by the current detector 43a is calculated as follows: VCM_A If "I2+ix" exists between I2 and I3, the inductance voltage V corresponding to I2 is L = Inductance voltage V corresponding to V2 and I3 L =V3 is read from the conversion table 45a, and the two read inductance voltages V L The inductance voltage V between L Calculate "V2+vx".

[0057] After estimating the coil resistance R, the controller 30 calculates the deceleration drive current I VCM_D Adjust (S6).

[0058] Figure 12 shows the deceleration drive current I when the ambient temperature (coil temperature T) is at room temperature. VCM_D The three limit values ​​I when the ambient temperature (coil temperature T) is high, normal, or low are shown. Lim_D The magnetic disk drive is designed under a room temperature environment, and the deceleration drive current I VCM_D is the standard current at the time of design. As shown in Figure 12, I VCM_D is its maximum value I DecMax Even at room temperature, the limit value I Lim_D It is designed not to exceed the limit value I. Lim_D can be theoretically calculated using the following formula: Lis different from the value estimated during acceleration. I Lim_D =(|V VCM |-|V L |-|V BEMF |) / R

[0059] From the above equation, the limit value I Lim_D It is clear that is inversely proportional to the coil resistance R, i.e., the coil temperature T. In design, the deceleration drive current I VCM_D The maximum value of I DecMax is the limit value at room temperature I Lim_D It is guaranteed that the deceleration drive current I VCM_D The maximum value of I DecMax By varying the limit value I that can be changed due to fluctuations in the coil temperature T, Lim_D Following I DecMax It is possible to set the deceleration drive current I VCM_D The maximum value of I DecMax I DecMaxM It is called. I DecMaxM =I DecMax ×(1 / R)

[0060] As described above, by estimating the coil resistance R, the deceleration drive current I VCM_D The maximum value of I DecMax The limit value I Lim_D In other words, the maximum value I DecMax and limit value I Lim_D The current margin I Mgn This allows for a significant reduction in the deceleration drive current I VCM_D This allows the seek deceleration to be increased as much as possible without saturating the drive. This means that the access performance during the seek deceleration is improved (high performance).

[0061] The controller 30 executes the deceleration of the seek (S7) and proceeds to the settling determination (S8). In the settling determination, the controller 30 determines that the magnetic head 10 has reached the target position Pt when a certain period (settling period) has elapsed while the capture position Pos of the position capture section 30a is within a specified range that includes the target position Pt. The controller 30 regards this determination result as the end of the seek (YES in S9) and ends the seek.

[0062] [2] Variation In the above embodiment, the inductance voltage V L The acceleration drive current I detected by the current detector 43a VCM_A However, the acceleration driving current I detected by the current detector 43a is calculated by referring to the conversion table 45a based on the VCM_A Above V L =L(dI VCM / dt)I VCM and differentiate it to obtain the inductance voltage V L In this case, it is not necessary to generate the conversion table 45a in the manufacturing process of the magnetic disk device 1.

[0063] The above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0064] 1...magnetic disk device, 2...magnetic disk, 10...magnetic head, 23...voice coil motor, 30...controller, 30a...position acquisition section, 30b...seek control section, 30c...settling determination section, 30d...speed detection section, 30e...back electromotive force estimation section, 30f...coil resistance estimation section, 30g...deceleration current adjustment section, 43a...current detector, 43b...voltage detector.

Claims

1. A magnetic disk, a magnetic head for writing and reading data to and from the magnetic disk; a voice coil motor including a magnet and a coil for causing the magnetic head to seek in the radial direction of the magnetic disk; a controller that controls the rotation of the magnetic disk and the seek of the magnetic head; Equipped with The controller a seek control means for controlling a drive current of the voice coil motor to cause the magnetic head to seek, including accelerating and decelerating, from a stop position on the magnetic disk to a target position; a speed detection means for detecting the speed of the magnetic head during the seek; a back electromotive force estimating means for estimating a back electromotive force induced in the coil of the voice coil motor based on the speed detected by the speed detecting means and the position of the seek during the acceleration of the seek; a coil resistance estimation means for estimating a resistance of the coil of the voice coil motor based on the inductance voltage generated in the inductance component of the coil of the voice coil motor during acceleration of the seek, the inductance voltage being calculated from the drive current of the voice coil motor, the drive voltage of the voice coil motor, the drive current of the voice coil motor, and the back electromotive force estimated by the back electromotive force estimation means; Including, Magnetic disk device.

2. The controller a deceleration current adjusting means for adjusting a deceleration drive current for the voice coil motor during deceleration of the seek based on the resistance estimated by the coil resistance estimating means; further comprising:

2. The magnetic disk drive according to claim 1.

3. The acceleration drive current I is the drive current for the voice coil motor during the acceleration of the seek. ＶＣＭ_A a current detection means for detecting the The driving voltage V of the voice coil motor ＶＣＭ a voltage detection means for detecting the Furthermore, The coil resistance estimation means estimates an inductance voltage V generated in an inductance component L of the voice coil motor during acceleration of the seek. Ｌ The acceleration driving current I detected by the current detection means ＶＣＭ_A The inductance voltage V Ｌ , the drive voltage V detected by the voltage detection means ＶＣＭ , the back electromotive voltage V estimated by the back electromotive voltage estimation means ＢＥＭＦ、 and the acceleration drive current I detected by the current detection means. ＶＣＭ_A The resistance component R of the coil of the voice coil motor is estimated by the calculation of the following equation based on R=(|V ＶＣＭ |-|V Ｌ |-|V ＢＥＭＦ |) / |I ＶＣＭ_A | 2. The magnetic disk drive according to claim 1.

4. The plurality of acceleration drive currents I ＶＣＭ_A and these acceleration drive currents I ＶＣＭ_A The plurality of inductance voltages V Ｌ a conversion table in which the Furthermore, The coil resistance estimation means estimates the acceleration drive current I detected by the current detection means. ＶＣＭ_A The inductance voltage V Ｌ is obtained by referring to the conversion table.

4. The magnetic disk drive according to claim 3.

5. The acceleration driving current I stored in the conversion table ＶＣＭ_A is the acceleration drive current I recorded sequentially during the rise of acceleration of the plurality of seeks performed at at least two or more environmental temperatures. ＶＣＭ_A and The inductance voltages V stored in the conversion table Ｌ is the inductance component L of the voice coil motor and the acceleration drive current I ＶＣＭ_A is calculated by fitting it into the following formula: 6 Ｌ =L(dｩ ＶＣＭ_A / dt) 5. The magnetic disk drive according to claim 4.

6. Each inductance voltage V Ｌ is the inductance component L of the voice coil motor and the acceleration drive current I ＶＣＭ_A is calculated by fitting it into the following formula: 6 Ｌ =L(dｩ ＶＣＭ_A / dt) 4. The magnetic disk drive according to claim 3.

7. The controller a position capture means for capturing the position of the magnetic head on the magnetic disk based on read data of the magnetic head; further comprising:

2. The magnetic disk drive according to claim 1.

8. the velocity detection means detects the velocity of the magnetic head during the seek by differentially calculating the position captured by the position capture means; 8. The magnetic disk drive according to claim 7.

9. the back electromotive force estimation means estimates the back electromotive force by multiplying the speed detected by the speed detection means by a BL constant corresponding to the captured position by the position capture means; 8. The magnetic disk drive according to claim 7.

10. A magnetic disk, a magnetic head for writing and reading data to and from the magnetic disk; a voice coil motor including a magnet and a coil for causing the magnetic head to seek in the radial direction of the magnetic disk; a controller that controls the rotation of the magnetic disk and the seek of the magnetic head; A method for controlling a magnetic disk drive comprising: By controlling the drive current of the voice coil motor, the magnetic head is caused to seek, including acceleration and deceleration, from a stop position on the magnetic disk to a target position; detecting the speed of the magnetic head during the seek; During the acceleration of the seek, a back electromotive force induced in the coil of the voice coil motor is estimated based on the detected speed and the position of the seek; an inductance voltage generated in an inductance component of the coil of the voice coil motor during acceleration of the seek is obtained from a drive current of the voice coil motor, and a resistance of the coil of the voice coil motor is estimated based on the obtained inductance voltage, the drive voltage of the voice coil motor, the drive current of the voice coil motor, and the back electromotive force estimated by the back electromotive force estimation means; A method for controlling a magnetic disk device.

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