JPH08263950A - Rotary type storage device - Google Patents

Abstract

PURPOSE: To shorten the time required for deciding positioning setting in positioning a head of the rotary type storage device without deteriorating its operational reliability. CONSTITUTION: The device has magnetic disks 1 for storing data and position information on their disk surfaces, magnetic heads 2 disposed opposite to the disk surfaces, a head supporting mechanism 3 for supporting the magnetic heads 2, a driving part 7 for moving the head supporting mechanism 3, a head position detecting part 6 for detecting positions of the magnetic heads 2 and a head position control part 9 for outputting driving command values to the head position detecting part 6 and the driving part 7 and controlling head positions. In this case, when a head positioned into a target position, a head position ahead of a prescribed time by using a model of a head positioning control system or a head position ahead of a prescribed time from reference time is estimated. A setting decision part 10 is provided for making a setting decision for the head positioning operation based on the above estimated value and outputting the decision as a positioning setting signal 100 without a waiting time for the setting at all.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary memory device, and more particularly to a technique effectively applied to a magnetic head positioning control technique in a magnetic disk device.

[0002]

2. Description of the Related Art Conventionally, in a settling judgment of a positioning operation of a magnetic head in a magnetic disk device, a deviation between a head position and a target position is continuously below a permissible value for a predetermined time (hereinafter referred to as settling monitoring time). Was going by. That is, the head starts moving to the target position (hereinafter referred to as seek operation), measures the time after reaching the vicinity of the target position and the position deviation is below the allowable value, and continuously measuring during the settling monitoring time. It is determined that the positioning operation is completed (settled) when the value falls below the allowable value. Alternatively, at a time point when a preset time has elapsed after reaching the vicinity of the target position,
In some cases, the positioning operation may be completed (settled). For example, in the technique disclosed in Japanese Patent Laid-Open No. 63-42065, the length of the settling time (settling waiting time) at each positioning position is adjusted to be optimized based on the conditions such as the excitation phase of the motor that drives the magnetic head. The balance between shortening and prevention of malfunctions is aimed at.

[0003]

Therefore, assuming that the time from the start of movement of the head to the target position until the settling judgment is made is the positioning settling time, the positioning settling time is actually measured after the head starts to move to the target position. In addition, the time until the position deviation continues to be below the allowable value (hereinafter referred to as the positioning operation time) is longer by the settling monitoring time, and the data recording / reproducing operation for an arbitrary area on the magnetic disk is performed. The required time becomes longer by the amount of the settling judgment, which causes a decrease in the data transfer performance including the seek operation.

On the contrary, if the settling monitoring time is not sufficiently long with respect to the response time determined by the natural frequency of the positioning control system, once it is determined that the positioning operation has settled, the position deviation of the head is allowed again. Is likely to exceed. In this case, since the magnetic disk device starts reading / writing data when it is determined that the positioning operation has settled, there is a high possibility that a failure such as a data recording / reproducing error will occur, and the reliability of the magnetic disk device will increase. Lower.

In the technique of the above-mentioned Japanese Patent Laid-Open No. 63-42065, it is possible to improve the performance by optimizing the settling waiting time for each positioning area of the magnetic disk on the assumption that settling time (settling waiting time) is provided. , But there is no change in the idea of providing a fixed settling waiting time for each positioning operation.

It is an object of the present invention to reduce the time required for the positioning settling judgment in the positioning operation of the head with respect to an arbitrary recording area of the rotary storage medium without lowering the reliability of the operation. To provide a device.

Another object of the present invention is to realize an improvement in data transfer performance including a positioning operation of a head with respect to an arbitrary recording area of a rotary storage medium without deteriorating operational reliability. An object is to provide a rotatable storage device that can be used.

[0008]

According to the present invention, there is provided a rotary storage medium in which at least one of an area for storing data and an area for storing position information is arranged, and a head arranged so as to face the rotary storage medium. And a head positioning control system for positioning the head at an arbitrary position on the rotary storage medium based on the position information, the head is positioned when the head is positioned at a target position on the rotary storage medium. It is provided with a control logic for estimating a head position after a predetermined time using a model of a positioning control system and making a settling judgment of the head positioning operation based on the estimated value of the head position.

Further, the control logic estimates the head position from the reference time to a predetermined time ahead using the model of the head positioning control system when positioning the head at the target position, and based on this estimated value The settling judgment of the positioning operation can be performed.

Further, when the head is positioned at the target position, the control logic estimates the head position a predetermined time ahead using a model of the head positioning control system, and based on this estimated value, the head position a predetermined time ahead. The target position can be corrected so that is within a desired deviation range from the target position.

[0011]

By using the above means, for example,
In the sequence of the positioning operation of the magnetic head in the rotary storage device such as the magnetic disk device, the positioning settling judgment can be surely made earlier, for example, when a constant settling waiting time is provided as in the conventional case. In comparison with the above, it is possible to improve the reliability of a rotary storage device such as a magnetic disk device and improve the data transfer performance by shortening the positioning settling time.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing an example of a positioning control system of a rotary memory device according to an embodiment of the present invention. In the present embodiment, as an example of the rotary storage device, a case of applying to a magnetic disk device will be described.

As illustrated in FIG. 1, a magnetic head 2 is provided on each recording surface of a plurality of magnetic disks 1 supported and rotated in a parallel posture at a predetermined interval of a drive shaft 5 of a spindle motor 4. The magnetic heads 2 arranged to face each other are collectively supported by a head support mechanism 3 so as to be movable in the radial direction of the magnetic disk 1. The head support mechanism 3 includes a drive unit 7 such as a voice coil motor.
The drive section 7 is connected to the magnetic disk 1 of the plurality of magnetic heads 2 via the head support mechanism 3 according to a control signal input from the head position control section 9 via the D / A converter 8. Positioning operation is performed for any position in the direction.

A servo signal 12 recorded on the magnetic disk 1 is read from the magnetic head 2, converted into a head position signal 13 via a head position detector 6, and then inputted from the outside. It is input to the subtractor 11 together with the position signal 14. The subtractor 11 uses the target position signal 14
And a position deviation signal 15 which is a difference between the head position signal 13 and the head position signal 13. The head position controller 9 includes a seek controller 91 for controlling a seek operation, a following controller 92 for controlling a following operation, and a switch section 93 for selectively switching the both. The position detection unit 6 is a servo signal demodulation circuit 6
1, an A / D converter 62, and a head position calculator 63.

In this case, the head position signal 13 and the position deviation signal 15 are input to a part of the closed loop for controlling the positioning of the magnetic head 2 and are connected to the following controller 92 of the head position controller 9. Settling determination unit 10
Is provided, and the operation for outputting the positioning settling signal 100 is performed by the operation described later.

First, the basic operation of the head positioning control system of this embodiment will be described with reference to FIG. As mentioned above, at least one magnetic disk 1 for recording information is
It is attached to the drive shaft 5 of the spindle motor 4.
The magnetic head 2 arranged so as to face the magnetic disk 1
It is integrally supported by the head support mechanism 3. The head support mechanism 3 is driven by the drive unit 7. As a result, the magnetic head 2 moves from the outer circumference to the inner circumference of the magnetic disk 1 or from the inner circumference to the outer circumference of the magnetic disk 1 to be positioned at a target position (a target concentric circular recording area) for recording and reproducing information. .

At this time, the position of the magnetic head 2 is detected by the head position detector 6 (converted into a digital signal) from the servo signal 12 read from the magnetic disk 1 at a constant sampling period (hereinafter also referred to as a control period). Then, the subtractor 11 calculates the deviation (position deviation) from the target position signal 14 and fetches it in the head position controller 9. The head position control unit 9 performs a control calculation based on the fetched position deviation signal 15 and outputs a drive command value to the drive unit 7 via the D / A converter 8. The switching of the seek controller 91 and the following controller 92 in the head position controller 9 is performed mainly based on the magnitude of the position deviation. When the position deviation is large, the seek controller 91 and when the position deviation is small. The following controller 92 is selected. Here, the subtractor 11, the head position control unit 9, the settling determination unit 10 and the head position calculation unit 63 in FIG. 1 are generally realized by software.

Next, the operation of this embodiment will be described with reference to FIGS. The head positioning control system shown in FIG. 1 is schematically shown in FIG. 2 (the settling determination unit 10 is omitted). That is, FIG. 2 is a schematic diagram of the head positioning control system of the present embodiment, which includes the D / A converter 8, the drive unit 7,
The head support mechanism 3, the magnetic head 2, the magnetic disk 1, the spindle motor 4, the drive shaft 5, and the head position detection unit 6 are collectively controlled (only the behavior in the head positioning direction is considered), and the seek controller 91 and the follower. The ing controller 92 is modeled as the controller 17, and the settling determination unit 1
0 etc. are omitted.

As can be seen from the above description of the basic operation,
Since the head positioning control system shown in FIG. 1 is a digital control system that performs control based on the head position detected at a fixed sample period (control period), the drive unit 7, the head support mechanism 3, The magnetic head 2, the magnetic disk 1, the spindle motor 4, the drive shaft 5, the head position detection unit 6, and the D / A converter 8 are collectively set as a control target 16 (only the behavior in the head positioning direction is considered), and this is discrete. If it is realized, the whole head positioning control system can be modeled as one discrete time system. Further, in the magnetic disk device, when a target position is given to the head positioning control system and the positioning operation is started, the target position does not change until the positioning operation is completed, so that a signal input from the outside to the head positioning control system is constant. it is conceivable that. Therefore,
When the entire head positioning control system is modeled as one discrete time system, a predetermined time ahead (the predetermined time is n of the control cycle).
Double. n is an integer. Hereinafter, a predetermined time ahead will be referred to as n samples ahead. ) Head position or position deviation can be estimated as follows.

In FIG. 2, if the head positioning control system surrounded by a dotted line is modeled as a discrete time system, it can be expressed by the following equation of state.

X _{i + 1} = Ax _i + br (r: constant) (1) y _i = cx _i (2) where x is a state variable (vector), y is a head position,
r is the target position, A is the state transition matrix, and b is the state variable x from the input r to the model at the (i + 1) th sampling period.
_It is a vector or matrix representing the influence (relationship) on _{i + 1} , and c is the state variable x _i of the i-th sampling period and the output y _i
Is a vector or matrix that expresses the relationship with
i + 1 indicates the value of the i-th sampling period and the value of the i + 1-th sampling period, respectively. If the control period is Ts with reference to a certain time (time t = 0), the i-th sampling period is time t = iTs. , The i + 1th sampling period is time t = (i + 1) Ts (since r is constant, no subscript is added).

That is, the equation (1) is expressed by the state variable x _i and the target position r at the _i -th sampling period (time t = iTs).
And the next i + 1st sampling period (time t = (i + 1)
Ts) shows the relationship of state variables x _{i + 1} ,
Equation (2) shows the relationship between the state variable x _i and the head position y _i in the i-th sampling period. Therefore, (1)
Equation (2) is a recurrence formula, and the state variable x _i at the i-th sampling period (time t = iTs) and the i + n-th sampling period (time t = (i + n) Ts), that is, n samples ahead When the relation of the state variables x _{i + n} is obtained, the following formula is obtained (I is an identity matrix), and x _{i + 2} = Ax _{i + 1} + br = A ² x _i + (A + I) br (3) x _{i + 3} = Ax _{i + 2} + br = A ³ x _i + (A ² + A + I) br (4) :: x _{i + n} = Ax _{i + n-1} + br = A ⁿ x _i + (A ^n-1 + ... + A + I) br (5) In addition, the head position y _{i + n} and the position deviation e of n samples ahead
_{i + n} is the following formula, respectively. That is, y _{i + n} = cx _{i + n} = cA ⁿ x _i + c (A ^n-1 + ... + A + I) br (6) = h ₁ x _i + h ₂ r (7) e _{i + n} = r−y _{i + n = -h 1 x i +} (1-h 2) where _{r (8), h 1,} h 2 in accordance with the following ^{_{formula, h 1 = cA n (9}} ) h 2 = c (A n-1 + ... + A + I) b (10) can be calculated in advance.

Therefore, from the equation (8), when the information of the state variable x _i at the i-th sampling period (time t = iTs) is acquired, n samples ahead (time t = (i + n) T
It can be seen that the position deviation e _{i + n in} s) can be estimated. It should be noted that, regarding the state variables x _i , information is directly obtained (measured)
If not possible, it is also possible to use a state estimator that models elements such as the D / A converter 8, the drive unit 7, the spindle motor 4, the drive shaft 5, the magnetic disk 1, the magnetic head 2, and the head support mechanism 3. To be

In the head positioning control system shown in FIG. 1, after the target position is given and the positioning operation is started,
For example, when the head position reaches one track before the target position, the seek controller 91 changes to the following controller 9
If the position deviation is equal to or less than the allowable value after switching to 2, the settling determination unit 10 determines the state variables such as the head position, the head speed and the internal variables of the following controller 92 at the time when the positional deviation is equal to or less than the allowable value. To n samples ahead position deviation or the current time to n samples ahead position deviation is estimated, and the settling of the positioning operation can be determined depending on whether the estimated value is less than or equal to the allowable value. The reference time (i-th sampling period) at which the settling determination unit 10 estimates the position deviation n samples ahead is the current time,
At the time of switching from the seek controller 91 to the following controller 92, when the position deviation becomes equal to or less than the allowable value, and when the position deviation exceeds the allowable value thereafter, at the time when the position deviation becomes equal to or less than the allowable value again. As in the conventional settling judgment, it is conceivable that the position deviation becomes equal to or less than the allowable value continuously for a certain period of time. If the head movement distance is small, the positioning operation may be performed only by the following controller 92 after the target position is given. In this case, therefore, the positioning start time may be used. Is the natural frequency of the head positioning control system is fp
Then, since the position deviation often becomes maximum within 1 / (2fp) seconds, it is effective to select between n = 1 to 1 / (2fpTs) (n: integer) (11).

Here, an example of an algorithm for estimating a settling deviation from the current time to n samples ahead and making a settling judgment will be shown. FIG. 11 is a flowchart of the settling determination algorithm (one example) according to this embodiment. After positioning the head and reaching near the target value (step F11
a) After detecting the position deviation e _i at the current time for each sampling period (step F11b), the position deviations e _{i + 1 to} e _{i + n} are estimated for all integers n corresponding to the equation (11). (Step F11c), current position deviation | e _i | (absolute value) and its estimated value | e _{i + 1} | to | e _{i + n} | (absolute value)
The maximum value e _max is extracted from (step F11d), and the settling judgment of the positioning operation is performed (step F1e) depending on whether the maximum value e _max is less than or equal to the allowable value (step F11e).
1f).

Next, the case where there is a force disturbance 19 or a position disturbance 18 will be described. FIG. 3 is a schematic diagram of the head positioning control system when the force disturbance 19 and the position disturbance 18 cannot be ignored. In this case, when the head positioning control system surrounded by the dotted line in FIG. 3 is modeled as a discrete time system, x _{i + 1} = Ax _i + Bw _i (12) y _i = cx _i + Dw _i (13) where w Is the target position, force disturbance 19 and position disturbance 18
Is a vector that represents the input vector added from the outside to the head positioning control system. B is a vector or matrix showing the influence of the disturbance input (w _i ) to the model on the state variable x _{i + 1 of the i +} 1th sampling period, and D is the influence of the disturbance input (w _i ) on the output y _i . It is a vector or matrix. Further, unlike the equations (1) and (2), the input vector w is not always constant, and therefore a subscript is added to indicate that it is a value at the i-th sample period. Similar to the equation (8) derived from the equations (1) and (2), the equations (12) and (13) are used as recurrence equations to obtain the relationship of the state variables x _{i + n} n samples ahead. Then, the following equation is obtained: x _{i + 2} = Ax _{i + 1} + Bw _{i + 1} = A ² x _i + (ABw _i + Bw _{i + 1} ) (14) x _{i + 3} = Ax _{i + 2} + Bw _{i +2} = A ³ x _i + (A ² Bw _i + ABw _{i + 1} + Bw _{i + 2} ) (15) :: x _{i + n} = Ax _{i + n-1} + Bw _n-1 = A ⁿ x _i + (A ^n-1 Bw _i + ... + ABw _n-1 + Bw _n-1 ) (16) Further, the head position y _{i + n n} positions ahead and the position deviation e
_{i + n} is the following formula, respectively. That is, y _{i + n} = cx _i + Dw _{i + n} = cA ⁿ x _i + c (A ^n-1 Bw _i + ... + ABw _n-1 + Bw _n-1 ) + Dw _{i + n} (17) = h ₁₁ x _i + h ₁₂ (18) e _{i + n} = r−y _{i + n} = r−h ₁ x _i −h ₁₂ (19) If the input vector w from the i-th sample to the i + n-th sample period is known, h ₁ and h ₂ can be calculated according to the following formula, and h ₁ = cA ⁿ (20) h ₂ = c (A ^n-1 Bw _i + ... + ABw _n-1 + Bw _n-1 ) + Dw _{i + n} (21) ( Similar to the equation (8), it is understood that the equation (19) can also estimate the position deviation e _{i + n} n samples ahead when the information of the state variable x _i in the i-th sampling period is acquired.

In the case of a magnetic disk device, the force disturbance 19 is a constant force disturbance caused by wiring to the head,
Since the position disturbance 18 is predominantly a rotation-synchronized disturbance synchronized with the rotation of the magnetic disk (a repetitive disturbance depending on the circumferential position of the magnetic disk), the i-th sample to the i-th sample.
The above assumption that the input vector w up to the + nth sample period is known is considered to be a realistic assumption.

FIG. 4 is a diagram showing an example of a time response at the time of head positioning settling, FIGS. 5 and 6 are diagrams showing an example of a positioning settling signal and a write inhibit signal at the time of head positioning settling according to the conventional example, and FIG. FIG. 8 is a diagram showing an example of the maximum value of the position deviation (absolute value) estimated from the current time to n samples ahead, and FIG. 8 is a diagram showing an example of the positioning settling signal and write inhibit signal at the time of positioning settling according to this embodiment. is there.

Taking the time response (simulation) at the time of head positioning settling shown in FIG. 4 as an example, the difference between the positioning settling judgment according to the present embodiment and the conventional settling judgment will be shown. In this example, the control cycle is 0.05 ms, the head positioning control system is a secondary delay system with a natural frequency of 1 kHz, the initial value of the head position is standardized to 1, the target position is 0, and the allowable value of the position deviation is Is set to 0.25.

In the conventional settling judgment shown in FIG. 5, since the settling monitoring time is not set to a sufficiently long value of 0.15 ms (3 sample periods), the position deviation once becomes less than the allowable value.
Although it is determined that the positioning operation has settled after the elapse of the sample period (the positioning settling signal becomes 1 and information writing is permitted), the position deviation exceeds the allowable value again, so information writing is performed. It is prohibited (write protect signal becomes 1). In the conventional example shown in FIG. 6, the settling monitoring time is set to a large 0.5 ms (3 control cycles).
Although there is no error in the settling judgment as shown in Fig. 5, conversely, the positioning operation is settled with a delay of the settling monitoring time (0.5 ms) after the position deviation starts to be continuously below the allowable value. Has been determined.

In contrast to these conventional techniques, in the case of the present embodiment shown in FIG. 8, since the settling judgment is performed according to the flow chart shown in FIG. 11, the position deviation in FIG. It can be seen that it is determined that the positioning operation has been settled at the point of convergence. That is, it is possible to perform the settling determination in a short time without the need for the settling waiting time without causing a malfunction due to the redoing of the settling determination.

Next, a method for correcting the target position so that the head position falls within a desired deviation range from the target position based on the head position after the predetermined time estimated as described above will be described. FIG. 9 is a diagram showing an example of improving the vibration during positioning settling by the target position correction of this embodiment, and FIG. 10 is a diagram showing an example of the target position correction according to this embodiment. As described above, when the information of the state variable x _i in the i-th sampling period is obtained by the equation (8), n
The position deviation e _{i + n} at the sample destination can be estimated. here,
On the contrary, the target position r is corrected so that the position deviation e _{i + n} of n samples ahead becomes a desired value. Position deviation e n samples ahead
_{In order to set} the desired value of _{i + n} to e _rn , that is, to set the head position n samples ahead to r−e _rn , the target position r
Correct c as rc = (r−e _rn −h ₁ x _i ) / h ₂ (22). When the effect of the target position correction according to this embodiment was confirmed by simulation, the results shown in FIGS. 9 and 10 were obtained. It can be seen that, compared with the case where the target position correction is not performed, the deviation of n samples ahead (set as t = 0.5 ms) can be realized according to the set value (set as 0.05).

As described above, according to the magnetic disk device of the present embodiment, in the head positioning operation of the magnetic disk device, n samples ahead or n samples ahead from the reference time using the discrete time system model of the positioning control system. Since the position deviation up to is estimated, the positioning settling can be reliably determined without extending the positioning settling time. As a result, the entire data transfer required time including the positioning operation is shortened and the data transfer performance of the magnetic disk device is improved without impairing the reliability of the operation.

Further, by performing the target position correction by utilizing the estimation of the head position deviation using the discrete time system model of the positioning control system, the swing width of the head position near the target position is reduced, and after the settling judgment. The probability that the swing width of the head position deviates from the allowable range becomes small.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the rotary storage device is not limited to the magnetic disk device, but can be widely applied to general rotary storage devices that require the positioning operation of the head with respect to the rotary storage medium.

[0038]

According to the rotary storage device of the present invention, the time required for the positioning settling judgment in the positioning operation of the head with respect to an arbitrary recording area of the rotary storage medium is shortened without lowering the reliability of the operation. The effect that can be obtained is obtained.

According to the rotary type storage device of the present invention, the improvement of the data transfer performance including the positioning operation of the head with respect to an arbitrary recording area of the rotary type storage medium is realized without lowering the reliability of the operation. The effect of being able to do is obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a positioning control system of a rotary storage device which is an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a head positioning control system in the rotary storage device which is an embodiment of the present invention.

FIG. 3 is a schematic diagram showing an example of a head positioning control system when force disturbance and position disturbance cannot be ignored in the rotary memory device according to the embodiment of the present invention.

FIG. 4 is a diagram showing a time response example at the time of head positioning settling in a general magnetic disk device.

FIG. 5 is a diagram showing an example of a relationship between a positioning settling signal and a write inhibit signal at the time of head positioning settling according to a conventional technique.

FIG. 6 is a diagram showing an example of a relationship between a positioning settling signal and a write inhibit signal at the time of head positioning settling according to a conventional technique.

FIG. 7 is a diagram showing an example of an operation in head position estimation in the rotary memory device according to the embodiment of the present invention.

FIG. 8 is a diagram showing an example of a relationship between a positioning settling signal and a write inhibit signal at the time of positioning settling in the rotary memory device according to the embodiment of the present invention.

FIG. 9 is a diagram showing an example of an effect at the time of positioning settling by target position correction in the rotary storage device which is an embodiment of the present invention.

FIG. 10 is a diagram showing a result of confirming the effect of target position correction in the rotary memory device according to the embodiment of the present invention by simulation.

FIG. 11 is a flowchart showing an example of a settling determination algorithm in the rotary memory device according to the embodiment of the present invention.

[Explanation of Codes] 1 ... Magnetic disk, 2 ... Magnetic head, 3 ... Head support mechanism, 4 ... Spindle motor, 5 ... Drive shaft, 6 ... Head position detection unit, 7 ... Drive unit, 8 ... D / A converter , 9 ... Head position control unit, 10 ... Settling determination unit, 11 ... Subtractor, 12 ...
Servo signal, 13 ... Head position signal, 14 ... Target position signal, 15 ... Position deviation signal, 16 ... Control object, 17 ... Controller, 18 ... Position disturbance, 19 ... Force disturbance, 61 ... Servo signal demodulation circuit, 62 ... A / D converter, 63 ... Head position calculation unit, 91 ... Seek controller, 92 ... Following controller, 93 ... Switch unit, 100 ... Positioning settling signal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Watanabe 2880 Kunizu, Odawara, Kanagawa Stock Company Hitachi Storage Systems Division (72) Kazuhisa Shishida 2880, Kunizu, Odawara, Kanagawa Hitachi Storage Co., Ltd. System Division

Claims (1)

[Claims] 1. A rotary storage medium in which at least one of an area for storing data and an area for storing position information is arranged, a head arranged to face the rotary storage medium, and based on the position information. And a head positioning control system for positioning the head at an arbitrary position on the rotary storage medium, wherein the head is positioned at a target position on the rotary storage medium, A rotary storage device having a control logic for estimating a head position after a predetermined time by using a model of a head positioning control system and performing settling judgment of a head positioning operation based on the estimated value of the head position. .