TW556159B - Magnetic disk drive, position controlling method of magnetic heads and recorded medium storing program of the method - Google Patents

Abstract

In a magnetic disk drive, the time required for that the magnetic head brought into the off-track state due to vibration or shock restores into the on-track state, is shortened. A selector 15 selects, as the magnetic head position information, either the position information estimated by an observer 16 or the position information detected from a magnetic disk 22, depending on the degree of vibration or shock, the presence of a detection error of servo information and the degree of an estimating error. The position information selected is used in the calculation of a control value of the actuator. Accordingly, the estimated position information is used if there is a fault in the detection of servo information or detected servo information is probably inaccurate. Therefore, the magnetic head can restore rapidly from the off-track state to the on-track state.

Description

556159 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Description of the Invention (1) Technical Field The present invention relates to a magnetic disk drive and a method for recovering the position of a magnetic head. Return to track status. BACKGROUND OF THE INVENTION In a magnetic disk drive, a magnetic head is suspended on a rotating magnetic sheet to read or write data; in this example, the control of the position of the magnetic head is by using the head servo information (hereinafter referred to as servo information), It is recorded on a magnetic disk. When the magnetic head receives external vibration or vibration that exceeds a predetermined level, it will cause the magnetic head to leave the track where data can be written or read. The magnetic head is restored to the original track by control based on servo information; the above mentioned The predetermined degree of vibration or vibration must not be so strong in the discussion of the present invention. For example, it caused the head to collide with the disc surface, but it is assumed that under normal use, a fairly slight vibration occurs in the disc drive; In the present invention, "in the track state" means that the magnetic head is located on a track where data can be written or read, and "in the track state" means that the magnetic head is not in the track state. In particular, the process of returning the magnetic head from the off-track state to the on-track state is as follows: When the servo information is not continuously detected, it will check whether the drive has received external vibration or vibration exceeding a predetermined level. If this happens Vibration or vibration, and it is inferred that the action of detecting servo information is not performed synchronously with the servo information, or the head has been moved to a place where servo information is not recorded. In this case, the action of detecting servo information and Servo information synchronization. When the servo information is detected, the magnetic head will return to the tracked state. The paper size is free of Chinese National Standard (CNS) A4 specifications (210X297 mm) (Please read the precautions on the back before filling this page) Pei · Order · Line-4- 556159 A7 B7 Consumption Cooperation between Employees and Intellectual Property Bureau of the Ministry of Economic Affairs, Printing 5. Description of Invention (2) 〇 If the magnetic head goes off-track during reading and writing, reading and writing will stop immediately, so The magnetic head in the off-track state can avoid writing data to the place where the data should not be written. In this way, the magnetic head in the off-track state will not destroy the existing data on the magnetic disk. Recently, in order to increase the capacity of the magnetic disk, the track density has been considerably improved, that is, the track pitch has been significantly narrowed. In addition, the degree of suspension of the magnetic head has been reduced to improve the sensitivity of the magnetic head. As a result, the magnetic head may enter the off-track state due to external slight vibration-vibration, especially when data is written, so it will destroy or cause the magnetic disk data to fail to write. To avoid such damage or write failure, before The method of large-capacity disk drives is to set the tracking range to a small range. The on-track range is a narrow area on the magnetic disk. If the magnetic head is within this range, the magnetic head is in the tracking state. In addition, the threshold of vibration-vibration detected by the vibration sensor is also set to be very small, so when the capacity of the disk drive increases, when encountering a slight off-track state and a slight vibration-vibration, the magnetic head Writing will be stopped. In this way, a large-capacity disk drive can prevent the magnetic head from being damaged or cause the writing of magnetic disk data to fail when the track is off track. However, the procedure for returning the magnetic head from the off-track state to the on-track state mentioned above often takes several seconds. In the meantime, the magnetic head can neither write nor read, and furthermore, for a large-capacity disk drive, It is said that the magnetic head often enters the off-track state. In such a disk drive, data reproduction is often discontinuous, and the end time of each reproduction is also very long (please read the precautions on the back before filling this page) ) • Pei. The paper size of the book applies to the Chinese National Standard (CNS) A4 (210 X 297 mm) -5- 556159 A7 B7 V. The description of the invention (3) is long. Therefore, the reproduction of the audiovisual information of the previous disk drive is There is a big problem. During the reproduction of sound or video, it is often interrupted. On the other hand, under the demands of capacity expansion and miniaturization of the magnetic disk drive, it is difficult to suppress external vibration-vibration to such an extent that the magnetic head does not substantially enter the off-track state. In order to solve this problem, one of the objectives of the present invention is to shorten the time required for the magnetic head to return from the off-track state to the on-track state due to vibration-vibration. DESCRIPTION OF THE INVENTION A magnetic disk drive according to the present invention includes: a magnetic disk, a magnetic head for writing and / or reading data on the magnetic disk, and a read / write circuit that can control the writing and / Or a data actuator can support the magnetic head, and an actuator drive can drive the actuator and move the magnetic head to a predetermined position, a magnetic head position sensor, as: a ) The servo information is detected by the magnetic head from the magnetic disk, b) when the servo information is detected correctly, based on the servo information, the detected position information is calculated, and c) when the servo information is detected When there is an error, a servo information detection error signal is output, and a vibration sensor is used to detect and measure the external vibration-vibration. This paper size applies the Chinese National Standard (CNS) Α4 specification (210 × 297 mm) Li) I ------- β-pack-(Please read the notes on the back before filling out this page), 11 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs-6- 556159 Employees of the Intellectual Property Bureau of the Ministry of Economic Affairs Printed by Consumer Cooperative A7 ______B7__ V. Description of Invention (4) A vibration-vibration detector that can detect the extent to which the vibration-vibration exceeds a predetermined threshold, based on the vibration or vibration signal of the vibration sensor, and output a vibration-vibration detection signal, A calculator that controls the number of frames includes: A) an observer, which is used to estimate the position-velocity information of the magnetic head, and B) a selector, which can choose one of the two: a) from the magnetic head position detector Normal position-velocity information, or b) estimated position-velocity information from the observer, this information is based on the vibration-vibration detection signal and the servo information error detection signal, selected by the selector The received information is used as the head position-speed information, and based on this information, the control number of the actuator is calculated. According to this structure, when the servo information is detected incorrectly, the head position is controlled by the estimated position-velocity information of the observer, so the return time of the head from the off-track state can be shortened. According to the present invention, in addition to the structure of the magnetic disk drive described above, it is even better that the observer is able to calculate an estimated error of the estimated position-velocity information, and when there is an error in the detection of the servo information, The selector can select the estimated position-velocity information as the position-velocity information of the magnetic head, or when the degree of vibration-vibration exceeds the critical threshold, and the estimation is wrong (please read the precautions on the back before filling in this Page)

1T · Line · This paper size applies to Chinese National Standard (CNS) A4 specification (210 × 297 mm) 556159 A7 B7 5. Description of the invention (5) The degree of difference exceeds the predetermined critical threshold. When the head position information can be detected, but the detected position information may have errors due to vibration-vibration, the control of the head position is based on the position-velocity information estimated from the observer, not the detected position information. Therefore, we get more reliable head position information, so the head can recover faster from the off-track state. According to the present invention, a method for controlling the position of a magnetic head in a magnetic disk drive includes the steps of: using a vibration sensor to detect external vibration-the degree of vibration exceeds a critical threshold, and detecting a servo read by the magnetic head; Information, detects the detection error of the servo information, and calculates the position information detected by the magnetic head, and calculates a control number of a control actuator to move the magnetic head to a predetermined position. The steps include: a) by An observer to estimate the position-velocity information of the magnetic head, and b) when the degree of the vibration-vibration exceeds the critical threshold, the position-velocity information estimated from the observer can be selected, or when the servo information is detected When there is an error; and rely on the control number to drive the actuator and move the magnetic head to a predetermined position. According to the magnetic head position control method of the present invention, when the detection of the magnetic head position information is wrong, the control of the magnetic head position is based on the position-velocity information estimated from the observer. Therefore, the recovery time of the magnetic head from the off-track state can be reduced. Standards are applicable to China National Standard (CNS) A4 specifications (210X297 mm) (Please read the precautions on the back before filling out this page) -Printed · Printed by the Intellectual Property Bureau of the Ministry of Economic Affairs, Employee Consumption Cooperatives-8-556159 Printed by the Consumer Property Cooperative of Intellectual Property Bureau A7 B7 V. Description of Invention (6) Short. In addition to the above steps, according to the present invention, the method for controlling the position of a magnetic head may include the steps of: estimating the estimated position-velocity information obtained by the observer and the detected position information, and calculating an estimation error, when the servo When the information is detected incorrectly, the estimated position-velocity information can be selected, or when the degree of the vibration-vibration exceeds the critical threshold, and the estimation error exceeds a predetermined critical threshold. When the head position information can be detected and the estimation error is large, that is, the detected position information may be wrong due to vibration-vibration. The control of the head position is based on the position-velocity information estimated from the observer, not the detection. The measured position information, therefore, we have more reliable head position information, so the return of the head from the off-track state can be faster. According to the present invention, a position control program for a magnetic head includes: using a vibration sensor to detect external vibration-the degree of vibration exceeds a predetermined threshold; detecting servo information read by the magnetic head; detecting detection of the servo information; Measure the error, and calculate the position information detected by the magnetic head, calculate a control number 値 of the control actuator to move the magnetic head to a predetermined position, including: a) estimate the position of the magnetic head by the observer word- Speed information, and b) when the degree of vibration-vibration exceeds the critical threshold, the position-velocity information estimated from the observer can be selected, or when the paper size of this paper applies the Chinese National Standard (CNS) A4 specification ( 210 X 297 mm) (Please read the precautions on the back before filling out this page) • Binding. Order! · Line -9-556159 A7 B7 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (7) When the information is detected incorrectly; and the control data is used to drive the actuator and move the magnetic head to a predetermined position. When there is an error in the detection of the head position information, the control of the head position is based on the position-velocity information estimated from the observer. Therefore, the recovery time of the head from the off-track state can be shortened. In addition to the above procedures, according to the present invention, the position control program of the magnetic head may include: the estimated position-velocity information obtained by the observer, and the detected position information, an estimation error may be calculated, and when the servo information is detected When there is an error in the measurement, the estimated position-velocity information can be selected, or when the degree of the vibration-vibration exceeds the critical threshold, and the estimation error exceeds a predetermined critical threshold. When the head position information can be detected and the estimation error is large, that is, the detected position information may be wrong due to vibration-vibration. The control of the head position is based on the position-velocity information estimated from the observer, not the detection. The measured position information, therefore, we have more reliable head position information, so the return of the head from the off-track state can be faster. Furthermore, according to the present invention, the above-mentioned magnetic head position control program can be stored on a recording medium in an executable form, and according to the present invention, the magnetic head position control method can be implemented in a previous magnetic disk drive. Computer with recording media. Although the novel features of the invention will be specially proposed in the scope of additional patent applications, from the detailed descriptions shown below, there are other objects and their features. This paper size applies the Chinese National Standard (CNS) A4 specification (21GX297 mm) (Please Read the precautions on the back before filling in this page) Binding · Order -10- 556159 A7 B7 Printed by the Consumers' Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs V. Invention Description (8) You will have a deeper understanding of this invention in terms of organization and content And experience. Brief description of the drawings Figure 1 is a block diagram of an embodiment of the present invention: controlling a data calculator 2 〇 Figure 2 is a block diagram of an embodiment of the present invention: a hard disk drive hardware. Figure 3 is a diagram showing the track T format on the magnetic sheet 22 and the recording area 30 of servo information, (a) part is the range of the track T, and the recording area 30 of the servo information on the magnetic sheet 22; Part (b) is an enlarged illustration of the track T 0-T 3 format and the servo information recording area 30, which is a part circled in an ellipse in part (a). FIG. 4 is a block diagram of an observer 16 according to an embodiment of the present invention. FIG. 5 is a block diagram of a vibration-vibration detector 11 according to an embodiment of the present invention. FIG. 6 is a block diagram of the selector 15 according to an embodiment of the present invention. FIG. 7 is a table showing signals of the position-speed information 108 used by the selector 15 in the embodiment of the present invention to calculate the control data and the position-speed information 1 0 9 for the observer. It depends on whether the output of each vibration-vibration detection signal 1 0 1 is true or false, the servo information detection error signal 1 0 3 and the estimation error 1 0 6. FIG. 8 is a flowchart of a vibration-vibration detection process S 0 according to an embodiment of the present invention. FIG. 9A is a flowchart of steps S 1 to S 3 of the position control process of the magnetic head 23 according to an embodiment of the present invention. (Please read the notes on the back before filling this page)

、 1T-The paper size of the paper is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) -11-556159 A7 B7 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (9) Figure 9 B is An embodiment of the present invention: a flowchart of steps S 4 to S 8 of the position control process of the magnetic head 23. Main components comparison table 1 〇 Vibration sensor 1 1 Vibration—Vibration detector 1 2 Actuator drive 1 3 Actuator 1 4 Head position detector 1 5 Selector 1 6 Observer 1 7 Matrix distributor 1 8 Matrix affinity 1 9 Gain 2 0 Control data calculator 2 1 Read and write circuit 1 0 0 Vibration or vibration signal 1 〇1 Vibration-vibration detection 1 〇2 Write error signal 1 0 3 Servo information detection False 1 0 4 Servo information 1 〇5 Detection position information 1 0 6 Estimated error 7 Corrected position-speed information (Please read the precautions on the back before filling this page)

This paper size applies Chinese National Standard (CNS) A4 specification (210X297 mm) -12- 556159 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (1 () 10 7b Estimated position-speed information 10 8 Position-velocity information for control data calculation 10 9 Position-velocity information for observer 110 Control data 111 position-speed last information 112a Head speed information 112b Bias information 112c Position error 1 1 2 d Head position information 13a Arm 2 2 Magnetic disk 2 3 Magnetic head 2 4 Actuator 2 5 Spindle motor 26 Spindle motor drive 30 Recording area of servo information 31 First area 32 Second area 33 Third area 34a, b, c, d Fourth area 4 0 Input matrix 40a, b, c Adder 4 1 1 Sampling delay element 4 2 Output matrix (Please read the precautions on the back before filling this page)

， 1T i · line paper size is applicable to Chinese National Standard (CNS) A4 specification (210X297 mm) -13 · 556159 Printed by the Consumer Cooperatives of Intellectual Property Bureau of the Ministry of Economic Affairs A7 _________ B7 V. Description of the invention (4 3 System Matrix 44 Observation Gain 4 0 0 position-speed next sampling information 4 0 1 estimated position-speed information of the magnetic head 50 amplifying circuit 5 1 low-pass filter 5 2 comparator 53 detection element 1 0 0 a, b, C signal component 6 0 Distributor 6 1 Coupler 62 Selection section 1 6 2 a, b First / second selection section 600 Normal position-velocity information so Vibration-vibration detection process We recognize some or all of the graphics for illustration Graphical representation, does not necessarily draw the true relative size or component position. Best Modes for Implementing the Invention A preferred embodiment of the present invention is described with reference to FIGS. 1 to 8. FIG. 2 is an embodiment of the present invention: magnetic Block diagram of the disc player hardware. The spindle motor drive unit 2 6 provides the drive current to the spindle motor 2 5 (Please read the precautions on the back before filling this page).

、 1T I · line paper size is applicable to China National Standard (CNS) A4 specification (210 × 297 mm) -14- 556159 A7 B7 Printed by the Consumers ’Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (θ, the main axis of current supply The motor 2 5 rotates the magnetic sheet 2 2 at a predetermined rotation speed. The actuator 1 3 supports a magnetic head 2 3 and is located above the boom 1 3 a. The boom 1 3 a is driven by an electric motor to drive the actuator. 24, and move the magnetic head 23 to a predetermined track (not shown) recorded on the magnetic sheet 22. The magnetic head 23 reads or writes data from the predetermined track. For example, an electric motor that drives an actuator It can be a voice coil motor. A read-write circuit 2 1 controls the read-write operation performed on the magnetic sheet 22 by the magnetic head 2 3, and then the servo information 1 〇4 is sent to the magnetic head position detector 1 4. This information is included in the data read by the magnetic head 2 3 from the magnetic sheet 22 2 The head position detector 1 4 detects the servo information 1 0 4 from the data input of the read-write circuit 21 1, based on this, and Calculate the position of the magnetic head 2 3, and then use this calculation result as the The measured position information 1 0 5 is sent to the control data calculator 2 0. If the servo information 1 0 4 mentioned above is detected incorrectly, the head position detector 1 4 will send a servo information detection error signal 1 0 3 for the control data calculator 2 0. A vibration sensor 10 measures the acceleration of the vibration or vibration received by the disk drive from the outside, and sends a vibration or vibration signal 1 0 to display the direction of acceleration. The degree of vibration is given to the vibration-vibration detector 1 1. When the vibration-vibration level shown in the vibration-vibration signal 1 00 exceeds a predetermined threshold, the vibration-vibration detector 1 1 sends out a vibration-this paper size Applicable to China National Standard (CNS) A4 specification (210X297 mm) (Please read the precautions on the back before filling out this page)-Install ·-Order I · Line. -15- 556159 A7 B7 Employees ’Cooperatives, Intellectual Property Bureau, Ministry of Economic Affairs Printed 5. Description of the invention (Vibration detection signal 1 0 1 is given to the control data calculator 2 0. If the vibration-vibration degree exceeds another predetermined threshold different from the above-mentioned critical threshold, the vibration-vibration detector 1 1 Will send a write error signal i 〇2 to read Circuit 2 1. Control data calculator 20, based on the detected position information 1 0 5, servo information detection error signal 1 0 3 and vibration-vibration detection signal 1 0 1, calculate the actuator 1 3 The control number 値 1 1 〇, and the calculated control number 値 1 1 〇 is sent to the actuator driving device 12. The actuator driving device 12 provides an electric motor to be relative to the control number 値 1 1 0 Current to drive the actuator 2 4. FIG. 3 shows the format of the track T on the magnetic sheet 22 and the recording area 30 of servo information. In the display diagram of part (a) of FIG. 3, some tracks T are recorded concentrically on the magnetic sheet 22, and the servo information The recording area 30 on the magnetic sheet 22 is recorded radially at predetermined intervals. Figure 3 (b) is an enlarged view of the recording area 30 of the track T 0-T 3 format and servo information. It is shown in part (a) that is circled in an ellipse; each T 0-T 3 track has the same width, and the reading and writing of data on this area by the magnetic head 23 is based on the predetermined setting of the track center. Width, the area read and / or written by the magnetic head 23 is called the on-track area. In part (b) of FIG. 3, the track area c0 of the tracks T0, T1, T2 and T3, c1, c2, and c3 are indicated by broken lines, respectively, and the width of the track area is set to about 10% of the track width. (Please read the precautions on the back before filling out this page) Binding, binding, thread_ This paper size applies to China National Standard (CNS) A4 specification (210X297 mm) -16- 556159 Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs System A7 _ B7 ____ V. Description of the invention (The servo information recording area 30 is composed of the following 3 1 — 3 4 areas. The servo information recording area 30 is the first area 3 1 of the synchronization signal for recording. In order to synchronize the reading action, this action is derived from the servo information 1 0 4 (see Fig. 2) on the magnetic head 2 3 (see Fig. 2) and the magnetic sheet 22; as shown in part (a) of Fig. 3, the servo The information recording area 3 0 periodically exists in the tangential direction on the magnetic sheet 2 2. Therefore, when the magnetic sheet 2 2 rotates at a constant speed, the servo information 1 04 is transmitted to the magnetic head 2 3 as a signal of a predetermined frequency. The magnetic head 2 3 repeats the reading operation in synchronization with this signal cycle. The second area 3 2 records the servo identification signal. The purpose of the servo identification signal is that the magnetic head position detector 14 can detect the magnetic head 2 3 reading. Output servo data 1 0 4 data, if it is the head position Detector 1 4 can't distinguish the servo mark signal, it will infer that the detection result is wrong. The third area 3 3 records the track number signal to display the true track position of the detected servo information 104. Using the track number signal, the track number closest to the 23 position of the magnetic head will be detected. The fourth area 3 4 records four kinds of burst signals A-D. The purpose of these burst signals A-D is being detected. The degree of deviation of the magnetic head 23 from the magnetic track 22 in the radial direction with respect to the center line of the predetermined track (for example, the center line c 1 of the predetermined track t 1). In addition, the fourth area 34 is composed of 34a, 34b, 34c and It is composed of four areas, 3 4 d, and 3 4 a, 3 4 b, 3 4 c, and 34 d. These areas record the burst signals A, B, C, and D, respectively. The paper size applies to the Chinese National Standard (CNS) A4. Specifications (210X297mm1 (Please read the precautions on the back before filling this page)

'JL loaded ·

， 1T —line-17- 556159 A7 B7 Printed by the Consumer Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of invention (15) Signals A — D are recorded periodically on the magnetic sheet 2 2 along the radius, each The period interval is equal to the track width. Burst signals A to D are recorded only in each half cycle. However, the individual phase offsets of the recording areas 34d, 34a, 3 4 c, and 3 4 b are different by π / 2, that is, , When the burst signal D is recorded on the (2 η-1) track (η is an integer greater than 1) calculated from the inside of the magnetic sheet 22, the burst signal A is centered on the (2 η-1) ) And the 2 η orbit, the burst signal C is located on the 2 η orbit, and the burst signal B is centered on the boundary between the 2 nd orbit and the (2 η + 1) orbit. The transmitted signals A-D are recorded in an offset manner. Therefore, the relative strength of the individual burst signals A-D is included in the detected servo information 104, and when the servo information 104 is read, , Can inform the degree of deviation of the magnetic head 23 from the track area. Figure 1 is a block diagram of the control data calculator 2 0. The control data calculator 20 is composed of an observer 16, a selector 15, a matrix divider 1 7, a matrix coupler 18, and a feedback gain 19. composition. The observer 16 shapes the actuator driving device 12 and the actuator 1 3. The observer 16 receives the input of the control number 値 1 0 0 calculated in the previous step, and the position-speed information 1 0 used by the observer. Input 9 (hereinafter referred to as the position-speed information for the observer), and based on this to estimate the position and speed of the magnetic head 2 3, the estimated position-speed information is output as the estimated position-speed information 1 0 7 b to the selector 1 5; It should be noted that this position-velocity information contains the position, speed, and bias of the magnetic head 23. The bias is a continuous disturbance applied to the actuator 13, for example, including driving the actuator 2 4 The friction force of the rotating shaft of the electric motor, the paper size of the observer applies the Chinese National Standard (CNS) A4 specification (210X 297 mm) (please read the precautions on the back before filling in this X).

1T line-18-556159 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the invention (1 to 16 compared the head detection position information of the head position detector 1 to 4 and the estimated The position-speed information 1 0 7 b, and the estimated error 10 6 is calculated. Furthermore, based on the estimated error 1 6, the observer 16 corrects the estimated position-speed information 1 0 7 b, and the correction result is output as a correction. Position-velocity information 1 0 7 a to selector 15 together with the estimated error 10 6. If the head position detector 14 cannot find the track number signal in the output data of the read-write circuit 21 (Figure 3), That is, if there is an error in the detection of the servo information 104, the head position detector 14 will output a servo information detection error signal to the selector 15 and the vibration-vibration detector 1 1 outputs a vibration one. Vibration detection signal 1 0 1 to selector 15 in response to vibration or vibration signal 1 0 0 of vibration sensor 10 0. Selector 15 selects detected position information 1 0 5 or estimated position-speed Information 107b, as output to the matrix distributor 17, these are based on servo data Signal detection error signal 1 0 3 and vibration-vibration detection signal 1 0 1; At the same time, the selector 15 selects the estimated position-speed information 107b or the corrected position-speed information 107a for output to observation. 16 and the information selected to be output to the matrix distributor 1 7 is used as the position-speed information for calculating the control number 値 1 1 0 (hereinafter referred to as the position-speed information for the calculation of the control number ：): another In terms of information, the information selected for output to the observer 16 is the position-velocity information 1 0 9 for the above-mentioned observers. The matrix divider 17 separates the position-velocity information 108 for the control number calculation, forming three elements. · Head speed information 11 2 a, I --------- (Please read the precautions on the back before filling this page)

1. The paper size of the 1T line is applicable to the Chinese National Standard (CNS) A4 specification (210 × 297 mm) -19- 556159 A7 B7 5. Description of the invention (1 is bias information 1 1 2 b and head position information 1 1 2 d, must Note that the head position information 1 1 2 d is one of the following: the detected position information 1 0 5 or the position information estimated by the observer 16 (hereinafter referred to as the estimated position information), depending on the choice of the selector 15 The head speed information 1 1 2 a and the bias information 1 1 2 b are output to the matrix coupler 1 8, and the head position information 1 1 2 d is output to the adder 17 a. The control target position of the magnetic head 2 3 The information (hereinafter referred to as target information 1 1 3) is input from the outside to the adder 1 7 a (not shown, for example, a photo duplicator), and the adder 1 7 a calculates the target information 1 1 3 and the head position Information 1 1 2 d (detected position information 105 or estimated position information), and then output it as a position error 112c to the matrix coupler 18. The matrix coupler 18 couples three elements ... Head speed information 1 1 2 a, bias information 1 1 2 b and position error 1 1 2 c Then the position-speed final information 1 1 1 is generated, and the position-speed final information 1 1 1 is multiplied by the feedback gain 1 9 to generate the control number 値 1 1 0, and the control number 値 1 1 0 is output to the observer 16 and Actuator driving device 12. The block diagram of Fig. 4 shows the structure of the observer 16. The observer 16 is composed of a system matrix 4 3, an input matrix 4 0, and an output matrix 4 2. -1-a sampling delay element 4 1-an observer gain 44 and three adders 40a, 40b and 40c. Multiply the control number 値 1 1 0 of the observer 16 by the input matrix 40, and then output it to the adder. 40 a, On the other hand, the position and velocity information of the observer 1 0 9 from the selector 15 is multiplied by the system matrix. The paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) I --- ----- ^-装-(Please read the notes on the back before filling this page)

Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs of the 1T line -20-556159 A7 B7 V. Description of the invention (4 3, and then output it to the adder 4 0 a, the adder 4 0 a calculates the sum of the two inputs The output is position-speed information 4 0 0 for the next estimation step (hereinafter referred to as position-speed next sampling information); the estimated position-speed information 1 0 7 b is composed of 1-sampling delay element 4 1 and The position-speed next sampling information 4 0 0 is multiplied, and the estimated position information of the magnetic head 4 0 1 is obtained by multiplying the estimated position-speed information 1 〇 7 b and the output matrix 4 2. The adder 4 0 b Calculate the difference between the head detection position information 1 05 from the head position detector 14 and the estimated position information 4 0 1 of the magnetic head, and output the estimation error 1 0. This estimation error 1 0 6 is multiplied by The observer gain 4 4 is then output to the adder 4 0 c and added to the estimated position-speed information 1 0 7 b. As a result, the adder 4 0 c outputs the corrected position-speed information 1 0 7 a. Figure 5 Block diagram of vibration-vibration detector 1 1 ， Vibration-vibration detector 1 1 It consists of the following: an amplifier circuit 50, a low-pass filter 51, a comparator 5 2 and a detection element 5 3; a magnetic disk drive 1 receiving external vibration or vibration, and a vibration sensor 1 0 measures this acceleration. The vibration sensor 1 0 provides a vibration or vibration signal 1 0 0 relative to the acceleration to the vibration-vibration detector 1 1. The vibration or vibration signal 1 0 0 includes 1 0 0 a, 1 Three signal components of 〇〇b and 〇〇c respectively correspond to the components of vibration or vibration in three directions, which are perpendicular to each other; in the embodiment of the present invention, the signal component of the vibration or vibration signal 1 0 0 1 0 0 a, 1 0 0 b, and 1 0 ° C, with respect to the components of the vibration or vibration in the radial direction, the tangential direction, and the vertical direction of the magnetic sheet, respectively, the signal component of the vibration or vibration signal 1 0 0 1 0 0 a, 1 0 0 b and 1 0 0 C are respectively applicable to the Chinese National Standard (CNS) A4 specifications (21〇 ×: 297 mm) of this paper standard (please read the precautions on the back before filling this page) Printed by the Intellectual Property Bureau Employee Consumption Cooperative -21-556159 A7 B7 Employee Consumption of the Intellectual Property Bureau of the Ministry of Economic Affairs Cooperative printed 5. Description of the invention (1 $ Amplifier circuit 50 is amplified, its waveform is subjected to a shaping process by the low-pass filter 51; the comparator 5 2 determines the output of the low-pass filter 51: the signal component 10 Which of 0a, 100b, and 100c exceeds a predetermined write error level, when the comparator 5 2 concludes that at least one of the signal components 1 0 0 a, 100 b, and 1 0 0 c exceeds the above-mentioned write error level , The detection element 5 3 outputs a write error signal 102 to the read / write circuit 21; In addition, if the signal component 1 0 0 c of the vibration or vibration signal 1 0 0 exceeds a predetermined threshold, or The degree of servo information that cannot be detected. The detection element 5 3 will output a vibration-vibration detection signal 1 0 1 to the selector 15. If the vibration or vibration exceeds the degree of servo information that cannot be detected, it will occur on the magnetic disk. The vertical direction of 2 2 will infer that the interval between the magnetic head 2 3 and the magnetic sheet 2 2 cannot allow the normal reading of the servo information 104. In practice, the degree of servo information that cannot be detected will be set at, for example, That said, it's almost 100 m / s 2 for a traditional drive. Figure 6 is a block diagram of the selector 15. The selector 15 is composed of a distributor 60, a coupler 61 and a selection section 62, and the selection section 62 is composed of a first selection section 6 2a and a second The selection part 6 2 b is composed of the modified position-speed information 1 0 7 a. Input from the observer 16 to the distributor 6 0 and the second selection part 6 2 b. On the other hand, the estimated position-speed information 1 0 7 b is input from the observer 16 to the first selection portion 6 2 a and the second selection portion 6 2 b. The second selection part 6 2 b is selected as the position of the observer-speed data (please read the precautions on the back before filling this page)-binding, binding, I, and paper size are applicable to China National Standard (CNS) A4 specifications ( 210X297 mm) -22- 556159 A7 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs V. Invention Description (2 () News 1 0 9) is the revised position—speed information 1 07 a or estimated position- Speed information 1 0 7 b, both are based on vibration-vibration detection signal 1 0 1, servo information detection error signal 1 0 3 and estimation error 10 6 ° are similar to the above-mentioned matrix distributor 17 (see Figure 1) Mode, the distributor 60 generates three elements: head speed information, bias information, and head position information, and the head speed information and bias information of the three elements are output to the coupler 61. The coupler 61 is from the head position detector. 1 4 receives the input of head detection position information 1 0 5 in a similar manner to the matrix coupler 18 (see Figure 1) above. Coupler 6 1 couples head speed information, bias information, and head detection position information 1 0 5 and output it as normal bit Set-speed information 600 to the first selection part 62a. In this way, normal position-speed information 6 0 0 is equivalent to corrected position-speed information 1 0 7 a, and its head position information is replaced by head detection position information 1 0 5 The first selection part 6 2 a chooses the position-speed information 1 0 8 for calculating the control number ，, which is the normal position-speed information 6 0 0 or the estimated position-speed information 1 0 7 b, both of which are based on Vibration-vibration detection signal 1 0 1, servo information detection error signal 1 0 3 and estimation error 10 6. In the embodiment of the present invention, the above structure is provided, and the position of the magnetic head 2 3 is controlled as follows: Figure 8 The flowchart shows the vibration-vibration detection process S 〇, with vibration sensor 10 and vibration-vibration detector 1 1; vibration-vibration detection equipment — (Please read the precautions on the back before filling this page) Order-line · This paper size applies the Chinese National Standard (CNS) A4 specification (210 × 297 mm) -23-556159 A7 B7 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (2 $ Repeat of process S 0 Operation with the following magnetic head 2 3 position control S 1-S 8 are irrelevant. When the disk drive of the present invention receives external vibration or vibration, the vibration and vibration are detected by the vibration sensor 10, and the output of the vibration sensor 10 corresponds to the vibration-vibration direction and The degree of vibration or vibration signal to the vibration-vibration detector 1 1. When the vibration or vibration signal exceeds the degree of servo information that cannot be detected, the vibration-vibration detector 1 1 outputs "true" 値 's vibration-vibration detection Signal, otherwise it outputs "false". 9A and 9B show a flowchart of the position control process of the magnetic head 23. The position control process of the magnetic head 23 is divided into steps S1 to S8, which are described as follows. Please refer to FIGS. 9A and 9B, and FIG. 9A shows Steps S1 to S3 of the process, and FIG. 9B from steps S4 to S8. "Step S 1" (Figure 9A) The head position detector 1 4 detects servo information 1 0 4 from the data read by the head 23. When the detection is correct, the head position detector 14 calculates the head Detect position information 1 0 5, using track number signal and burst signals A, B, C and D included in servo information 104; at the same time, head position detector 1 4 outputs servo information detection error signal 1 0 3 "false" 値 output. In contrast, when the servo information 1 0 4 is detected incorrectly, the head position detector 14 outputs servo information detection error signal 1 〇 3 "true" 値 output. "Step S 2" (Figure 9 A) Observer 16 calculates estimated position-speed information 1 〇 7 b and estimation (Please read the precautions on the back before filling this page)

This paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) -24- 556159 A7 B7 V. Description of the invention (position information calculated by 2 $ 401, especially in the detailed steps of step S2, The estimated error 1 0 6 from the position-speed next sampling information 4 0 0 is expressed by the following equations (1), (2), and (3): X b = X bb / z (1) X b 1 = Η X χ × b (2) X err = y -X b 1 (3) where X b is the estimated position-speed information 1 0 7 by X bb Printed as position-speed under the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs The sub-sampling information 4 Ο Ο, X b 1 is the estimated position information 401, Hx is the output matrix 42, Xerr is the estimation error 106, and y is the detected position information 1 05. "Step S 3" (Figure 9 A) The observer calculates the corrected position-velocity information from the following equation (4): 1 0 7 a: Xh = Xb + LcxXe rr (4) where Xh is the corrected position-velocity information 107a, and Lc is the observer gain 4 4 "Step S 4" (Figure 9 B) The table in Figure 7 shows the individual selectors 15 Select it as the position-speed information signal to calculate the position-speed information required for the control number 値 1 0 8 and the observer 1 0 9. The output depends on the vibration detection signal 1 0 1 for each vibration. True or false, servo information detection error signal 1 〇3 and estimated error 1 〇 6. There are three choices of selector 15, the situation is as follows: m ml I Bli ^ I— i (Please read the precautions on the back first (Fill in this page again),?! I · The size of the paper is applicable to the Chinese National Standard (CNS) A4 (21 × 297 mm) -25- 556159 A7 --B7 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs Description of the invention (2 $ to three, as shown in Figure 7. Situation 7 of Figure 7: When the servo information detection error signal 1 0 3 and the vibration-vibration detection signal 1 0 1 are both "false", the first The selection section 6 2 a selects the normal position-speed information 6 〇〇 as the position-speed information to calculate the control number 値 1 0 8; on the other hand, the second selection section 6 2 b selects the corrected position-speed information 1 〇 7 a is the position-velocity information of the observer 1.09. When the service information detection error signal 1 〇3 is "true", the first selection part 6 2 a and the second selection part 6 2 b both select the estimated position-speed information 1 0 7 b, and ignore the vibration-vibration detection. The output of the test signal 1 〇1 is true or false. Figure 7 Condition Three: When the servo information detection error signal 103 is "false" and the vibration-vibration detection signal 1 01 is "true", the degree of estimation error 1 〇6 can be further divided into two cases : Figure 7 Condition 3a: When the estimated error 1 〇6 exceeds a predetermined threshold 値, both the first selection part 6 2 a and the second selection part 6 2 b select the estimated position-speed data (please read the precautions on the back first) (Fill in this page again.)-Bae · Order-The paper size of the paper is applicable to the Chinese National Standards (CNS) A4 specification (210X 297 mm) -26- 556159 Α7 Β7 Printed by the Consumer Cooperative of Intellectual Property Bureau of the Ministry of Economic Affairs Explanation (24 messages 1 0 7 b. Fig. 7 Condition 3 b: When the estimation error 10 6 does not exceed a predetermined threshold, the first selection section 6 2 a selects the corrected position-speed information 1 〇 7 a, on the other hand The second selection part 6 2 b selects the normal position-speed information 6 0 0. The selection of the selector 15 shown in FIG. 7 is illustrated in step S 4 and the detailed selection of step S 4 a in step S 4 in FIG. 9B The result is equivalent to situation two and situation three a of FIG. 7, and the detailed item S of step s 4 The selection result of 4 b is equivalent to situation 1 and situation 3 b in Fig. 7. "Step S 5" (Fig. 9 B) The position-speed information selected in step S 4 as the calculation control number 値 1 〇 08 is in The control number 値 20 was processed in the calculator, so the position-speed final information 1 1 1. "Step S 6" (Figure 9B) According to the following equation (5), the position-speed final information 1 1 1 multiplies The last feedback gain 19 can generate the control number 値 110: u-Κ χχ (5) where u is the control number 値 1 1 0, κ is the feedback gain 19, and X is the position-speed final information 1 1 1; The actuator driving device 12 drives the actuator 1 3 according to the control number 値 1 1 0, so the position of the magnetic head 2 3 is moved according to the display of the target information 1 1 3. (Please read the precautions on the back before filling this page )

This paper size applies Chinese National Standard (CNS) A4 specification (21 × 297 mm) -27- 556159 A7 B7 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Description of the invention (2 $ "Step S 7" (Figure 9 B) In Condition 1 of Figure 7, based on the normal detection position of the magnetic head 23, it will check whether the magnetic head 23 is in the tracked state (hereinafter referred to as the tracked state check), and especially check the position error 1 1 2 c (See Figure 1), or is the difference between the target information 1 1 3 and the head position information 1 1 2 d (detected position information 1 0 5 or estimated position information 4 0 1) within the predetermined range; check results If the magnetic head 23 is in the track-in state, the magnetic head 23 is still written and read as usual. On the contrary, if the magnetic head 23 is in the off-track state, the magnetic head 23 will not be written or read. In the second condition, the tracking status check is not performed, and the magnetic head 23 is not written or read. If the vibration-vibration detection signal 1 0 1 is "false", the detection of the servo information 1 0 4 will be performed a predetermined number of times. Repeated execution, as a result, if the servo information detection error signal 1 0 3 is continuously "true" The program of synchronous reading operation between the magnetic head 23 and the servo information 104 is executed. In particular, the detection of the servo information 104 or the first area 2 recorded in the servo information 30 recording area 1 (See part (b) of Figure 3) The detection of the synchronization signal takes longer than normal. If the vibration and vibration detection signal 1 0 1 is "true", the magnetic head 2 3 will remain without reading and writing. Until the vibration-vibration detection signal 1 〇1 becomes “false”, that is, until the vibration or vibration stops. In the condition three a of FIG. 7, the estimation error of the observer 16 exceeds a predetermined critical threshold, so, It may be detected due to the effects of vibration or vibration —-------- install— (Please read the precautions on the back before filling this page) Order I · Line · This paper size applies to Chinese national standards (CNS ) A4 specification (210X297 mm) -28- 556159 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 ____ B7 V. Description of the invention (The position information of the 2 bows is incorrect, so the track status check has not been performed , The magnetic head 2 3 remains in a state of no reading and writing until a vibration The motion detection signal 1 0 1 becomes "false", that is, until the vibration or vibration stops. In the condition 3b of Fig. 7, since the estimation error of the observer 16 is less than a predetermined threshold, the detected position information is It is not seriously affected by vibration or vibration. Therefore, the tracking status check is performed based on the detected position information of the magnetic head, similar to the situation in Figure 7 or in a normal condition. If the magnetic head 23 is in the tracking status, the magnetic head 2 3 writes or reads, but if the off-track state occurs, the magnetic head 2 3 will not write or read. "Step S 8" (Figure 9B) The observer 16 calculates the position-velocity next sampling information by the following equation (6) 4 0 0: Xb b = Φβχχ e + Texu (6) where Xbb is the system matrix 43, Xe Is the position-velocity information of the observer 10, and re is the input matrix 40. By repeating steps S1 to S8, the position of the magnetic head 23 can be controlled. In the second situation in Fig. 7, because the servo information 1 0 4 performed by the head position detector 1 4 has an error, the true position of the head 2 3 is not detected. Therefore, the position control of the head 2 3 is based on The position of the magnetic head 23 estimated by the observer 16; although the estimated position-speed information 1 0 7 b contains some errors, it is quite similar to the position and speed of the real magnetic head 2 3, so usually the magnetic head 2 3 really The re-detection of the position is faster than the traditional method that the magnetic head 2 3 remains stationary. As a result, the magnetic head 2 3 standard is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) '-29-(Please read first Note on the back, please fill in this page again)-Binding and ordering I. Thread 556159 A7 B7 V. Description of the invention (2) The response time can be shortened compared with the traditional method. In situation three a of Figure 7, due to vibration or vibration The detected servo information is often not equal to the true position of the magnetic head 23, so the position control of the magnetic head 23 is based on the estimated position-speed information 1 0 7 b, rather than the detected position information 1 0 5; when vibration or shock stops and The status changes to status 3b or status 1 in Figure 7. The execution of the track-in status check is usually based on the detected position information 1 0. Therefore, the recovery time of the magnetic head 23 from the off-track status remains stationary compared to the magnetic head 23. According to the above embodiment, the method for controlling the position of the magnetic head can be written in a computer program according to the flowcharts of FIGS. 9A and 9B, and it is particularly easy for those skilled in the art. Understand that the calculator with control number 値 20 can be built with software; as shown in Figure 1, except for the calculator with control number 値 20, its structure is very common to the previous drive technology, so The calculator that controls 値 20 is built as software and can be stored on the recording medium in an executable form. Therefore, using a computer equipped with a recording medium, the head position control method according to the present invention can be used in the disk drive of the prior art. Realized, the recording medium can be any kind of data recording device, including floppy disk drive, read-only optical disk drive, digital multi-purpose optical disk drive, magneto-optical disk drive, removable hard disk and flash memory Although the present invention is described using the presently preferred embodiments, we must understand that such disclosure is not a restrictive interpretation. For those skilled in the art, after reading the above description, it is very relevant to make different changes or modifications to the present invention. Obvious. The size of this paper is applicable to Chinese National Standard (CNS) A4 specification (2) 0 × 297 mm) (Please read the precautions on the back before filling this page) r.

1T printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economics -30- 556159 A7 B7 printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs Changes or corrections within the true spirit and scope. Industrial Applicability According to the present invention, the hindrance of the disk drive in the reproduction of audiovisual information is alleviated. As such, because the disk drive uses the head position control method according to the present invention, The previous technology of the drive has more advantages in the reproduction of audiovisual information, so the drive has its industrial applicability. (Please read the precautions on the back before filling this page)

、 1T This paper size is applicable to China National Standard (CNS) Α4 size (210x297 mm) -31-

Claims (1)

556159 Printed by the Consumer Property Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A8 B8 C8 D8 VI. Patent application scope i 1. A magnetic disk drive comprising: a magnetic disk; a magnetic head for writing and / or reading on the magnetic disk Data. A read / write circuit that uses the magnetic head to control the writing and / or reading of data; an actuator to support the magnetic head, and a uniform drive device to drive the actuator and move the A magnetic head position sensor is used to: a) detect the servo information read from the magnetic disk by the magnetic head, b) when the servo information is detected correctly, according to the servo information To calculate the detected position information of the magnetic head, and c) when the servo information is detected incorrectly, output a servo information detection error signal, a vibration sensor for detecting and measuring from the outside Vibration or vibration, a vibration-vibration detector for detecting that the degree of the vibration or vibration exceeds a predetermined threshold, which is based on the vibration or vibration signal from the vibration sensor and outputs a vibration-vibration The detection signal, and a calculator for controlling the data, include: A) — an observer to estimate the position-speed information of the head, B) — a selector to select one of the following: the paper size Applicable Chinese National Standard (CNS) A4 specification (210X297 mm) (Please read the precautions on the back before filling this page) 556159 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs A8 B8 C8 D8 VI. Patent application scope 2 a) Normal position-velocity information from the head position detector, or b) Estimated position-velocity from the observer Information, this information is based on the vibration-vibration detection signal and the servo information error detection signal, and the information selected by the selector is used as the head position-speed information, and the actuator is calculated based on this information Control number 控制. 2. The magnetic disk drive according to item 1 of the patent application scope, wherein the observer calculates an estimation error from the estimated position-speed information and the detected position information, and when the servo information is detected incorrectly, or when When the degree of the vibration or vibration exceeds the critical threshold, and the degree of the estimated error exceeds a predetermined critical threshold, the selector can select the estimated position-speed information as the position-speed information of the magnetic head. 3. A method for controlling the position of a magnetic head, including the steps of using a vibration sensor to detect the degree of vibration or vibration from the outside exceeding a predetermined threshold, detecting servo information read by the magnetic head, and detecting the servo information The step of detecting the error and calculating the position information detected by the magnetic head, and the step of calculating a control number for controlling the actuator, which is required to move the magnetic head to a predetermined position, include: a) an observer Sub-steps to estimate the position-velocity information of the magnetic head, and b) when the degree of the vibration or vibration exceeds the critical threshold, or the paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) (please read first (Notes on the back then fill out this page) 556159 A8 B8 C8 D8 (3) When the servo information is detected incorrectly, select the sub-step of the estimated position-speed information from the observer, and drive the actuator according to the control data. And moving the magnetic head to a predetermined position. 4. The position control method of the magnetic head according to item 3 of the patent application scope, including: the step of calculating the estimation error from the estimated position-speed information and the detected position-speed information by the observer, and when the servo information is detected When there is an error in the measurement, or when the degree of vibration or vibration exceeds the critical threshold, and the degree of the estimated error exceeds a predetermined critical threshold, the selector can select the estimated position-velocity information as the position-velocity of the magnetic head. Information steps. 5. A recording medium storing a position control program of the magnetic head, the program includes: using a vibration sensor to detect the degree of vibration or vibration from the outside exceeding a predetermined threshold 値, detecting servo information read by the magnetic head, Detecting a detection error in the servo information, and calculating the detected position information of the magnetic head, and calculating a control number 値 of the control actuator, as necessary for moving the magnetic head to a predetermined position, including: a) The position-velocity information of the magnetic head is estimated by an observer, and b) when the degree of the vibration or vibration exceeds the critical threshold, or when the detection of the servo information is wrong, an estimated (please select from the observer) Read the precautions on the back before filling this page.) Binding and printing. Printed on the paper by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. The paper size is applicable to China National Standard (CNS) A4 (210X297 mm) -34- 556159 A8, B8, C8, D8 printed by the Bureau ’s Consumer Cooperatives 6. Patent application scope 4 Position-speed information, and drive the actuator based on the control data , Move the head to the predetermined position. 6 · If the recording medium of the position control program of the magnetic head is stored in item 5 of the patent application, the program includes: the observer calculates the estimation error from the estimated position to the speed information and the detected position-speed information, and when When the servo information is detected incorrectly, or when the degree of vibration or vibration exceeds the critical threshold, and the degree of the estimated error exceeds a predetermined critical threshold, the selector can select the estimated position-velocity information as the Head position-speed information. This paper size applies to Chinese National Standard (CNS) A4 specification (210 X 297 mm) 燊-(Please read the precautions on the back before filling this page), τ