Evaluation method, manufacturing method, and disk device

Abstract

The embodiment of the invention provides an evaluation method, a manufacturing method and a disk device capable of properly performing evaluation. An evaluation method according to an embodiment includes obtaining first accuracy information. The first accuracy information relates to the positioning accuracy of the head when the head is seeked to a first radial position in the disk medium. The evaluation method includes determining whether the first radial position is good or not on the basis of the first accuracy information.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2024-181532 (filed on October 17, 2024). This application incorporates the entire contents of the basic application by reference to that basic application. Technical Field

[0002] The embodiments of the present invention relate to evaluation methods, manufacturing methods, and disk apparatus. Background Technology

[0003] Sometimes, in the manufacturing process of a disk assembly containing a disk medium, multiple tracks are specified for the disk medium, and then each track is evaluated. It is desirable to perform this evaluation appropriately during the disk assembly manufacturing process. Summary of the Invention

[0004] Embodiments of the present invention provide an evaluation method, a manufacturing method, and a disc apparatus capable of performing appropriate evaluations.

[0005] The evaluation method for the implementation includes determining the positioning accuracy of the head when it seeks to a first radial position on the disk medium. The evaluation method further includes determining the quality of the first radial position based on the determined positioning accuracy. Attached Figure Description

[0006] Figure 1 This is a diagram showing the general configuration of the disk device according to the embodiment.

[0007] Figure 2 This is a diagram showing the configuration of the control system for the disc device in the embodiment.

[0008] Figure 3 This is a flowchart illustrating the seek process in the implementation method.

[0009] Figure 4 This is a flowchart illustrating the tracking process in the implementation method.

[0010] Figure 5 This is a flowchart illustrating the evaluation process in the implementation method.

[0011] Figure 6 This is a graph showing the change in track deviation over time in the implementation method (in the case of a lenient track completion determination).

[0012] Figure 7 This is a graph showing the distribution of settling accuracy (positioning accuracy) at each radial position in the implementation.

[0013] Figure 8 This is a graph showing the change in track deviation over time in the implementation method (in the case of strict track completion determination).

[0014] Figure 9 This is a graph showing the distribution of the number of samples (seeking time) required for each radial position in the implementation.

[0015] Explanation of reference numerals in the attached figures

[0016] 1 device, 2 heads, 5 media trays, 13 controllers. Detailed Implementation

[0017] The evaluation method of the embodiments will now be described in detail with reference to the accompanying drawings. Furthermore, these embodiments do not constitute a limitation on the present invention.

[0018] (Implementation Method)

[0019] In the manufacturing process of the disk device according to the embodiment, multiple tracks are defined for the disk medium, and then each track among the multiple tracks is evaluated. In order to conduct the evaluation appropriately, a study was conducted.

[0020] Disk device 1 can be as follows Figure 1 It is constructed as shown. Figure 1 This is a diagram showing the general configuration of the disk assembly 1.

[0021] The disk device 1 includes a disk medium 5, a spindle motor (SPM) 19, an SPM drive circuit 20, a head 2, an arm 3, a voice coil motor (VCM) 4, a signal processing circuit 9, a position detection circuit 10, a controller 13, a voice coil motor (VCM) drive circuit 14, a micro actuator (MA) drive circuit 15, a micro actuator (MA) 16, a vibration sensor 17, and an A / D conversion circuit 18.

[0022] The controller 13 is capable of comprehensively controlling all parts of the disk device 1, including the processor 11 and the non-volatile memory 12.

[0023] The disc medium 5 is rotatably supported on the housing (not shown) of the disc assembly 1 via an SPM 19. The SPM 19 is driven to rotate by the SPM drive circuit 20. The head 2 is positioned corresponding to the recording surface of the disc medium 5. The head 2 can face the recording surface of the disc medium 5.

[0024] Servo information is written to disk medium 5 during the manufacturing process. Figure 1 In the example shown, servo regions 7 are arranged radially, representing a configuration of servo regions where servo information has been written.

[0025] Data areas 8, capable of being written to, are provided between servo areas 7. Each servo area 7 and the subsequent data area 8 constitute a servo sector 6. When the number of servo sectors of the disk medium 5 is set to N, a reference sector is designated as number 0 on the circumference, and numbers from 0 to N-1 are marked around the direction of rotation of the disk. Each servo area 7 has a servo information record at the beginning of each servo sector 6. The servo information includes positional information indicating the location of the servo sector 6 in the disk medium 5. Multiple concentric servo tracks TR, defined by the servo information, are set radially on the disk medium 5. Because the disk medium 5 rotates at a certain angular velocity, servo information is read from the head 2 at regular time intervals. Data areas 8 can store data according to write commands.

[0026] The first part 2 includes a write element and a read element. In the first part 2, the write element and the read element are arranged offset from each other in the radial direction of the disk medium 5.

[0027] Arm 3 has head 2 mounted at its front end. Arm 3 is capable of rotating about axis 3a, which is located between it and VCM4.

[0028] VCM4 is driven by VCM drive circuit 14, which drives arm 3 to rotate around shaft 3a, thereby enabling head 2 to move along the radial direction of disk medium 5.

[0029] MA16 is mounted between the front end of arm 3 and head 2. MA16 causes the head to move slightly according to the applied voltage.

[0030] The signal processing circuit 9 demodulates the signal detected by the head 2 to generate a read signal and performs error correction on the read signal. The read signal contains data and servo information. The signal processing circuit 9 supplies the read signal to the position detection circuit 10.

[0031] The position detection circuit 10 separates the data and servo information from the data signal. The position detection circuit 10 extracts position information from the servo information. The position detection circuit 10 uses the position information to determine the position of head 2. The position detection circuit 10 supplies the data and the position of head 2 to the controller 13.

[0032] The processor 11 includes a CPU (Central Processing Unit).

[0033] Non-volatile memory 12 stores firmware and parameters in a non-volatile manner. The firmware includes descriptions of various control methods. The parameters are used in various control methods. Non-volatile memory 12 may be flash memory.

[0034] The volatile memory 21 is connected to the processor 11. The volatile memory 21 can temporarily store information. The volatile memory 21 can be used as the working area of ​​the processor 11.

[0035] When the disk device 1 is started, the processor 11 can read the firmware from the non-volatile memory 12 and unfold the functional modules of the firmware on the volatile memory 21, and execute various control methods according to the functional modules of the firmware.

[0036] For example, the processor 11 can receive the position of the head 2 from the position detection circuit 10 at regular intervals, calculate the position error based on the target position of the head 2, and perform positioning control of the head 2 via the MA drive circuit 15 and the VCM drive circuit 14 in such a way that the position error is close to zero (0).

[0037] The processor 11 reads parameters from the non-volatile memory 12 according to the firmware, determines the control values ​​of VCM4 and MA16 at predetermined sampling periods, and supplies them to the VCM drive circuit 14 and MA drive circuit 15 respectively. The sampling period can be constant.

[0038] The VCM drive circuit 14 controls the current flowing to the VCM4 based on the control quantity of the VCM4 based on the processor 11. Thus, the VCM4 is driven with an indicated current corresponding to the control quantity of the VCM4 based on the processor 11.

[0039] MA drive circuit 15 controls the voltage applied to MA16 according to the control quantity of MA16 based on processor 11. As a result, MA16 is driven with an indicated current corresponding to the control quantity of MA16 based on processor 11.

[0040] Vibration sensor 17 can detect external vibrations applied by the disk assembly 1. Vibration sensor 17 supplies the detection signal, which is the detection result, to A / D conversion circuit 18 in the form of an analog signal.

[0041] The A / D conversion circuit 18 performs A / D conversion on the detection signal (analog signal) from the vibration sensor to generate detection information (digital signal). The A / D conversion circuit 18 supplies the detection information to the processor 11. Thus, the processor 11 can perform predetermined control based on the detection information from the vibration sensor 17.

[0042] In the disk assembly 1, the controller 13 rotates the disk medium 5 at a certain angular velocity during operation. The controller 13 determines the head position based on servo information read synchronously from the servo region 7 at the beginning of each servo sector 6, which is synchronized with the rotation angle of the disk medium 5. Therefore, the controller 13 functionally constitutes a sampled-value control system that determines the input to the controlled object at regular time intervals. The controller 13 performs multi-rate control of VCM4 and MA16 driven by 1 / N periods (N being an integer greater than 2) of the head position observation period. The timing of the A / D conversion of the analog value of the vibration sensor 17 can be the same as or different from the head position observation period. The timing of the A / D conversion differs less from the servo information on the disk 5, thus allowing for multi-rate observation of the analog value of the vibration sensor 17.

[0043] Disk device 1 has a random seek evaluation function, which can, for example... Figure 2 It is constructed as shown. Figure 2 This is a diagram showing the configuration of the control system of the disk device 1.

[0044] The disk assembly 1 includes a control unit 21, a driver 22, a controlled object 23, and a position detector 24. The control unit 21 corresponds to the controller 13. The driver 22 corresponds to the VCM drive circuit 14 and the MA drive circuit 15. The controlled object 23 corresponds to the head 2, VCM 4, and MA 16. The position detector 24 corresponds to the signal processing circuit 9 and the position detection circuit 10.

[0045] In the control unit 21, with the positioning control system 21a as the center, there is a block 21b that realizes the path-finding action, a block 21c that determines the path-finding completion, and a block 21d that records and evaluates the path-finding action.

[0046] The positioning control system 21a includes a subtractor 21a1, a target speedometer 21a2, a seek speed adjuster 21a3, a subtractor 21a4, a seek controller 21a5, and a head speed estimator 21a6. Block 21b includes a random head cylinder generator 21b1 and a target head position generator 21b2. Block 21c includes a seek completion determiner 21c1. The seek completion determiner 21c1 includes a seek counter 21c1a. Block 21d includes a seek motion recorder 21d1 and a drive determiner 21d2.

[0047] Furthermore, the seek completion determiner 21c1 can be configured to select an off-track limit from multiple different off-track slices for seeking completion determination. The larger off-track limit among the multiple off-track limits is used for a lenient seek completion determination. The smaller off-track limit among the multiple off-track limits is used for a strict seek completion determination.

[0048] In addition, for simplicity, the diagram is omitted. The control unit 21 also includes a tracking processing unit for performing tracking processing. The tracking processing unit includes a tracking counter and an evaluation counter.

[0049] As a term used here, the tracking action immediately after the pathfinding action is completed is referred to as "settling".

[0050] Disk device 1 performs as follows Figure 3 The pathfinding process is as shown. Figure 3 This is a flowchart showing the seek process of disk device 1.

[0051] During the track seek process, the control unit 21 sets the operating mode of the head 2 to track seek mode. At this time, the track seek completion determiner 21c1 can select a track deviation limit from a plurality of different track deviation limits for determining track seek completion. The track deviation limit with the larger value among the plurality of track deviation limits is used for the case of lenient track seek completion determination. The track deviation limit with the smaller value among the plurality of track deviation limits is used for the case of strict track seek completion determination.

[0052] Position detector 24 detects the head position (S1) and supplies it to subtractor 21a1. Target head position generator 21b2 supplies the target position to subtractor 21a1. Subtractor 21a1 calculates the difference between the head position and the target position (S2) and supplies it to target speed meter 21a2. Target speed meter 21a2 calculates the target speed by dividing the difference by the sampling period (S3) and supplies it to subtractor 21a4. Head speed estimator 21a6 estimates the head speed based on the difference between the head position and the target position and the control input of seek controller 21a5 (S4) and supplies it to subtractor 21a4. Subtractor 21a4 calculates the difference between the estimated head speed and the target speed (S5) and supplies it to seek controller 21a5. Seeker controller 21a5 determines the control input based on the difference (S6) and supplies it to driver 22 (S7). The control input includes the indicator current of VCM4 and the indicator current of MA16.

[0053] Subsequently, the seek completion determiner 21c1 increments the count value of the seek counter 21c1a by 1 (S8). The count value of the seek counter 21c1a represents the number of samples taken since the start of seek execution. The seek completion determiner 21c1 performs a seek completion determination (S9) and supplies the determination result to the random head cylinder generator 21b1 and the seek action recorder 21d1. The seek completion determiner 21c1 determines that the seek is not completed when the deviation of the head 2 from the track exceeds the deviation limit, and determines that the seek is completed when the deviation of the head 2 is within the deviation limit.

[0054] If the seek operation is determined to be complete (S9: Yes), the seek action recorder 21d1 records the current count value of the seek counter 21c1a as the seek execution sample number (S10). The control unit 21 performs tracking action settings (S11). As a setting for the tracking accumulation value (S12), the control unit 21 initializes the tracking accumulation value. As a setting for the tracking counter (S13), the control unit 21 initializes the tracking counter.

[0055] Then, the control unit 21 switches the motion mode of the head 2 from seek mode to tracking mode, and performs the following... Figure 4 The tracking process is as shown. Figure 4 This is a flowchart showing the tracking process of disk device 1.

[0056] In the tracking process, position detector 24 detects the head position (S21) and supplies it to positioning control system 21a. Positioning control system 21a performs tracking control calculation (22), determines the control quantity (S23), and supplies it to driver 22 (S24). The control quantity includes the indicating current of VCM4 and the indicating current of MA16.

[0057] Then, the control unit 21 increments the count value of the tracking counter by 1 (S25). The count value of the tracking counter represents the number of samples taken since the start of tracking execution.

[0058] The control unit 21 determines whether the count value of the tracking counter exceeds the threshold (S26).

[0059] When the count value of the tracking counter is below the threshold (S26: No), the control unit 21 adds the square of the head position error at that sampling time point to the cumulative tracking value (S27).

[0060] When the count value of the tracking counter exceeds the threshold (S26: Yes), the control unit 21 records the cumulative tracking value as stable accuracy (S28) and increments the count value of the evaluation counter by 1 (S29).

[0061] The control unit 21 determines whether the count value of the evaluation counter exceeds the threshold (S30).

[0062] When the count value of the evaluation counter is below the threshold (S30: No), the control unit 21 randomly generates the next seek head cylinder using the random head cylinder generator 21b1 (S31) and records the next seek head cylinder using the seek motion recorder 21b1 (S32). Afterwards, the control unit 21 switches the head 2's motion mode from tracking mode to seek mode (S33), generates the target position using the target head position generator 21b2 (S34), and initializes the seek counter count value to zero (S35).

[0063] Here, although the multiple tracks TR in the disk medium 5 are defined by the servo information recorded in the servo area 7, due to manufacturing errors, there may sometimes be localized areas with large deviations in track spacing. If data is written to and / or read from areas with large deviations in track spacing under such circumstances, write errors and / or read errors may occur frequently, resulting in a decrease in the performance of the disk device 1.

[0064] In contrast, when the count value of the evaluation counter exceeds the threshold (S30: Yes), the control unit 21, as background processing, delegates the evaluation processing to block 21d (S36). The evaluation processing is performed to "identify the areas with large deviations in track spacing by evaluating the track seeking operation and register them as error areas".

[0065] For example, block 21d can be as follows Figure 5 The evaluation process was carried out as shown. Figure 5 This is a flowchart illustrating the evaluation process.

[0066] Block 21d remains in standby mode until an evaluation processing execution request is received (S41: No). When an evaluation processing execution request is received (S41: Yes), block 21d sets the number of partitions to Z (S42) regarding the radial position of head 2. Z is an integer greater than or equal to 2. The number of partitions Z corresponds to the number of tracks being evaluated. When evaluating all tracks, the number of partitions Z can be the same as the number of tracks. When evaluating every N tracks, the number of partitions Z can be one-Nth of the number of tracks. N is an integer greater than or equal to 2. The identification information for each partition can be a number from 1 to N.

[0067] Block 21d generates a standard value table t[1…Z] representing the center position of a track for each partition (S43). The standard value table t[1…Z] establishes a correlation between the partition identification information and the center position of the track and multiple partitions. The center position of the track corresponding to a partition can be determined by referring to the standard value table t[1…Z]. The standard value table t[1…Z] can also be regarded as an array that returns the center position of the track corresponding to a given partition identification information.

[0068] Block 21d sets the decision limit to be used for evaluation as s (S44). The decision limit s corresponds to the allowable limit of the deviation from the track. The decision limit s corresponds to the deviation from the track used for seek completion determination. When the deviation from the track used for seek completion determination is large (when seek completion determination is lenient), the decision limit s is set to a larger value. When the deviation from the track used for seek completion determination is small (when seek completion determination is strict), the decision limit s is set to a smaller value.

[0069] Block 21d sets the initial value of the region variable c, which is designated as the evaluation object, to 1 (S45). The region variable c stores the identification information of the partition. The initial value of 1 is the identification information of the initially selected partition.

[0070] Block 21d calculates the average radial position a within region c (S46). Block 21d can obtain the radial position of head 2 with respect to multiple circumferential positions after a predetermined time Δt has elapsed since the timing of the completion of the seek operation. Block 21d can calculate the average radial position a by averaging the obtained radial positions of head 2 at multiple circumferential positions.

[0071] Block 21d determines whether the average value 'a' of the radial position obtained in S46 satisfies at[c]>s…Equation 1 (S47). t[c] represents the center position of the track in region c. at[c] represents the average value of the deviation of the head 2 from the track in region c. “Satisfying Equation 1” means that “the average value of the deviation of the head 2 from the track exceeds the judgment limit s, and this region is the part with the most deviation in track spacing.”

[0072] If the average value 'a' of the radial position calculated by block 21d in S46 satisfies Equation 1 (S47: Yes), then region c is registered as an error region (S48). For example, error region information can be stored in the management information storage area of ​​the disk medium 5 or the non-volatile memory 12. The error region information can associate track identification information and error flags with multiple tracks. Block 21d can obtain the error region information from the management information storage area of ​​the disk medium 5 or the non-volatile memory 12 and update the error flag corresponding to the track identification information of region c from 0 (inactive) to 1 (active) by overwriting. As a result, the controller 13 can write and / or read data in subsequent write and / or read operations without avoiding error regions where the error flag is active. As a result, the performance of the disk device 1 can be improved.

[0073] Block 21d adds 1 to the region variable c (S49), changing the evaluation object to the next region.

[0074] Block 21d continues processing S46 to S49 until the region variable c exceeds the number of partitions Z (S50: No). When the region variable c exceeds the number of partitions Z (S50: Yes), the processing ends. Thus, each partition 1 to N can be evaluated sequentially, and areas with significant deviations in track spacing can be identified and registered as error regions.

[0075] Next, an example of the evaluation results based on block 21d will be explained.

[0076] When the deviation from the track limit used for track seek completion determination is large (when track seek completion determination is lenient), such as Figure 6 of (a), Figure 6 As shown in (b), at the timings t0 and t2 when the track seeker completes, the residual vibration of the first 2 does not converge, and the deviation of the first 2 from the track is relatively large. Figure 6 This is a graph showing the change in track deviation over time (in the case of a lenient track completion determination). At this time, Figure 5 The decision limit s of S47 shown is set to a large value. At the radial position with a large deviation in track spacing, after a predetermined time Δt has elapsed since the track seeker completed, as shown... Figure 6 As indicated by the arrow under the dotted line in (a), the deviation from the track increases when it exceeds the judgment limit s. At the radial position where the track spacing deviation is small, at a timing t3 after a predetermined time Δt has elapsed since the track seeker completed, as shown... Figure 6 As indicated by the arrow under the dotted line in (b), the deviation from the magnetic track falls within the judgment limit s. Therefore, in Figure 5 In S47 and S48, it is possible to Figure 6 The region corresponding to (a) is identified as an erroneous region, which can... Figure 6 The region corresponding to (b) is determined not to be an erroneous region.

[0077] Organizing on multiple radial positions Figure 6 When the result is shown, it becomes Figure 7 As shown. Figure 7 This is a graph showing the distribution of stabilization accuracy at each radial position. Stabilization accuracy indicates the degree to which stabilization can be achieved within a predetermined time Δt. Stabilization accuracy is equivalent to the positioning accuracy of head 2.

[0078] For multiple radial positions, the stability accuracy is plotted as is to obtain the following: Figure 7 (a) is obtained by averaging the stability accuracy at multiple circumferential positions. Figure 7 (b). For example Figure 7 of (a), Figure 7 As shown in (b), it can be seen that the stability accuracy decreases at radial positions with larger track spacing deviations compared to radial positions with smaller track spacing deviations. Regarding this tendency, ... Figure 7 Compared to (a), in Figure 7 It is more significant in (b), therefore, it can be concluded that: through such Figure 5 By averaging the radial position as in S46, the accuracy of identifying error regions in S47 and S48 can be improved.

[0079] In addition, Figure 7 of (a), Figure 7 In (b), the evaluation results of disk devices with small overall track spacing deviations are shown in gray, and the evaluation results of disk devices with large overall track spacing deviations are shown in black.

[0080] When the deviation from the track limit used for track seek completion determination is small (when track seek completion determination is strict), such as Figure 8 of (a), Figure 8 As shown in (b), at the timings t0 and t2 when the track seek is completed, the residual vibration of head 2 converges, and the deviation of head 2 from the track is relatively small. Figure 8 This is a graph showing the change in track deviation over time (in the case of strict track completion determination). At this time, Figure 5 The decision limit s shown in S47 is set to a small value. Figure 8 The deviation of the radial position of the track spacing shown in (a) is large compared to the deviation of the track spacing. Figure 8 As shown in (b), the difference in radial position deviation from the track is small for tracks with smaller deviations in track spacing. Therefore, Figure 5 The accuracy of identifying error areas in S47 and S48 is easily reduced.

[0081] On the other hand, when the deviation from the track used for track completion determination is small (when track completion determination is strict), if the number of samples required for track completion is used, it is possible to achieve the following: Figure 9 As shown, this clearly distinguishes between radial positions with large track spacing deviations and positions with small track spacing deviations. The number of samples required for track seeking is the number of sampling periods from the start of the seek to its completion. If we consider the case where the sampling period is constant, then we can say that the number of samples required for track seeking is equivalent to the seek time.

[0082] For multiple radial positions, the number of samples required for the seek is plotted as is, resulting in... Figure 9 (a) is obtained by averaging the number of samples required for path seeking at multiple circumferential positions. Figure 9 (b). For example Figure 9 of (a), Figure 9 As shown in (b), it can be seen that compared with radial positions with small track spacing deviations, radial positions with large track spacing deviations require more samples for seeking (i.e., longer seek time). Regarding this tendency, ... Figure 9 Compared to (a), Figure 9 The significance is more pronounced in (b), therefore, it can be concluded that: through such... Figure 5 By averaging the radial position as in S46, the accuracy of identifying error regions in S47 and S48 can be improved.

[0083] In addition, Figure 9 of (a), Figure 9 In (b), the evaluation results of disk devices with small overall track spacing deviations are shown in gray, and the evaluation results of disk devices with large overall track spacing deviations are shown in black.

[0084] As described above, in this embodiment, in the disk drive 1, the controller 30 evaluates the stability accuracy of the head 2 at each radial position and determines whether the radial position is good or bad. Alternatively, the controller 30 evaluates the number of samples required for the head 2 to seek at each radial position and determines whether the radial position is good or bad. Therefore, the controller 13 can avoid writing and / or reading data in subsequent write and / or read operations by avoiding radial positions determined to be bad. As a result, the performance of the disk drive 1 can be improved.

[0085] Several embodiments of the present invention have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

Claims

1. An evaluation method, comprising: Determine the positioning accuracy of the head when it seeks to the first radial position in the disk medium; and The quality of the first radial position is determined based on the calculated positioning accuracy.

2. The evaluation method according to claim 1, The evaluation method further comprises: Choose a judgment criterion from multiple judgment criteria. The determination of whether the first radial position is good or bad includes: determining whether the first radial position is good or bad based on the selected determination criterion and the calculated positioning accuracy.

3. An evaluation method, comprising: Calculate the number of seek samples required until the head is positioned when it seeks to the first radial position in the disk medium. and The quality of the first radial position is determined based on the number of samples required for the path finding.

4. The evaluation method according to claim 3, The evaluation method further comprises: Choose a judgment criterion from multiple judgment criteria. The determination of whether the first radial position is good or bad includes: determining whether the first radial position is good or bad based on the selected determination criteria and the calculated number of samples required for the seek.

5. A method for manufacturing a disc device, comprising: The evaluation shall be carried out using the evaluation method described in any one of claims 1 to 4; and The disk device is configured in accordance with the evaluation.

6. A disk device comprising: head; Disk media; and The controller calculates the positioning accuracy of the head when it seeks to the first radial position in the disk medium, and determines whether the first radial position is good or bad based on the calculated positioning accuracy.

7. A disk device comprising: head; Disk media; and The controller calculates the number of samples required for the head to seek to the first radial position in the disk medium until the head is positioned, and determines whether the first radial position is good or bad based on the calculated number of samples required for seeking.

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