Evaluation method, manufacturing method, and disk device

Abstract

One embodiment aims to provide an evaluation method, a manufacturing method, and a disk device that can perform evaluation appropriately. [Solution] According to one embodiment, an evaluation method is provided. The evaluation method includes obtaining first accuracy information. The first accuracy information relates to the positioning accuracy of the head when the head seeks to a first radial position on the disk medium. The evaluation method includes determining whether the first radial position is good or bad according to the first accuracy information.

Description

Technical Field

[0001] This embodiment relates to an evaluation method, a manufacturing method, and a disk device.

Background Art

[0002] In the manufacturing process of a disk device having a disk medium, a plurality of tracks may be defined on the disk medium, and then evaluation may be performed on each of the plurality of tracks. In the manufacturing process of the disk device, it is desirable that the evaluation be appropriately performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] One embodiment aims to provide an evaluation method, a manufacturing method, and a disk device capable of appropriately performing evaluation.

Means for Solving the Problems

[0005] According to one embodiment, an evaluation method is provided. The evaluation method includes obtaining the positioning accuracy of the head when the head is seeked to a first radial position on the disk medium. The evaluation method includes determining whether the first radial position is good or bad according to the obtained positioning accuracy.

Brief Description of the Drawings

[0006] [Figure 1]A diagram showing the schematic configuration of a disk device according to an embodiment. [Figure 2] A diagram showing the configuration of the control system for the disk device in the embodiment. [Figure 3] A flowchart illustrating the seek process in the embodiment. [Figure 4] A flowchart illustrating the tracking process in the embodiment. [Figure 5] A flowchart illustrating the evaluation process in the embodiment. [Figure 6] This figure shows the temporal change in the amount of off-track data in the embodiment (when the seek completion determination is lenient). [Figure 7] A figure showing the distribution of settling accuracy (positioning accuracy) for each radial position in the embodiment. [Figure 8] A diagram showing the temporal change in the amount of off-tracking in the embodiment (when the seek completion determination is strict). [Figure 9] A figure showing the distribution of the number of samples required for seeking (seek time) for each radial position in the embodiment. [Modes for carrying out the invention]

[0007] The evaluation method according to the embodiment will be described in detail below with reference to the attached drawings. However, the present invention is not limited by this embodiment.

[0008] (Embodiment) In the disk device according to the embodiment, multiple tracks are defined on the disk medium during the manufacturing process of the disk device having a disk medium, and then each of the multiple tracks is evaluated, with measures taken to ensure that the evaluation is performed appropriately.

[0009] The disk drive 1 may be configured as shown in Figure 1. Figure 1 is a diagram showing the schematic configuration of the disk drive 1.

[0010] The disk drive 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 microactuator (MA) drive circuit 15, a microactuator (MA) 16, a vibration sensor 17, and an A / D conversion circuit 18.

[0011] The controller 13 can comprehensively control each part of the disk drive 1. It includes a processor 11 and non-volatile memory 12.

[0012] The disk medium 5 is rotatably supported in the housing (not shown) of the disk drive 1 via an SPM 19. The SPM 19 is rotationally driven by an SPM drive circuit 20. The head 2 is provided corresponding to the recording surface of the disk medium 5. The head 2 is capable of facing the recording surface of the disk medium 5.

[0013] During the manufacturing process, servo information is written to the disk medium 5. Figure 1 shows an example of the arrangement of servo areas 7 arranged radially, where servo information is written.

[0014] Between the servo areas 7, there are data areas 8 on which data can be written. One servo area 7 and one data area 8 following it constitute a servo sector 6. If the number of servo sectors in the disk medium 5 is N, the reference sector is numbered 0 on the circumference, and the sectors are numbered from 0 to N-1 around the direction of rotation of the disk. One servo area 7 is provided at the beginning of each servo sector 6, and its servo information is recorded therein. The servo information includes position information indicating the position of the servo sector 6 on the disk medium 5. Multiple concentric servo tracks TR, defined by the servo information, are set in the radial direction of the disk medium 5. Because the disk medium 5 rotates at a constant angular velocity, the servo information is read by the head 2 at regular time intervals. The data area 8 can store data in response to write commands.

[0015] The head 2 includes a light element and a lead element. In the head 2, the light element and the lead element are installed with a shift in the radial direction of the disk medium 5.

[0016] The arm 3 has the head 2 attached to its tip. The arm 3 is rotatable about a shaft 3a provided between it and the VCM 4.

[0017] The VCM 4 is driven by a VCM drive circuit 14, and by rotationally driving the arm 3 about the shaft 3a, the head 2 can be seeked and moved along the radial direction of the disk medium 5.

[0018] MA16 is attached between the tip of the arm 3 and the head 2. MA16 moves the head slightly according to the applied voltage.

[0019] The signal processing circuit 9 can demodulate the signal detected by the head 2 to generate a read signal and perform error correction on the read signal. The read signal includes data and servo information. The signal processing circuit 9 supplies the read signal to the position detection circuit 10.

[0020] The position detection circuit 10 separates 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 obtains the position of the head 2 using the position information. The position detection circuit 10 supplies the data and the position of the head 2 to the controller 13.

[0021] The processor 11 includes a CPU (Central Processing Unit).

[0022] The 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. The non-volatile memory 12 may be a flash memory.

[0023] 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 a work area by the processor 11.

[0024] When the disk device 1 is started up, the processor 11 reads the firmware from the non-volatile memory 12, deploys the firmware's functional modules onto the volatile memory 21, and can execute various control methods according to the firmware's functional modules.

[0025] For example, the processor 11 receives the position of the head 2 from the position detection circuit 10 at regular intervals, calculates the position error from the target position of the head 2, and can control the position of the head 2 via the MA drive circuit 15 and the VCM drive circuit 14 so that the position error approaches zero.

[0026] The processor 11 reads parameters from the non-volatile memory 12 according to the firmware, determines the control amount for VCM4 and MA16 at predetermined sample cycles, and supplies them to the VCM drive circuit 14 and MA drive circuit 15, respectively. The sample cycle may be constant.

[0027] The VCM drive circuit 14 controls the current flowing to the VCM4 according to the amount of control of the VCM4 by the processor 11. As a result, the VCM4 is driven by an instructed current corresponding to the amount of control of the VCM4 by the processor 11.

[0028] The MA drive circuit 15 controls the voltage supplied to MA16 according to the amount controlled by the processor 11. As a result, MA16 is driven with an instruction current corresponding to the amount controlled by the processor 11.

[0029] The vibration sensor 17 can detect external vibrations applied to the disk drive 1. The vibration sensor 17 supplies the detection signal as a result of the detection to the A / D conversion circuit 18 in the form of an analog signal.

[0030] The A / D conversion circuit 18 converts the detection signal (analog signal) from the vibration sensor into detection information (digital signal). The A / D conversion circuit 18 supplies the detection information to the processor 11. As a result, the processor 11 can perform predetermined control according to the detection information from the vibration sensor 17.

[0031] In the disk drive 1, the controller 13 rotates the disk medium 5 at a constant angular velocity during operation. The controller 13 determines the head position in accordance with the servo information read from the leading servo area 7 of each servo sector 6, synchronized with the rotation angle of the disk medium 5. Therefore, the controller 13 functionally configures a sample value control system that determines the input to the controlled object at regular time intervals. The controller 13 performs multi-rate control in which the VCM 4 and MA 16 are driven at a period of 1 / N of the head position observation period (where N is an integer greater than or equal to 2). The timing of A / D conversion of the analog value of the vibration sensor 17 may be the same as the head position observation period, or it may be different from the head position observation period. The timing of A / D conversion has fewer constraints than the servo information on the disk 5. Therefore, the analog value of the vibration sensor 17 may be observed at a multi-rate.

[0032] Disk drive 1 has a random seek evaluation function and can be configured as shown in Figure 2. Figure 2 is a diagram showing the configuration of the control system of disk drive 1.

[0033] The disk drive 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.

[0034] The control unit 21 includes a positioning control system 21a, a block 21b that implements the seek operation, a block 21c that determines the completion of the seek operation, and a block 21d that records and evaluates the seek operation.

[0035] The positioning control system 21a includes a subtractor 21a1, a target speed table 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 operation recorder 21d1 and a drive determiner 21d2.

[0036] The seek completion criterion 21c1 may be configured to allow selection of an off-track slice to be used for seek completion determination from a plurality of different off-track slices. Off-track slices with relatively large values ​​among the plurality of off-track slices are used when the seek completion determination is lenient. Off-track slices with relatively small values ​​among the plurality of off-track slices are used when the seek completion determination is strict.

[0037] Furthermore, although not shown in the diagram for simplicity, the control unit 21 also includes a tracking processing unit that performs tracking processing. The tracking processing unit includes a tracking counter and an evaluation counter.

[0038] In this context, we will refer to the tracking action immediately following the completion of a seek operation as "settling."

[0039] Disk drive 1 performs a seek operation as shown in Figure 3. Figure 3 is a flowchart of the seek operation of disk drive 1.

[0040] During the seek process, the control unit 21 sets the operating mode of the head 2 to seek mode. At this time, the seek completion determination unit 21c1 may select an off-track slice to be used for seek completion determination from a plurality of different off-track slices. Off-track slices with relatively large values ​​among the plurality of off-track slices are used when the seek completion determination is lenient. Off-track slices with relatively small values ​​among the plurality of off-track slices are used when the seek completion determination is strict.

[0041] The position detector 24 detects the head position and (S1) supplies it to the subtractor 21a1. The target head position generator 21b2 supplies the target position to the subtractor 21a1. The subtractor 21a1 calculates the difference between the head position and the target position and (S2) supplies it to the target speed table 21a2. The target speed table 21a2 calculates the target speed by dividing the difference by the sample period and (S3) supplies it to the subtractor 21a4. The head speed estimator 21a6 estimates the head speed according to the difference between the head position and the target position and the control amount of the seek controller 21a5 and (S4) supplies it to the subtractor 21a4. The subtractor 21a4 calculates the difference between the estimated head speed and the target speed and (S5) supplies it to the seek controller 21a5. The seek controller 21a5 determines the control amount according to the difference (S6) and supplies it to the driver 22 (S7). The control amount includes the instruction current of VCM4 and the instruction current of MA16.

[0042] Subsequently, the seek completion determination unit 21c1 increments the count value of the seek counter 21c1a by 1 (S8). The count value of the seek counter 21c1a indicates the number of samples since the start of the seek operation. The seek completion determination unit 21c1 performs a seek completion determination (S9) and supplies the determination result to the random head cylinder generator 21b1 and the seek operation recorder 21d1. The seek completion determination unit 21c1 determines that the seek is not complete if the off-track amount of head 2 exceeds the off-track slice, and determines that the seek is complete if the off-track amount of head 2 is within the off-track slice.

[0043] If it is determined that the seek is complete (Yes in S9), the seek operation recorder 21d1 records the count value of the seek counter 21c1a at that time as the number of samples sought (S10). The control unit 21 sets the tracking operation (S11). The control unit 21 initializes the tracking cumulative value as setting the tracking cumulative value (S12). The control unit 21 initializes the tracking counter as setting the tracking counter (S13).

[0044] Subsequently, the control unit 21 switches the operation mode of the head 2 from seek mode to tracking mode and performs tracking processing as shown in Figure 4. Figure 4 is a flowchart of the tracking processing of the disk device 1.

[0045] In the tracking process, the position detector 24 detects the head position (S21) and supplies it to the positioning control system 21a. The positioning control system 21a performs tracking control calculations (22), determines the control amount (S23), and supplies it to the driver 22 (S24). The control amount includes the instruction current of the VCM4 and the instruction current of the MA16.

[0046] Subsequently, the control unit 21 increments the tracking counter's count value by 1 (S25). The tracking counter's count value indicates the number of samples taken since tracking began.

[0047] The control unit 21 determines whether the count value of the tracking counter exceeds a threshold (S26).

[0048] If the count value of the tracking counter is below a threshold (No in S26), the control unit 21 adds the square of the head position error at that sampling point to the tracking cumulative value (S27).

[0049] If the count value of the tracking counter exceeds a threshold (Yes in S26), the control unit 21 records the tracking cumulative value as the settling accuracy (S28) and increments the count value of the evaluation counter by 1 (S29).

[0050] The control unit 21 determines whether the count value of the evaluation counter exceeds a threshold (S30).

[0051] If the count value of the evaluation counter is below a threshold (No in S30), the control unit 21 randomly generates the head cylinder for the next seek using the random head cylinder generator 21b1 (S31), and records the head cylinder for the next seek using the seek operation recorder 21b1 (S32). After that, the control unit 21 switches the operation mode of the head 2 from tracking mode to seek mode (S33), generates the target position using the target head position generator 21b2 (S34), and initializes the count value of the seek counter to zero (S35).

[0052] Here, the multiple tracks TR on the disk medium 5 are defined by the servo information recorded in the servo area 7, but due to manufacturing errors, there may be localized areas with significant variations in track pitch. In this case, if data is written and / or read to areas with significant variations in track pitch, write errors and / or read errors may occur frequently, potentially degrading the performance of the disk device 1.

[0053] In response, if the count value of the evaluation counter exceeds a threshold (Yes in S30), the control unit 21 requests block 21d to perform the evaluation process as background processing (S36). The evaluation process is performed to find areas with a large variation in track pitch by evaluating the seek operation and register them as error areas.

[0054] For example, block 21d may perform an evaluation process as shown in Figure 5. Figure 5 is a flowchart of the evaluation process.

[0055] Block 21d waits until a request to perform the evaluation process is received (No in S41). When a request to perform the evaluation process is received (Yes in S41), block 21d sets the number of divisions to Z for the radial position of head 2 (S42). Z is an integer of 2 or more. The number of divisions Z corresponds to the number of tracks to be evaluated. If all tracks are to be evaluated, the number of divisions Z may be the same as the number of tracks. If N tracks are to be thinned out and evaluated, the number of divisions Z may be 1 / N of the number of tracks. N is an integer of 2 or more. The identification information for each division may be a number from 1 to N.

[0056] Block 21d generates a standard value table t[1···Z] indicating the track center position for each section (S43). The standard value table t[1···Z] associates section identification information with track center positions for multiple sections. By referring to the standard value table t[1···Z], the track center position corresponding to a section can be identified. The standard value table t[1···Z] can also be considered an array that returns the corresponding track center position given the section identification information.

[0057] Block 21d sets the judgment slice to be used for evaluation to s (S44). The judgment slice s corresponds to the acceptable limit of the off-track amount. The judgment slice s corresponds to the off-track slice used for seek completion determination. If the off-track slice used for seek completion determination is relatively large (the seek completion determination is lenient), the judgment slice s is set to a relatively large value. If the off-track slice used for seek completion determination is relatively small (the seek completion determination is strict), the judgment slice s is set to a relatively small value.

[0058] Block 21d sets the initial value of the region variable c, which specifies the category to be evaluated, to 1 (S45). The region variable c stores the identification information of the category. The initial value of 1 is the identification information of the category that is selected first.

[0059] Block 21d calculates the average value a of the radial positions within region c (S46). Block 21d may acquire the radial position of the head 2 for multiple circumferential positions at a predetermined time Δt after the timing of the seek completion. Block 21d may calculate the average value a of the radial positions by adding the acquired radial positions of the head 2 to the multiple circumferential positions.

[0060] Block 21d has an average value a of radial position obtained in S46. at[c]>s···Formula 1 It is determined whether the condition is met (S47). t[c] indicates the track center position in region c. at[c] indicates the average off-track amount of head 2 in region c. If equation 1 is satisfied, it means that the average off-track amount of head 2 exceeds the determination slice s, and that region is an area with a large variation in track pitch.

[0061] Block 21d registers area c as an error area (S48) if the average value a of the radial positions obtained in S46 satisfies formula 1 (Yes in S47). For example, error area information may be stored in the management information storage area of ​​the disk medium 5 or the non-volatile memory 12. The error area information may associate track identification information and error flags for multiple tracks. Block 21d may obtain error area information from the management information storage area of ​​the disk medium 5 or the non-volatile memory 12 and overwrite update the error flag corresponding to the track identification information corresponding to area c from 0 (non-active) to 1 (active). As a result, the controller 13 can write and / or read data while avoiding error areas where the error flag is active in subsequent write and / or read operations. This can improve the performance of the disk device 1.

[0062] Block 21d increments the region variable c by 1 (S49) and changes the region to be evaluated to the next region.

[0063] Block 21d repeats the process from S46 to S49 until the region variable c exceeds the number of divisions Z (No in S50), and terminates the process when the region variable c exceeds the number of divisions Z (Yes in S50). This allows evaluation processing to be performed sequentially for each division from 1 to N, and among them, areas with a large variation in track pitch can be found and registered as error areas.

[0064] Next, we will explain an example of the results of the evaluation process performed by block 21d.

[0065] When the off-track slice used for determining the completion of the seek is relatively large (when the seek completion determination is lenient), as shown in Figures 6(a) and 6(b), the residual vibration of head 2 has not subsided at the timings t0 and t2 when the seek is completed, and the amount of off-track of head 2 is relatively large. Figure 6 shows the temporal change in the amount of off-track (when the seek completion determination is lenient). In this case, the determination slice s of S47 shown in Figure 5 is set to a relatively large value. At radial positions where the variation in track pitch is large, at timing t1, after a predetermined time Δt has elapsed since the completion of the seek, the amount of off-track exceeds the determination slice s, as shown by the dashed arrow in Figure 6(a). At radial positions where the variation in track pitch is small, at timing t3, after a predetermined time Δt has elapsed since the completion of the seek, the amount of off-track falls within the determination slice s, as shown by the dashed arrow in Figure 6(b). As a result, in steps S47 and S48 of Figure 5, the region corresponding to Figure 6(a) can be determined to be an error region, and the region corresponding to Figure 6(b) can be determined to be not an error region.

[0066] When the results shown in Figure 6 are organized for multiple radial positions, the result is as shown in Figure 7. Figure 7 shows the distribution of settling accuracy for each radial position. Settling accuracy indicates the accuracy of how much settling can be completed within a predetermined time Δt. Settling accuracy corresponds to the positioning accuracy of head 2.

[0067] Figure 7(a) plots the settling accuracy directly for multiple radial positions, while Figure 7(b) shows the settling accuracy averaged over multiple circumferential positions. As shown in Figures 7(a) and 7(b), the settling accuracy decreases at radial positions with greater track pitch variation compared to radial positions with smaller variation. This trend is more pronounced in Figure 7(b) than in Figure 7(a), indicating that averaging the radial positions, as shown in S46 of Figure 5, can improve the accuracy of error area determination in S47 and S48.

[0068] In Figures 7(a) and 7(b), the gray areas indicate evaluation results for disk drives with generally small track pitch variations, while the black areas indicate evaluation results for disk drives with generally large track pitch variations.

[0069] When the off-track slice used for seek completion determination is relatively small (when the seek completion determination is strict), as shown in Figures 8(a) and 8(b), the residual vibration of head 2 subsides at the timings t0 and t2 when the seek is completed, and the amount of off-track of head 2 is relatively small. Figure 8 shows the temporal change in the amount of off-track (when the seek completion determination is strict). In this case, the determination slice s in S47 shown in Figure 5 is set to a relatively small value, but the difference between the amount of off-track at radial positions with large track pitch variation shown in Figure 8(a) and the amount of off-track at radial positions with small track pitch variation shown in Figure 8(b) is small. For this reason, the accuracy of error area determination in S47 and S48 in Figure 5 tends to decrease.

[0070] On the other hand, when the off-track slice used for determining the completion of a seek is relatively small (i.e., when the criteria for determining the completion of a seek are strict), the number of samples required for a seek can be used to clearly distinguish between radial positions with large and small variations in track pitch, as shown in Figure 9. The number of samples required for a seek is the number of sample cycles from the start of the seek until the seek is completed. Considering that the sample cycle is constant, the number of samples required for a seek can be said to correspond to the seek time.

[0071] Figure 9(a) plots the number of seek samples required for multiple radial positions directly, while Figure 9(b) plots the number of seek samples required by adding them together across multiple circumferential positions. As shown in Figures 9(a) and 9(b), it can be seen that the number of seek samples required is higher (i.e., the seek time is longer) at radial positions with greater variation in track pitch compared to radial positions with less variation in track pitch. This trend is more pronounced in Figure 9(b) than in Figure 9(a), indicating that averaging the radial positions, as shown in S46 of Figure 5, can improve the accuracy of error area determination in S47 and S48.

[0072] In Figures 9(a) and 9(b), the gray areas indicate evaluation results for disk drives with generally small track pitch variations, while the black areas indicate evaluation results for disk drives with generally large track pitch variations.

[0073] As described above, in the embodiment, the controller 30 in the disk drive 1 evaluates the settling accuracy of the head 2 for each radial position and determines whether the radial position is good or bad. Alternatively, the controller 30 evaluates the number of seek samples required for the head 2 for each radial position and determines whether the radial position is good or bad. As a result, the controller 13 can write and / or read data while avoiding the radial positions determined to be bad during subsequent write and / or read operations. This improves the performance of the disk drive 1.

[0074] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0075] 1 disk drive, 2 heads, 5 disk media, 13 controllers.

Claims

1. To determine the positioning accuracy of the head when the head is sought at a first radial position on the disk medium, Based on the positioning accuracy obtained, the goodness or badness of the first radial position is determined, An evaluation method that includes this.

2. This further includes selecting criteria from multiple criteria, The determination of whether the first radial position is good or bad is as follows: This includes determining whether the first radial position is good or bad according to the selected judgment criteria and the determined positioning accuracy. The evaluation method according to claim 1.

3. To determine the number of seek samples required until the head's positioning is completed when the head is sought to a first radial position on the disk medium, The goodness or badness of the first radial position is determined according to the number of seek samples obtained above, An evaluation method that includes this.

4. This further includes selecting criteria from multiple criteria, The determination of whether the first radial position is good or bad is as follows: This includes determining whether the first radial position is good or bad according to the selected judgment criteria and the required number of seek samples. The evaluation method described in claim 3.

5. The evaluation is performed using the evaluation method described in any one of claims 1 to 4, The disk device is configured according to the aforementioned evaluation, A method for manufacturing a disk device including a disk drive.

6. The head and, Disk media and A controller that determines the positioning accuracy of the head when the head seeks to a first radial position on the disk medium, and determines whether the first radial position is good or bad according to the determined positioning accuracy, A disk drive equipped with a disk drive.

7. The head and, Disk media and A controller that determines the number of seek samples required until the head is positioned when the head seeks to a first radial position on the disk medium, and determines whether the first radial position is good or bad according to the determined number of seek samples, A disk drive equipped with a disk drive.

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