Disc device and parameter setting method for disc device

Abstract

Provided are a disk device and a parameter setting method for the disk device. The disk device includes a control object, a controller that controls the operation of the control object, a loop shaping filter that is connected in parallel to the controller, determines a parameter for suppressing a rotational asynchronous disturbance using a transfer function from an output thereof to an input of the rotational asynchronous disturbance acting on the control object, and a notch filter that suppresses resonance of a head. In a case where the control object is changed due to manufacturing fluctuations and the like, the loop shaping filter is redesigned while reflecting a change in the transfer function, while the parameter of the notch filter is changed in accordance with the change. Thus, even in a case where the characteristics of an actuator as the control object differ from those at the time of design, the NRRO disturbance can be suppressed as intended, and the positioning accuracy of the head can be improved.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2022-008025 (filed on January 21, 2022). This application incorporates the entire contents of that basic application by reference. Technical Field

[0002] The implementation methods relate to disk devices and methods for setting parameters of disk devices. Background Technology

[0003] In disk drives mounted in servers and similar applications, the positioning accuracy of the read / write head relative to the disk is reduced due to rotational asynchronous runout (NRRO) interference, such as vibrations caused by server rack fans. To improve this positioning accuracy, one known technique for suppressing NRRO interference is to add an NRRO interference filter (loop shaping filter) to the typical feedback system. This filter is designed to eliminate interference by considering the gain and phase changes of the signal added to the filter output until it reaches the point where the interference enters, based on the estimated value of the interference derived from the position error signal. Furthermore, the read / write head includes an actuator that moves it to a predetermined position on the disk, and a notch filter is used to suppress resonance (mechanical characteristics) of the actuator.

[0004] However, in disk drives, the characteristics of the actuators, which are the controlled components, can differ from their pre-designed characteristics due to manufacturing variations (production errors). Therefore, the parameters of the notch filter used to suppress actuator vibration also need to be changed from the original design parameters. However, changing the parameters of the notch filter can affect the interference suppression performance of the loop shaping filter used to suppress rotating asynchronous interference (NRRO interference). Summary of the Invention

[0005] The embodiments provide a disk drive and a method for setting parameters of the disk drive that can suppress NRRO interference as intended and improve the positioning accuracy of the read / write head even when the characteristics of the actuator being controlled differ from those in the design.

[0006] One embodiment of the disk device includes: a control object; a controller that controls the operation of the control object; a loop shaping filter connected in parallel with the controller, which uses a transfer function from its output to the input of a rotational asynchronous disturbance acting on the position of the control object to determine the filter coefficients for suppressing the rotational asynchronous disturbance; and a notch filter that suppresses resonance of the control object, and redesigns the loop shaping filter in response to changes in the transfer function while changing the parameters of the notch filter according to the characteristics of the control object that change due to factors such as manufacturing fluctuations. Attached Figure Description

[0007] Figure 1 This is a block diagram illustrating an example of the configuration of a disk device according to an implementation method.

[0008] Figure 2 (a) and (b) are block diagrams showing a comparison between the configuration of the control system for suppressing interference according to this embodiment and that of the conventional one.

[0009] Figure 3 This is a flowchart illustrating an example of the main process of processing the setting parameters involved in this embodiment.

[0010] Figure 4 This is a graph showing the results obtained by comparing the sensitivity function difference with and without loop shaping when only the notch filter is changed in Embodiment 2 of this implementation.

[0011] Label Explanation

[0012] 1. Disk drive; 15. Magnetic head; 16. Voice coil motor; 17. Head amplifier IC; 24. Positioning controller; 25. Memory; 26. Coefficient storage unit; 30. Controller; 40. Loop shaping filter; 50. Controlled object; 60. Notch filter. Detailed Implementation

[0013] The embodiments will now be described with reference to the accompanying drawings. Furthermore, the disclosure is merely an example and is not intended to limit the invention by the content described in the following embodiments. Modifications readily conceived by those skilled in the art are naturally included within the scope of the disclosure. To make the description clearer, the dimensions, shapes, etc., of various parts are schematically shown in the drawings, with variations relative to the actual embodiments. In multiple drawings, corresponding elements may be labeled with the same reference numerals, and detailed descriptions may be omitted.

[0014] Figure 1 This is a block diagram illustrating an example of the configuration of disk device 1.

[0015] The disk device 1 includes a head disk assembly (HDA) 10, a head amplifier integrated circuit (hereinafter, head amplifier IC) 17, and a system on a chip (SOC) 20.

[0016] The HDA10 includes a disk 11, a spindle motor (SPM) 12, an arm 13, and a voice coil motor (VCM) 16. The disk 11 is rotated by the SPM 12. A load beam 14 is mounted at the front end of the arm 13, and a read / write head 15 is mounted at the front end of the load beam 14. The arm 13, driven by the VCM 16, controls the read / write head 15 to move to a designated position on the disk 11.

[0017] The read / write head 15 has a structure in which a read head element and a write head element are separately mounted on a slider. The read head element reads the data recorded on the disk 11. The write head element writes data to the disk 11.

[0018] The head amplifier IC17 includes a read amplifier and a write driver. The read amplifier amplifies the read signal read by the read head element and transmits it to the read / write (R / W) channel 22. On the other hand, the write driver transmits the write current corresponding to the write (write) data output from the R / W channel 22 to the write head element.

[0019] The SOC 20 includes a microprocessor (CPU) 21, a read / write channel 22, a disk controller 23, and a positioning controller 24. The CPU 21 is the main controller of the drive unit, performing servo control for positioning the read / write head 15 via the positioning controller 24 and data read / write control via the head amplifier IC 17. The read / write channel 22 includes a read channel for performing signal processing for reading data and a write channel for performing signal processing for writing data. The disk controller 23 performs interface control for data forwarding between the host system (not shown) and the read / write channel 22. Furthermore, the positioning controller 24 can be implemented either in hardware or in software (firmware).

[0020] The memory 25 includes volatile memory and non-volatile memory. For example, the memory 25 includes a buffer memory formed by DRAM and a flash memory. The non-volatile memory of the memory 25 has a storage section (not shown) for storing programs and other data required for processing by the CPU 21, and a coefficient storage section 26 for storing parameters during parameter setting processing described later. The parameters stored in the coefficient storage section 26 will be explained later. Furthermore, the coefficient storage section 26 can be stored in any storage area within the disk drive 1 even if it is not stored in the memory 25.

[0021] Here, refer to Figure 2 The technique of loop shaping filter for suppressing NRRO interference is explained.

[0022] Figure 2 These are block diagrams comparing the configurations of control systems for suppressing interference; (a) shows the existing configuration, and (b) shows the configuration of the implemented method. Figure 2In (a) and (b), 30 represents the controller (C[z]), and 40 represents the loop shaping filter (A[z]). ), 50 represents the controlled object (P[z], ), 60 represents the notch filter (N[z], At this point, the target signal is represented by r[k], the position signal is represented by y[k], and the output of the loop shaping filter 40 is represented by u. d [k] represents the interference, which is represented by d[k].

[0023] The aforementioned loop shaping filter 40 is configured in parallel with the controller 30, and its synthesized output is input to the controlled object 50 via a notch filter 60, thereby causing the controlled object 50 to operate. Thus, by reflecting the output of the loop shaping filter 40 and adding the filtering effect of the notch filter 60, the controlled object 50 is made to operate, thereby controlling the system to eliminate the effects of interference.

[0024] Specifically, in the disk drive 1 of this embodiment, the controller 30, the loop shaping filter 40, and the notch filter 60 are included in the positioning controller 24, and the controlled object 50 is equivalent to the VCM 16. Furthermore, if the disk drive is a type of micro-actuator mounted on the read / write head that causes minute movements of the write and read elements, the micro-actuator may also be included in the controlled object along with the VCM 16.

[0025] In the above configuration, the loop shaping filter (A[z]) 40, which is installed in parallel with the controller (C[z]) 30, uses the following formula (1).

[0026]

[0027] Here, T is the sampling period, and η, μ, and ω0 are design parameters.

[0028] Additionally, regarding the parameters α and β in the coefficients of the loop shaping filter (A[z])40 They are represented by the following equation (2).

[0029]

[0030] Here, parameter α and parameter It is used to obtain the output u from the loop shaping filter (A[z])40 d The transfer function Mu from [k] up to the input of the disturbance d[k]. d d[z] represents the gain (α) and phase of the suppressed object's angular frequency ω0. To obtain the matching parameters. That is, parameter α and parameter The design means that the signal u output from the loop shaping filter (A[z])40 should be considered. d[k] is the gain (α) and phase up to the position where the input interference d[k] is reached. A loop shaping filter was designed to suppress the estimated value of the interference d[k] derived from the position error signal in the loop shaping filter (A[z])40, thereby eliminating the interference d[z].

[0031] For example, in a control system designed for a nominally controlled object (P[z]) 50, such as a notch filter (N[z]) 60 and a controller (C[z]) 30, if the parameters of a portion of the notch filter 60 are subsequently changed from N[z] to N[z] according to the actual parameters of the controlled object (P[z]) 50, then the output u of the loop shaping filter (A[z]) 40 will be affected. d The transfer function Mu from [k] up to the input of the disturbance d[k]. d d[z] will change, and therefore the desired properties will not be obtained.

[0032] Therefore, in the implementation method, such as Figure 2 As shown in (b), the parameter of the controlled object 50 is changed from P[z] at design time to In this case, the parameters of the notch filter 60 are changed from N[z] to [the specified value]. At the same time, the parameters of the loop shaping filter 40 are changed from A[z] to

[0033]

[0034] Figure 3 This is a flowchart illustrating an example of the main process of setting filter coefficients (parameters) in this embodiment.

[0035] First, during the initial design phase, the parameters P[z], N[z], and C[z] of the controller 30, the controlled object 50, and the notch filter 60 are designed, and the parameters A[z] of the loop shaping filter 40 are designed (step S1). The transfer function Mu based on the loop shaping filter (A[z]) 40 is then saved. d d[z] represents the gain α and phase expressed by Equation 2 at the angular frequency ω0 of the suppressed object. (Step S2)

[0036] Next, save the transfer function P[e] of the control object 50 at the suppressed object angular frequency ω0. jω0T ] and P[e jω0T ]N[e jω0T ]C[e jω0T ] / (1+P[e jω0T ]N[e jω0T ]C[e jω0T (Step S3), determine And save (Step S4), Design and corresponding (Step S5). Here, the ratio of the notch filter 60 before and after the parameter change is approximately calculated. Update α, A[z](step S6), and end a series of processes.

[0037] As described above, in this implementation method, the transfer function Mu... d When d[z] changes due to the modification of the notch filter 60 from N[z] to N[z] according to individual mechanical characteristics, the original parameters α and β are adjusted accordingly. The amount of change in the notch filter 60, etc., is reflected to obtain the desired characteristics.

[0038] Specifically, if the parameters of the notch filter 60 are changed to Mu d d[z]、α、 Set as follows They are represented by the following equation (3).

[0039]

[0040] The parameter N[z] in the design of the notch filter 60 is represented by the following equation (4).

[0041]

[0042] Here, d pi ζ i ω npi These are the depth, attenuation, and suppressed angular frequency of the parameter N[z] used in the design of the notch filter 60. According to the above formula, the ratio before and after the change in the transfer function... It becomes the following formula (5).

[0043]

[0044] Here, P[e jω0T ] / P[e jω0T This can be obtained through actual measurement when the parameters of the notch filter 60 are changed. Additionally, P[e jω0T ]N[e jω0T ]C[e jω0T ] / (1+P[e jω0T ]N[e jω0T ]C[e jω0T The results can be obtained at design time. Therefore, if defined as Q and R respectively, then... As shown in the following formula (6), it becomes The function.

[0045]

[0046] As described above, according to this embodiment, when the parameters of the notch filter are changed in accordance with the controlled object, the loop shaping filter is redesigned (adjusted) to reflect the change in the transfer function. Therefore, even if the controlled object 50 is different from the design, the positioning accuracy of the magnetic head can be improved while suppressing rotational asynchronous interference.

[0047] The following describes an embodiment of the calculation method for the parameter setting (change) in the above configuration.

[0048] (Example 1)

[0049] In equation (6), Alternatively, it can be based on the pre-calculated N[e] jω0T ] and N[e after parameter changes jω0T ]calculate.

[0050] (Example 2)

[0051] Alternatively, an approximation such as equation (7) can be used.

[0052]

[0053] In equation (7), f1(d pi , ζ i Ω i ), g1(d pi , ζ i Ω i h1(d) pi , ζ i Ω i They can be calculated in advance during the design phase using methods such as Taylor expansion, and can therefore be easily obtained by the product of the differences with the parameters.

[0054] Here, Ω i =ω ni / ω0, where n is the number of stages in the notch filter.

[0055] Figure 4 This represents the result obtained by comparing the sensitivity function difference with and without loop shaping when only the notch filter 60 is changed, using this embodiment. Figure 4In the text, "initial difference" refers to the state before the notch filter change; "ideal Notch change" refers to the state after the notch filter change when the loop shaping filter is recalculated using the usual method (ideal after notch filter change); "after Notch change" refers to the state after the notch filter change when the loop shaping filter is not updated; and "proposed method" refers to the state after the notch filter change when the loop shaping filter is updated using the proposed method of Example 2. Figure 4 It can be seen that by utilizing the approximation of the proposed method, loop shaping that is close to the ideal after notch modification is also obtained.

[0056] (Example 3)

[0057] Regarding the region with low angular frequency ω0

[0058]

[0059] Established, and therefore became

[0060]

[0061] At this point, the following equation (8) can be used to...

[0062]

[0063] Approximately, it can be achieved using the following equation (9) to...

[0064]

[0065] approximate.

[0066]

[0067]

[0068] In equations (8) and (9),

[0069]

[0070] It can be calculated in advance using Taylor expansion and other methods during the design phase, and therefore can be easily obtained by the product of the differences with the parameters.

[0071] (Example 4)

[0072] The relationship between the setpoints and resetting values ​​of the control object 50 and the notch filter 60 can also be set as follows:

[0073]

[0074]

[0075] Furthermore, while several embodiments of the invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in a wide variety of other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and / or variations thereof are included within the scope and / or spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

Claims

1. A disk drive, comprising: Controlled objects; A controller that controls the actions of the controlled object; A loop shaping filter, connected in parallel with the controller, uses a transfer function from the output of the loop shaping filter to the input of a rotating asynchronous disturbance acting on the controlled object to determine the parameters for suppressing the rotating asynchronous disturbance; and Notch filters suppress resonance of the magnetic head. While changing the parameters of the notch filter according to the changes in the controlled object, the loop shaping filter is redesigned to reflect the changes in the transfer function.

2. The disk drive according to claim 1, Replace the changes in the transfer function with an approximation.

3. The disk drive according to claim 1, Information about the initial design of the controlled object, the notch filter, and the controller is stored in advance and used as a comparison object when calculating the change of the transfer function.

4. A method for setting parameters of a disk device, which is a method used in a disk device, the disk device comprising: Controlled objects; A controller that controls the actions of the controlled object; A loop shaping filter, connected in parallel with the controller, uses a transfer function from the output of the loop shaping filter to the input of a rotating asynchronous disturbance acting on the controlled object to determine the parameters for suppressing the rotating asynchronous disturbance; and Notch filters suppress resonance of the magnetic head. The parameter setting method for the disk device changes the parameters of the notch filter according to the changes in the controlled object, and redesigns the parameters of the loop shaping filter to reflect the changes in the transfer function.

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