JPH08195043A - Positioning control system and its gain adjusting method for data recording and reproducing device - Google Patents

Abstract

PURPOSE: To maintain the stability of a system by monitoring the gain of the system while making a detection means detect the positional error between the present position and the target position of a head and output the positional signal corresponding to a positional error. CONSTITUTION: A CPU 1 obtains a positional error signal Y corresponding to the positional error between a target position PT and a present position PE by a positional error detecting element 1a. In this case, the CPU 1 converts a calculated control quantity corresponding to the positional error into an analog signal by a D/A conversion circuit 10 to supply it to a VCM driver 9. A driving current corresponding to the control quantity is supplied from the VCM drriver 9 to a VCM 8 to control the VCM 8 so that the positional error of the head 6 is eliminated. Thus, a feed back system operates so that the postional error between the target position and the present position becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning control system for a data recording / reproducing apparatus, which is used in, for example, a magnetic disk apparatus and controls the positioning of a head at a target position.

[0002]

2. Description of the Related Art Conventionally, a magnetic disk device such as a hard disk device (HDD) is provided with a positioning control system for positioning a head at a target position (target track) on a disk.

The positioning control system comprises a feedback control system for driving and controlling a voice coil motor (VCM) that drives the head. In the feedback control system, according to a predetermined control target model,
Gain is adjusted and set.

In the HDD positioning control system, it is important to stabilize the gain set to maintain the positioning accuracy. However, the gain set at the time of designing the system fluctuates due to variations in the accuracy of component parts constituting the system, secular change, etc., and an error often occurs with respect to the reference value at the time of design. When the gain error amount becomes large, the stability of the system is lost, which causes deterioration of the positioning accuracy.

[0005]

In the HDD positioning control system, it is important to stabilize the gain set at the time of designing the system. However, due to variations in the accuracy of component parts and aging, there is an error with respect to the reference value. May occur. When the error amount of the gain becomes large, the positioning accuracy is deteriorated, so that it is necessary to adjust the gain. But,
It is difficult to adjust the gain in the conventional system.

An object of the present invention is to maintain the stability of a system in a positioning control system such as an HDD by monitoring the gain of the system and adjusting it so as to match the reference value at the time of design.

[0007]

According to the present invention, in a positioning control system of a data recording / reproducing apparatus for controlling the positioning of a head at a target position on a disk, a position error corresponding to a position error between the current position of the head and the target position. The system is provided with a gain adjusting unit that has a detecting unit that outputs a signal, and that adjusts the gain of the system so that the amplitude values of the reference measurement signal and the position error signal are compared and the comparison results match.

[0008]

According to the present invention, the detecting means detects the position error between the current position of the head and the target position and outputs the position error signal corresponding to the position error. A reference measurement signal is added to this position error signal and input to the comparison means. The reference measurement signal has a constant amplitude and a constant frequency. The comparing means compares the respective amplitude values of the additional signal and the position error signal. The gain adjusting means adjusts the gain of the system so that the comparison results of the comparing means match.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a main part of a positioning control system according to the present embodiment, FIG. 2 is a block diagram showing a main part of an HDD according to the present embodiment, and FIG. 3 is a signal waveform for explaining the operation of the present embodiment. 4 and 5 are flowcharts for explaining the operation of this embodiment. (Structure of HDD) In this embodiment, a positioning control system applied to a head positioning control system of the HDD is assumed.
As shown in FIG. 1, the HDD is roughly divided into a disk mechanism system, a head drive system, a signal processing system, and a head positioning control system.

The disk mechanism system has a spindle motor 5 for rotating a disk 4 as a recording medium at a high speed. The head drive system includes a head 6 for reading / writing data, a head actuator 7, a voice coil motor (V
CM) 8 and VCM driver 9.

The VCM 8 is supplied with a drive current from the VCM driver 9 to drive the head actuator 7 to the disk 4
Move in the radial direction. The head 6 is held at the tip of the head actuator 7, and is moved to the target position (target track) of the disk 4 by the driving force of the VCM 8.

The signal processing system has a head amplifier 11, a signal processing circuit 12 and an A / D conversion circuit 13. The head amplifier 11 amplifies the read signal read from the head 6. The signal processing circuit 12 is composed of various processing circuits necessary for reproducing the read data from the read signal. In the present embodiment, the signal processing circuit 12 includes a sample hold circuit that samples and holds the peak of burst data (position signal) required for positioning control of the head 6. The A / D conversion circuit 13 converts the burst data sampled and held by the sample and hold circuit of the signal processing circuit 12 into digital data and outputs the digital data to the microprocessor (CPU) 1.

In the present embodiment, in the signal processing circuit 12, description of circuits related to normal reproduction and recording of user data is omitted. Further, in the positioning control, the description of the reproducing process of the servo data other than the burst data will be omitted.

The head positioning control system includes a CPU 1 for executing positioning control processing, a memory 14, and a D / A for converting the positioning control amount into an analog signal (voltage signal).
It has a conversion circuit 10. The CPU 1 executes a positioning control process corresponding to a positioning control system (see FIG. 1) described later. The memory 14 is controlled by the CPU 1 and stores various data necessary for the positioning control processing of the CPU 1.

The disk controller (HDC) 2 is
The interface between the DD and the host system 3 and recording / reproducing control of data are executed. In this embodiment, the HDC
Since item 2 is not directly related, the description is omitted. (Positioning Control System) As shown in FIG. 1, the positioning control system of the present embodiment obtains a control amount according to an error between the target position PT of the head 6 and the current position PE, and determines the VCM 8 which is the control target 20. It is a feedback control system for driving and positioning the head 6 at the target position PT. In this feedback control system, the controlled object 20
The other elements are actually contents corresponding to the processing of the CPU 1.

The positioning control system includes a position error detection element 1a, a signal addition element 1b for adding the reference measurement signal S to the position error signal Y, a gain adjustment element 1c for adjusting the gain of the system, and stabilization of the system. It has a stabilizing compensation element 1d for realization.

As shown in FIG. 3C, the reference measurement signal S has a constant amplitude a and a constant frequency (a cross frequency described later).
It is a sine wave signal having f and is supplied from outside the system during gain adjustment.

Next, the operation of this embodiment will be described. (Head Positioning Control Operation of HDD) In the HDD, a physical address is determined by the HDC 2 in accordance with an access request from the host system 3. This physical address determines the target position (target track) to which the head 6 should move.

The CPU 1 executes seek control processing based on the cylinder code (track address) indicating the current position of the head 6 in the servo data reproduced by the signal processing system. The cylinder code is recorded in advance in the servo area (servo data recording area) on the disk 4 together with burst data described later.

By the seek control processing, the CPU 1 calculates the moving distance from the error between the current position and the target position, and determines the target speed according to this moving distance. The VCM 8 is drive-controlled so that the moving speed of the head 6 matches the target speed.

When the head 6 approaches the target position by the seek control processing, the CPU 1 shifts from the seek control processing to the position control related to this embodiment (in this embodiment, positioning control in a narrow sense), and moves the head 6 to the target track. Positioning control at the center of.

The positioning control operation will be described below with reference to FIG. Based on the burst data output from the A / D conversion circuit 13 of the signal processing system, the CPU 1
The position error of the head 6 with respect to the target position (center of the target track) is calculated. That is, as shown in FIG. 1, the position error detection element 1a obtains the position error signal Y corresponding to the position error between the target position PT and the current position PE.

The CPU 1 converts the control amount corresponding to the calculated position error into an analog signal by the D / A conversion circuit 10 and supplies it to the VCM driver 9. A drive current corresponding to the control amount is supplied from the VCM driver 9 to the VCM 8,
The VCM 8 is drive-controlled so that the position error of the head 6 is eliminated.

That is, as shown in FIG. 1, the position error signal Y from the position error detecting element 1a is multiplied by the gain determined by the gain adjusting element 1c, and the stabilizing compensating element 1 is obtained.
It is supplied as a controlled variable to the controlled object 20 via d. As a result, the position error between the target position PT and the current position PE is 0.
Therefore, the feedback system of FIG. 1 operates.

In such a VCM position control system for an HDD, the relationship between the frequency f and the gain dB which is the input / output ratio (frequency characteristic of the position control system) is designed so as to show the characteristics shown in FIG. ing. FIG. 5 means that in the case of control at a low frequency, the design is such that the ratio of the output to the input becomes large, and the ratio of the input / output becomes small as the control at the high frequency increases. are doing. Such a design makes the VCM position control system the most stable system.

Here, the point K in FIG. 5 is called a cross frequency. Input X and output Y of the position control system at this cross frequency
The relational expression for and is as follows. 2log (Y / X) = 0 (dB) That is, the point K is the point where the input X and the output Y coincide. This cross frequency is used by the gain adjusting operation described later. (Gain Adjusting Operation) As described above, the positioning control system shown in FIG. 1 controls the positioning of the head 6 to the target position PT. Here, for example, the controlled object 20 (VCM)
However, if the characteristics of the position control system fluctuate due to changes over time, the frequency characteristics of the position control system will shift up and down, making the system unstable and degrading the positioning accuracy.

Therefore, according to the present invention, by adjusting the gain of the system of the position control system, the frequency characteristic is constantly corrected to the set value as shown in FIG. 5 to prevent the system from becoming unstable. Such a shift in the frequency characteristics is caused not only by aging but also by variations in parts. For this reason, the gain adjustment process is first executed at the time of manufacturing the HDD, and then executed at regular intervals such as when the operation of the commercialized HDD is started.

The gain adjusting operation of this embodiment will be described below with reference to FIGS. 1, 3 and 4. First, the reference measurement signal S is input to the signal addition element 1b shown in FIG. 1 (step S1). As shown in FIG. 3 (C), the reference measurement signal S is a sine wave signal having a constant amplitude a and a constant frequency f, and corresponds to the cross frequency K in FIG.

The signal addition element 1b outputs a position error signal Z obtained by adding the reference measurement signal S to the position error signal Y (step S2). The position error signal Z is a sine wave signal having an amplitude a and a frequency f, as shown in FIG.

As shown in FIG. 3D, the CPU 1 calculates the absolute value of the position error signal Z (step S3). C
PU1 temporarily stores the amplitude value a of the position error signal Z in the memory 14 (step S4).

In the system, the position error signal Z is multiplied by the gain by the gain adjusting element 1c and supplied to the controlled object 20 as a controlled variable via the stabilization compensating element 1d. As a result, a new position error signal Y is obtained from the position error detecting element 1a (step S5).

Position error signal Y passing through the controlled object 20
Is, for example, an amplitude b and a frequency f as shown in FIG.
Suppose that it is a sinusoidal signal with. The CPU 1 calculates the absolute value of the position error signal Y (see FIG. 3A),
The amplitude value b is temporarily stored in the memory 14 (steps S6 and S7). Here, since the amplitude value (a) of the position error signal Z varies, the reliability is improved by using an average value sampled a plurality of times. The amplitude value b is also preferably an average value like the amplitude value a.

The CPU 1 compares the amplitude value a and the amplitude value b stored in the memory 14 and determines whether or not the comparison results match (steps S8 and S9). If the comparison results match, the CPU 1 determines that the system gain has not changed from the reference value (YES in step S9).

On the other hand, if the comparison results do not match, CP
The U1 adjusts the gain value of the gain adjusting element 1c by the gain adjusting signal G (step S10). CPU1
Adjusts the gain until the results of comparison between the amplitude value a and the amplitude value b match (steps S1 to S10).

If the frequency of the sine wave given as the reference measurement signal is set to the cross frequency of the control system, the fact that the comparison results of the amplitude values a and b agree means that the open loop characteristics of the control system are crossed. This means that the gain is 0 (dB) at the frequency f of the reference measurement signal S, which is the frequency, which means that the gain is adjusted to the optimum value.

As described above, according to this embodiment, the reference measurement signal S, which is a sine wave signal having the constant amplitude a and the constant frequency f, is input, and each amplitude value a of the position error signal before and after the input is inputted. , B are compared. If the comparison results match, it is assumed that the frequency characteristic of the system position control system is a predetermined reference value (design value), and the gain is adjusted until the comparison results match. The reference measurement signal S does not necessarily have to be the cross frequency. However, when the cross frequency is input, it is only necessary to determine the coincidence of the amplitude values a and b of the position error signal before and after passing through the control system, which has the effect of simplifying the calculation process.

[0037]

As described above in detail, according to the present invention, H
In a positioning control system such as a DD, even if the frequency characteristic of the system fluctuates from the design reference value due to variations in the accuracy of component parts, secular change, etc., it is possible to adjust to the design reference value by gain adjustment processing. it can. Therefore, it is possible to prevent the situation in which the system becomes unstable and the positioning accuracy is deteriorated due to the fluctuation of the system gain. This makes it possible to constantly monitor the gain of the system and maintain the stability of the system with an appropriate gain.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a positioning control system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main part of an HDD according to this embodiment.

FIG. 3 is a signal waveform diagram for explaining the operation of the present embodiment.

FIG. 4 is a flowchart for explaining the operation of this embodiment.

FIG. 5 is a diagram showing frequency characteristics for explaining the operation of the present embodiment.

[Explanation of symbols]

1 ... CPU, 1a ... Position error detection element, 1b ... Signal addition element, 1c ... Gain adjustment element, 1d ... Stabilization compensation element,
2 ... Disk controller (HDC), 3 ... Host system, 4 ... Disk, 5 ... Spindle motor, 6 ... Head, 7 ... Head actuator, 8 ... Voice coil motor (VCM), 9 ... VCM driver, 10 ... D / A Conversion circuit, 11 ... Head amplifier, 12 ... Signal processing circuit, 13
... A / D conversion circuit, 14 ... Memory.

Claims (5)

[Claims] 1. A positioning control system for a data recording / reproducing apparatus, which controls the positioning of a head for recording and reproducing data to a target position on a recording medium, wherein a positional error between the current position of the head and the target position is detected. Detecting means for detecting and outputting a position error signal corresponding to the position error; input means for inputting a reference measurement signal having a constant amplitude and a constant frequency; and the position error before and after the input of the reference measurement signal A positioning control system for a data recording / reproducing apparatus, comprising: comparing means for comparing respective amplitude values of signals; and gain adjusting means for adjusting a gain of the system according to a comparison result of the comparing means. 2. A positioning control system for a data recording / reproducing apparatus, which controls the positioning of a head for recording and reproducing data to a target position on a recording medium, wherein a position error between the current position of the head and the target position is detected. Detecting means for detecting and outputting a position error signal corresponding to the position error, input means for inputting a reference measurement signal having a constant amplitude and a constant frequency, and adding means for adding the reference measurement signal to the position error signal And a comparing means for comparing the output signal of the adding means with each amplitude value of the position error signal, and a gain adjusting means for optimally adjusting the gain of the system according to the comparison result of the comparing means. Positioning control system for data recording / reproducing device. 3. A positioning control system for a data recording / reproducing apparatus, which controls positioning of a head for recording and reproducing data to a target position on a recording medium, wherein a position error between a current position of the head and the target position is detected. Detecting and outputting a position error signal corresponding to the position error; inputting a reference measurement signal having a constant amplitude and a constant frequency; adding the reference measurement signal to the position error signal; A gain adjusting method comprising: a step of comparing amplitude values of the generated output signal and the position error signal; and a step of adjusting a gain of the system according to a comparison result of the amplitude values. 4. A positioning control system for a data recording / reproducing apparatus, which controls the positioning of a head for recording and reproducing data at a target position on a recording medium, wherein the head is positioned at the center of the track which is the target position. Sometimes, a detection unit that detects a position error with respect to the target position; a control unit that multiplies a position error signal corresponding to the position error by a predetermined gain to obtain a control amount required for positioning control of the head; Input means for inputting a reference measurement signal that is a sine wave signal having a constant amplitude and a constant frequency during adjustment, and an amplitude value of a position error signal according to the position error before the input of the reference measurement signal during the gain adjustment. And a comparison means for comparing the amplitude value of the position error signal according to the position error after the input of the reference measurement signal, and the comparison result of the comparison means. It is determined whether or not the respective amplitude values match based on the judgment value, and in the case of non-coincidence, a judgment means for judging that the gain of the system has fluctuated from the reference value; A gain control means for adjusting the gain of the control means until the comparison results of the comparison means coincide with each other, and a positioning control system for a data recording / reproducing apparatus. 5. The positioning control system for a data recording / reproducing apparatus according to claim 4, wherein the frequency of the reference measurement signal is set to a cross frequency in the frequency characteristic of the positioning control system.