JP2001209402A - Controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method that estimates a control volume using values obtained continuously at a high speed, interpolates the value between discrete values, assures to track a high frequency target value, and suppresses influence caused by high frequency external noises over equipment. SOLUTION: The method provides a controller 2a that makes the target value track a control target object 1 and a detector 4a that detects the discrete values of the control target object 1. The controller 2a detects differentiated and the second derivative of control values for the control target object 1, interpolates the discrete value by estimating values detected by the detector 4a, and controls the control target object 1 with a help of the interpolated value and the desired value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In controlling a control target, there is a so-called feedback control method in which a control result is measured and compared with a target value, and an appropriate correction operation is given according to the result. The present invention relates to a control device capable of realizing a high-speed target value tracking performance and a high-frequency disturbance suppression characteristic even in a case where a control amount is not measured at high speed in the control of such a feedback control method or the like. It is.

[0002]

2. Description of the Related Art FIG. 8 is an explanatory view of a conventional example.
(A) is a description of a feedback control system (continuous system). In FIG. 8A, a control target 1, a controller 2, and a subtractor 5 are provided.

In general, when a certain control amount follows a certain target value, as shown in FIG. 8A, the control amount of the control target 1 is observed by a certain method, and the difference from the target value is subtracted from the subtractor 5 by the controller 2. , The follow-up of the target value can be improved, and the influence of disturbance applied to the system can be reduced.

The control system shown in FIG. 8A is called a continuous system (analog system) composed of continuous signals. The actual control is often performed using a computer,
In some cases, control variables can only be monitored intermittently.
As shown in FIG. 8B, a so-called discrete (digital) system is often included, including a sampler 3 for sampling a continuous signal (control amount) at a certain frequency.

FIG. 8B is an explanatory diagram of a feedback control system (discrete system). In FIG. 8B, the control target 1,
A controller 2, a sampler 3, and a subtractor 5 are provided.
The control system shown in FIG. 8B is called a discrete system.
The control amount actually observed was obtained only intermittently by the sampler 3.

FIG. 8C is a diagram for explaining the actual control amount and the observed control amount. In FIG. 8C, the dotted line is the actual control amount, and the solid line is the observed control amount. In the case of the control system in FIG. 8B, the control amount actually observed by the sampler 3 is a step-like shape as shown by the solid line in FIG. .

[0007]

The above-mentioned prior art has the following problems.

In the case of the conventional control system shown in FIG. 8B, the actually observed control amount has a step-like shape as shown by the solid line in FIG. 8C. As a result, the ability to follow a high frequency target value is deteriorated, and the influence of high frequency (high frequency) disturbance cannot be suppressed.

The present invention solves such a conventional problem, estimates a control amount using values obtained continuously or at a high speed other than the control amount, interpolates between discrete values, and obtains a high frequency. The purpose of the present invention is to secure the ability to follow the target value of the above and to suppress the influence of high-frequency disturbance.

[0010]

FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. 1, 1 is a control object, 2a is a control means,
a is a detecting means.

The present invention is configured as follows to solve the above-mentioned conventional problems.

(1): Control means 2a for controlling the control target 1 to follow the target value, and detection means 4a for discretely detecting the control amount of the control target 1, the control means 2a A value obtained by differentiating the control amount of the control target 1 or a value obtained by differentiating the control amount twice is detected, and a discrete interval value detected by the detection means 2a is estimated and interpolated, and the interpolated value and the target value are used. The control target 1 is controlled.

(2) In the control device of (1),
It is assumed that the control target 1 is a head of a disk device, the control amount is a position, and the detected value is an acceleration of the head.

(Operation) The operation based on the above configuration will be described.

A control means 2a for controlling the control target 1 to follow the target value detects a value obtained by differentiating the control amount of the control target 1 or a value obtained by differentiating the control amount twice, and detects the discrete value detected by the detection means 2a. The control target 1 is controlled based on the interpolated value and the target value by estimating a value between the values. For this reason, the control amount is estimated by using a value obtained continuously or at high speed other than the control amount, so that the followability to the high frequency target value can be ensured, and the influence of the high frequency disturbance can be suppressed.

The control target 1 is the head of the disk drive, the control amount is the position, and the value detected at high speed is the acceleration of the head. For this reason, it is possible to estimate a position between pieces of position information that can be obtained only discretely from the acceleration, secure the followability to a high-frequency target position, and suppress the influence of high-frequency disturbance.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1): Explanation by feedback control FIG. 2 is an explanatory diagram of feedback control, and FIG.
Is a description of a feedback control system using a multi-rate estimator.

In FIG. 2A, a control target 1, a controller 2, a sampler 3, an estimator 4, and a subtractor 5 are provided. The control target 1 is a control target such as a head of the magnetic disk device (when the control amount is a position), a heater of a heater (when the control amount is a temperature), and the like. The controller 2 controls the control target 1. The sampler 3 discretely observes (detects) the control amount of the control target 1. The estimator 4 estimates a control amount from a sample value of the control amount and an amount (speed, acceleration, etc.) other than the control amount, and is a multi-rate estimator having a plurality of sampling rates. Subtractor 5
Is for comparing the output of the estimator 4 with the target value.

Conventional problems, such as deterioration of the ability to follow a high frequency target value and the inability to suppress the effects of high frequency (high frequency) disturbances, are that the control amount cannot be obtained continuously, or This is due to the fact that it cannot be obtained with early sampling. Therefore, in the present invention, the control amount is estimated by the estimator 4 using values obtained continuously or at high speed other than the control amount, and interpolation is performed between discrete values. As a result, the control amount after the estimation and the interpolation becomes continuous information, and the followability to the high frequency target value is secured,
The effect of high-frequency disturbance can be suppressed.

FIG. 2B illustrates the observed control amount and the estimated control amount. In FIG. 2B, the dotted line indicates the observed control amount, and the solid line indicates the estimated control amount. With respect to the observed control amount indicated by the dotted line, the solid line indicates the estimated control amount, and interpolation is performed between discrete values.

(Explanation of the case where the control amount is the position) Here, when the control amount is the position, the information (an amount other than the control amount) used for the interpolation is the speed and the acceleration. (1) When speed information can be obtained, a method of using speed for position interpolation is represented by the following equation, and there is no particular problem. (2) On the other hand, when the speed is not obtained and only the acceleration information is obtained, the position is estimated by the expression after estimating the speed as in the expression.

X (T + t) = X (T) + V (T) × t... V (T + t) = V (T) + α (T) × t. Where X (T) is the position at the time T, V (T) is the velocity at the time T, α (T) is the acceleration at the time T, and t is the sampling time (in units of time). is there.

In the case of the above (2), since the initial value V (T) of the speed is unknown, an error such as an offset (DC component) is inevitably superimposed (generated) on the estimated speed value, and an error is also found on the estimated position. Occurs. Therefore, in order to remove an offset-like error of the speed estimation value obtained by the expression, the position is estimated by the expression after passing through a high-pass filter. As a result, the position information after the estimation and the interpolation becomes continuous information, the followability to the high frequency target value is secured, and the influence of the high frequency disturbance can be suppressed.

(2) Description when applied to following control of a magnetic disk drive A description will be given of a case where the present invention is applied to following control of a data surface servo method (magnetic disk drive). In the data surface servo method (sector servo), position information (servo sector) is embedded between sectors provided on a magnetic disk (medium). Therefore, position information on the number of sectors per one rotation of the medium is obtained.

In the positioning control of the head of the magnetic disk drive, seek control and subsequent following control (fine adjustment) are performed. The positioning control (following control) of the magnetic disk device of the data surface servo system is essentially a digital (discrete) control system.

Excessive writing of servo information on the data surface lowers the recording density, and in most cases, the sampling frequency cannot be set sufficiently high. On the other hand, if the rotation speed of the disk is increased, the sampling frequency can be increased, but the rotation speed is limited due to problems such as bearing resistance.

In the present embodiment, position information in a frequency region higher than the sampling frequency is estimated by the acceleration sensor, and a system can be constructed as if the sampling frequency were high. Further, since the position information between samplings can be estimated, the time waveform of the control output to the motor becomes smooth, and highly accurate positioning can be realized.

FIG. 3 is an explanatory diagram of the positioning control of the magnetic disk drive. In FIG. 3, the subtractor 5, the magnetic disk device 11, the controller (controller) 12, the sampler 13, and the sampler 1 are used for positioning control of the magnetic disk device.
4, a band pass filter 15, a speed estimator 16, a high pass filter 17, and a position estimator 18 are provided.

The subtracter 5 calculates a position error from the estimated position and the target position. The magnetic disk device 11
It reads / writes information from / to a magnetic disk. The controller 12 outputs a current to the motor using the estimated position error information. Sampler 13
The position information is obtained from the magnetic disk and the sampling time T
s. The sampler 14 detects the acceleration and holds the sampling time Tsm. The bandpass filter 15 removes unnecessary noise. The speed estimator 16 estimates the speed based on the acceleration (see formula). The high-pass filter 17 is
The offset (DC component) is removed. The position estimator 18 is for estimating the position from the speed (see formula).

(Explanation of Operation) The information obtained from the magnetic disk drive 11 includes the position information (X) written on the data surface of the magnetic disk and the information (α) from the acceleration sensor mounted on the end of the arm of the magnetic disk head. ). The sampling time of the former (X) by the sampler 13 is Ts,
The sampling time of the latter (α) by the sampler 14 is T
sm. And Tsm was set to 1/5 of Ts.
That is, a loop (ΔF) of the acceleration signal constitutes a multi-rate (frequency) control system in which the sampling rate is five times the sampling rate of the position signal loop (ΔE). Hereinafter, the control operation will be described with reference to FIG.

(1): The sampler 14 obtains the acceleration α from the acceleration sensor mounted on the tip of the arm and outputs the sampled acceleration α (n).

[Α⇒α (n)] (2): The acceleration α ′ (n) is obtained by removing unnecessary noise from the acceleration α (n) through the band-pass filter 15.

[Α (n) ⇒α ′ (n)] (3): The speed estimator 16 calculates an estimated speed v ′ (n). v ′ (n) = v ′ (n−1) + a (n) × t (corresponding to equation) [α ′ (n), v ′ (n−1) → v ′ (n)] (4): Estimated speed v '(n) is passed through a high-pass filter 17 to remove the offset to obtain a true estimated speed V' (n).

[V '(n) ⇒V' (n)] (5): The position estimator 18 calculates the estimated position X from the true estimated speed V '(n) and the position information X (k) from the sampler 13. '
(n) is calculated (corresponding to the equation).

[V '(n), X (k) ⇒X' (n)] (6): The estimated position X '(n) and the target position T are calculated by the subtractor 5.
The position error E '(n) is calculated from (k).

[X ′ (n), T (k) → E ′ (n)] (7): Using the estimated position error E ′ (n) information, the controller 12 sends the current i (n) to the motor. Perform output.

[E '(n) .fwdarw.i (n)] Next, n is incremented (n = n + 1), and the process returns to (1).

However, the estimated value is indicated by "'" at the right shoulder of the variable. The meaning of the above variables is as follows.

Acceleration: α Acceleration after passing through the band-pass filter: α 'Estimated speed: v' True estimated speed: V 'Estimated position: X' Target position: T Estimated position error: E 'Control output: i Sample number: k (k = int (Tsm / Ts) × n) Note that “int” means an integer. In this example, when n increases by 5, k is incremented.

Sample number of acceleration signal: n Arm tip position (head position): Y (3): The simulation result of the above operation is shown in FIG.
This will be described with reference to FIG.

FIG. 4 is an explanatory diagram of the acceleration signal. In FIG. 4, the horizontal axis represents time (sampling step n), and the vertical axis represents a graph of an example of the acceleration signal α output from the sampler 14 when the amplitude of the acceleration signal α is ± 1.

FIG. 5 is an explanatory diagram of the estimated speed and the true estimated speed. FIG. 5 shows a graph of the estimated speed v ′ output from the speed estimator 16 and the true estimated speed V ′ obtained by removing the DC component through the high-pass filter 17.

FIG. 6 is an explanatory diagram of the position signal and the estimated position signal. FIG. 6 shows a graph of a position signal X output from the sampler 13 and an estimated position signal X ′ output from the position estimator 18.

FIG. 7 is an explanatory diagram of the control output. FIG. 7 shows a graph of the control output i from the controller 12.

In all of these graphs (FIGS. 4 to 7), the horizontal axis represents time (sampling interval n). The estimated speed obtained from the acceleration signal using the position signal written on the magnetic disk surface as an initial value necessarily includes a DC component and is different from the actual speed. The estimated speed approaches the actual speed over time. As a result, the estimated position is closer to the actual position, and is smoother than the position signal written on the magnetic disk surface. As a result, the control output becomes smooth, and high-precision positioning control is possible.

In the above embodiment, the positioning control of the magnetic disk drive has been described. However, the present invention can be applied to other controls such as temperature control. For example, when the temperature can be obtained only discretely (intermittently) by temperature control by electric heating, the current becomes a value obtained by differentiating the temperature (control amount), so that the current is detected continuously (or at high speed). By integrating, it is possible to interpolate between discrete (low-speed) control amounts. In the above embodiment, the feedback control has been described, but the present invention is also applicable to the feedforward control.

[0047]

As described above, the present invention has the following effects.

(1): A control means for controlling a control object to follow a target value. The control means detects a value obtained by differentiating the control amount of the control object or a value obtained by differentiating the control amount twice, and detects the discrete value detected by the detection means. In order to control the controlled object by the interpolated value and the target value, the control amount is estimated using a value obtained continuously or at high speed other than the control amount. Therefore, the ability to follow a high frequency target value can be ensured, and the effect of high frequency disturbance can be suppressed.

(2) Since the control target is the head of the disk drive, the control amount is the position, and the value detected at high speed is the acceleration of the head, the position between the position information that can be obtained only discretely is the acceleration. , The ability to follow a high-frequency target position can be ensured, and the effects of high-frequency disturbance can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of feedback control in the embodiment.

FIG. 3 is an explanatory diagram of positioning control of the magnetic disk device in the embodiment.

FIG. 4 is an explanatory diagram of an acceleration signal in the embodiment.

FIG. 5 is an explanatory diagram of an estimated speed and a true estimated speed in the embodiment.

FIG. 6 is an explanatory diagram of a position signal and an estimated position signal according to the embodiment.

FIG. 7 is an explanatory diagram of a control output in the embodiment.

FIG. 8 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control object 2a Control means 4a Detection means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 21/08 G11B 21/08 B F-term (Reference) 5D066 DA03 DA11 DA16 5D088 BB01 PP01 SS01 UU01 5H004 GA05 GA07 GA40 GB20 HA07 HB07 HB08 HB09 JA03 JB11 JB15 JB29 JB30 KA34 MA13 MA14 MA44 5H303 AA22 CC02 DD01 EE03 FF04 GG27 JJ01 JJ04 MM05

Claims (2)

[Claims] A control unit for controlling the control target to follow a target value; and a detection unit for discretely detecting a control amount of the control target, wherein the control unit detects the control amount of the control target. Detecting a differentiated value or a value differentiated twice, estimating and interpolating a value between discrete values detected by the detection means, and controlling the control object by the interpolated value and the target value. Control device. 2. The control device according to claim 1, wherein the control object is a head of a disk drive, the control amount is a position, and the detected value is an acceleration of the head.