JPS61147302A - Digital servocontrol system - Google Patents

Abstract

PURPOSE:To control a servo system to a required resolution in response to a position deviation by selecting a large gain of an A/D conversion section and a D/A conversion section when a detected analog servo signal is small and selecting a small gain when the signal is large conversely. CONSTITUTION:When a magnetic head moves and enters the fixed operation, a position error signal becomes a value as small as 1V or below. The value is detected by a detection section 3 and the gain of an A/D converter 2 is regulated based on the value. Thus, the position of the magnetic head is adjusted minutely and positioned with high accuracy. A digital value representing the shift amount corresponding to a position error signal S is fed to the 2nd gain controller 7 and the gain of a D/A converter 6 is adjusted corresponding to said value. Thus, the digital resolution is increased apparently without increasing the bit number of the A/C converter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a digital servo control system using analog signals, and in particular to analog/digital and digital servo control systems.
The present invention relates to a digital servo control method that allows the gain in analog conversion to be switched stepwise using a signal from a digital processing section.

[Conventional technology]

In the conventional digital servo control method using analog signals, the gain (resolution: analog-to-digital conversion rate) of the analog-to-digital (A/D) converter and digital-to-analog (D/A) converter is fixed. There is. Therefore, in order to obtain high resolution,
A/D converter with a large number of bits (hereinafter abbreviated as A/DC).

Alternatively, it is necessary to use a D/A converter (hereinafter abbreviated as D/AC).

For example, when analog quantity 0-1 (V) is A/D and D/A converted with digital quantity 4 bits, the result is 62.5 mV/bit, but A/D and D/A are converted at 31.25 mV/bit.
When converting, use a 5-bit digital A/DC,
D/AC is required.

[Problem that the invention seeks to solve]

If an attempt is made to increase the resolution in order to improve accuracy in this way, a converter with a large number of bits is required, resulting in an increase in cost, and there are disadvantages in that the larger the number of bits, the longer the conversion time. Furthermore, there is another problem in that the number of usable bits is limited by the processing bits of the CPU of the digital processing section.

[Means for solving problems]

The purpose of the present invention is to make it possible to select the gains of A/DC and D/AC, so that the digital resolution of analog quantities can be increased in appearance, and the CP of the digital processing section can be reduced.
The object of the present invention is to provide a digital servo control method that is not limited by the number of processing bits of U.

This purpose is achieved by converting an analog servo signal as an error signal corresponding to a controlled amount of a controlled object into an analog signal.
After converting into a digital signal by a digital converter and performing digital processing on the digital signal, converting into an analog signal by a digital-to-analog converter,
When controlling the controlled object based on the analog signal, detecting the magnitude of the analog servo signal and selecting the gain of the analog-to-digital converter and the digital-to-analog converter based on the detection result. This is achieved by making the digital resolution of analog quantities variable.

[Effect]

The magnitude of the input analog servo signal corresponding to the above-mentioned controlled quantity is detected, and when the detection result is small, the gain of the analog-to-digital converter and digital-to-analog converter is selected to be large, and when it is large, the gain is selected to be small. By doing this, the analog/digital converter and digital
High resolution can be obtained over a wide range of analog servo signals without increasing the number of bits processed by the analog converter.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main part of a system configuration of an embodiment of a magnetic disk head positioning method using a digital servo control method according to the present invention.

In the figure, ■ is the central processing unit (CPU), and 2 is the A
/DC, 3 is the detection unit, 4 is the first gain controller (
GAC), 5 is a read-only storage device (ROM)
, 6 indicates the D/AC 17, and the second GAC 18 indicates control data.

Head control includes a moving operation (MOVE) for moving from the current position to a target position, and a fixing operation (FIX) for positioning the head at the target position, but the amount of position fluctuation in the fixing operation is smaller than in the moving operation.

FIG. 2 is a diagram showing the magnitude of the position error signal S with respect to the position fluctuation 11L. Now, when positioning from the position of -1OLIIll to Om+Il, the position error signal S will be displaced by about 10V in the moving operation, but it will be displaced by 0.0V in the fixed operation. l～t
Only a displacement of about V is required.

Therefore, if the number of processing bits of the CPUI is, for example, 8 bits, the resolution (gain) during movement operation is 78IIlv.
/l hit (-10V to +10V). Here, the resolution is (voltage (V) corresponding to the required movement 1i1L
)/Number of CPUI processing bits). In such a configuration, since the gain is constant in the conventional digital servo control method, the resolution is 78% even in fixed operation.
It is no different from mV/1 bit.

In order to accurately position the magnetic head, it is necessary to increase the resolution during the fixing operation.

In this embodiment, in order to satisfy such a requirement, the magnitude of the position error signal S is detected by the detection unit 3, and based on the detected magnitude, the CPU activates the first GAC 4 to increase the gain of the A/DC 2. is adjusted to a value corresponding to the magnitude of the position error signal S. Therefore, if the position error signal S is, for example, IOV, the resolution is set to 78 mV/1 bit.

When the magnetic head moves and enters the fixed operation, the position error signal becomes small to approximately IV or less.

This value is detected by the detection unit 3 as described above, and the gain of the A/DC 2 is adjusted based on this value, and the resolution is 0.7.
It is set at 8 mV/1 bit, and thereby the position of the magnetic head is finely adjusted by wJ and positioned with high accuracy.

- On the force output side, the amount of movement corresponding to the position error signal S is calculated and sent to the D/AC 6 as a digital signal. The signal is then converted into an analog signal by the D/AC 6 and output to the outside.

In this series of operations, a digital value indicating the amount of movement is also sent to the second GAC 7, and the D
/AC6 gain adjustment is performed.

As described above, in this embodiment, the A/DC and D/AC gains are adjusted in stages according to the input value and output value, so that the resolution is lowered during moving operation and lowered during fixed operation. This allows for high control. As a result, the conversion speed does not decrease in a moving operation with a large amount of positional variation, while high resolution can be obtained when the amount of positional variation is small, such as in a fixed operation. Moreover, there is no restriction on the number of processing bits of the CPUI of the digital processing section.

If you try to obtain the accuracy required for fixed operation without gain control as in the past, in moving operation, ±IO
Since the displacement is performed by V, the number of processing bits of the CPU is required to be 15 bits or more.

〔Effect of the invention〕

According to the present invention as described above, an A/DC.

It becomes possible to control the required resolution according to the position error signal, that is, according to the amount of position variation, without increasing the number of bits of the D/AC and CPU, and therefore without reducing the conversion speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main part showing a system configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing a position error signal S for a position fluctuation meter. In the figure, 1 is the CPU, 2 is the A/DC, 3 is the detection unit,
4 indicates the first GAC 15 is a ROM, 6 indicates a D/AC, 7 indicates a second GAC, and 8 indicates control data. Figure 1 $212 τ

Claims (1)

[Claims] The analog servo signal as an error signal corresponding to the controlled amount of the controlled object is converted into a digital signal by the analog-to-digital converter, and after performing digital processing on the digital signal, the digital-to-analog converter converts it into an analog signal. When converting into a signal and controlling the controlled object based on the analog signal, the magnitude of the analog servo signal is detected, and the analog-to-digital converter and the digital-to-analog converter are controlled based on the detection result. A digital servo control system characterized by being able to vary the digital resolution of an analog quantity by selecting a gain.