JPH01227278A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To shorten head positioning time by selecting the gain of a servo system most suitably in accordance with a head speed at the time of getting into a position mode. CONSTITUTION:When getting into the position mode, a timer 10-2 is turned on and the state of a head speed signal (b) is held by a latch circuit 10-1. The output of the circuit 10-1 is compared with a reference speed 10-4 by a comparing circuit 10-3 and one circuit of analog switches 12-2-12-4 is turned on and one of gain resistances 12-7-12-9 fit for the speed at that time is selected. The gain is adjusted only while the timer 10-2 is ON state, and when the timer 10-2 is OFF state, a resistance 12-10 is selected. Thus, the head positioning time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device that uses a servo type for head positioning.

[Conventional technology]

Conventionally, for this type of magnetic disk random placement, a method has been adopted in which the low-pass filter is unconditionally short-circuited for a certain period of time when entering the position mode to improve the response characteristics of the servo loose.

[Problem to be solved by the invention]

In the above-mentioned conventional magnetic disk drive, when entering position mode, the speed of the head is not constant due to various factors, and undershoot and overshoot occur depending on the speed at that time, which takes time until positioning. The problem was that it took a long time.

[Means to solve the problem]

The magnetic disk drive of the present invention has a circuit for detecting the position of the head and a circuit for detecting the speed of the head, and has a speed mode in which the servo motor 1 is driven to follow a set speed until near the target cylinder, and a speed mode as described above. A comparator circuit capable of distinguishing between at least two or more levels of head speed in a magnetic disk drive having a servo positioning means consisting of two position modes for driving a servo motor so that the difference between a target cylinder and a current head position is always zero. and a servo positioning means having a setting circuit which can be switched for each step of the head speed using this comparison circuit.

[Effect]

In the present invention, if the head speed at the time of entering the position mode is not uniform due to individual conditions, the gain of the servo system is optimally selected according to the head speed at that time.

〔Example〕

Hereinafter, embodiments of the invention will be described in detail based on the sections.

The first part is a block diagram showing one embodiment of the present invention.

In the figure, 1 is a servo motor, 2 is a means for obtaining a position 1A representing the position t of the head, such as an encoder,
3 is a position signal demodulation circuit that receives the output of this encoder 2; 4 and 5 are slope select circuits and differentiators that receive the output of this position signal demodulation circuit 3; and 6 is a speed signal a from this differentiation circuit 5. 7 is an error detection circuit whose inputs are the output of the slope select circuit 6 and the output of the reference speed generation circuit 8;
9 is a mode switching circuit, and 9a and 9b are connection points of this mode switching circuit 9. 10 is a speed comparison circuit which inputs the head speed signal from the slope select circuit 6 and the output of the timing circuit 11 and is capable of distinguishing head speeds in at least two or more stages; 12 is a speed comparison circuit for each stage of head speed by this speed comparison circuit 10; Setting circuit that can be switched to 13
14 is a low-pass filter inputting the output of the summing amplifier circuit 14; and 15 is a motor drive circuit that drives the servo motor 1 based on the switching output from the mode switching circuit 9. Note that C indicates velocity mode and d indicates position mode.

The servo type head positioning used in magnetic disk drives usually consists of two modes. In other words, speed mode C drives the servo motor to follow the set speed until it approaches the target cylinder.
and position mode d in which the servo motor is driven so that the difference between the target cylinder and the current head position is always zero. Here, in speed mode C, the mode switching circuit 9 is sb
When the position mode is 6, it is closed to the 91 side. Then, the head is moved in speed mode C to near the target cylinder, for example, 1/2 cylinder, and switched to position mode d from 1/2 cylinder to the target cylinder.

Furthermore, although the position at which the mode is switched is fixed with respect to the target cylinder, the speed of the head when the mode is switched to the position mode is not constant due to various factors.

FIG. 2 is a diagram showing an example of the waveform of the head speed signal in FIG. 1 in the position mode. In the figure, SS indicates a reference speed, SM indicates a speed mode, and PM indicates a position mode. 16 shows the characteristics in the normal case υ, 17 shows the characteristics when the entry speed to the position mode is fast, and 18 shows the characteristics when the entry speed to the position mode is slow. It is.

In both cases of characteristics 17 and 18, the time required to reach the target cylinder is extended.

Therefore, by reducing the gain of the servo system in the position mode when the characteristic is 1T and increasing the gain of the servo system in the position mode when the characteristic is 18, the time required to reach the target cylinder can be shortened.

Next, the operation will be explained according to FIG.

FIG. 3 is a block diagram of an embodiment in which portions related to the speed comparison circuit 10 and setting circuit 12 in FIG. 1 are extracted and shown.

In FIG. 3, parts corresponding to those in FIG. 10-4 is a comparison circuit that can distinguish between at least two levels of head speed, and 10-4 is a reference speed. In addition, 12-1゜12-2...@-@12- in the setting circuit 12
5 is an analog switch, 12-6 is an inverter, 12
-7, No. 12-8...12-10 is the gain resistor. 12-11 indicates a summing amplifier feedback loop.

When entering the mass/position mode, the timer 10-2 is turned on, and the state of the head speed signal is held by the latch circuit 10-1.

Next, the output of this latch circuit 10-1 is transferred to the comparison circuit 10-1.
-3, the reference speed is compared with the reference speed 10-4, and depending on the comparison result, any one circuit of the analog switches 12-2 to 12-4 is turned on, and the gain resistor 12-7 to 12- is selected to suit the speed at that time. Select 9.

Gain adjustment is performed only while the timer 10-2 is on, and the gain resistor 12-10 is always selected when the timer 10-2 is off.

Note that 2 in FIG. 1 does not necessarily have to be an encoder, but may be any means that can obtain a position signal representing the position of the head.

[Original side effect]

As explained above, when the head speed at the time when the position mode is entered is not uniform due to various conditions, the present invention optimally selects the gain of the servo system according to the head speed at that time, thereby improving the performance of the magnetic disk device. This has the effect of shortening the head positioning time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of the waveform of head speed No. 1 in FIG. 1, and FIG. 3 is a speed comparison circuit and settings in FIG. 1. FIG. 2 is a block diagram of an embodiment showing extracted portions related to the circuit. 1.-Match servo motor, 2＠sha*-encoder, 9.
・Reference mode switching circuit, 9a, 9b... Connection point, 1
0...Speed comparison circuit, 10-1・ΦFist/Latch circuit, 10-2-・・Timer, 10-3…Comparison circuit, 10-49ΦWork reference speed, 12・φ・Setting circuit,
12-1 to 12-5... Ro analog switch, 12-
7-12-10 ・Conflict/gain resistance. Patent applicant: NEC Corporation

Claims (1)

[Claims] A speed mode that has a circuit that detects the position of the head and a circuit that detects the speed of the head, and drives the servo motor to follow the set speed until it approaches the target cylinder;
In a magnetic disk drive having a servo positioning means consisting of two modes, a position mode in which a servo motor is driven so that the difference between the target cylinder and the current head position is always zero, a comparison capable of distinguishing at least two or more levels of head speed. 1. A magnetic disk drive comprising: a circuit; and servo positioning means having a setting circuit which can be switched for each stage of head speed by the comparison circuit.