JPH03222170A - Positioning circuit for magnetic head - Google Patents

Abstract

PURPOSE:To position a magnetic head at high speed and in addition, precisely by changing summing amplifier gain by detecting that the stationary error of a speed control system is inadequate when said state occurred. CONSTITUTION:A speed error amplifier 5 is provided with a speed error detector 15 to output a summing amplifier gain adjusting signal 16 corresponding to the stationary error between a speed reference signal 2 and a speed signal 4, and an adjustment circuit 14 to adjust the summing amplifier gain according to the signal 16. Then, by moving the magnetic head, the signals 2 and 4 at the time of deceleration are compared with each other by the detector 15, and the stationary error is detected, and the signal 16 is outputted, and the adjustment circuit 14 adjusts the gain so that the stationary error between the signals 2 and 4 becomes an adequate value. Accordingly, even in the case the force constant of a voice coil motor or the weight of a movable part varies, the adequate speed loop gain of the speed control system can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head positioning circuit used in a magnetic disk drive.

[Conventional technology]

Conventionally, in a magnetic disk drive, speed control is performed by a magnetic head positioning circuit as shown in FIG. 2 in order to move the magnetic head to a target track. During acceleration, the power amplifier 7 is saturated to move the magnetic head at maximum acceleration, and during deceleration, the position information 11 read by the magnetic head attached to the movable part 10 is converted into a position signal by the position detector 12. 13, and the error between the speed signal 4 obtained by differentiating this position signal 13 with the speed detector 3 and the speed reference signal 2 output by the speed reference signal generation circuit 1 based on the position signal 13 is called the speed error. The amplifier 5 detects the signal and outputs a speed error signal 6, and the power amplifier 7 sends a drive current signal 8 proportional to the speed error signal 6 to the voice coil motor 9. By generating a proportional force and driving the movable part 10, control is performed such that the speed signal 4 follows the speed reference signal 2, and the magnetic head is moved to the target track.

FIG. 3 is a block diagram showing the transfer function of the positioning circuit for this magnetic head. U (x) is a speed profile 17 indicating a predetermined reference speed during deceleration; Ko is a speed gain 18 indicating a voltage value generated per unit speed. Next, referring to FIG. 2, Ksv is the summing amplifier gain 19 indicating the gain of the speed error amplifier 5, G is the power amplifier gain 20 indicating the current value generated per unit voltage of the power amplifier 7, and K is Voice coil motor 9
A force constant 21 indicates the force generated per unit current of , M is the weight of the movable part 10, and velocity 23 of the magnetic head, X is the position 24 of the magnetic head. Therefore, since the type of speed control system 25 in FIG.
A steady-state error determined by the speed loop gain expressed as /M occurs in proportion to the slope of the speed reference signal. This steady-state error becomes smaller if the speed loop gain is increased, but the stability of the system decreases.On the other hand, if the speed loop gain is lowered, the steady-state error increases, and the system becomes stable, but the speed signal relative to the speed reference signal decreases. It has the property of decreasing followability.

[Problem to be solved by the invention]

In the conventional magnetic head positioning circuit described above, the speed gain, summing amplifier gain, and power amplifier gain of the speed control circuit are almost constant due to circuit constants.
If the force constant and weight of the movable part of the voice coil motor vary during manufacturing, the speed loop gain of the speed control system changes in proportion to this. As a result, the amount of steady-state error that occurs in proportion to the slope of the speed profile is no longer appropriate, resulting in a decrease in the ability to follow the speed profile or a decrease in the stability of the speed control system, making it difficult to position the magnetic head at high speed and with high precision. cannot be done.

[Means to solve the problem]

The magnetic head positioning circuit of the present invention includes a movable part to which a magnetic head is attached, a position detector that inputs position information output from the first movable part and outputs it as a position signal, and a position sensor that obtains a position signal by differentiating the first position signal. a speed reference signal generation circuit that inputs the position signal and outputs it as a speed reference signal; and a speed reference signal generation circuit that inputs the error between the speed reference signal and the speed signal and generates a speed error signal. a power amplifier that outputs a drive current signal proportional to the magnitude of the speed error signal, and a voice coil that generates a force proportional to the magnitude of the drive current signal to drive the movable part. In the magnetic head positioning circuit comprising a motor, the speed error amplifier inputs the speed signal and the speed reference signal to detect a steady error;
The power amplifier includes a speed error detector that outputs a summing amplifier gain adjustment signal, and a summing amplifier gain adjustment circuit that inputs the summing amplifier gain adjustment signal and the error to adjust the amplification degree of the power amplifier.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, the difference from the conventional magnetic head positioning circuit is that the speed reference signal 2 and the speed signal 4 are compared, a steady-state error is detected, and a summing amplifier gain adjustment signal 16 is output in accordance with this. The speed error amplifier 5 includes a speed error detector 15 and a summing amplifier gain adjustment circuit 14 that adjusts the summing amplifier gain according to a summing amplifier gain adjustment signal 16.

Therefore, the speed error amplifier 5 of the magnetic head positioning circuit of the present invention performs the following operation. By moving the magnetic head, a speed error detector 15 compares the speed reference signal 2 and the speed signal 4 during deceleration, detects a steady error, and outputs a summing amplifier gain adjustment signal 16, thereby adjusting the summing amplifier gain. The adjustment circuit 14 adjusts the gain so that the steady-state error of the speed signal 4 with respect to the speed reference signal 2 becomes an appropriate value. Therefore, even if the force constant of the voice coil motor or the weight of the movable part varies, an appropriate speed loop gain of the speed control system can be obtained by the speed error amplifier.

〔Effect of the invention〕

As explained above, the present invention can be used even when the speed loop gain of the speed control system changes due to variations in the force constant of the voice coil motor and the weight of the moving part, and the steady-state error that occurs in proportion to the speed profile is no longer appropriate. , is equipped with a summing amplifier gain adjustment circuit that adjusts the speed loop gain of the speed control system by detecting this with a speed error detector and varying the summing amplifier gain, so the next time the magnetic head is moved, The steady-state error that occurs in proportion to the speed profile has an appropriate value, and the followability of the speed signal to the speed reference signal can be improved, making it possible to position the magnetic head at high speed and with high precision.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the magnetic head positioning circuit of the present invention, FIG. 2 is a block diagram showing a conventional example, and FIG. 3 is a block diagram showing the conventional magnetic head positioning circuit using a transfer function. be. DESCRIPTION OF SYMBOLS 1... Speed reference signal generation circuit, 2... Speed reference signal, 3... Speed detector, 4... Speed signal, 5... Speed error amplifier, 6... Speed error signal, 7 ... Power amplifier, 8... Drive current signal, 9... Voice coil motor, 10... Movable part, 11... Position information, 12
... Position detector, 13... Position signal, 14... Summing amplifier gain adjustment circuit, 15... Speed error detector, 16... Summing amplifier gain adjustment signal, 17.
...Speed profile, 18...Speed gain, 19.
...Summing amplifier gain, 20...Power amplifier gain, 21...Force constant, 22...Moving part weight reciprocal,
23... Speed, 24... Position, 25... Speed control system, 26... Integral term.

Claims (1)

[Claims] A movable part to which a magnetic head is attached, a position detector that inputs the position information output from the first movable part and outputs it as a position signal, and a speed detector that outputs a speed signal obtained by differentiating the first position signal. a speed reference signal generation circuit that inputs the position signal and outputs it as a speed reference signal; a speed error amplifier that inputs the error between the speed reference signal and the speed signal and outputs it as a speed error signal; A magnetic head positioning circuit comprising a power amplifier that outputs a drive current signal proportional to the magnitude of an error signal, and a voice coil motor that generates a force proportional to the magnitude of the drive current signal to drive the movable part. a speed error detector in which the speed error amplifier inputs the speed signal and the speed reference signal to detect a steady-state error and outputs it as a summing amplifier gain adjustment signal; and a summing amplifier gain adjustment circuit that inputs a summing amplifier gain adjustment circuit to adjust the amplification degree of the power amplifier.