JPH0330152A - Seek control system for magnetic disk device - Google Patents

Abstract

PURPOSE:To reduce the settling time after the end of seek even when the sampling frequency is low by calculating the rate of change of an input signal to an actuator positioning a head depending on the speed deviation and that of preceding and succeeding input signals and limiting the rate of change when the permissible value is exceeded. CONSTITUTION:A signal resulting from the rate of change in the speed deviation limited is obtained at the output of a saturation circuit 20 and the speed deviation is corrected into the limited rate of change in the speed deviation at the point of current sample time by adding the output of the saturation circuit 20 and a speed deviation DELTAvm(k-1) of one preceding sample by an adder 21. The corrected speed deviation is converted into an analog quantity by a D/A converter 22 and subjected to voltage/current conversion with a current amplifier 23, the current drives the actuator 24 to apply the seek control (speed control) of a magnetic head 2. Since the fluctuation of a manipulation variable is controlled, even when the sampling frequency is low, the setting time of seek control is shortened.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a magnetic disk storage device in which servo information recorded in advance on a magnetic disk is read out using a magnetic head, and the temporally sampled servo information is read out using a magnetic head. This paper relates to an improvement of a seek control method that performs head positioning based on information.

[Conventional technology]

In a conventional device, for example, the device described in US Pat. No. 4,669,004, seek control for positioning a magnetic head based on servo information temporally sampled from an information storage disk is performed as follows. That is, in the control circuit shown in FIG. 4, the reproduction signal detected by the magnetic head 2 from the magnetic disk is amplified by the preamplifier 3,
Then, only the servo signal is extracted by the data/servo separation circuit 4. This servo signal includes an absolute track number and head position error information with respect to the track center, and the absolute track number is converted by a track number demodulator 5 into a binary code corresponding to the absolute track number. Also,
The head position error information with respect to the track center is converted by a position signal demodulator 6 into an electric signal corresponding to the position error, and this electric signal is converted into a digital quantity by an A/D converter 7. As described above, the binary encoded absolute track number and the digitized position error amount are added by the adder 8, and the absolute position [xx(k)] of the head is determined.

Head absolute position x at the time of the previous sample of this head
s(k-1) is obtained by passing xt(k) through a delay circuit 9, and a deviation Δx1(k) between the head positions between the current sample and the previous sample is obtained by a subtraction circuit 10. When this positional deviation Δx1(k) is multiplied by the reciprocal 1/T of the sampling period T by a multiplication circuit 1, the velocity vm of the head between the sampling times is determined by vm=-Δx1(k)T. In addition, the target track number NTRK is stored in the memory 13 from the upper host king 2, and this target track number NTRκ and the head absolute position fi at the current sample time are
Remaining track RTRK from xt(k) to the target track
is obtained from the subtractor 14, and the speed deviation between the command value of the speed function generator 15 which outputs the command speed value VT according to the remaining track RTRκ and the head speed vm is obtained by subtraction @path l6. This speed deviation signal is multiplied by a gain K in a multiplier circuit 17, converted into an analog quantity by a D/A converter 22, converted from voltage to current by a current amplifier 23, and this current drives an actuator 24 to drive a magnetic head. 2 and performs seek control.

As mentioned above, the part surrounded by the dotted line in FIG. 4 can be constructed by hardware, but from the viewpoint of cost, it is possible to construct it by software of a microcomputer.

[Problem to be solved by the invention]

In the above conventional technology, when a low-cost 8-bit microcomputer is used to reduce the cost of the seek control circuit, the stability of the seek control system deteriorates due to the phase delay caused by the computer's calculation time, so the sampling frequency The maximum value of is limited to approximately 2.5 KHz. In addition, in the method of calculating the speed from the difference in absolute track numbers at each sample time, as in this method, if the node travels on the boundary between tracks at the sample time, an error of one track will occur, and the detected speed will be This results in a speed detection error equivalent to two tracks. Due to this detection error,
In particular, when the head speed decreases, such as immediately before the end of seek to the target track, the S/N of the speed detection signal deteriorates relatively, so the S/N of the operation amount to the actuator also deteriorates, as shown in Figure 5. As shown in section a-b, the amount of operation is oscillatorily damped and does not decrease smoothly. If this phenomenon occurs and the sampling frequency is high,
Although it does not have a large effect on the movement of the actuator, if the sampling frequency is 2.5 KHz or less, it will affect the movement of the actuator, excite the head support function, and increase the settling time after the end of the seek. This problem has been an obstacle to shortening the seek time.

[Means to solve the problem]

In order to achieve the purpose of not prolonging the settling time after the end of a seek even when the sampling frequency is low, the present invention monitors the rate of change of the speed deviation signal and detects the change rate of the speed deviation signal when the rate of change exceeds a preset value. The rate of change is limited.

[Effect]

Limit the rate of change of speed deviation. This suppresses the behavior of the operation amount to the actuator, so even if the S/N value of the detected speed signal deteriorates when the head is moving at a low speed, such as immediately before the end of a seek, malfunctions due to detection noise can be avoided. I don't have anything to do.

〔Example〕

An embodiment of the present invention will be described below. This example is the fourth example.
The invention is applied to the well-known digital servo circuit shown in the figure. Note that parts corresponding to those in FIG. 4 are given the same reference numerals.

In FIG. 1, servo information pre-recorded on a magnetic disk 1 is read by a magnetic head 2, amplified by a preamplifier 3, and amplified by a data/servo separation circuit 4.
Only the servo signal is extracted, and the absolute track number included in the servo signal is converted into a binary code by a track number demodulator 5 corresponding to the absolute track number on the disk 1 of the head 2. The position error information is converted by a position signal demodulator 6 into an electrical signal corresponding to the position error of the track center of the magnetic head 2. This electrical signal is converted into a digital quantity by an A/D converter 7. As described above, the binary encoded absolute track number and the digitized position error amount are added by the adder 8, and the absolute position of the head 2) I
) can be found. The head position xxck-1) of this head 2 at the previous sample time is x 1(k) in the delay circuit 9
The deviation ΔX1(k) between the head position between the current sample and the previous sample is obtained by subtracting circuit 1o.
When the positional deviation Δxx(k) is multiplied by the reciprocal of the sampling period 1/T by the multiplication circuit 1, the velocity vm of the head 2 is obtained as 1 vm=−●ΔX1(k) T . Also, store the target track number NTRK from the upper host ↓2 in the memory l3, and store this target track number NTRK and the head absolute position x1 at the current sample time.
(k) A circuit that subtracts the command value VT of the speed function generator 5 and the speed Vm of the head 2, which calculates the remaining track RTRK to the target track from the subtracter 14 and outputs the command speed value VT according to the remaining track RTRK. By subtracting by 16, the speed deviation is obtained. The speed deviation signal is multiplied by a gain K in a multiplier circuit 17, and the speed deviation signal amplified by the gain K is sent to a delay circuit 1 which performs sample delay.
8, and the velocity deviation Δvm (
k-1) is obtained, and by subtracting the speed deviation of the previous sample from the speed deviation Δvm(k) of the current sample in the subtraction circuit 9, the difference in speed deviation Δv (k) becomes Δv (
k) = Δvm (k) - Δvm(k-1). The difference Δv (k) output enters the saturation circuit 20. In the saturation circuit 2o, when the absolute value of the difference in speed deviation is larger than the preset value ε, the output Δvs (k)
saturate. However, ε is a positive number.

When Δv (k) > ε, Δvs (k)=εΔv (
If the configuration is such that Δvs (k)=-ε or more when k) <-ε, a signal in which the rate of change of speed deviation is limited can be obtained as the output of the saturation circuit 20, and the output of the saturation circuit 20 By adding the velocity deviation value Δvm(k-1) before the upper sample using an adder 21, the velocity deviation Δv' m (k) at the current sample time is corrected to one that limits the rate of change of the velocity deviation.

Δv' m(k) = Δvs(k) + Δvm(k-1) The corrected speed deviation value Δv'm(k) is converted into an analog quantity by the D/A converter 22, and converted into a voltage by the current amplifier 23. One current is converted, and this current drives the actuator 24 to perform seek control (speed control) of the magnetic head 2. As described above, the range within the dotted line in FIG. 1 can be realized by microcomputer software.

FIG. 2 shows a second embodiment of the invention.

In FIG. 2, servo information recorded in advance on a magnetic disk l is read out by a magnetic head 2, and is read out by a preamplifier 3.
A data/servo separation circuit 4 extracts only the servo signal, and a track number demodulator 5 converts the absolute track number included in the servo signal into a signal that corresponds to the absolute track number on the disk 1 of the head 2. A binary code corresponding to the track center is obtained, and the position error information corresponding to the track center is transmitted to the head 2 by the position signal demodulator 6.
is converted into an electrical signal corresponding to the position error of the track center. The electrical signal is converted into a digital quantity by an A/D converter 7. As described above, the binary encoded absolute track number and the digitalized position error signal are added by the adder 8, and the absolute position 42 x t (k) of the head 2 is determined. The head position [x L(k-1) of head 2 at the previous sample time is determined by passing xt(k) through the delay circuit 9, and the deviation Δxx between the head position of the current sample and the previous sample time is calculated by (k) is obtained by the subtraction circuit 10, and when the positional deviation Δxz(k) is multiplied by the reciprocal of the sampling period 1/T by the multiplication circuit 11, the speed vm of head 2 is obtained as vm=1・ΔXI(k) I want more T maru. Also, the target track number N is set by the upper host 12.
TRK is stored in the memory 13, and this target track number NTRK and the head absolute position xl(k
), the remaining track RTRK up to the target track is obtained from the subtractor 14, and the command value v of the speed function generator 15 outputs the command speed value VT according to this remaining track RTRK.
7 and the speed vm of the head 2 by the subtraction circuit 16, the speed deviation can be obtained. The speed deviation signal is multiplied by a gain K in a multiplier circuit 17, the speed deviation signal amplified by the gain K is delayed by a delay circuit 18 that delays by one sample, and added by a subtraction circuit 19 to calculate the speed deviation. Find the rate of change. A rate of change determination circuit 25 determines whether the rate of change of the speed deviation is within a preset value, and drives a switch 26 with a control signal from the rate of change determination circuit 25. If the rate of change of the speed deviation is greater than the value, the switch is connected to the A side. The transfer function G (z) of the circuit surrounded by the dashed-dotted line in FIG. 2 is composed of the delay circuit 26, 27, the multiplication circuit 28 with double the gain, the adder 29, and the multiplication circuit 30 with the gain 1/4. 1 G(z)=-(1+2Z-'+Z-")4, and this board characteristic is set by a low-pass filter as shown in Figure 3. Therefore, the speed deviation signal is filtered by this low-pass filter. The speed deviation signal that has passed through the low-pass filter is converted into an analog quantity by the D/A converter 22, is converted from voltage to current by the current amplifier 23, and is converted by the output current of the current amplifier. The actuator 24 is driven to perform seek control.

Further, when the rate of change of the speed deviation is within a set value, the switch 26 is connected to the B side, and the speed deviation signal goes directly to the D/A converter 22, and is converted into an analog value by the D/A converter. The output current of the current amplifier 23 drives the actuator 24 to perform seek control.

Various other configurations of the low-pass filter described above are possible.

〔Effect of the invention〕

According to the present invention, it is possible to suppress fluctuations in the operation amount in order to limit the rate of change of the speed deviation value, which is the operation amount to the actuator during seek control, so even when the sampling frequency is 2.5 KHz or less, Excellent performance in seek control can be obtained in that the settling time of seek control can be shortened. In addition, since the sampling frequency can be lowered, seek control can be performed using low-cost microcomputer software, reducing the cost of the control circuit by about half compared to conventional configurations that are entirely made of hardware. It has the advantage of being able to

[Brief explanation of drawings]

FIG. 1 is a control block diagram of a first embodiment of the present invention, FIG. 2 is a control block diagram of a second embodiment of the present invention, FIG. 3 is a Bode diagram of a low-pass filter, and FIG. 4 is a control block diagram of a second embodiment of the present invention. FIG. 5 is a control block diagram of the conventional method. DESCRIPTION OF SYMBOLS 1...Magnetic disk, 2...Head, 18...Delay circuit, 20...Saturation circuit, 25...Change rate determination circuit, 26...Fig. 3 Shuzeju Cth) Tomi 5 figure

Claims (1)

[Claims] 1. Every time servo information on the magnetic disk is sampled, the absolute position and head speed of the head are calculated,
On the other hand, the absolute head position calculates a commanded head speed as a function of the distance to the target track, calculates a speed deviation amount from the head speed and partial speed, and inputs the speed deviation amount to an actuator that positions the head. A magnetic disk position seek control method that calculates a signal, calculates the rate of change of the input signal before and after, and limits the rate of change when the rate of change of the input signal exceeds a tolerance value. 2. The seek control method for a magnetic disk drive according to claim 1, wherein the rate of change of the input signal of the actuator is limited by saturation of the rate of change in speed. 3. The seek control method for a magnetic disk drive according to claim 1, wherein the rate of change of the input signal to the actuator is limited by attenuating high frequency components of the input signal to the actuator. 4. Claim 1 in which an optical disk is used instead of a magnetic disk.
, 2 or 3.