JPS6032170A - Speed signal composing circuit - Google Patents

Abstract

PURPOSE:To give the stable servo control to the seeking action speed of a movable head of a magnetic disk by composing a speed signal after a harmful mechanical vibration component is satisfactorily attenuated by means of a secondary LPF. CONSTITUTION:The speed detection signal of a disk movable head obtained by a head movable part 102 and a speed detecting circuit 103 is mixed with the output of a gain matching element 6 obtained on the basis of the detection current of a servo current detecting circuit 104 through a mixer 8. Then a high frequency component is deleted by the secondary LPF3 together with a harmful mechanical vibration component. The speed signal having a low S/N and passing through the LPF3 is mixed with a servo current detection signal passed through a gain matching element 7 and the secondary BPF4 through a mixer 9. As a result, a speed signal containing no harmful mechanical vibration component is composed with a good S/N. Thus it is possible to give the stable servo control to the seeking action speed of a movable head of a magnetic disk.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed signal synthesis circuit used in a head positioning servo mechanism of a magnetic disk device.

As shown in Figure 1, recent magnetic disk drives have all adopted a two-phase sabot system that uses two position signals l and 2t that are 90 degrees out of phase with each other. One continuous speed signal is created by selecting and connecting a total of four signals, the 2t-differentiated signal and their inverted signals, every 174 cycles. The speed signal resulting from this position signal differentiation has an S/N ratio (S/N) of
signal/noise ratio) is not sufficient. Therefore, a current detection signal for detecting the drive current of the surge motor is added to a speed signal obtained by position signal differentiation, and the signal is passed through a first-order low-pass filter 87N1. It's improving. The reason for adding the current detection signal is to compensate for the loss of high frequency components of the speed signal in the low-pass filter.

That is, the drive current of the servo motor is 2Io, the force constant tl
-, if the mass of the moving part is 2M, acceleration A#1A=
loK, /M. Since acceleration A is the differential of velocity V,
If the differential operator 2B is A, (V. Also, if the cutoff frequency of the first-order low-pass filter is fo,
Its characteristic is expressed as 1/(1-1/2πfa).

If the drive current lo is multiplied by /2πf0M and added to V, the previous go relation K
x f 0M= v+A/2 πf 0= V (1
+8/2πf, ), so the transfer function is 1/(
When passed through a first-order low-pass filter with a value of 1−+−8/2πf,), (1+8/2πf.) is canceled and the speed ■
will be synthesized. This is a conventional speed signal synthesis circuit.

In such a conventional configuration, the S/N is improved as the cutoff frequency fa of the low-pass filter is lowered, but the cutoff frequency f. If the current detection signal component is lowered, the current detection signal component that occupies the synthesized speed signal will increase.Accurately, the acceleration A will be reduced by the drive current I due to the influence of external forces such as the wind force, springs, and deflection of the flexible cable that the movable head receives. . Since it is not proportional to , accuracy deteriorates. Therefore, the cutoff frequency f0 is usually selected to be several hundred Hz. However, when the position signal is differentiated, in addition to random noise, vibration components due to mechanical resonance of movable parts such as the head block, which are not at the original speed, are mixed into the position signal. When this mechanical vibration is between 1 KHz and 2 KHz, the conventional speed signal synthesis circuit described above is unable to sufficiently attenuate the mechanical vibration component because the low-pass filter is a first-order filter, and therefore the servo loop There are disadvantages in that the customization becomes unstable, the operation noise becomes louder during the seek operation to move the head to the target position, and in some cases, malfunctions may occur.

An object of the present invention is to provide a new speed signal synthesis circuit that can sufficiently attenuate harmful mechanical vibration components as described above.

This allows the servo to be fully stabilized, making it possible to realize a highly reliable servo mechanism.

The circuit of the present invention includes a speed signal synthesis circuit that obtains a speed signal based on a position signal of the movable head and a drive current of the movable head in order to control the seek operation speed of the movable head of a magnetic disk device. Speed detection means for performing differential 2 of the position signal and gain adjustment of the differentiation result; gain adjustment means for performing gain adjustment for the drive current; and said gain adjustment! ml mixer for adding the output of the means and the output of the speed detection means; a first filtering means for filtering high frequency components included in the output of the first mixer; and another output of the gain matching means. A second filter that combines all gains and filters high frequency components included in the output.
The present invention is characterized in that it includes a filtration means, and a second mixer that adds the output of the first filtration means and the output of the second filtration means to obtain the speed signal.

Next, embodiments of the present invention will be described with reference to all the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention.

This embodiment includes a two-way low-pass filter 3, a second-order band-pass filter 4, three gain matching elements 5, 6 and 7, two mixers 8 and 9, and a servo Tanabata 101.
, a movable head 5102 , a speed detection circuit 103 , and a current detection circuit 104 . What is written on the top of each block is the transfer function of that block.

The servo motor 101 has a driving current l. driven by
Its force constant is . The iJ'm head section 102 (quality i is IV) is driven by a servo motor 101,
Perform a seek operation. The speed detection circuit 103 receives the position signal X. is divided into values and the gain is increased (gain '-1Gv) to obtain the first speed detection signal v0, and the current detection circuit 104 adds the gain of the drive current 10 't (gain is Go) Detection signal ■, (obtain.

The gain GK of the gain matching element 5 is determined as Gt = (GvKy)/(GoM). Then,
Output of gain matching element 5■8 is I,=oeI,=G
Go. ■.

= CGv KF IM ) ” o.On the other hand, the transfer gain v to the first speed detection signal V□ which is 1° drive current
t/”o=(GvKp)/(M8)
Therefore, v1S=(GvK2/M)■. The output I of the gain matching element 5 can be expressed as t, V1S.

The amount of transmission between the two-way low-pass filter 3 and the second-order band-pass filter 4 is ω. ”/(8”+2ζω.S+ω.′) and 2ζω. 8
/C8"+2ζω.S+ω.'). Here, ω.

This is the cutoff angular frequency of the second-order low-pass filter 3 and also the center angular frequency of the second-order band-pass filter 4. In addition, 1 and ζ are the damping factors of the second-order system, and 2
What is necessary is just to choose so that the next locus filter 30 debris characteristic will become a desired characteristic. Butterworth characteristic (flatest characteristic) is ζ
= t/v/2.

The gains of gain matching elements 6 and 7 are 2ζ/ω, respectively.

The at flow detection signal 1 determined by l/(2ζω.)K is added to the first speed detection signal v0 by the mixer 8 via the gain matching elements 5 and 6, and is input to the second-order low-pass filter 3. . The current detection signal 10 is also input to the second-order bandpass filter 4 through the gain adjustment element 5.7t. The outputs of both filters are added in a mixer 9 to form a second speed detection signal V. Here, v, all block diagrams are vs=("1+vl(2ζ/ωomonthωo'/(8
"+2(ωoS+cc+.')+(Im/(zζω.Moon(2ζωO8)/(S"+2ζω.S+ωoJ).

By substituting I, = V18 t-, V attack == V, (ω♂
+2ζωoS+”)/C8”+2(ω.b+ω,y)=
v.

becomes. The second speed detection signal V is equivalent to the first speed detection signal V.

It can be seen that is correctly synthesized as a speed signal.

The secondary low-pass filter 3 and the secondary band-pass filter 4 can be easily realized with active R and C filters using operational amplifiers, and their specific circuits are described in handbooks and are well known, so they will not be described here. I will omit it here. Also,
It is also possible to implement it with an LC filter. The present invention
Conventionally, 1st order low pass filter 3 was used, but 2
Since the second-order low-pass filter is used, harmful high-frequency mechanical imaging components can be sufficiently attenuated. but,
Simply changing the first-order low-pass filter to the second-order low-pass filter 3 will not synthesize the correct speed signal, so in order to correct this, the current detection signal 'xk is added to the signal passed through the second-order band-pass filter 4. be.

FIG. 2 shows one embodiment, and the arrangement of each gain matching element can be changed depending on the actual circuit configuration without changing the essence. For example, the gain of the center frequency of the second-order bandpass filter 4 in FIG. 2 is 1, but in an actual circuit, there is a value rs input t y t that is thicker than idl. In that case, the value of the gain adjustment element 7 will be changed in accordance with the gain of the secondary bandpass filter 4. In addition, gain adjustment element 7
may be placed after the secondary bandpass filter 4.

Note that this @8At can also be used in cascade with a conventional speed signal synthesis circuit. When the output signal of the conventional speed signal synthesis circuit is used as the first speed signal, the fast wave signal resulting from position signal differentiation passes through the first-order low-pass filter of the conventional circuit and the second-order low-pass filter of the present invention. As a result, harmful surface area mechanical vibration components can be more effectively attenuated by the overall third-order low-pass filter.

As explained above, the present invention is capable of synthesizing a speed signal in which harmful mechanical vibration components are attenuated by using a second-order low-pass filter, and has the effect of realizing a stable servo mechanism. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing the position key of a two-phase single-bore system, and FIG. 2 is a block diagram showing an embodiment of the present invention. l...First position signal, 2...River/second position signal, 3...Second order low pass filter, 4...Old...
Secondary band pass filter 9, '5, 6.7... Gain matching element, 8.9... Mixer, 101.
... Servo motor, 102 ... Head moving part, 103 ... Quick summer detection circuit, 104 ...
...Current detection circuit.

Claims (1)

[Scope of Claims] A speed signal synthesis circuit that obtains a speed signal based on a position signal of the movable head and a drive current of the movable head in order to fully control the seek operation speed of the movable head of a magnetic disk device, comprising the steps of: A speed detecting means for performing all signal differentiation and gain adjustment of the differential result; a gain adjusting means for performing gain adjustment of the drive current; and a first mixing method for adding the output of the gain adjusting means and the output of the speed detecting means. a first filtering means for filtering a high frequency component included in the output of the first mixer; and a first filtering means for filtering a high frequency component included in the output of the first mixer; The second to filter
A speed signal synthesis circuit comprising: a filtering means; and a second mixer for adding the output of the first filtering means and the output of the second filtering means to obtain the speed signal.