JPH02242407A - Speed signal generation circuit for servo circuit - Google Patents

Abstract

PURPOSE:To prevent loop response in seek control occurring and to perform stable and fast seek even when a seek difference quantity is few by varying the band area of a speed signal generation circuit corresponding to the seek difference quantity. CONSTITUTION:The speed signal generation circuit 14A generates real speed Vr that is a servo object based on a position signal Ps from a position signal demodulation circuit. A band area variable circuit 140 varies the band area of the speed signal generation circuit 14A corresponding to the seek difference quantity. In other words, a frequency is set at the one nearer to the resonance point of the servo object when the seek difference quantity is few, and it is set at the one lower than the resonance point as increasing the seek difference quantity. Thereby, it is possible to block the occurrence of the loop resonance in the seek control regardless of the level of the seek difference quantity, and also, to perform the stable and fast seek even when the seek difference quantity is few.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a speed signal generation circuit that determines the actual speed in a servo circuit that controls the speed of a servo target based on the speed error between its target speed and actual speed. The purpose is to effectively prevent the occurrence of loop resonance during seek control regardless of the speed difference between the target speed and the actual speed of the servo target, and to make stable high-speed seek variable even in the case of a small difference amount. In the speed signal generation circuit that is installed in the servo circuit that controls the speed based on the position signal of the servo target and generates the actual speed of the servo target based on the position signal of the servo target, the band of the speed signal generation circuit is changed in accordance with the seek difference amount. The configuration is such that a band variable circuit is provided to

[Industrial application field]

The present invention relates to a speed signal generation circuit that generates the actual speed in a servo circuit that controls the speed of a servo target based on a speed error between its target speed and actual speed.

[Conventional technology]

Servo circuits are widely used for track positioning of magnetic heads in magnetic disk drives.

For such servo circuits, there is a need for technology that allows stable positioning even at higher speeds.

FIG. 4 is a block diagram showing the basic configuration of a servo circuit (hereinafter referred to as the original servo circuit) proposed in the same application to satisfy such requirements.

In FIG. 4, reference numeral 11 denotes a magnetic disk mechanism as a servo target, and a carriage 1 on which a voice coil motor (hereinafter referred to as VCM) 111 and a magnetic head 112 are mounted.
13 and a magnetic disk 114.

Reference numeral 12 denotes a position signal demodulation circuit, which generates a position signal PS indicating the movement position of the servo head 112 eight times based on servo information read from the servo surface of the magnetic disk 114.

Reference numeral 13 denotes a target speed generation circuit, which generates a target speed Vc for positioning the magnetic head 112 of the servo target 11 to a target position in accordance with a movement amount instructed by a main control section (described later).

Reference numeral 14 denotes a speed signal generation circuit, which generates an actual speed Vr of the magnetic head 112 in the servo target 11 based on a position signal PS and a current signal ic to be described later.

The current signal ic is a correction signal added to generate a smooth actual speed Vr.

15 is a speed error creation circuit, which includes a filter 15 inside.
0, and generates a speed error signal ΔV for controlling the servo target 11 based on the speed error between the target speed Vc and the actual speed Vr.

Reference numeral 16 denotes a position error generation circuit, which generates a position error with respect to the target position of the servo target 11 from the position signal PS and the current signal IC, and generates a position control signal ΔP.

Reference numeral 17 denotes a servo target drive circuit, which performs a process of switching from speed control of the speed error generation circuit 15 to position control of the position error generation circuit 16 in response to a coarse (speed control)/fine (position control) switching signal from the main control section; Eight ■ or ΔP
Each error signal is power amplified and the VCM of the 11 servo targets is
Processing to output the VCM current 1c that drives the VC
Processing is performed to detect the M current IC and generate a current signal IC.

18 is a main control unit, which is composed of a microprocessor, detects the position of the magnetic head 112 based on the position signal Ps, outputs the remaining movement amount, that is, the remaining difference ■ to the target speed generation circuit 13, and detects the position near the target position. Decoarse/
Generates fine switching signal.

Reference numeral 19 denotes an acceleration detection circuit, which detects the speed error signal ΔV generated by the speed error creation circuit 15 and changes the band of the speed error creation circuit 15 during acceleration and deceleration in accordance with the seek difference amount during acceleration. Generates signal SKA.

The servo circuit configured as described above performs speed control until it approaches the target position, and then switches to position control to perform positioning control to the target position. Since the control operation is the same as the servo control operation of a conventional servo circuit, the operation of the speed error generation circuit 15 will be mainly explained below with reference to FIG.

When speed control is started by a command from the main control section 18, the target speed generation circuit 13 generates a target speed Vc during acceleration control based on the movement amount, ie, the difference amount, instructed by the main control section 18.

Further, the speed signal generation circuit 14 is connected to the position signal demodulation circuit 12.
The actual speed Vr of the servo target 11 (magnetic head) is created by receiving the position signal Ps from the servo target drive circuit 17 and the current signal ic from the servo target drive circuit 17 (for details, refer to FIGS. 6 and 7). ).

The speed error generation circuit 15 generates a speed error signal ΔV corresponding to the speed error between the target speed Vc generated by the target speed generation circuit 13 and the actual speed Vr generated by the speed signal generation circuit 14.

On the other hand, when the acceleration detection circuit 19 detects that the speed error creation circuit 15 is under acceleration control from the speed error signal V generated by the speed error creation circuit 15, it generates an acceleration signal SKA and creates a speed error. Add to circuit 15.

When the filter 150 of the speed error creation circuit 15 receives the acceleration signal SKA from one acceleration detection circuit, the off frequency flO of the cuff 1□ is set to infinity or higher than the resonance point f2 of the servo target 11. As a result, the cutoff frequency flQ of the speed error creation circuit 15 during acceleration control is
As shown in FIG. 5(A), it becomes infinite or higher than the resonance point f2 of the servo target 11. In this case, the finite high cutoff frequency f1o is set to a high frequency within a range where no vibration occurs in the accelerating current.

The servo target drive circuit 17 amplifies the power of the speed error signal ΔV received from the speed error generation circuit to drive the servo target 11.
It outputs a VCM current 1c that accelerates and drives VCMIII of , and also generates a current signal ic that is a detection current of this VCM current Tc.

By doing this, the speed error generation circuit 15 applies the V corresponding to V to the speed error signal generated during acceleration control.
As shown in FIG. 5(B), the characteristic of the CM current 1c is a steep characteristic with little rounding, so that the acceleration control can be completed in a short time.

When the acceleration control ends, the main control section 18 switches to deceleration control.

When switching to deceleration control in response to a command from the main control unit 18, the target speed generation circuit 13 outputs the target speed Vc during deceleration control.
will occur. The speed error generation circuit 15 uses the target speed Vc generated by the target speed generation circuit 130 and the speed signal generation circuit 1.
A speed error signal Δ■ (negative) corresponding to the speed error of the actual speed Vr generated in step 4 is generated.

On the other hand, when the acceleration control of the speed error generation circuit 15 is completed, the acceleration detection circuit 19 stops generating the acceleration detection signal SKA.

The filter 150 of the speed error creation circuit 15 lowers its cutoff frequency to a frequency lower than the resonance point f2 of the servo target 11 when the speed error creation circuit 15 enters deceleration control. At this time, the larger the difference amount, the lower the cutoff frequency. As a result, the cutoff frequency of the speed error generation circuit 15 during deceleration control becomes ff1 as the difference amount becomes larger, as shown in FIG. 5(A).
□...fl, decreases as follows.

The servo target drive circuit 17 amplifies the power of V to the speed error signal received from the speed error generation circuit 15 and converts it into VCMI.
It outputs a VCM current 1c that decelerates and drives the VCM current Ic, and also generates a current signal ic that is a detection current of this VCM current Ic.

By doing this, the speed error generation circuit 15 can generate a V corresponding to the speed error signal ΔV generated during deceleration control.
The characteristics of the CM current IC, that is, the deceleration current, are shown in Figure 5 (B).
It becomes as shown in . That is, the smaller the difference amount, the less rounded the deceleration characteristics, and the deceleration control time, that is, the speed control time, is reduced to 1. l,...j2+ tl
It decreases as follows.

As described above, the cutoff frequency of the speed error creation circuit is changed during acceleration control and deceleration control, and the cutoff frequency during deceleration control is changed in accordance with the difference amount, so acceleration control In addition to uniformly reducing the rounding of the acceleration current supplied to the servo target during deceleration control, the smaller the difference amount, the lower the rounding rate of the deceleration current during deceleration control, reducing the speed control time even when the difference amount is small. It can be stably shortened. As a result, even in the case of an extremely small difference amount such as one difference amount, speed control can be performed quickly and stably, and high-speed seek can be performed stably.

Next, the configuration and operation of the speed signal generation circuit 14 will be explained with reference to FIGS. 6 and 7.

In FIG. 6, 141 is a differentiating circuit, and the position signal P
s is differentiated to generate a differential velocity Vps.

An amplifier 143 amplifies the current signal IC to a predetermined level.

144 is an offset adjustment circuit, which generates an offset correction signal for adjusting the offset of the actual speed Vr generated from the speed signal generation circuit 14.

145a and 145C are variable resistors, and variable resistor 14
5a adjusts the output gain of the amplifier 143a, the variable resistor 145b adjusts the output gain of the differentiation circuit 141, and the variable resistor 145C adjusts the output cane of the offset adjustment circuit 144.

Reference numeral 142 denotes an actual speed generation circuit, which amplifies and integrates the sum signal of the level-adjusted differential speed Vps, the current speed IC, and the offset I signal to generate the actual speed Vr. In the actual speed generation circuit 142, 142a is an amplifier, 142b
142C is an integrating resistor, and 142C is an integrating capacitor, and the time constant of both defines the band of the actual speed generating circuit 142, that is, the speed signal generating circuit 14.

In this configuration, the seventh
A position signal Ps shown in FIG. The position signal Ps has a waveform that crosses zero every time the magnetic head passes a track. Differential circuit 1
41 pulverizes this position signal PS to generate a differential velocity Vps shown in FIG. 7(b). This differential velocity Vps is
Each maximum point of the position signal Ps becomes a zero value, each zero cross point becomes a peak value, and the envelope of the peak point gives the actual speed Vr of the servo target 11 (magnetic head).

When only the differential velocity Vps generated from the differentiating circuit 141 is added to the actual velocity generating circuit 142, it is integrated and the differential velocity Vps is
An envelope of ps is obtained. In this case, good envelope characteristics can be obtained where the peak interval of the differential speed Vps is narrow, that is, where the speed is fast, but good envelope characteristics are obtained where the peak interval is wide, that is, where the speed is slow (seek start and end period). Line characteristics cannot be obtained. A current signal ic is added to correct this shift in envelope characteristic.

From the servo target drive circuit 17, a current signal IC shown in FIG. 7 tc+ is amplified by an amplifier 143 and added to the differential speed Vps. Since the current signal ic is similar to the VCM current IC supplied to the target to be erected, the above-mentioned envelope deviation can be effectively corrected.

The actual speed generation circuit 142 has a differential speed Vps and a current signal i.
By integrating and amplifying the sum signal of c and the offset correction signal, the actual speed Vr having the smooth characteristics shown in FIG. 7 Fdl is obtained.
will occur. In order to generate an accurate actual speed Vr, the output canes of the current signal ic, the differential speed ps, and the offset correction signal are initialized by the variable resistors 145a to 45c.

[Problem to be solved by the invention]

The frequency band of the speed signal generating circuit 14 in the original S-H circuit is constant regardless of the seek difference amount. The band of the speed signal generating circuit 14 is defined by the band of the actual speed generating circuit 142, that is, the time constant of the integrating resistor 142b and the capacitor 142C.

Therefore, if vibration occurs during seek acceleration control due to mechanical resonance of the servo target 11, as shown in FIG.
As shown in the figure, the position signal Ps has a waveform on which vibrations are superimposed. When the amount of movement of the servo target 11 (magnetic head), that is, the amount of seek difference is large, the acceleration period and acceleration VCM current Ic become large, which tends to cause vibration.

When vibration occurs in the position signal Ps in this way, as shown in Fig. 7 (
As shown in fl, vibrations also occur in the differential velocity Vps, and vibrations also occur in the actual velocity Vr generated by the actual velocity generating circuit 142 (FIG. 7(g)).

In response to this vibrating actual speed Vr, vibration occurs in the speed error signal Δ■ generated by the speed error generation circuit 15, so that the VCM current 1c generated by the servo target drive circuit 17
Vibration also occurs (Fig. 7 (h)).

As a result, the vibration of the servo target 11 is amplified, loop resonance occurs, and the seek operation is no longer performed normally.

Such loop resonance is more likely to occur as the seek difference amount increases, but in order to prevent this, it is recommended to limit the band of one or both of the speed signal generation circuit 14 and the speed error creation circuit 15 to suppress the vibration component. If this is the case, the speed control time becomes long, and a problem arises in that high-speed seek, especially high-speed seek with a small difference amount such as 1-difference seek, becomes difficult. These problems are common to conventional servo circuits other than the original servo circuit.

The present invention provides an improved servo circuit that effectively prevents the occurrence of loop resonance during seek control regardless of the size of the seek difference amount, and also enables stable high-speed seek even when the difference amount is small. The purpose of this invention is to provide a speed signal generation circuit.

Corresponds to the raw circuit 14, but to distinguish it from this, the following r
It will be shown as 14AJ.

In the speed signal generation circuit 14A, 140 is a band variable circuit that changes the band of the speed signal generation circuit 14A in accordance with the seek difference amount.

As shown in FIG. 2 (a+), when the seek difference amount is small, the frequency f31 is set close to the resonance point f2 of the servo target 11, and as the seek difference amount increases, the frequency f3□ is set lower than the resonance point f2. ,...f3.
, is set to .

[Means to solve the problem]

The means adopted by the present invention to solve the above-mentioned problems are as follows:
This will be explained with reference to FIG. FIG. 1 is a block diagram showing the basic configuration of the present invention.

In FIG. 1, 14A is a speed signal generation circuit, which generates the actual speed Vr of the servo target based on a position signal Ps from a position signal demodulation circuit (not shown). Speed signal generation in the servo circuit shown in FIG. 4 [Operation] The operation of the present invention will be explained with reference to the operation characteristic diagrams shown in FIG. 2.

Before the start of the seek operation, the speed signal generation circuit 144 and the band variable circuit 140 change the band in accordance with the seek difference amount. As shown in FIG. 2 fa), the larger the seek difference amount, the narrower the band is set.

The speed signal generation circuit 14A generates the actual speed Vr of the servo target based on the position signal Ps. The actual velocity Vr is created, for example, by differentiating the position signal Ps to generate a differential velocity Vps, and then integrating (smoothing) the differential signal Vps.

1 In the case of a small difference amount such as a difference seek, the band of the speed error generation circuit is set wide as explained in FIG. 4, but the band of the speed signal generation circuit 14A is correspondingly set wide. Since this is set, the speed control time is shortened and high-speed seek can be performed. In the case of a small difference amount, the generated vibration frequency also becomes high, so even if the bands of the speed signal generation circuit 14A and speed error creation circuit are widened, the vibration component is effectively suppressed and loop resonance is prevented from occurring. be able to.

When the seek difference amount is large, the speed signal generation circuit 14. Since the band of A becomes narrow, even if vibration occurs in the position signal Ps due to mechanical vibration generated in the servo target as shown in Fig. 2(b), the output actual speed Vr
In this case, the vibration component is effectively suppressed and does not appear (Fig. 2(d)). Therefore, occurrence of loop resonance is prevented and stable shift control can be performed.

When the band of the speed signal generation circuit 14A is narrowed, the time constant of the speed signal generation circuit 14A increases, so the speed control time increases, but since the overall speed control time is long, the rate of increase is small, and the seek difference increases. The increase in speed control time in quantity is not a problem in practice.

As described above, since the band of the speed signal generation circuit is changed in accordance with the seek difference amount, the occurrence of loop resonance during seek control can be effectively prevented regardless of the size of the seek difference amount. In addition, even in the case of a small seek difference such as 1 difference, high-speed seek can be performed stably.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. 3 is a block diagram showing the configuration of one embodiment of the speed signal generating circuit of the present invention. Each operating characteristic diagram in FIG. 2 is also used to explain the operation of this embodiment.

(A) Configuration of Embodiment In FIG. 1, the speed signal generating circuit 14A and the variable band circuit 140 are as described in FIG.

Further, regarding other configurations, those corresponding to the configuration of the original servo circuit shown in FIG. 4 are given the same reference numerals.

Of course, 11 is the servo target, and 12 is the position signal P.
This is a position signal demodulation circuit that generates s.

13 is a target speed generation circuit that generates the target speed Vc, and 15 is a speed error signal Δ from the speed error between this target speed c and the actual speed Vr generated by the speed signal generation circuit 14A.
This is a speed error creation circuit that generates V.

16 is a position error generation circuit that generates a position error signal P based on the position signal Ps and the current signal ic.

Reference numeral 17 is a servo target drive circuit, which amplifies the power of the speed error signal Δ■ during speed (coarse) control and the position error signal ΔP during position (fine) control, and generates a VCM current that drives the servo target 11. (2) It generates a current signal c and supplies it to the servo target 1], and detects a VCM current Ic to generate a current signal ic.

18 is a main control unit that supplies band switching signals BCX to CX to the variable band circuit 140 of the speed signal generation circuit 14A, and also sends necessary control signals to each circuit to control the overall seek operation of the servo circuit. Control.

Reference numeral 19 denotes an acceleration detection circuit, which detects V in the speed error signal generated by the speed error creation circuit 15, and changes the band of the speed error creation circuit 15 between acceleration and deceleration in accordance with the seek difference amount. Generates medium signal SKA.

Next, in the speed signal generation circuit 14A, 142 is an actual speed generation circuit. In this actual speed generation circuit 142, 142a is an amplifier such as an operational amplifier;
b is an integration resistor, and 142C is an integration capacitor. 142d is offset resistor 1 to compensation resistor of amplifier 142a.

144 is an offset adjustment circuit that adjusts the offset of the actual speed Vr. 145a, 145b and 145c
is the differential circuit 141. This is a variable resistor for adjusting each cane of the amplifier 143 and the offset adjustment circuit 144.

In the case of the present invention, the capacitance of the integrating capacitor 142C may be a small capacitance required for the minimum seek difference amount (1 difference).

In the variable band circuit 140, 1461 to 146o,
This is a capacitor for band adjustment. 147-147o are corresponding capacitors 146. ~146n in series, and receives the band switching signal BC from the main control unit 18.
It is turned on and off by X, ~BCXn.

(B) Operation of the embodiment In the servo circuit shown in FIG. 3, the speed signal generation circuit 1.4
The operation of each circuit other than the actual speed Vr generation operation of A and the overall seek operation are the same as each circuit and the overall seek operation of the original servo circuit in FIG. 4, so the operation of the speed signal generation circuit 14A will be described below. I will mainly explain.

Before starting the seek operation, the main control unit 18 turns on the band switching signal BCX8 in accordance with the seek difference amount.

Upon receiving this band switching signal BCX, the variable band circuit 140 of the speed signal generating circuit 14A switches the corresponding switch I.
47. Turn on. This causes capacitor 146.
is connected in parallel with the resistor 142b along with the capacitor 142C, so the band of the actual speed generating circuit 142, that is, the speed signal generating circuit 14A is set to become narrower as the seek difference amount increases, as shown in FIG. 2(a). be done.

Further, the offset adjustment circuit 144 generates an offset correction signal that adjusts the offset of the actual speed Vr generated by the speed signal generation circuit 14A to zero. Furthermore, the differentiating circuit 141 .
Each of the variable resistors 146a to 146c corresponding to the output gains of the amplifier 143 and the offset adjustment circuit 144 is initialized.

When a seek operation is started, the differentiating circuit 141 differentiates the position signal PS input from the position signal demodulating circuit 12, and
Generate differential signal Vps (Fig. 2 (b), (C))
. Note that FIGS. 2(b) and 2(C) show a case where vibration is present on the position signal Ps and the differential signal Vps.

On the other hand, the amplifier 143 amplifies the current signal IC generated from the servo target 11.

The actual speed generation circuit 142 includes variable resistors 145a to 145c.
The differential velocity Vps current signal ic whose level is adjusted by
and the offset correction signal are amplified and integrated to obtain the actual speed Vr.
Create. Actual speed generation circuit 142 is a band variable circuit]
Since the band is limited by /IQ, the differential speed Vps
Even if vibration exists in the actual speed Vr that is output, this vibration component is suppressed and does not appear (Fig.
dl).

Therefore, based on the speed error between the actual speed Vr and the target speed Vc from the target speed generation circuit 13, the speed error signal Δ■ generated by the speed fluctuation generation circuit 15 and the CM current generated by the target drive circuit 17 Also in 1c, the vibration component is suppressed and does not appear.

As a result, even if mechanical vibrations occasionally occur in the servo target 11 at the start of a seek, loop resonance can be prevented from occurring and high-speed seek can be performed stably.

Although one embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this embodiment.

For example, the variable band circuit 140 may be configured as a filter and inserted into the output side or the input side of the actual speed generation circuit 142, and the band may be variably controlled in accordance with the seek difference amount.

Further, in the variable band circuit 140 of FIG. 3, a desired capacitance may be obtained by combining a plurality of capacitors. With this, it is possible to generate a desired capacitor capacity corresponding to each seek difference amount using a small number of capacitors.

It goes without saying that the speed signal generating circuit of the present invention can also be applied to servo circuits other than the original servo circuit shown in FIG.

〔Effect of the invention〕

As explained above, in the present invention, the band of the speed signal generation circuit is changed in accordance with the seek difference amount, so that L-J loop resonance occurs during seek control regardless of the size of the seek difference amount. can be effectively prevented from occurring.

Thereby, even in the case of a small seek difference amount such as 1 difference, high-speed seek can be performed stably.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the basic configuration of the present invention, FIG. 2 is an explanatory diagram of each operating characteristic of the speed signal generation circuit of the present invention, and FIG. 3 is an explanatory diagram of the configuration of an embodiment of the present invention. , FIG. 4 is an explanatory diagram of the configuration of the original servo circuit, FIG. 5 is an explanatory diagram of each operating characteristic of the original servo circuit, and FIG. 6 is a configuration of the speed signal generation circuit of the original servo circuit. FIG. 7 is an explanatory diagram of operating waveforms of the speed signal generation circuit of the original servo circuit. In FIGS. 1 and 3, 11... servo target, 12... position signal demodulation circuit,
DESCRIPTION OF SYMBOLS 13... Target speed generation circuit, 14Δ... Speed signal generation circuit, 140... Bandwidth variable circuit, 141... Differentiation circuit, 142... Actual speed generation circuit, 143... Amplifier, 15. ... Speed error creation circuit, 16... Position error creation circuit, 17... Servo target drive circuit, 18.
...Main control section, 19...Acceleration detection circuit.

Claims (1)

[Scope of Claims] 1. A speed that is provided in a servo circuit that controls the speed of a servo target based on a speed error between its target speed and actual speed, and that generates the actual speed of the servo target based on a position signal of the servo target. In the signal generation circuit (14A), a speed signal generation circuit (14A) is generated corresponding to the seek differential amount.
4B) A speed signal generation circuit for a servo circuit, characterized in that a variable band circuit (140) for changing the band is provided. 2. Differentiator circuit (14) that differentiates the position signal to generate velocity
1), an actual speed generation circuit (142) that generates an actual speed based on the differential signal, and a variable band circuit (140) that changes the band of the actual speed generation circuit (142) in accordance with the seek difference amount. Claim 1 characterized by comprising:
A speed signal generation circuit for the servo circuit described.