JPH087623B2 - Servo circuit speed signal generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A speed signal generating circuit for obtaining an actual speed in a servo circuit that controls the speed of a servo object based on a speed error between a target speed and the actual speed, and relates to a magnitude of a seek difference amount. In order to effectively prevent the occurrence of loop resonance during seek control and to make stable high-speed seek variable even with a small amount of difference, the servo target is set to the speed error between its target speed and actual speed. In the speed signal generation circuit provided in the servo circuit that controls the speed based on the position signal of the servo object, the band of the speed signal generation circuit is changed according to the seek difference amount in the speed signal generation circuit. A band variable circuit is provided.

[Industrial application field]

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

[Conventional technology]

Servo circuits are widely used for track positioning of a magnetic head of a magnetic disk device.

In such a servo circuit, there is a demand for a technique capable of stably positioning even if the speed is increased.

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

In FIG. 4, reference numeral 11 denotes a magnetic disk mechanism as a servo target, a voice coil motor (hereinafter, referred to as VCM) 111, a carriage 113 on which a magnetic head 112 is mounted,
And a magnetic disk 114.

A position signal demodulation circuit 12 demodulates the position signal Ps indicating the moving position of the servo information read from the servo surface of the magnetic disk 114 by the servo head 112.

Reference numeral 13 is a target speed generation circuit, which is a magnetic head 11 of the servo target 11 according to a movement amount instructed by a main control unit (described later).
2 Generate the target velocity Vc for positioning to the target position.

Reference numeral 14 denotes a speed signal generating circuit, which uses the position signal Ps and a current signal ic described later to detect the magnetic head 112 in the servo target 11.
Create the actual speed Vr of. The current signal ic has a smooth actual speed
This is a correction signal added to generate Vr.

Reference numeral 15 is a speed error creating circuit, which internally has a filter 150.
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.

A position error creating circuit 16 creates a position error for 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 switches from speed control of the speed error creating circuit 15 to position control of the position error creating circuit 16 by a coarse (speed control) / fine (position control) switching signal from the main control unit, A process of amplifying each error signal of ΔV or ΔP and outputting a VCM current Ic for driving the VCM 111 of the servo target 11 and a process of detecting the VCM current Ic and generating a current signal ic are performed.

Reference numeral 18 denotes 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 amount to the target speed generation circuit 13, and outputs the vicinity of the target position. Generate coarse / fine switching signal with.

Reference numeral 19 denotes an acceleration detection circuit, which detects the speed error signal ΔV generated by the speed error creating circuit 15 and changes the band of the speed error creating circuit 15 according to the seek difference amount during acceleration and during deceleration. Generate signal SKA.

The servo circuit configured as described above controls the speed to the vicinity of the target position and then switches to position control to perform positioning control at the target position. Since the control operation is the same as the servo control operation of the conventional servo circuit, the operation of the speed error creating circuit 15 will be mainly described below with reference to FIG.

When the speed control is started by the command from the main control unit 18, the target speed generation circuit 13 generates the target speed Vc at the time of acceleration control from the movement amount, that is, the difference amount, instructed by the main control unit 18.

Further, the speed signal generation circuit 14 receives the position signal Ps from the position signal demodulation circuit 12 and the current signal ic from the servo target drive circuit 17, and receives the actual speed Vr of the servo target 11 (magnetic head).
(Details will be described with reference to FIGS. 6 and 7).

The speed error creation circuit 15 is a target speed Vc generated by the target speed generation circuit 13 and an actual speed generated by the speed signal generation circuit 14.
A velocity error signal ΔV corresponding to the velocity error of Vr is generated.

On the other hand, the acceleration detection circuit 19 determines from the speed error signal ΔV generated by the speed error generation circuit 15 that the speed error generation circuit 15
Is detected during acceleration control, the acceleration signal SKA
Is generated and added to the speed error creating circuit 15.

When the filter 150 of the speed error creating circuit 15 receives the accelerating signal SKA from the acceleration detecting circuit 19, its cutoff frequency f ₁₀ becomes infinity or higher than the resonance point f ₂ of the servo target 11. Thus, the cut-off frequency f ₁₀ of the speed error generation circuit 15 in the acceleration control is higher than the resonance point f ₂ infinity or servo object 11 as shown in FIG. 5 (A). The finite high cutoff frequency f _{10 in} this case is set to a high frequency within a range where the acceleration current does not vibrate.

The servo target drive circuit 17 power-amplifies the speed error signal ΔV received from the speed error generation circuit and outputs the servo target 11 of the servo target 11.
While outputting VCM current Ic that accelerates VCM111,
A current signal ic that is a detection current of this VCM current Ic is generated.

By doing so, the speed error generation circuit 15 can generate a VC corresponding to the speed error signal ΔV generated during acceleration control.
As shown in FIG. 5 (B), the characteristic of the M current Ic 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 unit 18 switches to the deceleration control.

When switching to deceleration control by a command from the main control unit 18, the target speed generation circuit 13 generates the target speed Vc at the time of deceleration control. The speed error creating circuit 15 is a target speed generating circuit.
A speed error signal ΔV corresponding to the speed error between the target speed Vc generated by 13 and the actual speed Vr generated by the speed signal generation circuit 14.
Generates (negative).

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

When the speed error creating circuit 15 enters deceleration control, the filter 150 of the speed error creating circuit 15 reduces the cutoff frequency to a frequency lower than the resonance point f ₂ of the servo target 11.
At that time, the cutoff frequency is lowered as the difference amount is increased. As a result, the cutoff frequency of the speed error creating circuit 15 during deceleration control decreases as f ₁₁ , f _12, ... F _{1n as} the difference amount increases, as shown in FIG. 5 (A).

The servo target drive circuit 17 outputs the VCM current Ic for decelerating and driving the VCM 111 by power-amplifying the speed error signal ΔV received from the speed error creating circuit 15, and at the same time, this VCM current Ic
Generates a current signal ic, which is a detection current of.

By doing so, the speed error generation circuit 15 can generate a VC corresponding to the speed error signal ΔV generated during deceleration control.
The characteristic of the M current Ic, that is, the deceleration current, is as shown in FIG. 5 (B). That is, the smaller the difference amount is, the less the rounding of the deceleration characteristic is, and the deceleration control time, that is, the speed control time is reduced as t _n , ... T ₂ , t ₁ .

As described above, the cutoff frequency of the speed error creation circuit is changed between during acceleration control and during deceleration control, and the cutoff frequency during deceleration control is changed according to the difference amount. Sometimes the rounding of the acceleration current supplied to the servo target is uniformly reduced, and the rate of the rounding of the deceleration current during deceleration control is reduced as the difference amount is smaller, so that the speed control time is reduced even when the difference amount is small. It can be shortened stably. 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 stable high-speed seek can be performed.

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

In FIG. 6, reference numeral 141 denotes a differentiating circuit, which is a position signal Ps.
Is differentiated to generate the differential velocity Vps. An amplifier 143 amplifies the current signal ic to a predetermined level.

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

145a to 145c are variable resistors, and the variable resistor 145a is an amplifier.
Adjust the output gain of 143 and adjust the variable resistor 145b to differentiate circuit 141.
Of the offset adjustment circuit 144 is adjusted by the variable resistor 145c.

142 is an actual speed generation circuit, which amplifies and integrates the level-adjusted differential speed Vps, the current speed ic, and the added signal of the offset signal to create the actual speed Vr. Actual speed generation circuit
In 142, 142a is an amplifier, 142b is an integrating resistor, 142
c is a capacitor for integration, and the band of the actual speed generation circuit 142, that is, the speed signal generation circuit 14 is defined by the time constants of both capacitors.

In this configuration, the position signal demodulation circuit 12
The position signal Ps shown in FIG. 9A is applied to the differentiating circuit 141. The position signal Ps has a waveform of zero crossing each time the magnetic head passes a track. The differentiating circuit 141 is
This position signal Ps is finely divided and the differential velocity shown in FIG.
Generate Vps. The differential velocity Vps has a zero value at each maximum point of the position signal Ps and a peak value at each zero cross point, and the envelope of the peak point gives the actual velocity Vr of the servo target 11 (magnetic head).

When only the differential speed Vps generated from the differentiating circuit 141 is added to the actual speed generating circuit 142, the differential speed Vps is integrated and the envelope of the differential speed Vps is obtained. In this case, good envelope characteristics can be obtained at a place where the peak interval of the differential velocity Vps is narrow, that is, at a high velocity, but at a place where the peak interval is wide, that is, at a slow velocity (seek start and end periods), a good envelope characteristic is obtained. Line characteristics cannot be obtained. In order to correct the deviation of this envelope characteristic,
The current signal ic is applied.

From the servo target drive circuit 17, the current signal ic shown in FIG. 7C is amplified by the amplifier 143 and added to the differential speed Vps. The current signal ic is VCM supplied to the servo target
Since it is similar to the current Ic, it is possible to effectively correct the deviation of the envelope described above.

The actual speed generation circuit 142 integrates and amplifies the added signal of the differential speed Vps, the current signal ic, and the offset correction signal to generate the seventh signal.
The actual velocity Vr having the smooth characteristic shown in FIG. In order to generate the accurate actual speed Vr, the variable resistances 145a to 145c are used to generate the current signal ic and the differential speed Vp.
s and the output gain of the offset correction signal are initialized.

[Problems to be Solved by the Invention]

The frequency signal generation circuit 14 in the original servo circuit has a constant frequency band regardless of the seek difference amount. The band of this speed signal generating circuit 14 is the band of the actual speed generating circuit 142, that is, the resistor 142b for integration and the capacitor 1
Specified by the time constant of 42c.

Therefore, when vibration occurs during seek acceleration control due to mechanical resonance of the servo target 11, FIG. 7 (e)
As shown in, the position signal Ps has a waveform in which vibration is superimposed. If the movement amount of the servo target 11 (magnetic head), that is, the seek difference amount is large, the acceleration period and the acceleration VCM are increased.
Since the current Ic becomes large, vibration easily occurs.

When the position signal Ps thus vibrates, the differential velocity Vps also vibrates, as shown in FIG. 7 (f), and the actual velocity Vr generated by the actual velocity generating circuit 142 also vibrates (seventh period). (Figure (g)).

Since the speed error signal ΔV generated by the speed error creating circuit 15 is vibrated in response to the actual speed Vr with this vibration, the VCM current Ic generated by the servo target drive circuit 17 also vibrates (see FIG. 7 ( h)).

As a result, the vibration of the servo target 11 is amplified and loop resonance occurs, and the seek operation cannot be performed normally.

Such loop resonance is more likely to occur as the seek difference amount is larger, but in order to prevent this, try to suppress the vibration component by limiting the band of one or both of the speed signal generation circuit 14 and the speed error generation circuit 15. In this case, the speed control time becomes long, which makes it difficult to perform a high-speed seek, particularly a high-speed seek with a small difference amount such as 1-difference seek. These matters have problems common to conventional servo circuits other than the original servo circuit.

The present invention is an improved servo circuit that effectively prevents the occurrence of loop resonance during seek control regardless of the magnitude of the seek difference amount, and that enables stable high-speed seek even with a small difference amount. It is an object of the present invention to provide a speed signal generation circuit of

[Means for solving the problem]

Means adopted by the present invention to solve the above problems will be described 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 generating circuit, which generates an actual speed Vr of a servo object based on a position signal Ps from a position signal demodulating circuit (not shown). This corresponds to the speed signal generating circuit 14 in the servo circuit of FIG. 4, but will be indicated as "14A" below to distinguish it from this.

In the speed signal generation circuit 14A, 140 is a band variable circuit that changes the band so that it becomes narrow when the amount of seek difference is large and wide when the amount of seek difference is small. As shown in FIG. 2A, when the seek difference amount is small, the frequency f ₃₁ is set to be close to the resonance point f ₂ of the servo target 11, and as the seek difference amount increases, the resonance point f ₂ becomes smaller than the resonance point f _2. It is set to a low frequency f ₃₂ , ... f _3n .

[Action]

The operation of the present invention will be described with reference to the operational characteristic diagrams of FIG.

Before the seek operation is started, the band of the speed signal generation circuit 14A is changed by the band variable circuit 140 according to the seek difference amount. As shown in FIG. 2 (a), 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 object based on the position signal Ps. The actual speed Vr is created, for example, by differentiating the position signal Ps to generate a differential speed Vps, and then integrating (smoothing) the differential signal Vps.

In the case of a small difference amount such as 1 difference seek, the band of the speed error generation circuit is set wide as described in FIG. 4, but the band of the speed signal generation circuit 14A is also set correspondingly wide. As a result, 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 band of the speed signal generation circuit 14A and the speed error generation circuit is widened, the vibration component is effectively suppressed to prevent the occurrence of loop resonance. be able to.

When the amount of seek difference is large, the band of the speed signal generation circuit 14A becomes narrow, so even if the position signal Ps vibrates due to mechanical vibration generated in the servo target as shown in FIG. 2 (b), At the output actual speed Vr, the vibration component is effectively suppressed and does not appear (second
Figure (d)). Therefore, occurrence of loop resonance is prevented, and stable seek 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 the increase rate is small because the overall speed control time is long, and the seek difference Increasing the speed control time in quantity does not really matter.

As described above, since the band of the speed signal generation circuit is changed according to the seek difference amount, it is possible to effectively prevent the occurrence of loop resonance during seek control regardless of the magnitude of the seek difference amount. In addition, it is possible to stably perform high-speed seek even in the case of a small seek difference amount such as one difference.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. 2 and FIG. FIG. 3 is a block diagram showing the configuration of an embodiment of the speed signal generating circuit of the present invention. The operational characteristic diagrams of FIG. 2 are also used for explaining the operation of this embodiment.

(A) Configuration of the embodiment In FIG. 1, a speed signal generation circuit 14A, a band variable circuit
About 140, it is as described in FIG. Further, with respect to other configurations, those corresponding to the configuration of the original servo circuit shown in FIG. 4 are denoted by the same reference numerals.

That is, 11 is a servo target, and 12 is a position signal demodulation circuit that generates a position signal Ps.

13 is a target speed generation circuit that generates a target speed Vc,
Reference numeral 15 is a speed error generation circuit for generating a speed error signal ΔV from the speed error between the target speed Vc and the actual speed Vr generated by the speed signal generation circuit 14A.

Reference numeral 16 is a position error creating circuit that creates a position error signal ΔP based on the position signal Ps and the current signal ic.

Reference numeral 17 denotes a servo target drive circuit, which amplifies the speed error signal ΔV during speed (coarse) control and the position error signal ΔP during position (fine) control to generate a VCM current Ic for driving the servo target 11. Then, the VCM current Ic is detected and a current signal ic is generated while being supplied to the servo target 11.

Reference numeral 18 denotes a main control unit, which supplies the band switching signals BCX _{1 to} CX _n to the band variable circuit 140 of the speed signal generation circuit 14A and sends necessary control signals to each circuit to perform the seek operation of the entire servo circuit. Control.

Reference numeral 19 denotes an acceleration detection circuit, which detects the speed error signal ΔV generated by the speed error creating circuit 15 and changes the band of the speed error creating circuit 15 according to the seek difference amount during acceleration and during deceleration. Generate 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, 142b is a resistor for integration, and 142c is a capacitor for integration. 142d amplifier
The offset compensation resistor of 142a.

Reference numeral 144 is an offset adjusting circuit, which adjusts the offset of the actual speed Vr. 145a, 145b and 145c are differentiating circuits 141,
It is a variable resistor for adjusting each gain of the amplifier 143 and the offset adjusting circuit 144.

In the case of the present invention, the capacitance of the integrating capacitor 142c is the minimum seek difference amount (1 difference).
The one with the small capacity necessary for

In the band variable circuit 140, 146 ₁ to 146 _n is a capacitor for band adjustment. 147 _{1 to} 147 _n are switches provided in series with the corresponding capacitors 146 ₁ to 146 _n , and are turned on / off by the band switching signals BCX _{1 to} BCX _n from the main control unit 18.

(B) Operation of the embodiment In the servo circuit of FIG. 3, the speed signal generating circuit 14A is used.
Since the operation of each circuit other than the actual speed Vr creating operation and the seek operation of the whole are the same as the seek operation of each circuit and the whole of the original servo circuit of FIG. 4, the speed signal generating circuit 14 will be described below.
The operation of A will be mainly described.

Before starting the seek operation, the main control unit 18 turns on the band switching signal BCX _i corresponding to the seek difference amount.

When the band variable circuit 140 of the speed signal generation circuit 14A receives this band switching signal BCX _i , it turns on the corresponding switch 147 _i . As a result, the capacitor 146 _i becomes the capacitor 142c.
Since it goes in parallel with the resistor 142b, the actual speed generator circuit 14
2, that is, the band of the speed signal generation circuit 14A is shown in FIG.
As shown in, the larger the seek difference amount, the narrower it is set.

Further, the offset adjustment circuit 144 includes the speed signal generation circuit 1
An offset correction signal for adjusting the offset of the actual speed Vr generated by 4A to zero is generated. Further, the values of the variable resistors 146a to 146c corresponding to the output gains of the differentiating circuit 141, the amplifier 143, and the offset adjusting circuit 144 are initialized so that the correct actual speed Vr is synthesized.

When the seek operation is started, the differentiating circuit 141 differentiates the position signal Ps input from the position signal demodulating circuit 12 to generate a differential signal Vps (FIGS. 2B and 2C). In addition,
2 (b) and (c), the position signal Ps and the differential signal are shown.
The case where vibration is on Vps is shown.

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

The actual speed generation circuit 142 amplifies and integrates the differential speed Vps, the current signal ic, and the offset correction signal whose levels are adjusted by the variable resistors 145a to 145c to create the actual speed Vr. Since the actual speed generation circuit 142 is band-limited by the band variable circuit 140, even if vibration is present in the differential speed Vps,
This vibration component is suppressed and does not appear in the output actual speed Vr (Figs. 2 (c) and (d)).

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 creation circuit
Speed error signal ΔV generated by 15 and servo target drive circuit
The vibration component is suppressed even in the VCM current Ic generated by 17 and does not appear.

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

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 band variable circuit 140 may have a filter configuration, and may be inserted into the output side or the input side of the actual speed generation circuit 142 to variably control the band in accordance with the seek difference amount.

Further, in the band variable circuit 140 shown in FIG. 3, a desired capacitance may be obtained by combining a plurality of capacitors. As a result, a desired capacitor capacity corresponding to each seek difference amount can be generated with a small number of capacitors.

Of course, the speed signal generating circuit of the present invention can be applied to servo circuits other than the original servo circuit of FIG.

〔The invention's effect〕

As described above, according to the present invention, the band of the speed signal generating circuit is changed according to the seek difference amount. Therefore, the occurrence of loop resonance during seek control is effective regardless of the magnitude of the seek difference amount. Can be prevented.

As a result, it is possible to stably perform high-speed seek even in the case of a small seek difference amount such as one difference.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention, FIG. 2 is an explanatory diagram of each operating characteristic of a speed signal generation circuit of the present invention, and FIG. 3 is an explanatory diagram of a configuration of an embodiment of the present invention. 4, 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, FIG. 6 is an explanatory diagram of the configuration of the speed signal generation circuit of the original servo circuit, FIG. 7 is an explanatory diagram of operation waveforms of the speed signal generation circuit of the original servo circuit. 1 and 3, 11 ... Servo object, 12 ... Position signal demodulation circuit, 13 ... Target speed generation circuit, 14A ... Speed signal generation circuit, 140 ... Band 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 unit, 19 ... Acceleration detection circuit.

Claims (2)

[Claims] 1. A servo circuit for controlling the speed of a servo object based on a speed error between its target speed and actual speed,
In a speed signal generator circuit that generates the actual speed of the servo target based on the position signal of the servo target, the speed signal generation circuit should be narrow when the seek difference amount is large and wide when the seek difference amount is small. A speed signal generating circuit of a servo circuit, characterized in that a band changing means for changing the band of is provided. 2. A differentiating means for differentiating a position signal to generate a speed, an actual speed generating circuit for generating an actual speed based on the differential signal, and a narrower when the seek difference amount is large,
2. A speed signal generating circuit for a servo circuit according to claim 1, further comprising band variable variable means for changing the band of the actual speed generating circuit so as to widen when the seek difference amount is small.