JPH0786777B2 - Servo circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] A servo circuit for controlling the speed of a servo target based on a speed error between a target speed and an actual speed, in which a rounding of an acceleration current is reduced and a rounding of a deceleration current is set as a difference amount. The target speed generation circuit that generates the target speed according to the movement amount and the servo for the purpose of changing the speed control time according to the difference amount while effectively reducing the vibration and effectively preventing the vibration from occurring. A speed signal creation circuit that creates the actual speed from the target position signal, a speed error creation circuit that creates a speed error signal from the target and actual speed errors, and controls each circuit to perform speed control to decelerate after acceleration. In the servo circuit equipped with the main control unit, an acceleration detection circuit for detecting the acceleration during the speed error signal is provided, and based on the acceleration signal from the circuit, the speed error generation circuit The off frequency with varied and decelerating and accelerating, configured to vary the cutoff frequency during deceleration corresponding to the movement amount.

[Industrial application field]

The present invention relates to a servo circuit that controls a speed of a servo target based on a speed error between a target speed and an actual speed.

In magnetic disk devices and the like, a servo circuit is used for track positioning of a magnetic head.

In such a servo circuit, it is required to shorten the access time by shortening the time required for speed control.

[Conventional technology]

FIG. 9 is an explanatory diagram of a conventional servo circuit, and FIG. 10 is an explanatory diagram of its operation characteristics.

In FIG. 9, 11 is a magnetic disk mechanism as a servo target, and a voice coil motor (hereinafter, referred to as VCM) 1
11, a carriage 113 on which the 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 13a is a target speed generation circuit, which is a main control unit (described later).
A target speed Vc for positioning the magnetic head 112 of the servo target 11 to a target position is generated according to the movement amount instructed from. Reference numeral 13b is an FWD / RVS switching circuit, which responds to a forward (FWD) / reverse (RVS) switching signal of the main control section to obtain a target speed FwVc in the forward direction from the target speed generating circuit 13a.
Alternatively, the target speed RvVc in the reverse direction is switched and output.

Reference numeral 14 denotes a speed signal creation circuit, which creates the actual speed Vr of the magnetic head 112 in the servo target 11 based on the position signal Ps and a current signal ic described later. The current signal ic has a smooth actual speed Vr
Is a correction signal added to generate

Reference numeral 15 is a speed error creating circuit, which is a target speed Vc and an actual speed Vr.
A speed error signal ΔV for controlling the servo target 11 is generated based on the speed error between An amplifier 155 for generating the speed error signal ΔV and a filter 150 are provided. 156
Reference numerals 157 and 157 are coupling resistances with the FWD / RVS switching circuit 13b, 158 is a coupling resistance with the speed signal generating circuit 14, and 159 is a compensation resistance of the AMP 155. The filter 150 is composed of a parallel circuit of a resistor 151 and a capacitor 152, and together with the amplifier 155 and the resistors 156 to 158 form an integral type high-frequency cutoff filter.

16 is a position error creating circuit, which is used for position signal Ps and current signal
A position error for the target position of the servo target 11 is generated from ic and the position control signal ΔP.

Reference numeral 17a denotes a coarse / fine switching section, 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 section. I do. 17b
Is a power amplifier, which amplifies the output of the switching unit 17a and outputs a VCM current Ic for driving the VCM 111 of the servo target 11. 1
7c is a current detection circuit, and V generated by the power amplifier 17b
The CM current Ic is detected and the current signal ic is generated.

18 is a main control unit, which is composed of a microprocessor,
The position of the magnetic head 112 is detected based on the position signal Ps,
The remaining movement amount, that is, the remaining difference amount is output to the target speed generation circuit 13, and FW is output according to the forward / reverse direction.
Generates an O / RVS switching signal and generates a coarse / fine switching signal near the target position.

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.

By the way, the frequency characteristic of the servo target 11 is shown in FIG.
As shown in, it has a resonance point f ₂ . The resonance point f ₂ is a torsion resonance point of a servo arm such as the carriage 113 of the servo target 11.

When the frequency of the speed error signal ΔV appears up to a band covering such a resonance point, mechanical vibration in the servo target 11 appears during seek operation, and the floating stability of the magnetic head 112 and after fine switching are performed. Stability improvement cannot be expected.

Therefore, the cutoff frequency f ₁ of the speed error creation circuit 15
Needs to be smaller than the resonance point f ₂ . Therefore, the frequency band of the speed error creating circuit 15 is filtered by the filter 150.
The time constant of the resistor 151 and capacitor 152 of
As shown in FIG. 6B, the cutoff frequency f ₁ is smaller than the resonance point f ₂ . This frequency f ₁ is, for example, f ₂
= 2f _{1 to} 1.5f ₁ are set.

However, in such a conventional servo circuit, in the 1-difference seek that requires high-speed access, the cycle of the speed control period including the acceleration period and the deceleration period is cut off by the speed error detection circuit 15. The frequency becomes close to the frequency f _1, and the VCM current Ic at the time of acceleration, that is, the rising of the acceleration current is blunted by the cutoff frequency, and there is a problem that a sufficient acceleration current cannot be obtained.

That is, the amount of movement of the servo target 11 (the amount of difference)
Position signal and VCM of object 11 when is 1 difference
The change of the current Ic is as shown in FIG. In this case, 1 in 1 difference seek acceleration period and 1 deceleration period
Since the frequency determined by the cycle of VCM current Ic that draws a cycle is close to the cutoff frequency f ₁ , if the cutoff frequency is sufficiently high, the seek current rises quickly as shown by the broken line and sufficient acceleration can be obtained. However, the seek current is blunted as shown by the solid line. Therefore time t ₁
In which can be reached at the target track position is delayed as shown at time t ₂ with a time T becomes to reach the target track position, it is difficult to speed access 1 Difference seek.

It is conceivable that the vibration point f ₂ of the servo target 11 should be raised, but since the servo target 11 is a mechanical system, its resonance point f ₂
It is extremely difficult to raise.

Therefore, the same applicant has proposed a servo circuit improved so as to reduce the dullness during acceleration of the VCM current Ic when the difference amount is small and to shorten the speed control time.

FIG. 7 shows the configuration of this improved servo circuit (hereinafter referred to as the original servo circuit). The original servo circuit shown in FIG. 7 is different from the conventional servo circuit shown in FIG. 9 in that an acceleration detection circuit 19 is newly added and the configuration of the filter 150 of the speed error creating circuit 15 is modified. ing. Below, the speed error detection circuit of the conventional servo circuit
In order to distinguish it from the filter 15 and the filter 150, the speed error detection circuit of the original servo circuit and its filter are shown as 15A and 150A, respectively. Since other configurations are the same as those of the conventional servo circuit in FIG. 9, corresponding configurations have the same reference numerals.

In the filter 150A of FIG. 7, the filter resistor 151
The configuration of the capacitor 152 and the capacitor 152 is the same as that of the filter 150 of the conventional servo circuit, but in the case of the original servo circuit, the switch 153 is provided in series with the capacitor 152 and the acceleration detection circuit is provided.
Controlled by 19. Depending on the type of the servo target 11, vibration may occur if the capacitor 152 is opened during the acceleration control and the filter 150 does not have any capacitor component. Therefore, in the case of such a servo target 11, the generation of vibration is prevented. In order to ensure that the capacitance of the capacitor 125
₀ is connected in parallel.

The acceleration detection circuit 19 detects that the speed error generation circuit 15 is in the acceleration control, and generates the acceleration signal SKA for opening the switch 153 only during the acceleration control.

By this configuration, the switch 153 of the acceleration control period in the filter 150A is configured of only the resistor 151 off (or configuration capacitor 152 ₀ minute capacitance enters the parallel), the speed error generating circuit 15A cutoff frequency is Figure 8 (a) are shown as infinite (no capacitor 152 ₀₎ or FIG. (B) to a higher f ₁ than f ₁ and f ₂ as shown '
It becomes _{(if 0} capacitor 152 is inserted). When shifting to deceleration control, switch 153 turns on and capacitor 1
Since 52 enters in parallel with resistor 151, speed error creating circuit 15A
The cutoff frequency of returns to f ₁ again.

8C and 8D show the characteristics of the VCM current Ic at the time of acceleration and deceleration in the case of the cutoff frequency characteristics of FIGS. 8A and 8B, and the solid line shows the original servo. The characteristics of the circuit are shown, and the broken line shows the characteristics of the conventional servo circuit.

As shown in FIG. 8, according to the original servo circuit, the VCM current Ic at the time of acceleration control, that is, the dullness of the acceleration current is reduced, the acceleration time is shortened, and the speed control time can be shortened.

The power amplifier 17b does not work as a current source during acceleration control,
Since voltage control is performed, a sufficiently large voltage is input so that the power supply voltage is applied to VCM111. For this reason VCM111
The accelerating current supplied to is only unconditionally increased, and is in the same state without servo control. Therefore, even if the cutoff frequency of the speed error creating circuit 15A in the acceleration control stage is set to infinity or a value higher than the resonance point f ₂ , the servo target 11 (mechanical system) is less likely to vibrate. Further, since the cutoff frequency of the speed error creating circuit 15A is returned to a low f ₁ during deceleration, it is possible to prevent the vibration generated in the servo target 11 as a whole.

As described above, according to the original servo circuit, it is possible to reduce the dullness of the acceleration current in the speed control of the seek operation with a small difference amount, shorten the speed control time, and perform stable high-speed seek.

[Problems to be Solved by the Invention]

When speed control (coarse control) is performed to circulate the servo target 11 to the target position, the frequency of the VCM current Ic changes depending on the amount of difference, and the smaller the amount of difference, the higher. Therefore, it is necessary to shorten the speed control time as the difference amount is smaller.

However, in the original servo circuit, the capacity of the filter 150A during deceleration control is constant regardless of the magnitude of the difference amount (the capacitor 152 or the capacitor 152 and the capacitor 152).
152 ₀ parallel). Therefore, VCM current I during deceleration control
_c that is the proportion physician accent deceleration current characteristic becomes greater as smaller Difference amount, there is a disadvantage that can not sufficiently reduce the speed control time. In particular, minute capacity 152 ₀
In the case of arranging in parallel with each other, when the amount of difference is small as in the case of one amount of difference, it is possible to effectively prevent the vibration generated in the servo target 11 and realize an acceleration current characteristic that allows sufficient acceleration current to flow. There is an inconvenience that it is difficult.

The present invention reduces the dullness of the acceleration current in the speed control during the seek operation and the dullness of the deceleration current corresponding to the difference amount, effectively preventing the occurrence of vibrations, and reducing the velocity control time. It is an object of the present invention to provide a servo circuit which is changed according to the amount of change and is capable of performing stable high-speed seek even when the amount of difference is small.

[Means for Solving the Problems]

Means adopted by the present invention to solve the above problems,
A description will be given with reference to FIG. FIG. 1 is a block diagram showing the basic configuration of the present invention.

In FIG. 1, the same components as those of the original servo circuit shown in FIG. 7 are designated by the same reference numerals.

That is, 11 is a servo target, 12 is a position signal demodulation circuit that generates a position signal Ps, 13a is a target speed generation circuit that generates a target speed Vc, and 14 is a speed signal generation that generates an actual speed Vr. Reference numeral 18 is a circuit, reference numeral 18 is a main controller, and reference numeral 19 is an acceleration detection circuit for generating an accelerating signal SKA.

15B is a speed error creating circuit, and has a filter 150B inside.
And generates a speed error signal ΔV for controlling the server target 11 based on the speed error between the target speed Vc and the actual speed Vr. The filter 150B has the original servo circuit as described below.
The speed error creating circuit of the present invention is indicated by 15B because it has a different configuration from the filter 150A of 15A, and is distinguished from the speed error creating circuit of the original servo circuit.

The filter 150B changes the cutoff frequency of the speed error generation circuit 15 between the acceleration control and the deceleration control by the acceleration detection circuit signal SKA from the acceleration detection circuit 19, and
The cutoff frequency during deceleration control is changed according to the difference amount.

[Work]

The servo circuit of FIG. 1 has different operation characteristics of the speed error creating circuit 15B, but its basic servo control operation is common to the servo control operation of the original servo circuit of FIG. 7 or the conventional servo circuit of FIG. Therefore, the operation of the speed error creating circuit 15B will be mainly described below with reference to FIG.

When speed control is started by a command from the main control unit 19,
The target speed generation circuit 13a determines the target speed during acceleration control from the movement amount, that is, the difference amount instructed by the main control unit 18.
Generate FwVc. The speed error generation circuit 15B generates a speed error signal ΔV corresponding to the speed error between the target speed FwVc generated by the target speed generation circuit 13a and the actual speed Vr generated by the speed signal generation circuit 14.

On the other hand, when the acceleration detection circuit 19 detects from the speed error signal ΔV generated by the speed error generation circuit that the speed error generation circuit 15B is in the acceleration control, it generates an in-acceleration signal SKA to generate the speed error generation circuit 15B. Add to.

Filter 150B of speed error generating circuit 15B receives the acceleration in the signal SKA from the acceleration detecting circuit 19 is higher than the resonance point f ₂ infinity or servo target 11 and the cut-off frequency f _10. Thus, the cut-off frequency f ₁₀ of the speed error generating circuit 15B in the acceleration control is higher than the resonance point f ₂ infinity or servo object 11 as shown in FIG. 2 (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.

By doing so, the characteristic of the speed control signal Ic generated by the speed error creating circuit 15B during the acceleration control becomes a sharp characteristic with little rounding, as shown in FIG. The acceleration control can be ended with.

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 13a generates the target speed RvVc during deceleration control. The speed error creation circuit 15B is the target speed generation circuit 1
The target speed RvVc generated by 3a, the speed error signal ΔV corresponding to the speed error of 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 15B enters the deceleration control, the filter 150B of the speed error creating circuit 15B 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 generating circuit 15B during deceleration control is f ₁₁ , f as the difference amount increases as shown in FIG. 2 (A).
Decreases like ₁₂ ... f _1n .

By doing so, the characteristic of the VCM current Ic, that is, the deceleration current generated by the speed error creating circuit 15B during the deceleration control is as shown in FIG. 2 (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 t _n , ... T ₂ , t ₁
To decrease.

As described above, the cutoff frequency of the speed error creation circuit is changed 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. Can be stably short-circuited. 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.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. FIG. 3 is an explanatory diagram of a configuration of an embodiment of the present invention, FIG. 4 is an operation waveform diagram of the same embodiment, FIG. 5 is an explanatory diagram of a speed error generating circuit and its operation waveform of the first embodiment, FIG. 6 is an explanatory diagram of the speed error generating circuit of the second embodiment and its operation waveform.

(A) Configuration of the embodiment In FIG. 3, the servo target 11, the VCM 111, the magnetic head 112,
Carriage 113, magnetic disk 114, position signal demodulation circuit 12,
Target signal generation circuit 13a, FWD / RVS switching circuit 13b, speed signal creation circuit 14, speed error creation circuit 15B, filter 150B, amplifier
155, resistors 156 to 159, position error creating circuit 16, coarse / fine switching section 17a, power amplifier 17b, current detection circuit 17c, main control section 18 and acceleration detection circuit 19 are shown in FIGS.
This is as described with reference to FIGS.

In the acceleration detection circuit 19 of FIG. 3, reference numeral 190 denotes a comparator, which slices the speed error signal ΔV output from the speed error generation circuit 15B into zero volts and outputs a speed slice signal VSL. 191 is an inverting circuit that inverts the velocity slice signal VSL.

192 and 193 are 3-input AND gates, respectively, and the acceleration end signal EA of "high" level only when all 3 inputs are "high" level.
Generates C. The AND gate 192 is a high level AND of the forward movement signal * MvF supplied from the main control unit 18, the capture velocity signal * CVL similarly generated when the actual speed Vr is below a certain level, and the output of the comparator 190. Take The AND gate 193 receives the reverse movement signal * MvR from the main controller 18 and the capture velocity signal c * CVL.
And a high level AND with the output of the inverting circuit 191.

194 is an OR gate, which takes the OR of the acceleration end signal EAC of the AND gates 192 and 193. 195 is an inverting circuit, which is an OR gate 19
Inverts the acceleration end signal EAC of 4 and generates the acceleration end signal * EAC.

Reference numeral 196 is a flip-flop (hereinafter referred to as FF), which is cleared by the access start * ASP from the main control unit 18 and inverted by using the acceleration end signal * EAC as a clock, and * Q
The acceleration signal SKA is generated from the terminal.

FIG. 5 (A) shows the speed error creating circuit 15B and its filter 150B in the first embodiment of the present invention, and FIG. 6 (A) shows the speed error creating circuit in the embodiment of FIG. It shows a circuit 15B and its filter 150B. Filter 150B of FIG. 6 (A), except that the minute capacitance 152 ₀ are juxtaposed, other configurations are FIG. 5 (A)
Filter 150B is the same.

Figure 5 (A) and FIG. 6 in (A), 151 is the resistance of the filter, 152 ₀ -152 _n is a filter capacitor, 153 ₁ ~153 _n is a switch. The capacitor 152 ₁ is
It is connected in series with the switch 153 _1. Capacitor 152 _2-15
2 _n are respectively connected to the corresponding switch 153 ₂ ~153 _n in series, which are connected in parallel with the capacitor 152 _1. Switch 153 _1, during acceleration from the acceleration detecting circuit 19 detects the signal AC
Switched by K. Switch 153 ₂ ~153 _n are respectively switched by the filter switching signal FCX ₂ ~FCX _n issued from the main control unit 18. The main control unit 18 corresponds to the Difference amount to turn on the switch 153 ₂ ~153 _n corresponding turn on one of the filter switching signal FCX ₂ ~FCX _n, a large capacity when the Difference amount greater resistance
151 is connected in parallel, and when the difference amount is small, a small capacitance is connected in parallel to the resistor 151. The number n of capacitors provided in parallel is one or more.

In addition, the capacitor 125 of the filter 150B of FIG.
₀ is set to the smallest possible capacity within the range where vibration does not occur in the servo target 11.

(B) Operation of the first embodiment Since the seek control operation of the servo circuit of FIG. 3 is basically the same as the seek control operation of the servo circuit of FIG. 7 and the conventional servo circuit of FIG. 9, The operation of the first embodiment of the present invention will be described below with reference to FIGS. 4 and 5 focusing on the operations of the speed error creating circuit 15B and the acceleration detecting circuit 19.

(1) Speed control operation during forward movement In the speed control operation during forward movement, the main control unit
18 sends an FWD switching signal instructing the forward side to the FWD / RVS switching circuit 13b and a coarse signal switching signal instructing coarse to the coarse / fine switching section 17a to generate the forward movement amount (difference amount) to generate the target speed. Filter switching signal FC corresponding to the amount of difference sent to circuit 13a
X _i and the forward movement signal * MvF are sent to the acceleration detection circuit 19 and the access start signal * ASP is sent to each circuit to start seek access (FIG. 4, (e), (g),
Fig. 5 (a), (b), (c)).

When the FWD / RVS switching circuit 13b receives the FWD switching signal, it switches to the forward side, and the target speed FwVc in the forward direction generated by the target speed generating circuit 13a is set to the speed error creating circuit 15B.
Supply to. When receiving the coarse switching signal, the coarse / fine switching section 17a switches to the coarse side, and supplies the speed error signal ΔV generated by the speed error creating circuit 15B to the power amplifier 17b.

The target speed generation circuit 13a generates a target speed FwVc in the forward direction from the forward movement amount, and the FWD / RVS switching circuit 13b.
Is supplied to the speed error creating circuit 15B via. The speed signal generation circuit 14 is a position signal generated by the position signal demodulation circuit 12.
The actual speed Vr of the servo target 11 (magnetic head 112) is obtained from Ps and the current signal ic generated by the current detection circuit 17c, and is supplied to the speed error creation circuit 15B.

The speed error creation circuit 15B uses the target speed FwVc and the actual speed V
The speed difference of r is calculated and the corresponding speed error signal ΔV
Is generated (FIG. 4 (a)).

When the seek difference amount is small, the main control unit 18 detects that the speed signal generation circuit 14 has generated the actual speed Vr, generates the capture velocity signal * CVL, and supplies it to the acceleration detection circuit 19. (Fig. 4 (d)).

On the other hand, in the acceleration detection circuit 19, FF196 is cleared by the access start signal * ASP received at the seek access start, and the high level acceleration signal SKA from the * Q terminal is cleared.
Is generated (FIGS. 4 (g), (i), (c), (e) in FIG. 5 (B)).

When this acceleration signal SKA is received, the speed error creation circuit 15B
Switch 153 ₁ of the filter 150B is turned off. Therefore, since the filter 150B has only the resistor 151, the filter 1
The cutoff frequency of 50B and speed error creation circuit 15B is
It becomes infinite as shown in FIG. This allows
The speed error generation circuit 15B generates a speed error signal ΔV having a rapid rising characteristic (FIG. 4 (a)).

The speed error signal ΔV is supplied to the coarse / fine switching section 17a.
To the VCM current Ic
(Acceleration current) and drives VCM111.

On the other hand, the speed error signal ΔV is the comparator of the acceleration detection circuit 19.
Also added to 190. The comparator 190 outputs the speed error signal ΔV
Is sliced to zero volts, and a high level speed slice signal VSL is generated when the speed error signal ΔV is positive (fourth
Figure (c)).

The AND gate 192 generates the high-level acceleration end signal EAC because the input signals * MvF, * CVL, and VSL are all at the high level, and the AND gate 192 generates the inverting circuit 195 through the OR gate 194.
Send to. The inverting circuit 195 inverts the input acceleration end signal EAC and generates a low level acceleration end signal * EAC during the acceleration control period (Figs. 4 (c), (d), (e),
(H), (d) of FIG. 5 (B). In addition, since the reverse movement signal * MvR is low level during forward, AND
Gate 193 does not work.

During the period when the acceleration end signal * EAC is at the low level, that is, during the acceleration control period, the acceleration signal SKA generated from the * Q terminal of FF196 keeps the high level.
The switches 153 ₁ maintained in the OFF state (FIG. 4 (i),
(E) of FIG. 5 (B).

When the actual speed Vr increases due to the acceleration control, the difference from the target speed Vc gradually decreases, and finally the speed error signal ΔV generated by the speed error creating circuit 15B becomes zero (FIG. 4 (a)).

When the speed error signal ΔV becomes zero, the speed slice signal VSL of the comparator 190 becomes low level, so the AND gate 190
AND output also goes low. The acceleration end signal * EAC generated by the inverting circuit 195 in response to this low level AND output
Changes from low level to high level. Using this change point as a clock, the FF196 is inverted, the accelerating signal SKA generated from the * Q terminal changes from high level to low level, and acceleration control ends (Figs. 4 (a), (b),
(H), (i), FIG. 5 (d), (e)).

Due to the above acceleration control, VCM current
c (acceleration current) is VC of servo target 11 from power amplifier 17b
It is supplied to the M111, and acceleration control is promptly performed (FIG. 2 (B), FIG. 4 (b), FIG. 5 (B) (f)).

When the acceleration control ends, the main controller 18 performs deceleration control.
During the deceleration operation, the speed error signal ΔV generated by the speed error creating circuit 15B becomes a negative level below zero. Therefore, the velocity slice signal VSL generated by the comparator 190 becomes low level, and the acceleration end signal EAC generated by the AND gate 192.
Becomes low level, the acceleration end signal * EAC generated by the inverting circuit 195 becomes high level, and the in-acceleration signal SKA generated by FF196 becomes low level. This state is maintained during the period of deceleration control (Figs. 4 (a), (c), (h),
(I), (d) and (e) of FIG. 5 (B).

Accelerating signal SKA switches 153 ₁ filter 150B is at a low level is turned on, further turned the switch 153 _i is turned on corresponding to the filter switching signal FCX _i, the capacitor 151
And 153 _i are connected in parallel with the resistor 151. Accordingly, the cutoff frequency of the filter 150B and the speed error generating circuit 15B is reduced from f ₁₀ to f _1i. In this case, when the amount of difference is large, the capacitors with large capacitance are arranged in parallel to increase the cutoff frequency drop, and when the amount of difference is small, capacitors with small capacitance are arranged in parallel. To reduce the cutoff frequency decrease (FIG. 2 (A)).

As a result, the smaller the difference amount, the less the rounding of the speed error signal ΔV generated by the speed error generation circuit 15B and the VCM current Ic generated by the power amplifier 17b, and the deceleration control time is t _n , ..., T ₂ , t. Reduced as ₁ . Therefore, even in the case of a small difference amount such as one difference amount, speed control can be performed at high speed and stably ((f) in FIGS. 2 (B) and 5 (B)).

When the speed control (coarse control) ends, the main controller 18
Switches from coarse to fine. This allows
Position error creation circuit 16 → Coarse / fine switching section 17a
→ Power amplifier 17b → Servo target 11 → Position signal demodulation circuit 1
2 → Position control (fine control) by the loop of the position error generating circuit 16 is performed in the same manner as the conventional method, but the description of the contents is omitted because it is not necessary for the present invention.

(2) Speed control operation during reverse movement In the speed control operation during reverse movement, the main control unit 18
Sends an RVS switching signal instructing the reverse side to the FWD / RVS switching circuit 13b, sending a coarse switching signal instructing coarse to the coarse / fine switching section 17a, sending a reverse movement amount to the target speed generating circuit 13a, and Filter switching signal FCX _j and reverse movement signal * Mv corresponding to the amount of reference
Send R to the acceleration detection circuit 19 and access start signal * ASP
To each circuit to start seek access (Figs. 4 (f), (g), 5 (a), (b),
(C)).

Upon receiving the RVS switching signal, the FWD / RVS switching circuit 13b switches to the reverse side and supplies the target speed RvVc in the reverse direction generated by the target speed generating circuit 13a to the speed error creating circuit 15B. When the coarse / fine switching unit 17a receives the coarse switching signal, it switches to the coarse side and supplies the speed error signal ΔV generated by the speed error creating circuit 15B to the power amplifier 17b.

The target speed generation circuit 13a generates a target speed RvVc in the reverse direction from the reverse movement amount and supplies it to the speed error creation circuit 15B via the FWD / RVS switching circuit 13b.

The speed signal generation circuit 14 includes a position signal Ps generated by the position signal demodulation circuit 12 and a current signal ic generated by the current detection circuit 17c.
The actual speed Vr of the servo target 11 (the magnetic head 112) is obtained from this and supplied to the speed error creating circuit 15.

The speed error creation circuit 15B uses this target speed RvVc actual speed Vr.
A negative level speed error signal ΔV corresponding to the speed difference is generated (FIG. 4 (a)).

When the seek difference amount is small, the main control unit 18 detects that the speed signal generation circuit 14 has generated the actual speed Vr, generates the capture velocity * CVL, and supplies it to the acceleration detection circuit 19. (FIG. 4 (d)).

On the other hand, in the acceleration detection circuit 19, FF196 is cleared by the access start signal * ASP received at the start of seek access, and a high-level accelerating signal SKA is generated from its * Q terminal (Fig. 4 (g), (i)). ), (C) of FIG.
(E)).

At the time of reverse, the comparator 190 of the acceleration detection circuit 19 generates the speed slice signal VSL of a negative level, so the inverting circuit 191
A high level acceleration signal EAC is generated by the AND gate 193. The acceleration end signal EAC is sent to the inverting circuit 195 through the OR gate 194, and the low level acceleration signal end signal * EAC is generated. At the time of reverse, since * MvF is at a low level, the AND gate 192 does not operate (Figs. 4 (a), (c), (f), (h), and (d) in Fig. 5 (B)). )).

During the period when the acceleration end signal * EAC is at the low level, that is, during the acceleration control period, the acceleration signal SKA generated from the * Q terminal of FF196 keeps the high level.
The switches 153 ₁ maintained in the OFF state (FIG. 4 (i),
FIG. 5 (B) (e).

As a result, the filter 150B and the speed error creating circuit 15B
Has a cutoff frequency of infinity (f ₁₀ ), which has less bluntness, similar to the acceleration control operation during forward movement.
The VCM current Ic is supplied to the VCM 111 for high speed and acceleration control (FIG. 2 (B), FIG. 4 (b), FIG. 5 (B) (f)).

When the acceleration control ends, the main control unit 18 shifts to the deceleration control. During the deceleration operation, the speed error signal ΔV generated by the speed error creating circuit 15B has a positive level. Therefore, the speed slice signal VSL generated by the comparator 190 becomes high level, the acceleration end signal EAC generated by the AND gate 193 becomes low level, and the acceleration end signal * E generated by the rotation circuit 195 is generated.
AC becomes high level, FF196 generates acceleration signal SKA
Goes low. This state is maintained during the period of deceleration control (Figs. 4 (a), (c), (h), (i), (d) and (e) in Fig. 5 (B)).

Accelerating signal SKA switches 153 ₁ filter 150B is at a low level is turned on, further turned the switch 153 _j is turned on corresponding to the filter switching signal FCX _i, capacitor 152 ₁
And 152 _j are connected in parallel with the resistor 151. Thus the cut-off frequency of the filter 150B and speed generating circuit 15B is reduced from 1 ₁₀ to f _1j (FIG. 2 (A)).

Similarly to the deceleration control during forward movement, the smaller the difference amount, the less the speed error signal ΔV generated by the speed error generation circuit 15B and the VCM current Ic generated by the power amplifier 17b, and the less the deceleration control time. Is reduced. Therefore, speed control can be performed at high speed and stably even in the case of a small difference amount such as one difference amount even in reverse (FIG. 2 (B), FIG. 5 (B) (f)). .

(C) Operation of the second embodiment In the second embodiment, the filter 1 of the speed error creating circuit 15B is used.
The filter 150B shown in FIG. 6 is used as 50B.

In the filter 150B of Figure 6, a capacitor 152 ₀ of the minute volume, always parallel to the resistor 151. This limits the filter 150B and the error creating circuit 15 cutoff frequency to a finite frequency f ₁₀ during acceleration control, so V
It is possible to effectively prevent the CM current Ic from vibrating.

Deceleration control, along with capacitors 152 _1, the capacitor 152 _i corresponding to the Difference amount enters in parallel, the capacitance of the capacitor 152 _0, than capacitors 152 ₀ in the filter 150A of the original servo circuit shown in FIG. 7 Can be made smaller. Therefore, in the case of the second embodiment, the rounding of the VCM current Ic during acceleration control is smaller than that in the original servo circuit, so that acceleration control can be performed even faster and more stably than in the case of the original servo circuit. Speed control can be further speeded up.

The acceleration and deceleration control operations during the forward and reverse movements of the second embodiment are the same as those of the first embodiment, so a description thereof will be omitted.

Although each embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this embodiment. For example, in the filter 150B shown in FIGS. 5B and 6, the number of capacitors 152 _i that are in parallel with the capacitor 152 ₁ may be one. Further, a plurality of capacitors 152 _{2 to} 152 _n may be provided, and a capacity corresponding to the difference amount may be realized by combining some of the capacitors therein.

〔The invention's effect〕

As described above, according to the present invention, the following various effects can be obtained.

(1) Since the cutoff frequency of the speed error creating circuit is changed during acceleration control and during deceleration control, and the cutoff frequency during deceleration control is changed according to the difference amount, during acceleration control The acceleration current supplied to the servo target is uniformly reduced, and the rate of the deceleration current during deceleration control is reduced as the difference amount is smaller, so that the speed control time is stable even when the difference amount is small. Can be shortened to

(2) According to the above (1), speed control can be performed quickly and stably even in the case of an extremely small difference amount such as one difference amount, and stable high speed seek can be performed.

[Brief description 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 present invention, FIG. 3 is an explanatory diagram of the configuration of each embodiment of the present invention, and FIG. FIG. 5 is an operation waveform diagram of each embodiment, FIG. 5 is an explanatory diagram of a speed error generating circuit and its operation waveform of the first embodiment of the present invention, and FIG. 6 is a second embodiment of the present invention. FIG. 7 is an explanatory diagram of the speed error generating circuit and its operation waveform, FIG. 7 is an explanatory diagram of the configuration of the original servo circuit, FIG. 8 is an explanatory diagram of each operation characteristic of the original servo circuit, and FIG. 9 is a conventional servo FIG. 10 is an explanatory diagram of a circuit configuration, and FIG. 10 is an explanatory diagram of respective operating characteristics of a conventional servo circuit. 1 and 3, 11 ... Servo object, 12 ... Position signal demodulation circuit, 13a ...
Target speed generation circuit, 13b ... FWD / RVS switching circuit, 14 ... Speed signal creation circuit, 15B ... Speed error creation circuit, 150B ...
... filter, 151 ...... resistors, 152 ₀ -152 _n ...... capacitor, 153 ₁ ~153 _n ...... switch, 16 ...... position error generating circuit, 17a ...... coarse / fine switching section, 17b ...... power amplifier, 17c …… Current detection circuit, 18 …… Main control section.

Claims (3)

[Claims] 1. A target speed generating circuit (13a) for generating a target speed according to a moving amount, and a speed signal generating circuit (14) for generating an actual speed of the servo target (11) based on a position signal indicating the moving position. ), A speed error creating circuit (15B) that creates a speed error signal for controlling the servo target (11) based on the speed error between the target speed and the actual speed, and sets each movement amount and controls each circuit. In a servo circuit equipped with a main control unit (18) that controls the servo target (11) to decelerate after acceleration and position it at the target position, (a) Acceleration from the speed error signal generated by the speed error generation circuit (15B) An acceleration detection circuit (19) for detecting the inside is provided. (B) Based on the acceleration signal from the acceleration detection circuit (19), the cutoff frequency of the speed error creation circuit (15B) can be changed between accelerating and decelerating. Change and move Servo circuit according to claim filter (150B) provided on the speed error generating circuit (15B), that for changing the cutoff frequency during deceleration in response to. 2. A filter (150B) for reducing the cutoff frequency of the speed error generating circuit (15B) to infinity during acceleration and decreasing as the movement amount increases during deceleration. The described servo circuit. 3. A filter (150B) for reducing the cutoff frequency of the speed error creating circuit (15B) to a finite frequency higher than the resonance point of the servo target (11) during acceleration and decreasing as the movement amount increases during deceleration. 3. The method according to claim 1, wherein
The described servo circuit.