JPS62120677A - Floppy disk servo device - Google Patents

Abstract

PURPOSE:To carry a step motor with fine pitches independently of carrying pitches determined from the mechanical structure of the step motor by adding a step motor fine pitch carrying circuit to the step motor and connecting a 2nd component sine wave digital filter in series to a circular loop of a magnetic head positioning control system. CONSTITUTION:Receiving a position error signal (a), an output (h) from an integrator 1 and an output (c) from the 2nd component sine wave digital filter 2, a stabilized digital filter 3 calculates a balance point address value (u) for the two-phase linear step motor 5 and outputs the address value (u) to the fine pitch carrying circuit 4 for a sampling time T after DELTA time in the sampling time T. The circuit 4 makes currents d, d' corresponding to the output value (u) flow into respective phases of the step motor 5 to change the balance point of the step motor 5, move the step motor 5 and position the magnetic head on a data track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head positioning control device for a floppy disk file using a sector servo method and a rotational speed control device for a spindle motor.

[Prior art]

In a floppy disk drive (FDD) device, a step motor is used as an actuator for positioning a magnetic head because of the simplification of the servo mechanism, the size of the device, and cost considerations.

However, as the pitch between data tracks on magnetic disks becomes narrower due to miniaturization and increase in capacity, the eccentricity of the data tracks can no longer be ignored. Efforts are being made to improve accuracy.

As is well known, the sector servo method divides the data surface of a magnetic disk into several sectors, and by writing track position information at the beginning of each sector, track position information is recorded at each sampling time determined by the number of sectors and the rotation speed of the magnetic disk. This method uses feedback control to position the magnetic head.

Conventionally, in feedback control using a sector servo system in an FDD device, as disclosed in Japanese Patent Laid-Open No. 151613/1982, a magnetic head is moved by a step motor at a rate of one step per sector according to track position information obtained from the beginning of the sector. Accordingly, a method is adopted in which the material is fed in the inner circumferential direction or the outer circumferential direction.

On the other hand, regarding a spindle motor that rotates a disk, a method is used in which rotational speed is controlled by a phase locked loop (PLL) method using a position detector such as an encoder.

[Problem that the invention seeks to solve]

In the magnetic head positioning method described above, the data track tracking error of the magnetic head is approximately equal to the magnetic head feeding pitch determined by the maximum eccentricity per sector of the data track, so unless the number of sectors is increased, the data There is a problem in that it is difficult to increase the track pitch density. Furthermore, since the dynamic characteristics of a step motor have spring-mass characteristics, positioning by step feeding causes the magnetic head to vibrate, making it difficult to perform high-precision positioning.

Furthermore, in order to control the rotational speed of the spindle motor, it was necessary to have a position detector such as an encoder.

The purpose of the present invention is to compensate for the vibrational characteristics of a step motor, and to enable a magnetic head to follow an eccentric data track with high precision even at a low sampling frequency. An object of the present invention is to provide a floppy disk servo device that does not require a position detector such as the above.

[Means for solving problems]

The present invention provides a position error detection means driven by a link pulse signal, which obtains a position error signal indicating a position error indicating a difference between a target position to be followed by a magnetic head and the position of the magnetic head at regular sampling times. A floppy disk servo device in a floppy disk drive device comprising: a step motor for driving the magnetic head; an integrating means for integrating the position error signal at each sampling time; a digital filter that generates a sine wave having the same frequency as a second frequency component among the fluctuation components of the target position in response to an impulse input; and sampling the output of the digital filter, the position error signal, and the output of the integrating means. a stabilizing digital filter that receives input at each time; a memory element that outputs excitation current values to each phase of the step motor according to the output of the stabilizing digital filter; a first control means for controlling the positioning of a magnetic head, comprising a step motor micro-feed circuit including an amplifier that applies a current through a low-pass filter after a predetermined sampling time;
a first timer that starts and stops in response to the sync pulse signal; and a first timer that starts and stops in response to the sync pulse signal;
a second timer that stops when the timer starts and starts when the timer stops; storage means that stores a reference timer value; and an output value of the first or second timer and the reference timer value. and an amplifier that receives the output value of the subtracter and outputs a drive voltage for driving the spindle motor of the floppy disk drive device, and controls the rotational speed of the spindle motor. It is characterized by comprising: a second control means;

[Effect]

In FDD devices, step motors are used as actuators for positioning the magnetic head due to cost and size considerations, but in order to promote miniaturization and increase in capacity, more accurate step motor positioning is required. . By memorizing the relationship between the excitation current to each phase of the step motor and the position of the equilibrium point, the micro feed circuit can perform micro positioning of the step motor, regardless of the feed pinch determined by the mechanical structure of the step motor. is possible.

Furthermore, with the sector servo method in FDD devices, the number of sectors and the rotational speed of the magnetic disk cannot be increased very much.
Therefore, the sampling frequency does not necessarily become high.

In order to make the magnetic head follow the eccentric data track under such an environment, eccentricity is the dominant mode.

A second component sine wave digital filter that generates a sine wave with a frequency equal to twice the rotational frequency of the magnetic disk is inserted in series in the first loop of the magnetic head positioning control system to improve the steady tracking characteristics of the magnetic head. As a result, it is possible to reduce the positional error between the magnetic head and the data track position.

On the other hand, track position information written at the beginning of a sector usually includes a signal to distinguish between data and position information.
That is, a sync pulse signal is included, and this signal opens the gate of the position error detection means to detect the position error. Therefore, by counting the intervals of the sync pulse signals using a timer, the rotational speed of the spindle motor can be detected without using an encoder, and feedback control of the rotational speed can be performed.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

However, in the following description, signal names will be represented by the same symbols as signal values.

FIG. 1 is a block diagram showing the configuration of a floppy disk servo device that controls the positioning of a magnetic head and the rotational speed of a spindle motor according to an embodiment of the present invention. First, positioning control of the magnetic head will be explained.

When the sampling time is T, the position error detection means 1 is detected by the sync pulse signal 1 every sampling time T.
2 is driven, and the position information signal ε read by the magnetic head 6 is sent from the position error detection means 12 as a position 1 error signal indicating the difference between the position of the magnetic head 6 and the target data track device to be tracked by the magnetic head 6. It is output as a. The position error signal a is input to the integrator 1 and the stabilizing digital filter 3 at every sampling time T.

The integrator 1 integrates the position error a at each sampling time, and outputs the integrated value to the second component sine wave digital filter 2 and the stabilizing digital filter 3 during the sampling time 1.

The second component sine wave digital filter 2 is a digital filter that generates, in response to an impulse input, a sine wave having a frequency equal to the second frequency component of the fluctuation component of the target value signal to be followed by the magnetic hept 6.

The stabilizing digital filter 3 receives the output of the position error signal a1 from the integrator 1 and the output C from the second component sine wave digital filter 2, calculates the equilibrium point address value U of the two-phase linear step motor 5, and performs minute feed. The signal is outputted to the circuit 4 for sampling time 1 after Δ time of sampling time T, that is, at time (T+Δ). Δ is a delay time corresponding to the calculation time of the stabilizing digital filter 3.

The minute feed circuit 4 receives the output value U of the stabilizing digital filter 3 and sends the output value U of the stabilizing digital filter 3 to each phase (phase A and phase B) of the two-phase linear step motor 5.
Currents d and d' corresponding to the currents are applied to change the equilibrium point of the two-phase linear step motor 5, and the two-phase linear step motor 5 is moved to position the magnetic head 6 on the data track. The position error a between the position X of the magnetic head 6 and the target track position to be followed by the magnetic head 6 is detected again at the next sampling time and inputted to the integrator 1 and the stabilizing digital filter 3, thereby forming a feedback loop. configured. Here, the sampling time T1 and the delay time Δ are managed by a timer.

FIG. 2 is a block diagram showing an example of the configuration of the minute feed circuit 4. As shown in FIG. The minute feed circuit 4 receives an externally applied equilibrium point address value U of the two-phase linear step motor 5, and is a ROM (read-only) that outputs excitation current values to be applied to each of the A and B phases of the two-phase linear step motor. D/A converts digital signals, which are the output values e and e' of memory) 7.7' and ROM7.7', into analog signals.
Output signal f of converter 8°8' and D/A converter 8.8'
, f, and the A phase of the two-phase linear step motor 5 according to the outputs g and g' of the low-pass filters 9 and 9'. and an amplifier 10.10' which causes currents d and d' to flow in the B phase.

The two-phase linear step motor 5 has its equilibrium point at A
By appropriately combining the phase current value d and the B-phase current value d', the feed pitch can be arbitrarily set regardless of the feed pitch determined from the mechanical structure of the two-phase linear step motor 5.

In other words, when a certain amount of current is passed through each of the A-phase and B-phase, there is always an equilibrium point depending on the combination of the current values, and the position of this equilibrium point depends only on the excitation current of the A-phase and B-phase. It is unrelated to the feed pitch determined by the mechanical structure.

Therefore, when the equilibrium point position due to a certain combination of currents is set as a reference address (address value 0), the amount of deviation from that point can be taken as the equilibrium point address of the linear step motor, and the above-mentioned ROM7 and 7' The combination of current values corresponding to this equilibrium point address is stored. However, the combination of the A-phase current value and the B-phase current value is set so that the maximum static thrust is constant. for example,
When the feed pitch of the two-phase linear step motor 5 is λ, the equilibrium point position of the two-phase linear step motor 5 when a current of +0.1 ampere is applied to both the A phase and B phase is set as the reference address, and furthermore, this If the maximum static thrust at that time is the standard maximum static thrust, if the position of the equilibrium point is from the standard address to λ/8, ROM7 has +0.1 ampere (address 0) to 0.0 ampere (address λ/8).
The values for passing a current up to +0.1 ampere (address 0) to +0.1 x σ ampere (address λ/8) to the B phase are sequentially stored in ROM7' at the equilibrium point. It is stored according to the address.

Figure 3 shows this situation, with a reference address (address value 0) determined by a certain combination of currents and equilibrium point addresses u, u, which are deviations from that point.
It shows the static thrust characteristics at 'u'. Furthermore, the position X of the two-phase linear step motor 5 (magnetic head 6) is similarly given as a positional deviation from the reference address.

FIG. 4 is a circuit diagram showing a specific example of the configuration of the low-pass filters 9, 9'. The low-pass filter in FIG. 4 has a second-order transfer function Gj! shown below. It is represented by p(S).

However, S is a Laplace transform operator.

The following relationship exists between equation (1) and the circuit constants shown in FIG.

ζ=c2・(R1+R2)/(2・r π] [Seal also)(
3) As described above, the minute feed circuit allows the position of the equilibrium point of the two-phase linear step motor 5 to be arbitrarily selected regardless of the feed pitch determined from the mechanical structure.

When the minute feed circuit 4 is connected to the two-phase linear step motor 5, as shown in FIG. ) and the position X is expressed by equation (4).

M★+kx=ku (
4) Here, M is the mass of the movable part driven by the two-phase linear step motor 5, k is a constant determined by the feed pitch λ of the two-phase linear step motor 5 and the maximum static thrust F, and Equation (5) It is represented by Also, my father is X
It is the second derivative with respect to time, that is, the acceleration α.

In a system whose input is the equilibrium point address value U of the two-phase linear step motor 5 and whose output is the position X of the magnetic head 6, as shown in FIG. Add the dead time, t=N
Focusing on the sampling time of T (N=0.1, 2°...), and deriving the state equation at discrete time values, we get (6
) is as follows. In FIG. 5, V is the input to the dead time 11.

X ((N+1)T) =A −X(NT)+ b −
v (NT) (6-a) Y (NT) = C-X (NT)
(6-b) Here, X (NT) is a state vector, Y (NT) is an output vector, and is given by the following equation.

X (NT) = [X (NT), β(NT)
, u (NT) ) ”Y(NT) = [x(NT)
, u(NT)) "Here, β represents the speed of the magnetic head 6.

Furthermore, each coefficient matrix in equation (6) has the following structure.

However, exp(·) is a matrix exponential function.

The system expressed by equation (6) is controllable and observable, and has an observability index of 2.

FIG. 6 is a block diagram showing the function of the integrator using Z-transform operator 2. z-1 is a shift register that operates at every sampling time T, integrates the position error signal a at every sampling time, and outputs the integration result for every sampling time T.

FIG. 7 is a block diagram showing an example of the configuration of the second component sine wave digital filter 2 described using the Z-transform operator Z. In FIG. 7, ml, m2. m3゜m4.
m5. m6 is a real constant. Further, CI and C2 represent the outputs of the second component sine wave digital filter. FD
Since the magnetic disk sheet in the D device deforms into an elliptical shape due to changes in temperature and humidity, the eccentric mode of the data track appears at a frequency approximately twice the rotational frequency of the magnetic disk. That is, the tracking control system for the magnetic head 6 must have sufficient tracking accuracy for the target value signal that fluctuates at a frequency approximately twice the rotational frequency of the magnetic disk. One way to do this is to widen the bandwidth of the control system, but with the sector servo method in FDD devices, the number of sectors and the rotational speed of the magnetic disk cannot be set very large, so the sampling frequency cannot be set that high. However, the bandwidth of the control system cannot be widened.

The second component sine wave digital filter 2 is a digital filter added for the purpose of making the magnetic heald 6 follow the eccentricity of the data track with sufficient accuracy even when the sampling frequency is low.

In FIG. 7, the pulse transfer function cs from the integrator output to the output C1 of the second component sine wave digital filter 2
+r and (z) are as shown in equation (7).

For example, if the data track eccentric mode is 10Hz and the sampling time T is 6m5ec, S2
By discretizing +3948 with sampling time T, ml
, =2. =3. =4. =5. =6 becomes as follows. However, t represents time.

ml = 1.7788 Xl0-5. =2 =5.
8590 x 10-3m3 =5.8590X10-
', m4=0.92985゜m5=0.92985.
m6=-23,10706 The stability of the control system will be described later, but it is assumed that the control system has now been stabilized.

At this time, the pulse transfer function W(z) from the target position to be tracked by the magnetic head 6 to the position error a is expressed by the first cycle pulse transfer function of equation (7) and the pulse transfer function of the integrator 1/(z-
Since it includes 1), it always has the following form.

Here, δ(Z) is a σ-th real coefficient polynomial whose roots of δ(Z)=O are all within the unit circle of one plane of Z, and r
(z) is a real coefficient polynomial of (σ-3) order.

Based on equation (8), the final value theorem of Z-transformation, and the fact that the eccentricity of the data track occurs at a frequency twice the rotational frequency of the magnetic disk, the position error a is equal to j2im a(t) and z − It can be seen that the magnetic head follows the data track with sufficient tracking accuracy. Here, K is a suitable real constant.

FIG. 8 shows an example of the configuration of the stabilizing digital filter 3. Since the system expressed by the above equation (6) is controllable and observable, and the observability index is 2, the magnetic head positioning control system can be stabilized by the first-order stabilizing digital filter. In Figure 8, I! 1,12. β3.
β4. β5. N6. β7 is a real constant, and by selecting these appropriately, the denominator polynomial δ(Z) in equation (8) can be arbitrarily specified, and although there is a limit due to the sampling frequency, the control system can be controlled within that range. Bandwidth can be set arbitrarily.

The second component sine wave digital filter 2 and stabilizing digital filter 3 shown in FIGS. 7 and 8 are a shift register, an adder, ml, =2. =3. =4. =5
Or β1. ! 2. I13. β4,15. β6,17
It can be configured by a multiplier that multiplies by a constant, a timer that manages the sampling time T and the timing Δ for outputting the equilibrium point address value U to the two-phase linear step motor 5.

Next, referring to FIG. 1, the rotational speed control of the DC brushless smoke 19 for the spindle will be explained.

The sync pulse signal 1 is input to the timer selection circuit 13 at every sampling time T, and the timers 14 and 14' are alternately selected at every sampling time T. timer 14
(14') is activated by the output j (j') of the timer selection circuit, performs a reset operation, starts counting, and
Counting is stopped by the output j'(j) of the timer selection circuit. The stopped timer 14 or 14' outputs the count value p or p' to the subtracter 15. The subtracter 15 calculates the reference timer value ν preset in the reference timer value storage means 16 and the count value p(p) of the timer 14 (14').
'), and the subtraction result q is converted to an analog signal r through the D/A converter 17. Analog signal r is input to amplifier 18. The amplifier 18 multiplies the analog signal r by a predetermined multiplication factor and outputs a speed command voltage μ to the DCC brushless morph driver 1. D.C.
The C brushless morph driver 1 applies a drive current W to the DCC brushless morph 2 in accordance with the speed command voltage μ.

At the next sampling time, timer 14 (14
The output value p(p') of the subtracter 15 is compared with the reference timer value ν, and the output q of the subtracter 15 is sent to the D/Δ converter 17. A feedback loop is configured by inputting the signal to the DCC brushless morph driver 1 through the amplifier 18.

The timer selection circuit 13 can be realized by a flip-flop circuit. Furthermore, the timers 14 and 14' can be realized by an oscillator that generates a clock and a counter. Further, the rotational speed control system of the DC brushless smoke 20 for the spindle can be stabilized by the gain of the amplifier 18.

Naturally, the integrator 1, the second component sine wave digital filter 2 and the stabilizing digital filter 3
As shown in Figs. 7 and 8, the Z-transform operator Z
Since it is expressed by , it is also possible to realize it programmatically by solving the difference equation using a digital computer such as a microprocessor.

Further, the present invention provides a two-phase linear step motor and a DCC motor.
The present invention is not limited to FDD devices that use brushless morphs, but can also be applied to FDD devices that use other step motors and spindle motors.

〔Effect of the invention〕

As explained above, according to the present invention, a minute feed circuit for the step motor is added to the step motor, and a second component sine wave digital filter is inserted in series in the loop of the magnetic head positioning control system. , it is possible to finely feed the step motor regardless of the feed pitch determined by the mechanical structure of the step motor, and it is possible to make the magnetic head follow the target data track with high precision even at low sampling frequencies. It becomes possible to control the rotational speed of the spindle motor without using a position detector such as the above.

[Brief Description of the Drawings] Figure 1 shows a servo for a floppy disk file that controls the positioning of a magnetic head using a two-phase linear step motor and controls the rotational speed of a spindle using a DCC brushless morph according to an embodiment of the present invention. Figure 2 is a block diagram showing an example of the configuration of the minute feed circuit shown in Figure 1. Figure 3 shows the addresses of each equilibrium point of the two-stroke linear step motor and the two points at that point. Figure 4 shows an example of the specific configuration of the low-pass filter shown in Figure 2. Figure 5 shows the static thrust characteristics of a phase linear step motor. Figure 5 shows the static thrust characteristics of a phase linear step motor. A block diagram of a two-phase linear step motor, Figure 6 is a block diagram showing the function of an integrator, and Figure 7 describes an example of the configuration of a second component sine wave digital filter using Z-transform operator 2. FIG. 8 is a block diagram showing an example of the configuration of a stabilizing digital filter using Z-transform operator 2. 1... Arithmetic unit 2... Second component sine wave digital filter 3
... Stabilizing digital filter 4 ... Micro feed circuit 5 ... Two-phase linear step motor 6 ... Magnetic head 7.7'... ROM 8.8'... D/A converter 9. 9'... Low-pass filter 10.10'... Amplifier 11... Dead time 12... Position error detection means 13... Timer selection circuit 14... Timer 15... Subtractor 16... - Reference timer storage means 17...D/A converter 18...Amplifier 19...DCC brushless morph driver 2
... DC brushless smoke a ... Position error signal c, C1, C2 ... Second component sine wave digital filter output d, d' ... Fine feed circuit output e, e' ... ROM output f , f', r... D/A converter output g, g'...
Low-pass filter output h... Integrator output 1... Sink pulse signal, j'... Timer selection circuit output p, p'... Timer output q... Subtractor output u, u', u '... Equilibrium point position of two-phase linear step motor ■... Input to dead time W... DCC brushless morph driver force X ・
... Position μ of magnetic head ... Amplifier output signal ... Reference timer value ε ... Position information signal R1, R2 ... Resistance CI, C2 ... Capacitor 1!1. R2, R3, R4, R5, j26. R7゜ml
, m2. m3. m4. m5. m6 ・
・・・・・・・・・ Real constant Z ・・・ Z-conversion operator agent Patent attorney Yoshiyuki Iwasa Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) A position error detection means driven by a sync pulse signal that obtains a position error signal indicating a position error indicating the difference between the target position to be followed by the magnetic head and the position of the magnetic head at regular sampling times. A floppy disk servo device in a floppy disk drive device comprising: a step motor for driving the magnetic head; an integrating means for integrating the position error signal at each sampling time; a digital filter that generates a sine wave having the same frequency as a second frequency component among the fluctuation components of the target position in response to an impulse input; and sampling the output of the digital filter, the position error signal, and the output of the integrating means. a stabilizing digital filter that receives input at each time; a memory element that outputs excitation current values to each phase of the step motor according to the output of the stabilizing digital filter; a first control means for controlling the positioning of a magnetic head, comprising a step motor micro-feed circuit including an amplifier that applies a current through a low-pass filter after a predetermined sampling time;
a first timer that starts and stops in response to the sync pulse signal; and a first timer that starts and stops in response to the sync pulse signal;
a second timer that stops when the timer starts and starts when the timer stops; storage means that stores a reference timer value; and an output value of the first or second timer and the reference timer value. and an amplifier that receives the output value of the subtracter and outputs a drive voltage for driving the spindle motor of the floppy disk drive device, and controls the rotational speed of the spindle motor. A floppy disk servo device comprising: a second control means;