JPH03272065A - Tracking servo-circuit - Google Patents

Abstract

PURPOSE:To improve the servo-characteristic by executing the time division of a proportional error signal and a differential error signal generated from a position error signal corresponding to a head position by a proportional error generating means and a differential error generating means, respectively in order of the differential error signal and the proportional error signal whose influence to a time delay of servo is large and supplying them to an actuator. CONSTITUTION:The circuit is provided with an actuator motor 2 for positioning a head in a prescribed track on a disk, position error detecting means 3 - 5 and 13 for detecting a position of the head to a target track on the disk and generating a position error signal DGPE, a proportional error generating means 14 for multiplying the position error signal DGPE by a first coefficient KP and generating a proportional error signal DGPEP, and a differential error generating means 16 for differentiating the position error signal DGPE, and also, multiplying it by a second coefficient KD and generating a differential error signal DGPED. In such a state the proportional error signal DGPEP and the differential error signal DGPED are subjected to time division in order of the differential error signal DGPED and the proportional error signal DGPEP whose influence to a time delay of servo is large and supplied to the actuator motor 2. In such a way, the servo-characteristic is improved.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Industrial field of application B. Overview of the invention C. Conventional technology (Figures 3 to 5) D. Problems to be solved by the invention (Figures 4 and 5) E! #! Means for Solving the Problem (Fig. 1) 1 Effect (Fig. 1) G Embodiment (Figs. 1 and 2) IT Invention Effect A Industrial Field of Application The present invention relates to a tracking servo circuit, for example. It can be applied to those that position the head of a hard disk drive.

B Summary of the Invention The present invention provides a tracking servo circuit in which a proportional error signal and a differential error signal generated from a position error signal corresponding to the head position are generated by a proportional error generating means and a differential error generating means, respectively, to determine the influence on the time delay of the servo. By time-sharing and supplying the differential error signal and proportional error signal to the actuator in the order of the large differential error signal and proportional error signal, the servo characteristics can be further improved.

C. PRIOR TECHNOLOGY In conventional hard disk drives, a tracking servo circuit designed to process digital signals is used to control an actuator motor that drives an actuator arm on which a magnetic head is arranged. Some are designed to be positioned on a track.

In practice, a hard disk drive has a magnetic head of, for example, 10
When seeking 100 tracks from track 0 to track 0, as shown in FIG. 3(A), first, from the start of the seek to time L0 when the magnetic head reaches a position of, for example, ±1 track with respect to the target O track. During, speed servo S
By controlling the actuator motor with v and then controlling the actuator motor with position servo SP, it is possible to position the magnetic head disposed on the actuator arm to the target track in a short time.

During the period in which the actuator motor is controlled by the speed servo SV, the magnetic head is accelerated at the acceleration (αvt) for a predetermined period as shown in FIG. It is decelerated by β ■.

Note that the speed of such a magnetic head is controlled according to a speed profile PFV corresponding to the remaining distance to the target track as shown in FIG. 3(C).

As shown in FIG. 4, in the tracking servo circuit 1 that realizes such servo control, the position of the actuator motor 2, which is a voice coil motor, for example, is
P is detected by a position sensor 3 using an optical scale, and a position signal 5PI obtained thereby (FIG. 5(A)) is input to a sample and hold circuit 4.

This sample hold circuit 4 receives the input position signal S□
is a time point t corresponding to a sampling period TI (for example, 200 [μsec]). ,t□,to,・・・・・・
The sample is sampled at every timing of , and held for the following sampling period T, and this hold output H□ is inputted to the analog-to-digital conversion circuit 5.

The analog-to-digital conversion circuit 5 converts the input hold output H6 into digital data for a predetermined time ΔL, thereby obtaining current position data DC□ representing the current position, which is converted into time points t0, t□, to, . . . Time points t, a, t□, L al are delayed by hours and minutes from ...
The signal is input to the servo arithmetic processing circuit 6 of the digital signal processing processor (DSP) at the timing of s....

This servo arithmetic processing circuit 6 includes a speed servo system 6A and a position servo system 6B. First, in the speed servo system 6A, current position data DC6 is transferred to a differential circuit 7 and a ROM (read) in which a speed profile PFV is stored in advance.
only ae+mory) is input to the speed profile generation circuit 8.

Target position data DGPO representing a target track to be sought is input to the speed profile generation circuit 8 in advance, and the speed profile P of the ROM is thereby
The FV is read out, and as a result, speed setting data DGva corresponding to the remaining distance to the target track is added and input to the subtraction circuit 9.

Further, the differentiation circuit 7 differentiates the manually input current position data DC□, and the resulting current actual speed data DC□ is subtracted and input to the subtraction circuit 9.

As a result, the subtraction circuit 9 subtracts the actual speed data DC0 from the speed setting data DGvo to obtain speed error data DGw.
t is generated and supplied to the first input terminal a of the selection circuit 10.

In this selection circuit 10, the first input terminal a is selected by the control signal CSW from the start of seek until reaching a predetermined track position with respect to the target track, that is, during the period of the speed servo Sv. Speed error data DG v t passes through output terminal C, error data DC,
The signal is supplied to the digital-to-analog conversion circuit 11 as a signal.

The digital-to-analog conversion circuit 11 converts the input error data D G t into an error voltage v1 made of an analog signal, and supplies this to the actuator drive circuit 12 .

The actuator drive circuit 12 receives the input error voltage vt.
By converting the drive current I into a drive current I and supplying this to the actuator motor 2, a speed servo loop is formed as a whole. The head can be controlled by a speed servo Sv.

On the other hand, the position servo system 6 of the servo arithmetic processing circuit 6
In B, the current position data DC□ is subtracted and inputted to the subtraction circuit 13, and the target position data DC0 is added and inputted, so that the first position error data DC□ representing the remaining distance to the target track to be sought is obtained. , are input to a proportional error generation circuit 14, an integral error generation circuit 15, and a differential error generation circuit 16, respectively.

The proportional error generation circuit 14 has a transfer characteristic expressed by the following formula (1), and the input first position error data DC□ is multiplied by a predetermined coefficient to generate the proportional error data DGI! Generate F.

Further, the integral error generation circuit 15 has a transfer characteristic expressed by the following formula (2), and the input first position error data D G r
t is integrated and multiplied by 9 by a predetermined coefficient to generate integral error data DGp**.

Furthermore, the differential error generation circuit 16 has a transfer characteristic expressed by the following formula (%) (3), and differentiates the input first position error data DC□ and multiplies it by a predetermined coefficient to generate the differential error data DGP.
E11 is generated.

Thereafter, the adding circuit 17 adds the proportional error data DGptp, the integral error data DC, □, and the differential error data DGrto, and the resulting second position error data DGrt
0 is applied to the second input of the selection circuit 10.

In this selection circuit IO, the second input terminal is selected by the control signal CSW during the period of the position servo SP,
As a result, the second position error data DGrto is supplied to the digital-to-analog conversion circuit 11 through the output terminal C as error data D G t.

In this position servo system 6B, servo calculation processing DSPO, DSP, ,DSP! It takes time Δt1 for ,..., which results in digital-to-analog conversion times! 11111 is second position error data DG□.

at time t. , L□, Lag, ...... time Δ
The time point delayed by L, [,. , tl, Lo,...
As a result, the second position error data DC,E is converted into an error voltage V, which is an analog signal, and this is supplied to the actuator drive circuit 12.

The actuator drive circuit 12 is manually operated with an error voltage ■1
By converting the drive current I into a drive current I and supplying this to the actuator motor 2, the overall PID (proportional (p
ropoLional), integral
, differential) compensation method to form a position servo loop, thereby ensuring that the magnetic head can be positioned on the target track.

In practice, the actuator motor 2 is supplied with a drive flow 1i according to the acceleration, and has a transmission characteristic of the following formula (%) (4), and the current position P is obtained by integrating the acceleration twice. be able to.

In such a servo loop system, the phase is shifted by 180 degrees by integrating twice, and if feedback is continued as it is, the servo loop system will oscillate.

Therefore, in this tracking servo circuit 1, by calculating the differential error data DGpta using the PID compensation method, the phase is advanced by 90 degrees so that the servo loop system as a whole can operate stably.

D Problems to be Solved by the Invention However, in a tracking servo circuit that is digitally controlled in this way, errors in the calculation time DSP of the servo calculation processing circuit 6 constituting the DSP structure and the error in the digital-analog conversion circuit ll. There has been a problem in that the responsiveness and stability of the servo deteriorate depending on the time delay in holding the voltage vt.

In order to solve the problem of the computation time DSP of the servo arithmetic processing circuit 6, it would be better to use a DSP of the servo arithmetic processing circuit 6 that has higher performance and is capable of high-speed arithmetic processing. However, in this case, there is an unavoidable problem that the circuit scale becomes complicated.

In addition, in order to solve the problem of time delay due to holding in the digital-to-analog conversion circuit N111, the error voltage vt obtained from the digital-to-analog conversion circuit 11 is held according to the sampling period T, as shown in FIG. Instead of the configuration, it is conceivable to hold the error voltage ■ only during the period τ4.

However, if this is done, the drive current I sent out from the actuator drive circuit 12 will occur discontinuously, resulting in a problem that the stability of the servo will deteriorate.

The present invention has been made in consideration of the above points, and is a PI that can significantly improve the stability and followability of the servo with a simple tank bottom.
This paper attempts to propose a D-compensation type tracking servo circuit.

E! ! Means for Solving the Problem In order to solve the problem of Lllff, the present invention includes an actuator motor 2 that positions the head at a predetermined track on the disk, and a position error signal DC that detects the position of the head with respect to a target track on the disk. , t, and the position error signal DGrt is multiplied by a first coefficient to produce a proportional error signal DC;
vtp, and a differential error generating means 16 that differentiates the N error signal DC□ and multiplies the second coefficient by 8 to generate a differential error signal DG4. D(1, □. and proportional error signal DG
rtr is time-divided and supplied to the actuator motor 2 in that order.

1 action proportional error generation means 14 and differential error generation means 16 respectively generate proportional error signals D from the position error signal DGPl.
By supplying GPtP and differential error signal DC□ to the actuator motor 2 in a time-divided manner in the order of differential error signal DCPED and proportional error signal DGptr, which have a large influence on servo time delay, the servo characteristics can be further improved. It can be improved.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, in which parts corresponding to those in FIG. 4 are given the same reference numerals, 20 indicates the tracking servo circuit according to the present invention as a whole, and the parts other than the servo arithmetic processing circuit 21 are the same as the tracking servo circuit l (FIG. 4). are configured similarly.

This servo arithmetic processing circuit 21 includes a speed servo system 2IA and a position servo system 21B. First, in the speed servo system 21A, which has the same configuration as the conventional one, the current position data DC6 inputted from the analog-to-digital conversion circuit 5 is differentiated. The signal is input to a circuit 7 and a speed profile generation circuit 8.

This speed profile generation circuit 8 contains current position data D.
In addition to G, target position data DC, , is input, thereby generating speed setting data D G v o corresponding to the remaining distance from the speed profile PFV to the target track, and adding and inputting this to the subtraction circuit 9. .

As a result, the subtraction circuit 9 outputs the speed setting data DGv.

The actual speed data DC□ inputted from the differentiating circuit 7 is subtracted from the actual speed data DC□ to generate speed error data DG■, which is supplied to the first input terminal a of the selection circuit 10.

In this selection circuit 10, the first input terminal a is selected by the control signal CSW during the period of the speed servo S■, and as a result, the speed error data DC□ is passed through the output terminal C to the error data D
G. The error voltage ■t obtained as a result is input to the actuator drive circuit 12.

As a result, the actuator drive circuit 12 has an error voltage ■,
. Driving II flow I□. By converting this into the following and supplying it to the actuator motor 2, a speed servo loop is formed as a whole, whereby the magnetic head is controlled by the speed servo from the start of seek until reaching a predetermined track position with respect to the target track. It is possible to control it.

On the other hand, in the position servo system 21B of the servo arithmetic processing circuit 21, the current position data DC is input to the subtraction circuit 13.
□ is subtracted and inputted, and target position data DC'rs is added and inputted, so that the first positional error data DC's representing the remaining distance to the target track to be sought is generated by the proportional error generation circuit 14 and the integral error generation circuit 14. The signal is input to the circuit 15 and the differential error generation circuit 16.

The proportional error generation circuit 14, the integral error generation circuit 15, and the differential error generation circuit 16 are calculated using equations (1), (2), and (3).
The same arithmetic processing as described above for the equations is executed, and the proportional error data DGP□r, integral error data DGP□, and differential error data DG2tb obtained as the results are used as the first, second, and third terminals of the time division selection circuit 22. is input to input terminals a, b, and C of.

In reality, this time division selection circuit 22 is the servo arithmetic processing circuit 2.
0, the first to third input terminals a-C are selected in the order of third, first and second input terminals c, a and b for each predetermined period according to one sample period Ts. is being done.

As a result, from the output terminal d of the time division selection circuit 22, the PI
Differential error data DC□ is based on the order in which the influence of time delay is greatest when realizing a D-compensation type servo system. , proportional error data DC□, and integral error data DC,□ are supplied to the second input terminal of the selection circuit 10 in this order.

In this selection circuit 10, during the period of the position servo SP, the second input terminal is selected by the control signal C5,
As a result, differential error data DGptb, proportional error data D
C□, and integral error data DGri+ are passed through the output terminal C to error data DG.

The signal is then supplied to the digital-to-analog conversion circuit 11.

In the case of this position servo SP, the servo arithmetic processing circuit 6
is arithmetic processing DSP, ,DSP,,DSP,...
・It takes time Δt for
Grir and integral error data DGri+ are added in a time-divisional manner at time t. , tm+, to, . . . at time Δt, every time point L1. . , to, to,...
Digital to analog conversion is performed at the timing of...

As a result, differential error data DC, , proportional error data D
Gpwp and integral error data DGPEI are shown in Figure 2 (D)
As shown in FIG.
! This is converted into I and supplied to the actuator drive circuit 12.

The actuator drive circuit 12 uses a manual differential error voltage ■. , proportional error voltage V F P % integral error voltage VEI
Drive current 1. . By converting it into (I E8, I, , It,) and supplying it to the actuator motor 2, a dipping system-voloop is formed as a whole in the PIDMJ compensation system, thereby ensuring that the magnetic head is It is designed so that it can be positioned on a target track.

In fact, in this tracking servo circuit 20, the error data obtained by the PID compensation method is time-divided into differential error data DG. , the drive current in the order according to the proportional error data DC□, and the integral error data DGPEI! □.

(Iio, 1., , 1□) as actuator motor 2
By supplying the same amount of time, the influence of time delay can be kept to a minimum, and thus servo characteristics such as response and stability can be significantly improved.

According to the above configuration, regarding the position servo system 21B of the tracking servo, the differential error data DGPEtl, the proportional error data DGptp, the integral error data DC, and the integral error data DC are time-divided and sent to the actuator motor 2 in this order.
Drive current I□ according to C0°. (I!,,hP,■□)
By supplying this, it is possible to realize a tracking servo circuit 20 that can further improve servo characteristics by taking advantage of the characteristics of the PID compensation method.

In addition, in the above embodiment, a case has been described in which the predetermined time corresponding to the sampling period is divided into three and differential error data, proportional error data, and integral error data are sent.
Not limited to this, the predetermined time τ within the time divided into three
4. Even if the differential error data, proportional error data, and integral error data are sent out in this manner, the same effect as in the above-described embodiment can be achieved.

Incidentally, when the differential error data, proportional error data, and integral error data are input in this way, the digital-to-analog conversion circuit 11 outputs the differential error voltage Vte+ as shown in FIG. 2(E). , proportional error voltage V, □. , an integral error voltage v1,1° is sent out.

Furthermore, in the above embodiment, a case was described in which a position servo loop is formed using differential error data, proportional error data, and integral error data in the PID compensation method, but instead of this, only differential error data and proportional error data are used. Even if a position servo loop is formed, the same effects as in the above embodiment can be achieved.

Further, in the above-described embodiment, the present invention was applied to a tracking servo circuit of a hard disk drive, but instead of this, it can be widely applied to a tracking servo circuit for positioning the head of other disk drives such as a floppy disk drive or an optical disk drive. It is suitable for application.

Effects of the Invention As described above, according to the present invention, the proportional error signal and the differential error signal are time-divided and supplied to the actuator motor in the order of the differential error signal and the proportional error signal, which have a large influence on the time delay of the servo. By doing so, it is possible to realize a tracking servo circuit that can further improve servo characteristics with a simple configuration.

... Sample hold circuit, 5 ... Analog-digital conversion circuit, 6.21 ... Servo arithmetic processing circuit.

Claims (1)

[Scope of Claims] An actuator that positions the head on a predetermined track on the disk; a position error detection means that detects the position of the head with respect to a target track on the disk and generates a position error signal; a proportional error generating means for multiplying the position error signal by a first coefficient to generate a proportional error signal; and a differential error generating means for differentiating the position error signal and multiplying the position error signal by a second coefficient to generate a differential error signal. A tracking servo circuit characterized in that the error signal and the proportional error signal are time-divisionally supplied to the actuator in that order.