JPH0461428B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a positioning control circuit for moving a servo head (also simply referred to as a head) to the center of a target track in a disk storage device used as an external storage device for a computer. In the following description of each figure, the same reference numerals indicate the same or corresponding parts.

[Prior art and its problems]

First, the prior art and its problems will be explained using FIGS. 6 to 8. Fig. 6 is a generally used positioning control circuit diagram of this type, Fig. 7 is a signal waveform diagram of the main part to explain the operation shown in Fig. 6, and Fig. 8 is a characteristic of the seek operation shown in Fig. 6. It is a diagram. 7, 1, 2, and 3 are two-phase signals 8, respectively.
a, the waveforms of the ramp signal 6a and the track pulse 9a, and the horizontal axis in each figure indicates the position of the servo head SH. Here, Figure 1 shows the servo head output
Two-layer signal 8 obtained by applying SHa to the demodulation circuit 8
a, and the zero crossing points P of the solid line waveform and the dotted line waveform correspond to the centers of the even and odd tracks, respectively. Further, the waveforms indicated by solid lines and dotted lines in FIGS. 2 and 3 also correspond to those in FIG. 1, respectively. Further, FIGS. 1 and 2 show the head speed, that is, the speed detection signal 4a (solid line) of the servo head, the speed command 2a (dotted line), and the voice coil current, respectively. Next, the configuration and operation of FIG. 6 will be explained with reference to FIGS. 7 and 8. The so-called seek operation, in which the servo head SH on the actuator 7 uses the voice coil VC as the driving force source, tracks the target track.
The process is started by presetting the target number of moving tracks NS in the counter CT in the logical operation circuit 1, which includes a CPU (however, if the number of moving tracks NS is given as a pulse train, counting of the pulse train is started). At this point, a mode switching command is given from logic operation circuit 1 to mode switching switch SW1.
The MD switches to the speed control side (the side where contact a is turned on), and speed control is performed according to the analog speed command 2a (output of the D/A converter 2). In other words, the output of the counter CT (referred to as the number of remaining tracks) CTa
represents the number of remaining tracks that the servo head SH must pass before reaching the target track, and this number of remaining tracks is
CTa is converted into speed data SD by a speed table ST according to its value, and further passed through a D/A converter 2 and input into a speed control circuit 3 as an analog speed command 2a. Also, the speed detection signal 4a
is obtained from the ramp signal 6a (also used as a position error signal PE, which will be described later) in FIG. Make polarity input. The speed control circuit 3 adjusts and amplifies this deviation and applies it to the voice coil VC of the actuator 7 to drive the actuator 7. Servo head output from servo head SH on actuator 7
SHa is converted by the demodulation circuit 8 into a two-phase signal 8a as shown in FIG. The pulsing circuit 9 is this 2
Input the phase signal 8a and while the servo head SH is moving,
Each time the track passes through the center of the track, a track pulse 9a as shown in FIG. 7 is output. This track pulse 9a is input to the counter CT of the logic operation circuit 1 for both even and odd tracks.
While counting down the previously preset target number of moving tracks NS, use this as the new number of remaining tracks.
Output as CTa. In this way, the counter output value (number of remaining tracks)
CTa) decreases and reaches a predetermined value (generally 1 or 0), the mode switching command MD is switched to the position control side (the side where contact b of switch SW1 is turned ON), and the servo head SH is moved to the center of the target track.
Starts position control operation to follow. As the position error signal PE at this time, a ramp signal 6a as shown in FIG. 72 obtained by converting the two-phase signal 8a by the ramp conversion circuit 6 is used. However, the even number ramp signal 6aE or the odd number ramp signal 6aO is selected depending on whether the target track number is an even number or an odd number. The waveform of the ramp signal 6a (6aE, 6aO) is such that the zero cross point of the ramp section is the center of the even or odd track, and is repeated at a cycle twice the track interval G. FIG. 8 shows the characteristics of the above seek operation, that is, the speed response of the servo head and the voice coil current response during the positioning control operation. That is, the maximum speed V _nax and the maximum current I _nax are generally determined by various constraints. The period from time t ₀ to time t ₃ is the speed control section. Of these, t ₀
The period from t1 to _t1 is an acceleration period in which the actual speed value (speed detection signal 4a) is too small relative to the speed command 2a, so the control system is saturated and acceleration is performed at the maximum limit current I _nax . Next, after time _t1 , the actual speed value 4a follows the speed command value 2a, and speed control is achieved. Among these, the speed command 2a is constant (maximum speed) from t ₁ to t ₂ , but in the section from t ₂ to t ₃ when the number of remaining trucks is below a predetermined value, a deceleration command is issued according to the number of remaining trucks. becomes. Next, we will discuss the problems with the conventional control methods described so far. First, as shown in FIG. 8, the deceleration time (t ₃ -t ₂ ) during seek is considerably longer than the acceleration time (t ₁ -t ₀ ). As mentioned above, when accelerating, the maximum limit current I _nax is used to accelerate, whereas when decelerating, the actual speed value (speed detection signal 4
Since it is necessary to make a) accurately follow the speed command value 2a, the speed slope is made gentle so that the restriction system does not become saturated.
This is to decelerate the current below the limit current. Generally speaking, the speed command 2a (therefore, the speed table ST) has a margin in which the deceleration time (t ₃ - _{t 2} ) is equal to 2 times the acceleration time (t ₁ - t ₀ ).
It is determined that the amount will be approximately doubled. Second, as shown in Fig. 7, the linear range of the ramp signal 6a used as the position error signal PE during position control is only ±1 track interval G, and various disturbances may occur during control mode switching and track settling. It is possible that the vehicle will jump over the truck. Third, this control method requires high-precision speed calculation over a wide range, making the circuit complex and making adjustments troublesome.

[Purpose of the invention]

The purpose of the invention is to solve the aforementioned problems. In other words, it is an object of the present invention to provide a control circuit that speeds up and stabilizes positioning operations and that is simplified.

[Key points of the invention]

The key point of the present invention is that, before entering the position control mode, the target movement is performed by combining the operation modes of full acceleration and deceleration using the limited current _Inax , and constant speed with zero current as necessary to reach the vicinity of the target track. The number of remaining tracks when switching each driving mode is determined based on the number of trucks, the seek operation is started, and each driving mode is switched while monitoring the number of remaining tracks calculated every moment. After the following, the position control mode is entered. In this mode, the position error signal is determined by adding the D/A output of the counter count value for calculating the number of remaining tracks to the conventional ramp signal. The main point is that the linear range of the error signal is greatly expanded to facilitate position control. In other words, the gist of the present invention is to provide means (current control circuit, current detection circuit, etc.) for controlling the servo head driving force current (voice coil current, etc.) applied to the driving force source that drives the servo head in order to track a target track. , the target number of moving tracks is set as the total number of tracks that the servo head must pass before reaching the target track center, and the number of remaining tracks corresponding to the remaining number of tracks to the target track center is set each time this track passes. A means (counter, etc.) for calculating and outputting the number of tracks, determines when the number of remaining tracks is less than a predetermined value, and sets the center of the target track as the zero-crossing point of the ramp section, and positions the ramp signal that is repeated at a cycle twice the track interval. In a disk storage device (magnetic disk device, etc.) that is equipped with a means for controlling the position of the servo head as an error signal (logical operation circuit, lamp conversion circuit, compensation circuit, current control circuit, etc.), the servo head drive power source current is limited to a predetermined value. Based on the number of passing tracks and the target number of moving tracks when accelerating and decelerating the servo head by a predetermined speed while maintaining the current, the acceleration and deceleration period of the servo head by the limited current and the servo head driving power source current are set to zero as necessary. a means (such as a logical operation circuit) for determining the number of remaining tracks at each switching point of a constant speed period; means (logical operation circuit, mode changeover switch, limiter, etc.) for performing the above-mentioned acceleration, deceleration, and constant speed operations as necessary, and whether the target track number is an even number or an odd number. If the number is a number, the number of even tracks is calculated from the number of remaining tracks, and if the number is an odd number, the number of odd tracks is calculated from the number of remaining tracks.・Means for calculating the number of remaining tracks (1/2 divider, etc.)
and a means (such as a D/A converter) for obtaining the D/A conversion signal of the even/odd number and remaining track number, and after entering the position control, the ramp signal and the D/A conversion signal are provided. The point is that the sum of the above is used as a new position error signal.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on FIGS. 1 to 5. FIG. 1 is a block circuit diagram as an embodiment of the present invention, and corresponds to FIG. 6. 2 is a block circuit diagram showing the detailed configuration of the position control circuit in FIG. 1, FIG. 3 is an explanatory diagram of the position error signal in FIG. 1, and FIGS. There are different seek operation characteristics diagrams in the figure. In Fig. 1, compared to Fig. 6, the speed control circuit is omitted, the logic operation circuit is newly replaced with 1A, and the position control circuit is replaced with 5A. given by. Next, in the new logical operation circuit 1A, a new counter CT1 is preset with the target moving track number NS, and counts down the preset track number NS as before each time a track pulse 9a is input while tracking the target track. At the same time, the remaining track number CTa as the number of remaining tracks up to the target track is output. However, if the servo head passes the target track and the moving direction of the servo head is reversed, the direction determination circuit 13 is output via the two-layer signal 8a. (newly installed) detects the reversal of the moving direction of the servo head SH, the counter CT1 inputs this direction discrimination signal 13a, and thereafter counts up the track pulse 9a to count up the number of remaining tracks.
Find CTa. Note that if the target number of moving tracks NS is given by a pulse train, a method of counting the pulse train may be used instead of the simultaneous preset method. Also, this logic operation circuit 1A has a 1/2 divider 10.
has been newly established. This divider 10 halves the counter output (remaining track number CTa) and rounds up (to +1) if there is a fraction (0.5), even if the target track number is an even (odd) number. For example, the number of even (odd) tracks among the remaining number of tracks is calculated. The output 10a of this divider 10 is input to the D/A converter 12 in the newly provided position error calculation circuit 11, and its output signal (D/A
The output signal) 12a is added to the conventional ramp signal 6a to form a new position error signal PE, which is input to the newly installed position control circuit 5A. Further, this logical operation circuit 1A determines the timing at which to output a limit current limit mode command, a limit current control mode command, and a position control mode command as a mode switching command MDA, as described later, in advance, based on the preset target moving track number NS. (Value of remaining track number CTa at the time of mode switching)
During the seek operation, while monitoring the remaining track number CTa output from counter CT1 every moment,
Each of the above-mentioned commands, . . . is output to the position control circuit 5A. FIG. 2 shows the configuration of this position control circuit 5A,
A limited current limit mode command, a limited current control mode command as the mode switching command MDA,
The mode changeover switches SW, SW, SW are selectively turned on according to the position control mode command. Next, 23 and 24 in the figure are current control circuits that constitute a closed loop for voice coil current control, respectively;
A current detection circuit, where V and V are positive and negative power supplies for creating a current command value given to the closed loop for current control in response to turning on of switches SW and SW, respectively, and 22 is a current command value, respectively.
This is a limiter to limit the current to the upper and lower limit current values ±I _nax . Further, 21 is a compensation circuit which compensates the phase of the input position error signal PE in the position control mode (switch SW ON mode) and provides it as a command value to the closed loop for current control. In this position control mode, position error calculation circuit 1
Using the new position error signal PE from 1, control is performed to position the servo head SH at the zero cross point. Now, the switching timing of the mode switching command MDA is determined as follows. Now, the head and the specified maximum speed are V _nax , the voice coil maximum current is I _nax , the force conversion coefficient (coefficient that converts the voice coil current into driving force) is K _F , the equivalent mass of the actuator moving part is M, and the current I _nax If the time taken for the head speed to go from 0 to V _nax and the travel distance are Ta and Xa, respectively, the following relational expression holds true. V _nax = I _nax・K _F・(1/M)・Ta ...(1) Xa=(1/2)・I _nax・K _F・(1/M)・Ta ²
...(2) If time Ta is eliminated from equations (1) and (2): Xa = (1/2) (M/I _nax・K _F )・V _nax ²
...(3) In other words, Xa is the current that limits the voice coil current.
This is the travel distance required to accelerate (decelerate) the servo head from speed 0 to V _nax (from speed V _nax to 0) while maintaining I _nax (-I _nax ).
The number of tracks corresponding to Xa (maximum addition (subtraction) for convenience)
(referred to as the number of fast section tracks) is Na. Therefore, when the target moving track number NS is given, the output timings of the limit current limit mode command, limit current control mode command, and position control mode command are determined as shown in Tables 1 and 2 below. Here, (i) In the case of NS2Na (i.e., the target number of moving tracks
When NS is greater than the sum of the maximum acceleration section track number and maximum deceleration section track number (2Na) and includes a constant speed section)...See Table 1 (ii) When NS < 2Na (i.e., when it does not include a constant speed section) )...See Table 2

【table】

[Table] In response to the above mode switching command MDA, each control mode is switched in the position control circuit 5A shown in FIG. In other words, when a command is output, the switch SW
is turned on, and a command to maintain the voice coil current at the limit current +I _nax by the internal limiter 22 and accelerate is input to the current control circuit 23. Similarly, when a command is output, the switch SW is turned on, and a command to maintain the voice coil current at the limit current -I _nax and decelerate is input to the current control circuit 23.
When the command is output, the switch SW is turned on and a position control closed loop is established. Also, when commanding constant speed mode, all switches SW, SW, SW are
When it is turned off, the current command value becomes zero and the servo head performs constant speed operation. The seek operation characteristics in the above case (i) (NS2Na) are shown in FIG. 4, and the seek operation characteristics in the case (ii) (NS<2Na) are shown in FIG. These figures 4 and 5
In the figure, 1 to 3 are track pulses 9, respectively.
a, mode switching SW~, voice coil current,
In Fig. 4, time _t10 to _t11 is an acceleration period, time _t11 to _t12 is a constant speed period,
The period from time _t12 to _t21 is the deceleration period, and the period after time _t13 is the position control period. Moreover, in FIG. 5, there is no constant speed period, the time t ₂₀ to t ₂₁ is the acceleration period, the time t ₂₁ to t ₂₂ is the deceleration period,
The period after time _t22 is the position control period. In this way, in both cases of FIG. 4 and FIG. 5, acceleration and deceleration are performed at the maximum limit current ±I _nax , and the time required for the seek operation is shortened compared to the conventional one. Note that if the seek direction (tracking direction of the target track) is reversed, the command and command are turned ON.
The timing is reversed. Next, as described above, the position error signal PE in the position control mode is converted into a D/A converter of the conventional ramp signal 6a and the remaining track number CTa, which is halved via the divider 10, in the position error calculation circuit 11. It is obtained by adding the value (D/A output signal 12a). In FIG. 3, the horizontal axis is the head position, and the value of the divider output 10a is calibrated on this, and the ramp signal 6
a, D/A output signal 12a and signals 6a and 12a
The waveform of the position error signal PE as a result of adding . As can be seen from this figure, the position error signal corresponding to the deviation of the head position from the target track center P0
In principle, the linear range of PE can be expanded from the conventional ±1 track interval G (corresponding to the cycle of ramp signal 6a) to the entire track range (however, in practice it is limited by the D/A converter used and the analog signal level). ). This greatly expands the position control range and allows the head to be centered on the target track, unlike conventional methods.
If the deviation from P0 transiently becomes one track interval G or more due to disturbances, an error phenomenon can be avoided, and stable track following becomes possible. In addition, the conditions for closing the position control loop do not have to be as strict as in conventional control. In order not to exceed the linear range, the head position at the time of switching to the position control mode had to be sufficiently close to the target track, and the head residual speed had to be sufficiently small. Therefore, the aforementioned maximum limit current ±
Acceleration/deceleration by I _nax (At this time, position control is controlled in an open loop.)
After that, it becomes possible to take advantage of closed-loop position control. Note that the output timings of the limit current limit mode command, limit current control mode command, and position control mode command output from the logical operation circuit 1A to the position control circuit 5A are basically as described above, but the limit current - When the head is decelerated with I _nax , the remaining track number CTa does not become zero due to some factor (disturbance, circuit imbalance, etc.) and the direction of head movement is reversed. In other words, in limited current control mode. If the output 13a of the direction determination circuit 13 is reversed while the command is being output, the command is invalidated and a position control mode command is output. Also, if the target number of moving tracks NS is small,
It is also conceivable to directly output a command and enter the position control mode without outputting the command or command from the logical operation circuit 1A.

【Effect of the invention】

As is clear from the above description, according to the present invention, instead of conventional speed control, acceleration and deceleration are performed while maintaining a limited current, so that the moving time of the head is shortened and the circuit is simplified. Moreover, by adopting a circuit configuration that can greatly expand the linear range of the position error signal during position control, the position control range is expanded and stable control that is resistant to external disturbances is possible.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram as an embodiment of the present invention, FIG. 2 is a block circuit diagram showing the detailed configuration of the position control circuit in FIG. 1, and FIG. 3 is a position error signal as shown in FIG. 1. Explanatory diagrams, Figures 4 and 5
The diagrams are different seek operation characteristic diagrams of Figure 1,
6 is a conventional block circuit diagram corresponding to FIG. 1, FIG. 7 is a waveform diagram of essential parts for explaining the operation of FIG. 6, and FIG. 8 is a seek operation characteristic diagram of FIG. 6. 1A: Logical operation circuit, CT1: Counter, 5
A: Position control circuit, 6: Lamp conversion circuit, 7: Actuator, VC: Voice coil, SH: Servo head, 8: Demodulation circuit, 9: Pulsing circuit, 1
0: 1/2 divider, 11: Position error calculation circuit, 1
2: D/A converter, 13: Direction discrimination circuit, 2
1: Compensation circuit, 22: Limiter, 23: Current control circuit, 24: Current detection circuit, SW, SW, SW
:Mode change switch, MDA: Mode change command, NS: Target number of moving tracks, CTa: Number of remaining tracks, 10a: Divider output, 6a: Ramp signal,
12a: D/A output signal, PE: position error signal.

Claims (1)

[Scope of Claims] 1. Means for controlling the servo head driving power source current applied to the driving power source for driving the servo head in order to track the target track, all the tracks that the servo head must pass until it reaches the center of the target track. means for setting a target number of moving tracks as a number and calculating and outputting the number of remaining tracks corresponding to the number of remaining tracks to the center of the target track each time this track passes; In a disk storage device, the servo head is driven by means for determining the target track center as the zero cross point of the ramp section and using a ramp signal repeated at a cycle twice the track interval as a position error signal to control the position of the servo head. Based on the number of tracks passed and the target number of moving tracks when accelerating and decelerating the servo head by a predetermined speed while maintaining the power source current at a predetermined limit current, determine the period of acceleration and deceleration of the servo head by the limit current, and as necessary. means for determining the number of remaining tracks at each switching point of a constant speed period in which the servo head drive power source current is set to zero; and switching a current command value for the current control means in accordance with the determination of the number of remaining tracks; means for performing the acceleration, deceleration, and, if necessary, constant speed operations of the servo head; means for calculating the number of even/odd tracks and the number of remaining tracks according to each case by calculating the number of even tracks or, if the number is an odd number, the number of odd tracks out of the number of remaining tracks; / means for obtaining a D/A conversion signal for an odd number/number of remaining tracks, and after entering the position control, the sum of the ramp signal and the D/A conversion signal is used as a new position error signal. A track positioning control circuit for a disk storage device, characterized in that: