JPS6217245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positioning control device, and particularly to a positioning control device suitable for application to a magnetic disk device. It is well known that positioning control using a movable head of a magnetic disk device as an object to be positioned is generally divided into a speed control section until reaching near the target position and a position control section after reaching the target position. As the recording density (also referred to as track density) in the radial direction of the medium increases, the influence of mechanical resonance of the object to be positioned cannot be ignored. This mechanical resonance occurs in the movement control section (speed control section).
This is because the base part (supporting member) to which the object to be positioned or the guide mechanism for the object to be positioned is attached vibrates due to the acceleration/deceleration force on the object to be positioned, and is induced by one movement operation. Even if the amplitude of the mechanical resonance is small, if the moving operation is performed multiple times in succession, the amplitude will gradually increase, and the permissible range for reading and writing to the medium will increase during the position control section after the moving operation is completed. This leads to mechanical resonance that exceeds . Such problems are
In recent years, the time required for positioning a movable head (access time) has tended to become shorter and shorter, and accelerating/decelerating forces have tended to increase accordingly, so there is a strong demand for a solution to this problem. In addition, the recording density in the radial direction tends to increase, and the above-mentioned tolerance range, that is, the permissible amplitude of mechanical resonance caused by moving motion, tends to become smaller, making it even more difficult to solve the above problem. has become an important issue.

Thus, the purpose of the present invention is to solve the above problem, and the purpose is to check the magnitude of the vibration of the movable member during the position control section after the end of the movement operation, and when the amplitude of the vibration exceeds the permissible value, This is achieved by a positioning control device that damps mechanical resonance by suppressing the speed of the immediate movement operation to a low level.

That is, the features of the present invention include position servo means for driving the object to be positioned according to the difference between a given target position and the current position of the object to be positioned, and a position servo means for driving the object to be positioned according to the difference between a given target position and the current position of the object to be positioned; speed servo means for driving the object to be positioned according to the difference between the positions;
In the positioning control device, the positioning control device includes a switching means that switches between the position servo means and the speed servo means depending on whether the difference between the target position and the current position is less than or equal to a predetermined value. vibration detecting means for detecting the magnitude of vibration of the object to be positioned that occurs during a period of time; and target speed switching means for changing the target speed when the speed servo means operates thereafter based on the output of the vibration detecting means. However, one embodiment of the present invention will be described in detail below with reference to the drawings.

First, a position servo means and a speed servo means are provided, and while the carriage reaches the target stop position,
A typical configuration of a magnetic disk device that controls the moving speed of the carriage along a predetermined ideal deceleration curve, and after reaching the vicinity of the target stop position, performs positioning control based on minute positional deviations. Explain.

FIG. 1 shows a control section of a magnetic disk device that performs such control. In the figure, 1 is a rotating disk-shaped medium, 2 is an arm with a magnetic head attached to its tip, etc., 3 is a carriage that supports a plurality of arms 2 and is movable in the radial direction of the medium 1.
4 ₁ is a field device 4 provided at the rear end of the carriage 3.
₂ is a drive coil housed in the servo head; 5 is a position detector for detecting the reproduced signal from the servo head;
6 is a speed detector that differentiates the output A of the position detector 5, integrates the energization signal of the drive coil ₄₁ , and mutually interpolates the two to obtain a speed signal B; 7 shapes the output A of the position detector 5; 8 is a subtraction counter that is set as an initial value to the moving distance to the target position given from the control logic circuit 9 and then counts down based on the output C of the pulse generation circuit 7; 10 is a subtraction counter; A target speed signal generation circuit 11 generates a target speed signal according to an analog quantity signal obtained by D/A converting the count output of 8, and a target speed signal from the output B of the speed detector 6 and the nonlinear circuit. 12 is a power amplifier that amplifies the difference signal from the speed error amplifier 11 and applies it to the drive coil ₄₁ ; 13 is the output of the position detector 5 and the output of the speed detector 6; 14 is a switch, and 15 is a current detector.

On one surface of the medium 1, servo information consisting of odd and even signals arranged concentrically and alternately at a predetermined pitch is recorded.

Therefore, the position detector 5 detects the difference between the odd track signal component and the even track signal component of the servo information reproduced by the servo head, and outputs it as a servo signal A. That is, if the servo head is located exactly between the odd, rack, and even tracks, the odd track signal component and the even track signal component are equal in magnitude, so the servo signal A is "0". .

Furthermore, when the servo head deviates from this position, the servo signal A shifts in the positive or negative direction and changes almost proportionally, and if it deviates even further, it passes through a maximum or minimum value and becomes a response in the signal component of the next track. In the end, the servo signal A becomes a sine wave.

By differentiating a portion of such a servo signal A that is close to a straight line, highly accurate speed signals can be obtained at intervals, and the drive coil 4 which becomes the accelerating force of the carriage 3
By integrating _one energization amount, a continuous speed signal is obtained.

Therefore, the speed detector 6 detects between the discrete speed signals obtained by differentiating the servo signal A, and the current detector 1
Interpolation is performed using the integral value of the output of step 6, and a continuous and highly accurate speed signal B is output.

On the other hand, regarding the signal representing the position, the pulse generating circuit 7 first detects a portion of the servo signal A that is close to "0" and generates the pulse signal C. next,
The subtraction counter 8 counts this pulse signal C, and the number of track crossings to the target stopping point is initially set in the subtraction counter 8, and the counting direction is negative. Therefore, the output E of this subtraction counter represents the current position with respect to the target stopping point in terms of track numbers. In other words, this output E does not represent a position that changes smoothly.

Therefore, within the target speed signal generation circuit, a continuous minute interpolation value signal is generated by integrating the speed signal B every time during the period in which the subtraction counter 8 is stopped, and the signal is sent via the D/A converter. The output E of the subtraction counter 8 and this interpolation value signal are added to obtain a continuous position signal.

Thereafter, a target speed signal D is generated according to this position signal, and then the difference between the speed signal B and the target speed signal is detected in the speed error amplifier 11, and this signal is outputted via the terminal V of the switch 14 and the power amplifier 12. A difference signal is applied to the drive coil ₄₁ . When the carriage 3 moves due to the acceleration (deceleration) force generated in the drive coil ₄₁ and approaches within one track width of the target stop position, the content of the subtraction counter 8 becomes "0" and the switch 14
is connected to the terminal P side. Therefore, from now on, the output of the error amplifier 13 is applied to the power amplifier 12 through the terminal P of the switch 14, and as a result, the carriage 3 is held at the target stop position.

Now, the present invention is a carriage drive control device for a magnetic disk device as described above, which is provided with a target speed switching circuit 16 shown by a broken line in FIG. This target speed switching circuit 16 functions to limit the target speed signal D output from the target speed generating circuit 10. That is, as shown in FIG. 4, the target speed signal (solid line) generated when the magnitude of vibration during positioning is below a predetermined level is reduced by a constant ratio as shown by the broken line, or
As shown in the figure, the target speed switching circuit 16 performs a restriction that reduces only the maximum speed of the target speed signal (solid line) that occurs when the vibration is small. It is carried out on the basis of exceeding the level.

FIG. 2 is a diagram showing a specific example of the configuration of such a target speed switching circuit 16, and FIG. 3 is a diagram showing signal waveforms of various parts of the circuit shown in FIG. In FIG. 2, CMP ₁ and CMP ₂ indicate that the position signal A corresponding to the amount of deviation of the current position from the center position of the truck, which is the stop target, is applied to a reference voltage Ref of a predetermined amount in the positive and negative directions.
+, Comparator to detect whether Ref- is exceeded, NOT is an inverting circuit, AND is an AND gate, M#1, M#2 are from the time when the signal F is input to select position control/speed control. The operating monostable multivibrator M#1 outputs a minute width trigger and pulse, M#2 outputs a relatively long time width pulse, and M#3 is the output pulse of the nonostable multivibrator M#2. A monostable multivibrator is activated by the trailing edge of the oscillator and outputs a minute width trigger pulse, OR is an OR gate, and FF is an R-S type flip-flop. The monostable multivibrators M#2 and M#3 can generate output pulses only when the position control/speed control selection signal F indicates the position control side. Next, the operation will be explained. First, as shown in Figure 3A, the position signal A is sent to two comparators.
Positive and negative reference voltage Ref in CMP ₁ and CMP ₂
+, Ref- (dashed line), and only when the position signal A is between the reference voltages Ref+ and Ref-, 2
None of the outputs of the comparators CMP ₁ and CMP ₂ absorb current, therefore, a positive signal (logic "1") is input to the input of the inverting circuit NOT from the positive power supply +E.
More added. Therefore, conversely, when the position signal A is not between the reference voltages Ref+ and Ref-, a low level signal (logic "0") is applied to the inverting circuit NOT, and as a result, the inverting circuit NOT
As shown in FIG. 3G, the output G becomes "1" when the absolute value of the position signal A is larger than a predetermined level (Ref+, Ref-). On the other hand, the position control/speed control selection signal F shown in FIG. It rises when the content of the subtraction counter 8 that counts the number of zeros corresponding to the track center position becomes "0".Then, it falls when the new movement amount is stored in the subtraction counter 8.As a result, The output H of the AND gate AND outputs "1" when both the above signals G and F become "1" as shown in FIG. , sets the flip-flop FF. Then, when the next movement is started with this flip-flop FF set (see Mode 3), the target speed signal D output from the target speed generating circuit 10 becomes a low value due to the output L. However, normally, the periods before and during the movement corresponding to the three movements in Figure 3: Mode ₁ , Mode ₂ ,
As seen in the first two periods of Mode ₃ , Mode ₁ and Mode ₂ , the flip-flop FF is reset before the start of movement. That is, period Mode ₁
Then, when the position control/speed control selection signal F switches to the state indicating position control (logic "1"), after the flip-flop FF is reset by the trigger pulse _R1 generated from the monostable multivibrator M#1, This is because the flip-flop FF starts moving without being set, and in period Mode ₂ , the flip-flop FF is reset by the trigger pulse _R2 generated from the monostable multivibrator M#1, and then set by the output pulse of the Argon AND. However, another trigger pulse _R3 is generated from the monostable multivibrator M#3 due to the output of the monostable multivibrator M#2 which operates for T#2 hours from the start of the period Mode ₂ , and eventually resets the flip-flop FF. This is because you will need to start moving after doing so. In this way, T#2
Even if large vibrations occur during the position control period immediately after the previous movement, if the start of the next movement does not occur within a period of time from the end of the previous movement, the vibrations will gradually decrease. After time T#2, it has been attenuated to such an extent that it is no longer a problem, so the next movement can use the normal high target speed.

It will then be understood that the vibrations described above become a problem only when there is only a short period of time between the previous movement and the next movement.

Therefore, in this embodiment, in such a case, as in the Mode ₃ period of FIG.
After the flip-flop FF is set by the output pulse _S2 from the AND, the position control/speed control selection signal F becomes "0" before the operating time T# ₂ of the monostable multivibrators M# ₂ and M# ₃ elapses.
(speed control side), the next movement is started without the flip-flop FF being reset. Therefore, in this case, since the output L of the flip-flop FF continues to be "1" during movement, the target speed signal D is suppressed to a low value as shown by the broken line in FIG. 4 or the broken line in FIG. 5.

As described above, according to the present invention, it is possible to prevent a dangerous situation in which the vibrations that occur when a magnetic head or the like is held at a stopped position increase with each movement, making it impossible to hold the magnetic head in its normal position. This makes it possible to improve the reliability of recording and reproducing operations in magnetic disk devices and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a carriage drive control section of a magnetic disk device according to the present invention, and FIG. 2 is a diagram showing an example of the configuration of a target speed switching circuit, which is a main additional part according to the present invention. This figure shows each part of the circuit shown in FIG. 2, and FIGS. 4 and 5 show practical examples of how to limit the target speed signal. 5...Position detector, 6...Speed detector, 7...
Pulse generation circuit, 8... Subtraction counter, 9... Control logic circuit, 10... Target speed generation circuit, 11...
…Speed error amplifier, 12…Power amplifier, 13
...Error amplifier, 14...Switch, 15...Current detector, 16...Target speed switching circuit, CMP ₁ ,
CMP ₂ ...Comparator, NOT...Inverting circuit,
AND...and gate, OR...or gate,
FF...Flip-flop, M#1, M#2, M
#3... Monostable multivibrator.

Claims (1)

[Claims] 1 Position servo means for driving the object to be positioned according to the difference between a given target position and the current position of the object to be positioned; Positioning comprising a speed servo means for driving a positioning object, and a switching means for switching between the position servo means and the speed servo means depending on whether the difference between the target position and the current position is less than or equal to a predetermined value. In the control device,
Vibration detection means for detecting the magnitude of vibration of the object to be positioned that occurs during the period in which the position servo means is working, and a target for changing the target speed when the speed servo means works thereafter based on the output of the vibration detection means. 1. A positioning control device comprising: speed switching means.