JPH0415548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic disk device with an improved servo control method for positioning a magnetic head.

[Technical background of the invention and its problems]

Generally, in a magnetic disk device, it is necessary to position a magnetic head with high precision with respect to a magnetic disk plate (hereinafter simply referred to as a disk). Such head positioning control is usually called servo control and is performed by detecting the position and moving speed of the head.

In the conventional servo control system, as shown in FIG. 1, a servo signal Sv is taken out by a transducer 1. This servo signal Sv is obtained by reading servo information recorded in advance on the servo surface of the disk as a voltage signal. Transducer 1
Usually consists of a head, preamplifier, low-pass filter, AGC amplifier, etc. The servo signal Sv is given to each of the timing generation circuit 2 and peak hold circuits 3a to 3d. Timing generation circuit 2 uses servo signal Sv
PLL (phase
The servo signal Sv generates sample pulses _P1 to _P4 for sampling head position information included in the servo signal Sv.
Further, the peak hold circuits 3a to 3d detect and hold the peak value (wave height value) of the servo signal Sv in synchronization with the sample pulses _P1 to _P4 .

Here, FIG. 2 shows the state of servo information recorded on the disk. That is, as shown in FIG. 2, the servo information includes synchronization signals S1 to S4 for sampling servo data (position information) and two sets of data A, B and C, D for obtaining position information. It is. Note that a to h in the figure indicate boundaries between tracks of servo sectors in which servo information is recorded. Furthermore, FIG. 3 shows the output signal Sv of the transducer 1 when the servo data recorded as shown in FIG. 2 is read out by a head twice the size of the servo track. Furthermore, the third
In the figure, a to h are the heads of a to h in Figure 2.
This is the servo signal that corresponds to the position in the position. Further, the synchronizing signals S1 to S4 are outputted so as to always have the maximum amplitude regardless of the position of the head.

The position information whose peak value is held by the peak hold circuits 3a to 3d as described above is corrected and amplified by differential amplifiers (hereinafter referred to as operational amplifiers) 4a and 4b. The output signal of this operational amplifier 4a is given to a differentiating circuit 6a and an inverting amplifier (an operational amplifier) 5a. Also operational amplifier 4b
The output signal is sent to the differentiating circuit 6c and the inverting amplifier 5
given to b. Each output signal of inverting amplifiers 5a and 5b is given to differentiating circuits 6b and 6d, respectively. Further, each output signal of the operational amplifiers 4a, 4b and the inverting amplifiers 5a, 5b is provided to a discrimination circuit 7. This discrimination circuit 7 discriminates the magnitude of the position signal, and depending on the result, differentiates circuits 6a to 6d.
Create a selection signal Se to select the output of .
In response to this selection signal Se, a switch circuit (usually an analog switch circuit) 8 selects each output signal of the differentiating circuits 6a to 6d and outputs it as a speed signal V indicating the moving speed of the head. Further, the output signal of the operational amplifier 4a is transferred as a position signal I indicating the position of the head.

In the above servo control method, the timing chart when creating position information based on the servo signal Sv from the transducer 1 is shown in the fourth diagram.
As shown in the figure. First, a in the figure is an inverted version of the output signal Sv of the transistor 1. This signal a
The synchronization signals S1 to S4 are determined from the synchronization pulse b
Detect. The timing generation circuit 2 includes a PLL that is synchronized with the synchronization pulse b, and generates sampling pulses P ₁ to _{P 4} based on this PLL. Further, the signal e in the figure is a peak hold signal that extracts the peak value (wave height value) of the position information A' of the signal a in accordance with the sampling pulse _P1 . Position information indicated by a broken line in this signal e
A' is held as shown in FIG. Further, the signal f in the figure is a schematic representation of the signal A' that changes when the head moves and the state of the peak hold signal at that time.

Here, the peak hold circuits 3a to 3d shown in FIG. 1 are specifically circuits as shown in FIG. 5, for example. That is, a sampling pulse (for example, P ₁ ) is supplied to the signal line 73, and a servo signal Sv is supplied to the signal line 74. now,
When the sampling pulse P1 becomes " ₁ ", the output of the gate circuit 70 becomes "1", and the servo signal
Transistors 71 and 72 operate due to Sv.
Then, the capacitor 76 is charged so that the signal line 77 has a value corresponding to the servo signal Sv.
When this servo signal Sv becomes smaller than the signal on the signal line 77, the transistor 72 is turned off. Therefore, the signal on signal line 77 is connected to resistor 75.
It is discharged slowly through the In this case, the discharge constant is the position information that changes as the head moves.
It is determined so that the maximum change in A' can be identified. Furthermore, when the sampling pulse _P1 becomes "0", the output of the gate circuit 70 becomes "0",
Both transistors 71 and 72 are turned off.
Therefore, in this case as well, the signal on the signal line 77 is slowly discharged through the resistor 75, and the position information is appropriately peak-held. Note that R ₁ to _{R 3} in FIG. 5 are resistors. Next, FIG. 6 shows a specific circuit for creating a position signal I and a speed signal V based on the peak hold signal as described above. That is, it consists of circuits corresponding to operational amplifiers 4a and 4b, inverting amplifiers 5a and 5b, differentiating circuits 6a to 6d, and analog switch circuit 8 shown in FIG. Further, the discrimination circuit 7 includes operational amplifiers 9a, 9b and a decoder 10, as shown in FIG. In addition, in the figure, R ₁₀ to _{R 35} are resistors, and C ₁ to C ₄ are capacitors.

In such a circuit, as the head moves across the track, the envelope of the sampled peak-held position information is equal to the servo signal Sv.
The signals A to D in FIG. 7 are created corresponding to A-A', B-B', C-C', and D-D' (shown in FIG. 3). These signals A to D are applied to each input terminal of operational amplifiers 4a and 4b as shown in FIG. Therefore, the signal A-B is output from the operational amplifier 4a, and the signal CD is output from the operational amplifier 4b. In this case, the signal A-B has a waveform whose phase is shifted by 90 degrees from the signal CD. Note that a to h in the figure correspond to values at the moment when the head passes the track position with the same symbol as shown in FIG.
Here, since a head whose width (read width) is twice that of the servo track is used,
Assuming that the data track width is twice the servo track width, the head is brought to rest at the position shown in FIG. 2a. If this position is defined as track "0", then the next track (for example, track "1") that can stand still without overlapping tracks is at position e. In this way, the positions a and e where the head can stop are determined by the signal C-
This corresponds to the position where the magnitude of D is "0". Next, the signal E in the figure is the result of voltage comparison such that when the signal A-B is positive, it is "1" and when it is negative, it is "0". A signal F is obtained by taking out and connecting the signal CD when the signal E is "1" and the inverted signal of the signal CD when the signal E is "0". In this signal F, the zero cross position of the slope corresponds to the center of the data track, and if it deviates from this position to the left in the figure, it takes a negative value, and if it deviates to the right, it takes a positive value.
The value changes depending on the amount of deviation. Therefore,
The signal F is a position signal including the direction of displacement.
When controlling the position so that the head comes to rest on the track, the position signal is created so that the polarity of the position signal becomes signal F with respect to the track center. Therefore, when the stop position of the head corresponds to point a in the figure, it moves in accordance with the signal CD and performs position control on the target track in accordance with its polarity. Further, when the head is to be stopped at a position corresponding to point e in the figure, it moves in accordance with the signal D-C indicated by J in the figure and performs position control on the target track. Therefore, it is necessary to determine whether to use the signal CD or the signal D-C as a position signal depending on whether the target track is an even numbered track or an odd numbered track before moving the head. be. According to this determination, by changing the order of the sampling pulses P ₁ to _{P 4} of the timing generation circuit 2, for example, the data input to the operational amplifier 4a is converted, and the signal C-D or the signal D-C is converted as necessary. can be obtained on the signal line 11. In this way, the signal line 11 changes depending on the moving speed when the head moves, and also makes a zero crossing when the head crosses the track, so that the amount of displacement from the track center always matches the polarity on the target track. Position signals I that are the same including direction correspondence
is obtained.

Furthermore, during a seek operation in which the head moves,
It is necessary to detect the speed of the head. This speed signal is obtained by differentiating the position signal from differentiating circuits 6a to 6d.
It is obtained by differentiating by. For example, signal line 13
A signal A-B is outputted to a signal B, which is a signal H obtained by inverting this signal A-B by an inverting amplifier 5a.
-A is obtained on the signal line 14. Similarly, signal line 11
When the signal CD (signal K) is obtained on the signal line 12, the signal D-C, which is the inverted signal J, is obtained on the signal line 12. These signals H, J, K are operational amplifiers 9a, 9
b, and the size is determined. When the output is decoded by the decoder 10, signals L to P shown in FIG. 7 are obtained. When this signal L is "1", the signal C-D, when the signal M is "1", the signal B-A, and when the signal N is "1", the signal D-
When signal C and signal P are "1", signal Q can be obtained by extracting and connecting signals A and B. This signal Q extracts only the portion of the position signal with good linearity, and accurately represents the amount of movement except for the connection portion. Also, the direction is expressed by a negative slope for movement to the left in the figure, and a positive slope for movement to the right. Therefore, this signal Q is differentiated. By doing so, accurate speed signals can be obtained. In reality, in order to eliminate problems with the connection part, signal lines 11 to 1 are
The results obtained by differentiating each of the four signals by the differentiating circuits 6a to 6d are selected from the analog switch circuit 8 operated by the selection signals L to P. This selected signal is output as a desired speed signal V.

As described above, the position and moving speed of the head can be detected to perform servo control. However, in such conventional methods,
As described above, since it is constituted by an analog signal processing circuit that makes extensive use of operational amplifiers and the like, it requires a very large number of rotating elements. Furthermore, it is extremely difficult to accommodate the characteristics of the servo control system, which differs from magnetic disk device to magnetic disk device, resulting in drawbacks such as difficulty in downsizing the component parts.

[Purpose of the invention]

This invention has been made in view of the above circumstances, and in the servo control system, by configuring the circuit for detecting the position and moving speed of the head as a digital signal processing circuit, the servo control circuit can be highly integrated and versatile. An object of the present invention is to provide a magnetic disk device that can realize the following.

[Summary of the invention]

That is, in the present invention, in the servo control circuit, the peak hold signal output from the peak hold circuit is converted into a digital signal by the analog-to-digital conversion circuit. Based on this digital signal, head position information is calculated by a first digital adder/subtracter. Then, based on this calculation result, the moving speed information of the head is calculated by the second digital adder/subtractor. Thereby, the main part of the servo control circuit can be configured as a digital signal processing circuit.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 8 is a block diagram showing the configuration of a servo control circuit according to the present invention. In the figure, 21 is a selection circuit (for example, an analog switch circuit) that selects one of the peak hold signals output from the peak hold circuits 3a to 3d using sampling pulses _P1 to _P4 from the timing generation circuit 20. . The sampling pulses P ₁ to _{P 4} are created based on the synchronization signal included in the servo signal Sv output from the transducer 1 as described above. The peak hold signal selected by the select circuit 21 is sent to an analog-to-digital conversion circuit (hereinafter referred to as an A/D converter) 22.
and converted into a digital signal. Each of these digital signals corresponds to the sampling pulse P ₁ ~
Register 23 which performs storage operation by each of _P4
It is stored in a to 23d. Each digital signal stored in registers 23a and 23c is applied to multiplexer 24a. Similarly, each digital signal stored in registers 23b and 23d is applied to multiplexer 24b. Multiplexers 24a and 24b select one of the input signals according to a selection signal (for example, sampling pulse P ₁ ). This multiplexer 24
Each of the digital signals selected by a and 24b is applied to a digital adder/subtractor 25a, where, for example, a subtraction process is performed. The calculation result of the digital adder/subtractor 25a is applied to registers 26, 27 and a flip-flop 28. The register 26 performs a storage operation in response to the sampling pulse _P3 , and outputs the stored digital signal (calculation result) as the head position signal Id. The flip-flop 28 latches the above calculation result using the clock signal φ ₁ from the timing generation circuit 20. Also, register 27
stores the above calculation result using the clock signal φ ₂ from the timing generation circuit 20, and outputs it to the digital adder/subtractor 25b. Digital adder/subtractor 25b
is the output of the register 27 and the digital adder/subtractor 25
For example, subtraction processing is performed on the output of a, and the calculation result is output to the register 29. The register 29 performs a storage operation in response to the clock signal _φ2 , and outputs the stored calculation result as the head movement speed signal Vd. For other configurations,
Since it is the same as that in FIG. 1 above, the same reference numerals are given and the explanation will be omitted.

In such a configuration, FIGS. 9 and 10
The operation will be explained with reference to the figure. The peak values (A to D) of the servo signal Sv output from the transducer 1 are held in peak hold circuits 3a to 3d. In this case, for example, the peak hold circuit 3a holds the peak hold signal A in response to the sampling pulse _P1 . Similarly, peak hold circuits 3a to 3d output peak hold signals B to D in response to sampling pulses _P2 to _P4 .
Hold each. Peak hold circuit 3
Each of the peak hold signals A to D held at points a to 3d is given to the select circuit 21. The selection circuit 21 selects, for example, the signal A whose peak was held by the sampling pulse P ₁ shown in FIG. 9 during the period of the sampling pulse P ₂ and outputs it to the A/D converter 22. The A/D converter 22 converts the signal A into a digital signal Ad, which is stored in the register 23a at the start of the sampling pulse _P3 . Such operations are repeated in sequence, and digital signals Ad to Dd corresponding to the envelope signals of the position information are stored in the registers 23a to 23d, respectively.

Each output signal Ad to Dd of registers 23a to 23d
is applied to multiplexers 24a and 24b. The multiplexers 24a and 24b, for example, output the digital signal Ad of the register 23a corresponding to the position information A and the register 23 corresponding to the position information B.
b digital signals Bd are selected and output to the digital adder/subtractor 25a. The digital adder/subtracter 25a performs, for example, subtraction processing to
Calculate and output B. This calculation result is stored in the register 26 at the timing of the sampling pulse _P3 . In this case, the sign (positive or negative) of the above calculation result is recorded in the flip-flop 28 at the timing of the clock signal _φ1 (10th
Signal FF in figure). The register 26 outputs a position signal Id corresponding to the signal A-B as shown in FIG. Similarly, digital adder/subtractor 2
5a performs subtraction processing on each of the digital signals Cd and Dd corresponding to the position information C and D to obtain the signal C.
-Calculate D. Therefore, the position signal Id corresponding to the signal CD as shown in FIG. 10 can be obtained from the register 26.

Further, as described above, the calculation result of the digital adder/subtractor 25a is stored in the register 27. This register 27 performs a storage operation in response to a clock signal _φ2 as shown in FIG. This clock signal _φ2
is always a sampling pulse when it occurs
It is created by the timing creation circuit 20 so that it starts at the same timing as _P2 . Furthermore, the clock signal φ ₂ is input to the digital adder/subtractor 25 at the start.
At step a, the generation of signal CD is controlled so that the calculation of signal CD is in the completed state. The digital adder/subtractor 25b calculates the difference between the calculation result of the digital adder/subtracter 25a and the output of the register 27, and stores the result in the register 29. In this way, the register 29 can output the head movement speed signal Vd corresponding to the amount of change in the position signal (signal CD), that is, the speed, which changes within the interval of the clock signal _φ2 .

[Effect on invention]

As described in detail above, according to the present invention, the main part of the servo control circuit for detecting the position and moving speed of the head can be constructed as a digital signal processing circuit. Therefore, a large number of various circuit elements such as operational amplifiers can be omitted, and analog circuits can be largely converted into digital circuits, thereby achieving high integration and general-purpose servo control circuits. Furthermore, there is an effect that the cost of the entire magnetic disk device can be reduced.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a conventional servo control circuit, Figure 2 is a diagram showing the state of servo information recorded on a magnetic disk, and Figures 3 and 4 show the operation of a conventional servo control circuit. A signal waveform diagram for explanation, FIG. 5 is a specific circuit diagram of the peak hold circuit shown in FIG. 1, FIG. 6 is a specific circuit diagram of the main part of the servo control circuit shown in FIG. 1, and FIG. is a signal waveform diagram for explaining its operation, FIG. 8 is a block diagram showing the configuration of a servo control circuit according to an embodiment of the present invention, and FIGS. 9 and 10 are signal waveform diagrams for explaining its operation. FIG. 1... Transducer, 3a to 3d... Peak hold circuit, 20... Timing creation circuit,
22...Analog-digital conversion circuit, 23a~
23d, 26, 27, 29...Register, 24
a, 24b... multiplexer, 25a, 25b
...Digital adder/subtractor, 28...Flip-flop.

Claims (1)

[Claims] 1. In a magnetic disk device that positions a magnetic head based on servo information recorded in advance on a magnetic disk board, there is a peak detection circuit that samples the servo information and detects its peak value, and a detection output from this peak detection circuit. An analog-to-digital conversion circuit that converts a signal into a digital signal, a first digital adder/subtracter that calculates a value corresponding to position information of the magnetic head based on the digital signal, and a calculation result of the first digital adder/subtracter. A second digital adder/subtracter that calculates a value corresponding to the moving speed information of the magnetic head based on the magnetic head.