JPS6032907B2 - Speed control servo circuit in magnetic disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control servo circuit in a magnetic disk device that allows stable operation without being affected by high frequency noise.

FIG. 1 schematically shows the configuration of an actuator portion of a head positioning mechanism in a magnetic disk drive, and FIG. 2 is a diagram showing the angular gradient of a roller with respect to a drive shaft.

1 in both FIGS. 1 and 2 is a drive shaft, and the drive shaft 1 rotates at a constant speed. When the drive shaft 1 is rotated at a constant speed, the rollers in contact with it rotate at a constant angle without slipping due to friction. Therefore, when the loaf 2 is set at an angle by the voice coil motor 3, the roller 2 moves along the drive shaft at a speed corresponding to the angle as shown by the arrow (Fig. 2). Therefore, the roller 2 is placed on the carriage 4, and a magnetic head (not shown) is attached to the tip of the roller 2.
By controlling the current flowing through the voice coil 5 of the voice coil motor 3, the speed of the head movement can be controlled. That is, the axis of the roller 2 is more inclined to the drive shaft 1, and the roller 2 follows a spiral path along the drive shaft 1 while being frictionally coupled between the roller 2 and the drive shaft 1.

The roller 2 is not only rotated by the drive shaft, but also performs linear motion in a direction parallel to the rotation axis of the drive shaft. Since the roller 2 is moved by the carriage 4, a magnetic head attached via an arm (not shown) of the carriage 4 reciprocates in the radial direction over a magnetic disk (not shown). In this way, carriage 4
The desired movement is obtained by simply changing the angle between the axis of rotation of the roller 2 and the axis of rotation of the drive shaft. The speed control servo circuit of the head positioning mechanism in such a magnetic disk drive is constructed as shown in FIG.

Reference numeral 101 in FIG. 3 is an adder, which provides a target speed signal 101a.
This is to calculate the difference between the carriage speed signal 101b and the carriage speed signal 101b. The output of this adder 101, that is, the error signal, is applied to a differentiating circuit 102 to calculate the frequency deviation of the error signal. The differentiating circuit 102 is required to be of second or higher order. The output of the differentiating circuit 102 is the voltage-current converter 10
It can be added to 3.

The voltage-current converter 103 receives the output of the differentiating circuit 102 and converts it from voltage to current, and the output of this voltage-current converter 103 is applied to the head positioning mechanism 104.
It is now sent to . This head positioning mechanism 104 has the structure shown in FIG. Also, 1
05 is a device for detecting the speed of the carriage and converting it into voltage, that is, a speed detector. This speed detector 105 converts the carriage speed signal 101b into the adder 1 described above.
01. The transfer function from the voltage-current converter 103 to the speed detector 105 is of so-called third order or higher. The operation of the speed control servo circuit as shown in FIG. 3 is such that when the head is moved from one track to another, when a target speed signal 101a corresponding to the distance to be moved is given to the adder 101,
An error signal appears at the output end of this adder 101, and after frequency compensation is performed in a differentiating circuit 102, this error signal is converted into a current that moves the voice coil 5 of the voice coil motor 3 by a voltage-current converter 103.

This current causes the voice coil 5 of the voice coil motor 3 to move, and the roller 2 is angled so that the carriage 4 begins to move. The movement of the carriage 4 is detected by a speed detector 10.
5 is detected as a carriage speed signal 101b. This carriage speed signal 101b is fed back to the adder 101 with a polarity opposite to that of the target speed 101a. In this way, the servo circuit moves so that the output (error signal) of the adder 101 becomes 0, and performs a predetermined operation (head movement, carriage movement) according to the target speed.
Do the following. However, in a servo circuit with such a configuration, a second-order or higher-order differentiator is used as the differentiator 102 for frequency compensation, so the gain at high frequencies increases and the output of the differentiator 102 has a larger amount than necessary. Contains high frequency components.

For example, if a discontinuous point is unexpectedly created in the input, the operation becomes unstable. The present invention has been made to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a speed control servo circuit for a magnetic disk device that is not affected by high frequency noise and is capable of stable operation.

Embodiments of a speed control servo circuit in a magnetic disk drive of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram showing the configuration of one embodiment.
201 in FIG. 4 is an adder, and the adder 2
A target speed signal a, a carriage speed signal b, and an integral output c are inputted to the input terminal of 01. Adder 2
The error signal d is sent to the differentiating circuit 202 from the output terminal of 01. This differentiating circuit 202 uses an error signal d
This is for frequency compensation, and a first-order differentiator circuit is used. The output e of the differentiating circuit 202 is sent to a voltage-current converter 203.

This voltage-current converter 203 is the output e of the differentiating circuit 202.
(hereinafter referred to as a voltage signal e) to a current signal f. This current signal f is output to the head positioning mechanism 204. The head positioning mechanism 204 is the head positioning mechanism shown in FIG.
The head positioning mechanism 204 generates outputs g and h, and the output g is sent to a speed detector 205 and an output detector 206. The speed detector 205 is for detecting the speed of the carriage and converting it into a voltage, and outputs the carriage speed signal b from its output terminal as described above.
is added to the input terminal of the adder 201. The current detector 206 is for detecting the output g of the head position detection mechanism 204, that is, the current flowing through the voice coil 5 of the voice coil motor 3 in the head position detection mechanism, and outputs the output i to the integrator 207. It is set to be sent.

The integrator 207 integrates this output i, and as described above,
The integral output c is sent to the input terminal of the force calculator 201. Next, the operation of the speed control servo circuit in the magnetic disk drive of the present invention configured as described above will be explained.

First, when the head is moved from one track to another, when a target speed signal a corresponding to the distance to be moved is given to the adder 201, an error signal d appears at the output end of the adder 201. This error signal d is transmitted to the differentiating circuit 202.
, where a first-order differential operation is performed. After that, the differentiating circuit 202 outputs the voltage signal e. This voltage signal e is sent to a voltage-current converter 203. This voltage-to-current converter 203 is applied to the voltage signal e, which is then converted into a current signal. This current signal f becomes a current that moves the voice coil 5 of the voice coil motor 3 in the head positioning mechanism 204.

When a current signal f is applied to the voice coil 5, the voice coil 5 moves, the roller 2 is angled, and the carriage 4 begins to move. This movement of the carriage 4 is detected by a speed detector 20 as a carriage speed signal b.
It is detected and taken out at step 5. This carriage speed signal b
has a polarity opposite to that of the target speed signal a. Further, the current flowing through the voice coil 5 is detected by a current detector 206 and sent to an integrator 207 as an output j.

This integrator 207 integrates the output i of the current detector 206 and adds the integrated output c to the adder 201. This integral output c
has a polarity opposite to that of the target speed signal a. The integral output c, carriage speed b, and target speed signal a thus obtained are input to an adder 201. The adder 201 adds this integral output c, the carriage speed signal b, and the target speed signal a, and controls the speed control server so that the error signal d becomes 0.
The entire Bo circuit moves. In this way, the required movement is performed in accordance with the target velocity signal, and the head moves to the desired track. FIG. 5 is a block diagram showing the structure of a second embodiment of the invention.

In the embodiment shown in FIG. 5, frequency compensation for the error signal d due to differentiation is omitted by increasing or subtracting the order of the integrator 207, so that the differentiation circuit 202 in FIG. 4 is not required. This is what I did. The other configurations and operating principles are the same as those in FIG. 4, and the same parts as in FIG. 4 are given the same reference numerals and their explanations will be omitted. FIG. 6 is a block diagram showing the configuration of a third embodiment of the present invention.

The operating principle of the embodiment shown in FIG. 6 is the same as that of FIGS. 4 and 5, but the integrator 2 is different from FIGS.
07 is taken out from the input terminal of the voltage-current converter 203. This allows the current detection circuit 206 to be omitted. Since the other parts are the same as those in the embodiment shown in FIG. 4, the same parts as in FIG. FIG. 7 is a block diagram showing a fourth embodiment of the invention.

In the case of FIG. 7, the order of the integrator 207 is increased or decreased, and the differentiating circuit 202 for frequency compensation for the error signal d is omitted. The input of the integrator 207 is the voltage -
The current is introduced from the input end of the current converter 203, and the current detector 206 is omitted. The other parts are the same as those in FIG. 4, and the same parts as in FIG. 4 are given the same reference numerals and their explanations will be omitted. As described in detail above, according to the speed control servo circuit in the magnetic disk device of the present invention, the carriage roller to which the head is attached is rotated, and the voice coil motor rotates this roller at an angle at a constant speed. In a head positioning means in which the head rotates along a drive shaft and performs linear motion in a direction parallel to the rotation axis of the drive shaft, the head reciprocates in a radial direction over a magnetic disk. When positioning the head on the target track, the head is determined based on a preset target value corresponding to the distance traveled from one track to another, the integral value of the current flowing through the voice coil of the voice coil motor, and the movement of the carriage. and the carriage speed signal obtained from the adder to obtain an error signal, converting the voltage of this error signal into a current flowing through the voice coil, and extracting the above-mentioned integral value and carriage speed signal from this current,
Since the entire circuit is operated so that the error signal becomes 0, it is not affected by high frequency noise and the operation can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an actuator portion of a head positioning mechanism applied to a speed control servo circuit in a magnetic disk drive of the present invention, and FIG. 2 is a diagram showing the angle of the roller with respect to the drive shaft in the head positioning mechanism. 3 is a block diagram showing the configuration of a speed control servo circuit in a conventional magnetic disk drive, and FIG. 4 is a block diagram showing the configuration of an embodiment of the speed control servo circuit in a magnetic disk drive of the present invention. The block diagrams shown in FIGS. 5 to 7 are block diagrams showing the configurations of other embodiments of the present invention, respectively. 1... Drive shaft, 2... Roller,
3... Voice coil motor, 4... Carriage, 5... Voice coil motor, 201...
・Adder, 202...Differential circuit, 203...
... Voltage-current converter, 204... Head positioning mechanism, 205... Speed detector, 206...
...Current detector, 207...Integrator. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A roller placed on a carriage to which a head is attached and angled by a voice coil motor rotates along a drive shaft rotating at a constant speed and rotates along the rotation axis of this drive shaft. head positioning means for causing the head to reciprocate in the radial direction on the magnetic disk by linear motion in parallel directions; an adder that outputs an error signal by adding a target speed signal preset corresponding to the distance to be traveled, a carriage speed signal obtained from the movement of the carriage, and an integrated output of the voice coil current of the voice coil motor; , a voltage-current converter that converts the voltage of this error signal into a current and energizes the voice coil of the voice coil motor, and the voice coil is moved by the current obtained by the voltage-current converter, so that the carriage Speed control in a magnetic disk device comprising a speed detector that extracts the carriage speed signal from the movement of the carriage and sends it to the adder, and an integrator that integrates the voice coil current and sends the integrated output to the adder. servo circuit. 2. The speed control servo circuit for a magnetic disk device according to claim 1, wherein the error signal is differentiated by a differentiating circuit and subjected to frequency compensation before being input to the voltage-current converter. 3. The speed control servo in the magnetic disk device according to claim 1, wherein the integrator integrates the output of a current detector that detects the current of the voice coil and adds an integrated output to the adder. circuit. 4. A speed control servo in a magnetic disk device according to claim 1 or 2, wherein the integrator integrates the error signal or the output of the differentiation circuit and adds an integral output to the adder. circuit.