JPS6028238B2 - Voice coil motor control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voice coil motor control system, and more particularly to a voice coil motor drive control system used as a drive motor for a write/read head of a disk pack device.

Random access files are essential in modern computer systems that process large amounts of information.
It is no exaggeration to say that file performance affects system performance.

Disk pack devices have come to occupy the mainstream position for random access files due to their large storage capacity, interchangeable storage media, and relatively high-speed access. However, there is a strong demand for improved performance. One of the factors contributing to this performance improvement is increasing the track density of the disk to further increase its storage capacity, and another is increasing the speed of the drive of the read/write head to improve access time. . The present invention aims to improve the conventional drawbacks, particularly in the latter of the above-mentioned performance improvement factors. Here, the structure of the disk pack device will be briefly mentioned.

FIG. 1 is a diagram schematically showing a disk pack device and its peripheral circuits. In the figure, reference numeral 1 denotes a disk for storing information, and a plurality of disks are stacked on the same central axis to form the storage section of the disk pack device. Each of the disks 1 has a large number of concentric tracks arranged at very small intervals. Reference numeral 2 denotes a read/write head for recording and reproducing desired information on a designated track on the disk 1.

The read-no-light head 2 is provided corresponding to the front and back sides of a plurality of disks, and is integrally held by a support cart 3.
This support cart 3 moves on a rail 4. As a result, the read-no-write head 2 can move freely forward and backward in a direction perpendicular to the circle of the disk 1, and can capture a designated track in a short time. Generally, one side of a disk placed approximately in the center of a plurality of stacked disks is used for track position detection and is used as a servo disk 1'. Therefore, the read/write head 2 facing this acts as a read head 2' and sends track position information to the control section 5. On the other hand, the support cart 3 is driven forward and backward by a voice coil motor (hereinafter abbreviated as V・C・M) 6 which is drive-controlled by this control unit 5, and is attached to the other end of a coil 7 that moves linearly on the rail 4. The speed information from the speed detector 8 thus obtained is also processed in the control section 5 in a manner to be described later. An output from the central processing unit (CPU) 9 is also input to the control section 5 to designate the track on the disk 1 where the read-no-write head 2 should stop.

The control section 5 further includes a function generator (described in detail later), and this function generator determines the optimum and maximum speed at which the read/write head 2 should move on the disk 1 and the maximum speed near a designated track. Specify the deceleration speed. Of course, this specified speed is optimally controlled depending on the distance to the next truck to be stopped. However, although there are currently several types of specified speed curve shapes from the function generator, all of them have the following common drawbacks. Generally, the specified speed curve is set based on the maximum voltage that can be applied to V/C/M6 (usually about 5 steps [V] considering various conditions) and the minimum mechanical constant of the V/C/M movable system. It is preferable to do so. However, in reality, the mechanical constant inherent to the V/C/M movable system increases by up to about 10%, which is induced by a fluctuation (decrease) in the power supply voltage of about 10% or by an increase in coil resistance due to temperature rise during use. Due to increase etc.
If the specified maximum voltage is not applied to C.M or due to an increase in the mechanical constant of V.C.M, a situation arises in which the movable system of V.C.M does not operate as quickly as specified. As a natural consequence of this situation, the access time deteriorates due to a decrease in the moving speed of the read/write head 2, but an even worse result is that the read/write head is unable to capture the designated track, resulting in malfunction. It's about putting it away. This is caused by insufficient braking force of the V, C, and M caused by a drop in applied voltage during deceleration near the track, or by an increase in the mechanical constants of the V, C, and M movable system. It is considered that due to the increase in the inertial force of the system, it is no longer possible to follow the specified deviation curve. Therefore, in any of the several kinds of designated speed curves mentioned above, there is a drawback that the speed at each time must be lowered by a predetermined value in advance. That is, the maximum specified speed of the specified speed curve is smaller than the speed obtained when the maximum voltage is applied to V・C・M, and also smaller than the maximum negative acceleration that can be applied during deceleration near the specified track. There was a drawback that the specified speed curve had to be set for the negative acceleration. This is V
- This means a decrease in the cost performance of the C/M control unit 5 and the like. The present invention eliminates the above-mentioned drawbacks.
The purpose is to provide a C/M control method.

In order to achieve the above object, the present invention is characterized in that the control section 5 is provided with a feedback circuit that uses fluctuations in the power supply voltage or temperature fluctuations of the coil as feedback amounts.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows the cross-sectional structure of V.C.M6 shown in FIG. 1. However, the speed detector 8 (
Figure 1) is a well-known type that has a permanent magnet attached to a coil 7 and a detection coil surrounding it, and a detection voltage proportional to the speed is obtained from the detection coil based on Biot-Savart's law. was omitted. In this figure, magnetic flux 1 generated from a cylindrical or box-shaped permanent magnet 10
1 is a ring-shaped or rectangular magnetic pole 12, a cylindrical iron core 1
3 and a circular or square magnetic pole 14. On the other hand, the coil 7 moves while being guided in and out of the circular minute gap 15. This moving force is the magnetic pole 1
It is generated by the electromagnetic force between the magnetic flux generated between the coil 2 and the iron core 13 and the current passed through the coil. Therefore, the moving direction of the coil 7 can be easily moved forward or backward by switching the direction of the direct current applied to the coil 7. Further, the magnitude of this moving force, that is, acceleration force and deceleration force (braking force), is determined by the magnitude of the DC power value. The magnitude and direction of this DC current are applied by a DC power amplifier 21 connected to V.C.M6 in FIG. Further, the DC power amplifier 21 is controlled by a differential amplifier 22. That is, the differential amplifier 22 outputs a control signal proportional to the voltage difference between the output voltage of the function generator 23 applied to its first input and the detected voltage from the speed detector 8 applied to its second input. It is sent to the DC power amplifier 21. The function generator 23 in the block diagram shown in FIG. 3 will be explained in more detail. FIG. 4 is a block diagram showing the configuration of the function generator 23. As mentioned above, the function generator has the function of giving a specified speed curve, and this specified speed curve is generated depending on the distance difference between the current track where the read-no-write head 2 is currently located and the target track specified by the CPU 9. and change. The address of the track designated by the CPU 9 is stored in the register 31, and furthermore, this designated address is stored in the subtraction counter 32 in the function generator 23.
is applied to the first input of. On the other hand, the current position address of the read/write head 2 sent from the read head 2' (FIG. 1) is applied to the second input of the subtraction counter 32. The difference between the address of the target track output from the subtraction counter 32 and the address of the current position of the read/write head is input to the D/A converter 33 and converted into an analog quantity. Therefore, from when the read/write head starts accessing until it reaches the target track, the D/A
The output of the converter 33 changes as L, , - shown in FIG. In this figure, the vertical axis V represents the output voltage of the D/A converter, and the horizontal axis t represents the elapsed time. However, graph L shows a curve obtained when the address difference to the target track is large, and graph L2 shows a curve obtained when the address difference is small. This graph L or L2 corresponds to the specified speed curve, and the coil 7 moves along this specified speed curve. However, actually L,
Alternatively, it is not preferable to change the speed linearly like L2 in order to accurately capture the track, and unnecessarily increasing V33 because the address difference is large will not shorten the time much. In consideration of the balance of factors, a curve called V33 was put into practical use. This curve V33 is obtained by inputting the output of the D/A converter 33 (FIG. 4) to the nonlinear circuit 34. In FIG. 5, graph L3 shows this curve V33, and this L is a practical specified speed curve. The explanation will be given again according to FIG.

The input L3 (Fig. 5) from the function generator 23 is input to the first input of the differential amplifier 22, and the detected voltage from the speed detector 8 is input to the second input. 6th
The relationship is as shown in the figure. In this figure, V23 is the output voltage from the function generator 23, that is, the designated speed curve, and VB is the detected voltage from the speed detector 8. Further, the vertical axis represents voltages V23 and V8, and the horizontal axis represents elapsed time t from the start of data access. As mentioned above, there are several shapes of designated speed curves, including the shapes shown in FIGS. 7 and 8, but it will be explained later that the present invention can be implemented regardless of the shape of these designated speed curves. I think it will become clear. In FIG. 6, near the data access start time (t=0), the difference between voltages V23 and V8 is △V
, and the DC power amplifier 21 applies a large positive DC power to the coil 7 of the V.C.M6, and the coil 7 of the V.C.M6 is accelerated at high speed. Along with this, the voltage V8 from the speed detector 8 also rises rapidly, and the difference between the voltages V23 and V8 is △
Although V2 becomes smaller, the coil 7 continues to be accelerated. With further acceleration, voltage V8 reaches voltage V23, and V8 further increases due to the inertia of coil 7 and support cart 3 (FIG. 1). At this time, the polarity of the differential voltage △3 (Fig. 6) changes, and the DC power amplifier 21' transfers negative polarity DC power to V.C.
Since the voltage is applied to the coil M6, the brake is rapidly applied to the coil 7, and the specified speed curve V23 is approached again. By repeating these operations, the vehicle follows the specified speed curve endlessly and reaches the target track. However, if there is a fluctuation (decrease) in the power supply voltage during deceleration of the specified speed curve, a sufficiently large negative DC power (braking force) applied from the DC power amplifier 21 to the V/C/M6 coil 7 cannot be obtained. , the speed reaches 0 without following the specified speed curve at all, as indicated by the dotted line V8' in FIG.

Furthermore, even when the coil resistance increases due to a rise in the temperature of the coil, the mechanical time constant of the V/C/M6 movable system increases, so that the route shown by the -dotted chain line V8' is followed. As described above, this result causes malfunctions in data access. In order to prevent this, the specified speed curve V3 is used at a slightly lower level as shown by the two-dot chain line V3'.
As mentioned above, the cost performance of the C/M control system is also lowered. One embodiment based on the present invention is shown in block diagram form in FIG. 9-1.

As is clear from this figure, feedback is applied to the function generator 23 via the stranded wire 41 of the DC power amplifier 21 to which the DC power supply voltage is applied, and the output gain of the function generator 23 is changed to change the designated speed curve. ing. In other words, when the power supply voltage is at the specified maximum voltage, the coil 7 is controlled in the state of the specified speed curve V23 (Fig. 6) that can shorten the access time the most, while when the power supply voltage decreases, the output of the function generator 23 is controlled. The gain is also lowered to drop the specified speed curve to V3' (Figure 6), which is easier to control. In this way, the coil 7 is always controlled at the optimum and maximum speed.
Only when the power supply voltage decreases, the coil 7 is controlled under the specified speed curve V3', which is easy to control, but the access time is somewhat reduced. Specifically, the feedback line 41 shown in FIG. 911 may be connected to the D/A converter 33 shown in FIG. 4 or to the nonlinear circuit 34. 9th-
1, numeral 42 is a low-pass filter inserted to cut out small fluctuations in the power supply voltage and noise. Its configuration may be a normal RC smoothing circuit. FIG. 9-2 is a block diagram of the second embodiment, and most of the configuration is the same as FIG. 9-1.

In this second embodiment, as shown in the figure, an element 51 having a large resistance-temperature coefficient such as a thermistor is provided in the vicinity of the V/C/M6 coil 7, and an increase in coil resistance due to a rise in coil temperature is converted into a voltage value. This is converted and fed back to the function generator 23 via the buffer amplifier circuit 52, and the function is generated even more accurately by simultaneously taking into account information indicating the decrease in the power supply voltage and information indicating the increase in the mechanical time constant due to the increase in coil resistance. This is intended to change the output gain of the device 23, that is, the designated speed curve. As explained above, according to the present invention, the cost performance of the voice coil motor drive system in a dispack device is improved by skillfully utilizing the well-known feedback method without making any changes to the conventional V/C/M drive system. I can do it.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the disk pack device and its peripheral circuitry, Figure 2 is a cross-sectional structural diagram of the voice coil motor, Figure 3 is a block diagram of a conventional voice coil motor control system, and Figure 4 is a function diagram. A block diagram showing the contents of the generator 23, FIG. 5 is a graph for explaining the specified speed curve,
FIG. 6 is a diagram showing the relationship between the designated speed curve and the detected voltage from the speed detector, FIGS. 7 and 8 are diagrams showing examples of other designated speed curves, and FIGS. 9-1 and 2 are diagrams according to the present invention. 1 is a block diagram illustrating first and second embodiments based on FIG. In each figure, 1 is a disk, 2 is a read/write head, 6 is a voice coil motor, 7 is a coil, 8 is a speed detector, 1 is a permanent magnet, 21 is a DC power amplifier, 22 is a differential amplifier, and 23 is a A function generator, V23 is a voltage waveform representing a designated speed curve, V8 is a voltage representing the moving speed of the coil 7, 41 is a feedback circuit, and 51 is a thermistor. Figure 2 Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9-1 Figure 9-2

Claims (1)

[Claims] 1. A voice coil motor comprising a coil for linearly moving a plurality of read/write heads disposed opposite to each other on each of a plurality of disks, and a means for generating magnetic flux interlinked with the coil; a power amplifier that excites a motor; a control amplifier that controls the power amplifier according to a voltage difference between a voltage proportional to the moving speed of the coil and a voltage proportional to a predetermined designated speed curve;
A voice coil motor control method in a disk pack device comprising: a function generator that generates a voltage waveform proportional to the designated speed curve; A voice coil motor control system characterized in that a signal proportional to a change in resistance is constantly fed back to the function generator, and a voltage waveform output from the function generator proportional to the designated speed curve is changed at any time.