GB2266388A

GB2266388A - Hard disc head postioning drive system

Info

Publication number: GB2266388A
Application number: GB9307872A
Authority: GB
Inventors: Satoshi Yamamoto; Tetsuo Ueda; Isao Yoneda
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1992-04-20
Filing date: 1993-04-16
Publication date: 1993-10-27
Anticipated expiration: 2013-04-16
Also published as: KR0128265B1; KR930022345A; BR9301407A; GB9307872D0; JP2528585B2; TW207018B; MY110153A; JPH05303827A; GB2266388B

Abstract

The head 1 of a disc data store is driven to a target position by energising the motor 2 to produce a first, acceleration phase, a second, constant speed phase and a third, deceleration phase. During the constant speed phase, the speed is monitored to determine whether it is within a predetermined range of speeds. If it is, no drive current is applied to the motor. If it is outside the range, correcting drive current is applied. The purpose is to reduce audible noise and power consumption. The system may be used in a computer. <IMAGE>

Description

A METHOD FOR CONTROLLING THE DRIVE OF A HARD DISC AND AN APPARATUS THEREFOR, AND A PERSONAL COMPUTER Detailed Description of the Invention Field of the Industrial Application The present invention relates to a method for controlling the drive of a hard disc and an apparatus therefor, and a personal computer.

Prior Art As an example of a mechanism for positioning a head for use in a magnetic disc storage apparatus, a rotary type has been known. Such rotary type positioning mechanism comprises a carriage on which a head arm is mounted, and a voice coil motor for driving the carriage. The motor comprises a flat voice coil and magnets provided so as to sandwich the voice coil. In such motor, the intensity and direction of an electric current supplied to the voice coil is controlled to generate a force in proportion to the intensity of the current. The force thus produced allows the voice coil to be activated so as to swing the head arm.

As an example of a technique for positioning the head, a sector servo method has been known in which the head is positioned by using servo information (a servo pattern) embedded between sectors. In accordance with the method set forth above, a position signal is represented by a sampled value for each sector. In order to carry out high-speed positioning operations in accordance with the above method, when a target track is far apart from the head, the head is accelerated to shorten a moving time, while when the target track comes close, the head is decelerated fully enough to minimize the overshoot which occurs in switching to the step of operations.

In view of this, a speed curve showing a relationship between a position and a speed is constructed beforehand. When the speed control operation is carried out, the moving speed of the head is controlled to fit the curve prepared in advance.

A seek time consists of a moving period and a settling period. The moving period is a time period during which the head is continuously moved at a high speed until the head comes immediately before a target track. The moving period consists of a uniformly accelerated moving period, a constant moving period, and a decelerated moving period. The settling period is a time period during which operations are continued until the head is accurately positioned in accordance with a target servo signal. Fig ll(B) is a speed profile relating to a speed in the case where a time-head position characteristic as shown in Fig. 11(A) is used.

In order to realize the speed profile shown in Fig. 11(B), the constant current is supplied to the voice coil motor during the uniformly accelerated moving period, the current having a value calculated in accordance with a difference between a target speed (tabulated) at the current position of the head and an actual speed is supplied during the constant moving period, and the current having a value which is gradually reduced so as to fit a predetermined speed curve is supplied during the decelerated moving period starting at a point at which the deceleration of the head is started. Fig. ll(C) is a profile showing a relationship between time and a value of the current to be supplied to the voice coil motor.

Problems to Be Solved by the Invention However, the prior art mechanism for positioning a head set forth above has some drawbacks. The current value changes drastically because the intensity and direction of the current supplied to the voice coil motor is controlled in accordance with a difference between a target speed (referred as a tabulated speed value) and an actual speed at each position of the head during the constant moving period. Because of this, an actuator, a head arm, a head or the like resonate, causing large noises.

A further problem is that since the current is constantly supplied to control the speed during seek period, reduction in the power consumption is limited, and a further reduction is impossible heretofore.

In order to resolve the above problems, an object of the present invention is to provide a method and an apparatus for controlling the drive of a hard disc, in which not only noises but also the power consumption during the seek period is reduced.

Another object of the present invention is to provide a personal computer which can reduce noises due to the resonance occurring with the apparatus for controlling the drive of a hard disc during the seek period.

Means for Solving the Above Problems In order to achieve the above objects, a method for controlling the drive of a hard disc of the present invention is characterized by comprising a first step of accelerating a head during a period from a point at which a seeking operation starts to a point at which a moving speed of the head reaches a predetermined target speed; a second step of moving the head at a constant speed during a period from the point at which the head reaches the target speed to a predetermined point at which deceleration of the head starts; and a third step of decelerating the head during a period from the point at which the deceleration of the head starts, to a point which is just before the head reaches a target track; wherein the second step comprises the step of determining whether or not a moving speed of the head between servo sectors is within a predetermined range including the target speed each time servo information is detected, and the step of turning off an electric current supplied to a voice coil motor for driving the head if the determination obtained by the determining step is positive, or supplying the current to the voice coil motor if the determination is negative.

v An apparatus for controlling the drive of a hard disc of the present invention is characterized by comprising a voice coil motor for driving a head; detecting means for detecting servo information of a servo sector; calculating means for calculating a moving speed of the head in accordance with a sector time and the servo information detected by the detecting means; and speed control means for controlling a current supplied to the voice coil motor so that the head is accelerated during a period from a point at which a seeking operation starts to a point at which the moving speed of the head calculated by the calculating means reaches a predetermined target speed, the head is moved at a constant speed during a period from a point at which the head reaches the target speed to a predetermined point at which deceleration of the head starts, and the head is decelerated during a period from the point at which the deceleration of the head starts to a point which is just before the head reaches a target track; wherein the speed control means comprises a determining means for determining whether or not the moving speed of the head is within a predetermined range including the target speed every time servo information is detected by the detecting means, during a period from the point at which the head reaches the target speed to the predetermined point at which deceleration of the head starts; and current control means for turning off the current supplied to the voice coil motor if the determination obtained by the determining means is positive, or supplying the current to the voice coil motor if the determination is negative.

Further, a personal computer is characterized by comprising: an apparatus for controlling the drive of a hard disc having a voice coil motor for driving the head, detecting means for detecting servo information of a servo sector, calculating means for calculating a moving speed of the head in accordance with a sector time and servo information detected by the detecting means, and speed control means for controlling a current supplied to the voice coil motor so that the head is accelerated during a period from a point at which a seeking operation starts to a point at which the moving speed of the head as calculated by the calculating means reaches a predetermined target speed, the head is moved at a constant speed from a point at which the head reaches the target speed to a predetermined point at which deceleration of the head starts, and the head is decelerated during a period from the point at which the deceleration of the head starts to a point which is just before the head reaches a target track, the speed control means having a determining means for determining whether or not the moving speed of the head is within a predetermined range including the target speed every time servo information is detected by the detecting means, during a period from the point at which the head reaches the target speed to a predetermined point at which deceleration of the head starts, and current control means for turning off the current supplied to the voice coil motor if the determination obtained by the determining means is positive, or supplying the current to the voice coil motor if the determination is negative; and read/write control means for controlling reading/writing of the apparatus for controlling the drive of a hard disc.

Effects In accordance with the present invention, at step 2, each time servo information is detected, it is determined whether or not a moving speed between servo sectors of the head is within a predetermined range including a target speed. If the determination is positive, the supply of the current to the voice coil motor for driving the head is turned off. If the determination is negative, the current is supplied to the voice coil motor.

Further, in accordance with the present invention, the determining means determines whether or not the moving speed of the head is within a predetermined range including a target speed, during a period from a point at which the head reaches the target speed to a predetermined point at which deceleration of the head starts; and the current supplied to the voice coil motor is turned off if the determination obtained by the determining means is positive, or the current is supplied to the voice coil motor if the determination is negative.

Embodiments The present invention is explained in detail by way of embodiments with reference to the accompanying drawings.

Brief Descriptions of the Drawings Fig. 1 is a block diagram showing one embodiment of the present invention.

Fig. 2 is a graph provided to explain a procedure for controlling the speed of the head during the constant moving period.

Fig. 3 is a flow chart showing a procedure for MPU 8 to control the speed during the constant moving period at the seek time as shown in Fig.

1.

Fig. 4 is a characteristic chart illustrating a relationship between time and a cylinder number, and a relationship between time and a speed characteristic in the practically used machine which uses the present invention.

Fig. 5 is a characteristic chart illustrating a relationship between time and a cylinder number, and a relationship between time and a speed characteristic in the practically used prior machine of a conventional type.

Fig. 6 illustrates waveform charts obtained from experimental results with respect to the value of the current flowing in the voice coil motor, and noises in the practically used machine which uses the present invention.

Fig. 7 illustrates waveforms obtained from experiments with respect to the value of the current flowing in the voice coil motor, and noises in the practically used machine of the conventional type.

Fig. 8 is a power spectrum chart illustrating the power spectrum of noises produced by the practically used machine which uses the present invention and that of noises produced by the conventional type practically used machine.

Fig. 9 is a perspective view showing a personal computer according to one embodiment of the present invention.

Fig. 10 is a block diagram showing each electrical connection between respective parts shown in Fig. 9.

Fig. 11 are charts useful to explain the control of the head speed during the seek time as has been carried out conventionally.

In Fig. 1, a head 1 is mounted on a head arm. The head arm is rotarydriven by a voice coil motor 2.

A signal amplifier 3 amplifies data and analog servo signals from the head 1. A filter 4 removes noises from the data and the analog servo signals from the signal amplifier 3.

A signal processing circuit 5 comprises a peak detector 5A, VFO (Variable Frequency Oscillator) 5B and a code converter 5C. A readout signal from the filter 4 is converted into a digital signal, which is then supplied to a hard disc controller 6. In a writing operation, digital data from the hard disc controller 6 are directly supplied from the code converter 5C to the signal amplifier 3 to be converted into current values, which are then supplied to the head 1.

A servo digital data processing circuit 12 acting as a detecting means provides track number information (16 bits) based on servo information from the peak detector 58.

A servo analog data processing circuit 7 acting as a detecting means comprises an amplifier, a sample and hold circuit, and an A/D converter.

The circuit 7 provides offset information (8 bits) between tracks based on the servo information from the filter 4. MPU 8 acting as a calculating means detects a moving speed of the head 1 based upon the track number information from the servo digital data processing circuit 12, the offset information between tracks from the servo analog data processing circuit 7, and a sector time, namely, a time period from detection of one sector to detection of a next sector. The MPU 8 also acting as a determining means determines whether or not the moving speed of the head 1 is within a predetermined range including the target speed, each time servo information is detected, during a period from a point at which the speed reaches the target speed to a predetermined point at which the deceleration of the head is started.

A D/A convertor 9 converts an 8-bit digital signal from the MPU 8 into an analog signal. A notch filter 10 removes mechanical resonances. A motor driver 11 acting as a current control means controls the intensity and direction of the current supplied to the voice coil motor 2 based upon an analog signal supplied from the notch filter 10.

In comparison with the technology of the prior art, the present invention differs from it in a method for controlling a speed during a uniform motion (transfer) period. When it is detected that the moving speed of the head between sectors reaches the target speed, and that a distance from the current position of the head to the target position is greater than a maximum distance in the deceleration table, the MPU 8 determines a current period as being the constant moving period. In accordance with the embodiment described above, the MPU 8 determines whether or not a mean speed Vmean of the head 1 between sectors satisfies the following formula (1), during the constant moving period. (See Fig. 2) The mean speed Vmean is calculated based upon a sector time and a distance between the servo sectors.

V + 6 2 Vmean > V - 6 - (1) wherein V represents a target speed, and 6 represents a tolerable speed error.

It is assumed that y represents a distance to a target track, and ytable represents a maximum distance in a speed table used for uniformly accelerating and decelerating the speed (wherein a relationship between the moving speed of the head and the distance to the target track is tabulated), in other words, ytable represents a position at which a decelerating motion is started. Then, a relationship between y and ytable is expressed by the following formula (2): y 2 ytable .~.... (2) When the MPU 8 makes the determination with respect to the formula (1), and when the determination is negative, the MPU 8 supplies 8-bit digital signals to the motor driver 11 via the D/A converter 9 and the notch filter 10 to cause the current to be supplied to the voice coil motor 2 so that the speed of the head 1 is controlled to fit the formula (1).In the meantime, if the determination is positive, the MPU 8 supplies an 8-bit digital signal representative of zero to the motor driver 11 so that a value of the current to be supplied to the voice coil motor 2 is reduced to zero.

Fig. 3 is a flow chart showing a procedure under which the MPU 8 shown in Fig. 1 controls the speed of the head for each sector during the constant moving period of the seek time.

When the MPU 8 starts seeking operations, at step 1, the MPU 8 determines whether the following relation is satisfied or not: A distance to a target track > A distance to start the use of the speed table If the determination is negative, the process goes to step 2. At step 2, a flag for indicating that the target speed has been reached is cleared.

At step 3, a normal control routine is carried out, and thereafter, the process returns to the initial step.

In the normal control routine, the MPU 8 carries out the following operations, depending upon to which period a current period belongs, among the uniformly accelerated moving period, the constant moving period, and a decelerating moving period. More specifically, when the current period is the uniformly accelerated moving period, the MPU 8 controls the head to make the uniformly accelerated movement. When the current period is the constant moving period, the MPU 8 controls the head to make the constant movement.

When the current period is the decelerated moving period, the MPU 8 controls the head to make the decelerated movement.

In the meantime, if the determination obtained at step 1 is positive, that is,: the result is: A distance to a target track > A distance to start the use of the speed table, then, the process goes to step 4. At step 4, the MPU 8 determines whether or not the flag indicating that the target speed has been reached is set to 1, namely, whether or not the speed of the head in the previous sector has reached the target speed, and at the same time the speed was within the range of an allowable speed error. If the determination is negative, the process goes to step 5. At step 5, the MPU 8 determines whether the following relation is satisfied or not: A current speed > A target speed If the determination is negative, the process goes to the step 3. In the meantime, if the determination obtained at step 5 is positive, the process goes to step 6.At step 6, the flag indicating that the target speed has been reached is set to 1. Then, the process goes to step 7.

In the meantime, if the determination obtained at step 4 is that the flag indicating that the target speed has been reached is set to 1, the process goes to step 7. At step 7, the MPU 8 determines whether or not the following relation is satisfied: A Current Speed-A Target Speed < An Allowable Speed Error If the determination is negative, the process goes to step 9. At step 9, the flag indicating that the target speed has been reached is cleared. Then, the process goes to step 3. In the meantime, if the determination obtained at step 7 is positive, that is, the following relation is satisfied: A Current Speed-A Target Speed < An Allowable Speed Error then, the value of the current to be supplied to the voice coil motor 2 is reduced to zero by the motor driver 11, and thereafter, the process returns to the initial step.

Algorithm illustrated by the flowchart in Fig. 3 is restarted by the MPU 8 when a next sector is detected by the MPU 8.

When external forces such as for example, the friction of shafts of a head actuator, or the tension of a flexible cable are sufficiently small, and thus, a change in the speed of the head is small even if the current supplied to the voice coil motor is reduced to zero during the constant moving period (not more than about 10 msec), the speed control described above is more effectively performed.

Test Results: Fig. 4 is a chart which illustrates a relationship between the time and the speed, and a relationship between the time and the track of a head in a practically used machine which uses the present invention. Fig. 5 is a chart which illustrates a relationship between the time and the speed, and a relationship between the time and the track of a head in a practically used prior machine of a conventional type. As is apparent from Figs. 4 and 5, a change in the speed occurring when the value of the current supplied to the voice coil motor 2 is reduced to zero during the constant moving period, in accordance with the present invention is remarkably smaller than a speed change which occurs with the prior art.

Figs. 6 and 7 are respective charts illustrating a current flowing in the voice coil motor and a noise when the speed of the head 1 is controlled as shown in Fig. 4, and those when the speed of the head 1 is controlled as shown in Fig. 5.

By comparing Fig. 6 with Fig. 7 with respect to the change in the current flowing in the voice coil motor during the constant moving period, it is seen that the change which occurred in the case of the machine which uses the present invention is smaller than that in the case of the conventional prior machine. Further, the noise in the same period as produced by the machine which uses the present invention is smaller than that produced by the conventional prior machine.

Further, as seen from Fig. 8 which illustrates a noise power spectrum of the machine which uses the present invention, and that of the practically used prior machine of the conventional type, the noise produced by the machine which uses the present invention is smaller by about 5dB than that produced by the conventional type practically used prior machine.

Power consumption of the machine of the present invention during the seek time was reduced by about 4%.

Fig. 9 is a laptop type personal computer which has the built-in apparatus for controlling the drive of a hard disc according to one embodiment of the present invention, as shown in Fig. 1.

In Fig. 9, a reference numeral 91 denotes a main body. A reference numeral 90 denotes the apparatus for controlling the drive of a hard disc as shown in Fig. 1. A reference numeral 94 denotes a keyboard in which predetermined keys are arranged which are used to input a command and others. A reference numeral 93 denotes an apparatus for controlling the drive of a floppy disc.

Fig. 10 is a block diagram showing each electrical connection between respective units of the personal computer shown in Fig. 9.

In Fig. 10, the reference numerals 90, and 92 to 95 denote the same parts as in Fig. 9, and a reference numeral 8 denotes the same part as in Fig. 1. The reference numeral 95 is a CPU which functions to serve as a read/write control means. The CPU controls the apparatus 90 for controlling the drive of a hard disc via I/F96.

The personal computer of one embodiment of the present invention can reduce resonances among an actuator, a head arm, and a head and others in the apparatus 90 for controlling the drive of a hard disc during the seek time so that resonances between the apparatus 90 and the main body 91 are reduced, thus resulting in reduction in noises due to the resonances.

Advantageous Effects of the Invention As has been described thus far, in accordance with the present invention, the MPU 8 determines whether the moving speed is within the predetermined range including the target speed or not. If the determination is positive, the current supplied to the voice coil motor is turned off.

If it is negative, the current is supplied to the voice coil motor. Thus, the present invention has the advantage that not only noises produced during the seek time is reduced but also the power consumption is reduced.

Further, the present invention has the built-in apparatus for controlling the drive of a hard disc capable of reducing noises produced during the seek time so that resonances between the apparatus for controlling the drive of a hard disc and the main body are reduced, resulting in reduction in noises during the seek time.

Claims

1. A method for controlling the drive of a hard disc, comprising: a first step of accelerating a head during a period from a point at which a seeking operation starts to a point at which a moving speed of said head reaches a predetermined target speed; a second step of moving said head at a constant speed during a period from said point at which said head reaches said target speed to a predetermined point at which deceleration of said head starts; and a third step of decelerating said head during a period from said point at which said deceleration of said head starts, to a point which is just before said head reaches a target track; said method characterized in that said second step comprises the step of determining whether or not a moving speed of said head between servo sectors is within a predetermined range including said target speed each time servo information is detected, and the step of turning off an electric current supplied to a voice coil motor for driving said head if the determination obtained by said determining step is positive, or supplying the current to said voice coil motor if said determination is negative.

2. Apparatus for controlling the drive of a hard disc, comprising: a voice coil motor for driving a head; detecting means for detecting servo information of a servo sector; calculating means for calculating a moving speed of said head in accordance with a sector time and the servo information detected by said detecting means; and speed control means for controlling a current supplied to said voice coil motor so that said head is accelerated during a period from a point at which a seeking operation starts to a point at which the moving speed of said head calculated by said calculating means reaches a predetermined target speed, said head is moved at a constant speed during a period from a point at which said head reaches said target speed to a predetermined point at which deceleration of said head starts, and said head is decelerated during a period from said point at which the deceleration of said head starts to a point which is just before said head reaches a target track; said apparatus characterized in that said speed control means comprises:: determining means for determining whether or not the moving speed of said head is within a predetermined range including said target speed every time servo information is detected by said detecting means, during a period from said point at which said head reaches said target speed to said predetermined point at which deceleration of said head starts; and current control means for turning off the current supplied to said voice coil motor if said determination obtained by said determining means is positive, or supplying the current to said voice coil motor if said determination is negative.

3. A personal computer comprising: an apparatus for controlling the drive of a hard disc having a voice coil motor for driving said head, detecting means for detecting servo information of a servo sector, calculating means for calculating a moving speed of said head in accordance with a sector time and servo information detected by said detecting means, and speed control means for controlling a current supplied to said voice coil motor so that said head is accelerated during a period from a point at which a seeking operation starts to a point at which the moving speed of said head calculated by said calculating means reaches a predetermined target speed, said head is moved at a constant speed from a point at which said head reaches said target speed to a predetermined point at which deceleration of said head starts, and said head is decelerated during a period from said point at which the deceleration of said head starts, to a point which is just before said head reaches a target track, said speed control means having a determining means for determining whether or not the moving speed of said head is within a predetermined range including said target speed every time servo information is detected by said detecting means, during a period from said point at which said head reaches said target speed to a predetermined point at which deceleration of said head starts, and current control means for turning off the current supplied to said voice coil motor if the determination obtained by said determining means is positive, or supplying the current to said voice coil motor if said determination is negative; and read/write control means for controlling reading/writing of said apparatus for controlling the drive of a hard disc.