Seeking control apparatus and method for disk drives, using slew-rate limit for control output

Claim 2

A seeking control method for disk drives, the method comprising steps of: detecting a velocity difference between a moving velocity of a read-write means of a disk drive to be controlled and a reference velocity which is defined as a function of the number of residual tracks; generating a control output which is proportional to the detected velocity difference; limiting rate of change of the control output to be lower than a predetermined level; and converting the control output, which experienced the step of limiting a rate of change, into current supplied to a positioner.

Claim 3

A seeking control method for disk drives as claimed in claim 1, further comprising a step of: limiting the upper limit of the control output generated in the step of generating a control output to a value corresponding to a maximum possible value of the current supplied to the positioner.

Claim 4

A seeking control method for disk drives as claimed in claim 2, further comprising a step of: limiting the upper limit of the control output generated in the step of generating a control output to a value corresponding to a maximum possible value of the current supplied to the positioner.

Claim 5

A seeking control method for disk drives as claimed in claim 3, wherein: the reference velocity is determined by calculating moving velocities which are obtained by integrating a time-scaled waveform of design acceleration for driving the read-write means from an end point of positioning towards a starting point for positioning; each moving velocity corresponds to a number of tracks transformed from each of calculated distances of the read-write means, the distances being obtained by further integrating the results of the above integration, and each integration is performed: with respect to the reference velocity for the slowdown stage, in an interval from an end point of positioning up to the time of said switching of the reference velocity; and with respect to the reference velocity for the speedup stage, in an interval from an end point of positioning up to time T a which satisfies the following conditions: V(T.sub.a)=V(T.sub.s)+V.sub.error where V(T a ) is the calculated moving velocity at T a , V(T s ) is the calculated moving velocity at a point when the control output which experienced the step of limiting a rate of change and which belongs to a speedup stage begins to change with a constant slope so as to enter a slowdown stage; and V error is a velocity error necessary for generating a maximum control output which is the control output at a point when the control output which experienced the step of limiting a rate of change and which belongs to a speedup stage begins to change with a constant slope so as to enter a slowdown stage.

Claim 6

A seeking control method for disk drives as claimed in claim 3, wherein the comparison level is set to a value at which a difference between the actual moving velocity and the reference velocity which is caused by the limiting of the rate of change is corrected.

Claim 7

A seeking control method for disk drives as claimed in claim 1, wherein: the reference velocity is defined based on different functions for speedup and slowdown stages, and the switching of the reference velocity from a speedup stage to a slowdown stage is performed when the control output which experienced the step of limiting a rate of change enters a slowdown stage with respect to the signal level thereof and reaches a comparison level.

Claim 8

A seeking control method for disk drives as claimed in claim 1, wherein: the reference velocity is defined based on different functions for speedup, constant-speed, and slowdown, and the first switching of the reference velocity from a speedup stage to a constant-speed stage is performed when the control output which experienced the step of limiting a rate of change and which belongs to the speedup stage reaches a comparison level corresponding to a point when the control output converges on zero, and the second switching of the reference velocity from the constant-speed stage to a slowdown stage is performed when the control output which experienced the step of limiting a rate of change enters the slowdown stage with respect to the signal level thereof and reaches a comparison level.

Claim 9

A seeking control method for disk drives as claimed in claim 7, further comprising the step of: limiting the upper limit of the control output generated in the step of generating a control output to a value corresponding to a maximum possible value of the current supplied to the positioner.

Claim 10

A seeking control method for disk drives as claimed in claim 7, wherein: the reference velocity is determined by calculating moving velocities which are obtained by integrating a time-scaled waveform of design acceleration for driving the read-write means from an end point of positioning towards a starting point for positioning; each moving velocity corresponds to a number of tracks transformed from each of calculated distances of the read-write means, the distances being obtained by further integrating the results of the above integration, and each integration is performed: with respect to the reference velocity for the slowdown stage, in an interval from an end point of positioning up to the time of said second switching; with respect to the reference velocity for the constant-speed stage, in an interval from an end point of positioning up to the time of said first switching; and with respect to the reference velocity for the speedup stage, in an interval from an end point of positioning up to time T a which satisfies the following conditions: V(T.sub.a)=V(T.sub.s)=V.sub.error where V(T a ) is the calculated moving velocity at T a , V(T s ) is the calculated moving velocity at a point when the control output which experienced the step of limiting a rate of change and which belongs to a speedup stage begins to change with a constant slope so as to enter a slowdown stage; and V error is a velocity error necessary for generating a maximum control output which is the control output at a point when the control output which experienced the step of limiting a rate of change and which belongs to a speedup stage begins to change with a constant slope so as to enter a slowdown stage.

Claim 11

A seeking control method for disk drives as claimed in claim 7, wherein each comparison level is set to a value at which a difference between the actual moving velocity and the reference velocity which is caused by the limiting of the rate of change is corrected.

Claim 12

A seeking control method for disk drives as claimed in claim 1, wherein: the step of limiting a rate of change of the control output lower than a predetermined level is performed by means of limiting the rate of change with respect to a step-form voltage variation of the control output immediately before the conversion into current, and transforming the variation into a variation having constant slope.

Claim 13

A seeking control method for disk drives as claimed in claim 1, wherein the disk drive is a magnetic disk drive and the read-write means is a magnetic head.

Claim 14

A seeking control method for disk drive as claimed in claim 1, wherein the disk drive is an optical disk drive and the read-write means is a beam.

Claim 15

A seeking control apparatus for disk drives, the apparatus comprising: a reference velocity generator for generating a reference velocity which is defined as a function of the number of residual tracks; a subtractor for detecting a velocity difference between a moving velocity of a read-write means of a disk drive to be controlled and the reference velocity, and outputting the detected difference; a proportional amplifier for amplifying the output from the subtractor; a slew-rate limiter for limiting a rate of change of the control output from the proportional amplifier to be lower than a predetermined level, and outputting a limited output; and a power amplifier for converting the control output from the slew-rate limiter into current supplied to a positioner.

Claim 16

A seeking control apparatus for disk drives, the apparatus comprising: a reference velocity generator for generating a reference velocity which is defined as a function of the number of residual tracks; a subtractor for detecting a velocity difference between a moving velocity of a read-write means of a disk drive to be controlled and the reference velocity, and outputting the detected difference; a proportional amplifier for amplifying the output from the subtractor; a slew-rate limiter for limiting a rate of change of the control output from the proportional amplifier to be lower than a predetermined level, and outputting a limited output; and a power amplifier for converting the control output from the slew-rate limiter into current supplied to a positioner.

Claim 17

A seeking control apparatus for disk drives as claimed in claim 14, further comprising: an output limiter, inserted between the proportional amplifier and the slew-rate limiter, for limiting the maximum value of the control output from the proportional amplifier.

Claim 18

A seeking control apparatus for disk drives as claimed in claim 15, further comprising: a selector switch, provided between the output limiter and the slew-rate limiter, the switch setting the output limiter to be operational only at the speedup stage of seeking.

Claim 19

A seeking control apparatus for disk drives as claimed in claim 14, further comprising: a feedforward output generator for outputting a feedforward output which corrects the output from the proportional amplifier, the feedforward output being defined as a function of the number of residual tracks; and an adder, inserted between the proportional amplifier and the output limiter, for adding the slew-rate from the proportional amplifier and the output from the feedforward output generator and outputting the added result.

Claim 20

A seeking control apparatus for disk drives as claimed in claim 17, further comprising: a selector switch, provided between the feedforward output generator and the adder, the switch setting the feedforward output generator to be non-operational only at the speedup stage of seeking.

Claim 21

A seeking control apparatus for disk drives as claimed in claim 14, wherein: the reference velocity generator generates the reference velocity which is defined based on different functions for speedup and slowdown stages; and the switching of the reference velocity from the speedup stage to the slowdown stage is performed when the control output from the slew-rate limiter enters a slowdown stage with respect to the signal level thereof and reaches a comparison level.

Claim 22

A seeking control apparatus for disk drives as claimed in claim 19, further comprising: an output limiter, inserted between the proportional amplifier and the slew-rate limiter, for limiting the maximum value of the control output from the proportional amplifier.

Claim 23

A seeking control apparatus for the disk drives as claimed in claim 19, wherein the comparison level is set to a value at which a difference between the actual moving velocity and the reference velocity which is caused by the limiting of the rate of change is corrected.

Claim 24

A seeking control apparatus for disk drives as claimed in claim 14, wherein: the reference velocity generator generates the reference velocity which is defined based on different functions for speedup, constant-speed, and slowdown stages; a first switching of the reference velocity from the speedup stage to the constant-speed stage is performed when the control output from the slew-rate limiter, which belongs to the speed up stage, reaches a comparison level corresponding to a point when the control output converges on zero; and a second switching of the reference velocity from the constant-speed stage to the slowdown stage is performed when the control output from the slew-rate limiter enters a slowdown stage with respect to the signal level thereof and reaches a comparison level.

Claim 25

A seeking control apparatus for disk drives as claimed in claim 22, further comprising: an output limiter, inserted between the proportional amplifier and the slew-rate limiter, for limiting the maximum value of the control output from the proportional amplifier.

Claim 26

A seeking control apparatus for disk drives as claimed in claim 22, wherein each comparison level is set to a value at which a difference between the actual moving velocity and the reference velocity which is caused by the limiting of the rate of change is corrected.

Claim 27

A seeking control apparatus for disk drives as claimed in claim 14, further comprising: a selector switch, provided between the slew-rate limiter and the power amplifier, the switch setting the slew-rate limiter to be non-operational at the slowdown stage of seeking.

Claim 28

A seeking control apparatus for disk drives as claimed in claim 14, wherein the disk drive is a magnetic disk drive and the read-write means is a magnetic head.

Claim 29

A seeking control apparatus for disk drive as claimed in claim 14, wherein the disk drive is an optical disk drive and the read-write means is a beam.