Servo gain optimization using model reference seeks in a disc drive

Claim 3

The method of claim 1, wherein the seek is characterized as a model reference seek wherein the reference current signal is generated from a modified sinusoidal waveform having both positive and negative components.

Claim 4

The method of claim 2, wherein the reference current signal is further characterized as a modified one minus cosine waveform scaled in relation to the length of the seek and the reference velocity and position signals are derived from the reference current signal.

Claim 5

The method of claim 1, wherein step (e) is further characterized by dividing the difference between the normalized accumulated position error value and the nominal position error value by a predetermined scale factor, the scale factor controlling a rate of convergence of the gain of the servo circuit so that the gain is converged to an optimal value over a plurality of successive seeks.

Claim 6

The method of claim 1, wherein the reference current, velocity and position signals are generated by a reference generator, the estimated position signal is generated by a multi-rate observer and the time periods are determined as multi-rate periods of the observer occurring at a multiple of a frequency at which servo information is sampled from a disc of the disc drive.

Claim 7

The method of claim 1, wherein an accumulator is used to accumulate the accumulated position error value and the accumulator is initialized at the beginning of the seek.

Claim 8

The method of claim 1, wherein the method is performed as a calibration routine when the disc drive servo circuit is in an idle mode of operation.

Claim 9

In a disc drive of the type having a rotatable disc upon which a plurality of tracks are defined, a head and a servo circuit for controllably positioning the head with respect to the tracks, an apparatus for optimizing the performance of the servo circuit comprising: reference generator circuitry generating a reference current, velocity and position for the head during a seek of selected length; observer circuitry generating an estimated position of the head during the seek; gain block circuitry having a first gain of selected magnitude, the first gain utilized during the seek; and accumulator circuitry accumulating position error during the seek, the position error corresponding to the difference between the reference position and the estimated position, the accumulator updating the first gain of the gain block circuitry by subtracting a gain adjustment factor from the first gain to obtain the second gain, the second gain stored by the gain block circuitry and used during a subsequent seek.

Claim 10

In a disc drive of the type having a rotatable disc upon which a plurality of tracks are defined, a head and a servo circuit for controllably positioning the head with respect to the tracks, an apparatus for optimizing the performance of the servo circuit comprising: reference generator circuitry generating a reference current, velocity and position for the head during a seek of selected length; observer circuitry generating an estimated position of the head during the seek; gain block circuitry having a first gain of selected magnitude, the first gain utilized during the seek; and accumulator circuitry accumulating position error during the seek, the position error corresponding to the difference between the reference position and the estimated position, the accumulator updating the first gain of the gain block circuitry by subtracting a gain adjustment factor from the first gain to obtain the second gain, the second gain stored by the gain block circuitry and used during a subsequent seek.

Claim 11

The apparatus of claim 8, wherein the seek is characterized as a model reference seek wherein the reference current signal is generated from a modified sinusoidal waveform.

Claim 12

The apparatus of claim 9, wherein the reference current signal is further characterized as a modified one minus cosine waveform scaled in relation to the length of the seek and the reference velocity and position signals are derived from the reference current signal.

Claim 13

The apparatus of claim 8, wherein the accumulator circuitry further normalizes the accumulated position error in relation to the length of the seek to provide a normalized accumulated position error.

Claim 14

The apparatus of claim 11, wherein the accumulator circuitry further determines the difference between the normalized accumulated position error and a nominal position error associated with a nominal value of gain for the servo circuit to generate a gain adjustment value, and wherein the accumulator circuitry updates the gain of the gain block through application of the gain adjustment value.

Claim 15

The apparatus of claim 12, wherein accumulator circuitry further scales the difference between the normalized accumulated position error and the nominal value of the gain.

Claim 16

A disc drive, comprising: a rotatable disc on which a plurality of tracks are defined; a head adjacent the disc; a servo circuit controllably positioning the head, the servo circuit having a servo processor which optimizes gain of the servo circuit over a plurality of model reference seeks in which the head is moved from an initial track to a destination track in accordance with sinusoidally derived reference current, velocity and position signals, wherein the servo processor is programmed to: accumulate position error during each model reference seek to determine an accumulated position error, the position error determined in relation to the difference between the reference position and an estimated position for the head at each of a plurality of multi-rate periods of the seek; determine a normalized position error by normalizing the position error in relation to the length of the seek; determine a gain adjustment value in relation to the difference between the normalized position error and a nominal position error value associated with a nominal value of gain for the servo circuit; scale the gain adjustmnent value by a scale factor, the scale factor controlling convergence of the gain of the servo circuit over the plurality of model reference seeks; and use the gain adjustment value to adjust the gain of the servo circuit.

Claim 17

A disc drive, comprising: a rotatable disc on which a plurality of tracks are defined; a head adjacent the disc; a servo circuit controllably positioning the head, the servo circuit having a servo processor which optimizes gain of the servo circuit over a plurality of model reference seeks in which the head is moved from an initial track to a destination track in accordance with sinusoidally derived reference current, velocity and position signals, wherein the servo processor is programmed to: accumulate position error during each model reference seek to determine an accumulated position error, the position error determined in relation to the difference between the reference position and an estimated position for the head at each of a plurality of multi-rate periods of the seek; determine a normalized position error by normalizing the position error in relation to the length of the seek; determine a gain adjustment value in relation to the difference between the normalized position error and a nominal position error value associated with a nominal value of gain for the servo circuit; scale the gain adjustmnent value by a scale factor, the scale factor controlling convergence of the gain of the servo circuit over the plurality of model reference seeks; and use the gain adjustment value to adjust the gain of the servo circuit.

Claim 18

The disc drive of claim 14, wherein the reference current signal used in each of the plurality of model reference seeks is characterized as a modified one minus cosine waveform, having amplitudes and durations determined in relation to the length of each seek.

Claim 19

The disc drive of claim 14, wherein at least selected ones of the plurality of model reference seeks are performed as part of a calibration routine at times when the disc drive is in an idle mode of operation.