US 5,708,581 A · Method for maximizing feedforward orthogonality for minimizing servo system nuller instability

Abstract

An n-around nuller in a disk drive track-follow loop servo system is optimized by maximizing its feedforward orthogonality (channel separation). Sine and cosine terms (signals) are injected into the track-follow loop, thereby creating the separate channels (signals), to reduce the amplitude of the n-around component. The Fourier sum is then taken in connection with a phase delay variable and integrated to produce the proper feedback for maximizing orthogonality and minimizing instability. Specifically, the feedforward cosine term is low-pass filtered to find its average value. A step is then fed into the feedforward sine term and the response of feedforward cosine is observed. Feedforward cosine is then integrated to evaluate how much "cross talk" there is between the two channels. Once the integral sum is found, it is used as a feedback element for tuning the sine and cosine terms injected into the channels, thereby maximizing feedforward orthogonality and minimizing servo system nuller instability.

Claims22

Dependent claims

A method of optimizing a track-follow loop signal in a disk drive servo system, the signal comprising separate channel feedforward signals and separate channel feedback signals, the method comprising the steps of:

(a) injecting a step signal into one of the separate channel feedforward signals;
(b) monitoring a response signal produced by the other of the separate channel feedforward signals in response to the injecting of the step signal;
and,
(c) in the event the response signal exceeds a predetermined threshold level, then further including the steps of:
(i) injecting an adaption signal into the separate channel feedback signals for producing output signals for modifying the respective channel feedforward signals and for reducing a next response signal upon a next injecting of a step signal;
and,
(ii) repeating steps (a) through (c), as necessary, with a modified adaption signal until the response signal is monitored to be within the predetermined threshold level.

4 more elements

A method of optimizing an n-around nuller for a track-follow loop signal in a servo loop of a disk drive servo system, the signal comprising separate channel feedforward signals, and separate channel feedback signals, the method comprising the steps of:

(a) injecting a step signal into one of the separate channel feedforward signals, whereby a response signal is generated at the other of the separate channel feedforward signals;
(b) effecting a Fourier sum upon each of the separate channel feedback signals in connection with a predetermined phase delay signal for producing output signals for modifying the respective channel feedforward signals;
(c) integrating the response signal to produce an integral sum for determining an amount of separation of the separate channel feedforward signals;
and,
(d) in the event the amount of separation of the separate channel feedforward signals is insufficient relative to a predetermined threshold, then further including the steps of:
(i) determining a modified phase delay signal for increasing the separation of the separate channel feedforward signals;
and
(ii) repeating steps (a) through (d), as necessary, with the modified phase delay signal until the threshold is achieved, the threshold being indicative of a separation of the separate channel feedforward signals being optimized and nuller instability being minimized.

5 more elements

A disk drive servo system comprising:

(a) a track-follow loop signal having separate channel feedforward signals and separate channel feedback signals;
(b) means for injecting a step value into one of the separate channel feedforward signals, whereby a step response signal is generated in the other of the separate channel feedforward signals;
(d) means for monitoring the step response signal;
(e) means for determining an adaption signal in response to the step response signal for reducing an amplitude of an n-around component of the track-follow loop signal;
and,
(f) means for injecting the adaption signal into the separate channel feedback signals for producing respective channel output signals for modifying the respective channel feedforward signals, wherein the respective channel feedforward signals are modified for improving separate channel signal separation and for reducing instability of the track-follow loop signal.

3 more elements

Dependencies are inferred from the claim text.

Method for maximizing feedforward orthogonality for minimizing servo system nuller instability

Life of this patent

Method for maximizing feedforward orthogonality for minimizing servo system nuller instability

Life of this patent

Abstract

Claims22