Read Retry Offset via ADC Distribution Analysis

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Solution Overview

Problem

Existing disc drive read retry methods, such as sweeping the read transducer across the track center, induce mechanical resonance and rotational latency, making it difficult to accurately position the read transducer and causing unwanted vibrations.

Innovation Solution

A system and method that determines the offset direction for read retries by storing ADC values, calculating indicator values from their distribution, and moving the data reader based on these calculations to optimize read retry operations, thereby minimizing mechanical resonance and latency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the read transducer is swept across the track center for read retry, then read retry coverage is improved, but mechanical resonance and rotational latency increase

Engineering Contradiction:

Improveread retry coverageVSAvoidrotational latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary analysis of ADC value distributions from the failed read attempt to determine the optimal offset direction before executing the read retry operation. This preliminary action eliminates the need for sweeping across the track center, directly reducing rotational latency while maintaining read retry coverage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical sweeping approach with a calculated offset position determined through signal analysis. By substituting the mechanical sweep with a precisely calculated single-position retry based on ADC distribution analysis, the system eliminates mechanical resonance while maintaining retrieval reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the read transducer is swept across the track center for read retry, then read retry coverage is improved, but mechanical resonance increases

Engineering Contradiction:

Improveread retry coverageVSAvoidmechanical resonance

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The system performs preliminary analysis of ADC value distributions from the failed read attempt to determine the optimal offset direction before executing the read retry operation. This preliminary action eliminates the need for sweeping across the track center, directly reducing mechanical resonance while maintaining read retry coverage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of time

If the read transducer is positioned with calculated offset based on ADC distribution, then mechanical resonance and rotational latency are reduced, but positioning complexity increases

Engineering Contradiction:

Improverotational latencyVSAvoidpositioning complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The system uses the ADC values already captured during the failed read attempt to automatically determine the optimal offset position. The ADC distribution analysis is performed on existing data without requiring additional sensing hardware or complex external positioning systems, allowing the read channel itself to provide the positioning information.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces complex mechanical positioning systems with signal-based offset calculation. By using ADC value distributions to determine the optimal read position, the system substitutes mechanical complexity with straightforward signal processing, reducing rotational latency without significantly increasing overall system complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Loss of time

If the read transducer is positioned with calculated offset based on ADC distribution, then mechanical resonance and rotational latency are reduced, but measurement precision requirements increase

Engineering Contradiction:

Improverotational latencyVSAvoidADC value analysis precision

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11682427B2System and method for managing off-track read retry

Publication Date: 2023.06.20 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

The technology disclosed herein pertains to a system and method for managing off-track retry. An implementation of a method of determining offset direction for read off-track retry includes storing analog to digital converter (ADC) values of data read from a data sector by a data reader in a read channel buffer, calculating an indicator value of the distribution of the ADC values, determining an amount of offset for the data reader based on the indicator value, and moving the data reader by the amount of offset before performing a read retry operation.