Tape Drive Position Control via Dithered Sampling

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Solution Overview

Problem

Servo control systems in magnetic tape storage face instability and oscillations due to signal aliases from structural resonances during the sampling process, affecting accurate positioning of read/write elements.

Innovation Solution

Implementing a dithered control rate by fluctuating the sampling frequency around a design frequency to de-tune alias signals, thereby reducing interference and oscillations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a sampling routine is used to collect position information from servo patterns, then position information can be obtained, but images or aliases of signals from structural resonances are created causing instability and oscillations

Engineering Contradiction:

Improveposition information accuracyVSAvoidcontrol system stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies dynamics by making the sampling frequency variable rather than fixed. The sampling frequency is dynamically adjusted based on detected resonance conditions, transitioning from a static sampling rate to an adaptive one that responds to system state changes, thereby eliminating aliasing while maintaining measurement accuracy

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the sampling frequency parameter in response to detected structural resonances. When resonance is detected, the sampling frequency is modified to avoid creating aliases, directly altering the sampling parameter to resolve the contradiction between obtaining position information and avoiding instability

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the number of tracks across the width of tape is increased or track width is reduced, then data storage density is increased, but accurate positioning of read/write elements becomes more difficult

Engineering Contradiction:

Improvedata storage densityVSAvoidread/write element positioning accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent implements feedback by continuously monitoring servo patterns and using the position information to adjust the read/write element positioning. The feedback loop detects deviations caused by resonance and corrects them, enabling accurate positioning even as track density increases

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical positioning adjustments with electronic servo control. Instead of relying solely on mechanical precision, the system uses electronic feedback and adjustment mechanisms to maintain accurate positioning, allowing higher track densities to be managed through control rather than pure mechanical precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7697230B2Tape drive position control

Publication Date: 2010.04.13 HEWLETT PACKARD ENTERPRISE DEV LP

AI summary

In one embodiment a tape drive system comprises a reel adapted to engage a tape cartridge, the tape cartridge comprising a tape media having a servo code written along a length of the tape media, a tape head comprising at least one servo element to detect the servo code, a drive assembly to induce relative motion between the tape and the tape drive, a servo system to control a rate of relative motion between the tape and the tape drive, wherein the servo system comprises a sampling module to sample servo code from the tape media and the sampling module implements a dithered sampling routine centered around a design sampling frequency.