Coarse Servo Actuator Midpoint Positioning for Tape Shift Tracking

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Solution Overview

Problem

Servo systems for longitudinal tape face challenges in accurately following lateral motion due to rapid shifts without flange constraints, leading to excessive wear and power usage of coarse actuators as they attempt to track the tape's rapid lateral movement.

Innovation Solution

A servo system that includes a servo sensor, fine actuator, and coarse actuator, with a position error signal loop to sense lateral shifts and operate the coarse actuator to position at the midpoint of the excursion, allowing the fine actuator to reach both sides of the shift, thereby reducing position errors and extending actuator lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If flangeless tape guides are used to eliminate tape flexing and debris accumulation, then tape lifetime is improved, but the tape rapidly shifts laterally between guides causing excessive wear and power consumption of the coarse actuator

Engineering Contradiction:

Improvetape lifetimeVSAvoidcoarse actuator power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The actuator system is segmented into two independent components: a coarse actuator for large-range positioning and a fine actuator for precise tracking. This segmentation allows each actuator to operate within its optimal range, with the fine actuator handling rapid lateral tape shifts and the coarse actuator maintaining the head at the midpoint, thereby reducing coarse actuator power consumption while preserving tape lifetime benefits from flangeless guides

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fine actuator serves as an intermediary between the tape's lateral motion and the coarse actuator. It absorbs the rapid lateral shifts of the tape, allowing the coarse actuator to remain stationary at the midpoint rather than continuously tracking the tape's lateral excursions, thus eliminating excessive power consumption

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the coarse actuator continuously tracks the tape's rapid lateral shifts, then track following accuracy is maintained, but the coarse actuator experiences excessive wear and shortened lifespan

Engineering Contradiction:

Improvetrack following accuracyVSAvoidcoarse actuator lifespan

Core Design Contradiction:

Measurement precisionVSDuration of action of stationary object

Solution Approach 1:

The tracking function is segmented between two actuators: the coarse actuator provides stable midpoint positioning with minimal movement, while the fine actuator handles rapid lateral tracking. This segmentation reduces mechanical wear on the coarse actuator, extending its lifespan while maintaining overall track following accuracy through the fine actuator's high-speed response

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of having the coarse actuator follow the tape's lateral motion, the system inverts the approach by having the coarse actuator remain stationary at the midpoint while the fine actuator follows the tape shifts. This inversion reduces wear on the coarse actuator while preserving tracking accuracy

Inventive Principle:

Principle #13The other way round (Inversion)

3Measurement precision

If the fine actuator has a limited range of travel to attain high bandwidth, then tracking precision is improved, but the fine actuator cannot handle large lateral excursions without coarse actuator assistance

Engineering Contradiction:

Improvetracking precisionVSAvoidlateral travel range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The lateral travel range is segmented between two actuators: the fine actuator provides high-precision movement over a limited range for accurate tracking, while the coarse actuator provides large-range positioning capability. This segmentation allows the fine actuator to maintain high bandwidth and precision without requiring excessive travel range, as the coarse actuator handles the large excursions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system merges the capabilities of two actuators with different strengths: the fine actuator's high-precision, high-bandwidth movement over a limited range is combined with the coarse actuator's large-range positioning. This combination provides both tracking precision and adaptability to large lateral excursions

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP2433281B1Positioning coarse servo actuator of tape servo system to allow fine servo actuator to follow tape shift excursions

Publication Date: 2012.12.19 INTERNATIONAL BUSINESS MACHINE CORPORATION

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AI summary

Methods, servo systems, and data storage drives follow the lateral shift excursions of longitudinal tape, for example, from flangeless tape guides. A servo sensor is configured to sense lateral position of a tape head with respect to longitudinal servo tracks of the tape, a fine actuator is configured to translate the head laterally, and a coarse actuator is configured to translate the fine actuator laterally. Position error is determined between the head and a desired position related to the servo track, and the fine actuator operated to translate the head laterally to reduce the position error. In the embodiment, lateral shift excursion is sensed from the position error, and the coarse actuator is positioned substantially at a midpoint of the lateral shift excursion. Thus, the fine actuator follows the lateral shift excursions, while the coarse actuator remains at the midpoint.