Actuator Velocity Measurement via Sync Mark Frequency
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Solution Overview
Problem
In hard disk drives (HDDs), the actuator velocity at which servo spirals are written is not accurately known due to variations in mechanics, affecting position demodulation gain and requiring precise measurement.
Innovation Solution
A system comprising a positioning module, a frequency measuring module, and a simulation module calculates the actuator velocity by measuring and analyzing the frequency of sync marks on prewritten spirals, using a sensitivity function based on disk geometry and track radius, to determine the velocity at which spirals were written during self-servo-write operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-servo-write is used to write servo spirals, then productivity is improved, but measurement precision of actuator velocity deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the actuator velocity is measured by detecting the frequency of sync marks read from the servo spirals. The measured velocity is then fed back to adjust the actuator control, creating a closed-loop system that improves measurement precision while maintaining self-servo-write productivity.
Solution Approach 2:
The patent replaces direct mechanical velocity sensing with an electrical/electronic measurement approach. Instead of using mechanical sensors on the actuator, the system uses the read/write head to read sync marks from the servo spirals and calculates velocity from the frequency of these marks, substituting mechanical measurement with signal processing.
2Adaptability or versatility
If actuator velocity varies due to mechanical variations, then adaptability is improved, but manufacturing precision of servo spirals deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-writing test servo spirals at a nominal actuator velocity before actual data writing. These pre-written spirals serve as reference patterns that allow the system to measure and determine the actual actuator velocity, enabling subsequent compensation and correction to achieve precise servo positioning.
Solution Approach 2:
The patent changes the parameter being measured from direct mechanical velocity to the frequency of sync marks. By measuring the frequency of sync marks read from the servo spirals and converting this to actuator velocity, the system adapts to mechanical variations while maintaining manufacturing precision through parameter transformation and compensation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately measures the actuator velocity at which servo spirals are written, ensuring precise positioning and data storage in HDDs by accounting for radial and circumferential components of the actuator velocity, thereby improving data read and write operations.
Implementation Method 1
The read/write device 59 also includes a read element (such as a magneto-resistive (MR) element, also not shown) that senses magnetic field on the platters 52
Data Source
AI summary
A system comprises a positioning module that positions an actuator arm to read spirals that are prewritten. A frequency measuring module measures a first frequency of sync marks of said spirals. An estimation module calculates a second frequency of said sync marks when said actuator arm moves at a predetermined actuator velocity. A control module calculates an actuator velocity at which said spirals are prewritten based on said first frequency, said second frequency, and said predetermined actuator velocity.