RRO Timing Control for Constant Density Servo Systems
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Solution Overview
Problem
In constant-density magnetic storage devices, the timing of writing repeatable run-out (RRO) data is challenging due to varying track frequencies and head positions, leading to position errors and inaccuracies in data density across different tracks.
Innovation Solution
A method is implemented to determine the track pattern frequency based on track location and desired data density, with RRO data written at a time delay inversely proportional to the track radius, using servo sync mark detection to locate positions in the servo wedge and adjust the clock source to maintain synchronization, and taking corrective action for timing discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If constant-frequency writing is used across all tracks, then the writing process is simple, but data density varies across tracks with position errors
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant-frequency writing approach to a dynamic frequency-adjustment approach. The writing frequency is dynamically modified based on track radius, with inner tracks receiving higher frequencies and outer tracks receiving lower frequencies. This dynamic adaptation ensures constant linear density across all tracks while maintaining a manageable writing process through automated frequency control.
2Manufacturing precision
If constant-density writing is implemented with frequency adjustment, then data density consistency is improved, but writing complexity increases
Solution Approach 1:
The patent implements parameter changes by systematically varying the writing frequency parameter as a function of track radius. Specifically, the frequency is adjusted inversely proportional to the track radius to maintain constant linear density. This parameter modification is achieved through automated control mechanisms that calculate and apply the appropriate frequency for each track, balancing precision with operational complexity.
Solution Approach 2:
The patent employs feedback mechanisms to monitor and adjust writing parameters in real-time. By detecting the actual writing density and comparing it with the target constant density, the system automatically modifies the writing frequency to compensate for variations. This closed-loop control reduces the perceived complexity by automating the adjustment process and providing real-time correction.
3Ease of operation
If RRO data is written without timing adjustment, then the writing process is straightforward, but position errors occur due to varying track frequencies
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-setting the appropriate writing frequency and timing parameters for each track before the actual writing operation begins. The system determines the required frequency adjustment based on track radius and prepares the writing mechanism with the correct parameters, eliminating the need for complex real-time adjustments during writing and maintaining position accuracy.
4Measurement precision
If timing delay is adjusted inversely proportional to radius to achieve predetermined offset, then position accuracy is improved, but operation complexity increases
Solution Approach 1:
The patent implements self-service by enabling the writing system to automatically determine and apply the appropriate timing delays for each track based on their radial positions. The system self-adjusts the writing timing by calculating the inverse relationship between delay and radius, eliminating the need for manual intervention or complex external control. This automated self-adjustment maintains position accuracy while simplifying the operational interface.
Data Source
AI summary
A method for writing repeatable run-out data, representing a recurring contribution to position error, to a rotating constant-density magnetic storage medium, includes repeating, for each respective track at a respective radius of the constant-density magnetic storage medium, (1) determining a respective track pattern frequency based on track location and desired data density, (2) locating a position in a respective servo wedge on the respective track based on servo sync mark detection, (3) writing the repeatable run-out data to the respective servo wedge at a time delay, from the location of the position in the respective servo wedge, that is inversely proportional to the respective radius, to achieve a predetermined offset, and (4) repeating the determining, the locating and the writing for each servo wedge on the respective track of the constant-density magnetic storage medium.