Servo Burst Demodulation for Frequency Acquisition Error Compensation
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Solution Overview
Problem
As the areal density of magnetic disc drives increases, there is a growing need for more precise position control during track following, especially in the presence of vibrations that cause non-repeatable runout, which existing technologies fail to address effectively.
Innovation Solution
A servo control loop that uses a demodulation module to partially remove frequency acquisition error from position error signals by reading servo burst patterns, generating a frequency acquisition error compensated position error signal, and a servo control module to control the movement of the read/write head relative to the track on the storage media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency acquisition error is present in servo burst signals, then the position error signal can be generated, but the positioning accuracy deteriorates
Solution Approach 1:
The patent applies feedback by using the position error signal generated from servo burst patterns to control the head actuator, which in turn adjusts the head position. This closed-loop feedback mechanism continuously corrects positioning errors, improving positioning accuracy despite the presence of frequency acquisition errors in the servo burst signals.
Solution Approach 2:
The patent changes the parameter of the position error signal by compensating for frequency acquisition error effects. Through signal processing techniques, the system adjusts the PES parameters to eliminate the detrimental impact of frequency errors, thereby maintaining high positioning accuracy even when the underlying servo burst signals contain frequency acquisition errors.
2Manufacturing precision
If vibrations cause non-repeatable runout, then the head position varies, but the positioning precision deteriorates
Solution Approach 1:
The system uses feedback control where the position error signal, which includes information about head position deviations caused by vibrations, is fed back to the actuator. This enables continuous compensation for vibration-induced position variations, maintaining manufacturing precision despite the presence of harmful vibrations.
Solution Approach 2:
The patent employs preliminary action by pre-compensating for frequency acquisition errors in the servo burst signals before they affect the position error signal generation. This anticipatory correction prevents vibration-induced positioning errors from degrading precision, rather than merely reacting to them after they occur.
3Productivity
If areal density increases, then data storage capacity improves, but the position control requirement becomes more stringent
Solution Approach 1:
The patent changes the parameter of position control accuracy by implementing error compensation techniques that adapt to the increased precision requirements of high areal density systems. The frequency acquisition error compensation in the position error signal ensures that positioning accuracy is maintained even as areal density increases and positioning becomes more critical.
Solution Approach 2:
The feedback control mechanism is enhanced to provide more precise position control for high areal density systems. The closed-loop system continuously monitors and corrects head position, ensuring that the increased data storage capacity requirements do not compromise positioning accuracy, thereby resolving the contradiction between productivity and measurement precision.
Data Source
AI summary
In a servo control loop, servo burst signals that are read from a plurality of servo burst patterns that include a split servo burst pattern contain frequency acquisition error. The frequency acquisition error is at least partially removed to generate a frequency acquisition error compensated position error signal (PES).