Disk Device Gain Correction for Uniform Track Width
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Solution Overview
Problem
Existing disk device manufacturing methods face challenges in achieving uniform track widths due to variations in the inclination of servo patterns on the disk medium, leading to non-uniform detection sensitivity and positioning control issues during servo pattern writing.
Innovation Solution
A method is introduced to measure the gain of the fine motion actuator's control signal at each radial position, calculate gain correction values, and adjust the track width accordingly, using an auxiliary servo pattern to normalize the gain and correct for variations in the inclination of the spiral pattern, thereby ensuring uniform track widths across the disk medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If servo pattern writing is performed without gain correction, then the manufacturing process is simple, but the track width uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring the gain of the fine motion actuator in advance at multiple radial positions before servo pattern writing, and storing these gain values for later correction during the writing process. This preliminary measurement and storage of gain information enables subsequent track width uniformity correction without adding complex real-time processing during writing.
Solution Approach 2:
The patent changes the control parameter by introducing gain correction values that are applied to the fine motion actuator control signal during servo pattern writing. By adjusting the gain parameter based on pre-measured values at different radial positions, the system compensates for variations in detection sensitivity and achieves uniform track widths across the disk medium.
2Manufacturing precision
If gain measurement and correction is implemented, then track width uniformity improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies self-service by using the auxiliary servo pattern already present on the disk medium to perform self-measurement of the fine motion actuator gain at various radial positions. The system utilizes its own existing resources (auxiliary servo pattern, head positioning capability) to automatically characterize and correct its own performance variations, eliminating the need for external measurement equipment or complex external calibration procedures.
3Measurement precision
If additional auxiliary patterns are added for gain measurement, then positioning control accuracy improves, but the disk medium complexity increases
Solution Approach 1:
The patent applies universality by making the auxiliary servo pattern serve multiple functions: it is used both for normal head positioning during operation and for measuring the fine motion actuator gain characteristics. By extracting multiple uses from a single existing pattern, the system achieves accurate gain measurement without requiring additional dedicated test patterns, thereby maintaining disk medium simplicity.
Data Source
AI summary
A method for manufacturing a disk device includes the steps of measuring a first gain of a control signal of a fine motion actuator while positioning a head to a first radial position of a disk medium using a coarse motion actuator but not the fine motion actuator, based on an auxiliary servo pattern recorded on the disk medium, measuring a second gain of a control signal of the fine motion actuator while positioning the head to a second radial position of the disk medium using the coarse motion actuator but not the fine motion actuator, based on the auxiliary servo pattern recorded on the disk medium, and determining gain correction values which are to be applied to a control signal for the fine motion actuator while performing servo pattern writing on the disk medium, based on the first and second gains.