Disk Drive Fly Height Calibration Ratio Verification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Calibrating fly height settings for disk drive heads is challenging due to potential failures of integrated fly height sensors and degradation of test patterns, leading to inaccurate measurements and prolonged verification processes.
Innovation Solution
Implementing a control circuitry that adjusts and compares fly height settings between heads, using a baseline ratio and margins to detect and correct inaccuracies, and disabling fly height measurements for faulty sensors to ensure accurate calibration and maintain target fly height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fly height calibration methods using integrated sensors and test patterns are used, then fly height can be measured and adjusted, but the process is time-consuming and prone to inaccuracies due to sensor failures and pattern degradation
Solution Approach 1:
The patent creates a virtual model of the fly height calibration process by computing expected ratios from design parameters and comparing them against actual measurements. This virtual reference model eliminates the need for time-consuming physical verification steps while maintaining measurement accuracy, directly resolving the contradiction between precision and time loss.
Solution Approach 2:
The system implements feedback by continuously monitoring the ratio of fly height settings and comparing it against expected values. When deviations are detected, the system automatically adjusts the fly height actuator settings and re-verification, creating a closed-loop control system that reduces both time and improves accuracy through iterative correction.
2Reliability
If traditional verification processes are used to ensure accurate fly height calibration, then calibration accuracy can be maintained, but the verification process becomes prolonged and complex
Solution Approach 1:
The patent extracts the essential verification function from the complex traditional process by isolating the critical comparison step. Instead of performing multiple redundant verification steps, the system extracts and computes only the necessary ratio comparison against design parameters, maintaining reliability while dramatically simplifying the verification process.
Solution Approach 2:
The system performs preliminary computation of expected fly height ratios from design parameters before actual calibration occurs. This preliminary action creates a reference model that guides the calibration process, eliminating the need for complex post-calibration verification steps and reducing overall process complexity while maintaining accuracy.
3Extent of automation
If fly height sensors are used for measurement, then automated fly height control can be achieved, but sensor failures lead to inaccurate measurements and require extended verification
Solution Approach 1:
The patent introduces an intermediary computational model that mediates between the physical sensor measurements and the final calibration decision. Instead of relying directly on sensor readings, the system computes expected values from design parameters and uses this intermediary model to verify sensor accuracy, maintaining automation while improving reliability through cross-validation.
Data Source
AI summary
A disk drive is disclosed comprising a first head actuated over a first disk surface, and a second head actuated over a second disk surface. A first fly height (FH) setting is adjusted for the first head, and a second FH setting is adjusted for the second head. When a ratio of the first FH setting to the second FH setting exceeds a threshold, corrective action is taken.