Thermal Actuator Control Value Setting for Magnetic Disk Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic disk devices face challenges in accurately detecting abnormal contact between the magnetic head and the recording medium during control value setting of thermal actuators, leading to erroneous contact detection and difficulty in maintaining a constant gap.
Innovation Solution
A control value setting method for thermal actuators that performs curve fitting using a quadratic or higher function at multiple radial positions on the magnetic disk, determining abnormal contact based on the Root Mean Square (RMS) of fitting residuals exceeding a predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact detection methods are used with repetitive trials at the same radial position, then reproducibility is improved, but accuracy of abnormal contact detection deteriorates due to algorithmic bias and contact detection shifts
Solution Approach 1:
The patent transitions from single-point repetitive detection to multi-radial-position detection, adding the dimension of radial position variation. By performing contact detection at multiple radial positions (at least five) instead of repeatedly at the same position, the system can identify abnormal contacts through spatial distribution patterns rather than temporal repetition, thereby improving detection accuracy while maintaining reliability
Solution Approach 2:
The patent divides the detection process into multiple independent radial position measurements rather than single repetitive trials. Each radial position provides an independent data point, and the collective set of measurements from multiple positions enables more accurate abnormal contact detection through statistical analysis of the detection results across the segmented radial positions
2Manufacturing precision
If high-order functions (polynomials) are used for fitting, then control precision for maintaining constant gap is improved, but ability to accurately determine abnormal contact deteriorates due to insufficient discrimination of fitting errors
Solution Approach 1:
The patent changes the evaluation parameter from simple fitting error magnitude to a composite criterion that includes both fitting error (RMS) and the distribution pattern of residuals across radial positions. By analyzing whether residual errors are randomly distributed (normal) or systematically biased (abnormal contact), the system can accurately determine abnormal contacts even when using high-order fitting functions, thereby maintaining gap control precision while improving abnormal contact detection
Solution Approach 2:
The patent introduces residual analysis as an intermediary step between fitting and abnormal contact determination. Instead of directly using fitting error to judge abnormal contact, the system first calculates residuals from the high-order fit, then analyzes the residual distribution pattern to identify abnormal contacts. This intermediary analysis enables accurate discrimination between normal variations and actual abnormal contacts while preserving the benefits of high-order fitting for gap control
Data Source
AI summary
According to one embodiment, curve fitting, which uses power supplied to the thermal actuator when a magnetic head is brought into contact with a magnetic disk by the thermal actuator and a quadratic or higher curve, is performed at at least five radial positions in a radial direction of the magnetic disk in a case of setting a control value of the thermal actuator, and it is determined as abnormal contact detection when a Z value of an RMS of a fitting residual from the quadratic or higher curve of each power exceeds a predetermined value.