Actuation Efficiency Clearance Control for Hard Disk Drives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fly height control systems in data storage devices, such as hard disc drives, are inaccurate due to thermal decay and reader degradation, leading to incorrect clearance adjustments and potential damage or read errors, as they rely on absolute amplitude measurements which are affected by these factors.
Innovation Solution
A clearance control system that uses actuation efficiency, measured by comparing passive and active amplitudes, to maintain a target close point clearance between the transducing head and the storage surface, adjusting power to a clearance adjustment mechanism to achieve a target actuation efficiency slope that is a linear function of temperature, thereby eliminating the effects of thermal decay and reader degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If absolute amplitude measurements are used for fly height control, then the control system is simple to implement, but measurement precision deteriorates due to thermal decay and reader degradation
Solution Approach 1:
The patent introduces actuation efficiency as an intermediary measurement parameter. Instead of directly measuring absolute amplitude which is affected by thermal decay and reader degradation, the system measures the efficiency of actuation by comparing expected versus actual response. This intermediary metric isolates the fly height information from the degrading factors, maintaining measurement precision without increasing overall system complexity.
Solution Approach 2:
The patent changes the measurement parameter from absolute amplitude to actuation efficiency ratio. By measuring the ratio of actual amplitude to expected amplitude (or similar comparative metric), the system transforms the measurement into a relative parameter that cancels out common degrading factors. This parameter transformation maintains simplicity while improving accuracy over the absolute amplitude approach.
2Ease of operation
If absolute amplitude-based clearance adjustment is used, then the control mechanism is straightforward, but reliability deteriorates due to incorrect clearance adjustments from thermal decay and reader degradation
Solution Approach 1:
The patent implements a feedback mechanism where the measured actuation efficiency is compared against target values, and clearance adjustments are made based on the deviation. This closed-loop feedback ensures that thermal decay and reader degradation do not lead to incorrect adjustments, as the system continuously corrects based on actual performance rather than relying on absolute amplitude thresholds that drift over time.
Solution Approach 2:
The patent changes the control parameter from absolute amplitude to actuation efficiency ratio. This parameter transformation makes the clearance control reliable because the ratio metric is insensitive to thermal decay and reader degradation. The control mechanism remains straightforward as it uses the same comparative approach, but now based on a parameter that maintains its meaning over time and temperature variations.
3Measurement precision
If actuation efficiency measurement is implemented, then measurement precision improves by eliminating thermal decay and reader degradation effects, but device complexity increases
Solution Approach 1:
The patent uses actuation efficiency as an intermediary that can be derived from existing measurements without adding significant hardware complexity. The efficiency metric is calculated from the ratio of actual to expected amplitude (or similar existing signals), transforming available data into a more reliable measurement rather than requiring entirely new sensors or measurement systems.
Solution Approach 2:
The patent achieves improved measurement precision through parameter transformation rather than hardware addition. By changing from absolute amplitude measurement to actuation efficiency ratio calculation, the system extracts more reliable information from the same or existing measurement channels, minimizing the increase in device complexity while maximizing measurement accuracy.
4Device complexity
If traditional clearance control is used, then the system operates simply, but productivity deteriorates due to increased bit error rates and reduced device lifespan
Solution Approach 1:
The patent implements feedback control where actuation efficiency measurements continuously inform clearance adjustments. This ensures optimal fly height maintenance throughout device operation, preventing the accumulation of errors that would lead to bit errors and reduced lifespan. The feedback mechanism automatically compensates for thermal decay and reader degradation, maintaining high productivity without requiring complex manual intervention.
Solution Approach 2:
The patent changes the operational parameter from absolute amplitude to actuation efficiency ratio, enabling more reliable clearance control over time. This parameter transformation allows the system to maintain optimal performance characteristics throughout its operational life, reducing bit error rates and extending useful lifespan while keeping the control logic relatively simple through ratio-based comparisons.
Data Source
AI summary
A method including obtaining a target actuation efficiency slope that is a linear function of temperature when a fixed active clearance is maintained between a transducing head and an adjacent storage surface in a sealed storage device. The target efficiency slope is obtained at least in part by a temperature dependence calibration of actuation efficiency. An operating temperature of the storage device is measure. Power to a clearance adjustment mechanism is adjusted to achieve the target actuation efficiency slope at the measured operating temperature.