Hard Disk Head Contamination Detection via Touchdown Power
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Solution Overview
Problem
Magnetic hard disk drives face performance degradation due to metal contamination on the disk surface, leading to reduced head performance and potential tribological issues, necessitating a method to test for head contamination effectively.
Innovation Solution
A method involving detecting the touchdown power of a head with a flying height actuator, calculating back-off power, and applying operating power to determine contamination levels by measuring touchdown power before and after passing over magnetic media, with multiple cycles to assess contamination thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the flying height is reduced to increase areal density, then data storage capacity is improved, but tribological performance deteriorates
Solution Approach 1:
The patent implements dynamic flying height control by applying power to a flying height actuator during seek operations. This dynamically adjusts the flying height to be lower during seeking (improving tribological performance by reducing friction) while maintaining appropriate height during data operations. The controller coordinates this dynamic adjustment with the seek operation timing, allowing the system to optimize both areal density utilization and tribological performance at different operational phases.
2Reliability
If dynamic flying height control is implemented to balance tribological performance and data operations, then reliability is improved, but device complexity increases
Solution Approach 1:
The flying height actuator serves multiple functions: it controls flying height during seek operations to improve tribological performance, maintains optimal flying height during data read/write operations, and works coordination with the existing controller without requiring separate dedicated components. The controller integrates the actuator control into its existing operation management, making the system multi-functional without proportionally increasing complexity.
Solution Approach 2:
The system employs feedback control where the controller monitors seek operation status and accordingly adjusts the power applied to the flying height actuator. The controller determines when seeking is occurring and dynamically modifies the flying height in response, creating a closed-loop control system that automatically optimizes tribological performance based on operational conditions without requiring complex external control systems.
3Reliability
If metal contamination occurs on the disk surface, then head performance is degraded, but detection capability is insufficient
Solution Approach 1:
The patent replaces direct physical inspection or complex analytical methods with a mechanical-based detection approach using touchdown power measurement. By measuring the power required for the head to touchdown on the disk surface and comparing it before and after operations, the system detects contamination indirectly through changes in mechanical interaction characteristics. This substitution simplifies the detection mechanism while maintaining effectiveness in identifying contamination that degrades head performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for accurate detection of contamination on the head, enabling the identification of unacceptable contamination levels and potential manufacturing process adjustments to prevent contamination, thereby improving disk drive performance and reliability.
Implementation Method 1
The magnetic transducer comprises a writer and a read element. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer may be inductive or magnetoresistive.
Implementation Method 2
The magnetic transducer is supported in proximity to the magnetic disk by a hydrodynamic air bearing. As the motor rotates the magnetic disk, the hydrodynamic air bearing is formed between an air bearing surface of the slider of the head, and a surface of the magnetic disk. The air bearing serves to reduce friction and wear (between the slider and the disk surface) to an acceptable level.
Implementation Method 3
As the motor rotates the magnetic disk, the hydrodynamic air bearing is formed between an air bearing surface of the slider of the head, and a surface of the magnetic disk.
Data Source
AI summary
A method of testing a head for contamination includes detecting a first touchdown power of the head, the head having a flying height actuator; calculating a back-off power for the head using an estimated relationship between back-off power and touchdown power; determining an operating power that is equal to the detected first touchdown power minus the calculated back-off power; passing the head over a magnetic media one or more times while applying the determined operating power to the flying height actuator; detecting a second touchdown power after passing the head over the magnetic media; and determining whether contamination on the head exceeds a threshold amount based on the detected second touchdown power.