Disk Drive Head Heater Power Limiting for Contact Detection
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Solution Overview
Problem
Existing disk drives face challenges in detecting and preventing head disk contact during calibration and operation, which can lead to permanent damage and data unavailability, especially with advanced recording heads like Dynamic Fly Height technology.
Innovation Solution
A disk drive system with a heater element on the read/write head and control circuitry that limits power to prevent contact by determining a maximum heater power level through parameter monitoring, such as motor current thresholds, to ensure the fly height is maintained above the disk surface during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heater power is increased to adjust fly height for higher recording density, then recording density is improved, but head/disk contact occurs causing friction and overheating
Solution Approach 1:
The system continuously monitors a parameter (such as motor current) that changes when head/disk contact occurs. When the monitored parameter exceeds a threshold, the control circuitry responds by limiting heater power to prevent contact, creating a closed-loop feedback system that dynamically adjusts heater power to maintain safe operation while enabling high-density recording
Solution Approach 2:
The system dynamically changes the heater power parameter based on monitored conditions. During calibration, the maximum safe heater power level is determined by gradually increasing power until contact is detected (parameter threshold exceeded). This calibrated maximum power level is then used during operation to maintain high recording density without causing contact
2Reliability
If heater power is limited to prevent head/disk contact, then reliability is improved, but fly height adjustment capability is reduced
Solution Approach 1:
The system performs preliminary calibration during drive initialization or manufacturing to determine the maximum heater power level that prevents head/disk contact for each specific drive. This pre-determined safe power limit is stored and applied during normal operation, allowing the drive to reliably use the maximum safe heater power for fly height adjustment without risk of contact
3Reliability
If head/disk contact is detected during calibration, then contact prevention is achieved, but calibration time increases
Solution Approach 1:
The system replaces complex mechanical contact detection mechanisms with electrical parameter monitoring. During calibration, the system monitors an electrical parameter (such as motor current) that naturally changes when head/disk contact occurs, eliminating the need for complex mechanical sensors or switches and enabling rapid, accurate contact detection
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
Effectively detects and prevents head disk contact during calibration and operation, ensuring drive reliability and data integrity by setting a power limit that prevents thermal expansion-induced contact, thus avoiding friction and overheating issues.
Implementation Method 1
Localized thermal expansion when the heater is powered allows the fly height of the transducer be adjusted
Implementation Method 2
The transducer rides along a cushion of air generated by the motion of the disk
Data Source
AI summary
A disk drive having a heater element on the read/write head includes control circuitry to prevent head/disk contact by limiting power to the heater element. As the power to the heater element increases, thermal expansion reduces the fly height until head/disk contact occurs. During drive calibration, a maximum power level allowed to the heater element is determined by detecting heater power at a level where a parameter value such as motor current exceeds a threshold level.