Heat-Assisted Magnetic Recording Laser Power Control
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Solution Overview
Problem
Existing disk drive technologies face challenges in reliably writing data due to high fly heights of the head during heat-assisted magnetic recording, which can lead to collisions and decreased data reliability, as the increased laser power for heating causes a protrusion transient that requires adjustments in fly height to prevent collisions but compromises writing reliability.
Innovation Solution
The implementation of a control circuitry that adjusts the power applied to the laser and fly height actuator to compensate for high fly heights by increasing laser power initially and then decreasing it exponentially, along with controlling the fly height actuator to maintain optimal head positioning during write operations, ensuring reliable data writing by managing the thermal effects and fly height dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser power is increased for heat-assisted magnetic recording, then data writing reliability is improved, but fly height stability deteriorates causing head collisions
Solution Approach 1:
The patent applies preliminary action by increasing laser power before the actual write operation begins. This pre-heating of the disk surface reduces coercivity in advance, allowing the write head to more easily magnetize the medium when writing occurs. The laser power is increased during a pre-heat interval before data writing starts, ensuring thermal effects are established prior to the critical write moment.
Solution Approach 2:
The patent implements dynamics by continuously adjusting laser power based on fly height measurements. The system dynamically modulates laser power levels during operation, increasing power when fly height is high and decreasing power when fly height approaches normal levels. This dynamic adjustment ensures optimal heating effect while preventing head-disk collisions throughout the write operation.
2Reliability
If laser power is increased to compensate for high fly height, then data writing reliability is improved, but head collision risk increases due to protrusion transient
Solution Approach 1:
The patent employs feedback control by measuring fly height in real-time during write operations and using this information to adjust laser power accordingly. The system monitors fly height throughout the write process and dynamically modifies laser power to maintain safe separation between the head and disk surface, preventing collisions while ensuring adequate heating for reliable data writing.
Solution Approach 2:
The patent applies parameter changes by modifying laser power levels based on measured fly height conditions. When fly height is detected to be higher than normal, the system increases laser power to compensate for the reduced heating effect. This dynamic parameter adjustment ensures consistent thermal effects on the disk surface regardless of fly height variations, maintaining data writing reliability while preventing head collisions.
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 approach enhances data writing reliability by stabilizing the head position and maintaining optimal fly height, preventing collisions and ensuring consistent data quality across the disk surface, even as the laser power is increased for heat-assisted magnetic recording.
Implementation Method 1
heating the disk surface with a laser during write operations in order to decrease the coercivity of the magnetic medium
Implementation Method 2
Data is typically written to the disk by modulating a write current in an inductive coil to record magnetic transitions onto the disk surface
Data Source
AI summary
A disk drive is disclosed comprising a disk comprising a plurality of data tracks, wherein each data track comprises a plurality of data sectors. A head is actuated over the disk, wherein the head comprises a laser operable to heat the disk while writing data to the disk. When a write command is received to write data to a target data sector of a target data track, the head is positioned over the target data track. When the head reaches the target data sector, a power applied to the laser is increased to above a steady state value to compensate for a high fly height of the head. The power applied to the laser is decreased toward the steady state value while writing at least part of the data to the target data sector.