HAMR Laser and Heater Power Iterative Control
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Solution Overview
Problem
Heat-assisted magnetic recording devices face challenges in controlling head-to-media spacing due to the introduction of an energy source like a laser, which complicates the control of thermal protrusion and can lead to data errors and potential damage if contact occurs during recording.
Innovation Solution
A method is developed to set the heater power of a heat-assisted magnetic recording head based on initial head-medium clearance estimates, iteratively determining optimum laser and heater powers to maintain a desired clearance, using a controller to adjust heating elements and laser power, and stopping iterations when differences in power thresholds are met to prevent head-medium contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser power is increased to improve recording performance, then recording performance is improved, but head-medium contact risk increases causing potential damage
Solution Approach 1:
The patent implements an iterative feedback mechanism where the controller monitors head-medium clearance during recording operations. Based on detected clearance variations, the controller dynamically adjusts heater power to maintain safe spacing while enabling optimal laser power for recording performance. This closed-loop feedback resolves the contradiction by allowing high laser power when clearance is sufficient while preventing contact when clearance decreases.
Solution Approach 2:
The patent dynamically changes the heater power parameter in response to detected clearance conditions. By adjusting the heater power parameter based on real-time clearance measurements, the system maintains optimal head-medium spacing that enables high laser power operation without contact risk, thus resolving the contradiction between recording performance and damage prevention.
2Manufacturing precision
If heater power is increased to maintain head-medium clearance, then clearance control is improved, but thermal protrusion control becomes complicated
Solution Approach 1:
The patent employs a self-regulating mechanism where the heater automatically adjusts its power output based on real-time clearance feedback. The controller monitors clearance and modulates heater power accordingly, creating a self-correcting system that maintains precise clearance control without requiring complex external intervention. This self-service approach simplifies the overall control architecture while achieving precise clearance management.
3Productivity
If iterative optimization is performed to determine optimal laser and heater powers, then recording performance is optimized, but processing time increases
Solution Approach 1:
The patent performs preliminary iterative optimization during the qualification process to establish baseline optimal laser and heater power settings for each head. These pre-determined optimal settings are stored and used during normal operation, eliminating the need for time-consuming iterations during production. This preliminary action resolves the contradiction by investing time upfront to gain efficiency during operational phases.
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 ensures consistent head-to-media spacing and optimal recording performance by determining operational heater and laser powers, reducing data errors and preventing damage to the recording head, allowing for precise control of thermal protrusion and maintaining desired clearances.
Implementation Method 1
The heaters heat a portion of the recording head that faces the recording medium. The heating causes a local protrusion due to thermal expansion of the material.
Implementation Method 2
uses an energy source such as a laser to heat a small spot on a magnetic disk during recording. The heat lowers magnetic coercivity at the spot, allowing a write transducer to change magnetic orientation.
Data Source
AI summary
A heater power of a heat-assisted magnetic recording head is set based on an initial head-medium clearance estimate in response to the heater power. For a plurality of iterations, an optimum laser power of the recording head is determined and a heater power is set for a next iteration that results in an optimum heater power for the optimum laser power. If differences in the heater and laser powers between two subsequent iterations are below thresholds, the iterations are stopped and the optimum heater power and the optimum laser power for one of the subsequent iterations are used as an operational heater power and an operational laser power.