Dynamic Fly Height Heater Power Control for Disk Drive Latency
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Solution Overview
Problem
Conventional disk drives experience latency in positioning the head at the correct fly height for write operations due to the need for a minimum period of time to transition from an initial to a suitable height, often requiring the disk to complete another revolution if the target location appears before this height is achieved.
Innovation Solution
The method involves applying an initial higher power to the dynamic fly height (DFH) heater and then decreasing it until a target power is reached, allowing the head to reach the necessary height sooner than with constant power, thereby reducing the number of servo wedges or time required to achieve the correct fly height for data access operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If constant power is applied to the DFH heater, then the head transitions to the target fly height, but the transition time is excessive and may require waiting for the next disk revolution
Solution Approach 1:
The patent applies a preliminary higher power level to the DFH heater before the head needs to reach the target fly height. This preliminary action of heating the heater at elevated power prepares the thermal system in advance, enabling the head to transition to the correct fly height sooner than with constant power application, thereby reducing the waiting time potentially required for the next disk revolution.
Solution Approach 2:
The patent dynamically adjusts the DFH heater power level based on the timing requirements for head positioning. Instead of using a static constant power level, the system varies the power application - applying higher power when time is available and lower power when the target location is approaching - optimizing the balance between transition speed and energy consumption.
2Speed
If higher power is applied to the DFH heater initially, then the head reaches the correct height faster, but more energy is consumed during the transition period
Solution Approach 1:
The patent implements dynamic power adjustment where the DFH heater power level is varied over time based on the head's positioning requirements. Higher power is applied only when needed for rapid positioning, and power is reduced when the head is already positioned or when the target location is approaching, thereby optimizing the balance between positioning speed and energy consumption.
Solution Approach 2:
The patent employs periodic modulation of the DFH heater power in response to the rotational position of the disk. The power application is synchronized with the disk rotation, applying higher power during periods when the target location has not yet arrived and reducing power when the target is approaching or has arrived, creating a periodic on-demand heating pattern.
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 reduces latency by enabling the head to be positioned at a suitable height for writing sooner, resulting in better drive performance characteristics such as lower average seek times and improved data access efficiency.
Implementation Method 1
a dynamic fly height (DFH) heater operable to actuate the head vertically over the rotating disk
Data Source
AI summary
A disk drive is disclosed including a disk having a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors. The disk drive further comprises a spindle motor for rotating the disk, and a head actuated radially over the disk, wherein the head comprises a dynamic fly height (DFH) heater. Control circuitry within the disk drive is operable to position the head over one of the tracks; determine a number of servo sectors to pass under the head before a target location over the track is reached, apply an initial amount of power to the DFH heater that is dependent at least in part on the determined number of servo sectors, and decrease the initially-applied amount of power applied to the DFH heater until a predetermined target power is reached.