HDD Head Preheating Time Adjustment for Fly Height Stability
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Solution Overview
Problem
Hard disk drives (HDDs) face performance variations due to structural differences in head portions, such as core width and manufacturing variations, which affect write processing performance, and there is a need to optimize fly height control to avoid collisions with magnetic disk projections.
Innovation Solution
The HDD employs a preheating time adjustment method, where the preheating time for the heater element is adjusted based on read and write processing operations to optimize the fly height, using a CPU-controlled process that determines the optimal preheating time by evaluating read results and adjusting the preheating interval to stabilize the fly height before data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed preheating time is used for all head portions, then the control process is simple, but performance variations occur due to structural differences in head portions
Solution Approach 1:
The patent implements dynamic preheating time adjustment by determining optimal preheating times for each head portion based on read processing results and writing processing characteristics. The control circuit dynamically selects different preheating times from a plurality of predetermined values, transforming the static fixed-time approach into a dynamic adaptive system that responds to actual head portion performance characteristics.
Solution Approach 2:
The patent changes the preheating time parameter based on measured performance characteristics. By determining optimal preheating times through read/write operations and adjusting the preheating time parameter accordingly, the system adapts to structural variations in different head portions, improving write processing performance while maintaining control simplicity through predetermined time values.
2Stability of the object's composition
If preheating starts early to ensure stable fly height, then fly height stability is improved, but collision with magnetic disk projections may occur
Solution Approach 1:
The patent applies preliminary action by determining the optimal preheating time in advance through read processing results and storing these values for future writing operations. This preliminary determination allows the system to start preheating at the precisely calculated optimal time, achieving stable fly height while avoiding premature heating that could cause collision with magnetic disk projections.
Solution Approach 2:
The patent implements feedback by using read processing results to determine optimal preheating times for subsequent writing operations. The control circuit continuously adjusts preheating timing based on feedback from read operations, creating a closed-loop system that optimizes fly height stability while preventing collision with projections through adaptive timing adjustment.
3Reliability
If different preheating times are determined for each head portion, then performance is optimized, but the control process becomes more complex
Solution Approach 1:
The patent applies segmentation by determining optimal preheating times for each head portion individually based on its specific characteristics. The control circuit maintains separate preheating time values for different head portions, allowing each to be optimized independently for its structural characteristics while managing complexity through systematic determination methods.
Solution Approach 2:
The patent changes the preheating time parameter for each head portion based on measured performance characteristics. By determining optimal preheating times through read/write operations and adjusting the preheating time parameter accordingly for each head, the system achieves performance optimization while managing control complexity through predetermined time values stored in memory.
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 equalizes performance differences caused by structural variations, optimizes the start time of preheating to avoid disk projections, and stabilizes fly height for improved read and write operations, enhancing HDD performance and reliability.
Implementation Method 1
a first heater which generates heat via a first electric power
Implementation Method 2
the head portion... floats over the rotating magnetic disk... controlling floating of the slider over the magnetic disk so as to shorten a distance between the head portion and the magnetic disk
Data Source
AI summary
A disk device includes first and second recording surfaces, a first head for the first recording surface, including a first heater which generates heat via a first electric power, a second head for the second recording surface, including a second heater which generates heat via a second electric power, and a control circuit configured to execute a first preheating operation in which the first electric power is supplied to the first heater for a first time interval prior to starting a first writing process to write data on the first recording surface by the first head, and to execute a second preheating operation in which the second electric power is supplied to the second heater for a second time interval prior to starting a second writing process to write data on the second recording surface by the second head. The first time interval is different from the second time interval.