Disc Drive Head Fly Height Control During Power-Up
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Solution Overview
Problem
Disc drives face issues with fly height changes due to non-operational shocks, leading to increased probability of head-medium contact events or bit error rates, which can result in 'drive not ready' failure modes, requiring effective fly height control during power-up initialization without significantly increasing time-to-ready.
Innovation Solution
A disc drive system with a control circuit that applies a fly height control value to direct the head to a first target fly height for reading system data, determining if the actual fly height is equal, and performing fly height correction when necessary, using a transfer function to adjust heater DAC values for maintaining optimal fly height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fly height control is applied during power-up initialization to prevent head-medium contact, then reliability is improved, but time-to-ready increases
Solution Approach 1:
The patent applies fly height control values during power-up initialization to proactively adjust the head fly height before normal operation begins. This preliminary action prevents head-medium contact events that could occur during early operation, thereby improving reliability without significantly extending time-to-ready because the control is applied during the existing initialization sequence
2Productivity
If fly height is reduced to increase storage capacity, then productivity is improved, but the probability of head-medium contact increases
Solution Approach 1:
The patent utilizes heater DAC values to dynamically control and adjust the fly height parameter. By changing the heater DAC parameter, the system can optimize fly height to balance storage capacity requirements with head-medium contact prevention, allowing reduced fly height for higher capacity while maintaining reliability through active control
3Reliability
If fly height control values are applied to maintain optimal head fly height, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the system automatically determines and applies appropriate fly height control values during power-up initialization based on detected conditions. This self-service approach improves reliability through active fly height management while minimizing device complexity by using existing initialization sequences and automatic determination logic rather than requiring complex external control systems
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 effectively addresses fly height changes caused by non-operational shocks, minimizing the risk of head-medium contact and bit error rates, ensuring normal operation without extending power-up initialization time or increasing time-to-ready.
Implementation Method 1
adjusting a fly height of the head over the data storage surface
Data Source
AI summary
A disc drive includes a data storage surface having a system data zone and a user data zone, and a head that communicates with the data storage surface. The disc drive also includes a control circuit communicatively coupled to the head. The control circuit is configured to, during power up initialization of the disc drive, apply a fly height control value to direct the head to fly at a first target fly height for reading system data from the system data zone. The first target fly height is substantially higher than a second target fly height for reading user data from the user data zone. The control circuit determines whether an actual fly height of the head is substantially equal to the first target fly height. The control circuit performs fly height correction when the actual fly height is not substantially equal to the first target fly height.