Disk Drive Head Ramp Detection via Fly Height Actuator
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Solution Overview
Problem
Existing disk drives face issues with accurately determining the head's parked state and detecting the ramp location, leading to potential failures during host command execution due to malfunctioning control firmware and inefficient use of disk space.
Innovation Solution
Implementing a fly height actuator and control circuitry to decrease the head's fly height and evaluate the corresponding fly height signal to detect whether the head is on the ramp, with a calibrated threshold to distinguish between parked and flying states, allowing for precise ramp detection and maximizing usable disk space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control firmware is used to maintain the head state (parked or un-parked), then the disk drive can track head position, but the system may fail when the firmware malfunctions in determining the head state
Solution Approach 1:
The system uses the existing fly height actuator and its inherent signal capabilities to self-determine head state without requiring complex external sensors or additional control systems. The fly height signal itself serves as the detection mechanism, allowing the system to service its own state determination needs.
Solution Approach 2:
The patent replaces complex firmware-based state determination with a physical signal-based detection method. By using the fly height actuator signal to directly indicate head state, the system substitutes mechanical/electrical signal analysis for software-based state tracking, improving reliability.
2Area of stationary object
If the ramp location is determined prior to self-servo writing, then the servo tracks can be written to maximize usable disk space, but inaccurate ramp detection reduces the maximum stroke of the actuator arm
Solution Approach 1:
The system performs preliminary ramp detection and fly height calibration before the self-servo writing process. By determining the ramp location and establishing the fly height signal threshold in advance, the system ensures that subsequent servo track writing can extend to the maximum possible radius, maximizing usable disk space.
Solution Approach 2:
The patent changes the operational parameters of the fly height actuator during the detection process. By sweeping the fly height signal across a range of values and identifying the transition point where the head contacts the ramp, the system precisely determines ramp location. This parameter sweeping approach enables accurate detection that maximizes the actuator's stroke utilization.
3Measurement precision
If the fly height signal is used to detect ramp contact, then the head state can be accurately determined, but the system requires a calibrated threshold to distinguish between parked and flying states
Solution Approach 1:
The system performs self-calibration by automatically determining the threshold value that distinguishes between parked and flying states. During the detection process, the system sweeps through fly height values and automatically identifies the transition point, eliminating the need for manual calibration procedures or external reference standards.
Solution Approach 2:
The system uses feedback from the fly height signal itself to determine both the ramp location and the calibration threshold. By monitoring the signal behavior as the head approaches and contacts the ramp, the system automatically establishes the threshold value, creating a self-referential calibration process that simplifies manufacturing.
Data Source
AI summary
A disk drive is disclosed comprising a head actuated over a disk surface, the head comprising a fly height actuator for controlling a fly height of the head, and a ramp for parking the head. A ramp procedure is executed by applying a control signal to the fly height actuator to decrease the fly height and receiving a corresponding fly height signal, and detecting whether the head is on the ramp in response to the fly height signal.