Spiral Track Servo for Disk Seek Reliability
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Solution Overview
Problem
Conventional data storage devices using voice coil motors struggle with efficient head positioning over disk surfaces due to limitations in servo sector design, particularly when seeking in the same radial direction as the written spiral tracks, leading to reduced performance or failed seeks.
Innovation Solution
The implementation of spiral tracks on disk surfaces that provide servo information for seeking and tracking operations, allowing for alternative radial directions to increase the number of track crossings and enhance seek operations, with control circuitry managing the read and write processes to optimize head positioning using demodulated position information and synchronized servo clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional servo sectors are used for head positioning, then the disk drive can maintain compatibility with existing read/write heads, but seek operations in the same radial direction as the written spiral tracks fail or perform poorly
Solution Approach 1:
The patent inverts the conventional approach by writing spiral tracks in the opposite radial direction to the desired seek direction. When a seek operation is required in a particular radial direction, the system instead uses spiral tracks written in the opposite direction, allowing the head to cross the tracks effectively during the seek operation. This inversion resolves the contradiction by enabling reliable seeks in both directions while maintaining compatibility with existing head mechanisms.
Solution Approach 2:
The patent transitions from conventional two-dimensional concentric track layout to a spiral track configuration that utilizes radial and angular dimensions differently. By arranging tracks as spirals rather than concentric circles, the system creates additional dimensional complexity that enables effective seeking in both radial directions, thereby improving both reliability and adaptability simultaneously.
2Productivity
If spiral tracks are written in a specific radial direction, then the track structure is simplified, but the number of track crossings during seek operations is reduced
Solution Approach 1:
The patent applies inversion by writing spiral tracks in the opposite radial direction to the desired seek direction. This creates more track crossings during seek operations because the head must traverse the spiral track in the opposite direction to the seek motion, increasing the number of intersections between the seek path and track. This resolves the contradiction by prioritizing seek speed and track crossing frequency over simplified track writing direction.
3Measurement precision
If conventional concentric tracks are used, then the disk format is simpler to implement, but the head positioning precision during seek operations deteriorates
Solution Approach 1:
The patent transitions from conventional two-dimensional concentric tracks to a spiral track configuration that utilizes both radial and angular dimensions. This dimensional change creates more opportunities for track crossings during seek operations, providing additional reference points for position error signal generation. The increased dimensional complexity of the spiral structure enables finer-grained position measurement and thus improves head positioning precision.
Solution Approach 2:
The spiral track configuration provides continuous track crossings throughout the seek operation, unlike concentric tracks which may be skipped or not crossed during radial movements. The continuous nature of spiral tracks ensures that the head constantly generates position error signals during seeking, maintaining continuous positioning feedback and improving precision without requiring additional complex structures.
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 improves seek operation efficiency by increasing spiral track crossings when seeking in opposite directions, allowing for more effective head positioning and data access, even when seeking in the same radial direction as the written spiral track.
Implementation Method 1
a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk
Implementation Method 2
Each servo sector 6i comprises a preamble 8 for storing a periodic pattern, which allows proper gain adjustment and timing synchronization of the read signal, and a sync mark 10 for storing a special pattern used to symbol synchronize to a servo data field 12
Data Source
AI summary
A data storage device is disclosed comprising a first head actuated over a first disk surface comprising a first spiral track written from an outer diameter (OD) of the first disk surface to an inner diameter (ID) of the first disk surface, and a second head actuated over a second disk surface comprising a second spiral track written from an ID of the second disk surface to an OD of the second disk surface. A seek operation of the first head over the first disk surface is performed in order to access the first disk surface by reading the second spiral track from the second disk surface, seeking the second head over the second disk surface based on reading the second spiral track, and after seeking the second head over the second disk surface, accessing the first disk surface using the first head.