Magnetic Disk Head Position Correction via Segmented RRO Data
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic disk drives face challenges in accurately positioning the head due to repeatable runout (RRO) errors caused by spindle motor wobble, leading to position errors and potential data track misalignment, which can result in reduced write performance and increased rotational delays.
Innovation Solution
The magnetic disk drive employs a method to write RRO correction data in specific offset positions within permitted ranges on the disk, allowing for accurate head positioning by reading and applying correction amounts to maintain the head within a permissible range, thereby reducing Repeatable Position Error (RPE) and improving data track pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If RRO correction data is written only at the track center, then the correction is simple and straightforward, but the head positioning accuracy deteriorates when the head is at offset positions
Solution Approach 1:
The patent divides the single track center location into multiple segment points (first through fifth segment points) distributed at different radial positions including offset positions. RRO correction data is written at each segment point separately, allowing the system to handle offset position corrections in discrete segments rather than attempting a single comprehensive correction at the track center.
Solution Approach 2:
The patent transitions from a one-dimensional correction approach (single track center point) to a multi-dimensional approach by distributing correction data across multiple radial positions and offset positions. This dimensional expansion allows the system to capture RRO characteristics at various positions throughout the track, significantly improving positioning accuracy at offset positions.
2Adaptability or versatility
If the head is positioned at offset positions during RRO learning, then comprehensive correction coverage is achieved, but the correction amount becomes inaccurate leading to large RPE
Solution Approach 1:
The patent segments the RRO correction process into multiple independent learning operations, each executed at a specific segment point. Rather than attempting to learn RRO at offset positions directly, the system performs separate RRO learning at each segmented location, obtaining correction data that is accurate for that specific segment while maintaining overall coverage.
Solution Approach 2:
The patent performs preliminary RRO learning at multiple segment points before actual data writing operations. By pre-acquiring correction data at all segment points including offset positions, the system prepares accurate correction amounts in advance, ensuring that when the head operates at offset positions, the correct correction data is already available and accurate.
3Productivity
If RRO correction data is not written at offset positions, then the writing process is simpler and faster, but head positioning accuracy deteriorates and retries occur causing rotational delay
Solution Approach 1:
The patent segments the disk surface into multiple radial zones with segment points at different positions. By distributing RRO correction data writing across these segmented zones rather than concentrating all corrections at the track center, the system achieves comprehensive coverage without requiring excessive retries, thus maintaining writing speed while improving reliability.
Solution Approach 2:
The patent performs preliminary RRO correction data writing at all segment points including offset positions before actual data writing operations commence. This preliminary action ensures that accurate correction data is already in place, preventing positioning errors and retries during subsequent data writing, thereby maintaining both speed and reliability.
4Reliability
If the track center is distorted due to spindle motor wobble, then RRO correction is necessary, but writing correction data at the distorted track center alone is insufficient for accurate positioning
Solution Approach 1:
The patent divides the distorted track into multiple segment points (first through fifth segment points) at different radial positions. By writing RRO correction data at each segmented location rather than attempting to correct the entire distorted track from a single point, the system accurately captures the local distortion characteristics at each position, significantly improving positioning accuracy despite track center distortion.
Solution Approach 2:
The patent addresses the two-dimensional distortion of the track center caused by spindle wobble by distributing correction measurements across multiple positions and offset distances. This multi-dimensional approach to correction data collection and writing captures the complex distortion pattern throughout the track, enabling accurate positioning despite the distorted track center.
Data Source
AI summary
According to one embodiment, a magnetic disk drive in the present embodiment includes a disk including tracks, each including servo sectors, a head, and a controller configured to acquire first correction data for repeatable runout occurring in a first direction, and second correction data different from the first correction data, to write the first correction data within a first permitted range in the first direction, to write the second correction data within a write permitted range including the first permitted range and a second permitted range in a second direction opposite to the first direction, to read at least one of the first correction data and the second correction data, and to correctly place the head.