Unstable Read Sensor Detection in Hard Disk Drives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing data storage systems, particularly hard disc drives, face challenges in reliably detecting unstable read sensors, such as magneto-resistive (MR) read sensors, due to their transitory and unpredictable nature, leading to significant degradation in bit error rate and signal-to-noise ratio.
Innovation Solution
A method involving a transducer with a read sensor that reads servo and calibration test data patterns at a passive fly height, with error locations identified and re-read multiple times to characterize instability, using a fly height adjustment mechanism and data channel processing to determine error conditions and reject unstable readers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read sensors are used to read data from rotating media, then data storage and retrieval is enabled, but reader instability causes transient errors and degradation in bit error rate and signal-to-noise ratio
Solution Approach 1:
The patent applies preliminary action by performing instability detection during the manufacturing process. Read sensors are tested on a test medium with known patterns before being installed in the final storage device. This allows unstable readers to be identified and rejected early, preventing them from causing bit error rate degradation in production devices.
Solution Approach 2:
The patent implements feedback by using the test medium with known servo and calibration patterns to provide reference information. The read sensor's output is compared against these known patterns to detect instability. The feedback loop includes error detection, location identification, and characterization of unstable readers based on their reading behavior.
2Productivity
If multiple transducers are tested concurrently to improve productivity, then testing efficiency increases, but system complexity and coordination requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the test medium into multiple tracks, each assigned to a specific transducer being tested. The test medium contains multiple concentric tracks with servo and calibration patterns distributed throughout. This allows multiple transducers to be tested simultaneously on different tracks without interference, improving throughput while maintaining manageable system complexity through structured organization.
Solution Approach 2:
The patent implements universality by designing a single test medium that can be used to test multiple transducers concurrently. The same test medium with its specific pattern structure serves all transducers being tested, eliminating the need for separate test media for each device and reducing overall system complexity.
3Measurement precision
If read sensors are re-read multiple times at error locations to characterize instability, then detection accuracy improves, but test time increases
Solution Approach 1:
The patent applies preliminary action by performing multiple re-reads at error locations during the initial manufacturing test phase. This preliminary characterization identifies unstable readers before they are installed in production devices, allowing for early rejection. The multiple reads are performed efficiently during the manufacturing process rather than in the field, minimizing time loss.
Solution Approach 2:
The patent implements partial action by performing multiple re-reads only at specific error locations rather than continuously scanning the entire medium. The controller identifies error locations from initial reads and then performs targeted re-reads only at those positions, reducing unnecessary testing time while maintaining detection accuracy.
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 identifies and screens out unstable read sensors, reducing bit error rates and improving channel quality by repeatedly detecting and characterizing instability conditions, enabling corrective actions during manufacturing or in-field use.
Implementation Method 1
magneto-resistive (MR) read sensors in a hard disc drive (HDD)
Data Source
AI summary
Method and apparatus for detecting unstable read sensors (readers) for data storage systems. In some embodiments, a transducer is supported adjacent a rotating data recording medium having servo data patterns interspersed with calibration test data patterns. A read sensor of the transducer reads the servo and calibration test data patterns while the transducer is maintained at a passive fly height adjacent the medium. A corresponding location on the medium is identified for an error detected during the reading of the servo and calibration test patterns. The servo and calibration test patterns at the location are reread using the read sensor to characterize the read sensor as an unstable reader.