Magnetic Disk Head Position Prediction Using Hybrid Servo Demodulation
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Solution Overview
Problem
In magnetic disk devices, the detection errors of head positions using a short servo system are significant, leading to inaccuracies in tracking control and data writing processes.
Innovation Solution
A magnetic disk device that incorporates a head position demodulation unit capable of switching between normal servo and short servo demodulation, along with a controller that includes a head position prediction unit. This unit predicts head positions using the latest demodulated position and past normal servo demodulation positions, and a write inhibition determination unit to prevent data write errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If head position demodulation using a short servo system is employed, then the occupancy of servo information on disks is decreased, but the detection errors of head positions increase
Solution Approach 1:
The patent introduces an intermediary prediction process between the short servo demodulation and the actual head positioning. The prediction unit uses the latest short servo demodulated position and past normal servo demodulated positions to predict the current head position, thereby mediating the conflict between reduced servo occupancy and maintained position accuracy.
Solution Approach 2:
The patent changes the parameter of position prediction by switching between different demodulation methods (normal servo vs. short servo) and using a prediction algorithm that combines results from both methods. This parameter change allows the system to maintain accurate head position detection while using the more space-efficient short servo system.
2Measurement precision
If head position prediction is performed using latest demodulated position and past normal servo demodulation positions, then detection errors are reduced, but the complexity of the control system increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing past normal servo demodulated positions, which are then used in the prediction process. This preliminary preparation of position data simplifies the real-time prediction operation, reducing the computational complexity during actual head positioning while maintaining high prediction accuracy.
3Reliability
If write inhibition determination is performed based on predicted head position, then data write errors are prevented, but the time required for tracking control increases
Solution Approach 1:
The patent performs preliminary position prediction and write inhibition determination before the actual data write operation. By predicting the head position in advance and determining whether write inhibition is needed beforehand, the system ensures data write accuracy without adding significant time to the overall tracking control process.
Data Source
AI summary
According to one embodiment, a magnetic disk device comprises a head position demodulation unit which demodulates a position of the head by performing switching between normal servo demodulation for processing servo information written to a servo sector of the disk and short servo demodulation for processing servo information by a short servo system, and a controller comprises a head position prediction unit which predicts a head position, and the head position prediction unit performs position prediction by using a latest head position obtained by demodulation by the head position demodulation unit and a head position obtained by past demodulation by normal servo demodulation.