Actuator Control for Magnetic Disk Head Positioning
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Solution Overview
Problem
Magnetic disk devices face difficulties in accurately positioning heads due to vibrations caused by disturbances, leading to displacement and synchronization of heads and disks, which affects read/write operations and servo control accuracy.
Innovation Solution
A magnetic disk device with a controller that adjusts actuator control based on waveforms and amplitudes to suppress disturbance components, inverting polarity and correcting phases to maintain accurate head positioning during head changes, especially in synchronous resonance modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plurality of disks are vibrated by disturbance, then the heads are displaced to different positions, but positioning accuracy deteriorates
Solution Approach 1:
The controller applies preliminary anti-action by inverting the polarity of the actuator control waveform in anticipation of head displacement caused by disk vibration. When disk vibration displaces heads from their target positions, the controller detects this displacement and applies a corrected control signal with inverted polarity to counteract the displacement, thereby maintaining positioning accuracy despite the presence of vibration disturbances.
Solution Approach 2:
The system employs feedback mechanisms where the controller continuously monitors head position and disk vibration states, then adjusts the actuator control waveform accordingly. The controller uses feedback information about head displacement to dynamically correct the control signal polarity, creating a closed-loop system that compensates for vibration-induced positioning errors and maintains reliable head positioning.
2Adaptability or versatility
If one of the heads is changed to a different head, then head selection is flexible, but positioning accuracy deteriorates due to vibration
Solution Approach 1:
When switching between different heads, the controller applies preliminary anti-action by pre-inverting the polarity of the actuator control waveform based on the detected disk vibration state. This ensures that regardless of which head is selected, the control signal is already corrected to compensate for anticipated vibration effects, maintaining positioning precision while preserving head selection flexibility.
Solution Approach 2:
The system dynamically adapts the actuator control waveform polarity based on real-time detection of disk vibration states and head change events. The controller continuously adjusts the control signal characteristics to match the current operating conditions, enabling flexible head selection while maintaining positioning accuracy through dynamic compensation for vibration effects.
3Measurement precision
If the controller adjusts actuator control to suppress disturbance components, then positioning accuracy improves, but control complexity increases
Solution Approach 1:
The controller implements a relatively simple inversion-based correction mechanism rather than complex multi-parameter adjustment systems. By simply inverting the polarity of the actuator control waveform when disk vibration is detected, the system achieves improved servo control accuracy with minimal increase in control complexity. This inversion approach is computationally straightforward and easy to implement compared to more sophisticated disturbance rejection techniques.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk, a first head, a second head, an actuator configured to position the first head and the second head over the disk, and a controller configured to control the actuator based on a first value having a first waveform suppressing a disturbance component, wherein the controller is configured to invert, in the first waveform, a polarity of a third waveform succeeding a first timing with respect to a polarity of a second waveform preceding the first timing in a case where the first head is changed to the second head at the first timing.