Magnetic Disk Actuator Filter Design for Rotation Asynchronous Disturbance
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Solution Overview
Problem
The positioning accuracy of a magnetic head in a magnetic disk device deteriorates due to rotation asynchronous disturbances, such as vibrations from server rack fans, and existing methods struggle to effectively suppress these disturbances when the actuator's frequency response changes due to manufacturing variations.
Innovation Solution
A magnetic disk device configuration that includes a loop shaping filter and a notch filter, where the parameters of the notch filter are adjusted to reflect changes in the actuator's frequency response, allowing the loop shaping filter to be redesigned to maintain effective disturbance suppression and improve positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a loop shaping filter is added to suppress rotation asynchronous disturbance, then positioning accuracy is improved, but the system becomes sensitive to actuator frequency response changes due to manufacturing variations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple filter coefficient sets corresponding to different actuator frequency response characteristics before the system operates. When manufacturing variations cause actuator frequency response changes, the system can directly select from pre-prepared coefficient sets without requiring real-time redesign, thus maintaining disturbance suppression effectiveness while adapting to variations.
Solution Approach 2:
The patent implements parameter changes by adjusting the filter coefficients of the loop shaping filter based on the actual actuator frequency response. Instead of fixing the filter parameters during design, the system measures the actual actuator characteristics and modifies the filter coefficients accordingly, enabling the filter to adapt to manufacturing variations and maintain optimal disturbance suppression performance.
2Reliability
If notch filter parameters are adjusted to match actual actuator frequency response, then actuator resonance suppression is improved, but loop shaping filter performance deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating coordinated parameter sets for both the notch filter and loop shaping filter before system operation. These pre-calculated sets ensure that when notch filter parameters are adjusted for actuator resonance suppression, the loop shaping filter parameters are simultaneously updated to maintain disturbance suppression performance, avoiding the deterioration that would occur with sequential adjustments.
Solution Approach 2:
The patent merges the design of the notch filter and loop shaping filter into a unified parameter adjustment system. Instead of treating them as independent filters that would conflict when parameters are adjusted, the system combines their parameter optimization, ensuring that changes to notch filter parameters for resonance suppression are coordinated with corresponding changes to loop shaping filter parameters for disturbance suppression.
Data Source
AI summary
According to one embodiment, a magnetic disk device comprises an actuator, a controller that controls the actuator, a loop shaping filter connected in parallel with the controller, the loop shaping filter having a parameter for suppressing a rotation asynchronous disturbance affecting the actuator, the parameter of the loop shaping filter being determined using a transfer function from an output of the loop shaping filter to before an input of the rotation asynchronous disturbance, and a notch filter that suppresses mechanical resonance of the actuator.