Magnetic Disk Head Control via Plant Model Segmentation
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Solution Overview
Problem
In magnetic disk devices, residual vibration due to coil twist mode is difficult to suppress using feedforward control, as this mode is buried within rigid body and main resonance modes, making it challenging to clearly identify and address.
Innovation Solution
The magnetic disk device employs a feedforward control unit with a plant model processing unit that decomposes the plant model into submodels representing different vibration modes, including a coil twist mode, and uses these submodels to generate correction values for the microactuator to suppress vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transfer function model is used for feedforward control, then control precision is improved, but the coil twist mode cannot be clearly identified because it is buried in rigid body mode and main resonance mode
Solution Approach 1:
The patent divides the plant model into multiple submodels, each corresponding to a specific vibration mode (rigid body mode, main resonance mode, coil twist mode, etc.). This segmentation allows the system to independently process and identify each mode's characteristics without interference from other modes, thereby enabling clear identification of the previously buried coil twist mode while maintaining manageable model complexity.
2Measurement precision
If the plant model is decomposed into submodels, then identification precision of coil twist mode is improved, but device complexity increases
Solution Approach 1:
The plant model is divided into multiple submodels, each corresponding to a specific vibration mode (rigid body mode, main resonance mode, coil twist mode, etc.). This segmentation allows the system to independently process and identify each mode's characteristics without interference from other modes, thereby enabling clear identification of the previously buried coil twist mode while maintaining manageable model complexity.
Solution Approach 2:
The patent introduces a mode separation filter as an intermediary component that processes the output signals from the submodels. This filter separates and isolates the characteristics of each vibration mode, making it easier to identify the coil twist mode while managing the complexity introduced by the multiple submodels through systematic signal processing.
3Loss of time
If feedforward control is applied to suppress residual vibration, then settling time is reduced, but the coil twist mode with small damping coefficient causes continuous vibration
Solution Approach 1:
The patent divides the plant model into multiple submodels, each corresponding to a specific vibration mode (rigid body mode, main resonance mode, coil twist mode, etc.). This segmentation allows the system to independently process and identify each mode's characteristics without interference from other modes, thereby enabling clear identification of the previously buried coil twist mode while maintaining manageable model complexity.
Solution Approach 2:
The patent implements feedback control using the identified characteristics of the coil twist mode from the submodels. By continuously monitoring and adjusting based on the separated mode characteristics, the system can effectively suppress the continuous vibration caused by the underdamped coil twist mode, improving overall vibration suppression reliability.
Data Source
AI summary
According to one embodiment, a magnetic disk device comprises a feedforward control unit, which includes a plant model processing unit including a plurality of submodel processing units. Each of the submodel processing units generates a submodel output value that is an output value for an input value to be input, and the feedforward control unit generates the output value based on a plurality of the submodel output values.