Dual State Actuator Gain Estimation for Magnetic Recording
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Solution Overview
Problem
Magnetic disk devices lack sensors to measure microactuator displacements, leading to errors in estimating microactuator gains due to variations in transfer function gains with excitation amplitudes during measurement.
Innovation Solution
A magnetic disk device with a control portion that determines and updates the second measurement signal amplitude based on the first gain estimated value and calculates the second gain estimated value of the microactuator by dividing the first transfer function by the second transfer function, reducing measurement errors by equalizing signal amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transfer function measurement is performed with fixed excitation amplitude, then measurement process is simple, but gain estimation accuracy deteriorates due to gain variations with excitation amplitude
Solution Approach 1:
The patent implements dynamic adjustment of excitation amplitude during transfer function measurement. The control portion modifies the excitation signal amplitude based on the current gain estimated value to maintain consistent output levels, transforming the measurement process from static to dynamic adaptation, thereby resolving the contradiction between measurement simplicity and accuracy.
Solution Approach 2:
The patent employs feedback mechanisms where the measured transfer function gains are fed back to adjust subsequent excitation amplitudes. The control portion uses previously obtained gain estimates to determine optimal excitation levels for next measurements, creating a closed-loop system that continuously improves measurement accuracy while managing complexity through systematic feedback control.
2Adaptability or versatility
If excitation amplitude varies during measurement, then measurement flexibility increases, but measurement accuracy deteriorates due to gain variations
Solution Approach 1:
The patent systematically changes the excitation amplitude parameter during measurement based on adaptability requirements, while simultaneously adjusting other parameters (output level normalization) to maintain measurement accuracy. This coordinated parameter adjustment allows the system to adapt to different measurement conditions without sacrificing precision.
3Measurement precision
If multiple measurements are performed with different excitation amplitudes, then gain estimation accuracy improves, but measurement time increases
Solution Approach 1:
The patent performs preliminary measurements to obtain initial gain estimates before conducting final precise measurements. These preliminary actions provide baseline data that guides subsequent measurement planning, allowing the system to achieve high accuracy without excessive measurement time by strategically selecting subsequent excitation amplitudes based on preliminary results.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a first actuator which actuates a magnetic head portion including a magnetic head, a second actuator which adjusts a position of the magnetic head on a magnetic disk in a radial direction of the magnetic disk, and a control portion which determines a second measurement signal amplitude when a second transfer function is measured in accordance with a first gain estimated value of the second actuator and an amplitude of a first measurement signal amplitude to the second actuator applied when a first transfer function is measured, which calculates a second gain estimated value of the second actuator based on the first transfer function and the second transfer function, and which updates the first gain estimated value, using the calculated second gain estimated value.