Voice Coil Motor Resistance Estimation for Disk Seek Control
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Solution Overview
Problem
Magnetic disk apparatus seek control becomes unstable due to changes in VCM resistance caused by heat generation and variations in component properties and environmental changes, leading to inaccuracies in positioning and extended seek times.
Innovation Solution
Incorporating a VCM resistance estimation unit and an equivalent current force constant estimation unit to calculate VCM resistance and equivalent current force constant based on acceleration and velocity with saturated VCM voltage, allowing for precise control of VCM current profiles to improve positioning accuracy and reduce seek time without the need for a voltage sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If VCM resistance changes due to heat generation during seek, then positioning accuracy deteriorates, but seek control stability is maintained only with fixed parameters
Solution Approach 1:
The patent implements dynamic parameter adaptation by continuously estimating VCM resistance and equivalent current force constant during operation, and adjusting the seek control parameters accordingly. This transforms the static control system into a dynamic one that adapts to changing conditions, resolving the contradiction between maintaining stability with fixed parameters and achieving accuracy with changing parameters.
Solution Approach 2:
The patent employs feedback mechanisms by measuring acceleration and velocity during seek operations, using these measurements to estimate VCM resistance and force constant, and then using these estimates to adjust subsequent control actions. This closed-loop feedback system enables the controller to compensate for parameter changes, maintaining both stability and accuracy.
2Measurement precision
If equivalent current force constant changes due to environmental variations, then seek control accuracy deteriorates, but system simplicity is maintained with fixed control parameters
Solution Approach 1:
The system performs self-diagnosis and self-adjustment by automatically estimating its own parameters (VCM resistance and force constant) from operational data without requiring external calibration or complex manual adjustment mechanisms. This self-service approach maintains accuracy while avoiding the complexity of external calibration systems.
Solution Approach 2:
The patent changes the control parameters (VCM resistance and equivalent current force constant) from fixed values to dynamically adjusted values based on real-time estimates. This parameter adaptation enables the system to maintain accuracy under varying environmental conditions without requiring a completely complex reconfigurable control architecture.
3Measurement precision
If VCM voltage is saturated during acceleration seek, then estimation accuracy improves, but additional measurement requirements increase system complexity
Solution Approach 1:
The patent uses acceleration and velocity measurements as intermediary variables to indirectly estimate VCM resistance and force constant. Instead of directly measuring resistance (which would require additional sensors), the system uses readily available motion data as intermediaries to infer the electrical parameters, maintaining accuracy without adding measurement complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the accuracy of VCM resistance estimation, improves the precision of magnetic head movement, and shortens seek times by stabilizing seek control despite changes in VCM resistance and equivalent current force constant.
Implementation Method 1
a voice coil motor, a driving circuit that applies a VCM current to the voice coil motor
Data Source
AI summary
According to one embodiment, a VCM resistance estimation unit estimates a VCM resistance in a voice coil motor based on an acceleration and a velocity of a magnetic head with a VCM voltage saturated, and an equivalent current force constant estimation unit estimates an equivalent current force constant of the voice coil motor based on the acceleration and the velocity of the magnetic head with the VCM voltage saturated.