Magnetic Disk Head Position Control Using Adaptive IIR Filter
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Solution Overview
Problem
Existing magnetic disk devices face challenges in configuring adaptive filters for feedback control systems, particularly in suppressing noise frequencies, due to the complexity and cost associated with implementing Fast Fourier Transform (FFT) in hardware or software.
Innovation Solution
A magnetic disk device and head-position control method that utilizes a high-order infinite impulse response (IIR) digital filter with variable coefficients to estimate and suppress noise frequencies without relying on FFT, configuring the adaptive filter through software modules executed by the CPU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FFT is implemented in hardware to estimate frequency components for adaptive filtering, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the hardware-based FFT computation system with a software-based filter coefficient adjustment mechanism. Instead of using complex hardware FFT processors, the system uses a microcontroller to execute software that dynamically adjusts filter coefficients based on observed vibration patterns, thereby achieving frequency estimation without dedicated FFT hardware.
Solution Approach 2:
The patent creates a virtual model of the mechanical vibration system through software simulation. By copying the essential dynamics of the mechanical system into a software environment, the system can estimate frequency components through virtual experimentation and coefficient optimization rather than direct hardware measurement.
2Device complexity
If FFT is implemented in software to estimate frequency components, then device complexity is reduced, but ease of operation and computational efficiency worsen
Solution Approach 1:
The patent implements a self-adjusting filter system where the microcontroller automatically monitors vibration patterns and dynamically modifies filter coefficients without requiring manual intervention. The system serves itself by detecting resonance conditions and autonomously optimizing the adaptive filter parameters, making operation as simple as power-on.
Solution Approach 2:
The patent establishes a closed-loop feedback mechanism where the output of the adaptive filter is continuously monitored, and the filter coefficients are adjusted based on the observed performance. This automatic feedback loop eliminates the need for manual filter tuning while maintaining optimal performance across varying operating conditions.
3Measurement precision
If hardware FFT is used for noise frequency estimation, then measurement precision is improved, but on-chip die area increases
Solution Approach 1:
The patent makes the microcontroller serve multiple functions: it acts as both the control processor and the frequency analysis engine. By programming the microcontroller to perform both general control tasks and specific frequency estimation functions, the system eliminates the need for separate dedicated FFT hardware, thereby reducing overall chip area while maintaining measurement precision.
Data Source
AI summary
A magnetic disk device includes a magnetic disk on which servo information is recorded, a head to read the servo information of the magnetic disk, and a position control module. When carrying out positioning control of the head, the position control module estimates frequency components of noise in a head positioning control process, using a high-order digital filter that includes first and second variable coefficients that are each based on position error information generated from the servo information read by the head.