Adaptive Digital Filter for Magnetic Disc Position Control

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Solution Overview

Problem

Existing magnetic disc devices face difficulties in self-adaptation for changes in external vibration frequency due to fixed filter coefficients in adaptive digital filters, leading to degraded performance when the estimated frequency significantly differs from the filter design frequency.

Innovation Solution

A magnetic disc device employs a quadratic adaptive digital filter that adjusts all filter coefficients based on estimated frequency, using a coefficient memory unit to store filter coefficients for a wide frequency range, allowing for self-adaptation and improved filtering accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed filter coefficient is used in the adaptive digital filter, then the device complexity is reduced, but the adaptability to changes in external vibration frequency deteriorates

Engineering Contradiction:

Improvefilter coefficient structureVSAvoidself-adaptation capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The filter coefficient is changed from a fixed value to a variable that dynamically adapts to the estimated frequency. The adaptive digital filter continuously updates the filter coefficient based on the estimated frequency of external vibrations, enabling the system to automatically adjust to changing vibration conditions without increasing overall device complexity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The filter coefficient parameter is made variable instead of fixed. By changing the filter coefficient based on the estimated frequency, the system achieves adaptability to different vibration frequencies. This parameter change allows the filter to maintain optimal performance across a wide frequency range while keeping the device structure relatively simple.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the filter design frequency is fixed, then the manufacturing precision is improved, but the reliability under varying vibration frequencies deteriorates

Engineering Contradiction:

Improvefilter design frequencyVSAvoidperformance consistency

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The system implements a feedback mechanism where the estimated frequency of external vibrations is continuously monitored and used to adjust the filter coefficient. This feedback loop ensures that the filter maintains high reliability and performance consistency across varying vibration frequencies by adapting to the actual operating conditions in real-time.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The filter design transitions from a static fixed frequency approach to a dynamic adaptive approach. The filter coefficient dynamically changes based on the estimated frequency, allowing the system to maintain reliable performance across a wide range of vibration frequencies while preserving the precision benefits of a well-designed fixed filter as a baseline.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If an adaptive digital filter with variable filter coefficient is used, then the adaptability to frequency changes is improved, but the device complexity increases

Engineering Contradiction:

Improveself-adaptation capabilityVSAvoidfilter coefficient structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system achieves adaptability by changing only the filter coefficient parameter based on the estimated frequency, rather than redesigning the entire filter structure. This approach minimizes the increase in device complexity while maintaining strong self-adaptation capability, as only a single parameter needs to be dynamically adjusted.

Inventive Principle:

Principle #35Parameter changes

4Productivity

If filtering is performed with significant frequency difference, then the productivity is maintained, but the measurement precision of position control deteriorates

Engineering Contradiction:

Improveposition control speedVSAvoidposition accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The filter coefficient is adjusted based on the estimated frequency to maintain filtering effectiveness even when there is a significant frequency difference between the filter design frequency and the actual vibration frequency. This parameter adaptation ensures that position control accuracy is maintained without sacrificing productivity, as the filter continues to effectively suppress vibrations across different frequency conditions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20190066727A1Magnetic disc device and position control method

Publication Date: 2019.02.28 KK TOSHIBA

AI summary

A magnetic disc device according to an embodiment has a head, a position detector, and a filter unit. The position detector detects position information of the head on the basis of servo information. The filter unit performs filtering of an estimated frequency estimated by a quadratic adaptive digital filter that performs self-adaptation for a transfer function on the basis of positional difference information between position information and target position information of the head and adjusts all filter coefficients included in the transfer function on the basis of the estimated frequency.