Resonance Frequency Detection Circuit Phase Minimization

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Solution Overview

Problem

Existing resonance frequency detection methods for shock sensors in hard disk drives are inaccurate due to external disturbances and limited sensitivity, particularly when determining the resonance frequency for noise immunity and preventing signal saturation.

Innovation Solution

A method involving stimulating the resonant device with a periodic input signal, measuring the phase-difference between the input and output signals, and adjusting the signal frequency to determine the resonance frequency by minimizing the phase-difference, using a circuit with a square-wave generator, XOR gate, and processor to control the frequency, and optionally using a notch filter for noise reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If zero-cross detection method is used to determine resonance frequency, then the detection process is simple, but the measurement precision is poor due to external disturbances and limited sensitivity

Engineering Contradiction:

Improvedetection process simplicityVSAvoidresonance frequency determination accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical zero-cross detection method with an electrical phase difference measurement method. Instead of detecting when the voltage signal crosses zero (which is sensitive to external disturbances), the system measures the phase difference between the input excitation signal and the output sensor signal using electrical circuits. This substitution of detection mechanism fundamentally improves measurement precision while maintaining operational simplicity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary measurement approach by using phase difference as an intermediate parameter to determine resonance frequency. Rather than directly measuring the resonance frequency or detecting zero-crosses, the system measures the phase difference between input and output signals, which serves as an intermediary that is more robust to external disturbances and provides higher measurement precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If notch filtering is applied to prevent saturation, then noise immunity improves, but the implementation requires precise knowledge of resonance frequency which is difficult to obtain accurately

Engineering Contradiction:

Improvenoise immunityVSAvoidresonance frequency knowledge accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent employs a feedback approach where the resonance frequency determination (through phase difference measurement) feeds into the notch filter configuration. The system first accurately measures the phase difference to determine the actual resonance frequency, then uses this information to configure the notch filter parameters. This feedback loop ensures that the notch filter is precisely tuned to the actual resonance frequency, maximizing noise immunity while avoiding saturation.

Inventive Principle:

Principle #23Feedback

3Reliability

If low pass filtering is used before amplification, then signal saturation is prevented, but the useful signal bandwidth is reduced

Engineering Contradiction:

Improvesaturation preventionVSAvoiduseful signal bandwidth

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the filtering approach from broad low-pass filtering to targeted notch filtering. Instead of using a low-pass filter that attenuates all frequencies above a certain threshold (thereby reducing useful signal bandwidth), the system uses a notch filter that selectively attenuates only the specific resonance frequency. This parameter change in filtering strategy prevents saturation while preserving the useful signal bandwidth.

Inventive Principle:

Principle #35Parameter changes

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 approach provides a simple and accurate method for determining resonance frequencies, enhancing noise immunity and preventing signal saturation by effectively filtering out resonance noise, thereby maintaining signal integrity and bandwidth.

Implementation Method 1

a frequency value for the periodic input signal is determined in the pre-established frequency interval for which the phase-difference between the periodic input signal and a corresponding periodic output signal of the resonant device is minimum

Methodology Applied

Scientific EffectPhase difference:

Implementation Method 2

determining a resonance frequency of a resonant device

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS9709533B2Method and circuit for determining resonant frequencies of a resonant device

Publication Date: 2017.07.18 STMICROELECTRONICS SRL

AI summary

A method determines a resonance frequency of a resonant device. The method includes stimulating the resonant device with a periodic input signal having a frequency in a frequency interval; determining a frequency value for said periodic input signal in said frequency interval for which a phase-difference between said periodic input signal and a corresponding periodic output signal of the resonant device is minimum; generating a flag indicating that a resonance frequency has been determined; and generating signals representing said resonance frequency as a value of the frequency of said periodic input signal.