Resonant Sensor Module With Synchronous Filtering for Linear Output

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Solution Overview

Problem

Physical quantity sensors, such as those detecting acceleration, face challenges with nonlinearity in their output values, which existing solutions address by increasing the circuit scale and cost through dedicated correction circuits.

Innovation Solution

A physical quantity sensor module incorporating a resonant frequency shift sensor, a reference signal oscillator, and frequency delta-sigma modulators, along with filters that operate synchronously with the measurement and reference signals, corrects nonlinearity without the need for additional dedicated circuits, by adjusting the cutoff frequency and smoothing timing through filter taps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a nonlinearity correction circuit is provided to correct the nonlinearity of the measurement target signal, then the measurement precision is improved, but the device complexity and cost increase

Engineering Contradiction:

Improvemeasurement precisionVSAvoidcircuit scale

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the traditional hardware-based nonlinearity correction circuit with a software-based correction method. The measurement target signal is corrected by applying a nonlinearity correction value calculated from the relationship between the measurement target signal and the output signal, eliminating the need for additional physical correction circuits and reducing device complexity while maintaining measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the parameter correction approach by calculating a nonlinearity correction value based on the relationship between the measurement target signal and output signal. This correction value is then applied to adjust the measurement target signal, achieving nonlinearity correction through parameter transformation rather than additional hardware circuits.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a nonlinearity correction circuit is provided to correct the nonlinearity of the measurement target signal, then the measurement precision is improved, but the manufacturing cost increases

Engineering Contradiction:

Improvemeasurement precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses a computationally inexpensive correction approach that calculates nonlinearity correction values based on the relationship between measurement target signals and output signals. This software-based method is cheaper to implement than hardware correction circuits, reducing manufacturing cost while achieving the required measurement precision.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If filter taps are adjusted to reduce noise and vibration rectification errors, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:

Improvemeasurement precisionVSAvoidfilter configuration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements dynamic adjustment of filter tap coefficients based on the detected vibration frequency. The arithmetic processing unit calculates the vibration frequency from the measurement target signal and adjusts the tap coefficients of the smoothing filter accordingly. This dynamic adaptation allows the filter to optimally reduce noise and vibration rectification errors without requiring complex fixed filter designs, improving measurement precision while keeping the device complexity manageable through adaptive rather than statically complex filtering.

Inventive Principle:

Principle #15Dynamics

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 reduces noise and vibration rectification errors, achieving linearization of the measurement target signal while maintaining a compact module size and low cost, enhancing accuracy in applications like clinometers and inertial measurement devices.

Implementation Method 1

a resonant frequency shift based physical quantity sensor whose frequency adjusts with a adjust in physical quantity

Methodology Applied

Scientific EffectResonant frequency shift: Resonance

Implementation Method 2

a frequency delta-sigma modulator which performs frequency delta-sigma modulation of the reference signal, using an operation signal based on a measurement target signal

Methodology Applied

Scientific EffectFrequency delta-sigma modulation: Phase Modulation

Implementation Method 3

a first filter provided at an output of the frequency delta-sigma modulator and operating synchronously with the measurement target signal; a second filter provided on an output side of the first filter and operating synchronously with the reference signal

Methodology Applied

Scientific EffectSynchronous filtering: Filter (electronic)

Data Source

PatentUS11733262B2Physical quantity sensor module, clinometer, and structure monitoring device

Publication Date: 2023.08.22 SEIKO EPSON CORP

AI summary

A physical quantity sensor module includes: a resonant frequency shift based physical quantity sensor whose frequency adjusts with a adjust in physical quantity; a reference signal oscillator which outputs a reference signal; a frequency delta-sigma modulator which performs frequency delta-sigma modulation of the reference signal, using an operation signal based on a measurement target signal as an output from the resonant frequency shift based physical quantity sensor, and generates a frequency delta-sigma modulated signal; a first low-pass filter provided on an output side of the frequency delta-sigma modulator and operating synchronously with the measurement target signal as the output from the resonant frequency shift based physical quantity sensor; and a second low-pass filter provided on an output side of the first low-pass filter and operating synchronously with the reference signal.