Thermal Accelerometer Variable Width Pulse Feedback

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Solution Overview

Problem

Existing thermal accelerometers with feedback mechanisms are complex to manage and sensitive to electromagnetic interference, compromising their ability to maintain precision and detect high-frequency acceleration variations effectively.

Innovation Solution

A thermal accelerometer design featuring two temperature-sensitive detection strands, a feedback system that generates signals with variable widths based on a comparison between sawtooth and continuous signals, and a multiplexing element for automatic temperature compensation, ensuring balanced feedback signals with zero mean value to mitigate electromagnetic interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If feedback strands with constant width pulse signals are used, then temperature compensation is achieved, but the management of feedback signals becomes complex

Engineering Contradiction:
Improvetemperature compensation precisionVSAvoidfeedback signal management complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent transitions from constant width pulse signals to variable width pulse signals where the pulse width dynamically adjusts based on the temperature difference magnitude. This dynamic approach simplifies the feedback signal management while maintaining effective temperature compensation, as the pulse width directly represents the compensation amount needed without requiring complex timing control

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention changes the parameter of pulse signal width from constant to variable, where the width is modulated according to the temperature difference detected. This parameter change allows the feedback mechanism to convey temperature compensation information more efficiently, reducing the complexity of signal management while preserving measurement precision

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If feedback signals are applied to improve detection precision, then the accelerometer becomes sensitive to electromagnetic disturbances

Engineering Contradiction:
Improveacceleration detection precisionVSAvoidelectromagnetic interference sensitivity
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where temperature difference detection triggers compensatory pulse signals applied to the detection strands. This feedback loop continuously corrects temperature-induced resistance changes, maintaining detection precision while the controlled application of feedback signals minimizes electromagnetic interference sensitivity through balanced current patterns

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The invention introduces temperature compensation as an intermediary mechanism that mediates between the detection strands and the measurement circuit. By compensating for temperature effects before they reach the measurement stage, the system maintains precision without requiring additional feedback signals that would increase electromagnetic sensitivity

Inventive Principle:
Principle #24Intermediary (Mediator)

3Device complexity

If variable width pulse signals are used, then feedback management is simplified, but signal synchronization becomes more difficult

Engineering Contradiction:
Improvefeedback signal management complexityVSAvoidsignal synchronization difficulty
Core Design Contradiction:
Device complexityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent employs periodic sawtooth waveforms as the basis for generating variable width pulse signals. This periodic action provides a regular, predictable timing structure that simplifies synchronization, as the repeating pattern establishes consistent reference points for signal alignment while still allowing variable pulse widths to encode temperature difference information

Inventive Principle:
Principle #19Periodic action

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

Simplifies the management of feedback signals, enhances precision in detecting acceleration variations, and maintains insensitivity to electromagnetic disturbances, achieving performance comparable to zero-feedback accelerometers.

Implementation Method 1

two detection strands (1, 2) having a resistivity sensitive to the temperature

Methodology Applied
Scientific EffectResistivity sensitive to temperature: Electrical Resistance

Implementation Method 2

a counter-reaction device for establishing a balance of temperature between the sensing strands by supplying the sensing strands with feedback signals

Methodology Applied
Scientific EffectTemperature compensation through feedback: Feedback

Implementation Method 3

The detection strands are mounted in a Wheatstone bridge with fixed resistors. The Wheatstone bridge is connected to a measurement circuit providing an electrical signal representative of a temperature difference between the detection strands

Methodology Applied
Scientific EffectWheatstone bridge measurement: Wheatstone Bridge

Implementation Method 4

a central heating strand (Bc) on either side of which extend detection strands

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP1722240B1Thermal accelerometer using multiplexed detection and counter-reaction
Publication Date: 2010.08.11 SAFRAN ELECTRONICS & DEFENSE SAS
  • EP1722240B1 patent drawingFigure 1~2

AI summary

The accelerometer has detection lines and a detection unit detecting a temperature difference between the lines. A multiplexing unit is connected to the lines, the detection unit and an acceleration calculation and feedback unit to alternatively measure the temperature difference and to provide a feed-back signal to the lines. The width of the signal is determined by comparing a saw-tooth signal and a continuous signal that represents the temperature difference, where the continuous signal is symmetric with respect to an average value of the saw-tooth signal.