Capacitive Interdigitated Combs for Harmonic-Corrected Displacement
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Solution Overview
Problem
High-precision resonant sensors face challenges in accurately processing mechanical displacement due to harmonic terms generated by capacitive detection along the y-axis, which are not effectively addressed by existing methods, particularly in the production and alignment of electrodes.
Innovation Solution
A capacitive displacement sensor system with interdigitated combs uses a harmonic estimator and signal reconstruction module to estimate and correct harmonics, utilizing a phase-locked loop and closed-loop feedback to reconstruct the displacement signal, thereby eliminating unwanted harmonic terms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive detection is used along the y-axis to determine displacement, then the sensor can detect displacement in the perpendicular direction, but harmonic terms are generated that degrade measurement precision
Solution Approach 1:
The patent implements a feedback mechanism where the measured signal is fed back through a phase-locked loop to generate correction signals. These correction signals are used to compensate for harmonic distortions in the displacement measurement, allowing the system to maintain high measurement precision while preserving the versatility of capacitive detection along the y-axis
Solution Approach 2:
The patent changes the parameter representation by transforming the raw capacitive signal into a corrected signal domain. Through phase-locked loop processing and harmonic estimation, the system converts the distorted measurement into a linearized displacement signal, eliminating harmonic terms while preserving the detection capability
2Measurement precision
If complementary combs are used to eliminate even harmonic terms, then measurement precision improves for resonant sensors, but device complexity increases due to additional electrodes and processing
Solution Approach 1:
The patent extracts and eliminates harmonic terms from the measurement signal through digital signal processing. Instead of adding physical components to eliminate harmonics at the source, the system extracts the harmonic components and removes them through computational methods, reducing device complexity while maintaining precision
Solution Approach 2:
The patent replaces the mechanical/complex electrode structure with a digital processing approach. Rather than using complementary combs with additional electrodes to physically eliminate harmonics, the system uses digital signal processing and phase-locked loop techniques to eliminate harmonic terms computationally, simplifying the physical device structure
3Device complexity
If traditional capacitive combs are used for detection, then the sensor structure is simple, but harmonic terms cannot be effectively corrected in high-precision resonant sensors
Solution Approach 1:
The patent uses feedback through phase-locked loop to continuously correct harmonic distortions in the measurement signal. The system monitors the raw signal, extracts harmonic components, and feeds back correction signals to eliminate these harmonics, achieving high processing accuracy while maintaining simple sensor structure
Solution Approach 2:
The patent performs preliminary harmonic estimation and correction before final signal processing. By identifying and correcting harmonic terms in advance through phase-locked loop processing, the system prepares the signal for accurate displacement measurement, achieving high manufacturing precision without complicating the sensor structure
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
The system achieves improved processing accuracy by dynamically correcting harmonic defects, enhancing the performance of resonant sensors like microelectromechanical system (Mems) gyrometers, making the detection chain entirely linear and reducing implementation complexity.
Implementation Method 1
The elementary capacitance C generally consists of a fixed surface facing a mobile surface... C=εS/d... The capacitance may thus be expressed by the following relationship: C=ε.n.h.r.(1/e1+1/e2)
Implementation Method 2
ε represents the dielectric permittivity of the material
Implementation Method 3
a phase-locked loop, locked to the digitized signal delivered by the analog/digital converter, delivering the reference angle
Implementation Method 4
a first multiplier multiplying the reference angle by the order of the harmonic amplitude, a cosine module if the order is even or a sine module if the order is odd, receiving the output of the first multiplier at input, a second multiplier multiplying the output delivered by the increase module by the harmonic amplitude of the order delivered by the harmonic estimator, and a low-pass filter having a static gain inverse to the trigonometric expansion coefficient
Implementation Method 5
a low-pass filter having a static gain inverse to the trigonometric expansion coefficient, delivering the harmonic amplitude of the order
Data Source
AI summary
A capacitive displacement sensor system with interdigitated combs, includes capacitive detection in a direction perpendicular to the surfaces of the combs facing one another, the combs being subjected to a sinusoidal movement in the direction, comprising: a device for converting the capacitance delivered by the sensor into a voltage; an analog/digital converter configured to digitize the voltage delivered by the conversion device, and supply a digitized signal; and a control unit comprising: a harmonic estimator configured to estimate the amplitudes of the harmonics of order less than or equal to a maximum order based on the digitized signal and a reference angle corresponding to the instantaneous angle of the input angular frequency; and a signal reconstruction module for reconstructing the signal from the amplitudes and the reference angle that are supplied by the harmonic estimator and from the digitized signal delivered by the analog/digital converter.