Servo Voltage Inertia Sensor Capacitance Cancellation
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Solution Overview
Problem
Existing acceleration sensors face challenges in achieving low noise and high sensitivity, particularly in detecting infinitesimal vibration acceleration, due to fabrication accuracy variations between MEMS and CMOS components, leading to incomplete cancellation of external noise and reduced detection sensitivity.
Innovation Solution
The proposed solution involves an inertia sensor with a detection capacitor unit and a servo capacitor unit connected mechanically through an insulation material, where modulation signals with opposite phases are applied to cancel capacitance changes caused by acceleration, and a servo voltage is used to cancel displacement, thereby reducing noise and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If modulation signals with opposite phases are applied to capacitance elements, then detection sensitivity is improved, but fabrication accuracy variations between MEMS and CMOS components cause incomplete noise cancellation
Solution Approach 1:
The capacitance elements are divided into two separate groups: detection capacitance elements (C1, C2) and servo capacitance elements (C3, C4). This segmentation allows independent optimization of each group's function and reduces the impact of fabrication variations on overall performance.
Solution Approach 2:
A servo voltage is introduced as an intermediary control mechanism that generates electrostatic force to cancel displacement of the proof mass. This intermediary force field compensates for incomplete noise cancellation caused by fabrication inaccuracies in the capacitance elements.
2Object-affected harmful factors
If a servo voltage is applied to cancel displacement, then noise reduction is achieved, but device complexity increases
Solution Approach 1:
The detection and servo functions are merged into a unified capacitive system where the same capacitance elements (C1-C4) serve both detection purposes and servo control purposes, reducing the need for separate component sets and simplifying the overall device structure.
Solution Approach 2:
The capacitance elements themselves generate the electrostatic force needed for servo control through the applied servo voltage, eliminating the need for separate actuation mechanisms and reducing device complexity.
3Measurement precision
If separate detection and servo capacitor units are used, then detection sensitivity improves, but manufacturing complexity increases
Solution Approach 1:
The capacitance elements are designed to serve multiple functions: they act as both detection capacitors for measuring acceleration and as servo capacitors for generating corrective electrostatic force. This multi-functionality reduces the total number of components needed and simplifies manufacturing.
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 configuration effectively reduces external noise interference and improves detection sensitivity by ensuring accurate capacitance cancellation and signal amplification, resulting in a high sensitivity acceleration sensor with a better signal-to-noise ratio.
Implementation Method 1
a detection capacitor unit which captures the acceleration as a change of electrostatic capacitance
Implementation Method 2
a servo voltage generating electrostatic force that cancels the change of the electrostatic capacitance
Data Source
AI summary
There is provided an inertia sensor with low noise and high sensitivity. The inertia sensor captures a physical quantity as a change of electrostatic capacitance and detects the physical quantity based on a servo voltage generating electrostatic force that cancels the change of the electrostatic capacitance. The inertia sensor includes a detection capacitor unit that captures the physical quantity as the change of the electrostatic capacitance and a servo capacitor unit to which the servo voltage is applied. Here, the detection capacitor unit and the servo capacitor unit are connected mechanically through an insulation material.