Variable Capacitance Control for MEMS Gyroscope Quadrature Compensation
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Solution Overview
Problem
Microelectromechanical systems (MEMS) gyroscopes face signal degradation due to spurious components caused by constructional imperfections, leading to a degraded signal-to-noise ratio and altered dynamics in reading interfaces.
Innovation Solution
A variable-capacitance electronic device with a capacitive component and a control stage, utilizing a reference signal and an excitation signal with specific frequency relationships, and a sign circuit to periodically switch capacitors and generate control signals that compensate for spurious quadrature components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MEMS gyroscope structures are used, then the device can detect angular velocity through Coriolis force, but spurious quadrature components arise due to constructional imperfections that degrade signal-to-noise ratio
Solution Approach 1:
The patent extracts and separates the quadrature disturbance component from the useful signal by applying a compensating voltage through switched capacitors. The control stage identifies the quadrature component and removes it through electronic compensation, isolating the harmful factor from the measurement signal.
Solution Approach 2:
The patent introduces switched capacitors and a control stage as intermediary elements between the MEMS structure and the readout circuitry. These intermediaries generate compensating voltages that counteract the quadrature components, acting as a mediator to eliminate the harmful effect before it degrades the measurement.
2Manufacturing precision
If constructional precision is increased to reduce manufacturing defects, then quadrature components are reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent implements self-service by providing electronic compensation within the device itself. The control stage continuously monitors and compensates for quadrature components generated by manufacturing imperfections, allowing the device to self-correct without requiring ultra-precise manufacturing processes.
Solution Approach 2:
The patent changes the electrical parameters (capacitance values, switching timing, compensating voltages) dynamically to compensate for fixed manufacturing imperfections. By adjusting these electrical parameters, the system compensates for mechanical imperfections without requiring re-manufacturing.
3Reliability
If switched capacitors are periodically switched to compensate quadrature components, then signal-to-noise ratio improves, but additional control circuitry is required
Solution Approach 1:
The patent applies periodic action by switching the capacitors at specific intervals synchronized with the drive frequency. The switched capacitors apply compensating voltages periodically at twice the drive frequency, effectively counteracting the quadrature components that arise from mechanical imperfections.
Solution Approach 2:
The patent introduces dynamic elements (switched capacitors that change state periodically) to counteract static manufacturing imperfections. The control stage dynamically adjusts the compensation based on the oscillation state, creating a dynamic system that adapts to eliminate the harmful quadrature components.
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
Effectively suppresses quadrature disturbance components, improving the signal-to-noise ratio and maintaining accurate angular velocity measurements by fine-tuning the calibration capacitance to adjust for structural imperfections.
Implementation Method 1
a capacitive component (15), having a variable capacitance and a control stage (8), coupled to the capacitive component (15) configured to control the variable capacitance
Implementation Method 2
by supplying appropriate biasing voltages, it is possible to apply an electrostatic force to the movable mass to set it in motion
Data Source
AI summary
An electronic device includes a capacitive component with variable capacitance coupled to a control stage that controls the capacitance, based on a reference signal, with a reference frequency, and an excitation signal, that is a multiple of the reference frequency. The capacitive component includes a variable capacitive network having a plurality of switched capacitors, each being switchable between a first configuration, where it is connected between connection terminals of the capacitive component, and a second configuration, where it is connected at most to one of the connection terminals. The control stage includes a logic module, coupled to the variable capacitive network for switching periodically each capacitor between the first configuration and the second configuration. A sign circuit, coupled to the capacitive component supplies a control signal having edges concordant with the excitation signal in one half-period of each cycle of the reference signal and discordant edges in the other half-period.