MEMS Gyroscope Open-Loop Readout with Calibration for Electrostatic Softening
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Solution Overview
Problem
Micro-electro-mechanical gyroscopes face interference from disturbance components that superimpose on signal components caused by rotation, leading to inaccurate angular velocity measurements due to non-linear electro-mechanical interactions and production imperfections.
Innovation Solution
A micro-electro-mechanical gyroscope with an open-loop reading device that includes a charge amplifier and low-pass filter to convert charge packets into a charge-integration signal, and a calibration stage to minimize the 2ωR component at twice the resonance frequency, using a feedback control loop to maintain the driving mass in oscillation and detect displacements of the driven mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance reading is performed to detect angular velocity, then measurement capability is provided, but electrostatic softening occurs which modifies resonance frequency and introduces disturbance components
Solution Approach 1:
The patent applies preliminary action by performing calibration before normal operation. A calibration stage is provided that operates in a first operational mode to determine calibration data, which is then used in the second operational mode to compensate for electrostatic softening effects. This preliminary calibration allows the system to account for and correct the resonance frequency modifications caused by electrostatic softening during actual measurement operations.
Solution Approach 2:
The patent implements feedback through the calibration process where the reading device monitors the actual resonance frequency and compares it against expected values. The calibration stage adjusts the drive signal characteristics based on measured deviations, creating a feedback loop that compensates for electrostatic softening effects and maintains accurate angular velocity measurements despite the harmful electrostatic forces.
2Measurement precision
If driving mass oscillation is maintained at resonance frequency, then sensitivity is improved, but non-linear electro-mechanical interactions generate spurious components at the same frequency
Solution Approach 1:
The patent segments the operational modes into calibration mode and measurement mode. During calibration, the system operates in a first operational mode that characterizes the mass oscillation system. During measurement, the system switches to a second operational mode that uses the calibration data to compensate for non-linearities. This segmentation allows the system to separate the characterization phase from the measurement phase, enabling accurate angular velocity detection while managing spurious components through calibration-based compensation.
3Reliability
If production imperfections exist, then manufacturing reality is acknowledged, but they introduce statistically unpredictable variations in device behavior
Solution Approach 1:
The patent applies self-service by enabling each individual device to perform its own calibration using its specific characteristics. The calibration stage allows the device to measure and compensate for its unique production variations and imperfections. This self-calibration approach transforms production imperfections from sources of unpredictable variability into correctable characteristics, as each device automatically adapts to its own manufacturing variations through the calibration process before operational use.
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 solution reduces the influence of disturbance components, enhancing the accuracy of angular velocity measurements by filtering out unwanted frequency components and optimizing the dynamics of the system.
Implementation Method 1
a charge amplifier for receiving charge packets from the inertial sensor and converting the charge packets into a charge-integration signal
Implementation Method 2
a low-pass filter for filtering the charge-integration signal
Implementation Method 3
The movable mass and the stator are capacitively coupled by a plurality of respective comb-fingered and mutually facing electrodes so as to form capacitors. By supplying appropriate biasing voltages, it is possible to apply an electrostatic force to the movable mass in order to set it in motion.
Implementation Method 4
a feedback control loop coupled to the first mass so as to maintain the first mass in oscillation at a resonance frequency
Implementation Method 5
The movable mass and the stator are capacitively coupled by a plurality of respective comb-fingered and mutually facing electrodes so as to form capacitors. The movement of the movable mass with respect to the stator modifies the capacitance of the capacitors.
Implementation Method 6
the driven mass operates as an accelerometer, which enables detection of the Coriolis' force and acceleration and hence tracing-back to the angular velocity
Data Source
AI summary
A micro-electro-mechanical gyroscope includes a first mass, which is able to oscillate along a first axis with respect to a fixed body, an inertial sensor having a second mass constrained to the first mass so as to oscillate along a second axis in response to a rotation of the gyroscope, a driving device coupled to the first mass that forms a control loop for maintaining the first mass in oscillation at a resonance frequency, and a reading device that detects displacements of the second mass along the second axis, which includes a charge amplifier for converting charge packets supplied by the inertial sensor into a charge-integration signal, and a low-pass filter. A calibration stage enables modification of a voltage between the second mass and the fixed body so as to minimize a component at a frequency that is twice the resonance frequency in the charge-integration signal.