MEMS Accelerometer Feedback Control for Temperature Bias Correction
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Solution Overview
Problem
Traditional MEMS accelerometers suffer from bias errors due to temperature variations and high-frequency noise, and are unable to accurately estimate input acceleration during transient motion, especially in avionics systems.
Innovation Solution
Implementing a robust controller (RC) with closed-loop feedback control, which includes a robust loop-shaping stabilization module, digital pulse-width modulation correction, and low-pass filtering to compensate for temperature-induced deformations and noise, allowing for accurate estimation of input acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional MEMS accelerometers are used without active temperature compensation, then the system complexity is low, but bias errors occur due to temperature variations
Solution Approach 1:
The patent implements a feedback control system where the controller continuously monitors the transducer signal and adjusts the drive signal based on temperature variations. The controller uses the transducer signal to determine proof-mass position and actively drives the proof-mass back to the initial position, compensating for temperature-induced bias errors in real-time.
Solution Approach 2:
The patent changes the operating parameters of the MEMS accelerometer by actively adjusting the drive signal to the proof-mass based on temperature conditions. The controller modifies the drive signal parameters (amplitude, frequency) in response to temperature variations, thereby compensating for thermal effects on the capacitor plates and proof-mass position.
2Measurement precision
If traditional MEMS accelerometers are used without noise filtering, then the system complexity is low, but high-frequency noise degrades measurement accuracy
Solution Approach 1:
The controller uses feedback from the transducer signal to continuously monitor proof-mass position and distinguish between actual acceleration-induced displacement and noise-induced displacement. By actively controlling the driver based on this feedback, the system can filter high-frequency noise while maintaining responsiveness to genuine acceleration events.
3Speed
If traditional MEMS accelerometers are used without active control, then the system complexity is low, but transient performance is poor during rapid motion
Solution Approach 1:
The patent implements dynamic control by actively adjusting the drive signal in real-time based on the transducer feedback. The controller dynamically modifies the drive signal parameters during transient motion to maintain optimal proof-mass positioning, enabling rapid response to acceleration changes while compensating for thermal and noise effects.
Solution Approach 2:
The real-time feedback from the transducer enables the controller to detect and respond to transient acceleration events rapidly. The closed-loop control system adjusts the drive signal immediately in response to proof-mass displacement, improving transient response performance compared to passive systems.
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 RC enhances the accuracy of acceleration estimation by reducing bias errors and noise, improving transient performance, and maintaining stability across varying operational conditions, while maintaining a reduced system complexity.
Implementation Method 1
external applied specific acceleration (hereafter called the input acceleration) displaces a proof-mass and varies the distance of the formed capacitor plates, and hence the overall capacitance. The above capacitance variation is transduced to an electrical voltage by a displacement transducer
Implementation Method 2
The purpose of the accelerometer device is to sense the input acceleration and output an accurate estimate of the input acceleration which may either be used by another system, recorded, transmitted or displayed as required
Data Source
AI summary
A Micro-Electrical-Mechanical-Systems (MEMS) accelerometer system includes a proof-mass device having a proof-mass that moves from an initial position in response to an input acceleration, a transducer connected to the proof-mass device to output a transducer signal correlating to movement and/or position of the proof-mass, and a driver configured to drive the proof-mass. A controller actively controls the driver to actively drive the proof-mass toward an initial position, and actively adjusts the drive signal based on a temperature signal (T) indicative of given temperature, a transducer voltage signal (Vref) indicative of a transducer voltage reference, and the transducer signal to actively generate a corrected drive signal and delivers the corrected drive signal to the driver to actively control the driver. The controller can also utilize a robust loop-shaping stabilization operation to produce both an unfiltered estimate of the input acceleration and an uncorrected drive signal to stabilize the proof mass.