MEMS Gyroscope Sensitivity Drift Compensation
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Solution Overview
Problem
MEMS gyroscopes face challenges in maintaining sensitivity accuracy due to small-scale instabilities in gap width and voltage errors, leading to excessive sensitivity shifts over time, particularly due to temperature variations and environmental stress.
Innovation Solution
A method and apparatus that utilize a test signal with specific frequencies to detect changes in gain and phase shifts, allowing for the calculation of a gain coefficient to compensate for sensitivity drift caused by temperature variations, humidity, and environmental instability, thereby improving angular rate measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual trimming is applied after manufacturing to ensure accuracy, then initial measurement precision is improved, but sensitivity drift occurs over time due to small changes in gap width and voltage
Solution Approach 1:
The patent implements a feedback mechanism where the gyroscope continuously monitors its own sensitivity by measuring the relationship between drive signal voltage and sense signal output. A compensation algorithm processes these measurements and adjusts the sensitivity accordingly, creating a closed-loop system that maintains accuracy over time without requiring manual re-trimming.
Solution Approach 2:
The gyroscope performs self-diagnosis and self-compensation by internally measuring its own sensitivity drift through correlated measurements of drive and sense signals. The device automatically calculates compensation factors and applies corrections without external intervention, enabling it to maintain its own measurement precision throughout its operational life.
2Reliability
If continuous self-testing is implemented to detect errors, then reliability monitoring is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing drive and sense signals serve dual purposes: their primary function for normal gyroscope operation and a secondary function for continuous self-testing and sensitivity compensation. By correlating these existing signals, the system achieves comprehensive health monitoring without adding separate dedicated test signal paths or additional sensing elements.
Solution Approach 2:
The patent introduces a compensation algorithm as an intermediary processing layer that analyzes the relationship between drive and sense signals. This algorithm acts as a mediator that extracts sensitivity information from existing operational signals and generates compensation factors, avoiding the need for complex hardware-based diagnostic circuits.
3Measurement precision
If closed-loop feedback control is applied to enhance performance, then measurement precision is improved, but sensitivity becomes dependent on electrostatic force stability
Solution Approach 1:
The patent implements a sensitivity compensation feedback loop that continuously monitors the actual sensitivity of the closed-loop gyroscope and applies corrections to counteract drift. By measuring the correlation between drive signal voltage and sense signal output, the system detects electrostatic force variations and compensates for them, effectively decoupling measurement precision from electrostatic force stability.
Solution Approach 2:
The patent dynamically adjusts the sensitivity parameter of the gyroscope based on measured drift characteristics. By continuously updating the sensitivity compensation factor according to the relationship between drive and sense signals, the system adapts to changing electrostatic conditions and maintains accurate measurements despite variations in electrostatic force.
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 solution effectively compensates for sensitivity drift, enhancing the accuracy of angular rate measurements by mitigating the effects of long-term error mechanisms, particularly temperature changes and unstable biasing environments, resulting in improved precision and reliability.
Implementation Method 1
MEMS gyroscopes use the Coriolis Effect to measure the angular rate. When a mass is moving in one direction and rotational angular velocity is applied, the mass experiences a force in orthogonal direction as a result of the Coriolis force.
Implementation Method 2
A parallel plate capacitor is provided between a rotor (120) and an electrode (130), both electrically coupled (not shown) to a transducer (not shown). For detection function, the transducer converts a detected capacitance into an electrical signal.
Implementation Method 3
For driving operation, also referred to as actuation operation, an electrical signal is used for charging the capacitor, which creates an electrostatic force that is used for driving the rotor (120) into a motion.
Data Source
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AI summary
The present invention relates to a MEMS gyroscope and a method for compensating drift of sensitivity of a MEMS gyroscope. The method performed by circuitry of the MEMS gyroscope comprises demodulating an angular rate signal with an in-phase carrier signal for producing a raw rate signal, obtaining a DC test signal by processing the angular rate signal or by further processing the raw rate signal, low-pass filtering the DC test signal for obtaining a raw test signal, and zeroing offset of the raw test signal by comparing each sample of the raw test signal to a test signal normalization value for producing an offset zeroed test signal that represents a deviation of the sample of the raw test signal from the test signal normalization value. The method further comprises determining a sensitivity compensation multiplier on basis of the offset zeroed test signal and a predefined gain coefficient and compensating drift of sensitivity by multiplying the raw rate signal with the sensitivity compensation multiplier for providing a sensitivity compensated rate signal.