Triaxial Accelerometer Assembly with In-Situ Gravity Calibration
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Solution Overview
Problem
Traditional seismic and geodetic measurement devices lack sensitivity and stability for long-term measurements, particularly in capturing strong seismic events and do not have an absolute reference for rotational invariance, leading to issues with instrument drift and misalignment.
Innovation Solution
A triaxial accelerometer assembly with full-scale ranges greater than ±1 G on three orthogonal axes, capable of rotating to maintain rotational invariance with respect to Earth's 1 G static gravity vector, allowing for in-situ calibration and compensation of drift using an internal alignment matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional seismic and geodetic measurement devices are used, then the device structure is simple, but the measurement precision and long-term stability are insufficient
Solution Approach 1:
The measurement system is divided into three independent orthogonal accelerometer axes, each capable of independent calibration and measurement. This segmentation allows each axis to be optimized for precision while maintaining overall system manageability, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The system changes the measurement parameter range by using full-scale ranges greater than ±1 G on all three axes, enabling the capture of strong seismic events while maintaining sensitivity for subtle geodetic measurements. This parameter expansion improves measurement precision across multiple scales without requiring entirely different device architectures.
2Reliability
If traditional devices without rotational invariance are used, then the device complexity is low, but the reliability for long-term measurements deteriorates due to instrument drift
Solution Approach 1:
The system implements feedback through in-situ calibration procedures that use the known Earth gravity vector as a reference. By repeatedly measuring the gravity vector in different orientations and comparing against the known reference, the system detects and corrects drift in accelerometer sensitivity and alignment, maintaining long-term reliability.
Solution Approach 2:
The system introduces dynamic calibration capability through rotation mechanisms that allow the accelerometer assembly to be rotated to known orientations. This dynamic approach enables continuous verification and correction of measurement accuracy, transforming a static instrument into one that can self-validate and maintain reliability over time.
3Measurement precision
If traditional devices without absolute reference are used, then the ease of operation is high, but the measurement precision deteriorates due to misalignment
Solution Approach 1:
The system performs preliminary alignment calibration by measuring the gravity vector in multiple predetermined orientations before actual measurements begin. This preliminary action establishes the correct orientation relationships between the three accelerometer axes and the Earth reference frame, ensuring high alignment accuracy without requiring complex real-time adjustments during operation.
Solution Approach 2:
The three orthogonal accelerometer axes serve multiple functions: they simultaneously measure seismic events, perform in-situ calibration by detecting the gravity vector, and provide redundant verification of alignment. This multi-functionality improves alignment accuracy while maintaining ease of operation, as the same hardware performs both measurement and self-calibration.
4Productivity
If traditional devices with limited dynamic range are used, then the device complexity is low, but the productivity for capturing strong seismic events is insufficient
Solution Approach 1:
The system changes the operational parameter range by specifying full-scale ranges greater than ±1 G on all three axes. This parameter expansion enables the accelerometers to capture strong seismic events that exceed the ±1 G limit of traditional instruments, significantly improving productivity for seismic monitoring without requiring fundamentally different device architectures.
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
Enables improved seismic and geodetic measurements by maintaining measurement accuracy and distinguishing between real signals and instrument drift, providing long-term stability and rotational invariance.
Implementation Method 1
measuring the components of Earth's 1 G static gravity vector on three orthogonal axes
Data Source
AI summary
A device and method for improved geodetic and seismic measurements are disclosed. The device comprises a triaxial accelerometer assembly, mounted to a reference structure, having full scale ranges greater than +/−1 G on three orthogonal axes and a mechanism for rotating the triaxial accelerometer assembly on the reference structure. The triaxial acceleration assembly is calibrated with an internal alignment matrix such that measurements of Earth's gravity vector are rotationally invariant with respect to the direction of Earth's 1 G static gravity vector irrespective of the orientation of the triaxial assembly on the reference structure. In-situ calibrations are performed by rotating the axes of the triaxial acceleration assembly in the direction of Earth's static gravity vector. Drift of the triaxial accelerometer assembly is compensated for by measuring changes in the values of the invariant static gravity vector for each axis and correcting for the drift with new calibration coefficients.