Accelerometer Error Compensation Using Matrix Calibration
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Solution Overview
Problem
Existing accelerometers, particularly 3-axis accelerometers used in flight recorders, face challenges such as alignment errors, temperature effects, and electronic offsets, which affect the accuracy of acceleration readings and are not adequately addressed by current error compensation methods.
Innovation Solution
A 3-axis accelerometer system that integrates MEMS capacitive acceleration sensors with an application-specific signal processor (ASSP) for real-time correction of sensor errors, using calibration data to adjust for offsets, non-linearities, and temperature drift, ensuring accurate and reliable acceleration measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MEMS capacitive acceleration sensors are used, then reliability is improved compared to fluid-based sensors, but alignment errors between sense element chip and substrate occur affecting measurement precision
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements during manufacturing to determine correction coefficients before the accelerometer is deployed. The system pre-calculates alignment error corrections by measuring the actual orientation of each sensing element relative to the package coordinate system and stores these correction coefficients in memory for later application during operation, thereby eliminating alignment errors without requiring perfect mechanical alignment.
2Adaptability or versatility
If 3-axis accelerometer with multiple sensing elements is used, then comprehensive acceleration measurement is improved, but device complexity increases due to multiple chips and substrates
Solution Approach 1:
The patent applies merging by integrating multiple acceleration sensing elements and their associated correction functionality into a single calibrated system. The system combines the outputs of multiple sensing elements (X, Y, Z axes) with their respective correction coefficients into a unified coordinate transformation process, where all corrections are applied simultaneously through matrix operations rather than as separate independent corrections.
Solution Approach 2:
The patent applies universality by creating a multi-functional correction system that handles multiple types of errors (alignment errors, cross-axis sensitivity, scale factor errors) through a single coordinate transformation framework. The correction coefficients stored in memory serve multiple purposes: correcting alignment errors, compensating for cross-axis interference, and adjusting scale factors, thereby providing universal error compensation for all three sensing axes.
3Measurement precision
If correction coefficients are stored in memory, then error compensation accuracy is improved, but loss of time occurs during calibration and data storage
Solution Approach 1:
The patent applies preliminary action by performing the time-consuming calibration measurements and correction coefficient calculations during the manufacturing process, before the accelerometer is deployed in the field. The calibration data is pre-computed and stored in non-volatile memory, so that during actual operation, the system only needs to retrieve and apply the pre-calculated correction coefficients, eliminating the need for time-consuming real-time calibration.
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 system provides high-accuracy, linear interface to aircraft instrumentation systems, effectively compensating for errors and enhancing the reliability and range of operation of the accelerometer, thereby improving the accuracy of flight data recordings.
Implementation Method 1
These acceleration sensors use a capacitance bridge to sense capacitance change due to acceleration
Data Source
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AI summary
An accelerometer has an acceleration transducer producing uncorrected analog acceleration signals representing vertical, lateral, and longitudinal components of acceleration. An error correction system is connected to the acceleration transducer for receiving the uncorrected analog acceleration signals. The error correction system includes a system controller for generating a plurality of correction coefficients, an analog to digital converter which converts the uncorrected analog acceleration signals to uncorrected digital acceleration signals, a filter for filtering the uncorrected digital acceleration signals, an error compensation circuit receiving the correction coefficients to compensate the uncorrected digital acceleration signals, and a digital to analog converter which converts the corrected digital acceleration signals to corrected analog acceleration signals. The error compensation circuit corrects for bias offset, cross-axis alignment errors, scaling errors, and thermal offset. The system controller arranges a plurality of calibration measurements into a matrix and inverts the matrix to calculate the correction coefficients.