Accelerometer Range-Dependent Bias Calibration
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Solution Overview
Problem
Accelerometer scale-factor and bias uncertainty, particularly in dynamic environments, lead to errors in inertial measurement and navigation systems due to transient behavior, non-modelability, temperature instability, and mismatches in electrode fabrication, resulting in inaccurate measurements.
Innovation Solution
An accelerometer sensor system with a proofmass and electrodes that generates acceleration feedback signals based on control signals, featuring a calibration component to continuously adjust scale-factor ranges and calculate range-dependent bias errors in real-time, thereby mitigating bias errors by subtracting the estimated error from input acceleration measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If accelerometer measurements are taken across wide dynamic ranges, then the system can handle various acceleration magnitudes, but range-dependent bias errors increase measurement accuracy
Solution Approach 1:
The patent implements dynamic scale-factor range switching that adapts to the magnitude of input acceleration. The system automatically selects between first and second scale-factor ranges based on real-time acceleration levels, allowing the accelerometer to optimize its measurement range dynamically. This resolves the contradiction by enabling wide dynamic range adaptability while maintaining measurement precision through appropriate range selection.
Solution Approach 2:
The patent changes the scale-factor parameter based on input acceleration magnitude. By switching between different scale-factor ranges (first scale-factor range for lower accelerations, second scale-factor range for higher accelerations), the system adjusts its sensitivity parameter to match the input conditions. This parameter change strategy enables the system to handle wide dynamic ranges while minimizing range-dependent bias errors.
2Measurement precision
If continuous calibration is performed to reduce bias errors, then measurement accuracy improves, but system complexity and computational load increase
Solution Approach 1:
The patent implements a self-calibrating system that automatically performs bias error mitigation without external intervention. The calibration component continuously monitors accelerometer output and autonomously switches between scale-factor ranges and applies appropriate bias corrections. This self-service approach reduces measurement bias errors while avoiding the complexity of external calibration equipment and manual calibration procedures.
Solution Approach 2:
The system employs continuous feedback from the accelerometer output to the calibration component. The calibration component uses this feedback to detect when bias errors are present and automatically adjusts the scale-factor range and applies corrections. This closed-loop feedback mechanism improves measurement precision through continuous calibration while keeping the system relatively simple by using the existing accelerometer output as the calibration input.
3Measurement precision
If scale-factor ranges are switched frequently to maintain accuracy, then measurement precision improves, but transient behavior and instability increase
Solution Approach 1:
The patent applies preliminary bias error mitigation by pre-calculating and storing bias corrections for different scale-factor ranges. Before switching ranges or taking measurements, the system has the necessary calibration data ready, allowing for smooth transitions without transient instability. This preliminary preparation maintains measurement precision while ensuring stability during scale-factor range switching.
Solution Approach 2:
The system implements periodic calibration updates rather than continuous switching. The calibration component periodically reassesses the need for scale-factor range changes and applies corrections at optimized intervals. This periodic approach maintains measurement precision by updating calibration when necessary while avoiding excessive switching that would cause transient behavior and instability.
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 achieves continuous self-calibration, maintaining accurate input acceleration measurements by periodically alternating between scale-factor ranges and updating bias error estimates, significantly reducing range-dependent bias errors and improving navigation system performance.
Implementation Method 1
In an electrostatic force balanced accelerometer, electrostatic forcing in a closed loop system is employed to position and obtain an output from a pendulous inertial mass or proof mass
Implementation Method 2
The electrostatic forcing system employs a capacitive pickoff electrode on each side of a pendulous member that has been etched from a silicon substrate
Data Source
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AI summary
One embodiment of the invention includes an accelerometer sensor system. The system includes a sensor comprising a proofmass and electrodes and being configured to generate acceleration feedback signals based on control signals applied to the electrodes in response to an input acceleration. The system also includes an acceleration component configured to measure the input acceleration based on the acceleration feedback signals. The system further includes an acceleration controller configured to generate the control signals to define a first scale-factor range associated with the sensor and to define a second scale-factor range associated with the sensor. The control system includes a calibration component configured to calibrate the accelerometer sensor system with respect to range-dependent bias error based on a difference between the measured input acceleration at each of the first scale-factor range and the second scale-factor range.