Accelerometer Range-Dependent Bias Calibration
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Solution Overview
Problem
Accelerometer sensor systems face significant errors due to scale-factor and bias uncertainties, particularly in dynamic environments, arising from non-linear relationships between feedback forces and input conditions, which affect the accuracy of inertial measurement and navigation systems.
Innovation Solution
An accelerometer sensor system that includes a proofmass and electrodes, capable of generating acceleration feedback signals, with an acceleration controller that defines two scale-factor ranges and a calibration component to continuously calibrate range-dependent bias errors by measuring input acceleration in both ranges and implementing an algorithm to calculate and subtract the estimated bias error, thereby maintaining accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the accelerometer operates in a dynamic environment with varying acceleration ranges, then the sensor can adapt to different measurement conditions, but range-dependent bias errors increase measurement precision
Solution Approach 1:
The patent implements dynamic scale-factor range switching that adapts to the current acceleration magnitude. The system transitions between a first scale-factor range for low acceleration and a second scale-factor range for high acceleration, allowing the sensor to optimize its measurement characteristics based on real-time conditions. This dynamic adaptation resolves the contradiction by enabling the system to maintain measurement precision across varying acceleration ranges while preserving adaptability to different measurement conditions.
Solution Approach 2:
The patent changes the scale-factor parameter based on the measured acceleration magnitude. When acceleration exceeds a threshold, the system switches from a first scale-factor to a second scale-factor, effectively changing the measurement parameter to match the current operating conditions. This parameter change approach allows the system to maintain accuracy across different ranges while adapting to varying measurement requirements, thereby resolving the bias error issue in dynamic environments.
2Measurement precision
If real-time calibration is implemented to mitigate bias errors, then measurement precision improves, but device complexity increases due to additional control algorithms
Solution Approach 1:
The patent implements a self-calibration mechanism where the accelerometer automatically detects its own bias errors and applies corrections without external intervention. The system uses the difference between measurements in different scale-factor ranges to calculate and compensate for range-dependent bias errors autonomously. This self-service approach improves measurement precision while minimizing additional system complexity, as the calibration functionality is integrated into the existing sensor operation rather than requiring separate external calibration equipment or complex control systems.
3Measurement precision
If continuous calibration is performed to maintain accuracy, then measurement precision is maintained, but productivity decreases due to calibration processing time
Solution Approach 1:
The patent performs calibration continuously during normal sensor operation without interrupting the measurement process. The system alternates between the two scale-factor ranges and uses the measurement differences to calculate bias errors in real-time, maintaining continuous calibration while preserving measurement throughput. This approach ensures measurement precision is maintained while avoiding productivity losses that would occur with periodic external calibration interruptions.
Solution Approach 2:
The patent employs periodic switching between the first and second scale-factor ranges to gather calibration data. By alternating between ranges at optimized intervals, the system collects the necessary measurement differences for bias error calculation while minimizing the time spent in calibration mode. This periodic action approach maintains measurement accuracy through continuous calibration while preserving measurement productivity by efficiently scheduling the calibration measurements within the normal operational flow.
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 real-time self-calibration, continuously mitigating range-dependent bias errors, ensuring accurate input acceleration measurements without interrupting the sensor's operation, thereby enhancing the performance of inertial measurement and navigation systems.
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
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.