Accelerometer Self-Calibration via Proof-Mass Displacement
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Solution Overview
Problem
Accelerometer systems face significant errors due to scale-factor and bias issues, particularly in dynamic environments, which affect the accuracy of inertial measurement and navigation systems.
Innovation Solution
A dynamic self-calibration method for accelerometer systems, involving the forced displacement of proof-masses to predetermined positions and the use of dual sensors with opposing input axes to measure and adjust scale-factors and biases, ensuring accurate acceleration measurements by mitigating scale-factor and bias errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrostatic forcing is used to position the inertial mass in a force balanced sensing instrument, then the instrument can measure acceleration, but the forces applied by the forcer are not linearly related to the feedback voltage or current supplied to the forcer, causing scale-factor errors
Solution Approach 1:
The patent applies preliminary calibration actions by forcing the proof-mass to predetermined positions and measuring the actual forces required. These measurements are used to calculate calibration factors that compensate for non-linearities in the electrostatic forcing system, thereby improving measurement precision without requiring perfect manufacturing linearity
Solution Approach 2:
The patent changes the operating parameters by applying different feedback voltages or currents to force the proof-mass to predetermined positions. By measuring the actual forces at these different parameter points and calculating calibration factors, the system compensates for non-linear relationships between feedback signals and applied forces
2Measurement precision
If special techniques are employed to obtain linearity between feedback force and sensed input, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent implements self-service calibration where the accelerometer system performs its own calibration by forcing its internal proof-mass to predetermined positions and measuring the required forces. This eliminates the need for external calibration equipment or complex manual calibration procedures, reducing device complexity while maintaining measurement precision
Solution Approach 2:
The calibration method serves multiple functions: it characterizes the electrostatic forcing non-linearities, determines scale-factor calibration factors, and validates sensor performance. This multi-functional approach achieves linearity correction without requiring separate dedicated calibration systems
3Measurement precision
If accelerometer scale-factor and bias error are not mitigated, then the system operates simply, but significant errors occur in inertial measurement and navigation systems
Solution Approach 1:
The patent applies periodic calibration actions by forcing the proof-mass to predetermined positions at specific intervals (e.g., at power-up, after temperature changes, or at scheduled times). This periodic recalibration maintains measurement precision over time while keeping the system operationally simple during normal acceleration measurement tasks
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 method significantly improves the accuracy of acceleration measurements by periodically recalculating and adjusting scale-factors and biases, reducing errors and maintaining precision over varying environmental conditions.
Implementation Method 1
An electrostatic forcing system employs a capacitive pickoff/forcer electrode on each side of a pendulous member that has been etched from a silicon substrate
Implementation Method 2
The electrostatic forcing system employs a capacitive pickoff/forcer electrode on each side of a pendulous member
Data Source
AI summary
One embodiment includes a method for dynamic self-calibration of an accelerometer system. The method includes forcing a proof-mass associated with a sensor of the accelerometer system in a first direction to a first predetermined position and obtaining a first measurement associated with the sensor in the first predetermined position via at least one force/detection element of the sensor. The method also includes forcing the proof-mass to a second predetermined position and obtaining a second measurement associated with the sensor in the second predetermined position via the at least one force/detection element of the sensor. The method further includes calibrating the accelerometer system based on the first and second measurements.