Absolute Vector Gravimeter Bias Drift Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gravimeters face inherent measurement errors due to bias drift over time, which complicates comparisons and requires complex calibration schemes when measuring gravity at different times.
Innovation Solution
An absolute vector gravimeter with single-axis gimbals and processors that take multiple measurements along perpendicular axes, combining them to reduce noise and calculate accurate gravity components, and using angle sensors for end-to-end calibration to correct measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are taken at different times to improve measurement accuracy, then measurement precision improves, but bias drift causes errors in comparing measurements taken at different times
Solution Approach 1:
The system performs measurements in periodic cycles, alternating between different orientations (e.g., up-down, left-right, forward-backward). Each cycle includes multiple measurements taken at different times, and the bias is continuously updated using these periodic measurements to maintain accuracy despite drift over time.
Solution Approach 2:
The system uses feedback by continuously updating the bias estimate based on measurements taken in opposite orientations. The calculated bias from one cycle is fed back to correct subsequent measurements, compensating for drift and maintaining measurement reliability over extended periods.
2Reliability
If complex calibration schemes are implemented to correct bias drift, then measurement reliability improves, but device complexity increases
Solution Approach 1:
The system performs self-calibration by automatically determining its own bias through measurements taken in opposite orientations. The processor calculates the bias from the difference between opposite measurements and uses this to correct subsequent readings, eliminating the need for external calibration equipment or complex manual calibration procedures.
Solution Approach 2:
The calibration process is segmented into simple, independent measurement cycles along orthogonal axes. Each axis is calibrated separately through a series of simple up-down or left-right measurements, breaking down the complex task of three-dimensional bias correction into manageable one-dimensional segments that can be processed independently.
3Measurement precision
If the instrument is aligned with the gravity vector to improve measurement accuracy, then measurement precision improves, but ease of operation deteriorates due to alignment requirements
Solution Approach 1:
The system transitions from requiring alignment in one dimension (vertical alignment with gravity vector) to measuring in three dimensions using orthogonal axes. By measuring gravity components along x, y, and z axes independently and combining them vectorially, the system eliminates the need for precise alignment while maintaining measurement accuracy.
Solution Approach 2:
The measurement system becomes universal by being able to accurately measure gravity in any orientation without requiring alignment. The same orthogonal measurement apparatus can measure gravity components regardless of the instrument's orientation, making the system adaptable to various operational scenarios without alignment constraints.
4Reliability
If measurements are taken quickly to reduce bias drift effects, then measurement reliability improves, but noise increases reducing measurement precision
Solution Approach 1:
The system merges multiple individual measurements taken along the same axis into a combined result. By taking several measurements during up-down cycles and averaging or otherwise combining them, the system reduces the impact of random noise while maintaining the quick measurement cycle needed to minimize bias drift effects.
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
This approach allows for precise determination of the local gravity vector with reduced noise and bias errors, enabling accurate measurements without requiring the instrument to be aligned with the gravity vector, simplifying gimbal design and improving operational efficiency.
Implementation Method 1
first and further accelerometers, electrically connected to a processor
Implementation Method 2
a first single axis gimbal operatively connected to the base, the first single axis gimbals which support first and further accelerometers
Implementation Method 3
determining a first bias for the first accelerometer; determining a first gravity component along the first measurement axis using the first measured acceleration and the first bias
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An absolute vector gravimeter and method of use is provided. The absolute vector gravimeter includes one or more single axis accelerometers, each capable of pointing in at least two directions and calculating an estimated gravity component. Further embodiments provide for estimating a bias in the single axis accelerometer, as well as measuring non-ballistic accelerations along multiple axes and calculating estimated gravity components for each. A resultant non-ballistic acceleration vector can be calculated. Examples for reducing the RMS error in the estimated gravity components are also provided.