Lidar Agitated Fluid Level Sensing via Signal Variability
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Solution Overview
Problem
Lidar tank-gauging devices face challenges in accurately measuring the level of agitated fluids under degraded visibility conditions, where surface waves and turbulent conditions lead to signal fluctuations and interference from optically scattering or absorbing media, making it difficult to distinguish the useful signal echo from the background noise.
Innovation Solution
A method utilizing the pulsed time-of-flight modulation scheme combined with digitization of signal waveforms, where a waveform vector is computed using a statistical estimator of signal echo amplitude variability, such as standard deviation, to enhance the retrieval of the signal echo from agitated fluid surfaces, allowing for reliable level measurements without additional hardware modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical beams are used for level measurement of agitated fluids, then non-contact measurement is achieved, but signal fluctuations and interference from optically scattering or absorbing media occur
Solution Approach 1:
The patent replaces mechanical contact-based level measurement systems with optical detection. The optical beam detection system measures fluid level without physical contact by detecting changes in light transmission or reflection properties of the fluid, thereby achieving non-contact measurement while the statistical processing methods compensate for signal reliability issues
Solution Approach 2:
The patent introduces statistical estimators (mean, standard deviation, skewness, kurtosis) as intermediaries between the raw optical signals and the final level measurement. These statistical parameters process the fluctuating optical signals to extract reliable level information, acting as a mediator that converts unreliable raw data into accurate measurements
2Measurement precision
If statistical estimators are used to process signal waveforms, then signal echo retrieval is improved, but computational complexity increases
Solution Approach 1:
The patent applies multiple statistical estimators (mean, standard deviation, skewness, kurtosis) to process the signal waveforms. While this exceeds the minimum processing needed, it provides comprehensive characterization of the signal distribution, improving echo retrieval accuracy by capturing different aspects of the signal statistics
Solution Approach 2:
The patent transforms the raw signal waveforms into statistical parameter space by computing mean, standard deviation, skewness, and kurtosis. This parameter transformation converts complex waveform analysis into simpler statistical metric comparison, improving measurement precision while managing computational complexity through dimensionality reduction
3Measurement precision
If optical beams propagate through turbulent atmosphere above agitated fluids, then level measurement is possible, but absorption and scattering of optical beams occur
Solution Approach 1:
The patent converts the harmful effect of optical beam attenuation into a useful measurement signal. By detecting the reduced light transmission or altered reflection properties caused by the turbulent atmosphere and agitated fluid, the system extracts level information from what would otherwise be considered signal degradation
Solution Approach 2:
The patent uses statistical analysis of the received optical signals to provide feedback about the measurement conditions. The calculated statistical parameters (mean, standard deviation, skewness, kurtosis) feedback on the signal quality and help distinguish between attenuation effects and actual level changes, enabling compensation for atmospheric interference
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 significantly improves the identification and retrieval of the useful signal echo from agitated fluid surfaces, even when buried in stronger background signals, enabling accurate level measurements in challenging conditions.
Implementation Method 1
an optical receiver module for detecting a plurality of optical signals reflected off the surface of the fluid
Implementation Method 2
The vertical distance D that separates the surface 80 of the stored liquid 110 from the front panel of the optical unit 30 is then obtained by measuring the time delay T the optical pulses take to travel a full round trip
Data Source
AI summary
A method and apparatus provide for non-contact optical measurement of the level of a fluid stored in a tank or container, the surface of the fluid being possibly agitated. The method processes numerically the digitized signal waveforms generated by a lidar apparatus based on a pulsed time-of-flight modulation scheme. A key step of the numerical processing is the computation of a waveform in which each data point is obtained from a statistical estimator of the variability of the amplitude signal echo measured at the distance from the lidar apparatus that corresponds to the rank of the data point in the waveform. The statistical estimator is preferably the standard deviation. By using a statistical estimator of the variability of the captured signal amplitude, the specific signal echo returned from an agitated fluid surface can be greatly amplified as compared to the signal echoes returned from any obstacle or medium that could be present along the path of the optical beam radiated by the lidar apparatus. The method then allows for an efficient retrieval of the useful signal echo from which the level of the fluid surface can be reliably measured with greater accuracy, particularly in situations where the useful signal echo would be buried in a strong signal echo returned from any optically scattering or absorbing medium that would fill in the volume of the tank above the fluid surface.