Phased Array Transducer Bias Removal for Doppler Velocity Accuracy
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Solution Overview
Problem
Current velocity measurement systems, such as acoustic Doppler current profilers, face challenges in achieving accurate velocity measurements due to bias caused by asymmetries in bandlimited system components, particularly in measuring large-scale features like temperature and salinity interfaces, which persist even after long-term averaging.
Innovation Solution
A method and system utilizing a phased array transducer with a two-dimensional array configuration to generate multiple beams, receive echoes, and calculate raw velocity estimates, while removing bias related to a first velocity orthogonal to the array face, thereby improving velocity measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional velocity measurement systems are used, then velocity profiles can be obtained, but measurement accuracy deteriorates due to bias caused by asymmetries in bandlimited system components
Solution Approach 1:
The patent extracts and removes the bias component from the velocity measurement system. Specifically, it separates the measured velocity signal into a true velocity component and a bias component caused by system asymmetries, then removes the bias component to obtain an accurate velocity measurement. This is achieved through mathematical processing that identifies and eliminates the systematic error introduced by bandlimited system components.
Solution Approach 2:
The patent changes the parameter representation of velocity measurements by transforming the raw velocity data into a corrected velocity space. It applies parameter transformations that account for the asymmetries in the system, adjusting the measurement parameters to compensate for the bias introduced by bandlimited components, thereby improving measurement accuracy.
2Measurement precision
If long-term averaging is applied to reduce variance, then velocity variance decreases, but measurement bias persists and cannot be eliminated
Solution Approach 1:
The patent applies preliminary action by removing the bias component before performing averaging operations. Instead of averaging first and then dealing with bias, it preprocesses the velocity measurements to eliminate the systematic error source, ensuring that subsequent averaging operations work with unbiased data, thereby achieving both low variance and unbiased results.
Solution Approach 2:
The patent implements a feedback mechanism where the measured velocity data is continuously analyzed to detect and correct bias components. The system uses the relationship between multiple velocity measurements to identify systematic errors and applies corrective feedback to eliminate the bias, ensuring accurate measurements even when variance is reduced through averaging.
3Measurement precision
If a phased array transducer with two-dimensional array is used, then bias related to orthogonal velocity can be removed, but device complexity increases
Solution Approach 1:
The patent transitions from conventional single-beam or simple multi-beam transducer configurations to a two-dimensional phased array transducer. This dimensional expansion allows the system to measure velocity components in multiple directions simultaneously, enabling the removal of bias related to orthogonal velocity components through sophisticated signal processing that exploits the spatial distribution of array elements.
Solution Approach 2:
The phased array transducer serves multiple functions: it can measure velocity in different directions, characterize system asymmetries, and remove bias components. The same transducer array that measures primary velocity also provides the data needed to identify and eliminate bias, making the system multi-functional and reducing the need for separate calibration or correction devices.
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 solution effectively reduces bias in velocity measurements, enhancing the accuracy and reliability of velocity profiles in fluid media, including underwater and atmospheric applications.
Implementation Method 1
The received sound has a Doppler frequency shift proportionate to the relative velocity between the scatters and the transducer
Implementation Method 2
generate pulses of sound (which when downconverted to human hearing frequencies sound like 'pings') that backscatter as echoes from plankton, small particles, and small-scale inhomogeneities in the water
Data Source
AI summary
A system and method for measuring velocity in a fluid medium utilizing a phased array transducer are disclosed. The phased array transducer comprises a plurality of transducer elements arranged to form a single two-dimensional array. In one aspect, the method comprises receiving echoes of a plurality of beams generated by the transducer, calculating raw velocity estimates based at least in part on the echoes, and removing substantially a bias related to a first velocity from the raw velocity estimates. The first velocity is orthogonal to the face of the two-dimensional array.