Underwater Position Deviation Correction Using Acoustic Doppler
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Solution Overview
Problem
Underwater navigation systems, such as USBL, LBL, and SBL, suffer from limitations like a restricted area of use and high costs, leading to positioning deviations in underwater vehicles over time.
Innovation Solution
A method and system that determine position deviation by obtaining input data at different times, calculating velocity vectors, and using acoustic signals to find an intersection point between estimated and actual positions, utilizing statistical models to handle non-intersecting lines of direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional underwater acoustic positioning systems (USBL, LBL, SBL) are used, then positioning capability is provided, but the area of use is limited and costs are high
Solution Approach 1:
The system divides the positioning task into multiple acoustic signals exchanged between the underwater vehicle and surface vessels, with each signal providing partial information (time of flight, Doppler shift) that is combined to achieve complete positioning
Solution Approach 2:
The acoustic positioning system is designed to work with different types of surface vessels (ships, boats, platforms) and can operate in various underwater environments, making it universally applicable without being limited to specific base station configurations
2Reliability
If conventional underwater acoustic positioning systems (USBL, LBL, SBL) are used, then positioning capability is provided, but purchase and integration costs are high
Solution Approach 1:
The underwater vehicle performs self-positioning by autonomously exchanging acoustic signals with surface vessels and independently calculating its position based on time of flight and Doppler shift measurements, eliminating the need for expensive integrated base station systems
Solution Approach 2:
The system uses readily available acoustic transducers and signal processing techniques that can be implemented on commercial off-the-shelf hardware platforms, avoiding the need for specialized expensive positioning equipment
3Productivity
If internal navigation system is used, then navigation is provided, but positioning deviation accumulates over time
Solution Approach 1:
The system continuously receives acoustic signals from surface vessels to provide real feedback on the actual position of the underwater vehicle, allowing it to correct accumulated navigation deviations by comparing estimated position with measured position
Solution Approach 2:
The system pre-calculates expected signal characteristics (time of flight, Doppler shift) based on the navigation system's estimated position and course, then uses the actual measured values to determine and correct positioning errors
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
Accurately updates the position of underwater vehicles by determining the deviation vector, enabling precise navigation even in dangerous or long-duration underwater operations.
Implementation Method 1
calculating on basis of said observed frequency and said emitted frequency, a second velocity vector which defines the velocity of the first node in relation to the second node, and wherein the calculation of the second velocity vector is based on relationship between observed frequency and emitted frequency of the acoustic signal node
Data Source
AI summary
A method (1000) for determining a position deviation of a first node the method comprising obtaining (1110) input data, at a first and second position. Said input data comprises, an estimated position of the first node (p1) and a first velocity vector (v1) of the first node, obtaining (1120) the exact position (p2*) of the second node; obtaining (1125) the emitted frequency (fe) of an acoustic signal a source; (1130) receiving the acoustic signal (S) and measuring the observed frequency; calculating (1140) a second velocity vector (v12) which defines the velocity of the first node in relation to the second node; and calculating (1150), the angle (α) between the first velocity vector and the second velocity vector; determining (1160) based on the angle, the first velocity vector, and the estimated position of the first node, a line of direction (L) indicating the direction from the estimated position of the first node towards an estimated position of the second node, and determining (1300) based on a first and second line of direction an intersection point defining the estimated position of the second node (p2); determining (1400) a deviation vector (Vd) corresponding to the difference between the estimated position of the second node and the exact position of the second node, and determining (1500) the position deviation of the first node which corresponds to the deviation vector. The disclosure further relates to a positioning system for determining a position deviation for a first node and an underwater vehicle.