Asynchronous Underwater Vehicle Tracking via TDOA
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Solution Overview
Problem
Existing acoustic tracking systems for underwater vehicles require complex synchronization of clocks between the vehicle and the processing unit, which is time-consuming and resource-intensive.
Innovation Solution
An asynchronous tracking system that uses Time Difference of Arrival (TDOA) measurements from multiple electroacoustic sensors to determine the position of the underwater vehicle without synchronizing the clocks, employing a hyperbolic iteration algorithm and a pseudolinear Kalman-Bucy filter for accurate position estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If synchronous acoustic transmission is used with clock synchronization between the underwater vehicle and processing unit, then the trajectory tracking accuracy is improved, but the system complexity and resource expenditure increase significantly
Solution Approach 1:
The patent extracts and eliminates the clock synchronization requirement from the system. By using TDOA measurements between multiple sensors rather than requiring synchronized clocks between the vehicle and processing unit, the complex synchronization subsystem is removed entirely while preserving trajectory tracking capability through hyperbolic position line intersection
Solution Approach 2:
The patent introduces TDOA (Time Difference of Arrival) measurements as an intermediary parameter. Instead of directly using synchronized timestamps from vehicle and processor, the system uses time differences measured by multiple sensors relative to each other, which eliminates the need for absolute clock synchronization while still enabling precise position calculation
2Reliability
If clock synchronization is performed using cables or radio transmission before vehicle launch, then the time base correlation is achieved, but the setup time and resource expenditure increase
Solution Approach 1:
The patent performs preliminary positioning of the sensors in a known geometric configuration before the test. The sensor coordinates are pre-measured and stored, enabling direct calculation of TDOA position lines without requiring any synchronization setup at the time of vehicle launch. This preliminary sensor setup eliminates the need for time-consuming clock synchronization procedures
Solution Approach 2:
The system uses the natural time differences measured by the sensor array itself to determine position, without requiring external synchronization services. Each sensor independently records arrival times, and the relative time differences are calculated directly from these independent measurements, making the system self-sufficient and eliminating dependency on external clock synchronization infrastructure
3Measurement precision
If multiple electroacoustic sensors are deployed for triangulation, then the position determination accuracy is improved, but the system complexity and cost increase
Solution Approach 1:
The patent transitions from using multiple sensors in a simple triangulation geometry to utilizing TDOA hyperbolic position lines in a more sophisticated geometric framework. By measuring time differences between multiple sensor pairs, the system creates hyperbolic position lines whose intersections provide position determination, effectively using the time dimension differently to achieve better precision without linearly increasing sensor requirements
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
Enables real-time tracking and recovery of underwater vehicles with reduced setup time and resource expenditure, allowing for flexible launch positions and post-launch analysis of vehicle performance.
Implementation Method 1
the underwater vehicle to be tracked emits underwater acoustic signals, in particular a train of periodic pulses, which are detected by the electroacoustic sensors
Implementation Method 2
by calculating how long the acoustic signals take to travel the distance between the transmitting underwater vehicle and the receiving electroacoustic sensors. Given the speed of sound in water, this calculation enables calculation of the distance
Data Source
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AI summary
A system (1) for tracking the trajectory (T) of an underwater vehicle (2) moving in a monitoring area (3), the system having: a number of sensors (6) located in known positions (S1, S2, S3) in the monitoring area (3) to detect, at respective receiving times (t ik ), an acoustic signal emitted by the underwater vehicle (2); and a processing unit (8) operatively coupled to the sensors (6) to determine the trajectory (T) as a function of the receiving times (t ik ). More specifically, the processing unit (8) determines an approximate position (P tk ) of the underwater vehicle (2) as a function of differences between the receiving times (t ik ) ; and processes the approximate position (P tk ) using a time-varying predictive filter, in particular a pseudolinear Kalman-Bucy filter, to estimate the position of the underwater vehicle (2) and derive the trajectory (T).