Underwater Acoustic Navigation Using Surface Transmitter Arrays
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Solution Overview
Problem
Current underwater positioning systems face challenges in accurately determining absolute position due to the inability of high frequency radio waves to propagate through water, leading to cumbersome and costly long baseline positioning systems and limitations in tracking multiple underwater units with reduced battery life and increased size.
Innovation Solution
An underwater acoustic navigation system that uses a compact array of acoustic transmitters near the water surface to broadcast signals encoded with position and attitude information, allowing submerged receivers to calculate their absolute position using hydrophones and synchronized clocks, enabling precise ranging and position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long baseline positioning systems use multiple transponders placed far apart on the seafloor, then positioning accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The system segments the positioning function by separating the transmitter array (which remains stationary and provides reference signals) from the mobile receivers. Each receiver independently calculates its position using signals from multiple array elements, eliminating the need for multiple distributed transponders while maintaining positioning accuracy through the array's geometric configuration.
Solution Approach 2:
The transmitter array acts as an intermediary that provides encoded position and timing information to multiple receivers simultaneously. Instead of requiring direct communication between multiple transponders and receivers, the array mediates the positioning process by broadcasting signals that contain embedded array position and attitude data, simplifying the overall system architecture.
2Measurement precision
If USBL array tracks pings from underwater units, then location determination is achieved, but battery life is reduced and unit size increases
Solution Approach 1:
The system inverts the traditional USBL approach by having stationary transmitters broadcast signals containing encoded position information, rather than having mobile units transmit pings that are received by an array. This inversion allows receivers to passively determine their location using embedded data in the transmitted signals, dramatically reducing their power consumption and eliminating the need for active transmission.
Solution Approach 2:
The transmitter array performs preliminary action by pre-encoding position and attitude information into the broadcast signals before transmission. Receivers simply need to decode this pre-prepared information to determine their location, eliminating the need for complex active tracking and reducing receiver power requirements.
3Adaptability or versatility
If USBL array tracks multiple underwater units, then tracking capability is provided, but the number of trackable units is limited
Solution Approach 1:
The transmitter array provides universal service to multiple receivers simultaneously by broadcasting signals that contain encoded position and timing information valid for all receivers in the coverage area. Each receiver independently processes the same broadcast signals to determine its own position, allowing unlimited numbers of receivers to be tracked without additional infrastructure, unlike USBL systems that require dedicated tracking resources for each unit.
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 accurate and efficient determination of absolute position for underwater receivers, allowing for modern GPS-like functionality such as tracking, navigation, and mapping, while reducing power consumption and increasing the number of trackable units.
Implementation Method 1
Each of the acoustic transmitters transmits a respective navigation signal
Implementation Method 2
The receiver comprises a hydrophone and a clock synchronized with GPS time. The receiver configured to use the time-base and data from the hydrophone to estimate a range
Implementation Method 3
The underwater receiver uses the acoustic signal to compute its absolute position
Data Source
AI summary
An acoustic underwater navigation system is disclosed. For instance, an underwater receiver determines its position using signals broadcast from an array of acoustic transmitters located near the surface. The position of the array is measured using global positioning system (GPS) technology and the transmitters collectively produce an acoustic signal in which the position and attitude of the array and the GPS time of transmission are encoded. An underwater receiver which is synchronized with the GPS time uses the transmitted position and attitude of the array and the transmission time information to calculate its position.