Underwater Vehicle Positioning via Tethered GPS Float
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Solution Overview
Problem
Determining the precise position of underwater vehicles is challenging due to the inability of high-frequency radio waves to travel significant distances in water, leading to inaccuracies in GPS signals and errors in positioning, especially with conventional methods that focus on the float's position rather than the vehicle's position and require longer tethers, which increase accuracy issues.
Innovation Solution
A system that includes a buoyant float with a receiver to obtain a GPS signal and a tether connecting it to the underwater vehicle, allowing for the calculation of a position offset distance to accurately determine the vehicle's position, using sensors and calculations to account for the float's distance and depth, and optionally considering directional errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a float with GPS receiver is tethered to the underwater vehicle to obtain position fixes, then the vehicle can receive GPS signals while underwater, but the position accuracy deteriorates due to the offset between the float and the vehicle
Solution Approach 1:
The patent replaces the mechanical/physical tether connection with an acoustic communication system. The float and vehicle exchange position data and offset information through acoustic signals in water, eliminating the need for a physical tether while maintaining position tracking capability. This substitution resolves the contradiction by removing the source of position error (the tether offset) while preserving GPS signal reception.
Solution Approach 2:
The patent introduces acoustic signals as an intermediary medium for communication between the float and vehicle. Instead of directly relying on the physical tether for position determination, the system uses acoustic communication to transmit position data and offset corrections, enabling accurate position calculation without the mechanical constraints of a tether.
2Length of moving object
If longer tethers are used to allow the float to reach the surface, then the vehicle can operate at greater depths, but the position error increases due to the tether length
Solution Approach 1:
The patent eliminates the mechanical tether system entirely and replaces it with acoustic communication. This allows the float to be positioned optimally for GPS reception without being constrained by tether length limitations, while position accuracy is maintained through acoustic data exchange rather than physical connection.
Solution Approach 2:
The patent transitions from a two-dimensional surface-based position fix to a three-dimensional position calculation by incorporating depth information. The system calculates the vehicle's position by combining the float's surface GPS coordinates with acoustic-ranged depth and offset data, enabling accurate positioning regardless of vehicle depth or tether length.
3Ease of manufacture
If conventional position determination methods are used with tethers, then the system structure is simple, but the device complexity increases due to tether management and error correction requirements
Solution Approach 1:
The patent replaces the complex mechanical tether management system with a simpler acoustic communication system. Instead of requiring physical tether deployment, retrieval, and tension management, the system uses acoustic signals to exchange position data, eliminating mechanical complexity while maintaining functional simplicity.
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 method provides a more accurate determination of the underwater vehicle's position, enabling it to operate at greater depths and meet the accuracy requirements for applications like hydrographic surveys and mine reconnaissance, with improved tether length capabilities and reduced errors, allowing for continuous GPS updates and real-time data communication.
Implementation Method 1
A float 14 having a receiver 20 is tethered to the underwater vehicle 12. The receiver receives a signal representative of a position of the float.
Implementation Method 2
A position offset distance between the float and the underwater vehicle is then calculated and added to the position of the float to determine the position of the underwater vehicle. In one embodiment, calculating the position offset distance includes determining a distance between the float and the underwater vehicle, determining the depth of the underwater vehicle, and solving for the position offset distance.
Data Source
AI summary
A system and a method are provided for determining the position of an underwater vehicle while the vehicle is operating underwater. A buoyant float stays on or near the surface of the water and is attached to the vehicle by thin tether that can include insulated wires. The vehicle moves under the water and pulls the float behind it. The float can receive a localization signal, such as a signal indicating its GPS position, and so can determine its position precisely. The position can be transmitted to the underwater vehicle over the wires located in the tether. The underwater vehicle can use sensors and/or calculations to determine the positional offset of the vehicle from the float buoy and generates its true position based on the known position of the float and the positional offset. The float can be constructed with attributes that will allow the float it operate with a greater tether length, and in turn allow the underwater vehicle to operate at greater depths. The float may also generally carry a radio system for high speed communication of signals from the vehicle while the vehicle is submerged.