AUVs can greatly enhance their survey capabilities if they can dock. Our goal has been to demonstrate a working docking system, including both the needed elements on the vehicle and the mooring. We will show bidirectional data transfer and power transfer to the vehicle. Another goal of the program is to implement acoustic communications on the Odyssey class AUVs, taking advantage of synergism with ARPA programs and other ONR efforts.
In FY 96, our primary objective was to demonstrate a docking system that is robust, reliable, and can work on a deep-water mooring. Our immediate objective is to demonstrate the system in shallow water in preparation for the deep-water AOSN deployment in the Labrador Sea.
We were provided with an Odyssey IIb AUV from MIT. We then added the appropriate systems to the vehicle for docking, enhanced the standard Odyssey IIb control algorithms and software, and built docking station. We also integrated power and data transfer system provided by Electronic Design Consultants.
Our approach directly addresses the most important problems for docking to a mooring in deep water. Unlike a system for shallow water where the dock can be stabilized on the seafloor, in mid water on an open-ocean mooring the dock can point any direction.
We identified several possible approaches: measure the dock orientation and communicate its direction to the vehicle, actively control the dock orientation, or build a system that did not require knowledge of dock orientation. We chose the third alternative and chose to have the vehicle clamp to a vertical pole from any direction. After connecting to the pole, a single degree-of-freedom mechanism then aligns the vehicle and brings inductive power and data transfer elements into sufficient proximity.
We chose an ultra shortbaseline sensor to measure the range, bearing, and elevation angle of the mooring relative to the vehicle.We designed homing algorithms and refined the low-level control algorithms provided by MIT.
For acoustic comms, our approach has been to leverage WHOI-led developments conducted under the DARPA AMMT program. Also, we addressed problems specific to small vehicles: limited size and payload space, limited power, and vehicle acoustic noise.
In FY 96, we completed a series of tasks leading to a full docking demonstration in shallow water in early FY 97.
We built a USBL sensor, drawing on an existing transducer design and utilizing the AMS digital signal processing system originally developed for acoustic communications, and integrated it into Odyssey.
We designed homing algorithms and refined existing Odyssey heading and depth control.
We tested basic docking performance in Buzzards Bay in collaboration with MIT, NRaD, and EDC.
We built a prototype docking station suitable for shallow-water testing that can also be extended to deep water operation.
We refined the USBL approach to include range measurement from a synchronous beacon.
We integrated the inductive power and data transfer provided by EDC and tested them in the lab.
We tested all elements with the exception of the power and data transfer at the WHOI dock in preparation for a shallow water test in early FY 97 using a functional mooring.
We demonstrated successful docking from arbitrary approach directions in shallow water from ranges out to 200 meters.
We designed and built a docking station, and tested it off our dock.
We designed a shallow-water test mooring in preparation for tests in early FY97.
We demonstrated acoustic transmission of data from an Odyssey class vehicle.
In cooperation with collaborators at MIT and NUWC, we identified vehicle self-noise as the limiting factor in vehicle downlink performance.
We have shown that our docking approach is practical. We have shown that high resolution USBL acoustic tracking at ranges out to several hundred meters, yet also has sufficient resolution to permit docking.
The results of this effort will enable the AOSN program to implement a multiple mooring/vehicle system. The acoustic communications portion of this effort has made contributions to the acoustic communications ATD.