Experimental Results in Synchronous-Clock One-Way-Travel-Time Acoustic Navigation for Autonomous Underwater Vehicles

Abstract

Abstract-This paper reports recent experimental results in the development and deployment of a synchronous-clock acoustic navigation system suitable for the simultaneous navigation of multiple underwater vehicles. The goal of this work is to enable the task of navigating multiple autonomous underwater vehicles (AUVs) over length scales of O(100 km), while maintaining error tolerances commensurate with conventional longbaseline transponder-based navigation systems (i.e., O(1 m)), but without the requisite need for deploying, calibrating, and recovering seafloor anchored acoustic transponders. Our navigation system is comprised of an acoustic modem-based communication/navigation system that allows for onboard navigational data to be broadcast as a data packet by a source node, and for all passively receiving nodes to be able to decode the data packet to obtain a one-way travel time pseudo-range measurement and ephemeris data. We present results for two different field experiments using a two-node configuration consisting of a global positioning system (GPS) equipped surface ship acting as a global navigation aid to a Doppler-aided AUV. In each experiment, vehicle position was independently corroborated by other standard navigation means. Initial results for a maximumlikelihood sensor fusion framework are reported.

An overview of AUV algorithms research and testbed at the University of Michigan

“…Fig. 2 depicts preliminary results, reported in [9], [17], demonstrating the OWTT proof of concept. Here, a global positioning system (GPS)-equipped surface ship navigationally aided a submerged AUV by broadcasting ship GPS position to the network while the AUV measured its range to the ship via the OWTTs.…”

“…In previous work, Eustice et al developed a synchronousclock acoustic modem-based navigation system capable of supporting multi-vehicle ranging [9], [17]. The system consisted of a WHOI Micro-Modem [18], [19] (an underwater acoustic modem developed by Woods Hole Oceanographic Institution (WHOI)) and a low-power stable clock board.…”

“…2. Preliminary OWTT results as reported in [9], [17] for a two node network consisting of an AUV and a surface ship. Shown in blue is the raw dead-reckoned AUV trajectory; in cyan is the GPS-derived ship position; in red is the OWTT fused AUV trajectory; and in green is the (on-surface) GPSmeasured AUV position, which serves as an independent ground-truth.…”

Closed‐loop one‐way‐travel‐time navigation using low‐grade odometry for autonomous underwater vehicles

“…The vehicles used during all of the field trials were Ocean-Server, For timing, a PPSBoard, as discussed previously, 40,41 that incorporates a SeaScan Inc. temperature-compensated crystalline oscillator was integrated for use as a precision reference. The PPSBoard is linked to the vehicle's pulse per second (PPS) signal output from the GPS receiver.…”

Simultaneous Localization and Mapping in Marine Environments

“…The most accurate inter-vehicle ranging is through one-way travel-time ranging with precisely synchronized clocks, for example, using the design by Eustice [17], which also allows for broadcast ranging to any number of vehicles in the vicinity of the transmitting vehicle. An alternative is round-trip ranging, which, while resulting in more complexity during operation and higher variance, requires no modification of existing vehicles.…”