UC San Diego

Reliable underwater acoustic communication is important for Unmanned Underwater Vehicle (UUV) operations but is affected by environmental conditions and vehicle geometry. The objective of this research was to identify factors affecting acoustic communication performance for a REMUS 100 UUV and to develop autonomous behaviors that could improve communication reliability during mission execution. Laboratory and field experiments conducted through the Scripps Institution of Oceanography (SIO) Coastal Observing Research and Development Center (CORDC) evaluated the effects of vehicle self-noise, vehicle depth, and vehicle orientation on communication performance using a WHOI Micromodem-2 operating at 25 kHz. Communication success was evaluated under varying operating conditions, and BELLHOP acoustic propagation modeling was used to support interpretation of depth-dependent communication performance. Results showed that changes in vehicle propulsion RPM produced minimal changes in acoustic energy near the communication frequency and did not provide a strong basis for adaptive behavior development. In contrast, communication performance varied with vehicle depth and orientation relative to the receiver, identifying both as controllable parameters that could be used by the vehicle to respond to communication degradation. Based on these findings, autonomous depth-seeking and broadside-deviation behaviors were developed and integrated into the REMUS 100 software architecture. Field testing demonstrated that the vehicle could autonomously modify its depth or orientation following communication degradation and subsequently return to the planned mission trackline. Successful communication recovery was observed during both adaptive behavior assessments, demonstrating that communication status can be incorporated into UUV autonomy and used to influence vehicle motion in response to degraded underwater acoustic communication conditions.