Underwater acoustics--Computer simulation

A computer algorithm is developed to provide real-time cross range spatial quantization for a single beam forward look SONAR similar in operation to a typical sidescan SONAR. This involves the computer simulation of return time signals generated by scanning a surface profile. The time signals are normalized with respect to the scanning altitude to simulate the application of a time varying gain, and then are used as input to the surface estimation algorithm. The algorithm requires two time signals acquired from adjacent scanning positions and solves a stereoscopic geometry in arriving at the surface estimate. Final estimates have an error of less than 1% in target height determination within a set range of operation.

Response time to a threat or incident for coastline security is an area needing improvement. Currently, the U.S. Coast Guard is tasked with monitoring and responding to threats in coastal and port environments using boats or planes, and SCUBA divers. This can significantly hinder the response time to an incident. A solution to this problem is to use autonomous underwater vehicles (AUVs) to continuously monitor a port. The AUV must be able to navigate the environment without colliding into objects for it to operate effectively. Therefore, an obstacle avoidance system (OAS) is essential to the activity of the AUV. This thesis describes a systematic approach to characterize the OAS performance in terms of environments, obstacles, SONAR configuration and signal processing methods via modeling and simulation. A fuzzy logic based OAS is created using the simulation. Subsequent testing of the OAS demonstrates its effectiveness in unknown environments.