Technical Approach

Automated acoustic interrogation of seabeds for identification of abandoned munitions will enable the application of mature sensor technology to the vast data throughput necessary in practical application. However, unmanned systems in particular require high confidence in system robustness, and this has not been achieved to date given the limited physical motivation even for algorithms which currently perform well in limited tests. FE modeling of munitions has allowed high-fidelity prediction of scattered acoustic returns from sources too complex to analyze using empirical models. The researchers’ laboratory has been focused on developing specific FE techniques not just to predict responses but to isolate the effects of individual physical mechanisms contributing to the response. The researchers can illuminate the effects of specific interior structure on the received signal. Because complex target responses are broken down into individual components in this approach, it is more straightforward to understand the environmental effects on such components than on the complete return. In this project, the researchers will investigate the effects of burial state (amount and material) on these individual components and use the results to predict the complete response and allow a physically justifiable assessment of the robustness of features which are being used or proposed for automated munitions identification.

The researchers utilize a variety of techniques to isolate particular components of a predicted return as opposed to simulating the complex total return. Addition of wave-absorbing regions allows the researchers to remove certain fluid-borne return components. Alteration of target elasticity makes it possible to isolate specular components. Limiting the support region for the incoming wave allows identification of key coupling regions for the interrogating waveform. Most importantly for identifying the importance of target interior structure, the incident wave can be reduced to its effects as a fluid loading in specific regions of the target.

The researchers will use these techniques to characterize the effects of burial state on target physics for key components of observed signatures. This proof-of-concept study will identify the key mechanisms contributing to the response for a munition-like target, simulate the effects at different burial states, and predict and verify the changes in the resulting features as a function of burial state.