Risk analysis and decision making for autonomous underwater vehicles

Chen, Xi (2023) Risk analysis and decision making for autonomous underwater vehicles. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Risk analysis for autonomous underwater vehicles (AUVs) is essential to enable AUVs to explore extreme and dynamic environments. This research aims to augment existing risk analysis methods for AUVs, and it proposes a suite of methods to quantify mission risks and to support the implementation of safety-based decision making strategies for AUVs in harsh marine environments. This research firstly provides a systematic review of past progress of risk analysis research for AUV operations. The review answers key questions including fundamental concepts and evolving methods in the domain of risk analysis for AUVs, and it highlights future research trends to bridge existing gaps. Based on the state-of-the-art research, a copula-based approach is proposed for predicting the risk of AUV loss in underwater environments. The developed copula Bayesian network (CBN) aims to handle non-linear dependencies among environmental variables and inherent technical failures for AUVs, and therefore achieve accurate risk estimation for vehicle loss given various environmental observations. Furthermore, path planning for AUVs is an effective decision making strategy for mitigating risks and ensuring safer routing. A further study presents an offboard risk-based path planning approach for AUVs, considering a challenging environment with oil spill scenarios incorporated. The proposed global Risk-A* planner combines a Bayesian-based risk model for probabilistic risk reasoning and an A*-based algorithm for path searching. However, global path planning designed for static environments cannot handle the unpredictable situations that may emerge, and real-time replanned solutions are required to account for dynamic environmental observations. Therefore, a hybrid risk-aware decision making strategy is investigated for AUVs to combine static global planning with dynamic local re-planning. A dynamic risk analysis model based on the system theoretic process analysis (STPA) and BN is applied for generating a real-time risk map in target mission areas. The dynamic window algorithm (DWA) serves for local path planning to avoid moving obstacles. The proposed hybrid risk-aware decisionmaking architecture is essential for the real-life implementation of AUVs, leading eventually to a real-time adaptive path planning process onboard the AUV.

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