Sammendrag
A methodology for automatic simulation-based testing of control systems for autonomous vessels is proposed. The
work is motivated by the need for increased test coverage and formalism in the verification efforts. It aims to achieve
this by formulating requirements in the formal logic Signal Temporal Logic (STL). This enables automatic evaluation of
simulations against requirements using the STL robustness metric, resulting in a robustness score for requirements satisfaction. Furthermore, the proposed method uses a Gaussian Process (GP) model for estimating robustness scores
including levels of uncertainty for untested cases. The GP model is updated by running simulations and observing the
resulting robustness, and its estimates are used to automatically guide the test case selection toward cases with low
robustness or high uncertainty. The main scientific contribution is the development of an automatic testing method
which incrementally runs new simulations until the entire parameter space of the case is covered to the desired confidence level, or until a case which falsifies the requirement is identified. The methodology is demonstrated through a case
study, where the test object is a Collision Avoidance (CA) system for a small high-speed vessel. STL requirements for
safety distance, mission compliance, and COLREG compliance are developed. The proposed method shows promise, by
both achieving verification in feasible time and identifying falsifying behaviors which would be difficult to detect manually
or using brute-force methods. An additional contribution of this work is a formalization of COLREG using temporal
logic, which appears to be an interesting direction for future work.
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