Refining Perception Contracts: Case Studies in Vision-based Safe
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Yangge Li Benjamin C Yang Yixuan Jia Daniel Zhuang Sayan Mitra
Perception contracts provide a method for evaluating safety of control
systems that use machine learning for perception. A perception contract is a
specification for testing the ML components, and it gives a method for proving
end-to-end system-level safety requirements. The feasibility of contract-based
testing and assurance was established earlier in the context of straight lane
keeping: a 3-dimensional system with relatively simple dynamics. This paper
presents the analysis of two 6 and 12-dimensional flight control systems that
use multi-stage, heterogeneous, ML-enabled perception. The paper advances
methodology by introducing an algorithm for constructing data and requirement
guided refinement of perception contracts (DaRePC). The resulting analysis
provides testable contracts which establish the state and environment
conditions under which an aircraft can safety touchdown on the runway and a
drone can safely pass through a sequence of gates. It can also discover
conditions (e.g., low-horizon sun) that can possibly violate the safety of the
vision-based control system.