Safe CPS from unsafe controllers
Usama Mehmood, Stanley Bak, Scott A. Smolka, Scott D. Stoller · 2021
Modern cyber-physical systems (CPS) interact with the physical world, hence their correctness is important. In this work, we build upon the Simplex Architecture, where control authority may switch from an unverified and potentially unsafe advanced controller to a verified-safe baseline controller in order to maintain system safety. We take the approach further by lifting the requirement that the baseline controller must be verified or even correct, instead also treating it as a black-box component. This change is important; there are many types of powerful control techniques---model predictive control and neural network controllers---that often work well in practice, but are unlikely to be formally proven correct due to complexity. We prove such an architecture maintains safety, and present case studies where model-predictive control provides safety for multi-robot coordination, and unverified neural networks provably prevent collisions for groups of F-16 aircraft.