Formal Techniques for Safety-Critical Systems

Operational requirements of safety-critical systems are often written in restricted specification logics. These restricted logics are amenable to automated analysis techniques such as model-checking, but are not rich enough to express complex requirements of unmanned systems that involve, for example, the physical environment. This talk advocates the use of expressive logics, such as higher-order logic, to specify the complex operational requirements and safety properties of unmanned systems. These rich logics are less amenable to automation and, hence, require the use of interactive theorem proving techniques. However, they enable the formal verification of complex numerically intensive algorithms and the rigorous validation of their implementations. The proposed approach is illustrated with two cases studies from NASA’s research on Unmanned Aircraft Systems (UAS): Detect and Avoid Alerting Logic for Unmanned Systems (DAIDALUS) and Independent Configurable Architecture for Reliable Operations of Unmanned Systems (ICAROUS). DAIDALUS is the reference implementation of detect and avoid for UAS in FAA DO-365. ICAROUS is a software architecture built on top of DAIDALUS that enables the development of autonomous UAS applications.