Fault-Injection Experiment for the Statistical Characterization of Faults in Avionics Communication System

Since flight control systems perform safety-critical functions, it is important to understand the possible effects on the closed-loop dynamical system's performance caused by these faults. The purpose of this project is to design the software and hardware needed to add fault-injection and monitoring capabilities to ROBUS-2, a flight communication system. ROBUS-2 is the current version of the fault-tolerant computer communication system used by the Scalable Processor-Independent Design for Enhanced Reliability (SPIDER), a general-purpose fault-tolerant integrated modular architecture (IMA) developed at the NASA Langley Research Center. The major components of SPIDER include processing elements (PEs) to perform calculations, bus interface units (BIUs) to connect the PEs to the bus, and redundancy management units (RMUs) to manage the communication traffic and provide robust bus-level fault-tolerance. The interconnected system of interest is a distributed closed-loop flight control system, where an aircraft is controlled by a fault-tolerant interconnection of flight control computers (FCCs). The aircraft's sensors and actuators communicate with the FCCs via ROBUS-2. The new fault-injection capability is intended to simulate faults in ROBUS-2 that could be triggered by harsh environments such as high energy atmospheric neutrons and high intensity radiated fields (HIRF). The fault-monitoring capability will be used to make observations on fault occurrences while the hardware is exposed to harsh environments. The observation data can then be used to develop statistical models of the faults that result in similar degradation of performance of a closed-loop dynamical system. These models will help to predict the effects of harsh environments on closed-loop system performance as a function of specific features of the communication system. The main accomplishments are the design of the fault injection and monitoring mechanism, specification for the faults that will be injected, specifications for the software and hardware components that are needed for implementation, and preliminary statistical characterizations of fault processes. The implementation of this design will provide information about the severity of a variety of faults on control systems and how to compensate for these faults, which is directly in accordance with Sub-goal 3E of the NASA Strategic Plan to "advance knowledge in the fundamental disciplines of aeronautics, and develop technologies for safer aircraft and higher capacity airspace systems."