Design of a tolerant flight control system in response to multiple actuator control signal faults induced by cosmic rays

Due to continued miniaturization, semiconductor-based components used in high-performance digital microelectronics are becoming increasingly sensitive to cosmic rays and solar particle events. In the context of high-altitude flight control systems based on fly-by-wire techniques, this may produce sensor noise or affect actuator control signals. Although the consequences so far have been simply reductions in aircraft performance, catastrophic scenarios may be envisioned. In this article, we propose a novel architecture for a fault-tolerant flight control system able to detect and compensate for cosmic ray-induced multiple-bit upsets that affect actuator control signals in modern fly-by-wire avionics systems while assuming that the actuator itself remains healthy. A fault detection and diagnosis procedure was designed using a geometric approach combined with an extended multiple-model adaptive estimation technique. This procedure is able to process multiple faulty actuator-control signals and identify their parameters. The parameters thus obtained are then used with a reconfigurable sliding-mode control to compensate for such errors by mobilizing the remaining actuators' healthy control signals. Lyapunov stability theory is used to analyze the closed-loop system stability. Simulation results using Matlab®/Simulink® showed the effectiveness of the proposed approach in the case of a system challenged with double faults.