Closing Gaps for Aircraft Attitude Higher Order Sliding Mode Control Certification

Prior to be implemented in aircraft flight control system, Higher Order Sliding Mode (HOSM) controllers must be certified for robustness to unmodeled dynamics. There exist certain standards imposed on Phase Margin (PM) and Gain Margin (GM) for linear controller to be certified for controlling aircrafts. In this work, the conventional control system certification approach based on PM and GM is extended to HOSM controllers. The proposed Practical Stability Phase Margin (PSPM) and Practical Stability Gain Margin (PSGM) are used to quantify the robustness of an attitude F-16 aircraft control against unmodeled dynamics. The algorithms for the identification of PSPM and PSGM are developed using Describing Function-Harmonic Balance method. HOSM control is cascaded with linear compensator to satisfy required PS PM and PSGM. The presented HOSM control-based technology that includes enforcement of PS PM and PSGM is closing the gap for certification of aircraft HOSM controllers.