Development of the model-/sensor-based nonlinear dynamic inversion control technique for highly maneuverability fighter

Abstract

This paper evaluates the flying qualities and stability of the nonlinear dynamic inversion (NDI) control law, in which angular acceleration is analyzed by a mathematical model or measured by an angular acceleration sensor based on the T-50 Advanced Supersonic Trainer model. The NDI has been considered the suitable nonlinear control technique for fighter aircrafts in aerospace industries, since it replaces nonlinear characteristics with the user-defined desired dynamics by inverting the original plant dynamics. To obtain the angular acceleration of the aircraft, two approaches are considered in this paper: estimating from the analytic model (model-based) or measuring from the angular acceleration sensor (sensor-based). To evaluate the robustness of the model-based or sensor-based NDI, the sensitivity analyses with model uncertainties and wide Center-of-Gravity (CG) travel situations are considered. The evaluation results of flying qualities and stability show that the sensor-based NDI considerably degrades the stability margin and pitch equivalent time delay compared with model-based NDI. However, it has the advantages of decreasing the inter-axes coupling effects and improving the robustness throughout the overall flight envelope. ? ICROS 2018.