Modeling and identification of highly maneuverable fighter aircraft dynamics using block-oriented nonlinear models

Abstract

In this paper, a new approach based on block-oriented nonlinear models for the modeling and identification of aircraft nonlinear dynamics is proposed. Some of the block-oriented nonlinear models are regarded as flexible structures, which are suitable for the identification of widely applicable dynamic systems. These models are able to approximate a wide range of system dynamics. In general, aircraft flight dynamics is considered as a nonlinear and coupled system whose dynamics—in addition to pilot control inputs—depend on the flight conditions such as Mach number and altitude, which cause the aircraft dynamics to have various operational points. In this study, three types of block-oriented models, namely the Hammerstein, Wiener, and Hammerstein–Wiener models with different nonlinear functions, have been used and compared in order to identify and model the aircraft nonlinear dynamics. These models have been employed in three forms of single-input single-output, multi-input multi-output, and multi-input single-output (MISO); of which, multi-input single-output has been recognized to have fewer errors in aircraft nonlinear dynamics identification. Thus, it has been demonstrated that six separate multi-input single-output models (with three inputs and one output), which have been trained with experimental flight test data, can model the coupled nonlinear six-degree-of-freedom dynamics of a highly maneuverable aircraft.