Nonlinear Modeling and Parameter Identification of Air Rudder System

The modeling accuracy of the air rudder system directly affects the quality of aircraft attitude control. However, the commonly used simplified second-order model cannot accurately represent its nonlinear transfer characteristics. To this end, a dynamic model of the air rudder system considering three types of nonlinear factors, such as saturation, clearance, and dry friction, was established. On this basis, a stepwise identification test modeling method based on frequency characteristic data was proposed. By designing two different excitation levels of test conditions to excite or suppress the influence of some nonlinear factors, the stepwise identification of each unknown physical parameter was completed. The identification results show that the air rudder system model established in this paper can accurately characterize its nonlinear transfer characteristics, and the transfer characteristic curve of the identification results is in good agreement with the measured data.