Fig.1

Modeling of algebraic polynomial unsteady pitch moment coefficient

Fig.2

Unsteady lift coefficient of an aircraft

Fig.3

Curves of aircraft attitude angles and airflow angles during pitch-roll coupled oscillation

Fig.4

Pitch moment coefficients of pitch-roll coupled oscillation and single-axis pitch oscillation

Fig.5

Unsteady pitch moment coefficient under different oscillation frequencies

Fig.6

Extreme learning machine network

Table 1

PSO core parameter settings

Fig.7

RMSE optimization convergence and dynamic parameter adjustment curves

Fig.8

Unsteady dynamic model structure based on PSO-ELM

Fig.9

Principle of Newton-Raphson iteration method

Fig.10

Core flow of conventional BACTM continuous algorithm

Table 2

Influence of various parameters on solution of improved bifurcation analysis algorithm

Table 3

Division of aerodynamic data

Fig.11

Comparison of unsteady aerodynamic Cmu modeling results

Fig.12

Comparison of RMSE between different models and data groups

Table 4

Model performance comparison

Fig.13

Branch curves of aircraft longitudinal open loop system

Fig.14

Phase plane and saddle point manifold of aircraft longitudinal open-loop system

Fig.15

Phase plane and saddle point manifold of longitudinal open-loop system under steady aerodynamics

Fig.16

Angle of attack branch of aircraft longitudinal closed loop system with backstepping control

Fig.17

Phase plane and manifold of aircraft longitudinal closed loop system with backstepping control