Aircraft Longitudinal Stability Augmentation System Using Linear Quadratic Integral Control

This paper presents a complete control system for the longitudinal dynamics of an F-16 aircraft. The nonlinear equations of motion are linearized around cruise conditions, and the trimmed state, input, and derivative values are calculated to form the state-space model. To improve damping and transient response, a state-feedback Stability Augmentation System is developed. The Stability Augmentation System has been reduced time. To improve tracking performance, a linear quadratic integral-action controller is developed. The controller gain hatK is calculated by solving the Riccati equation with carefully selected weighting matrices. The linear quadratic integrator enables accurate pitch tracking to eliminate the steady-state error and reduce the settling time to approximately 4.27 seconds. The system's eigenvalues have been confirmed to improve stability and damping characteristics. Simulation results in both the time and frequency domains confirmed the effectiveness of the proposed SAS and LQI designs. Bode analysis shows an increase in the system bandwidth, particularly in autopilot mode, with a closed-loop bandwidth of approximately 1 rad / s. Overall, the proposed control architecture provides a robust solution for stabilising and precisely controlling high-performance aircraft.