A new state observer and flight control of highly maneuverable aircraft

In this paper, a new nonlinear observer (thetas - D observer) is proposed to estimate the feedback states for optimal control of a highly maneuverable aircraft. This observer is derived by constructing the dual of a recently developed nonlinear optimal control technique-known as the thetas - D technique. The thetas - D optimal control approach provides an approximate closed-form solution to the Hamilton-Jacobi-Bellman (HJB) equation. An optimal flight controller using this technique is designed for a highly maneuverable aircraft operating at high angle of attack where the thetas - D observer is employed to estimate the states for feedback. The structure of this observer is similar to the state dependent Riccati equation filter (SDREF). However, the new method provides a closed-form observer gain and does not need time-consuming online computations of the algebraic Riccati equation at each instant as the SDREF. The theoretical results about this new observer are given. The simulation shows that the thetas - D control and observer exhibit excellent performance for this flight control problem.