Unified nonlinear optimal flight control and state estimation of highly maneuverable aircraft

In this paper, a nonlinear flight control and a nonlinear state observer are designed in one unified framework for a high performance aircraft. The flight control is formulated as a nonlinear optimal control problem and the θ-D technique is utilized to design a closed-form optimal control law by solving the associated Hamilton–Jacobi–Bellman equation approximately via a perturbation process. Motivated by the notion that control and estimation are dual concepts, a new θ-D observer is developed to estimate the state used in the feedback by constructing the dual of the θ-D controller. Theoretical analysis of the proposed observer is given. Since both the optimal flight control and the state observer are unified in the same θ-D algorithm that leads to closed-form solutions to the optimal control and observer gains, this scheme greatly facilitates onboard implementation due to its computation efficiency. The unified design method is applied to a highly maneuverable aircraft operating at high angles of attack. Simulation results show that the θ-D control-θ-D observer suite exhibits excellent performance.