In this paper, a new nonlinear observer (θ-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 θ-D technique. The θ-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 θ-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 θ-D control and observer exhibit excellent performance for this flight control problem.

Meeting Name

American Control Conference


Mechanical and Aerospace Engineering

Keywords and Phrases

Flight Control; Observers for Nonlinear Systems; Optimal Control

Document Type

Article - Conference proceedings

Document Version

Final Version

File Type





© 2009 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jun 2009