Aerospace applications of nonlinear observer theory

The concept of nonlinear observer theory is used to address control problems typical of many aerospace applications requiring high performance. Basically, nonlinear observers are employed to reconstruct system states which are related in some nonlinear way. A feed-forward technique, called the command generator tracker (Ref. 1), is then constructed to feed this information forward to the control channels to optimize performance The design structure is set up in such a way that conventional (optimal) feedback techniques are implemented independently to stabilize the system about trajectory perturbations Examples of this technique are given for three widely different aerospace applications and performance improvement is compared to classical and linear optimal designs.