Towards Verifiable Adaptive Flight Control for Safety Critical Applications

One of the main obstacles to the implementation of adaptive controllers for safety critical applications is the absence of analytically justified Verification and Validation (V&V) techniques for such systems. This paper seeks to provide the beginnings of a theoretically motivated V&V technique for adaptive controllers in the context of controlling uncertain flight vehicle dynamics. A set of tools for characterizing the transient properties of direct adaptive systems is developed using a combination of Lyapunov theory, asymptotic analysis, and linear systems theory. A Lyapunov approach is used to prove stability and global properties. Asymptotic analysis allows for the behavior of the nonlinear adaptive system to be practically characterized by a Reduced Linear Asymptotic System (RLAS). Techniques used in linear systems theory then can be applied straightforwardly to the RLAS. The tools are demonstrated on a simulation of the short period mode in aircraft dynamics and on a full nonlinear six degree of freedom aircraft simulation.