Adaptive Optimizing Nonlinear Control Design for an Over-actuated Aircraft Model

Abstract

In this paper nonlinear adaptive flight control laws based on the backstepping approach are proposed which are applicable to over-actuated nonlinear systems. Instead of solving the control allocation exactly, update laws for the desired control effector signals are defined such that they converge to the optimal solution. Stability and boundedness of the resulting closed-loop system can be shown by means of Lyapunov analysis. Three different update laws are defined, the integrated, modular and composite adaptive designs. The last can be seen as a combination between the first two and has the best convergence and numerical properties. Second-order actuator dynamics are taken into account in the control designs. The control design is evaluated using numerical simulations where several cases of locked control surface failures are considered during two different maneuvers. No sensor information about these failures is fed back to the control system. The tracking performance of the adaptive control design is excellent for the nominal case and all considered failure cases. The failures are recognized shortly after they are introduced into the system, and the new dynamics are rapidly identified.