A Simple Fuzzy-approximation-based Adaptive Control of Uncertain Unmanned Helicopters

This paper presents a simple adaptive approximation design for attitude and altitude control of uncertain helicopters with actuator dynamics. Multi-input multi-output nonlinear helicopter dynamics with model uncertainties and external disturbances are considered. Although uncertain nonlinearities and disturbances unmatched in the control input exist in the nonlinear dynamics, single fuzzy approximator (SFA) is only employed to estimate their effects in the proposed backstepping control design at the last step. Compared with the existing literature using the backstepping technique in the presence of unknown nonlinearities, function approximators in virtual controllers are not used and thus their derivatives are not required to design an actual controller. An unknown functions including all model uncertainties and the bounds of the external disturbances are lumped by the recursive and systematic design procedure at the last design step. Then, an actual control law using SFA is designed and is only used to implement the proposed controller, without any calculations of virtual controllers including function approximators. Therefore, the proposed control system is simpler than the existing backstepping control systems for unmanned helicopters. The stability of the controlled closed-loop system is established through rigorous Lyapunov analysis.