Nonlinear adaptive backstepping controller design for trajectory flight control of UAHs

Abstract

Considering the external disturbances, this paper proposes a new control approach, with the intention of improving the trajectory flight control in the longitudinal-lateral trajectory plane with constant altitude, to design a nonlinear adaptive controller for an unmanned autonomous helicopter (UAH). The unknown external disturbances are considered within the system model and estimated through adaption laws and incorporated with the control law to attest the robustness property of the intended control scheme. The designed controller is able to provide the robustness property against external turbulences as well as can overcome the over-parameterization problem which generally emerges in some conventional adaptive methods. To prove the convergence of longitudinal and lateral dynamics to a desired equilibrium point, in every stage of the design procedure a control Lyapunov function (CLF) is formulated and stability of the whole system is proved through the negative definiteness of the derivative of CLF. Finally, the performance of the proposed controller is verified in a MATLAB/SIMULINK model in the presence of external turbulence into the system. The robustness of the proposed controller, in terms of rejecting external disturbances, is illustrated through the simulation results.