Robust attitude tracking control of a quadrotor helicopter in the presence of uncertainty

A robust attitude tracking controller is presented in this paper, which achieves asymptotic tracking of a quadrotor helicopter in the presence of parametric uncertainty and unknown, nonlinear, non-vanishing disturbances, which do not satisfy the linear-in-the-parameters assumption. One of the challenges encountered in the control design is that the control input is premultiplied by a nonlinear, state-varying matrix containing parametric uncertainty. An integral sliding mode control technique is employed to compensate for the nonlinear disturbances, and the input-multiplicative uncertainty is mitigated through innovative algebraic manipulation in the error system development. The proposed robust control law is designed to be practically implementable, requiring no observers, function approximators, or online adaptation laws. Asymptotic trajectory tracking is proven via Lyapunov-based stability analysis, and simulation results are provided to verify the performance of the proposed controller.