Unknown input observer-based appointed-time funnel control for quadrotors

In this paper, an unknown input observer-based appointed-time funnel control policy is proposed for quadrotors suffering from environmental disturbances and parametric uncertainties. To improve the robustness of quadrotors, unknown input observers (UIOs) are respectively devised in trajectory and attitude levels to online identify unknown system dynamics via utilizing filtering manipulations, possessing a concise structure, low calculation consumption and asymptotic error convergence. Then, an appointed-time funnel control consisting of a modified funnel variable is proposed to regulate trajectory tracking error profiles within preassigned boundary without incurring singularity problem, where a continuous piecewise function is embedded to specify the funnel envelop, such that the stringent temporal constraints can be arbitrarily prescribed by operators, independent of initial states and system arguments. All error signals involved in quadrotor dynamics are demonstrated to be ultimately uniformly bounded (UUB) and trajectory tracking errors are constrained to designed funnel. Eventually, simulations and comparisons validate the effectiveness of proposed control approach.