The paper considers systems for tracking an unmanned aerial vehicle under external disturbances. A combined control law is developed, which ensures invariance with respect to external disturbances in a closed system by means of linear control with saturation. Dynamic differentiators with piecewise linear correcting influences are designed to estimate unknown derivatives of given signals. The problem is considered in a deterministic setting. These differentiators are replicas of canonical virtual models with unknown inputs (their outputs are given actions) and provide estimates of the derivatives of deterministic signals with a given accuracy in a given time. The peculiarity of the proposed approach is that the dynamic order of the differentiators is lowered in comparison with the observed system. The simulation results for control system of unmanned aerial vehicle are presented.