“…Classified by the applied control techniques, we can roughly see two categories when treating the uncertainty (such as external disturbance): the robust control where we design controller to suppress the unknown uncertainty, and the estimation-based controller where we design a dynamical system to estimate the unknown uncertainty, and compensate it by using the closed-loop controller. For the first category, we can cite the Lyapunov theory based controllers [2,3,4,5,6], the Line of Sight guidance laws for path following [7,8], gain scheduling controllers [9,10], sliding mode controls [11,12], model predictive controls [13,14], etc. For the second type, it is also named as active disturbance rejection control in the literature, which has been applied in [15] to control the horizontal trajectory of an airship.…”