This paper proposes the creative idea that an unmanned fixed-wing aircraft should automatically adjust its 3D landing trajectory online to land on a given touchdown point, instead of following a pre-designed fixed glide slope angle or a landing path composed of two waypoints. A fixed-wing aircraft is a typical under-actuated and nonholonomic constrained system, and its landing procedure—which involves complex kinematic and dynamic constraints—is challenging, especially in some scenarios such as landing on an aircraft carrier, which has a runway that is very short and narrow. The conventional solution of setting a very conservative landing path in advance and controlling the aircraft to follow it without dynamic adjustment of the reference path has not performed satisfactorily due to the variation in initial states and widespread environmental uncertainties. The motion planner shown in this study can adjust an aircraft’s landing trajectory online and guide the aircraft to land at a given fixed or moving point while conforming to the strict constraints. Such a planner is composed of two parts: one is used to generate a series of motion primitives which conform to the dynamic constraints, and the other is used to evaluate those primitives and choose the best one for the aircraft to execute. In this paper, numerical simulations demonstrate that when given a landing configuration composed of position, altitude, and direction, the planner can provide a feasible guidance path for the aircraft to land accurately.

To deal with the challenging problem of unmanned surface vehicle (USV) path following, a method based on model predictive control (MPC) is designed in this paper. An USV is a typical nonholonomic constrained and under-actuated system, and it has huge inertia while there is no effective brake system to control its drift. In order to follow a given path better, prediction based method should be used to take the future states into account. The kinetic model of USV has been established to simulate the prediction horizon while the inertia and hydrodynamic forces are considered. Numerical simulations are carried out and demonstrate that the controller can command the USV to follow a series of waypoints smoothly and accurately.