CLF-based tracking control for UAV kinematic models with saturation constraints

This paper considers the trajectory tracking problem for unmanned air vehicles (UAVs). We assume that the UAV is equipped with an autopilot which reduces the twelve degree-of-freedom (DOF) model to a six DOF model with altitude, heading, and velocity command inputs. In this paper we restrict our attention to planar motion. One of the novel features of our approach is that we explicitly account for heading and velocity input constraints. For a fixed wing UAV, the velocity is constrained to lie between two positive constants, and therefore presents particular challenges for the control design. We propose a control Lyapunov function (CLF) approach. We first introduce a CLF for the input constrained case, and then construct the set of all constrained inputs that render the CLF negative. The control input is then selected from this "feasible" set. The proposed approach is then applied to a simulation scenario, where a UAV is assigned to transition through several targets in the presence of multiple dynamic threats.