Predictive Path Following Control for Fixed Wing UAVs Using the qLMPC Framework in the Presence of Wind Disturbances

This paper presents a cascaded approach for a predictive path-following scheme using quasi-linear parameter-varying model predictive control (qLMPC) applied to a 25 kg unmanned aerobatic aircraft. The quasi-linear parameter-varying (qLPV) representation provides a semi-linear model of the nonlinear system, while fast solvers are utilized to solve quadratic optimization problems (QOPs) in milliseconds. To incorporate integral action and overcome wind disturbances, a velocity-based linearization of the model is employed. Two scenarios with nine waypoints each are evaluated using a hybrid strategy that combines arc-length parameterization with cubic splines and a synthetic waypoint path-planner. The path-following strategy is applied to both simplified kinematic and high-fidelity models of the aircraft, with constant wind in the first scenario and time-varying wind in the second scenario. The algorithm achieves good performance in both scenarios with short computation times. Lastly, a performance analysis of the strategy with the two path-planning techniques is presented.