Optimal Control For Power-Off Landing Of A Small-Scale Helicopter A Pseudospectral Approach

Abstract-We derive optimal power-off landing trajectories, for the case of a small-scale helicopter UAV. These open-loop optimal trajectories represent the solution to the minimization of a cost objective, given system dynamics, controls and states equality and inequality constraints. The plant dynamics features a 3-D nonlinear helicopter model, including dynamics from the rigid body, the main rotor Revolutions Per Minute (RPM), and the actuators. The novel part of this paper is threefold. First, we provide a new cost functional which, during the flight, maximizes helicopter performance and control smoothness, while minimizing roll-yaw cross-coupling. Second, and aside from the standard state and control bounds, we provide a trajectory constraint on tail rotor blade tip, to avoid ground strike when the helicopters pitches up, just before touch-down. Third, we apply the pseudospectral collocation discretization scheme, through a direct optimal control method, to solve our problem. The advantage of the pseudospectral method, compared to other direct optimal control approaches, lies in its exponential convergence, implying increased computational efficiency, provided the functions under considerations are sufficiently smooth. Finally, we conclude by a discussion of several simulation examples

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Trajectory planning and trajectory tracking for a small-scale helicopter in autorotation

The design of a high-performance guidance and control system for a small-scale helicopterUnmanned Aerial Vehicle (UAV), with an engine OFF flight condition (i.e. autorotation), is known to be a challenging task. It is the purpose of this paper to present a Trajectory Planning (TP) and Trajectory Tracking (TT) system, having onlinecomputational tractability. The presented Flight Control System (FCS) is anchored within the aggregated paradigms of differential flatness based optimal planning, and robust control based tracking. In particular the first real-time feasible, model-based TP and model-based TT, for a small-scale helicopter in autorotation is being demonstrated using a high-fidelity, high-order, nonlinear helicopter simulation