An Offline Path Planner for Full Scale Helicopters

In this paper, an offline path planning module, which is capable of generating dynamically feasible 3D trajectories for a class of Vertical Takeoff and Landing (VTOL) vehicles is presented. Input to the module is a flight plan defined by a set of way-points and its output is twofold: first, it produces an improved flight plan introducing additional waypoints and speed changes based on the heuristics and dynamical constraints of the vehicle. This new plan facilitates the pilot by providing information on specific locations and changes of the original flight path. Second, it generates a set of reference points, which can be used as the initial set of inputs for an online reactive trajectory optimization algorithm. The proposed development is capable of processing both climbs and descents as well as both fly-by and flyover waypoints, and speed changes in between those way-points. The module was also designed to capture the pilot's perspective of an abstract way-point mission. NRC has implemented a nominal Nonlinear Model Predictive Control (NMPC) based online planner using the reference trajectories generated by the proposed offline planning module successfully. The generated improved mission was implemented on a simulator having Bell 412 flight dynamics and promising results were obtained.