Chair: Prof. Ella Atkins

Abstract:
Emerging Advanced Air Mobility (AAM) aircraft designs offer electric Vertical Take Off and Landing (eVTOL) capability. Lift+Cruise configurations combine the efficiency of wing lift flight or "cruise" mode with a maneuverable vertical or “lift” mode for vertiport departure and approach. small Uncrewed Aircraft Systems (sUAS) can also benefit from the maneuverability and endurance of Lift+Cruise designs for missions including surveillance and package delivery. Numerous AAM designs have been proposed, but industry aeropropulsion models are proprietary. This dissertation provides an open experimentally validated Lift+Cruise sUAS model and uses this model in defining energy efficient trajectories applicable to delivery, surveillance, and inspection applications.

The first contribution of this dissertation is the QuadPlane sUAS, an easily manufactured and simple Lift+Cruise configuration combining quadrotor and fixed-wing aircraft structural elements and control effectors. QuadPlane wind tunnel experiments were conducted over a wide range of angles of attack and airspeeds in each of three QuadPlane flight modes. QuadPlane propulsion modules were characterized in lab and wind tunnel tests. Full-envelope dynamic models are presented based on surface fits for the three QuadPlane flight modes.

The second contribution is the development of multi-mode accelerated energy optimal traversal profiles between hover waypoint pairs with no wind and steady wind. A multi-variable optimization problem is formally defined and solved. Energy consumption over accelerated and cruise flight in each flight mode is modeled and analyzed to prove energy optimality of the proposed direct multi-mode traversal in zero wind. In steady wind, this thesis defines constraints under which direct traversal is possible given wind magnitude and direction and an assumption that the Lift+Cruise aircraft points into the wind at each hover waypoint to maximize stability. The QuadPlane model is used to demonstrate optimal traversal properties across trajectory segments of varied length and acceleration limits with and without ambient wind.

The third contribution is definition and evaluation of an energy aware path planner and multi-mode guidance capability for Lift+Cruise sUAS with emphasis on sUAS coverage missions. A meta-level path planning function for energy aware coverage assigns the most energy efficient flight mode for each trajectory segment subject to segment length and performance constraints. QuadPlane nonlinear simulation and control modules are developed based on the experimentally validated model. Waypoint-based flight simulations are presented with zero and steady wind. Conventional aircraft and multicopter controllers are defined for Plane (cruise) and Quad (hover) flight modes, while a novel combination of the two supports transition and sustained Hybrid mode flight offering flexibility in pitch angle within envelope constraints. A modified carrot guidance methodology with varying time horizon provides flexibility in prioritizing tracking accuracy or control robustness. Flight plan waypoints can be flexibly chosen from Hover, Fly-Over, Fly-By and Fly-Coverage options. QuadPlane flight simulations confirm accurate trajectory tracking and smooth transitions between flight modes.

This dissertation describes a novel Lift+Cruise sUAS design and experimental characterization of its performance and dynamics. Innovations include formal definition of Lift+Cruise traversals between hover waypoints and definition of Lift+Cruise trajectories for coverage missions. The QuadPlane is one of the first open Lift+Cruise sUAS models. Energy optimal trajectory solutions between hover waypoints provide a framework for future work to consider wind gusts, altitude change, and further refinement with optimal control.

Zoom link: https://umich.zoom.us/j/92566489824, Passcode: 783620