Seminars

Transport aircraft designs are evolving toward higher-aspect-ratio wings to improve aerodynamic performance and meet demanding flight mission specifications for reduced fuel consumption, lower emissions, and more efficient flight. With the resulting increased wing structural flexibility, flight loads also increase. Airworthiness certification mandated by regulatory agencies requires demonstrating that critical loads in these aircraft do not exceed specified limits that ensure safety and structural integrity. Active load alleviation schemes can enable reduced structural mass while satisfying certification requirements. Conventional approaches to maneuver load alleviation call for automatically deflecting control surfaces, such as elevons, to shift lift inboard and reduce the wing bending moment at critical stations. These control surfaces are deflected in proportion to monitored parameters (e.g., load factor or wing curvature) derived from sensor measurements.
This presentation will address the challenges encountered in load alleviation in those very flexible aircraft (VFA). It will start by reviewing the unique aeroservoelastic challenges that arise from large deformations of the wings and coupled aeroelastics—flight mechanics behavior, and the importance of having a framework able to capture geometric nonlinearities to allow the study of how the loads (and vibration) characteristics change when compared with a more traditional, less flexible aircraft. This will lead to a proposed control technique for maneuver load alleviation based on a reference governor and model predictive control. Based on these numerical studies, a half-aircraft model of a VFA is studied in the wind tunnel. The experimental results confirmed the control technique's ability to reduce loads but also identified remaining challenges to be addressed for this solution. The presentation will end with a short outlook on how we intend to extend the approach in future studies.

Bio: Carlos E. S. Cesnik is the Richard A. Auhll Aerospace Engineering Department Chair and the François-Xavier Bagnoud Endowed Chair Professor of Aerospace Engineering at the University of Michigan. He is also the founding Director of the Active Aeroelasticity and Structures Research Laboratory. His research interests have focused on computational and experimental structural mechanics and aeroelasticity; aerothermoelastic modeling, analysis, and simulation of hypersonic vehicles; coupled nonlinear aeroelasticity and flight dynamic response of very flexible aircraft; active vibration and noise reductions in helicopters; and structural health monitoring for metallic and composite structures. He has over three decades of experience in the multi-fidelity, multi-physics modeling, design, simulation, and experimentation of various aircraft concepts, spanning fundamental and applied research.

Professor Cesnik is a Fellow of the American Institute of Aeronautics and Astronautics, the Vertical Flight Society, and the Royal Aeronautical Society. He has over 400 publications in archival journals and conference proceedings, a recent book on the dynamics of flexible aircraft, and several invited lectures in aeroelasticity, smart structures, structural mechanics, and structural health monitoring. Professor Cesnik has been an active private pilot since 1981.