Aerodynamic Implications of a Bio‐Inspired Rotating Empennage Design for Control of a Fighter Aircraft

This dissertation presents an analysis of the aerodynamics for an aircraft using a novel, bio-inspired control system. The control system is a rotating tail, that is inspired by the way in which birds use their tail to control their flight. An aerodynamic model for a baseline aircraft and a bio-inspired variant are created by referencing well-known relationships for the aerodynamics of flight, which are then used to analyze the available flight envelope at which each aircraft can reach two different equilibrium states. An analysis of the total aerodynamic control authority of each aircraft is also included along with a preliminary control system to bring the aircraft back to equilibrium when influenced by a wind gust. These studies indicate some of the benefits and trade-offs of using this bio-inspired rotating tail design

A Sine-Summation Algorithm for the Prediction of Ship Deck Motion

Landing a fixed-wing aircraft on a moving aircraft carrier is a risky and inefficient process. Having an accurate prediction of ship deck motion decreases the risk posed to both the pilot and the aircraft and increases the efficiency of landing maneuvers. The present work proposes the use of a sine-summation algorithm to predict future ship motion. The algorithm decomposes recorded ship acceleration data into its characteristic harmonic parameters using a fast Fourier transform. The harmonic parameters are then used in a summation of sine waves to create a fit for the acceleration data, which is projected into future time intervals to predict ship motion. An aircraft carrier can supply the prediction made by the algorithm to an autopilot, which then decides to land or make another attempt. Included in this work is a brief overview of ship motion with six degrees of freedom and a description of the method. The results generated by the algorithm are presented for a specific ship motion dataset to provide a point of comparison between the proposed method and other common methods used. The proposed method appears to be accurate in comparison to similar prediction methods, while reducing the computational cost required to make a prediction

Attainable Moment Set and Actuation Time of a Bio-Inspired Rotating Empennage

Future tactical aircraft will likely demonstrate improvements in efficiency, weight, and control by implementing bio-inspired control systems. This work analyzes a novel control system for a fighter aircraft inspired by the function of – and the degrees of freedom available in – a bird’s tail. The control system is introduced to an existing fighter aircraft design by removing the vertical tail and allowing the horizontal tail surfaces to rotate about the roll axis. Using a low-fidelity aerodynamic model, an analysis on the available controlling moments and actuation speeds of the baseline aircraft is compared to that of the bio-inspired rotating empennage design. The results of this analysis at a takeoff and approach flight condition indicate that the bio-inspired tail design is able to improve upon the baseline in terms of control power available for yaw by up to 170%, while also improving the actuation speed by about 450 milliseconds for moments about the pitch axis. The bio-inspired design is shown to have actuation times that are up to 600 milliseconds slower for generating yawing moments and a reduced roll control contribution from the tail in certain moment combinations. The impacts of these issues on control will need to be determined with analysis at additional flight conditions and a flight dynamics analysis

A Review of Avian-Inspired Morphing for UAV Flight Control

The impressive maneuverability demonstrated by birds has so far eluded comparably sized uncrewed aerial vehicles (UAVs). Modern studies have shown that birds’ ability to change the shape of their wings and tail in flight, known as morphing, allows birds to actively control their longitudinal and lateral flight characteristics. These advances in our understanding of avian flight paired with advances in UAV manufacturing capabilities and applications has, in part, led to a growing field of researchers studying and developing avian-inspired morphing aircraft. Because avian-inspired morphing bridges at least two distinct fields (biology and engineering), it becomes challenging to compare and contrast the current state of knowledge. Here, we have compiled and reviewed the literature on flight control and stability of avian-inspired morphing UAVs and birds to incorporate both an engineering and a biological perspective. We focused our survey on the longitudinal and lateral control provided by wing morphing (sweep, dihedral, twist, and camber) and tail morphing (incidence, spread, and rotation). In this work, we discussed each degree of freedom individually while highlighting some potential implications of coupled morphing designs. Our survey revealed that wing morphing can be used to tailor lift distributions through morphing mechanisms such as sweep, twist, and camber, and produce lateral control through asymmetric morphing mechanisms. Tail morphing contributes to pitching moment generation through tail spread and incidence, with tail rotation allowing for lateral moment control. The coupled effects of wing–tail morphing represent an emerging area of study that shows promise in maximizing the control of its morphing components. By contrasting the existing studies, we identified multiple novel avian flight control methodologies that engineering studies could validate and incorporate to enhance maneuverability. In addition, we discussed specific situations where avian-inspired UAVs can provide new insights to researchers studying bird flight. Collectively, our results serve a dual purpose: to provide testable hypotheses of flight control mechanisms that birds may use in flight as well as to support the design of highly maneuverable and multi-functional UAV designs

Computational Models for Fracture and Degradation of Structures

IASS-IACM 2008 Session: Computational Models for Fracture and Degradation of Structures Session Organizers: Gunther MESCHKE (Ruhr University Bochum), Jan ROTS (TU-Delft) -- "Stepwise softening for concrete and masonry structures" by Jan G. ROTS, Max A.N. HENDRIKS, Matt J. DEJONG (TU-Delft), Beatrice BELLETTI (University of Parma) -- "The multi-scale approach of masonry, paradigm of the clay brick" by Konrad J. KRAKOWIAK, Paulo B. LOURENCO (University of Minho), Franz-J. ULM (MIT) -- "Simplified modeling strategies for non linear dynamic calculations of RC structural walls including soil-structure interaction" by Panagiotis KOTRONIS, J. MAZARS, S. GRANGE, C. GIRY (Grenoble Universites) -- "Modeling mixed-mode crack propagation in reinforced concrete" by Rena C. YU, Gonzalo RUIZ, Jacinto R. CARMONA (University of Castilla-La Mancha) -- "Limit-analysis based identification of fracture and degradation mechanisms in two-phase composite materials" by Josef FUSSL (TU Vienna), Roman LACKNER (TU Munich) -- "Fracture analyses of fiber-reinforced concrete structures" by John BOLANDER (University of California, Davis) -- "Crack-centered enrichment for debonding in two-phase composite applied to textile reinforced concrete" by Rostislav CHUDOBA, Jakub JERABEK, Frank PEIFFER, Joseph HEGGER (RWTH Aachen) -- "Three-dimensional higher order X-FEM model for multifield durability and failure analysis of concrete structures" by Stefan JOX, Christian BECKER, G?nther MESCHKE (Ruhr University Bochum) -- "From multi-scale to multi-grid FE analysis of concrete fracture" by Chris J. PEARCE, Lukasz KACZMARCZYK, Nenad BICANIC (University of Glasgow) -- "Analysis of thin layer ductile concrete as a seismic retrofit for masonry infill walls" by Marios A. KYRIAKIDES, Sarah L. BILLINGTON (Stanford University) -- "Mesoscopic failure simulation of concrete and life-cycle computation of concrete structures" by Kohei NAGAI, Koich MAEKAWA (University of Tokyo