Longitudinal dynamics, optimization and control of aircraft transition maneuver using aerodynamic vectoring

• Main Author: Adnan Maqsood
• Other Authors: Go Tiauw Hiong
• Format: Theses and Dissertations
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Aeronautical engineering::Aircraft; DRNTU::Engineering::Aeronautical engineering::Flight simulation
• Online Access: https://hdl.handle.net/10356/48041
• Institution: Nanyang Technological University

In order to enhance the flight envelope of Unmanned Air Vehicles (UAVs), there have been efforts to combine the excellent hover capabilities of rotorcraft with the endurance and speed performance of fixed-wing aircraft. Such efforts lead to a type of agile aircraft that can perform hover coupled with efficient flight during forward cruise. An inherent problem for such vehicles is the transition maneuver between forward flight and hover, which usually exhibits significant altitude variation, long transition time, large control effort, high thrust-to-weight ratio and loss of partial control. These characteristics are undesirable and reduce the maneuver potential of the vehicle in tight spaces. Moreover, the underlying flight dynamic characteristics of convertible platforms are still not fully explored. To mitigate the problems associated with the transition maneuvers above, this work proposes the use of variable-incidence wing, where the angle of incidence of the wing with reference to the fuselage of the aircraft can be controlled during flight. This phenomenon is also referred as “aerodynamic vectoring” as the changing of the wing-incidence changes significantly the direction of the resultant aerodynamic force. A feasibility study of the usefulness of the variable-incidence wing scheme is conducted in comparison to a conventional fixed-wing platform. The study is focusing longitudinal motion only. The lateral-directional motion is considered to be de-coupled and is out of the scope of the study. Two kind of transition maneuvers are discussed in the thesis: Steady and Unsteady transition maneuvers. Steady transition maneuvers refer to the category in which the aircraft can sustain flight with certain pitch attitude between hover and cruise. In such transitions the aircraft can be considered to be at trim during the maneuver. Unsteady transition maneuvers refer to fast aerobatic/agile transition maneuvers between hover and cruise. In such maneuvers, the aircraft may not be in trimmed conditions between its initial and final desired states. For the analysis, the aerodynamic forces and moments database is developed over the whole maneuver range using wind-tunnel-testing. For the steady transition case, the advantages of the variable-incidence wing feature are found, however eigenvalue analysis reveals that the dynamics may have some peculiarities. For this reason, further nonlinear dynamic analysis is carried out. Specifically, Multiple Time Scales (MTS) method in conjunction with bifurcation theory is used to uncover the peculiar system behavior and to understand the steady transition dynamics further.