Biomimetic Insect Flapping Aerodynamics and Controls for Micro Air Vehicles

Abstract :-
The goal of the current research is to develop a hover capable, fully autonomous, flapping wing micro air vehicle with a thorough understanding of the associated aerodynamics and aeroelasticity. The approach followed in this work is to look at this problem from three different perspectives: 1) Instantaneous Rigid Wing Aerodynamics, 2) Time Averaged Flexible Wing Aerodynamics, and 3) Vehicle Integration and Control. Unlike prior studies that have focused on one of these aspects, this study will encompass each aspect using a different methodology. The commonality between these three elements in this study is the flapping mechanism. Continue reading Biomimetic Insect Flapping Aerodynamics and Controls for Micro Air Vehicles

Damping Augmentation of Helicopter Rotors Using Magnetorheological Dampers

Abstract :-
This thesis describes an investigation exploring the use of magnetorheological (MR) dampers to augment the stability of helicopter rotors. Helicopters with advanced soft in-plane rotors are susceptible to ground resonance instabilities due to the coupling of the lightly damped rotor lag modes and fuselage modes. Traditional passive lag dampers, such as hydraulic or elastomeric dampers, can be used to alleviate these instabilities. However, these passive dampers suffer from the disadvantages that they produce large damper loads in forward flight conditions. These damper forces increase fatigue loads and reduce component life. Continue reading Damping Augmentation of Helicopter Rotors Using Magnetorheological Dampers

Departure Phase Aborts for Manned Mars Missions

Abstract :-
The present investigation will focus on the formulation and analysis of possible abort modes during the Earth departure phase of manned Mars interplanetary transfers. Though of short duration, the departure phase encompasses a mission timeline where failures have frequently become manifest in historical manned spacecraft necessitating the inclusion of a departure phase abort capability. Investigated abort modes included aborts to atmospheric entry, and to Earth or Moon orbit. Considered interplanetary trajectory types included conjunction, opposition, and free-return trajectory classes. Continue reading Departure Phase Aborts for Manned Mars Missions

Control-Oriented Reduced Order Modeling of Dipteran Flapping Flight

Abstract :-
The work begins with automated measurement of insect wing motions in free flight, which are then used to calculate flight forces via an empirically-derived aerodynamics model. When paired with rigid body dynamics and experimentally measured state feedback, both the bare airframe and closed loop systems may be analyzed using frequency domain system identification. Flight dynamics models describing maneuvering about hover and cruise conditions are presented for example fruit flies (Drosophila melanogaster) and blowflies (Calliphorids). The results show that biologically measured feedback paths are appropriate for flight stabilization and sexual dimorphism is only a minor factor in flight dynamics. Continue reading Control-Oriented Reduced Order Modeling of Dipteran Flapping Flight

Critical Parameter Optimization of Launch Vehicle Costs

Abstract :-
A parametric analysis aimed at minimizing costs of payload to low earth orbit is undertaken. By identifying a range of payload sizes, the effects of manipulating a number of critical parameters involving vehicle configurations on payload costs were examined. Vehicle configurations encompass single stage and multistage vehicles with combinations of airbreathing and/or rocket propulsion systems. Launch systems could be expendable or reusable on a stage-by-stage basis. Continue reading Critical Parameter Optimization of Launch Vehicle Costs

Contributions to the dynamics of Helicopters with active rotor controls

Abstract :-
This dissertation presents an aeromechanical closed loop stability and response analysis of a hingeless rotor helicopter with a Higher Harmonic Control (HHC) system for vibration reduction. The analysis includes the rigid body dynamics of the helicopter and blade flexibility. The gain matrix is assumed to be fixed and computed off-line. The discrete elements of the HHC control loop are rigorously modeled, including the presence of two different time scales in the loop. By also formulating the coupled rotor-fuselage dynamics in discrete form, Continue reading Contributions to the dynamics of Helicopters with active rotor controls