Aerospace Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2737
Browse
4 results
Search Results
Item GRAMIAN-AWARE CLOSED LOOP FLIGHT CONTROL DESIGN FOR ENERGY HARVESTING THROUGH MODULATING DISTURBANCE SENSITIVITY(2017) Saxena, Utsav; Faruque, Imraan A; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many desired micro aerial vehicle missions are significantly larger than the mission endurance of the vehicles. Due to extreme constraints on size, weight and power available, small scale air vehicles are highly sensitive to atmospheric disturbance. This work introduces a control-theoretic framework that models the magnitude of the vehicle's disturbance sensitivity and observability in conjunction with each other under a gramian-based formulation. To implement atmospheric gust response modulatiom, a ``gramian-aware'' flight control law is designed using open loop plant models across various scales and assuming perfect gust measurement. Time-domain system identification was conducted using data collected from repeatable automated flights in a motion capture arena in order to derive the plant model. Closed-loop simulation results as well as experimental data modulating the plant using cruise speed are presented to illustrate that the gramian-based control laws can be utilized to facilitate atmospheric energy scavenging in gusting environments.Item Quaternion-Based Control for Aggressive Trajectory Tracking with a Micro-Quadrotor UAV(2014) Kehlenbeck, Andrew Gale; Humbert, James S; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With potential missions for quadrotor micro-air vehicles (MAVs) calling for smaller, more agile vehicles, it is important to implement attitude controllers that allow the vehicle to reach any desired attitude without encountering computational singularities, as is the case when using an Euler angle representation. A computationally efficient quaternion-based state estimator is presented that enables the Army Research Laboratory's (ARL) 100-gram micro-quadrotor to determine its attitude during agile maneuvers using only an on-board gyroscope and accelerometer and a low-power processor. Inner and outer loop attitude and position controllers are also discussed that use the quaternion attitude representation to control the vehicle along aggressive trajectories with the assistance of an outside motion capture system. A trajectory generation algorithm is then described that leverages the quadrotor's inherent dynamics to allow it to reach extreme attitudes for applications such as perching on walls or ceilings and flying through small openings.Item Biomimetic Insect Flapping Aerodynamics and Controls for Micro Air Vehicles(2011) Seshadri, Pranay; Chopra, Inderjit; Benedict, Moble; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)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. At the core of this work is a simplified, elegant flapping actuation system that is capable of emulating insect wing kinematics in all its degrees of freedom. The mechanism is shown to be novel compared to existing flapping mechanisms and is easily scalable.Item Aerodynamic Analysis and Simulation of a Twin-Tail Tilt-Duct Unmanned Aerial Vehicle(2010) Abdollahi, Cyrus; Humbert, James S; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The tilt-duct vertical takeoff and landing (VTOL) concept has been around since the early 1960s; however, to date the design has never passed the research and development phase. Nearly 50 years later, American Dynamics Flight Systems (ADFS) is developing the AD-150, a 2,250lb weight class unmanned aerial vehicle (UAV) configured with rotating ducts on each wingtip. Unlike its predecessor, the Doak VZ-4, the AD-150 features a V tail and wing sweep- both of which affect the aerodynamic behavior of the aircraft. Because no aircraft of this type has been built and tested, vital aerodynamic research was conducted on the bare airframe behavior (without wingtip ducts). Two weeks of static and dynamic test were performed on a 3/10th scale model at the University of Maryland's 7'x10' low speed wind tunnel to facilitate the construction of a nonlinear flight simulator. A total of 70 dynamic tests were performed to obtain damping parameter estimates using the ordinary least squares methodology. Validation, based on agreement between static and dynamic estimates of the pitch and yaw stiffness terms, showed an average percent error of 14.0% and 39.6%, respectively. These inconsistencies were attributed to: large dynamic displacements not encountered during static testing, regressor collinearity, and, while not conclusively proven, dierences in static and dynamic boundary layer development. Overall, the damping estimates were consistent and repeatable, with low scatter over a 95% confidence interval. Finally, a basic open loop simulation was executed to demonstrate the instability of the aircraft. As a result, it is recommended that future work be performed to determine trim points and linear models for controls development.