A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Browse
6 results
Search Results
Item Demonstrating Cognition by Task Execution and Motion Planning with different algorithms for Manipulation(2018) DIMITRIADIS, DIMITRIOS; Baras, John S.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this Thesis we demonstrate the whole path until the manipulation and the planning of the Baxter Robot. We start by analyzing the kinematic analysis of a six degrees of freedom robot. We build our analysis starting from the Denavit-Hartenberg method. We proceed with the kinematic equations of the robot and with the inverse kinematics as well as with a kinematic simulation of its movement with matlab. In order to reach our final goal we continue with the kinematic and dynamic analysis of the Baxter robot. We again state the Denavit-Hartenberg matrix, but this time we continue by building the dynamic model of the Baxter robot through the Euler-Lagrange equations. Moving on, we explore planning algorithms. The knowledge of which will help us in order to finally be able to formulate our path planner for the Baxter robot. We experiment ourselves by implementing four planning algorithms in different path planning problems. We construct the RRT and the RRT* algorithms in Python and we process them in different planning problems. Moving on, we also implement a planning problem in which Q-Learning and Sarsa algorithms are being used. We demonstrate how those two planning and learning algorithms work in our specified problem and we compare our results. Having knowledge on dynamic and kinematic robotic analysis and planning and motion planning algorithms we then experiment ourselves with the Baxter simulator on Gazebo. Also we plan the Baxter robot with Moveit!, getting familiar with the use of ROS as well as with the software. We add obstacles in our world and we plan our Baxter robot measuring its speed. We finally build a different plan algorithm RRT+ by focusing on searching for a secure and realizable path plan starting from the lower dimension space and then adding degrees of freedom to our Baxter robot. Concluding, we have built the desired steps for someone in order to build up the required knowledge to deal with robots and artificial intelligence planning.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 Cyclic Pursuit: Symmetry, Reduction and Nonlinear Dynamics(2011) Galloway, Kevin; Krishnaprasad, Perinkulam S; Justh, Eric W; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation, we explore the use of pursuit interactions as a building block for collective behavior, primarily in the context of constant bearing (CB) cyclic pursuit. Pursuit phenomena are observed throughout the natural environment and also play an important role in technological contexts, such as missile-aircraft encounters and interactions between unmanned vehicles. While pursuit is typically regarded as adversarial, we demonstrate that pursuit interactions within a cyclic pursuit framework give rise to seemingly coordinated group maneuvers. We model a system of agents (e.g. birds, vehicles) as particles tracing out curves in the plane, and illustrate reduction to the shape space of relative positions and velocities. Introducing the CB pursuit strategy and associated pursuit law, we consider the case for which agent i pursues agent i+1 (modulo n) with the CB pursuit law. After deriving closed-loop cyclic pursuit dynamics, we demonstrate asymptotic convergence to an invariant submanifold (corresponding to each agent attaining the CB pursuit strategy), and proceed by analysis of the reduced dynamics restricted to the submanifold. For the general setting, we derive existence conditions for relative equilibria (circling and rectilinear) as well as for system trajectories which preserve the shape of the collective (up to similarity), which we refer to as pure shape equilibria. For two illustrative low-dimensional cases, we provide a more comprehensive analysis, deriving explicit trajectory solutions for the two-particle "mutual pursuit" case, and detailing the stability properties of three-particle relative equilibria and pure shape equilibria. For the three-particle case, we show that a particular choice of CB pursuit parameters gives rise to remarkable almost-periodic trajectories in the physical space. We also extend our study to consider CB pursuit in three dimensions, deriving a feedback law for executing the CB pursuit strategy, and providing a detailed analysis of the two-particle mutual pursuit case. We complete the work by considering evasive strategies to counter the motion camouflage (MC) pursuit law. After demonstrating that a stochastically steering evader is unable to thwart the MC pursuit strategy, we propose a (deterministic) feedback law for the evader and demonstrate the existence of circling equilibria for the closed-loop pursuer-evader dynamics.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.