This thesis describes a motion planning method that is designed to guide an autonomous quadrotor. The proposed method is based on a novel lossless convexication, which was first introduced in (12), that allows convex representations of many non-convex control constraints, such as that of the quadrotors. The second contribution of this thesis is to include two separate methods to generate path constraints that capture non-convex position constraints. Using the convexied optimal trajectory generation problem with physical and path constraints, an algorithm is developed that generates fuel optimal trajectories given the initial state and desired final state. As a proof of concept, a quadrotor testbed is developed that utilize a state-of-the-art motion tracking system. The quadrotor is commanded via a ground station where the convexified optimal trajectory generation algorithm is successfully implemented together with a trajectory tracking feedback controller. / text

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Asthma is a heterogeneous group of conditions that typically begin in early life and result in recurrent, reversible bronchial obstruction. The role played by epigenetic mechanisms in the pathogenesis of childhood asthma is understood only in part. Here we discuss asthma epigenetics within a developmental perspective based on our recent demonstration that the epigenetic trajectory to childhood asthma begins at birth. We next discuss how this trajectory may be affected by prenatal environmental exposures. Finally, we examine in vitro studies that model the impact of asthma-associated exposures on the epigenome. All of these studies specifically surveyed human DNA methylation and involved a genome-wide component. In combination, their results broaden our understanding of asthma pathogenesis and the role the methylome plays in this process.

Two possible sets of planning variables for human arm movement are point angles and hand position. Although one might expect these possibilities to be mutually exclusive, recently an apparently contradictory set of data has appeared that indicated straight-line trajectories in both hand space and joint space at the same time. To assist in distinguishing between these viewpoints applied to the same data, we have theoretically characterized the set of trajectories derivable from a joint based planning strategy and have compared them to experimental measurements. We conclude that the apparent straight-lines in joint space happen to be artifacts of movement kinematics near the workspace boundary.

In an effort to understand the resuspension phenomena, interactions of spherical micro-meter particles (glass beads (GB) and Stainless steel (SS)) were investigated experimentally on different surfaces (glass, ceramic, hardwood, metal and chemical agent resistant coated metal (CARC)). Particles were deposited on the lower surface of a 10 cm square wind tunnel by gravitational settling. Air flows were imposed from an open entrance at average velocities up to 16 m/s. Individual particle trajectories obtained by high-speed imaging reveal three different types of motion: rolling/bouncing, immediate liftoff and complex motion. Surface roughness significantly affects the particle initial motion prior to liftoff. The majority of particle trajectories from the glass substrate were parallel to the surface with complex motion, covering 25% of the total distance traveled in rolling/bouncing motion before liftoff. Hardwood substrates took the longest time for initial particle movement (t >1 s) causing a more rapid liftoff. The ceramic substrate showed the most rolling/bouncing motion, for 80% of the particles. Additionally, single layer detachment showed that the detachment percentage initially follow an exponentially increasing trend for a period of ~ 1 s, followed by a plateau phase for a period of 5 s. Changing velocity, substrate and particle size significantly affects GB particle detachment. Furthermore, detachment from the metal substrate was consistently higher than the CARC substrates. However, particle density is not a significant difference in the bigger particle size studied. Initial 3-D particle tracking showed that particles seem to travel in a constant angle to the left rather than going straight in the flow direction. A detachment mode model showed that the detachment by direct liftoff required a much higher speed than rolling motion with a minimum of 14 m/s for both GB70 and SS70 on glass and metal surface, and the velocity increased to 21 m/s for the smaller particle. Incorporating the different types of particle motion prior to liftoff into resuspension models, and how their relative contributions change with different particle and substrate materials, can potentially yield improved predictive capabilities.

A widespread use of robotic technology in civilian and military applications has generated a need for advanced motion planning algorithms that are real-time implementable. These algorithms are required to navigate autonomous vehicles through obstacle-rich environments. This research has led to the development of the multilayer trajectory generation approach. It is built on the principle of separation of concerns, which partitions a given problem into multiple independent layers, and addresses complexity that is inherent at each level. We partition the motion planning algorithm into a roadmap layer and an optimal control layer. At the roadmap layer, elements of computational geometry are used to process the obstacle rich environment and generate feasible sets. These are used by the optimal control layer to generate trajectories while satisfying dynamics of the vehicle. The roadmap layer ignores the dynamics of the system, and the optimal control layer ignores the complexity of the environment, thus achieving a separation of concern. This decomposition enables computationally tractable methods to be developed for addressing motion planning in complex environments. The approach is applied in known and unknown environments. The methodology developed in this thesis has been successfully applied to a 6 DOF planar robotic testbed. Simulation results suggest that the planner can generate trajectories that navigate through obstacles while satisfying dynamical constraints.

Considered is a class of cooperative control problems that has a special affine characterization. Included in this class of multi-agent problems are the so called radar deception problem, formation keeping and formation reconfiguration. An intrinsic geometric formulation of the associated constraints unifies this class of problems and it is the first time such a generalization has been presented. Based on this geometric formulation, a real-time motion planning algorithm is proposed to generate dynamically feasible reference trajectories for the class. The proposed approach explicitly considers actuator and operating constraints of the individual agents and constrained dynamics are derived intrinsically for the multi-agent system which makes these constraints transparent. Deriving the constrained dynamics eliminates the need for nonlinear programming to account for the system constraints, making the approach amenable to real-time control. Explicit consideration of actuator and operating limitations and nonholonomic constraints in the design of the reference trajectories addresses the important issue of dynamic feasibility. The motion planning algorithm developed here is verified through simulations for the radar deception, rigid formation keeping and formation reconfiguration problems. A key objective of this study is to advocate a change in paradigm in the approach to formation control by addressing the key issues of dynamic feasibility and computational complexity. The other important contributions of this study are: Unifying formulation of constrained dynamics for a class of problems in formation control through the intrinsic geometry of their nonholonomic and holonomic constraints; Deriving these constrained dynamics in any choice of frame that can even be coordinate free; Explicit consideration of actuator and operating limits in formation control to design dynamically feasible reference trajectories and Developing a real-time, distributed, scalable motion planning algorithm applicable to a class of autonomous multi-agent systems in formation control.

The development of a self-contained, onboard, fully autonomous trajectory guidance tool for spacecraft is presented. To be considered completely autonomous requires the capability to both identify an appropriate startup solution, and then use that solution to target a set of user-defined path and endpoint constraints. To minimize the cost of flight software development and validation, both the generation of the startup solution and the targeting algorithm are designed to be as computationally efficient as possible. This study addresses both the determination of a startup arc and the subsequent targeting process. The first part of the investigation considers the targeting algorithm. Linear targeting through differential corrections is a well-known approach for identifying feasible solutions that meet specified mission and trajectory constraints. However, to date, these methods relied on the assumption that the associated control inputs were impulsive in nature. This research focuses on the theoretical development and numerical validation of a generalized linear targeting algorithm capable of accommodating finite periods of continuous control action for a wide range of applications. Examples are presented to illustrate the general concept and to contrast the performance of this new targeting process against more classical impulsive targeting methods. The second section of the study introduces a novel approach utilizing artificial potential function methods to identify suitable startup solutions. Although common in other types of path planning, these methods have not yet been used for orbital or interplanetary trajectory design, primarily due to their inherent suboptimality. However, results show that this issue can be addressed with relative ease by the targeting algorithm. / text

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