Jack Elston

Lyapunov Guidance Vector Fields for Unmanned Aircraft Applications

This paper presents results implementing Lyapunov vector fields for the guidance of unmanned aircraft. The vector fields yield globally stable tracking of circular loiter patterns. These loiter patterns are used in several unmanned aircraft applications including hierarchical micro air vehicle control for cooperative plume tracking, extremum seeking for electronic chaining, and cooperative tracking of moving targets. Extensions of the basic LGVF approach are made for each application including: warping the circular pattern to form other closed orbit patterns; driving the center of the LGVF orbit using virtual dynamics; and spacing multiple unmanned aircraft around a circular orbit. Hardware-in-the- loop simulation results and flight data are given to validate performance.

The tempest unmanned aircraft system for in situ observations of tornadic supercells: Design and VORTEX2 flight results

This paper reports results from field deployments of the Tempest Unmanned Aircraft System, the first of its kind of unmanned aircraft system designed to perform in situ sampling of supercell thunderstorms, including those that produce tornadoes. A description of the critical system components, consisting of the unmanned aircraft, ground support vehicles, communications network, and custom software, is given. The unique concept of operations and regulatory issues for this type of highly nomadic and dynamic system are summarized, including airspace regulatory decisions from the Federal Aviation Administration to accommodate unmanned aircraft system operations for the study of supercell thunderstorms. A review of the system performance and concept of operations effectiveness during flights conducted for the spring 2010 campaign of the VORTEX2 project is provided. These flights resulted in the first-ever sampling of the rear flank gust front and airmass associated with the rear flank downdraft of a supercell thunderstorm by an unmanned aircraft system. A summary of the lessons learned, future work, and next steps is provided.

The Collaborative Colorado–Nebraska Unmanned Aircraft System Experiment

The Collaborative Colorado–Nebraska Unmanned Aircraft System Experiment (CoCoNUE) was executed on 1 March and 30 September 2009. The principal objective of this project was to examine the feasibility of using a small unmanned aircraft operating semi-autonomously with an onboard autopilot to observe atmospheric phenomena within the terrestrial boundary layer covered by the United States National Airspace System. The application of an unmanned aircraft system (UAS; the aircraft along with the communications and logistics infrastructure required for operation) is beset by a number of engineering and regulatory challenges. This article discusses the strategies implemented to meet these challenges. Airmass boundaries served as the target of the flights conducted. These atmospheric phenomena have the fortuitous combination of an across-boundary scale that yields a coherent signal in the in situ meteorological data that can be collected by a UAS and an along-boundary scale that can be easily tracked via the exis...

Hierarchical distributed control for search and tracking by heterogeneous aerial robot networks

This paper presents a hierarchical control architecture that enables cooperative surveillance by a heterogeneous aerial robot network comprised of mothership unmanned aircraft and daughtership micro air vehicles. Combining the endurance, range, and processing capabilities of the motherships with the stealth, flexibility, and maneuverability of swarms of daughterships enables robust control of aerial robot networks conducting collaborative operations. The hierarchical control structure decomposes the system into components that take advantage of the abilities of the different types of vehicles. The motherships act as distributed databases, fusion centers, negotiation agents, and task supervisors while daughtership control is achieved using cooperative vector field tracking. This paper describes the overall architecture and then focuses on the assignment and tracking algorithms used once sub- teams of daughtership vehicles have been deployed. A summary of the communication, command, and control structure of a heterogeneous unmanned aircraft system is also given in this paper along with hardware-in-the-loop and software simulation results verifying several components of the distributed control architecture.

Unmanned Aircraft Guidance for Penetration of Pretornadic Storms

This paper investigates unmanned aircraft guidance for a severe storm penetrator to assess the feasibility of such a mission and to optimize ingress in terms of flight time and exposure to precipitation. Understanding guidance-layer behavior and deriving control strategies will provide tools for developing mission-level concepts of operation and making vehicle design tradeoffs. A backward propagating wave front algorithm based on ordered upwind methods is developed for guidance-layer planning of severe storm penetration. Target areas for investigation by the aircraft are identified within simulated storm wind, hail, and precipitation data. The simulated data are used to determine the feasibility of storm penetration to the points of interest, along with calculating airframe exposure to precipitation. Ingress planning is also considered for a dynamic wind field using a receding horizon control approach to adapt the flight path in response to environmental changes.

Overview of Small Fixed-Wing Unmanned Aircraft for Meteorological Sampling

AbstractSampling the atmospheric boundary layer with small unmanned aircraft is a difficult task requiring informed selection of sensors and algorithms that are suited to the particular platform and mission. Many factors must be considered during the design process to ensure the desired measurement accuracy and resolution is achieved, as is demonstrated through an examination of previous and current efforts. A taxonomy is developed from these approaches and is used to guide a review of the systems that have been employed to make in situ wind and thermodynamic measurements, along with the campaigns that have employed them. Details about the airframe parameters, estimation algorithms, sensors, and calibration methods are given.

Net-Centric Communication and Control for a Heterogeneous Unmanned Aircraft System

This paper presents a net-centric communication, command, and control architecture for a heterogeneous unmanned aircraft system comprised of small and miniature unmanned aircraft. An integrated system was developed using a bottom-up design approach to reflect and enhance the interplay between networked communication and autonomous aircraft coordination. The advantages of the approach are demonstrated through a description of the unmanned system that resulted from using this design process. First, the hardware system is described, including both small and miniature unmanned aircraft along with their respective avionics systems. Second, a network architecture is described that seamlessly combines the miniature aircraft’s IEEE 802.15.4 components with IEEE 802.11 (WiFi) components on the small aircraft. Integration of intravehicle communication and service discovery is also described. Third, a hierarchical control architecture is presented that uses the network architecture to coordinate the small and miniature aircraft at several layers in the control hierarchy. Hardware in the loop demonstrations are performed to validate the capabilities of the heterogeneous unmanned aircraft system.

Networked Communication, Command, and Control of an Unmanned Aircraft System

Fullyautonomous,cooperative,multivehicleoperationrequiresthedevelopmentandintegration of various levels of intra- and intervehicle communication, sensing, control, and autonomy. This paper describes the Networked unmanned aircraft system Communication, Command, and Control (NetUASC3) architecture that combines meshed network intelligence, mission-level tasking information, and automatic flight control into an integrated unmanned aircraft system. The NetUASC3 architecture described includes: the University of Colorado at Boulder Ares unmanned aircraft, the onboard flight management architecture, and monitoring and command and control software that exploits the existing ad hoc Unmanned Aircraft System Ground network mesh network. Results from flight demonstration of the NetUASC3 architecture are provided to highlight the interplay between the various subsystems. Specific results demonstrate sensor-reactive and communicationreactive control, meshed network performance, atmospheric data collection, validation of radio-propagationmodels,anddeliveryofstreamingvideooveramultihopairborne‐ground network.

A Distributed Avionics Package for Small UAVs

This paper presents the design and implementation of a distributed computing architecture used to accommodate a wide range of operational environments. The architecture’s advantages include fault-tolerance and redundancy through an abstracted high and lowlevel bus protocol, and significant system scaling enabled by its modular nature. The current implementation was created for use in an avionics context, where it accommodates many payload sizes, levels of complexity, and configurations. Each of these advantages are evident in one of the many RECUV (Research and Engineering Center for Unmanned Vehicles at the University of Colorado) sponsored projects that use this system. This paper will describe some of these projects and how each maintains very dierent system requirements, ranging from providing a full-featured avionics system, to enabling control of a micro-UAV.

A reliable sensor data collection network using unmanned aircraft

This paper presents a method for reliably collecting data events from sensors and forwarding the data via a MANET to sensor monitoring stations located on an external network. A the core is a MANET concept that consists of ground and unmanned aircraf nodes. Unmanned aircraf enable a model whereby widely-spaced sensors are intermittently connected to the network and data is sent in stages as connections become available along each stage. The paper describes the sensor data collection model, the reliable multicast data delivery mechanism, and our experiences on a network test bed including the control of an unmanned aircraft through a MANET.