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Full-Text Articles in Mechanical Engineering
Large Eddy Simulation Of The Wakes Of Three Urban Air Mobility Vehicles, Denis-Gabriel Caprace, Andrew Ning
Large Eddy Simulation Of The Wakes Of Three Urban Air Mobility Vehicles, Denis-Gabriel Caprace, Andrew Ning
Faculty Publications
Recent advances in urban air mobility have driven the development of many new VTOL concepts. These vehicles often feature original designs and futuristic shapes. Due to their novelty, the wake characteristics of such aircraft are unknown. However, large wake-induced velocities, should they exist, may be dangerous for any other vehicle evolving in their close proximity. Therefore, improved knowledge about the wakes of VTOL vehicles is needed to guarantee the safety of urban air mobility operations. In this work, we study the wake of three VTOL aircraft in cruise by means of large eddy simulation. We present a two-stage numerical procedure …
A Well Clear Recommendation For Small Uas In High-Density, Ads-B-Enabled Airspace, Timothy Mclain, Matthew O. Duffield
A Well Clear Recommendation For Small Uas In High-Density, Ads-B-Enabled Airspace, Timothy Mclain, Matthew O. Duffield
Faculty Publications
With the growing popularity of small unmanned aircraft systems (UAS), there is a significant need to enable small UAS to detect and avoid collisions with both manned and unmanned aircraft. The capabilities of ADS-B make it an attractive sensor for detect and avoid (DAA), but it is susceptible to frequency congestion. This paper quantitatively analyzes the frequency limitations of 978 MHz ADS-B. It then uses these limitations to make a recommendation for well clear in ADS-B-equipped airspace that has a high density of small UAS operations.
Cushioned Extended-Periphery Avoidance: A Reactive Obstacle Avoidance Plugin, Timothy Mclain, James Jackson, David Wheeler
Cushioned Extended-Periphery Avoidance: A Reactive Obstacle Avoidance Plugin, Timothy Mclain, James Jackson, David Wheeler
Faculty Publications
While collision avoidance and flight stability are generally a micro air vehicle’s (MAVs) highest priority, many map-based path planning algorithms focus on path optimality, often assuming a static, known environment. For many MAV applications a robust navigation solution requires responding quickly to obstacles in dynamic, tight environments with non- negligible disturbances. This article first outlines the Reactive Obstacle Avoidance Plugin framework as a method for leveraging map-based algorithms while providing low-latency, high-bandwidth response to obstacles. Further, we propose and demonstrate the effectiveness of the Cushioned Extended- Periphery Avoidance (CEPA) algorithm. By representing recent laser scans in the current body-fixed polar …
Rosflight: A Lightweight, Inexpensive Mav Research And Development Tool, Timothy Mclain, James Jackson, Gary J. Ellingson
Rosflight: A Lightweight, Inexpensive Mav Research And Development Tool, Timothy Mclain, James Jackson, Gary J. Ellingson
Faculty Publications
To accelerate research and development of the autonomous capabilities of micro aerial vehicles we have developed flight control framework, ROSflight, as a research tool. ROSflight makes development of autopilot code easier and more efficient by minimizing the use of embedded systems, incorporating the Robot Operating System and using off-the-shelf and open-source hardware and software. Motivation and applications for use in the research community are discussed. Analysis of loop rate and communication bandwidth are presented as well as results from flight demonstration of two multi-rotor aircraft.
Multi-Sensor Robust Relative Estimation Framework For Gps-Denied Multirotor Aircraft, Tim Mclain, Daniel P. Koch, Kevin M. Brink
Multi-Sensor Robust Relative Estimation Framework For Gps-Denied Multirotor Aircraft, Tim Mclain, Daniel P. Koch, Kevin M. Brink
Faculty Publications
An estimation framework is presented that improves the robustness of GPS-denied state estimation to changing environmental conditions by fusing updates from multiple view-based odometry algorithms. This allows the vehicle to utilize a suite of complementary exteroceptive sensors or sensing modalities. By estimating the vehicle states relative to a local coordinate frame collocated with an odometry keyframe, observability of the relative state is maintained. A description of the general framework is given, as well as the specific equations for a multiplicative extended Kalman filter with a multirotor vehicle. Experimental results are presented that demonstrate the ability of the proposed algorithm to …
Automatic Dependent Surveillance-Broadcast For Detect And Avoid On Small Unmanned Aircraft, Matthew Owen Duffield
Automatic Dependent Surveillance-Broadcast For Detect And Avoid On Small Unmanned Aircraft, Matthew Owen Duffield
Theses and Dissertations
Small unmanned aircraft systems (UAS) are rapidly gaining popularity. As the excitement surrounding small UAS has grown, the Federal Aviation Administration (FAA) has repeatedly stated that UAS must be capable of detecting and avoiding manned and unmanned aircraft. In developing detect-and-avoid (DAA) technology, one of the key challenges is identifying a suitable sensor. Automatic Dependent Surveillance-Broadcast (ADS-B) has gained much attention in both the research and consumer sectors as a promising solution. While ADS-B has many positive characteristics, further analysis is necessary to determine if it is suitable as a DAA sensor in environments with high-density small UAS operations. To …
Landing Zone Determination For Autonomous Rotorcraft In Surveillance Applications, Timothy Mclain, Gary J. Ellingson, Justin Mackay
Landing Zone Determination For Autonomous Rotorcraft In Surveillance Applications, Timothy Mclain, Gary J. Ellingson, Justin Mackay
Faculty Publications
This paper presents an approach for finding possible landing sites for a rotorcraft from an inertially referenced point-cloud model of the environment. To identify potential landing sites that are suitably flat and level, a grid-based random sample consensus algorithm separates the terrain map into discrete areas for plane-fitting analysis. Landing sites are selected that satisfy constraints on flatness and levelness while optimizing the surveillance target’s visibility. Flight test results are presented from a small multirotor aircraft flying over a scale-model cityscape. Results from real-time landing-site experiments are presented and discussed.
Detect And Avoid For Small Unmanned Aircraft Systems Using Ads-B, Timothy Mclain, Laith R. Sahawneh, Matthew O. Duffield, Randall W. Beard
Detect And Avoid For Small Unmanned Aircraft Systems Using Ads-B, Timothy Mclain, Laith R. Sahawneh, Matthew O. Duffield, Randall W. Beard
Faculty Publications
With the increasing demand to integrate unmanned aircraft systems (UAS) into the National Airspace System (NAS), new procedures and technologies are necessary to ensure safe airspace operations and minimize the impact of UAS on current airspace users. Currently, small UAS face limitations on their use in civil airspace because they lack the ability to detect and avoid other aircraft. This article presents a framework that consists of an Automatic Dependent Surveillance-Broadcast (ADS-B)-based sensor, track estimator, conflict/collision detection, and resolution that mitigates collision risk. ADS-B offers long-range, omni-directional intruder detection with comparatively few size, weight, power, and cost demands. The proposed …
Implementing Dubins Airplane Paths On Fixed-Wing Uavs, Timothy Mclain, Randall W. Beard, Mark Owen
Implementing Dubins Airplane Paths On Fixed-Wing Uavs, Timothy Mclain, Randall W. Beard, Mark Owen
Faculty Publications
A well-known path-planning technique for mobile robots or planar aerial vehicles is to use Dubins paths, which are minimum-distance paths between two configurations subject to the constraints of the Dubins car model. An extension of this method to a three-dimensional Dubins airplane model has recently been proposed. This chapter builds on that work showing a complete architecture for implementing Dubins airplane paths on small fixed-wing UAVs. The existing Dubins airplane model is modified to be more consistent with the kinematics of a fixed-wing aircraft. The chapter then shows how a recently proposed vector-field method can be used to design a …
Vision-Based Guidance For Air-To-Air Tracking And Rendezvous Of Unmanned Aircraft Systems, Joseph Walter Nichols
Vision-Based Guidance For Air-To-Air Tracking And Rendezvous Of Unmanned Aircraft Systems, Joseph Walter Nichols
Theses and Dissertations
This dissertation develops the visual pursuit method for air-to-air tracking and rendezvous of unmanned aircraft systems. It also shows the development of vector-field and proportional-integral methods for controlling UAS flight in formation with other aircraft. The visual pursuit method is a nonlinear guidance method that uses vision-based line of sight angles as inputs to the algorithm that produces pitch rate, bank angle and airspeed commands for the autopilot to use in aircraft control. The method is shown to be convergent about the center of the camera image frame and to be stable in the sense of Lyapunov. In the lateral …
Development Of A Sense And Avoid System For Small Unmanned Aircraft Systems, Robert Andrew Klaus
Development Of A Sense And Avoid System For Small Unmanned Aircraft Systems, Robert Andrew Klaus
Theses and Dissertations
Unmanned aircraft systems (UAS) represent the future of modern aviation. Over the past 10 years their use abroad by the military has become commonplace for surveillance and combat. Unfortunately, their use at home has been far more restrictive. Due to safety and regulatory concerns, UAS are prohibited from flying in the National Airspace System without special authorization from the FAA. One main reason for this is the lack of an on-board pilot to "see and avoid" other air traffic and thereby maintain the safety of the skies. Development of a comparable capability, known as "Sense and Avoid" (SAA), has therefore …
Experiments In Cooperative Timing For Miniature Air Vehicles, Timothy Mclain, Derek R. Nelson, Randal W. Beard
Experiments In Cooperative Timing For Miniature Air Vehicles, Timothy Mclain, Derek R. Nelson, Randal W. Beard
Faculty Publications
This paper presents experimental results for two cooperative timing missions carried out using a team of three miniature air vehicles (MAVs). Using a cooperative timing algorithm based on coordination functions and coordination variables, the MAV team executed a series of simultaneous arrival and cooperative fly-by missions. In the presence of significant wind disturbances, the average time difference between the first and last vehicle in the simultaneous arrival experiments was 1.6 s. For the cooperative fly-by experiments, the average timing error between vehicle arrivals was 0.6 s. These results demonstrate the practical feasibility of the cooperative timing approach.
Vector Field Path Following For Miniature Air Vehicles, Timothy Mclain, Derek R. Nelson, D. Blake Barber, Randall W. Beard
Vector Field Path Following For Miniature Air Vehicles, Timothy Mclain, Derek R. Nelson, D. Blake Barber, Randall W. Beard
Faculty Publications
In this paper, a method for accurate path following for miniature air vehicles is developed. The method is based on the notion of vector fields, which are used to generate desired course inputs to inner-loop attitude control laws. Vector-field path-following control laws are developed for straight-line paths and circular arcs and orbits. Lyapunov stability arguments are used to demonstrate asymptotic decay of path-following errors in the presence of constant wind disturbances. Experimental flight tests have demonstrated mean path-following errors on less than one wingspan for straight-line and orbit paths and less than three wingspans for paths with frequent changes in …
Obstacle And Terrain Avoidance For Miniature Aerial Vehicles, Timothy Mclain, Jeff Saunders, Blake Barber, Randall W. Beard, Stephen R. Griffiths
Obstacle And Terrain Avoidance For Miniature Aerial Vehicles, Timothy Mclain, Jeff Saunders, Blake Barber, Randall W. Beard, Stephen R. Griffiths
Faculty Publications
Unmanned aerial vehicles (UAVs) are playing increasingly prominent roles in defense programs and strategy around the world. Technology advancements have enabled the development of large UAVs (e.g., Global Hawk, Predator) and the creation of smaller, increasingly capable UAVs. The focus of this Chapter is on smaller fixed-wing miniature aerial vehicles (MAVs), which range in size from % to 2 m in wingspan. As recent conflicts have demonstrated, there are numerous military applications for MAVs including reconnaissance, surveillance, battle damage assessment, and communications relays.