Online Optimal Obstacle Avoidance for Rotary-wing Autonomous Unmanned Aerial Vehicles PDF Download

Author: Keeryun Kang
Publisher:
ISBN:
Category : Drone aircraft
Languages : en
Pages :

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Book Description
This thesis presents an integrated framework for online obstacle avoidance of rotary-wing unmanned aerial vehicles (UAVs), which can provide UAVs an obstacle field navigation capability in a partially or completely unknown obstacle-rich environment. The framework is composed of a LIDAR interface, a local obstacle grid generation, a receding horizon (RH) trajectory optimizer, a global shortest path search algorithm, and a climb rate limit detection logic. The key feature of the framework is the use of an optimization-based trajectory generation in which the obstacle avoidance problem is formulated as a nonlinear trajectory optimization problem with state and input constraints over the finite range of the sensor. This local trajectory optimization is combined with a global path search algorithm which provides a useful initial guess to the nonlinear optimization solver. Optimization is the natural process of finding the best trajectory that is dynamically feasible, safe within the vehicle's flight envelope, and collision-free at the same time. The optimal trajectory is continuously updated in real time by the numerical optimization solver, Nonlinear Trajectory Generation (NTG), which is a direct solver based on the spline approximation of trajectory for dynamically flat systems. In fact, the overall approach of this thesis to finding the optimal trajectory is similar to the model predictive control (MPC) or the receding horizon control (RHC), except that this thesis followed a two-layer design; thus, the optimal solution works as a guidance command to be followed by the controller of the vehicle. The framework is implemented in a real-time simulation environment, the Georgia Tech UAV Simulation Tool (GUST), and integrated in the onboard software of the rotary-wing UAV test-bed at Georgia Tech. Initially, the 2D vertical avoidance capability of real obstacles was tested in flight. Then the flight test evaluations were extended to the benchmark tests for 3D avoidance capability over the virtual obstacles, and finally it was demonstrated on real obstacles located at the McKenna MOUT site in Fort Benning, Georgia. Simulations and flight test evaluations demonstrate the feasibility of the developed framework for UAV applications involving low-altitude flight in an urban area.

Author: Eitan Bulka
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
"Unmanned aerial vehicles (UAVs) have been increasingly proposed for aerial surveillance, mapping, and delivery tasks. Historically these vehicles fall into two categories: conventional fixed-wing aircraft, which are capable of efficient flight over long distances but lack maneuverability, and rotorcraft, which are capable of agile and maneuverable flight but lack efficiency and endurance. Recent advancements in aerial vehicle design aim to incorporate characteristics from both rotorcraft and conventional fixed-wing aircraft, ultimately creating aircraft that are capable of both maneuverable and efficient long distance flight. These type of platforms are ideal for tasks that require both the ability to maneuver through cluttered environments, and the ability to fly long distances efficiently. An aircraft of this type, the agile fixed-wing aircraft, is a fixed-wing aircraft characterized by a high thrust-to-weight ratio (> 1), and large control surfaces capable of large deflections.The objective of this thesis is to further the autonomous capabilities of agile fixed-wing aircraft; specifically in the context of control systems and real-time collision avoidance. The thesis begins with a discussion of a previously developed flight dynamics model, and presents a method for validating a flight dynamics model in flight regimes that rely on feedback control. Subsequently, a single control architecture is developed that can track trajectories within both conventional and aerobatic flight regimes. This architecture is then extended to be applicable to many other types of vehicles, specifically vehicles which can generate a torque in an arbitrary direction, and can apply a single body-fixed force. We demonstrate autonomous aerobatic trajectories with an agile fixed-wing aircraft, specifically knife-edge, rolling harrier, aggressive turnaround and hovering maneuvers within conventional simulations, hardware-in-the-loop simulations, indoor flight tests and outdoor flight tests. We also validate the extension to other platforms by demonstrating flips with a quadrotor in both simulation and outdoor flight tests. All flights were performed with on-board sensing and computation.We then present a reactive obstacle avoidance algorithm that utilizes the maneuvering capabilities of agile fixed-wing aircraft and can be run in real-time with on-board sensing and computation. At each time step, trajectories are selected in real-time from a pre-computed library that lead to various positions on the edge of the obstacle sensor's field-of-view. A cost is assigned to each collision-free trajectory based on its heading toward the goal and minimum distance to obstacles, and the lowest cost trajectory is tracked. If all of the potential trajectories leading to the various positions at the edge of the obstacle sensor's field-of-view result in a collision, the aircraft has enough space to hover and come to a stop, which theoretically guarantees collision-free flight in unknown static environments. Autonomous flight in unknown and unstructured environments using only on-board sensing (stereo camera, IMU, and GPS) and computation is demonstrated with an agile fixed-wing aircraft in both simulation and outdoor flight tests. During the flight testing campaign, the aircraft autonomously flew 4.4 km in a tree-filled environment with an average speed of 8.1 m/s and a top speed of 14.4 m/s"--

Author: Yucong Lin
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 113

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Book Description
There has been a vast increase in applications of Unmanned Aerial Vehicles (UAVs) in civilian domains. To operate in the civilian airspace, a UAV must be able to sense and avoid both static and moving obstacles for flight safety. While indoor and low-altitude environments are mainly occupied by static obstacles, risks in space of higher altitude primarily come from moving obstacles such as other aircraft or flying vehicles in the airspace. Therefore, the ability to avoid moving obstacles becomes a necessityfor Unmanned Aerial Vehicles. Towards enabling a UAV to autonomously sense and avoid moving obstacles, this thesis makes the following contributions. Initially, an image-based reactive motion planner is developed for a quadrotor to avoid a fast approaching obstacle. Furthermore, A Dubins curve based geometry method is developed as a global path planner for a fixed-wing UAV to avoid collisions with aircraft. The image-based method is unable to produce an optimal path and the geometry method uses a simplified UAV model. To compensatethese two disadvantages, a series of algorithms built upon the Closed-Loop Rapid Exploratory Random Tree are developed as global path planners to generate collision avoidance paths in real time. The algorithms are validated in Software-In-the-Loop (SITL) and Hardware-In-the-Loop (HIL) simulations using a fixed-wing UAV model and in real flight experiments using quadrotors. It is observed that the algorithm enables a UAV to avoid moving obstacles approaching to it with different directions and speeds.

Author: James A. Devens
Publisher:
ISBN:
Category :
Languages : en
Pages : 88

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Book Description
Autonomous coordination among multiple aerial vehicles to ensure a collision free airspace is a critical aspect of today's airspace. With the rise of Unmanned Aerial Vehicles (UAVs) in the military and commercial sectors, obstacle avoidance in a densely populated airspace is necessary. This thesis investigates finding optimal or near-optimal trajectories in real-time for aircraft in complex airspaces containing a large number of obstacles. The solution for the trajectories is described as a linear program subject to mixed integer constraints, known as a Mixed Integer Linear Program (MILP). The resulting MILP problem is solved in real time using a well-known, public domain MILP solver. In addition, an Exhaustive, Breadth-First Search algorithm was implemented and is used for comparison in terms of execution time and flight path optimality. The Exhaustive Search algorithm is comprised of a multi-branch tree structure that iterates through all possible flight paths from source to target. The MILP solution was implemented in both PC based and embedded system environments. The embedded system environment was implemented on an onboard processor to develop trajectories for each individual aircraft in real time.

Author: Laird-Philip Ryan Lewis
Publisher:
ISBN:
Category : Engineering
Languages : en
Pages : 161

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Book Description
This work introduces the use of optimal control methods for path planning and control of autonomous vehicles in an obstacle-rich environment. Traditional techniques harbor non-optimal, closed architectures primarily derived at a time when computational complexity could significantly hinder overall system performance. Advancements in computing power, miniaturization, and numerical methods permit the utilization of online, optimal path planning and control, thereby improving system flexibility and autonomy. The backbone of this concept is state-of-the-art optimal control techniques involving pseudospectral methods and sequential quadratic programming. Although this research focuses on a robotic car or Unmanned Ground Vehicle (UGV), several systems, including an Unmanned Aerial Vehicle (UAV) and a pendulum on a rotational base, are detailed for the purpose of illustrating the technique's modularity. With respect to the UGV, optimal control methods permit the optimization of maneuver parameters while accounting for complex vehicle kinematics and workspace obstacles, represented as dynamic and path constraints respectively. The path constraints are modeled such that an obstacle of any shape or size can be included. Maneuvering trajectories are first generated in an open-loop architecture, followed by an application of these same techniques in feedback form. Lastly, model fidelity is increased to improve control over vehicle behavior and closed-loop performance and a local knowledge scenario is evaluated.

Author: Victor Becerra
Publisher: MDPI
ISBN: 3039210300
Category : Technology & Engineering
Languages : en
Pages : 476

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Book Description
Unmanned aerial vehicles (UAVs) are being increasingly used in different applications in both military and civilian domains. These applications include surveillance, reconnaissance, remote sensing, target acquisition, border patrol, infrastructure monitoring, aerial imaging, industrial inspection, and emergency medical aid. Vehicles that can be considered autonomous must be able to make decisions and react to events without direct intervention by humans. Although some UAVs are able to perform increasingly complex autonomous manoeuvres, most UAVs are not fully autonomous; instead, they are mostly operated remotely by humans. To make UAVs fully autonomous, many technological and algorithmic developments are still required. For instance, UAVs will need to improve their sensing of obstacles and subsequent avoidance. This becomes particularly important as autonomous UAVs start to operate in civilian airspaces that are occupied by other aircraft. The aim of this volume is to bring together the work of leading researchers and practitioners in the field of unmanned aerial vehicles with a common interest in their autonomy. The contributions that are part of this volume present key challenges associated with the autonomous control of unmanned aerial vehicles, and propose solution methodologies to address such challenges, analyse the proposed methodologies, and evaluate their performance.

Author: Reg Austin
Publisher: John Wiley & Sons
ISBN: 1119964261
Category : Technology & Engineering
Languages : en
Pages : 353

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Book Description
Unmanned Aircraft Systems delivers a much needed introduction to UAV System technology, taking an integrated approach that avoids compartmentalising the subject. Arranged in four sections, parts 1-3 examine the way in which various engineering disciplines affect the design, development and deployment of UAS. The fourth section assesses the future challenges and opportunities of UAS. Technological innovation and increasingly diverse applications are two key drivers of the rapid expansion of UAS technology. The global defence budget for UAS procurement is expanding, and in the future the market for civilian UAVs is expected to outmatch that of the military. Agriculture, meteorology, conservation and border control are just a few of the diverse areas in which UAVs are making a significant impact; the author addresses all of these applications, looking at the roles and technology behind both fixed wing and rotorcraft UAVs. Leading aeronautical consultant Reg Austin co-founded the Bristol International Remotely Piloted Vehicle (RPV) conferences in 1979, which are now the longest-established UAS conferences worldwide. In addition, Austin has over 40 years' experience in the design and development of UAS. One of Austin's programmes, the "Sprite UAV System" has been deployed around the world and operated by day and night, in all weathers.

Author: Andrew James Barry
Publisher:
ISBN:
Category :
Languages : en
Pages : 127

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Book Description
This thesis presents the design and implementation of a small autonomous unmanned aerial vehicle capable of high-speed flight through complex natural environments. Using only onboard sensing and computation, we perform obstacle detection, planning, and feedback control in realtime. We introduce a novel stereo vision algorithm, pushbroom stereo, capable of detecting obstacles at 120 frames per second without overburdening our lightweight processors. Our use of model-based planning and control techniques allows us to track precise trajectories that avoid obstacles identified by the vision system. We demonstrate a complete working system avoiding trees at up to 14 m/s (31 MPH). To the best of our knowledge this is the fastest lightweight aerial vehicle to perform collision avoidance in such a complex environment.

Author: Plamen Angelov
Publisher: John Wiley & Sons
ISBN: 0470979755
Category : Technology & Engineering
Languages : en
Pages : 381

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Book Description
There is increasing interest in the potential of UAV (Unmanned Aerial Vehicle) and MAV (Micro Air Vehicle) technology and their wide ranging applications including defence missions, reconnaissance and surveillance, border patrol, disaster zone assessment and atmospheric research. High investment levels from the military sector globally is driving research and development and increasing the viability of autonomous platforms as replacements for the remotely piloted vehicles more commonly in use. UAV/UAS pose a number of new challenges, with the autonomy and in particular collision avoidance, detect and avoid, or sense and avoid, as the most challenging one, involving both regulatory and technical issues. Sense and Avoid in UAS: Research and Applications covers the problem of detect, sense and avoid in UAS (Unmanned Aircraft Systems) in depth and combines the theoretical and application results by leading academics and researchers from industry and academia. Key features: Presents a holistic view of the sense and avoid problem in the wider application of autonomous systems Includes information on human factors, regulatory issues and navigation, control, aerodynamics and physics aspects of the sense and avoid problem in UAS Provides professional, scientific and reliable content that is easy to understand, and Includes contributions from leading engineers and researchers in the field Sense and Avoid in UAS: Research and Applications is an invaluable source of original and specialised information. It acts as a reference manual for practising engineers and advanced theoretical researchers and also forms a useful resource for younger engineers and postgraduate students. With its credible sources and thorough review process, Sense and Avoid in UAS: Research and Applications provides a reliable source of information in an area that is fast expanding but scarcely covered.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Successful operation of next-generation unmanned air vehicles will demand a high level of autonomy. Autonomous low-level operation in a high-threat environment dictates a need for on-hoard, robust, reliable and efficient trajectory optimization. in this report, we develop and demonstrate an innovative combination of traditional analytical and numerical solution procedures to produce efficient, robust and reliable means for nonlinear Light path optimization in the presence of time-varying obstacles and threats. The solution procedure exploits the natural time-scale separation that exists in the aircraft dynamics using singular perturbation theory. A reduced order problem involving only the kinematics of the position subspace is treated numerically. The nonlinear aircraft dynamics are to be treated analytically in phase II using a boundary layer analysis that results in an optimal feedback guidance solution. The developed algorithms were coupled with a neural network adaptive autopilot and integrated in an existing unmanned test-bed. This report documents the phase I effort, which produced a demonstration of the developed algorithm in near-real-time flight simulation, and included a simple evaluation of tracking computed trajectories on a rotary wing UAV.