Powerline perching with a fixed-wing UAV

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 109-112).Small and micro UAVs have enabled a number of new mission capabilities, including navigating in and around buildings and performing perch-and-stare surveillance. However, one of the primary limitations of these small vehicles is endurance, simply because they cannot carry sufficient power for long missions. Recent advances in fixed-wing perching have made it possible to consider a new solution to this problem - landing on a powerline to recharge. Furthermore, because a current carrying conductor generates a magnetic field, a unique opportunity exists to use the powerline not just for recharging, but for localization as well. In this thesis, we seek to develop technologies that will enable a fixed-wing aircraft to land on a powerline using only the powerline's magnetic field and an inertial measurement unit for localization. To achieve this goal, an experimental set-up and preliminary sensing hardware are developed to detect the magnetic field at least 4 meters from the wire. Then, the necessary signal processing and state estimation algorithms are applied to achieve successful localization and overcome problematic field ambiguities. Following this, an onboard sensing system is developed and the high speed tracking of a perching trajectory is demonstrated experimentally. Finally, the position error associated with the aircraft tracking algorithm is analyzed carefully and assessed to be suitable for achieving closed loop perching. The work culminates in a light weight, 30 gram, on-board sensor system with the capability of estimating the position of a perching aircraft in real time at update rates up to 320 Hz, positional accuracies ranging from 2 to 20 centimeters, and delays of about 17 Ms.by Joseph L. Moore.S.M

Master of Science

thesisFlying rotorcraft, such as helicopters and quadrotors, can gather useful information without the need for human presence, but they consume a great deal of power and have limited on-board energy resources. Our work aims to provide a passive perching mechanism so that a rotorcraft is able to grip branch-like perches and resist external wind disturbances, using only the weight of the rotorcraft to maintain the grip. Deviating from previous bio-inspired approaches, in this thesis, we propose a mechanism that incorporates a Sarrus linkage to convert the weight of the rotorcraft into grip force. We provide an analysis of the mechanism's kinematics, we present the static force equations that describe how the weight of the rotorcraft is converted into grip force onto a cylindrical perch, and we describe how grip forces relate to the ability to reject horizontal disturbances such as wind gusts. The mechanism is then optimized for use on a single perch size, and then for a range of perch sizes. We conclude by constructing a prototype mechanism, and we demonstrate its use with a remote-controlled helicopter

A Vision-Based Navigation System for Perching Aircraft

This is the final version of the article. Available from Springer via the DOI in this record.This paper presents the investigation of the use of position-sensing diode (PSD) - a light source direction sensor - for designing a vision-based navigation system for a perching aircraft. Aircraft perching maneuvers mimic bird’s landing by climbing for touching down with low velocity or negligible impact. They are optimized to reduce their spatial requirements, like altitude gain or trajectory length. Due to disturbances and uncertainties, real-time perching is realized by tracking the optimal trajectories. As the performance of the controllers depends on the accuracy of estimated aircraft state, the use of PSD measurements as observations in the state estimation model is proposed to achieve precise landing. The performance and the suitability of this navigation system are investigated through numerical simulations. An optimal perching trajectory is computed by minimizing the trajectory length. Accelerations, angular-rates and PSD readings are determined from this trajectory and then added with experimentally obtained noise to create simulated sensor measurements. The initial state of the optimal perching trajectory is perturbed, and by assuming zero biases, extended Kalman filter is implemented for aircraft state estimation. It is shown that the errors between estimated and actual aircraft states reduce along the trajectory, validating the proposed navigation system

Robust post-stall perching with a simple fixed-wing glider using LQR-Trees

Birds routinely execute post-stall maneuvers with a speed and precision far beyond the capabilities of our best aircraft control systems. One remarkable example is a bird exploiting post-stall pressure drag in order to rapidly decelerate to land on a perch. Stall is typically associated with a loss of control authority, and it is tempting to attribute this agility of birds to the intricate morphology of the wings and tail, to their precision sensing apparatus, or their ability to perform thrust vectoring. Here we ask whether an extremely simple fixed-wing glider (no propeller) with only a single actuator in the tail is capable of landing precisely on a perch from a large range of initial conditions. To answer this question, we focus on the design of the flight control system; building upon previous work which used linear feedback control design based on quadratic regulators (LQR), we develop nonlinear feedback control based on nonlinear model-predictive control and 'LQR-Trees'. Through simulation using a flat-plate model of the glider, we find that both nonlinear methods are capable of achieving an accurate bird-like perching maneuver from a large range of initial conditions; the 'LQR-Trees' algorithm is particularly useful due to its low computational burden at runtime and its inherent performance guarantees. With this in mind, we then implement the 'LQR-Trees' algorithm on real hardware and demonstrate a 95 percent perching success rate over 147 flights for a wide range of initial speeds. These results suggest that, at least in the absence of significant disturbances like wind gusts, complex wing morphology and sensing are not strictly required to achieve accurate and robust perching even in the post-stall flow regime.United States. Office of Naval Research. Multidisciplinary University Research Initiative (N00014-10-1-0951)National Science Foundation (U.S.) (Award IIS-0915148

On power line positioning systems

Power line infrastructure is available almost everywhere. Positioning systems aim to estimate where a device or target is. Consequently, there may be an opportunity to use power lines for positioning purposes. This survey article reports the different efforts, working principles, and possibilities for implementing positioning systems relying on power line infrastructure for power line positioning systems (PLPS). Since Power Line Communication (PLC) systems of different characteristics have been deployed to provide communication services using the existing mains, we also address how PLC systems may be employed to build positioning systems. Although some efforts exist, PLPS are still prospective and thus open to research and development, and we try to indicate the possible directions and potential applications for PLPS.European Commissio

LiDAR-based Autonomous Power-line Perching with Multirotors

Este trabajo trata sobre el desarrollo de un método para permitir que vehículos aéreos de tipo multirotor puedan colgarse autónomamente de líneas eléctricas. Se ha desarrollado un sistema de percepción basado en dos LiDARs 2D rotacionales que se encarga de obtener con exactitud la posición y orientación relativa de la línea eléctrica con el robot. Estas estimaciones son recibidas por el sistema de control, que actúa sobre la velocidad del multirotor para alcanzar la posición que permite la actuación del mecanismo de enganche. El método se ha validado con un quadrotor real en el que se ejecutaba todo el software a bordo para controlar de forma precisa la posición relativa del robot con la línea.This work addresses the development of a method to enable autonomous multirotors to perch on power-lines. A perception system based on two rotatory 2D LiDARs has been designed and implemented to accurately estimate the pose of the power-line. These estimations are received by the control system of the aerial robot, which acts on the velocity of the platform to achieve the relative pose with the power-line that allows the actuation of a mechanism to grab the line. The method has been evaluated with a real multirotor that executed all the software on board to accurately control its relative pose with respect to a real power-line cable

Science, technology and the future of small autonomous drones

We are witnessing the advent of a new era of robots — drones — that can autonomously fly in natural and man-made environments. These robots, often associated with defence applications, could have a major impact on civilian tasks, including transportation, communication, agriculture, disaster mitigation and environment preservation. Autonomous flight in confined spaces presents great scientific and technical challenges owing to the energetic cost of staying airborne and to the perceptual intelligence required to negotiate complex environments. We identify scientific and technological advances that are expected to translate, within appropriate regulatory frameworks, into pervasive use of autonomous drones for civilian applications

Design of a Wireless Drone Recharging Station and a Special Robot End Effector for Installation on a Power Line

Drone autonomous operations near power lines are growing steadily and require innovative techniques to keep them on air. This paper presents a novel electromechanical recharging station that can be mounted on energized AC power line to charge the drone battery wirelessly without a need to modify the electrical infrastructure. The work shows a thorough analysis of the electrical and mechanical core components to build a flexible, lightweight and efficient recharging station that can be attached to a robotic arm. The work also discusses the recharging station design and its special robot end effector that mechanically couples the station with an aerial manipulator. Finally, the recharging station has been tested in the lab and in a real power line setup to validate its design and efficiency. The total achieved mass is 2300 grams with a harvesting efficiency of 77% at 250 A primary current

Aerial Robotics for Inspection and Maintenance

Aerial robots with perception, navigation, and manipulation capabilities are extending the range of applications of drones, allowing the integration of different sensor devices and robotic manipulators to perform inspection and maintenance operations on infrastructures such as power lines, bridges, viaducts, or walls, involving typically physical interactions on flight. New research and technological challenges arise from applications demanding the benefits of aerial robots, particularly in outdoor environments. This book collects eleven papers from different research groups from Spain, Croatia, Italy, Japan, the USA, the Netherlands, and Denmark, focused on the design, development, and experimental validation of methods and technologies for inspection and maintenance using aerial robots