Fault Tolerant Flight Control of Unmanned Aerial Vehicles

Safety, reliability and acceptable level of performance of dynamic control systems are the major keys in all control systems especially in safety-critical control systems. A controller should be capable of handling noises and uncertainties imposed to the controlled process. A fault-tolerant controller should be able to control a system with guaranteed stability and good or acceptable performance not only in normal operation conditions but also in the presence of partial faults or total failures that can be occurred in the components of the system. When a fault occurs in a system, it suddenly starts to behave in an unanticipated manner. Thereby, a fault-tolerant controller should be designed for being able to handle the fault and guarantee system stability and acceptable performance in the presence of faults/damages. This shows the importance and necessity of Fault-Tolerant Control (FTC) to safety-critical and even nowadays for some new and non-safety-critical systems. During recent years, Unmanned Aerial Vehicles (UAVs) have proved to play a significant role in military and civil applications. The success of UAVs in different missions guarantees the growing number of UAVs to be considerable in future. Reliability of UAVs and their components against faults and failures is one of the most important objectives for safety-critical systems including manned airplanes and UAVs. The reliability importance of UAVs is implied in the acknowledgement of the Office of the Secretary of Defense in the UAV Roadmap 2005-2030 by stating that, ”Improving UA [unmanned aircraft] reliability is the single most immediate and long-reaching need to ensure their success”. This statement gives a wide future scenery of safety, reliability and Fault-Tolerant Flight Control (FTFC) systems of UAVs. The main objective of this thesis is to investigate and compare some aspects of fault tolerant flight control techniques such as performance, robustness and capability of handling the faults and failures during the flight of UAVs. Several control techniques have been developed and tested on two main platforms at Concordia University for fault-tolerant control techniques development, implementation and flight test purposes: quadrotor and fixedwing UAVs. The FTC techniques developed are: Gain-Scheduled Proportional-Integral-Derivative (GS-PID), Control Allocation and Re-allocation (CA/RA), Model Reference Adaptive Control (MRAC), and finally the Linear Parameter Varying (LPV) control as an alternative and theoretically more comprehensive gain scheduling based control technique. The LPV technique is used to control the quadrotor helicopter for fault-free conditions. Also a GS-PID controller is used as a fault-tolerant controller and implemented on a fixedwing UAV in the presence of a stuck rudder failure case

Small business innovation research: Abstracts of 1984. Phase 1 awards

On September 27, 1984, the National Aeronautics and Space Administration announced the selection of Phase I projects for the Small Business Innovation Research Program. These awards resulted from the evaluation of proposals submitted in response to the 1984 Program Solicitation, SBIR 84-1. In order to make available information on the technical content of the Phase I projects supported by the NASA SBIR Program, the abstracts of those proposals which resulted in awards of contracts are given. In addition, the name and address of the firm performing the work are given for those who may desired additional information about the project. Propulsion, aerodynamics, computer techniques, exobiology and composite materials are among the areas covered

Aerodynamic force interactions and measurements for micro quadrotors

Unmanned Aerial Vehicles (UAVs) have become mainstream through the success of several large commercial drone manufacturers. Quadrotors have been widely adopted due to their mechanical simplicity, ability to take off from a small area and hover at a fixed location. As these aircraft are increasingly being used in urban environments and indoors their ability to maintain stable flight in the presence of disturbances and nearby obstacles is of growing importance.Understanding the aerodynamics acting in these environments is the first step to improving quadrotor behaviour. This presents a challenge, as to characterise and verify models of the aerodynamic phenomena it is essential to collect numerous consistent experimental data points. On a typical quadrotor the motor response changes as the battery discharges, leading to variation in flight performance. Typically, this is addressed through the use high gain feedback control regulating attitude and position. To overcome this a unique voltage regulator for quadrotor power was developed to maintain constant supply voltage over the quadrotors flight. This enables the quadrotor to produce consistent and repeatable behaviour as the battery discharges.One way to improve the performance of quadrotors flying in constrained environments with limited sensing is to exploit aerodynamic effects for passive control and stability. Ground effect and rotor inflow damping are two effects of interest: ground effect provides a quadratic increase in thrust as a rotor moves closer to the ground; rotor inflow damping acts to resist axial motion by causing a change thrust opposing the movement. By canting the rotors of a quadrotor these effects were brought from the vertical axis into the lateral axis as well. A canted quadrotor flying over a v-shaped channel was modeled and found to exhibit passive stability in position. A demonstrator aircraft and v-shaped channel were tested in a number of configurations and shown to be stable for a channel slope of 10, 15 or 20 degrees with a rotor cant of 15 or 20 degrees.In order to observe more subtle aerodynamic effects, such as wall effect, it is necessary to have a method to measure rotor forces directly during quadrotor flight. Existing force torque sensors are too bulky, heavy, expensive or insensitive. To overcome these limitations a novel force torque sensor was developed that costs less than $50, weighs 3g and is capable of measuring sub mN forces. These sensors utilise an array of micro-electro-mechanical system (MEMS) barometers encapsulated in rubber to measure the strain field imparted by forces acting on the attached load plate. Mounting force torque sensors under the motors of a quadrotor allows the lateral rotor forces to be transmitted through the motor body and measured as torques at the base.Closely related to this, one of the key limitations faced by quadrotors is their inability to directly measure the airspeed of the aircraft. Providing an oncoming wind speed measurement will allow them to compensate for disturbances improving trajectory tracking and gust rejection. Blade flapping and induced drag are aerodynamic phenomena which relate lateral motion to a force acting in opposition to the rotors motion. By measuring this force using a rotor force sensor the airspeed of the aircraft is computed directly using induced drag and rotor blade flapping models. It was found that lateral velocity could be measured for the velocities tested, up to 1.5m/s, and showed a strong linear relationship to ground truth measurements.The work of this thesis has led to the development of: a quadrotor platform for consistent flight behaviour; a passive position-keeping quadrotor; and a novel rotor force sensor for direct measurement of quadrotor airspeed. These technologies open up avenues to improve the flight performance of quadrotors and better understand subtle aerodynamic interactions in flight

Conception d’une interface adaptative en réalité augmentée pour gérer des systèmes autonomes dans le déroulement de missions critiques

RÉSUMÉ : Dans une situation critique, de nombreux humains risquent leur vie pour en sauver d’autres. Les technologies innovantes pourraient grandement améliorer la conscience de la situation des acteurs de l’urgence, réduire le risque humain ainsi qu’augmenter la facilité de résolution des missions. Nous avons étudié cette idée en concevant une interface en réalité augmentée (RA) pour contrôler un essaim de drones durant une situation d’urgence.Durant ce travail, nous avons conçu cette interface pour gérer plusieurs drones et accroître la connaissance de la situation dans les situations critiques. L’essaim était composé de drones autonomes qui fournissaient un flux important d’informations. Le projet consistait à com-prendre les besoins humains dans les situations d’urgence et concevoir une application AR pour un visiocasque.Nous nous sommes concentrés sur la situation et les besoins du SIM (Service de sécurité incen-die de Montréal). Nous avons développé une solution qui conjointement avec un planificateur de mission dirige l’essaim fonctionnant sous l’infrastructure développée par le partenaire in-dustriel. Nous avons ensuite mis en place une simulation d’urgence avec un bâtiment de grande hauteur en feu où les participants devaient comprendre la situation en utilisant le visiocasque AR.Pour tester notre technologie et valider nos hypothèses, nous avons conçu une une simula-tion stressante et diÿcile pour être testée avec des gens de Polytechnique Montréal. Nous comparons l’eÿcacité d’un ordinateur basique et d’un visiocasque de réalité augmentée afin d’établir une comparaison et de mesurer l’eÿcacité de la RA. Nous terminons en expliquant que le casque de RA était moins eÿcace qu’un ordinateur dû notamment à la toute première utilisation de cet outil. Cependant, le visiocasque montre des résultats proches de l’ordina-teur et la technologie a été appréciée par tous les participants.----------ABSTRACT : In critical situations, many humans risk their lives to save others. Innovative technologies could greatly improve the situational awareness of emergency responders, reduce human risk and increase the resolution’s mission. We investigated this idea by designing an augmented reality (AR) interface to control a swarm of drones during an emergency situation.During this work, we designed an interface to manage multiple unmanned aerial vehicles (UAVs) and increase situational awareness in critical situations. The swarm was composed of autonomous UAVs that provided a significant flow of information. The project consisted of understanding human needs in emergency situations and designing an AR application for a headset.We focused on the situation and the needs of the SIM (Montreal Fire Safety Service). We developed a solution that, simultaneously with a mission planner, manages drones in the field operating with the infrastructure developed by the industrial partner. We then set up an emergency simulation with a high-rise building on fire where participants had to understand the situation using AR headset.To test our technology and validate our hypotheses, we tested our solution with people from Polytechnique Montreal during a stressful and diÿcult simulation. We compare the e˙ectiveness of a basic computer and an augmented reality headset to compare and measure the e˙ectiveness of AR. We concluded by explaining that the AR headset was less e˙ective than a computer, due in part to the very first use of this tool. However, the headset shows results close to the basic computer, and the technology was appreciated by all participants. We saw an improvement with the headset almost similar to the computer. Our results showed that augmented reality could, with more training and practice, improve conditions in emergency situations

Autonomisen multikopteriparven hallinta etsintä- ja pelastustehtävissä

This thesis presents the requirements and implementation of a Ground Control Station (GCS) application for controlling a fleet of multicopters to perform a Search And Rescue (SAR) mission. The requirements are put together by analysing existing drone types, SAR practices, and available GCS applications. Multicopters are found to be the most feasible drone to use for the SAR use case because of their maneuverability, despite not having the best endurance. Several existing area coverage methods are presented and their usefulness is analyzed for SAR scenarios where different amounts of prior knowledge is available. It is stated that most search patterns can be used with a fleet of drones, by creating drone formations and by dividing the target area into sub-areas. It is noted that most currently available GCS applications are focused on controlling a single drone for either industrial or hobby use. A proof of concept prototype is developed on top of an open source GCS and tested in field tests. Based on all the previous learnings from the protype and research, a new GCS is designed and developed. The development on optimizing communications between the GCS and the autopilot leads to a filed patent application. The new software is tested with three multicopters in a water rescue scenario and several user interface improvements are made as a result of the learnings. The development of a GCS for controlling a drone fleet for search and rescue is proven feasible.Työssä esitetään multikopteriparven hallintaan käytettävän Ground Control Station (GCS) ohjelmiston vaatimukset ja toteutus Search And Rescue (SAR) etsintä- ja pelastustehtävien suorittamiseksi. Vaatimukset kootaan yhteen analysoimalla saatavilla olevia droonityyppejä, SAR pelastuskäytäntöjä, sekä GCS ohjelmistoja. Multikopterit osoittautuvat liikkuvuutensa ansiosta pelastustehtäviin sopivimmaksi vaihtoehdoksi, vaikka niiden saavutettavissa oleva lentoaika ei ole parhaimmasta päästä. Erilaisia etsintämetodeja esitetään alueiden kattamiseksi ja niiden hyödyllisyyttä analysoidaan SAR tilanteissa, joissa ennakkotietoa on saatavilla vaihtelevasti. Osoitetaan, että useimpia etsintäalgoritmeja voidaan hyödyntää drooniparvella, muodostamalla lentomuodostelmia, sekä jakamalla kohdealue pienempiin osa-alueisiin. Huomataan, että suurin osa tällä hetkellä saatavilla olevista GCS ohjelmistoista on suunnattu teollisuuden tai harrastelijoiden käyttöön, pääasiassa yksittäisen droonin hallintaan. Prototyyppi kehitetään avoimen lähdekoodin GCS ohjelmiston pohjalta ja testataan kenttätesteissä. Tästä saadun tiedon avulla suunnitellaan ja kehitetään uusi GCS ohjelmisto. Kehitystyö viestinnän optimoinniksi autopilotin ja GCS ohjelmiston välillä johtaa patenttihakemukseen. Uusi ohjelmisto testataan kolmella multikopterilla vesipelastustilanteessa ja sen seurauksena käyttöliittymään tehdään useita parannuksia. GCS ohjelmiston luominen drooniparven hallintaan etsintä- ja pelastustehtävissä todetaan mahdolliseksi

The Public Secondary School And Teacher In American Films Of The 1990s

This study examined how public secondary schools and educators were portrayed in American films of the 1990s. Thirty films were selected for study that were produced and released in the decade of the 1990s. Content analysis and a Film Analysis Form produced answers to eight questions regarding the learning environments, portrayal of educators and students, the academic and life lessons taught, and positive or negative statements about education in the films of this decade. The results shoa series of complex environments, educators, students, and academic and life lessons delivered. An assessment of the positive and negative portrayal provided more negative views of the public secondary school than positive ones