The problem of stand-off tracking of a moving target using a quadrotor unmanned aerial vehicle (UAV) based on vision-sensing is investigated. A PID (Proportional-Integral-Derivative) controller is implemented for attitude stabilization of the quadrotor. An LQG-based (Linear-Quadratic-Gaussian) control law is designed and implemented for position control of the quadrotor for a moving target tracking task. A novel vision-based estimation algorithm is developed, enabling estimation of quadrotor’s position, altitude and yaw relative to the target based on limited information about the target. Two image processing algorithms are implemented and compared for the task of feature detection and feature tracking in a series of images. Image processing algorithms are integrated with quadrotor control and experiments are performed to validate proposed control and estimation approaches.

The problem of stand-off tracking of a moving target using a quadrotor unmanned aerial vehicle (UAV) based on vision-sensing is investigated. A PID (Proportional-Integral-Derivative) controller is implemented for attitude stabilization of the quadrotor. An LQG-based (Linear-Quadratic-Gaussian) control law is designed and implemented for position control of the quadrotor for a moving target tracking task. A novel vision-based estimation algorithm is developed, enabling estimation of quadrotor’s position, altitude and yaw relative to the target based on limited information about the target. Two image processing algorithms are implemented and compared for the task of feature detection and feature tracking in a series of images. Image processing algorithms are integrated with quadrotor control and experiments are performed to validate proposed control and estimation approaches.

Les principaux travaux développés dans cette thèse traitent de la commande, du diagnostic et de la tolérance aux fautes utilisant le concept de la commande sans modèle récemment proposé dans la littérature. Les méthodes développées sont testées en temps réel et validées sur un quadrotor. Dans un premier temps, le modèle du quadrotor est présenté et analysé dans l'objectif de concevoir et implanter une loi de commande robuste aux perturbations et aux incertitudes de modèle. Pour cela, le concept de commande sans modèle est utilisé. Ce concept est basé sur la détermination d'une loi de commande calculée à partir de modèles ultra-locaux ajoutée à la commande calculée par des régulateurs classiques. Une technique utilisant le régulateur linéaire quadratique ainsi que la technique non linéaire de backstepping avec intégrateur augmentées de ce concept de commande sans modèle ont été proposées. Ces deux approches ont été testées et validées en les appliquant en temps-réel au drone considéré. Une étude comparative des lois de commandes avec et sans l'utilisation du concept de commande sans modèle a été proposée mettant en évidence les avantages de l'utilisation de ce concept. Le diagnostic de défauts est une étape importante pour la commande tolérante aux fautes. Les techniques de diagnostic développées dans cette thèse sont basées sur la génération de résidus issus de la comparaison entre les mesures réelles et les estimations de ces mesures obtenues par des estimateurs. La génération de résidus dépend de la qualité du modèle utilisé ainsi que des perturbations qui peuvent conduire à des fausses alarmes ou des non détections. Une nouvelle technique "d’estimation intelligente" inspirée du concept de commande sans modèle a été proposée et implantée afin de rendre la génération de résidus insensible aux incertitudes de modèle et aux perturbations et ainsi améliorer la décision quant à la présence de défauts. Deux "estimateurs intelligents" ont été proposés en rajoutant à l'observateur d'état classique et l'observateur de Thau un concept inspiré de la technique de commande sans modèle. L'estimation des sorties du système obtenue par l'estimateur intelligent est utilisée afin d'estimer l'amplitude des défauts d'actionneurs et de capteurs. L'estimation des défauts d'actionneurs est basée sur des modèles ultra-locaux. Quant aux défauts de capteurs, un algorithme structure a été proposé pour estimer leur amplitude en utilisant les résidus générés à partir de cet estimateur. Les résultats de détection et estimation de défauts ainsi obtenus sont ensuite utilisés pour compenser l'effet des défauts sur les performances du drone. La commande tolérante aux fautes mise en œuvre permet de modifier la loi de commande par rapport à l'estimation de l'amplitude du défaut d'actionneur, alors que lorsqu'un défaut de capteur est détecté et estimé, la trajectoire de référence est régénérée afin de compenser l'effet du défaut et maintenir le drone sur la trajectoire initialement définie. Les algorithmes proposés ont été implantés et testés sur un quadrotor Qball-X4. Les résultats de vol en temps-réel ont été analysés et ont permis de valider les techniques de commande et de tolérance aux fautes de capteurs et d'actionneurs. Des vidéos illustrant différentes expérimentations sont disponibles en ligne / The main objectives of this thesis consist of developing Control, Fault Detection and Diagnosis (FDD) and Fault-Tolerant Control (FTC) techniques based on a the Model-Free (MF) concept recently introduced in the literature. The proposed approaches are implemented, tested and validated on a quadrotor platform. The first step of this work consisted of the modelling of the quadrotor, and then analyzing, designing and implementing new robust control strategies based on the Model-Free Control (MFC) technique recently developed in the literature. The MFC algorithm helps compensating for disturbances and model uncertainties. The advantage of this recent concept is in the simplicity of the design of the controller by adding a control law using ultra-local models to the classical control techniques. To test and validate this new approach, the Linear-Quadratic-Regulator (LQR) and the Nonlinear-Integral-Backstepping (NIB) controllers have been considered by integrating the MFC concept to design a (LQR-MFC) and a (NIB-MFC), respectively. Both algorithms are validated through analytical and experimental procedures and the robustness checked and compared with respect to the initial controllers in the presence of disturbances and model uncertainties.The FDD is a very important step towards the development of FTC techniques. The FDD approach developed in this thesis is based on the residual generation between the measured outputs and the estimated outputs obtained using observers/estimators. Residuals are expected to be close to zero in the fault free case and deviate from zero in the presence of a fault or failure. However, as the residuals are generated using models, they highly depend on the quality of the model used and on the presence of disturbances which may lead to false alarms or to non-detections. A novel “intelligent estimator” inspired from the MF concept has been developed and used in order to improve the residual generation and the fault diagnostic. Two intelligent estimators have been designed by integrating the MF scheme with the state and Thau observers for Multi-Input-Multi-Output (MIMO) systems, where the intelligent Output-Estimator (iOE) represents the integration between the MF technique with the state observer, and the intelligent Thau Output-Estimator (iTOE) represents the augmentation of the MF technique with the Thau Observer. The estimation of the system outputs obtained using the iOE are then used to estimate the actuator and sensor faults. The estimation of the actuator faults is improved by using the ultra-local models. A structured algorithm is then developed and implemented in order to estimate sensor fault magnitudes using the residuals generated by the intelligent estimator. The results obtained from the fault detection and estimation are then used to compensate for the fault effect on the flight control performance. The implemented fault-tolerant control technique compensates for the actuator faults by adjusting the control law based on the fault estimation. In case a sensor fault is detected and estimated, the desired path is regenerated according to the estimated fault magnitude in order to compensate for the fault effect.The proposed algorithms are implemented and tested on the Qball-X4 quadrotor. The results of the real-time flight tests validate the proposed techniques and compensate for sensor and actuator faults. Footages of the flight tests are available online.

The field of robotics and mechatronics is advancing at an ever-increasing rate and we are starting to see robots making the transition from the factories to the workplace and homes as cost is reduced and they become more useful. In recent years quadrotors have become a popular unmanned air vehicle (UAV) platform. These UAVs or micro air vehicles (MAV) are being used for many new and exciting applications such as aerial monitoring of wildlife, disaster sites, riots and protests. They are also being used in the film industry, as they are significantly cheaper means of getting aerial footage. While quadrotors are not extremely expensive a good system can cost in the range of $3000 - $8000 and thus too costly as a research platform for many. There are a number of cheaper open source platforms. The ArduCopter is under constant development, has the largest community and is inexpensive making it an ideal platform to work with. The goal of this thesis was to implement video processing on a ground control station allowing for the ArduCopter to track moving objects. This was achieved by using the OpenCV video-processing library to implement object tracking and the MAVLink communication protocol, available on the ArduCopter platform, for communication.

Recent development in the fields of MEMS sensors, miniature, energy efficient and very powerful microcontrollers and microprocessors has given the opportunity to build small autonomous flying vehicles. This thesis is studying one type of these vehicles, so called quadrotor. The quadrotor is flying vehicle similar to helicopter but having four rotors which are situated in one plane. Each propeller is actuated by an independently controlled motor. This feature allows to control Euler angles of the quadrotor such as yaw, pitch and roll thus giving the possibility to control quadrotor's position and velocity. The CTU Department of Cybernetics bought such a quadrotor prototype called Linkquad. The goal is to use this prototype for indoor flights using camera vision as a navigation reference. Unfortunately the prototype has no autonomous control loops implemented. The focal point of this thesis is design of a control law for the already mentioned prototype. This leads to other tasks such as an identification of the models 's parameters, creating mathematical nonlinear model, linearization of this model in certain trim points, design and testing of the linear controller and finally implementation and testing using the real system. / <p>Validerat; 20111004 (anonymous)</p>

This thesis describes a motion planning method that is designed to guide an autonomous quadrotor. The proposed method is based on a novel lossless convexication, which was first introduced in (12), that allows convex representations of many non-convex control constraints, such as that of the quadrotors. The second contribution of this thesis is to include two separate methods to generate path constraints that capture non-convex position constraints. Using the convexied optimal trajectory generation problem with physical and path constraints, an algorithm is developed that generates fuel optimal trajectories given the initial state and desired final state. As a proof of concept, a quadrotor testbed is developed that utilize a state-of-the-art motion tracking system. The quadrotor is commanded via a ground station where the convexified optimal trajectory generation algorithm is successfully implemented together with a trajectory tracking feedback controller. / text

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The vertical take-off and landing capabilities of quadrotors, and their maneuverability has contributed towards their recent popularity. They are widely used for indoors applications, where robust control strategies and automation of mission planning is necessary. In this thesis, a mathematical model for a quadrotor is derived using Newton's and Euler's laws. The model is linearized around hover and optimal control theory is used to derive a standard linear quadratic regulator controller for trajectory following. A feedorward of the tracking error is introduced to the standard LQR to improve its transient response. The performance of the proposed controller is compared with a conventional PID controller and the standard LQR controller for a variety of trajectories. The proposed controller produced a faster transient response with better disturbance rejection. A* algorithm is used to generate collisionree paths for the quadrotor where the proposed LQR is used to follow the trajectory.

This thesis describes work in a variety of topics related to aerial robotics, including system identification, state estimation, control, and path planning. The path planners described in this thesis are used to guide a fixed-wing UAV along paths that optimize the aircraft's ability to track a ground target. Existing path planners in the literature either ignore occlusions entirely, or they have limited capability to handle different types of paths. The planners described in this thesis are novel in that they specifically account for the effect of occlusions in urban environments, and they can produce a much richer set of paths than existing planners that account for occlusions. A 3D camera positioning system from Motion Analysis is also described in the context of state estimation, system identification, and control of small unmanned rotorcraft. Specifically, the camera positioning system is integrated inside a control architecture that allows a quadrotor helicopter to fly autonomously using truth data from the positioning system. This thesis describes the system architecture in addition to experiments in state estimation, control, and system identification. There are subtleties involved in using accelerometers for state estimation onboard flying rotorcraft that are often ignored even by researchers well-acquainted with the UAV field. In this thesis, accelerometer-rotorcraft behavior is described in detail. The consequences of ignoring accelerometer-rotorcraft behavior are evaluated, and an observer is presented that achieves better performance by specifically modeling actual accelerometer behavior. The observer is implemented in hardware and results are presented.

abstract: Unmanned aerial vehicles (UAVs) are widely used in many applications because of their small size, great mobility and hover performance. This has been a consequence of the fast development of electronics, cheap lightweight flight controllers for accurate positioning and cameras. This thesis describes modeling, control and design of an oblique-cross-quadcopter platform for indoor-environments. One contribution of the work was the design of a new printed-circuit-board (PCB) flight controller (called MARK3). Key features/capabilities are as follows: (1) a Teensy 3.2 microcontroller with 168MHz overclock –used for communications, full-state estimation and inner-outer loop hierarchical rate-angle-speed-position control, (2) an on-board MEMS inertial-measurement-unit (IMU) which includes an LSM303D (3DOF-accelerometer and magnetometer), an L3GD20 (3DOF-gyroscope) and a BMP180 (barometer) for attitude estimation (barometer/magnetometer not used), (3) 6 pulse-width-modulator (PWM) output pins supports up to 6 rotors (4) 8 PWM input pins support up to 8-channel 2.4 GHz transmitter/receiver for manual control, (5) 2 5V servo extension outputs for other requirements (e.g. gimbals), (6) 2 universal-asynchronous-receiver-transmitter (UART) serial ports - used by flight controller to process data from Xbee; can be used for accepting outer-loop position commands from NVIDIA TX2 (future work), (7) 1 I2C-serial-protocol two-wire port for additional modules (used to read data from IMU at 400 Hz), (8) a 20-pin port for Xbee telemetry module connection; permits Xbee transceiver on desktop PC to send position/attitude commands to Xbee transceiver on quadcopter. The quadcopter platform consists of the new MARK3 PCB Flight Controller, an ATG-250 carbon-fiber frame (250 mm), a DJI Snail propulsion-system (brushless-three-phase-motor, electronic-speed-controller (ESC) and propeller), an HTC VIVE Tracker and RadioLink R9DS 9-Channel 2.4GHz Receiver. This platform is completely compatible with the HTC VIVE Tracking System (HVTS) which has 7ms latency, submillimeter accuracy and a much lower price compared to other millimeter-level tracking systems. The thesis describes nonlinear and linear modeling of the quadcopter’s 6DOF rigid-body dynamics and brushless-motor-actuator dynamics. These are used for hierarchical-classical-control-law development near hover. The HVTS was used to demonstrate precision hover-control and path-following. Simulation and measured flight-data are shown to be similar. This work provides a foundation for future precision multi-quadcopter formation-flight-control. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018