Pour les systèmes de commande sous la forme de dx/dt = f (x, u), dans la littérature, les chercheurs s'intéressaient à la stabilisation de ce système de différentes manières : asymptotique, uniformément asymptotique, partielle, en temps fini, etc. Pour aboutir à ces résultats, les méthodes utilisées font appel aux techniques suivantes : Lyapunov, Lasalle, Barbalat, surface glissante, etc. Dans cette thèse, nous nous sommes intéressés à une autre fonctionnalité de la commande, dite commande répulsive stabilisante. Les résultats ont été généralisés au cas d'un système avec dérive et sans dérive. Comme résultat, l'approche de commande qu'on propose assure la stabilité du système autour d'une position désirée et la répulsion de celui-ci par rapport à un ensemble indésirable, construit dans l'espace de navigation. Toute forme d'application sera concernée par nos résultats théoriques, on peut citer, la navigation terrestre et aérienne dans un environnement peu ou pas connu. De même, la commande qu'on propose préserve la communication inter-agent, une fois planifiées. En terme d'application, on a considéré le modèle d'un véhicule à roues type unicycle, sans tenir compte de l'orientation (cas non holonôme) et dans le cas où l'environnement contient un ou plusieurs obstacle(s). Contrairement aux résultats de la littérature, qui sont basés sur une commande à structure variable pour l'évitement d'un obstacle, la commande répulsive-stabilisante trouvée est une commande continue sur l'espace de navigation. La deuxième partie de cette thèse traite le problème de stabilité d'une formation d'agents (système multi-véhicules) qui évolue dans un environnement hostile tout en préservant la communication entre les agents. Pour réussir la formation, la décentralisation de la commande par rapport aux agents est rendue robuste à travers des graphes de communication. Ces graphes relèvent de la stratégie et objectifs de la formation. Nos résultats de stabilité ont fait l'objet d'une implémentation rigoureuse sur un simulateur réalisé sous Matlab. / For control systems in the form dx/dt = f (x, u), in the literature, researchers were interested in stabilizing the system in different ways : asymptotic, uniformly asymptotic, partial, in #nite time, etc. To achieve these results, the methods involve the following techniques : Lyapunov, LaSalle, Barbalat, sliding surface, etc. In this thesis, we became interested in another feature form of the controller, called repulsive stabilizing controller. The results were generalized to the case of a system with drift and without drift. As a result, the proposed control approach ensures the system stability around a desired position and the repulsion of the latter over a set junk, built in the navigation space. Any form of application will be concerned by our theoretical results including, terrestrial and aerial navigations in a little known or not known environment. Similarly, the proposed control law, once planned, preserves the inter-agent communication. In terms of application, we considered the model of a unicycle-type wheeled vehicle, regardless of orientation (non-holonomic case) and where the environment contains one or more obstacle(s). Contrary to the results of the literature, which are based on a switching control structure for avoidance of an obstacle, the stabilizing repulsive found is a smooth and continuous controller on the navigation space. The second part of this thesis addresses the stability problem of a formation of agents (multi-vehicle) operating in a hostile environment while maintaining the communication between agents. To successfully the strategy of the formation, the decentralized controller over agents is made robust through communication graphs. These graphs are performed according to the formation strategy and objectives. Our stability results have been implemented in a simulator made in Matlab.

Controlling a formation of unmanned autonomous vehicles is a daunting prospect even when the formation operates under ideal conditions. When communication between vehicles is limited, maintaining a formation becomes difficult. In some cases the formation may become unstable. While a control law may stabilize a formation of vehicles with good communication, it may not be able to do so with poor communication. The resulting lack of formation stability affects the level of ï¬ delity the formation has to the original control law. Formation ï¬ delity is the degree to which the vehicles in a formation follow the trajectories prescribed by a control law. Many formation control laws assume certain conditions. Perfect formation ï¬ delity is not guaranteed when the vehicles in a formation are no longer operated under those conditions. We seek to mitigate the detrimental effects of poor communication and other real-world phenomena on formation ï¬ delity. Through simulation we test the effectiveness of a new way to implement an existing formation control law. Real-world conditions such as rigid-body motion, swarm dynamics, poor communication, and other phenomena are assessed and discussed. It is concluded through testing in simulation that it is possible to control a formation of boats by directing each boat with a unique set of waypoints in simulation. While these waypoints do not lead to perfect formation behavior, testing shows that implementing this control law using these waypoints allows the formation to be more robust to reduced communication. / Master of Science

The development, implementation, and testing of a leader-follower based robust nonlinear formation controller is discussed in this thesis. This controller uses sliding mode control on the length and angle between the leader and follower vessels to produce the desired formation. A boat model, assuming planar motion (three degrees of freedom), is used as the bases for the controller. Open loop testing is performed to determine parameter values to match the simulation model to the physical one and, upon tuning of the controller to match, closed loop testing of the controller with a virtual leader is also performed. From these tests it is found that the controller is unstable, thus improvements to the controller, through changes made to the model and to the parameter identification process, are undertaken. Simulations comparing the initial and updated models of the vehicle to open loop data show an improvement in the new model.

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Due to the limitations of GPS in areas where line of sight to the sky is obstructed the development of a GPS-free algorithm for relative formation control is an asset to collaborative vehicles. This paper presents a novel approach based on the Received Signal Strength Indication (RSSI) measurement between broadcast and receive nodes to calculate distance and using the data transfer capability to allow each vehicle to develop a table of relative positions. These relative positions are used to create a potential field that results in an absolute minimum at the vehicles desired position. All vehicles are numbered sequentially. The numbering defines the order in which they will broadcast their data, as well as their position along the perimeter. This thesis looks at two control methods for achieving a formation. The first is the circular motion method that puts perimeter nodes in an orbit around around the perimeter center. The second is a gradient descent method that calculates the gradient of the potential field. Both methods achieve a formation when all perimeter nodes are at their absolute minimums in the potential field. Tests were conducted to analyze RSSI measurements using the 802.15.4 protocol, and a mathematical simulation was conducted for each control algorithm. / Master of Science

We present real-time autonomous implementations of a practical distributed formation control scheme for a multi-quadrotor system for two different cases: parameters of linearized dynamics are exactly known, and uncertain system parameters. For first case, we design a hierarchical, decentralized controller based on the leader-follower formation approach to control a multi-quadrotor swarm in rigid formation motion. The proposed control approach has a two-level structure: high-level and low-level. At the high level, a distributed control scheme is designed with respect to the relative and global position information of the quadrotor vehicles. In the low-level, we analyze each single quadrotor control design in three parts. The first is a linear quadratic controller for the pitch and roll dynamics of quadrotors. The second is proportional controller for the yaw motion. The third is proportional-integral-derivative controller in altitude model. For the second case, where inertial uncertainties in the pitch and roll dynamics of quadrotors are considered, we design an on-line parameter estimation with the least squares approach, keeping the yaw, altitude and the high-level controllers the same as the first case. An adaptive linear quadratic controller is then designed to be used with lookup table based on the estimation of uncertain parameters. Additionally, we study on enhancement of self and inter-agent relative localization of the quadrotor agents using a single-view distance-estimation based localization methodology as a practical and inexpensive tool to be used in indoor environments for future works. Throughout the formation control implementations, the controllers successfully satisfy the objective of formation maintenance for non-adaptive and adaptive cases. Simulations and experimental results are presented considering various scenarios, and positive results obtained for the effectiveness of our algorithm.

This work presents a new approach to human-swarm interactions, a discipline which addresses the problem of how a human operator can influence the behavior of large groups of robots, providing high-level information understandable by the team. While there exist potential advantages of introducing a human in the control loop of a robot swarm, how the human must be incorporated is not a simple problem. For the intervention of a human operator to be favorable to the performance of the team, the means and form of the information between the human and the robot swarm must be adequately defined: we need to design which device will be provided to the operator to interact with the swarm and how the information will be shaped so that both the human and the robot team understand it. Coordination of multi-robot systems involves the generation of involved motion patterns for the individual agents that result in an overall organized movement. We introduce in this thesis a new human-swarm interaction modality based on music theory, a discipline studied for centuries and capable of creating complex sound structures. In particular, we have focused on understanding how we can apply rules and structures from music theory to an operator's input so that each command both specifies the goal location to be visited and the geometry to be adopted by the swarm. We interpret the sequence of locations to be visited by the swarm as a musical melody, identifying each note with a certain location in the robots' workspace. Once the objective path is defined in the form of a melody, we can apply rules from harmony, a discipline of music theory, to create chords that harmonize the input melody. The interest in using these chords lies fundamentally in that they are structured combinations of pitches, heard simultaneously. These inherent structures will be used to determine the geometry that should be displayed by the team. The developed multi-robot control is applied to a team of differential drive mobile robots through an electronic piano.

Navigation and guidance of mobile robots towards steady or maneuvering objects (targets) is one of the most important areas of robotics that has attracted a lot of attention in recent decades. However, in most of the existing methods, both the line-of-sight angle (bearing) and the relative distance (range) are assumed to be available for navigation and guidance algorithms. There is also a relatively large body of research on navigation and guidance with bearings-only measurements. In contrast, only a few results on navigation and guidance towards an unknown target using range-only measurements have been published. Various problems of navigation, guidance, location estimation and target tracking based on range-only measurements often arise in new wireless networks related applications. Recent advances in these applications allow us to use inexpensive transponders and receivers for range-only measurements which provide information in dynamic and noisy environments without the necessity of line-of-sight. To take advantage of these sensors, algorithms must be developed for range-only navigation. The main part of this thesis is concerned with the problem of real-time navigation and guidance of Wheeled Mobile Robots (WMRs) towards an unknown stationary or moving target using range-only measurements. The range can be estimated using the signal strength and the robust extended Kalman filtering. Several similar algorithms for navigation and guidance termed Equiangular Navigation and Guidance (ENG) laws are proposed and mathematically rigorous proofs of convergence and stability of the proposed guidance laws are given. The experimental investigation into the use of range data for a WMR navigation is documented and the results and discussions on the performance of the proposed guidance strategies are presented, where a wheeled robot successfully approach a stationary or follow a maneuvering target. In order to safely navigate and reliably operate in populated environments, ENG is then modified into Augmented-ENG (AENG), which enables the robot to approach a stationary target or follow an unpredictable maneuvering object in an unknown environment, while keeping a safe distance from the target, and simultaneously preserving a safety margin from the obstacles. Furthermore, we propose and experimentally investigate a new biologically inspired method for local obstacle avoidance and give the mathematically rigorous proof of the idea. In order for the robot to avoid collision and bypass the enroute obstacles in this method, the angle between the instantaneous moving direction of the robot and a reference point on the surface of the obstacle is kept constant. The proposed idea is combined with the ENG law, which leads to a reliable and fast long-range navigation. The performance of both navigation strategy and local obstacle avoidance techniques are confirmed with computer simulations and several experiments with ActivMedia Pioneer 3-DX wheeled robots. The second part of the thesis investigates some challenging problems in the area of wheeled robot navigation. We first address the problem of bearing-only guidance of an autonomous vehicle following a moving target with smaller minimum turning radius compared to that of the follower and propose a simple and constructive navigation law. In compliance with the increasing research on decentralized control laws for groups of mobile autonomous robots, we consider the problems of decentralized navigation of network of WMRs with limited communication and decentralized stabilization of formation of WMRs. New control laws are presented and simulation results are provided to illustrate the control laws and their applications.

Navigation and guidance of mobile robots towards steady or maneuvering objects (targets) is one of the most important areas of robotics that has attracted a lot of attention in recent decades. However, in most of the existing methods, both the line-of-sight angle (bearing) and the relative distance (range) are assumed to be available for navigation and guidance algorithms. There is also a relatively large body of research on navigation and guidance with bearings-only measurements. In contrast, only a few results on navigation and guidance towards an unknown target using range-only measurements have been published. Various problems of navigation, guidance, location estimation and target tracking based on range-only measurements often arise in new wireless networks related applications. Recent advances in these applications allow us to use inexpensive transponders and receivers for range-only measurements which provide information in dynamic and noisy environments without the necessity of line-of-sight. To take advantage of these sensors, algorithms must be developed for range-only navigation. The main part of this thesis is concerned with the problem of real-time navigation and guidance of Wheeled Mobile Robots (WMRs) towards an unknown stationary or moving target using range-only measurements. The range can be estimated using the signal strength and the robust extended Kalman filtering. Several similar algorithms for navigation and guidance termed Equiangular Navigation and Guidance (ENG) laws are proposed and mathematically rigorous proofs of convergence and stability of the proposed guidance laws are given. The experimental investigation into the use of range data for a WMR navigation is documented and the results and discussions on the performance of the proposed guidance strategies are presented, where a wheeled robot successfully approach a stationary or follow a maneuvering target. In order to safely navigate and reliably operate in populated environments, ENG is then modified into Augmented-ENG (AENG), which enables the robot to approach a stationary target or follow an unpredictable maneuvering object in an unknown environment, while keeping a safe distance from the target, and simultaneously preserving a safety margin from the obstacles. Furthermore, we propose and experimentally investigate a new biologically inspired method for local obstacle avoidance and give the mathematically rigorous proof of the idea. In order for the robot to avoid collision and bypass the enroute obstacles in this method, the angle between the instantaneous moving direction of the robot and a reference point on the surface of the obstacle is kept constant. The proposed idea is combined with the ENG law, which leads to a reliable and fast long-range navigation. The performance of both navigation strategy and local obstacle avoidance techniques are confirmed with computer simulations and several experiments with ActivMedia Pioneer 3-DX wheeled robots. The second part of the thesis investigates some challenging problems in the area of wheeled robot navigation. We first address the problem of bearing-only guidance of an autonomous vehicle following a moving target with smaller minimum turning radius compared to that of the follower and propose a simple and constructive navigation law. In compliance with the increasing research on decentralized control laws for groups of mobile autonomous robots, we consider the problems of decentralized navigation of network of WMRs with limited communication and decentralized stabilization of formation of WMRs. New control laws are presented and simulation results are provided to illustrate the control laws and their applications.