Control of large groups of robotic agents is driven by applications including military, aeronautics and astronautics, transportation network, and environmental monitoring. Cooperative control of networked multi-agent systems aims at driving the behavior of the group via feedback control inputs that encode the groups’ dynamics based on information sharing, with inter-agent communications that can be time varying and be spatially non-uniform. Notably, local interaction rules can induce coordinated behaviour, provided suitable network topologies. Distributed learning paradigms are often necessary for this class of systems to be able to operate autonomously and robustly, without the need of external units providing centralized information. Compared with model-based protocols that can be computationally prohibitive due to their mathematical complexity and requirements in terms of feedback information, we present an online model-free algorithm for some nonlinear tracking problems with unknown system dynamics. This method prescribes the actuation forces of agents to follow the time-varying trajectory of a moving target. The tracking problem is addressed by an online value iteration process which requires measurements collected along the trajectories. A set of simulations are conducted to illustrate that the presented algorithm is well functioning in various reference-tracking scenarios.

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Este trabalho apresenta o desenvolvimento de uma técnica de controle cooperativo aplicado para embarcações dotadas de sistema de posicionamento dinâmico (sistema DP). Um caso ilustrativo é estudado: o lançamento de um equipamento submarino utilizando duas embarcações DP. Neste exemplo, o sistema cooperativo controla a distância relativa das duas embarcações DP. As vantagens deste método se da no aumento da janela operacional, na tensão no cabo de lançamento que pode ser reduzida pela metade, entre outras. Um mapeamento dinâmico foi obtido utilizando um simulador 2D simplificado previamente validado por comparação com testes experimentais e o simulador no domínio do tempo TPN Tanque de Provas Numérico. Nestes mapas, duas regiões foram definidas, de ocorrência e não ocorrência de afrouxamento nos cabos em função da distancia entre as embarcações, profundidade do equipamento submarino e período da onda. Este mapa definiu as posições desejadas das embarcações para cada profundidade do equipamento. Foi proposto um controle da posição relativa das embarcações tentando manter os movimentos do ponto de conexão em oposição de fase. Isto evita a ocorrência de afrouxamentos no cabo de lançamento. Para isso, um algoritmo baseado em estimação de fase (Transformada de Hilbert) associado a um controlador PD foi implementado. Os resultados mostraram que o controle para ondas regulares é efetivo. Adicionalmente, o controle de pagamento de linha recebe as medidas do movimento vertical do ponto de conexão, e compensa esse movimento, mantendo constante seu comprimento. O controle foi implementado considerando erros de 10% e atrasos de até 1,5s nas medidas. Os resultados confirmaram que o controle pode eliminar os picos de tensão e a ocorrência de afrouxamento no cabo de lançamento. A conclusão deste trabalho sugere que a estratégia apropriada do controle, considerando ondas regulares, é combinar o controle de posição e o controle de pagamento de linha. O controle de posição, acoplado ao mapeamento dinâmico, define um caminho ótimo a ser seguido durante o içamento do equipamento, tentando manter as embarcações próximas da região de não ocorrência de afrouxamentos. / This work presents the development of cooperative control technique applied to vessels equipped with dynamic positioning (DP) system. An illustrative case study is suggested: the launching of subsea equipment using two DP vessels. In this example, the cooperative system controls the relative distance between the DP vessels. One of the advantages of this method is the increase of operations safety and operational window, since, among other factors, the tension in the launching cable is reduced by half. Initially, it was proposed the control of vessels relative positions, trying to keep the connection point movements in counter-phase. This avoids the slackening of the launching cable. For this, an algorithm based on phase estimator (Hilbert transform) associated with a PD control was implemented. The results showed that for regular waves this strategy was effective. A dynamic mapping was then obtained using simplified 2D simulator, previously validated by comparison with experimental tests. In these maps, two regions are defined - occurrence or non-occurrence of cable slackening - as a function of the distance of the vessels and the depth of the subsea equipment. This map defines the proper set-point for the DP systems for each depth of the subsea equipment. This map is used to define the best relative position for the vessels. In addition, the hoisting control receives the measurements of the vertical motion of the connection point, and compensates its motion, trying to maintain a constant lowering velocity. This control was implemented considering errors of 10% and delay of 0.5s in the measurements. The results confirmed that the control is able to eliminate the tension peaks and the occurrence of slackening in the launching cable. The conclusion is that the appropriate control strategy, considering regular waves, is to combine the control of both position of the vessels and hoisting of the cable. Therefore the position control, coupled with dynamic mapping, defines the \"optimal path\" to be followed during the line hoisting, trying to keep the vessels as close as possible to the \"no slackening\" region.

Intra-operative imaging is sometimes available to assist in needle biopsy, but typical open- loop insertion does not account for unmodeled needle deflection or target shift. Robotic closed-loop compensation for deviation from an initial straight-line trajectory can reduce the targeting error, using image-guidance for rotational control of an asymmetric bevel tip. By pairing closed-loop trajectory compensation with a hands-on cooperatively controlled needle insertion, a physician's control of the procedure can be maintained while incorporating benefits of robotic accuracy. Additionally, if puncture of a membrane can be detected, an enhanced haptic response can assist the physician in perceived anatomical localization of the needle tip. Functionality was implemented on a needle placement robot suitable for use in the MR environment and capable of holding a typical clinically used biopsy gun. The robot is configured for cooperatively controlled needle insertion with continuous closed-loop image- guided needle rotation. The robot and custom controller were tested for their effect on the Signal-to-Noise ratio (SNR) of MR images, and the results showed an approximate drop of only 12% in signal when the robot was present, and no additional signal drop when the robot was powered on or moving. The hardware and software subsystems were developed for clinical translation, and after each was validated in the lab they were integrated into the clinical environment to mimic the workflow of MRI-guided targeted biopsy. The full system was evaluated in-bore at Brigham and Women’s Hospital in Boston, MA where experiments for real-time puncture detection and MR image-guided targeted needle insertions under cooperative control were performed. Results showed overall targeting accuracy was 3.42mm RMS, improving accuracy by approximately 50% as compared to clinical trials of prostate biopsy using manual needle insertion. A cooperatively controlled robotic biopsy is more likely to gain acceptance by physicians over teleoperation due to maintaining proximity to the surgical site, but regulatory hurdles regarding robotic needle insertion still exist. The current robotic system framework is suitable for clinical use as it was fully validated in-bore, but some modifications could be made to increase the likelihood of regulatory approval. With these modifications the system could be ready for cadaver and pre- clinical animal trials within one year, and ready for in-human clinical trials in the next two to three years.

This dissertation focuses on how to design and employ networked unmanned vehicles for remote sensing and distributed control purposes in the current information-rich world. The target scenarios are environmental or agricultural applications such as river/reservoir surveillance, wind profiling measurement, and monitoring/control of chemical leaks, etc. AggieAir, a small and low-cost unmanned aircraft system, is designed based on the remote sensing requirements from environmental monitoring missions. The state estimation problem and the advanced lateral flight controller design problem are further attacked focusing on the small unmanned aerial vehicle (UAV) platform. Then the UAV-based remote sensing problem is focused with further flight test results. Given the measurements from unmanned vehicles, the actuation algorithms are needed for missions like the diffusion control. A consensus-based central Voronoi tessellation (CVT) algorithm is proposed for better control of the diffusion process. Finally, the dissertation conclusion and some new research suggestions are presented.

La congestion du trafic dans nos villes est un problème qui entrave la qualité de vie. L'intersection est un endroit où les congestions se produisent le plus fréquemment. Par conséquent, au lieu d'étendre les infrastructures, il serait plus intéressant économiquement de s’ocupper de la résolution du problème des retards en développant les stratégies de contrôle de la circulation.Les travaux de cette thèse concerne l’étude des intersections dites « intelligentes » dépourvues de feux de signalisation, et où la coopération est réalisée à partir de la communication véhicule-infrastructure (V2I). L’objectif étant de proposer une modélisation coopérative de ces intersections visant à réduire à la fois les temps de retards et la consommation de carburant.La méthode de résolution du problème comporte deux volets principaux. Le premier volet concerne l'itinéraire devant être choisi par les véhicules pour arriver à leur destination à partir d’un point de départ. Le deuxième volet étant les procédures coopératives proposées afin de permettre aux véhicules de passer rapidement et économiquement à travers chaque intersection. D'une part, selon les informations envoyées en temps réel par les véhicules via la communication V2I à l’intérieur d’une zone de communication, chaque intersection exécute un algorithme soit de « Programmation Dynamique » soit de « Colonie d'Abeilles Artificielles » suivant la taille du trafic et ceci afin de donner aux véhicules l’ordre de passage minimisant le temps de retard dans les intersections. D'autre part, et après avoir reçu l’ordre de passage, chaque véhicule doit calculer son profil optimal de vitesse lui assurant une consommation minimale de carburant.Une série de simulations a ainsi été exécutée sous différents volumes de trafic afin de montrer la robustesse et la performance des méthodes proposées. Les résultats ont aussi été comparés avec d'autres méthodes de contrôle de la littérature et leur efficacité a ainsi été validée. / The traffic congestion is one of the most serious problems limiting the improvement of standing of life. The intersection is a place where the jams occur the most frequently. Therefore, it is more effective and economical to relieve the problem of the heavy traffic delays by ameliorating the traffic control strategies, instead of extending the infrastructures.The proposed method is a cooperative modeling to solve the problem of reducing traffic delays and decreasing fuel consumption simultaneously in a network of intersections without traffic lights, where the cooperation is executed based on the connection of Vehicle-to-Infrastructure (V2I). The resolution contains two main steps. The first step concerns the itinerary. An itinerary presents a list of intersections chosen by vehicles to arrive at their destinations from their origins. The second step is related to the following proposed cooperative procedures to make vehicles to pass through each intersection rapidly and economically: on the one hand, according to the real-time information sent by vehicles in the edge of the communication zone via V2I, each intersection applies Dynamic Programming (DP) or Artificial Bee Colony (ABC) to cooperatively optimize the vehicle passing sequence in intersection with the minimal time delay under the relevant safety constraints; on the other hand, after receiving this sequence, each vehicle finds the optimal speed profiles with the minimal fuel consumption by an exhaustive search.A series of simulation are executed under different traffic volumes to present the performance of proposed method. The results are compared with other control methods and research papers to prove the our new traffic control strategy.

<p>This thesis contains new results on the problem of coordinating a group of vehicles. The main motivation driving this work is the development of control laws that steer individual members of a formation, such that desired group behavior emerges. Special attention is paid to analysis of coordination issues, in particular formation control of marine craft where robustness to unknown environmental forces is important. Coordinated control applications for marine craft include: underway replenishment, maintaining a formation for increased safety during travel and instrument resolution, and cooperative transportation. A review of formation control structures is given, together with a discussion of special issues that arise in coordination of independent vehicles.</p><p>The main contributions of this thesis may be grouped into two categories:</p><p>• Path-following designs for controlling a group of vehicles</p><p>• Multi-body motivated formation modeling and control</p><p>A previously developed path following design is used to control a group of vehicles by synchronizing the individual path parameters. The path following design is advantageous since the path parameter, i.e., that parameter which determines position along a path, is scalar; hence coordination is achieved with a little amount of real-time communication. The path following design is also extended to the output-feedback case for systems where only parts of the state vector are known. The path following scheme is exploited further in a passivity-based design for coordination where the structural properties render an extended selection of functions for synchronization available. Performance and robustness properties in different operational conditions can be enhanced with a careful selection of these functions. Two designs are presented; a cascaded interconnection where a consensus system provides synchronized path parameters as input to the individual path following systems renders time-varying formations possible and increases robustness to communication problems; a feedback interconnection which is more robust to vehicle failures. Both designs are extended to sampled-data designs where plant and controller dynamics are updated in continuous-time and path parameters are exchanged over a communication network where transmission occurs at discrete intervals. Bias estimation is included to provide integral action against slowlyvarying environmental forces and model uncertainties.</p><p>A scheme for formation modeling and control, inspired by analytical mechanics of multi-body systems and Lagrangian multipliers, is proposed. In this approach to formation control, various formation behaviors are determined by imposing constraint functions on group members. Several examples illustrate these formation behaviors. The stabilization scheme presented is made more robust with respect to unknown time-varying disturbances. In addition, the scheme is extended towards adaptive estimation of unknown plant and parameters. Furthermore, it can be applied with no major modifications to the case of position control for a single vehicle.</p><p>The formation control scheme is such that it may be used in combination with a set of position control laws for a single vessel, thus enabling the designer to choose from a large class of control laws available in the literature. The input-to-state stability (ISS) framework is utilised to investigate robustness to environmental and communication disturbances. A loop-transform, together with the ISS framework, yields an upper bound on the inter-vessel time delay below which formation stability is maintained.</p>