La durée de vie utile résiduelle (RUL) peut être simplement définie comme une prédiction du temps restant pendant lequel un système est capable d'exécuter sa fonction prévue ; elle est mesurée à partir de l'instant présent jusqu'à la défaillance finale. Cette durée prévue dépend principalement de l'état de détérioration des composants du système et de leurs conditions de fonctionnement futures prévues. Ainsi, la prédiction de la RUL est un processus incertain et son contrôle n'est pas une tâche triviale. En général, le but de la prévision de la RUL est d'influencer la prise de décision pour le système. Dans cette thèse, on a présenté un cadre compréhensible pour le contrôle de la RUL. Les incertitudes du modèle ainsi que les perturbations du système ont été prises en compte dans le cadre proposé. Des questions telles que le traitement de l'incertitude et l'inclusion d'objectifs RUL dans la stratégie de contrôle sont étudiées, depuis la modélisation jusqu'à une architecture de contrôle globale finale. On a montré que l'on peut prédire la RUL à partir d'une estimation appropriée de la détérioration et d'hypothèses sur les conditions de fonctionnement futures. Les systèmes d'entraînement par friction sont utilisés pour illustrer l'utilité de l'architecture globale susmentionnée. Pour ce type de système, le frottement est à la fois source du mouvement et source de la détérioration. Ce double caractéristique de frottement est une motivation pour contrôler automatiquement la détérioration du système en maintenant un compromis entre les exigences de mouvement et les valeurs RUL souhaitées. Dans cette thèse, un nouveau modèle orienté contrôle pour les systèmes d'entraînement par friction, qui inclut un modèle dynamique de la détérioration, est proposé. Le degré de détérioration est considéré en fonction de l'énergie dissipée, à la surface de contact, pendant la transmission mécanique de puissance. Une approche est proposée pour estimer l'état actuel de la détérioration d'un système d'entraînement par friction. L'approche est basée sur un Filtre de Kalman Etendu (EKF en anglais) qui utilise un modèle augmenté incluant le système mécanique dynamique et la dynamique de détérioration. L'EKF fournit également des intervalles qui incluent sûrement la valeur de détérioration réelle avec une valeur de probabilité. Une nouvelle architecture de commande de la RUL est proposée, elle comprend : un système de surveillance de l'état de détérioration (par exemple l'EKF proposé), un estimateur de l'état de fonctionnement du système, un système de commande de la RUL et un principe actionneur de la RUL. L'estimateur des conditions de fonctionnement est basé sur l'hypothèse qu'il est possible de quantifier certaines caractéristiques des exigences de mouvement, par exemple le rapport cyclique des couples moteur. Le contrôleur RUL utilise une fonction de coût qui pondère les exigences de mouvement et les valeurs RUL souhaitées pour modifier un filtre à paramètres variables, utilisé ici comme principe actionneur RUL. Le principe actionneur RUL est basé sur une modification des couples exigés, provenant d'un éventuel système de contrôle de mouvement. Les résultats préliminaires montrent qu'il est possible de contrôler la RUL, selon le cadre théorique proposé. / Remaining Useful Lifetime (RUL) can be simply defined as a prediction of the remaining time that a system is able to perform its intended function, from the current time to the final failure. This predicted time mostly depends on the state of deterioration of the system components and their expected future operating conditions. Thus, the RUL prediction is an uncertain process and its control is not trivial task.In general, the purpose for predicting the RUL is to influence decision-making for the system. In this dissertation a comprehensive framework for controlling the RUL is presented. Model uncertainties as well as system disturbances have been considered into the proposed framework. Issues as uncertainty treatment and inclusion of RUL objectives in the control strategy are studied from the modeling until a final global control architecture. It is shown that the RUL can be predicted from a suitable estimation of the deterioration, and from hypothesis on the future operation conditions. Friction drive systems are used for illustrating the usefulness of the aforementioned global architecture. For this kind of system, the friction is the source of motion and at the same time the source of deterioration. This double characteristic of friction is a motivation for controlling automatically the deterioration of the system by keeping a trade-off, between motion requirements and desired RUL values. In this thesis, a new control-oriented model for friction drive systems, which includes a dynamical model of the deterioration is proposed. The amount of deterioration has been considered as a function of the dissipated energy, at the contact surface, during the mechanical power transmission. An approach to estimate the current deterioration condition of a friction drive system is proposed. The approach is based on an Extended Kalman Filter (EKF) which uses an augmented model including the mechanical dynamical system and the deterioration dynamics. At every time instant, the EKF also provides intervals which surely includes the actual deterioration value which a given probability. A new architecture for controlling the RUL is proposed, which includes: a deterioration condition monitoring system (for instance the proposed EKF), a system operation condition estimator, a RUL controller system, and a RUL actuation principle. The operation condition estimator is based on the assumption that it is possible quantify certain characteristics of the motion requirements, for instance the duty cycle of motor torques. The RUL controller uses a cost function that weights the motion requirements and the desired RUL values to modify a varying-parameter filter, used here as the RUL-actuating-principle. The RUL-actuating-principle is based on a modification of the demanded torques, coming from a possible motion controller system. Preliminary results show that it is possible to control de RUL according to the proposed theoretical framework.

A fabricação de moldes e matrizes são ricas em detalhes e geometrias complexas, exigindo tecnologias mais inovadoras e precisas. Um dos processos que se destaca na fabricação de moldes e matrizes, é o de eletroerosão por penetração (Electrical Discharge Machining - EDM). A usinagem por descargas elétricas é classificada como um processo de fabricação de geometria não definida, onde a remoção de material é realizada por repetidas descargas elétricas entre dois eletrodos eletricamente condutores. O desgaste da ferramenta é um dos principais parâmetros de medida no desempenho da usinagem por EDM. O maior problema ocasionado pelo desgaste de canto do eletrodo é a mudança de geometria da ferramenta no decorrer da usinagem, alterando a tolerância geométrica e o dimensional da cavidade. O presente trabalho propõe avaliação dimensional do desgaste de canto do eletrodo, no decorrer da usinagem do processo de EDM, variando o ângulo de superfície frontal do eletrodo. Outro propósito é a criação de um índice, chamado de taxa de arredondamento, que leva em consideração as áreas de desgaste de canto do eletrodo em função da área removida de material da peça. Os resultados mostraram que os eletrodos de cobre, cobre tungstênio e grafite, tem um grande crescimento de raio de canto no inicio da usinagem, estabilizando esses valores com tempo maiores de processo. O ângulo de superfície frontal do eletrodo influência diretamente no desgaste de canto do eletrodo. Os eletrodos de grafite não apresentaram comportamento de arredondamento de desgaste de canto durante os ensaios. Para o índice de taxa de arredondamento os eletrodos de cobre tungstênio tiveram o menor valor apresentado na usinagem do AISI H13. / The manufacture of molds and dies are rich in detail and complex geometries, requiring more innovative and precise technologes. One of the processes that stands out in the manufacture of molds and dies, is to EDM by penetration (Electrical Discharge Machining - EDM). The cutting by electrical discharge is classified as a non-defined geometry manufacturing process where material removal is carried out by repeated electrical discharge between two electrodes electrically conductive. The tool wear is a major measurement parameters in machining performance by EDM. The biggest problem caused by the electrode corner wear is the tool geometry change during the machining by changing the geometric tolerance and dimensional cavity. This paper proposes dimensional evaluation of the electrode corner wear, during the machining of the EDM process, varying the front surface of the electrode angle. Another purpose is to create an index, called rounding rate, which takes into account the areas of electrode corner wear due to the removed area of the workpiece material. The results showed that the copper electrode, copper tungsten and graphite, has a large corner radius growth at the beginning of machining, stabilizing these values with higher process time. The front surface of the electrode angle influence directly on the electrode corner wear. Graphite electrodes showed no corner wear rounding behavior during the tests. For rounding rate index tungsten copper electrodes had the lowest value presented in the machining of AISI H13.

A fabricação de moldes e matrizes são ricas em detalhes e geometrias complexas, exigindo tecnologias mais inovadoras e precisas. Um dos processos que se destaca na fabricação de moldes e matrizes, é o de eletroerosão por penetração (Electrical Discharge Machining - EDM). A usinagem por descargas elétricas é classificada como um processo de fabricação de geometria não definida, onde a remoção de material é realizada por repetidas descargas elétricas entre dois eletrodos eletricamente condutores. O desgaste da ferramenta é um dos principais parâmetros de medida no desempenho da usinagem por EDM. O maior problema ocasionado pelo desgaste de canto do eletrodo é a mudança de geometria da ferramenta no decorrer da usinagem, alterando a tolerância geométrica e o dimensional da cavidade. O presente trabalho propõe avaliação dimensional do desgaste de canto do eletrodo, no decorrer da usinagem do processo de EDM, variando o ângulo de superfície frontal do eletrodo. Outro propósito é a criação de um índice, chamado de taxa de arredondamento, que leva em consideração as áreas de desgaste de canto do eletrodo em função da área removida de material da peça. Os resultados mostraram que os eletrodos de cobre, cobre tungstênio e grafite, tem um grande crescimento de raio de canto no inicio da usinagem, estabilizando esses valores com tempo maiores de processo. O ângulo de superfície frontal do eletrodo influência diretamente no desgaste de canto do eletrodo. Os eletrodos de grafite não apresentaram comportamento de arredondamento de desgaste de canto durante os ensaios. Para o índice de taxa de arredondamento os eletrodos de cobre tungstênio tiveram o menor valor apresentado na usinagem do AISI H13. / The manufacture of molds and dies are rich in detail and complex geometries, requiring more innovative and precise technologes. One of the processes that stands out in the manufacture of molds and dies, is to EDM by penetration (Electrical Discharge Machining - EDM). The cutting by electrical discharge is classified as a non-defined geometry manufacturing process where material removal is carried out by repeated electrical discharge between two electrodes electrically conductive. The tool wear is a major measurement parameters in machining performance by EDM. The biggest problem caused by the electrode corner wear is the tool geometry change during the machining by changing the geometric tolerance and dimensional cavity. This paper proposes dimensional evaluation of the electrode corner wear, during the machining of the EDM process, varying the front surface of the electrode angle. Another purpose is to create an index, called rounding rate, which takes into account the areas of electrode corner wear due to the removed area of the workpiece material. The results showed that the copper electrode, copper tungsten and graphite, has a large corner radius growth at the beginning of machining, stabilizing these values with higher process time. The front surface of the electrode angle influence directly on the electrode corner wear. Graphite electrodes showed no corner wear rounding behavior during the tests. For rounding rate index tungsten copper electrodes had the lowest value presented in the machining of AISI H13.

Indiana University-Purdue University Indianapolis (IUPUI) / Yan, Jiaxiang. M.S.E.C.E., Purdue University, May 2013. Modeling, Monitoring and Optimization of Discrete Event Systems Using Petri Nets. Major Professor: Lingxi Li. In last decades, the research of discrete event systems (DESs) has attracts more and more attention because of the fast development of intelligent control strategies. Such control measures combine the conventional control strategies with discrete decision-making processes which simulate human decision-making processes. Due to the scale and complexity of common DESs, the dedicated models, monitoring methods and optimal control strategies for them are necessary. Among various DES models, Petri nets are famous for the advantage in dealing with asynchronous processes. They have been widely applied in intelligent transportation systems (ITS) and communication technology in recent years. With encoding of the Petri net state, we can also enable fault detection and identification capability in DESs and mitigate potential human errors. This thesis studies various problems in the context of DESs that can be modeled by Petri nets. In particular, we focus on systematic modeling, asynchronous monitoring and optimal control strategies design of Petri nets. This thesis starts by looking at the systematic modeling of ITS. A microscopic model of signalized intersection and its two-layer timed Petri net representation is proposed in this thesis, where the first layer is the representation of the intersection and the second layer is the representation of the traffic light system. Deterministic and stochastic transitions are both involved in such Petri net representation. The detailed operation process of such Petri net representation is stated. The improvement of such Petri net representation is also provided with comparison to previous models. Then we study the asynchronous monitoring of sensor networks. An event sequence reconstruction algorithm for a given sensor network based on asynchronous observations of its state changes is proposed in this thesis. We assume that the sensor network is modeled as a Petri net and the asynchronous observations are in the form of state (token) changes at different places in the Petri net. More specifically, the observed sequences of state changes are provided by local sensors and are asynchronous, i.e., they only contain partial information about the ordering of the state changes that occur. We propose an approach that is able to partition the given net into several subnets and reconstruct the event sequence for each subnet. Then we develop an algorithm that is able to reconstruct the event sequences for the entire net that are consistent with: 1) the asynchronous observations of state changes; 2) the event sequences of each subnet; and 3) the structure of the given Petri net. We discuss the algorithmic complexity. The final problem studied in this thesis is the optimal design method of Petri net controllers with fault-tolerant ability. In particular, we consider multiple faults detection and identification in Petri nets that have state machine structures (i.e., every transition in the net has only one input place and one output place). We develop the approximation algorithms to design the fault-tolerant Petri net controller which achieves the minimal number of connections with the original controller. A design example for an automated guided vehicle (AGV) system is also provided to illustrate our approaches.

Indiana University-Purdue University Indianapolis (IUPUI) / Lithium ion (Li-ion) batteries have become integral parts of our lives; they are widely used in applications like handheld consumer products, automotive systems, and power tools among others. To extract maximum output from a Li-ion battery under optimal conditions it is imperative to have access to the state of the battery under every operating condition. Faults occurring in the battery when left unchecked can lead to irreversible, and under extreme conditions, catastrophic damage. In this thesis, an adaptive fault diagnosis technique is developed for Li-ion batteries. For the purpose of fault diagnosis the battery is modeled by using lumped electrical elements under the equivalent circuit paradigm. The model takes into account much of the electro-chemical phenomenon while keeping the computational effort at the minimum. The diagnosis process consists of multiple models representing the various conditions of the battery. A bank of observers is used to estimate the output of each model; the estimated output is compared with the measurement for generating residual signals. These residuals are then used in the multiple model adaptive estimation (MMAE) technique for generating probabilities and for detecting the signature faults. The effectiveness of the fault detection and identification process is also dependent on the model uncertainties caused by the battery modeling process. The diagnosis performance is compared for both the linear and nonlinear battery models. The non-linear battery model better captures the actual system dynamics and results in considerable improvement and hence robust battery fault diagnosis in real time. Furthermore, it is shown that the non-linear battery model enables precise battery condition monitoring in different degrees of over-discharge.

Indiana University-Purdue University Indianapolis (IUPUI) / The substantial increase demand for electrical energy requires high efficient apparatus dealing with energy conversion. Several technologies have been suggested to implement power supplies with higher efficiency, such as multilevel and interleaved converters. This thesis proposes an energy conversion unit with an optimized number of output voltage levels per number of switches nL=nS. The proposed five-level four-switch per phase converter has nL=nS=5/4 which is by far the best relationship among the converters presented in technical literature. A comprehensive literature review on existing five-level converter topologies is done to compare the proposed topology with conventional multilevel converters. The most important characteristics of the proposed configuration are: (i) reduced number of semiconductor devices, while keeping a high number of levels at the output converter side, (ii) only one DC source without any need to balance capacitor voltages, (iii) high efficiency, (iv) there is no dead-time requirement for the converters operation, (v) leg isolation procedure with lower stress for the DC-link capacitor. Single-phase and three-phase version of the proposed converter is presented in this thesis. Details regarding the operation of the configuration and modulation strategy are presented, as well as the comparison between the proposed converter and the conventional ones. Simulated results are presented to validate the theoretical expectations. In addition a fault tolerant converter based on proposed topology for micro-grid systems is presented. A hybrid pulse-width-modulation for the pre-fault operation and transition from the pre-fault to post-fault operation will be discussed. Selected steady-state and transient results are demonstrated to validate the theoretical modeling.