Deregulation of electricity markets, increased usage of intermittent energy sources, and growing environmental concerns have created a volatile process manufacturing environment. Survival under this new paradigm requires chemical manufactures to shift from the traditional steady-state operation to a more dynamic and flexible operation mode. Under more frequent operating changes, the transition dynamics become increasingly relevant, rendering the traditional steady-state based scheduling decision-making suboptimal. This has motivated calls for the integration of scheduling and control. In an integrated scheduling and control framework, the scheduling decisions are based on a dynamic representation of the process. While various integration paradigms are proposed in the literature, our study concentrates on the closed-loop integration of scheduling and control. There are two main advantages to this approach: (i) seamless integration with the existing control system (i.e. it does not require a new control system infrastructure), (ii) the framework is aware of the control system dynamics, and hence has knowledge of the closed-loop process dynamics. The later aspect is particularly important as the control system plays a key role in determining the transition dynamics. The first part of our work is dedicated to developing an integrated scheduling and control framework that computes set-point trajectories, to be tracked by the lower-level linear model predictive control system, that are robust to demand uncertainty. We employ a piecewise linear representation of the nonlinear process model to obtain a mixed-integer linear programming (MILP) problem, thus alleviating the computational complexity compared to a mixed-integer nonlinear programming formulation. The value of the stochastic solution is used to confirm the superiority of the robust formulation against a nominal one that disregards uncertainty. In the second part of this study, we expand the framework to accommodate additional uncertainty types, including model and cost uncertainty. In the third part of this thesis, a deterministic integrated scheduling and control framework for processes controlled by distributed linear model predictive control is developed. The integrated problem is formulated as a MILP. To reduce the solution time, we introduce strategies to approximate the feedback control action. Through case studies, we demonstrate that knowledge of the control system enables the framework to effectively coordinate the MPC subsystems. The framework performs well even under conditions of plant-model mismatch conditions. In the final part of this study, we introduce an integrated scheduling and control formulation for processes controlled by nonlinear model predictive control (NMPC). Here, discrete scheduling decisions are represented using complementarity conditions. Additionally, we use the first-order Karush-Kuhn-Tucker conditions of the NMPC controller to compute the input values in the integrated problem. The resulting problem is a mathematical program with complementarity constraints that we solve using a regularization approach. For all case studies, the complementarity formulation effectively capture discrete scheduling decisions, and the KKT conditions always provides a local optimum of the associated NMPC problem. In summary, this study of the integration of scheduling and control addresses various control systems, uncertainty, and strategies for enhancing the solution time. Furthermore, we assess the performance of the proposed frameworks under conditions of plant-model mismatch, a common scenario in real-life applications. / Thesis / Doctor of Philosophy (PhD)

Identification of thermoacoustic dynamics that exhibit limit cycle behavior is needed to gain a better intuitive feel of the system, to design complex control strategies, and to validate modeling efforts. Limit cycle oscillations arise in thermoacoustic systems due to the coupling between a nonlinear heat release process and the acoustic dynamics of the combustor. This response arises in lean premixed gaseous power generating turbines and is a concern due to the detrimental effect of the pressure oscillations on the structural integrity of the combustor. Due to the volatile environment intrinsic in the combustor, multiple sensing apparatuses are not available. Therefore, in the current study, an identification approach is assessed considering only a single output from the thermoacoustic system. As a means to further investigate the thermoacoustic limit cycle behavior, a scaled version of the industry-based turbine was constructed. By anchoring a flame halfway from end-to-end of a closed-open tube, a similar nonlinear response is achieved. A harmonic balance technique that linearly incorporates the nonlinearity is developed which uses frequency entrainment to offer sufficient information for the identification. Its validity is assessed on a model, which is based on known dynamics of the thermoacoustic system. The structure of the identification algorithm is based on a two-mode acoustic model with both dynamics and nonlinearity in the feedback loop. The limitations of using only a two-mode identification structure for a system with more than two modes is discussed as well as future efforts that may alleviate this problem. / Master of Science

Dentre os fatores limitantes dos sistemas de controle, o tempo morto está entre os mais críticos e de difícil detecção sem testes intrusivos. O conhecimento do seu valor é essencial para a identificação de modelos e na auditoria de desempenho de sistemas de controle. Em virtude disto, o presente trabalho propõe uma metodologia eficaz para estimá-lo utilizando apenas dados históricos de processo em malha fechada. A principal vantagem frente a técnicas disponíveis na literatura é a não necessidade de testes intrusivos. A metodologia é baseada em um tratamento de sinal para remoção dos efeitos do distúrbio não medido e dos erros de modelo. O tratamento de sinal consiste na minimização das oscilações do sinal erro em malha aberta suavizado como função do tempo morto. Diversas formulações de função objetivo e procedimentos de suavização foram estudados visando facilitar a estimação do parâmetro. A qualidade da metodologia é ilustrada através de simulações em uma série de cenários, os quais simulam processos lineares de diferentes características sob o efeito de distúrbios distintos. A metodologia também é testada frente a estudo de casos com dados reais de processo industrial em malhas de nível e temperatura. Os resultados são comparados com métodos da literatura e demonstram que o método proposto foi eficaz na estimação do tempo morto para a maioria dos casos. / Among the limiting factors of control systems, the pure time delay is one of the most critical and difficult to estimate without an intrusive perturbation. The knowledge of its value is essential for model identification and control loop performance assessment. This work proposes a methodology to determine dead time using ordinary closed loop operating data. The main advantage over available techniques is the non-necessity of intrusive plant tests. The proposed approach is based on a signal processing for removing the effects of the unmeasured disturbances and the model-plant mismatches. The signal processing consists of the minimization of the oscillations of the smoothing open loop error as a function of the pure time delay. Several objective function formulations and smoothing procedures were studied in order to facilitate parameter estimation. The quality of the methodology is illustrated by simulations in a series of scenarios, which simulate linear processes of different characteristics under the effect of different disturbances. The methodology is also tested in case studies with real industrial process data. Results are compared to literature approaches and show the method was effective to estimate the pure time delay for most cases.

Rigid multibody systems have been studied extensivley due to its direct application in design and analysis of various mechanical systems such as robots and spacecraft structures. The dynamics of multibody system is governed by its equations of motion and various terms associated with it, such as the mass matrix, the generalized force vector, are well known..Forward dynamics algorithms play an important role in the simulation of multibody systems and the recursive forward dynamics algorithm for branched multibody systems is very popular. The recursive forward dynamic algorithm is highly efficient algorithm with O(n) computational complexity and scores over other algorithms when number of rigid bodies n in the system is very large. The algorithm involves finding an important mass matrix, which has been popularly termed as articulated body inertia (AB inertia). To find ijth term of any general mass matrix, we separately give virtual change to ith and jth generalized coordinates. At each point of the multibody system, the dot product of the resulting virtual displacements are taken with each other and eventually integrated over the entire multibody system, weighted by the mass. This quantity divided by the virtual changes in ith and jth coordinates gives the ijth element of the mass matrix. This is one of the fundamental ways of looking at the mass matrix. However, in literature, the AB inertia is obtained as a result of mathematical manipulation and its physical or geometrical significance from the above view point is not clear. In this thesis we present a more geometric and physical explanation for the AB inertia. The main step is to obtain a new set of generalized coordinates which relate directly to the AB inertia. We have also shown the equivalence of our method with existing methods. A comprehensive treatement on change of generalized coordinates and its effect on equations of motion has also been presented as preliminaries. The second part of the thesis deals with closed loop multibody systems.A few years ago an iterative algorithm called the sequential regularization method (SRM) was proposed for simulation of closed loop multibody systems with attractive claims on its efficiency. In literature we find that this algorithm has been implemented and studied only for planar multibody systems. As a part of the thesis work, we have developed a C-programming language code which can simulate 3-dimensional spatial multibody systems using the SRM algorithm. The programme can also perform simulation using a relatively efficient Conventional algorithm having O(n+m3) complexity, where m denotes number of closed loop constraints. Simulation studies have been carried out on a few multibody systems using the two algorithms. Some of the results have been also been validated using the commercial simulation package -ADAMS. As a result of our simulation studies, we have detected certain points, after which the solution from SRM loses it convergence. More study is required to understand this lack of convergence.

Dentre os fatores limitantes dos sistemas de controle, o tempo morto está entre os mais críticos e de difícil detecção sem testes intrusivos. O conhecimento do seu valor é essencial para a identificação de modelos e na auditoria de desempenho de sistemas de controle. Em virtude disto, o presente trabalho propõe uma metodologia eficaz para estimá-lo utilizando apenas dados históricos de processo em malha fechada. A principal vantagem frente a técnicas disponíveis na literatura é a não necessidade de testes intrusivos. A metodologia é baseada em um tratamento de sinal para remoção dos efeitos do distúrbio não medido e dos erros de modelo. O tratamento de sinal consiste na minimização das oscilações do sinal erro em malha aberta suavizado como função do tempo morto. Diversas formulações de função objetivo e procedimentos de suavização foram estudados visando facilitar a estimação do parâmetro. A qualidade da metodologia é ilustrada através de simulações em uma série de cenários, os quais simulam processos lineares de diferentes características sob o efeito de distúrbios distintos. A metodologia também é testada frente a estudo de casos com dados reais de processo industrial em malhas de nível e temperatura. Os resultados são comparados com métodos da literatura e demonstram que o método proposto foi eficaz na estimação do tempo morto para a maioria dos casos. / Among the limiting factors of control systems, the pure time delay is one of the most critical and difficult to estimate without an intrusive perturbation. The knowledge of its value is essential for model identification and control loop performance assessment. This work proposes a methodology to determine dead time using ordinary closed loop operating data. The main advantage over available techniques is the non-necessity of intrusive plant tests. The proposed approach is based on a signal processing for removing the effects of the unmeasured disturbances and the model-plant mismatches. The signal processing consists of the minimization of the oscillations of the smoothing open loop error as a function of the pure time delay. Several objective function formulations and smoothing procedures were studied in order to facilitate parameter estimation. The quality of the methodology is illustrated by simulations in a series of scenarios, which simulate linear processes of different characteristics under the effect of different disturbances. The methodology is also tested in case studies with real industrial process data. Results are compared to literature approaches and show the method was effective to estimate the pure time delay for most cases.

Dentre os fatores limitantes dos sistemas de controle, o tempo morto está entre os mais críticos e de difícil detecção sem testes intrusivos. O conhecimento do seu valor é essencial para a identificação de modelos e na auditoria de desempenho de sistemas de controle. Em virtude disto, o presente trabalho propõe uma metodologia eficaz para estimá-lo utilizando apenas dados históricos de processo em malha fechada. A principal vantagem frente a técnicas disponíveis na literatura é a não necessidade de testes intrusivos. A metodologia é baseada em um tratamento de sinal para remoção dos efeitos do distúrbio não medido e dos erros de modelo. O tratamento de sinal consiste na minimização das oscilações do sinal erro em malha aberta suavizado como função do tempo morto. Diversas formulações de função objetivo e procedimentos de suavização foram estudados visando facilitar a estimação do parâmetro. A qualidade da metodologia é ilustrada através de simulações em uma série de cenários, os quais simulam processos lineares de diferentes características sob o efeito de distúrbios distintos. A metodologia também é testada frente a estudo de casos com dados reais de processo industrial em malhas de nível e temperatura. Os resultados são comparados com métodos da literatura e demonstram que o método proposto foi eficaz na estimação do tempo morto para a maioria dos casos. / Among the limiting factors of control systems, the pure time delay is one of the most critical and difficult to estimate without an intrusive perturbation. The knowledge of its value is essential for model identification and control loop performance assessment. This work proposes a methodology to determine dead time using ordinary closed loop operating data. The main advantage over available techniques is the non-necessity of intrusive plant tests. The proposed approach is based on a signal processing for removing the effects of the unmeasured disturbances and the model-plant mismatches. The signal processing consists of the minimization of the oscillations of the smoothing open loop error as a function of the pure time delay. Several objective function formulations and smoothing procedures were studied in order to facilitate parameter estimation. The quality of the methodology is illustrated by simulations in a series of scenarios, which simulate linear processes of different characteristics under the effect of different disturbances. The methodology is also tested in case studies with real industrial process data. Results are compared to literature approaches and show the method was effective to estimate the pure time delay for most cases.

No description available.

Um aspecto importante relacionado à operação de sistemas de distribuição é o referente à segurança nas ações de restabelecimento pós-perturbações, em manobras emergenciais e programadas, onde necessite de transferência de cargas entre alimentadores aéreos primários de uma mesma subestação ou para uma subestação adjacente, de forma segura e confiável. Devem-se observar os requisitos de carregamento, tensão a nível sistêmico, proteção, entre outros. Atualmente as decisões e tomadas de ações referentes às manobras necessárias para os remanejamentos de cargas são de competência dos operadores que atuam nas salas de controle de operações e, em muitos casos, respaldadas somente na experiência de cada operador, acumulada ao longo do tempo. Este trabalho visa o estudo dos fenômenos físicos envolvidos em situações que coloquem alimentadores aéreos primários de distribuição em paralelo ou mesmo quando se forme uma configuração em anel fechado. Estas manobras podem ser executadas através de alimentadores e transformadores distintos, de mesma potência ou de potências diferentes, estabelecendo diretrizes e respaldando os operadores das salas de controle em situações de emergência, urgência ou programadas no sistema aéreo de distribuição. O objetivo principal é oferecer informações técnicas, possibilitando as tomadas de decisões mais adequadas na coordenação de manobras no sistema aéreo de distribuição, em tempo real. Cada uma delas tem condições que se pode considerar como a mais adequada para a execução dos procedimentos estabelecidos, porém sem os principais subsídios técnicos. Desta forma, algumas variáveis como tensão mínima, limites de carregamento de equipamentos, ângulo de fase dos transformadores, restrições operativas do sistema e de consumidores, devem ser aplicadas em tempo real para a tomada de decisão por parte dos operadores do sistema elétrico. / An important aspect related to the distribution systems operation concerns the safety required in the post-disturbances restorement actions or in the emergency and scheduled maneuvers, which involve the need for load transfer between primary overhead feeders of a same sub-station or for an adjacent sub-station, in a safe and reliable way, complying with the loading requirements, voltage at systemic level and protection, among others. Currently the decisions and taking actions related to the necessary maneuvers to carry out the load transfers are responsibility of the operators who work in the operations control rooms, and in many cases, only endorsed by each operator´s own experience, gathered along the time. This paper aims at the study of the involved physical phenomena in situations that place distribution primary overhead feeders in parallel or even when a configuration in closed ring is formed, via distinct transformers and feeders of same or different powers, establishing guidelines and endorsing the control rooms operators in emergency, urgency or scheduled situations in the distribution overhead system. The main objective is to provide technical information, enabling more adequate taking decisions in the distribution overhead system maneuvers coordination, in real time. Each of them has conditions that can be considered the most adequate to carry out the established procedures, however without the main technical information. Thus, some variables such as minimum voltage, equipment loading limits, transformers´ phase angle, the operational restrictions of the system and customers must be applied in real time for the taking decision by the electrical system operators.

Um aspecto importante relacionado à operação de sistemas de distribuição é o referente à segurança nas ações de restabelecimento pós-perturbações, em manobras emergenciais e programadas, onde necessite de transferência de cargas entre alimentadores aéreos primários de uma mesma subestação ou para uma subestação adjacente, de forma segura e confiável. Devem-se observar os requisitos de carregamento, tensão a nível sistêmico, proteção, entre outros. Atualmente as decisões e tomadas de ações referentes às manobras necessárias para os remanejamentos de cargas são de competência dos operadores que atuam nas salas de controle de operações e, em muitos casos, respaldadas somente na experiência de cada operador, acumulada ao longo do tempo. Este trabalho visa o estudo dos fenômenos físicos envolvidos em situações que coloquem alimentadores aéreos primários de distribuição em paralelo ou mesmo quando se forme uma configuração em anel fechado. Estas manobras podem ser executadas através de alimentadores e transformadores distintos, de mesma potência ou de potências diferentes, estabelecendo diretrizes e respaldando os operadores das salas de controle em situações de emergência, urgência ou programadas no sistema aéreo de distribuição. O objetivo principal é oferecer informações técnicas, possibilitando as tomadas de decisões mais adequadas na coordenação de manobras no sistema aéreo de distribuição, em tempo real. Cada uma delas tem condições que se pode considerar como a mais adequada para a execução dos procedimentos estabelecidos, porém sem os principais subsídios técnicos. Desta forma, algumas variáveis como tensão mínima, limites de carregamento de equipamentos, ângulo de fase dos transformadores, restrições operativas do sistema e de consumidores, devem ser aplicadas em tempo real para a tomada de decisão por parte dos operadores do sistema elétrico. / An important aspect related to the distribution systems operation concerns the safety required in the post-disturbances restorement actions or in the emergency and scheduled maneuvers, which involve the need for load transfer between primary overhead feeders of a same sub-station or for an adjacent sub-station, in a safe and reliable way, complying with the loading requirements, voltage at systemic level and protection, among others. Currently the decisions and taking actions related to the necessary maneuvers to carry out the load transfers are responsibility of the operators who work in the operations control rooms, and in many cases, only endorsed by each operator´s own experience, gathered along the time. This paper aims at the study of the involved physical phenomena in situations that place distribution primary overhead feeders in parallel or even when a configuration in closed ring is formed, via distinct transformers and feeders of same or different powers, establishing guidelines and endorsing the control rooms operators in emergency, urgency or scheduled situations in the distribution overhead system. The main objective is to provide technical information, enabling more adequate taking decisions in the distribution overhead system maneuvers coordination, in real time. Each of them has conditions that can be considered the most adequate to carry out the established procedures, however without the main technical information. Thus, some variables such as minimum voltage, equipment loading limits, transformers´ phase angle, the operational restrictions of the system and customers must be applied in real time for the taking decision by the electrical system operators.

Den ökade konsumtionen i dagens samhälle leder till en större efterfrågan på nya råvaror. Samtidigt är jordens resurser begränsade och råvarupriserna höjs i samband med att resurserna håller på att ta slut. Därför är det viktigt att ta till vara på de resurser som finns genom att öka nyttjandegraden av material och sluta produkters livscykler, då kan materialet återvinnas och återanvändas vid tillverkning av nya produkter. Om tillverkande företag väljer att använda återvunnet material i sin produktion sparas jordens resurser in eftersom inte en lika stor mängd jungfruligt material behövs. Det bidrar till en ekologisk vinst som i vissa fall också kan leda till en ekonomisk vinst. Syftet med arbetet var att undersöka om materialåtervinningen kan göras ekonomiskt lönsam för de företag som väljer att sluta produkters livscykler och samla in returmaterialet. Detta genomfördes genom att undersöka vilka faktorer som påverkar den ekonomiska lönsamheten i värdekedjan och hur insamlingssystemet bör utformas för att maximera mängden insamlat installationsspill. För att kunna genomföra arbetet har vetenskaplig litteratur i form av rapporter och artiklar studerats för de ämnesspecifika områdena som studien behandlar, dessa stod till grund för rapportens teoretiska del. Sedan genomfördes en empirisk datainsamling i form av kvalitativ numerisk data, intervjuer hölls med golvläggare och logistikansvarig för extern returmaterialshantering. Utöver detta genomfördes observationer av uppvisade beteenden relaterat till insamling av installationsspill ute på byggarbetsplatser. En kvantitativ fältstudie genomfördes också som inkluderade respektive installationsprojekt. Resultatet av studien visar att generellt sätt är golvläggare positiva till att samla in returmaterial utan att företaget får betalt genom ekonomiska styrmedel så länge insamlingen inte medför något extra arbete. De resterande aktörerna i den omvända flödeskedjan har ett större ekonomiskt incitament än ett ekologiskt incitament till att medverka för att samla in returmaterial. Det försvårar för producenten att skapa en ekonomiskt lönsam returmaterialshantering då det skapas höga kostnader som produktens vinstmarginal ska klara av att täcka. Transport är den faktor som ackumulerar störst kostnad per insamlad enhet. För att sänka kostnaderna är det nödvändigt att returmaterial i höga kvantiteter och med hög kvalitet samlas in. Om ett företag lyckas skapa en lönsam returmaterialshantering kan det leda till minskade kostnader i form av material- och produktionskostnader. Resultatets betydelse från studien är viktig då det saknas studier som direkt behandlar och visar hur returmaterialshantering kan genomföras och göras ekonomiskt lönsam. Därmed bidrar studien till vidare diskussion och inspiration. Studien avgränsas till att analysera den ekonomiska lönsamheten av den externa returmaterialshanteringen. / The increased consumption in the modern society leads to a higher demand for new raw materials. At the same time, the earth's resources are limited and the prices increase when the resources decrease. Therefore, it is important to take advantage of the resources by increasing the utilization rate of material and close product lifecycles. The material can be recycled and reused in the manufacture of new products. If manufacturing companies choose to use recycled materials in their production the earth’s resources would be saved because less virgin material is needed. This contributes to an ecological profit which in some cases may also lead to a financial gain. The purpose of this work was to investigate whether recycling of materials could be economically profitable for the companies that choose to close product lifecycles and collect the end-of-use material. This was done by examining the factors that affect the economic viability of the value chain and how the collection system should be designed to maximize the amount of collected installation waste. In order to implement the work, scientific literature in the form of reports and articles are studied in the subject-specific areas that the study covers, these were the basis for the report's theoretical part. An empirical data collection was also done in the form of qualitative numerical data, interviews were held with flooring contractors and the logistics manager for external recycled material, and observations were conducted of exhibited behaviors related to the collection of installation waste out on construction sites. A quantitative field study was also conducted which included each installation project. The results of the study show that the flooring contractors are generally positive to collecting recycling material without any financial benefits as long as it does not involve any additional work. The remaining companies in the reverse supply chain have a higher financial incentive than an ecological incentive to participate and collect recycling material. This makes it difficult for the producer to create an economically viable collection system of recycling materials since it creates too high costs for the product's profit margin to be able to cover these costs. Transport is the factor that accumulates the highest cost per collected unit. To reduce the costs it is necessary to return material in high quantities and with high quality. If a company manages to create a profitable return of used materials it can lead to reduced costs in terms of material and production costs. The impact of the result is important because there are no or just a few previous studies that directly treat and show how a system of collecting recycling material can be implemented in a company and be economically viable. The study contributes to further discussions and inspiration. The study is limited to analyzing the economic viability of the external collection system of recycling material.