It is well known that the optimal nonblocking supervisory control problem of timed discrete event systems is NP-hard, subject in particular to state space explosion that is exponential in the number of system components. In this thesis, we propose to manage complexity by organizing the system as a Timed State Tree Structure (TSTS). TSTS are an adaptation of STS to timed Supervisory Control Theory (SCT). Based on TSTS we present an e±cient recursive symbolic algorithm that can perform nonblocking supervisory control design for systems of state size 10^12 and higher. Failure diagnosis is the process of detecting and identifying deviations of a system from its normal behavior using the information available through sensors. A method for fault diagnosis of the TSTS model is proposed. A state based diagnoser is constructed for each timed holon of TSTS. Fault diagnosis is accomplished using the state estimates provided by the timed holon diagnosers. The diagnosers may communicate among each other in order to update their state estimates. At any given time, only a subset of the diagnosers are operational, and as a result, instead of the entire model of the system, only the models of the timed holons associated with the operational diagnosers are used. It is shown that the computational complexity of constructing and storing the transition systems required for diagnosis in the proposed approach is polynomial in the number of system components, whereas in the original monolithic approach the computational complexity is exponential.

It is well known that the optimal nonblocking supervisory control problem of timed discrete event systems is NP-hard, subject in particular to state space explosion that is exponential in the number of system components. In this thesis, we propose to manage complexity by organizing the system as a Timed State Tree Structure (TSTS). TSTS are an adaptation of STS to timed Supervisory Control Theory (SCT). Based on TSTS we present an e±cient recursive symbolic algorithm that can perform nonblocking supervisory control design for systems of state size 10^12 and higher. Failure diagnosis is the process of detecting and identifying deviations of a system from its normal behavior using the information available through sensors. A method for fault diagnosis of the TSTS model is proposed. A state based diagnoser is constructed for each timed holon of TSTS. Fault diagnosis is accomplished using the state estimates provided by the timed holon diagnosers. The diagnosers may communicate among each other in order to update their state estimates. At any given time, only a subset of the diagnosers are operational, and as a result, instead of the entire model of the system, only the models of the timed holons associated with the operational diagnosers are used. It is shown that the computational complexity of constructing and storing the transition systems required for diagnosis in the proposed approach is polynomial in the number of system components, whereas in the original monolithic approach the computational complexity is exponential.

Modern industrial control systems use a multitude of spatially distributed sensors and actuators to continuously monitor and control physical processes. Information exchange among control system components is traditionally done through physical wires. The need to physically wire sensors and actuators limits flexibility, scalability and reliability, since the cabling cost is high, cable connectors are prone to wear and tear, and connector failures can be hard to isolate. By replacing some of the cables with wireless communication networks, costs and risks of connector failures can be decreased, resulting in a more cost-efficient and reliable system. Integrating wireless communication into industrial control systems is challenging, since wireless communication channels introduce imperfections such as stochastic delays and information losses. These imperfections deteriorate the closed-loop control performance, and may even cause instability. In this thesis, we aim at developing design frameworks that take these imperfections into account and improve the performance of closed-loop control systems. The thesis first considers the joint design of packet forwarding policies and controllers for wireless control loops where sensor measurements are sent to the controller over an unreliable and energy-constrained multi-hop wireless network. For a fixed sampling rate of the sensor, the co-design problem separates into two well-defined and independent subproblems: transmission scheduling for maximizing the deadline-constrained reliability and optimal control under packet losses. We develop optimal and implementable solutions for these subproblems and show that the optimally co-designed system can be obtained efficiently. The thesis continues by examining event-triggered control systems that can help to reduce the energy consumption of the network by transmitting data less frequently. To this end, we consider a stochastic system where the communication between the controller and the actuator is triggered by a threshold-based rule. The communication is performed across an unreliable link that stochastically erases transmitted packets. As a partial protection against dropped packets, the controller sends a sequence of control commands to the actuator in each packet. These commands are stored in a buffer and applied sequentially until the next control packet arrives. We derive analytical expressions that quantify the trade-off between the communication cost and the control performance for this class of event-triggered control systems. The thesis finally proposes a supervisory control structure for wireless control systems with time-varying delays. The supervisor has access to a crude indicator of the overall network state, and we assume that individual upper and lower bounds on network time-delays can be associated to each value of the indicator. Based on this information, the supervisor triggers the most appropriate controller from a multi-controller unit. The performance of such a supervisory controller allows for improving the performance over a single robust controller. As the granularity of the network state measurements increases, the performance of the supervisory controller improves at the expense of increased computational complexity. / <p>QC 20150504</p>

What does it mean to do the disco? Or perform a cheerleading routine? Or move in a style appropriate for a given mode of human interaction? Answering these questions requires an interpretation of what differentiates two distinct movement styles and a method for parsing this difference into quantitative parameters. Furthermore, such an understanding of principles of style has applications in control, robotics, and dance theory. This thesis present a definition for “style of motion” that is rooted in dance theory, a framework for stylistic motion generation that separates basic movement ordering from its precise trajectory, and an inverse optimal control method for extracting these stylistic parameters from real data. On the part of generation, the processes of sequencing and scaling are modulated by the stylistic parameters enumerated: an automation that lists basic primary movements, sets which determine the final structure of the state machine that encodes allowable sequences, and weights in an optimal control problem that generates motions of the desired quality. This generation framework is demonstrated on a humanoid robotic platform for two distinct case studies – disco dancing and cheerleading. In order to extract the parameters that comprise the stylistic definition put forth, two inverse optimal control problems are posed and solved -- one to classify individual movements and one to segment longer movement sequences into smaller motion primitives. The motion of a real human leg (recorded via motion capture) is classified in an example. Thus, the contents of the thesis comprise a tool to produce and understand stylistic motion.

The purpose of this thesis is to explore the theoretical and practical issues associated with the design, execution and analysis of an empirical evaluation of novel process control displays in a collaborative control room environment. An important feature of the thesis is how practical constraints associated with limited access to industry controllers were handled and how convergent lines of evidence were used to achieve the evaluation. As a novel research domain, hydropower systems (HPS) present many design challenges, because controllers must coordinate multiple domains across different time frames. If controllers are to maintain effective situation awareness and if they are to exercise effective control, the displays must integrate controllers’ problem solving across water, generation, market, and transmission concerns and across time frames. However, these needs are ignored in the current displays in a hydropower control room. The two new ecologically-inspired displays, called “Functional Displays”, evaluated in this thesis, are intended to overcome the above shortcomings. The evaluation was done with industry hydropower controllers and coordinators on a medium fidelity simulator which represented the working environment of a large hydropower control room. The core issue of this thesis is how the evaluation was conceptualized, operationalized and analysed given practical constraints arising from limited access to industry controllers, limited capacity of the simulator, and the complexity of the hydropower domain. Of key concern was the design of test scenarios, selection of measures of performance, and data analysis in the face of these constraints. The rationale of the scenario design was to combine representative contingencies within and outside the hydropower scheme, emergent storage problems and different market contexts so that controllers or coordinators would be required to act in different domains. Only by placing controllers in such challenging and time pressured situations could we maximize our chances of seeing the expected benefits of the new display, given the limited length of the experiment. Multiple measures were proposed to capture the quality of in-the-loop coupling between human controllers and the system under various disturbances. The measures of performance include: (1) control quality, which investigates how the new displays tame “temporal complexity” by helping the control team construct a more effective pattern of activities to handle contingencies; and (2) control strategy, which exposes how the new display support the coordination between storage, generation and market to meet the strategic or tangible objectives. The measures of cognition and affect include: (1) situation awareness (SA), which represents controllers’ or coordinators’ degree of cognitive coupling with different time frames and different levels of the hydropower scheme and (2) controllers’ or coordinators’ trust in the supporting displays, and their self-confidence in their own ability to control the hydropower scheme. Through the effort of triangulating the different measures, balancing the elements in designing scenarios, and extracting and integrating raw data from the study, convergent lines of evidence were achieved for evaluation. It was found that the new Functional Displays led the participant teams to a better pattern of work which was reflected in their situation awareness, their discretionary control activity, and the outcome of their control with respect to system productivity and stability. However, limitations of these findings because of the constraints of the experiment are discussed. This research contributes to many theoretical and practical issues in Human-System Interface (HSI). For example, it outlines how some of the principles of ecological interface design (EID) can be used and it highlights the value of using time as a basis for distinguishing interfaces. Moreover, this research provides fruitful insights into the selection and development of measures to assess human control in real world complex work environments. Because a key issue of this thesis is how practical constraints were handled; pragmatic approaches for measuring SA and control were developed. Because industry often performs evaluations under similar intensive constraints, the approaches and solutions developed in this thesis for evaluating novel interfaces could be easily adapted to various industrial settings.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: As control problems become more and more complex, techniques are required that surpass the capabilities of simple controllers that are linearized about certain parametric set points. Controllers that can operate over a large range of model parameter variations and even controllers that are largely model-independent are becoming more valuable and necessary. In this control application, voltage regulation is done on a direct AC-AC medium voltage regulator, making use of a type of regulated autotransformer configuration. The fifth order system is shown to be prone to oscillations on the input bus. This, together with the control requirement of robustness to load variations, provides a challenging control problem that is rarely addressed in literature. This thesis solves the control problem by means of applying sliding mode control on voltage regulator module level, and supervisory control on system level. / AFRIKAANSE OPSOMMING: Soos die soeke na oplossings vir hedendaagse beheer probleme al hoe meer uitdagend raak, word die behoefte vir model onafhanklike en robuuste beheerders dienooreenkomstig groter. Eenvoudige beheerders wat gelineariseer is om ’n parametriese werkpunt raak ondoeltreffend vir vandag se vereistes vir doeltreffende beheer ongeag van parametriese veranderinge. In hierdie tesis word spanning regulasie toegepas deur ’n direkte WS-na-WS medium spanning reguleerder in te span. Hierdie toestel maak gebruik van ’n tipe van outotransformator opstelling waar die sekondêre wikkelings gereguleer word deur die skakelaksie van die drywingselektroniese regulasie modules. Die vyfde-orde stelsel se intree bus is geneigd om onstabiel te raak, en moet dus aktief gedemp word terwyl die uitreespanning reguleer word. Die vereiste dat die beheer boonop robuus ten opsigte van las veranderings moet wees maak hierdie probleem ’n monster van ’n uitdaging wat skaars in die literatuur aangeraak is. Hierdie tesis los die probleem van robuuste beheer op deur glymodus beheer toe te pas op reguleerder module vlak, en ook deur toesighoudende beheer op stelsel vlak toe te pas.

Social reasoning and norms of a group of individuals that share a set of cultural traits are largely fashioned by those traits. We explored a few predominant sociological, cultural traits and developed a methodology for parametrically adjusting them. This exploratory study shows promise toward a capability to deliberately tune cultural group traits in order to produce desired group behavior. In order to validate our methodology, we implemented a prototypical agent based simulated intelligence, surveillance, and reconnaissance scenario. In this simulation, a group of simulated agents traverse a hostile territory while a user adjusts cultural group trait values. The group and individual utilities are dynamically observed against values of selected cultural traits. Uncertainty avoidance index and individualism are the cultural traits we explored in depth. Upon user's training of the correspondence between cultural values and system utilities, the user is able to deliberately produce desired system utilities by issuing changes to trait values. Appropriateness of specific cultural values is not universal but determined by the domain and scenarios. This work heralds a path for control of large systems via parametric cultural adjustments.

A crescente competitividade entre as indústrias de manufatura faz com que as empresas se preocupem cada vez mais com questões relacionadas à qualidade, produtividade e redução de custo. A concorrência internacional, bastante incisiva nos setores industriais de transformação de matérias-primas é, de fato, uma questão preocupante. Para tornarem-se competitivas, as empresas precisam extrair mais produtos com uma mesma quantidade de insumos e produzir mais, em menores frações de tempo, tornando as restrições de tempo e recursos cada vez mais severas. Melhores desempenhos e processos mais eficientes podem ser obtidos por meio da automação industrial. Porém, tais projetos são normalmente desenvolvidos sem a utilização de abordagens formais e os resultados obtidos dependem, quase que exclusivamente, da experiência dos projetistas. Não é possível afirmar que um conjunto de máquinas esteja operando sem qualquer situação de bloqueio, ou ainda, que esteja produzindo da maneira mais eficiente possível, tendo-se como critério o tempo de execução das operações. Por intermédio de abordagens formais, como a Teoria de Controle Supervisório (TCS), é possível a síntese automática de supervisores, que permitem a operação de uma planta, os quais, além de atender aos requisitos de segurança, evitam que o sistema atinja uma situação de bloqueio. Este trabalho apresenta algumas extensões dessa teoria, de modo que o supervisor ótimo satisfaça também às especificações de sequenciamento de operações e de prazo de finalização de tarefas, com a abordagem de autômatos temporizados. O problema de escalonamento de tarefas, diretamente relacionado ao planejamento de produção nas indústrias, é um problema de otimização, de tal maneira que a sequência de execução das etapas seja organizada para que o tempo total de processamento seja minimizado. Nessa pesquisa, uma proposta de um método para a obtenção de escalonamento de operações, com a utilização de autômatos temporizados e conceitos da teoria de controle supervisório, é apresentada. Propõe-se um algoritmo para a obtenção de uma sequência ótima de operações, tendo-se como critério o tempo total para a finalização do processo. O método é aplicado em uma célula automatizada em uma indústria fabricante de elevadores, onde foi possível determinar o tempo mínimo de processamento de um determinado item. Por meio da pesquisa de métodos e algoritmos para a obtenção de escalonamento de tarefas em ambientes fabris, procura-se atender às necessidades estratégicas das indústrias, na busca por sistemas de manufatura cada vez mais eficientes e competitivos. / The growing competition among manufacturing industries causes companies to worry more and more with issues related to quality, productivity and cost reduction. International competition, quite incisive among raw material processing manufacturers, is actually a very concerning situation. To become more competitive, enterprises have to produce more with the same amount of raw materials, or in a shorter time, making the constraints of time and resources increasingly severe. A better performance and more efficient processes can be obtained by means of industrial automation. However, such projects are normally designed without any formal approach and the achieved results depend, more than anything else, on engineers’ expertise. It cannot be stated that a machine set is working without any deadlock situation, or is producing in the most efficient way possible, considering operations´ execution time as efficiency criteria. By means of formal approaches such as Supervisory Control Theory (SCT), it is possible to synthesize supervisors automatically, that allow a plant to operate, in a way that, not only safety requirements are fulfilled, but the system is also prevented to reach a deadlock situation. This work presents this theory and its extensions, so the optimal supervisor satisfies task scheduling requirements and job completion deadlines, by using timed automata frameworks. The job shop scheduling problem, which directly relates to manufacturers´ production planning, is an optimization problem, where all the processing steps are organized in way that the total processing time is minimized. A methodology is presented for the job shop scheduling, by means of timed automata and supervisory control theory. An algorithm for acquiring an optimal operation sequence is proposed, considering the total time needed to finalize a process as the optimization criteria. The method is applied in an automated cell in a elevator manufacturing industry, where it was possible to obtain the minimal time needed to process a certain part. Through algorithms and methods for job shop scheduling in industrial environments, it is intended to meet the manufacturers´ strategic needs, in their search for manufacturing systems that are increasingly more efficient and competitive.

A crescente competitividade entre as indústrias de manufatura faz com que as empresas se preocupem cada vez mais com questões relacionadas à qualidade, produtividade e redução de custo. A concorrência internacional, bastante incisiva nos setores industriais de transformação de matérias-primas é, de fato, uma questão preocupante. Para tornarem-se competitivas, as empresas precisam extrair mais produtos com uma mesma quantidade de insumos e produzir mais, em menores frações de tempo, tornando as restrições de tempo e recursos cada vez mais severas. Melhores desempenhos e processos mais eficientes podem ser obtidos por meio da automação industrial. Porém, tais projetos são normalmente desenvolvidos sem a utilização de abordagens formais e os resultados obtidos dependem, quase que exclusivamente, da experiência dos projetistas. Não é possível afirmar que um conjunto de máquinas esteja operando sem qualquer situação de bloqueio, ou ainda, que esteja produzindo da maneira mais eficiente possível, tendo-se como critério o tempo de execução das operações. Por intermédio de abordagens formais, como a Teoria de Controle Supervisório (TCS), é possível a síntese automática de supervisores, que permitem a operação de uma planta, os quais, além de atender aos requisitos de segurança, evitam que o sistema atinja uma situação de bloqueio. Este trabalho apresenta algumas extensões dessa teoria, de modo que o supervisor ótimo satisfaça também às especificações de sequenciamento de operações e de prazo de finalização de tarefas, com a abordagem de autômatos temporizados. O problema de escalonamento de tarefas, diretamente relacionado ao planejamento de produção nas indústrias, é um problema de otimização, de tal maneira que a sequência de execução das etapas seja organizada para que o tempo total de processamento seja minimizado. Nessa pesquisa, uma proposta de um método para a obtenção de escalonamento de operações, com a utilização de autômatos temporizados e conceitos da teoria de controle supervisório, é apresentada. Propõe-se um algoritmo para a obtenção de uma sequência ótima de operações, tendo-se como critério o tempo total para a finalização do processo. O método é aplicado em uma célula automatizada em uma indústria fabricante de elevadores, onde foi possível determinar o tempo mínimo de processamento de um determinado item. Por meio da pesquisa de métodos e algoritmos para a obtenção de escalonamento de tarefas em ambientes fabris, procura-se atender às necessidades estratégicas das indústrias, na busca por sistemas de manufatura cada vez mais eficientes e competitivos. / The growing competition among manufacturing industries causes companies to worry more and more with issues related to quality, productivity and cost reduction. International competition, quite incisive among raw material processing manufacturers, is actually a very concerning situation. To become more competitive, enterprises have to produce more with the same amount of raw materials, or in a shorter time, making the constraints of time and resources increasingly severe. A better performance and more efficient processes can be obtained by means of industrial automation. However, such projects are normally designed without any formal approach and the achieved results depend, more than anything else, on engineers’ expertise. It cannot be stated that a machine set is working without any deadlock situation, or is producing in the most efficient way possible, considering operations´ execution time as efficiency criteria. By means of formal approaches such as Supervisory Control Theory (SCT), it is possible to synthesize supervisors automatically, that allow a plant to operate, in a way that, not only safety requirements are fulfilled, but the system is also prevented to reach a deadlock situation. This work presents this theory and its extensions, so the optimal supervisor satisfies task scheduling requirements and job completion deadlines, by using timed automata frameworks. The job shop scheduling problem, which directly relates to manufacturers´ production planning, is an optimization problem, where all the processing steps are organized in way that the total processing time is minimized. A methodology is presented for the job shop scheduling, by means of timed automata and supervisory control theory. An algorithm for acquiring an optimal operation sequence is proposed, considering the total time needed to finalize a process as the optimization criteria. The method is applied in an automated cell in a elevator manufacturing industry, where it was possible to obtain the minimal time needed to process a certain part. Through algorithms and methods for job shop scheduling in industrial environments, it is intended to meet the manufacturers´ strategic needs, in their search for manufacturing systems that are increasingly more efficient and competitive.

Neste trabalho à apresentada uma proposta de conversÃo de modelos de cÃlulas de manufatura (FMS) em Redes de Petri Coloridas (RPC) para Ladder Logic Diagram (LLD). Explora-se modelos de RPC controlados - construidos usando-se como metodologia de controle supervisÃrio as RestriÃÃes de Controle sobre Cores Decompostas (RCCD) - e modelos nÃo controlados. Enfatiza-se a transformaÃÃo de RPC nÃo controlada para LLD e a facilidade de inclusÃo do controle. Os resultados aqui descritos demonstram que a metodologia facilita o trabalho de um programador de CLP em LLD minimizando os possÃveis erros durante a fase de programaÃÃo. Para exemplificar a metodologia foi desenvolvido um conversor de RPC para LLD, produzido em ambiente JAVA, afim de evidenciar a dinÃmica de conversÃo. Para a validaÃÃo dos resultados do conversor à usado um robà articulado vertical controlado via CLP, que opera comparativamente com e sem supervisÃo, o qual fora modelado primeiramente em RPC sem supervisÃo, depois aplicada a tÃcnica RCCD, a supervisÃo e a conversÃo para LLD. / In this dissertation, is presented a proposal of conversion of models of manufacturing cell (FMS) from Colored Petri Nets (CPN) to Ladder Logic Diagram (LLD). It explores the controlled CPN models - constructed using the methodology of supervisory Control Restrictions on Decomposed Colors (CRDC) - and not controlled models. It emphasizes the transformation of CPN not controlled for the LLD and ease for inclusion of control. The results described herein demonstrate that the methodology facilitates the work of a PLC programmer in LLD minimizing possible errors during the programming phase. To illustrate the methodology we developed a converter from CPN to LLD, produced in JAVA, in order to clarify the dynamic conversion environment. To validate the results of the converter, is controlled by PLC, a vertical articulated robot which works compared with and without supervision which had been firstly modeled in CPN without supervision, then applied to CRDC, the supervision and the conversion technique for LLD.