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No description available.

This thesis addresses the scheduling and control of shop-floor production units that operate in a highly autonomous and distributed environment. The distinct feature of this environment is the heterarchical nature of the control where the scheduling function is quite independently carried out by the units. The units solve only part of the overall problem while resolving conflicts to maintain consistent global schedules. The need for communication and coordination, in such circumstances, introduces many complexities that affects the quality of the schedules produced. These include lapses of open-loop control due to uncertainty of up-to-date status information, asynchronous behaviour, and uncontrollable propagation of conflicts. / A behaviour-based approach is introduced to solve these problems. Using this approach, the organisation of the shop-floor is viewed as similar to a colony of ants or an eco-system. The units operate quite independently but continue to adapt their schedules to changes in their environment. While they may not directly negotiate to resolve conflicts, their cooperation is innate or in-built through their local adaptive actions. This individual cooperative action of the units brings about a collective behaviour that produces the desired emergent global schedules. The major focus of this research is in examining the link between the individual and collective behaviours and developing a model that realises the desired scheduling functionality at the shop level. / In order to achieve high scheduling performance (both locally and globally) a model of a unit incorporating dynamic problem decomposition, allocation algorithms and adaptation mechanisms is developed. For the latter, a reinforcement learning model is used to adapt the scheduling horizon. In fact, an important contribution if this research is the novel view we take of the problem and the manner of adaptation. In addition, a communication model for simulating the scheduling behaviours is designed using concepts of Holonic and other emerging concepts of manufacturing systems. / The model is tested for a number of scheduling problems representing a variety of production situations. Preliminary results indicate an impressive scheduling performance comparable to well-known heuristics. Further examination indicates the types of dynamic behaviour that can be expected of such a model, including the levels of unresolved conflicts, the adaptability in the face of uncertainty, consequence of alternative communication policies and the sensitivities to adaptation. / This thesis has also a strong qualitative theme in reviewing and consolidating the concepts underlying the design and operational attributes of autonomous distributed organisations of the shop-floor.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Intelligent Tutoring Systems; Machine Learning; Behavior; Learning. Includes bibliographical references. (p.49)

Vita. / Digitized by Kansas State University Libraries

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 85-87). Also available in electronic format on the Internet.

Thesis (M. App. Sc.)--Carleton University, 2005. / Includes bibliographical references (p. 63-64). Also available in electronic format on the Internet.

The behavior of large and tightly interconnected power systems resembles, in certain circumstances, the behavior of a continuously distributed system. This resemblance motivated the derivation of continuum models, which were used to explain and predict disturbance propagation, un-damped power oscillations, and the stability of power systems. In this dissertation, we propose a one-dimensional continuum representation suitable for meshed power systems. Previous continuous representations of meshed power systems used two-dimensional spatial domains. Thus our approach has the potential to provide better resolution for comparable computational burden. It is important to note that, the computational burden required to obtain solutions for PDEs involved in the continuum representation varies notably with the solver implementation. The contributions of this dissertation are: a) Reviewing a previous continuum model and providing a detailed derivation for the one-dimensional version of it. b) Providing and describing in detail a parameter distribution technique adequate for the continuum approach. c) Identifying and documenting limitations on the continuum model voltage calculation. e) Providing a procedure to simulate the behavior of meshed power systems using the one dimensional continuum model. And f) Identifying and applying a numerical PDE solver for the continuum approach. / Ph. D.

A modeling approach suitable for simulating solid-state-controlled machine systems, including component failures within either the electronics or machine(s), is presented in detail. The capability of modeling unbalanced-machine operation is included in the modeling approach. The approach is directly amenable to computer implementation. Computer implementation of the modeling approach was performed and the simulated results were compared with actual oscillograms, obtained from the performance tests of an Electric Vehicle Propulsion Unit, in order to verify the proposed modeling approach. Excellent correlation between the simulated waveforms and the oscillograms existed in all the simulated cases. The modeling approach was used also to simulate the electrical behavior of a brushless-excitation system used for large turbine generators. The simulations consisted of normal steady-state operation as well as a scenario of fault conditions occurring within the rotating rectifier assembly of the brushless exciter. The simulated results are displayed and a discussion of intrinsic features of these results needed to identify the specific fault is presented. Fault detection schemes are warranted for such expensive systems. Actual voltage and/or current waveforms could be telemetered to an controller for fault detection and classification. The elements of this modeling approach which allow inexpensive computer simulation of such systems, that can contain nonlinearities and/or spontaneous faults in any of its components, are listed as follows: 1. The capability of automatically generating the systems' governing state equations, from a minimal set of topological data and component values, at any point within the simulation run; 2. Inclusion of unbalanced machine operation is a result of having no topological restrictions placed upon the mutual coupling. 3. Using piece-wise linear I-V characteristics of the solid-state switching components decreases the computation time needed for a given simulation run since iteration for the status of the equivalent resistance values for each switch is only required at their threshold (I-V) points. 4. Employment of an implicit (predictor-corrector) integration algorithm designed specifically for solving stiff differential equations, typically associated with solid-state controlled machine systems, allows realistic modeling of the solid-state switches' equivalent resistance values. Also, implicit algorithms (like the one employed in this work) result in a drastic reduction of computer execution time and an increase in accuracy, when compared to explicit algorithms, systems. for simulating these types of stiff systems. / Ph. D.

Simulation is one of the oldest and also among the most important tools available to engineers. In the building Heating, Ventilating and Air-Conditioning (HVAC) community the availability and/or functionality of simulation tools is limited and it is difficult to determine whether the simulation models accurately represent reality. The purpose of this study was to accurately verify one such a simulation model and then to extend the study to two unique applications. Comprehensive structural, comfort and energy audits were performed to construct a suitable simulation model with the aid of the control simulation package: QUICK Control. The model was then verified against measured building data to ensure an accurate representation of the actual dynamic building response. For the first application various control retrofits were evaluated and the highest potential for energy saving was found. Thereafter the model was implemented to investigate the change in indoor air conditions due to failure of HVAC equipment. Heating, ventilating and air-conditioning in buildings consume a significant portion of the available electrical energy in South Africa. Of this energy up to 30% can be saved by improving the HVAC systems currently installed in the buildings. This could result in savings of up to R400 million. For the building used in this study it was found that up to 66% of the HVAC system’s electrical energy consumption could be saved with a payback period of only 9 months. These savings could be achieved by implementing a setback control strategy with an improved time management procedure. Predicting the impact of failing equipment is a difficult task because of the integrated dynamic effect every HVAC component has on the next. With the aid of a comprehensive integrated simulation model the implications of failing can be determined and necessary assessments and precautions can be taken. The results of this study showed that the air-conditioning system under investigation was approximately 100% over designed. Failure of up to 50% was allowable in the cooling equipment before any noticeable impact could be observed in the indoor climate. With further failure the required comfort conditions could not be sustained. <p The substantial savings calculation and possibility of predicting climate deterioration would not have been possible without the aid of a comprehensive simulation package and model. This study clearly highlights the worth of integrated simulation. / Dissertation (MSc (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted