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M.Ing. / This research project is dedicated to the automation of environmental control within greenhouses. To create an optimal climate in the greenhouse, the main environmental parameters that need to be controlled are temperature, humidity and light intensity. As a result of process dead times and the extreme interdependence of these parameters, the control problem can be classified as non-linear and multi-variable. In the past, most greenhouse environmental control systems depended on the decision making of an experienced human operator. This often gave rise to trial and error, especially when new species were established. With the current advances in "intelligent" control systems and high accuracy sensors, more and more of the decisions involved in greenhouse control can be automated. In this way more emphasis can be placed on emulating the abilities of an expert operator, by means of a computerbased automatic control system. In this research project, "intelligent" as well as "non-intelligent" control techniques, for addressing the problem of automated climate control in a greenhouse, are investigated. These include PID-control as a "non-intelligent" technique, and rule-based fuzzy logic control and self-learning fuzzy logic control as two "intelligent" control techniques. These techniques are all applied to experimental greenhouse which is equipped with management mechanisms, such as fans, heaters, sprinklers and lights. The results of the experiments are evaluated according to two performance parameters: the Control Performance Index (CPI) and the Mean Square Error (MSE). The three techniques are not only assessed for their efficiency, but also for their applicability to the greenhouse environmental problem. Each of the control techniques has a unique characteristic response to the non-linear, non-stationary, multi-variable problem of environmental control and are subsequently addressed in the respective chapter.

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. / A new approach to the problem ofdesigning a control system for a run-of-mine (ROM) milling circuit is described. The ROM mill control problem is formalized in terms or a general linear system synthesis and analysis framework. Using this framework, u-synthesis and analysis is applied to a model of an industrial ROM milling circuit. The milling circuit uncertainty structure is obtained from plant perturbation tests. Correlations of plant parameter uncertainties and the choice of the location of uncertainty weights within the plant transfer function matrix structure, are discussed. Some comments are made as to possible sources of the plant uncertainties, and practical measures that can be taken to minimize them. The choice of performance weighting functions is discussed with regard to the economic and process-related importance of each plant output and issues of implementation such as the sampling rate to be used. A u-controller is obtained which provides robust performance in the face of significant model uncertainties. This controller is tested on a real industrial ROM milling circuit It is shown that the u-controller could be made to work on an industrial plant. Practical problems encountered are discussed, and reasons are given as to why the behaviour of the physical system differs form that observed in computer simulations. (Abbreviation abstract) / AC 2018

Chen Zhiyong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 54-57). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Nonlinear Control --- p.1 / Chapter 1.2 --- Global Stabilization --- p.2 / Chapter 1.3 --- Output Regulation --- p.3 / Chapter 1.4 --- Contributions of the Thesis --- p.4 / Chapter 2 --- Global Robust Stabilization of Cascaded Polynomial Systems --- p.5 / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- Preliminaries --- p.6 / Chapter 2.3 --- Basic Results --- p.8 / Chapter 2.4 --- The Algorithm --- p.11 / Chapter 2.5 --- An Example --- p.14 / Chapter 2.6 --- Concluding Remarks --- p.16 / Chapter 3 --- Output Regulation of Singular Nonlinear Systems by Normal Output Feedback --- p.18 / Chapter 3.1 --- Introduction --- p.18 / Chapter 3.2 --- Preliminaries --- p.20 / Chapter 3.3 --- Main Result --- p.24 / Chapter 3.4 --- An Example --- p.34 / Chapter 3.5 --- Concluding Remarks --- p.35 / Chapter 4 --- Robust Output Regulation of Singular Nonlinear Systems --- p.37 / Chapter 4.1 --- Introduction --- p.37 / Chapter 4.2 --- Problem Description and Standard Assumptions --- p.38 / Chapter 4.3 --- A Preliminary Result --- p.40 / Chapter 4.4 --- Solvability of the Problem --- p.48 / Chapter 4.5 --- Concluding Remarks --- p.51 / Chapter 5 --- Conclusions --- p.52 / Bibliography --- p.54 / Biography --- p.58

Decision Feedback Equalization (DFE) in a data recovery channel filters the bit decision in the current symbol period in generating the sample at the comparator in the subsequent clock period. The operations of sampling, comparing, filtering the decision bits into a feedback signal, and subtraction of that feedback signal are cascaded, thereby establishing the critical timing path. Thus, this system, though simple, requires its components to have large bandwidths in order to achieve the high-speed response necessary to perform the described feedback function. For the entire system to run at speeds comparable to those of competing technologies (100MHz to 250MHz), the components must have bandwidths greater than 100MHz, and work together to provide a loop bandwidth of at least 100MHz. A 300MHz latching comparator and a 125MHz 6-bit current-DAC were designed in a 5V, 1 um CMOS n-well process for use in a DFE loop. Both blocks are fully differential and achieve an accuracy of 1/2 LSB (10uA) over a differential signal range of 1.28mA. This is true for their operations at speed, in isolated simulation and as contiguous blocks. The DAC power consumption is relatively high at 23mW, due to internal switching circuits which require a static current, but the comparator's power consumption is minimal at 5mW. / Graduation date: 1997

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. Title from title screen (viewed Mar. 27, 2007). Includes bibliographical references (leaves 66-68). Online version of the print original.

Tot i la seva senzillesa, la idea de la realimentació negativa (o "feedback" en anglès) és extremadament poderosa i ha tingut un gran impacte en la societat des de la revolució industrial ençà. En l'actualitat, els sistemes de control estan a tot arreu. A la indústria de processos, per exemple, s'encarreguen de mantenir les variables d'interès aprop dels valors de consigna. Encara més, els sistemes de control han de garantir aquests objectius tot i la presència d'incertesa en el procés i l'existència de pertorbacions. En aquest sentit, la realimentació representa un mecanisme essencial alhora de millorar tant la qualitat com l'eficiència energètica en molts processos de fabricació. El tema cabdal d'aquesta tesi consisteix en el disseny analític de compensadors (també anomenats controladors) fent servir l'esquema convencial en realimentació unitària. El marc adoptat és del control lineal i invariant en el temps (LTI). Encara que la realitat és de naturalesa no lineal, la simplificació al cas lineal no suposa una restricció greu ja que, localment, sempre podem considerar l'aproximació lineal del procés sota control. Posteriorment, el rang d'operació del compensador es pot extendre fent servir algun procediment de control adaptatiu. Des del punt de vista del disseny del controlador, l'escenari considerat planteja, entre d’altres, dos compromisos fonamentals. D'una banda, el controlador haurà de sel·leccionar-se per tal d'assolir un bon balanç entre rendiment i robustesa de modelat. D'altra banda, existeix també un conflicte entre el rendiment tipus "regulatori" (rebuig de pertorbacions) i el rendiment tipus "servo" (seguiment de la consigna), essent de vegades convenient trobar-ne un equilibri entre aquests dos modes de funcionament. L'objectiu d'aquesta tesi és proporcionar procediments de disseny analítics basats en un model de la planta i els compromisos de robustesa/rendiment i servo/regulació. A diferència d'altres mètodes, els procediments presentats eximeixen el dissenyador d'haver de pensar pesos o models de referència adients. A més, els paràmetres de sintonia tenen un significat intuitiu per tal de simplificar l'ajustament dels paràmetres del controlador. Com que els controladors de tipus Proporcional-Integral-Derivatiu (PID) continuen sent els més emprats en la pràctica, s'ha considerat l'aplicació a aquest tipus particular de controlador. Per últim, val a dir que l'apropament analític d'aquesta tesi permet determinar, de manera explícita, com els diferents compromisos considerats afecten l'el·lecció final del controlador. Aquesta característica, creiem, és també valuosa des del punt de vista docent. / La idea de la realimentación negativa (o "feedback" en inglés), si bien sencilla, es extremadamente poderosa y ha tenido un gran impacto en la sociedad desde la revolución industrial. En la actualidad, los sistemas de control están en todas partes. En la industria de procesos, por ejemplo, son los encargados de mantener las variables de interés próximas a los valores de consigna, todo ello pese a la incerteza en el proceso y las perturbaciones externas. En este sentido, la realimentación es la única manera de estabilizar una planta inestable, y se presenta así como un mecanismo esencial en procesos de fabricación con el fin de mejorar la calidad del producto final y la eficiencia energética. El tema central de esta tesis es el diseño analítico de compensadores (también llamados controladores) en realimentación. El marco de control adoptado es del control lineal e invariante en el tiempo (LTI). Aunque la realidad raramente es de naturaleza lineal, la restricción al caso LTI obedece a su simplicidad y al hecho de que, localmente, es siempre posible aproximar un proceso no lineal por otro lineal. Desde este punto de vista, el rango de operación del compensador puede extenderse posteriormente mediante planificación de ganancia o control adaptable. Respecto a la configuración de control, esta tesis considera el esquema convencional en realimentación unitaria. En el escenario considerado, tenemos por un lado que el controlador debe diseñarse para proporcionar un buen compromiso entre el rendimiento y la robustez ante incerteza en el proceso. Por otro lado, también existe un conflicto entre el rendimiento tipo "servo" (seguimiento de la referencia o consigna) y el rendimiento tipo "regulatorio" (rechazo de las perturbaciones), siendo a veces deseable encontrar un equilibrio entre ambos modos de funcionamiento. El objetivo de esta tesis es proporcionar procedimientos de diseño analíticos basados en un modelo del proceso y los compromisos de robustez/rendimiento y servo/regulación. En los métodos propuestos no es necesario que el diseñador seleccione pesos o modelos de referencia como pasa con otros enfoques. Además, los parámetros de sintonía tienen un significado intuitivo con el fin de simplificar el ajuste de los parámetros del controlador. Debido a que los controladores de tipo Proporcional-Integral-Derivativo (PID) son ampliamente utilizados en la industria, se ha considerado la aplicación a este tipo de controladores. Por último, mencionar que el enfoque analítico de la tesis permite plasmar, de forma explícita, cómo los diferentes compromisos considerados influyen en la elección final del compensador. Esta característica es también valiosa desde el punto de vista de la docencia del control automático. / The concept of (negative) feedback, albeit simple, is extremely powerful, and has since the Industrial Revolution changed our world dramatically. Nowadays, control systems are everywhere. In process industry, for example, they keep the manipulated variables close to the set-points in spite of disturbances and changes in the plant. Moreover, feedback provides the only means to stabilize unstable processes. This way, the feedback mechanism reveals essential for improving product quality and energy efficiency, which yields better (sustainable) economy. The theme of this thesis is on analytical design of feedback compensators through linear control theory. The restriction to the Linear Time Invariant (LTI) case is not severe in the sense that most processes are well modeled locally by LTI systems. The operating range of the controller can then be extended using gain scheduling or adaptation. Within this work, the standard single-loop feedback configuration is assumed. Among the control objectives, stability and robustness are important considerations because of the presence of uncertainty in practice. Apart from that, the controller faces servo (set-point tracking) and regulation (disturbance rejection) objectives. In the considered scenario, it is well-known that there is an inherent compromise between robustness and performance. In general, the servo and regulation objectives are also conflicting and sometimes a balance is desirable. An example is in cascade configurations: the inner loop should be tuned based on tracking as it receives the set-points from the master loop. However, the inner loop may also need acceptable load disturbance suppression capabilities. Another good example is found in Model Predictive Control (MPC) applications due to frequent changes of set-points by the server. Finally, there may be a trade-off between the response to disturbances entering at the input and at the output of the plant, which can be understood as a servo/regulator trade-off too. The goal of this thesis is to provide model-based design procedures in terms of the Robustness/Performance and Servo/Regulator trade-offs, and give insight into how the tuning depends on the process parameters. In the presented methods, the designer is not required to choose weighting functions nor reference models as in other approaches, and the involved parameters have a clear meaning to facilitate the tuning process. Because PID controllers are prevalent in industry, application to PID tuning is considered most of the times. Although numerical methods for controller derivation may yield superior performance than analytical ones, the latter category has been preferred for several reasons. First, analytical procedures help understand the problem at hand. Second, when applied to low-order models, well-motivated tuning rules which are simple and easy to memorize can be obtained. These features are very desirable from the operator's point of view as well as for teaching purposes.

Recently, The Land, Air and Space Robotics (LASR) Laboratory has demonstrated a state-of-the-art proximity operations test bed that will revolutionize the concept of portable space systems simulation. The Holonomic Omni-directional Motion Emulation Robot (HOMER) permits in nite, un-tethered circumnavigations of one object by another. To allow this platform to operate at the desired performance, an appropriate implementation of feedback control is essential. The dynamic model is derived and presented using a Lagrangian approach. A Lyapunov method is used to form proportional-derivative (PD) and proportional-integral-derivative (PID) feedback controllers. These controllers are validated with computer-based simulation and compared through experimental results. Finally, a frequency analysis is performed in an effort to identify the bandwidth of the system and provide a better understanding of the expected system performance for reference motions containing harmonic perturbations.