Thesis (MTech (Electrical Engineering))--Peninsula Technikon, 2002 / In this thesis fuzzy control is analyzed and applied to two complex processes. A process is deemed to be complex if it possesses characteristics that make it non-linear. Examples of such characteristics are backlash, hysteresis, saturation and dead zones, which are common in industrial processes. These characteristics do not allow for the easy implementation of controllers and often there would be a requirement to employ some non-linear form of control. Often with complex processes linearization techniques would be employed to enable the application of linear controllers. However, these controllers will only operate over a limited range and will have degradation in performance when subjected to unpredictable changes in parameters. Fuzzy controllers can handle nonlinear characteristics in complex processes very well and also provides some transparency between the human machine interface. Fuzzy control is based upon the fuzzy methodology that was introduced by Lotfi Zadeh (Zadeh, 1965) in his seminal paper on fuzzy sets. The first practical application (Mamdani and Assilian, 1975) paved the way for fuzzy control and although this alternate paradigm of control came up against much criticism it managed to capture the interest of many researchers. Although research into fuzzy control saw a slump in the late 70's and early 80's it rapidly progressed in the 90's with literally thousands of research papers being published. In this study this alternate paradigm of control is investigated and applied to two processes. An initial study was done on the fundamental concepts of fuzzy logic and how this methodology can be applied to develop a controller that is fuzzy logic based. A plethora of information exist on fuzzy theory however only the fundamental concepts are dealt with here. This is sufficient for the realization of a rudimentary controller. A detailed investigation was also done on the development of the rules of the knowledge base of the controller with the emphasis on the development of a fuzzy controller that has characteristics akin to a proportional-integral (PI) controller.

Dissertation submitted in compliance with the requirements for Masters Degree in Technology in Electrical Engineering (Light Current) at Technikon Natal, 1998. / Designing compensators in the frequency domain is a complicated problem even for linear systems that have dead time. The situation is far more difficult if the system is also nonlinear. This study introduces a new method for the design of compensators for time-invariant, nonlinear systems that have dead time. The method is based on an optimization approach and utilizes large signal linearization methodology. / M

Dissertation submitted in compliance with the requirements for Masters Degree in Technology: Electrical Engineering (Light Current), Technikon Natal, 1997. / This report details the findings of work carried out over the course of 1994 and 1995 to determine if it is feasible to use an electrostatic technique for the measurement of mass flow rate of pneumatically conveyed solids. This includes results from tests done on a flow rig and at various power stations. / M

M.Com. / Please refer to full text to view abstract

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

Thesis submitted in compliance with the requirements for the Masters Degree in Technology: Electrical Engineering (Light Current), Technikon Natal, 1997. / In this study we propose an analogue nonlinear PID controller with antiwindup and dead-time compensation to optimise the control of loops experiencing degradation in the control performance as a result of dead-time and saturation nonlinearity. Loops containing a significant dead-time are notoriously difficult to control. The proposed controller optimises the control of loops experiencing the negative effects of saturation and dead-time. / M

A new model for power system transient stability tests has been developed. It includes a dc motor simulated prime mover with a governor control synthesized by dc booster generator field control, a solid state voltage regulator and exciter, a synchronous machine with a large field time constant realized by negative resistance in the field circuit, a transmission system with time setting SCR controlled fault and clear sequence switchings, an accurate torque angle deviation transducer (Chapter 2), and analogs to realize conventional stabilization and nonlinear optimal control (Chapter 5). Three state variable mathematical models of the test model with various degrees of detail are derived in Chapter 3. Comparisons of results of digital computation and real model tests of a typical power system disturbed by a short circuit are given also in Chapter 3. A parameter sensitivity study is carried out in Chapter 4. Comparisons of digital computation of transient stability with a nonlinear optimal control derived in this thesis and power and speed stabilization derived by another colleague of the power group at U.B.C., with the transient stability tests on the test model are given in Chapter 5. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

In this thesis some numerical techniques for obtaining the time optimal control of a class of time delay systems are studied and compared. The delays may be fixed or time varying. The delay systems considered, which need not be linear or time invariant, are those for which the time optimal control is bang-bang. The optimal control is found by carrying out a search in switching interval space. The method of Rosenbrock⁽²’³⁾ is used to find the switching intervals which maximize a performance index of the final states and terminal time. Kelly's⁽²¹⁾ method of gradients is shown to be applicable to systems with time varying time delays by using the costate equations of ref. [10]. The perturbations in the control are chosen in such a way that the descent in function space is changed to a steepest descent in switching interval space. In a third approach, a technique similar to that of Bryson and Denham⁽¹⁹⁾ is used to account for the terminal conditions directly. All the methods are illustrated by examples. The advantages of the direct search based on Rosenbrock's method are a) ease of programming and b) rapid convergence close to the optimum. However, initial convergence is slow when compared to that of either gradient method. Of the two gradient methods, that based on a penalty function approach was superior in ease of programming and convergence close to the optimum to that based on a descent to the final target set. Neither gradient scheme could match the rapid convergence of the Rosenbrock method close to the optimum / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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