Thesis (Ph. D.)--City University of Hong Kong, 2005. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 109-118).

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University of Macau / Faculty of Science and Technology / Department of Electrical and Computer 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

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This thesis investigates the use of correlation techniques to perform system identification tests, with the objective of developing online test methods to perform mechanical parameter extraction as well as machine diagnostics. More specifically, these test methods must be implemented on a Programmable Logic Controller (PLC) in combination with Variable Speed Drives (VSD). Models for motor-based mechanical systems are derived and other documented methods for parameter identification of mechanical systems are discussed. An investigation is undertaken into the principle that the impulse response of a system may be obtained when a test signal with an impulsive autocorrelation is injected into the system. The theory of using correlation functions to determine the numerical impulse response of a system is presented. Suitable test signals, pseudorandom binary sequences (PRBS) are analysed, and their generation and properties are discussed. Simulations are presented as to how the various properties of the PRBS test signals influence the resulting impulse response curve. Further simulations are presented that demonstrate how PRBS-based tests in conjunction with a curve-fitting method, in this case the method of linear least squares, can provide a fair estimation of the parameters of a mechanical system. The implementation of a correlation based online testing routine on a PLC is presented. Results from these tests are reviewed and discussed. A SCADA system that has been designed is discussed and it is shown how this system allows the user to perform diagnostics on networked drives in a distributed automation system. Identification of other mechanical phenomena such as elasticity and the non-linearity introduced by the presence of backlash is also investigated. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Thesis submitted in fulfillment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / A new control strategy for control of the nonlinear process of Dissolved Oxygen (DO) concentration in the aerobic tank of wastewater treatment process is proposed. It provides means to improve the performance of the Linear Proportional Integration and Derivative (LPID) controller by extending it to a Nonlinear Proportional Integration and Derivative (NLPID) controller. The aim of the thesis is to develop methods, algorithms and software for design, simulation, and programmable logic controller (PLC) implementation of NLPID controllers in order to control the nonlinear process of dissolved oxygen. The thesis investigates the possibilities the widely used in theory and industry methods for the design of the LPID controllers for linear processes as Ziegler- Nichols and Pole Placement, to be applied to the design of NLPID controllers for the nonlinear process of DO concentration. Three cases are considered: Case 1: Application of the values of the parameters the linear PID controller designed by the Ziegler-Niched method for the linearized DO process model to be used as parameters of the nonlinear PID controllers to control the DO nonlinear process. Case 2: Application of the values of the parameters of the linear PID controller designed by the Pole placement method for the linearized DO process model, to be used as parameters of the nonlinear PID controller to control the nonlinear DO process. Case 3: Novel, proposed in the thesis, method based on the Pole placement method for direct design of the parameters of the linear and nonlinear PID controllers to control the nonlinear DO process. Software is developed to simulate in MATLAB environment the behavior of the closed loop DO process for the considered cases of controller designs. The results of the simulations show that in the Case1 and the Case 2 it is not possible to use the values of the LPID controller parameters designed for the linearized DO process, directly to control the nonlinear process by the NPID controllers. Additional tuning for some of the parameters is needed. The simulation in the Case 3 shows the excellent behaviors of the closed loop system for all linear and nonlinear PID controllers which prove that the new method is effective and applicable. Real-time simulations of the closed loop system are done in a TwinCAT 3 simulation environment of the Bechkoff EX5020 PLC. The deliverables of the thesis are applicable to many type nonlinear processes in chemical, manufacturing, and other industries.

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