Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009 / More than 70% of the earth's surface is covered by water, only a small part of which is suitable for either human consumption or agricultural use. Due to pollution from agriculture, households and industry reaching rivers, lakes and seas it is Important for wastewater to be properly treated in order to remove harmful substances before it reaches the environment. Strict environmental and health regulations together with a demand for cost effective ways of wastewater treatment have made control technology in wastewater Treatment Plants an important priority. Dissolved oxygen (DO) is the amount of oxygen in the effluent and it plays a vital role of controlling VV\YTP. Oxygen dissolves in water through mixing water surface with the atmosphere, The dissolved oxygen concentration in the aerobic part of an activated sludge process should be sufficiently high to supply enough oxygen to the microorganisms in the sludge. an excessive high DO leads to high energy consumption and may also deteriorate the sludge quality, A high DO concentration in the internally recirculated water also makes the denitrification less efficient Hence, both for economical and process reasons, it is of interest to control the DO. The used controllers are normally linear controllers, proportional integral (PI) or proportional integral derivative (PID) ones. The work of these controllers leads to bad system performance, because, the process of dissolving oxygen into the wastewater is a nonlinear process and requires nonlinear control. The aim of the research project is to develop methods for design of linear and nonlinear controllers of the concentration of the DO in the aeration tank of the WWTP and to implement the designed controllers in the frameworks of PLC. The nonlinear linearizing controller based on a reference model and Lyapunov second method is designed. Additionally a linear controller is developed in a form of PI controller based on pole placement method to improve, the performance of the closed loop system. The resultant controller is to be on a PLC as a part of Adroit SCADA system. The developed programmes are used to control the wastewater treatment process in laboratory scale plant and can be applied as a part of SCADA software for control of the wastewater treatment plants.

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / Majority of the industrial systems encountered are significantly non-linear in nature, so if they are synthesised and designed by linear methods, then some of salient features characterising of their performance may not be captured. Therefore designing a control system that captures the nonlinearities is important. This research focuses on the control design strategies for the Continuous Stirred Tank Reactor (CSTR) process. To control such a process a careful design strategy is required because of the nonlinearities, loop interaction and the potentially unstable dynamics characterizing the system. In these systems, linear control methods alone may not perform satisfactorily. Three different control design strategies (Dynamic decoupling, Decentralized and Input-output feedback linearization controller) are proposed and implemented .in the Matlab/Simulink platform and the developed strategies are then deployed to the design of distributed automation control system configuration using the IEC 61499 standard based functional block programming language. Twin CAT 3.1 system real-time and Matlab/Simulink (www.mathworks.com) environment are used to test the effectiveness of the models The simulation results from the investigation done between Simulink and TwinCAT 3 software (Beckhoff Automation) platforms in the case of the model transformation and closed loop simulation of the process for the considered cases have shown the suitability and the potentials of merging the Matlab/Simulink control function blocks into the TwinCAT 3.1 function blocks in real-time. The merits derived from such integration imply that the existing software and software components can be re-used. This is in line with one of the IEC 6144 standard requirements such as portability and interoperability. Similarly, the simplification of programming applications is greatly achieved. The investigation has also shown that the integration the of Matlab/Simulink models running in the TwinCAT 3.1 PLC do not need any modification, hence confirming that the TwinCAT 3.1 development platform can be used for the design and implementation of controllers from different platforms. Also, based on the steps required for model transformation the between the Matlab/Simulink to the TwinCAT 3 functional blocks, the algorithms of the control design methodologies developed, simulation results are used to verify the suitability of the controls to find whether the effective set-point tracking control and disturbance effect minimisation for the output variables can be achieved in real-time using the transformed Simulink blocks to the TwinCAT 3 functional blocks, then downloaded to the Beckhoff CX5020 PLC for real-time execution. Good set-point tracking control is achieved for the MIMO closed loop nonlinear CSTR process for the considered cases of the developed control methodologies. Similarly, the effects of disturbances are investigated. TwinCAT functional modules achieved good set-point tracking with these disturbances minimization under all the cases considered.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering in the Control Research Group School of Electrical and Information Engineering, Johannesburg, 2017 / In this research, we observed a torque-related limitation in the swing-up control of underactuated mechanical systems which had been integrated with viscous damping in the unactuated joint. The objective of this research project was thus to develop a practical work-around solution to this limitation. The nth order underactuated robotic system is represented in this research as a collection of compounded pendulums with n-1 actuators placed at each joint with the exception of the first joint. This system is referred to as the PAn-1 robot (Passive first joint, followed by n-1 Active joints), with the Acrobot (PA1 robot) and the PAA robot (or PA2 robot) being among the most well-known examples. A number of friction models exist in literature, which include, and are not exclusive to, the Coulomb and the Stribeck effect models, but the viscous damping model was selected for this research since it is more extensively covered in existing literature. The effectiveness of swing-up control using Lyapunov’s direct method when applied on the undamped PAn-1 robot has been vigorously demonstrated in existing literature, but there is no literature that discusses the swing-up control of viscously damped systems. We show, however, that the application of satisfactory swing-up control using Lyapunov’s direct method is constrained to underactuated systems that are either undamped or actively damped (viscous damping integrated into the actuated joints only). The violation of this constraint results in the derivation of a torque expression that cannot be solved for (invertibility problem, for systems described by n > 2) or a torque expression which contains a conditional singularity (singularity problem, for systems with n = 2). This constraint is formally summarised as the matched damping condition, and highlights a clear limitation in the Lyapunov-related swing-up control of underactuated mechanical systems. This condition has significant implications on the practical realisation of the swing-up control of underactuated mechanical systems, which justifies the investigation into the possibility of a work-around. We thus show that the limitation highlighted by the matched damping condition can be overcome through the implementation of the partial feedback linearisation (PFL) technique. Two key contributions are generated from this research as a result, which iii include the gain selection criterion (for Traditional Collocated PFL), and the convergence algorithm (for noncollocated PFL). The gain selection criterion is an analytical solution that is composed of a set of inequalities that map out a geometric region of appropriate gains in the swing-up gain space. Selecting a gain combination within this region will ensure that the fully-pendent equilibrium point (FPEP) is unstable, which is a necessary condition for swing-up control when the system is initialised near the FPEP. The convergence algorithm is an experimental solution that, once executed, will provide information about the distal pendulum’s angular initial condition that is required to swing-up a robot with a particular angular initial condition for the proximal pendulum, along with the minimum gain that is required to execute the swing-up control in this particular configuration. Significant future contributions on this topic may result from the inclusion of more complex friction models. Additionally, the degree of actuation of the system may be reduced through the implementation of energy storing components, such as torsional springs, at the joint. In summary, we present two contributions in the form of the gain selection criterion and the convergence algorithm which accommodate the circumnavigation of the limitation formalised as the matched damping condition. This condition pertains to the Lyapunov-related swing-up control of underactuated mechanical systems that have been integrated with viscous damping in the unactuated joint. / CK2018

In this thesis, the plant identification, state estimation based on the identified plant and also the design of a neuro-controller using multi-layer perceptrons (MLPs) for a complex system are presented. The quasi-linear system to be controlled is both unstable and nonlinear. The complete nonlinear feedback control system is designed without a priori information of the plant dynamics, using only measured input/output data. The first design step is to combine a conventional method of multivariable system identification with a dynamic multi-layer perceptron (MLP) to achieve a constructive method of system identification. Based on the identified linear model of the system, states will be estimated and converted to more appropriate state for control in the second design step. The class of quasilinear nonlinear systems is assumed to operate nominally around an equilibrium point in the neighborhood of which a linearized model exists to represent the system, although normal operation is not limited to the linear region. The results presented here provide an accurate discrete-time nonlinear model, which is used in the design of a nonlinear state estimator. The controller design is derived from a switched-linear feedback controller from the estimated states using the identified linearized model of the system around each suitable operating point, as a role model for the neuro-controller in the initial phase. Finally, using the partially trained controller, the neuro-controller can be further trained "on-line" using a selected performance index to guide the learning. A prototype problem, an inverted pendulum system, is simulated as a physical system to be identified and to be controlled. Simulation results indicate that the present design method is very reliable comparing with other methods and hence is suitable for both identifying and controlling critical industrial processes. The prominent feature of this method is that no specific model information is initially required throughout the identification and control of the nonlinear plant. As an application of identifying an unknown plant in power electronics systems, an empirical data modeling approach which aims at generating small-signal equivalent models and also nonlinear models for a general class of converters, including resonant converters, and subsystems in a distributed power system is presented. / Ph. D.

In this paper we consider the problem of designing dynamic compensators to control a class of nonlinear parabolic distributed parameter systems. We concentrate on a system with unbounded input and output operators governed by Burgers’ equation. This equation provide a one dimensional model for certain convection—diffusion phenomena. A linearized model is used to compute a robust controller (MinMax), a LQG controller and a fixed-order-finite-dimensional control law (Optimal Projection) by minimizing various energy functionals. These control laws are then applied to the nonlinear model. Different approximation schemes are used to design suboptimal active feedback controllers. This approach provides important practical information. In particular, we show how functional gains can be used to locate new sensors. Numerical results are given to illustrate the basic ideas and to compare the various controllers. / Ph. D.

Research on collaboration among unmanned platforms is essential to improve the applications for autonomous missions, by expanding the working environment of the robotic systems, and reducing the risks and the costs associated with conducting manned operations. This research is devoted to enable the collaboration between an Unmanned Surface Vehicle (USV) and an Autonomous Underwater Vehicle (AUV), by allowing the first one to launch and recover the second one. The objective of this dissertation is to identify possible methods to launch and recover a REMUS 100 AUV from a WAM-V 16 USV, thus developing this capability by designing and implementing a launch and recovery system (LARS). To meet this objective, a series of preliminary experiments was first performed to identify two distinct methods to launch and recover the AUV: mobile and semi-stationary. Both methods have been simulated using the Orcaflex software. Subsequently, the necessary control systems to create the mandatory USV autonomy for the purpose of launch and recovery were developed. Specifically, a series of low-level controllers were designed and implemented to enable two autonomous maneuvers on the USV: station-keeping and speed & heading control. In addition, a level of intelligence to autonomously identify the optimal operating conditions within the vehicles' working environment, was derived and integrated on the USV. Lastly, a LARS was designed and implemented on the vehicles to perform the operation following the proposed methodology. The LARS and all subsystems developed for this research were extensively tested through sea-trials. The methodology for launch and recovery, the design of the LARS and the experimental findings are reported in this document. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

There have been much technological advances and research in Unmanned Surface Vehicles (USV) as a support and delivery platform for Autonomous/Unmanned Underwater Vehicles (AUV/UUV). Advantages include extending underwater search and survey operations time and reach, improving underwater positioning and mission awareness, in addition to minimizing the costs and risks associated with similar manned vessel operations. The objective of this thesis is to present the design and development a high-level fuzzy logic guidance controller for a WAM-V 14 USV in order to autonomously launch and recover a REMUS 100 AUV. The approach to meeting this objective is to develop ability for the USV to intercept and rendezvous with an AUV that is in transit in order to maximize the probability of a final mobile docking maneuver. Specifically, a fuzzy logic Rendezvous Docking controller has been developed that generates Waypoint-Heading goals for the USV to minimize the cross-track errors between the USV and AUV. A subsequent fuzzy logic Waypoint-Heading controller has been developed to provide the desired heading and speed commands to the low-level controller given the Waypoint-Heading goals. High-level mission control has been extensively simulated using Matlab and partially characterized in real-time during testing. Detailed simulation, experimental results and findings will be reported in this paper. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Despite the fact that significant progress has been made on the research of these two problems for nonlinear systems for over two decades, many problems are still open. In particular, so far the output regulation problem is mainly handled by robust control approach. This approach has certain fundamental limitations and cannot handle the following three cases. (1) The control direction is unknown. (2) The boundaries of system uncertainties are unknown. (3) The exosystem is not known precisely. / Stabilization and output regulation are two fundamental control problems. The output regulation problem aims to design a feedback controller to achieve asymptotic tracking of a class of reference inputs and rejection of a class of disturbances in an uncertain system while maintaining the internal stability of the closed-loop system. Thus the output regulation problem is more demanding than the stabilization problem. Nevertheless, under some assumptions, the output regulation problem can be converted into a stabilization problem for a well defined augmented system and the solvability of the stabilization problem for this augmented system implies that of the output regulation problem for the original plant. Therefore, to a large extent, the study of the stabilization problem will also lay a foundation for that of the output regulation problem. / To handle these problems and overcome the shortcomings of the robust control approach, in this thesis, we have incorporated the adaptive control approach with the robust control approach. Both stabilization problem and output regulation problem are considered for two important classes of nonlinear systems, namely, the output feedback systems and lower triangular systems. The main contributions are summarized as follows. (1) The adaptive output regulation problem for nonlinear systems in output feedback form is addressed without knowing the control direction. The Nussbaum gain technique is incorporated with the robust control technique to handle the unknown control direction and the nonlinearly parameterized uncertainties in the system. To overcome the dilemma caused by the unknown control direction and the nonlinearly parameterized uncertainties, we have adopted a Lyapunov direct method to solve the adaptive output regulation problem. (2) The adaptive stabilization problem for nonlinear systems in lower triangular form is solved when both static and dynamic uncertainties are present and the control direction is unknown. Technically, the presence of dynamic uncertainty has made the stabilization problem more difficult than the previous work. We have managed to combine the changing supply rate technique and the Nussbaum gain technique to deal with this difficulty. The result is also applied to solve the output regulation problem for lower triangular systems with unknown control direction. (3) The adaptive output regulation problem for nonlinear systems in output feed-back form with unknown exosystem is studied. The adaptive control technique is applied to estimate the unknown parameter results from the unknown exosystem. The condition under which the parameter estimation converges to its real value is also discussed. Further, the global disturbance rejection problem for nonlinear systems in lower triangular form is solved by formulating the unknown external disturbance as a signal produced by an unknown exosystem. (4) The theoretical results have been applied to several typical control systems leading to the solution of some long standing open problems. Some exemplified applications are: (a) Global adaptive stabilization of Chua's circuit without knowing the control direction; (b) Global output synchronization of the Chua's circuit and the harmonic system; (c) Global adaptive disturbance rejection problem of the Duffing's system with all parameters unknown; (d) Global adaptive output regulation of Van der Pol oscillator with an uncertain exosystem. / Liu, Lu. / Adviser: Jie Huang. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3693. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 204-214). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

In this thesis, we develop a feedback-invariant theory of local controllability for affine distributions. We begin by developing an unexplored notion in control theory that we call proper small-time local controllability (PSTLC). The notion of PSTLC is developed for an abstraction of the well-known notion of a control-affine system, which we call an affine system. Associated to every affine system is an affine distribution, an adaptation of the notion of a distribution. Roughly speaking, an affine distribution is PSTLC if the local behaviour of every affine system that locally approximates the affine distribution is locally controllable in the standard sense. We prove that, under a regularity condition, the PSTLC property can be characterized by studying control-affine systems. The main object that we use to study PSTLC is a cone of high-order tangent vectors, or variations, and these are defined using the vector fields of the affine system. To better understand these variations, we study how they depend on the jets of the vector fields by studying the Taylor expansion of a composition of flows. Some connections are made between labeled rooted trees and the coefficients appearing in the Taylor expansion of a composition of flows. Also, a relation between variations and the formal Campbell-Baker-Hausdorff formula is established. After deriving some algebraic properties of variations, we define a variational cone for an affine system and relate it to the local controllability problem. We then study the notion of neutralizable variations and give a method for constructing subspaces of variations. Finally, using the tools developed to study variations, we consider two important classes of systems: driftless and homogeneous systems. For both classes, we are able to characterize the PSTLC property. / Thesis (Ph.D, Mathematics & Statistics) -- Queen's University, 2010-01-11 20:11:45.466

The study of turbulence has been dominated historically by a bottom-up approach, with a much stronger emphasis on the physical structure of flows than on that of the dynam- ical state space. Turbulence has traditionally been described in terms of various visually recognizable physical features, such as waves and vortices. Thanks to recent theoretical as well as experimental advancements, it is now possible to take a more top-down approach to turbulence. Recent work has uncovered non-trivial equilibria as well as relative periodic orbits in several turbulent systems. Furthermore, it is now possible to verify theoretical results at a high degree of precision, thanks to an experimental technique known as Particle Image Velocimetry. These results squarely frame moderate Reynolds number Re turbulence in boundary shear flows as a tractable dynamical systems problem. In this thesis, I intend to elucidate the finer structure of the state space of moderate Re wall-bounded turbulent flows in hope of providing a more accurate and precise description of this complex phenomenon. Computation of new undiscovered equilibria, relative equilibria, and their heteroclinic connections provide a skeleton upon which a numerically accurate description of turbulence can be framed. The behavior of the equilibria under variation of Reynolds number and cell aspect ratios is also examined. It is hoped that this description of the state space will provide new avenues for research into nonlinear control systems for shear flows as well as quantitative predictions of transport properties of moderate Re fluid flows.