Companies which design automation control for the metal rolling industry are faced with a growing demand for systems with higher performance standards than ever before. Along with these demanding specifications is always the problem of system stability at any given speed. A multi-ton rolling stand with uncontrolled oscillations not only destroys the product being rolled but may cause serious damage to the plant and endanger the lives of mill personnel. Therefore stability analysis is critical whether modeling individual mills or analyzing old products and strategies so as to invent better, cheaper control methods. Cost is another major consideration for the firm ordering these systems and the companies which design them. Suppliers are trimming time from design and production schedules wherever possible in order to compete in the world market. It is for these, and other reasons that computer aided stability analysis is so important. The object is to ensure a safe and stable system and yet minimize the time (and therefore cost) needed For design and installation. This paper describes a program (ROOT LOCUS) which was created to fill this need while using the tools and methods readily at hand. It was written for personal computers as these machines are rapidly proving to be cost effective solutions to problems in computing power. / Master of Science

The computer simulation language written in Fortran was used to model the Navy's PHALANX Mount and Antenna Compensation Network. This network is a feedback control system that filters out the effects of surface ship motion on a weapon's response to commands from the ship's fire control center. The network includes a number of non-standard elements that prevent mathematical prediction of its closed-loop response; therefore, a computer model was required to predict the network's output. The computer models were developed, validated and tested with a number of different inputs. The resultant outputs were compared with actual test data taken from a functional PHALANX mount compensation network. / Master of Science

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A nonlinear analysis is developed for eddy-current couplings in feedback control systems. The analysis makes use of the describing function method to predict transient response. Effects of the nonlinearity are discussed and backed with an analog computer study. Conclusions arrived at show the absquare nonlinearity to be advantageous under conditions of zero steady state loading or offset. Under conditions of steady state loading, shifting of the load operating point causes a wide variation in response. This situation is remedied with nonlinear compensation. / Master of Science

This dissertation is concerned with the problem of synthesizing a robust stabilizing feedback controller for linear time-invariant systems with constant uncertainties that are not required to satisfy matching conditions. Only the bounds on the uncertainties are required and no statistical property of the uncertainties is assumed. The systems under consideration are described by linear state equations with uncertainties. I.e. x(t) = A̅(γ)x(t) +B̅(γ)u(t), where A̅(γ) is an n x n matrix and B̅(γ) is an n x m matrix. Lyapunov theory is exploited to establish the conditions for stabilizability of the closed loop system. We consider a Lyapunov function with an uncertain symmetric positive definite matrix P. The uncertain matrix P satisfies the Lyapunov equation A^TP + PA + Q = 0, where the matrix A is in companion form and the matrix Q is symmetric and positive definite. In the solution of the Lyapunov equation, m rows of the matrix P are fixed in our approach of designing a robust controller. We derive necessary and sufficient conditions on these fixed m rows of the matrix P such that for given positive definite and symmetric Q the solution of the Lyapunov equation yields a positive definite matrix P and a companion matrix A that is Hurwitz. A discontinuous robust stabilizing controller is given. Linear controller design is also investigated in this research. Under the same assumptions for the existence of a stabilizing discontinuous controller, we show that a linear robust stabilizing controller always exists. The dissertation includes three examples to illustrate the design procedures for robust controllers. Example 2 shows that the design procedure may be applied to time-varying nonlinear systems. / Ph. D.

The design requirements for future aircraft demand increased performance and multimission capability. Active, in-flight, aerodynamic surface shaping is currently being investigated to increase the flight envelope of tomorrow's aircraft. The primary application of this research is to aid the evaluation of active airfoil and wing shape control using an active truss. This specific research addresses the effect of replacing position feedback with strain feedback for shape control of an active truss. There are two research objectives: a comparison of multiple-beam shape control using position and strain feedback, and to confirm a system displacement model through experimentation. The experimental setup uses two cantilevered aluminum T-sections attached by one to three-ball screw actuators. The actuators have been pinned at each beam location to allow rotation during extension, while also allowing the effect of a variable number of actuators to be examined. The three-actuator arrangement enables independent specification of three positions along the two beams; therefore, the system is a multiple input-multiple output (MIMO) system. The controller consists of three pulse-width modulated amplifiers converted for use with a position feedback loop. A model is developed which consists of a spring-actuator arrangement with the equivalent spring constants corresponding to the beam deflection equations. The system model is first examined based on the results of the actuator length feedback experiments. The model is confirmed for the single actuator system. The joint gap accounts for the inconclusive results in confirming the multiple actuator displacement models. The next set of experiments demonstrate that strain feedback may indeed replace the actuator length feedback. It is shown that a signal may be produced which is proportional to the actuator extension, this may then replace the length sensor. / Master of Science

This dissertation is concerned with the problem of the exact pole-placement by minimum control effort using state and output feedback for linear multivariable systems. The novelty of the design lies in obtaining a direct transformation of the system matrices into a modified controllable canonical form. Two realizations are identified, and the algorithms to obtain them are derived. In both cases, the transformation matrix has some degrees of freedom by tuning a scalar or a set of scalars within the matrix. These degrees of freedom are utilized in the solution to reduce further the norm of the state feedback matrix. Then the pole-placement problem is solved by minimizing a certain functional, subject to a set of specified constraints. A non-canonical form approach to the problem is also proposed, where it was only necessary to transform the input matrix to a special form. The transformation matrix, in this method, has larger degrees of freedom which can be utilized in the solution. Moreover, a new pole-placement method based on the non-canonical approach is derived. The solution, in this method, was made possible by solving the Lyapunov matrix equation. Finally, an iterative algorithm for pole-placement by output feedback is extended so as to obtain an output feedback matrix with a small norm. The extension has been accomplished by applying the successive pole shifting method. Two schemes for the pole shifting are proposed. The first is to successively shift the poles through straight paths starting from the open loop poles and ending at the desired poles, whereas the second scheme shifts the poles according to a successive change of their characteristic polynomial coefficients. / Ph. D. / incomplete_metadata

Call number: LD2668 .T4 1985 S648 / Master of Science

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Position calculation of mobile objects has challenged engineers and designers for years and is still continuing to do so. There are many solutions available today. Probably the best known and most widely used outdoor system today is the Global Positioning System (GPS). There are very little systems available for indoor use. An absolute positioning system was developed for this thesis. It uses a combination of ultrasonic and Radio Frequency (RF) communications to calculate a position fix in doors. Radar techniques were used to ensure robustness and reliability even in noisy environments. A small mobile robot was designed and built to test and illustrate the use of the system.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, .Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. / As industrial plants become more complex. there is a growing need for new approaches to control and supervision. This research investigates the issues involved in applying Artificial Intelligence (AI) techniques in the real-world engineering problem of process control supervision. Current AI theory is examined and some techniques modified to design a general-purpose, reactive planner. The planner forms the basis of a supervisory control system. The system is implemented and interfaced with an existing Laboratory plant, so that its performance can he tested and evaluated by comparing with a conventional feedback controller This real life testing necessitates explicit treatment of issues such as data: sampling. situation assessment and CPU scheduling. The case study shows that by combining AI techniques with conventional control, a system can be built which displays superior performance under normal operating conditions and which can deal with abnormal conditions such as equipment failures. / Andrew Chakane 2018