M.Ing. / Previous studies on the four-pulse dynamic compensator showed the existence of a stable limit cycle in the compensating current. Attempts were made to eliminate this limit cycle by placing a small signal active filter in the feedback path of the system, as it influenced the efficiency of the compensator. The efficiency of the active filter depends, on system parameters such as the impedance of the supply network and the load. Thus the small signal active filter eliminated the limit cycle only conditionally. A control method referred to as error modulation, was developed in order to eliminate the limit cycle unconditionally. According to this method the amplitude of the error is used to determine the modulation depth. Results showed that this method completely eliminates the limit cycle. In order to analyse this method analytically, a dual-input describing function for the altered non-linearity was derived. It was possible, by using the describing function, to explain the stability of the system with error modulation. Tests on the system revealed a poor dynamic response. The undamped nature of the system decreased the efficiency of the system. Damping was introduced to the system in such a way, that losses were kept at a minimum, while the dynamic response of the system improved. It has also been experienced that the losses in the system tends to use all the stored energy in the inductor. Previous attempts to stabilise the amount of stored energy in the inductor,did not succeed. 'n Control system using feedback was thus developed to stabilise the energy in the inductor, and the dynamic compensator losses are drawn from the supply.

No description available.

Shikao Ikehara. / "December 10, 1951." / Bibliography: p. 21-22. / Army Signal Corps Contract DA36-039 sc-100, Project no. 8-102B-0. Dept. of the Army Project no. 3-99-10-022.

D. B. Armstrong. / "October 4, 1951." / Bibliography: p. 15. / Army Signal Corps Contract DA36-039 sc-100, Project no. 8-102B-0. Dept. of the Army Project no. 3-99-10-022. Bureau of Ordinance Contract NOrd 9661.

[by] L. Weinberg [and] L.G. Kraft. / Bibliography: p. 29. / Army Signal Corps Contract no. DA36-039 sc-100, Project no. 8-102B-0. Dept. of the Army Project No. 3-99-10-022.

Thesis (M. Eng.)--Carleton University, 1995. / Includes bibliographical references. Also available in electronic format on the Internet.

Thesis submitted in fulfilment of the requirements for the degree Doctor of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / This thesis focuses on the design, development and real-time simulation of a robust nonlinear networked control for the dissolved oxygen concentration as part of the wastewater distributed systems. This concept differs from previous methods of wastewater control in the sense that the controller and the wastewater treatment plants are separated by a wide geographical distance and exchange data through a communication medium. The communication network introduced between the controller and the DO process creates imperfections during its operation, as time delays which are an object of investigation in the thesis. Due to the communication network imperfections, new control strategies that take cognisance of the network imperfections in the process of the controller design are needed to provide adequate robustness for the DO process control system. This thesis first investigates the effects of constant and random network induced time delays and the effects of controller parameters on the DO process behaviour with a view to using the obtained information to design an appropriate controller for the networked closed loop system. On the basis of the above information, a Smith predictor delay compensation controller is developed in the thesis to eliminate the deadtime, provide robustness and improve the performance of the DO process. Two approaches are adopted in the design of the Smith predictor compensation scheme. The first is the transfer function approach that allows a linearized model of the DO process to be described in the frequency domain. The second one is the nonlinear linearising approach in the time domain. Simulation results reveal that the developed Smith predictor controllers out-performed the nonlinear linearising controller designed for the DO process without time delays by compensating for the network imperfections and maintaining the DO concentration within a desired acceptable level. The transfer function approach of designing the Smith predictor is found to perform better under small time delays but the performance deteriorates under large time delays and disturbances. It is also found to respond faster than the nonlinear approach. The nonlinear feedback linearisig approach is slower in response time but out-performs the transfer function approach in providing robustness and performance for the DO process under large time delays and disturbances. The developed Smith predictor compensation schemes were later simulated in a real-time platform using LabVIEW. The Smith predictor controllers developed in this thesis can be applied to other process control plants apart from the wastewater plants, where distributed control is required. It can also be applied in the nuclear reactor plants where remote control is required in hazardous conditions. The developed LabVIEW real-time simulation environment would be a valuable tool for researchers and students in the field of control system engineering. Lastly, this thesis would form the basis for further research in the field of distributed wastewater control.