Techniques in Treating Nonlinear Closed-Cycle Systems

Citation

Neiswander, Robert South (1954) Techniques in Treating Nonlinear Closed-Cycle Systems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/8T8F-3S33. https://resolver.caltech.edu/CaltechETD:etd-12042003-111341

Abstract

The objective of this research is to examine and to develop methods of treating nonlinear closed-cycle, single loop systems. Analytical and graphical methods are immediately rejected for their failure to include the complexities of realistic systems. Experimental techniques as, for example, electrical analog modeling are flexible and can accommodate complicated system descriptions. Associated with such a technique are three important steps: 1) selection of suitable analog elements, 2) arraying or modeling these elements to properly simulate the actual system, and 3) devising an experimental test procedure that produces appropriate insight into the cause and the control of results. Designed for the exploratory testing of nonlinear systems the electronic, logarithm type function generator is a nonlinear element that creates an easily modified function of two or more input variables. Its computing speed is sufficient for oscilloscope monitoring of solutions. System modeling is the most critical step; as demonstrated by two system examples, the deceptively simple hydraulic servomechanism. and the supersonic diffuser instability. Based upon a limited Taylor series approximation of the input function the experimental procedure used to design a realistic servomechanism for best saturated performance is quite simple. It utilizes intentional shaping of the rate feedback function (or the static error). Performance within the systems customarily linear region can be improved by intentional saturation.

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