Robertson, James Ritchie (1971) A new transfer function analyser. PhD thesis, University of Warwick.

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Abstract

This thesis investigates the concept and design of a portable on-line transfer function analyser (TFA). It is eminently suitable for the identification of plants and other controlled feedback systems in which normal operating records are available.

A point by point representation in the frequency domain, requiring a maximum of three records, allows Nyquist plots to be carried out, either visually or by plotter facilities. The basic theory relies heavily upon statistical concepts whereby, least squares estimates of the transfer function are obtained from a combination of heterodyning, exact filtering and adaptive loops. The resultant output, on both channels (real and imaginary), is the culmination of the solution to two linear differential equations with stochastic coefficients, so mechanised when the adaptive loops reach a stable equilibrium.

Throughout, emphasis is placed upon the electronics combining the best of analog and digital techniques, in order that six parallel paths may be analysed in similar mode. This is especially true of the heterodyning and filtering operations. Practical shortcomings of the instrument noted by comparing estimates with those from the best currently available commercial apparatus, operating on deterministic signals. Examples of a feedback loop, subjected to both deterministic and random stimuli, with and without the presence of extraneous noise sources, are used to illustrate the ease and simplicity by which the instrument can be used in place of complex computing schemes, which tend, in consequence, to be solely of local academic interest.

The practical features of the thesis have led to the submission of four papers to the technical press. Two of them deal, exclusively, with a capacitor ratio commutated filter – not apparently described in publications to date - which is also the subject of a proposed patent application in conjunction with NRDC. It is intended, in the near future, to submit the complete instrument as the basis for a second patent proposal.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TJ Mechanical engineering and machinery
Library of Congress Subject Headings (LCSH):	Transfer functions, Transfer functions
Official Date:	1971
Dates:	Date Event 1971 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Hughes, M.T.G.
Sponsors:	Science Research Council (Great Britain)
Extent:	118 leaves
Language:	eng

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