Doctoral Dissertations


"This dissertation describes the design and construction of a closed-loop computer controlled expansion system for a cloud simulation chamber. The chamber is used to simulate atmospheric phenomena for the study of microphysical processes. In order to accomplish this, the sample gas inside the chamber must be expanded adiabatically. This means the wall temperature and the gas temperature must be made to agree as closely as possible. The wall is cooled by thermoelectric modules, and the temperature is controlled by analog controllers. The gas is cooled by the adiabatic expansion, and the corresponding pressure is controlled by a laboratory minicomputer, a NOVA 840. The range of operation of the expansion system is specified to be 20.7 kPa (3 psi) change in pressure. The accuracy and the rms error must be better than ±0.0207 kPa (±0.003 psi) and 0.0414 kPa (0.006 psi), respectively. This range of operation is large enough that an analog controller can not obtain an adequate result. The error arises due to the fact that the input function is a ramp and the expansion system has multiple non-linearities.

In order to obtain zero steady state error, the time- optimal control is implemented by the minicomputer. Table look-up and on-line identification schemes for the system parameters have been investigated. An adaptive control algorithm using on-line identification outperforms the table look-up method due the flexibility of the identification scheme. Special efforts are made to adjust the identification scheme so that the model parameters converge close to the system parameters within one step. The results indicate that the closed-loop computer controlled expansion system yields the desired specification"--Abstract, pages ii-iii.


Fannin, D. Ronald

Committee Member(s)

Kassner, James L.
Kern, Frank J.
Pagano, Sylvester J., 1924-2006
Stigall, Paul D.
Richards, Earl F., 1923-


Electrical and Computer Engineering

Degree Name

Ph. D. in Electrical Engineering


United States. National Aeronautics and Space Administration


All the work was supported by the Cloud Physics Research Center and NASA, Grant Number NAS8-31849.


University of Missouri--Rolla

Publication Date



x, 78 pages

Note about bibliography

Includes bibliographic references (pages 73-77).


© 1978 Katiya Greigarn, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Thesis Number

T 4386

Print OCLC #


Electronic OCLC #