Date on Master's Thesis/Doctoral Dissertation

8-2017

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Electrical and Computer Engineering

Degree Program

Electrical Engineering, PhD

Committee Chair

McIntyre, Michael

Committee Member

Naber, John

Committee Member

Inanc, Tamer

Committee Member

Richards, Chris

Author's Keywords

compressors; electric machines; nonlinear controls; observers

Abstract

Linear vapor compressors have become widely investigated for refrigeration applications due to their high efficiency in comparison to the more common rotary type compressors. However, the nature of the linear compressor adds complexity to the control of these machines. The unconstrained motion of the piston in a linear compressor allows for continuous modulation of the compressor output, but requires knowledge of the mechanical dynamics to effectively control the compressor and prevent collision of the piston with the cylinder head. This control is made more difficult by the highly nonlinear nature of the force of gas compression acting against the piston. As this gas force changes so does the resonant frequency of the system. Efficient control of the compressor requires knowledge and tracking of this resonant frequency in addition to other objectives. Sensorless control of the system is preferred for reliability, ease of production, and cost effectiveness. To this end a series of nonlinear observers and a combination of controllers have been developed for the linear vapor compressor.

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