A study of piezoelectric transducers in application to active control of reciprocating compressor noise

Fumin Pan, Purdue University

Abstract

The objective of this thesis was to study the feasibility of using piezoelectric transducers in application to active control of compressor noise. A uniformly thin spherical shell was utilized to represent the hermetic shell and an annular space within two concentrically spherical shells was employed to model the gas cavity inside the test compressor. The analytically predicted mode shapes and natural frequencies were found to be in good agreement with experimental measurements. While comparing the analytical prediction and experimental data, it was found that the sound radiation from the top of the test compressor could be best represented by the circular plate model. The shape, size, location, thickness and material properties of piezoelectric actuators and sensors were studied to maximize the modal force and the developed charge. Based on these results, a circular disk-shaped piezoelectric actuator was selected for implementation. Three potential control algorithms were employed, according to the noise spectrum and dynamic characteristics of the test compressor. Due to unstable motor speed associated with motor slippage, the performance of the filtered-x LMS control algorithm showed that only minor noise reduction occurred at some discrete frequencies. A robust feedback controller was designed by loop-shaping the open-loop system transfer function to satisfy a stability criterion. Simulation results showed that a global reduction of about 3 to 5 dB could be expected with this robust feedback controller. Based on the special characteristics of piezoelectric materials, the surface-bonded piezoelectric patch could be employed as an actuator and a sensor simultaneously. Experimental results showed that compressor noise reduction only occurred at discrete frequencies but could not be audibly discerned. Further study of the simply-supported plate showed that this collocated actuator/sensor approach is suitable for applications with low structural density.

Degree

Ph.D.

Advisors

Jones, Purdue University.

Subject Area

Mechanical engineering|Industrial engineering

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