Date of Award

Summer 2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Colin P. Britcher

Committee Member

Robert Ash

Committee Member

Tian-Bing Xu

Committee Member

Mark Schoenenberger

Abstract

The purpose of this project was to improve an existing system currently in use by NASA Langley Research Center (LaRC). The 6-inch Magnetic Suspension and Balance System (MSBS) built at MIT is operational with control in three degrees of freedom, with two additional degrees of freedom exhibiting passive stability. The means for measuring model displacement within the magnetic environment is an Electromagnetic Position Sensor (EPS), consisting of excitation coils at 20 kHz and multiple sets of pickup coils. The pickup coil voltages are proportional to model displacement in each degree of freedom. However, the EPS electronic signal processing system is analog and outdated; setup and adjustment are time consuming. The task was to construct a one degree of freedom model of the EPS including its electronics system in order to explore digital signal processing. The model core is allowed only axial displacement for simplicity; this model coil set is essentially a Linear Variable Differential Transformer (LVDT). The source signal was chosen to be 2.36 kHz for convenience, with scaling up to the full size system at 20 kHz possible. An amplification and filtering circuit board was constructed to modify the signal for the proper functionality of the model EPS. By comparing the reference or excitation coil signal and the measured or pickup coil signal by means of a digital phase measurement method using cross-correlation analysis, the digital algorithm resolves the phase shift between the two signals and their amplitude ratio. The key proof of concept is the digital signal processing algorithm; since the defining characteristics of any signal are the amplitude and phase this algorithm can be adapted to suit various control and setup needs of the MSBS and EPS. By proving that a digital interface with the EPS is possible, the analog interface can be replaced with a digital system.

DOI

10.25777/zg4c-ye02

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