Date of Award

Summer 2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Drew Landman

Committee Member

Onur Bilgen

Committee Member

Colin Britcher

Committee Member

Sean Commo

Call Number for Print

Special Collections; LD4331.E56 T67 2013

Abstract

The In-situ Load System (ILS) was designed at NASA Langley Research Center (LaRC) to perform multi-component check loads on a force balance at a test facility. The ILS is designed to allow a force balance to be placed at off nominal orientations, while maintaining an applied load in the gravitational direction. This allows for multicomponent loads to be applied to a balance as a function of balance orientation and ILS configuration. The system is designed to be used in conjunction with a facilities existing pitch and roll control systems.

The ILS was modified to provide higher load ranges than those permissible on the original design. The modification allowed movement of the load application point in two dimensions. These modifications allow the ILS to generate close to full scale moments and a greater load combination range than the original design. The modifications facilitated exercising a balance over larger load ranges, hence improving the effectiveness of a check load or calibration schedule. Stress analyses were performed to ensure that structural integrity was not compromised by the modifications.

A tare method was implemented to remove the loads generated by the unloaded ILS system. The method uses unloaded points that straddle a loaded data point, resulting in reduced experimental time due to the lack of pre- and post-test tare schedules. A regression on the unloaded data was created using the g-vector output from the angle measurement system (AMS) as well as a multiple linear regression.

Several sets of experiments were conducted on the ILS to evaluate the system's performance to applied known loads. The results from the experiments provided mixed results of the systems performance. Several results showed that the system can replicate a given load within acceptable uncertainty bounds for several of the load components. Conversely the total calculated load, the root sum squared of the force components, was found to be on average 2.5 pounds higher than was expected.

A Monte Carlo simulation was conducted to investigate the effect of a small change in the calibration coefficients. The simulation assumed that the standard deviations of the calibration coefficients and the primary sensitivities are a percentage of their estimated values. The simulation has shown that small changes in the primary sensitivities can lead to significant changes in the estimated load. It was also shown that small changes in the interaction calibration coefficients do not to have a significant change on the estimated load compared to the primary sensitivities.

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DOI

10.25777/s3j6-9k49

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