The software package BALFIT was developed for both the processing of wind tunnel strain-gage balance data and the analysis of more general multivariate experimental data sets. The software uses automatically generated regression models for the analysis. These optimized regression models are the result of the application of a math model search algorithm to a given multivariate data set. This important feature of BALFIT greatly reduces the time it takes to do an analysis. It has also made the prediction of the dependent variable values more reliable because widely accepted objective metrics are used for the regression model term selection.

BALFIT supports both the Iterative and Non-Iterative Strain-Gage Balance Data Analysis approaches that are used in the aerospace testing community for the processing of wind tunnel balance data. More general multivariate data sets can also be analyzed by using the software’s Classical Regression Analysis mode. All three regression analysis types are accessed using an easy-to-use graphical user interface. The software has expert-system-like characteristics that detect formatting errors in data input files and provide debugging advice whenever an analysis fails. In addition, a detailed analysis report in PostScript format is generated after the completion of an analysis. This report lists all input data and input choices, documents the most important analysis steps, and supports the final analysis results.

The software was written in the IDL programming language. Its executable can be run on the Macintosh or the Windows operating system using a free runtime utility called the IDL Virtual Machine. A complete set of documentation supports both implementation and use of the BALFIT software. It consists of a Reference Guide, a User Guide, and Training Class Slides. In addition, an extensive library of tested input file templates is supplied with the software that assists a user during the preparation of the input data. The software has also been put under configuration control.

This work was done by Norbert Ulbrich and Thomas Volden of Jacobs Technology Inc. for Ames Research Center. This software is available for use. To request a copy, please visit https://software.nasa.gov/software/ARC-15804-1A .

NASA Tech Briefs Magazine

This article first appeared in the May, 2016 issue of NASA Tech Briefs Magazine.

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