Sequential Application of a Third-Order Test Design in Six Dimensions Incorporating an Orthogonality Constraint

• Activity Number: 189
• Type: Invited
• Date/Time: Monday, August 2, 2010 : 10:30 AM to 12:20 PM
• Sponsor: Section on Physical and Engineering Sciences
• Author(s): William Line*+ and Mike Morton and Norman Draper
• Companies: DOES Institute and DOES Institute and University of Wisconsin-Madison
• Keywords: Sequential Test Design ; Third Order Test Design ; Orthogonality Constraint ; Six Dimensions ; NASA wind tunnel application ; Cost Savings

Abstract

The Wrights used the 1st wind tunnel balance in 1903. This paper shows a designed test in 2000 on a NASA wind tunnel balance calibration application. Previously NASA used the one factor test method to calibrate balances. Both methods were tested on the same balance. Compared to the one-factor method, the designed test reduced costs by 85% and improved data quality. NASA patented this work, though they usually make innovations public domain. The 3 Force and and 3 moment balance dimensions must be orthogonal because of interaction effects. This constraint was satisfied by crossing a 3-variable design with a 2-variable design. In aersospace work, 2nd order models are often insufficient when there is lack of fit. A sequential design was needed whereby a 3rd order design was added to the 2nd order design. The ANOVA tables, 2nd and 3rd order test designs, and confounded terms will be shown.