Kaci Lemler

Date of Award

January 2012

Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

William H. Semke


This thesis focuses on experimental structural analysis using contemporary testing techniques. This includes modal testing topics such as data acquisition, data processing, sensor placement, and multiple excitation methods. It also presents a novel sensor placing procedure that uses a laser vibrometer to identify key sensor locations. These techniques are applied in a case study on a small unmanned aerial system, (UAS). The airframe, the BTE Super Hauler, is a small UAS used by the Unmanned Aircraft Systems Engineering (UASE) Laboratory at the University of North Dakota as a test platform for flight testing multiple payloads. An antenna system, designed for use in sense and avoid applications, was developed that requires the addition of wing pods to the current airframe to minimize electro-magnetic interference from the engine of the UAS. Modal testing is used to determine the effect of two wing pods on the structural dynamic behavior of the UAS. Flutter analysis is also performed to ensure that the surface bending and torsional modes of the UAS do not create an unstable airframe.

Data acquisition was performed using ModalVIEW, a structural analysis program supported by LabVIEW. ModalVIEW outputs a frequency response function to which various windowing methods can be applied. The aircraft was excited both by an impact hammer and a shaker.

The new sensor placement procedure was developed to assist in placing sensors in key locations in an efficient method to reduce the number of channels needed. It is also a fast, non-contact method implementing a laser vibrometer. A statistical method was used to determine appropriate sensor locations.