Modal Testing And Analysis Techniques And Their Application On A Small Uas

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

The Reduction of Modal Sensor Channels through a Pareto Chart Methodology

Presented herein is a new experimental sensor placement procedure developed to assist in placing sensors in key locations in an efficient method to reduce the number of channels for a full modal analysis. It is a fast, noncontact method that uses a laser vibrometer to gather a candidate set of sensor locations. These locations are then evaluated using a Pareto chart to obtain a reduced set of sensor locations that still captures the motion of the structure. The Pareto chart is employed to identify the points on a structure that have the largest reaction to an input excitation and thus reduce the number of channels while capturing the most significant data. This method enhances the correct and efficient placement of sensors which is crucial in modal testing. Previously this required the development and/or use of a complicated model or set of equations. This new technique is applied in a case study on a small unmanned aerial system. The test procedure is presented and the results are discussed