Ground Vibration Testing of Very Flexible Aircraft

Student : Bilal Sharqi

Sponsor : Center for Unmanned Aircraft Systems (C-UAS)


Summary:

Ground Vibration testing (GVT) is a method for determining the modal parameters (frequencies, damping and mode shapes) of a structure. This data is used to compare, validate and update computational aeroelastic models for a structure. In this project, a Ground Vibration Test is being performed on the X-HALE testbed developed at the University of Michigan in the A2SRL lab.

A GVT is helpful in guaranteeing the aeroelastic and aeroservoelastic stability of new and untested aircraft.  Modifications made over the course of the X-HALE project also necessitate better validation and understanding of the analytical vibration and flight control modes. The goal is for the GVT to be used to assist in flutter testing and planning and for resolving in-flight aeroelastic related anomalies.

A very flexible craft like the X-HALE also exhibits non-linear coupling between the rigid body and elastic degrees of freedom, and validating the models developed in UM/NAST is necessary for effective design, simulation and control of such UAV.

The impact of different suspension conditions (effectively changing the shape of the UAV) is being studied and the RRV test vehicle (part of the X-HALE program) is being used as a testbed before eventually moving on to the fully instrumented UAV for further testing.

 

Figure 1: GVT Setup of the RRV suspended in the Outboard configuration
Figure 2: GVT Setup of RRV suspended in the inboard configuration