High fidelity moment of inertia testing of unmanned aircraft

Knowledge of moment of inertia data for an aircraft is critical for both aircraft analysis as well as model development for control. There have been a variety of different methods employed to measure moment of inertia including: physical pendulums, bifilar pendulums, compound pendulums, torsional pendulums, and torque. The accuracy of the moments of inertia determined using these methods depend upon a variety of factors, such as friction, drag, and vibrations. These contributions can be significant, as errors due to drag can increase quadratically with velocity and errors due to friction can increase as mass is added to the system. This paper seeks to build upon previous moment of inertia measurement techniques by considering the effects of drag on experimental measurements. A torque-based moment of inertia testing rig was fabricated in house, made up of a4x6x6ftsteel framework and a pulley torque system. The testing rig allows for quick and reliable measurement with minimal error. Validation was performed using a series of bars to quantify how much error is expected and then using a flat plate to demonstrate that drag is negligible. Finally, the testing rig was used to measure the moment of inertia of two unmanned aircraft.