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Meeting	ACGS Committee Meeting 117 - Napa, CA - March 2016
Agenda Location	4 GENERAL COMMITTEE TECHNICAL SESSION 4.2 Research Institutions, Industry, and University Reports 4.2.3 Universities 4.2.3.1 Ohio State University
Title	Ohio State University
Presenter	Rama Yedavalli
Available Downloads*	presentation
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Abstract	In the new research being carried out by Yedavalli at The Ohio State University, considerable insight is being gained by the role of elemental sign structure on the Hurwitz stability of linear state space systems. Typically, engineers are used to analyze the dynamic stability of linear state space systems by eigenvalue/eigenvector methods which are essentially quantitative based with little attention paid to the details of the role played by signs only information of the elements of the real square matrix representing a linear state space system. This type of Qualitative (sign only) stability analysis is carried out extensively by ecologists and economists. In this research, we borrow from the principles of ecology and highlight the importance of the elemental sign structure on the Hurwitz stability/instability of real matrices. In this presentation, we apply these new research results specifically to aircraft linear dynamics and point out how the importance of various stability derivatives can be ranked from stability and robustness point of view. The results indicate that in the aircraft longitudinal dynamics, it can be easily established that the most important stability derivative is the rate of change of pitching moment with respect to the pitch angle, whose sign has profound effect on the dynamic motion of the aircraft. Then the rate of change of drag with respect to the speed, the rate of change of lift with respect to lift and so on become important. It is also established that the rate of change of drag with respect to pitch angle and the rate of change of lift with respect to pitch angle are the least important compared to other stability derivatives. This type of analysis is deemed highly useful in the design of flight control systems.