Bi-Normal Coordinates in Discrete Systems with Application to an Aircraft Shimmy Problem.
AIR FORCE FLIGHT DYNAMICS LAB WRIGHT-PATTERSON AFB OHIO
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The use of bi-normal coordinate theory in the analysis of practical discrete systems provides the substantial benefits of conceptual valuephysical insight, computational utility, and enhanced redesign capability. These benefits are explained and demonstrated in the present effort with attention to practical considerations. Section 1 extends the theory and presents the new material together with some previously available results in a coordinated manner. In particular, the nature of response in a single homogenous phasor mode is described in detail. Also, an expression for the derivative of an eigenvalue is developed and explained. Section 2 reports the analysis of an aircraft nosegear shimmy problem using bi-normal coordinate methods. Stability boundaries, mode shapes, and sensitivities to parameter changes are presented. Derivatives of eigenvalues are used in Section 3 to illustrate automated minimum weight design for a shimmy-free nosegear. Recommendations for further research are made. Author