Abstract: A modified theoretical model is developed to analyze the limiting conical motion characteristics of rotary fin-stablized projectiles. The amplitude plane equation of projectiles in the state of quasi-circular motion is expanded as Taylor series, by which the value change of the square-root term in the amplitude plane equation is fully considered. The existence and stability of the nonzero singular points for the amplitude plane equation are analyzed comprehensively according to the different parameter values. The analytic criteria are presented, which present the necessary conditions for the formation of stable conical motion under the action of nonlinear static moment and nonlinear Magnus moment. Furthermore, two condition expressions denoted as J₁>0 and J₂>0, which just relate to the initial parameters of the angle-of-attack equation, are claimed as the comprehensive criterions in this paper and are used for the primary analysis of conical motion stability. Finally, a rotary fin-stablized projectile with known aerodynamic and structural parameters is taken as an example to verify the theoretical critera. The results indicate that the stability criteria for the limiting Conical Motion of rotary fin-stablized projectiles proposed in this paper are more comprehensive and explicit than those of the current theory. Based on the proposed criteria, the characteristics of limiting conical motion can be analyzed and estimated conveniently and effectively. Key

Key words: limitingconicalmotion, nonlinearmotion, Magnusmoment, motionstability, Taylorexpansion