Coupling analysis and dynamic stability boundary of spinning missiles considering actuator dynamics and autopilot

This paper focuses on coupling property and dynamic stability of spinning missiles equipped with a two-loop autopilot. The closed-loop characteristic equation is established in the complex form, on which we investigated the dominant factors of the cross coupling, i.e., actuator dynamics, airframe configuration and autopilot, to provide physical understandings of coupling property. By coupling analysis, it is found that coupling can be mitigated by the autopilot. However, the proposed static decoupling approach is necessary to eliminate steady coupling completely. Furthermore, by solving the forth-order characteristic equations with Cardan formula, the dynamic stability boundary is derived numerically. As actuator dynamics is extremely significant to stability, the proposed stability boundary is derived with consideration of it, and thus, it is more practical than results in previous studies. The effectiveness of decoupling method and the correctness of dynamic stability boundary is verified by mathematical simulations. Theoretical and numerical results also reveal that high actuator bandwidth and less time delay is beneficial to dynamic stability.