Accessibility Analysis and Robust Control Design of Dual-Spin Projectiles

The present work deals with accessibility analysis and robust controller design of dual-spin projectiles (DSPs). Applying linear controllability checks to a nonlinear system by linearizing about the operating points may prove inconclusive while examining the controllability of the system because such checks specify only the sufficient conditions for controllability. Thus, tools based on differential geometry have to be used to assess the controllability of nonlinear systems. One such tool is the Lie algebraic rank condition, used in the accessibility analysis of a system. In this study, the accessibility analysis is carried out for three different configurations of DSPs: the skid-to-turn (STT), the bank-to-turn (BTT), and the precision guidance kit (PGK). The analysis reveals the inaccessibility of the PGK configuration. Consequently, the controllers are designed for the STT and BTT configurations. A robust pitch/yaw autopilot is designed based on Lyapunov theory and a roll autopilot is designed based on robust backstepping. The efficacy of the designed controllers to intercept the target and handle uncertainties in the initial conditions and aerodynamic coefficients is validated through simulations. The results are compared for the STT and BTT configurations, and the equivalency of the dynamics of the two configurations is proven.