Three-Dimensional Nonlinear Impact Time Guidance for Stationary Targets

This work addresses the problem of designing an impact time constrained guidance strategy for three-dimensional engagements, without decoupling the engagement dynamics in two mutually orthogonal planes. The guidance command is derived while considering nonlinear engagement dynamics, and with a time-to-go prediction that accounts for the interceptor's heading error. Power rate reaching law is used while designing sliding mode guidance strategy, since this law offers inherent robustness, smooth control and finite-time convergence to the sliding manifold. Further, the interceptor lateral acceleration components are obtained using a control allocation technique, that minimizes the instantaneous lateral acceleration, which aids in minimizing the total drag during interceptor's flight. Conditions for the interceptor to reach the collision course are derived and analyses are presented. Finally, simulations are provided to demonstrate the efficacy of the proposed guidance scheme.