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In this article, a nonlinear three-dimensional guidance strategy for multiple identical constant speed interceptors is proposed to capture a stationary target simultaneously. To design this proposed guidance strategy, a proportional navigation based time-to-go estimate, without any small angle assumption, is used. Based on the maximum value of time-to-go estimates of all interceptors, the range error for each interceptors is computed. Sufficiency conditions for simultaneous capture are satisfied by ensuring the range errors and their rates converge to zero for all interceptors. The proposed guidance strategy employs Lyapunov and sliding-mode control-based techniques to achieve these sufficiency conditions. Simulation studies demonstrate that this proposed strategy performs satisfactorily for various geometric engagements and in the presence of a first-order autopilot. [ABSTRACT FROM AUTHOR]

In this paper, sliding mode control-based impact time guidance laws are proposed. Even for large heading angle errors and negative initial closing speeds, the desired impact time is achieved by enforcing a sliding mode on a switching surface designed by using the concepts of collision course and estimated time-to-go. Unlike existing guidance laws, the proposed guidance strategy achieves impact time successfully even when the estimated interception time is greater than the desired impact time. Simulation results are also presented. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear suboptimal three-dimensional guidance strategy based on a finite-time state-dependent Riccati equation technique is proposed to achieve interception of a non-maneuvering target at a desired impact time. To design the proposed guidance, range error for a spatial engagement between an interceptor and non-maneuvering target is introduced as the difference between the desired range-to-go and range-to-go of the predicted interception point. It is shown that forcing the range error and its rate to the origin are sufficient to achieve impact time constrained interception. Several existing impact time guidance strategies require a time-to-go estimate, to implement their guidance command, which may become erroneous in the presence of measurement noise and affect their performance. However, the proposed guidance does not require any such time-to-go estimate in its design process. Furthermore, guidance for the case of planar engagements is shown to be a special case of the proposed guidance scheme. Finally, numerical simulation studies for multiple engagement geometries, along with a comparison study with an existing strategy, are provided to demonstrate the efficacy of the proposed technique. [ABSTRACT FROM AUTHOR]