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This article proposes a guidance strategy that enables the interceptor to control its impact time against stationary targets, while also meeting the field-of-view (FOV) constraints of the on-board seeker. The guidance strategy, so designed, always keeps the target within its FOV using its seeker. A barrier Lyapunov function is used to meet the FOV constraints, and an approximate expression for the interceptor's lead angle is obtained analytically. This facilitates the computation, as well as control, of impact time. The proposed guidance consists of two stages, with the former stage being deviated pursuit, while during the latter stage, the deviation angle or lead angle decreases to zero. This, in turn, ensures a zero terminal lateral acceleration. Furthermore, through a cooperative selection of tuning parameters, simultaneous interception of the target by multiple interceptors (also called salvo) can be achieved. Simulations, that are run for different engagement scenarios and with varying tuning parameters, vindicate the efficacy of the proposed strategy. [ABSTRACT FROM AUTHOR]

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]

This article proposes sliding-mode-control-based guidance strategies for a team comprised of aircraft and a defending interceptor against an attacker. The proposed guidance strategies are based on the line-of-sight guidance concept. Problems such as performance degradation under large heading angle errors, arising from linearization of engagement dynamics, are circumvented due to the nonlinear framework considered here. We show that knowledge of the bound on attacker acceleration suffices to ensure interception of an attacking interceptor. Cooperative strategies are derived for the aircraft–defender team, corresponding to cost functions based on the $\ell _p$ norm, using static optimization at each time instant. Simulations validate the efficacy of the proposed strategies. [ABSTRACT FROM AUTHOR]

This article proposes a leader–follower cooperative salvo guidance strategy to intercept nonmaneuvering targets by exploiting the advantages of supertwisting sliding mode control. An improved estimate of time-to-go, that does not assume interceptor's small heading angle, is used in the guidance design. This allows the guidance strategy to remain effective even for large initial heading of the interceptor. Under the action of supertwisting control, the error in impact time settles precisely to zero in finite time. The proposed guidance strategy provides robustness against uncertainties and a smooth control signal, along with finite-time convergence of error. The guidance performance has been shown for one-to-one engagement, and in a cooperative framework, to achieve a salvo in a predetermined time. Numerical simulations are presented for various engagement scenarios to aid the analysis, and illustrate the efficacy of the proposed guidance scheme, even under noisy environment. [ABSTRACT FROM AUTHOR]

This paper presents impact angle guidance based on finite-horizon robust optimal control. This approach, a fusion of newly proposed finite-time state-dependent Riccati equation and integral sliding-mode-control, solves finite-horizon tracking problem for input-affine nonlinear systems with specified terminal conditions. It also ensures robustness against external disturbances and uncertainties from beginning. The technique for ensuring specified final-time involves deriving closed-form control expression in terms of approximate solution of differential Riccati equation, which further reduces to solutions of algebraic Riccati and Lyapunov equations. This yields computationally efficient algorithm. To alleviate chattering, the supertwisting algorithm is incorporated with the proposed technique. Guidance strategy is derived after converting impact angle problem to tracking one using the proposed algorithm. Efficacy of the proposed guidance is vindicated for various engagement geometries, and also compared with an existing guidance strategy. [ABSTRACT FROM AUTHOR]

A cooperative salvo guidance strategy using fixed finite-time consensus is proposed here. The consensus algorithm is based on sliding mode control. The cooperative salvo attack problem is transformed to a consensus problem over a cycle digraph. This aids in designing a guidance strategy through selection of heterogeneous gains. The proposed strategy guarantees convergence to a common impact time for all the interceptors, within a fixed time, from a wide range of initial heading angles. Subsequently, the guidance strategy is extended to cooperatively intercept a constant velocity target. The efficacy of the proposed algorithm is vindicated through simulations on both stationary and constant velocity targets. Numerical simulations are also performed on realistic missile models that account for aerodynamic parameter variations, yielding satisfactory performance. [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]