Three-dimensional optimal impact time guidance for antiship missiles

Introduction: The primary objective of missile guidance laws is to drive the missile to intercept a specific target with zero miss distance. Proportional navigation guidance (PNG) has been proved to be an efficient and simple guidance algorithm for missile systems, thus showing wide applications in the past few decades [1]. The optimality of PNG was analyzed in [2] and its extension to three-dimensional (3D) scenario can be found at [3]. In the context of modern warfare, many high-value battleships, like destroyers and aircraft carriers, are equipped with powerful self-defense systems against anti-ship missiles [4]. In order to penetrate these formidable defensive systems, the concept of salvo attack or simultaneous attack was introduced: many missiles are required to hit a battleship simultaneously, albeit their di.erent initial locations. One typical solution of simultaneous attack is impact time control guidance. Generally, impact time control can be classified into two categories: (1) specify the desired impact time and control each missile to satisfy the desired impact time constraint individually; and (2) synchronize the impact time either in a distributed or decentralized fashion through a communication network among all interceptors

Optimal proportional-integral guidance with reduced sensitivity to target maneuvers

This paper proposes a new optimal guidance law based on proportional-integral (PI) concept to reduce the sensitivity to unknown target maneuvers. Compared to existing PI guidance laws, the proposed guidance command is derived in the optimal control framework while guaranteeing finite time convergence. The kinematics equation with respect to the zero-effortmiss (ZEM) is utilized and the integral ZEM is augmented as a new system state. The proposed guidance law is derived through the Schwarz's inequality method. The closed-form solution of proposed guidance law is presented to provide better insight of its properties. Additionally, the working principle of the integral command is investigated to show why the proposed guidance law is robust against unknown target accelerations. The analytical results reveal that the proposed optimal guidance law is exactly the same as an instantaneous direct model reference adaptive guidance law with a pre-specified reference model. The potential significance of the obtained results is that it can provide a point of connection between PI guidance laws and adaptive guidance laws. Therefore, it allows us to have better understanding of the physical meaning of both guidance laws and provides the possibility in designing a new guidance law that takes advantages of both approaches. Finally, the performance of the guidance law developed is demonstrated by nonlinear numerical simulations with extensive comparisons

Optimal impact angle guidance for exo-atmospheric interception utilizing gravitational effect

This paper aims to develop a new optimal intercept angle guidance law for exo-atmospheric interception by utilizing gravity. A finite-time optimal regulation problem is formulated by considering the instantaneous zero-effort-miss (ZEM) and the intercept angle error as the system states. The analytical guidance command is then derived based on Schwarz's inequality approach and Lagrange multiplier concept. Capturability analysis using instantaneous linear time-invariant system concept is also presented to provide better insights of the proposed guidance law. Theoretical analysis reveals that the proposed optimal guidance law encompasses previously suggested optimal impact angle constrained guidance laws. Numerical simulations with some comparisons clearly demonstrate the effectiveness of the proposed guidance law

Gravity-turn-assisted optimal guidance law

This paper proposes a new optimal guidance law that directly uses (instead of compensating for) gravity for accelerating missiles. The desired collision triangle that considers both gravity and the vehicle’s axial acceleration is analytically derived based on geometric conditions. The concept of instantaneous zero-effort-miss is introduced to allow for analytical guidance command derivation. By formulating a finite time instantaneous zero-effort-miss regulation problem, the proposed optimal guidance law is derived through Schwarz’s inequality approach. The relationships of the proposed formulation with conventional proportional navigation guidance and guidance-to-collision are analyzed, and the results show that the proposed guidance law encompasses previously suggested approaches. The significant contribution of the proposed guidance law lies in that it ensures zero final guidance command and enables energy saving with the aid of using gravity turn. Nonlinear numerical simulations clearly demonstrate the effectiveness of the proposed approach

Effectiveness of different resuscitation methods for severe uncontrolled hemorrhagic shock in a dog model

Purpose: To compare the effects of pituitrin resuscitation, hypertonic saline resuscitation and limited fluid resuscitation on a novel dog model of severe uncontrolled hemorrhagic shock (UCHS). Methods: Severe UCHS was produced in healthy Chinese dogs (n = 24) using a standard method. The hemorrhaged dogs were randomly divided into three groups of 8 dogs each: vasopressin group (group A), hypertonic saline group (group B), and low-volume fluid resuscitation group (group C). Group A received pituitrin at an initial dose of 0.1U/kg intravenously, which was thereafter reduced to 0.04 U/kg/min. Group B dogs received 7.5 % hypertonic saline (6 mL/kg), while dogs in group C were treated with 6 % hydroxyethyl starch (HES) 200/0.5. Mean arterial pressure (MAP) of the dogs was maintained between 50 and 55 mmHg, and after 1 h, full-volume resuscitation was administered. Hemodynamic parameters, blood gas, levels of inflammatory factors and blood loss were assessed at different time points. Results: Compared with group A, hemodynamic parameters in group B were higher; hematocrit of group B was lower; IL-10 of groups B and C were reduced, but TNF-α, TNF-α/IL-10 and ACTH were elevated (p < 0.05). Relative to group C, base deficits in groups A and B were low. During uncontrolled hemorrhage phase, blood loss in group B was higher than that in other groups (p < 0.05). Conclusion: The results obtained in this study suggest that pituitrin resuscitation produces relatively optimal effect through effective maintenance of coronary perfusion pressure (CPP) and reduction of inflammatory responses

Integral global sliding mode guidance for impact angle control

This Correspondence proposes a new guidance law based on integral sliding mode control (ISMC) technique for maneuvering target interception with impact angle constraint. A time-varying function weighted line-of-sight (LOS) error dynamics, representing the nominal guidance performance, is introduced first. The proposed guidance law is derived by utilizing ISMC to follow the desired error dynamics. The convergence of the guidance law developed is supported by Lyapunov stability. Simulations with extensive comparisons explicitly demonstrate the effectiveness of the proposed approach

Optimal active target localisation strategy with range-only measurements

This paper investigates the problem of one-step ahead optimal active sensing strategy to minimise estimation errors with range-only measurements for non-manoeuvring target. The determinant of Fisher Information Matrix (FIM) is utilized as the objective function in the proposed optimisation problem since it quantifies the volume of uncertainty ellipsoid of any efficient estimator. In consideration of physical velocity and turning rate constraints, the optimal heading angle command that maximises the cost function is derived analytically. Simulations are conducted to validate the analytical findings