Stochastic two-target pursuit-evasion differential games in the plane

A stochastic version of a two-target homicidal chauffeur, pursuit-evasion differential game (using polar coordinates) is considered. This is used to model a dogfight between a very agile playerQ and a less maneuverable playerP. First, the case where both players have complete observation of the state of the game is considered. A numerical study is conducted, by solving numerically a nonlinear partial differential equation on a torus in ², to investigate the role of the parameters of speed, maneuverability, and performance of the weapon systems, in the encounter. Second, the model is extended to include the case where playerP is jamming playerQ's measurements of , where denotes the bearing ofQ fromP. A numerical study is conducted, by solving numerically a nonlinear partial differential equation on a generalized torus in ³, to investigate the role of the jamming parameter on the outcome of the combat.     

A pursuit-evasion differential game with noisy measurements of the evader's bearing from the pursuer

A stochastic pursuit-evasion differential game involving two players, E and P, moving in the plane is considered. It is assumed that player E (the evader) has complete observation of the position and velocity of player P, whereas player P (the pursuer) can measure the distanced (P, E) between P and E but receives noise-corrupted measurements of the bearing of E from P. Three cases are dealt with: (a) using the noise-corrupted measurements of , player P applies the proportional navigation guidance law; (b) P has complete observation ofd (P, E) and (this case is treated for the sake of completeness); (c) using the noise-corrupted measurements of , P applies an erroneous line-of sight guidance law. For each of the cases, sufficient conditions on optimal strategies are derived. In each of the cases, these conditions require the solution of a nonlinear partial differential equation on a in ². Finally, optimal strategies are computed by solving the corresponding equations numerically.     

Singular surfaces in a linear pursuit-evasion game with elliptical vectograms

In a linear pursuit-evasion game with elliptical vectograms, singular surfaces appear in the plane of symmetry containing the ellipses minor axes and, as a consequence, locally nonsmooth isocost tubes are generated. Both dispersal and attractive focal surfaces are encountered. The dispersal surface is a zone of initial conditions for trajectories leaving the plane of symmetry. Optimal trajectories attracted by the focal surface merge tangentially to the plane of symmetry and remain there until the boundary of the dispersal zone is reached. Determination of the saddle-point strategies in the focal surface leads to constructing the isocost surfaces in the entire game space.     

Planar pursuit-evasion with variable speeds,part 2, barrier sections

An iterative method of constructing sections of the game surfaces from the players' extremal trajectory maps is discussed. Barrier sections are presented for aircraft pursuit-evasion at constant altitude, with one aircraft flying at sustained speed and the other varying its speed.     

Planar pursuit-evasion with variable speeds,part 1, extremal trajectory maps

Pursuit evasion in a plane is formulated with both players allowed to vary their speeds between fixed limits. A suitable choice of real-space coordinates confers open-loop optimality on the game. The solution in the small is described in terms of the individual players' extremal trajectory maps (ETM). Each map is independent of role, adversary, and capture radius. An ETM depicts the actual real-space trajectories. A template method of generating constant control arcs is described. Examples of ETM for an aircraft flying at a constant altitude with fixed and varying speeds are presented.     

A stochastic homicidal chauffeur pursuit-evasion differential game

A certain stochastic pursuit-evasion problem of the homicidal chauffeur type is considered. The pursuer strategy synthesized in this paper is fairly simple in contrast to the less straightforward swerve maneuver employed in the deterministic model. The analysis may partially explain why relatively simple pursuit strategies are apparently always adopted in practice.This work was partially supported by a grant from Control Data.The authors wish to thank Dr. D. H. Martin for a very enlightening discussion.     

On-line solution of a stochastic pursuit-evasion game

In this paper, the concepts of prior-commitment and delayed-commitment strategies for zero-sum, linear-quadratic differential games with noise-corrupted measurements are applied to a detailed example of a pursuit-evasion game. Quasilinearization is used to solve the nonlinear two-point boundary-value problem of the prior-commitment game. A closed form solution is obtained for the delayed-commitment strategies. Comparison of the payoff functionals confirms the relationships discussed in Ref. 1.     

A differential game with two pursuers and one evader

This paper is concerned with a coplanar pursuit-evasion problem in which a faster evaderE with constant speedw>1 must pass between two pursuersP ₁,P ₂ having unit speed, the payoff being the distance of closest approach to either one of the pursuers. The control variables are the directions of the velocities ofP ₁,P ₂, andE. The path equations are integrated, and a closed-form solution is obtained in terms of elliptic functions of the first and second kind. A closed-loop solution is given graphically in several diagrams, for different values ofw.     

Existence of value in pursuit-evasion games with restricted phase coordinates

Almost all results referring to the problem of the existence of a value in differential games concern games without restricted phase coordinates. In this paper, we introduce a concept of value for differential games of pursuit and evasion and prove, under some general assumption, the existence of it. The players are required to satisfy some general phase constraints. The arguments employed in this paper are based on some extent on Krasovskii's method of extremal construction. We also show that the lower value in the Friedman sense is a generalization of our value. In a special linear case, the equivalence between pursuit differential games and time-optimal control problems is established.     

Approximate solution of singularly perturbed nonlinear pursuit-evasion games

A methodology to obtain an approximate solution of a singularly perturbed nonlinear differential game is presented. The outcome of the game with approximate strategies, defined as extended value, is related to the saddle-point value of the game. In an example of a simple pursuit-evasion game, it is shown that the proposed methodology leads to an easily implementable feedback form solution with fairly accurate results. This approach seems to be attractive for analyzing realistic air-combat models without solving a two-point boundary-value problem.This research was partially supported by AFSC Contract No. F-49620-79-6-0135. The authors are grateful to Prof. J. V. Breakwell for encouraging the approach taken in this research. Thanks are also due to Dr. S. Gutman and Dr. J. Lewin for their useful comments.     

A basic searchlight game

A searchlight game is a two-person zero-sum dynamic game of the pursuit-evasion type in which at least one of the two players has a searchlight. A searchlight can be flashed a given number of times within a fixed time period and the objective is to catch the opponent in the region illuminated by the flash. Olsder and Papavassilopoulos instituted the study of these games and, in this paper, we supplement their results, obtaining a closed formula for the value and optimal strategies for the players in their basic game.     

Approximate solution of singularly perturbed nonlinear pursuit-evasion games

Several errors in Ref. 1 are corrected.     

The gold-mine game

The paper considers the following two-person zero-sum game. The minimizing player chooses to hide his gold and a mine in two distinct boxes from an infinite number of boxes labelled 1, 2, 3,.... The maximizing player now chooses to open the boxes in some order, and if he finds the gold before the mine the payoff to him is 1; otherwise, the payoff is zero. The game is solved in the sense of Kindler.     

Complex differential games of pursuit-evasion type with state constraints,part 1: Necessary conditions for optimal open-loop strategies

Complex pursuit-evasion games with state variable inequality constraints are investigated. Necessary conditions of the first and the second order for optimal trajectories are developed, which enable the calculation of optimal open-loop strategies. The necessary conditions on singular surfaces induced by state constraints and non-smooth data are discussed in detail. These conditions lead to multi-point boundary-value problems which can be solved very efficiently and very accurately by the multiple shooting method. A realistically modelled pursuit-evasion problem for one air-to-air missile versus one high performance aircraft in a vertical plane serves as an example. For this pursuit-evasion game, the barrier surface is investigated, which determines the firing range of the missile. The numerical method for solving this problem and extensive numerical results will be presented and discussed in Part 2 of this paper; see Ref. 1.This paper is dedicated to the memory of Professor John V. Breakwell.The authors would like to express their sincere and grateful appreciation to Professors R. Bulirsch and K. H. Well for their encouraging interest in this work.     

A markov chain game with dynamic information

Two players, not knowing each other's position, move in a domain and can flash a searchlight. The game terminates when one player is caught within the area illuminated by the flash of the other. However, if this first player is not in this area, then the other player has disclosed his position to the former one, who may be able to exploit this information. The game is considered on a finite state space and in discrete time.The work of the second author was supported by ZWO, The Netherlands Organization for the Advancement of Pure Research, Contract No. B62-239, by the US Air Force Office of Scientific Research, Grant No. AFOSR-85-0245, and by the National Science Foundation, Grant No. NSF-INT-8504097.Visiting Professor at Delft University of Technology during 1986.     

A multistage game with incomplete information requiring an infinite memory

This paper describes a zero-sum, discrete, multistage, time-lag game in which, for one player, there is no integerk such that an optimal strategy, for a new move during play, can always be determined as a function of the pastk state positions; that is, the player requires an infinite memory. The game is a pursuit-evasion game with the payoff to the maximizing player being the time to capture.This paper is the result of work carried out at the University of Adelaide, Adelaide, Australia, under an Australian Commonwealth Postgraduate Award.The author should like to thank the referee for his valued suggestions.     

Saddle-point equilibrium sequence in one class of singular infinite horizon zero-sum linear-quadratic differential games with state delays

ABSTRACT

We consider an infinite horizon zero-sum linear-quadratic differential game with state delays in the dynamics. The cost functional of this game does not contain a control cost of the minimizing player (the minimizer), meaning that the considered game is singular. For this game, definitions of the saddle-point equilibrium and the game value are proposed. These saddle-point equilibrium and game value are obtained by a regularization of the singular game. Namely, we associate this game with a new differential game for the same equation of dynamics. The cost functional in the new game is the sum of the original cost functional and an infinite horizon integral of the square of the minimizer's control with a small positive weight coefficient. This new game is regular, and it is a cheap control game. An asymptotic analysis of this cheap control game is carried out. Using this asymptotic analysis, the existence of the saddle-point equilibrium and the value of the original game is established, and their expressions are derived. Illustrative example is presented.     

On a square haystack game

A haystack game is a hider-seeker zero-sum game of locating a needle in a haystack. Baston and Bostock have obtained partial solutions to this game for the case of a square haystack. This paper supplements their results, thus confirming their belief that a complete solution is difficult.The author would like to thank a referee for his helpful comments, in particular for suggesting Lemma 2.1 which has led to a more concise and transparent treatment of Section 2.     

Analysis of a combat problem: The turret game

The turret game is defined and solved to illustrate the nature of games of combat. This game represents a highly simplified version of air combat, yet it is sufficiently complex so as to exhibit a rich variety of combat phenomena. A review of the formulation of -combat games is included in this paper.on sabbatical leave from Technion, Israel Institute of Technology, Haifa, Israel.     

Role of information in the stochastic zero-sum differential game

In this paper, a linear-quadratic Gaussian zero-sum differential game is studied. Maneuverability is defined to measure players' strength. It is shown that a more maneuverable player would prefer a more observable information system. An example is given to show that a more controllable player might not prefer more observable measurements in the stochastic environment.The research reported in this paper was made possible through support extended to the Division of Engineering and Applied Physics, Harvard University, by the US Office of Naval Research under the Joint Services Electronics Program by Contract No. N00014-75-c-0648 and by the National Science Foundation under Grant No. GK31511.