Showing papers by "Tal Shima published in 2012"

Guidance Strategies Against Defended Aerial Targets

Abstract: The three-body engagement scenario is considered where an aerial missile, homing onto a target aircraft, encounters a defender missile launched by the aircraft. A given set of defender-missile guidance laws, namely, proportional navigation and line-of-sight guidance, are considered, and analysis is carried out for proportional navigation and pure pursuit attacking missile strategies. Analytic launch envelopes and lateral accelerations ratios for the four resulting scenarios are derived. Closed-form expressions for attackingmissile initial position and launch angles are derived for a successful evasion from the defender. Numerical simulations are carried out which comply with the analytical findings. The resulting launch envelopes are highly sensitive to the adversary’s guidance strategy, and thus, concerning practical implementation, a game theoretic analysis is carried out. Game solutions are obtained in pure and mixed strategies, resulting in the missile’s evasion probability envelope, that is, based on the four individual launch envelopes.

Exo-Atmospheric Guidance of an Accelerating Interceptor Missile

Abstract: An exo-atmospheric interception scenario between an accelerating missile and its target is investigated. It is assumed that the maneuvering acceleration is obtained by instantaneous rotation of the missile's body to the required attitude. Two different guidance laws are derived for such an interceptor using the sliding mode control methodology. The difference is in the definition of the sliding surface enforcing different trajectories for the interceptor. It is shown that if this surface is chosen as the zero-effort-miss of the well-known proportional navigation guidance law, then the missile is commanded to point its acceleration vector along the line-of-sight and consequently fly along a curved trajectory. For the second guidance law, a unique sliding surface is chosen enforcing the missile to fly on a straight line towards collision, after the initial heading error is nulled. The performance of the guidance laws is analyzed and compared using a nonlinear two dimensional simulation. It is shown that on top of enforcing a different flight geometry for the interceptor, the use of the new guidance to collision sliding mode guidance law can enhance the capture zone of the interceptor.

A Process Algebra Genetic Algorithm

Abstract: A genetic algorithm that utilizes process algebra for coding of solution chromosomes and for defining evolutionary based operators is presented. The algorithm is applicable to mission planning and optimization problems. As an example the high level mission planning for a cooperative group of uninhabited aerial vehicles is investigated. The mission planning problem is cast as an assignment problem, and solutions to the assignment problem are given in the form of chromosomes that are manipulated by evolutionary operators. The evolutionary operators of crossover and mutation are formally defined using the process algebra methodology, along with specific algorithms needed for their execution. The viability of the approach is investigated using simulations and the effectiveness of the algorithm is shown in small, medium, and large scale problems.

Formation-Flying Guidance for Cooperative Radar Deception

Abstract: teammates and their respective radar positions based on their individual transmitted constraints. All the information obtained in the decentralized individual messages was extracted and group coordination was obtained. The team coordination was shown to be maintained in presence of communication gaps. Numerical solution of the three-dimensional deception as a parameter optimization problem was described by Lee and Bang [6] and sample scenarios were presented. Therein the control input parameterization converts theoptimalcontrolproblemintotheparameteroptimizationproblem with inequality constraints. Xu and Basset [7] used bio inspired camouflagetechniquetosolvetheconstantspeedphantomtargetand maximumtimedeceptioncases.Thetechniquehighlightstheuseofa bio inspired approach to represent the model dynamics by a single degree of freedom vector and thus eases the optimization problem. By definition, each ECAV generates the phantom target along its line-of-sight(LOS)withrespecttotheengagedradar.Inotherwords, the ECAV is always positioned on the line joining the radar and

Cooperative Optimal Guidance Laws for Imposing a Relative Intercept Angle

Abstract: Optimal control-based cooperative guidance laws, which enforce at intercept a relative geometry in between a group of missiles and a single maneuvering target, are presented. An example scenario of interest is that of intercepting a high-value target (such as a ballistic missile) by a team of cooperating interceptors arriving from different directions. The problem is posed in the linear quadratic framework, and closed-form analytic solutions are obtained for any team size with any linear missile dynamics. The performance of the cooperative guidance laws is investigated using a nonlinear two-dimensional simulation of the missiles’ lateral dynamics and relative kinematics. It is shown that cooperatively imposing a relative intercept angle between the missiles provides substantially better results than when each missile independently enforces, using a one-on-one strategy, a preselected intercept angle that satisfies the relative intercept requirement. It is also shown that the missiles’ acceleration requirem...

Intercept Angle Missile Guidance under Time-Varying Acceleration Bounds

Abstract: A linear quadratic guidance law for a missile with a time varying acceleration constraint is presented. By introducing the constraint into the running cost, the optimization produces time varying gains that shape the missile’s trajectory for avoiding no-capture zones. The guidance law is derived for a missile with high-order autopilot dynamics and a terminal intercept angle constraint against a maneuvering target. The acceleration constraint of aerodynamic steering missiles is usually trajectory dependent rather than time dependent. Transforming the constraint into a time-dependent function by analytical means might not be possible, due to the nonlinear nature of the constraint. The problem is alleviated using a simple iterative calculation. For practical implementation reasons, and in order to improve the guidance performance under model uncertainties and disturbances, the guidance command is decomposed into two separate optimizations: one for the acceleration constraint, for which the guidance gains are...