M.Sc Student | Taub Ilan |
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Subject | Optimal Trajectory Shaping Guidance of Time-Varying Acceleration-Constrained Missiles |

Department | Department of Aerospace Engineering |

Supervisor | Professor Tal Shima |

Full Thesis text |

In the following thesis we address
the problem of shaping the trajectory of a missile, subject to a varying
lateral acceleration constraint, in order to obtain a maximal acceleration
margin and avoid entering no-capture zones. The specific problem at hand is of
an interceptor with imperfect dynamics intercepting a moving and maneuvering
target at a predetermined terminal intercept angle. The problem is treated with
the aid of linear quadratic optimization, where the varying acceleration
constraint is assumed to be a function of time. 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, where the guidance gains are calculated by a predicted time-to-go,
and the other for the autopilot dynamics, where the gains are obtained by a
real-time time-to-go calculation, resulting in a sub-optimal guidance law. The
performance of the proposed law is investigated using nonlinear planar
simulation, for a missile with 1^{st} order autopilot dynamics.