Hybrid Computation of the Optimal Control for an Entry Vehicle With Three Degrees of Freedom.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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The mathematical model for the entry problem is developed and the hybrid computer solution for the optimal control is presented. Important characteristics of hybrid computation are discussed and related to their effect on the solution to the entry problem. Also, several programming techniques that were used to overcome simulation problems are explained. A right-circular cone is used to model the entry vehicle which has a single flap control. Five nonlinear differential equations that describe longitudinal planar motion along the entry trajectory are developed. The state equations were solved in parallel on digital and analog computers to simulate the vehicle entry while determining the optimal control. A conjugate gradient algorithm is used to determine the optimal flap control for vehicle entry along a trajectory that gives the maximum signal-to-noise ratio for an on-board guidance radar. An attitude, integral, inequality constraint is imposed by using an interior penalty method and a final altitude is defined by a terminal cost function. The advantages of hybrid computation that are illustrated by solution of the entry problem indicate its potential role in solving technical problems in the future. Extension of the problem to six degrees of freedom and with other mission objectives is recommended for further application of the hybrid computer in the area of aerospaceoptimal control research. Author
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