Files in this item
Files  Description  Format 

application/pdf 3301243.pdf (3MB)  (no description provided) 
Description
Title:  Technology for the Solution of Hybrid Optimal Control Problems in Astronautics 
Author(s):  Wall, Bradley James 
Doctoral Committee Chair(s):  Bruce Conway 
Department / Program:  Aerospace Engineering 
Discipline:  Aerospace Engineering 
Degree Granting Institution:  University of Illinois at UrbanaChampaign 
Degree:  Ph.D. 
Genre:  Dissertation 
Subject(s):  Engineering, Aerospace 
Abstract:  Many interesting problems in spacecraft mission design are hybrid optimal control problems (HOCP) however there are only a small number of successful solutions of such problems in the literature because the problems are so challenging. The difficulty stems partly from the size of the problems and the fact that every solution method requires the solution of a very large number of individual optimal control problems. Since present technology for solving even one optimal control problem can be problematic and time consuming, improved technologies are needed for the solution of HOCP's. The principal contributions of this work are the development of new methods and the refinement of existing methods for the efficient and robust solution of optimal trajectory problems in astrodynamics. This enables the very large number of solutions required by HOCP solvers to be quickly and reliably obtained and is accomplished in several ways. First, genetic algorithm (GA) based methods are specialized to solve several types of orbit transfer problems. The resulting solutions are less exact than a conventional direct or indirect method would yield but are shown to in fact be quite good. Then a "shapebased" method is developed for rapidly approximating spacecraft trajectories that use lowthrust propulsion. Two new shapes are developed for the solution of timefree and timefixed rendezvous problems respectively. The shapebased trajectories are compared to "exact" solutions and shown to be effective in determining nearoptimal orbit transfers, interception, rendezvous, and escape or capture trajectories. The GA and shapebased methods offer the possibility of finding a large number of (near) optimal trajectories required by HOCP solvers robustly and rapidly. These nearoptimal trajectory solvers are then used in the development of efficient strategies for constructing HOCP solvers using a combined outerloop problem solver and innerloop problem solver approach. The advantages and disadvantages of various methods available as either outerloop or innerloop problem solvers are described and illustrated by example. A capstone problem, a lowthrust multiple asteroid tour problem, is solved with two algorithms, (i) using a B&B outerloop problem solver with a GA innerloop problem solver (B&B+GA) and (ii) using a GA outerloop problem solver with a GA innerloop problem solver (GA+GA) where both the GA innerloop problem solvers implement the shapebased method. The solution to the capstone problem shows that the GA+GA solution method is an improvement on current HOCP solution methods and is capable of solving very large hybrid optimal control problems. 
Issue Date:  2007 
Type:  Text 
Language:  English 
Description:  149 p. Thesis (Ph.D.)University of Illinois at UrbanaChampaign, 2007. 
URI:  http://hdl.handle.net/2142/85106 
Other Identifier(s):  (MiAaPQ)AAI3301243 
Date Available in IDEALS:  20150925 
Date Deposited:  2007 
This item appears in the following Collection(s)

Dissertations and Theses  Aerospace Engineering

Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois