Accession Number : ADA267942


Title :   Neighboring Extremal Guidance for Systems with Piecewise Linear Control Using Time As the Reference Variable


Descriptive Note : Master's thesis,


Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH


Personal Author(s) : Libby, William A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a267942.pdf


Report Date : May 1993


Pagination or Media Count : 58


Abstract : A guidance law for the control of a system in the neighborhood of a nominal suboptimal trajectory is developed. The guidance law is demonstrated using a lunar launch problem with constraints at orbit entry. A set of precomputed gains is used by the guidance law to operate on an extremal path in the neighborhood of the suboptimal trajectory. The guidance law and gains are designed to minimize the change in the desired performance index while still satisfying the final path constraints. In the lunar launch problem, the nominal suboptimal trajectory minimizes the final time using piecewise linear control. This trajectory is obtained to provide a nominal control history. The guidance law is found by minimizing the second variation of the suboptimal trajectory performance index subject to the final constraints being satisfied. For the lunar launch problem, the guidance law leads to a set of gains that relates deviations from the suboptimal trajectory to required changes in the nominal control history. The deviations from the suboptimal trajectory, used together with the precomputed gains, determines the change in the nominal control history required to meet the final constraints while minimizing the change in the final time.


Descriptors :   *CONTROL , *GUIDANCE , ORBITS , THESES , TIME , TRAJECTORIES , VARIATIONS , HISTORY , INDEXES


Subject Categories : Spacecraft Trajectories and Reentry


Distribution Statement : APPROVED FOR PUBLIC RELEASE