Accession Number:

ADA243349

Title:

Control Algorithms for Aerobraking in the Martian Atmosphere

Descriptive Note:

Doctoral thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1991-12-01

Pagination or Media Count:

187.0

Abstract:

The Analytic Predictor Corrector APC and Energy Controller EC atmospheric guidance concepts have been adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. Modifications are made to the APC to improve its robustness to density variations. These modifications include adaptation of a new exit phase algorithm, an adaptive transition velocity to initiate the exit phase, refinement of the reference dynamic pressure calculation and two hybrid density estimation techniques. The modified controller with the hybrid density estimation technique is called the Mars Hybrid Predictor corrector MHPC, while the modified controller with a polynomial density estimator is called the Mars Predictor Corrector MPC. A lyapunov Steepest Descent Controller LSDC is adapted to control the vehicle. The LSDC lacked robustness, so a Lyapunov tracking exit phase algorithm is developed to guide the vehicle along a reference trajectory. The equilibrium glide entry phase is employed for the first part of the trajectory. This algorithm, when using the hybrid density estimation technique to define the reference path, is called the Lyapunov Hybrid Tracking Controller LHTC. With the polynomial density estimator used to define the reference trajectory, the algorithm is called the Lyapunov Tracking Controller LTC. The four new controllers are tested using a six degree of freedom computer simulation to evaluate their robustness.

Subject Categories:

  • Astronautics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE