Control Algorithms for Aerobraking in the Martian Atmosphere
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1991
- Accession Number
- ADA243349
Entities
People
- Buford W. Shipley Jr.
Organizations
- Air Force Institute of Technology