Seminars

Autonomous spacecraft systems increasingly operate in environments characterized by significant uncertainty, limited sensing, and strict actuation constraints. This dissertation covers different problems related to attitude estimation and control of space systems under structured uncertainty. In debris capture and on-orbit servicing missions, the composite inertia of the spacecraft-debris system is not fully known. To despin and reorient the debris, a finite-time attitude maneuver planning and control architecture is introduced considering uncertain inertia properties and torque limits. The proposed approach relies only on upper and lower bounds on the principal inertias and guarantees that commanded torques remain within prescribed limits throughout the maneuver. Next, an attitude and gyro bias estimator is developed for spacecraft operating with intermittently available attitude measurements. The estimator explicitly accounts for measurement blackouts while maintaining bounded estimation error in both attitude and gyro bias. Sufficient conditions are established to guarantee convergence and robustness despite extended periods of measurement blackout. Finally, two six degree-of-freedom adaptive tracking controllers for a lunar hopping vehicle are presented, utilizing both certainty equivalence and non-certainty equivalence frameworks. The certaintyequivalence based adaptive controller adopts the congelation of variables technique to attenuate to the time varying nature of the center of gravity. The non-certainty equivalence adaptive controller uses the immersion and invariance technique to achieve trajectory tracking. The performance of the presented controllers are compared by analyzing the flight and landing requirement failure rate and behavior of the parameter estimate in Monte Carlo simulations.