Robust Adaptive Attitude Control of Crew Exploration Vehicles (CEVs) with Guaranteed Performance

High precision attitude control is vital to achieve safe and reliable operation of crew exploration vehicles (CEVs) such as docking (with service module) and landing (on the moon or earth). This work investigates a robust adaptive approach to adjusting CEV´s orientation through the driving forces produced by various RCS engines mounted on the vehicle. By using the structural properties of the capsule vehicle and the 4-parameter (quaternion) orientation representation, a set of control algorithms are developed to ensure adaptive and robust attitude tracking of CEV. The proposed control scheme explicitly addresses 1) uncertain aerodynamics due to unpredictable disturbances; 2) time-varying and uncertain mass property of the vehicle due to fuel consumption, payload release, and/or modules separation; and 3) guaranteed tracking performance under varying operation conditions. It is shown that the developed control scheme does not demand detail vehicle system parameters/dynamics and asymptotic orientation tracking is achieved. Furthermore, tracking performance index is guaranteed bounded and there is no need to redesign or reprogram the control scheme under varying flight/operation conditions. Both theoretic analysis and simulation studies confirm the effectiveness of the proposed method.