Robust autopilot design for lunar spacecraft powered descent using high order sliding mode control

Robust performance of a flight control system in the presence of parametric uncertainty and external disturbances is of paramount importance to a manned space flight program. The present research is concerned with the design of an autopilot that uses sliding mode control principles so as to enhance the robustness properties of a lunar landing vehicle during the approach phase of powered descent.;A high-fidelity simulation of the Apollo Lunar Module is constructed that includes models of liquid slosh and various subsystems. The application of a high order sliding mode autopilot that detects and compensates disturbances is shown to provide performance comparable to that of the heritage autopilot and in fact may avoid some difficulties encountered in the Apollo flights. Performance is maintained in the presence of a realistic sensor model and with severe actuator constraints, demonstrating a unique application of sliding mode control to a complex aerospace system.