ESTEC Guidance, Navigation, and Control activities for the Crew Return Vehicle (CRV)

摘要

The Crew Return Vehicle (CRV) is a spacecraft attached to the International Space Station (ISS) which will serve as a re-entry vehicle for astronauts on-board. The CRV will departure from its docking port of ISS and will reach a particular landing site on Earth previously specified. The goal of the paper is to describe the ESA/ESTEC activities concerning the design, development, and testing of a guidance, navigation, and spacecraft control for the CRV vehicle. The system is centered around the problem of are-entry vehicle, which carries astronauts on-board coming from a space station. The article starts with an introduction about the CRV spacecraft, the NASA and ESA plans and the different involvement of all partners in its construction. The paper continues with a description of the spacecraft on-board systems, including the six degrees of freedom control problem. The paper further explains that the future trajectory prediction is calculated by the ESA/University of Stuttgart optimal trajectory finder ALTOS, while the navigation and control sub-systems are computed in the ESA/TU-Delft trajectory re-entry simulator GESARED. Two different control techniques are detailed and briefly explored: model-based predictive control and fuzzy logic based control. Model based predictive control uses a model of the system to incorporate the knowledge of the predicted behavior of the spacecraft into the controller design cycle. This method of control design requires a model of the spacecraft to be controlled, a predictor equation, a known trajectory, and a cost function. An introduction about model-based predictive control techniques applied to spacecraft systems with six degrees of freedom control problems is given. The paper continues with a description of the mission chosen for the implementation explaining the various components of the control technique: the Newtonian system model used, the predictor equation, and the cost function. Fuzzy set theory was originally introduced by Prof. Zadeh in 1965. Since then, many researchers have introduced fuzzy logic (FL) techniques to solve different types of control problems. The ability to model problems in a simple and human-oriented way and the ability to produce smooth control actions around the set points make fuzzy logic an especially suitable candidate for use in space applications. Fuzzy logic seems to provide a method of reducing system complexity while maintaining control performance. Finally, the paper discusses the impact in the immediate applicability of the results of the work in the future ESA Crew Return Vehicle missions.