Fuzzy logic techniques for rendezvous and docking of two geostationary satellites

Assembling large structures in space requires the ability to manage rendezvous and docking operations. In future these techniques will be required for the gradual build up of big telecommunications platforms in geostationary orbit. This paper discusses the use of fuzzy logic to model and implement a control system for the docking/berthing of two satellites in geostationary orbit. The system mounted in a chaser vehicle determines the actual state of both satellites and generates torques to execute manoeuvres to establish the structural latching. The paper describes the proximity operations to collocate the two satellites in the same orbital window, the fuzzy guidance and navigation of the chaser approaching the target, and the final fuzzy berthing. The fuzzy logic system represents a knowledge-based controller that realizes the closed-loop operations autonomously, replacing the conventional control algorithms. The goal is to produce smooth control actions in the proximity of the target and during the docking to avoid disturbance torques in the final assembly orbit. The knowledge of the fuzzy controller consists of a data base of rules and the definitions of the fuzzy sets. The knowledge of an experienced spacecraft controller is captured into a set of rules forming the rules data base.