Hierarchical control of a space-based deployable manipulator using fuzzy logic

Application of the fuzzy logic intelligent control of space-based systems h as received relatively less attention compared to conventional control proc edures. Basic concepts involved in development of a hierarchical control sy stem using fuzzy logic are explained. Next, fuzzy logic is applied to contr ol a novel two-link robotic arm, composed of revolute and prismatic joints, supported by a mobile base traversing along an orbiting platform. The cont rol system that is developed has three levels. A conventional controller, c onsisting of the feedback linearization technique combined with proportiona l-derivative control is used in the bottom level of the hierarchical system , to control the servomotors of the robot. A second layer consists of a ser vo-expert that preprocesses the high-resolution information coming from joi nt encoders and extracts the status of the system. A third, intelligent lay er is added at the top of the hierarchy to complete the control structure. The main purpose of the top level is to tune the parameters of the crisp (c onventional) controller to improve the response of the system. A decision t able is developed offline, for tuning the parameters of the crisp (nonfuzzy ) controller, which considerably reduces the real-time computational effort . Typical pick-and-place results from the robot are presented that show tha t extra tuning can significantly improve the performance of the manipulator .