Recursive Decentralized Control for Trajectory Tracking of Flexible Space Manipulators

A recursive decentralized control scheme is presented for the trajectory tracking issue of flexible space manipulator. In the traditional decentralized control for manipulators, each link in the manipulator is viewed as an isolated second-order subsystem. Its interconnections with other links are viewed as disturbances. As a consequence, the obtained decentralized control has a simple structure but lacks high control performance. In this paper, the manipulator is considered as a set of connected second-order subsystems. The interconnections between two adjacent links are revealed by the recursive kinematics and dynamics. In such a manner, the nominal value of the interaction forces is constructed and used for compensation to improve the tracking accuracy. Then, decentralized control is devised for each link to achieve trajectory tracking and vibration suppression of the flexible manipulator. The actuators are chosen as the joint motors and the distributed force or torque actuators on the flexible links. Under the assumption that the modal information of the flexible links is obtainable by the modal filter technique, an adaptive term in the controller is deduced for estimating the bound of the model uncertainties. Moreover, a steering logic is devised for the actuators to produce the required control. The obtained controller inherits the simple structure of the decentralized control and also achieves a higher tracking performance. The numerical examples of a free flying flexible manipulator are given to illustrate the effectiveness of the proposed control scheme.