Decentralized control of redundant manipulators: A control scheme that generates a cyclic solution to the inverse problem

A decentralized control scheme is proposed for three-dimensional (3-D) positioning of spatial redundant manipulators having all rotational joints. A cyclic kinematic algorithm is introduced that generates a closed joint-space trajectory corresponding to a closed end-effector path in Cartesian space. Cyclicity is a very important property for manipulators that must perform repeated tasks without the requirement for intermediate re-configuration maneuvers. Once the joint-space trajectory is generated, control of the manipulator becomes a joint-based control; independent control units for each joint are formed by the implementation of a proportional/derivative (PD) feedback controller and a disturbance observer at each joint. The validity of the proposed control scheme is shown by several simulations on multi-jointed redundant spatial manipulators and by experimental results from a 6-link planar redundant manipulator.