Cooperative positioning system for large objects consisting of three position-controlled manipulators with six wires

Abstract

A new positioning method for large objects by cooperation of three position-controlled manipulators is proposed. To realize the cooperative positioning system by position-controlled manipulators, it is necessary to avoid excessive inner forces among manipulators caused by mutual positioning errors. To solve this problem, two wires with independent directions are installed between each manipulator tip and the positioned object. As a result, the object is suspended by six wires those directions are linearly independent of each other. Then, if the tensions of all wires are positive during the execution of the positioning tasks, the excessive inner forces don’t generate by positioning errors of the manipulator tips and sway motion of the object doesn’t occur against external forces in some extent. On the other hand, this system has 12 kinematical redundant degrees of freedom. Therefore, we propose a positioning control algorithm to keep all wire tensions positive and to avoid the concentration of tension on any one wire by utilizing kinematical redundancy. The effectiveness of the proposed method and the developed system are verified by a fundamental experiment and simulations.