Stiffness study on a 6-DOF parallel wire driven robot

In this paper the stress of a parallel wire driven (PWD) manipulator, which is driven by at least n + 1(n is the number of the degrees of freedom of the mechanism) wires, is studied. It is shown that the stress of this kind of manipulator depends not only on its structural parameters including the physical dimensions, the stress of wires and motors and the position and pose of the end effecter but also on the tension of the wires. In what extent the wire tension affects on the manipulating stress is researched theoretically in this paper. Based on the differential motion principle, the stress matrix of the manipulator consisting of structural stress and wire-tension-caused-stress is produced. Then, the stress of the actuating unit consists of the wire stress and the motor stress generated by the control law is analyzed. Those works lead to the conclusion that the stress of the PWD manipulator can be controlled by regulating the control laws or the internal tension of wires.