An Eight-Wire Passively Driven Parallel Manipulator: Development and Analysis

The article presents development of an eight-wire passively driven parallel manipulator and discusses its workspace and stiffness behaviour. The uniqueness is in the passively driven design. The device can be used in biomechanics study of human movements and for calibration of manipulator arms, among many others. Manipulator kinematics and the force closure workspace (with inextensible wires) are analysed. A procedure is presented to numerically determine the workspace. Task space stiffness at end effector is examined through a stiffness tensor for directional stiffness behaviour in the workspace. A stiffness index characterizes the degree of isotropy of the stiffness. Experimental validation of forward kinematics and simulation results of force closure workspace and stiffness behaviour of actuated manipulator are reported.