Development of a Haptic Device with Wire-Driven Parallel Structure

This study focuses on the specific problems that may arise in the development of a parallel, cable-driven device designed for teleoperations systems utilizing force-reflection feedback. A redundant six degrees-of-freedom structure, actuated by nine wires, is described as a convenient layout for a haptic master for telemanipulation. A methodology for the kinematic and static analysis and the evaluation of the device workspace is described. The condition of force closure is used to find all available poses of the end-effector, thereby defining the workspace, whose characteristics are assessed by opportunely conceived indexes. Typical characteristics of cable and implementations thereof in the device are considered. Regarding the realization of the device, relevant attention is given to the definition of the control logic, which can be complex for parallel devices. The selection of the actuators, crucial in realizing force feedback, is discussed. In particular, pneumatic actuation is considered, verified as the most appropriate method for implementation and force control of the cylinders.