Error Analysis by Kinetics for Parallel-Wire Driven System Using Approximated Inverse Kinematics

Parallel-wire driven systems, which use light flexible wires in place of rigid links, control the position of a target object by controlling their wire lengths. In the kinematics for such a parallel-wire driven system, when the relationship between the end-effector position and the wire lengths is investigated, a fixed point for the wire-contacting point on the winding reel in the actuator (or guide pulley) is often approximated to simplify the calculation. The approximated kinematics however could lead to a number of positioning errors in the positioning control. This study proposes a framework for evaluating these positioning control errors by using approximated inverse kinematics. In view of the system dynamics, this study analyzes the positioning control errors for the control method in the wire-length coordinates. We discuss a case study on a two degrees-of-freedom planar system using three wires.