Kinematically Controllable Cable Robots with Reconfigurable End-effectors

TL;DR

This paper introduces a reconfigurable end-effector design for cable robots that expands the rotational workspace and simplifies kinematic control by converting linear motions into rotations and adding a rotational degree of freedom.

Contribution

The authors propose a novel end-effector mechanism with spring, helical shaft, and bearing that enhances workspace and enables tension-free kinematic control.

Findings

Expanded rotational workspace achieved

Kinematic control performed without tension sensing

Mechanism is structurally simple and non-redundant

Abstract

To enlarge the translational workspace of cable-driven robots, one common approach is to increase the number of cables. However, this introduces two challenges: (1) cable interference significantly reduces the rotational workspace, and (2) the solution of tensions in cables becomes non-unique, resulting in difficulties for kinematic control of the robot. In this work, we design structurally simple reconfigurable end-effectors for cable robots. By incorporating a spring, a helical-grooved shaft, and a matching nut, relative linear motions between end-effector components are converted into relative rotations, thereby expanding the rotational workspace of the mechanism. Meanwhile, a bearing is introduced to provide an additional rotational degree of freedom, making the mechanism non-redundant. As a result, the robot's motion can be controlled purely through kinematics without additional tension sensing and control.