Design of a planar cable driven parallel robot using the concept of Capacity Margin Index

Abstract

The research work presented in this paper introduces a new approach of determining the design parameters of a fully-constrained cable-driven parallel robot (CDPR) using an index-based methodology. The concept of this index known as “Minimum degree of constraint satisfaction” or “Capacity Margin Index” has been used in the past to determine the Wrench Feasible Workspace (WFW) and Interference-Free Constant Orientation Workspace (IFCOW) of a constrained cable robot. In this paper, the use of this index has been extended to propose a new methodology for the design process of fully-constrained planar CDPR. The design process has two major objectives. Firstly, the tensions in the cables will be minimized in order to help in selecting a lower-powered actuators and thus decreasing the overall power requirement of the manipulator. Simultaneously, the interest will be in determining an optimal size of robot platform, corresponding to the minimal tensions in the cable. A comparison of the most common cable layouts has also been prepared to investigate the optimum layout for tension minimization in the cables. A case study of a fully-constrained planar robot have been presented in which the proposed methodology is implemented.