Stiffness feasible workspace of cable-driven parallel robots with application to optimal design of a planar cable robot

Abstract

In this paper stiffness of cable-driven parallel robots (CDPRs) is analyzed in detail and based on this analysis, the stiffness-feasible workspace is introduced. This workspace includes all stable poses which increasing the internal forces can modify the total stiffness of the robot. It has been shown that in the CDPRs, the concept of the internal forces can be applied for keeping cables in tension and increasing stiffness. However, it should be noted that increasing the internal forces may decrease the overall stiffness of the mechanism and it is only applicable in stabilizable poses of the workspace. Therefore, stiffness-feasible workspace determines the allowable internal forces range which can increase the stiffness and it will guarantee that in this range of the internal forces, the structure of the robot is stable. In this paper, by employing this criterion and evolutionary algorithms, a CDPR is optimally designed, and a set of answers is presented. In this design, in addition to the stiffness-feasible workspace, another criterion as stiffness number is presented which is useful for specifying the distribution of the stiffness and stiffness-feasibility of the robot.