Experimental validation of a trajectory planning approach avoiding cable slackness and excessive tension in underconstrained translational planar cable-driven robots

Abstract

The objective of this paper is providing the first experimental evidence of the effectiveness of an off-line trajectory planning approach developed to ensure positive and bounded cable tensions in under constrained planar two-degree-of-freedom translational cable robots. The hybrid (serial/parallel) topology of the investigated robot is general enough to ensure wide applicability of the proposed trajectory planning method, which translates the usual bilateral tensile cable force constraints into kinematic constraints on the velocity and acceleration of the robot tool center point along the desired path. Kinematic constraints are computed making use of the robot dynamic model and can then be incorporated in any trajectory planning algorithm. In this work a smooth trajectory planning algorithm based on quintic polynomials is adopted. The experimental setup is presented and the results obtained by applying the method to two sample paths are discussed.