Explicit dynamics of redundant parallel cable robots

Abstract

Precise model-based control of parallel robots necessitates an analytically accurate and consolidated model of the robotic platform. Lack of accuracy in modeling causes lots of dynamic uncertainties. This fact can result in higher control gains and efforts. Furthermore, imposing modification for optimization purposes is implausible without the derivation of an exact model. Hence, in this paper an elaborative kinematical and dynamical model of redundant cable-driven parallel robots is studied. In fact, a general procedure for modeling of cable-actuated parallel robots is presented to tackle down the difficulties for model-based control. The presented dynamic modeling approach rigorously enumerates the kinematics of robot winches and pulleys. The intrinsic behavior of cables is represented with a linear spring and damper having variable mass and constant density in the workspace. To this end, sagging in cables is neglected as a computationally intractable effect with insignificant impact on robot’s dynamics. Next, model validation is carried out within an experimental study of a redundant cable-driven parallel robot, the RoboCab which is designed and manufactured in Advanced Robotics and Automated Systems (ARAS) Lab. Experimental results reveal the merits and capabilities of proposed model to capture the explicit dynamics of robot. Results also demonstrate the high rate of flexibility and applicability of model for dealing with diverse control applications.