Dynamic Modeling and Feedback Linearization Control of Wheeled Mobile Cable-Driven Parallel Robot Considering Cable Sag

Abstract

Cable robots are one of the subcategories of parallel robots used particularly for the applications where the large workspace is required. This type of robots can cover larger workspace compared with serial robots or parallel robots with rigid links. The main issues of cable robots are the cable flexibility due to the need to long cable length as well as inappropriate cable tension distribution in the proximity of the workspace boundaries. By combining a cable robot with a wheeled mobile robot, an unlimited area of workspace can be reached with shorter cable length. Moreover, as the end-effector does not need to come close to its boundary in the mobile platform frame to reach any desired point in the workspace, the tensions are distributed appropriately. The cable sagging in the cable robots is another issue that increases the system error and deviation of the end-effector from the desired trajectory. Therefore, this paper presents the dynamic modeling and control of a cable-suspended parallel robot with a wheeled mobile platform considering the weight of the cable. To this end, the dynamic equations of the wheeled mobile cable robot are obtained using Gibbs–Appel method. Then, the equations related to the weight and sagging of the cable are added to the equations of motion. Control of the system using feedback linearization method is presented. Furthermore, investigating the effect of cable sag on the tension and the end-effector pose of the closed-loop system is demonstrated. Finally, verification is carried out by comparing the simulation and experimental results.