Design and Experiment of a Compact Cable-Driving Module for Reconfigurable Cable-Driven Parallel Robots

Abstract

Cable-driven parallel robots (CDPRs) have the characteristics of reconfigurability, which endows CDPRs with flexible workspace, freely configurable degrees of freedom and various configurations, greatly expanding their range of applications. Modular design provides great convenience and feasibility for the realization of reconfiguration, which is a key issue of reconfiguration research. However, most existing CDPRs have problems of low modularity and low system integration, which brings inconvenience to the realization of reconfiguration. In this paper, a highly integrated and high precision cable-driving module is designed, which can accurately control the length and tension of the cable. In addition, experimental verification is performed. The single-module experiment shows that the module has good ability for cable length and cable tension control. The cable length control error is less than 0.2mm, and the cable tension control error is less than 0.8N. Furthermore, based on the proposed module, a CDPR with 8 cables and 6 degrees of freedom is constructed rapidly. The open-loop tracking error of the robot is measured by laser tracker. Results show that the tracking error is less than 4.5mm and the Root-Mean-Square-Error (RMSE) is 2.1mm. Besides, the compliance control experiment of the robot shows that the tracking error in impedance control mode is less than 2mm, and the RMSE is 0.95mm, and the drag force in teaching mode is less than 2.5N, which demonstrates good follow-up performance. The proposed compact cable-driving module with high precision could be useful for the design and rapid construction of reconfigurable CDPRs.