Modified Pre-stretching Assembly Method for Cable-Driven Systems

Abstract

Soft cable-driven systems have been employed in many assembled mechanisms, such as industrial robots, parallel kinematic mechanism machines, medical devices, and humaniform hands. A pre-stretching process is necessary to guarantee the quality of cable-driven systems during the assembly process. However, the stress relaxation of cables becomes a critical concern during long-term operation. This study investigates the effects of non-uniform deformation and long-term stress relaxation of the driven cables owing to moving parts in the system. A simple closed-loop cable-driven system is built and an alternating load is applied to it to replicate the operation of transmission cables. Under different experimental conditions, the cable tension is recorded and the boundary data are selected to be curve-fitted. Based on the fitted results, a formula is presented to estimate the stress relaxation of cables to evaluate the assembly performance. Further experimental results show that the stress relaxation is mainly caused by cable creep and the assembly procedure. To remove the influence of the assembly procedure, a modified pre-stretching assembly method based on the stress relaxation theory is proposed and verification experiments are performed. Finally, the assembly performance is optimized using a cable-driven surgical robot as an example. This paper proposes a dual stretching method instead of the pre-stretching method to assemble the cable-driven system to improve its performance and prolong its service life. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Authors' ContributionsJL and SW were in charge of the whole trial; GZ designed the experiments and wrote the manuscript; XR assisted with experimental setup; KK finished the comparison experiment with the needle holder; JS assisted with data analysis. All authors read and approved the final manuscript.

A Hyper-redundant Elephant’s Trunk Robot with an Open Structure: Design, Kinematics, Control and Prototype

“…After the simulation, the displacement, velocity, acceleration and force curve of the driving joint of each unit parallel mechanism module can be obtained as outputs. The simulation results are shown in Figures 8,9,10,11,12,13. where x, y, z, φ x , φ y , and φ z denote the position and orientation of the distal moving platform of the HRETR. By observing the kinematic diagram of Figures 8,9,10,11,12,13 the kinematic law of each limb meets the preset requirements (both the initial and terminal velocity and the acceleration are 0).…”

“…With the introduction of the concept of Industry 4.0, robots have become more and more essential in intelligent manufacturing [1]. Despite the wide application of robots in the industry [2][3][4][5], medical sector [6][7][8][9][10], aerospace field [11,12], and other fields, consumers' needs are becoming increasingly dynamic and complex [13]. This challenge can be resolved with better motion flexibility, stiffness and load capacity of robots.…”