Nonlinear dynamic modeling of a mobile spatial cable-driven robot with flexible cables

In this paper, the modeling of a novel moving cable-driven robot is conducted considering the vibration of the cables in its nonlinear format. The robot has 6 DOFs, while the controlling input number is 12. Considering the fact that the elasticity of the cables is coupled with the dynamic model of the system, their vibration affects the robot's performance and accuracy. This paper aims to model the robot considering the cable's elasticity and study its effect on the robot performance. This study can be considered in designing the controller of tower cranes, decreasing the cable's swing, and increasing their stability. In order to cover the mentioned aim, the continuous vibration of the cables is modeled as a nonlinear system and added to the moving platform dynamics. Moreover, the differences between the nonlinear modeling of the cable's vibration and estimating them as a linear system are studied, and their related results are compared and analyzed. The correctness of modeling is shown by comparing the results with previous research, and the superiority of modeling the cable's vibration in its nonlinear format is verified by the aid of a series of simulation scenarios in MATLAB. Moreover, by conducting some experimental tests on the manufactured moving cable-driven robot of IUST, it is illustrated that modeling the cables in these robots as a nonlinear system results in more accurate results. It is shown that not only considering the cable's vibration is significant in analyzing the robot dynamic, but also it is shown that promoting the mentioned model into a nonlinear one increases the accuracy of the robot modeling, which sequentially can provide a stronger controller for stabilizing and controlling the end-effector within a predefined trajectory.