Importance of cable vibration in dynamics of cable-driven parallel robots

In this paper, an original method to analyze the vibrations of Cable-Driven Parallel Robots (CDPRs) is presented. A nonlinear oscillating model of CDPRs able to capture the dynamic behavior of the cables is developed from the Dynamic Stiffness Matrix method. The system modeling considers the dynamic load-deformation behavior of the cables, the end-effector vibrations and their coupling through the computation of a frequency-dependent dynamic stiffness matrix. There results new and numerous cable vibration modes, as well as nonlinear end-effector modes. System modeling and methods analysis are firstly illustrated with reference to the two degree-of-freedom (DOF) model of a cable-mass system. Then both numerical investigations and experimental analyses carried out on a 6-DOF CDPR prototype suspended by 6 cables give highlights about the effect of the cable modes on the end-effector response. The paper ends with a discussion on the main perspectives on analysis and reduction of vibrations of CDPRs.