Dynamic Analysis of Cable-Driven Parallel Manipulators Using a Variable Length Finite Element

Cable-driven parallel manipulator (CDPM) is a good solution to achieving large workspace. However, unavoidable vibrations of long cables can dramatically degrade the positioning performance in large workspace applications. Most work so far on cable-driven parallel manipulators (CDPMs) simply neglected the dynamics of the cables themselves. In this paper dynamic modeling of large CDPMs is addressed using a variable domain finite element method (FEM). A cable element with variable length is derived using the absolute nodal coordinate formulation to facilitate motion analysis of CDPMs. The effects of cable length variation and the resulting mass variation are also considered. Based on this element dynamics model of CDPMs can be readily obtained using the standard assembling operation in the FEM. Numerical results showed that the effect of the derivatives of cable length variation and that of the mass variation are trivial.