Abstract: In the large radio telescope mechanism design, due to the weight of the feedback cabin’s decrease, a four cable-driven parallel manipulator to control the three directors’ pure translations is proposed for expanding the workspace of the feedback cabin. For discussing the dimension design of the nonlinear cable-driven mechanism, due to the catenaries caused by cable’s weight, a method is adopted to approximate the catenaries as parabolas at a known position to solve the nonlinear static equivalent equations of the four cable-driven parallel manipulator. The simplified static equivalent equations are given. The relation of the workspace and the preferences are explained through the simplified static equivalent equations. Meanwhile, the four cables’ tensile forces and the elongate in the demanded workspace are given by using an optimized arithmetic. At last, the dimension parameter of the mechanism satisfying the demand is presented by comprehensive analysis.

Key words: Cable-driven parallel manipulator, Catenary, Large radio telescope, Workspace