China is now building the world’s largest single dish radio telescope in Guizhou province, which is called Five-hundred meter Aperture Spherical radio Telescope (FAST). The main purpose of this paper is to present an effective dimensional design method on the six-cable driven parallel manipulator of FAST. Sensitivity design method is adopted for the six-cable driven parallel manipulator of FAST. Cable has the capability to bear tension but not compression, so that cable driven parallel manipulator may not be controlled as expected if tension of one cable is small or zero. Therefore, for dimensional design of the six-cable driven parallel manipulator, three functions to evaluate tension performance were proposed. The tension performance functions can reflect the uniformity of cable tension and controllability of the six-cable driven parallel manipulator. According to the sensitivity design method and tension performance evaluating functions, a set of optimized dimensional parameters is calculated for constructing the six-cable driven parallel manipulator of FAST. In order to verify the optimization design result, a similarity model of the six-cable driven parallel manipulator was set up in Beijing. A serial of experiments shows that tension performance of the six-cable driven parallel manipulator satisfies the system’s requirement. More importantly, it provides a theoretical reference for further study on dimensional design of a cable driven parallel manipulator with large span.

In this paper, to solve the problem of variable stiffness of cable-driven parallel robots (CDPR), a new static stiffness analysis and cable tension distribution method are proposed for studying the CDPRs’ controllable stiffness. First, a three-dimensional Hessian matrix of the structure matrix to position differential is deduced by introducing a line vector and differential transform, and a static stiffness model is established for analyzing the relationship between cable tension and the stiffness of the robots. Furthermore, a calculation algorithm for cable tension polygons based on Graham's Scan is introduced that effectively obtains the cable tension feasible region (CTFR) of CDPRs. Next, a method involving “the relationship between the external force and the pose change value of the moving-platform” is proposed to measure the variation of system stiffness. The CDPR's controllable stiffness is also analyzed based on the CTFR by considering the variation of each driving-cable's tension and each component of the moving-platform's pose. The results of experimental and theoretical analyses verify the correctness and efficacy of the proposed method. In addition, they show that the proposed method is computationally efficient and easily establishes the relationship between cable tension and the CDPR's controllable stiffness.