Cable Driven Parallel Robots (CDPRs) are parallel robots, in which the limbs are replaced by cables that are guided by pulleys. In many papers, the pulleys are considered as fixed points of passage and the cable elasticity is neglected. Those approximations simplify the robot modelling, but lead to some Moving-Platform (MP) pose errors. This paper deals with the modelling of suspended CDPRs considering the geometry and kinematics of the pulleys as well as the cable elasticity. Furthermore, a novel pulley architecture with an universal joint is designed. It is introduced to increase the accuracy of CDPRs and limit the bending moment in the pulleys. Then a sensitivity analysis conducted on these newly established models allows to precisely quantify the effect of design parameters on the MP pose and to exhibit the set of the most influentials elasto-geometric parameters. Both standard and extended direct elasto-geometric static models of the CDPRs are numerically solved to determine the MP pose for given cable lengths and external wrench. Then, an index is defined based on the MP pose difference, the latter being traced through the robot Cartesian workspace. This index is used to analyze and compare the pulleys effects on the MP pose errors. It turns out that the interaction between pulleys geometrical parameters are significant and should be considered in the elasto-geometric static models. Finally, it is shown that a CDPR equipped with the novel pulley architecture is more sensitive to cable elasticity, but this new architecture helps reducing the overall MP error.

Cable-Driven Parallel Robots (CDPRs) are systems driven exclusively by cables, giving them advantages in operation. However, this also introduces complexity into their mechanical behavior. Indeed, the cable elasticity is affected by a hysteresis phenomenon. There is therefore an uncertainty about the actual value of the cable's Young's modulus. However, uncertainty analysis on design parameters of CDPR has not been conducted yet. So, this paper first introduces a new modeling of CDPRs allowing to take in consideration the sagging of the cables while considering different pulley architectures as well as the cable dead length between the winch and the pulley. Then, a sensitivity analysis of the main design parameters on the positioning error of the Moving-Platform (MP) is performed through a design of experiments conducted on a suspended CDPR with four cables. For this purpose, the variation of the Young's modulus of the cables is determined. This allows to quantify and to rank the effects on the theoretical MP pose error of important design parameters that are the type of pulley joint, cable's Young's modulus, the cable mass and the MP mass. This study is conducted for different sizes of CDPR. The results obtained show that the evolution of the effects of the design parameters is not the same depending on the size of the CDPR. Technical major considerations are derived from the presented results as guidelines for CDPR designer, keeping the modeling relatively simple but robust enough for real-time control of CDPRs.