Sensitivity analysis of a suspended CDPR to design parameters

Cable Driven Parallel Robots (CDPR) are systems driven exclusively by cables, giving them advantages in operation and use. However, this also introduces complexity into their mechanical behavior. Indeed, a cable is non-rigid, so it bends and lengthens in response to external forces. In addition, its elasticity is affected by a hysteresis phenomenon. This paper first introduces a new modelling of CDPRs allowing to take in consideration the deflection and elongation of the cables within the actuating chain while considering the pulleys. In a second step, a design of experiments is conducted on a suspended CDPR with four cables. This allows to quantify the effects on the theoretical MP pose error of important design parametres that are the type of pulley joint, cable' Young's modulus, the cable mass and the Mobile Platform (MP) mass. Interaction between theses parameters is also studied. This study is conducted for different sizes of CDPR. It appears that the variation of the Young's modulus and the MP mass has a significant impact on the theoretical MP pose error regardless of the size of the CDPR. based on the obtained results, the type of pulley joint seems to have very little influence on the theoretical MP pose error. It is also shown that the cable mass should be taken into account when modelling CDPRs over 10m.