Cable elasticity can significantly impact the accuracy of Cable-Driven Parallel Robots (CDPRs). However, it’s frequently disregarded as negligible in CDPR simulations and designs. In this paper, we propose a numerical approach, referred to as SEECR, which is designed to estimate the behavior of a CDPR featuring elastic cables while ensuring the Static Equilibrium (SE) of the Moving-Platform (MP). By modeling the cables as elastic springs, the proposed approach correctly predicts which cables become slack, estimates the tension distribution among cables and computes unwanted MP motions, allowing to predict the impact of design choices. The results have been validated experimentally on two cable types and configurations.

Some cable-driven parallel robots (CDPRs) can be rapidly deployed on-site. To achieve such deployability, the fixed frame is usually substituted by four masts. However, not having any rigid fixture between the masts reduces the overall stiffness of the CDPR. This paper introduces a CDPR called Rocaspect, that has four compliant masts. The robot behavior and accuracy is evaluated experimentally and three different mast models are proposed.

Cable-driven parallel robots (CDPRs) are a type of parallel robots, where cables are used instead of rigid links. This leads to many advantages, such as large workspace, low mass in motion and simple reconfiguration. The drawbacks are accuracy issues and complex cable management. Indeed, it is usual that cables become slack. That can be caused by, for example, cable mass, uncertainties in the system, and a higher number of cables than the number of degrees of freedom of the moving-platform. This reduces CDPR stiffness and degree of actuation. While visual servoing provides good accuracy and is robust to different perturbations in the system and to modeling errors, it does not deal with cable slackness. Thus, a CDPR with visual servoing can become underactuated due to cable slack. We propose in this paper to enrich visual servoing with a tension correction algorithm. Experimental results show reduction of slackness and thus avoiding slackness-related trajectory perturbations and loss of stability.

Cable-Driven Parallel Robots (CDPRs) are parallel robots with rigid links replaced by cables. As for most parallel robots the determination of the analytical solutions to the direct geometrico-static model (DGSM) is a difficult task that is often not feasible online. However, the knowledge of the moving-platform (MP) pose is necessary in order to control the CDPR, e.g. with visual servoing. When the MP pose measurement is not available, an estimation can be sufficient. This paper compares three estimation methods: (a) control-based; (b) image-based; and (c) model-based. The three methods are implemented experimentally with an open-loop velocity controller and a closed-loop visual servoing controller. Overall, very good results are shown with model-based and control-based methods for both controllers. Finally, it is shown that the visual servoing controller leads to a better accuracy of the robot than the velocity controller.