Kinematic modeling of cable-driven parallel robots with unlimited rotational axis
Production Automation and Assembly Technology
Final Report Abstract
Cable-driven parallel robots (short: cable robots) are special parallel robots that use cables instead of rigid joints for the movement of the platform. By coordinating the length and shortening of the cables, the platform can be positioned and oriented within the frame. Due to the low inertia of the cables and platform, cable robots can be considered a lightweight form of the Gough-Stewart platform. High platform speeds of up to 30 m/s and accelerations of up to 400 m/s² are possible due to the low moving mass. In addition, the workspace of a cable robot can be flexibly designed due to the small number and low weight of the com- ponents used. However, due to potential cable-cable collisions, the orientation workspace of a cable robot is limited. In contrast, unlimited rotating axes are a standard feature of commercial serial robots. However, if a reach of >15 m is also required, serial robot kinematics are ruled out and cable robots can assert their system-related advantages. Unlimited rotation, which is generated solely by actuating the cables, offers an opportunity to avoid additional actuators on the platform and thus the expense, error-proneness and addi- tional weight of a media storage device or an external media supply. Unlimited rotation can thus be per- formed in all degrees of freedom without reducing the dynamic limits. To generate the endless rotation, serially coupled sub-platforms, within a parallel cable robot structure, are necessary, which can move relative to each other. Therefore, methods for modeling and controlling cable robots with this hybrid structure were developed in the project and the results were finally validated on the testbed COPacabana. First, the generic kinematic model of the hybrid cable robot as a multibody system was developed, and then the workspace hull (wrench-feasible workspace) with the acting cable forces was calculated. Known calculation methods from cable robotics were extended with regard to the additional reaction forces and degrees of freedom that result from interlinking of the platforms. In addition to the cable force and workspace calculation, the pose-dependent cable-cable collisions were considered. The result of the theoretical investigation confirms a strong dependence of the workspace volume on the number of actuated cables and platforms. Therefore, for experimental validation, a cable robot with 12 cables and 3 coupled platforms was built and integrated into the existing control architecture. The cable forces measured during a complete rotation of the end effector show similar curves as the calculated cable forces.
Publications
- Static Analysis of a Two-Platform Planar Cable-Driven Parallel Robot with Unlimited Rotation. In: Pott, Andreas; Bruckmann, Tobias (Hrsg.): Cable-Driven Parallel Robots : Proceedings of the Fourth International Conference on Cable-Driven Parallel Robots. Cham, Switzerland : Springer, 2019 (Advances in Mechanism and Machine Science, Bd. 74)
Reichenbach, Thomas; Tempel, Philipp; Verl, Alexander; Pott, Andreas
(See online at https://doi.org/10.1007/978-3-030-20751-9_11) - Umdrehungen ohne Ende : Seilroboter mit endloser Rotationsachse. In: handling (2019), Nr. 6, S. 24
Reichenbach, Thomas; Verl, Alexander
- COPacabana - Ein modularer paralleler Seilroboter. In: Sechste IFToMM D-A-CH Konferenz 2020: 27./28. Februar 2020, Campus Technik Lienz 2020
Trautwein, Felix; Reichenbach, Thomas; Tempel, Philipp; Pott, Andreas; Verl, Alexander
- On Kinetostatics and Workspace Analysis of Multi-Platform Cable-Driven Parallel Robots with Unlimited Rotation. In: Kuo Chin-Hsing; Lin, Pei-Chun; Essomba Terence; Chen Guan-Chen (Hrsg.): International Symposium on Robotics and Mechatronics. Proceedings of the 6th IFToMM World Congress. Cham, Switzerland : Springer International Publishing, 2020, Bd. 78, S. 79–90
Reichenbach, Thomas; Tempel, Philipp; Verl, Alexander; Pott, Andreas
(See online at https://doi.org/10.1007/978-3-030-30036-4_7)
