Dynamic models for simulation of Cable-Driven Parallel Robots with elasticity and sagging

Abstract

Cable-Driven Parallel Robots (CDPRs) are a type of parallel robots that uses cables instead of rigid links, making accurate modeling complex due to intricate cable dynamics. For simulation and control applications, it is appropriate to employ simplifying hypotheses to account for cable deformations. However, when high precision is necessary, models capturing the cable deformation become compulsory, making it challenging to balance model fidelity with computation time. This paper addresses this challenge, by proposing and comparing dynamic models of CDPRs that are both accurate and suitable for controller design. Leveraging recent advances in Finite Element Method (FEM) modeling for robotics, this paper extends recent findings and adapts them to the specific case of CDPRs. Additionally, a second model based on the assumed mode approach is extended to 3D context. The accuracy of both models is then compared with that of a lumped parameter model provided by the commercial software MapleSim, focusing on pick-and-place tasks to highlight the strengths and limitations of each approach for establishing a common benchmark. Following initial experimental validation of the models’ precision in a single-cable setup, the FEM model was selected as a comparison reference. Finally, simulation results for an eight-cable 3D suspended robot are presented.