Adaptive Cross-Coupled Control of Cable-Driven Parallel Robots With Model Uncertainties

Abstract

Cable-driven parallel robots (CDPRs) are robots with novel structures, wherein flexible cables, instead of rigid links, are employed to pull mobile platforms. This structural change enables CDPRs to not only offer potential advantages, but also introduces control challenges with regard to frictional uncertainties, dynamic modeling errors, and multi-cable motion coordination. To address these concerns, a novel adaptive cross-coupled control (ACCC) scheme, capable of achieving high-accuracy trajectory tracking control, has been proposed in this study. In the proposed ACCC scheme, a new synchronization error variable has been defined to adjust the coordination motion of adjacent cables; additionally, an adaptive dynamic control strategy has been designed to compensate for the inertia and friction of winches linked to cables. Lastly, an adaptive robust control has been used to restrain un-modeled dynamics and external disturbances. The proposed ACCC scheme was compared against the synchronization control (SC) scheme and the well-known adaptive control (AC) scheme of Slotine-Li by applying them to an actual non-redundant CDPR during trajectory tracking experiments. Corresponding results demonstrated that compared to the SC and the AC scheme, the proposed ACCC scheme serves to improve both tracking and synchronization accuracies of cables, thereby ultimately enhancing the control performance of mobile platforms. Robustness of the ACCC scheme against external disturbance has also been verified.