A Force-free Control Architecture Integrated with Digital Twin for Collaborative Manipulators

Force-free Control (FFC) efficiently accomplishes trajectory generating through manual interaction with a robotic manipulator in physical space, and the digital twin (DT) provides a comprehensive simulation and understanding of physical systems. In this study, an approach for facilitating human-robot collaboration (HRC) combining FFC and DT is implemented on a six-degree-of-freedom (6-DoF) collaborative manipulator. FFC has been realized by adopting three-tier control architecture that incorporates admittance control. DT is established to accurately and synchronously reflect the bi-directional mapping between the physical entity and its virtual counterpart. Experimental findings show that the proposed FFC architecture supports seamless interaction between the manipulator and external forces exerted by humans. Test results also indicate that DT enables data monitoring and singularity alert during FFC task execution, promisingly guaranteeing personnel safety and sustainable operation of equipment on industrial production lines.