Title:  A Cooperation Control Framework Based on Admittance Control and Time-varying Semi-passive Velocity Field Control for Human-Robot Co-carrying Tasks 

Abstract: Developing a cooperation control framework for human-robot co-carrying tasks in achieving safe interaction and completing the shared tasks, especially in scenarios where human intentions vary due to changes in the environment or task demands, remains an open challenge. Passivity-based control theory realizes safe operation by preserving the energetically passive relationship between the closed-loop system and its physical environment. However, solely adhering to passivity constraints may impose fundamental limitations on control performance and, in some cases, prevent the successful execution of controlled tasks. To address these issues, a cooperation control framework for human-robot co-carrying tasks was constructed by utilizing a reference generator and a time-varying semi-passive velocity field control in this study. Firstly, the human motion predictions are corrected in the event of prediction errors based on human-robot conflicts measured by the interaction forces through admittance control, thereby mitigating conflict levels. Subsequently, a time-varying semi-passive velocity field control approach is proposed, which utilizes the output of the motion generator to regulate robot behaviors during physical interaction with the human. In this manner, the proposed framework relaxes the inherently conservative nature in a controlled manner, which ensures the passivity of the closed-loop system when the energy level exceeds the designed one; and vice versa. Furthermore, the proposed control approach ensures that the system's kinetic energy is compensated within a finite time interval. The passivity, stability, convergence rate of energy, and power flow regulation are analyzed from theoretical viewpoints. 

Language of the presentation: English