A Cooperation Control Framework Based on Admittance Control and Time-Varying Passive Velocity Field Control for Human-Robot Co-Carrying Tasks (I)

Abstract

Human-robot co-carrying tasks reveal their potential in both industrial and everyday applications by leveraging the strengths of both parties. However, such collaborative tasks pose numerous challenges due to varied human intentions under time-varying workspaces, leading to human-robot conflicts. In this paper, we develop a cooperation control framework for human-robot co-carrying tasks constructed by utilizing reference generator and low-level controller to aim to achieve safe interaction and synchronized human-robot movement. Firstly, the human motion predictions are corrected in the event of prediction errors based on the conflicts measured by the interaction forces through admittance control, thereby mitigating conflict levels. Low-level controller using an energy-compensation passive velocity field control approach allows encoding the corrected motion to produce control torques for the robot. In this manner, the closed-loop robotic system is passive when the energy level exceeds the predetermined threshold, and otherwise. Furthermore, the passivity, stability, energy-compensation rate, and power flow regulation are analyzed from theoretical viewpoints. Human-in-the-loop experiments involving 18 participants have demonstrated that the proposed method significantly enhances task performance and reduces human workload, as evidenced by both objective metrics and subjective evaluations.