Visual-Impedance-Based Human–Robot Cotransportation With a Tethered Aerial Vehicle

Physical human–robot interaction in the field of aerial vehicles has received more research attention in recent years. In this article, a visual impedance control strategy for human–aerial robot cooperative transportation with a tethered vehicle is presented. Without a positioning system, the aerial vehicle is controlled to follow the human partner by using cable force and visual features of the object as feedback. Furthermore, being aware of human motion is important to improve efficiency and smoothness of the cooperation. Without measuring velocities of the aerial vehicle and the human, we propose to directly estimate the relative velocity of them by a vision-based velocity observer. This estimated velocity is then integrated into a visual impedance scheme. The stability of the system is rigorously proved by Lyapunov analysis and passivity analysis. Indoor experiments where a human participant transports a long bar with a tethered aerial vehicle are conducted. Results of experiments under different human velocities and intentions demonstrate the effectiveness and reliability of the proposed method.