Virtual impedance based remote tele-collaboration with time delay

In this paper, a collision-free coordinated control scheme is discussed for Multi-Operator-Multi-Robot (MOMR) teleoperation through a network with communication time delay. Recently, collaboration tasks have rapidly emerged in many possible applications such as the plant maintenance, construction, and surgery, because multi-robot collaboration would have a significant advantage over a single robot in such cases. However, the effect of time-delay would pose a more difficult problem to MOMR teleoperation systems and seriously affect their performance. In this work, the virtual impedance based coordinated control method is proposed to cope with the collision arising from the communication delay in MOMR teleoperation system. We impose a variable impedance on the master hand and change the impedance according to the distance between two slave arms in local predictor simulator. When the possible collision is expected during the task, a high impedance is set to master hand and signals the operator to stop or to change her master command. This adjustable impedance of the master hand safely guides an operator through unexpected collisions in time-delayed MOMR teleoperation. To verify the validity of the proposed scheme, an experimental setup is built and a block arrangement task is performed by two slave arras based on simulation models.