Switchings between trajectory tracking and force minimizationForce minimization in Human–Robot Collaboration(HRC)

A framework of switchings between trajectory tracking and force minimization is proposed for human-robot collaboration through physical interactions. In particular, the robot is able to follow a predefined reference trajectory when there is no human intervention and the robot’s control objective is trajectory tracking; and the robot can be intervened by the human on the fly and moved to the human’s target position by applying an interaction force when the robot’s control objective is minimization of the interaction force. Dynamic models of both the robot and the human are considered and their control objectives described. Switchings are realized by adaptation of the cost function. An optimal control problem is formulated to achieve the robot’s control objective, which is solved by employing dynamic programming. The validity of the proposed framework is verified through simulation studies.