Assimilation Control of a Robotic Exoskeleton for Physical Human-Robot Interaction

The ability of human operators in estimating the partners' motion intention and utilizing it for collaboration brings valuable enlightenment to human-robot systems. Motivated by these observations, this letter introduces an assimilation control method that reshapes the physical interaction trajectory in the interaction task, which enables the exoskeleton robot to estimate the subject's virtual target from the interaction force and adapt its own behavior. Under the assumption that the virtual target is determined by the control gains, the stability of the human-robot system is guaranteed, and the proposed scheme realizes continuous interaction behaviors from cooperation to competition. Then an adaptive controller is designed to enable the robot to directly deal with uncertain dynamics and joint space constraints. The experiment verifies how the assimilation control method assists the subjects in a collaborative execution or gradually competes with them to avoid collisions. Compared with related literature, our approach is able to realize safe manipulation (e.g., obstacle avoidance) and broader interaction behaviors by reshaping the interactive trajectory using force feedback only, without continuous manual guidance as in many existing methods.