Force Augmentation in Human-Robot Interaction

A human\´s ability to perform physical tasks is limited, not by his intellect, but by his^l physical strength. If, in an appropriate environment, a machine\´s mechanical power is closely integrated with a human arm\´s mechanical strength under the control of the human intellect, the resulting system will be superior to a loosely integrated combination of a human and a fully automated robot. Therefore, we ought to develop a fundamental solution to the problem of "extending" human mechanical power via integrating with a robot. "Extenders" are defined in this work as a class of robot manipulators worn by humans to increase human mechanical strength, while the wearer\´s intellect remains the central control system for manipulating the extender. The human, in physical contact with the extender, exchanges power and information signals with the extender. The analysis in this paper focuses on the dynamics and control of the robotic systems worn by humans. General models for the human, the extender, and the interaction between the human and the extender are developed. The stability of the system of human, extender, and object being manipulated² is analyzed and the conditions for stable maneuvers are derived. An expression for the extender performance is defined to quantify the force³ augmentation. The trade-off between stability and performance is described. The theoretical predictions are verified experimentally.