Dynamics and Control of Human-Robot Interaction

A human\´s ability to perform physical tasks is limited by physical strength, not by intelligence. We have used the word "extenders" as a class of robot manipulators worn by humans to augment human mechanical strength, while the wearer\´s intellect remains the central control system for manipulating the extender. Our research objective is to determine the ground rules for the control of robotic systems worn by humans through the design, construction, and control of several prototype experimental direct-drive/non-direct-drive multi-degree-of-freedom hydraulic/electric extenders. The design of extenders is different from the design of conventional robots because the extender interfaces with the human on a physical level. The work discussed in this article involves the dynamics and control of a prototype hydraulic six-degree-of-freedom extender. This extender\´s architecture is a direct drive system with all revolute joints. Its linkage consists of two identical subsystems, the arm and the hand, each having three degrees of freedom. Two sets of force sensors measure the forces imposed on the extender by the human and by the environment (i.e., the load). The extender\´s compliances in response to such contact forces were designed by selecting appropriate force compensators. A mathematical expression for the extender performance was determined to quantify the force augmentation.