Extender: a case study for human-robot interaction via transfer of power and information signals

A human´s ability to perform physical tasks is limited by physical strength, not by intelligence. The author defines “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. The author´s 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. 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. The stability of the system of human, extender, and object being manipulated was analyzed. A mathematical expression for the extender performance was determined to quantify the force augmentation. Experimental studies on the control and performance of the experimental extender were conducted to verify the theoretical predictions