Realization of fictitious gain in human: Experimental verification on an elbow joint

Augmentation of human power is an important problem in the design of human assist devices such as an exoskeleton system. The overall system consisting of a human and an assistive device is a parallel control system that includes two controllers: the human brain and the assistive device controller. It has been postulated in a previous work that the motion control system of a human is regarded as a feedback control loop that consists of the brain, muscles, and the dynamics of the extended human body, and that the brain function is modeled as a control algorithm amplified by a fictitious gain. The fictitious gain compensates for characteristic changes in the muscle and dynamics. If the human is physically impaired or subjected to demanding work, the fictitious gain is increased to assist the human. The assistive device is controlled to augment human power, the amount of which is equivalent to the one attained by the fictitious gain. This paper presents the design and verification of an assistive device for elbow joint and the controller for the device based on the fictitious gain concept.