Model of the human arm stiffness exerted by two antagoniste muscles

Due to the increasing working age, in the last years more and more attention is turned to exoskeleton for industrial applications. Exoskeletons reduce fatigue and the effort that would cause injuries on the operator. Exoskeletons designed for industrial applications are mostly finalized to relieve the operator from a heavy load. However in industrial practice, worker fatigue is not only due to heavy load carrying, but also to the increase of the arm stiffening requested by some operations, like drilling, screwing or precision operations. This paper represents the first step for a new approach of exoskeleton stiffness control, whose input is given in real time directly by electromyographic signal from muscles. In this paper we attempt to study the stiffness of the elbow on which two muscles act as agonist-antagonist. The model used for the muscles is the one proposed by Hill.