Characteristics of the Human Arm Based on a Musculoskeletal Model of Cooperative Motion between Two Humans

Abstract

In this study, we considered a single rotational degree-of-freedom experimental system, in addition to a mass-spring-damper-friction biomechanical model of the human arm, and then investigated master-slave and master-semi-master cooperative motions. For the master-slave cooperative motion, we developed a mass-spring-friction biomechanical model for the slave's arm. Within the investigated range, we found the damping factor to be zero, and the stiffness and dynamic friction to be individually constant. We also determined the torque characteristics in the master-slave and master-semi-master cooperative motions. In the master-slave cooperative motion, although the master subject had to overcome the entire impedance resistance of the slave subject's arm, the master found it easier to slow down and stop the motion. In master-semi-master cooperative motion, when the semi-master subject switched from passive arm movement to active arm movement, the stiffness characteristics disappeared and constant torque characteristics were observed. At that moment, the master subject felt it took less effort to perform active arm movement. As a result, we assume that in human-robot cooperative tasks, during accelerating motion, we can apply the characteristics of the semi-master to a robot through torque control, and during deceleration (braking) motion, we can apply the slave characteristics to a robot by means of impedance control.