Development of a human symbiotic assist arm PAS-Arm

This paper presents the PAS-Arm (Passive ASsist Arm), a novel assist arm based on passive robotics. PAS-Arms are intended for direct physical interaction with a human operator. PAS-Arms are physically passive. Their purpose is not to enhance human strength but to produce specified but arbitrary two-dimensional guiding surfaces that constrain and guide the motion of the human operator. PAS-Arms have three joints and a three dimensional workspace but possess only two degrees of freedom due to the reduction of degrees of freedom created by a combination of continuously variable transmissions (CVTs) and a differential mechanism. This paper proposes the basic concept and principle of PAS-Arms. We also describe the design and experimental results of a prototype PAS-Arm.