The ACT-4D: A novel rehabilitation robot for the quantification of upper limb motor impairments following brain injury

Rehabilitation robots and other controlled diagnostic devices are useful tools to objectively quantify debilitating, post-stroke impairments. The goal of this paper is to describe the design of the ACT-4D rehabilitation robot which can quantify arm impairments during functional movement. The robot can instantly switch between a compliant mode that minimizes impedance of voluntary movement, and a stiff mode that applies controlled position/speed perturbations to the elbow (up to 75 Nm or 450 deg/s at 4500 deg/s²). It has a limited range of movement of the shoulder and elbow, which is further reduced when a damper is needed to enhance the positional stiffness of the base robot. In recent experiments, the ACT-4D has been used successfully for the quantification of elbow impairments.